Simvastatin reduces MMP1 expression in human smooth muscle cells cultured on polymerized collagen by inhibiting Rac1 activation

In vivo and in vitro evidences suggest that activation of collagen receptors (alpha2betal integrin and discoidin domain receptors) expressed in smooth muscle cells (SMCs), by type I collagen, induces metalloproteinases (MMPs) expression. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, statins, have been shown to interfere with integrin signaling but their effect on MMP expression mediated by collagen receptors have not been investigated. In the present study, we showed that simvastatin (3 umol/L) reduced MMP1 expression in human SMCs cultured on polymerized type I collagen, measured by western blot analysis of both total cell lysates (-39.9-t-11.2%) and conditioned media (-36.0-t-2.3%), but had no effect on MMP2 levels and activation. Reduced MMP1 expression levels correlated with the inhibition of MMP1 promoter activity (-33.0-t-8.9%) and MMP1 mRNA levels (-37.8-t-10.5%), and was associated with a strong decreased of smooth muscle collagen degradation (-94.5-t-13.7%). Mevalonate, and the isoprenoid derivative geranylgeraniol, substrate of protein geranylgeranyl transferases, completely prevented the effect of simvastatin on MMP1 expression levels. Retroviral overexpression of dominant negative mutants of geranylgeranylated Racl and Cdc42 led to a reduction of protein and mRNA MMP1 levels, while dominant negative RhoA had no effect. Finally, Racl activity was inhibited by simvastatin in SMCs cultured on polymerized collagen. These results demonstrated that simvastatin, by inhibiting Racl activity, reduced MMP1 expression and collagen degradation in human SMCs.