Experimental Study On Melatonin Inhibiting Hydrogen Peroxide-induced Cataract In Rats

OBJECTIVECataract can lead to blindness,oxidative damage is the significant factor inducing cataract. Melatonin (MLT) is a hormone of benzopyrrole secreted from epiphyseal gland. MLT is an active free radical scavenger and antioxidant. This experiment used the melatonin to act on hydrogen peroxide-induced lenses in rats in vitro and detected the antioxidative capability.This study will investigate the effects of melatonin in preventing hydrogen peroxide-induced cataract in rats and supply the theoretical bases of antioxidative drug.METHODSThe lenses of the cultured normal Wistar rats in vitro were randomly divided into 3 groups:the control group (group A), the group treated by hydrogen peroxide(group B), and the group treated by hydrogen peroxide and melatonin(10,30,50,100 and 200μmol/L) (group C1, group C2, group C3, group C4 and group C5). At the end of the study period (24th hour), the lenticular opacification of lenses was examined and the mean densities of black bands under the lenses were analyzed by Image-Pro Plus (IPP) 6.0 software.At the same time, the levels of protein, glutathione(GSH), malondialdehyde(MDA), total antioxidiation ability(T-AOC), superoxide dismutase(SOD) and catalase (CAT) were tested. The lens epithelial cells (LECs) were stained with HE and examined with microscope.RESULTS1.The quantitative analysis and observation of lenses:The lenses were observed with slit-lamp microscope after 24 hours of culture. The lenses of the control group were transparent.The lenses treated by hydrogen peroxide were white, meanwhile, the opacification of lenses treated by hydrogen peroxide and melatonin were significantly lighter than that of group B. The mean density of lenses in group C was significantly higher than lenses in group B (P<0.05). The mean density of lenses in group C3 and C4 were higher,and there wasn't statistical significance (P>0.05)2.The mensuration of biochemical indicator of lenses:To compare with the biochemical parameters of group B, the levesl of GSH,T-AOC,SOD and CAT of the group C increased statistically; the level of MDA reduced statistically(P<0.05).The levels of GSH,T-AOC and CAT of the group C3 were statistically higher than other groups; the level of MDA reduced statistically(P<0.05). The levels of MDA between the groups C3,C4 and C5 weren't statistically different(P>0.05).3. The morphology of lenses:The lens anterior capsular membrane(LACM) of the control group was continual and smooth, lens epithelial cells(LECs) arranged in line and nucleus appeared rhabditiform, the lens cortex fiber layers(LCFL) arranged regularly. LACM of group B was uncomplete and discontinual, LECs proliferated and arranged disorderly,LECs partly moved to deep layer,cells waxed,nucleus appeared multiformity. In MLT10μmol/L group, LACM was complete and continuation, LECs proliferated and cells appeared rhabditiform,LECs arranged multilayer, and most of LECs were in deep layer. In MLT30μmol/L group, partial LECs proliferated and missed monostratified arrangement,these LECs appeared crowding phenomenon. LCFL arranged regularly. In group MLT50μmol/L, LACM was complete,LACM became thinner, LECs arranged in line and gaps arranged unanimouse, nucleus appeared rhabditiform and unanimouse. There was vesicle in MLT100μmol/L group. The LECs'morphology of group C were more near to those of the control group.CONCLUSIONThe lenses treated by hydrogen peroxide were white, meanwhile, the opacification of lenses treated by hydrogen peroxide and melatonin were significantly lighter than that of group B. MLT and it's oxygenized metabolic products have high antioxidation, accordingly,they can counteract the oxidation of hydrogen to lenses. To compare with the biochemical parameters of H2O2 group, the levels of GSH,T-AOC,SOD and CAT of the group C increased statistically; the level of MDA reduced statistically, this result indicated that the antioxygen capability of lenses in MLT group was improved. The level of MLT was more higher, the antioxygen capability of lenses was more stronger from MLT 10μmol/L to MLT50μmol/L. MLT50μmol/L was the effective level. LACM of group B was uncomplete and discontinual, LECs proliferated and arranged disorderly,LECs partly moved to deep layer,cells waxed,nucleus appears multiformity. The cytoclasis of the group MLT were lighter than H2O2 group. The LECs'morphology of group C were more near to those of the control group.Melatonin can effectively enhance antioxidant ability of the oxidative damaged lenses, and also can inhibit the development of hydrogen peroxide-induced cataract of rats in vitro.