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

OBJECTIVE - Activation of collagen receptors expressed by smooth muscle cells induces matrix metalloproteinase (MMP) expression. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have been shown to interfere with integrin signaling, but their effects on collagen receptor-mediated MMP expression have not been investigated. METHODS AND RESULTS - In the present study, we show that simvastatin (3 μmol/L) reduces MMP1 expression and secretion in human smooth muscle cells cultured on polymerized type I collagen by 39.9±11.2% and 36.0±2.3%, respectively. Reduced MMP1 protein levels correlate with a similar decrease in MMP1 promoter activity (-33.0±8.9%), MMP1 mRNA levels (-37.8±10.5%), and attenuation of smooth muscle cell collagen degradation (-34.2±6.1%). Mevalonate, and the isoprenoid derivative geranylgeraniol, precursors of geranylgeranylated proteins, completely prevent the inhibitory effect of simvastatin on MMP1. Moreover, the protein geranylgeranyltransferase inhibitor GGTI-286 significantly decreases MMP1 expression. Retroviral overexpression of dominant-negative mutants of geranylgeranylated Rac1 lead to a reduction of MMP1 protein (-50.4±5.4%) and mRNA levels (-97.9±1.0%), and knockdown of Rac1 by small interfering RNA downregulates MMP1 expression. Finally, simvastatin reduces GTP-bound Rac1 expression levels in smooth muscle cells cultured on polymerized collagen. CONCLUSIONS - These results demonstrate that simvastatin, by inhibiting Rac1 activity, reduces MMP1 expression and collagen degradation in human smooth muscle cells.