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X. Yang, C. Luo, D. W. Powell, M. H. Kuehn, G. Tezel; Regulation of Complement Factor H in Human Glaucoma and Oxidative Stress. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2671.
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To better understand the role of complement activation in glaucomatous neurodegeneration, this study focused on the altered regulation of complement factor H (CFH) recently detected in human glaucoma.
Human retinal protein samples were obtained from donors with (n:10) or without (n:10) glaucoma. Protein expression was analyzed by label-free quantitative LC-MS/MS, and bioinformatic analysis of the MS/MS data utilized the Ingenuity Pathways Analysis. For further validation of the proteomic findings, quantitative western blot analysis was performed using a specific CFH antibody, and the extent and cellular localization of CFH immunolabeling were determined in an additional group of human donor eyes with glaucoma (n:34) and age-matched controls (n:20). In addition, in vitro experiments were performed to determine the regulation of CFH expression by oxidative stress using primary cultures of rat RGCs and glia incubated in the presence and absence of hydrogen peroxide.
Quantitative proteomic analysis of glaucomatous samples supported a trend toward down-regulation of CFH expression. Western blot analysis validated an approximately two-fold decrease in retinal CFH expression in 8 out of 10 glaucomatous samples relative to non-glaucomatous controls (p<0.01). Immunohistochemical findings were also consistent with a prominent down-regulation of CFH expression in the glaucomatous human retina. Double immunofluorescense labeling revealed that both GFAP-positive macroglia and NeuN- and Brn-3-positive RGCs were immunolabeled for CFH in the human retina, while neuronal CFH immunolabeling exhibited an over two-fold decrease in the glaucomatous eyes relative to controls. Findings of in vitro experiments using flow cytometry, western blot analysis, and immunocytochemistry demonstrated that CFH expression is down-regulated by oxidative stress. Bioinformatic analysis highlighted functional networks associated with the regulation of complement activation in glaucoma.
These findings support the possibility of an intrinsic deficiency in the regulation of complement activation under oxidative stress evident in glaucomatous tissues. Such a dysregulation in the complement-mediated tissue cleaning/healing process in glaucoma may lead to an uncontrolled complement attack facilitating the progression of neurodegeneration by secondary injury. Better understanding of cellular mechanisms involved in the regulation/dysregulation of immune activity in glaucoma can provide neuroprotective treatment possibilities using immunomodulation.
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