This study, along with others has reported an increase in airway neutrophils in COPD sub jects and it is plausible that this accumulation of neutrophils may be due to both increased recruitment in the airways and inhibition this website of apoptosis. Our findings show that the percentage of neutrophils in early stage apoptosis are significantly reduced in COPD subjects and in healthy smokers and concomitantly have a higher percentage of neutrophils undergoing secondary necrosis compared to non smokers. Similar results were shown using by both the Tunel method and by light microscopic morphological identification. Several factors can influence the process of neutrophil apoptosis. While data suggests that corticosteroids inhibit neutrophil apop Apoptotic Inhibitors,Modulators,Libraries sputum neutrophils identified using light micros Assays investigating apoptosis should be interpreted with care.
Firstly, cells can display morphological features of apoptosis without DNA fragmentation Inhibitors,Modulators,Libraries and it is also possible that the Tunel assay can generate false posi tive results since random DNA fragmentation during necrosis may also generate 3OH DNA ends. Despite the concept that the morphological detection and quanti fication of apoptotic cells is regarded as the gold standard method, results from this study support the notion that in some instances morphological identification of apoptotic cells may underestimate apoptosis. There fore it is imperative that at least 2 different methods are used in the quantification of apoptosis, to confirm data and to ensure different stages of apoptosis are investi gated.
Despite differences in methods, all three assays showed significant reduction in the percentage of apop totic Inhibitors,Modulators,Libraries neutrophils between COPD subjects and non smok ers. Quantification of apoptosis by Annexin V PI staining also showed a decrease in healthy smoking subjects com tosis, others have shown that corticosteroids do not affect spontaneous neutrophil Inhibitors,Modulators,Libraries apoptosis in COPD patients. More recently work suggests that 2 agonists alone have negligible effects on neutrophils but together with corticosteroids actually enhances inhibition of apop tosis. One limitation of this study is the lack of inves tigation of the influence of medication on neutrophil apoptosis.
Although COPD treatment included 2 ago nists, corticosteroids and or anti cholinergics, all Inhibitors,Modulators,Libraries healthy smokers recruited in this study had not received any recent oral inhaled steroids and therefore it is likely that the similar inflammatory status observed in COPD and healthy smokers is not a consequence of corticosteroid treatment. Furthermore it has been suggested that in vitro findings showing delayed neutrophil apoptosis overnight delivery due to corticosteroids is more than likely overwhelmed by the in vivo inhibition of the anti apoptotic effects of inflamma tory cytokines.