The cytotoxic effects of diesel exhaust particles on human pulmonary artery endothelial cells in vitro: Role of active oxygen species

Diesel exhaust particles (DEP) have been proved to induce serious pulmonary injury, among which lethal pulmonary edema has been assumed to be mediated by vascular endothelial cell damage. In the present study, we investigated the cytotoxic mechanism of DEP on human pulmonary artery endothelial cells focusing on the role of active oxygen species. Endothelial cell viability was assessed by WST-8, a novel tetrazolium salt. Nitric oxide (NO) producti on was measured by using a new fluorescence indicator, diaminofluorescein-2 (DAF-2). Organic compounds in DEP were extracted by dichloromethane and me thanol. DEP-extracts damaged endothelial cells under both subconfluent and confluent conditions. The DEP-extract-induced cytotoxicity was markedly red uced by treatment with SOD, catalase, N-(2-mercaptopropionyl)-glycine (MPG) , or ebselen (a selenium-containing compound with glutathione peroxidase-li ke activity). Thus superoxide, hydrogen peroxide, and other oxygen-derived free radicals are likely to be implicated in DEP-extract-induced endothelia l cell damage. Moreover, L-NAME and L-NMA, inhibitors of NO synthase, also attenuated DEP-extract-induced cytotoxicity, while sepiapterin, the precurs or of tetrahydrobiopterin (BH4, a NO synthase cofactor) interestingly enhan ced DEP-extract-induced cell damage. These findings suggest that NO is also involved in DEP-extract-mediated cytotoxicity, which was confirmed by dire ct measurement of NO production. These active oxygen species, including per oxynitrite, may explain the mechanism of endothelial cell damage upon DEP e xposure during the early stage. (C) 2001 Elsevier Science Inc.