Simvastatin impairs smad-3 phosphorylation and modulates transforming growth factor β1-mediated activation of intestinal fibroblasts

Background: Transforming growth factor (TGF) beta 1, acting through the smad pathway, is critical to fibroblast-mediated intestinal fibrosis. Simvastatin exhibits antifibrotic properties. This study assessed the effects of simvastatin on TGF-beta 1-mediated intestinal fibroblast activation. Methods: Human intestinal fibroblasts were activated with TGF-beta 1 with or without simvastatin or the cholesterol pathway intermediates farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). Collagen-I alpha 2 expression was assessed by reverse transcriptase-polymerase chain reaction. Connective tissue growth factor (CTGF) and smad phosphorylation were evaluated by western blot, and plasminogen activator inhibitor (PAI) 1 activity by enzyme-linked immunosorbent assay. Fibroblast filamentous (F)-actin accumulation was assessed by confocal microscopy and contraction by a fibroblast-populated collagen lattice (FPCL) model. Results: TGF-beta 1 treatment of fibroblasts induced smad-2/3 phosphorylation, CTGT and collagen-I alpha 2 production, F-actin bundling, FPCL contraction and PAI-1 activation. Pretreatment with simvastatin inhibited the induction of CTGT and collagen-I alpha 2, PAI-1 activation, F-actin bundling and FPCL contraction. The inhibitory effect of simvastatin on PAI-1 activation was reversed by GGPP and FPP. Simvastatin pretreatment inhibited TGF-beta 1-mediated phosphorylation of smad-3. Conclusion: Simvastatin abrogates TGF-beta 1-mediated intestinal fibroblast activation by inhibition of smad-3 phosphorylation. These findings offer a mechanism for the antifibrotic effects of simvastatin and a therapeutic entry point in the treatment of intestinal fibrosis.