May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
The Role of HtrA2/Omi in Oxidative Injury to Human Retinal Pigment Epithelial Cells and in Eyes With Age-Related Macular Degeneration
Author Affiliations & Notes
  • X. Ding
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • M. Patel
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • A. A. Herzlich
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • D. Shen
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • R. Fariss
    NIH, Bethesda, Maryland
    Imaging Core, NEI,
  • J. Tuo
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • C.-C. Chan
    NIH, Bethesda, Maryland
    Immunopathology Section,LI, NEI,
  • Footnotes
    Commercial Relationships  X. Ding, None; M. Patel, None; A.A. Herzlich, None; D. Shen, None; R. Fariss, None; J. Tuo, None; C. Chan, None.
  • Footnotes
    Support  NEI Intramural Research Program
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 1369. doi:https://doi.org/
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      X. Ding, M. Patel, A. A. Herzlich, D. Shen, R. Fariss, J. Tuo, C.-C. Chan; The Role of HtrA2/Omi in Oxidative Injury to Human Retinal Pigment Epithelial Cells and in Eyes With Age-Related Macular Degeneration. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1369. doi: https://doi.org/.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose: : HtrA2/Omi is a nuclear-encoded mitochondrial serine protease with a pro-apoptotic role in caspase dependent cell death. Given that oxidative stress is one of the most important suspected risk factors for age-related macular degeneration (AMD), we investigated the role of HtrA2/Omi in ARPE-19 cells exposed to hydrogen peroxide-induced oxidative stress and in archived eyes with AMD.

Methods: : Oxidative stress was induced in ARPE-19 cells by 1mM hydrogen peroxide for 2 hours. Expression of HtrA2/Omi in these cells was evaluated using real-time RT-PCR, immunohistochemistry, and western blot analysis. XIAP, caspase-3 and caspase-9 expression was evaluated by immunohistochemistry or western blot analysis. Cellular expression of HtrA2/Omi, activated caspase-3, and activated caspase-9 were also measured after adding UCF-101, an HtrA2/Omi inhibitor, to ARPE-19 cells under H2O2-induced oxidative stress. Cellular expression of HtrA2/Omi, activated caspase-3 and activated caspase-9 were measured. Cell viability was detected by MTT assay. HtrA2 was localized in the retina of AMD and non-AMD control archived eyes by immunohistochemistry.

Results: : HtrA2/Omi mRNA was upregulated after 2 hour treated with 1mM H2O2. H2O2-induced oxidative stress led to translocation of HtrA2/Omi from mitochondria to the cytosol, neutralization of XIAP, and increased levels of activated caspase-3 and activated caspase-9 in the cytosol. UCF-101 reduced the upregulation of HtrA2 in cytosol and in turn, exerted significant protective effects including inhibition of caspase-9 and caspase-3 activities and decreased cell death. HtrA2/Omi was found in normal retina and was markedly decreased in both wet and dry AMD lesions, especially in the photoreceptor inner segments, where abundant mitochondria reside.

Conclusions: : H2O2-induced oxidative damage results in HtrA2/Omi relocation from mitochondria to cytosol, where it induces RPE cell apoptosis via a caspase-mediated pathway, possibly resulting in RPE degeneration. UCF-101, a specific HtrA2/Omi inhibitor, reduces expression and cytosolic translocation of HtrA2/Omi, attenuates caspase-3 and caspase-9 activation, and decreases apoptosis of RPE cells. HtrA2/Omi is highly expressed in normal retina, but is decreased in late-stage lesions from both wet and dry AMD, where RPE and photoreceptor are lost. Therefore, HtrA2/Omi-mediated RPE apoptosis due to oxidative stress might play an important role in AMD pathogenesis.

Keywords: apoptosis/cell death • retinal pigment epithelium • age-related macular degeneration 
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