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Zeev Dvashi, Ayala Pollack, ; Protective effect of TGF-b1 in RPE cells upon oxidative stress as a model for oxidative damage during dry AMD. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1805.
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The aim of the study was to investigate the role of the TGF-b1 (transforming growth factor beta1) on the survival and proliferation of human RPE (retinal pigment epithelium) cell culture as a model for the dry form of AMD(age-related macular degeneration). TGF-beta1 was previously reported to be involved in the regulation of RPE proliferation on one hand, and in the regulation of cell senescence, on the other. Upon TGF-b1 stimulation multiple signaling cascades are activated, including: Smads, TAK1 (transforming growth factor β-activated kinase 1), stress kinases such as p38 MAPK and phosphatases such as PTEN. Therefore, TGF-b1 can potentially lead to many variations in cellular responses depending on the cell type. The goal of the present study was to delineate TGF-beta1 involvement in the RPE cells fate upon oxidative stress for better understanding of diseases associated with RPE atrophy.
To investigate the effect of TGF-b1 on oxidative stress-induced by H2O2, cultured human RPE cells were pre-treated with TAK1 inhibitor (5Z-7-oxozeaenol 1mM) or with TGF-b1 receptor kinase inhibitor (SB431542 1mM) following exposure to 1mM hydrogen peroxide (H2O2) for 1 hours or treated with or without 2.5 ng/mL TGF-b1 for 24.Cell were harvested, stained with propidium iodide (PI) and subjected to FACS analysis. For proliferation assays, cells were seeded and medium was replaced to serum free medium. After 16 hours of starvation cells were treated with TGF-b1, TAK1 or TGF-b1 receptor kinase inhibitors, followed by XTT assay.
Treatment of H2O2, with or without the addition of TGF-b1, enhanced the number of cells demonstrating oxidative damage and apoptosis (from 0.2% to 1.66% of the cells). However, inhibition of the TGF-b1 substrate TAK1 or the receptor activity increases cell apoptosis to 6% and 7.8%, respectively. Moreover, TGF-b1 stimulation did not affect cell proliferation, although inhibition of the TAK1 reduces cells propagation.
This study demonstrates that TGF-b1 may protect RPE cells via TAK1 activation. The progressive oxidative damage of macromolecules resulting from exposure of cellular components to oxidative stress has long been implicated in aging and AMD diseases. The present study suggests a novel approach to reduce RPE cell death upon oxidative stress by activating TAK1, aiming at halting the progression of dry AMD.
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