Protective Role Of Renalase In Ischemic Acute Kidney Injury By Activating Transcription Factor Nrf2

Objectives To investigate the effect and mechanism of Renalase in preventing acute kidney injury(AKI)induced by renal ischemia/reperfusion(IR)in vivo and in vitro.Methods in vivo,a total of 24 Sprague-Dawley(SD)rats were randomly divided into three groups,a sham-operated group(Shame group,n=8),an ischemic group(IR group,n=8)and a renalase intervention group(IR+Ren group,n=8).In the IR group and IR+Ren group,rats were subjected to 60 min occlusion of bilateral renal pedicles,followed by reperfusion for 24 hours and administrated with renalase 1mg/kg or saline 1ml at 30 min before IR inducing operation,in the Shame group,renal pedicles were separated without renal artery clipping.After IR 24 hours,the kidneys and blood samples were collected.serum parameters,renal morphology was assessed in groups.Renal intracellular Malondialdehyde(MDA)and superoxide dismutase(SOD)were measured with commercial kit.Renal expression of nuclear factor E2-related factor 2(Nrf2),hemeoxygenase-1(HO-1),NADPH quinine oxidoreductase(NQO-1)were analyzed by western blot.in vitro,human renal proximal epithelial tubular cells(h RPTEC)were treated with hydrogen peroxide(0.5 mmol/L)to induce oxidative injuries.To determine whether renalase can protect against cellular injury,h RPTEC cells were pre-incubated with/without renalase at 1 or 5 ?g/ml.MDA and SOD were measured,Nrf2,HO-1 and NQO-1 were analyzed.Results Renal tubular inflammation and necrosis were more severe and serum creatinine and blood urea nitrogen levels were higher in IR group subjected to renal ischemia reperfusion compared with Shame group(P<0.05).Administration of renalase reduced SCr and BUN levels and ameliorated IR-AKI in IR+Ren group(P<0.05).Renal levels of MDA were elevated in the IR group compared with the shame group(P<0.05).Moreover,lower renal levels of SOD were observed in the IR groups.Pretreatment with recombinant renalase decreased renal MDA levels and increased renal SOD levels dramatically(P<0.05),which demonstrated that renalase could reduce oxidative stress in rats with IR-AKI.The expression of Nrf2,HO-1 and NQO-1 in the renal tissue were increased by renal I/R,and markedly elevated by treatment with recombinant renalase(P<0.05).Hydrogen peroxide increased the levels of MDA and reduced SOD.Renalase restored the change of MDA and SOD in h RPTEC cells(P<0.05).Moreover,Hydrogen peroxide evokes activation of Nrf2,HO-1 and NQO-1,most likely due to intracellular oxidative stress.Renalase pretreatment increased the levels of cytoplasmic Nrf2,HO-1,NQO-1 and nuclear Nrf2 expression.Conclusions The mechanisms of renalase protecting ischemic acute kidney injury may be related with reducing the levels of oxidative stress via activation of Nrf2.