Effect of electro-acupuncture at Zusanli and Neiguan acupoints on endotoxic shock-induced myocardial injury in rabbits and the role of heme oxygenase-1

Abstract

Objective To evaluate the effect of electro-acupuncture (EA) at Zusanli (ST-36) and Neiguan (PC6) acupoints on endotoxic shock (ES)-induced myocardial injury in rabbits and the role of heme oxygenase-1 (HO-1).Methods Sixty healthy male New Zealand white rabbits,aged 2 months,weighing 1.5-2.0 kg,were randomly assigned into 6 groups (n =10 each) using a random number table:sham operation group (group S) ; heme oxygenase-1 inhibitor zinc protoporphyrin-Ⅸ (ZnPP-Ⅸ) group (group Z) ; group ES; EA + ES group (group EES); sham EA + ES group (group SEES); EA + ES + ZnPP-Ⅸ group (group EESZ).The rabbits were anesthetized with intravenous 20％ urethane 5 ml/kg.Right common carotid artery was cannulated for BP monitoring.Ear vein was cannulated for drug administration.ES was induced with lipopolysaccharide (LPS) 5 mg/kg injected intravenously in ES,EES,SEES and EESZ groups,while the equal volume of normal saline was given in S and Z groups.ES was confirmed by decrease in MAP to 75 ％ of the baseline value.ZnPP-Ⅸ 10 μmol/kg (in 1 ml of NaHCO3 50 mmol/L) was injected intraperitoneally at 2 h after LPS or normal saline administration in EESZ and Z groups,while the equal volume of NaHCO3 was injected intraperitoneally in the other groups.In EES and EESZ groups,bilateral 30 min EA stimulation (0.2-0.6 ms,2/100 Hz,2-3 mA) of ST36 and PC6 was performed once a day on days 1-4 before induction of ES and on the day of induction of ES (from the onset of LPS injection until the end of induction of ES).In SEES group,electro-stimulation was performed at the points 0.5 cm lateral to the acupoints of ST36 and PC6 and the method was similar to those previously described in group EES.Blood samples were taken from the right common carotid artery at 6 h after LPS or normal saline administration for measurement of serum tumor necrosis factor-alpha (TNF-α),creatine kinase (CK),and lactic dehydrogenase (LDH) levels.Then the rabbits were sacrificed by exsanguination,and the myocardial tissues were removed for microscopic examination of the pathological changes which were scored and for determination of HO-1 protein (by Western blot) and mRNA (using fluorescence quantitative PCR) expression.Results Compared with group S,the pathological scores and concentrations of serum TNF-α,CK,and LDH were significantly increased,and the expression of HO-1 protein and mRNA was up-regulated in ES,EES,SEES and EESZ groups (P ＜ 0.05),and no significant change was found in the parameters mentioned above in group Z (P ＞ 0.05).Compared with group ES,the pathological scores and concentrations of serum TNF-α,CK,and LDH were significantly decreased,and the expression of HO-1 protein and mRNA was up-regulated in group EES (P ＜ 0.05),while no significant change in the parameters mentioned above was found in SEES and EESZ groups (P ＞ 0.05).Compared with group EES,the pathological scores and concentrations of serum TNF-α,CK,and LDH were significantly increased,and the expression of HO-1 protein and mRNA was down-regulated in group EESZ (P ＜ 0.05).Conclusion EA at ST-36 and PC6 acupoints can attenuate ES-induced myocardial injury in rabbits and upregulation of HO-1 expression and inhibition of inflammatory responses may be involved in the mechanism. Key words: Electric stimulation therapy; POINT ST36 (ZUSANLI) ; POINT PC6 (NEIGUAN) ; Shock,septic; Myocardium; Heme oxygenase-1