Delayed apoptosis by neutrophils from COPD patients is associated with altered bak, bcl-xl, and mcl-1 mRNA expression

BACKGROUND: Delayed neutrophil apoptosis may be an important factor in the persistent inflammation associated with chronic obstructive pulmonary disease (COPD). Bcl-2 family proteins are important regulators of neutrophil apoptosis. We determined the mRNA levels of pro-apoptotic Bak and anti-aptototic Bcl-xl and Mcl-1 members of the Bcl-2 family in unstimulated peripheral blood neutrophils from patients with mild to moderate COPD and compared these to neutrophils from healthy controls. METHODS: Neutrophils were isolated from peripheral blood samples of 47 COPD patients (smokers: N = 24) and 47 healthy controls (smokers: N = 24). Percentages of apoptotic cells were determined at 4, 24, and 36 h for unstimulated neutrophils cultured in vitro. Neutrophil mRNA expression of Bak, Bcl-xl, and Mcl-1 was determined by real-time polymerase chain reaction (PCR). FEV1 (% predicted) and FVC were determined by spirometry and correlations between mRNA levels and lung function parameters were determined. RESULTS: The percentages of apoptotic cells among unstimulated neutrophils from COPD patients were significantly lower compared to cells from controls after 4, 24, and 36 h in culture; smoking history had only a minimal effect on these differences. Unstimulated neutrophils from COPD patients had significantly lower Bak mRNA expression and higher expressions of Bcl-xl and Mcl-1 mRNA than cells from healthy controls. Again, smoking history had only a minimal effect on these trends. Bak mRNA expression was significantly positively correlated with both % predicted FEV1 and the FEV1/FVC ratio, while Bcl-xl and Mcl-1 mRNA expressions were significantly negatively correlated with %predicted FEV1 and the FEV1/FVC ratio. CONCLUSIONS: The genes for pro-apoptotic Bak, and anti-apoptotic Bcl-xl and Mcl-1 may be important in regulating the delayed neutrophil apoptosis observed in COPD, which may contribute to COPD pathogenesis. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1605269445677066