Fenofibrate inhibits TGF-β-induced myofibroblast differentiation and activation in human lung fibroblasts in vitro.

Fenofibrate (FF), a peroxisome proliferator-activated receptor alpha (PPAR-α) agonist and a lipid-lowering agent, can decrease experimental pulmonary fibrosis. However, the mechanisms underlying the anti-fibrotic effect of FF remain unknown. Hence, this study was conducted to evaluate the effects of FF on transforming growth factor-beta (TGF-β)-induced myofibroblast differentiation and activation in lung fibroblasts. The results showed that FF inhibited alpha-smooth muscle actin (α-SMA) and connective-tissue growth-factor expression, collagen production, cell motility, SMAD3 phosphorylation and nuclear translocation, and metabolic reprogramming in TGF-β-exposed cells. The inhibitory effect of FF did not decrease with the addition of a PPAR-α antagonist. Moreover, the inhibitory effect given by FF could not be reproduced with the addition of an alternative PPAR-α agonist. FF inhibited mitochondrial respiration. However, rotenone, a complex I inhibitor, did not suppress TGF-β-induced myofibroblast differentiation. Furthermore, the TGF-β-induced nuclear reduction of protein phosphatase, Mg2+ /Mn2+ -dependent 1A (PPM1A), a SMAD phosphatase, was inhibited by FF. These results showed that FF suppressed TGF-β-induced myofibroblast differentiation and activation independent of PPAR-α activation and impaired mitochondrial respiration. In conclusion, this study provides information on the effects of FF on anti-TGF-β mechanisms.