硒对慢性镉暴露致大鼠肾损伤的保护作用与机制

Protective effect of selenium in chronic cadmium exposure-induced kidney injury in rats

目的:探讨硒对慢性镉暴露致大鼠肾脏损伤毒性的保护作用及其机制。方法:雄性SD大鼠48只,根据体质量随机分为对照组、镉暴露组、硒对照组、硒干预组,每组12只,分别给予去离子水、氯化镉(3 mg/kg)、亚硒酸钠(0.01 mg/kg)、氯化镉(3 mg/kg)和亚硒酸钠(0.01 mg/kg)联合灌胃,每周灌胃6 d,共计12周。造模成功后,收集血液、尿液和肾脏组织,测定血清和尿液中尿素氮(UN)、肌酐(CREA)及尿蛋白含量等肾脏功能指标,观察肾脏组织病理结构改变,测定肾组织中活性氧(ROS)、丙二醛(MDA)、超氧化物歧化酶(SOD)及N-乙酰-β-D-葡萄糖苷酶(NAG)水平和活性;蛋白印迹法检测SETD6、DJ-1和Nrf2蛋白的表达。结果:与对照组比较,生化与病理检查结果显示镉暴露能导致明显的大鼠肾脏损伤,引起肾小球肿胀,肾小管广泛性病变,肾间质充血,炎性细胞浸润。肾组织ROS和MDA水平升高(P<0.05),总SOD活力下降(P<0.05),表明镉暴露诱导肾脏组织发生氧化应激损伤。而硒干预后减轻了镉暴露导致的肾脏组织结构和功能损伤,表明硒对镉暴露导致的肾脏损伤具有保护作用。同时,与对照组相比,SETD6、DJ-1和Nrf2在镉暴露后出现不同程度的蛋白表达下调(P<0.05);而硒干预后,与镉暴露组比较,SETD6蛋白表达显著下调(P<0.05),DJ-1和Nrf2蛋白表达显著上调(P<0.05),肾脏损伤减轻,表明硒可能通过抑制SETD6表达、增强DJ-1和Nrf2表达来发挥保护作用。结论:硒能有效拮抗慢性镉暴露导致的大鼠肾脏毒性,其作用机制可能是在氧化应激条件下,硒通过抑制SETD6,促进DJ-1表达,上调抗氧化转录因子Nrf2,增强机体抗氧化能力,减轻镉暴露诱导的氧化应激损伤。

OBJECTIVE： To investigate the protective effect of selenium on toxicity of rat kidney injury caused by chronic cadmium exposure and its possible mechanism. MATERIALS：The forty-eight male SD rats were randomly divided into four groups：blank control,cadmium exposure,negative control,and selenium treatment groups. There were 12 rats in each group,and animals were given deionized water,cadmium chloride,sodium selenite,and co-processing with cadmium chloride and sodium selenite by gastric gavage,respectively,for six days a week for twelve weeks. After treatment,blood,urine and kidney tissues were collected to determinate renal function indexes,such as urea nitrogen,creatinine,and total protein in serum and urine. We observed the pathological changes and detected level and/or activity of ROS （reactive oxygen species）,MDA （malondialdehyde）,T-SOD （total superoxide dismutase）,and NAG （N-acetyl-beta-d-glucosidase） in renal tissue. The protein imprinting method was used to detect protein expression of SETD6,DJ-1,and Nrf2. RESULTS：Biochemical and pathological results show that cadmium induced renal injury in rats,caused glomerular swelling,generalized lesions of renal tubules,and renal interstitial congestion,inflammatory cell infiltration. The levels of ROS and MDA in the kidney tissues increased （P〈0.05）,and activities of T-SOD decreased （P〈0.05）,indicating that cadmium exposure induced oxidative stress injury in the renal tissue. However,after seleniumintervention,the renal tissue structure and functional damage caused by cadmium exposure were reduced,indicating that selenium had protective effect on kidney injury caused by cadmium exposure. At the same time,compared with the blank control,SETD6,DJ-1 and Nrf2 showed varying degrees of reduced protein expression after cadmium exposure （P〈0.05）. After selenium intervention,compared to cadmium exposure group,SETD6 protein expression was significantly down-regulated （P〈0.05）,DJ-1 and Nrf2 protein expression were significantly up-regulated （P〈0.05）,kidney damage was reduced,suggesting that selenium might have played a protective role by inhibiting the expression of SETD6 and enhancing the expression of DJ-1 and Nrf2. CONCLUSION：Selenium effectively reduced the rat renal toxicity induced by chronic cadmium exposure. Its mechanism might be that under oxidative stress condition,selenium promoted the expression of DJ-1 by inhibiting SETD6,and thus upregulated the expression of antioxidant transcription factor Nrf2,through which enhanced the antioxidant capacity,and reduced the oxidative stress injury which was induced by cadmium exposure.