Effects of plasticizer diisobutyl adipate on the Japanese medaka (Oryzias latipes) endocrine system

Occurrence and ecological risk assessment of 16 plasticizers in the rivers and estuaries in Japan

Owing to growing concerns about the adverse effects of phthalate plasticizers, non-phthalate plasticizers are being increasingly used as their replacement. However, information on the residual environmental concentrations and ecological risks posed by these plasticizers is limited. In this study, we analyzed the environmental contamination of 11 phthalates and 5 non-phthalate plasticizers in Class A and B rivers in Japan. In the considered river water samples, phthalates and non-phthalates were detected in the following order of detection frequency: phthalates (DEHP > DMP > DMEP > BBP > DNPP > DNP > DEEP > DBEP = DNOP) and non-phthalates (ATBC > DEHS > DEHA > TOTM = DIBA). Phthalate plasticizers were the most abundant and included DEHP (157-859 ng/L), DMP ( Collapse

Key Words

• Acetyl tributyl citrate (ATBC)
• Acute toxicity
• Chronic toxicity
• Non-phthalate plasticizers
• Phthalate plasticizer
• di-(2-Ethylhexyl) phthalate (DEHP)

Collapse

MESH Headings

• Plasticizers/analysis
• Japan
• Rivers/chemistry
• Risk Assessment
• Water Pollutants, Chemical/analysis
• Estuaries
• Environmental Monitoring
• Phthalic Acids/analysis

Collapse

Grants Collapse

Affiliation(s)

Dorcas Uaciquete Research Center for Inland Seas (KURCIS), Kobe University, Fukaeminami-machi, Higashinada-ku, Kobe, 658-0022, Japan.
Ayaka Sawada Faculty of Maritime Science, Kobe University, Fukaeminami-machi, Higashinada-ku, Kobe, 658-0022, Japan
Takashi Chiba College of Agriculture, Food and Environment Sciences, Department of Environmental and Symbiotic Science, Rakuno Gakuen University, Japan
Espino Maria Pythias Institute of Chemistry, University of the Philippines Diliman, Quezon City, 1101, Philippines
Taisen Iguchi Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan
Yoshifumi Horie Research Center for Inland Seas (KURCIS), Kobe University, Fukaeminami-machi, Higashinada-ku, Kobe, 658-0022, Japan

Collapse

Iopanoic acid alters thyroid hormone-related gene expression, thyroid hormone levels, swim bladder inflation, and swimming performance in Japanese medaka

Disruption of the thyroid hormone system by synthetic chemicals is gaining attention owing to its potential negative effects on organisms. In this study, the effects of the dio-inhibitor iopanoic acid (IOP) on the levels of thyroid hormone and related gene expression, swim bladder inflation, and swimming performance were investigated in Japanese medaka. Iopanoic acid exposure suppressed thyroid-stimulating hormone β (tshβ), tshβ-like, iodotyronin deiodinase 1 (dio1), and dio2 expression, and increased T4 and T3 levels. In addition, IOP exposure inhibited swim bladder inflation, reducing swimming performance. Although adverse outcome pathways of thyroid hormone disruption have been developed using zebrafish, no adverse outcome pathways have been developed using Japanese medaka. This study confirmed that IOP inhibits dio expression (a molecular initiating event), affects T3 and T4 levels (a key event), and reduces swim bladder inflation (a key event) and swimming performance (an adverse outcome) in Japanese medaka.

Effect of diisobutyl adipate on the expression of biomarker genes that respond to endocrine disruption and on gonadal sexual differentiation in Japanese medaka (Oryzias latipes)

Phthalate and non-phthalate plasticizers are used in polymer materials, such as plastic and rubber. It has recently been found that diisobutyl adipate (DIBA), which is considered an environmentally safe non-phthalate plasticizer, potentially acts as a thyroid disruptor in fish. Here, we investigated the sexual hormone effects of DIBA based on the expression levels of genes that respond to endocrine disruption and sexual hormone activity in the livers and gonads, and on gonadal sexual differentiation in Japanese medaka. Compared with the control group, the mRNA expression of chgH, vtg1, vtg2, and esr1 was significantly suppressed in the livers of DIBA exposed XX individuals. Furthermore, the mRNA expression of gsdf was significantly upregulated and downregulated in the gonads of XX and XY individuals, respectively. The mRNA expressions of esr1 and esr2b were significantly suppressed by DIBA exposure in the gonads of both XX and XY individuals. These observations suggest that DIBA has potential androgenic activity in Japanese medaka. However, normal testes and ovaries were observed in respective XY and XX medaka after DIBA exposure; therefore, these results suggest that DIBA may have weak androgenic activity.

Impact of acetyl tributyl citrate on gonadal sex differentiation and expression of biomarker genes for endocrine disruption in Japanese medaka

Plasticizers are broadly classified as phthalate or nonphthalate. Recently, acetyl tributyl citrate (ATBC), an environmentally friendly nonphthalate plasticizer, was revealed to have the ability to disrupt thyroid hormone activity in fish species. Therefore, we aimed to assess whether ATBC exhibits any sex hormone (i.e., androgenic or estrogenic) activities. First, we examined the effects of ATBC on gonadal sex differentiation. Subsequently, we analyzed the different expression of biomarker genes that respond to endocrine-disrupting chemicals (EDCs) with sexual hormone activity in the liver. We observed normal testes and ovaries after both XX and XY medakas were exposed to ATBC, indicating that ATBC is not an EDCs with strong sex hormone activity and that it does not induce intersex (testis-to-ova or ovo-to-testis) or sex changes in Japanese medaka. The vitellogenin 1 (vtg1) and vitellogenin 2 (vtg2) mRNA expression levels in the liver of XX medakas were significantly reduced compared with those in the control group, whereas the expression levels of these genes in the liver of XY medakas remained unchanged. Finally, we examined the changes in the expression of biomarker genes that respond to EDCs with sex hormone activity in the gonads. The expression levels of biomarker genes did not differ significantly from that of the control group, although the expression levels of gsdf mRNA tended to increase while that of aromatase mRNA tended to decrease in the ovary of XX medakas following ATBC exposure. Conversely, the expression levels of gsdf and aromatase mRNAs in the testis of XY medakas remained unchanged. These results suggest that ATBC does not exhibit estrogenic activity, although it may have weak androgenic activity or no sexual hormone activity.

Exploring the underlying molecular mechanism of tri(1,3-dichloropropyl) phosphate-induced neurodevelopmental toxicity via thyroid hormone disruption in zebrafish by multi-omics analysis

Tri(1,3-dichloropropyl) phosphate (TDCPP) is widespread in the environment as a typical thyroid hormone-disrupting chemical. Here, we aimed to explore the toxicological mechanisms of the thyroid hormone-disrupting effects induced by TDCPP in zebrafish embryos/larvae using multi-omics analysis. The results showed that TDCPP (400 and 600 µg/L) induced phenotypic alteration and thyroid hormone imbalance in zebrafish larvae. It resulted in behavioral abnormalities during zebrafish embryonic development, suggesting that this chemical might exhibit neurodevelopmental toxicity. Transcriptomic and proteomic analysis provided consistent evidence at the gene and protein levels that neurodevelopmental disorders were significantly enhanced by TDCPP exposure (p < 0.05). Additionally, multi-omics data indicated that membrane thyroid hormone receptor (mTR)-mediated non-genomic pathways, including cell communication (ECM-receptor interactions, focal adhesion, etc.) and signal transduction pathways (MAPK signaling pathway, calcium signaling pathway, neuroactive ligand-receptor interaction pathway, etc.), were significantly disturbed (p < 0.05) and might contribute to the neurodevelopmental toxicity induced by TDCPP. Therefore, behavioral abnormalities and neurodevelopmental disorders might be important phenotypic characteristics of TDCPP-induced thyroid hormone disruption, and mTR-mediated non-genomic networks might participate in the disruptive effects of this chemical. This study provides new insights into the toxicological mechanisms of TDCPP-induced thyroid hormone disruption and proposes a theoretical basis for risk management of this chemical.