The Protective Effect Of Apolipoprotein A-I On Renal Ischemia/Reperfusion Injury In Rats

High density lipoprotein(HDL) has the anti-inflammatory function and can protect kidney from ischemia-reperfusion(I/R) injury.In present study,we investigated the function of Apolipoprotein A-Ⅰ(ApoA-Ⅰ),the major apolipoprotein of HDL,in I/R injury.Human plasma precipitateⅣwas utilized to isolate ApoA-Ⅰby cold ethanol precipitation,which is modified by us.Purified ApoA-Ⅰwas identified by SDS-PAGE and Western blot.The study on the detoxification effect of ApoA-Ⅰon LPS-mediated macrophages activation and LPS binding test of ApoA-Ⅰin vitro showed that the prepared ApoA-Ⅰhas the same biological activity as natural wild type ApoA-Ⅰ.We investigated the protective role of ApoA-Ⅰin renal ischemia-reperfusion injury in SD rats anesthetized with urethane.Saline(I/R group) or ApoA-Ⅰ(25 mg/kg) (ApoA-Ⅰgroup) was administered intravenously 30 min before 45min-ischemia by occlusion of the renal pedicles.Rats in sham group were subjected to the same surgical procedures as I/R rats except that the renal pedicles were not occluded.Blood samples were collected at 6 h of reperfusion for determination of serum creatinine, BUN,TNF-αand IL-1βlevels.Kidneys were harvested at 6 h of reperfusion for assay of MDA content and MPO and SOD activity,as well as for observation of histopathological changes and for immunohistochemical analysis of ICAM-1 and P-selectin expression on endothelium.The results showed that administration of ApoA-Ⅰcould significantly reduce serum creatinine and BUN levels in I/R group(172.78±19.15μM vs 114.56±7.30μM,p＜0.05 and 18.43±2.96mM vs 11.25±1.94mM,p＜0.01,respectively),and also reduce serum TNF-αlevels from 10.95±3.63pg/ml to 6.43±1.43pg/ml(p＜0.05), as well as serum IL-1βlevels from 355.00±52.62pg/ml to 208.75±37.76pg/ml (p＜0.01) compared with I/R group.Tissue MDA content and MPO activity in ApoA-I-treated group were significantly reduced compared with I/R group(34.77±2.48nmol/g wet tissue vs 23.71±2.03nmol/g wet tissue,p＜0.01 and 6.14±0.58U/g wet tissue vs 3.03±0.51U/g wet tissue,p＜0.01,respectively),whereas tissue SOD activity in ApoA-I-treated group was significantly increased compared with I/R group(86.40±21.52 U/g wet tissue vs 59.38±15.86U/g wet tissue,p＜0.05).Moreover, ApoA-I treatment suppressed the expression of ICAM-1 on endothelium,and the similar trend could also be observed in the expression of P-selectin.The histopathological analysis of rat kidneys harvested at 6h of rperfusion showed that ApoA-I attenuated I/R-induced renal injury and tissue inflammation.These results suggest that ApoA-I can provide beneficial protective effect on renal ischemia-reperfusion injury in rats,and thus has promising clinical value for the treatment of I/R injury.