Role of PKCα in electroacupuncture-induced reduction of acute kidney injury induced by endotoxic shock in rabbits: the relationship with Nrf2/HO-1 pathway

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Objective To evaluate the role of protein kinase Ca (PKCα) in electroacupuncture (EA)-induced reduction of acute kidney injury (AKI) induced by endotoxic shock, and the relationship with nuclear factor E2-related factor 2/heme oxygenase-1 Nrf2/HO-1 pathway in rabbits. Methods Eighty healthy male New Zealand white rabbits, aged 2 months, weighing 1.5-2.0 kg, were randomly divided into 8 groups (n= 10 each) using a random number table: sham operation group (group S), group AKI, specific PKCα inhibitor chelerythrine + AKI group (group CHA), chelerythrine group (group Che), dimethyl sulfoxide (DMSO) group (group D), EA at acupoints + AKI group (group EA), EA at non-acupoints + AKI group (group SEA), and EA at acupoints + chelerythrine + AKI group (group CEA). Bilateral 30 min EA (disperse-dense wave, wave length 0.2-0.6 ms, frequency 2/15 Hz, intensity 1-2 mA) stimulation of Zusanli and Shenshu acupoints was performed once a day for 4 days before establishment of the model and during the process of establishment of the model in EA and CEA groups.In group SEA, EA was performed at the points 0.5 cm lateral to the acupoints of Zusanli and Shenshu with the same parameters.The animals were anesthetized with iv 20% urethane 5 ml/kg, tracheostomized and kept spontaneous breathing.Lipopolysaccharide 5 mg/kg (in 2 ml of normal saline) was injected via the auricular vein to establish the model of endotoxic shock-induced AKI in AKI, CHA, EA , SEA and CEA groups, while the equal volume of normal saline was given in S, Che and D groups.At 30 min before establishment of the model, chelerythrine 5 mg/kg (in 0.5 ml of 1% DMSO) was injected intravenously in CHA and CEA groups, the equal volume of chelerythrine was given in Che group, while the equal volume of DMSO was given in group D. At 6 h after lipopolysaccharide or normal saline injection, blood samples were taken from the internal carotid artery for determination of serum urea nitrogen (BUN) and creatinine (Cr) concentrations.The rabbits were then sacrificed by exsanguinations.The kidney specimens were removed for microscopic examination of pathologic changes which were scored and for determination of superoxide dismutase (SOD) activities, malondialdehyde (MDA) contents, and expression of PKCα protein and HO-1 protein, and expression of Nrf2 in nucleoprotein and total protein. Results Compared with group S, the serum BUN and Cr concentrations were significantly increased, MDA contents were increased, the activities of SOD were decreased, the kidney injury scores were increased, and the expression of PKCα protein, HO-1 protein, and Nrf2 in nucleoprotein and total protein was up-regulated in AKI, CHA, EA, SEA and CEA groups.Compared with group AKI, the serum BUN and Cr concentrations were significantly decreased, MDA contents were decreased, the activities of SOD were increased, the kidney injury scores were decreased, and the expression of PKCα protein, HO-1 protein, and Nrf2 in nucleoprotein and total protein was up-regulated in group EA, and the serum BUN and Cr concentrations were significantly increased, MDA contents were increased, the activities of SOD were decreased, the kidney injury scores were increased, and the expression of PKCα protein, HO-1 protein, and Nrf2 in nucleoprotein and total protein was down-regulated in CHA and CEA groups.The serum BUN and Cr concentrations were significantly higher, MDA contents were higher, the activities of SOD were lower, the kidney injury scores were higher, and the expression of PKCα protein, HO-1 protein, and Nrf2 in nucleoprotein and total protein was lower in group CEA than in group EA, and in CHA group than in CEA group. Conclusion PKCα mediates reduction of endotoxic shock-induced AKI by EA of Zusanli and Shenshu acupoints in rabbits, and the mechanism may be related to activation of Nrf2/HO-1. Key words: Electric stimulation therapy; Protein kinase C-alpha; NF-E2-related factor2; Heme oxygenase-1; Shock, septic; Acute kidney injury