The Effect Of Thermotolerance In The Lens Epithelial Cells Of Streptozotocin-diabetic Rats

Objective:The heat shock response is a conserved, immediate but transient cellular response to elevated temperatures and other types of injury. It involves the transcriptional activation of a small set of specific gens and a subsequent synthesis of the so-called heat shock proteins( HSPs). Recent studies have shown that a wide variety of stresses including ischemia, variation, hypoxia, oxidative stress, pH extremes, nutrient limitation, osmotic agents and noxiouos chemicals, can rapidly induce the expression of the gens for hsp, subsequent induce endogenous protective mechanisms. In mammalian cells, HSPs are commonly classified according to their size, for example, HSP90, HSP70, HSP60, HSP20 to HSP30 KDa(small HSP). Most of HSPs are constructive proteins, only parts of them can be induced by stress. Some studies have shown cataract is related with the abnormal of HSPs, but there is little study on the mechanism of traumatic cataract. Based on the establish of streptozotocin(STZ)-diabetic cataract model, this study was designed to investigate the dynamic expression of hsp70 in lens epithelial cells (LECs) in diabetic cataract eyes of rat, and to determine the effects of thermotolerance on them. After that, it put forwards the relevant theoretical mechanism for the medical prevention and cure of diabetic cataract.Method: 30 SD rats were randomly divided into three groups: A:normal control;B:diabetic-cataract ;C:diabetic-cataract after thermotolerance. Diabetic cataract was induced by STZ intraperitoneal injection(55mg/kg in 0.1 mo土/L sodium citrate buffer). Lens were examined using a slitlamp once a week. At the end of 8 weeks after STZ injection, eyeballs were isolated. Imunohistochemical streptavidin-peroxidases(S-P) method was used todetect the expression of HSP70,and the levels of MDA, SOD, GSH were examined. Results:1. The lens of control group were always completely transparent throughout the period of experiment,and the lens of cataract group began to exhibited vacuolar stage by week 2 and floccule by week 4,and nearly opacity by week 6.2. The expression of HSP70, LECs apoptosis were significantly different between B and C (P<0.05).3. The mean water soluble protein of C group was increased significantly than B group(P<0.05).4.MDA,SOD,GSH of B group was increased significantly than C group(P<0.05).Conclusions:Proliferation and apoptosis of were ubiquity during the progression of cataract and were significantly correlated with the development continually increased of diabetic cataract. The expression of HSP70 which played a critical role in the pathogenesis of diabetic cataract. It caught LECs proliferate, then migrate, fibrosis, and leaded to subcapsule opacity,but on the other hand it inhibited the progress of the LECs apoptosis, thus protected diabetic lens from opacity.