霉酚酸酯及缬沙坦对糖尿病大鼠足细胞的保护机制研究

目的探讨霉酚酸酯、缬沙坦及2者联合应用对糖尿病。肾病（DN）大鼠足细胞损伤的保护作用。方法雄性Wistar大鼠行右肾切除后，腹腔注射链脲佐菌素（STZ，65mg／kg）建立糖尿病模型。将实验动物随机分为右。肾切除对照组（NC）、糖尿病组（DM）、霉酚酸酯治疗组（M）、缬沙坦治疗组（V）、缬沙坦和霉酚酸酯联合治疗组（V＋M）。治疗组分别给予霉酚酸酯15mg·kg^-1·d^-1，缬沙坦40mg·kg^-1·d^-1；联合治疗组为上述两组之和。检测各组8周末的左肾质量／体质量比值、尿蛋白量（24h）、血糖（Glu）、Scr。光镜及电镜观察肾组织形态学变化。免疫组化检测肾组织中nephrin、结蛋白（desmin）及单核细胞趋化因子1（MCP-1）蛋白表达。实时PCR测定肾组织中nephrin及MCP-1mRNA表达。结果与NC组相比，DM组大鼠血糖、尿蛋白量及左肾质量／体质量比值均显著上升（P〈0．01）；肾小球硬化指数（GSI）及肾间质损害加重（P〈0．01）；肾组织内MCP-1、desmin蛋白表达均显著上调（P〈0．01）。与DM组比较，M组、V组及V＋M组上述指标除Glu、Scr外，均明显改善（P〈0．05或P〈0．01）。与NC组（100％）相比，DM组nephrinmRNA表达下调（78％，P〈0.05）；各治疗组nephrinmRNA表达增加，以M组增加最明显（134％，P〈0．01）。与NC组（100％）相比，DM组MCP-1mRNA表达明显上调（251％，P〈0.05）；各治疗组明显降低，以M组最显著（126％，P〈0．01）。nephrinmRNA与MCP-1mRNA表达呈负相关（r=-0，86。P〈0．01）。尿蛋白量（24h）与MCP-1mRNA呈正相关fr=0．82，P〈0．01）；与nephrinmRNA呈负相关（r=-0．78，P〈0．01）。结论霉酚酸酯及缬沙坦均能下调糖尿病大鼠肾组织中desmin及MCP-1基因及蛋白的表达，上调nephrin基因及蛋白表达，降低尿蛋白量，预防肾损伤。联合治疗不优于单一治疗。霉酚酸酯可能通过抗炎性反应减轻足细胞损伤，减少蛋白尿，对早期DN大鼠具有明显的肾保护作用。

Study on the protective mechanism of mycophenolate mofetil and valsartan for podocyte injury in diabetic rats

【Abstract】 Objective To investigate the influence of immunosuppressor mycophenolate mofetil(MMF) alone and in combination with valsartan (the angiotensinⅡ receptor blockers, ARB), on prevention of podocyte loss in streptozotocin(STZ) induced diabetic model. Methods Diabetes was induced in uninephrectomized male Wistar rats by peritoneal injection of STZ 65 mg/kg. Rats were randomly separated into five groups: control group(NC), diabetic without treatment group(DM), Valsartan treated group(V,40 mg•kg-1•d-1), MMF treated group(M,15 mg•kg-1•d-1), and combined treatment group(V+M). This study lasted for 8 weeks. Serum biochemistry, 24 h urinary protein and the ratio of kidney weight/body weight were determined after 8 weeks. The renal tissue morphology was observed by light microscopy and electron microscope. Expressions of nephrin, desmin and MCP-1 protein were examined by sem-quantitative immunohistochemical assays. Real-time quantitative PCR was used to detect the mRNA levels of nephrin and MCP-1 in renal tissue. Results Compared with NC, serum glucose level, 24 h urinary protein and the ratio of kidney weight/body weight in DM were significantly increased （P<0.01）. Treatment with either MMF or valsartan or combined treatment with valsartan and MMF significantly decreased 24 h urinary protein and the ratio of kidney weight/body weight, suppressed glomerulosclerosis and interstitial fibrotic lesions in diabetic rats. Nephrin mRNA expression in diabetic rats was lower than that of control rats(78%, P<0.05). Treatment with MMF in diabetic rats significantly restored nephrin mRNA expression. MCP-1 mRNA level in renal cortex was significantly higher in diabetic rats than that of control rats(251%, P<0.01).Over-expression of MCP-1 mRNA in diabetic rats was significantly suppressed by MMF(126%, P<0.01). There were significant negative correlations between nephrin and MCP-1 mRNA(r=-0.86, P<0.01), 24 h urinary protein and mRNA levels of MCP-1(r=0.56, P<0.01) or nephrin(r=-0.78, P<0.01). Conclusions MMF and valsartan can suppress MCP-1 and desmin expression, increase the nephrin expression, and decrease proteinuria level in diabetic rats. Combination of valsartan and MMF has no superiority over monotherapies on renal protection. These results suggest that MMF may have renoprotective effects on the early stages of diabetic nephropathy through an ant-inflammatory activity thus preventing podocytes loss.