Effect of pulmonary FXR on the senescence of lung fibroblasts

Objective To investigate the effect of farnesoid X receptor (FXR) on the senescence of lung fibroblasts. Methods Male wild-type C57BL/6J mice, aged 6-8 weeks, were randomly divided into two groups: a control group and a 5 mg/kg bleomycin (BLM) induced lung fibrosis group. Both groups were compared for the expression of FXR through immunohistochemistry. In vitro cultured human embryonic lung fibroblast HFL-1 cell line was treated with a FXR agonist GW-4064, while those with fibrosis caused by transformer growth factor (TGF)-β1 were set as a positive control to estimate FXR expression in HFL-1 cells. Furthermore, HFL-1 cells were exposed to a FXR inhibitor Z-GS to observe the expression of cellular senescence markers P16, P21 and P53 by Western blot. β-galactosidase (SA-β-Gal) staining was performed to detect the β-galactosidase positive HFL-1 cell rate.Results Compared with the normal group, fibrosis increased the expression of lung cellular FXR both in vitro and in vivo. Meanwhile, in vitro Western blot and SA-β-Gal staining results showed that the addition of FXR agonist GW-4064 resulted in increased levels of P16, P21, and P53 and an increased number of SA-β-Gal positive cells. In contrast, treatment with FXR inhibitor Z-GS resulted in decreased levels of P16, P21, and P53 and a decreased number of SA-β-Gal positive cells.Conclusions FXR is involved in the senescence of lung fibroblasts. These findings provide a solid experimental foundation for further investigating the role and mechanism of FXR induced lung fibroblast senescence in promoting pulmonary fibrosis.