Interventional Effect And Mechanism Of Selenium On The Galactose Cataract

Galactose cataract and diabetic cataract are together called “sugar cataract”.Galactose cataract rats,as experimental animal models,are widely used in investigating mechanisms of sugar cataract formation and screening for anti-cataract drugs.Previous researches have proved galactose cataract formation is closely related to lens epithelial cell apoptosis and oxidative damage in lens.Selenoprotein R(SelR),as the only selenoprotein in methionine sulfoxide reductase family(Msrs),has been reported to play an important role in protecting cells against oxidative damage.However,the action mechanism of SelR and some selenium supplements such as Na2SeO3 and ebselen in preventing or slowing cataract onset and progression remains virtually unclear.In this thesis,we used human lens epithelial(hLE)cell line SRA01/04 and D-galactose-induced cataractous rats to observe SelR expressions in hLE cells and rat lenses,and investigate SelR and selenium roles in protecting lens cells against galactose induced oxidative injury and inhibiting apoptosis,and so on.(1)In order to investigate the roles of SelR in protecting human lens epithelial(h LE)cells against damage,the influences of SelR gene knockdown on D-galactose-induced apoptosis in hLE cells were studied.The results showed that both D-galactose and SelR gene knockdown by siRNA independently induced oxidative stress.When SelR-gene-silenced h LE cells were exposed to D-galactose,glucose-regulated protein 78(GRP78)protein level was further increased,mitochondrial membrane potential was significantly decreased,accompanied by a release of mitochondrial cytochrome c.At the same time the apoptosis cells percentage and the caspase-3 activity were visibly elevated in hLE cells.These results suggested that SelR might protect h LE cell mitochondria and mitigating apoptosis in hLE cells against oxidative stress and endoplasmic reticulum(ER)stress induced by D-galactose,implying that selenium as a micronutrient may play important roles in hLE cells.(2)The present study was designed to evaluate the anti-cataract effects and the underlying mechanisms of selenite and ebselen supplementation on galactose induced cataract in rats.Transmission electron microscopy(TEM)images of lens fiber cells(LFC)and lens epithelial cells(LEC)were observed in D-galactose-induced experimental cataractous rats treated with or without selenite and ebselen,also redox homeostasis and expression of proteins such as selenoprotein R(SelR),15 kD selenoprotein(Sep15),superoxide dismutase 1(SOD1),catalase(CAT),?-crystallin protein,aldose reductase(AR)and Glucose-regulated protein 78(GRP78)were estimated in the lenses.The results showed that D-galactose injection injured rat lens and resulted in cataract formation;however,selenite and ebselen supplementation markedly alleviated ultrastructural injury of LFC and LEC.Moreover,selenite and ebselen supplementation could mitigate the oxidative damage in rat lens and increase the protein expressions of SelR,Sep15,SOD1,CAT and ?-crystallin,as well as decrease the protein expressions of AR and GRP78.Taken together,these findings for the first time reveal the anti-cataract potential of selenite and ebselen in galactosemic cataract,and provide important new insights into the anti-cataract mechanisms of selenite and ebselen in sugar cataract.(3)When SD rats were intraperitoneally injected with 10 g/kg BW D-galactose for 30 days,nuclear cataract was apparently formed;the D-galactose rats were intraperitoneally injected with Na2SeO3 or ebselen at the same time once a day for 30 days,then the rats were sacrificed by cervical dislocation,and the livers,kidneys and brains were used for the following detections.Measurement kits were used to estimate MDA,PC,TSH contents and GPx activity.The results showed that the MDA and PC contents were markedly increased,meanwhile,the TSH contents and GPx activity were sharply decreased in the livers and kidneys,when rats were intraperitoneally injected with D-galactose,suggesting that D-galactose substantially induced oxidative stress.However,Na2SeO3 or ebselen supplement could markedly lower the MDA and PC levels,and improve the TSH levels and GPx activity,in rat livers and kidneys.Due to the blood-brain barrier,the MDA,PC,TSH contents and GPx activity remained unchanged in brain.