Effect of Anti-fibrotic Drug (Pirfenidone) on TGF-β Signaling Pathway in Ocular Fibrotic Disorders

Abstract

Purpose: Transforming growth factor-β (TGF-β) plays a key role in transforming retinal pigment epithelial (RPE) cells into mesenchymal fibroblastic cells, which are implicated in fibrotic disorders of the retina. Herein, the effect of pirfenidone, a novel anti-fibrotic agent, on TGF-β1-mediated fibrogenesis in the human RPE cell line (ARPE)-19 was tested.

Methods: The effect of pirfenidone on the TGF-β1-induced phenotype in ARPE-19 cells was measured with immunocytochemistry as the change in F-actin. Fibronectin and collagen production was measured with enzyme-linked immunosorbent assay, and cell migration activity was investigated using a scratch assay. Immunoblot analyses of cofilin, Smad protein (Smad) 2/3, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and extracellular signal related kinase expression were conducted to elucidate the cell signaling networks that contribute to the anti-fibrotic effect of pirfenidone.

Results: Treatment with TGF-β1 induced typical phenotypic changes such as formation of stress fiber running parallel to the long axis of cells, and enhanced migration and production of extracellular matrix components such as collagen type I and fibronectin. This fibroblast-like phenotype induced by TGF-β1 was significantly inhibited by pretreatment with pirfenidone in a dose-dependent manner. Pirfenidone inhibited TGF-β signaling by preventing nuclear accumulation of active Smad2/3 complexes rather than phosphorylation of Smad2/3.

Conclusions: These results collectively provide a rational background for future evaluation of pirfenidone as a potential anti-fibrotic agent for treating proliferative vitreoretinopathy and other fibrotic retinal disorders.