This study evaluated the role of crystallins in retinal degeneration induced by chemical hypoxia. Wild type, αA-crystallin (−/−), and αB-crystallin (−/−) mice received intravitreal injection of 12 nmol (low dose), 33 nmol (intermediate dose) or 60 nmol (high dose) cobalt chloride (CoCl 2 ). Hematoxylin and eosin and TdT-mediated dUTP nick-end labeling (TUNEL) stains were performed after 24 hours, 96 hours, and 1 week post-injection, while immunofluorescent stains for αA-and αB-crystallin were performed 1 week post-injection. The in vitro effects of CoCl 2 on αB-crystallin expression in ARPE-19 cells were determined by real time RT-PCR, Western blot, and confocal microscopy and studies evaluating subcellular distribution of αB-crystallin in the mitochondria and cytosol were also performed. Histologic studies revealed progressive retinal degeneration with CoCl 2 injection in wild type mice. Retinas of CoCl 2 injected mice showed transient increased expression of HIF-1α which was maximal 24 hours after injection. Intermediate dose CoCl 2 injection was associated with increased retinal immunofluorescence for both αA-and αB-crystallin; however, after high dose injection, increased retinal degeneration was associated with decreased levels of crystallin expression. Injection of CoCl 2 at either intermediate or high dose in αA-crystallin (−/−) and αB-crystallin (−/−) mice resulted in much more severe retinal degeneration compared to wild type eyes. A decrease in ARPE-19 total and cytosolic αB-crystallin expression with increasing CoCl2 treatment and an increase in mitochondrial αB-crystallin were found. We conclude that lack of α-crystallins accentuates retinal degeneration in chemically-induced hypoxia in vivo.

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tBH increases oxidative stress, increases accumulation of ROS in the ER, and upregulates expression of GRP-78 and GADD153. This supports the connection between oxidative stress and ER stress, and suggests that GRP-78 may serve a protective role in the RPE response to oxidative stress.

The protective effect of HGF may be attributed in part to the elevation of mitochondrial GSH. BSO and HGF act in concert to enhance GSH-related gene expression in stressed RPE cells.

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