Experimental Study On Role Of Mitochondrial Reactive Oxygen Species In Diabetic Cataract And Intervention Of Green Tea Polyphenols

Aim:By vivo and vitro tests to investigate the preventive effects of Tea Polyphenols (TP) against hyperglycemia on rat lens epithelium cell (LEC), and to assess the potential effect and mechanism of TP in diabetic cataract organism.Methods:Rat lens epithelium cells were cultured in vitro in media with 5mmol/l glucose and 30mmol/l glucose concentration to simulate the hyperglycemia in vivo. Add 0.1?mol/1 and 0.3?mol/l TP to 30mmol/l glucose solution. The cell viability was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Flow cytometry was used to analyze the cell death rate (CDR) and mitochondrial membrane potential (MMP). The amount of mitochondrial reactive oxygen species (ROS) was examined and the expression of endocytoplasmic reticulum in rat LEC was detected with immunocytochemistry and immunofluorescence. All the results were used to analyze the effects of TP on LEC damage induced by hyperglycemia.. In vivo tests, by injected STZ through vena caudalis to establish rat model of dibetes mellitus.Wistar rats were divided into normal group, STZ induced diabetes mellitus group (STZ-DM) and TP intervened diabetes mellitus group(TP-DM). By HE dyeing?the ultramicrostructure of was observed with electron microscope (SEM). Some biochemical indicators'activity of rat lens in each group such as reduced glutathione hormone(GSH)?glutathione reductase(Gr) and catalase(CAT) was determined. RT-PCR was used to detected the expression of UCPs?MnSOD mRNA of rat lens in each group. investigate the preventive effects of Tea Polyphenols (TP) against STZ induced diabetes mellitus rat lens epithelium cell (LEC).Results:Rat LEC cultured in high concentration glucose medium lost their inherent characteristics and decreased sharply. The MMP in rat LEC decreased and ROS in mitochondria increased significantly. Whereas, the cells cultured in high concentration glucose interfered with TP maintained good morpha and viability. The MMP, ROS and endocytoplasmic reticulum in cells turned back to balance as cultured in normal medium. The results in media with different TP concentrations were almost the same. vitro test indicate in 8 weeks the models established,76.2% of diabetic rat lenses in STZ-DM group showed?class opacity, And that there were only 30% of diabetic rat lens showed?class opacity in TP-DM group,This opacity developed inevidently.In 12 weeks, lens of STZ-DM group were total opacity, and only 61.1% of the lens in TP-DM group showed?class opacity. When the ultramicrostructure of rat lens was observed with SEM, we found that the crystalline fibers were seriously damaged in STZ-DM group, but in TP-DM group the damages were obviously lessened. We observed the morphous of lens cells through HE dyeing and found that there were a great deal of cell organelles had not degraded in crystalline fiber cells of STZ-DM group, and the region with no cell organelle shrank. Nevertheless, we observed the reverse results in TP-DM group.The activity of CAT and the contents of GSH of lens significantly decreased in STZ-DM group, but remained original level in TP-DM group. The expression of UCP2 and MnSOD mRNA gradually decreased in STZ-DM group, but increased and retained at a relevantly high level in TP-DM group.Conclusion:TP can delay or prevent the changing and apoptosis of the rat LEC, which proves that it can inhibit the LEC damage induced by hyperglycemia. TP is a potential medicine for therapy of diabetic cataract and the healing mechanism may be related to its direct inhibition of rat LEC apoptosis. vivo test indicate TP can significantly lessen the ultrastructural lesion of diabetic rat lens, maintain normal degradation of cell organelle, TP can maintain the CAT activity and GSH contents, retain normal redox state of lens and even reverse the decrease of antioxidase activity. TP can also up-regulate and maintain at a high level of the expression of UCP2 and MnSOD mRNA in diabetic rat lens. Accordingly, it can influence the elimination of ROS in lens, prevent or delay the opacity of lens, and significantly delay the occurrence of diabetic cataract.