Department of Medicine , University of Iowa College of Medicine , Iowa City , Iowa 52242 , USA .
J Biol Chem 271 : 13324-32 ( 1996)
Abstract
Bradykinin and platelet-derived growth factor ( PDGF ) are inflammatory mediators important in the response to vascular injury .
Based upon the known effect of oncogenic Ras to increase bradykinin receptor expression and the ability of PDGF to stimulate Ras , we examined whether PDGF regulates bradykinin B2 receptor expression in cultured arterial smooth muscle cells .
Treatment with PDGF ( AB and BB , but not AA ) produced a dose- and time-dependent increase in both mRNA ( 6-7-fold increase at 2-4 h ) and cell surface receptors ( 2-4-fold at 6-12 h ) for the B2 receptor .
There was a 60-min delay between exposure to PDGF and the initial increase in B2 receptor mRNA .
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 , protein synthesis was not required , as treatment with cycloheximide did not block but rather superinduced the PDGF-induced increase in B2 receptor mRNA .
Comparison with the immediate early response gene c-fos demonstrated that the increase in B2 receptor mRNA was similarly inhibited by the tyrosine kinase inhibitor , tyrphostin , as well as staurosporine .
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 .
Taken together , these results demonstrate that the B2 receptor is a delayed early response gene for PDGF in vascular smooth muscle cells .