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Title: Effects of airborne pollutants on mitochondrial DNA methylation.

Authors: Byun, Hyang-Min; Panni, Tommaso; Motta, Valeria; Hou, Lifang; Nordio, Francesco; Apostoli, Pietro; Bertazzi, Pier Alberto; Baccarelli, Andrea A

Published In Part Fibre Toxicol, (2013 May 08)

Abstract: Mitochondria have small mitochondrial DNA (mtDNA) molecules independent from the nuclear DNA, a separate epigenetic machinery that generates mtDNA methylation, and are primary sources of oxidative-stress generation in response to exogenous environments. However, no study has yet investigated whether mitochondrial DNA methylation is sensitive to pro-oxidant environmental exposures.We sampled 40 male participants (20 high-, 20 low-exposure) from each of three studies on airborne pollutants, including investigations of steel workers exposed to metal-rich particulate matter (measured as PM1) in Brescia, Italy (Study 1); gas-station attendants exposed to air benzene in Milan, Italy (Study 2); and truck drivers exposed to traffic-derived Elemental Carbon (EC) in Beijing, China (Study 3). We have measured DNA methylation from buffy coats of the participants. We measured methylation by bisulfite-Pyrosequencing in three mtDNA regions, i.e., the transfer RNA phenylalanine (MT-TF), 12S ribosomal RNA (MT-RNR1) gene and "D-loop" control region. All analyses were adjusted for age and smoking.In Study 1, participants with high metal-rich PM1 exposure showed higher MT-TF and MT-RNR1 methylation than low-exposed controls (difference = 1.41, P = 0.002); MT-TF and MT-RNR1 methylation was significantly associated with PM1 exposure (beta = 1.35, P = 0.025); and MT-RNR1 methylation was positively correlated with mtDNA copy number (r = 0.36; P = 0.02). D-loop methylation was not associated with PM1 exposure. We found no effects on mtDNA methylation from air benzene (Study 2) and traffic-derived EC exposure (Study 3).Mitochondrial MT-TF and MT-RNR1 DNA methylation was associated with metal-rich PM1 exposure and mtDNA copy number. Our results suggest that locus-specific mtDNA methylation is correlated to selected exposures and mtDNA damage. Larger studies are needed to validate our observations.

PubMed ID: 23656717 Exiting the NIEHS site

MeSH Terms: Adult; Air Pollutants, Occupational/adverse effects*; Air Pollution*; Base Sequence; Benzene/adverse effects; China; DNA Methylation/drug effects*; DNA, Mitochondrial/drug effects*; DNA, Mitochondrial/metabolism; Gene Dosage; Humans; Inhalation Exposure/adverse effects; Italy; Male; Middle Aged; Molecular Sequence Data; Occupational Exposure/adverse effects; Particulate Matter/adverse effects; Real-Time Polymerase Chain Reaction; Sequence Analysis, DNA; Steel/adverse effects; Vehicle Emissions/toxicity

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