Abstract
Abstract: :
Purpose:Transforming growth factor–ß (TGF–ß) has been implicated as the key mediator of proliferative vitreoretinopathy, but the cellular mechanisms by which TGF–ß induces extracellular matrix protein (ECM) synthesis are not fully understood. We examined whether the mitogen–activated protein kinase (MAPK) pathway is involved in TGF–ß2–induced collagen expression in retinal pigment epithelium cells. Methods: Human retinal pigment epithelium cells, ARPE–19, were cultured and stimulated with various concentrations of TGF–ß2. The type I collagen gene (COL1A1, COL1A2) expression induced by TGF–ß2 were evaluated by real–time PCR. Synthesis of type I collagen was evaluated by the concentration of the C–terminal propeptide of type I (PICP) in the medium. The activation of MAPK pathways by TGF–ß2 was assessed by immunoblot with phospho–p38 and phospho–ERK1/2 antibodies. The role of MAPK was assessed using biochemical inhibitors. To examine the transcriptional activities of COL1A1 and COL1A2, luciferase reporter assays were also performed. Results: mRNA of COL1A1 and COL1A2, and type I collagen synthesis were activated by TGF–ß2. Both ERK and p38 MAPK pathways were also activated by TGF–ß2. The biochemical blockade of p38 MAPK activation, but not ERK activation, inhibited TGF–ß2 –induced type I collagen mRNA expression and type I collagen synthesis. Moreover, blockade of the p38 MAPK pathway inhibited the increase in both COL1A1 and COL1A2 promoter activities when induced by TGF–ß2. Conclusions: Our data have indicated that TGF–ß2 activates p38 MAPK and that p38 MAPK functions as a component in the TGF–ß2 signaling of type I collagen induction in the retinal pigment epithelium.
Keywords: extracellular matrix • retinal pigment epithelium • proliferative vitreoretinopathy