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Hongli Wu, Marjorie Lou; Age-dependent Biochemical Changes in the Retina of Glutaredoxin 2 (Grx2) Knockout Mice. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2009.
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Glutaredoxin 2 (Grx2) is a mitochondrial isozyme of thioltransferase in the oxidoreductase family that is a key regulator of redox homeostasis in the cells through dethiolation of protein-glutathione mixed disulfides (PSSG). Previously, we have found that Grx2 gene knockout (KO) mouse developed cataract faster during aging, and that the lens epithelial cells were more sensitive to oxidative stress-induced apoptosis. In this study, we investigated the presence of Grx2 in the mouse retina, and the potential biochemical changes in the mouse retina with Grx2 KO during aging.
Grx2 gene KO mouse model was used to study the age-dependent changes in the retina. Neruo-retina tissues from 1, 7, and 16 months old Grx2 KO mice were surgically removed. Five pairs of the retina tissues were pooled, homogenized with a glass-to-glass homogenizer. The mitochondrial fraction was isolated following published procedure. Retina from age-matched wild type (WT) littermates were processed in parallel and used as the control. The levels of glutathione (GSH) and protein thiols (PSH) were each quantified by DTNB colorimetric method. PSSG were analyzed using Western blot with GSH-specific antibody. Mitochondrial complex I, complex IV activity and ATP levels was each measured using microplate assay kit.
Grx2 was found in the neuro-retinal tissues with higher protein level and enzyme activity than that of the lens from the same animal. Grx2 was absent in the retina of the Grx2 KO model. With increasing age, both WT and Grx2 KO groups showed a gradual decrease in GSH and PSH levels, but this alteration was more exaggerated in the Grx2 KO group. Glutathionylated protein or PSSG accumulation in the retina was more prominent in the Grx2 KO mice than that of the WT controls. Remarkably, in comparison with the WT control, the retina in Grx2 gene KO mice showed extensive loss (50%) in complex I and complex IV enzyme activities. The ATP pool in the same Grx2 null retina was correspondingly suppressed to less than 30% as that of the WT control.
Grx2 was found in the retina and deletion of its gene affected the redox homeostasis and compromised the mitochondrial function. It is likely that mitochondrial dethiolase Grx2 may play an important role in regulating retinal function.
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