Cytokine production by alveolar macrophages is down regulated by the alpha-methylhydroxylation pathway of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

Abstract

NNK, a nicotine-derived nitrosamine, is a potent lung carcinogen that generates electrophilic intermediates capable of damaging DNA. The effects of NNK on the immune response, which may facilitate lung carcinogenesis, are poorly understood. Alveolar macrophages (AM), a key cell in the maintenance of lung homeostasis, metabolize NNK via two major metabolic activation pathways: alpha-methylhydroxylation and alpha-methylenehydroxylation. We have shown previously that NNK inhibits the production of interleukin-12 (IL-12) and tumor necrosis factor (TNF), but stimulates the production of IL-10 and prostaglandin E(2) (PGE(2)) by AM. In the present study, we investigated the contribution of each activation pathway in the modulation of AM function. We used two precursors, 4-[(acetoxymethyl)-nitrosamino]-1-(3-pyridyl)-1-butanone (NNKOAc) and N-nitro(acetoxymethyl)methylamine (NDMAOAc), which generate the reactive electrophilic intermediates [4-(3-pyridyl)-4-oxo-butanediazohydroxide and methanediazohydroxide, respectively] in high yield and exclusively. Rat AM cell line, NR8383, was stimulated and treated with different concentrations of NNKOAc or NDMAOAc (12, 25 and 50 microM). Mediator release was measured in cell-free supernatants. NNKOAc significantly inhibited the production of IL-10, IL-12, TNF and nitric oxide but increased the release of PGE(2) and cyclooxygenase-2 expression suggesting that the alpha-methylhydroxylation pathway might be responsible for NNK modulation of AM cytokine release. In contrast, NDMAOAc did not modulate AM mediator production. However, none of these precursors, alone or in combination, could explain the stimulation of AM IL-10 production by NNK. Our results suggest that the alpha-methylhydroxylation of NNK leading to DNA pyridyloxobutylation also modulates cytokine production in NNK-treated AM.