Antagonistic effects of animal sera, lung and liver cytosols, and sulfhydryl compounds on the cytotoxicity of diesel exhaust particle extracts

Abstract

The cytotoxicity of the dichloromethane extracts of exhaust particles from a light-duty diesel engine was studied in cultured Chinese hamster ovary (CHO) cells. The cytototoxicity was decreased when animal sera, bovine serum albumin (BSA), lung or liver cytosols, or sulfhydryl compounds were present. Sera from five animal species (chicken, cow, horse, human, and rabbit) were tested and they all decreased the cytotoxicity. The BSA was not more effective than serum, indicating that there are probably substances other than the serum albumin proteins involved in the decrease of the cytotoxic effects of diesel exhaust extracts. Three sulfhydryl compounds (glutathione, cysteine, and 2-mercaptoethanol) and their respective nonsulfhydryl analogs (oxidized glutathione, serine, and ethylene glycol) were tested. Only the sulfhydryl compounds were effective in decreasing the cytotoxicity of the diesel extract. Liver and lung cytosols (S-9) were effective, with their effectiveness increased when cofactors were present, suggesting that there may be enzymatic metabolism of the cytotoxic components in the diesel exhaust extracts. Using Sephadex LH-20 chromatography, the crude extract was separated into six fractions which contained different classes of chemicals. These fractions had different cytotoxicity. The cytotoxicity of each of the fractions were decreased by serum and glutathione. The findings suggest that protein binding, chemical reactions, and enzymatic metabolism may decrease the toxic effects of diesel extract.