Alveolar Macrophage Content of Isoferritins and Transferrin: Comparison of Nonsmokers and Smokers with and without Chronic Airflow Obstruction

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Abstract
Alveolar macrophages (AM) contain iron and ferritin, and concentrations of both are increased in AM of smokers compared with nonsmokers. Ferritin stores iron in a nontoxic form but can release iron in the presence of reducing agents and thereby catalyze the generation of toxic hydroxyl radicals via the Haber-Weiss reaction. Two distinct isoferritins are found in peripheral monocytes, L ferritin and H ferritin. H ferritin is the predominant isoferritin in human monocytes and is more effective than L ferritin in detoxifying iron in vitro. In this study we quantitated content of H and L ferritins, transferrin, and iron in AM recovered by bronchoalveolar lavage (BAL) of 24 subjects, including eight nonsmokers, eight smokers with normal spirometry, and eight smokers with chronic airflow obstruction (CAO). Of total AM ferritin in nonsmokers 95% was composed of L ferritin. Smokers without CAO demonstrated a 6.5-fold increase in the AM content of L ferritin (1,886 +/- 266 versus 290 +/- 51 ng, mean +/- SEM; p less than 0.0001) and a 3.8-fold increase in H ferritin (61 +/- 18 versus 16 +/- 2 ng per 1 x 10(6) AM, p less than 0.01) compared with nonsmokers. Compared with smokers without CAO, AM recovered from smokers with CAO demonstrated a greater increase in L ferritin (5,059 +/- 493 versus 1,886 +/- 266 ng per 1 x 10(6) AM, p less than 0.002) but a similar increase in H ferritin (64 +/- 8 versus 61 +/- 18 per 1 x 10(6) AM).(ABSTRACT TRUNCATED AT 250 WORDS)