Simvastatin inhibits transforming growth factor-β1-induced expression of type I collagen, CTGF, and α-SMA in keloid fibroblasts

Simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme-A reductase inhibitor, is used to reduce cholesterol levels. Accumulating evidence has revealed the immunomodulatory and anti-inflammatory effects of simvastatin that prevent cardiovascular diseases. In addition, the beneficial effects of statins on fibrosis of various organs have been reported. However, the functional effect of statins on dermal fibrosis of keloids has not yet been explored. The objective of this study was to determine whether simvastatin could affect dermal fibrosis associated with keloids. We examined the effect of simvastatin on transforming growth factor (TGF)-beta 1-induced production of type I collagen, connective tissue growth factor (CTGF or CCN2), and alpha-smooth muscle actin (alpha-SMA). Keloid fibroblasts were cultured and exposed to different concentrations of simvastatin in the presence of TGF-beta 1, and the effects of simvastatin on TGF-beta 1-induced collagen and CTGF production in keloid fibroblasts were determined. The type I collagen, CTGF, and alpha-SMA expression levels and the Smad2 and Smad3 phosphorylation levels were assessed by Western blotting. The effect of simvastatin on cell viability was evaluated by assessing the colorimetric conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide. Simvastatin suppressed TGF-beta 1-induced type I collagen, CTGF, and alpha-SMA production in a concentration-dependent manner. The TGF-beta 1-induced Smad2 and Smad3 phosphorylation levels were abrogated by simvastatin pretreatment. The inhibition of type I collagen, CTGF, and alpha-SMA expression by simvastatin was reversed by geranylgeranyl pyrophosphate, suggesting that the simvastatin-induced cellular responses were due to inhibition of small GTPase Rho involvement. A RhoA activation assay showed that preincubation with simvastatin significantly blocked TGF-beta 1-induced RhoA activation. The Rho-associated coiled kinase inhibitor Y27632 abrogated TGF-beta 1-induced production of type I collagen, CTGF, and alpha-SMA. However, Y27632 had no significant effect on TGF-beta 1-induced phosphorylation of Smad2 and Smad3. In conclusion, the present study suggests that simvastatin is an effective inhibitor of TGF-beta 1-induced type I collagen, CTGF, and alpha-SMA production in keloid fibroblasts.