Neutrophils Amplify the Formation of DNA Adducts by Benzo[a]pyrene in Lung Target Cells

Abstract

Inflammatory cells and their reactive oxygen metabolites can cause mutagenic effects in lung cells. The purpose of this study was to investigate the ability of activated neutrophils to modulate DNA binding of benzo[a]pyrene (B[a]P), a known carcinogen, in lung target cells. Equivalent numbers of rat lung epithelial cells (RLE-6TN cell line) and freshly isolated human blood neutrophils (PMN) were coincubated in vitro for 2 hr after addition of benzo[a]pyrene (0.5 microM) or two of its trans-diol metabolites, with or without stimulation with phorbol myristate acetate (PMA). DNA adducts of B[a]P-metabolites were determined in target cells using 32P-postlabeling; oxidative DNA damage (7-hydro-8-oxo-2'-deoxyguanosine [8-oxodG]) was evaluated by high performance liquid chromatography with electrochemical detection. Increased DNA adducts were observed in lung cells coincubated with polymorphonuclear leukocytes (PMN). Activation of PMN with PMA, or addition of more activated PMN in relation to the number of lung cells, further increased the number of adducts, the latter in a dose-response manner. Incubation with B[a]P-4,5-diol did not result in any adduct formation, while B[a]P-7,8-diol led to a significant number of adducts. Moreover, PMA-activated PMN strongly enhanced adduct formation by B[a]P-7,8-diol, but not 8-oxodG, in lung cells. The addition of antioxidants to the coincubations significantly reduced the number of adducts. Results suggest that an inflammatory response in the lung may increase the biologically effective dose of polycyclic aromatic hydrocarbons (PAHs), and may be relevant to data interpretation and risk assessment of PAH-containing particulates.

Neutrophils and respiratory tract DNA damage and mutagenesis: a review

“…Again, this effect was shown to be MPO dependent (143). More recently, these observations were confirmed by studies in our laboratory, showing that activated neutrophils enhance BPDE-DNA adduct formation in co-cultured alveolar epithelial target cells that were exposed to B[a]P-7,8-dihydrodiol (144).…”

“…Cigarette smoke is a potent source of chemical carcinogens and, at present, it is believed that the association between MPO and pulmonary carcinogenesis can be explained by the involvement of neutrophil-derived MPO in metabolic activation of inhaled chemical carcinogens, including aromatic amines (157)(158)(159) and heterocyclic amines (133). However, MPO activity has most frequently been linked to the metabolism of carcinogenic polycyclic aromatic hydrocarbons (PAHs) (126,(141)(142)(143)(144).…”

Chronic Mycobacterium marinum infection acts as a tumor promoter in Japanese Medaka (Oryzias latipes)

“…A requirement for exogenous DNA damage was surprising considering previous studies that suggested that the inflammatory response increases the effectiveness of PAHs, such as BaP, to form DNA adducts, not to mention DNA damage induced directly through the inflammatory response (Shacter et al, 1988; Borm et al, 1997; Zhuang et al, 2002; Kim & Wogan, 2006). Although this would suggest that inflammation alone or in the presence of BaP could lead to increased mutagenic lesions, we failed to observe such an effect.…”

The 1996 Veylien Henderson Award of the Society of Toxicology of Canada. Current concepts: neutrophils and the activation of carcinogens in the breast and other organs

“…They established an in vitro system for co-incubation of neutrophils and hamster V79 cells, and showed that reactive intermediates generated by neutrophil-mediated metabolism of BP-7,8-dihydrodiol (a proximate activated metabolite of BP) can induce sister chromatid exchanges in the V79 cells. Borm et al (1997) carried out similar experiments using co-incubations of human blood neutrophils and a rat epithelial lung cell line. Petruska et al (1992) showed that MPO can activate BP-7,8-dihydrodiol in the mouse lung in vivo, as measured by formation of DNA adducts.…”