Protective Effect of Ischemic Preconditioning on Lung Injury Induced by Intestinal Ischemia/Reperfusion in Rats

Objective To investigate the effect of ischemic preconditioning(IPC) on lung injury induced by intestinal ischemia/reperfusion(IIR) in rats and the mechanism.Methods Twenty-four male SD rats were randomly divided into 4 groups(n=6 each): control group undergoing sham operation,IIR group,ischemic preconditioning(IPC) group and the group receiving heme oxygenase-1(HO-1) inhibitor zinc protoporphyrin(ZnPP) 10 mg/kg one day before IPC(ZnPP group).The superior mesenteric artery(SMA) was exposed and occluded for 30 minutes of ischemia,then the clamp was removed for 180 minutes of reperfusion to establish a model of IIR injury.Ischemic preconditioning was induced by 3 episodes of 5 minutes occlusion of SMA at 5 minutes intervals before intestinal ischemia.The superior mesenteric artery was exposed but not occluded in control group.At the end of 180 minutes reperfusion,lung tissue samples were obtained to assess lung tissue HO-1 enzyme activity,lung tissue wet/dry ratio,malondialdehyde(MDA) level,superoxide dismutase(SOD) activity,histological changes of lung was observed,and serum tumor necrosis factor alpha(TNF-α) and interleukin-6(IL-6) concentrations were examined by enzyme-linked immunosorbent assay.Results Compared with IIR group,in IPC group,lung tissue HO-1 enzyme activity and SOD activity were significantly increased(P0.01),and lung wet/dry ratio,lung tissue MDA content,serum TNF-α and IL-6 concentrations and lung injury were significantly decreased(P0.01);in ZnPP group,lung tissue HO-1 enzyme activity was decreased(P0.05),lung wet/dry ratio,lung tissue MDA content,serum TNF-α and IL-6 concentrations and lung injury were increased(P0.05 or 0.01),and lung tissue SOD activity had no difference(P0.05).Compared with group IPC,in ZnPP group,lung tissue HO-1 enzyme activity and SOD activity were decreased(P0.01),and lung wet/dry ratio,lung tissue MDA content,serum TNF-α and IL-6 concentrations and lung injury were increased(P0.01).Conclusion IPC can protect against IIR induced lung injury by increasing HO-1 enzyme activity