表没食子儿茶素没食子酸酯对糖尿病大鼠肾脏细胞外调节蛋白激酶活性的影响

Effect of epigallocatechin-3-gallate on the activity of extracellular signal-regulated kinase in diabetic rats

目的 观察表没食子儿茶素没食子酸酯（EGCG）对糖尿病大鼠肾脏细胞外调节蛋白激酶（ERK）活性的影响。方法 采用链脲佐菌素腹腔注射建立糖尿病大鼠模型，实验分3组：正常对照组、糖尿病模型组和EGCG干预组。EGCG干预组于模型成功后1周给予EGCG5mg·kg^-1·d^-1腹腔注射。以免疫组织化学方法检测肾组织磷酸化ERK（p-ERK）的表达。大鼠肾系膜细胞株分组：正常对照组（NG，葡萄糖5mmol／L），高糖组（HG，葡萄糖30mmol／L），HG＋EGCG1组（100μg／L），HG＋EGCG2组（200μg／L），HG＋EGCG4组（400μg／L），甘露醇组（5mmol／L葡萄糖＋25mmol／L甘露醇）。用四甲基偶氮唑蓝比色（MTT）法检测细胞增殖活性；常规生化分析系膜细胞氧化应激状态；Western印迹检测ERK、p-ERK和p27蛋白表达水平。结果 EGCG呈剂量和时间依赖方式抑制高糖时系膜细胞的增殖活性及抗氧化作用。EGCG干预后糖尿病大鼠肾脏p-ERK蛋白免疫组化染色明显减弱。高糖时系膜细胞p-ERK及p27蛋白表达上调，EGCG呈剂量和时间依赖方式下调高糖时p-ERK蛋白的表达；呈剂量依赖方式下调p27蛋白的表达。结论 EGCG能有效改善糖尿病肾损伤程度，其作用机制可能是通过调节ERK活性，抑制p27蛋白表达而减少糖尿病肾病损害。

Objective To observe the influence of epigallocatechin-3-gallate （EGCG） on extracellular signal-regulated kinase in diabetics rats. Methods Diabetes mellitus was induced in male Sprague-Dawley （SD） rats （150-200 mg） by intraperitoneal injection of streptozotocin （65 mg/kg）. Blood glucose levels were measured three days after the injection to ensure a diabetic state （≥ 16.7 mmol/L）. Then diabetic rats were randomly assigned to one of the following groups： （1） diabetic model （DM）. （2） diabetic＋EGCG treatment （with intraperitoneal EGCG injections 7 days after diabetic model establishment）. In addition, the normal control group was injected with intraperitoneal citric acid. The treatment continued for 12 weeks, and then the rats were sacrificed and the kidneys were harvested for immunohistochemistry staining of p-ERK to evaluate the protein expression level. The rat mesangial cells were divided into six groups： normal glucose （NG, 5 mmol/L） control group, high glucose （HG, 30 mmol/L） control group, HG＋EGCG 1 （100 μg/L）, HG＋EGCG 2 （200 μg/L）, HG＋EGCG 4 （400 μg/L）, and mannitol group. The expression of ERK, p-ERK and p27 protein was examined by Western blot. Results Compared with control group, there was significant increase in p-ERK staining area in the glomeruli of untreated diabetic rats. EGCG treatment significantly suppressed the increased p-ERK staining area. Compared with normal glucose group, high glucose significantly increased the expression of p-ERK and p27 protein. EGCG could decrease the expression of p-ERK and p27 protein. Conclusions EGCG can inhibit p-ERK protein expression in kidneys of diabetic rats and rat mesangial cells cultured in high glucose. EGCG may be used to prevent or cure diabetic nephropathy.