A PPAR-Gamma Agonist Rosiglitazone Suppresses Fibrotic Response in Human Pterygium Fibroblasts by Modulating the p38 MAPK Pathway.

PURPOSE: Fibroblast activation may play an important role in pterygium progression. Synthetic peroxisome proliferator-activated receptor γ (PPAR-γ) ligands have been shown to be effective antifibrotic agents against transforming growth factor β1 (TGF-β1) induced fibrosis in several tissues. We aimed to investigate the antifibrotic effects of the PPAR-γ ligand rosiglitazone in pterygium fibroblasts and the underlying mechanisms.

METHODS: Profibrotic activation was induced by TGF-β1 in primary cultured human pterygium fibroblasts and the effect of rosiglitazone treatment on α-smooth muscle actin (α-SMA), and extra cellular matrix proteins synthesis was detected by western blotting, real-time PCR, immunostaining, and flow cytometry. Pharmaceutical inhibition of PPAR-γ receptor was used to determine the dependency or otherwise of rosiglitazone's action on PPAR-γ signaling. Major signaling pathways downstream of TGF-β1 were investigated by western blotting to assess their possible association with rosiglitazone's effect. Cell viability and apoptosis were investigated to assess drug-induced cytotoxicity, and the effect of rosiglitazone treatment on cell migration was further determined.

RESULTS: α-SMA and fibronectin synthesis induced by TGF-β1 were suppressed by rosiglitazone treatment in a dose-dependent manner. Rosiglitazone also inhibited intrinsic TGF-β1 expression. Smad2/3, ERK1/2, and P38 pathways were activated in response to TGF-β1. Rosiglitazone suppressed TGF-β1-induced P38 MAPK activation, while ERK1/2 and Smad2/3 signaling remained unaffected. The observed antifibrotic effect of rosiglitazone was not affected by the PPAR-γ antagonist GW9662, indicating it is not PPAR-γ dependent. Rosiglitazone also inhibited the proliferation and migration of pterygium fibroblasts.

CONCLUSIONS: Rosiglitazone suppresses TGF-β1-induced myofibroblast activation and extra cellular matrix synthesis in pterygium fibroblasts at least partly through the modulation of the p38 MAPK pathway.