| Objective In this study,the experimental model of acute kidney injury in rats was established by surgical method.The serum creatinine and urea nitrogen concentrations in each group were detected,and the renal tubular injury score was performed.The effects of ischemic postconditioning on renal function and structure were analyzed to preliminarily determine the protective effect of ischemic postconditioning on acute kidney injury.Endoplasmic reticulum stress-related proteins GRP78 and CHOP and apoptotic protein Cleaved Caspase3 were detected to analyze the correlation between endoplasmic reticulum stress and apoptosis and ischemic postconditioning in alleviating acute kidney injury.Methods The animal models were divided into three groups: Sham group,ischemia reperfusion group and ischemic postconditioning group.36 of male SD rats weighing180-200 g were used.After 24 hours of laparotomy,the blood of inferior vena cava was collected,the serum creatinine and urea nitrogen concentrations were detected,and the renal function was evaluated;The morphological changes of renal tubules in Sham group,IR group and IPO group were scored under light microscope,and the effect of ischemic postconditioning on the degree of renal tubule injury was analyzed;the expression of Cleaved Caspase3 protein in Sham group was detected by immunohistochemistry and Western blot.The effect of ischemic postconditioning on apoptosis was observed;TUNEL staining was used to observe the effect of ischemic postconditioning on apoptosis and necrosis in kidney of Sham group,IR group and IPO group;The expression of GRP78 and CHOP in positive Sham group,IR group and IPO group were detected by immunofluorescence to evaluate the regulation of ischemic postconditioning on endoplasmic reticulum stress.Results The results of serum creatinine and urea nitrogen showed that there were significant changes in serum creatinine and urea nitrogen concentrations in Sham group,IR group and IPO group(F=202.726,P<0.001;F=496.013,P<0.001).The results of pairwise comparison showed that the serum creatinine and urea nitrogen concentrations in IR group were significantly higher than those in Sham group;the serum creatinine and urea nitrogen concentrations in IPO group were lower than those in IR group(all P<0.05);indicating that ischemic postconditioning may improve renal function.The results of HE staining showed that in Sham group,the morphology and structure of kidney were normal;in IR group,the renal tissue was seriously damaged,the renal tubular epithelial cells in the renal cortex were edematous,a large number of vacuoles appeared,and a large number of epithelial cells fell off into the lumen,the capillary in the glomus was seriously congested,and the interstitial congestion;compared with IR group,the renal tissue injury in IPO group was mild,the renal tubular epithelial cells were slightly edematous,and the interstitial congestion was very small.Some of them showed vacuolar degeneration and slight congestion of capillaries in the glomus.The results of renal tubular injury score showed that there was significant difference in the degree of renal tubular injury between groups(F=61.439,P<0.001).The results showed that IR group was significantly serious than Sham group;IPO group was significantly weaker than IR group(P<0.05).These results showed that ischemic postconditioning could reduce renal tissue injury.TUNEL staining results showed that there was significant difference in positive expression rate among Sham group,IR group and IPO group(F=92.818,P<0.001),and there was little positive expression in Sham group;IR group showed strong positive expression,which was significantly brighter than Sham group(P<0.05);IPO group showed significantly light positive expression than IR group(P<0.05).The results of immunohistochemistry and Western blot showed that the positive expression of Cleaved Caspase3 in different groups was significantly different(F=195.804,P<0.001;F=439.230,P<0.001).There was little positive expression in the cytoplasm of renal tubular epithelial cells in Sham group,which belonged to normal physiological apoptosis;a large number of renal tubular epithelial cells in IR group showed brownish yellow cytoplasm;there was a small amount of positive expression in the cytoplasm of renal tubular epithelial cells in IPO group.The expression of Cleaved Caspase3 in Sham group was very less;the expression of Cleaved Caspase3 in IR group was more abundant than that in Sham group(P<0.05);the expression of Cleaved Caspase3 in IPO group was less than that in IR group(P<0.05).In immunofluorescence assay,E-Cadherin was used as reference to indicate the integrity of renal tubular cells.The results showed that GRP78 and CHOP fluorescence signals in renal tubular epithelial cells were almost absent in Sham group;In IR group,the fluorescence was enhanced and the area was larger;The intensity of fluorescence signal in IPO group was lower than that in IR group,indicating that endoplasmic reticulum stress affects the degree of apoptosis.Conclusion After renal ischemia-reperfusion injury,the expression of Cleaved Caspase-3was increased,and the expression of endoplasmic reticulum stress related factors GRP78 and CHOP were higher,which indicated that endoplasmic reticulum stress reaction occurred with high intensity,a large number of renal tubular epithelial cells apoptosis and severe tissue damage.After ischemic postconditioning,the expression of Cleaved Caspase3 decreased,and the expression of endoplasmic reticulum stress-related factors GRP78 and CHOP decreased,which indicated that ischemic postconditioning could reduce the intensity of endoplasmic reticulum stress,reduce cell apoptosis,maintain the structure and function of renal tubular epithelial cells,and reduce the damage degree of renal tissue.This study provides experimental basis for further study of the protective mechanism of ischemic postconditioning and search for the target of anti renal ischemia reperfusion injury. |
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