| Ischemic postconditioning is a new pattern against ischemia reperfusioninjury of target organs, which is defined as a series of brief interruptions betweenprereperfusions applied before whole regain of reperfusion, which has similarprotective effect and molecular mechanism to ischemic preconditioning on targetorgans including heart, liver and brain. Because ischemic postconditioning can beapplied after ischemia of target organs with high clinical controllability, it hasmore direct and wide clinical application value than ischemic preconditioning.However, there have not relevant reports about similar protective effect ofischemic postconditioning on kidney. Therefore, we established rat model ofischemic postconditioning based on the model of acute kidney ischemiareperfusion injury. Then we researched protective effect and molecularmechanism of kidney ischemic postconditioning based on the rat model of ischemic postconditioning.ObjectivesObjectives:To establish rat model of ischemic postconditioning based onthe model of acute kidney ischemia reperfusion injury. To investigate protectiveeffect of kidney ischemic postconditioning and effect on apoptosis of tubularepithelial cells. To discuss molecular mechanism of ischemic postconditioningdecreased apoptosis of kidney tubular epithelial cells.Methods:First, 40 SD rats were randomized into 5 groups: control group(S group), ischemia reperfusion group (IR group) and 3 ischemic postconditioninggroups (IPO1, IPO2 and IPO3 groups). IR group was induced by clamping thebilateral renal arteries for 45 minutes. IPO1, IPO2 and IPO3 groups were treatedby different postconditioning methods after kidney ischemia. Thepostconditioning method of IPO3 group was sequential 20 seconds reperfusionand another 20 seconds ischemia for a 10 cycles. After 24 hours reperfusion, theblood samples were draw from the inferior vena cava and the nephridial tissueswere fixed. Then renal function was detected by biochemical methods. Second,successful rat model was chosen as ischemic postconditioning group (IPO group).Morphology changes and tubular injury score of each group's nephridial tissueswere examined by HE staining and PAS staining under light microscope andultrastructural changes of each group's nephridial tissues were examined underelectron microscope. Third, the expression of apoptosis related molecules(Caspase-3, Fas, Bcl-2 and Bax protein) in each group's nephridial tissues wereexamined by immunohistochemical staining and western blot. Then molecularmechanism of ischemic postconditioning decreased apoptosis of kidney tubularepithelial cells was discussed.Results:In rat model experiment, the postconditioning method of IPO3 group was sequential 20 seconds reperfusion and another 20 seconds ischemia fora 10 cycles. Blood urea nitrogen level of IPO3 group was (27.95±3.21) mmol/Land serum creatinine level of IPO3 group was (232.00±49.23)μmol/L. Comparedwith the IR group, the above 3 indexes of the IPO3 group were decreasedremarkably (P<0.01). However, there was no significant difference between the IRgroup and the other 3 ischemic postconditioning groups (P>0.05).Morphology changes were examined under light microscope and electronmicroscope. In the IR group, interstitial edema, brush border disappearance ofresidual renal tubular epithelial cells, desquamation and necrosis of a large numberof epithelial were observed in renal tissues. Mitochondria disappeared,endoplasmic reticulum reduced and chromatin degeneration were examined underelectron microscope. The tubular injury score of IR group was 565.13±63.98. Inthe IPO group, brush border lost of some tubular epithelial cells and few particlecasts were observed in renal tissues. Relative ectasia of cell organelles and nuclearchromatin margination were examined under electron microscope. The tubularinjury score of IR group was 382.00±47.63. Compared with the IR group, themorphology changes under light microscope and electron microscope of IPOgroup were reduced and the tubular injury score of the IPO group were decreasedremarkably (P<0.01).The immunohistochemical staining results showed that there was nosignificant difference of Caspase-3 expression in renal tissues between the IRgroup and the IPO group (P>0.05). Positive index of Fas in IPO group renaltissues was (21.17±4.81) % and positive index of Bax was (21.60±3.79) %.Compared with the IR group, those were decreased remarkably (P<0.01). Positiveindex of Bcl-2 in IPO group renal tissues was (33.34±5.12) %. Compared with the IR group, it was increased remarkably (P<0.01). The western blot results showedthat the expression intensity of Procaspase-3 in IPO group renal tissues was0.77±0.05 which was higher than IR group. The expression intensity of active(cleaved) Caspase-3 was 1.12±0.27 which was lower than IR group. Comparedwith the IR group, those were significantly difference (P<0.01). There was nosignificant difference of total Caspase-3 expression in renal tissues between the IRgroup and the IPO group (P>0.05). Compared with the IR group, the expressionintensities of Fas, Bcl-2 and Bax proteins were similar to immunohistochemicalstaining results.Conclusions:The postconditioning method of the IPO3 group which wassequential 20 seconds reperfusion and another 20 seconds ischemia for a 10 cyclesafter the acute kidney ischemia can reduce acute kidney ischemia reperfusioninjury and help us to establish the postconditioning rat model of the acute kidneyischemia reperfusion injury.Functional study showed that kidney ischemic postconditioning can decreaseblood urea nitrogen and serum creatinine level and it can protect kidney functionof rats which have kidney ischemia reperfusion injury. Morphology study showedthat ischemic postconditioning can stabilize the ultrastructure of mitochondrionand endoplasmic reticulum of rats which have kidney ischemia reperfusion injury.It can decrease apoptosis and necrosis of tubular epithelial and tubular injury ofacute kidney ischemia reperfusion in rats.Kidney ischemic postconditioning has an inhibitory action on apoptosis ofrenal epithelial cells. It play the role mainly through trigger Fas of exogenousdeath receptor-dependent apoptosis pathway and triggers Bcl-2 and Bax ofendogenous mitochondrial apoptosis pathway. Compared with ischemia reperfusion injury, exogenous apoptosis pathway still play a relatively weak rolein promoting apoptosis, but endogenous apoptosis pathway mainly play the role ofapoptosis inhibition. |
