Department of Pharmacology , University of Washington , Seattle 98195 , USA .
J Biol Chem 271 : 505-11 ( 1996)
Abstract
The abilities of platelet-derived growth factor ( PDGF ) and insulin-like growth factor ( IGF-I ) to regulate cAMP metabolism and mitogen-activated protein kinase ( MAP kinase ) activity were compared in human arterial smooth muscle cells ( hSMC ) .
PDGF-BB stimulated cAMP accumulation up to -fold in a concentration-dependent manner ( EC50 approximately 0.7 nM ) .
The peak of cAMP formation and cAMP-dependent protein kinase ( PKA ) activity occurred approximately 5 min after the addition of PDGF and rapidly declined thereafter .
Incubating cells with PDGF and -isobutyl-1-methylxanthine ( IBMX , a phosphodiesterase inhibitor ) enhanced the accumulation of cAMP and PKA activity by an additional . 5-3-fold , whereas IBMX alone was essentially without effect .
The PDGF-stimulated increase in cAMP was prevented by addition of the cyclooxygenase inhibitor indomethacin , consistent with release of prostaglandins stimulating cAMP .
PDGF , but not IGF-I , stimulated MAPK activity , cytosolic phospholipase A2 ( cPLA2 ) phosphorylation , and cAMP synthesis which indicated a key role for MAP kinase in the activation of cPLA2 .
Further , PDGF stimulated the rapid release of arachidonic acid and synthesis of prostaglandin E2 ( PGE2 ) which could be inhibited by a cPLA2 inhibitor ( AACOCF3 ) .
Calcium mobilization was required for PDGF-induced arachidonic acid release and PGE2 synthesis but not for MAPK activation , whereas PKC was required for PGE2-mediated activation of PKA .
In summary , these results demonstrated that PDGF increases cAMP formation and PKA activity through a MAP kinase-mediated activation of cPLA2 , arachidonic acid release , and PGE2 synthesis in human arterial smooth muscle cells .