Ligand-specific transcriptional mechanisms underlie aryl hydrocarbon receptor-mediated developmental toxicity of oxygenated PAHs Goodale, B.C.* †, La Du, J. *, Tilton, S.C.* ‡, Sullivan, C.M.* §, Bisson, W.H. *, Waters, K.M. ‡ and Tanguay, R.L.* *Department of Environmental and Molecular Toxicology, the Environmental Health Sciences Center, Oregon State University, Corvallis, OR, 97330 †Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, 604 Remsen Bldg., Hanover, NH 03755 ‡Computational Biology and Bioinformatics, Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA 99354 §Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, 97330 Corresponding author: Robert Tanguay, Ph.D., Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97330. Email:
[email protected] Abstract Polycyclic aromatic hydrocarbons (PAHs) are priority environmental contaminants that exhibit mutagenic, carcinogenic, proinflammatory and teratogenic properties. Oxygen-substituted PAHs (OPAHs) are formed during combustion processes and via phototoxidation and biological degradation of parent (unsubstituted) PAHs. Despite their prevalence both in contaminated industrial sites and in urban air, OPAH mechanisms of action in biological systems are relatively understudied. Like parent PAHs, OPAHs exert structure-dependent mutagenic activities and activation of the aryl hydrocarbon receptor (AHR) and cytochrome p450 metabolic pathway (CYP1A). Four-ring OPAHs 1,9-benz-10-anthrone (BEZO) and benz(a)anthracene-7,12-dione (7,12-B[a]AQ) cause morphological aberrations and induce markers of oxidative stress in developing zebrafish with similar potency, but only 7,12-B[a]AQ induces robust Cyp1a protein expression. We investigated the role of the AHR in mediating the toxicity of BEZO and 7,12-B[a]AQ, and found that knockdown of AHR2 rescued developmental effects caused by both compounds.