Mitochondrial DNA Adducts in the Lung and Liver of F344 Rats Chronically Treated with 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone and (S)-4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol

Abstract

Two recent studies conducted in our laboratory have demonstrated formation and accumulation of pyridyloxobutyl (POB) and pyridylhydroxybutyl (PHB) adducts in lung and liver total DNA of F344 rats chronically treated with the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and (R)-and (S)-enantiomers of its metabolite, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL). In this study, we measured POB and PHB adducts in lung and liver mitochondrial DNA (mtDNA), as previous studies suggest a potentially important role of mtDNA in carcinogenesis. Rats were sacrificed after 1, 2, 5, 10, 16, and 20 weeks of treatment with 10 ppm of NNK or (S)-NNAL in drinking water, and mtDNA and nuclear DNA (nDNA) adduct levels in lung and liver were determined by LC-ESI-MS/MS-SRM. The mean levels of individual POB adducts in mtDNA at all time points were slightly higher than those in nDNA for both NNK and (S)-NNAL-treated rats in the lung (P < 0.001 for both treatments), but not in the liver (P > 0.05). Lung mtDNA of both NNK-and (S)-NNAL-treated rats contained higher concentrations of the sum of three POB adducts (P < 0.001 for both treatments) than nDNA, while the levels of mtDNA and nDNA total POB adducts in the liver were not significantly different in either NNK-or (S)-NNALtreated rats. Analysis of PHB adducts in mtDNA and nDNA produced results similar to those obtained for POB adducts. The steady accumulation of the lung and liver mtDNA adducts over the course of the study indicates inefficient repair of these adducts in mtDNA. This is the first study to examine the formation of NNK-and (S)-NNAL-derived adducts in rat mtDNA. The results support the hypothesis that preferential binding of tobacco carcinogens to mtDNA of the lung might be functionally important in the development of smoking-induced lung cancer. KeywordsNNK; NNAL; mitochondria; DNA adducts *To whom correspondence should be addressed. Phone: (612) 624-4998. Fax: (612) 626-5135. E-mail: stepa011@umn.edu. 1 Abbreviations: AKR, aldo-keto reductases; ATP, adenosine triphosphate; BaP, benzo[a]pyrene; HPLC-ESI-MS/MS, high performance liquid chromatography-electrospray ionization-tandem mass spectrometry; 11β-HSD1, 11β-hydroxysteroid dehydrogenase type 1;

Mitochondrial DNA damage and its consequences for mitochondrial gene expression

“…Benzo[ a ]pyrene (BaP) is metabolized by the liver cytochrome P450 CYP1A1 to benzo[ a ]pyrene 7,8-dihydrodiol-9,10-epoxide (BaPDE), and both BaP and BaPDE have been shown to accumulate in mitochondria and inhibit mtDNA synthesis [93–96]. The TSNA compounds, also activated by CYP enzymes, form DNA adducts that have been detected in the lung and liver mtDNA of carcinogen exposed rats, however the effects of TSNA adducts on mtDNA synthesis and gene expression have not been determined [97]. The BaP effects on mtDNA replication likely stem from BaPDE modifications of dG and dA, which block DNA pol γ and inhibit topoisomerase activity.…”

Mitochondrial Biomarkers Reflect Semen Quality: Results from the MARCHS Study in Chongqing, China

“…MtDNA copy number (mtDNAcn) and mtDNA integrity are two major mitochondrial genetic features. Because of the lack of protective histones and DNA repair capacity, mtDNA is particularly vulnerable to damage factors, such as reactive oxygen species (ROS) or adducts [13–14]. Therefore, mitochondrial markers may be sensitive predictors of semen quality damage.…”

Decreased Mitochondrial DNA Content in Association with Exposure to Polycyclic Aromatic Hydrocarbons in House Dust during Wintertime: From a Population Enquiry to Cell Culture

“…Compared with nuclear DNA, mitochondrial DNA is more susceptible to damage because it lacks protective histones and has a diminished DNA repair capacity. As a result mitochondrial DNA has a high mutation rate and is particularly vulnerable to ROS-induced damage [5], [6], as well as to damage directly by adducts [7]. Initially, cells challenged with ROS synthesize more copies of their mitochondrial DNA and increase the number of mitochondria to compensate for the damage, resulting in a vicious circle of more ROS production from damaged mitochondria.…”