title: Combining transcriptomics and PBPK modeling indicates a primary role of hypoxia and altered circadian signaling in dichloromethane carcinogenicity in mouse lung and liver.
abstract: Dichloromethane (DCM) is a lung and liver carcinogen in mice at inhalation exposures≥2000ppm. The modes of action (MOA) of these responses have been attributed to formation of genotoxic, reactive metabolite(s). Here, we examined gene expression in lung and liver from female B6C3F1 mice exposed to 0, 100, 500, 2000, 3000 and 4000ppm DCM for 90days. We also simulated dose measures - rates of DCM oxidation to carbon monoxide (CO) in lung and liver and expected blood carboxyhemoglobin (HbCO) time courses with a PBPK model inclusive of both conjugation and oxidation pathways. Expression of large numbers of genes was altered at 100ppm with maximal changes in the numbers occurring by 500 or 2000ppm. Most changes in genes common to the two tissues were related to cellular metabolism and circadian clock. At the lower concentrations, the changes in metabolism-related genes were discordant - up in liver and down in lung. These processes included organelle biogenesis, TCA cycle, and respiratory electron transport. Changes in circadian cycle genes - primarily transcription factors - showed strong concentration-related response at higher concentrations (Arntl, Npas2, and Clock were down-regulated; Cry2, Wee1, Bhlhe40, Per3, Nr1d1, Nr1d2 and Dbp) were up-regulated with similar directionality in both tissues. Overall, persistently elevated HbCO from DCM oxidation appears to cause extended periods of hypoxia, leading to altered circadian coupling to cellular metabolism. The dose response for altered circadian processes correlates with the cancer outcome. We found no evidence of changes in genes indicative of responses to cytotoxic, DNA-reactive metabolites.
authors.affiliation: ScitoVation LLC, Six Davis Drive, PO Box 110566, Research Triangle Park, NC 27709-5566, United States.
authors.forename: Melvin E
authors.initials: ME
authors.lastname: Andersen
authors.affiliation: ScitoVation LLC, Six Davis Drive, PO Box 110566, Research Triangle Park, NC 27709-5566, United States. Electronic address: mblack@scitovation.com.
authors.forename: Michael B
authors.initials: MB
authors.lastname: Black
authors.affiliation: Ramboll-Enviro, Inc., Six Davis Drive, PO Box 13441, Research Triangle Park, NC 27709, United States.
authors.forename: Jerry L
authors.initials: JL
authors.lastname: Campbell
authors.affiliation: ScitoVation LLC, Six Davis Drive, PO Box 110566, Research Triangle Park, NC 27709-5566, United States.
authors.forename: Salil N
authors.initials: SN
authors.lastname: Pendse
authors.affiliation: ScitoVation LLC, Six Davis Drive, PO Box 110566, Research Triangle Park, NC 27709-5566, United States.
authors.forename: Harvey J
authors.initials: HJ
authors.lastname: Clewell
authors.affiliation: Olin Corporation, 100 Larkin Center, Midland, MI 48674, United States.
authors.forename: Lynn H
authors.initials: LH
authors.lastname: Pottenger
authors.affiliation: Exponent, Inc., 5806 Woodberry Drive, Midland, MI 48640, United States.
authors.forename: James S
authors.initials: JS
authors.lastname: Bus
authors.affiliation: Charles River, 640 N. Elizabeth St., Spencerville, OH 45887, United States.
authors.forename: Darol E
authors.initials: DE
authors.lastname: Dodd
authors.affiliation: Quintiles, 4820 Emperor Blvd., Durham, NC 27703, United States.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Kemp
authors.affiliation: ScitoVation LLC, Six Davis Drive, PO Box 110566, Research Triangle Park, NC 27709-5566, United States.
authors.forename: Patrick D
authors.initials: PD
authors.lastname: McMullen
mesh_terms: D000818:Animals; D002263:Carboxyhemoglobin / Q000235:genetics / Q000378:metabolism; D002940:Circadian Rhythm / Q000187:drug effects / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation; D000860:Hypoxia / Q000139:chemically induced / Q000235:genetics* / Q000473:pathology; D019570:Inhalation Exposure / Q000009:adverse effects; D008099:Liver / Q000187:drug effects* / Q000378:metabolism; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D008752:Methylene Chloride / Q000633:toxicity*; D051379:Mice; D008815:Mice, Inbred Strains; D010599:Pharmacokinetics; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D059467:Transcriptome
chemical_list: D014157:Transcription Factors; D008752:Methylene Chloride; D002263:Carboxyhemoglobin
keywords: Carcinogen; Circadian cycle; Dichloromethane; Hypoxia; Mouse