Comparative developmental toxicity of a comprehensive suite of polycyclic aromatic hydrocarbons

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental contaminants that occur in complex mixtures. Several PAHs are known or suspected mutagens and/or carcinogens, but developmental toxicity data is lacking for PAHs, particularly their oxygenated and nitrated derivatives. Such data are necessary to understand and predict the toxicity of environmental mixtures. 123 PAHs were assessed for morphological and neurobehavioral effects for a range of concentrations between 0.1 and 50 µM, using a high throughput early-life stage zebrafish assay, including 33 parent, 22 nitrated, 17 oxygenated, 19 hydroxylated, 14 methylated, 16 heterocyclic, and 2 aminated PAHs. Additionally, each PAH was evaluated for AHR activation, by assessing CYP1A protein expression using whole animal immunohistochemistry (IHC). Responses to PAHs varied in a structurally dependent manner. High-molecular weight PAHs were significantly more developmentally toxic than the low-molecular weight PAHs, and CYP1A expression was detected in five distinct tissues, including vasculature, liver, skin, neuromasts and yolk.

Keywords: AHR; CYP1A; Developmental toxicity; PAH; Zebrafish.

Figure 1

Summary of the PAHs evaluated.

Figure 2

Heirarchically clustered heatmap of lowest effect levels for developmental toxicity endpoints, and neurobehavioral assays (left 5 columns). “Any Effect” and “Any Except Mortality” (right 2 columns) are aggregates of all morphological endpoints. Darker red color denotes decreased lowest concentration of effect, and higher toxicity. Class of PAH is denoted by color in rightmost column.

Figure 3

Representative images illustrating CYP1A expression patterns (a) None (b) Vasculature (c) Liver (d) Yolk (e) Skin and Neuromasts (f) Skin

Figure 4

(a) Proportion of PAHs with number of CYP1A expressing tissues. (b) Venn diagram of number of PAHs observed with specific tissue combinations expressing CYP1A.