大鼠肾脏缺血预处理中COX-2和iNOS间信号转导关系的研究

目的 探讨大鼠肾脏缺血预处理中COX-2和iNOS的表达及其两者之间的信号转导关系，从而进一步探明肾脏缺血预处理的保护机制。方法 60只大鼠随机分为五组：假手术组（Sham组）、缺血再灌注组（I／R组）、缺血预处理十缺血再灌注组（IPC组）、NS398干预组（NS398组）和AG干预组（AG组）。在再灌注后24h、48h两个时间点取材，测定血清Scr；光镜观察形态学改变；采用Western blot法测定COX-2和iNOS的蛋白表达量，进行半定量分析。结果 与I／R组相比较，无论24h、48h，IPC组和两给药组的Scr值均明显降低，具有统计学差异（P〈0．05）。HE染色形态学也表明IPC组损伤明显减轻，与I／R组相比差异显著。NS398组和AG组两个给药组的损伤程度介于I／R组和IPC组之间。IPC组中COX-2和iNOS均活化、表达，其表达量与sham组和I／R组相比明显增多，差异显著（P〈0.05），而且48h的表达量多于24h；AG组COX-2表达量明显少于IPC组（P〈0．05）；NS398组和IPC组间iNOS表达量无显著差异（P〉0．05）。结论 本实验证实了肾脏IPC对I／R损伤的保护效应；肾脏IPC时COX-2和iNOS均活化、表达，参与了其保护效应，而且主要参与其晚期保护作用；在其信号转导中，iNOS是COX-2的上游，iNOS介导COX-2活化表达。

Association of COX-2 and iNOS in ischemic preconditioning in rat kidney

Objective To investigate the role and association of COX-2 and iNOS in the rat renal ischemic preconditioning;and thereby to explore the mechanism of renal ischemic preconditioning.Methods Sixty Wistar rats were randomly divided into five groups: sham operation group(sham),ischemic reperfusion group(I/R),ischemic preconditioning group(IPC),NS398(inhibitor of COX-2) treated group(NS398);and AG(inhibitor of iNOS)treated group(AG).Renal I/R injury model was induced by clamping bilateral renal arteries for 45 min followed by reperfusion.Rats in IPC group underwent four cycles of IPC(8-min ischemia followed by 5-min reperfusion).Rats in AG treated group or NS398 treated group were pretreated with AG or NS398 respectively before ischemic preconditioning.Rats were killed at 24 and 48 h after reperfusion.Renal function was determined by measuring serum creatinine.Changes of renal morphology were measured by hematoxylin-eosine(HE) staining.Western blot analysis was used to detect protein expressions of COX-2 and iNOS.Results Serum creatinine significantly increased after renal I/R injury and the difference was significant in comparison with the IPC group and the other two treated groups(P<0.05).Kidneys of I/R injury model rats displayed most significant histology changes including a loss of brush-border membranes,tubular dilatation,flattened tubular epithelium,cast formation,luminal debris and interstitial infiltration.The morphology damage in the IPC group became slighter compared to the I/R group.The degree of damages in AG group and NS398 group were between those of degress of IPC group and I/R group.COX-2 and iNOS were all activated and expressed in IPC group,and the expression amount was much plentiful than sham group and I/R group.Additionally the expression amount at 48 h was higher than 24 h.The expression of COX-2 in AG group was significantly decreased in comparison with IPC groups(P<0.05);and the difference in the amount of iNOS was not significant between NS398 group and IPC group(P<0.05).Conclusion Ischemic preconditioning has protective effect on renal I/R injury,which may be at least partly by activating COX-2 and iNOS;moreover iNOS may be an up-stream of COX-2,and may mediate COX-2 expression.