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Shikun He, Nymph Chan, Jing Xu, Peng Zhou, S. J. Ryan, David. R. Hinton; The Expression Of PPAR-gamma In RPE Cells Is Epigenetically Regulated By DNA Methylation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):898.
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© ARVO (1962-2015); The Authors (2016-present)
Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) plays an important role in the negative regulation of epithelial cell differentiation and fibrosis. Recent research shows that expression of PPAR-gamma is regulated by epigenetic factors. However, the regulation of PPAR-gamma expression, especially by DNA methylation in RPE, is not fully understood. Our purpose was to investigate the expression of PPAR-gamma in human PVR membranes and the effects of DNA methylation inhibitor on the expression of PPAR-gamma in RPE cells in vitro.
Cultured early passage human fetal RPE cells and surgically excised human PVR membranes (5 cases) were used in the study. The expression of PPAR-gamma in human PVR membranes was analyzed using immunohistochemistry. The regulation of PPAR-gamma by 5-aza-2’-deoxycytidine (5-AZA, 0.1, 1, 2, uM) or Zebularine (1-6 uM) in RPE was evaluated by Western blot.The inhibitory effects of TGF-β on PPAR-gamma expression were analyzed by immunohistochemistry in cultured RPE cells after exposure to TGF-β2 (10 ng/ml) for 3 days. Chromatin immunoprecipitation (ChIP) was used to determine the methyl CpG binding protein 2 (MeCP2) binding to the genomic promoter region of PPAR-gamma.
Only scattered PPAR-gamma expression was detected in 5 human PVR membranes. Treatment with 5-AZA or Zebularine significantly increased expression of PPAR-gamma in RPE; however, PPAR-gamma expression was dramatically inhibited by the addition of TGF-β to RPE culture for 72 hours. ChIP assay showed that MeCP2 bound to the promoter region of PPAR-gamma.
PPAR-gamma expression is downregulated in human PVR. Inhibition of methylation is able to increase expression of PPAR-gamma. DNA methylation status appears to be involved in the regulation of PPAR-gamma in RPE and retinal fibrosis.
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