Hypoxia associated with increased systemic concentrations of MPO and NE during exacerbations of COPD

Abstract

Background: Chronic obstructive pulmonary disease (COPD) comprises local and systemic neutrophilic inflammation. Neutrophils contain the intracellular enzymes myeloperoxidase (MPO) and neutrophil elastase (NE) and these enzymes contribute to anti-bacterial activity in host defense. However, it is not known if hypoxia during COPD exacerbations is associated with systemic neutrophil activity resulting in MPO and NE release.

Aims: To determine if hypoxia during COPD exacerbations is associated with systemic neutrophil activity resulting in MPO and NE release.

Methods: Blood samples were harvested and hypoxia (ie. blood gas partial oxygen pressure) was analyzed from 18 smokers with COPD during exacerbations. In blood, neutrophil concentrations (blood differential count) as well as MPO (ELISA) and NE (latex bead concentration method) were analyzed.

Results: Neutrophil concentrations were increased from [4.3(2.3-9.6)](baseline)to[6.0 (3.7-13)](exacerbation) during COPD exacerbations (n=18).There were statistically significant (p<0.05) negative correlations (r=Spearman rank correlation) for PaO₂ and neutrophils (r=0.63), for PaO₂ and MPO (r=0.5) and finally, for PaO₂ and NE (r=0.56).

Conclusion: Hypoxia during COPD exacerbations is associated with systemic neutrophil activity resulting in MPO and NE release. Given that experimental hypoxia is known to cause neutrophil activity in vitro, it seems plausible that this phenomenon is relevant to COPD exacerbations as well. It can therefore be speculated that oxygen therapy may counteract this neutrophil activity during exacerbations of COPD.