title: Somatic-cell mutation induced by short exposures to cigarette smoke in urate-null, oxidative stress-sensitive Drosophila.
abstract: We previously reported that a urate-null strain of Drosophila is hypersensitive to cigarette smoke (CS), and we suggested that CS induces oxidative stress in Drosophila because uric acid is a potent antioxidant. Although the carcinogenic risk of CS exposure is widely recognized; documentation of in vivo genotoxic activity of environmental CS, especially gaseous-phase CS, remains inconclusive. To date, somatic-cell mutations in Drosophila resulting from exposure to CS have not been detected via the somatic mutation and recombination test (wing spot test) with wild-type flies, a widely used Drosophila assay for the detection of somatic-cell mutation; moreover, genotoxicity has not been documented via a DNA repair test that involves DNA repair-deficient Drosophila. In this study, we used a new Drosophila strain (y v ma-l; mwh) to examine the mutagenicity induced by gaseous-phase CS; these flies are urate-null due to a mutation in ma-l, and they are heterozygous for multiple wing hair (mwh), a mutation that functions as a marker for somatic-cell mutation. In an assay with this newly developed strain, a superoxide anion-producing weed-killer, paraquat, exhibited significant mutagenicity; in contrast, paraquat was hardly mutagenic with a wild-type strain. Drosophila larvae were exposed to CS for 2, 4 or 6h, and then kept at 25°C on instant medium until adulthood. After eclosion, mutant spots, which consisted of mutant hairs on wings, were scored. The number of mutant spots increased significantly in an exposure time-dependent manner in the urate-null females (ma-l (-/-)), but not in the urate-positive females (ma-l (+/-)). In this study, we showed that short-term exposure to CS was mutagenic in this in vivo system. In addition, we obtained suggestive data regarding reactive oxygen species production in larva after CS exposure using the fluorescence probe H2DCFDA. These results suggest that oxidative damage, which might be countered by uric acid, was partly responsible for induction of somatic cell mutations in Drosophila larvae exposed to CS.
authors.forename: Tomoyo
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Ryota
authors.initials: R
authors.lastname: Koike
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yuma
authors.forename: Keinosuke
authors.initials: K
authors.lastname: Okamoto
authors.forename: Sakae
authors.initials: S
authors.lastname: Arimoto-Kobayashi
authors.affiliation: School of Pharmacy, Shujitsu University, Okayama 703-8516, Japan.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Suzuki
authors.forename: Tomoe
authors.initials: T
authors.lastname: Negishi
mesh_terms: D000818:Animals; D004330:Drosophila / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D005260:Female; D007814:Larva / Q000187:drug effects / Q000235:genetics; D008297:Male; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D018384:Oxidative Stress; D017382:Reactive Oxygen Species; D012907:Smoking / Q000009:adverse effects*; D014527:Uric Acid; D014921:Wings, Animal
chemical_list: D009153:Mutagens; D017382:Reactive Oxygen Species; D014527:Uric Acid