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R. Sharma, P. Chaudhary, A. Sharma, R. Vatsyayan, S. Awasthi, Y. C. Awasthi; Role of 4-Hydroxynonenal in Oxidative Stress Induced Apoptotic Signaling in Retinal Pigment Epithelial (RPE) Cells. Invest. Ophthalmol. Vis. Sci. 2010;51(13):6000.
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© ARVO (1962-2015); The Authors (2016-present)
Oxidative stress induced lipid peroxidation (LPO) has been implicated in the etiology of age related macular degeneration. Previous studies have shown that exposure of cells to radiation and chemicals significantly elevate the intracellular levels of highly reactive LPO end product- 4-hydroxynonenal (4-HNE) which has been shown to be involved in the pathogenesis of ocular diseases. Recently, it has also been demonstrated that 4-HNE modulates stress induced signaling in mammalian cells through its interaction with the components of both extrinsic and intrinsic apoptotic signaling pathways. However, the contributions of 4-HNE in the toxic and apoptotic response of physico-chemical agents are not clear. During present studies, we have investigated the role of 4-HNE in the mechanisms of oxidative stress induced signaling in RPE cells exposed to UV-radiation and H2O2.
RPE-28 cells were exposed separately to UV-C (1.0 J/cm2) and H2O2 (0-1000µM) for different time intervals. The effect of UV-C and H2O2 on i. cell viability was measured by MTT assay, ii. intracellular 4-HNE levels by spectrophotometry iii expression of apoptosis related proteins by Western blot analysis. RPE cells were also stably transfected with cDNA of human glutathione transferase A4 (hGSTA4) isozymeand the effects of UV-C and H2O2 on cell viability, extent of lipid peroxidation, and expression of apoptosis related proteins were compared in empty vector and hGSTA4-transfected cells.
Results of these studies showed that both UV-C and H2O2 induced cytotoxic response in RPE cells in a dose dependent manner. Exposure of RPE cells to UV-C (5-20min,1.0 J/cm2) and H2O2 (100-500µM) caused an increase in intracellular 4-HNE levels and apoptosis which was found to be accompanied with the activation and stabilization of p53, and up regulation of the down stream target genes Bax and p21, and cleavage of PARP. These effects of UV-C and H2O2 were inhibited in cells transfected with 4-HNE metabolizing isozyme, hGSTA4-4.
We conclude that during exposure of RPE cells to UV-C and H2O2, endogenously generated 4-HNE significantly contributes to their toxic effects which could be ameliorated by the overexpression of GSTA4-4 in these cells.
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