Intracellular interaction of these receptors with the growth factor simultaneously produced may provide continuous stimulation to the proliferation of these cells .
Stimulation with TGF-beta 1 revealed decreased PDGF alpha-receptor mRNA expression in normal mesothelial cells .
In fetal rat calvaria , the most significant consequence of treatment with PDGF was the selective stimulation of fibroblast replication and function .
Stimulation of human fibroblasts by platelet-derived growth factor ( PDGF)-BB leads to a down-regulation of PDGF beta-receptors and a concomitant appearance of intracellular granular accumulations of receptors , as determined by stainings with the mAb PDGFR-B2 .
The formation of intracellular PDGF beta-receptor granules was dependent on PDGF-BB concentration and time of stimulation .
Finally , the decrease in PDGF beta-receptors after culturing of the cells in the presence of TNF-alpha and IL-1 was accompanied by a decreased incorporation of [ 3H]thymidine in response to PDGF-BB stimulation .
As a result of this autocrine stimulation , the PDGF receptors were down-regulated .
After 3 days , a concentration-dependent growth curve of fibroblast proliferation was demonstrated for PDGF alone , with near maximal stimulation reached at -20 ng/ml PDGF .
In contrast , PDGF-AA stimulation did not result in increased PA synthesis as neither PLD nor DAG kinase activities were affected .
Comparison of PDGF-AA with PDGF-BB stimulation showed that PDGF-BB induced prolonged expression of the c-fos gene in BALB/c-3T3 cells , but that PDGF-AA induced more potent activation of the serum response element ( SRE ) in transient transfection assays .
Islet cells transfected with the PDGF alpha-receptor construct did not respond with stimulation of [ 3H]thymidine incorporation to any of the PDGF isoforms ( PDGF-AA , -AB , or -BB ) .
As a result , stimulation of HepG2 cells that express the kinase-inactive receptor leads to activation of serine/threonine kinases of the MAP kinase cascade which include RAF-1 , MEK-1 and p42 MAP kinase .
Stimulation of L6 myoblasts with 10 ng/ml of PDGF-BB causes receptor internalization and concentration in granules at perinuclear regions .
Thus , PDGF stimulation of myoblasts causes a redistribution of PDGF-receptors to resemble receptor localization observed during muscle regeneration .
Thus diabetic SMC over-react on PDGF stimulation through over-expression of the PDGF beta-receptor gene .
These results suggest that autocrine stimulation of growth may occur both in cultured normal mesothelial cells ( PDGF-AA acting via the alpha-receptor ) and in malignant mesothelioma cell lines ( PDGF-BB acting via the beta-receptor ) .
In cultures of serum-starved stromal cells , PDGF stimulated [ 3H]-thymidine incorporation into DNA in a dose-dependent manner with a maximum stimulation of 15-fold at 500 ng/ml .
cAMP also blocked stimulation of PDGF A chain mRNA by PMA .
TNF-alpha stimulation of fibroblast proliferation .
Additionally , phospholipase C-gamma ( PLC-gamma ) a substrate of activated PDGF receptors , was found to be physically associated with PDGF receptors in the absence of PDGF stimulation in transformed cells .
In cultured normal mesothelial cells , the secreted PDGF A-chain protein might be involved in autocrine growth stimulation via PDGF alpha receptors .
In addition we found that KS cells produce PDGF-A chain mRNA in response to PDGF stimulation .
This suggests that a PDGF-induced autocrine stimulation involving PDGF-AA which could amplify the response to PDGF occurs in these cells .
Saliently , stimulation of p125FAK tyrosine phosphorylation was sustained at up to 100 ng/ml PDGF-BB and for prolonged times of treatment .
In Swiss 3T3 fibroblasts , PDGF-BB and -AA stimulated p125FAK tyrosine phosphorylation and cell migration only at low concentrations , and stimulation was abolished at 10-25 ng/ml .
It is known that platelet-derived growth factor ( PDGF ) stimulates both of these processes in a paracrine fashion , whereas autocrine stimulation has been shown only for proliferation .
Stimulation of FSC with phorbol myristate acetate ( 10(-7 ) mol/L ) or PDGF BB ( 20 ng/mL ) increased steady-state levels of PDGF A-chain and B-chain messenger RNA .
In addition we found that PDGF-AB binding and stimulation of these activities is strongly temperature-dependent , whereas PDGF-AB binding and activation of PDGFR beta in the presence of PDGFR alpha is not .
While normal alveolar macrophages constitutively transcribe both PDGF-A and PDGF-B genes , LPS stimulation increases the transcription of both genes more than threefold .
Importantly , IPF alveolar macrophages spontaneously transcribe both genes at a rate similar to that observed for normal macrophages after in vitro stimulation .
In this study we show that PDGF A RNA expression was induced in HL-60 and Jurkat T-cell leukemia cells and increased in U937 and MOLT-4 cells after a 1- to 2-h stimulation with an 8 pM concentration of transforming growth factor beta ( TGF-beta ) .
Ligand stimulation of the platelet-derived growth factor ( PDGF ) beta-receptor leads to autophosphorylation of tyrosine residues , which is known to mediate interactions with several SH2 domain-containing signaling molecules .
PDGF beta-receptor coprecipitation in Shc immunoprecipitates was dependent on stimulation with PDGF-BB .
This report demonstrates that the expression of transforming mos ( v-mos ) can block the stimulation of growth-related gene expression mediated by the platelet-derived growth factor ( PDGF-BB ) .
Although the expression of PDGF type-beta receptor , as detected by Western blot with anti-PDGF type-beta receptor antibody,was not diminished in v-mos transformed BALB/c-3T3 murine fibroblasts , the autophosphorylation of PDGF-beta receptor in response to ligand ( recombinant PDGF-BB homodimer ) stimulation was profoundly suppressed .
We have previously found that stimulation of normal neonatal fibroblasts with PDGF or EGF leads to a transient induction of PDGF A-chain mRNA and the synthesis of PDGF-AA proteins .
Although hydrocortisone had no effect on early growth signals stimulated by angiotensin II ( e.g. , activation of protein kinase C , stimulation of Na+/H+ exchange , and c-fos and c-myc expression ) , it significantly decreased angiotensin II-stimulated secretion of PDGF-like material into the medium from 0.4 to 0.1 ng/ml/24 h ( p < ; 0.01 ) .
Stimulation of PDGF receptors leads to a cascade of cellular events , which have been shown to require an intact receptor tyrosine kinase activity .
When data on PDGF A- and B-chains , as well as alpha- and beta-receptor expression are compiled and the pattern of receptor binding specificity is taken into account , the majority of glioma cell lines are found to have a phenotype that makes autocrine stimulation possible .
Stimulation of pyrophosphate production in articular cartilage by a platelet-derived factor is independent of mitogenesis .
We report herein that platelet derived growth factor ( PDGF ) is not the platelet factor responsible for PPi stimulation and that the active factor is not mitogenic for chondrocytes .
We have further characterized the platelet factor responsible for the stimulation of PPi by cartilage .
Endothelial cell hyperplasia in human glioblastoma : coexpression of mRNA for platelet-derived growth factor ( PDGF ) B chain and PDGF receptor suggests autocrine growth stimulation .
Thus , an autocrine stimulation by the PDGF B chain/c-sis product via its receptor , evoked by interaction with surrounding glioma cells , could be the mechanism behind the pathological proliferation of endothelial cells characteristically found in this type of malignancy .
The frequencies and amplitudes of the oscillatory responses were independent of agonist concentration after stimulation with PDGF-BB .
The minimum concentration which had a significant stimulating effect on colony forming unit megakaryocyte ( CFU-MK ) was 10 ng/ml and maximum stimulation occurred at ng/ml .
The proliferation rate of wound fibroblasts was stimulated by PDGF-BB which elicited a dose-dependent ( 1-30 ng/ml ) stimulation of cell proliferation , whereas PDGF-AB and -AA were less effective in this respect .
Activation of phospholipase C-gamma is necessary for stimulation of phospholipase D by platelet-derived growth factor .
Mutation of Tyr-1021 of the PDGF receptor to Phe caused loss of PDGF stimulation of both PLC and PLD .
Furthermore , receptors in which association with the GTPase-activating protein , phosphatidylinositol 3-kinase , or Syp was individually restored were unable to mediate PDGF stimulation of PLC or PLD .
In summary , these results indicate that activation of PLC gamma 1 and protein kinase C are necessary for the stimulation of PLD by PDGF and provide no evidence for alternative mechanisms .
Stimulation with platelet-derived growth factor ( PDGF ) results in the association of several SH2 domain-containing proteins with the activated PDGF receptor , including GAP , a GTPase-activating protein of p21ras , and phosphatidylinositol-3-kinase ( PI-3K ) .
To evaluate the biological capacity of PDGF , we investigated the proliferative response of bovine lens epithelial cells to stimulation with PDGF-AA , -AB and -BB .
Instead , PDGF stimulation induces the formation of a complex containing GRB2 ; - , 80- , and 110-kDa tyrosine-phosphorylated proteins ; and the PDGF receptor .
PDGF-BB stimulation of D-alpha R or beta R cells results in anti-P-Tyr recovery of cellular proteins possessing similar as well as distinct phosphotyrosine signals .
In synchronized SMC at the G0 phase , 1 , 10 and 100 ng/ml PDGF started DNA synthesis at 24 , 15-18 and 12 hr , respectively , after stimulation by 3% fetal bovine serum ( FBS ) or hypophysectomized rat plasma ( deficient in insulin-like growth factor-I ( IGF-I ) ) .
The stimulation with 1% FBS plus 30 ng/ml PDGF potentiated the DNA synthesis which was saturated with stimulation by % FBS alone , suggesting that prolonged treatment of PDGF transforms SMC .
After LPS stimulation , the PDGF-A mRNA level increased gradually , while the PDGF-B mRNA level increased markedly and then decreased rapidly .
Early alterations in cytosolic free Ca2+ concentration ( Ca2+i ) ( occurring within seconds to minutes ) following platelet-derived growth factor ( PDGF ) stimulation were demonstrated to be required , in both BALB/c3T3 fibroblasts and vascular smooth muscle cells , for subsequent DNA synthesis by introduction of Ca(2+)-antagonists at different times in relation to growth factor stimulation .
Heparin-binding growth factor-1 stimulation of human endothelial cells induces platelet-derived growth factor A-chain gene expression .
These findings provide insights into biologic properties of a growth factor responsible for potent autocrine stimulation of abnormal cell proliferation .
The data further establish the existence of vascular SMC phenotypes characterized by a refractoriness to growth stimulation by specific mitogens , and provide further evidence for the reiteration of developmentally regulated programs following vascular injury in vivo .
PDGF BB increased the levels of immunoreactive collagenase after 6 h , whereas the levels were decreased after 16 h . Stimulation of collagenase mRNA by PDGF BB was dependent on de novo protein synthesis and activation of protein kinase C. PDGF BB prolonged the half-life of collagenase mRNA in transcriptionally arrested cells .
Uterine artery SMC from pregnant guinea pigs grew to a higher plateau density with serum stimulation , had increased spontaneous DNA synthesis and persistent growth following serum with-drawal , and were more responsive to 3-30 ng/ml PDGF-BB than nonpregnant cells .
Stimulation of Syrian hamster embryo ( SHE ) cells with the mitogen platelet-derived growth factor A/B ( PDGF ) results in intracellular acidification and capacitative calcium entry involving the intracellular release of calcium via the inositol trisphosphate gamma receptor calcium channel , followed by an extracellular influx of calcium through a dihydropyridine-sensitive plasma membrane calcium channel .
Paradoxically , transient intracellular acidification , like that following PDGF stimulation , could not stimulate the activation of either calcium channel .
Autocrine stimulation by platelet-derived growth factor-B ( PDGF-B)-like factors has been widely implicated as an important mechanism in the cause and/or maintenance of a variety of human tumors .
The results show that T98G cells contain functional PDGF receptors that , upon sufficient stimulation , can cause greatly increased mitogenic response , which may account for the development of the malignant phenotype .
Metastatic tumor formation in athymic mice by PDGF stimulation has not been reported previously .
Functionality of these receptors was demonstrated by an increased [ 3H]-thymidine incorporation in response to PDGF ( stimulation index = 2.5 ) .
At concentrations of PDGF-BB between 5 and ng/ml , maximum stimulation occurred with 20 ng/ml .
Phosphorylation on tyrosine of a -kDa protein in response to PDGF stimulation of intact cells was demonstrated by western blot analysis probing with anti-phosphotyrosine antibody .
Activation of PDGF beta receptor tyrosine kinase activity , stimulation of MAP kinase , and upregulation of immediate-early gene expression are not sufficient to repress skeletal muscle differentiation .
The results suggest that PDGF isoforms are potentially important mitogens for lung fibroblasts , but other factors are likely to be involved in the stimulation of fibroblast procollagen synthesis that is observed in fibroproliferative disorders of lung .
Specifically we tested if the old SMC predominantly expressed the long form of the A-chain mRNA , leading to autocrine stimulation by cell-associated PDGF AA-homodimers .
Exposure of cells of a rabbit corneal epithelial cell line ( SIRC ) to platelet-derived growth factor-AB heterodimer ( PDGF-AB ) resulted in a rapid and transient elevation of cytosolic free calcium concentration with a maximum at 2 to 3 min after stimulation .
The results suggest that PDGF-AB may act only as a competence factor for the stimulation of SIRC cells via modification of the intracellular calcium homeostasis .
Thus , costimulation with PDGF-AA and TGF-beta selectively enhanced proliferation of fibroblasts with the SSc phenotype .
These findings of the inappropriate coexpression of a potent mitogen , PDGF , and its receptor in lung cancer epithelial cells suggest the presence of a powerful in vivo mechanism contributing to the self-stimulation and unregulated growth of lung cancer tumor cells .
These data provide further evidence that PLC gamma 1 is responsible for the PDGF-induced stimulation of Ins(1,4,5)P3 formation .
We describe that stimulation of human fibroblasts with platelet-derived growth factor BB ( PDGF-BB ) induces a transient up-regulation of the PDGF alpha- and beta-receptor transcript and protein levels .
In conclusion , PDGF-BB , but not PDGF-AA , induces increased synthesis of both PDGF alpha- and beta-receptor protein ; this constitutes a positive feed-back mechanism , which , for example , could serve to potentiate autocrine stimulation of growth .
Although normal fibroblasts only express platelet-derived growth factor ( PDGF ) A-chain mRNA for a brief period following mitogenic stimulation , one strain of Hutchinson-Gilford ( progeria ) syndrome fibroblasts , AG3513 , constitutively expresses PDGF A-chain mRNA and PDGF-AA homodimers .
The diminished response of AG3513 progeria fibroblasts to PDGF stimulation was examined in some detail .
Subsequent synthesis and release of PDGF activity into the medium was detected as early as 4 hours after IL-1 stimulation , and downregulation of the binding site for the PDGF-AA isoform of PDGF followed PDGF-AA secretion .
A synergistic stimulation ( p less than 0.02 ) of DNA synthesis was observed in both myometrial and leiomyoma cells when EGF was added with insulin .
The addition of PDGF with insulin caused only additive stimulation of DNA synthesis .
Suramin , which inhibits the interaction of PDGF with its receptors , caused dose-dependent inhibition of both the PDGF-evoked increase in [ Ca2+]i and stimulation of DNA synthesis by PDGF .
This demonstrates that the insert is essential in PDGF-induced mitogenesis , and that PDGF stimulation of the mutant receptor tyrosine kinase and phosphatidylinositol turnover are not sufficient to elicit a mitogenic response to PDGF .
After prolonged exposure to PDGF , the transfectants became refractory to subsequent PDGF stimulation and the receptor protein was no longer detectable .
Stimulation of DNA replication appears to be independent of SM-C/IGF-I release , and furthermore , the results indicate that the islets do not produce PDGF-like substances themselves .
Maximal stimulation was observed on three cultures with EGF and two cultures with PDGF BB .
Kinetic studies indicated that PDGF-induced inhibition was associated with a decrease in affinity for cationic amino acids , while the stimulation was mediated by an increase in transport capacity .
Transcriptional inhibitors , actinomycin D or 5 , 6-dichloro-1-beta-D-ribofuranosylbenzimidazole , completely blocked the increase in B2 receptor mRNA when added up to 60 min after stimulation with PDGF .
However , stimulation of c-fos was slightly more sensitive to genistein , while the B2 receptor mRNA was more sensitive to inhibition by the protein kinase C inhibitor , calphostin C. The increase in cell surface B2 receptors were functionally coupled to an increase in phosphoinositide-specific phospholipase C , and the effects of PDGF were selective as there was no increase in either angiotensin II- or arginine vasopressin-induced inositol phosphate formation or intracellular calcium release .
T98Gsis cells are % tumorigenic and occasionally develop pulmonary metastases , showing that endogenous PR-beta can mediate complete transformation upon sufficient stimulation .
We investigated the interaction of PTP2C with the PDGF receptor by examining the localization of both proteins after PDGF stimulation of 293 cells which stably express the human PDGF receptor .
Upon stimulation with PDGF , PTP2C was translocated from the cytoplasm to membrane ruffles .
However , the expression of a catalytically inactive mutant PTP2C substantially prolonged ruffling activity following PDGF stimulation .
Our results suggest that stimulation of the PDGF system is significantly involved in the development not only of diabetic atherosclerosis but also of microangiopathy .
Stimulation of DNA synthesis was correlated with an intense increase in lamellipodia formation and ruffling , whereas inhibition of the DNA synthesis was correlated with the development of elongated cell shape with few ruffles and lamellipodia , similarly to untreated control cells .
The U-2 OS cells are known to express the c-sis oncogene [ platelet-derived growth factor ( PDGF ) B-chain ] , PDGF-A , and receptors for PDGF , thus providing a potential autocrine loop of growth stimulation .
In the present study we examined effects of PDGF-BB stimulation on the synthesis of collagen-binding beta integrins by human diploid fibroblasts ( AG 1518 ) .
PDGF-BB stimulation led to an increase in the rare of integrin alpha 2-subunit synthesis .
In contrast , synthesis of the integrin alpha 1- or alpha 3-subunits were not affected by PDGF-BB stimulation .
Furthermore , levels of alpha -subunit mRNA relative to levels of glyceraldehyde-3-phosphate dehydrogenase ( GAPDH ) mRNA increased after PDGF-BB stimulation .
PDGF-BB stimulation did not influence the relation between levels of integrin beta 1-subunit mRNA and GAPDH mRNA .
In addition , the rate of synthesis or post-translational processing of the integrin beta 1-subunit were not , or only marginally , affected by PDGF-BB stimulation .
Stimulation of the platelet-derived growth factor beta receptor signaling pathway activates protein kinase C-delta .
Like TPA treatment , PDGF-BB stimulation caused striking phosphorylation of PKC-delta in vivo and translocation of some PKC-delta from the cytosol fraction to the membrane fraction in both cell systems .
Tyrosine-phosphorylated PKC-delta was observed only for the membrane fraction after stimulation with PDGF-BB or TPA .
The enzymatic activity of PKC-delta in the membrane fraction also increased after stimulation with TPA or PDGF , providing a positive correlation between PKC-delta tyrosine phosphorylation and its activation.(ABSTRACT TRUNCATED AT 250 WORDS )
Lovastatin inhibits platelet-derived growth factor ( PDGF ) stimulation of phosphatidylinositol 3-kinase activity as well as association of p85 subunit to tyrosine-phosphorylated PDGF receptor .
However , overnight pretreatment of cells with 10 microM lovastatin inhibits this stimulation of PI-3-kinase activity by PDGF and insulin .
However , upon exposure of cells to 10 microns lovastatin for 40 h , the level of autophosphorylated PDGFR associating with PI-3-kinase after PDGF stimulation decreases significantly ( 75% reduction ) .
PDGF ( 15 ng/ml ) stimulated PKC activity within 5 min , and the effect was sustained for 60 min. Pretreatment of mesangial cells with -(5-isoquinolinesulfonyl)-2-methylpiperazine ( H-7 ) , an inhibitor of PKC , abolished the stimulation of PKC and DNA synthesis in response to PDGF .
When lymphocytes from contacts of patients with tuberculosis , patients with tuberculosis , and normal subjects were compared following PPD stimulation , the lymphocytes from the contacts had the greatest proliferation response , the greatest production of interferon-gamma ( IFN-gamma ) , and their lymphokines induced the greatest increase in PDGF-B mRNA in macrophages .
An 11.3-fold increase in Egr-1 transcription rate was observed as early as 5 min after PDGF stimulation of MC .
Interestingly , electrophoretic mobility shift assays , with an Egr-1 SRE as probe , demonstrate that protein-SRE complexes of differing size undergo modest quantitative changes following PDGF stimulation .
These agents produce a rapid increase in steady-state concentrations of PDGF A- and B-chain mRNAs , peaking within 4-8 h of stimulation .
0.5 microM GDP and 0.5 microM GTP were equally potent competing for the formation of Ras.[alpha-32P]GTP upon PDGF stimulation .
We propose that chronic autostimulation of PDGF alpha-receptors occurs in pre-implantation embryos , whereas , following implantation , early mesoderm development is dependent on stimulation by ectodermally produced PDGF-A .
This study determined the effects of dexamethasone on growth-factor stimulation of gingival , periodontal ligament and pulp fibroblast proliferation in vitro .
These data suggest that dexamethasone may substitute for IGF-I in PDGF stimulation of cell proliferation .
Conversely , stimulation of hASMC proliferation was associated with the opposite phenomenon .
Both homodimers caused an increase in AP-activity , indicating stimulation of cell differentiation .
Cultured chondrocytes bound 125I-PDGF AA and 125I-PDGF BB and after stimulation with PDGF expressed c-fos protein .
PDGF induced marked increases in the concentration of inositol phosphates at 30 min after stimulation , but by this time point any effect of bradykinin had disappeared .
Response of low-passage human malignant gliomas in vitro to stimulation and selective inhibition of growth factor-mediated pathways .
Appropriate concentrations of an anti-PDGF neutralizing antibody inhibited baseline DNA synthesis and proliferation in the absence of added growth factors , suggesting the possible role of PDGF in autocrine stimulation of these cells .
It is concluded that , in the malignant gliomas studied , PDGF may be acting as a dominant mitogen to enhance DNA synthesis , and may function in autocrine stimulation .
This study demonstrates that in diploid human dermal fibroblasts , TGF-beta 1 is weakly mitogenic in the absence of serum or purified growth factors , and that TGF-beta 1 potentiates DNA synthesis in PDGF-stimulated fibroblasts with delayed kinetics when compared to stimulation with PDGF alone .
In contrast , only trace amounts of phosphotyrosine were incorporated into PLC-gamma and no intracellular calcium signal was detected after CSF-1 stimulation .
In fibroblasts , antiserum to PLC-gamma co-precipitated a fraction of the tyrosine phosphorylated form of the PDGF receptor ( PDGF-R ) after ligand stimulation , implying that phosphorylated PDGF-R and PLC-gamma were associated in a stable complex .
Two classes of sites were detected by Scatchard analysis with respectively 21,000 and 37,000 sites per cell , with a KD of 0.3 x 10(-10 ) M and KD of 0.5 x 10(-9 ) M. The stimulation of DNA synthesis by PDGF was quantified by [ 3H]thymidine incorporation .
An involvement of PDGF in autocrine and paracrine stimulation of normal cell growth is suggested by the finding that responsive ( arterial smooth muscle cells and placental cytotrophoblasts ) as well as nonresponsive ( endothelial cells and macrophages ) cells produce PDGF-like growth factors .
We have now used this approach to ask whether a functional SH3 domain of Src is required to transduce the mitogenic signal upon PDGF or EGF stimulation .
CONCLUSIONS : The induction of LO mRNA and its secretion by VSMC is an early event accompanying growth factor stimulation and may contribute to organization of the extracellular matrix .
The effect is specific to copper-zinc superoxide dismutase as glutathione peroxidase-overexpressing NIH3T3 cells , again produced by transfection of an expression vector , retain the ability to release PGE2 in response to growth factor stimulation .
Cell culture was used to determine if estrogen and progesterone stimulation modulated the expression of PDGF-B .
Estrogen and progesterone stimulation in aggressive fibromatosis resulted in an increase in the level of expression .
This stimulation was significantly attenuated in the presence of either anti-ET-1 antiserum or BQ-123 ( 10(-7)-10(-5)M ) .
Permeabilized rat kidney cells rapidly released glucose 6-phosphate dehydrogenase ( G6PD ) following stimulation with peptide growth factors ( Stanton , R.C. , Seifter , J.L. , Boxer , D.C. , Zimmerman , E. , and Cantley , L. C. ( 1991 ) J. Biol .
Mitogenic stimulation of connective tissue cells by transforming growth factor-beta ( TGF-beta ) has two unusual properties ; entry into S-phase is delayed compared with that induced by other mitogens , and the dose response is biphasic , with low concentrations stimulating and high concentrations inhibiting or having no effect .
We found that these cells do respond mitogenically to TGF-beta and interleukin-1 alpha , indicating that PDGF A-chain induction is not the sole mechanism of mitogenic stimulation .
Neutralizing anti-PDGF antiserum reduced TGF-beta stimulation of PDGFR alpha-expressing 3T3 cells by about 35% .
We conclude that induction of PDGF A-chain/PDGFR alpha autocrine stimulation does contribute to the ability of TGF-beta to stimulate connective tissue cells , but that there is , in addition , a PDGF-independent pathway .
Before the ligand-receptor complex is internalized and degraded , receptor stimulation is transmitted to the general transduction network , in which several tyrosine kinase substrates are activated by phosphorylation and changes the cytoplasmic biochemistry .
Cells transformed by SSV have been studied as a model system for the autocrine stimulation of the PDGF receptor .
The significance and mechanism of extracellular calcium influx in the stimulation by PDGF of cell replication was investigated in density-arrested C3H 10T1/2 mouse fibroblasts .
PDGF consistently stimulated a biphasic increase in the [ Ca2+]i composed of a rapid transient release of calcium from intracellular storage sites followed by a sustained elevation , significantly greater than prestimulated levels , which was dependent upon the [ Ca2+]e and persisted for at least h . The percentage of cells incorporating [ 3H]-TdR into DNA after stimulation with PDGF+insulin was closely correlated with the magnitude of the sustained [ Ca2+]i increase and to the [ Ca2+]e .
The cells expressed PDGF receptors and responded to PDGF stimulation by the activation of the PDGF signal transduction pathway and a dose-dependent stimulation of cell proliferation .
Human gingival fibroblasts were cultured in the presence of varying concentrations of platelet-derived growth factor ( PDGF ) or Salmonella enteritidis LPS to determine the optimal concentrations for stimulation and inhibition of proliferation respectively .
The results indicated that maximal inhibition of fibroblast proliferation was obtained with 50 micrograms/ml LPS and maximal stimulation of proliferation with 5 ng/ml PDGF .
In this study , using a receptor-blotting technique , we find that p85 is modified by PDGF stimulation of intact cells .
This study provides the first evidence that p85 is tyrosine phosphorylated upon PDGF stimulation of cells and suggests that tyrosine phosphorylation of p85 regulates its activity or its interaction with other proteins .
Stimulation of mesangial cells with PDGF-BB caused a dose-dependent formation of prostaglandin E2 .
Stimulation of growth of human breast cancer cells ( T47D ) by platelet derived growth factor .
PDGF stimulation of inositol phospholipid hydrolysis requires PLC-gamma phosphorylation on tyrosine residues 783 and 1254 .
Mitogenic stimulation of density-arrested C3H 10T1/2 mouse fibroblasts by serum or purified platelet-derived growth factor ( PDGF ) was potently inhibited by retinyl acetate ( RAc ; IC50 = 0.1 microgram/ml , 0.3 x 10(-6 ) M ) when administered during the first 2 hours of mitogen exposure .
Second , the kinetics of c-myc RNA elevation after treatment with PDGF or forskolin were similar , ruling out delayed onset of cAMP stimulation .
It in fact inhibited IL-1 stimulation of collagenase gene expression .
We have investigated the mechanism of fibroblast growth stimulation by IL-1 .
Competence induction and mitogenic stimulation by PDGF was associated with early induction of proteins P32 , P38 , P46-48 , P75 , and changes in cytoskeletal organization .
Examination of these early cellular changes showed that IL-1 did not produce similar induction of cellular proteins and the morphological changes associated with growth stimulation .
When IL-1 was added to cells rendered competent by brief exposure to PDGF , 10-15% additional DNA synthesis occurred during the first 24 h . Extended incubation of PDGF-treated cells in the presence of IL-1 revealed that the stimulation by IL-1 occurred predominantly during the subsequent cycle of DNA replication , wherein DNA synthesis reached three- to fivefold higher than the untreated cultures .
However , it shifted if the time point of initiation of DNA synthesis from about 14 h after stimulation with PDGF to about 18 to 21 h and decreased significantly the rate of the DNA synthesis .
rIFN-gamma could be added up to 6 h following stimulation with PDGF with no loss of its inhibitory effect .
Similarly , marked stimulations by PDGF were observed in NIH 3T3 cells , as well as in v-src-transformed 3T3 cells , but not in 3T3 cells transformed by Kirsten sarcoma virus or by transfection with v-Ha-ras DNA .
The stimulation was dose dependent .
Maximal stimulation of the binding was observed after 3 h of preincubation followed by a decrease after 4-5 h of preincubation .
Stimulation of quiescent Balb/c 3T3 fibroblasts into S phase requires the synergistic action of platelet-derived growth factor ( PDGF ) and progression factors found in platelet-poor plasma ( PPP ) .
Although plasma does not significantly increase the proportion of Kip1 bound to cyclin D1-Cdk4 , stimulation of PDGF-treated cells with plasma does overcome the threshold inhibition of p27kip1 by further increasing the expression of cyclins E and A and decreasing the amount of Kip1 over a prolonged time period .
Thus , TGF beta 1 has two roles in the growth of undifferentiated U9 colon carcinoma cells in vivo : direct stimulation of cell proliferation as we have showed in earlier studies , and an increase in angiogenesis by inducing PDGF-B .
Our data demonstrate that PDGF stimulation of quiescent cells leads to enhanced Sp1 binding to the LDL receptor gene .
Sequential stimulation of HPTC , first with 25 mmol/L D-glucose for 48 hours and then with platelet-derived growth factor ( PDGF ) isoforms , resulted in a dose-dependent secretion of TGF-beta 1 . Pre-exposure to 5 mmol/L D-glucose or 25 mmol/L L-glucose did not prime for TGF-beta 1 release .
TGF-beta 1 secretion was inhibited in a dose-dependent manner by pretreatment with cyclohexamide , but was not affected by pretreatment with actinomycin D. Stimulation of HPTC with a single dose of PDGF induced TGF-beta 1 mRNA ; however , only after application of a second dose of PDGF ( after TGF-beta 1 mRNA induction ) did TGF-beta 1 protein secretion occur .
We also demonstrated that PDGF stimulation of HPTC induced an inherently more stable TGF-beta 1 mRNA transcript .
[ 125I]-PDGF-BB binding to scleroderma fibroblasts was increased after TGF-beta 1 stimulation .
Signaling cascades elicited by angiotensin II resemble those characteristic of growth factor stimulation .
Stimulation of smooth muscle cells with angiotensin II resulted in tyrosine phosphorylation on Shc proteins and subsequent complex formation between Shc and growth factor receptor binding protein-2 ( GRB2 ) .
Importantly , stimulation of normal erythropoiesis in vivo in mice treated either with phenylhydrazine or with erythropoietin increased PDGF levels in the spleen by 11- to -fold and 20- to 34-fold , respectively .
The compound shows selectivity for inhibition of PDGF-mediated events such as PDGF receptor autophosphorylation , cellular tyrosine phosphorylation , and c-fos mRNA induction in response to PDGF stimulation of intact cells .
Coronary artery conditioned media produced significant stimulation of cell growth [ 127(SEM 29)% , n = 15 ] above that caused by culture medium alone .
Interestingly , the mitogenic and signaling responses of quiescent C2 cells to stimulation with fetal bovine serum or phorbol myristate acetate were unaffected by prior activation of delta Raf-1:ER .
Therefore , these results suggest that PDGF-induced PLD activation may be a consequence of primary stimulation of PLC-gamma 1 and that PLD may play a role downstream from PLC-gamma 1 in PDGF-triggered mitogenesis .
Ligand stimulation of the platelet-derived growth factor ( PDGF ) beta-receptor leads to activation of its intrinsic tyrosine kinase and autophosphorylation of the intracellular part of the receptor .
PGE caused no apparent diminution in the abundance of the surface PDGF beta receptor nor its subsequent activation and tyrosine phosphorylation following PDGF stimulation .
RN1a cells are relatively insensitive to stimulation by PDGF-AA and express fewer PDGF alpha receptors as shown by Northern blots and receptor-binding studies .
GLA caused no apparent diminution in the abundance of the surface PDGF-beta receptor nor its subsequent activation and tyrosine phosphorylation after PDGF stimulation .
Inhibition of platelet-derived growth factor autocrine growth stimulation by a monoclonal antibody to the human alpha platelet-derived growth factor receptor .
Monoclonal antibody alpha R1 also inhibited PDGF stimulation of [ 3H]thymidine uptake by 32D cells expressing the alpha PDGFR ( 32D alpha R ) as well as autocrine growth stimulation of 32D alpha R cells transfected with and expressing PDGF AA or PDGF BB .
Therefore , monoclonal antibody alpha R1 may be useful in the detection and growth inhibition of malignancies in which PDGF autocrine stimulation and/or alpha PDGFR overexpression plays an important role(s ) .
Stimulation of BLEC with PDGF isoforms showed no increase in cell proliferation under the culture conditions of this study .
In contrast , measurement of cytosolic free calcium concentration ( [ Ca2+]i ) , which has been shown to be an important second messenger for controlling multiple cellular processes in the lens , revealed a dose-dependent rise in [ Ca2+]i upon stimulation with PDGF-AB and -BB isoforms .
For EGF , bFGF , PDGF-AB and PDGF-BB there was no difference in the sensitivity of VSMC to stimulation of [ 3H]-thymidine incorporation between the strains .
Low current ( 0.25 , 3 mA ) stimulation through a miniature electrode cuff encased around the carotid artery of the rat was used to induce intimal hyperplasia , an important feature of the atherosclerotic plaque and a phenomenon limiting the long term success of angioplasty .
Compared to contralateral unstimulated arteries , 11-14 days of daily transmural stimulation of cuffed arteries ( 20 min period ) significantly increased the amount of extracted DNA ( diphenylamine colorimetric assay ) .
Gene expression of PDGF-A chain , PDGF-B chain and PDGF-beta receptor ( beta r ) ( Northern analysis of extracted carotid RNA ) increased within 4 h after electrical stimulation with 3 mA .
The pattern of gene expression for PDGF ligands and beta r during the 11-14 days of stimulation differed , but each remained above contralateral control levels .
A series of pieces of evidence have shown that Ras protein acts as a transducer of the platelet-derived growth factor ( PDGF ) receptor-mediated signaling pathway : ( i ) formation of Ras.GTP is detected immediately on PDGF stimulation , and ( ii ) a dominant inhibitory mutant Ras , as well as a neutralizing anti-Ras antibody , can interfere with PDGF-induced responses .
The activity of CDGF was different from that of SFCM ; i.e. , the onset of DNA synthesis was delayed for about 7 h . CDGF induced maximally 25% of the activity of serum or SFCM if the activity was measured with a 2-h[3H]thymidine pulse starting 15 h after stimulation of the cells , indicating loss of a protein which modulated the mitogenic activity of CDGF .
Regarding induction of cellular growth , only PDGF proved similar to serum , whereas cells stimulated with CDGF or TGF-beta showed a decreased rate of multiplication during the first day after stimulation .
FGF , IGF-I , and PDGF all enhanced CDGF-induced cell growth during the first day , whereas an additive stimulation over at least 2 days was observed with PDGF .
After PDGF and 5-HT stimulation , Egr-1 mRNA levels returned to baseline within 4 h , whereas AVP induced a sustained increase for up to 8 h . There was a very close correlation between doses required for Egr-1 induction and induction of MC proliferation .
Egr-1 mRNA after AVP stimulation remained elevated in control cells for up to 8 h but returned to baseline after 120 min in PKC-depleted cells .
We conclude that there is a strong correlation between induction of Egr-1 after stimulation with PDGF , AVP , 5-HT , and ANG II and the proliferative response elicited by these agents in MCs .
There was an increase in PDGF(B ) mRNA in macrophages from nonsmokers after stimulation with dexamethasone alone ( P less than 0.05 ) or in combination with IFN-gamma ( P less than 0.05 ) .
Platelet-derived growth factor stimulation of GTPase-activating protein tyrosine phosphorylation in control and c-H-ras-expressing NIH 3T3 cells correlates with p21ras activation .
Platelet-derived growth factor ( PDGF ) stimulation of NIH 3T3 cells leads to the rapid tyrosine phosphorylation of the GTPase-activating protein ( GAP ) and an associated 64- to 62-kDa tyrosine-phosphorylated protein ( p64/62 ) .
In NIH 3T3 cells , we found that PDGF stimulation led to the recovery of between 37 and 52% of GAP molecules by immunoprecipitation with monoclonal antiphosphotyrosine antibodies .
These results imply that the level of p21ras activation following PDGF stimulation of NIH T3 cells is sufficient to support mitogenic stimulation .
PDGFrecB transcripts were found in 24 out of 29 gliomas , in agreement with the hypothesis of an autocrine growth stimulation in these tumors .
One of the immediate cellular responses to stimulation by various growth factors is the activation of a phosphatidylinositol ( PI ) -kinase .
In this model 24 h stimulation with rhPDGF-BB induced an increase of the H-thymidine incorporation of 1190 +/- 280 ( 50 ng/ml ) % +/- s.e.m .
Less growth induction was noted after stimulation with ng/ml rhPDGF-AB ( 925 +/- 126% ) or rhPDGF-AA ( 575 +/- 24% ) .
Stimulation of HTh 74 cells with TSH led to a concentration-dependent increase in cAMP formation , showing a functional activity of the TSH receptors .
This is in agreement with the hypothesis of an autocrine growth stimulation in gliomas .
Thus , also a paracrine loop for endothelial cell growth stimulation may be suggested in malignant gliomas .
A phosphatidylinositol-3 ( PI-3 ) kinase activity of unknown biological function associates with tyrosine kinase-containing proteins , including a number of growth factor receptors after ligand stimulation .
Moreover , phosphatidylinositol turnover in response to ligand stimulation is unaffected .
The expression of the proto-oncogenes c-fos , c-jun , jun B and jun D was monitored in quiescent C3H10T1/2 fibroblasts after stimulation with PDGF .
PDGF treatment of Balb/c3T3 cells produces a 10-20-fold stimulation of mRNA for IL-1 receptor .
Investigation of the signal transduction pathways shows that activation of either the protein kinase C pathway or the cAMP-mediated pathway leads to the stimulation of IL-1 receptor expression in Balb/c3T3 cells .
Treatment of Balb/c3T3 cells with phorbol 12-myristate -acetate ( PMA ) , a known activator of protein kinase C , produced an increased 125I-IL-1 binding to cells and stimulation of IL-1R mRNA .
Down-regulation of protein kinase C by pretreatment with PMA reduced the subsequent stimulation by PDGF .
Evidence is presented that suggests that stimulation of IL-1R through these two pathways ( PMA/PDGF-stimulated and cAMP-stimulated ) occurs independent of each other .
Induction of PDGF receptor expression may render cells responsive to stimulation by PDGF , released from PDGF-producing cells , such as activated macrophages and from platelets .
Alpha 1-adrenergic stimulation of platelet-derived growth factor A-chain gene expression in rat aorta .
We report here that the alpha-adrenergic agonist phenylephrine ( PE ) produced dose-dependent stimulation of platelet-derived growth factor A-chain ( PDGF-A ) gene expression in rat thoracic aorta via agonist occupancy of alpha -adrenergic receptors .
Extensive evidence indicate that platelet-derived growth factor ( PDGF ) and epidermal growth factor ( EGF ) play a key role in the stimulation of the 3T3 fibroblast replication : in this connection , PDGF and EGF act as a competence and a progression factor , respectively .
Our data show a dose-related effect of EGF on DNA synthesis and cell growth , with maximal stimulation for both parameters at 20 ng/ml .
Both EGF and PDGF stimulate MG63 cellular tyrosine kinase activity , and such stimulation is inhibited by TGF-beta pretreatment .
Interestingly , the PDGF stimulation occurred at 3 as well as 37 degrees C and in the absence or presence of extracellular Ca2+ .
Furthermore , these immunoprecipitation studies showed that PLC-gamma is rapidly phosphorylated on tyrosine residues after PDGF stimulation .
The finding that PDGF production is common in normal as well as transformed cells indicate that PDGF has a function in autocrine and paracrine stimulation of cells in several physiological and pathological conditions .
The cellular effects ascribed to PDGF , growth stimulation , ruffling and chemotaxis , seems to be mainly associated with B chain containing dimers .
A high-molecular-weight PDGF-like factor secreted by v-sis transformed cells leads to growth stimulation and transformation [ published erratum appears in Oncogene Res 1988;3(3):299 ]
The partially purified high-molecular-weight factor competes with 125I-PDGF for receptor binding and leads to growth stimulation and anchorage-independent growth of normal cells .
Growth stimulation of postconfluent cultures with either FBS or PDGF resulted in marked repression of SM alpha actin synthesis but the level of repression was not directly related to entry into S phase in that PDGF was a more potent repressor of SM alpha actin synthesis than was FBS despite a lesser mitogenic effect .
NIH-3T3 cells transformed by the EJ-ras oncogene synthesize only 10-15% as much inositol 1,4,5-trisphosphate ( InsP3 ) as control cells after stimulation with platelet-derived growth factor ( PDGF ) .
The stimulation of paracrine and autocrine mitogenic pathways by the platelet-derived growth factor receptor .
The present studies demonstrate that PDGF produces a biphasic stimulation of reductase activity in cultured fibroblasts : a peak at 4 to 6 hours , followed by a decline , and then a second smaller peak at 24 hours , concurrent with DNA synthesis .
The stimulation of both peaks was PDGF concentration-dependent , although quantitative differences were observed .
The level of p27kip1 protein falls dramatically after mitogenic stimulation and is accompanied by a decrease in cyclin E associated p27kip1 , as well as a transient increase in cyclin D1-associated p27kip1 that later declines concomitantly with the loss of total p27kip1 .
Synthesis of p27kip1 as determined by incorporation of [ 35S]methionine was repressed upon mitogenic stimulation , and PDGF was sufficient to elicit this repression within 2 to 3 h . Pulse-chase experiments demonstrated the reduced rate of synthesis was not the result of an increased rate of degradation .
To understand how the stimulation of phosphoinositide 3-kinase ( PI -kinase ) by different growth factors can activate different subsets of downstream responses , growth-factor regulation of PI 3-kinase activity at different intracellular locations was investigated in 3T3-L1 adipocytes .
Insulin caused a large stimulation of glucose transport and stimulated recruitment of transferrin receptors to the plasma membrane ( PM ) in these cells , whereas platelet-derived growth factor ( PDGF)-bb was virtually without effect on these responses .
Subcellular fractionation studies after stimulation with PDGF-bb or insulin revealed a differential effect of these growth factors on subcellular localization of PI 3-kinase activity .
In the microsomal membrane fraction the insulin-stimulated recruitment of p85 alpha closely matched the increase PI 3-kinase activity , indicating that insulin stimulation of PI 3-kinase in this fraction is largely due to recruitment of PI 3-kinase enzyme rather than alterations in specific activity .
Decreased PDGFR expression in differentiated cells is associated with impaired biological responsiveness to PDGF , as shown by reduced activation of mitogen-activated protein-kinase following PDGF stimulation , and decreased chemotactic responsiveness to PDGF .
EGF or PDGF also caused a transient increase in the in vivo phosphorylation level and a change in the intracellular localization of aPKClambda from the nucleus to the cytosol , indicating the activation of aPKClambda in response to this growth factor stimulation .
Up to now all these proteins were shown to transmit and amplify the signal started with PDGF-R stimulation .
Stimulation by these drugs was not associated with a change in the abundance of the mRNA of the house-keeping gene , glyceraldehyde-3-phosphate dehydrogenase .
Treatment with either PDGF or bombesin caused a marked and persistent stimulation of p42MAPK and p44MAPK .
Furthermore , the upstream kinases MEK-1/MEK-2 and p74raf-1 were not activated by mitogenic combinations of cAMP while PDGF caused marked stimulation of their activity .
This study suggests that progression towards a glioblastoma in both the general population and in patients with Li-Fraumeni syndrome may involve potential autocrine and paracrine stimulation by growth factors such as PDGF .
Stimulation with either PDGF or IGF-1 induced substantial increases in DNA synthesis and cell number , as reflected by [ 3H]thymidine incorporation , flow cytometry , and methylene blue staining .
However , relative to EGF and -HT stimulation , late-phase MAP kinase activation was significantly greater after treatment with the mitogens PDGF and IGF-1 .
We conclude that in cultured bovine tracheal myocytes 1 ) PDGF and IGF-1 are potent mitogens ; 2 ) MAP kinase may be activated subsequent to stimulation of either receptor tyrosine kinases ( PDGF , EGF , IGF-1 ) or G protein-linked receptors lacking in known tyrosine kinase activity ( 5-HT ) ; and 3 ) unsustained MAP kinase activation is insufficient for mitogenesis .
However , PDGF stimulation results in a smaller fraction of tyrosine-phosphorylated PLC-gamma and a smaller accumulation of inositol trisphosphate in cells expressing the alpha-receptor as compared with cells expressing the beta-receptor .
Lowering of the intracellular PDGF content and prevention of extracellular growth factor receptor binding demonstrates that suramin disrupts autocrine loops and paracrine growth stimulation in meningioma tissue .
These data provide evidence that growth of cerebral meningiomas in culture is strongly inhibited by suramin at a concentration of 10(-4 ) M. Suramin acts as a scavenger neutralizing exogenous growth factors ; thus it can interrupt autocrine loops and paracrine stimulation of human meningioma cell growth .
Exposure of mesangial cells to platelet-derived growth factor ( PDGF ) BB caused a significant stimulation of cell proliferation and protein synthesis , as measured by [ 3H]thymidine incorporation and [ 3H]leucine incorporation respectively .
Whereas stimulation with PDGF-BB caused a potent and sustained ( for more than 30 min ) phosphorylation and activation of p42mapk and p44mapk , as well as of the upstream activators MAP kinase kinase and c-Raf , the effect of angiotensin II was less potent , reaching a peak at 5-10 min and thereafter declining rapidly .
In cells showing nonoscillatory Ca2+ responses to ET-1 , subsequent stimulation with PDGF was frequently followed by the development of an oscillatory Ca2+ response .
Activation of ETA and PDGF receptors was associated with differential stimulation of thymidine incorporation ; ET-1 induced a low-amplitude bell-shaped dose-response curve ; PDGF induced a sustained sigmoidal and dose-dependent rise .
However , in the presence of 2% serum , which induces half-maximal stimulation , IGF-I ( 100 ng/ml ) further increased the rate of 3H-thymidine incorporation in stromal but not smooth muscle cells ( p < ; 0.05 ) .
By stimulation inducing cell proliferation , transcription of the A chain is activated , resulting in an increase in mRNA .
By stimulation inducing cell differentiation , the A chain is activated at the post-transcriptional level , and the B chain at the transcriptional level , resulting in an increase in both mRNA .
Stimulation of quiescent fibroblasts or fibroblast-like cells with growth factors causes a sharp increase in the mRNA levels of several DNA synthesis genes .
Activation of phospholipase C-gamma 1 through transfected platelet-derived growth factor receptor enhances interleukin 2 production upon antigen stimulation in a T-cell line .
While EGF stimulation did not either cause phosphorylation of PLC gamma or induce Ca2+ mobilization in the EGF-R transfectant in this system , PDGF treatment induced tyrosine phosphorylation of PLC gamma 1 and Ca2+ mobilization in the PDGF-R transfectant .
Stimulation through PDGF-R enhanced IL-2 production upon antigen stimulation of the transfectants , although PDGF treatment alone did not induce IL-2 production .
Porcine aortic endothelial cells expressing the PDGF beta-receptor or a chimeric fibroblast growth factor ( FGF ) receptor , in which the endogenous kinase insert was replaced with the corresponding region from the PDGF beta-receptor , migrated efficiently towards a concentration gradient of PDGF-BB and bFGF , respectively , and exhibited both pronounced edge ruffling and circular membrane ruffling in response to ligand-stimulation .
To further investigate the ability of E5 to activate receptors of different classes and to determine whether this stimulation occurs through the extracellular domain required for ligand activation , we constructed chimeric genes encoding PDGF-R and EGF-R by interchanging the extracellular , membrane , and cytoplasmic coding domains .
Chimeric receptors that contained both of these domains exhibited the highest level of E5-induced biochemical and biological stimulation .
Injection of an antibody specific for Src , Fyn , and Yes also reduced signal transduction through the PDGF receptor but only when injected within 8 hr of PDGF stimulation .
Stimulation of human embryonic lung fibroblasts by TGF-beta and PDGF acting in synergism .
A number of cellular proteins , including PLC-gamma 2 , but not PLC-delta 1 , were phosphorylated on a tyrosine residue by the stimulation of either PDGF-BB or -AB .
Therefore , the functionality of this receptor in the D122 epithelial cell line was verified by immune complex kinase and ligand-stimulation assays .
In the 10T1/2 cells as well as the Cl 16 subclone , the dose-dependent PDGF stimulation of c-fos mRNA synthesis was similar in both logarithmically growing and confluent cultures .
Cotransfection of the PDGFR-beta and the chimeric PDGFR-beta/FGFR-1 constructs attenuated the stimulation of DNA synthesis in response to PDGF-BB .
Stimulation of proliferation of some cell types by TGF-beta has been linked to the secondary production of PDGF but the evidence we have suggests that this is unlikely in chicken adipocyte precursors .
Secreted PDGF and TGF- alpha are apparently not involved in or not essential for autocrine growth stimulation of melanoma cells .
Specific growth stimulation of cultured smooth muscle cells from spontaneously hypertensive rats by platelet-derived growth factor A-chain homodimer .
Stimulation of quiescent VSMC from SHR with PDGF-AA resulted in activation of S6-kinase and induction of phosphoinositide catabolism , as well as cellular proliferation when cultures were maintained for prolonged periods with daily supplementation of the growth factor .
A similarly modified form of the viral homologue pp60v-src occurs in vivo in the absence of stimulation by PDGF .
The kinase activities of all three enzymes were elevated after PDGF stimulation of quiescent fibroblasts , coincident with association of the src family kinases with the PDGF receptor and other proteins .
Treatment of quiescent cultures of Balb/c 3T3 fibroblasts with PDGF produced 20-30-fold stimulation of IL-1 R mRNA with a concomitant increase in cell surface 125I-binding .
The growth promoting activity of IL-1 was extremely potent producing half-maximum stimulation at a concentration of 0.5 pM .
In the present study we examined the mitogenic effects of PIP2 and its hydrolysis products introduced into the cytoplasm of BALB 3T3 cells by micro-injection to confirm the role of PIP2 hydrolysis in PDGF stimulation of cell proliferation .
Synovial tissue hyperplasia in basic calcium phosphate deposition disease has been suggested to develop through the stimulation of cell growth by basic calcium phosphate ( BCP ) crystals deposited in joints .
The stimulation of DNA synthesis , in density-arrested Balb/c T3 cells , by BCP crystals was inhibited after down-regulating protein kinase C activity with 12-O-tetradecanoyl-phorbol 13-acetate ( TPA ) .
The expression of c-myc and c-fos increased in response to BCP stimulation in a manner similar to the increase produced by stimulation with PDGF .
The BCP stimulation of c-fos and c-myc messages was inhibited 60 and 90% , respectively , in TPA-pretreated , protein kinase C-down-regulated cells .
Stimulation of the growth of metastatic clones of mouse colon adenocarcinoma 26 in vitro by platelet-derived growth factor .
We found that the growth of highly metastatic clones , NL-17 and NL-33 , of mouse colon 26 was well stimulated by platelet-derived growth factor ( PDGF ) and the stimulation was dependent on the concentration of the growth factor .
Suramin inhibits binding and degradation of platelet-derived growth factor in arterial smooth muscle cells but does not interfere with autocrine stimulation of DNA synthesis .
Transfectants expressing mutated receptors bind , I-labeled PDGF with a high affinity but had no PDGF-sensitive tyrosine kinase activity , phosphatidylinositol turnover , increase in the intracellular calcium concentration , change in cellular pH , or stimulation of DNA synthesis .
Early stimulation of glucose transport in the quiescent cells was also caused by serum , or by either PDGF or FGF .
The time courses for the stimulation of transport were identical for serum , PDGF and FGF , and the stimulated uptake in each case was associated with a 5-6-fold increase in Vmax .
These results suggest that cell cycle-dependent stimulation of glucose transport and expression of the transporter mRNA are regulated by a specific class of growth factors such as PDGF and FGF .
These stimulations were absent in PMA-pretreated cells .
When cytoplasmic [ Ca2+ ] was increased by addition of a Ca2+ ionophore ( A23187 or ionomycin ) , no stimulation of c-myc RNA was seen ; furthermore , these agents did not enhance the PDGF-modulated c-myc expression .
Stimulation of receptor-dependent and receptor-independent pathways of low-density lipoprotein degradation in arterial smooth muscle cells by platelet-derived growth factor .
Stimulation of LDL-receptor-independent LDL uptake and degradation by PDGF was demonstrated in three ways .
Thus , U-1810 is an example of a human tumor cell line that expresses multiple growth factor genes ; in the intact tumor the corresponding growth factors may operate in autocrine stimulation of the tumor cells as well as in paracrine growth reactions ( i.e. stroma recruitment ) .
In the action of PDGF-like compounds , what are the biochemical steps distal to receptor stimulation?(ABSTRACT TRUNCATED AT 250 WORDS )
It was necessary to add IFN within 6 hours after serum stimulation to inhibit nuclear labeling with [ 3H]thymidine .
Stimulation of MC by H2O2 alone resulted in an increase in H-TdR of 34.7 +/- 5.5% ( p < ; 0.01 ) .
Furthermore , analysis of the wild-type and mutant human PDGF beta-receptors stably expressed in porcine aortic endothelial cells also demonstrates that the Y740/751F mutant receptor , which cannot interact with PI 3-kinase due to the mutational alteration of its binding sites for PI 3-kinase , fails to increase FAK phosphorylation after PDGF-BB stimulation .
Integrin subunits , alpha 2 , alpha 3 , and alpha 5 , that define receptor specificity for collagen and provisional matrix , respectively , were measured at mRNA steady-state level before and after stimulation with platelet-derived growth factor-BB ( PDGF-BB ) , a potent mitogen and chemoattractant for fibroblasts .
Tranexamic acid , a plasmin inhibitor , abrogated the stimulation of SMC migration by IL-4 .
All agents exhibited dose-dependent stimulation of [ 3H ] thymidine uptake .
CAAX peptidomimetic FTI-244 decreases platelet-derived growth factor receptor tyrosine phosphorylation levels and inhibits stimulation of phosphatidylinositol 3-kinase but not mitogen-activated protein kinase .
Treatment of NIH-3T3 cells with FTI-244 inhibits PDGF-induced DNA synthesis but not stimulation of mitogen-activated protein kinase ( MAPK ) .
However , for maximal induction of MAP kinase synthesis , PDGF is required to be present for at least 4 h . In addition , an increased de-novo synthesis of MAP kinase kinase , the upstream activator of MAP kinase , is observed in response to PDGF stimulation .
Our previous experiments have shown that insulin , epidermal growth factor ( EGF ) , and Ca2+ induce a rapid and transient stimulation of binding of glycolytic enzymes to muscle cytoskeleton .
Incubation of rat diaphragm muscle in the presence of PDGF resulted in rapid and transient stimulation of binding of phosphofructokinase ( EC 2.7.11 ) and aldolase ( EC 4.1.2.13 ) to muscle cytoskeleton .
Similarly , we previously found that stimulation of cytoskeleton-bound glycolytic enzymes exerted by insulin , EGF , or Ca2+ , was also calmodulin mediated .
Stimulation of cells with either AVP or Ang II increased CAT activity 5- to 10-fold .
To identify regions of the promoter responsible for both the AVP stimulation and PDGF inhibition of promoter activity , a series of truncation mutants were prepared and transfected into vascular smooth muscle cells .
Truncation of both E-boxes and the most distal CArG element did not qualitatively alter either AVP-induced stimulation of CAT activity or PDGF inhibition .
However , removal of the middle CArG element resulted in a loss of AVP stimulation .
We have shown that stimulation of quiescent fibroblasts with platelet-derived growth factor ( PDGF ) causes Src , Fyn and Yes to become activated , and to associate transiently with the PDGF receptor .
In addition to the inhibition of cell growth , G alpha 16Q212L expression significantly inhibited the stimulation of protein kinase C , Raf-1 , MEK , mitogen-activated protein kinase , phospholipase A2 activity , and Ca2+ mobilization in response to PDGF .
The findings demonstrate that constitutively activated G alpha 16Q212L persistently activates phospholipase C activity and effectively inhibits a subset of cytoplasmic signal transduction pathways involved in growth factor tyrosine kinase receptor stimulation of cell growth .
Furthermore , the stimulation of E-selectin cell surface expression and the steady-state E-selectin mRNA levels by thrombin and TRAP were comparable .
These results suggest that activation of cell signaling by TRAP can mimic thrombin and is sufficient for the stimulation of monocyte adhesion to HUVEC ; however , thrombin-stimulated PDGF production by HUVEC may require mechanisms in addition to the signaling events initiated by TRAP or may require the participation of a novel thrombin receptor .
Stimulation by platelet-derived growth factor ( PDGF ) is known to increase the number of IGF-I binding sites in cells in culture .
These results suggest that an increase in RNA levels and in promoter activity may play an important role in the increase in IGF-1 receptor levels that occurs after stimulation by PDGF .
ICAM-1 expression was induced at 2h , reached a plateau at 4h , and continued for at least 24h after stimulation with PDGF .
Previous studies demonstrated that cell cycle progression after PDGF stimulation was dependent on extracellular calcium influx producing a sustained increase in the intracellular calcium concentration .
These data support the hypothesis that low-threshold VGCC can mediate extracellular calcium influx on the stimulation of cell proliferation by PDGF .
The protein kinase C ( PKC ) inhibitors , 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine , staurosporine , and PKC inhibitor peptide , inhibited such stimulation .
Results indicate that PDGF stimulates cellular proliferation and endothelin-1 secretion in cultured rat mesangial cells by a mechanism probably involving activation of PKC and that ANP and BNP inhibit such stimulation through a cGMP-dependent process .
Fusion proteins containing the central SH2-SH3-SH2 region of GAP or the C-terminal region of p85 alpha , which includes two SH2 domains , bound to PDGF receptors in response to PDGF stimulation .
Kinetic data show that restimulation by transforming growth factor beta ( TGF-beta ) and retinoic acid is delayed when compared to induction by platelet-derived growth factor ( PDGF ) , indicating that both TGF beta and retinoic acid may exert their growth-stimulating action by an indirect mechanism .
NRK cells also secrete low amounts of a PDGF-like growth factor into their extracellular medium , but the levels of secretion are insufficient to induce mitogenic stimulation and are unaffected by agents inducing phenotypic transformation .
Consequently , oxidized low density lipoproteins may participate in atherosclerotic lesion formation as a result of autocrine stimulation of PDGF-A .
Peak effects were observed at 3 and 6 h for PDGF and bFGF , respectively , returning to baseline levels by 12 h . Under basal conditions , detectable amounts of M-CSF , measured by radioimmunoassay , were found in cell supernatants conditioned for 8 and 24 h . PDGF and bFGF markedly stimulated the release of M-CSF as early as 8 h , an effect persisting for at least 24 h . These findings suggest that liver FSC release M-CSF upon stimulation by PDGF and bFGF and may contribute to the activation of resident or infiltrating cells in inflammatory liver diseases .
The alpha- and beta-receptor cells responded mitogenically to stimulation with the proper PDGF isoforms .
Three aspects of actin reorganization were examined after ligand stimulation : loss of stress fibres , appearance of edge ruffles and formation of circular membrane ruffles .
The beta-receptor cells showed a response to ligand stimulation which included all three features .
Upon stimulation by its ligand , the platelet-derived growth factor ( PDGF ) receptor associates with the 85-kDa subunit of phosphatidylinositol ( PI ) 3-kinase .
Our results indicate that more than half of the benign prostatic tissues showed cell proliferation which was modulated by DHT and/or PDGF , while none of the six carcinomas responded to such hormonal stimulation .
Stimulation with PDGF BB increased inositol phosphate production about 3.5-fold in control cells and about 10-fold in hPLC-gamma 2 overexpressing cells .
A dose-dependent [ Ca2+]i increase of up to 300% followed stimulation with PDGF ( 5-50 ng/ml ) in a medium containing Ca2+ .
The time course for uric acid stimulation of VSMC growth was slower than serum , suggesting induction of an autocrine growth mechanism .
Activation of the receptor also occurs upon acute E5-mediated transformation of these cells and precedes mitogenic stimulation in this system .
Instead , we find that optimal mitogenic stimulation requires the additional presence , besides PDGF and insulin , of hydrocortisone , prostaglandin E1 and an unidentified , non-dialysable component contained in serum treated with dithiothreitol ( DTT ) to inactivate endogenous growth factors .
The beta subunit of the platelet derived growth factor receptor ( PDGFR ) coprecipitates with a phosphatidyl-inositol 3 kinase activity ( PI3K ) following stimulation of cells by PDGF .
In addition , we found that PDGF stimulation of a cell results in the association of essentially all the PI3K activity with cellular PDGFRs .
Thus , Ca2+ increases in the nuclear and/or cytosolic compartments appear to be required for the stimulation of mitogenesis by polypeptide growth factors such as PDGF .
Stimulation of platelet-derived growth factor-induced DNA synthesis by angiotensin II in rabbit vascular smooth muscle cells .
Previously , we have shown that prostaglandins are necessary , but not sufficient , for the stimulation of mitogenesis in BALB/c 3T3 fibroblasts by epidermal growth factor ( EGF ) ( Nolan , R. D. , Danilowicz , R. M. , and Eling , T. E. ( 1988 ) Mol .
The purpose of this work was to extend these findings to another potent mitogen , platelet-derived growth factor ( PDGF ) , and to determine if metabolism of arachidonic acid to prostaglandins is necessary for stimulation of expression of the protooncogene c-myc by EGF , which is an early event in the mitogenic cascade .
These data support the hypothesis that metabolism of arachidonic acid to prostaglandins is necessary for stimulation of c-myc expression by EGF in BALB/c 3T3 cells .
Direct enhancement of matrix synthesis and stimulation of cell proliferation via induction of platelet-derived growth factor receptors .
These data suggest that changes in receptor conformation and efficient utilization of specific tyrosine kinase substrates are important for the stimulation of cell proliferation of PDGF and that phosphorylation of tyrosine 825 may be involved in signal transduction .
Fibroblasts expressing v-ras continued to express the same number of functional PDGF receptors on their surface as uninfected cells , yet the usual induction of transcription of the genes c-myc , c-fos , and JE in response to PDGF stimulation did not occur in the presence of newly introduced v-ras or chronic v-ras gene expression , and synthesis of c-myc protein did not occur .
Both the temporal production of these novel phospholipids after PDGF stimulation and the observation of the enzymatic activities that produce them in alpha-P-tyr immunoprecipitates suggest that these phospholipids are excellent candidates for mediators of the PDGF mitogenic response .
Autocrine stimulation by the v-sis gene product requires a ligand-receptor interaction at the cell surface .
These results demonstrate that autocrine stimulation , as monitored by c-fos induction and by PDGF receptor autophosphorylation , requires an interaction between the v-sis protein and the PDGF receptor that occurs at the cell surface , rather than an intracellular location .
These observations suggest induction of PDGF B-type receptors on vascular smooth muscle cells in inflamed tissues , which would render such cells responsive to growth stimulation by PDGF released from captured platelets , or produced locally ( eg , by inflammatory cells or smooth muscle cells ) .
Autocrine or paracrine stimulation of cell growth caused by the effect of PDGF on cells with induced receptors may be important in the formation of the proliferative lesions found in atherosclerosis and in certain forms of chronic inflammation .
These results may support the idea that an abnormal release of PDGF occurs from platelets or megakaryocytes in the bone marrow environment , resulting in the stimulation of fibroblast proliferation , and hence , the occurrence of myelofibrosis in patients with MPD .
Autocrine stimulation of intracellular PDGF receptors in v-sis-transformed cells .
In this study autocrine stimulation of the PDGF receptor was observed in v-sis-transformed normal rat kidney ( NRK ) cells .
Increased amounts of pure PDGF were required to give maximal stimulation of purified CML peripheral blood progenitors compared to normal bone marrow progenitors .
In addition , PDGF-regulated genes ( c-fos and c-myc ) were stimulated by transforming growth factor beta with delayed kinetics relative to that seen in other cell systems with direct PDGF stimulation .
A model is proposed in which the monolayer mitogenicity of transforming growth factor beta is mediated by the induction of c-sis and PDGF and the subsequent autocrine stimulation of c-fos , c-myc , and other PDGF-inducible genes .
Dose-response curves for PDGF showed that the activities of PtdIns kinase and PtdIns-P kinase at 24 h increased in proportion to the extent of mitogenic stimulation of the cells .
In this report , we describe the association of FAK with a -kDa protein ( pp200 ) that is tyrosine phosphorylated in response to PDGF stimulation in NIH 3T3 cells .
Furthermore , we found that the tyrosine phosphorylation of FAK-associated pp200 upon PDGF stimulation is largely independent of cell adhesion or the integrity of the cytoskeleton .
Both factors cause a rise in intracellular pH ( pHi ) in systemic vascular SMC through stimulation of the Na+/H+ exchanger , an event that has been thought to be permissive , allowing cell proliferation in response to the growth factor .
Thrombin receptor activation elicits rapid protein tyrosine phosphorylation and stimulation of the raf-1/MAP kinase pathway preceding delayed mitogenesis in cultured rat aortic smooth muscle cells : evidence for an obligate autocrine mechanism promoting cell proliferation induced by G-protein-coupled receptor agonist .
However , the time course and duration of Raf-1/MAP kinase activation after thrombin stimulation were similar to those elicited by PDGF-BB .
The ThR region consists of a repeat of a CCACCC element in an ABBA configuration , which , based on mutation analysis and transfection assays , appears to be critical in mediating thrombin stimulation of the PDGF B-chain gene .
Inhibition of in vitro meningioma proliferation after growth factor stimulation by calcium channel antagonists : Part II--Additional growth factors , growth factor receptor immunohistochemistry , and intracellular calcium measurements .
We have previously reported that calcium channel antagonists can block both the growth of meningiomas in culture and the potent growth stimulation of meningioma cells by epidermal growth factor ( EGF ) and platelet-derived growth factor ( PDGF ) .
Fibroblast growth factor or insulin-like growth factor-I growth stimulation in the presence of calcium channel antagonists was examined .
The growth stimulation of fibroblast growth factor and insulin-like growth factor-I on meningioma cells in culture was decreased in a dose-dependent manner by calcium channel antagonists .
The growth stimulation of fibroblast growth factor and insulin-like growth factor-I was not affected by a reduction of extracellular calcium , whereas the growth stimulation of EGF and PDGF was .
Interestingly , intracellular calcium was not increased after exposure to growth factors but was increased after serum stimulation .
Calcium channel antagonists can inhibit proliferation of meningioma cells in culture after stimulation with a number of growth factors .
Purification of these growth factors was monitored by the stimulation of [ 3H]thymidine incorporation into BALBc-3T3 cells and myometrial SMC .
The role of heparin-sensitive and -insensitive pathways in the stimulation of smooth muscle cell migration and proliferation .
Effect of virus-transformation and growth factor stimulation on isoprene biosynthesis in human fibroblasts : a correlation to cell growth .
This inhibitory action of EGF was associated with a potent stimulation of cell proliferation , up to 8-fold compared with cultures in the absence of EGF .
This effect could be partly explained by a stimulation of lipolysis , since EGF caused an increase of glycerol in the culture medium .
Maximum rate of DNA synthesis occurred 36-42 h after addition of 10% fetal calf serum , whereas maximum rate of DNA synthesis occurred 80-88 h after stimulation with PDGF-BB or basic fibroblast growth factor .
This effect was more pronounced with respect to fetal calf serum stimulation .
To further study the role of second messenger signaling , a more specific mode of SMC stimulation was used with thrombin ( 3 U/ml ) in the presence or absence of dibutyryl cyclic AMP ( Bu2-cAMP ; 0.5 mM ) .
Although redundantly expressed , message levels of cyclin D1 and D3 were differentially regulated in regard to kinetics of induction ; a modest increase in D3 mRNA was detected near the G1/S boundary , 12 h after serum stimulation of quiescent cells , while abundance of D1 transcript increased 20 to 30-fold , peaking 6 h after addition of serum .
However , protein synthesis was required 3-4 h after serum stimulation for the shut down of D1 transcription leading to the normal decline in message levels after peak induction .
Upon stimulation , the tyrosine kinase PDGF receptor-beta ( PDGFR-beta ) autophosphorylates and forms a complex that includes SII2(Src homology 2)-domain-containing proteins such as the phosphatidylinositol-specific phospholipase C-gamma , Ras-GTPase-activating protein ( GAP ) , and phosphatidylinositol-3-OH kinase .
Kinetics of DNA stimulation and experiments with anti-PDGF antibodies indicated that PDGF-A expression does not contribute significantly to CGF-induced DNA synthesis .
When the stimulation of various signaling pathways induced by CGF and other growth factors was compared , the pattern of stimulation by CGF was different from other growth factors .
TGF beta induces c-sis gene , suggesting possible involvement of secondary growth stimulation by PDGF-like proteins .
Translocation of pp60c-src from the plasma membrane to the cytosol after stimulation by platelet-derived growth factor .
We demonstrate that , following stimulation of quiescent cells with PDGF , pp60c-src is translocated from the plasma membrane to the cytosol .
Thus , PDGF stimulation activates at least two membrane-associated kinases ( pp60c-src and cAMP-dependent protein kinase ) very early in its signal transduction pathway .
Stimulation of cells expressing GAP-N with PDGF induced association of GAP-N with the beta PDGF receptor , and phosphorylation of GAP-N on tyrosine , consistent with the notion that GAP SH2 domains direct binding to the autophosphorylated beta PDGF receptor in vivo .
The BB homodimer yielded the greatest degree of growth stimulation for both pericytes and SMC .
EGF was moderately mitogenic for both types of mural cells , reaching maximum stimulation at 100 pg/ml of EGF .
Stimulation by both EGF and PDGF requires the presence of factors that recognize the AP-1 binding site in the stromelysin promoter , but PDGF stimulation requires induction of the protooncogene c-fos , while EGF acts through a FOS-independent pathway .
The protooncogene FOS is therefore involved in both stimulation and inhibition of stromelysin gene expression .
Submicromolar concentrations of CGP 41251 and staurosporine directly inhibited both the platelet-derived growth factor ( PDGF ) receptor autophosphorylation and the c-fos mRNA expression induced by PDGF stimulation of intact BALB/c 3T3 cells .
These findings demonstrate that autocrine PDGF stimulation contributes to proliferation of some human tumors and that agents which interfere with ligand-receptor interactions at the cell surface can significantly interfere in this process .
Furthermore , elevation of cAMP , either through receptor-mediated mechanisms ( e.g. prostaglandin E1 ) or by direct stimulation of adenylate cyclase ( e.g. forskolin ) , also caused a marked dose-dependent depletion of 80K/MARCKS mRNA levels , which were further reduced by co-administration with cAMP-phosphodiesterase inhibitors .
Remarkably , stromelysin antisera interfere with stimulation of dermal papilla cell growth , demonstrating that stromelysin production serves a functional role in mitogen-induced proliferation in these cells .
Stimulation of resting normal rat kidney fibroblasts , prelabeled with [ 3H]leucine , by platelet-derived growth factor ( PDGF ) caused inhibition of cellular protein degradation and a parallel increased nuclear translocation of 3H-labeled nonhistone proteins ( 3H-NHP ) and DNA synthesis .
3H-thymidine uptake with or without PDGF and PGE2 was examined , and results were expressed as the stimulation index .
TGF-beta 1 was effective only when added to the culture within 2 h after stimulation of the G0 state SMC with PDGF .
It also inhibited increase in transcription of the c-myc protooncogene on stimulation of SMC with PDGF .
It is currently accepted that the mechanism of growth stimulation or signal transduction after binding of each growth factor to the specific receptor depends on the kind of growth factor .
The finding supports the existence of a specific growth stimulation pathway for PDGF .
We previously demonstrated that clonal variation exists in the production of alpha 2M in a human melanoma and that this variation may be associated with growth stimulation .
The frequent expression of PDGF and PDGF receptors in normal as well as transformed cells , suggests roles for PDGF in autocrine and paracrine stimulation of cell growth in vivo .
Stimulation of DNA synthesis in cultured primary human mesothelial cells by specific growth factors .
This one-time stimulation is independent of other serum components .
Stimulation of growth by PDGF and TGF-beta 1 is unusual for an epithelial cell type , and indicates that mesothelial cells have growth regulatory properties similar to connective tissue cells .
In contrast , serum stimulation was shown to increase nonmuscle beta-actin mRNA level , whereas SM alpha-actin mRNA level remained constant .
When platelet-derived growth factor ( PDGF ) binds to its receptor on a quiescent fibroblast or smooth muscle cell , it stimulates a remarkably diverse group of biochemical responses , including changes in ion fluxes , activation of several kinases , alterations in cell shape , increased transcription of a number of genes , and stimulation of enzymes that regulate phospholipid metabolism .
Stimulation of density-arrested BALB/c-3T3 cells with either BCP crystal or platelet-derived growth factor ( PDGF ) results in maximal accumulation of c-fos mRNA at 30 min after stimulation .
Induction of c-myc transcription by BCP crystal or PDGF occurs within 1 h and is maximal at around 3 h after stimulation .
The delay in c-myc message induction after IFN-beta treatment cannot account for the observed delay in the onset of DNA synthesis , since IFN-beta can be added at up to 6 h after stimulation with either PDGF or BCP crystals , and a similar delay in the onset of DNA synthesis is still observed .
Stimulation of normal human foreskin fibroblasts with platelet-derived growth factor ( PDGF ) was inhibited by the addition of the synthetic double-stranded RNA polyinosinic-polycytidylic acid ( poly-I:C ) as measured by incorporation of 3H-thymidine ( 3H-TdR ) .
Similar stimulation was observed when the growth was induced by FGF or EGF .
These factors can act either externally through cell surface receptors or perhaps internally during the transport of receptors and growth factors through the ER and Golgi , causing autocrine stimulation of cell growth .
The induction of the myc and the fos proteins by growth factor stimulation of quiescent cells , as well as the potential for the p21 product of the ras oncogene to act as an intermediate in transducing adrenergic signals , provide direct evidence that these pathways are important for stimulation of cell growth .
HGF was purified from rat platelets to homogeneity by a three-step procedure : stimulation of its release from platelets by thrombin , cation-exchanger fast protein liquid chromatography on a Mono S column , and heparin-Sepharose chromatography .
Characterization of cells transformed by SSV has revealed PDGF-related proteins in subcellular organelles and in conditioned media consistent with the autocrine stimulation of cell growth through cell surface receptors and perhaps through an internal autocrine mechanism as the growth factor and its receptor are processed .
PDGF-like growth factors in autocrine stimulation of growth .
We now report that although the ras-transformed cells display markedly reduced phospholipase C activity , as measured by the levels of inositol , 4,5-trisphosphate synthesized after PDGF-stimulation , normal levels of phospholipase A2 activity can be uncovered ; thus , similar levels of prostaglandin E2 were synthesized in EJ-ras transformed and control cells after stimulation with phorbol myristate acetate ( PMA ) and/or the calcium ionophore A-23187 , agents which stimulate protein kinase C and intracellular Ca2+ levels , respectively .
These data suggest that the EJ-ras gene product uncouples the PDGF receptor from the phospholipase C , resulting in reduced PDGF-stimulated Ca2+ mobilization , protein kinase C stimulation and an apparent decrease in Ca2+-dependent phospholipase A2 .
With dimethyl sulfoxide there was no significant stimulation of the expression .
Three hours after PDGF stimulation , there were quantitative increases of at least 18 protein bands as compared to cells left in serum starvation medium .
Common elements in growth factor stimulation and oncogenic transformation : 85 kd phosphoprotein and phosphatidylinositol kinase activity .
Two common events were observed upon PDGF stimulation or MTAg transformation of cells : the appearance in the immunoprecipitates of an 85 kd phosphoprotein , and increased phosphatidylinositol ( PI ) kinase activity .
This effect was half-maximal at a TNF dose of 114 pM , reflected a 2.5-fold increase in PDGF-specific mRNA synthesis , and peaked at 15 h of TNF stimulation .
Stimulation of EC with IL-1 ( 60-240 pM ) led to the release of similar mitogenic activity .
Platelet-derived growth factor stimulation of [ 3H]-glucosamine incorporation in density-arrested BALB/c-3T3 cells .
We have identified the stimulation of a biochemical process specific to competence formation in BALB/c-3T3 cells .
Stimulation of [ 3H]-GlcN incorporation by PDGF was time dependent , and increased incorporation of [ 3H]-GlcN into protein required de novo protein synthesis .
We suggest that accumulation of the PDGFalphaR gene product may facilitate the exiting of cells from growth arrest upon mitogenic stimulation by PDGF , leading to the state of "competence" ; required for cell cycling .
We examined the role of protein kinase C alpha ( PKC alpha ) in the stimulation of DNA synthesis of Swiss 3T3 cells induced by bombesin , platelet-derived growth factor ( PDGF ) and phorbol 12-myristate -acetate ( PMA ) .
Our findings point out different roles that PKC alpha may play in diversely activated cells : while , in the case of PMA , stimulation of this kinase may be necessary and sufficient to induce proliferation , it appears to be necessary only for a full response to bombesin , and redundant among the mechanisms triggered by PDGF .
Overexpression of catalytically inactive SHPTP2 ( PTP2CS ) but not catalytically inactive SHPTP1 , inhibited mitogen-activated protein ( MAP ) kinase activation and Elk-1 transactivation following epidermal growth factor ( EGF ) stimulation of 293 cells .
Microinjection of anti-SHPTP2 antibodies prior to stimulation inhibited EGF- but no PDGF- or serum-induced S-phase entry .
Although MAP kinase activation was detected shortly after EGF stimulation , no MAP kinase activation was detected around the restriction point .
Only platelet-derived growth factor BB ( PDGF-BB ) treatment had a significant effect and induced FGFR-1 mRNA levels fourfold , with a peak around 8 h of stimulation .
The increase in mRNA levels was followed by an increased synthesis of FGFR-1 protein , which responded to basic FGF ( bFGF ) stimulation with induction of kinase activity and biological signaling .
Low molecular weight chitosan stimulation of mitogenic response to platelet-derived growth factor in vascular smooth muscle cells .
To evaluate the signaling pathways involved in the activation of PKC epsilon upon stimulation by platelet-derived growth factor ( PDGF ) receptor ( PDGFR ) , we used a series of PDGFR "add-back" ; mutants .
The translocation of PKC epsilon upon stimulation of PDGFR ( Y40/51 ) was inhibited by wortmannin , an inhibitor of PI 3-kinase .
Stimulation of NIH 3T3 cells with platelet-derived growth factor ( PDGF)-BB and 12-O-tetradecanoylphorbol-13-acetate ( TPA ) enhances vascular endothelial growth factor ( VEGF ) gene expression .
Stimulation with PDGF or TPA resulted in increased VEGF mRNA in all cell lines , with highest levels found in the transformed cells .
Both AP1 and Myc are activated in fibroblasts in response to growth factor stimulation , and various experiments suggest their importance in proliferation .
Patterns of tyrosine phosphorylation in whole cell extracts , following stimulation by FGF2 , indicated specific FGF2 phosphorylation of proteins of 150/145 , 90 , 42 , and 35 kDa in cells from both age groups .
[ Inhibition of growth factor stimulation of mitogen-activated protein kinase by prostaglandin E2 in rat renal mesangial cells ]
Stimulation with inflammatory mediator PGE2 ( 50 mumol/L ) or elevation of Intracellular cAMP by treatment of cells with forskolin ( 25 mumol/L ) markedly blunted activation of MAP kinase induced by PDGF and EGF , but not PMA .
Although stimulation by PGE1 increased intercellular cyclic AMP in R1 cells , it did not do so in NIH/lambda 2S-3 and NIH/lambda 2S-6 cells .
On the other hand , stimulation by PDGF or EGF induced far less DNA synthesis in NIH/lambda 2S-3 and NIH/lambda 2S-6 than in NIH/neo-3 and NIH/neo5 .
These responses did not correlate with protein kinase C stimulation nor with the activation of mitogen-activated protein ( MAP ) kinases .
However , neither anti-bFGF nor anti-PDGF abrogated the stimulation of tumor cells by normal mammary epithelial cells or normal mammary stromal cell .
In density-arrested ( nonstarved ) cells , PDGF-BB affords protection from cell death without stimulation of cell division .
There was no difference in starved or nonstarved cells regarding PLC-gamma activation , increase of [ Ca2+]i , and stimulation of PI-3 kinase activity .
When TR4 cells were incubated with TPA just before stimulation with these growth factors , growth factor-induced membrane ruffling was completely inhibited .
Binding of these signal transduction proteins to dynamin involves specific sorting to individual proline motif clusters and appears to be responsible for co-immunoprecipitation of tyrosine phosphorylated PDGF receptors with dynamin following PDGF stimulation of mammalian cells .
In isolated nuclei from GF-exposed cells only the alpha isozyme was detected : immunostaining was very intense after IGF-I treatment and clearly observable after PDGF and EGF stimulation .
In contrast , when assays were carried out for 48 h , AII induced a significant dose-dependent stimulation of DNA synthesis , which more than doubled at 3 nM AII , and was maximal ( five- to eightfold above control ) at 100 nM AII .
AII also stimulated smooth muscle cell proliferation , as indicated by an absolute increase in cell number after AII stimulation of RASM cells for 5 d . AII stimulation of RASM cell growth correlated with the increased expression of specific endogenous growth factors , including transforming growth factor beta 1 ( TGF-beta 1 ) and PDGF A-chain .
Upon stimulation with bombesin or PDGF , control cells displayed a 2-4-fold increase of [ Ca2+]i over the basal level , while the [ Ca2+]i response in nef-expressing NIH-3T3 cells was lacking or highly diminished .
The cytokines Interleukin 1 ( IL-1 ) and tumor necrosis factor-alpha ( TNF-alpha ) gave no stimulation , but IL-1 inhibited chondrocyte proliferation induced by TGF-beta or serum .
Okadaic acid ( OA ) at 100 ng/ml completely inhibited platelet-derived growth factor ( PDGF)-BB-induced DNA synthesis but had no effect on early signals , i.e. , PDGF receptor autophosphorylation or stimulation of inositolphosphate turnover .
Similarly , PIP2 bound to vinculin is decreased upon stimulation with PDGF .
PDGF stimulation decreases the intensity of PIP2 staining in these areas .
Growth factor stimulation of quiescent cells induces a series of intracellular early and late events that ultimately lead to DNA synthesis and cell division .
Choline kinase , the first step in the route of phosphatidylcholine synthesis appears to be the critical regulatory enzyme in phosphorylcholine production , indicating that regulation of choline kinase represents a key step during mitogenic stimulation .
This study examined and compared the growth characteristics of vascular smooth muscle cells ( VSMC ) isolated from 4 and 12 week old spontaneously hypertensive rats ( SHR ) and Wistar-Kyoto ( WKY ) rats following stimulation with platelet-derived growth factor-BB ( PDGF-BB ) .
Stimulation of protein kinase C ( PKC ) by exposure of quiescent RASMs to phorbol 12-myristate 13-acetate caused a biphasic response in IGF I binding ; there was a 42% decrease in receptor number at 45 minutes and a 238% increase at 24 hours .
Adult vascular smooth muscle cells dedifferentiate and reenter the cell cycle in response to growth factor stimulation .
This reduction in Gax mRNA is transient , with levels beginning to rise between 8 and 24 h after mitogen stimulation and returning to near normal by 24 to 48 h . The Gax down-regulation is dose dependent and can be correlated with the mitogen 's ability to stimulate DNA synthesis .
Further stimulation was observed when co-incubated macrophages were supplied with LDL or cholesterol .
However , the stimulation of VSMC proliferation did not result from co-incubation with macrophages supplemented with acetylated LDL or delipidated LDL .
The addition of anti-PDGF antibody partially abolished the stimulation of VSMC proliferation induced by co-incubation with macrophages supplemented with LDL or cholesterol .
Inhibitory effect of trapidil on human meningioma cell proliferation via interruption of autocrine growth stimulation .
Trapidil showed a dose-dependent inhibition of meningioma cell proliferation in the absence of any exogenous mitogenic stimulation .
The overall results suggest that trapidil exhibits an inhibitory effect on meningioma cell proliferation through blocking the mitogenic stimulation induced by autocrine or exogenous growth factors , and may be considered as a possible new approach to the medical treatment of meningiomas .
The antibody to EGF also prevented the stimulation , suggesting that both PDGF and EGF are required for the full expression of the VSMC growth-promoting activity of ET-1 .
After serum stimulation , inhibition of DNA synthesis was found with either an immediate or delayed ( 16-hour ) application of PUVA .
Flow cytometry of cells treated with PUVA at several times after serum stimulation demonstrated for each time point a block in further cell cycle progression for cells in all phases of the cell cycle .
Stimulation of pericyte growth was also achieved with platelet-derived growth factor ( PDGF ) , acidic fibroblast growth factor ( aFGF ) and basic fibroblast growth factor ( bFGF ) and could be blocked by using the appropriate antiserum ( anti-PDGF or anti-aFGF ) .
Stimulation of [ 3H]thymidine incorporation by ATP was dose-dependent ; the maximal effect was obtained at 100 microM .
The stimulation of proliferation was also determined by measurement of cellular DNA using bisbenzamide and by following the increase of mitochondrial dehydrogenase protein .
Down-regulation of protein kinase C ( PKC ) by long-term exposure to phorbol dibutyrate ( PDBu ) partially prevented stimulation of DNA synthesis and activation of the AA pathway by ATP .
Heparin , believed to have a regulatory role , partially inhibited the stimulation of DNA synthesis caused both by ATP and PDGF.(ABSTRACT TRUNCATED AT 400 WORDS )
The media collected from tuna AI ( 1 and 10 microM)-stimulated BAECs significantly exhibited the interleukin ( IL ) -1 activity that was detected by the thymocyte costimulation assay with phytohemagglutinin .
In addition , both peptides could attenuate the stimulation of cell division by serum and PDGF .
In a basal medium consisting of % DMEM , 25% Ham 's F-12 , 5 nM sodium selenite , 50 microM 2-amino ethanol , and 2 mM histidine , supplemented with 5% FBS , we showed that aFGF , bFGF , and PDGF were all capable of stimulating Schwann cell growth and the stimulation was greatly potentiated by forskolin and dibutyryl-cAMP .
No distinct effect on the stimulation of overall RNA and protein synthesis by PDGF-BB was observed , indicating that the drug was not of general cytotoxicity at the concentrations used .
Transforming growth factor beta ( TGF-beta ) also induced mRNA of TS at 8 hours after stimulation and the induction was blocked by cycloheximide , suggesting that TGF-beta requires the mediation of new protein synthesis to induce a TS gene .
Neonatal SMCs in early passage were found to have a high rate of spontaneous DNA synthesis and showed little response to stimulation with growth factors .
There was no difference in the gene or surface expression of receptors for platelet-derived growth factor ( PDGF ) between neonatal and adult cells , and there was no significant difference in the amount of inositol phosphate formed in the cells after stimulation with PDGF BB .
After subcultivation ( seven to nine passages ) neonatal SMCs started to become senescent , had a low rate of spontaneous DNA synthesis and were more sensitive to growth factor stimulation than in early passage .
In addition , PDGF-BB-dependent stimulation of transcription of c-fos mRNA was inhibited also by the Ca(2+)-channel blockers .
The time course of sulfate incorporation after stimulation indicates that both growth factors cause maximal incorporation of sulfate into glycosaminoglycan chains by 12-18 h . The PG that is most affected is a large CSPG ( Mr approximately 1.2 x 10(6 ) ) which can be immunoprecipitated by an antibody against versican , a large CSPG synthesized by human skin fibroblasts .
The hydrodynamic size of this molecule increases after PDGF and TGF-beta 1 stimulation , but the size of the core glycoprotein ( Mr approximately 450,000 ) remains the same .
The two growth factors also increase the glycosaminoglycan chain length of this PG accounting for the greater hydrodynamic size of the molecule after stimulation .
We now demonstrate tyrosine phosphorylation of p120 following stimulation of cells by growth factors whose receptors have intrinsic tyrosine-specific protein kinase activity .
Stimulation of quiescent NIH3T3 cells with platelet-derived growth factor ( PDGF ) resulted in the tyrosine phosphorylation of p120 that was maximal by 5 min and returned to background levels by 30 min. p120 was also phosphorylated on tyrosine after addition of colony-stimulating factor 1 ( CSF-1 ) or epidermal growth factor ( EGF ) to NIH3T3 cells engineered to express high levels of their respective receptors .
Despite a lack of any detectable receptor-associated PI-3 kinase activity , 32D cells expressing alpha R delta ki-1 showed only partially impaired chemotactic and mitogenic responses and were capable of sustained proliferation in vitro and in vivo under conditions of autocrine stimulation by the c-sis product .
In vitro complex formation was dependent on prior growth factor stimulation and was competed by intracellular PLC gamma 1 . Similar results were obtained for binding of GAP SH2 domains to the PDGF-receptor .
SH2 domains , therefore , provide a common mechanism by which enzymatically diverse regulatory proteins can physically associate with the same activated receptors and thereby couple growth factor stimulation to intracellular signal transduction pathways .
LPS-stimulated JE and KC mRNA expression was dependent upon the stimulation of transcription as determined by nuclear "run-on" ; studies .
Simultaneous stimulation with both factors produced an additive response , which approximated that obtained in medium supplemented with % fetal calf serum .
These data indicate that alteration of cellular sterol balance or metabolism leading to release of end product repression contributes to growth-related stimulation of LDL receptor gene expression .
Only minor changes in the Vmax occurred upon stimulation with PDGF .
Porcine PDGF gave half-maximal stimulation at 15 pM , and human PGDF an equivalent response at 1 nM .
Stimulation with interleukin-1 beta ( IL-1 beta ) or tumor necrosis factor alpha ( TNF alpha ) induced up to 18-fold ( IL-1 beta ) or up to fourfold ( TNF alpha ) increases of prostanoid release .
It was found to display a decreased autophosphorylation after ligand stimulation and had a decreased ability to phosphorylate exogenous substrates ; phosphofructokinase was not phosphorylated at all , whereas a peptide substrate was phosphorylated , albeit at a lower rate compared with phosphorylation by the wild-type receptor .
Receptor functions are potentially regulated through differential binding of ligands ( as proposed with PDGF ) , through interactions with other receptors , and through the "feedback" ; regulation mediated by protein kinase C. PDGF stimulation leads to modulation of the EGF receptor through protein kinase C ( Bowen-Pope et al. , 1983 ; Collins et al. , 1983 ; Davis and Czech , 1985 ) .
The clck product is physically and functionally associated with the T-cell receptors CD4 and CD8 , and becomes active upon specific stimulation of cells expressing those markers ( Veillette et al. , 1988a,b ) .
Stimulation by exogenous platelet-derived growth factor and inhibition by transforming growth factor-beta and retinoids .
However , the simultaneous addition of TNF and EGF to cells grown in serum-free medium resulted in a synergistic stimulation of DNA synthesis and cell growth .
To produce an optimal stimulation of DNA synthesis , EGF had to be present for a longer period of time than TNF .
Stimulation of mesangial cells by thrombin resulted in induction of messenger ribonucleic acids ( mRNAs ) encoding platelet-derived growth factor ( PDGF ) A- and B-chains .
Stimulation of p31 synthesis by growth factors , PDGF and fibroblast growth factor ; a tumor promoter , TPA ; and heavy metal salts suggests that there is overlap in the pathways for mitogenic stimulation and heavy metal stress .
We studied the possibility that cells derived from malignant gliomas produce mitogenic factors that bind to cell surface receptors , the activation of which could lead to excessive stimulation of cell proliferation .
Stimulation of human synovial fibroblast DNA synthesis by platelet-derived growth factor and fibroblast growth factor .
Thus PDGF and FGF , arising from stimulated monocyte-macrophages , may play a role in the stimulation of mesenchymal cell proliferation that often accompanies chronic inflammatory arthritic disease .
UV and TPA treated cells become refractory to a second stimulation by the same agent at 3 or 24 hours after the first treatment .
The maximal stimulation of DNA synthesis by FGF ( 0.4 ng/ml ) was further potentiated dose dependently by TGF-beta ( ED50 = . 1 ng/ml , maximum at 1 ng/ml ) .
In contrast , TGF-beta caused dose-dependent stimulation of glycosaminoglycan synthesis in confluent cultures of growth-plate chondrocytes ( ED50 = 0.3 ng/ml , maximum at 1 ng/ml ) .
This stimulation was mimicked by exposure of cells to biologically active phorbol esters , suggesting that thrombin action may be mediated through activation of kinase C ( Ca2+/phospholipid-dependent enzyme ) .
This stimulation was half that shown by PDGF .
However , stimulation of synovial cells with TGF beta 1 became markedly resistant to Fas antigen-mediated apoptosis .
NF-kappa B is induced in the nuclei of cultured rat aortic smooth muscle cells by stimulation of various growth factors .
Stimulation of clone 1C cells , which express 3.5 pmol/mg of protein of the human alpha2C10 receptor , with the alpha2 agonist UK 14304 led to a transient increase in p70s6k activity .
PDGF and serum stimulation resulted in a rapid phosphorylation of tyrosine and activation of mitogen-activated protein kinase ( MAP kinase ) , 70-kD-S6 kinase ( P70S6k ) and 90-kD-S6 kinase ( P90rsk ) .
In addition , these clones also inhibited colony formation in soft agar by epidermal growth factor ( EGF ) , platelet-derived growth factor ( PDGF ) , or serum stimulation .
The N116Y mutant blocked GDP/GTP exchange reaction by each growth stimulation .
On the other hand , this mutant could not have sufficient influence upon extracellular signal-regulated kinase 2 ( ERK2 ) phosphorylation , which located downstream of ras-mediated signal transduction , provoked by PDGF and serum stimulation .
The stimulation of gene expression by COM crystals was relatively crystal- and renal cell-type specific .
These results suggest that COM crystal-mediated stimulation of specific genes in renal tubular cells may contribute to the development of interstitial fibrosis in hyperoxaluric states .
Stimulation of cells with FGF-2 and IL-1 beta increased both DNA content and proliferation , an observation that was consistent with the thymidine incorporation experiments .
The signaling pathways for tyrosine kinase stimulation of integrin adhesiveness and their relation to pathways that regulate growth and differentiation over much longer time periods remain uncharacterized .
Incubation of NIH 3T3 fibroblasts with cycloheximide prevents both synthesis of CL100 and inactivation of p42mapk after stimulation with serum .
RESULTS : Depleting cells of CL100 and preventing its induction using cycloheximide stopped the inactivation of p42mapk in Swiss 3T3 fibroblasts following stimulation with epidermal growth factor ( EGF ) , but had no effect on the rapid inactivation of p42mapk in response to EGF in adipose ( 3T3-L1 ) or chromaffin ( PC12 ) cells or in response to platelet-derived growth factor ( PDGF ) in endothelial ( PAE ) cells .
Moreover , maximal induction of CL100 mRNA and a CL100-like activity did not trigger inactivation of p42mapk , which was sustained at a high level after stimulation of PC12 cells with nerve growth factor , PAE cells with serum , or Swiss 3T3 cells with PDGF .
Phosphorylation of Thr 183 also inhibited the dephosphorylation of Tyr in vitro by the major vanadate-sensitive Tyr 185-specific phosphatase , explaining why dephosphorylation of Thr 183 is rate-limiting for p42mapk inactivation in PC12 cells after stimulation with EGF .
CONCLUSIONS : The rapid inactivation of p42mapk initiated five minutes after stimulation of endothelial , adipose and chromaffin cells with growth factor is not catalysed by CL100 , but rather by protein phosphatase 2A and by a protein tyrosine phosphatase distinct from CL100 .
Stimulation of 3T3-L1 adipocytes with insulin significantly increased the tyrosine phosphorylation of caveolin and a 29-kD caveolin-associated protein in caveolin-enriched Triton-insoluble complexes .
The stimulation of caveolin tyrosine phosphorylation was specific for insulin and was not observed with PDGF or EGF , although PDGF stimulated the tyrosine phosphorylation of the 29-kD caveolin-associated protein .
In addition , Flt-1 , an endothelial cell-specific receptor for vascular endothelial growth factor ( VEGF ) , is expressed in renal mesangial cells and its gene expression is up-regulated upon the stimulation of platelet-derived growth factor ( PDGF ) with the concomitant up-regulation of VEGF .
Similarly the stimulation of matrix production by cells induced by TGF-beta 1 on plastic was reduced or even negated when cells were cultured in collagen gels .
Transport stimulation is consistent with an effect due to the activation of protein kinase C. Bradykinin ( 1 microM ) and PDGF-AA ( 100 ng/ml ) also stimulate the activity of system X-AG .
The bradykinin effect appears to be fully dependent upon PKC activation whereas the stimulation of aspartate transport by PDGF-AA is also due to PKC-independent mechanisms .
The percentage of non-cycling cells was initially more than 85% , and decreased to 55.40% , 24.22% , 11.50% , and 7.51% on days 1 , 2 , 4 , and 6 , respectively , after ET-1 stimulation .
The effect of IGF-I , EGF , PDGF and FGF on human granulosa cells of IVF-cycles , and the effect of IGF-I on granulosa cells of natural cycles ( day 7 to 13 of cycle ) were evaluated in vitro with and without hCG stimulation .
While IGF-I treatment with and without hCG stimulation did not alter steroid secretion of preovulatory granulosa cells , the progesterone secretion of granulosa cells of natural cycles was increased by combined treatment with 10 I.U. hCG + 25 ng IGF-I per ml culture medium .
Upon PDGF stimulation , SHPTP2 binds to the PDGFR and becomes tyrosine-phosphorylated .
Following PDGF stimulation , Grb2 binds tyrosine-phosphorylated SHPTP2 .
When NIH 3T3 cells prelabeled with [ 3H]inositol were synchronized by serum deprivation followed by stimulation with platelet-derived growth factor ( PDGF ) , the amounts of labeled InsP5 and InsP6 began to increase only after 12 h of stimulation , when cells entered the S-phase as indicated by increased [ 3H]thymidine incorporation .
Cytokines in human melanoma cells : synthesis , autocrine stimulation and regulatory functions--an overview .
The simultaneous synthesis of growth factors and expression of their receptors by melanoma cells , leading to permanent stimulation of cell proliferation , has been clearly shown for bFGF and MGSA .
This phenomenon has been designated autocrine growth stimulation .
Growth arrest-specific ( Gas2 ) protein has been shown to be a component of the microfilament system , that is highly expressed in growth arrested mouse and human fibroblasts and is hyperphosphorylated upon serum stimulation of quiescent cells .
METHODS : Transwell assay was used to study in vitro migration of human and rabbit SMCs after stimulation with platelet-derived growth factor ( PDGF ) .
Yet , the fold stimulation was higher in WKY rats , suggesting that TGF beta 1 may be partially activated in SHR VSMC .
The antibody abolished both S phase entry and the reorganization of actin assembly to ruffle formation upon stimulation with epidermal growth factor ( EGF ) and platelet-derived growth factor ( PDGF ) .
Cycloheximide did not block the large TGF-beta stimulation of CTGF gene expression , indicating that it is directly regulated by TGF-beta .
Detectable gene expression for B1 chain of laminin and heparan-sulphate proteoglycan was observed in the non-stimulated MCs but small in intensity , and no change was noted by stimulation of any growth factors examined.(ABSTRACT TRUNCATED AT 250 WORDS )
The heparin-binding growth factor eluted with . 1 M NaCl was shown to be structurally related to heparin-binding epidermal growth factor ( EGF)-like growth factor ( HB-EGF ) by several criteria , including binding to heparin affinity columns and elution with . 1 M NaCl , competition with the binding of 125I-EGF to the EGF receptor , triggering phosphorylation of the EGF receptor , immunodetection on a Western blot , and stimulation of fibroblast and keratinocyte growth .
Time course analysis of phorbol-ester induced phosphorylation of p90 and p52 revealed maximal stimulation of phosphorylation after 15-30 min. Phosphamino acid analysis showed that phosphorylation of p90 and p52 occurred mainly on serine residues .
A heat-sensitive dsI inhibitory activity could be demonstrated in v-ras-containing cells which functioned in trans when mixed with untransformed cell extracts prior to stimulation with dsRNA .
Many growth factors upon stimulation of their receptors induce the activity of extracellular signal-regulated kinases , ERKs , also known as MAP kinases .
Stimulation by TGF beta of chick embryo fibroblasts--inhibition by an IGFBP-3 .
An inhibitor of cell growth , that inhibits 100% of stimulation induced by serum in CEF , was purified to homogeneity from medium conditioned by mouse 3T3 cells .
In the present work , this mIGFBP-3 inhibited the TGF beta stimulation by about 50% , while the stimulation induced by PDGF or insulin was not inhibited by mIGFBP-3 .
Furthermore , TGF beta stimulation , in the presence of a high concentration of insulin in conditions which would saturate IGF receptors , was not significantly inhibited by mIGFBP-3 .
Down regulation of protein kinase C or inhibition of tyrosine kinase activity blocked the stimulation of AP activity caused by TPA or PDGF .
The fractions were tested for growth factor activity as measured by the stimulation of DNA synthesis in BALB/c 3T3 cells .
Stimulation of endothelin mRNA and secretion in rat vascular smooth muscle cells : a novel autocrine function .
A sustained loop of autocrine stimulation by ET-1 in SMC could contribute toward the pathogenesis of vasospasm and/or atherosclerosis .
Ang II induced a rapid ( within 2 h ) , dose ( 10(-6)-10(-9 ) M)-dependent stimulation ( 14-fold ) of thrombospondin ( TSP ) gene expression in rat VSMCs in the absence of additional factors .
After stimulation with 5% fetal calf serum , U-61,431F suppressed both the DNA synthesis and proliferation of SMC dose-dependently at the concentration of 3-100 microM , but had no effect on either of them in EC at a concentration of up to 30 microM .
When SMC were stimulated with platelet-derived growth factor ( PDGF ) for 2 hrs followed by a 22-hr incubation with insulin , U-61,431F ( 1-50 microM ) administered at the time of PDGF stimulation did not inhibit DNA synthesis .
SMC initiated and terminated DNA synthesis at about 15-18 h and 24 h after stimulation with serum , respectively .
Inhibition of DNA synthesis in serum-stimulated SMC as a function of the addition time of U-61,431F reduced at 3-12 h after the stimulation .
The c-sis oncogene encoding the B-chain of platelet-derived growth factor ( PDGF ) may be involved in an autocrine growth stimulation of tumours expressing the PDGF receptor , such as glioblastomas and sarcomas .
On the other hand , addition of U-46619 10 minutes prior to stimulation of the cells with 1 to 17% fetal bovine serum ( FBS ) for 24 hours , potently and dose-dependently inhibited FBS-stimulated [ 3H]-TdR incorporation .
TGF alpha and EGF caused concentration-dependent stimulation of soft agar colony growth of the MIA PACA 2 cells , while only TGF alpha caused a significant but less dramatic stimulation of soft agar growth of the PANC 1 cells .
Likewise , bFGF also caused a concentration-dependent stimulation of MIA PACA 2 but not PANC 1 growth in soft agar , and PDGF had no effect on the growth of either cell line .
Mitogenic activity , measured as 3H-thymidine incorporation by NIH 3T3 cells , following stimulation with platelet-rich-plasma-derived serum ( PRS ) , platelet-poor-plasma-derived serum and platelet extract was studied in 14 patients with myeloproliferative disorders ( MPD ) and 7 normal subjects .
Removal of PGF2 alpha after short-term stimulation ( 30 min ) did not reverse its mitogenic effect .
Stimulation of phosphatidylinositol 4,5-bisphosphate hydrolysis is an important signalling reaction involved in the responses of cells to some , but not all , stimuli that promote cell proliferation .
This requirement for external stimulation is abrogated by a second step .
Indeed , Keating and Williams have claimed that PDGF may react with an intracellular PDGF receptor resulting in autocrine stimulation.(ABSTRACT TRUNCATED AT 250 WORDS )
The dose-response relationships for activation of phospholipase D and stimulation of thymidine incorporation by PDGF and TPA were comparable .
In vitro stimulation of fibroblast activity by factors generated from human monocytes activated by biomedical polymers .
In this study , we found that colchicine , a microtubule-disrupting agent , acted synergistically with TPA , but not with insulin , to induce the maximal stimulation of DNA synthesis .
These included a significant increase in PTH-stimulated cyclic AMP and high basal levels of alkaline phosphatase activity , which were decreased on exposure to PTH and increased after stimulation by 1.25 dihydroxyvitamin D3 .
In contrast , PL7 and GF2 cells exhibited basal alkaline phosphatase levels that were low , and cyclic AMP levels were not modulated by PTH stimulation .
We have used these cells to test the hypothesis that autocrine stimulation by PDGF-like molecules leads to c-fos expression which is functional in the transformed phenotype .
This report examines the role of c-fos in growth factor stimulation of transin , a matrix-degrading secreted metalloproteinase .
Platelet-derived growth factor ( PDGF ) stimulation of transin RNA was blocked by a selective reduction in Fos synthesis with antisense c-fos mRNA , whereas epidermal growth factor ( EGF ) stimulation of transin occurred despite an equivalent inhibition of Fos levels .
Greater stimulation of megakaryocyte colony growth was provided when both serum and plasma were added to the culture medium than when plasma was added alone .
Stimulation of arrested cells by CSF-1 resulted in acute , transient elevation in c-fos and subsequently in c-myc mRNA levels .
Thus it would appear that the functions mediated by this early-gene program are not restricted to the mitogenic stimulation of arrested cells .
Additive stimulation was observed when FCS was supplemented by insulin,IGF-I or PDGF but not EGF .
TGF beta also reduced the stimulation induced by FCS by 65% .
By contrast , in competent cells briefly treated with EGF , IGF-II causes a marked stimulation of [ 3H]thymidine incorporation .
Differential responsiveness of myc- and ras-transfected cells to growth factors : selective stimulation of myc-transfected cells by epidermal growth factor .
These cells secreted elevated levels of both EGF-like factors and TGF-beta , suggesting that the lack of responsiveness of these cells to exogenous growth factors arose from autocrine stimulation .
These antibodies fail to induce DNA synthesis when added to quiescent fibroblasts , indicating that the Ca2+ and pHi signals can be dissociated from tyrosine kinase activity and suggesting that these signals are indispensable for the stimulation of cell proliferation .
EGF stimulated cellular proliferation and incorporation of [ 3H]thymidine and [ 3H]leucine into the cells in a dose-dependent fashion ; the approximate half-maximal stimulation was induced with 1.5 X 10(-10)M .
This induction of DNA synthesis was inefficient , and cell proliferation was not evident , suggesting that growth factors act through stimulation of c-myc expression together with other intracellular events .
BP3T3 , a clonal benzo(a)pyrene-transformed BALB/c-3T3 cell line , is conditionally responsive to growth factor stimulation .
Empirical evidence suggests the importance of mechanical stimulation in controlling the maintenance of the periodontal ligament space .
The wide range of effects of mechanical stimulation are briefly reviewed and the central role of prostaglandins is considered .
We have now investigated the activity of the IGF-I promoter , in response to stimulation of cells by either PDGF or EGF .
In the present study we investigated the generality of this observation , namely the presence of hyaluronan receptors and factors which induce stimulation of hyaluronan synthesis in primary mesothelioma and mesothelial cell cultures .
SHPTP2 associates with the platelet-derived growth factor ( PDGF ) receptor after ligand stimulation , and binding of SHPTP2 to this receptor promotes tyrosine phosphorylation of SHPTP2 .
The strong transcriptional stimulation by phorbol myristate acetate suggests protein kinase C ( PKC)-mediated signaling .
In contrast , bFGF , EGF , and PDGF were mainly delayed stimulators , with maximal stimulation being detected by 19 h . In addition , these growth factors potentiated the rapid induction of c-ets-1 by TNF alpha .
Maximal stimulation of mRNA was observed after 8 h of treatment with 10-50 microM progesterone , and the effect was suppressed by the progesterone antagonist RU-486 .
Induction by progesterone was cell-specific and equivalent to the stimulation mediated by PDGF .
Activation of adhesiveness is transient , and occurs at concentrations of steel factor 100-fold lower than required for growth stimulation .
Luciferase activity was significantly augmented ( 23-fold ) following mitogenic stimulation in vivo as compared with the control transfected coronary arteries .
Stimulation of DNA synthesis by low doses of serum in U-1242 MG cells is inhibited in a dose-responsive fashion by ganglioside GM1 .
Herein , we used primary cultures of human glomerular mesangial cells ( HMCs ) from five different donors to determine the autocrine growth-inducing capacity of their supernatants after stimulation with different cytokines and lipopolysaccharide ( LPS ) to determine whether this effect is due to basic fibroblast growth factor ( bFGF ) .
Immunoblots for bFGF protein of HMC demonstrated that only a approximate to 16 kd bFGF protein was released into HMC supernatants after stimulation with IL-1 beta , platelet-derived growth factor-BB , and LPS .
The 18 kd isoform of bFGF accumulated in the membranes but was not released after stimulation with IL-1 alpha , IL-6 , and bFGF , suggesting that its release was a prerequisite for autocrine growth stimulation .
Serum stimulation of quiescent mouse fibroblasts results in transcriptional activation of tissue factor ( TF ) , the cellular initiator of the protease cascade leading to blood coagulation .
While c-Fos is notably absent from these preexisting complexes , serum stimulation results in the rapid entry of c-Fos into the TF AP-1 DNA-binding complexes .
Importantly , overexpression of JunD and c-Fos abrogates the requirement for serum in the stimulation of TF promoter activity in fibroblasts .
An anti-sense oligonucleotide complementary to the first six codons of the Egr-1 mRNA abolishes the stimulation of protein synthesis induced by endothelin .
Tyrosine phosphorylation of the c-cbl proto-oncogene protein product and association with epidermal growth factor ( EGF ) receptor upon EGF stimulation .
Here we show that upon stimulation of human epidermal growth factor ( EGF ) receptor , p12ocbl becomes strongly tyrosine-phosphorylated and associates with activated EGF receptor in vivo .
Platelet-derived growth factor ( PDGF ) , fibroblast growth factor ( FGF ) , or nerve growth factor ( NGF ) stimulation also results in tyrosine phosphorylation of p120cbl .
IGF-I stimulation of cell proliferation and c-Fos expression in skeletal muscle cells is markedly enhanced by dexamethasone .
However , the control and the ras ( T24 ) oncogene transformed Rat-2 cells did not show any increase in GTP-binding on serum stimulation while showing a marginal decrease in GTP-binding in the presence of DMSO .
In addition , diazepam reduced the stimulation of DNA synthesis caused by epidermal growth factor ( EGF ) and platelet-derived growth factor ( PDGF ) , polypeptide growth factors coupled to receptor tyrosine kinases , as well as thrombin , an activator of G protein-coupled receptors .
Here we consider the role of the v-Src homology ( SH ) domains , SH3 and SH2 , and the tyrosine kinase catalytic domain , in the stimulation of v-Src-associated PI 3-kinase activity in response to rapid activation of the oncoprotein .
Generation of phosphorylcholine as an essential event in the activation of Raf-1 and MAP-kinases in growth factors-induced mitogenic stimulation .
We report here that growth factors induce a biphasic generation of phosphorylcholine ( PCho ) in quiescent NIH 3T3 cells , resulting in an early and transient increase at 100 s and a larger and sustained increase after 3 h of stimulation .
Generation of PCho at both early and late times of growth factors stimulation results from the consecutive activation of phospholipase D ( PLD ) and choline kinase ( ChoK ) .
Doses of less than 100 ng/ml of growth factor produced either no stimulation or a variable response .
A dose of 100 ng/ml resulted in consistent , significant ( p < ; . 05 ) stimulation in all groups in the peripheral region , and a dose of ng/ml provided more than a 2.5-fold increase .
The central region did not respond to stimulation with the growth factor at any of the doses tested .
After stimulation with IGF-1 , the major tyrosylphosphorylated protein that was associated with p85 was a 185-kilodalton protein , identified as IRS-1 .
In contrast , the PDGF receptor was the major protein associated with p85 upon stimulation .
In order to determine whether the SH2 domains of p85 were involved in its association with p185 in vivo after IGF-1 stimulation , different SH2-constructs of p85 were expressed in COS-1 cells .
After stimulation with IGF-1 , the expressed SH2 proteins were immunoprecipitated with specific antibodies , and associated p185 was detected on Western blots .
These results show that both the p85 N-SH2 and N+C-SH2 associate with IRS-1 after IGF-1 stimulation.(ABSTRACT TRUNCATED AT 250 WORDS )
On continuous thrombin stimulation the u-PAR message in SMC was 10 +/- 2.3-fold elevated reaching a maximum between 6 and 9 hours and declining to control values within 48 hours .
Stimulation with the thrombin receptor activation peptide S-F-L-L-R-N representing the NH2-terminus of the tethered ligand also increased u-PAR mRNA levels with an identical time course .
Thrombin stimulation also resulted in a 2 +/- 0.2-fold transient increase in thrombin receptor mRNA preceding the rise in u-PAR message .
In order to decide if the u-PAR mRNA increase was due to message stabilization or a consequence of transcriptional activation we used the RNA polymerase II inhibitor , 6-dichloro-1-beta-D-ribofuranosyl benzimidazole ( DRB ) during the stimulation experiments .
u-PAR mRNA levels on TGF beta 1 stimulation of SMC decayed after the addition of DRB indicating that enhancement of transcriptional activity was involved in the induction .
In contrast , the time course of u-PAR mRNA elevation on thrombin , bFGF , and PMA stimulation was not significantly altered in the presence of DRB suggesting that in these latter cases u-PAR mRNA message accumulation was at least in part due to mRNA stabilization .
Weak induction of LIF mRNA was observed after stimulation with basic fibroblast growth factor , endothelin and transforming growth factor beta .
The mitogenic action of cytokines such as epidermal growth factor ( EGF ) or platelet derived growth factor ( PDGF ) involves the stimulation of a signal cascade controlled by a small G protein called Ras .
Northern blot analysis demonstrated a severalfold increase in the PAI-1 mRNA 3 to hours after stimulation with 300 nmol/L Ang II .
After stimulation with Ang II , lysis caused by the in situ dissociation of TPA was also present in the region of the TPA/PAI-1 complex .
For matrix synthesis , IGF-I was the key factor , with the addition of TGF-beta , TGF-beta+bFGF , or serum producing further stimulation in matrix synthesis .
Addition of PDGF , insulin or both , induced a transitory stimulation of growth in G6 or G10-11 ED ; TGF beta did not modify growth of G6 ICM .
Whereas both scar and normal cells responded with increased thymidine uptake to serum and cytokines , the stimulation to EGF and serum was significantly lower in scar cells .
The phosphorylation on tyrosine of SHC and several other GRB2-associated proteins increased upon stimulation with CSF-1 .
The kinetics of thymidine incorporation and of activation of the c-myc proto-oncogene , observed already after 1 hr , in treated NIH3T3 and TR15 cells , suggests a direct mitogenic stimulation .
Mitogenic assays showed an increased sensitivity of ADPKD epithelia to stimulation by the combination of the endocrine factors hydrocortisone ( dexamethasone ) and insulin , and Northern analysis suggested increased levels of insulin receptor steady state mRNA .
The localization in vivo of EGF immunoreactivity in ADPKD cyst-lining epithelia and in ( apical ) cyst fluids and the demonstration of EGF-receptor immunostaining and specific [ 125I]EGF binding to apical cell surfaces suggested an autocrine mechanism of growth stimulation by EGF in ADPKD epithelia .
Transforming growth factor beta was an inhibitor of normal renal tubule proliferation but was unable to completely inhibit EGF stimulation in ADPKD cultures .
The present study employs a fibroblast mitogenic assay to determine whether tetrandrine directly inhibits the ability of fibroblasts to respond to stimulation by growth factors .
Tetrandrine is effective in inhibiting thymidine incorporation when added up to 6 hr after stimulation of quiescent cells , suggesting either that tetrandrine does not block the attainment of competence by fibroblasts or that its activity is not limited to blocking the attainment of competence by these cells .
Heparin-binding EGF-like growth factor stimulation of smooth muscle cell migration : dependence on interactions with cell surface heparan sulfate .
As a control for BASMC viability , and for specificity , it was found that heparitinase and P21 did not inhibit at all and chlorate inhibited only slightly the stimulation of BASMC migration by PDGF AB .
This stimulation can be abolished in g/G but not in NUC-5 cells by simultaneous addition of TGF beta .
Surprisingly , a purified nonrecombinant murine GM-CSF preparation induced proliferation of both blastocyst and ectoplacental cone trophoblast whereas recombinant murine ( and human ) GM-CSF had no effect , indicating that the growth stimulation may have been due to a contaminant .
In contrast , stimulation of the TCR/CD3 complex or PKC , results in a marked and rapid increase in phosphorylation of p85 beta on threonine residues .
Our results show that stimulation by serum of dense cultures of 3T3 cells rapidly induced increased synthesis of a growth inhibitor ( mIGFBP-3 ) capable of binding IGF .
Since we showed that mIGFBP-3 is able to inhibit bFGF stimulation of DNA synthesis in mouse fibroblasts , it is possible that the accumulation of mIGFBP-3 induces a feedback regulation of cell growth .
Propranolol ( 10 microM ) was the only beta-adrenoceptor antagonist tested that inhibited [ 3H]thymidine incorporation , with effects of approximately 50 and 75% on basal and endothelin-1-mediated stimulation , respectively .
In contrast , celiprolol ( 10 microM ) produced significant stimulation of DNA synthesis ( 125% over basal ) .
Axolemma-enriched fractions ( AEF ) were weak mitogens for OLGs ( less than 5% proliferation after 7 days of stimulation ) , however , heparin extracts of AEF were five-fold more mitogenic than the AEF from which they were derived .
Biol . , 11 , 5113-5124 ) , and that its phosphotyrosine content is increased cooperatively by c-src overexpression and EGF stimulation .
Platelet derived growth factor ( PDGF ) and cathepsin D had no effect in the presence or absence of oestradiol while TGF-beta slightly reduced the stimulation by oestradiol .
Stimulation of phosphatidylcholine breakdown by thrombin and carbachol but not by tyrosine kinase receptor ligands in cells transfected with M1 muscarinic receptors .
In order to evaluate the possible contribution of phospholipase D ( PLD ) stimulation to the mitogenic response , a screening of a variety of different compounds , some of which are known to be potent mitogens , was performed using the well characterized Chinese hamster lung fibroblast ( CCL39 ) cell line .
In each case , the stimulation of PLD correlated closely with the ability to stimulate inositol phospholipid breakdown and was entirely dependent on the activation of protein kinase C. Moreover , the ability of both thrombin and carbachol to stimulate PLD was found to be rapidly desensitized , with a similar time course of desensitization ( t1/2 desensitization , 90 s ) .
In this regard , in addition to stimulation of PLD , thrombin and carbachol were both able to stimulate the activity of a phosphocholine-specific phospholipase C ( PC-PLC ) , which did not appear to desensitize within the time course employed .
By contrast , EGF was unable to elicit the stimulation of PC-PLC .
Interestingly , c-fos induction is also required for stimulation of stromelysin expression by EGF in rat fibroblasts .
TGF-beta stimulation therefore initiates a cascade of events that results in a specific pattern of gene expression : the direct stimulation of early-response genes can lead to subsequent induction or repression of other genes .
Treatment of embryonic lungs in organ culture with the growth factors EGF or TGF-alpha results in stimulation of growth and inhibition of branching morphogenesis .
Stimulation of DNA synthesis in rat uterine cells by growth factors and uterine extracts .
After in vitro stimulation with AGE-modified proteins , normal human blood monocytes express IGF-IA mRNA leading to the secretion of IGF-IA prohormone .
The reduction of cytokine secretion in parallel with the stimulation of MC growth by coll I suggests that exposure to coll I may result in a change from secretory to proliferative phenotype in vitro .
BPH has been regarded as a kind of adenoma , as a stromal disease , as the result of either hormonal imbalance ( altered oestrogen/testosterone ratio ) or testosterone or dihydrotestosterone stimulation , and finally as the result of oestrogen stimulation , perinatally or involutionally .
In addition , K252a rapidly reverts the transformed phenotype of NIH3T3 cells transformed by either autocrine stimulation of the trk family of receptors by their cognate ligands or by expression of trk oncogenes isolated from human tumors .
A transient increase was observed at 6-9 h after serum restimulation .
An IGF binding protein is an inhibitor of FGF stimulation .
IDF-45 inhibited the stimulation induced by bFGF by about 65% , while stimulation induced by insulin , PDGF , or EGF was only weakly or not at all inhibited by IDF45 .
When bFGF stimulation was determined in the presence of a high concentration of insulin in conditions which minimize the effect of endogenous IGF-I or -II , this stimulation was decreased by about 50% in the presence of IDF45 .
This result suggests that addition of bFGF stimulates IGF secretion , thereby resulting in partial loss of inhibition , by IDF45 , of bFGF stimulation .
We found a single peak of ODC activity eight to ten hours after stimulation , declining to 22 to 34% of peak levels after 24 hours .
After serum stimulation there was a two- to 10-fold increase in ODC mRNA with a maximum after six hours .
We found that cocultures of SP1 and C1 or B5 cells with irradiated C1 , B5 , or SP1 "feeder" ; cells showed significant stimulation of C1 and B5 by SP1 "feeder" ; cells .
Cell growth stimulation in response to EGF , TGF-alpha , TGF-beta 1 , bFGF , PDGF , NGF , IGF-1 , or IGF-2 demonstrated that only TGF-beta 1 could duplicate this effect .
A repeat of the coculture experiment in the presence of specific neutralizing anti-TGF-beta antibodies was therefore undertaken and this was found to markedly reduce the stimulation of C1 or B5 cells by irradiated SP1 cells .
TEA production is found to be insensitive to mitogen stimulation such as concanavalin A , lipopolysaccharide , and phytohemagglutinin .
In general , vit D3 produced the strongest stimulation in all populations with TGF-beta producing a good response in the non-transformed cells and RA in the RC IV cells .
In both cells , transforming growth factor-beta 1 ( TGF-beta 1 ) inhibited EGF-induced stimulation of [ 3H]-thymidine uptake , but had no effects when it was added alone .
Stimulation of bumetanide-sensitive Na+/K+/Cl- cotransport by different mitogens in synchronized human skin fibroblasts is essential for cell proliferation .
Insulin stimulation of gene expression mediated by p21ras activation .
No increase in p21rasGTP levels was observed after PDGF and EGF stimulation of cells expressing high levels of the cognate receptor , stressing the specificity of the insulin-induced increase .
When stimulated with serum , quiescent Balb/C-3T3 fibroblasts were found to induce vinculin transcription transiently within 30 min , followed by accumulation of vinculin mRNA and protein synthesis between 2 and 4 h after stimulation and a decrease to the basal level by 6-8 h . Platelet-derived growth factor ( PDGF ) , fibroblast growth factor ( FGF ) , and 12-O-tetradecanoylphorbol-13-acetate ( TPA ) each could elicit a similar response , albeit to a lesser extent , whereas epidermal growth factor ( EGF ) was inefficient in inducing vinculin expression .
The results indicate that the changes in vinculin organization and expression in response to growth factor stimulation may reflect either a necessary step in the progression through the cell cycle or a response related to complex cellular processes such as wound repair and embryogenesis .
3 . rPDGF stimulation of wild type NIH-3T3 cells increases both prostaglandin H synthase ( PGHS ) mRNA levels and PGHS enzyme levels as measured by immunoblot .
With IL-1 , significant levels of both CSFs were first detected within 6 to 12 hours , with a maximum reached 24 to 48 hours after commencement of stimulation .
No evidence was obtained for the IL-1-induced effect to be mediated by induction of endogenous TNF nor for the TNF-induced stimulation to involve IL-1 .
In this study we investigated the correlation between the mitogenic effect and stimulation of Rb+ ( K+ ) fluxes in human skin fibroblasts treated by purified growth factors .
TGF-beta 1 did not modulate significantly the stimulatory effect of these growth factors on the activity of the enzyme glutamine synthetase ( GS ) ; but kinetic studies showed that TGF-beta 1 delays the stimulation of GS activity .
Stimulation occurred only when the bFGF treatment was continued after 12 h . Potentiation of the mitogenic effect of bFGF and shift of the maximum 125I-dUrd incorporation towards 24 h was seen with cells pretreated with TGF-beta 1 . This potentiation effect decreased with increasing time between the two treatments .
In contrast , morphologic transformation develops more slowly and does not appear until 72-96 h after Zn++ stimulation in cells with very low basal levels of activated p21 ( MR4 cells ) and 24-48 h in cells with higher basal levels ( MR5 cells ) .
Stimulation by hydrogen peroxide of DNA synthesis , competence family gene expression and phosphorylation of a specific protein in quiescent Balb/3T3 cells .
The pattern of phosphorylation was similar to that observed in cells chronically stimulated with EGF or PDGF , and is probably due to autocrine stimulation of receptor tyrosine kinases .
The inhibition of EGF stimulation by FGF is across the EGF dose-response curve , present at high and low culture densities , and stable for at least 3 days .
Specificity is indicated by lack of inhibition by PDGF pretreatment and much less inhibition of fetal calf serum-induced stimulations than EGF-induced stimulation .
Cell counts confirmed that the FGF pretreatment also inhibits EGF stimulation of cell division .
However , whereas a stimulation of cell proliferation rate was observed at that time in cultures containing 10% FCS , a dose-dependence inhibition of cell growth was detected , in contrast , for % FCS-treated cells .
The , the release of these cells may produce either apparent stimulation of cell proliferation if sufficient levels of an unknown serum factor are present ( 10% FCS ) or an inhibition of growth rate when only reduced amounts of this factor are available ( 2% FCS).(ABSTRACT TRUNCATED AT 400 WORDS )
The combination of E + I + T produced no additional stimulation of DNA synthesis .
Stimulation of DNA synthesis in human and bovine RPE by peptide growth factors : the response to TNF-alpha and EGF is dependent upon culture density .
For cultures which were subconfluent or in early confluence , TNF-alpha , a product of activated macrophages , was the most effective mitogen ; little or no growth stimulation was observed for PDGF , EGF , NGF , IGF-1 , IL-1B , bFGF or TGF-beta 1 . For TNF-alpha and EGF the growth response was analyzed in cultures of varying density .
TNF-alpha was more active in sparse RPE cultures whereas EGF stimulation was greater in dense cultures .
TGF beta showed synergistic stimulation with ATP in fibroblasts but it inhibited keratinocytes .
Differences in inhibition by IDF45 ( an inhibitory diffusible factor ) of early RNA synthesis stimulation induced by pp60 v-src and various mitogens .
In order to gain further insight into the IDF45 mode of action in normal and transformed CEF , we compared the effects of IDF45 on early stimulation of RNA synthesis induced in CEF by different mitogenic factors and by v-src gene expression .
Stimulation , by serum , of RNA synthesis was inhibited by IDF45 ; however , inhibition increased when cells were preincubated with IDF45 before addition of serum and cell labeling for 2 h . IDF45 was also able to inhibit partially the stimulation of RNA synthesis induced by PMA and PDGF but was unable to inhibit stimulation of RNA synthesis induced by insulin and v-src expression .
By contrast , stimulation of RNA synthesis induced by IGF-I was rapidly 100% inhibited by IDF45 .
These results suggest that the modes of action of IDF45 on stimulation of RNA synthesis by v-src and by insulin are similar .
Our present results agree with others showing the bifunctional activity of IDF45 as an IGF-binding protein and as an inhibitory molecule in DNA stimulation induced by serum .
Incorporation of [ 35S]sulfate into PG was increased during the first 24 h of growth stimulation , and this increase appeared to be principally in the large chondroitin sulfate proteoglycan ( CSPG ) .
However , we could only detect IL6 message in cells incubated with LPS under "superinduction" ; conditions with cycloheximide , consistent with lower levels of IL6 biological activity in response to LPS compared to IL1 stimulation .
Recently intimal thickening was shown to be due to stimulation of proliferation of arterial smooth muscle cells ( SMC ) by autocrine secretion of growth factor(s ) .
The continuous presence of CM was essential for its stimulation of DNA synthesis whereas the presence of PDGF for only the first 4 h of culture was sufficient to induce maximum stimulation of DNA synthesis .
TGF beta induces a sustained c-fos expression associated with stimulation or inhibition of cell growth in EL2 or NIH 3T3 fibroblasts .
Stimulation of c-fos mRNA by basic FGF in the cultured Sertoli cell presents questions regarding the role of FGF and c-fos in the male reproductive system .
They are probably weakly malignant neoplasms of endothelial cell origin , and paracrine growth stimulation appears to be important for their maintenance and progression .
Beta transforming growth factor ( TGF beta ) has multiple in vitro biological effects including stimulation or inhibition of proliferation of specific cell types .
We therefore compared highly purified TGF beta-1 and TGF beta-2 isolated from porcine platelets for inhibition of DNA synthesis in mink lung epithelial cells ( MvILu ) , and in AEC , and for stimulation of 3H-thymidine incorporation in calvarial bone cells ( CBC ) in 3 experiments .
The turnover of phosphatidylinositol 4,5-bisphosphate ( PIP2 ) is believed to constitute a crucial step in the signaling pathways for stimulation of cells by a variety of bioactive substances , including mitogens , but decisive evidence for the idea has not been obtained .
Mitogenic stimulation of human breast cancer cells in a growth factor-defined medium : synergistic action of insulin and estrogen .
To prevent background estrogenic stimulation , only phenol red-free media were used .
Acquisition of the activated ras gene confers hormone autonomy on the previously hormone-dependent tumorigenicity and results in upregulation in secretion of some of the growth factors in amounts compared to estradiol stimulation .
Thus , aberrant production of growth factors , triggered either by activated oncogenes and estrogen stimulation in hormone-dependent cells , or by increased constitutive production in hormone-independent cells may in an autocrine , paracrine , or endocrine manner be associated with neoplastic growth of breast cancer .
The transcription of myc and fos is induced by growth factor stimulation of quiescent cells .
Activation or inappropriate expression of either myc or fos could produce the same end result as stimulation of a growth factor pathway leading to a growth advantage .
In at least one circumstance , there is evidence that the stimulatory effects of TGF beta in fibroblastic cells is indirect through induction of c-sis and autocrine stimulation by platelet-derived growth factor ( PDGF)-like material .
Increased autocrine stimulation by endogenous TGF beta in fibroblastic cells or decreased inhibitory effects in epithelial cells ( or other cells normally inhibited by TGF beta ) could lead to an increased proliferative potential and thereby contribute to the neoplastic phenotype .
The stimulation was dose-dependent , and most of the stimulatory activity was extracted by acid .
From these data , it is apparent that the loop B insertion is critical for thrombin 's nonenzymic biological effects on cells , but additional sites are required for stimulation of cell movement .
The results suggest that the mitogenic stimulation of arterial smooth muscle cells involves a flux of calcium ions through the plasma membrane and requires participation of calmodulin .
It is thus concluded , that PGI2 inhibits smooth muscle cell proliferation most probably by inhibiting PDGF-release from the platelets and stimulation of smooth muscle cell cAMP .
The stimulation of DNA synthesis in quiescent fibroblasts was also observed upon the addition of PMGF and h-CMP .
On the basis of these results we suggest that : ( i ) MeWo and MeWo-LC1 melanoma cells have obviated allocrine stimulation of the division process characteristic of normal cells by responding to their own mitogens ; ( ii ) some of these mitogens are akin to TGFs ; ( iii ) the less efficient synthesis of autostimulatory factors by MeWo cells may account for their weaker proliferative capacity in vitro , and possibly in vivo .
A brief exposure of quiescent ( Go ) Swiss 3T3 mouse fibroblasts to inhibitors of protein synthesis can replace platelet-derived growth factor in the stimulation of cellular DNA synthesis .