Effects of enalapril and paricalcitol treatment on diabetic nephropathy and renal expressions of TNF-α, p53, caspase-3 and Bcl-2 in STZ-induced diabetic rats

This study aimed to assess the renopreventive effect of enalapril and/or paricalcitol on streptozotocin (STZ) diabetes-induced nephropathy and to elucidate their mechanisms of action through investigation of the effects on renal oxidative stress, antioxidant defense system and expressions of TNF-α, p53, caspase-3, and Bcl-2. Diabetes mellitus was induced in fasting male Wistar rats by single intraperitoneal injection of STZ (45 mg /kg b.w.) dissolved in citrate buffer (pH 4.5). Ten days after STZ injection, the diabetic rats were treated with enalapril (25 mg/l of drinking water) and/or paricalcitol (8 μg/kg b.w. per os) dissolved in 5% DMSO daily for 4 weeks. The obtained data revealed that the treatment of diabetic Wistar rats with enalapril and/or paricalcitol led to significant decreases in the elevated serum urea, uric acid, creatinine, sodium and potassium levels; thereby reflecting the improvement of the impaired kidney function. The deteriorated kidney lipid peroxidation, GSH content and GST and catalase activities in diabetic rats were significantly ameliorated as a result of treatment with enalapril and/or paricalcitol. The elevated fasting and post-prandial serum glucose levels and the lowered serum insulin and C-peptide levels were also improved. The treatment with enalapril and paricalcitol in combination was the most potent in decreasing the elevated serum glucose levels. Moreover, the treatment of diabetic rats successfully prevented the diabetes-induced histopathological deleterious changes of kidney and islets of Langerhans of pancreas. In association, the immunohistochemically detected pro-inflammatory cytokine, TNF-α, and apoptotic mediators, p53 and caspase-3, were remarkably decreased in kidney of diabetic rats as a result of treatment while the expression of anti-apoptotic protein Bcl-2 was increased. Based on these findings, it can be concluded that enalapril and paricalcitol alone or in combination can prevent STZ diabetes-induced nephropathy through amelioration of the glycemic state and antioxidant defense system together with the suppression of oxidative stress, inflammation and apoptosis. However, the treatment of diabetic rats with enalapril and paricalcitol in combination has no further significant improvement effects on renal function and damage when compared with enalapril or paclitaxel treated diabetic groups.本研究旨在评估依那普利（enalapril）和/或帕立骨化醇（paricalcitol）对链脲佐菌素（streptozotocin, STZ）诱导的糖尿病性肾病的肾脏保护作用，并通过探究其对肾脏氧化应激、抗氧化防御系统以及肿瘤坏死因子-α（TNF-α）、p53、半胱氨酸天冬氨酸蛋白酶-3（caspase-3）和B细胞淋巴瘤因子-2（Bcl-2）表达的影响，阐明二者的作用机制。 本研究通过向禁食的雄性Wistar大鼠单次腹腔注射溶于pH 4.5柠檬酸盐缓冲液的STZ（45 mg/kg体质量），构建糖尿病模型。STZ注射10天后，将糖尿病大鼠每日给予溶于5%二甲基亚砜（DMSO）的依那普利（25 mg/L饮用水）和/或帕立骨化醇（8 μg/kg体质量，经口给药），持续干预4周。 所得数据显示，依那普利和/或帕立骨化醇治疗糖尿病Wistar大鼠后，其升高的血清尿素、尿酸、肌酐、钠及钾水平显著降低，提示受损肾功能得到改善。糖尿病大鼠肾脏的脂质过氧化水平升高、谷胱甘肽（glutathione, GSH）含量降低以及谷胱甘肽S-转移酶（glutathione S-transferase, GST）和过氧化氢酶活性下降的情况，经上述药物治疗后均得到显著改善。同时，升高的空腹及餐后血糖水平、降低的血清胰岛素和C肽水平也得以恢复。联合使用依那普利与帕立骨化醇在降低升高的血糖水平方面效果最为显著。此外，该治疗方案成功阻止了糖尿病诱导的肾脏及胰腺胰岛组织病理学损伤。 免疫组织化学检测结果显示，经治疗后糖尿病大鼠肾脏中的促炎细胞因子TNF-α以及凋亡介质p53和caspase-3的表达显著下调，而抗凋亡蛋白Bcl-2的表达则有所上调。 基于上述研究结果，可得出结论：依那普利与帕立骨化醇单用或联合使用，均可通过改善血糖状态、修复抗氧化防御系统，同时抑制氧化应激、炎症反应与细胞凋亡，从而预防STZ诱导的糖尿病性肾病。然而，与单独使用依那普利或紫杉醇（paclitaxel）处理的糖尿病大鼠组相比，联合使用依那普利与帕立骨化醇对肾功能及肾脏损伤并未产生额外的显著改善效果。