| Oxygen has been widely and effectively used in the clinic. However, topical adverse effects may be induced with the long-term treatment. Such as cataract and retinopathy of prematurity. In addition, some eye diseases like nuclear cataract after vitrectomy are also related with hyperoxia which may result in the vision impairment.Although the causative factors of cataract are many and its etiology is still unclear, it has been reported that it is linked with oxidation. In the present work, rabbit lens are incubated with hyperoxia in vitro, which used to investigate the pathogenesis and prevention strategies of hyperoxia-induced oxidative stress. The results will be helpful to understand the development of the cataract after vitrectomy and hyperbaric oxygen (HBO) therapy starting from the primary stage of its formation. These will fundamentally benefit to the research of pathogenesis and medication of post-vitrectomy cataract, and also may provide a new thought for study the mechanism of the age-related cataract.ObjectiveTo explore the mechanisms of the hyperoxia-induced cataract and investigate the efficacies of N-acetylcysteine (NAC), Aspirin (ASA), Carnosine (Car) and Taurine (Taur) in preventing hyperoxia-induced lens opacification and the changes of biochemical parameters on organ cultured rabbit lenses, especially about the best concentrations of NAC. With the results of biochemical indicators, we could reveal the changes of the anti-oxidant system in the lens and the mechanism of anti-oxidant drugs.Methods(1) In the first set of experiment, fourty-two lenses from adult (1.5-2.0 Kg,4 months) rabbits were divided into the control group, the hyperoxia-exposed group, the NAC treated group (20 mM), the Car treated group (25 mM), the ASA treated group (2 mM) and the Taur treated group (80 mM), respectively. The lenses in the control group were incubated in the medium with an atmosphere of 95% room air and 5% CO2; the other groups were incubated with hyperoxia (O2>80%) for 4h per day for seven days. Lens histological changes, transparency, water-soluable protein, GSH contents and the activities of Na~+-K+-ATPase, CAT and GR were measured after this incubation. All the data were analyzed using the SPSS 13.0 statistical package.(2) Then based on the first set of experiment observation, thirty-six lenses from adult (1.5-2.0 Kg, 4 month old) rabbits were divided into the control group (Group A), the hyperoxia-exposed group (Group B), the hyperoxia-exposed group containing 5 mM of NAC (Group C), 10 mM of NAC (Group D), 20 mM of NAC (Group E) and 40 mM of NAC (Group F), respectively. The incubation condition and the measurements were same as the first set.Results1. The first set of experiment: effects of four different drugs on the hyperoxia-induced cataract(1) The grading of lenses between the control group and the hyperoxia-exposed group:On the 3rd day, 33% (2/6) lenses in the hyperoxia-exposed group were slight cortical opacification whereas lenses in the control group still kept clear; However, on the 4th day, diffuse opacification was observed in Group B lenses, about 17%(1/6), 33% (2/6) lenses in the control group were in slight cortical opacification and other lenses kept clear (P<0.05); After seven days incubation, 83% (5/6) lenses in the hyperoxia-exposed group exhibited total cortical opacification. In contrast, only 17% (1/6) lenses revealed less opacification in the control group (P<0.01). The lens epithelial cells in the control group were normal. The pattern of the lens fibres in cross section could be clearly found. But in the hyperoxia-exposed group, the lens epithelial cells were disorganized, lens fibres crumbled.(2) The grading of lenses between the hyperoxia-exposed group and the treated groups:On the 3rd day, 33% (2/6) lenses in the hyperoxia-exposed group were slight cortical opacification whereas lenses in the all treated groups still kept clear; on the 4th day, 17% (1/6) lenses in the Taur treated group and 17% (1/6) lenses in the ASA treated group were slight cortical opacification, and lenses in the NAC treated group and the Car treated group kept clear; After seven days incubation, 83% (5/6) lenses in the hyperoxia-exposed group exhibited total cortical opacification. In contrast, lenses in the NAC treated group, 17% (1/6) were diffuse opacification, 50% (3/6) were slight degree opacification, and 33% (2/6) were kept clear; the average degree of lenses opacification in the Car, ASA and Taur treated group was in the midrange. However, there were no statistically significant differences, except the difference between the hyperoxia-exposed group and the NAC treated group (P<0.05).(3) Biochemical indicators:After seven days incubation, the contents of the water-soluble protein and the GSH were significantly lower in the hyperoxia-exposed group compared with the control group, by 10.4% (P<0.05) and 37.3% (P<0.05), respectively. In addition, a reduction in the activities of Na~+-K+-ATPase, CAT and GR were also observed in the hyperoxia-exposed group, about 53.5% (P<0.05), 32.2% (P<0.05) and 12.8% (P>0.05), respectively. NAC treatment delayed the progression of opacification formation in rabbit lenses, the water-soluble protein and the GSH contents increased by 9.95% (P<0.05) and 38.4% (P<0.05), the activities of Na~+-K+-ATPase, CAT and GR were also increased in NAC-treated group, by 59.1% (P<0.05), 32.9% (P<0.05) and 8% (P>0.05), respectively. All the biochemical indicators in the Car treated group, the ASA treated group and the Taur treated group were higher than that in the hyperoxia-exposed group. The GSH content in the Car treated group increased by 20.9% (P<0.05), and the activities of Na~+-K+-ATPase and CAT were increased, by 48.6% (P<0.05) and 26.8% (P<0.05), respectively.2. The second set of experiment: effects of different concerations of NAC on the hyperoxia-induced cataract(1) The grading of lenses: None of the lenses in all groups exhibited opacification even after 3 day's incubation whereas only 33% (2/6) lenses in the hyperoxia-exposed group were slight opacification. However, on the 4th day, 50% (3/6) lenses cortical opacification was observed in the hyperoxia-exposed group, whereas 83% (5/6) lenses in the 20 mM and 40 mM NAC-treated groups kept clear (P<0.05). After seven days, 83% (5/6) lenses in the hyperoxia-exposed group exhibited total cortical opacification. In contrast, only few lenses revealed less opacification in the control group, the 5 mM treated group and the 10 mM NAC treated group, only 67% (4/6) lenses in the 20 mM NAC treated group and 50% (3/6) in the 40 mM NAC treated group were slight opacification, but no significant differences were found between these four with NAC treated groups and the control group. In the NAC treated group, slight oedema of partial lens fibres could be found.(2) Biochemical indicators:Compared with the hyperoxia-exposed group, all indicators were increased in the all NAC treated groups, especially in the 20 mM and 40 mM NAC treated groups. The water-soluble protein contents were increased by 10.6% (P<0.05) and 11.9% (P<0.05), respectively; the GSH contents were increased by 28.2% (P<0.05) and 23.9%. The enzymatic activities were also improved in the 20 mM and 40 mM NAC treated groups. The Na~+-K+-ATPase activity was increased by 53.9% (P<0.05) in the 20 mM NAC treated group and 56.0% (P<0.05) in the 40 mM NAC treated group; the CAT activity was increased by 34.7% (P<0.05) in the 20 mM NAC treated group and 37.5% (P<0.05) in the 40 mM NAC treated group. However, there was no difference between the control group and the all NAC treated groups, even between the 20 mM NAC treated group and the 40 mM NAC treated group. Conclusions1. Hyperoxia can induce the opacification of the rabbit lens in vitro;2. N-acetylcysteine, Carnosine, Aspirin and Taurine have different protective effects on the hyperoxia-induced lens cortical opacification;3. NAC (20 mM-40 mM) significantly prevents experimental hyperoxia-induced lens cortical opacification. It may maintain the lens transparency and function by serving as a precursor for glutathione biosynthesis, and function as antioxidant.
|
PDF Full Text Request