Inactivation of alpha 1-antitrypsin by aqueous coal solutions: possible relation to the emphysema of coal workers

Increasing evidence demonstrates that emphysema in coal workers may be related to their exposure to coal dusts. The hypothesis that emphysema could be related to the production of reactive oxygen species (ROS) generated by inhaled coal dusts was examined in the present study. Using ESR, we investigated whether the interaction of different coals with dissolved oxygen in aqueous medium could generate ROS. Indeed, we found that one of the five examined French coal samples, Vouters coal, was effective in oxidizing formate anions or ethanol by a radical pathway. Inactivation of alpha 1-antitrypsin (alpha 1-AT) in vitro was then examined for all five coal filtrates. The Vouters coal filtrate, which exhibits oxidative activity, can also inactivate alpha 1-AT. When this coal filtrate was crystallized and redissolved, its oxidative activity was found to be conserved. By use of various analytical techniques, the active component of this coal filtrate was identified to be primarily ferrous sulfate. We confirmed that pure ferrous sulfate can effectively reduce oxygen to produce ROS in aqueous medium in vitro and can also inactivate alpha 1-AT. In this report, the nature of the coal-generated oxidative species, the origin of ferrous sulfate, and the stability of ferrous sulfate in the different coal samples are discussed. These results offer evidence that some inhaled coal dusts are capable of producing ROS, which may play an important role in the development of coal workers' emphysema.