Ethanol differentially modulates the expression and activity of cell cycle regulatory proteins in rat aortic smooth muscle cells.

The aim of this study was to determine the effect of ethanol on cell cycle events during the G(1) and S phases in cultured vascular smooth muscle cells (VSMC). Flow cytometric analysis for the DNA content in rat aortic VSMC indicated that following ethanol treatment, the cell population in the G(0)/G(1) phase increased; 57.8+/-1.6% vs. 72.3+/-1.2%, concomitant with a decrease in cells in the S phase; 12.7+/-1.4% vs. 3.67+/-0.6%, for control vs. ethanol, respectively. Western blot analysis on VSMC lysates demonstrated that ethanol (10-160 mmol/l) dose-dependently inhibited serum-induced retinoblastoma (pRb) hyperphosphorylation. While having no effect on Cdk2 protein expression, ethanol dose-dependently decreased (IC(50) approximately 60 mmol/l) Cdk2 activity, assessed by histone H1 phosphorylation. Furthermore, ethanol induced the expression of the cyclin-dependent kinase (Cdk) inhibitor p21(waf1/cip1), and inhibited the induction of cyclin A. These data demonstrate that modulation of the expression and activity of key cell cycle regulatory molecules may be a mechanism by which ethanol inhibits VSMC proliferation. These actions of ethanol may be relevant to its cardiovascular protective effect in vivo.