Inhibition of growth in juvenile manila clam Ruditapes philippinarum: Potential adverse outcome pathway of TBBPA

Long-Term Tetrabromobisphenol A Exposure Induces Gut Microbiota Imbalance and Metabolic Disorders via the Peroxisome Proliferator-Activated Receptor Signaling Pathway in the Regenerated Gut of Apostichopus japonicus

Tetrabromobisphenol A (TBBPA), a commonly utilized brominated flame retardant, is found in many types of abiotic and biotic matrices. TBBPA can increase oxidative stress, disrupt the endocrine system, cause neurodevelopmental disorders and activate peroxisome proliferator-activated receptors to modulate lipid deposits in aquatic animals. However, the toxic mechanism of TBBPA on the gut microbiota and intestinal health remains unclear. Apostichopus japonicus is an ideal model for studying the relationship between environmental contaminants and intestinal health due to its unique capacity for evisceration and quickly regenerated intestine. In the present study, we investigated the toxic mechanism of TBBPA on the gut microbiota and intestinal health in the regenerated intestine of A. japonicus. The results show that TBBPA exposure decreased the health of the regenerated intestine and the enzymatic activities, alpha diversity indices, and the relative abundance of the gut microbiota. Transcriptome analysis shows that TBBPA exposure affected lipid metabolism via the PPAR signaling pathway during the process of intestinal regeneration in A. japonicus, suggesting that TBBPA exposure can affect the composition and function of the gut microbiota and intestinal health in the regenerated intestine of A. japonicus. These results provide a basis for further research on the potential toxicity of TBBPA to the intestinal health in animals.

Associations of bisphenol exposure with the risk of gestational diabetes mellitus: a nested case-control study in Guangxi, China

A growing number of epidemiologic studies have estimated the associations between endocrine-disrupting chemicals and gestational diabetes mellitus (GDM). However, reports on the association between bisphenol A (BPA) substitutes and GDM are limited. This investigation aimed to explore the associations of maternal serum BPA, bisphenol B (BPB), bisphenol F (BPF), bisphenol S (BPS), and tetrabromobisphenol A (TBBPA) with the risk of GDM. A nested case-control study was performed among 500 pregnant women. In conditional logistic regression models, the OR for BPS was significantly increased in the medium exposure groups (OR = 1.77; 95% CI: 1.01, 3.13) compared with the reference group, while BPA (OR: 0.38, 95%CI: 0.29, 0.50) and TBBPA (OR: 0.67, 95%CI: 0.54, 0.85) were negatively associated with the risk of GDM. In the Bayesian kernel machine regression (BKMR) analysis, the joint effect of bisphenols was positively associated with the risk of GDM. BPS showed positively relationship, while BPA and TBBPA showed negatively relationship, respectively. The quantile g-computation revealed a statistically significant and negative joint effect of the five bisphenols on the risk of GDM (OR: 0.57; 95% CI: 0.46, 0.72) with BPA (70.2%), TBBPA (21.3%), and BPB (8.5%) had positive contribution to the overall effect. These findings suggested that BPS had a positive effect on the risk of GDM, while BPA and TBBPA had negative effect on the risk of GDM. Moreover, exposure to the mixture of the five bisphenols was negatively associated with the risk of GDM.

Extruded polystyrene microplastics as a source of brominated flame retardant additives in the marine environment: long-term field and laboratory experiments

Microplastics (MPs) in the environment have become a global concern, not only for the physical effects of the plastic particles themselves but also for being vectors of chemical additives. In this context, little is known about the ability of MPs, particularly extruded polystyrene microplastics (XPS-MPs), to release organic chemical additives in the marine environment. In this study, a series of field and laboratory experiments were carried out to determine the leaching behaviour of organic additives including brominated flame retardants from XPS-MPs into seawater. The conducted experiments confirmed a rapid release of bisphenol A (BPA), 2,4,6-tribromophenol (TBP), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane diastereoisomers (α-, β-, and γ-HBCDD) from the studied MPs followed by a slower rate of release over time. The effects of environmental factors on the leaching rates of these additives were also examined. Increasing Dissolved Organic Matter (DOM) concentrations and the temperature of the seawater enhanced the release of additives by increasing their solubility and polymer flexibility. In contrast, pH tested at 7, 7.5 and 8 was found to have a minor effect on additives leaching; and salinity negatively affected the leaching rate likely due to their reduced solubility and reduced diffusion from the MPs. The present study provides empirical evidence of the behaviour of XPS-MPs as a source of organic additives in the marine environment that merit further investigation.

Time- and dose-dependent detoxification and reproductive endocrine disruption induced by tetrabromobisphenol A (TBBPA) in mussel Mytilus galloprovincialis

As a typical brominated flame retardant (BFR), tetrabromobisphenol A (TBBPA) has been frequently detected in both biotic and abiotic matrices in marine environment. Our previous study found that genes related to metabolism phase I/II/III as well as steroid metabolism in Mytilus galloprovincialis were significantly altered by TBBPA treatment. However, the time- and dose-dependent response profiles of these genes to TBBPA exposure were rarely reported. In this study, the time- and dose-dependent effects of TBBPA on detoxification and reproductive endocrine disruption in M. galloprovincialis were explored by evaluating the responses of related gene expressions, enzymatic activities and gametogenesis to different concentrations of TBBPA (0.6, 3, 15, 75 and 375 μg/L) for different durations (14, 21 and 28 days). The results showed that the TBBPA accumulation increased linearly with the increases of exposure time and dose. Cytochrome P450 family 3 (CYP3A1-like) cooperated with CYP4Y1 for phase I biotransformation of TBBPA in mussels. The dose-response curves of phase II/III genes (glutathione-S-transferase (GST), P-glycoprotein (ABCB), and multidrug resistance protein (ABCC)) showed similar response profiles to TBBPA exposure. The common induction of phase I/II/III (CYPs, GST, ABCB and ABCC) suggested TBBPA detoxification regulation in mussels probably occurred in a step-wise manner. Concurrently, direct sulfation mediated by sulfotransferases (SULTs) on TBBPA was also the vital metabolic mechanism for TBBPA detoxification, which was supported by the coincidence between up-regulation of SULT1B1 and TBBPA accumulation. The significant promotion of steroid sulfatase (STS) might result from TBBPA-sulfate catalyzed by SULT1B1 due to its chemical similarity to estrone-sulfate. Furthermore, the promotion of gametogenesis was consistent with the induction of STS, suggesting that STS might interrupt steroids hydrolysis process and was responsible for reproductive endocrine disruption in M. galloprovincialis. This study provides a better understanding of the detoxification and endocrine-disrupting mechanisms of TBBPA.

Microplastics boost the accumulation of tetrabromobisphenol A in a commercial clam and elevate corresponding food safety risks

Marine bivalve molluscs are one of the primary seafood for consumers. Inhabiting terrigenous pollutant-convergent coastal areas and feeding through seawater filtration, edible bivalves are subjected to waterborne emerging pollutants such as microplastics (MPs) and tetrabromobisphenol A (TBBPA). Nevertheless, the potential risks of consuming MP-TBBPA contaminated seafood are still largely unknown. With that, accumulation of TBBPA with and without the presence of MPs in a commercial bivalve species, blood clam (Tegillarca granosa), was determined in the present study. Meanwhile, corresponding target hazard quotients (THQs) as well as margins of exposure (MoEs) were estimated to evaluate the potential health risks for clam consumers. Furthermore, the impacts of pollutants accumulation on the detoxification process and energy supply were analysed. The data obtained demonstrated that MPs aggravate the accumulation of TBBPA in clams, leading to elevated potential food safety risks (indicated by higher THQ values and lower MoE values) for consumers. In addition, the in vivo contents of CYP1A1 and UDP-glucuronosyltransferase, the enzymatic activity of glutathione-S-transferase, and the expression levels of five detoxification-related genes were all dramatically suppressed by MP-TBBPA. Furthermore, clams exposed to MP-TBBPA had significantly lower adenosine triphosphate contents and lower pyruvate kinase and phosphofructokinase activities. These results indicated that the aggravation of TBBPA accumulation may be due to the hence disruption of detoxification process and limited energy available for detoxification.

Tetrabromobisphenol A acts a neurodevelopmental disruptor in early larval stages of Mytilus galloprovincialis

Tetrabromobisphenol A-TBBPA, a widely used brominated flame retardant detected in aquatic environments, is considered a potential endocrine disruptor-ED for its reproductive/developmental effects in vertebrates. In aquatic invertebrates, the modes of action of most EDs are largely unknown, due to partial knowledge of the mechanisms controlling neuroendocrine functions. In the marine bivalve Mytilus galloprovincialis, TBBPA has been previously shown to affect larval development in the 48 h larval toxicity assay at environmental concentrations. In this work, the effects of TBBPA were further investigated at different times post-fertilization. TBBPA, from 1 μg/L, affected shell biogenesis at 48 hours post fertilization-hpf, as shown by phenotypic and SEM analysis. The mechanisms of action of TBBPA were investigated at concentrations of the same order of magnitude as those found in highly polluted coastal areas (10 μg/L). At 28-32 hpf, TBBPA significantly affected deposition of both the organic matrix and CaCO₃ in the shell. TBBPA also altered expression of shell-related genes from 24 to 48 hpf, in particular of tyrosinase, a key enzyme in shell matrix remodeling. At earlier stages (24 hpf), TBBPA affected the development of dopaminergic, serotoninergic and GABAergic systems, as shown by in situ hybridization-ISH and immunocytochemistry. These data contribute draw adverse outcome pathways-AOPs, where TBBPA affects the synthesis of neutrotransmitters involved in key events (neurodevelopment and shell biogenesis), resulting in phenotypic changes on individuals (delayed or arrested development) that might lead to detrimental consequences on populations.

Carbon nanotubes mediating nano α-FeOOH reduction by Shewanella putrefaciens CN32 to enhance tetrabromobisphenol A removal

Carbon nanotubes (CNTs) mediation of the reduction of nano goethite (α-FeOOH) by Shewanella putrefaciens CN32 to improve the removal efficiency of tetrabromobisphenol A (TBBPA) was investigated in this study. The results showed that CNTs effectively promoted the biological reduction of α-FeOOH by strengthening the electron transfer process between Shewanella putrefaciens CN32 and α-FeOOH. After α-FeOOH was reduced to Fe(II), the adsorbed Fe(II) accounted for approximately 69.07% of the total Fe(II). And the secondary mineral vivianite was formed during the reduction of α-FeOOH, which was determined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The vivianite (Fe^II₃(PO₄)₂·8H₂O) was formed by the reaction of PO₄^3- and Fe(II). The degradation effect of TBBPA was the best at pH 8. CNT-α-FeOOH reduced the toxicity of TBBPA to CN32 and had good stability and reusability. The byproduct bisphenol A was detected which indicated that the degradation pathway of TBBPA involved reductive debromination. Electrochemical experiments and EPR analysis showed that the electron transfer capacities (ETC) of CNTs was an important factor in the removal of TBBPA, and it may greatly depend on semiquinone radicals (CO). This study provided a new method and theoretical support for the removal of TBBPA in the environment.

Tetrabromobisphenol A Perturbs Erythropoiesis and Impairs Blood Circulation in Zebrafish Embryos

Tetrabromobisphenol A (TBBPA), a ubiquitous environmental pollutant, has been implicated in developmental toxicity of aquatic animals. However, the impact of TBBPA on development and the related mechanism have not been fully elucidated. In this study, using a live imaging technique and transgenic labeling of zebrafish embryos, we described the toxic effects of TBBPA on hematopoietic development in zebrafish. We demonstrated that TBBPA induced erythroid precursor expansion in the intermediate cell mass (ICM), which perturbed the onset of blood circulation at 24-26 hours postfertilization (hpf). Consequently, excessive blood cells accumulated in the posterior blood island (PBI) and vascular cells formed defective caudal veins (CVs), preventing blood cell flow to the heart at 32-34 hpf. We found that the one-cell to 50% epiboly stage was the most sensitive period to TBBPA exposure during hematopoietic development. Furthermore, our results demonstrated that PBI malformation induced by TBBPA resulted from effects on erythroid precursor cells, which might involve THR signaling in complex ways. These findings will improve the understanding of TBBPA-induced developmental toxicity in teleost.

Tetrabromobisphenol A inhibits carboxylesterase activity of marine organisms from different trophic levels

Tetrabromobisphenol A (TBBPA), a brominated flame retardant used in synthetic polymers and electronics, is present in the aquatic environment and recent evidence suggests it can be potentially biomagnified in the marine ecosystem. However, the toxicity of TBBPA in the marine biota has not been investigated in detail. In this study we aimed to understand the role of carboxylesterases (CEs) in xenobiotic metabolism under the exposure of marine organisms to a chemical of environmental concern, TBBPA. Specifically, we tested for in vitro inhibition of CE activity in a range of marine organisms covering different ecological niches, from species from low (mussels and copepods), medium (sardines and anchovies) and high trophic levels (tuna). The results revealed that the highest inhibition of CE activity to 100 μM TBBPA was recorded in mussels (66.5% inhibition) and tunids (36.3-76.4%), whereas copepods and small pelagic fish showed comparatively lower effects (respectively, 30% and 36.5-55.6%). Our results suggest that CE-mediated detoxification and physiological processes could be compromised in TBBPA-exposed organisms and could ultimately affect humans as many of them are market species.