Sciences marines : recherche et développement

Abstrait

Toxicity Effects of the Environmental Hormone 4-Tert-Octylphenol in Zebrafish (Danio Rerio)

Saputra F, Chia-Hung Yen, Chi-Ying Hsieh, Tsung-Yin Ou, Risjani Y, Wee-Keat Cheah and Shao-Yang Hu

4-tert-octylphenol (4-t-OP), an environmental exogenous estrogen is produced by microbial degradation of alkylphenol polyethoxylates (APEOs). Although it is well known that 4-t-OP can cause the feminization of male, sterility and deficiency of gonad development of aquatic animals by disrupting the endocrine reproductive signaling, less is known about the effects of 4-t-OP on embryonic development. Moreover, the presence of 4-t-OP were detected in umbilical cord blood samples of newborns suggesting infants during development may expose to the risk of 4-t-OP contaminant, hence to investigate the effect of 4-t-OP on physiological function during embryonic development is necessary. In the present study, zebrafish embryos exposed to 4-t-OP were used to evaluate the toxicity of 4-t-OP. The 50% lethal dose (LD50) for wild type zebrafish embryos exposure to 4-t-OP for 3 days is approximately 1.0 μM, and a high ratio of cardiovascular defects were showed in survival embryos. To observe the cardiovascular defects more efficiently, Tg (fil-1: EGFP) zebrafish embryos was used in 4-t-OP exposure treatment. Following exposure Tg (fil-1: EGFP) zebrafish embryos to 4-t-OP at 1.0 μM for 4 days, a highly proportion of defects revealed in cardiovascular system, including pericardical edema, irregular shape or incomplete looping of ventricle and atrium, the absence of intersegmental vessel in the tail of notochord, unformed parachordal vessel and kinks in the caudal vein. The phenotype of cardiovascular defects was accompanied by reduced heart rate and impaired blood circulation. The mRNA expression levels of transcription factors, which are critical for zebrafish heart chamber formation and blood vessel development, were analyzed by RT-PCR. The results showed that the presence of 4-t-OP significantly induce expression level of ERα and ERβ2, and caused cardiovascular defects by suppressing transcription factor Nkx2.7, Hand2, Tbx2a, Tbx2b, Tbx5a, FGF1a, GATA-4, -5 and -6 in zebrafish. The present study suggests that 4-t-OP affects the cardiovascular development in zebrafish and elucidated that early life exposure to 4-t-OP potentially may take a risk of impaired cardiovascular function.