Mutagenesis Advance Access published online on November 5, 2009
Mutagenesis, doi:10.1093/mutage/gep053
Genotoxic effects of neutrophils and hypochlorous acid
1Department of Health Risk Analysis and Toxicology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands 2Cancer Risk Factor Branch, Molecular Biology Laboratory, ISPO-Cancer Prevention and Research Institute Florence, Via Cosimo il Vecchio 2, 50139 Florence, Italy 3Department of Pharmacology and Toxicology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, PO Box 616, 6200 MD, Maastricht, The Netherlands
Chronic inflammation has been recognized as a contributing factor in the pathogenesis of lung cancer. In this process, reactive oxygen species released by neutrophils may play an important role. The aim of the present study was to investigate the capacity of the major neutrophilic oxidant hypochlorous acid (HOCl), which is formed by myeloperoxidase (MPO), to induce DNA damage and mutagenicity in lung cells. HOCl was mutagenic in lung epithelial A549 cells in vitro, showing at physiological concentrations a significant induction of mutations in the HPRT gene. We studied three major types of DNA lesions that could be relevant for this HOCl-induced mutagenicity. Single strand DNA breakage and 8-oxo-7,8-dihydro-2'-deoxyguanosine were not found to be increased following HOCl treatment. On the other hand, HOCl caused a significant increase in the formation of 3-(2-deoxy-β-D-erythro-pentofuranosyl)pyrimido[1,2-
]purin-10(3H)-one (M1dG), which can be formed by either malondialdehyde (MDA) or base propenals. We observed an increased MDA formation upon exposure of A549 cells to HOCl, but a role of base propenals cannot be excluded. In line with this, we observed 4-fold increased M1dG adduct levels in mice that were intratracheally instilled with lipopolysaccharide to induce a pulmonary inflammation with neutrophil influx. Depletion of circulating neutrophils significantly reduced pulmonary MPO activity as well as M1dG adducts levels, thereby providing a causal link between neutrophils/HOCl and pulmonary genotoxicity in vivo. Taken together, these data indicate that MPO catalysed formation of HOCl during lung inflammation should be considered as a significant source of neutrophil-induced genotoxicity.
* To whom correspondence should be addressed. Tel: +31 43 3881100, Fax: +31 43 3884146, Email: f.vanschooten{at}grat.unimaas.nl
4 Present address: Department of Toxicology and Drug Disposition, Schering-Plough, PO Box 20, 5340 BH Oss, The Netherlands
Received on August 28, 2009; revised on October 7, 2009; accepted on October 9, 2009.