title: AHR2-Mediated transcriptomic responses underlying the synergistic cardiac developmental toxicity of PAHs.
abstract: Polycyclic aromatic hydrocarbons (PAHs) induce developmental defects including cardiac deformities in fish. The aryl hydrocarbon receptor (AHR) mediates the toxicity of some PAHs. Exposure to a simple PAH mixture during embryo development consisting of an AHR agonist (benzo(a)pyrene-BaP) with fluoranthene (FL), an inhibitor of cytochrome p450 1(CYP1)--a gene induced by AHR activation--results in cardiac deformities. Exposure to BaP or FL alone at similar concentrations alters heart rates, but does not induce morphological deformities. Furthermore, AHR2 knockdown prevents the toxicity of BaP + FL mixture. Here, we used a zebrafish microarray analysis to identify heart-specific transcriptomic changes during early development that might underlie cardiotoxicity of BaP + FL. We used AHR2 morphant embryos to determine the role of this receptor in mediating toxicity. Control and knockdown embryos at 36 h post-fertilization were exposed to DMSO, 100 μg/l BaP, 500 μg/l FL, or 100 μg/l BaP + 500 μg/l FL, and heart tissues for RNA were extracted at 2, 6, 12, and 18 h-post-exposure (hpe), prior to the appearance of cardiac deformities. Data show AHR2-dependent BaP + FL effects on expression of genes involved in protein biosynthesis and neuronal development in addition to signaling molecules and their associated molecular pathways. Ca(2+)-cycling and muscle contraction genes were the most significantly differentially expressed category of transcripts when comparing BaP + FL-treated AHR2 morphant and control embryos. These differences were most prominent at 2 and 6 hpe. Therefore, we postulate that BaP + FL may affect cellular Ca(2+) levels and subsequently cardiac muscle function, potentially underlying BaP + FL cardiotoxicity.
authors.affiliation: *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708 nishad.jayasundara@duke.edu.
authors.forename: Nishad
authors.initials: N
authors.lastname: Jayasundara
authors.affiliation: *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708 *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708 *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708.
authors.forename: Lindsey
authors.initials: L
authors.lastname: Van Tiem Garner
authors.affiliation: *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708.
authors.forename: Joel N
authors.initials: JN
authors.lastname: Meyer
authors.affiliation: *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708.
authors.forename: Kyle N
authors.initials: KN
authors.lastname: Erwin
authors.affiliation: *Nicholas School of the Environment and Department of Pediatrics, Duke University, Durham, North Carolina 27708.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Di Giulio
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000633:toxicity*; D002118:Calcium / Q000378:metabolism; D066126:Cardiotoxicity; D004357:Drug Synergism; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000378:metabolism; D047108:Embryonic Development / Q000187:drug effects* / Q000235:genetics; D005449:Fluorenes / Q000633:toxicity*; D006321:Heart / Q000187:drug effects* / Q000196:embryology; D006330:Heart Defects, Congenital / Q000139:chemically induced / Q000378:metabolism; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome / Q000187:drug effects* / Q000235:genetics; D015027:Zebrafish / Q000196:embryology; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C474372:AHR2 protein, zebrafish; D005449:Fluorenes; D018336:Receptors, Aryl Hydrocarbon; D029961:Zebrafish Proteins; D001564:Benzo(a)pyrene; C007738:fluoranthene; D002118:Calcium
keywords: aryl hydrocarbon receptor; cardiac development; cardiotoxicity; polycyclic aromatic hydrocarbons; transcriptomics; zebrafish