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  • Title: Enhanced HtrA2/Omi expression in oxidative injury to retinal pigment epithelial cells and murine models of neurodegeneration.
    Author: Ding X, Patel M, Shen D, Herzlich AA, Cao X, Villasmil R, Klupsch K, Tuo J, Downward J, Chan CC.
    Journal: Invest Ophthalmol Vis Sci; 2009 Oct; 50(10):4957-66. PubMed ID: 19443712.
    Abstract:
    PURPOSE: To investigate the role of HtrA2/Omi, a nuclear-encoded mitochondrial serine protease with a proapoptosis function, under H(2)O(2)-induced oxidative stress in human RPE, in the Ccl2(-)(/)(-)Cx3cr1(-)(/)(-) double-knockout (DKO) mouse retina, and the HtrA2/Omi-deficient mice. METHODS: Oxidative stress was induced in ARPE-19 cells by 1 mM H(2)O(2) for 2 hours. HtrA2/Omi and caspase-3 expression was evaluated using RQ-PCR, immunohistochemistry, or Western blot. Cell viability was detected by MTT assay. HtrA2/Omi expression in the subcellular components and activated caspase-3 were measured. These processes were also evaluated in cells treated with UCF-101, an HtrA2/Omi inhibitor or in cells subjected to RNAi against HtrA2/Omi. Oxidative stress was assayed and compared in retinas of DKO and wild-type (WT) mice by determining serum NADPH oxidase subunits and nitrite levels. Transmission electron microscopy was used to view the retinal ultrastructure of the HtrA2/Omi-deficient mice. RESULTS: H(2)O(2)-induced oxidative damage resulted in HtrA2/Omi translocation from mitochondria to cytosol, leading to RPE cell apoptosis via a caspase-mediated pathway. Treatment of RPE cells with UCF-101 reduced the cytosolic translocation of HtrA2/Omi, attenuated caspase-3 activation, and decreased apoptosis. After specific HtrA2 downregulation, increased cell viability was measured in H(2)O(2)-treated ARPE-19 cells. Retina of DKO mice exhibit increased oxidative stress and upregulation of HtrA2/Omi. Fewer and abnormal mitochondria were found in HtrA2/Omi(-)(/)(-) photoreceptors and RPE. CONCLUSIONS: These findings suggest that HtrA2/Omi is related to RPE apoptosis due to oxidative stress, which may play an important role in the integrity of mitochondria and the pathogenesis of AMD.
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