Direct inhibitory effects of simvastatin on matrix accumulation in cultured murine mesangial cells

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been demonstrated to suppress glomerular injuries in various renal diseases. These agents inhibit in vitro proliferation of several cell types, including mesangial cells. This effect indicates the ability to ameliorate mesangioproliferative lesions, independent of the improvement of hypercholesterolemia. On the other hand, it is not clear whether HMG-CoA reductase inhibitors directly regulate extracellular matrix (ECM) accumulation from mesangial cells.

In this study, to examine the in vitro effects of simvastatin, an HMG-CoA reductase inhibitor, on mRNA expressions of matrix proteins, growth factors, and matrix turnover proteins, we incubated cultured murine mesangial cells stimulated by fetal calf serum (FCS) with or without simvastatin for 24 hours, and Northern analysis was performed.

Simvastatin showed a slightly suppressive effect on mRNA expression of type IV collagen and fibronectin and a slightly up-regulative effect on that of type I collagen, whereas mRNA expression of type III collagen was markedly up-regulated. mRNA expression of platelet-derived growth factor (PDGF)-B chain and PDGF receptor beta-subunit was suppressed, whereas that of transforming growth factor-beta (TGF-beta) was not affected by simvastatin. Concerning matrix turnover proteins, simvastatin markedly reduced mRNA expression of plsminogen activator inhibitor-1 (PAI-1) without affecting the expression of tissue-type plasminogen activator (tPA).

These results suggest type-specific modulation of matrix protein production independent of TGF-beta and the suppressive effects of autocrine PDGF by administration of HMG-CoA reductase inhibitors in mesangial cells. Moreover, the beneficial effects of these agents on matrix protein accumulation may be through promoting ECM degradation derived from PAI-1 suppression.