Role of polymorphonuclear neutrophil apoptosis in rabbit acute lung injury after burns

Objective:To investigate the potential role of polymorphonuclear neutrophil(PMN) apoptosis in the development of rabbit acute lung injury(ALI).Methods:Thirty-six healthy New Zealand white rabbits were randomly divided into control group(n=6) and burn group(5 time points including 2,4,8,12,24 hours after burn,with 6 in each time point).The pathological changes of lung tissue were observed.Lung injury scores(LIS) and wet-dry weight ratio(W/D) of rabbit lung tissue were calculated.PMNs were isolated and purified in bronchoalveolar lavage fluid.PMN apoptosis,necrosis,survival cell ratio and the changes of respiratory burst function were measured by flow cytometry.Results:There were significant changes in pathological section of rabbit lung tissue in burn groups at different time.It was observed that alveolar spaces and interstitial edema were occurred with massive infiltration of PMN,pulmonary architecture was damaged at 2 hours,and worsened with prolongation of time.LIS and W/D were increased at 2 hours and reached the peak at 24 hours,the differences were significant after 8 hours between control group and burn group(P0.01).PMN apoptosis in rabbit lung lavage fluid in burn group were decreased(P0.01),PMN necrosis rate was significantly increased at 2 hours(P0.05),reached peak at 4 hours(P0.01),restored to normal level at 8 hours(P0.05).PMN survival rate in the 5 burn groups was higher than in control group(P0.01).The Respiratory burst of PMNs was significantly increased at 2 hours(P0.05),and the peak value was appeared at 8 hours(P0.01).Conclusions:PMN congregates in alveolar spaces from pulmonary blood vessel during the pathogenesis of ALI,and apoptotic pathway is disturbed,which induce persistent activation of PMN.It may play an important role in the pathogenesis of ALI.