The Role Of Nrf2-HO-1/NQO-1 Signaling Pathway In Chronic Renal Allograft Dysfunction

BackgroundChronic renal allograft dysfunction(CRAD)is a leading cause of long-term renal allograft loss,the main cause of CRAD is still unclear.Oxidative stress may account for the nonspecific interstitial fibrosis and tubular atrophy of CRAD.As one of the most important antioxidant defense systems of the body,the Nrf2-HO-1/NQO-1 signaling pathway may alter during CRAD,activation of Nrf2-HO-1/NQO-1 signaling pathway via sulforaphane could be benefical to the renal allograft.Objectivesi)To establish a rat model of CRAD and confirm oxidative stress status in CRAD.ii)To observe the changes of Nrf2-HO-1/NQO-1 signaling pathway in the renal allograft of CRAD.iii)To investigate whether continuous activation of Nrf2-HO-1/NQO-1 signaling pathway via sulforaphane can alleviate intrarenal oxidative stress,improve function,urinary protein and pathologic changes of the renal allograft of CRAD.MethodsKidneys of F344 rat were orthotopically transplanted into Lewis rat recipients to establish a CRAD model,sulforaphane was administered at 1.5 mg/kg intraperitoneally once daily.The uninephrectomized Lewis and F344 rats were used as control groups.Rats were divided into 4 groups:Lewis single nephrectomy control group(n=10),F344 single nephrectomy control group(n=10),CRAD group(n=10),CRAD+ sulforaphane group(n=10);all groups were observed for 24 weeks.Serum creatinine,urea nitrogen and 24 hour-urinary protein levels were monitored for variations at 8,12,16,20 and 24 weeks after transplantation.After 24 weeks,rats were harvested and intrarenal oxidative stress indicator malonaldehyde and toal superoxide dismutase activity were compared.The pathological degrees were assessed according to total Banff scores after hematoxylin eosin,masson's trichrome and periodic acid-schiff stainings.The amount and distribution of Nrf2,HO-1 and NQO-1 levels were observed and compared respectively via each ratio of integral optical density to measurement area.Western Blot analysis was conducted to further verify the changes of total Nrf2,HO-1,NQO-1 and nuclear Nrf2,the integral optical density ratio of target band to its internal reference was used for comparisons among groups.ResultsThe serum creatinine and urea nitrogen levels in the CRAD group were more than those in the Lewis and F344 single nephrectomy control group at 8,12,16,20,24 weeks.The 24-hour urinary protein level in the CRAD group was more than those in the Lewis and F344 single nephrectomy control group at 12,16,20,24 weeks while the CRAD+sulforaphane group had a less 24 hour-urinary protein level than those in CRAD group at 20 and 24 weeks.The sulforaphane intervention delayed the progression of serum creatinine and blood urea nitrogen levels,and that of the 24-hour urinary protein level,in particular.Compared to Lewis and F344 single nephrectomy control group,the CRAD group revealed increased oxidative stress,as indicated by increased renal malondialdehyde level and decreased total superoxide dismutase activity.Typical pathological manifestations of CRAD,including tubular atrophy,mononuclear cell infiltration,interstitial fibrosis and arterial intima proliferation in CRAD group can be observed.Significant decreased levels of total Nrf2,HO-1,NQO-1 and nuclear Nrf2 were found in CRAD group.In contrast,CRAD+sulforaphane group showed decreased renal malondialdehyde level and increased total superoxide dismutase activity,signifying alleviation of intrarenal oxidative stress.In addition,the pathological degree represented by total Banff scores was reduced and the upregulation of Nrf2,HO-1,NQO-1 and nuclear Nrf2 was observed.Conclusions?)Oxidative stress is involved in CRAD and may be responsible for the nonspecific interstitial fibrosis and tubular atrophy of CRAD.?)The Nrf2-HO-1/NQO-1 signaling pathway is downregulated in CRAD,suggesting the inhibition of its normal function.?)Oxidative stress alleviation via sulforaphane-induced Nrf2-HO-1/NQO-1 signaling pathway activation can improve renal function,especially the urinary protein and pathologic changes of the renal allograft in CRAD.