内质网应激导致间歇低氧模型大鼠肾脏损伤的机制及洛沙坦的干预作用

The mechanism of renal injury induced by endoplasmic reticulum stress in rats with intermittent hypoxia and the intervention effect of losartan

目的探究内质网应激导致间歇低氧模型大鼠肾小管上皮细胞凋亡的机制以及洛沙坦的干预作用。方法将60只SPF级健康雄性SD大鼠随机分为4组(每组15只),分别为A组(空白对照组)、B组(间歇低氧组)、C组(间歇低氧+洛沙坦组)和D组(间歇低氧+生理盐水组)。其中C组和D组每日实验开始前30 min分别腹腔注射洛沙坦液30 mg/kg和同剂量生理盐水,然后将B、C、D组置于间歇低氧舱内。造模6周后取各组大鼠血清检测肾功能,采用苏木精–伊红染色观察肾脏组织形态学变化,透射电镜观察肾脏超微结构改变,TUNEL法检测肾小管上皮细胞凋亡指数,逆转录–聚合酶链反应法检测肾脏Caspase-12、JNK、CHOP mRNA的表达情况。结果4组大鼠肾功能血清学指标差异有统计学意义(P<0.05)。与A组比较,B、C、D组肾脏组织形态学及超微结构发生改变,B、D组损伤较为显著。B、D组肾小管上皮细胞凋亡指数较A组显著升高(均P<0.01),C组与B、D组相较凋亡指数显著降低(均P<0.01)。B、D组Caspase-12、JNK和CHOP mRNA表达水平较A组显著升高(均P<0.01);C组与B、D组比较,Caspase-12 mRNA表达水平降低(P<0.01,P<0.05),CHOP mRNA表达水平显著降低(均P<0.01)。结论间歇低氧可能通过激活内质网应激的Caspase-12、JNK及CHOP三条凋亡通路导致大鼠肾小管上皮细胞凋亡,洛沙坦对间歇低氧模型大鼠的肾脏起保护作用,其机制可能与抑制内质网应激介导的凋亡相关通路有关。

Objective To explore the mechanism of renal tubular epithelial cell apoptosis induced by endoplasmic reticulum stress in rats with intermittent hypoxia(IH)and the intervention effect of losartan.Methods Sixty SPF grade healthy male SD rats were randomly divided into four groups(15 rats in each group),namely as group A(control group),group B(IH group),group C(IH+losartan group),and group D(IH+saline group).The group C and D were intraperitoneally injected with losartan 30 mg/kg and the same dose of saline 30 minutes daily before the experiment,and then the group B,C and D were placed in the intermittent hypoxia chamber.After 6 weeks of modeling,serum of the rats was sampled to detect the renal function.Hematoxylin-eosin staining was used to observe histomorphological changes of the kidney;transmission electron microscopy was used to observe ultrastructural changes of the kidney;TUNEL was used to detect apoptotic index of the renal tubular epithelial cells;and RT-PCR method was used to detect expressions of caspase-12,JNK and CHOP mRNA in the kidney.Results The differences of renal function among these four groups were statistically significant(all P<0.05).Hematoxylin-eosin staining and transmission electron microscopy showed the histomorphological and ultrastructural changes of the kidneys in group B,C and D compared with group A,and the damages in group B and D were more significant.TUNEL results showed that the apoptotic index of renal tubular epithelial cells in group B and D was significantly higher than that in group A(P<0.01),while that in group C was significantly lower than that in group B and D(all P<0.01).RT-PCR results showed that caspase-12,JNK and CHOP mRNA expressions were significantly higher in group B and D than those in group A(all P<0.01);caspase-12 mRNA expression was significantly lower in group C than that in group B and D(P<0.01;P<0.05);and CHOP mRNA expression was significantly lower in group C than that in group B and D(all P<0.01).Conclusions IH may induce apoptosis of renal tubular epithelial cells by activating endoplasmic reticulum stress through caspase-12,JNK and CHOP.Losartan has protective effects on the kidney of rats with intermittent hypoxia.Its mechanism may be related to the inhibition of apoptotic pathways mediated by endoplasmic reticulum stress.