The airways of patients with
chronic obstructive pulmonary disease (
COPD) are associated with increased numbers of inflammatory cells, in particular neutrophils and macrophages. Contained within the primary granules of neutrophils is the
heme enzyme called
myeloperoxidase (MPO) that has been used as a
biomarker of neutrophilic
inflammation in
COPD and other inflammatory diseases. MPO is the only
enzyme in the body that produces
hypochlorous acid (HOCl), which effectively chlorinates
tyrosine residues in
proteins. The presence of
3-chlorotyrosine (3Cl-Tyr) in sputum of
COPD patients has yet to be established. Spontaneously produced sputum was collected from 14 stable
COPD patients, and ultra-centrifuged to prepare
sol phase samples for analysis. Sputum 3Cl-Tyr levels were measured using Mass Spectrometry (LC-MSMS). Sputum MPO activity was measured using a standard
chromogenic substrate assay. The Spearman rank correlation was used to analyse the data. We report for the first time the measurement of 3Cl-Tyr in sputum from stable
COPD patients. The sputum levels of 3Cl-Tyr correlated well with sputum MPO activity (r = 0.88; p < 0.0001). The presence of 3Cl-Tyr in the sputum of stable
COPD patients suggests an active process related to MPO that may play a role in the pathophysiology of this disease.