Genotoxic bioactivation of constituents of a diesel exhaust particle extract by the human lung

Abstract

The ability of the human lung to catalyze genotoxic bioactivation of constituents of diesel exhaust particle (DEP) extract (DEPE) and the identity of the lung enzymes involved in the bioactivation were investigated using human lung tissues obtained from surgical resections. Genotoxicity was determined by lung S9-catalyzed mutagenicity of DEPE constituents to Salmonella typhimurium TA98NR in the Ames test and by DEPE-induced pneumocyte DNA damage response as determined by γH2Ax expression in ex vivo tissues. S9 was prepared from lung explants treated ex vivo with either DEPE to induce pulmonary enzymes (DEPE-S9) or vehicle only (CON-S9). TA98NR served as the tester strain for the purpose of enhancing and minimizing the contribution of lung S9 and Salmonella, respectively, to DEPE bioactivation. DEPE-S9 was 2.2-fold more active than CON-S9 or rat liver S9 in DEPE bioactivation and the bioactivation was inhibited 58, 45, 22, and 16% by α-naphthoflavone, dicumarol, ketoconazole, and ticlopidine, respectively. Alveolar S9 was less active than bronchioalveolar S9 in DEPE bioactivation. DEPE and diesel exhaust particles (DEP) induced γ-pH2Ax expression in pulmonary cells. Pulmonary CYP1A1 and NQO1 were induced by DEPE treatment, with the constitutive and induced CYP1A1 distributed throughout all peripheral lung regions, whereas NQO1 was limited in distribution to bronchiolar epithelium. The results show that the human lung is highly active in catalyzing genotoxic bioactivation of diesel emission constituents and that CYP1A and NQO1 play major roles in the reaction. The findings underscore the usefulness of human lung tissues in studies of the pneumotoxicity potential of chemicals to humans.

Comparative Analysis of Toxic Responses of Organic Extracts from Diesel and Selected Alternative Fuels Engine Emissions in Human Lung BEAS-2B Cells

“…However, to specifically reveal the potential carcinogenic effects of PAHs, application of organic extracts is more relevant. Although the genotoxicity of DEP extracts may be easily tested by standardized, well-established tests including cytotoxicity measurement [20], Ames test [20,21], analysis of double strand DNA breaks [21], apoptosis, frequency of micronuclei [22], bulky DNA adducts formation or oxidative DNA damage [12], for a comprehensive assessment of the biological processes induced by the DEP extracts the treatment of the whole genome gene expression analysis is a valuable tool.…”

Bioassay‐directed fractionation and sub‐fractionation for mutagenicity and chemical analysis of diesel exhaust particles

“…Polycyclic aromatic hydrocarbons (PAHs) and nitrorarenes (nitro-PAHs) are some of the primary chemical classes in DEP that are associated with the carcinogenicity and mutagenicity of DEP [US EPA, 2002]. Mechanistic support for this has been shown recently by the demonstration that the human lung is able to bio-activate the organics in DEP to produce detectable mutagenic activity via CYP1A1 and NQO1 enzymes and that this activation is associated with the mutagenicity of PAHs and nitro-PAHs [Iba and Caccavale, 2013].…”

Ultrafine Particles of Diesel Exhaust Induces Cytochrome P450 1A1 Mediated Oxidative Stress and DNA Damage in Cultured Blood and Lung Cells

“…Comet assay demonstrating increased DNA damage in IM9 or A549 cells exposed to MC prior to DEP has shown that CYP1A1 is involved in the increased generation of ROS resulting in increased DNA damage in these cells. In vivo and in vitro studies have also shown that bioactivation of PAHs present in DEPs by CYP1A isoenzymes is partially responsible in mediating genotoxic response as seen through DNA strand breaks or through formation of DNA adduct (8-OHdG) formation in exposed cells 8,48,[51][52][53] . The reduction in the extent of DNA damage following preincubation of A549 or IM9 cells with α-NF, has further demonstrated the role of PAH metabolising CYP1A1 in the metabolic activation and toxicity of DEP.…”