Effects of N-acetylcysteine and glutathione ethyl ester drops on streptozotocin-induced diabetic cataract in rats

摘要

Purpose: To evaluate the effect ofN-acetylcysteine (NAC) and glutathione ethyl ester (GSH-EE) eye dropson the progression of diabetic cataract formation induced bystreptozotocin (STZ). Methods: One hundred and thirtySprague-Dawley (SD) rats were selected, and diabetes was induced bystreptozotocin (65 mg/kg bodyweight) in a single intraperitonealinjection. The control group (group I) received only vehicle. Then, 78rats with random blood glucose above 14 mmol/l were divided into fourgroups (group II-V). The drug-treated rats received NAC and GSH-EE eyedrops five days before STZ injection. Group I and V animals receivedsodium phosphate buffer drops (pH 7.4), and those in groups II, III,and IV received 0.01% NAC, 0.05% NAC, and 0.1% GSH-EE drops,respectively. Lens transparency was monitored with a slit lampbiomicroscope and classified into six stages. At the end of four weeks,eight weeks, and 13 weeks, animals were killed and components involvedin the pathogenesis of diabetic cataract including thiols (fromglutathione and protein), glutathione reductase (GR), catalase (CAT),and glycated proteins were investigated in the lens extracts. Bloodglucose, urine glucose, and bodyweight were also determined. Results: The progression in lens opacityinduced by diabetes showed a biphasic pattern in which an initial slowincrease in the first seven weeks after STZ injection was followed by arapid increase in the next six weeks. The progression of lens opacityin the treated groups (group II-IV) was slower than that of theuntreated group (group V) in the earlier period and especially in thefourth week. There were statistically significant differences betweenthe treated groups and the untreated group (p0.05). However, thesedifferences became insignificant after the sixth week, and theprogression of lens opacification in all diabetic groups becameaggravated. The content of thiol (from glutathione and protein),glutathione reductase (GR), and catalase (CAT) were lower in the lensextracts of the diabetic rats four weeks, eight weeks, and 13 weeksafter the STZ injection while the levels of thiol and CAT activity wereboth higher in the treated groups (group II-IV) than in the untreatedgroup (group V) at every stage. However, there was no statisticallysignificant difference (p0.05). Moreover, the diabetes resulted inan increased level of glycated proteins in both the treated groups andthe untreated group, but there was no statistically significantdifference between all the diabetic groups (p0.05). Conclusions: NAC and GSH-EE can slightlyinhibit the progression of the diabetic cataract at the earlier stage.They may maintain lens transparency and function by serving as aprecursor for glutathione biosynthesis and by protecting sulfhydrylgroups from oxidation.