摘要：

In COPD, small airways are the main site of airflow obstruction. Neutrophil infiltration into small airways is significantly associated with lung function decline. This thesis investigated the effects of activated neutrophil products on ex vivo small airway structure and function using precision-cut lung slices (PCLS). Peripheral blood neutrophils were isolated from non-smokers, smokers and COPD patients; stimulated with fMLP, and supernatants obtained. Supernatant protease concentration/activity was assessed. There were significant increases in protease concentration/activity upon fMLP stimulation, but no significant differences between subject groups or correlations with subject demographics. Rat PCLS were incubated overnight with neutrophil supernatants, and small airway structure, function and PCLS viability assessed. Stimulated COPD neutrophil supernatants caused significant airway dysfunction. All neutrophil supernatants significantly reduced PCLS viability. There was a significant inverse correlation between supernatant active MMP-9 concentration and maximal airway closure. Incubation of rat PCLS with H2O2 or porcine pancreatic elastase did not fully reproduce the effects of neutrophil supernatants: both reduced maximal airway closure; whilst H2O2 alone significantly reduced PCLS viability. Pre-incubation of COPD neutrophil supernatants with a NE inhibitor led to restoration of maximal airway closure only. Pre-incubation with neither an antioxidant, N-acetyl-cysteine (NAC), nor a MMP-9 inhibitor, had any effect on neutrophil supernatant-induced PCLS damage. Finally, small airways in PCLS from COPD lung tissue had greater maximal airway closure, compared with smokers and non-smokers. There were no correlations between subject demographics and small airway function. Overall, neutrophils from COPD patients induce small airway dysfunction and reduce tissue viability. Neither oxidative stress nor elastase reproduced these effects fully; and pre-incubation with neither antioxidants nor protease inhibitors restored small airway function. Thus, there is greater complexity in neutrophil mediation of this damage. Finally, rat small airways do not fully reproduce the response of small airways in COPD lung tissue, which exhibit evidence of hypercontractility.

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