Two-generation exposure to 2-ethylhexyl 4-methoxycinnamate (EHMC) in Japanese medaka (Oryzias latipes) and its reproduction and endocrine related effects

Abstract

2-Ethylhexyl 4-methoxycinnamate (EHMC) is one of the most widely used UV-filters, and hence has been frequently detected in water environment. EHMC has been reported to induce short-term reproductive toxicity in fish, and thyroid disrupting effects in other animal studies. However, limited information is available for its long-term effects on fecundity, and thyroid disrupting effects in fish. In the present study, effects of EHMC on fecundity, measured as number of eggs, were evaluated in Japanese medaka (Oryzias latipes), and its underlying mechanisms on sex and thyroid hormone disruption were explored. For this purpose, a five-month long (154 d) exposure to F0 generation was conducted on fertilized eggs (<24 h post-fertilization (hpf)), with nominal concentration of 0, 0.05, 0.158, 0.5, 1.58, or 5 mg/L EHMC, followed by a 3-8-d exposure of F1 generation. After >3 months exposure, significant decreases in reproductive performances were observed at all test concentrations as low as 0.05 mg/L. Reproduction effects were not accompanied with sex hormone changes, but up-regulation of vitellogenin gene was observed. Thyroid hormones were decreased by EHMC exposure in F1 fish at -38 day post-fertilization (dpf). In addition, down-regulation of type II iodothyronine deiodinase (dio2) and up-regulation of thyrotropin releasing hormone (trh) were observed in both F0 and F1 juvenile fish, suggesting thyroid disruption potential of EHMC. Our observation suggests that EHMC at the levels one to two orders of magnitude higher than those detected in ambient water may affect reproduction and thyroid hormonal balance of fish.