MG132可增强糖尿病大鼠肾脏抗氧化能力

目的 探讨蛋白酶体抑制剂MG132对糖尿病肾病（DN）大鼠的治疗作用及其机制。 方法 72只大鼠随机分为正常对照组（NC）、DN组和MG132治疗组（DN+MG132），每组各24只。在治疗第4、8和12周末检测各组大鼠24 h尿蛋白排泄率（UPER）、24 h尿量和尿丙二醛（MDA）含量、肾组织26S蛋白酶体、超氧化物歧化酶（SOD）和谷胱甘肽过氧化物酶（GSH-PX）活性；实时荧光定量PCR法检测各组大鼠肾组织SOD、GSH-PX和p47phox mRNA的表达变化；Western印迹检测p47phox的蛋白表达变化。 结果 与NC组大鼠比较，在4、8和12周时，DN大鼠的UPER显著增高（均P < 0.05）；12周时病理显示DN组大鼠肾小球系膜显著增生和系膜基质积聚增多。与同期DN组大鼠比较，MG132治疗组大鼠的UPER显著降低（均P < 0.05），肾小球系膜增生和基质积聚均减少。在4、8和12周，DN组大鼠肾组织26S蛋白酶体活性比NC组分别增高了2.14倍、2.66倍和3.68倍（均P < 0.05）。与DN组大鼠比较，MG132治疗组大鼠26S蛋白酶体活性显著下降（均P < 0.05）。与NC组大鼠相比，DN组大鼠肾组织p47phox mRNA表达分别升高了155%、149%和120%（均P < 0.05）；p47phox蛋白表达分别升高了139%、152%和186%（均P < 0.05）；尿MDA含量分别升高了1.95倍、2.04倍和2.62倍（均P < 0.05）；而DN大鼠肾组织SOD活性分别下降23.09%、33.59%和53.31%（均P < 0.05）；GSH-PX的活性分别下降28.57%、33.06%和48.76%（均P < 0.05）；SOD mRNA表达分别下降38.09%、61.44%和76.53%（均P < 0.05），GSH-PX mRNA表达分别下降29.16%、37.26%和62.40%（均P < 0.05）。与DN组大鼠比较，MG132治疗组大鼠肾组织p47phox mRNA和蛋白表达以及尿MDA含量则显著下降（均P < 0.05），而SOD和GSH-PX的活性和mRNA均显著升高（均P < 0.05）。 结论 MG132对DN大鼠肾脏有显著的保护作用，其机制可能与增强肾组织抗氧化能力有关。

MG132 enhances the renal anti-oxidative ability in diabetic nephropathy rats

Objective To investigate the effects of MG132 on diabetic nephropathy (DN) rats induced with streptozocin. Methods Seventy-two male SD rats were randomly divided into three groups: normal control group (NC, n=24), DN group (n=24) and DN treated with MG132 group (DN+MG132, n=24). At the end of 4, 8 and 12 weeks, 24 hour urinary protein excretion rate (UPER) was detected. Morphology of kidney was examined by special staining of periodic acid-schiff (PAS). Renal 26S proteasome activity was determined by quantifying the hydrolysis of S-LLVY-AMC in a fluorescence reader. Urinary malondialdehyde (MDA) level and renal SOD and GSH-PX activity were detected by commercial kits. Renal SOD, GSH-PX and p47phox mRNA expressions were determined by real-time fluorescence PCR. Renal p47phox protein expression was determined by Western blotting. Results Compared with NC group, the DN group showed a significant increased of UPER at week 4, 8, 12 (all P<0.05), of mesangium proliferation and mesangial matrix expansion at week 12. In DN+MG132 group, UPER was significantly decreased compared with DN group at the end of 4, 8 and 12 weeks(P<0.05, respectively), and the glomeruler pathological alteration induced by diabetes was attenuated. Increased renal 26S proteasome activity in DN rats was significantly inhibited after MG132 administration (P<0.05). Moreover, renal p47phox mRNA expression in DN group was 155%, 149% and 120% more than those in NC group at 3 time points (all P<0.05), and so was the renal p47phox protein expression, 139%, 152% and 186% more (all P<0.05). Urinary MDA levels in DN group were 1.95-, 2.04- and 2.62-folds more than those in NC group (all P<0.05). In addition, compared with NC group at 3 time points, in DN group, renal SOD activity was decreased by 23.09%, 33.59% and 53.31% (all P<0.05); renal GSH-PX activity was decreased by 28.57%, 33.06% and 48.76% (all P<0.05); renal SOD mRNA was decreased by 38.09%, 61.44% and 76.53% (all P<0.05); renal GSH-PX mRNA group was decreased by 29.16%, 37.26% and 62.40% (all P<0.05). Compared with DN group, renal p47phox mRNA and protein expression, and urinary MDA levels were significantly lower in DN+MG132 group (all P<0.05); renal SOD and GSH-PX activity as well as mRNA expression were significantly increased in DN+MG132 group (all P<0.05). Conclusions MG132 treatment can provide renoprotection for DN rats effectively maybe through enhancing renal anti-oxidative ability.