Simvastatin inhibits MMP‐9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP‐9 mRNA levels

Abstract

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.