Role of Nrf2/HO-1 signaling pathway in reduction of acute kidney injury following orthotopic liver transplantation by hydrogen-rich saline in rats

Objective To investigate the role of nuclear factor erythroid 2-related factor 2(Nrf2)/heme oxygenase-1(HO-1)signaling pathway in reduction of acute kidney injury following orthotopic liver transplantation(OLT)by hydrogen-rich saline in rats. Methods Thirty-two healthy adult male Sprague-Dawley rats, weighing 220-250 g, were randomly assigned into 4 groups(n=8 each)using a random number table: sham operation group(S group), OLT group, hydrogen-rich saline group(HS group), and all-trans retinoic acid(ATRA)group.Laparotomy was performed, and the related blood vessels were isolated in group S. The model of orthotopic autologous liver transplantation was established in OLT, HS and ATRA groups.Normal saline and hydrogen-rich saline 6 ml/kg were injected through the inferior vena cava at 5 min before the portal vein was clamped in OLT and HS groups, respectively.In group ATRA, Nrf2 inhibitor ATRA 7 mg/kg was injected intraperitoneally once a day for 2 consecutive days, the model of orthotopic autologous liver transplantation was established at 16 h after the last injection of ATRA, and the other treatments were similar to those previously described in group HS.At 6 h of reperfusion, blood samples were collected for determination of serum blood urea nitrogen(BUN), creatinine(Cr), interleukin-10(IL-10)and tumor necrosis factor-alpha(TNF-α)concentrations.After blood sampling, the lungs were removed for determination of malondialdehyde(MDA)content, superoxide dismutase(SOD)activity, expression of HO-1, Bcl-2 and Bax mRNA(by using real-time reverse transcriptase polymerase chain reaction), and HO-1 protein expression in lung tissues(by Western blot)and for microscopic examination.The damage to the renal tubules was scored. Results Compared with group S, the serum BUN, Cr and TNF-α concentrations were significantly increased, the serum IL-10 concentrations were decreased, the MDA content and renal tubular damage score were increased, the SOD activity was decreased, and the expression of HO-1 protein and mRNA, and Bcl-2 and Bax mRNA was up-regulated in group OLT(P<0.05). Compared with group OLT, the serum BUN, Cr and TNF-α concentrations were significantly decreased, the serum IL-10 concentrations were increased, the MDA content and renal tubular damage score were decreased, the SOD activity was increased, the expression of HO-1 protein and mRNA and Bcl-2 mRNA was up-regulated, and the expression of Bax mRNA was down-regulated in group HS(P<0.05). Compared with group HS, the serum BUN, Cr and TNF-α concentrations were significantly increased, the serum IL-10 concentrations were decreased, the MDA content and renal tubular damage score were increased, the SOD activity was decreased, the expression of HO-1 protein and mRNA and Bcl-2 mRNA was down-regulated, and the expression of Bax mRNA was up-regulated in group ATRA(P<0.05). Conclusion The mechanism by which hydrogen-rich saline reduces acute kidney injury following OLT is probably associated with activation of Nrf2/HO-1 signaling pathway in rats. Key words: Hydrogen; NF-E2-related factor 2; Heme oxygenase-1; Liver transplantation; Kidney injury