Platelet-derived growth factor stimulates protein kinase A through a mitogen-activated protein kinase-dependent pathway in human arterial smooth muscle cells.
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 150-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 3-isobutyl-1-methylxanthine (IBMX, a phosphodiesterase inhibitor) enhanced the accumulation of cAMP and PKA activity by an additional 2.5-3-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.
Graves
L M
LM
Department of Pharmacology, University of Washington, Seattle 98195, USA.
Bornfeldt
K E
KE
Sidhu
J S
JS
Argast
G M
GM
Raines
E W
EW
Ross
R
R
Leslie
C C
CC
Krebs
E G
EG
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000595:Amino Acid Sequence; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology*; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*
D010726:Phosphodiesterase Inhibitors; D010982:Platelet-Derived Growth Factor; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D010741:Phospholipases A; D054467:Phospholipases A2; D015056:1-Methyl-3-isobutylxanthine