title: Nicotine causes genotoxic damage but is not metabolized during long-term exposure of human nasal miniorgan cultures.
abstract: Human nasal miniorgan cultures (MOC) are a useful tool in ecogenotoxicology. Repetitive exposure to nicotine showed reversible DNA damage, and stable CYP2A6 expression was demonstrated in nasal MOC in previous investigations. The aim of the present study was to evaluate the genotoxic effect of nicotine in nasal MOC after chronic nicotine exposure, and to monitor possible metabolism capacities. MOC were dissected from human nasal mucosa and cultured under standard cell culture conditions. MOC were exposed to nicotine for 3 weeks at concentrations of 1 μM and 1 mM. The concentrations were chosen based on nicotine plasma levels in heavy smokers, and possible concentrations used in topical application of nicotine nasal spray. DNA damage was assessed by the comet assay at days 7, 14 and 21. Concentrations of nicotine and cotinine were analyzed in cell culture medium by gas chromatography/mass spectrometry to determine a possible metabolism of nicotine by MOC. Distinct DNA damage in MOC could be demonstrated after 1 week of exposure to 1 μM and 1 mM nicotine. This effect decreased after 2 and 3 weeks with no statistically relevant DNA migration. No nicotine metabolism could be detected by changes in nicotine and cotinine concentrations in the supernatants. This is the first time genotoxic effects have been evaluated in nasal MOC after chronic nicotine exposure for up to 3 weeks. Genotoxic effects were present after 1 week of culture with a decrease over time. Down-regulation of nicotinic acetylcholine receptors, which are expressed in nasal mucosa, may be a possible explanation. The lack of nicotine metabolism in this model could be explained by the functional loss of CYP2A6 during chronic nicotine exposure. Further investigations are necessary to provide a more detailed description of the underlying mechanisms involved in DNA damage by nicotine.
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany. Electronic address: ginzkey_c@ukw.de.
authors.forename: Christian
authors.initials: C
authors.lastname: Ginzkey
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany.
authors.forename: Gudrun
authors.initials: G
authors.lastname: Steussloff
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Koehler
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Hackenberg
authors.affiliation: Walther Straub Institute, Department of Toxicology, Ludwig-Maximilians University Munich, Nussbaumstrasse 26, D-80336 Munich, Germany.
authors.forename: Elmar
authors.initials: E
authors.lastname: Richter
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Hagen
authors.affiliation: Department of Oto-Rhino-Laryngology, Plastic, Aesthetic and Reconstructive Head and Neck Surgery, Julius-Maximilian University Würzburg, Josef-Schneider-Str. 11, D-97080 Würzburg, Germany.
authors.forename: Norbert H
authors.initials: NH
authors.lastname: Kleinsasser
mesh_terms: D000293:Adolescent; D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D020552:Comet Assay; D003367:Cotinine / Q000378:metabolism; D065637:Cytochrome P-450 CYP2A6; D004249:DNA Damage; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008297:Male; D008741:Methyl Methanesulfonate / Q000378:metabolism; D008875:Middle Aged; D009153:Mutagens / Q000378:metabolism; D009297:Nasal Mucosa / Q000378:metabolism*; D009538:Nicotine / Q000378:metabolism* / Q000633:toxicity*; D018722:Nicotinic Agonists / Q000378:metabolism* / Q000633:toxicity*; D009924:Organ Culture Techniques; D011978:Receptors, Nicotinic / Q000096:biosynthesis / Q000187:drug effects; D012907:Smoking / Q000378:metabolism; D055815:Young Adult
chemical_list: D009153:Mutagens; D018722:Nicotinic Agonists; D011978:Receptors, Nicotinic; D009538:Nicotine; D008741:Methyl Methanesulfonate; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D003367:Cotinine
keywords: CYP2A6; Genotoxicity; Metabolism; Miniorgan culture; Nasal mucosa; Nicotine