Regional variation in iron and iron-binding proteins within the lungs of smokers

Abstract

The lungs of cigarette smokers are known to contain increased concentrations of extracellular ferritin-bound iron. Reductants present in cigarette smoke may mobilize alveolar ferritin-bound iron, which could then promote oxidative injury to lung cells. Because iron-mediated oxidative injury may be relevant to the pathogenesis of emphysema and lung cancer, which have a predilection for upper lobes, we sought to determine whether concentrations of extracellular iron, ferritin, and transferrin differed in upper and lower lobes of cigarette smokers. Bronchoalveolar lavage (BAL) was performed in the upper and lower lobes of 15 asymptomatic smokers and six healthy nonsmokers. BAL fluid recovered from upper lobes of smokers contained higher concentrations of iron (p < 0.01) and ferritin (p < 0.006) and lower concentrations of transferrin (p < 0.003) compared with the lower lobes. In contrast, BAL fluid recovered from upper and lower lobes of nonsmokers contained much lower concentrations of iron and ferritin, and concentrations were similar in both sites. These findings indicate that, compared with the lower lobes, upper lobes of the lungs of smokers contain higher extracellular concentrations of ferritin-bound iron and decreased concentrations of transferrin. This distribution of lung iron and iron-binding proteins may promote oxidative injury in the upper lobes of smokers.