Aryl Hydrocarbon Receptor–Independent Toxicity of Weathered Crude Oil during Fish Development

Ecotoxicology and Environmental Fish Health Program, Environmental Conservation Division, Northwest Fisheries Science Center, National Oceanic and Atmospheric Administration, Seattle, Washington 98112, USA.
Environmental Health Perspectives (Impact Factor: 7.98). 01/2006; 113(12):1755-62. DOI: 10.1289/ehp.8230
Source: PubMed


Polycyclic aromatic hydrocarbons (PAHs), derived largely from fossil fuels and their combustion, are pervasive contaminants in rivers, lakes, and nearshore marine habitats. Studies after the Exxon Valdez oil spill demonstrated that fish embryos exposed to low levels of PAHs in weathered crude oil develop a syndrome of edema and craniofacial and body axis defects. Although mechanisms leading to these defects are poorly understood, it is widely held that PAH toxicity is linked to aryl hydrocarbon receptor (AhR) binding and cytochrome P450 1A (CYP1A) induction. Using zebrafish embryos, we show that the weathered crude oil syndrome is distinct from the well-characterized AhR-dependent effects of dioxin toxicity. Blockade of AhR pathway components with antisense morpholino oligonucleotides demonstrated that the key developmental defects induced by weathered crude oil exposure are mediated by low-molecular-weight tricyclic PAHs through AhR-independent disruption of cardiovascular function and morphogenesis. These findings have multiple implications for the assessment of PAH impacts on coastal habitats.

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    • "The toxicity, carcinogenic, mutagenic, and teratogenic properties of PAHs are well documented (Boström et al., 2002; Stegeman et al., 1991). Studies have reported extreme impacts of crude oil and PAHs on the heart of exposed fish embryos including what was described as cardiogenic fluid accumulation syndrome (Brette et al., 2014; Carls et al., 1999; Heintz et al., 1999), and craniofacial and body axis defects (Incardona et al., 2005). George-Ares and Clark (2000) reported that oil spill dispersants, Corexit® 9500 and Corexit® 9527 induced low to moderate toxicity in most aquatic species in laboratory tests; while Berninger et al. (2011) studied the effect of oil and oil/9500 mixtures on fish and shrimp species and concluded that the toxicity of oil increases when mixed with dispersant 9500. "
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    ABSTRACT: Exposure of fish embryos to relatively low concentrations of oil has been implicated in sub-lethal toxicity. The objective of this study was to determine the effects of the exposure of Menidia beryllina embryos at 30-48h post-fertilization to the water accommodated fractions of oil (WAF, 200ppm, v/v), dispersants (20ppm, v/v, Corexit 9500 or 9527), and mixtures of oil and each of the dispersants to produce chemically enhanced water accommodated fractions (CEWAFs) over a 72-hour period. The polyaromatic hydrocarbon (PAH) and benzene, toluene, ethylene and xylene (BTEX) constituents of the 5X concentrated exposure solutions (control, WAF, dispersants and CEWAFs) were determined and those of the 1× exposures were derived using a dilution factor. PAH, BTEX and low molecular weight PAH constituents greater than 1ppb were observed in WAF and the dispersants, but at much higher levels in CEWAFs. The WAF and CEWAFs post-weathering were diluted at 1:5 (200ml WAF/CEWAF: 800ml 25ppt saltwater) for embryo exposures. Mortality, heartbeat, embryo normalcy, abnormality types and severities were recorded. The qPCR assay was used to quantify abundances of transcripts of target genes for sexual differentiation and sex determination (StAR, dmrt-1, amh, cyp19b, vtg and chg-L,), growth regulation (ghr) and stress response (cyp1a and Hsp90); and gapdh served as the housekeeping gene. Temperature was 21±1.5°C throughout the experimental period, while mortality was low and not significantly different (p=0.68) among treatments. Heartbeat was significantly different (0.0034) with the lowest heartbeats recorded in Corexit 9500 (67.5beats/min) and 9527 (67.1beats/min) exposed embryos compared with controls (82.7beats/min). Significantly more treated embryos were in a state of deterioration, with significantly more embryos presenting arrested tissue differentiation compared with controls (p=0.021). Exposure to WAF, dispersants and CEWAF induced aberrant expression of all the genes, with star, dmrt-1, ghr and hsp90 being significantly down-regulated in CEWAF and cyp19b in Corexit 9527. The cyp1a and cyp19b were significantly up-regulated in CEWAFs and WAF, respectively. The molecular endpoints were most sensitive, especially the expression of star, cyp19b, cyp1a, hsp90 and could therefore be used as early indicators of long term effects of Corexit 9500 and 9527 usage in oil spill management on M. beryllina, a valid sentinel for oil pollution events.
    Aquatic toxicology (Amsterdam, Netherlands) 09/2015; 168. DOI:10.1016/j.aquatox.2015.09.012 · 3.45 Impact Factor
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    • "Thus, their use near the coast is still debated, due in part to the lack of knowledge of their effects on organisms, and the question of the effects of both fuel oil and dispersed oil on coastal organisms should be raised. Petroleum compounds have been shown to affect numerous physiological functions such as respiration (Duarte et al., 2010), immunity (Fabiani et al., 1999; Reynaud et al., 2002), cell differentiation (Perez et al., 2003), development (Incardona et al., 2005), growth, reproduction and gene expression (Zhang et al., 2013). Alterations of fish metabolism are also reported (Davoodi and 0045-6535/Ó 2015 Elsevier Ltd. "
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    ABSTRACT: In this study, the impact of dispersed oil was assessed in Dicentrarchus labrax, a fish frequently used as an oil contamination indicator species. Fish were exposed for 48h to (mechanically and chemically) dispersed oil and dispersant alone. The impact of these exposure conditions was assessed on cardiac function by measuring (i) the contraction strength, the contraction and the relaxation speeds (ii) the cardiac energy metabolism using respirometry on permeabilized cardiac fibers. Compared to control, the increase of polycyclic aromatic metabolites observed in the bile indicated oil contamination in our fish. Following 48h of oil exposure at realistic oil concentrations, alterations of cardiac performances were observed. A decrease in contraction strength, contraction and relaxation speeds was observed in the presence of oil without effect of dispersant on these three parameters. Looking at cardiac energy metabolism, dispersant alone decreases all the activity of the respiratory chain and increases the proton leak. From these results, it appears that the observed decrease in cardiac performance in fish exposed to oil was not linked to a decrease in energy availability. Copyright © 2015 Elsevier Ltd. All rights reserved.
    Chemosphere 05/2015; 134:192-198. DOI:10.1016/j.chemosphere.2015.04.026 · 3.34 Impact Factor
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    • "Low molecular weight PAHs act preferentially through the narcosis pathway while high molecular weight PAHs involve binding to aryl hydrocarbon receptor AhR (Di Toro et al. 1991; Wassenberg and Di Giulio 2004). It has been recently demonstrated that three ring compounds can also act through an unknown AhR-independent pathway (Hawkins et al. 2002; Incardona et al. 2005). "
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    ABSTRACT: A new gravel-contact assay using rainbow trout, Oncorhynchus mykiss, embryos was developed to assess the toxicity of polycyclic aromatic hydrocarbons (PAHs) and other hydrophobic compounds. Environmentally realistic exposure conditions were mimicked with a direct exposure of eyed rainbow trout embryos incubated onto chemical-spiked gravels until hatching at 10 °C. Several endpoints were recorded including survival, hatching delay, hatching success, biometry, developmental abnormalities, and DNA damage (comet and micronucleus assays). This bioassay was firstly tested with two model PAHs, fluoranthene and benzo[a]pyrene. Then, the method was applied to compare the toxicity of three PAH complex mixtures characterized by different PAH compositions: a pyrolytic extract from a PAH-contaminated sediment (Seine estuary, France) and two petrogenic extracts from Arabian Light and Erika oils, at two environmental concentrations, 3 and 10 μg g−1 sum of PAHs. The degree and spectrum of toxicity were different according to the extract considered. Acute effects including embryo mortality and decreased hatching success were observed only for Erika oil extract. Arabian Light and pyrolytic extracts induced mainly sublethal effects including reduced larvae size and hemorrhages. Arabian Light and Erika extracts both induced repairable DNA damage as revealed by the comet assay versus the micronucleus assay. The concentration and proportion of methylphenanthrenes and methylanthracenes appeared to drive the toxicity of the three PAH fractions tested, featuring a toxic gradient as follows: pyrolytic < Arabian Light < Erika. The minimal concentration causing developmental defects was as low as 0.7 μg g−1 sum of PAHs, indicating the high sensitivity of the assay and validating its use for toxicity assessment of particle-bound pollutants.
    Environmental Science and Pollution Research 12/2014; 21(24). DOI:10.1007/s11356-014-2804-0 · 2.83 Impact Factor
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