坎地沙坦不同治疗时机对2型糖尿病KK/Ta小鼠肾脏硝化氧化应激的影响

The Effect of Candesartan Early or Late Treatment Inhibited Nitro-oxidative Stress in Type 2 Diabetic KK/Ta Mice Kidney

目的:本研究旨在探讨血管紧张素Ⅱ受体拮抗剂坎地沙坦治疗对自发性2型糖尿病KK/Ta小鼠肾内硝化氧化应激的影响及其作用机制。方法:KK/Ta小鼠随机分为(1)非治疗组;(2)早期治疗组:自6周龄起经口予坎地沙坦(4mg·kg-1·d-1)治疗;(3)晚期治疗组:自12周龄起予坎地沙坦治疗,正常对照组采用BALB/c小鼠。应用免疫组化和免疫荧光染色检测肾脏中硝化氧化应激的标志物硝基酪氨酸,诱导型(iNOS)和内皮型一氧化氮合酶(eNOS)蛋白的表达,竞争性RT-PCR检测iNOS和eNOSmRNA的表达。同时测定尿白蛋白排泄率,血压和糖耐量等临床指标。结果:28周龄KK/Ta小鼠尿白蛋白排泄率增加,肾脏iNOSmRNA和蛋白表达上调,硝基酪氨酸的形成增加。坎地沙坦治疗减少尿白蛋白排泄率,抑制肾脏iNOSmRNA和蛋白的表达,减少硝基酪氨酸的形成,早期治疗组和晚期治疗组的作用差异无统计学意义。4组小鼠eNOSmRNA和蛋白的表达水平无差异。结论:坎地沙坦治疗通过下调糖尿病状态下肾脏iNOS的表达,抑制过氧亚硝基阴离子的形成,抑制硝化氧化应激反应,发挥其降低尿白蛋白排泄率等肾脏保护作用。

Objective ：The effects of candesartan, an angiotensin II type 1 receptor blocker （ ARB）, were investigated on nitro -oxidative stress in type 2 diabetic KK/Ta mouse kidneys. Methods： KK/Ta mice divided into three groups were treated with eandesartan （4 mg · kg^-1 · d^-1 ） or vehicle from 6 or 12 to 28 weeks of age. BALB/c mice treated with vehicle were used as con- trols. Body weight, blood pressure, blood glucose,urinary microalbumin, urinary creatinine and serum creatinine were measured every four weeks. At 28 weeks, renal expressions of endothelial nitric oxide synthase（ eNOS）, induced nitric oxide synthase（iNOS） and ni- trotyrosine were evaluated by immunohistochemistry and/or competitive RT -PCR. Results： KK/Ta mice developed higher body weight, blood glucose, hypertension, and urinary microalbumin/creatinine ratio in KK/Ta mice at 28 weeks of age were significantly higher than that of BALB/c mice. Protein and mRNA expressions of iNOS were upregulated in KK/Ta kidneys with increased immu- nostaining intensities of nitrotyrosine. Treatment with eandesartan down - regulated the protein and mRNA expressions of iNOS and de- creased the formation of nitrotyrosine, albuminuria and mean blood pressure. There were no significant differences between the two treatment groups （from 6 or 12 weeks）. There were no significant differences in the expression of eNOS among the four groups. Conclusion：The results suggest that candesartan, an ARB, reduces nitro -oxidative stress and subsequent albuminuria by down -regula- ting iNOS in type 2 diabetic KK/Ta mouse kidneys.