硫醇转移酶对高糖诱导大鼠晶状体氧化应激的保护作用

目的：观察高浓度葡萄糖对离体大鼠晶状体氧化还原系统的影响,探讨硫醇转移酶( Thioltransferase,TTase)在糖尿病性白内障中抗氧化应激的作用。
　　方法：用不同浓度葡萄糖(35.5,65.5,95.5 mmol/L葡萄糖组以及相应的甘露醇等渗对照组)体外培养大鼠晶状体7d,动态观察晶状体的混浊情况。测定各组晶状体中TTase、超氧化物歧化酶( SOD )、过氧化氢酶( CAT )的活性,以及氧化型谷胱甘肽( GSSG)与总谷胱甘肽( T-GSH)的比值。
　　结果：高糖组晶状体早期就已出现雾状混浊,而对照组保持相对透明；在高糖刺激下, TTase活性增加较正常对照组增加,并在含35.5 mmol/L 葡萄糖的高糖组中最高(1.743±0.20mU/mg protein,P<0.01)。高糖组GSSG/T-GSH比值均较正常对照组增加,分别增加2.89倍、2.57倍和2.42倍,其组间互相比较无明显差异,相应等渗对照组和正常对照组比较差异不明显；高糖处理组的SOD和CAT较正常对照组降低,其中 SOD 分别为正常对照的0.71倍、0.52倍和0.49倍(P<0.05),CAT分别为正常对照的0.47倍、0.56倍、0.50倍(P<0.05),不同葡萄糖浓度处理组间差异无显著性。
　　结论：高糖环境激活晶状体内的抗氧化系统,诱导TTase活性增加,GSSG/T-GSH比例增高,CAT, SOD活性下降,晶状体抗氧化能力降低是糖尿病性白内障形成的重要机制。

Protective effects of thioltransferase in rat lens incubated with high glucose

AIM:To investigate the effect of high glucose on the redox system of the cultured rat lenses in vitro, and evaluate the effect of thioltransferase(TTase)against oxidative stress in diabetic cataract.

METHODS: Lenses were incubated with different concentrations of glucose: control group(5.5mmol/L), high glucose groups(35.5, 65.5, 95.5mmol/L)and mannitol control group for 7d. Following incubation, the lenses were evaluated daily using a dissecting microscope. After 7d of incubation, lenses were homogenized in lysis buffer and processed for measurement the activity of TTase, catalase(CAT), superoxide dismutase(SOD)and the specific value of GSSG/T-GSH.

RESULTS: The lenses treated with high glucose exhibited mistlike opacity in the early stages, while the lenses of control group remained relatively transparent. With the rise of the concentration of high glucose, the activity of TTase increased and the maximum appeared in 35.5mmol/L group(1.743±0.20mU/mg protein, P<0.01). No changes were observed in the mannitol control group(P>0.05). The specific value of GSSG/T-GSH of lenses with high glucose groups increased compared with the control groups, there were 2.89, 2.57 and 2.42 times to the normal control group(P<0.05). There was no significant difference between each group treated with high glucose, and the difference was also no significant between the mannitol group and the control group. Compared with the control group, the activities of CAT and SOD decreased in the high glucose treatment groups, the activities of SOD were 0.71, 0.52 and 0.49 times to the normal control group(P<0.05), and the activities of CAT were 0.47,0.56 and 0.50 times to the normal control group(P<0.05). There was no significantly different between each group treated with high glucose.

CONCLUSION: The antioxidant system of the lens was activated by the high glucose following the increased activity of TTase, the specific value of GSSG/T-GSH, and the decreased activities of CAT and SOD. The gradually decreased oxidation resistance in the lens may contribute to the development of diabetic cataract.