PM10 Mechanisms of Toxic Action
Exhibit Hall
8:00 AM - Monday
(PM170) Resistance to PCB induced CYP1A activity and oxidative stress in a chronically contaminated killifish (Fundulus heteroclitus) population.
Arzuaga, Xabier1, Elskus, Adria2, Harmel, Elena2, Di Giulio, Richard 3, Wassenberg, Deena3, 1 Graduate Center for Toxicology, University of Kentucky2 Department of Biology, University of Kentucky, Lexington, KY, USA3 Nicholas School of the Environment, Duke University, Durham, NC, USA
ABSTRACT- New Bedford Harbor, MA is a Superfund site highly contaminated with polychlorinated biphenyls (PCBs). Exposure to PCBs causes a variety of toxic effects in vertebrates, including developmental deformities and oxidative stress. The toxic effects of PCBs are believed to be mediated, in part, through activation of the aryl hydrocarbon receptor (AHR), which leads to induction of xenobiotic metabolizing enzymes, including cytochrome P450 1A (CYP1A). Since chronically exposed killifish (Fundulus heteroclitus) populations in NBH exhibit resilience to the lethal effects of PCB, we hypothesized that PCB resistance in these populations is mediated, at least in part, via AHR/CYP1A. Killifish embryos from NBH and a reference site were exposed to vehicle (acetone 0.001%) or the potent CYP1A inducer, PCB126, from day two to day seven post fertilization (pf). Superoxide production (detected with dihydroethidium) was measured on day 7 pf and in ovo CYP1A activity (ethoxyresorufin-o-deethylase, EROD) and cardiovascular deformities (tube heart) were quantified on day 9 pf. Exposure to 0.3nM PCB126 maximally increased CYP1A activity and reactive oxygen species (ROS) production in reference site, but not NBH, embryos. Exposure to a toxic PCB126 dose (1.5nM) significantly increased heart deformities in reference site embryos; but NBH embryos were unaffected. To determine if these effects are AHR/CYP1A dependent, reference site embryos were treated with the AHR/CYP1A inhibitor a-naphthoflavone (ANF) alone (367nM), or in combination with PCB126. ANF blocked PCB126 induction of CYP1A activity and developmental deformities, but did not block ROS production. Our results suggest that chronic exposure to PCBs has resulted in resistance to the toxic effects of PCB (oxidative stress and developmental deformities), that at least one of these effects (deformities) is AHR/CYP1A mediated, and that PCB induced ROS production may occur through non-AHR mechanisms.
Key words: AHR, killifish, CYP1A, oxidative stress