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S. He, M. Jin, E. Barron, S.J. Ryan, D.R. Hinton; GRP78 Expression in RPE Cells and in Eyes with Age-related Macular Degeneration . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1730.
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Purpose: Induction of glucose-regulated proteins (Grps) in the endoplasmic reticulum (ER) is one of the protection mechanisms used by the cell to adapt to oxidant stress. In this study, we evaluated the expression of Grp78 and its regulation by tert-butyl hydroperoxide (tbh) in human RPE cells and the expression of Grp78 in retinas with age-related macular degeneration (AMD). Methods: We analyzed Grp78 expression in normal human fetal and adult retinas, cultured adult human RPE cells and four retinas with AMD by immunohistochemistry. The effects of tbh (30-200uM) on Grp78 protein and mRNA expression in human RPE cells were studied using immunohistochemical staining, Western blot, and Real Time polymerase chain reaction (PCR).Results: Sections of fetal retinas were negative for Grp78. Adult retinas showed moderate cytoplasmic Grp78 staining in the RPE and choroid. Sections of retinas from patients with AMD showed focal localized Grp78 immunoreactivity in the basal portion of the drusen however the overlying RPE lacked Grp78 staining. Grp78 mRNA and protein expression in cultured fetal RPE cells was dramatically upregulated by treatment with tbh.Conclusion: RPE show increased expression of Grp78 in normal aging in vivo, and when stressed with tbh in vitro. The altered expression of Grp78 in AMD suggests the need for further studies evaluating the mechanism and effect of this stress response.
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