Genotoxicity in Atlantic killifish (Fundulus heteroclitus) from a PAH-contaminated Superfund site on the Elizabeth River, Virginia

The Atlantic Wood Industries Superfund site (AWI) on the Elizabeth River in Portsmouth, VA is heavily contaminated with polycyclic aromatic hydrocarbons (PAHs) from a wood treatment facility. Atlantic killifish, or mummichog (Fundulus heteroclitus), at this Superfund site are exposed to very high concentrations of several carcinogens. In this study, we measured PAH concentrations in both fish tissues and sediments. Concurrently, we assessed different aspects of genotoxicity in the killifish exposed in situ. Both sediment and tissue PAH levels were significantly higher in AWI samples, relative to a reference site, but the chemistry profile was different between sediments and tissues. Killifish at AWI exhibited higher levels of DNA damage compared to reference fish, as measured via the flow cytometric method (FCM), and the damage was consistent with sediment PAH concentrations. Covalent binding of benzo[a]pyrene (BaP) metabolites to DNA, as measured via LC-MS/MS adduct detection methods, were also elevated and could be partially responsible for the DNA damage. Using similar LC-MS/MS methods, we found no evidence that oxidative DNA adducts had a role in observed genotoxicity

Differential sensitivity to pro-oxidant exposure in two populations of killifish (Fundulus heteroclitus)

New Bedford Harbor (MA, U.S.A.; NBH) is a Superfund site inhabited by Atlantic killifish (Fundulus heteroclitus) with altered aryl hydrocarbon receptor (Ahr) signaling, leading to resistance to effects of polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The Ahr is a transcription factor that regulates gene expression of many Phase I and II detoxifying enzymes and interacts with Nrf2, a transcription factor that regulates the response to oxidative stress. This study tested the hypothesis that PCB-resistant killifish exhibit altered sensitivity to oxidative stress. Killifish F(1) embryos from NBH and a clean reference site (Scorton Creek, MA, U.S.A.; SC) were exposed to model pro-oxidant and Nrf2-activator, tert-butylhydroquinone (tBHQ). Embryos were exposed at specific embryonic developmental stages (5, 7, and 9 days post fertilization) and toxicity was assessed, using a deformity score, survival, heart rate, and gene expression to compare sensitivity between PCB-resistant and PCB-sensitive (reference) populations. Acute exposure to tBHQ resulted in transient reduction in heart rate in NBH and SC F(1) embryos. However, embryos from NBH were more sensitive to tBHQ, with more frequent and severe deformities, including pericardial edema, tail deformities, small body size, and reduced pigment and erythrocytes. NBH embryos had lower basal expression of antioxidant genes catalase and glutathione-S-transferase alpha (gsta), and upon exposure to tBHQ, exhibited lower levels of expression of catalase, gsta, and superoxide dismutase compared to controls. This result suggests that adaptation to tolerate PCBs has altered the sensitivity of NBH fish to oxidative stress during embryonic development, demonstrating a cost of the PCB resistance adaptation