Background: Statins are the most commonly prescribed drugs for the treatment of hypercholesterolemia. Statins exert not only lipid-lowering but also other cellular effects, including antifibrotic properties. The purpose of this study was to determine the effect of simvastatin on transforming growth factor (TGF)-beta-1-induced myofibroblast differentiation and collagen production in nasal polyp-derived fibroblasts (NPDFs) and to verify the mechanism of the effect of simvastatin in TGF-beta-1-induced myofibroblast differentiation in NPDFs.
Methods: NPDFs were pretreated with simvastatin with or without mevalonate or Y-27643 for 2 hours before induction by TGF-beta-1. The expression of alpha-smooth muscle actin (SMA) and collagen type IV mRNA was determined by a reverse transcription-polymerase chain reaction, and the expression of alpha-SMA protein was determined by immunofluorescent cytochemical staining. Total soluble collagen production was analyzed by the SirCol collagen dye-binding assay (Biocolor, Belfast, U.K.). Phosphorylation of Smad 2/3 was evaluated by Western blot analysis.
Results: In TGF-beta-1-induced NPDFs, simvastatin significantly inhibited the expressions of α-SMA and collagen type IV mRNA and reduced alpha-SMA and collagen protein levels. Pretreatment with mevalonate reversed the effect of simvastatin. The expression of alpha-SMA mRNA and protein was significantly decreased by pretreatment with Y-27632. The TGF-beta-1-induced expression of pSmad 2/3 protein was notably decreased by pretreatment with simvastatin.
Conclusion: We showed that simvastatin inhibits TGF-beta-1-induced myofibroblast differentiation (expression of alpha-SMA) and collagen production in NPDFs and Rho/Rock and TGF-β/Smad signaling is involved as an underlying mechanism. The results of our study suggest that simvastatin is a possible candidate for the suppression of nasal polyp formation.