Release of iron from ferritin by aqueous extracts of cigarette smoke

This study demonstrates the ability of aqueous extracts of cigarette smoke to reduce iron and cause its release from ferritin. Superoxide dismutase (SOD) increases the rates of iron release with the less filtered smoke extracts, but has no effect on the rate of iron release caused by aqueous extracts of well-filtered gas-phase cigarette smoke. Faster rates of iron release are observed under anaerobic conditions, and the reducing power of the cigarette smoke extracts is prolonged when incubated in argon. Hydroquinone and catechol, two of the major polyhydroxybenzenes in cigarette smoke, increase in concentration in the smoke extracts as these are subjected to less filtration, and higher concentrations of polyhydroxybenzenes correlate with higher rates of iron release from ferritin. Concomitant with iron release, depletions of amino acids in ferritin are observed. Depletion of histidine is partially prevented by bathophenanthrolinedisulfonate and mannitol, while lysine and arginine depletions remain unaffected. These observations suggest that cigarette smoke components react directly with these amino acid residues in ferritin. Cigarette smoke induced release of iron could alter iron metabolism in the lungs of chronic smokers and contribute to the increase in the total oxidative burden on the lungs of smokers.