葛根素减轻部分由过氧亚硝基阴离子导致的糖尿病大鼠晶状体上皮细胞凋亡

本研究观察葛根素是否减轻部分由过氧亚硝基阴离子（peroxynitrite,ONOO^-）导致的糖尿病大鼠晶状体上皮细胞（lens epithelium cell,LEC）凋亡。采用大鼠腹腔注射链脲佐菌素（streptozotocin,STZ）的方法建立糖尿病动物模型。36只大鼠作为对照组,腹腔注射生理盐水;其他72只大鼠腹腔注射STZ（45mg/kg）后分为STZ组和STZ＋葛根素组,每组36只。STZ注射3d后,STZ＋葛根素组大鼠每天腹腔注射葛根素（140mg／kg）。于实验开始后第20、40和60天用裂隙灯检查晶状体的形态学变化后处死动物。用流式细胞仪检测LEC凋亡,用免疫组化方法检测晶状体中ONOO^-的标志物——硝基酪氨酸（nitrotyrosine,NT）的表达,用基因芯片分析技术检测LEC凋亡相关基因iNOS等的表达。结果发现,对照组大鼠晶状体均透明,各项指标基本正常;STZ组大鼠第20天时即出现晶状体混浊,40-60d期间混浊不断加重;STZ＋葛根素组大鼠20-40d时晶状体混浊呈加重趋势,但40-60d以后明显减轻。对照组LEC轻度凋亡,而STZ组凋亡细胞呈持续性增长,STZ＋葛根素组大鼠20-40d时细胞凋亡呈增长趋势,但40-60d以后明显下降。对照组大鼠晶状体NT未见明显表达;STZ组大鼠NT表达明显加强;STZ＋葛根素组大鼠20-40d时NT表达呈增长趋势,但40-60d以后明显下降。对照组凋亡相关基因未见明显变化,STZ组凋亡相关基因iNOS表达明显上调。其他凋亡相关基因如BCL-2、SOD表达明显下调,但NF-κB和TNFR1-FADD-caspase信号转导途径明显上调;STZ＋葛根素组凋亡相关基因表达则呈相反改变。上述结果表明,在糖尿病大鼠晶状体中有ONOO^-的标志物NT表达,证明糖尿病大鼠LEC凋亡部分由ONOO^-诱导,这可能是氧化损伤导致白内障形成的新途径。葛根素能够部分逆转ONOO^-对LEC的致凋亡作用,提示葛根素可能是治疗糖尿病性白内障的有效药物,其治疗机制可能与葛根素直接抑制凋亡和对抗ONOO^-对糖尿病大鼠LEC的损伤有关。

Puerarin decreases lens epithelium cell apoptosis induced partly by peroxynitrite in diabetic rats

The present study was designed to observe if puerarin decreases lens epithelium cell (LEC) apoptosis induced partly by peroxynitrite (ONOO(-)). One hundred and eight rats were randomly divided into control group (n=36), streptozotocin (STZ) group (n=36) and STZ + puerarin group (n=36). The rats in the control group intraperitoneally (i.p.) received 0.5 ml of saline. The rats in STZ group and STZ + puerarin group received intraperitoneal injection of STZ (45 mg/kg). Three days later, the rats in STZ + puerarin group were given puerarin (140 mg/kg per day, i.p.). On days 20, 40 and 60 of the experiment, morphologic changes of lenses were observed with slit lamp. Then the animals were sacrificed for further analysis. The amount and percentage of apoptotic LECs were determined by flow cytometry. Nitrotyrosine (NT, the foot print of ONOO(-)) was examined by immunohistochemistry. Apoptosis-related genes (iNOS, etc.) were analyzed by gene array. The results showed that in the control group, all the lenses were clear. In STZ group, gradually severe opacity of the lens was observed on days 20, 40 and 60. But in STZ + puerarin group, mild opacity of the lens was observed on day 20 and more severe on day 40, but markedly decreased on day 60. In the control group, mild apoptosis of LECs was observed. In STZ group, time-dependent increase in apoptosis of LECs was observed. In STZ + puerarin group, mild apoptosis of LECs was observed on day 20, significantly increased on day 40, but markedly decreased on day 60. There was no expression of NT in the lens in the control group, but an increased expression of NT in STZ group. In STZ + puerarin group, mild expression of NT was observed on day 20, significantly increased on day 40, but markedly decreased on day 60. There was no expression of iNOS in the lens in the control group, but continuous up-regulation of iNOS expression in STZ group. In STZ + puerarin group, mild expression of iNOS was observed on day 20, significantly increased on day 40, but markedly decreased on day 60. Except the changes of iNOS related to NO production, the other apoptosis-related genes, including BCL-2 and SOD were down-regulated, while NF-kappaB and TNFR1-FADD-caspase signal transduction way were up-regulated in STZ group. The results were opposite in STZ + puerarin group and the control group. These findings show that NT is expressed in diabetic rat lens, which proves that LEC apoptosis in diabetic lens is partly induced by ONOO(-) which may be a new oxidative damage way to form cataract. Puerarin partly decreases LEC apoptosis induced by ONOO(-) and is a potential medicine for therapy of diabetic cataract. The mechanism of puerarin dealing with diabetic cataract may be related to its direct inhibition of LEC apoptosis and antagonism of ONOO(-) in diabetic rats.