INCREASED IRON AND FERRITIN CONTENT OF SPUTUM FROM PATIENTS WITH CYSTIC-FIBROSIS OR CHRONIC-BRONCHITIS

Purpose: Extracellular free iron, or iron bound to ferritin, may promo te oxidative injury and bacterial growth in airways of patients with c hronic airway inflammation due to cystic fibrosis (CF) or chronic bron chitis (CB). In this study, we assessed sputum content of total iron, ferritin, and transferrin in patients with CF or CB as well as sputum from normal subjects with acute airway inflammation caused by viral up per respiratory tract infections (URTIs). Methods: Spontaneously produ ced sputum was obtained from 33 subjects, including 10 subjects with C F, 18 subjects with CB (10 acute exacerbations, 8 with stable CB), and 5 subjects with URTIs (control subjects). After lysing and dilution, total iron concentrations were determined by controlled coulometry, fe rritin was measured by radioimmunoassay, and transferrin was measured by enzyme-linked immunosorbent assay. Results: Iron ,was not present i n detectable amounts in control sputums, but ferritin was present (6+/ -2 ng/mg protein, mean+/-SE), as was transferrin (2.37+/-0.44 mu g/mg) . Compared with control subjects, concentrations of iron in sputum wer e increased in patient groups with higher amounts in CF patients (242/-47 ng/mg, p<0.01) than CB patients with acute exacerbations or patie nts with stable CB (98+/-50 and 42+/-12 ng/mg, p<0.05 for both). Ferri tin content of sputum was also increased in each group, with CF patien ts (113+/-22 ng/mg, p<0.001) higher than CB patients (acute, 45+/-10 n g/mg; stable, 87+/-24 ng/mg; p<0.01 for both). Compared with control s ubjects, sputum transferrin was decreased in CF patients (1.09+/-0.40 mu g/mg, p<0.05), but not CB patients. Conclusions: These findings ind icate there are increased airway concentrations of total iron and ferr itin-bound iron in patients with CB and, to a greater extent, in patie nts with CF. Particularly in CF patients who also demonstrated decreas ed airway concentrations of transferrin, ferritin-bound iron in airway s may promote oxidative injury and enhance bacterial growth.