Isolation of metal-binding agents from coal dust and their effects on mitochondrial function.

Abstract

Abstract Bituminous coal samples from mines in Utah and Pennsylvania were extracted with a series of organic solvents, used in order of increasing polarity. The extracted materials, amounting to 58–70 mg/g of Utah coal and 12–15 mg/g of Pennsylvania coal, were each fractionated on a carboxymethyl cellulose column in the Cu (II) form. The copper-complexing fractions for Utah and Pennsylvania were 30% and 22%, respectively, of the total extract. Copper-binding capacity was 400 ug copper/g Utah coal and 40 ug/g for Pennsylvania. The copper-binding ligands from both coals uncoupled oxidative phosphorylation of isolated rat liver mitochondria, a system containing copper and iron metalloenzymes. The inhibitory activity per gram of extracted material was higher for Pennsylvania than Utah. These results suggest that the extraction and absorption of metal-binding agents from coal may adversely alter vital cellular energetics. Coal dust and its effects on human health is of concern because of the prevalence of respiratory disorders incurred by coal mine workers. In epidemiological studies it has been found that 10% of working miners showed definite radiological evidence of pneumoconiosis. Another survey revealed that nearly 50% of working miners suffered from some degree of dyspnea. Several investigators are studying the effects of coal as a particle. However, in the present study coal dust is being investigated as a carrier of chemicals. Coal dust has been shown to contain significant amounts of heavy metals such as Fe, Ni, Al, Cd, Pb, and many others. In this paper we are concerned with the nature of the organic chemicals in coal, particularly in the presence of metal-binding agents. It is our contention that metal-binding ligands in coal (if extractable and absorbed) may interfere with trace metal metabolism by interacting with essential trace metals. In this manner, they may act as metalloenzyme inhibitors and thus may play an important role in health effects such as pulmonary, cardiovascular, neoplastic, and collagen diseases in which alterations of trace metal metabolism have been implicated. Metal-binding agents have been isolated from tobacco smoke condensate and from the smoke of other burned vegetable matter. These constituents were found to inhibit several metalloenzymes, i.e., galactose oxidase and catalase as well as to inhibit the in vitro function of copper-and iron-requiring biological systems such as respiratory activity of rat liver slices and uncoupling of rat liver mitochondria (V. Elia, unpublished results). Therefore, the goal of this study was a) to devise a method for extraction of coal dust; b) to establish whether the extracts contain metal-binding agents; and c) to obtain evidence that these agents may interfere with trace metal metabolism or act as inhibitors of metalloenzyme-requiring biological systems. Two types of bituminous coal, one obtained from a mine in Pennsylvania and the other from a mine in Utah were examined. The Pennsylvania coal is a harder variety, contains more heavy metals, and causes higher incidence of coal miner's pneumoconiosis in comparison to the Utah coal.