Molecular mechanism of the suppression of larval skeleton by polycyclic aromatic hydrocarbons in early development of sea urchin Hemicentrotus pulcherrimus

Polycyclic aromatic hydrocarbons including benz[a]anthracene (BaA) are priority pollutants in the aquatic environment. Our previous study revealed that BaA and its metabolite, 4-monohydroxylated BaA (4-OHBaA) inhibit larval skeletogenesis in the sea urchin Hemicentrotus pulcherrimus. Here we report studies to elucidate the target of skeletogenesis inhibition elicited by BaA and 4-OHBaA. First, we performed an in vitro experiment using isolated micromeres which give rise to the larval skeletogenic mesenchyme. However, skeletogenesis was not repressed by BaA and 4-OHBaA, implying that these chemicals indirectly influence on the formation of larval skeleton. Next, we analyzed their influence in vivo using embryos. Vascular endothelial growth factor (VEGF) that is expressed in the ectoderm and induces spicule formation was inhibited by BaA and 4-OHBaA treatment. These chemicals also suppressed the expression of the heparan sulfate 6-O endosulfatase (Sulf) known as a VEGF signaling modulator. We, therefore, propose that BaA and 4-OHBaA effects on larval skeletogenesis via VEGF signaling. Furthermore, we showed that the expression of Endo16 mRNA, an endodermal marker, decreased after BaA and 4-OHBaA exposure, suggesting that these chemicals affect endodermal function together with skeletogenesis. This study demonstrates that BaA and 4-OHBaA exert multiple detrimental effects on the development of H. pulcherrimus.