NEUTROPHILS AMPLIFY THE FORMATION OF DNA-ADDUCTS BY BENZO[A]PYRENE INLUNG TARGET-CELLS

Inflammatory cells and their reactive oxygen metabolites can cause mut agenic effects in lung cells. The purpose of this study was to investi gate the ability of activated neutrophils to modulate DNA binding of b enzo[a]pyrene (B[a]P), a known carcinogen, in lung target cells. Equiv alent numbers of rat lung epithelial cells (RLE-6TN cell line) and fre shly isolated human blood neutrophils (PMN) were coincubated in vitro for 2 hr after addition of benzo[a]pyrene (0.5 mu M) or two of its tra ns-diol metabolites, with or without stimulation with phorbol myristat e acetate (PMA). DNA adducts of B[a]P-metabolites were determined in t arget, cells using P-32-postlabeling; oxidative DNA damage (7-hydro-8- oxo-2'-deoxyguanosine [8-oxodG]) was evaluated by high performance liq uid chromatography with electrochemical detection. Increased DNA adduc ts were observed in lung cells coincubated with polymorphonuclear leuk ocytes (PMN). Activation of PMN with PMA, or addition of more activate d PMN in relation to the number of lung cells, further increased the n umber of adducts, the latter in a dose-response manner. Incubation wit h 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-activate d 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 coincubation s significantly reduced the number of adducts. Results suggest that an inflammatory response in the lung may increase the biologically effec tive dose of polycyclic aromatic hydrocarbons (PAHs), and may be relev ant to data interpretation and risk assessment of PAH-containing parti culates.