| Background:Acute renal failure due to ischaemia-reperfusion injury is a common clinical problem with a high overall mortality. An effective treatment for the disease has remained elusive. In the haematopoietic system, the principal function of erythropoietin is the regulation of RBC production and differentiation. However, many researches discovered that EPO and its receptor were expressed in multiple tissues, including the vasculature, brain, uterus, heart and skeletal muscle. The EPO receptor is present in the glomerulus, mesangial and tubular epithelial cells in the kidney. More attention has been focused on the therapeutic use of EPO in acute renal failure. In vivo studies and our previous studies have shown that EPO attenuates the dysfunction associated with renal ischemia-reperfusion injury. However it is still unclear how EPO protect renal ischaemia-reperfusion injury. It is reported that anti-apoptosis is an important mechanism. Mitochondria are engaged via the intrinsic pathway of cell apoptosis. Once cytochrome C released from the mitochondrial intermembrane space (IMS), the cell is irreversibly committed to death.Objectives:This study was to identify whether the beneficial effect of erythropoietin on ischemia-reperfusion induced acute kidney injury was related to the inhibition of mitochondrial apoptotic pathway.Methods:One hundred and four300-350g male SD rats were randomly assigned into4experimental groups as Sham+NS (N=20), Sham+EPO (N=20), IR+NS (N=32) and IR+EPO (N=32). For the ischemia-reperfusion group, bilateral kidneys underwent90min ischemia by clamping renal pedicles. A single dose of5000IU/kg EPO was injected intraperitoneally2hrs prior to occlusion. Animals were sacrificed at1,3,6and24hrs after reperfusion to obtain kidney and venous blood samples. The serum concentration of Cr and BUN were measured. Anti-apoptotic effect was evaluated according to TUNEL and semi-quantitive analysis of tissue cytochome C levels by immunohistochemistry method. The serum concentration of MCP-1, IL-1β, IL-6and TNF-α were measured by ELISA.Results:(1) Compared with Sham+NS group, SCr and BUN level in the IR+NS group increased significantly at1h after reperfusion (P<0.001).(2)Compared with IR+NS group, the SCr level in the IR+EPO group were significantly lower at3h (P=0.004) and 24h (P<0.001) after reperfusion. Compared with IR+NS group, the BUN level in the IR+EPO group were significantly lower at24h after reperfusion (P=0.041).(3) Compared with Sham+NS group, the apoptotic cell number in the IR+NS group increased significantly at3h after reperfusion (P<0.001). Compared with IR+NS group, the apoptotic cell number in the IR+EPO group were significantly lower at3h (P=0.045) and24h (P=0.008) after reperfusion.(4) Compared with Sham+NS group, the cytochrome C expression in the IR+NS group increased significantly at1h after reperfusion (P<0.001). Compared with IR+NS group, the cytochrome C expression in the IR+EPO group were significantly lower at6h and24h after reperfusion (P<0.001).(5) Compared with Sham+NS group, the serum MCP-1, IL-1β, IL-6and TNF-α level in the IR+NS group increased significantly at1h after reperfusion (P<0.05). Compared with IR+NS group, the serum MCP-1, IL-1β and IL-6level in the IR+EPO group were significantly lower at24h after reperfusion (P<0.05).Conclusion:(1) Ischemia-reperfusion insult caused significant renal injury.(2) EPO appears to attenuate I/R-induced renal dysfunction.(3) EPO reduced the apoptotic cell number, and at the same time EPO prevented cytochrome C releasing from mitochondria. It is indicated that the beneficial effect of erythropoietin on acute kidney injury was probably related to the inhibition of mitochondrial apoptotic pathway.(4) EPO reduced the serum MCP-1, IL-1β and IL-6level. It is indicated that EPO had an inhibition effect on systemic inflammatory response. |
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