Genistein selectively inhibits platelet-derived growth factor-stimulated versican biosynthesis in monkey arterial smooth muscle cells.

Platelet-derived growth factor (PDGF) stimulates not only the proliferation and migration of arterial smooth muscle cells (ASMCs), but also the transcription, translation, and posttranslational processing of versican, a large chondroitin sulfate proteoglycan present in the extracellular matrix of blood vessels. PDGF receptor tyrosine kinase activity is required for signaling events associated with mitogenic and motogenic stimulation of cells by PDGF. Therefore, we have asked if inhibiton of tyrosine kinase activity by genistein also blocks the stimulation of both versican core protein synthesis and glycosaminoglycan (GAG) chain modifications induced by PDGF in ASMCs. The tyrosine kinase inhibitor, genistein, in a dose-dependent manner, reversibly inhibits PDGF-stimulated ASMC cell proliferation and RNA and core protein expression of versican, without affecting the expression of decorin and biglycan. In contrast, genistein does not affect the increase in GAG chain elongation that is induced by PDGF. This suggests that different aspects of the biosynthesis of versican are differentially regulated. To determine if such differential regulation involves downstream activation of protein kinase C, ASMCs were treated with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) to directly activate this kinase. In comparison to PDGF stimulation, TPA has little effect on expression of versican mRNA expression, nor does TPA stimulate ASMC cell proliferation. However, like PDGF, TPA increases [35S]sulfate incorporation into proteoglycans and GAG chain elongation. These results indicate that PDGF-induced GAG chain elongation, which is not inhibited by genistein treatment and is stimulated by protein kinase C activation, involves signaling pathways different from those that regulate PDGF-stimulated versican mRNA and protein expression.