Effect of electro-acupuncture on Nrf2 expression in renal tissues of rabbits with endotoxic shock-induced acute kidney injury: relationship with p38MAPK signaling pathway

Objective To investigate the effect of electro-acupuncture (EA) on nuclear factor E2-related factor 2 (Nrf2) expression in the renal tissues of rabbits with endotoxic shock-induced acute kidney injury (AKI) and the relationship with p38 mitogen-activated protein kinase (p38MAPK) signaling pathway.Methods Seventy male New Zealand white rabbits,weighing 1.5-2.0 kg,aged 2 months,were randomized into 7 groups (n =10 each) using a random number table:normal control group (C group),endotoxic shock-induced AKI group (AKI group),EA + endotoxic shock-induced AKI group (EA group),non-acupoints + endotoxic shock-induced AKI group (SA group),EA + endotoxic shock-induced AKI + specific p38MAPK blocker SB203580 group (EAS group),SB203580 group (S group),and ethanol group (A group).EA (intensity 1-2 mA,frequency 2/100 Hz,wave length 0.2-0.6 ms) of Zusanli and Shenyu lasting for 15 min was performed once a day for 5 consecutive days in EA and EAS groups.In SA group,EA was performed at the points 0.5 cm lateral to the acupoints of bilateral Zusanli and Shenyu using the parameters of EA mentioned above.At 24 h after the last EA,endotoxic shock-induced AKI was induced by injection of lipopolysaccharide (LPS) 5 mg/kg (in 2 ml normal saline) in AKI,EA,SA and EAS groups,while the equal volume of normal saline was given in the other groups.At 30 min before the model was established,5/μmol/kg SB203580 (in 0.5 ml ethanol) was injected intravenously in EAS and S groups,while ethanol 0.5 ml was given in A group and the equal volume of normal saline was given in the other groups.Blood samples were obtained at 6 h after administration of LPS or normal saline for determination of serum urea nitrogen (BUN) and creatinine (Cr) concentrations.The animals were sacrificed and kidney specimens were obtained for microscopic examination of pathological changes which were scored and for measurement of Nrf2 protein expression and phosphorylation of p38MAPK (by Western blot) and Nrf2 mRNA expression (using fluorescent quantitative PCR).Results Compared with C group,the pathological score and serum BUN and Cr concentrations were significantly increased,and Nrf2 mRNA and protein expression was up-regulated in AKI,EA,SA and EAS groups,the phosphorylation of p38MAPK was increased in AKI,EA and SA groups,and no significant changes were found in the parameters mentioned above in S and A groups.Compared with AKI group,the pathological score and serum BUN and Cr concentrations were significantly decreased,and Nrf2 mRNA and protein expression was up-regulated in EA and EAS groups,the phosphorylation of p38MAPK was increased in EA group,the phosphorylation of p38MAPK was decreased in EAS group,and no significant changes were found in the parameters mentioned above in SA group.Compared with EA group,the pathological score and serum BUN and Cr concentrations were significantly increased,Nrf2 mRNA and protein expression was down-regulated,and the phosphorylation of p38MAPK was decreased in EAS group.Conclusion The mechanism by which EA mitigates endotoxic shock-induced AKI may be related to activation of p38MAPK signaling pathway and up-regulation of Nrf2 expression in renal tissues of rabbits. Key words: Electroacupuncture;  NF-E2-related factor 2;  p38 Mitogen-activated protein kinases; Endotoxemia ;  Kidney