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

Comprehensive assessment of tris(2-ethylhexyl) trimellitate acute toxicity and ecological risks: Species-specific sensitivity and environmental monitoring

Tris(2-ethylhexyl) trimellitate (TOTM), a non-phthalate plasticizer, has gained popularity as a safer alternative to phthalates; however, its ecotoxicological impact and environmental behavior remain unclear. In this study, we investigated the species-specific sensitivity of Oryzias latipes (Japanese medaka) and Danio rerio (zebrafish) to TOTM exposure, and determined the residual concentrations in aquatic environments and ecological risk. Embryonic and larval toxicity tests revealed significant species differences: zebrafish showed higher sensitivity, with a lowest observed effect concentration (LOEC) of 43.7 μg/L, exhibiting increased mortality, swim bladder inflation failure, and growth inhibition. In contrast, the Japanese medaka showed no significant adverse effects under similar exposure conditions. TOTM residues were detected in a single sample (348.2 ng/L) after environmental monitoring of the Sumiyoshi River over 3 months, highlighting potential environmental persistence despite limited detection. Risk assessment using the ratio of the measured environmental concentration (MEC) to the predicted no effect concentration (PNEC) revealed a value > 13, indicating a significant ecological risk posed by the TOTM. These findings underscore the importance of evaluating species-specific responses, conducting comprehensive environmental monitoring, and addressing ecological risks associated with TOTM contamination in aquatic environments.

Non-Phthalate Plasticizer Bis(2-ethylhexyl) Sebacate Induces Testis-Ova Formation and Suppresses Reproduction in Japanese Medaka

Bis(2-ethylhexyl) sebacate (DEHS), a commonly used non-phthalate plasticizer considered relatively safe relative to phthalates, has been reported to disrupt the endocrine system, affect reproduction-related genes, and potentially induce thyroid hormone-disrupting and estrogenic effects on Japanese medaka (Oryzias latipes). However, the long-term effects of DEHS exposure on aquatic organisms remain unclear; further, data on residual DEHS concentrations in rivers are extremely limited. Here, the effects of DEHS on the reproductive performance and gonadal sex differentiation of Japanese medaka were determined. Japanese medaka embryos and larvae were exposed to varying DEHS concentrations that have been reported to induce thyroid hormone-disrupting effects. The residual concentrations of DEHS in the Sumiyoshi River were measured weekly from May to July in 2024. The formation of testis-ova was induced in XY medaka exposed to varying DEHS concentrations. DEHS exposure was shown to significantly reduce the number of eggs laid but did not affect fertilization rates. The DEHS levels in the Sumiyoshi River were either undetected or below the method quantification limit. Although significant changes in reproductive capacity and testis-ova were not observed at environmentally relevant residual concentrations, this study highlights the potentially harmful effects of a chemical that was previously considered environmentally friendly.

Effect of Acetyl tributyl citrate on bone metabolism based on network toxicology and molecular docking technology

This study aims to elucidate the intricate effects of Acetyl tributyl citrate (ATBC) on bone metabolism, disentangling the underlying molecular mechanisms that govern the impact of environmental contaminants on disease processes. Leveraging the exhaustive exploration of databases such as ChEMBL, STITCH, GeneCards, and OMIM, we have identified a comprehensive list of 164 potential targets intimately associated with both ATBC and bone metabolism. Following rigorous refinement using the STRING platform and Cytoscape software, we pinpointed ten core targets, encompassing KDM1A, EP300, HDAC2, EHMT2, DNMT1, and several others. In-depth Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, conducted within the Metascape database, revealed that the core targets of ATBC's influence on bone metabolism are predominantly concentrated within vital signaling cascades, including thyroid hormone signaling, FOXO signaling, glucagon signaling, AMPK signaling, insulin signaling, adipocytokine signaling, and Notch signaling pathways. Additionally, molecular docking simulations performed with AutoDock software confirmed the robust binding interactions between ATBC and these core targets, reinforcing our understanding of their interactions. To explore the cellular impact of ATBC, we performed in vitro experiments using osteoblasts (MC3T3-E1) exposed to relevant concentrations. Our findings revealed that low-dose ATBC (100 μM) significantly impaired cell proliferation and migration. Concurrently, we observed a downregulation in the transcriptional expression of key epigenetic regulators (KDM1A, EP300, HDAC2), suggesting that ATBC can disrupt bone metabolism at the cellular level. Collectively, our findings provide a theoretical scaffold for comprehending the intricate molecular mechanisms mediating ATBC's effects on bone metabolism, and paves the way for the development of preventive and therapeutic strategies against orthopedic disorders that may arise from exposure to plastic products containing ATBC or excessive ATBC environments.

Intergenerational metabolism-disrupting effects of maternal exposure to plasticizer acetyl tributyl citrate (ATBC)

Environmental chemicals and pollutants are increasingly recognized for their potential transgenerational effects. Acetyl tributyl citrate (ATBC), a widely used plasticizer substituting di-(2-ethylhexyl) phthalate (DEHP), was identified as an inducer of lipogenesis in male mice by our previous research. This study aimed to investigate the impact of ATBC exposure on the metabolic homeostasis of female mice and simultaneously evaluate its intergenerational effects. Female C57BL/6J mice were orally exposed to ATBC (0.01 or 1 μg/kg/day) for 10 weeks before mating with unexposed male mice. The resulting F1 female mice were bred with unexposed males to generate F2 offspring. Our results indicated that 10-week ATBC exposure disrupted glucose metabolism homeostasis and the reproductive system in F0 female mice. In F1 female mice, elevated liver lipid levels and mild insulin resistance were observed. In the F2 generation, maternal ATBC exposure resulted in increased weight gain, elevated liver triglycerides, and higher fasting blood glucose levels, primarily in F2 male mice. These findings suggest that maternal ATBC exposure may exert intergenerational disturbing effects on glucose metabolism across generations of mice. Further investigation is needed to evaluate the health risks associated with ATBC exposure.

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)

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MESH Headings

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

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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

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Global Environmental and Toxicological Data of Emerging Plasticizers: Current Knowledge, Regrettable Substitution Dilemma, Green Solution and Future Perspectives

The global plasticizer market is projected to increase from $17 billion in 2022 to $22.5 billion in 2027. Various emerging/alternative plasticizers entered the market following the ban on several phthalate plasticizers because of their harmful effects. However, there is limited data (especially peer-reviewed) on emerging plasticizers' toxicity and environmental impact. This review compiles available data on toxicity, exposure, environmental effects, and safe production of emerging plasticizers. It identifies gaps in scientific research and provides evidence that emerging plasticizers are potential cases of regrettable substitution. Several alternative plasticizers, such as acetyl tributyl citrate (ATBC), diisononyl cyclohexane-1,2 dicarboxylate (DINCH), tris-2-ethylhexyl phosphate (TEHP), tricresyl phosphate (TCP), tris-2-ethylhexyl phosphate (TPHP), bis-2-ethylhexyl terephthalate (DEHT), and tris-2-ethylhexyl trimellitate (TOTM), show potential as endocrine disrupting properties and other toxic characteristics. Some chemicals like bis-2-ethylhexyl adipate (DEHA), diisobutyl adipate (DIBA), ATBC, DINCH, bis-2-ethylhexyl sebacate (DOS), diethylene glycol dibenzoate (DEGDB), DEHT, and phosphate esters showed the potential to cause toxicity in aquatic species. Plus, there is great lack of information on compounds like diisononyl adipate (DINA), dibutyl adipate (DBA), diisodecyl adipate (DIDA), dipropylene glycol dibenzoate (DPGDB), dibutyl sebacate (DBS), alkylsulfonic phenyl ester (ASE), trimethyl pentanyl diisobutyrate (TXIB), DEGDB and bis-2-ethylhexyl sebacate (DOS). Some compounds like epoxidized soybean oil (ESBO), castor-oil-mono-hydrogenated acetate (COMGHA), and glycerin triacetate (GTA) are potentially safer or less toxic. Alternative plasticizers such as adipates (LogKow 4.3-10.1), cyclohexane dicarboxylic acids (LogKow 10), phosphate esters (LogKow 2.7-9.5), sebacates (LogKow 6.3-10.1), terephthalates (LogKow 8.4), and vegetable oil derivatives (LogKow 6.4-14.8) have logKow values that are comparable to phthalate plasticizers (LogKow 7.5-10.4), indicating potential bioaccumulation and health consequences. Field studies have demonstrated that phosphate esters can undergo bioaccumulation and biomagnification, but there is a lack of bioaccumulation studies for other compounds. We also discuss the metabolism of emerging plasticizers, though data is limited. Our article highlights that numerous alternative compounds display potential health and ecological risks, indicating they might not be suitable substitutes for legacy plasticizers. There is also a lack of scientific data on most emerging plasticizers. This way, we call for increased research and timely regulatory action to prevent global contamination and health risks. Finally, this study presents a scientifically robust protocol to avoid harmful substitutions and ensure the production of safer chemicals.

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.

Effects of two alternative plasticizers on the growth hormone-related endocrine system, neurodevelopment, and oxidative stress of zebrafish larvae

In response to the restriction of phthalate plasticizers, acetyl tributyl citrate (ATBC) and acetyl triethyl citrate (ATEC) have been used in medical devices and food packaging. In the present study, the effects of ATBC and ATEC on the development, behavior, growth hormone (GH)-related endocrine system, neurotransmitters, and oxidative stress of zebrafish embryo or larvae were investigated. After exposure of zebrafish to ATBC and ATEC (0, 0.03, 0.3, 3, 30, and 300 μg/L) for 96 h, developmental toxicity, behavioral changes under light/dark condition, changes in hormones and genes involved in GH/insulin-like growth factors (IGFs) axis, changes in hormone, enzyme, and genes related to neurodevelopment, antioxidant enzymes activities were determined. Larvae exposed to 30 or 300 μg/L ATBC showed significant reductions in body length and moving distance and speed, whereas no significant effects on development and locomotor behavior were observed in larvae exposed to ATEC. The contents of GH and IGF-I were significantly reduced in larvae exposed to 3, 30, and 300 μg/L ATBC. Hormonal changes in fish exposed to ATBC are well supported by regulation of genes related to GH (gh1) and the activity of IGF-I (igf1). In fish exposed to ATBC, reduced acetylcholinesterase activity and down-regulation of genes related to the central nervous system development (ache, gap43, mbpa, and syn21) were observed. ATBC increased the production of reactive oxygen species and the levels of superoxide dismutase, catalase, and glutathione peroxidase. Notably, pre-treatment with the classic antioxidant N-acetylcysteine alleviated ATBC-induced GH-related endocrine disruption and neurotoxicity. Our observations showed that exposure to low levels of ATBC could disturb the regulatory systems of GH/IGFs axis and neurobehavior, ultimately leading to developmental inhibition and hypoactivity, and that increased oxidative stress plays a major role in these toxicities.