BACKGROUNDBleomycin-induced fibrosis is extensively used to model aspects of the pathogenesis of interstitial pulmonary fibrosis. This study aimed to determine the benefic effects and mechanisms of simvastatin on bleomycin-induced pulmonary fibrosis in mice.

METHODSBleomycin-induced pulmonary fibrosis mice were administered with simvastatin in different doses for 28 days. We measured inflammatory response, fibrogenic cytokines and profibrogenic markers in both bleomycin-stimulated and control lungs, and correlated these parameters with pulmonary fibrosis.

RESULTSSimvastatin attenuated the histopathological change of bleomycin-induced pulmonary fibrosis and prevented the increase of lung hydroxyproline content and collagen (I and III) mRNA expression induced by bleomycin. Moreover, simvastatin down-regulated the increased expression of transforming growth factor-beta1 (TGF-beta1) and connective tissue growth factor (CTGF) induced by bleomycin at both gene and protein levels. Simultaneously, the accumulation of neutrophils and lymphocytes and the increased production of tumor necrosis factor-alpha (TNF-alpha) in bronchial alveolar lavage fluid were inhibited by simvastatin in early inflammatory phase after bleomycin infusion. The higher dose of simvastatin was associated with a more significant reduction in these inflammatory and fibrotic parameters. Furthermore, the inactivation of p38, RhoA and Smad2/3 signaling pathways was observed during simvastatin administration.

CONCLUSIONSSimvastatin attenuated bleomycin-induced pulmonary fibrosis, as indicated by decreases in Ashcroft score and lung collagen accumulation. The inhibitory effect of simvastatin on the progression of pulmonary fibrosis may be demonstrated by reducing inflammatory response and production of TGF-beta1 and CTGF. These findings indicate that simvastatin may be used in the treatment of pulmonary fibrosis.