Downregulation of AlphaB-crystallin in Retinal Pigment Epithelial Cells Exposed to Diabetes-related Stimuli In Vivo and In Vitro.

Abstract

AlphaB-crystallin plays a pivotal role in many diseases. However, the involvement of alphaB-crystallin in retinal pigment epithelial (RPE) cells with diabetes stimuli remains unknown. The aim of this study is to examine the alterations of RPE cells and alphaB-crystallin expression in diabetic models in vivo and in vitro. Diabetic conditions in mice were induced by streptozotocin (STZ). The thickness of the RPE/choroid complex was measured by optical coherence tomography (OCT). Periodic acid-Schiff (PAS) staining was used to investigate the choriocapillaris in histological sections of murine eyeballs and oxidative stress was evaluated using immunofluorescence with anti-4-hydroxynonenal (HNE) antibody. AlphaB-crystallin expression was examined in the RPE/choroid complex using ELISA. Real-Time PCR was performed to evaluate the alphaB-crystallin expression in cultured human RPE cells with high glucose or following advanced glycation end-products (AGE) stimulation. In diabetic mice, OCT-based RPE/choroidal layers were thickened 2 months after STZ stimulation, where PAS-positive dilated choriocapillaris was noted. Immunoreactivity of 4-HNE was strongly observed in the RPE layer, from which a significant number of RPE cells was lost. Meanwhile, alphaB-crystallin expression in 2-month STZ mice was significantly lower compared to controls. In accordance with these results, in vitro data showed that the alphaB-crystallin expression was also significantly lower in RPE cells with high glucose or following AGE stimulation compared to untreated cells. In both types of diabetic models the expression of alphaB-crystallin was found to be downregulated in RPE cells and was associated with increased levels of oxidative stress.