Changes in Gene Expression Profile of Early Diabetic Cataract Lenses of Rat and their Potentia Application

Abstract

Abstract: : Purpose: Osmotic stress and oxidative stress are causative factors in the development of diabetic cataract. Particular class of molecules have been studied on diabetic cataract, however, many factors may be related with the induction and progression of diabetic cataract. In the present study, we have analyzed the gene expression patterns of normal lens, and streprozotocine (STZ)-induced diabetic cataract by microarray analysis and by targeting specific expressed genes involved in anti-oxidative stress- and apoptosis-related genes. We also report bcl-2 related, down-regulation of lens epithelium-derived growth factor (LEDGF) and anti-oxidant protein 2 (AOP2) in STZ-induced cataract. Methods: All animal experiments followed the ARVO Statement for the Use of Animal in Ophthalmic and Vision Research. We used 4 week-old, Sprague-Dawley albino rats. These rats received a single intraperitoneal injection of 80mg/kg STZ after fasting overnight. These STZ-injected rats were given ad libitum access to regular chow MF for 4 or 12 weeks. At 4^th week after STZ-injection, all rats had blood glucose levels>600mg/dl. 8 weeks-old, rats were studied together, as control animals. On 4^th week after STZ injection, lenses were removed and total RNA from each sample was extracted. Labeled cDNA was hybridized to the Atlas^TM Glass Rat 1.0 Arrays (Clontech) following company’s protocol. The 1081 genes were normalized for overall background and compared on each slide using Atras^TM Iris software. The –fold change in expression in STZ group versus control group was calculated using Atras^TM Iris software. Data were confirmed by Reverse-transcription (RT)-PCR and protein blot. LEDGF and AOP2 expression in STZ-induced cataract were examined using protein blot. Results: Many genes on the cDNA microarray were up or down-regulated in STZ-induced, early diabetic lenses. Bcl-2 and protein kinase C delta mRNAs were up-regulated and heat shock protein (hsp)-27, LEDGF and AOP mRNAs were down-regulated in STZ-induced diabetic cataract. Bcl-2 protein as well as mRNA were also up-regulated at 4^th week after STZ-injection, however at 12^th week after STZ-injection, they were decreased in cataractous lenses of diabetic rats. Conclusions: Up-regulation of bcl-2 may cause the down regulation of LEDGF. LEDGF regulates the down regulation of AOP2 and hsp-27 increasing oxidative stress in early diabetic lenses. The down regulation of bcl-2 in progressed diabetic lenses may cause the apoptosis and progress cataractous changes in diabetic lenses.

Keywords: cataract • diabetes • oxidation/oxidative or free radical damage