DHEA attenuates PDGF-induced phenotypic proliferation of vascular smooth muscle A7r5 cells through redox regulation

Abstract

It is known that dehydroepiandrosterone (DHEA) inhibits a phenotypic switch in vascular smooth muscle cells (VSMC) induced by platelet-derived growth factor (PDGF)-BB. However, the mechanism behind the effect of DHEA on VSMC is not clear. Previously we reported that low molecular weight-protein tyrosine phosphatase (LMW-PTP) dephosphorylates PDGF receptor (PDGFR)-β via a redox-dependent mechanism involving glutathione (GSH)/glutaredoxin (GRX)1. Here we demonstrate that the redox regulation of PDGFR-β is involved in the effect of DHEA on VSMC. DHEA suppressed the PDGF-BB-dependent phosphorylation of PDGFR-β. As expected, DHEA increased the levels of GSH and GRX1, and the GSH/GRX1 system maintained the redox state of LMW-PTP. Down-regulation of the expression of LMW-PTP using siRNA restored the suppression of PDGFR-β-phosphorylation by DHEA. A promoter analysis of GRX1 and γ-glutamylcysteine synthetase (γ-GCS), a rate-limiting enzyme of GSH synthesis, showed that DHEA up-regulated the transcriptional activity at the peroxisome proliferator-activated receptor (PPAR) response element, suggesting PPARα plays a role in the induction of GRX1 and γ-GCS expression by DHEA. In conclusion, the redox regulation of PDGFR-β is involved in the suppressive effect of DHEA on VSMC proliferation through the up-regulation of GSH/GRX system.