Developmental exposure to a complex PAH mixture causes persistent behavioral effects in naive Fundulus heteroclitus (killifish) but not in a population of PAH-adapted killifish

Abstract

Acute exposures to some individual polycyclic aromatic hydrocarbons (PAHs) and complex PAH mixtures are known to cause cardiac malformations and edema in the developing fish embryo. However, the heart is not the only organ impacted by developmental PAH exposure. The developing brain is also affected, resulting in lasting behavioral dysfunction. While acute exposures to some PAHs are teratogenically lethal in fish, little is known about the later life consequences of early life, lower dose subteratogenic PAH exposures. We sought to determine and characterize the long-term behavioral consequences of subteratogenic developmental PAH mixture exposure in both naive killifish and PAH-adapted killifish using sediment pore water derived from the Atlantic Wood Industries Superfund Site. Killifish offspring were embryonically treated with two low-level PAH mixture dilutions of Elizabeth River sediment extract (ERSE) (TPAH 5.04 μg/L and 50.4 μg/L) at 24 hours post fertilization. Following exposure, killifish were raised to larval, juvenile, and adult life stages and subjected to a series of behavioral tests including: a locomotor activity test (4 days post-hatch), a sensorimotor response tap/habituation test (3 months post hatch), and a novel tank diving and exploration test (3 months post hatch). Killifish were also monitored for survival at 1, 2, and 5 months over 5-month rearing period. Developmental PAH exposure caused short-term as well as persistent behavioral impairments in naïve killifish. In contrast, the PAH-adapted killifish did not show behavioral alterations following PAH exposure. PAH mixture exposure caused increased mortality in reference killifish over time; yet, the PAH-adapted killifish, while demonstrating long-term rearing mortality, had no significant changes in mortality associated with ERSE exposure. This study demonstrated that early embryonic exposure to PAH-contaminated sediment pore water caused long-term locomotor and behavioral alterations in killifish, and that locomotor alterations could be observed in early larval stages. Additionally, our study highlights the resistance to behavioral alterations caused by low-level PAH mixture exposure in the adapted killifish population. Furthermore, this is the first longitudinal behavioral study to use killifish, an environmentally important estuarine teleost fish, and this testing framework can be used for future contaminant assessment.

Hepatic Responses of Juvenile Fundulus heteroclitus from Pollution-adapted and Nonadapted Populations Exposed to Elizabeth River Sediment Extract

“…Within 2-mo after ERSE exposure, AW fish in all groups, including the control, had higher mortality relative to KC fish, and only KC fish exposed to 1.0% ERSE had significantly higher mortality relative to other KC groups (Brown et al , 2016). By 5-mo, no differences in mortality between any exposure groups was seen (Brown et al , 2016).…”

Developmental benzo[a]pyrene (B[a]P) exposure impacts larval behavior and impairs adult learning in zebrafish

“…Our results are consistent with PAH mixture behavioral effects in fish species. Naïve killifish larvae exposed to a PAH mixture from an Elizabeth river sediment extract (ERSE) showed hyperactivity in a repeated light-dark transition assay (Brown 2016). Juvenile zebrafish fed a pyrolytic PAH fraction mixture were also hyperactive following a light-dark challenge (Vignet, Menach et al 2014).…”

“…Importantly, B[a]P AHR2 null larvae did not display a significant difference in LPR compared to unexposed AHR2 null fish, illustrating a role for AHR2 in this B[a]P induced hyperactivity. Previously, a PAH resistant killifish population from the Elizabeth River (ER) was also tested, and exposure to a PAH mixture from an Elizabeth river sediment extract (ERSE) did not lead to swimming differences in larval or juvenile killifish (Brown 2016). This ER population was shown to have resistance to induction of the phase I enzyme, CYP1A (Meyer 2002) and upregulation of phase II and phase III metabolizing enzymes (Gaworecki 2004) following PAH exposures.…”

“…Developmental B[a]P cardiotoxicity is AHR dependent in mice (Kerley-Hamilton 2012) and AHR2 dependent in zebrafish (Incardona, Collier et al 2011; Van Tiem and Di Giulio 2011). Additionally, both developmental and acute B[a]P exposure is associated with impaired motor activity, and lower cognitive performance in juvenile and adult rodents (Saunders, Das et al 2006; McCallister, Maguire et al 2008; Chen, Tang et al 2012; Cheng, Xia et al 2013; Brown 2016) and anxiety-like behavior in juvenile killifish and zebrafish developmentally exposed to B[a]P-containing PAH mixtures (Vignet, Menach et al 2014; Brown 2016). The observed neurotoxicity is also hypothesized to result from toxic metabolites (Saunders, Das et al 2006; Chepelev, Moffat et al 2015).…”

A bioenergetics assay for studying the effects of environmental stressors on mitochondrial function in vivo in zebrafish larvae

“…Due to urban expansion and increased use of automobiles, the concentration of these compounds in aquatic environments is steadily increasing (Lima et al, 2003). Potential adverse impacts of PAHs include carcinogenesis, effects on the reproductive, neurologic, and immune systems, and developmental abnormalities (Arkoosh and Kaattari, 1991; Brown et al, 2016; Hawkins et al, 1990; Incardona et al, 2011; Johnson, 1988; Van Tiem and Di Giulio, 2011; Vignet et al, 2014a; Vignet et al, 2014b). In fish, the most notable adverse developmental effects occur due to bioactivation of PAHs via the aryl hydrocarbon receptor (AHR) pathway, disrupting normal cardiovascular development and resulting in deformities such as elongated “stringy” hearts, impaired heart looping, decreased blood flow, and pericardial effusion (Billiard et al, 2006; Incardona et al, 2004; Van Tiem and Di Giulio, 2011; Wassenberg and Di Giulio, 2004).…”