Effect Of Ischemic Preconditioning Combined With ?7nAChR Agonist On Lung Injury Induced By Limb Ischemia-reperfusion In Rats

Background:To investigate the effect of ischemic preconditioning combined with ?7nAChR agonist on lung injury induced by limb ischemia-reperfusion in rats.Methods:Fifty healthy male SD rats were randomly divided into five groups(250~ 280g): sham operation group(group S),model group(group M),ischemic preconditioning group(group IP),?7nAChR agonist group(group PNU)and combined treatment group(group U).Group S: the rats were anesthetized for 6h,and 1ml normal saline(NS)was injected intraperitoneally at the moment before reperfusion.Group M: the rats were induced by applying rubber band tourniquets high around bilateral lower limb for 3 h followed by reperfusion for 3 h,and 1ml NS was injected intraperitoneally at the moment before reperfusion.Group IP: the rats were subjected to three cycles of bilateral lower limb I/R(i.e.,ischemia for 10 min followed by reperfusion for 10 min)and the remaining steps were consistent with group M.Group PNU: the whole process was basically consistent with group M except the 1 ml NS was replace by the ?7nAChR agonist(2.4mg/kg)which dissolved by 1ml NS.Group U: the whole process was basically consistent with group IP except the 1 ml NS was replace by the ?7nAChR agonist(2.4mg/kg)which dissolved by 1ml NS.After 3h of reperfusion,the change of arterial blood gas was analyzed and the specimens of lung tissue were obtained to measure lung index,maiondialdehyde(MDA)content,superoxide dismutase(SOD)activity and levels of TNF-? and IL-6 in the lung tissue.Then,the pathological changes of lung tissue were observed under light microscope and pathological score was performed.Results:1.Arterial blood gas analysis: compared with group S,the PO2 of group M was obviously lower(P<0.05);the PO2 of group IP,group PNU and group U were significantly higher than group M(P<0.05);and the PO2 of group U was significantly increased than group IP and PNU(P<0.05).The pH of group M was significantly lower than group S(P<0.05),while the PCO2 had no statistic significance between the two groups(P>0.05);there was no significant difference in PH and PCO2 compared group M with group IP,group PNU and group U(P>0.05);and there was no significant difference in pH and PCO2 compared group U with group IP and PNU(P>0.05).2.The lung index: compared with group S,the lung index of group M was obviously higher(P<0.05);the lung index of group IP,group PNU and group U were significantly lower than group M(P<0.05);and the lung index of group U was significantly lower than group IP and PNU(P<0.05).3.HE staining and pathological score of lung tissue: the lung tissue of group S was normal,but thickened alveolar wall,hemorrhage,edema and inflammatory cellular infiltration were observed in group M,group IP,group PNU and group U.Thereinto,the group M showed the most serious inflammation,while the group U showed the mildest.Compared with group S,the pathological score in lung tissue of group M was obviously higher(P<0.05);the pathological score in group M was significantly higher than the group S,group IP,group PNU and group U(P<0.05);and compared with the group IP and PNU,the pathological score in group U was significantly decreased(P<0.05).4.Variations of SOD and MDA in the lung tissue: in group M,MDA content was significantly higher than group S,but SOD activity was significantly lower than group S,and the differences were statistical significance(P <0.05);compared with the group M,MDA contents in group IP,group PNU and group U were significantly decreased,while SOD activitives were significantly increased,and the differences were statistical significance(P<0.05);in group U,MDA content was significantly lower than group IP and PNU,but SOD activity was significantly increased,and the differences were statistical significance(P<0.05).5.The levels of TNF-? and IL-6 in the lung tissue: the levels of TNF-? and IL-6 in group M were significantly higher than group S(P<0.05);the levels of TNF-? and IL-6 in group IP,group PNU and group U,compared with group M,were significantly decreased(P<0.05);in group U,the levels of TNF-? and IL-6 were significantly lower than group IP and PNU(P<0.05).Conclusion:Ischemic preconditioning and ?7nAChR agonists can alleviate lung injury induced by limb ischemia-reperfusion in rats,and the combined effect of them is better than used alone.