Toxicological responses following short-term exposure to Dechlorane Plus in zebrafish (Danio rerio)

Abstract

Dechlorane Plus (DP) is a widely used chlorinated flame retardant, and has been detected in various environmental matrices and biota including humans. Although DP is globally distributed in high frequency, there is limited information on its toxicity. In order to identify toxicity of DP in vertebrate, zebrafish were employed to evaluate possible toxicological responses including oxidative stress and endocrine disruption. DP was dissolved in corn oil, and delivered to adult male zebrafish via oral gavage feeding with doses of 0, 0.3, 1, and 3 μg/g zebrafish wet weight. Fish were fed with DP twice (days 0 and 2). On day 6, blood, liver, testis, and brain were collected and were evaluated for oxidative stress and endocrine disruption. Following DP exposure, catalase activity in liver showed a significant dose-dependent increase, while superoxide dismutase activity was not affected. In addition, plasma thyroxine (T4) concentrations increased following DP exposure. Transcriptions of corticotropin releasing hormone (crh) and thyroid stimulating hormone β (tshβ) gene in brain increased in a dose-dependent manner, explaining the changes of plasma T4 level. Transcriptional responses of sex hormone related genes in brain including aromatase gene (cyp19b) and estrogen receptor genes also showed sex hormone disruption potentials of DP in fish. Effects of water-borne DP exposure on thyroid hormone and development of early life stage of zebrafish were also evaluated. In contrast to results of adult fish, DP did not show any toxic effect on embryos/larvae. Our observations suggest that DP may have thyroid and sex endocrine disrupting potential by alternating hormonal regulatory systems in fish.