Neutrophil Apoptosis Of Peripheral Blood In Chronic Obstructive Pulmonary Disease And The Relationship Between Neutrophil Apoptosis And Bak Gene

BackgroundAs the main inflammatory cells in chronic obstructive pulmonary disease (COPD),neutrophils accumulate in the lungs of patients with COPD with increased activity.That a prolonged survival due to inhibition of spontaneous apoptosis could explain this phenomenon.Bcl-2 family plays an important role in the procedure of neutrophil apoptosis.The aim of this study was to assess the apoptotic behaviour and Bak mRNA expression of peripheral blood neutrophils in COPD patients compared with healthy volunteers.And then assess the correlation between the apoptosis and Bak.Patients10 hospitalised COPD patients with an acute exacerbation and ten in stable stage, 20 smokers with normal lung function,and 20 healthy nonsmoking subjects normal lung function.MethodsWe used discontinuous plasma-percoll gradients to isolate neutrophils from peripheral blood.Then we cultured circulating neutrophils that had been harvested from the study subjects at 4,18,and 36 h.Apoptosis was assessed using flow cytometry by annexin FITC-PI binding.Half-quantitative RT-PCR was used to measure the expression of Bak mRNA.ResultsStatistical analysis revealed spontaneous apoptosis rates in COPD patients with acute exacerbation were lower than other 3 groups(p＜0.001).Apoptosis rates at 36h in patients with stable COPD were higher than non-smokers(74.6%±5.3%vs 70.2%±6.8%p=0.042);Significantly reduced levels of Bak mRNA in COPD patients with acute exacerbation were found compared to smokers,non-smokers and patients with stable COPD(3.2±1.1 vs 5.2±1.2,p＜0.001;3.2±1.1 vs 4.9±1.6,p=0.002;3.2±1.1 vs 4.5±0.9,p=0.036).Linear regression analysis showed good correlation between apoptosis rates at 36h and FEV₁(r=0.619,p＜0.001),between apoptosis rates at 36h (r=0.634,p＜0.001) and between apoptosis rates at 36h and SpO₂%(r=0.528,p＜0.001). Significant correlation between levels of Bak mRNA and FEV₁,FEV₁/FVC%,SpO₂% were found(r=0.430,p＜0.001;r=0.437,p=0.001;r=0.301,p=0.019).We also found good correlation between apoptosis rates at all time points and levels of Bak mRNA (r=0.520,p＜0.001;r=0.527,p＜0.001;r=0.443,p＜0.001).ConclusionsIn conclusion,during acute exacerbations of COPD,neutrophil granulocytes show a reduced spontaneous apoptosis,and neutrophil apoptosis rates of COPD patients in stable stage reduced significantly compared to non-somkers.While Significantly reduced levels of Bak mRNA in COPD patients with acute exacerbation were found compared to smokers,non-smokers and patients with stable COPD. Reduced apoptosis of neutrophil may result in the accumulations and increased activity of neutrophil in the lungs of patients with COPD.Good correlations were found between neutrophil apoptosis and Bak and between Bak and FEV₁.This raises the question of the importance of neutrophil apoptosis and Bak in the development of COPD.