Hepatotoxicity of decabromodiphenyl ethane (DBDPE) and decabromodiphenyl ether (BDE-209) in 28-day exposed Sprague-Dawley rats

Co-exposure of decabromodiphenyl ethane and polystyrene nanoplastics damages grass carp (Ctenopharyngodon idella) hepatocytes: Focus on the role of oxidative stress, ferroptosis, and inflammatory reaction

Decabromodiphenyl ethane (DBDPE) and polystyrene nanoplastics (PS-NPs) are emerging pollutants that seriously threaten the ecological safety of the aquatic environment. However, the hepatotoxicity effect of their combined exposure on aquatic organisms has not been reported to date. In, this study, the effects of single or co-exposure of DBDPE and PS-NPs on grass carp hepatocytes were explored and biomarkers related to oxidative stress, ferroptosis, and inflammatory cytokines were evaluated. The results show that both single and co-exposure to DBDPE and PS-NPs caused oxidative stress. Oxidative stress was induced by increasing the contents of pro-oxidation factors (ROS, MDA, and LPO), inhibiting the activity of antioxidant enzymes (CAT, GPX, T-SOD, GSH, and T-AOC), and downregulating the mRNA expressions of antioxidant genes (GPX1, GSTO1, SOD1, and CAT); the effects of combined exposure were stronger overall. Both single and co-exposure to DBDPE and PS-NPs also elevated Fe2+ content, promoted the expressions of TFR1, STEAP3, and NCOA4, and inhibited the expressions of FTH1, SLC7A11, GCLC, GSS, and GPX4; these effects resulted in iron overload-induced ferroptosis, where co-exposure had stronger adverse effects on ferroptosis-related biomarkers than single exposure. Moreover, single or co-exposure enhanced inflammatory cytokine levels, as evidenced by increased mRNA expressions of IL-6, IL-12, IL-17, IL-18, IL-1β, TNF-α, IFN-γ, and MPO. Co-exposure exhibited higher expression of pro-inflammatory cytokines compared to single exposure. Interestingly, the ferroptosis inhibitor ferrostatin-1 intervention diminished the above changes. In brief, the results suggest that DBDPE and PS-NPs trigger elevated levels of inflammatory cytokines in grass crap hepatocytes. This elevation is achieved via oxidative stress and iron overload-mediated ferroptosis, where cytotoxicity was stronger under co-exposure compared to single exposure. Overall, the findings contribute to elucidating the potential hepatotoxicity mechanisms in aquatic organisms caused by co-exposure to DBDPE and PS-NPs.

Species-specific and habitat-dependent bioaccumulation of halogenated flame retardants in marine organisms from estuary to coastal seas

Halogenated flame retardants (HFRs) have attracted global attention owing to their adverse effects on ecosystems and humans. The Shandong Peninsula is the largest manufacturing base for HFRs in East Asia, yet its impacts on marine ecosystems are unclear. Seventeen HFRs were analyzed in organisms captured from the Xiaoqing River estuary, Bohai Sea (BS), Yellow Sea and Northern East China Sea to investigate the distribution and bioaccumulation of HFRs on a broad scale. The results showed a downward trend in ΣHFR concentrations from the estuary (37.7 ng/g lw on average) to Laizhou Bay (192 ng/g lw) and to coastal seas (3.13 ng/g lw). The concentrations of ΣHFRs were significantly higher in demersal fish (0.71-198 ng/g lw) and benthic invertebrates (0.81-3340 ng/g lw) than in pelagic fish (0.30-27.6 ng/g lw), reflecting a habitat dependence. The concentrations of higher-brominated homologs were greater in benthic invertebrates, whereas a greater level of lower-brominated PBDE congeners was observed in fish, suggesting different profiles between species. Furthermore, the analogue composition of HFRs in fish was similar to that in the dissolved phase of seawater, whereas the HFR pattern in benthic invertebrates was consistent with the profile in sediment. The concentrations of HFRs in organisms vary widely depending on emissions from anthropogenic activities, whereas bioaccumulation patterns are strongly influenced by species and habitat.

Combined exposure to decabromodiphenyl ether and nano zero-valent iron aggravated oxidative stress and interfered with metabolism in earthworms

Decabromodiphenyl ether (BDE-209) is a common brominated flame retardant in electronic waste, and nano zero-valent iron (nZVI) is a new material in the field of environmental remediation. Little is known about how BDE-209 and nZVI combined exposure influences soil organisms. During the 28 days study, we determined the effects of single and combined exposures to BDE-209 and nZVI on the oxidative stress and metabolic response of earthworms (Eisenia fetida). On day 7, compared to CK, malondialdehyde (MDA) content increased in most combined exposure groups. To remove MDA and reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were induced in most combined exposure groups. On day 28, compared to CK, the activities of SOD and CAT were inhibited, while POD activity was significantly induced, indicating that POD plays an important role in scavenging ROS. Combined exposure to BDE-209 and nZVI significantly affected amino acid biosynthesis and metabolism, purine metabolism, and aminoacyl-tRNA biosynthesis pathways, interfered with energy metabolism, and aggravated oxidative stress in earthworms. These findings provide a basis for assessing the ecological impacts of using nZVI to remediate soils contaminated with BDE-209 from electronic waste.

The role of Sertoli cells-secreted factors in different stages of germ cells development in mice exposed to BDE-209

Decabromodiphenyl ether (BDE-209), a frequently used brominated flame retardant, readily enters the environment and is difficult to degrade with bioaccumulation. BDE-209 could cause male reproductive toxicity, but the regulatory functions of Sertoli cells-secreted factors remain uncertain. In present study, male mice were treated with 75 mg/kg BDE-209 and then stopped exposure for 50 days. Exogenous Glial cell line-derived neurotrophic factor (GDNF), a Sertoli cell-secreted factor, was injected into testes of mice treated with BDE-209 for 50 days to explore the role of GDNF in BDE-209-induced reproductive toxicity. The mouse spermatogonia cell line GC-1 spg was used in vitro to further verify regulatory effects of Sertoli cells-secreted factors on meiotic initiation. The results showed that BDE-209 inhibited expressions of the self-renewal pathway GFRα-1/RAS/ERK1/2 in spermatogonial stem cells (SSCs), and reduced expressions of spermatogonia proliferation-related pathway NRG3/ERBB4 and meiosis initiation factor Stra8. Furthermore, BDE-209 decreased the levels of both GDNF and retinoic acid (RA) secreted by Sertoli cells in testes. Importantly, the alterations of above indicators induced by BDE-209 did not recover after 50-day recovery period. After exogenous GDNF injection, the decreased expression of GFRα-1/RAS/ERK in SSCs was reversed. However, the level of RA and expressions of NRG3/ERBB4/Stra8 were not restored. The in vitro experimental results showed that exogenous RA reversed the reductions in NRG3/ERBB4/Stra8 and ameliorated inhibition of GC-1 spg cells proliferation induced by BDE-209. These results suggested that Sertoli cells-secreted factors play roles in regulating various stages of germ cell development. Specifically, BDE-209 affected the self-renewal of SSCs by decreasing GDNF secretion resulting in the inhibition of GFRα-1/RAS/ERK pathway; BDE-209 hindered the proliferation of spermatogonia and initiation of meiosis by inhibiting the secretion of RA and preventing RA from binding to RARα, resulting in the suppression of NRG3/ERBB4/Stra8 pathway. As a consequence, spermatogenesis was compromised, leading to persistent male reproductive toxicity.

Organohalogen contaminants threaten the survival of indo-pacific humpback dolphin calves in their largest habitat

As long-lived apex predators, marine mammal adults often accumulate alarmingly levels of environmental contaminants. Nevertheless, the accumulation and risks of these contaminants in the critical calf stage of marine mammals remain largely unknown. Here, we investigated the exposure status and health risks of 74 organohalogen contaminants (OHCs) in Indo-Pacific humpback dolphin calves (Sousa chinensis) collected from the Pearl River Estuary (PRE), China, during 2005-2019. Our findings revealed moderate levels of polychlorinated biphenyls (PCBs), medium-high levels of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs), and the highest levels of polybrominated diphenyl ethers (PBDEs) and alternative halogenated flame retardants (AHFRs) compared to those reported for cetaceans elsewhere. Traditional OHCs like DDTs, PCBs, and PBDEs did not exhibit significant decreasing trends in the dolphin calves despite global restrictions on these compounds, and AHFRs as emerging OHCs showed an increasing trend over the study period. Risk quotients of DDTs, HCHs, PBDEs, and PCBs in most of the dolphin samples were > 1, indicating that humpback dolphin calves may have suffered long-term threats from OHC exposure. The significant correlation observed between the traditional OHC levels and the stranding death number of the dolphin calves suggests these OHCs may impact the survival of this endangered species.

Associations between inhalation of typical volatile and semi-volatile organic compounds in e-waste dismantling workers with liver function damage

Studies in cell culture and animal models suggest hepatotoxicity of some volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs), however, their effects in human populations under real exposure conditions have never been clarified. In this cross-sectional study, 224 participants, 38 e-waste dismantling workers and 186 subjects residing near to the dismantling sites in southern China, were evaluated for personal inhalational exposure to 72 VOCs and 91 SVOCs according to site-specific atmospheric chemical concentrations and personal exposure time. Additionally, their serum samples were subjected to liver function tests (LFTs), including total protein (TP), albumin (ALB), globulin (GLB), aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transpeptidase (GGT), and bilirubin. Linear regression analysis of the VOC/SVOC levels against the LFTs results indicated that VOC exposure was negatively associated with the TP, ALB, GLB levels (indicating liver-specific protein synthesis functions), while positively associated with AST, ALT, GGT activities (marking liver damage). Somehow, SVOC exposure appeared to be positively associated with not only AST and ALT but also TP and ALB. These findings were supported by the quantile g-computation analysis and confirmed in the Bayesian kernel machine regression model. This study indicates that simultaneous inhalation of VOCs and SVOCs may impair human liver functions.

A Review of the Occurrence of Metals and Xenobiotics in European Hedgehogs (Erinaceus europaeus)

Monitoring data from several European countries indicate that European hedgehog (Erinaceus europaeus) populations are declining, and research exploring the causes of the decline, including exposure to potentially harmful xenobiotics and metals, may inform conservation initiatives to protect this species in the wild. Hedgehogs are ground-dwelling mammals, feeding on a range of insects, slugs, snails, and earthworms, as well as eggs, live vertebrates, and carrion, including carcasses of apex predator species representing higher levels of the food chain. Consequently, hedgehogs come into close contact with contaminants present in their habitats and prey. This review investigated the studies available on the subject of the occurrence of metals and organic xenobiotics in hedgehogs. This study found that a vast range of different pesticides; persistent organic pollutants (POPs), including organochlorine compounds and brominated flame retardants (BFRs); as well as toxic heavy metals could be detected. Some compounds occurred in lethal concentrations, and some were associated with a potential adverse effect on hedgehog health and survival. Due to their ecology, combined with the opportunity to apply non-invasive sampling techniques using spines as sampling material, we suggest that the European hedgehog is a relevant bioindicator species for monitoring the exposure of terrestrial wildlife to potential toxicants in urban and rural environments.

Update of the risk assessment of polybrominated diphenyl ethers (PBDEs) in food

The European Commission asked EFSA to update its 2011 risk assessment on polybrominated diphenyl ethers (PBDEs) in food, focusing on 10 congeners: BDE-28, -47, -49, -99, -100, -138, -153, -154, -183 and ‑209. The CONTAM Panel concluded that the neurodevelopmental effects on behaviour and reproductive/developmental effects are the critical effects in rodent studies. For four congeners (BDE-47, -99, -153, -209) the Panel derived Reference Points, i.e. benchmark doses and corresponding lower 95% confidence limits (BMDLs), for endpoint-specific benchmark responses. Since repeated exposure to PBDEs results in accumulation of these chemicals in the body, the Panel estimated the body burden at the BMDL in rodents, and the chronic intake that would lead to the same body burden in humans. For the remaining six congeners no studies were available to identify Reference Points. The Panel concluded that there is scientific basis for inclusion of all 10 congeners in a common assessment group and performed a combined risk assessment. The Panel concluded that the combined margin of exposure (MOET) approach was the most appropriate risk metric and applied a tiered approach to the risk characterisation. Over 84,000 analytical results for the 10 congeners in food were used to estimate the exposure across dietary surveys and age groups of the European population. The most important contributors to the chronic dietary Lower Bound exposure to PBDEs were meat and meat products and fish and seafood. Taking into account the uncertainties affecting the assessment, the Panel concluded that it is likely that current dietary exposure to PBDEs in the European population raises a health concern.

A critical review on BDE-209: Source, distribution, influencing factors, toxicity, and degradation

As the most widely used polybrominated diphenyl ether, BDE-209 is commonly used in polymer-based commercial and household products. Due to its unique physicochemical properties, BDE-209 is ubiquitous in a variety of environmental compartments and can be exposed to organisms in various ways and cause toxic effects. The present review outlines the current state of knowledge on the occurrence of BDE-209 in the environment, influencing factors, toxicity, and degradation. BDE-209 has been detected in various environmental matrices including air, soil, water, and sediment. Additionally, environmental factors such as organic matter, total suspended particulate, hydrodynamic, wind, and temperature affecting BDE-209 are specifically discussed. Toxicity studies suggest BDE-209 may cause systemic toxic effects on living organisms, reproductive toxicity, embryo-fetal toxicity, genetic toxicity, endocrine toxicity, neurotoxicity, immunotoxicity, and developmental toxicity, or even be carcinogenic. BDE-209 has toxic effects on organisms mainly through epigenetic regulation and induction of oxidative stress. Evidence regarding the degradation of BDE-209, including biodegradation, photodegradation, Fenton degradation, zero-valent iron degradation, chemical oxidative degradation, and microwave radiation degradation is summarized. This review may contribute to assessing the environmental risks of BDE-209 to help develop rational management plans.

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

Environmental pollution is changing with economic development. Most environmental pollutants are characterized by stable chemical properties, strong migration, potential toxicity, and multiple exposure routes. Harmful substances are discharged excessively, and large quantities of unknown new compounds are emerging, being transmitted and amplifying in the food chain. The increasingly severe problems of environmental pollution have forced people to re-examine the relationship between environmental pollution and health. Pyroptosis and activation of the NLRP3 inflammasome are critical in maintaining the immune balance and regulating the inflammatory process. Numerous diseases caused by environmental pollutants are closely related to NLRP3 inflammasome activation and pyroptosis. We intend to systematically explain the steps and important events that are common in life but easily overlooked by which environmental pollutants activate the NLRP3 inflammasome and pyroptosis pathways. This comprehensive review also discusses the interaction network between environmental pollutants, the NLRP3 inflammasome, pyroptosis, and diseases. Thus, research progress on the impact of decreasing oxidative stress levels to inhibit the NLRP3 inflammasome and pyroptosis, thereby repairing homeostasis and reshaping health, is systematically examined. This review aims to deepen the understanding of the impact of environmental pollutants on life and health and provide a theoretical basis and potential programs for the development of corresponding treatment strategies.

Persistent immune injury induced by short-term decabromodiphenyl ether (BDE-209) exposure to female middle-aged Balb/c mice

Decabromodiphenyl ether (BDE-209), widely used in various industries for its excellent flame-retardant performance, could be enriched in humans and is closely associated with immune impairment. In addition, immune system is gradually declined and becoming more sensitive to environmental pollutants in the ageing process. Therefore, the immunotoxicity of BDE-209 (4, 40, and 400 mg/kg/day) to middle-aged mice and its recovery and susceptibility was first to be comprehensively investigated in this study. The results showed that BDE-209 exposure could lead to oxidative injury to immune organs (spleen, thymus, and liver), impair humoral (immunoglobulins), cellular (lymphopoiesis), and non-specific immunity, and disturb the expressions of the genes related to Th1/Th2 balance (T helper cells) in the middle-aged mice. In addition, Integrated Biomarker Response (IBR) indicated that BDE-209-induced immune impairment was challenging to self-regulated, and even exacerbated after 21 days of recovery and oxidative injury in immune organs could be the main reason. Furthermore, factorial analysis showed that middle-aged mice exposed to BDE-209 suffered from greater immune impairment than adult mice, and the immune impairment in aged mice is more difficult to be self-repaired than that in adult mice. It can be seen that the aged tend to suffer from BDE-209-induced persistent immune impairment and health threats.

A meta-analysis of randomized controlled studies on the hepatoxicity induced by polybrominated diphenyl ethers (PBDEs) in rats and mice

Several toxicological studies were conducted to evaluate the hepatoxicity of PBDEs using different animal models, congeners, duration of exposure, and other parameters. These variations in different animal models and conditions might have an impact on extrapolating experimental results to humans. Hence, by the meta-analysis, we aimed to clarify and elucidate the species differences in hepatoxicity induced by PBDE exposure in rats and mice across different conditions and moderators. Fourteen in vivo studies that utilized rats and mice models were identified, and data such as author names, year of publication, type of PBDE congeners, rodent species, life stage of exposure, dosage, duration, and hepatoxicity indicators were extracted. The pooled standard mean difference (SMD) with a 95% confidence interval (95% CI) was used to evaluate the association between hepatoxicity and PBDE exposure across multiple approaches of measurement. Subgroup analysis, meta-regression, and interaction analysis were utilized to elucidate the species-related differences among the results of the involved studies. The pooled SMD of hepatoxicity of PBDE exposure in the involved in vivo studies was 1.82 (p = 0.016), indicating exposure to PBDE congeners and mixtures is associated with a significant increase in liver toxicity in rodents. Moreover, findings showed that rats were more sensitive to PBDEs than mice with the BDE-209 had the highest SMD value. Among the life stages of exposure, embryonic stage was found to be the most sensitive to hepatoxicity induced by PBDE congeners. Positive relationships were found between the incidence of hepatoxicity with dosage and duration of exposure to PBDE. Interaction analyses showed significant interactions between rodent species (rats or mice), dosage, length of exposure, and hepatotoxicity endpoints. Rats demonstrated an increased susceptibility to variations in organ weight, histopathological changes, mitochondrial dysfunction, and oxidative stress markers. Conversely, mice showed pronounced lipid accumulation and modifications in liver enzyme expression levels. However, significant differences were not found in terms of endoplasmic reticular stress as a mechanistic endpoint for hepatotoxicity. In conclusion, this meta-analysis showed that there might be some species-related differences in hepatoxicity induced by PBDE exposure in rats and mice depending on the parameters used. This study highlights the importance of cross-species extrapolation of results from animal models to accurately assess the potential risks to human health from exposure to PBDEs.

Hepatotoxicity evaluation and possible mechanisms of decabrominated diphenyl ethers (BDE-209) in broilers: Oxidative stress, inflammatory, and transcriptomics

Decabrominated diphenyl ether (BDE-209), a persistent organic pollutant, is linked to a great number of health problems, the most severe of which impact the liver due to its role in the elimination and degradation of exogenous harmful substances. Though the hepatotoxicity of BDE-209 has been observed, its underlying mechanism is yet unknown. The purpose of this study is to thoroughly investigate the hepatotoxicity of BDE-209 and its molecular processes in broilers by subjecting 120 male broilers to varied concentrations of BDE-209 for 42 days. We observed that the bioaccumulation of BDE-209 in the liver in a dose-dependent manner, and that BDE-209 exposure can raise the concentrations of ALT, AST, and GGT, accompanied by hepatocyte fatty degeneration and inflammatory foci. In the hepatic homogenates, oxidative stress was evidenced by elevated levels of MDA and ROS and decreased activies of SOD and CAT. Additionally, pro-inflammatory cytokines including IL-1, IL-1β, TNF-α, IL-8 levels were increased, whereas anti-inflammatory cytokine IL-4 level was declined. Furthermore, RNA sequencing revealed that genes involved in inflammation were considerably dysregulated, and real-time PCR verified the expressed alterations of numerous genes related to the MAPK and WNT signaling pathways. The protein concentrations of NF-κB, β-catenin, and WNT5A, and the phosphorylation levels of JNK and ERK were all dramatically enhanced. The current study indicates that BDE-209 exposure can cause hepatotoxicity in broilers via bioaccumulation and oxidative stress, which then activates the MAPK and WNT signaling pathways, subsequently generating inflammation and hepatic injury.

Toxic Effects and Mechanisms of Polybrominated Diphenyl Ethers

Polybrominated diphenyl ethers (PBDEs) are a group of flame retardants used in plastics, textiles, polyurethane foam, and other materials. They contain two halogenated aromatic rings bonded by an ester bond and are classified according to the number and position of bromine atoms. Due to their widespread use, PBDEs have been detected in soil, air, water, dust, and animal tissues. Besides, PBDEs have been found in various tissues, including liver, kidney, adipose, brain, breast milk and plasma. The continued accumulation of PBDEs has raised concerns about their potential toxicity, including hepatotoxicity, kidney toxicity, gut toxicity, thyroid toxicity, embryotoxicity, reproductive toxicity, neurotoxicity, and immunotoxicity. Previous studies have suggested that there may be various mechanisms contributing to PBDEs toxicity. The present study aimed to outline PBDEs' toxic effects and mechanisms on different organ systems. Given PBDEs' bioaccumulation and adverse impacts on human health and other living organisms, we summarize PBDEs' effects and potential toxicity mechanisms and tend to broaden the horizons to facilitate the design of new prevention strategies for PBDEs-induced toxicity.

SeNPs alleviates BDE-209-induced intestinal damage by affecting necroptosis, inflammation, intestinal barrier and intestinal flora in layer chickens

As environmental pollutants, polybrominated diphenyl ethers (PBDEs) can have toxic effects on living organisms and has a bioaccumulative effect. Low doses of selenium nanoparticles (SeNPs) can exert antioxidant, anti-inflammatory and anti-toxin functions on the organism. This experiment evaluated SeNPs' ability to prevent chicken's intestinal damage from decabromodiphenyl ether (BDE-209) exposure. Sixty layer chickens were separated into four groups at randomly and equally: Control group, SeNPs group (1 mg/kg SeNPs), BDE-209 group (400 mg/kg BDE-209), and BDE-209 +SeNPs group (400 mg/kg BDE-209 and 1 mg/kg SeNPs), for 42 days. The results showed that BDE-209 increased MDA content, decreased the activities of T-SOD, T-AOC, GSH and iNOS, up-regulated the expression of TNF-α, RIPK1, RIPK3 and MLKL, promoted the production of inflammatory factors, reduced the levels of tight junction proteins (Claudin-1, Occludin, ZO-1). SeNPs attenuated intestinal oxidative stress, necroptosis, inflammation and intestinal barrier damage caused by BDE-209. This protective effect is associated with the MAPK/NF-κB signaling pathway. Moreover, SeNPs restores flora alpha and beta diversity, improves intestinal flora composition and its abundance. It shifts the dysbiosis of intestinal flora caused by BDE-209 to normal. Overall, SeNPs can alleviate BDE-209-induced intestinal barrier damage and intestinal flora disorders, which are associated with intestinal oxidative stress, necroptosis and inflammation.

Investigating the adverse outcome pathways (AOP) of neurotoxicity induced by DBDPE with a combination of in vitro and in silico approaches

Current studies have shown an association between DBDPE and neurotoxicity. In this study, the adverse outcome pathway (AOP) and mechanistic analysis of DBDPE-induced neurotoxicity were explored by a combination of in vitro and in silico approaches in SK-N-SH cells. DBDPE-induced oxidative stress caused DNA strand breaks, resulting in the activation of poly (ADP-ribose) (PAR) polymerase-1 (PARP-1). Activation of PARP1 could cause toxic damage in various organ systems, especially in the nervous system. DBDPE-induced apoptosis via the caspase-dependent intrinsic mitochondrial pathway and the PARP1-dependent pathway. Activation of PARP1 by DBDPE was deemed the initiating event, thereby affecting the key downstream biochemical events (e.g., ROS production, DNA damage, membrane potential changes, and ATP reduction), which induced apoptosis. Furthermore, excessive activation of PARP1 was accompanied by the translocation of the apoptosis-inducing factor (AIF), which was associated with PARP1-dependent cell death. The inhibition of PARP1 by PJ34 reduced DBDPE-induced apoptosis and maintained cellular ATP levels. PJ34 also prevented the translocation of AIF from the mitochondria to the nucleus. These findings improve the understanding of the mechanism of DBDPE-induced neurotoxic effects and provide a theoretical basis for the ecological risk of DBDPE.

Ferroptosis mediates decabromodiphenyl ether-induced liver damage and inflammation

Decabromodiphenyl ether (BDE-209) is an environmental toxin. Increasing evidence showed that BDE-209 exposure induced liver injury, but the mechanism still remains unknown. The present study explored the effect and mechanism of ferroptosis on hepatotoxicity triggered by BDE-209 in vivo and in vitro. In vivo experiment, ICR mice were exposed to BDE-209 for 50 days, and then recovered for 50 days; HepG2 and L02 cells were treated with BDE-209 or/and ferrostatin-1 (Fer-1) for establishing in vitro model. In vivo, the results showed that BDE-209 accumulated in liver and induced liver damage, increased Fe²⁺ and MDA contents, and blocked the activation of SLC7A11/GSH/GPX4 pathway in liver; BDE-209 also activated IKK/IκB/NF-κB pathway and elevated inflammatory cytokines levels in liver after exposure for 50 days. After BDE-209 stopping exposure 50 days, the severity of liver damage, ferroptosis and inflammatory response were still higher than the corresponding control group. In vitro, ferroptosis inhibitor Fer-1 rescued ferroptotic damage and attenuated cell death in BDE-209-treated HepG2 and L02 cells. In addition, Fer-1 reversed the activation of IKK/IκB/NF-κB pathway and the increase of pro-inflammatory cytokines levels in BDE-209-treated HepG2 and L02 cells. Together, the above results suggested that BDE-209 induced tissue damage and inflammatory response by activating ferroptosis through increasing iron-dependent lipid peroxidation and blocking the activation of SLC7A11/GSH/GPX4 pathway in liver, indicating that ferroptosis is a potential mechanism for BDE-209-induced hepatotoxicity.

Reprotoxic Effect of Tris(2,3-Dibromopropyl) Isocyanurate (TBC) on Spermatogenic Cells In Vitro

Tris(2,3-dibromopropyl) isocyanurate (TBC) belongs to the class of novel brominated flame retardants (NFBRs) that are widely used in industry. It has commonly been found in the environment, and its presence has been discovered in living organisms as well. TBC is also described as an endocrine disruptor that is able to affect male reproductive processes through the estrogen receptors (ERs) engaged in the male reproductive processes. With the worsening problem of male infertility in humans, a mechanism is being sought to explain such reproductive difficulties. However, so far, little is known about the mechanism of action of TBC in male reproductive models in vitro. Therefore, the aim of the study was to evaluate the effect of TBC alone and in cotreatment with BHPI (estrogen receptor antagonist), 17β-estradiol (E₂), and letrozole on the basic metabolic parameters in mouse spermatogenic cells (GC-1 spg) in vitro, as well as the effect of TBC on mRNA expression (Ki67, p53, Pparγ, Ahr, and Esr1). The presented results show the cytotoxic and apoptotic effects of high micromolar concentrations of TBC on mouse spermatogenic cells. Moreover, an increase in Pparγ mRNA levels and a decrease in Ahr and Esr1 gene expression were observed in GS-1spg cells cotreated with E₂. These results suggest the significant involvement of TBC in the dysregulation of the steroid-based pathway in the male reproductive cell models in vitro and may be the cause of the currently observed deterioration of male fertility. However, more research is needed to reveal the full mechanism of TBC engagement in this phenomenon.

Is it really safe to replace decabromodiphenyl ether (BDE209) with decabromodiphenyl ethane (DBDPE)?: A perspective from hepatotoxicity

In this paper, the hepatocytotoxicity and aryl hydrocarbon receptor (AHR) activity of decabromodiphenyl ethane (DBDPE), decabromodiphenyl ether (BDE209) and other 18 analogues were evaluated in vitro using human normal liver cell L02. These dioxin-like compounds showed differential hepatocytotoxicity (EC₅₀  = 0.38-17.87 mg/L) and AHR activity (EROD activity = 4.53-46.35 U/μg). In silico study indicated the distance of π-π bonds between the benzene ring of compounds and residue Phe234 of AHR played a key role in the binding of AHR, and the substituents on the benzene ring also influenced the activity. Combining molecular biology and bioomics, the comprehensive investigations on the hepatotoxic mechanisms have demonstrated the AHR signaling pathway was the key mediation mechanism for the hepatotoxicity of DBDPE/BDE209. The cytochrome P450s (CYP2 family) mediated formation of reactive oxygenated intermediates might be the dominant toxic mechanism, which could produce oxidative stress or cause genotoxicity. Although the experimental toxicity of DBDPE was smaller relative to BDE209, the health risk of DBDPE may be much greater than we expected, due to the high potential to form a variety of dioxin-like intermediates by microbial oxidation of ethyl group. Therefore, whether it is really safe to replace BDE209 with DBDPE is a debatable question, and more ecotoxicological and health data are needed to clarify this issue.

Histopathological and transcriptomic analyses reveal the reproductive endocrine-disrupting effects of decabromodiphenyl ethane (DBDPE) in mussel Mytilus galloprovincialis

The novel brominated flame retardant DBDPE has become a widespread environmental contaminant and could affect reproductive endocrine system in vertebrates. However, information about reproductive endocrine-disrupting effects of DBDPE on invertebrates is totally unknown. In this study, mussels Mytilus galloprovincialis were exposed to 1, 10, 50, 200 and 500 μg/L DBDPE for 30 days. Histopathological and transcriptomic analyses were performed to assess the reproductive endocrine-disrupting effects of DBDPE in mussels and the potential mechanisms. DBDPE promoted the gametogenesis in mussels of both sexes according to histological observation, gender-specific gene expression (VERL and VCL) and histological morphometric parameter analysis. Transcriptomic analysis demonstrated that DBDPE suppressed the genes related to cholesterol homeostasis and transport in both sexes via different LRPs- and ABCs-mediated pathways. DBDPE also disturbed nongenomic signaling pathway including signaling cascades (GPR157-IP3-Ca²⁺) in males and secondary messengers (cGMP) in females, and subsequently altered the expression levels of reproductive genes (VMO1, ZAN, Banf1 and Hook1). Additionally, dysregulation of energy metabolism in male mussels induced by DBDPE might interfere with the reproductive endocrine system. Overall, this is the first report that DBDPE evoked reproductive endocrine-disruptions in marine mussels. These findings will provide important references for ecological risk assessment of DBDPE pollution in marine environment.

A new consensus on reconciling fire safety with environmental & health impacts of chemical flame retardants

Flame retardants are chemical substances that are intended to mitigate fire safety risks posed by a range of goods including furniture, electronics, and building insulation. There are growing concerns about their effectiveness in ensuring fire safety and the potential harms they pose to human health and the environment. In response to these concerns, on 13 June 2022, a roundtable of experts was convened by the UKRI Six Clean Air Strategic Priorities Fund programme 7. The meeting produced a Consensus Statement that summarises the issues around the use of flame retardants, laying out a series of policy recommendations that should lead to more effective fire safety measures and reduce the human and environmental health risks posed by these potentially toxic chemicals.

Occurrence and tissue-specific partitioning of alternative brominated flame retardants in northwest Atlantic harbor seal pups (Phoca vitulina vitulina)

Brominated flame retardants such as polybrominated diphenyl ethers (PBDEs) have been used for decades until evidence of negative health effects led to bans in many countries. PBDEs have since been replaced by alternative legacy compounds or newly developed chemicals. In this study, eight alternative brominated flame retardants were analyzed in blubber and liver of harbor seal pups (≤6 months) from the Northwest Atlantic collected during 2001-2010 to elucidate concentrations, patterns, contamination trends, potential maternal transfer, and tissue partitioning. All compounds were detected in liver and blubber tissues with hexabromocyclododecane (HBCD) isomers and 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) predominating. Overall, α-HBCD was the dominant HBCD isomer in both tissues although the concentrations of γ-HBCD exceeded those of α-HBCD in seven pups, indicating their mothers may have had alternative dietary patterns or recent exposure to the commercial mixture. Although it was detected in less than half of the samples, to our knowledge, this is the first study to report tetrabromobisphenol A (TBBPA) concentrations in multiple tissues of a top marine predator. For the brominated components of Firemaster® flame retardants, TBB concentrations exceeded bis-(2-ethylhexyl)-tetrabromophthalate (TBPH). This pattern may result from recent exposure to commercial mixtures in which TBB exceeds TBPH 4:1 or from differences in perinatal or lactational transfer efficiency of the two compounds. Between the two tissues, lipid-normalized β-HBCD, γ-HBCD, TBB and decabromodiphenyl ethane (DBDPE) concentrations were significantly higher in liver than blubber. This indicates that the bioaccumulation of these chemicals is not simply related to lipid dynamics but may be linked to blood proteins. This study demonstrates that harbor seal pups from this region are contaminated with alternative flame retardants passed to them via placental or lactational transfer. Given the evidence for negative health effects of these chemicals, this contamination adds additional pressure on the first year survival of these young, developing animals.

Legacy and novel brominated flame retardants in animal-derived foods from China Total Diet Study (CTDS): Temporal trends, evidence of substitution, and dietary exposure assessment

Based on the 6th China Total Diet Study (CTDS) conducted in 2016-2019, the occurrence of both legacy and novel brominated flame retardants (BFRs) was measured in animal-derived foods collected across China. Most BFRs could be frequently detected in food samples, indicating their ubiquity in the environment. Decabromodiphenyl ethane (DBDPE), a typical novel BFR, presented the highest contamination level, whereas legacy BFRs, including decabrominated diphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCDD), still presented high detection frequencies and relatively abundant proportions in total BFRs. Compared with previous CTDSs conducted from 2007 to 2011, the levels and estimated dietary intakes (EDIs) of most BFRs showed a significant downtrend, which suggested that flame retardant consumption in China has transferred from legacy BFRs to novel BFRs (mainly DBDPE) and from BFRs to other kinds of flame retardants. Based on probabilistic estimation, the median EDIs of mainly used BFRs for the Chinese population ranged from 41.0 to 1.67 × 10³ pg/kg bw/day, and meat consumption was the primary source in dietary BFR intake. By conducting the margin of exposure (MOE) approach or comparing with the reference dose (RfD), it can be concluded that daily dietary intakes of BFRs were still unable to cause significant health risks to the general population in China.

DBDPE upregulates NOD-like receptor signaling to induce NLRP3 inflammasome-mediated HAECs pyroptosis

Decabromodiphenyl ethane (DBDPE), a typical new brominated flame retardant (BFR), is a widespread new pollutant in the environment. Several studies and our previous studies have found that DBDPE can cause aortic endothelial injury and aortic endothelial cell pyroptosis, whereas the molecular mechanism involved has not been elucidated. In this study, we exposed human aortic endothelial cells (HAECs) to 25 μmol/L of DBDPE and analyzed the gene expression profiles by Affymetrix PrimeView™ Human Gene Expression Chip. The results showed that 886 genes were differentially expressed in the DBDPE exposure group. Enrichment analyses revealed that differentially expressed genes were mainly enriched in the inflammatory response and NOD-like receptor signal pathway. Gene-gene functional interaction analyses and crossover genes and pathways analyses found that the NOD-like receptor signal pathway may be involved in regulating NLRP3 and IL-18. We found that NOD2 cannot interact with NLRP3 directly through an immunoprecipitation experiment. Thus, we construct the RIPK2 knockdown HAECs cell line to repress the NOD-like receptor signaling and further study the mechanism of DBDPE-activated NLRP3 inflammasome to induce HAECs pyroptosis. The results showed that RIPK2 knockdown could repress DBDPE-induced NOD-like receptor signaling pathway upregulation, inhibit NLRP3 inflammasome activation, and decrease HAECs pyroptosis. In addition, RIPK2 knockdown decreased the ROS generation in HAECs induced by DBDPE. And NAC pretreated HAECs inhibited DBDPE-induced NLRP3 inflammasome activation and HAECs pyroptosis. These results demonstrated that DBDPE upregulated NOD-like receptor signaling to induce ROS generation and, in turn, activated NLRP3 inflammasome, leading to HAECs pyroptosis.

Associated long-term effects of decabromodiphenyl ethane on the gut microbial profiles and metabolic homeostasis in Sprague-Dawley rat offspring

Decabromodiphenyl ethane (DBDPE) as a widely used brominated flame retardant is harmful to human health due to its toxicity, including cardiovascular toxicity, reproductive toxicity, and hepatotoxicity. However, the knowledge of the long-term effects and structural and metabolic function influence on gut microbiota from DBDPE exposure remains limited. This study was mainly aimed at the gut microbiome and fecal metabolome of female rats and their offspring exposed to DBDPE in early life. 16S rRNA gene sequencing demonstrated that maternal DBDPE exposure could increase the α-diversity of gut microbiota in immature offspring while decreasing the abundance of Bifidobacterium, Clostridium, Muribaculum, Escherichia, and Lactobacillus in adult offspring. The nonmetric multidimensional scaling showed a consistency in the alternation of β-diversity between pregnant rats and their adult offspring. Furthermore, the short-chain fatty acids produced by gut microbiota dramatically increased in adult offspring after maternal DBDPE exposure, revealing that DBDPE treatment disrupted the gut microbial compositions and altered the gut community's metabolic functions. Untargeted metabolomics identified 41 differential metabolites and seven metabolic pathways between adult offspring from various groups. Targeted metabolomic showed that maternal high dose DBDPE exposure obviously decreased the level of glutathione, taurine, and l-carnitine in their adult offspring, which verified the correlation between weight loss and amino acid metabolites. An interesting link between some gut bacteria (especially the Firmicutes) and fecal metabolites demonstrated the shifts in gut microbiota may drive the metabolic process of fecal metabolites. The current findings provide new insight into long-term effects on human health.

Hepatocellular Metabolic Abnormalities Induced by Long-Term Exposure to Novel Brominated Flame Retardant, Hexabromobenzene

Novel brominated flame retardants (NBFRs) are widely used to avoid environmental accumulation concerns and because of the regulations imposed on classical BFRs. However, recent studies have not revealed the negative effects of NBFR accumulation and exposure on humans. We conducted a metabolomics study on hexabromobenzene (HBB), one of the NBFRs, to investigate its effect on hepatocytes. Gas chromatography-mass spectrometry-based metabolite profiling was performed to observe metabolic perturbations by treating human livertissue-derived HepG2 cell lines with HBB for maximum 21 days. Metabolic pathway enrichment using 17 metabolite biomarkers determined via univariate and multivariate statistical analysis verified that long-term accumulation of HBB resulted in distinct diminution of eight amino acids and five other metabolites. Molecular docking of the biomarker-related enzymes revealed the potential molecular mechanism of hepatocellular response to HBB exposure, which disrupts the energy metabolism of hepatic cells. Collectively, this study may provide insights into the hidden toxicity of bioaccumulating HBB and unveil the risks associated with non-regulated NBFRs.

DBDPE and ZnO NPs synergistically induce neurotoxicity of SK-N-SH cells and activate mitochondrial apoptosis signaling pathway and Nrf2-mediated antioxidant pathway

Decabromodiphenyl ethane (DBDPE), a new brominated flame retardant, could negatively affect neurobehavior and pose health risks to humans. Humans are also exposed to widely used nanomaterials. This study investigated the combined toxic effects and action types of DBDPE and Zinc oxide nanoparticles (ZnO NPs) on human neuroblastoma SK-N-SH cells and the toxicity mechanisms. DBDPE inhibited the viability of SK-N-SH cells by 21.87% at 25 mg/L. ZnO NPs synergistically exacerbated the toxic effects of DBDPE. DBDPE and ZnO NPs caused excessive ROS production and inhibition of antioxidant enzyme (SOD and GSH) activity in cells, thus causing oxidative cellular damage. Moreover, DBDPE and ZnO NPs caused apoptosis by disrupting mitochondrial kinetic homeostasis, reducing mitochondrial membrane potential (MMP), increasing cytochrome C release and regulating Bax/Bcl-2 and Caspase-3 mRNA and protein expression. DBDPE and ZnO NPs increased the mRNA expression of nuclear factor erythroid 2- related factor (Nrf2) and its downstream genes. The molecular mechanisms revealed that oxidative stress, apoptosis and mitochondrial dysfunction were the critical factors in combined cytotoxicity. The bioinformatics analysis further indicated that co-exposure affected Nrf2 activation, apoptotic factors expression and mitochondrial fusion. The findings enrich the risk perception of neurotoxicity caused by DBDPE and ZnO NPs.

PBDEs disrupt homeostasis maintenance and regeneration of planarians due to DNA damage, proliferation and apoptosis anomaly

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants in the manufacturing industry, belonging to persistent organic pollutants in the environment. Planarians are the freshwater worms, with strong regenerative ability and extreme sensitivity to environmental toxicants. This study aimed to evaluate the potential acute comprehensive effects of PBDE-47/-209 on freshwater planarians. Methods to detect the effects include: detection of oxidative stress, observation of morphology and histology, detection of DNA fragmentation, and detection of cell proliferation and apoptosis. In the PBDE-47 treatment group, planarians showed increased oxidative stress intensity, severe tissue damage, increased DNA fragmentation level, and increased cell proliferation and apoptosis. In the PBDE-209 treatment group, planarians showed decreased oxidative stress intensity, slight tissue damage, almost unchanged DNA fragmentation level and apoptosis, proliferation increased only on the first day after treatment. In conclusion, both PBDE-47 and PBDE-209 are dangerous environmental hazardous material that can disrupt planarians homeostasis, while the toxicity of PBDE-47 is sever than PBDE-209 that PBDE-47 can lead to the death of planarians.

Toxicokinetics and edible tissues-specific bioaccumulation of decabrominated diphenyl ethers (BDE-209) after exposure to the broilers

Decabromodiphenyl ether (BDE-209), the primary constituent of a widely used flame retardant formulation, is often present in high levels in avian derived products and could be transferred to humans through consumption. The purpose of this study was to investigate the toxicokinetics and bioaccumulation patterns of BDE-209 in different tissues of broilers, which would benefit the evaluation of chicken product safety. Male broilers received a single oral administration of BDE-209 at 25 mg/kg.BW and then BDE-209 concentrations in the plasma, liver, leg muscle, breast muscle, and other tissues were measured using gas chromatography-electron capture detection (GC-ECD). The changes of BDE-209 concentrations in the plasma were fitted to a non-compartmental model for kinetic analysis. Peak values were observed at 24 h (t_1/2 =168.28 h), and trace levels remained for four weeks. Additionally, C_max in the liver was much higher than that in leg and breast muscles, and T_max from the liver and muscle were 12 and 24 h, respectively. Residual BDE-209 was detected in all broiler tissues after 2 weeks, and concentrations were ranked as follows: fat > liver > thymus gland > heart > testis > thigh muscle > skin > lung > kidney > breast muscles > spleen (wet weight (ww)). Our results suggested that BDE-209 was widely distributed in different tissues after intestinal absorption, and preferentially accumulated in adipose and liver tissues. Observations of bioaccumulation and slow elimination in the liver and muscles provide critical insight into the toxicity of BDE-209 and risk assessment of edible tissues from broilers.

Metabolism toxicity and susceptibility of decabromodiphenyl ether (BDE-209) exposure on BRL cells with insulin resistance

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by insulin resistance (IR) and has attracted worldwide attention due to its high prevalence. As a typical persistent organic pollutant, decabromodiphenyl ether (BDE-209) has been detected in food and human samples, and the concentration trends increase year by year. In addition, it has been proved to have the potential to increase the risk of IR, but it is rarely reported whether it could aggravate IR in T2DM. Therefore, in this study, the IR-BRL (buffalo rat liver cells with IR) model was applied to study the metabolism toxicity and susceptibility of BDE-209. Results showed that BDE-209 could inhibit glucose absorption and increase the levels of serum total cholesterol (TC) and triglyceride (TG), ultimately leading to the disorder of glucolipid metabolism in IR-BRL cells. Besides, it also could cause cell damage by increasing the levels of aspartate transaminase (AST), alanine aminotransferase (ALT), and malondialdehyde (MDA) in cells. Moreover, its potential mechanisms were to: (1) affect the transport of glucose, synthesis of glycogen and fatty acid via IRS-1/GLUT4 and IRS-1/PI3K/AKT/GSK-3β pathways; (2) impact the proliferation and differentiation by regulating the expression of Mek1/2, Erk1/2, and mTOR proteins and genes. Furthermore, susceptibility analysis showed that there was a significant synergism interaction between IR and BDE-209, which suggested that IR-BRL cells were more susceptible to the metabolism toxicity induced by BDE-209.

A comprehensive analysis on the relationship between BDE-209 exposure and erectile dysfunction

Decabromodiphenyl ether (mainly BDE-209) is a commonly used brominated flame retardant in various industrial products. Although its damage to the reproduction system has been established, its effect on erectile function remains unclear. The present study investigated whether BDE-209 induced erectile dysfunction in male SD rats and the underlying mechanisms. Pubertal male rats were exposed to BDE-209 orally (0, 5, 50, and 500 mg/kg/day) for 28 days and the ICP (intracavernous pressure) and MAP (mean arterial pressure) were measured. After the rats were euthanized, the fibrosis and apoptosis levels were evaluated. Additionally, the endothelial function of the rat vascular endothelium cells and the human umbilical vein endothelial cells were impaired after treatment with 50 μM and 100 μM BDE-209. Moreover, the bioinformatics based on CTD database and ChIP-X Enrichment Analysis, version 3 (ChEA3) and molecular docking analysis demonstrated that 5 transcription factors (NFKB1, NR3C1, E2F5, REL, IRF4) might regulate endothelial function by affecting the expression of interactive genes (BCL-2, CAP3, CAT, TNF, MAPK1, and MAPK3). In summary, the present study demonstrated that BDE-209 might affect downstream interactive genes by binding to transcription factors, leading to corpus cavernosum endothelial dysfunction, thus contributing to erectile dysfunction in rats.

Integration of transcriptomic and proteomic reveals the toxicological molecular mechanisms of decabromodiphenyl ethane (DBDPE) on Pleurotus ostreatus

Decabromodiphenyl ethane (DBDPE), as one of the most widely used new brominated flame retardants (NBFRs), can pose a potential threat to human health and the environment. An integrated transcriptome and proteome was performed for investigating the toxicological molecular mechanisms of Pleurotus ostreatus (P. ostreatus) during the biodegradation of DBDPE at the concentrations of 5 and 20 mg/L. A total of 1193/1018 and 92/126 differentially expressed genes/proteins (DEGs/DEPs) were found, respectively, with DBDPE exposure at 5 and 20 mg/L. These DEGs and DEPs were mainly involved in the cellular process as well as metabolic process. DEPs for oxidation-reduction process and hydrolase activity were up-regulated, and those for membrane, lipid metabolic process and transmembrane transport were down-regulated. The DEGs and DEPs related to some key enzymes were down-regulated, such as NADH dehydrogenase/oxidoreductase, succinate dehydrogenase, cytochrome C1 protein, cytochrome-c oxidase/reductase and ATP synthase, which indicated that DBDPE affected the oxidative phosphorylation as well as tricarboxylic acid (TCA) cycle. Cytochrome P450 enzymes (CYPs) might be involved in DBDPE degradation through hydroxylation and oxidation. Some stress proteins were induced to resist DBDPE toxicity, including major facilitator superfamily (MFS) transporter, superoxide dismutase (SOD), molecular chaperones, heat shock proteins (HSP20, HSP26, HSP42), 60S ribosomal protein and histone H4. The findings help revealing the toxicological molecular mechanisms of DBDPE on P. ostreatus, aiming to improve the removal of DBDPE.

Associations between polybrominated diphenyl ethers (PBDEs) levels in adipose tissues and blood lipids in women of Shantou, China

Animal studies have indicated that exposure to polybrominated diphenyl ethers (PBDEs) during development can permanently affect blood/liver lipid balance. However, no epidemiological study has assessed the relationship between PBDEs in adipose tissues and blood lipid metabolism. In this study, we explored the associations between PBDEs levels in female adipose tissues and lipid profiles. We recruited 150 female patients undergoing plastic surgery from hospital in Shantou, China, collected their characteristics, clinical information, and adipose tissue samples. Fourteen PBDE congeners in adipose tissues were analyzed by gas chromatography-mass spectrometry (GC-MS). Multiple linear and logistic regression models were used to explore the relationships between PBDEs and lipid profiles, while restricted cubic spline (RCS) regression and Bayesian kernel machine regression (BKMR) models were used to evaluate the nonlinearity of mixtures. Median levels of ΣPBDEs and dominant congeners BDE-153, -209, and -183 in adipose tissues were 73.91, 26.12, 14.10 and 9.01 ng/g lipid, respectively. In the multiple linear model, BDE-153 and BDE-209 were negatively associated with triglycerides (TG), similarly for BDE-190 and total cholesterol (TC). While in the adjusted logistic models, BDE-138 was negatively associated with TC (OR = 0.76, 95%CI: 0.58, 0.99) and total lipids (TL) (OR = 0.76, 95%CI: 0.58, 0.99). Diastolic blood pressure was positively correlated with BDE-28 and BDE-71 (P < 0.05). Furthermore, a non-linear relationship was observed in BDE-138 and blood lipid levels using a RCS model (P_nonlinearity<0.05). BKMR analysis indicated that with the cumulative levels across PBDEs increased, the health risks of hypertriglyceridemia gradually rebounded, and the health risks of hypercholesterolemia and high total lipid gradually rebounded and then declined, but without statistical significance. PBDEs pollution was still prevalent in Shantou city, and several PBDE congeners were significant risk factors for dyslipidemia and blood pressure alteration. There exist deleterious effects of PBDEs and blood lipids.

Fate and toxicity of legacy and novel brominated flame retardants in a sediment-water-clam system: Bioaccumulation, elimination, biotransformation and structural damage

Due to the characteristics of persistent organic pollutants (POPs), some legacy brominated flame retardants (LBFRs) were prohibited from use, and then gradually replaced by novel brominated flame retardants (NBFRs). However, till now little research focused on the effects of NBFRs on the benthos. In the present study, 0.5, 5, and 50 mg/kg dw of pentabromotoluene (PBT), hexabromobenzene (HBB), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenyl ethane (DBDPE) and decabromodiphenyl ether (BDE209) were added into sediments to test freshwater clams (Corbicula fluminea). In the 35-day exposure experiment, C. fluminea had different enrichment behaviors in three treatment groups. It was conjectured that in the lower dose group, the clams ingested contaminants and tended to be stable over time. While in higher dose groups, the clams were induced by the chemicals, leading to the changes in physiological activities so that the concentrations showed a downward trend first and then went up. The half-lives of contaminants in freshwater clams were between 0.911 and 11.6 days. DBDPE showed stronger bioaccumulation ability than BDE209 in this study. Parabolic relationships were observed between log BSAF and log K_ow values in clam tissues. Debromination, hydroxylation, and methoxylated products were detected. Additionally, the gill samples of C. fluminea exposed to 50 mg/kg dw of single substance were observed by scanning electron microscope (SEM), indicating that the adhesions, tissue hyperplasia, and messy cilia occurred on the surface. Our research potentially contributes to further evaluations of the environmental risks posed in sediments contaminated by PBT, HBB, BTBPE, DBDPE, and BDE209, particularly the benthic organisms.

Physiologically based pharmacokinetic (PBPK) modeling of BDE-209 following oral exposure in Chinese population

The wide usage of decabromodiphenyl ether (BDE-209) as additive brominated flame retardant has caused its widespread occurrence in the environment and high exposure risk in humans. Estimating its internal exposure dose and reconstruction of external exposure dose using physiologically based pharmacokinetic (PBPK) modelling approach is a key step in the risk assessment of BDE-209. However, the PBPK model for BDE-209 is currently unavailable. This study has established two oral permeability-limited PBPK models of BDE-209 without enterohepatic recirculation (EHR) (model 1) and with EHR (model 2) for Chinese population. Using the in vitro experiments, the average binding of BDE-209 to human plasma protein (99.64% ± 2.97%) was obtained. Moreover, blood sample analysis and systematic literature review were performed to obtain internal and external exposure data of BDE-209 used for model calibration and validation. The predictions of both models were within 2-fold of the observed, and a longer half-life of serum BDE-209 was observed in model 2 than model 1. Based on the models, a human biomonitoring guidance value (HBM-GV) of 93.61 μg/g lw was derived for BDE-209, and there is no health risk found for Chinese population currently. This study provides new quantitative assessment tools for health risk assessment of BDE-209.

Comparative Effects of Brominated Flame Retardants BDE-209, TBBPA, and HBCD on Neurotoxicity in Mice

Brominated flame retardants (BFRs) are ubiquitous industrial chemicals. In China, BFRs that are applied in large quantities include decabromodiphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCD). Although findings are not always unequivocal, mounting evidence in vivo suggests that the BFRs have potential neurotoxicity. The present study aimed to assess and compare the neurotoxic effects of these three BFRs' exposure. Male mice were orally exposed to BDE-209, TBBPA, or HBCD at 50 and 100 mg/kg bw/day for 28 days. The cognitive behavior, oxidative stress (ROS, MDA, and GSH), apoptosis-related genes (caspase-3, bax, and bcl-2), memory-related proteins (BDNF and PSD-95), and neurotransmitters (AChE and ChAT) were detected comparatively. Results showed that high doses of BDE-209, TBBPA, and HBCD exposure impaired spatial memory of mice, elevated ROS and MDA and reduced GSH levels of hippocampus, upregulated caspase-3 and bax expressions, decreased BDNF and PSD-95 levels, and disordered AChE and ChAT levels. Notably, BDE-209 caused greater adverse effects > HBCD > TBBPA. This study confirms and extends that these three BFRs had similar neurotoxic effects at current concentrations, although they may be more or less toxic.

The disruption on gut microbiome of Decabromodiphenyl ethane exposure in the simulator of the human intestinal microbial ecosystem (SHIME)

The health risks of Decabromodiphenyl ethane (DBDPE) with its cardiovascular toxicity, liver toxicity and cytotoxicity had been generally acknowledged. However, the influence on gut microbiome and short-chain fatty acids (SCFAs) metabolism caused by DBDPE exposure remained unknown. In this study, three exposure groups (5, 50, 500 mg/L) and control group were used to investigate the effect of DBDPE by using simulator of the human intestinal microbial ecosystem (SHIME). 16S rRNA gene high-throughput sequencing illustrated that high dose DBDPE exposure increased the α-diversity of gut microbiota, while reduced the abundance of Firmicutes and Proteobacteria. In addition, the low dose (5 mg/L) DBDPE inhibited the increasing of SCFAs, but the medium and high dose (50 and 500 mg/L) DBDPE promoted the advancement, especially in ascending colon. Notably, DBDPE exposure lead a similar changing of acetic acid and butyric acid contents in different sections of the colon. This study confirmed the alternation of composition and metabolic function in gut microbial community due to DBDPE exposure, indicating an intestinal damage and appealing for more attention concentrated on the health effects of DBDPE exposure.

Decabromodiphenyl ethane affects embryonic development by interfering with nuclear F-actin in zygotes and leads to cognitive and social disorders in offspring mice

Decabromodiphenyl ethane (DBDPE) is a novel retardant. DBDPE is used in various flammable consumer products such as electronics, building materials, textiles, and children's toys. The presence of DBDPE in humans makes it extremely urgent to assess the health effects of DBDPE exposure. Here, we used female mice as an animal model to investigate the effects of DBDPE on embryonic development and offspring health. The results showed that 50 μg/kg bw/day of DBDPE exposure did not affect spindle rotation in oocytes after fertilization, but led to a decrease of pronuclei (PN) in zygotes. Further investigation found that DBDPE interferes with the self-assembly of F-actin in PN, resulting in PN reduction, DNA damage, and reduced expression of zygotic genome activating genes, and finally leading to abnormal embryonic development. More importantly, we found that maternal DBDPE exposure did not affect the growth and development of the first generation of offspring (F1) mice, but resulted in behavioral defects in F1 mice. Female F1 mice from DBDPE-exposed mothers exhibited increased motor activity and deficits in social behavior. Both female and male F1 mice from DBDPE-exposed mothers exhibited cognitive memory impairment. These results suggest that DBDPE has developmental toxicity on embryos and has a cross-generational interference effect. It is suggested that people should pay attention to the reproductive toxicity of DBDPE. In addition, it also provides a reference for studying the origin of neurological diseases and indicates that adult diseases caused by environmental pollutants may have begun in the embryonic stage.

Aerobic Degradation Characteristics of Decabromodiphenyl ether through Rhodococcus ruber TAW-CT127 and Its Preliminary Genome Analysis

Decabromodiphenyl ether (BDE-209), a polybrominated diphenyl ether (PBDE) homolog, seriously threatens human health. In this study, a Rhodococcus ruber strain with high BDE-209 degradation activity, named TAW-CT127, was isolated from Tong’an Bay, Xiamen. Under laboratory conditions, the strain’s optimal growth temperature, pH, and salinity are 45 °C, 7.0, and 0–2.5%, respectively. Scanning electron microscopy (SEM) analysis shows that TAW-CT127 is damaged when grown in manual marine culture (MMC) medium with BDE-209 as the sole carbon source instead of eutrophic conditions. In the dark, under the conditions of 28 °C, 160 rpm, and 3 g/L (wet weight) TAW-CT127, the degradation rate of 50 mg/L BDE-209 is 81.07%. The intermediate metabolites are hexabromo-, octabromo-, and nonabromo-diphenyl ethers. Through whole-genome sequencing, multiple dehalogenases were found in the genome of TAW-CT127; these may be involved in the production of lower-brominated diphenyl ethers. Additionally, biphenyl-2,3-dioxygenase (BDO) in TAW-CT127 may catalyze the debromination reaction of BDE-209. Our research provides a new high-efficiency strain for bioremediation of BDE-209 pollution, and lays the foundation for the preliminary exploration of genes associated with BDE-209 degradation.

Toxicity evaluation of decabromodiphenyl ethane (DBDPE) to Pleurotus ostreatus: Oxidative stress, morphology and transcriptomics

Decabromodiphenyl ethane (DBDPE), one widely used new brominated flame retardant, was of great concern due to its biotoxicity. The toxic evaluation of DBDPE (1-50 mg/L) to white-rot fungus (Pleurotus ostreatus), including oxidative stress, morphology and transcriptomics was conducted aiming at improving its biodegradation. Fungal growth and ATPase activity were obviously inhibited by DBDPE at ≥ 10 mg/L with the exposure from 48 h to 96 h. DBDPE could induce oxidative stress to P. ostreatus. The activity of SOD (superoxide dismutase), CAT (catalase) and GSH (glutathione) were all promoted by DBDPE at ≤ 5 mg/L and inhibited at > 5 mg/L with 96-h exposure. MDA (malondialdehyde) content rose obviously with DBDPE exposure (10-50 mg/L). The mycelium was wizened under 20 mg/L DBDPE exposure according to SEM observation. Transcriptomics analysis suggested that DBDPE could change many functional genes expression of P. ostreatus. GO analysis indicated DBDPE could affect biological process and cellular component by inhibiting electron transport, mitochondrial ATP synthesis, oxidoreductase activity as well as transporter activity. KEGG enrichment pathways analysis indicated DBDPE could inhibit oxidative phosphorylation, tricarboxylic acid (TCA) cycle and carbon metabolism by down-regulating the genes related to NADH reductase/dehydrogenase, succinate dehydrogenase, cytochrome-c reductase/oxidase, cytochrome C1 protein and ATP synthase.

Fat mass and obesity-associated gene (FTO) hypermethylation induced by decabromodiphenyl ethane causing cardiac dysfunction via glucolipid metabolism disorder

Decabromodiphenyl ethane (DBDPE) is a major alternative to BDE-209 owing to its lower toxicity. However, the mass production and increased consumption of DBDPE in recent years have raised concerns related to its adverse health effects. However, the effect and mechanism of DBDPE on cardiotoxicity have rarely been studied. In the present study, we investigated the impacts of DBDPE on the cardiovascular system in male SD rats and then explored the underlying mechanisms to explain the cardiotoxicity of DBDPE using AC16 cells. Under in vivo conditions, male rats were administered with an oral dosage of DBDPE at 0, 5, 50, and 500 mg/kg/day for 28 days, respectively. Histopathological analysis demonstrated that DBDPE induced cardiomyocyte injury and fibrosis, and ultrastructural observation revealed that DBDPE could induce mitochondria damage and dissolution. DBDPE could thus decrease the level of MYH6 and increase the level of SERCA2, which are the two key proteins involved in the maintenance of homeostasis during myocardial contractile and diastolic processes. Furthermore, DBDPE could increase the serum levels of glucose and low-density lipoprotein but decrease the content of high-density lipoprotein. In addition, DBDPE could activate the PI3K/AKT/GLUT2 and PPARγ/RXRα signaling pathways in AC16 cells. In addition, DBDPE decreased the UCP2 level and ATP synthesis in mitochondria both under in vitro and in vivo conditions, consequently leading to apoptosis via the Cytochrome C/Caspase-9/Caspase-3 pathway. Bisulfite sequencing PCR (BSP) identified the hypermethylation status of fat mass and obesity-associated gene (FTO). 5-aza exerted the opposite effects on the PI3K/AKT/GLUT2, PPARγ/RXRα, and Cytochrome C/Caspase-9/Caspase-3 signaling pathways induced by DBDPE in AC16 cells. In addition, the DBDPE-treated altered levels of UCP2, ATP, and apoptosis were also found to be significantly reversed by 5-aza in AC16 cells. These results suggested that FTO hypermethylation played a regulative role in the pathological process of DBDPE-induced glycolipid metabolism disorder, thereby contributing to the dysfunction of myocardial contraction and relaxation through cardiomyocytes fibrosis and apoptosis via the mitochondrial-mediated apoptotic pathway resulting from mitochondrial dysfunction.

Sex-related deposition and metabolism of vanisulfane, a novel vanillin-derived pesticide, in rats and its hepatotoxic and gonadal effects

A series of vanillin derivatives have recently been synthesized as effective candidate antiviral agents, with vanisulfane exhibiting pronounced curative and protective activities against cucumber mosaic virus and potato virus Y. However, research on some new pesticides usually ignores their various metabolites and sex-related toxicity. Assisted by ¹⁴C labeling, a trial was conducted to investigate the tissue distribution, excretion, and metabolism of vanisulfane in male and female rats for the first time. The results showed that 83.30-87.51% of applied ¹⁴C activity was excreted in urine and feces within 24 h of oral administration, and ¹⁴C was most abundant in the liver and kidney in both sexes. Interestingly, sex differences were observed in the experiment, with lower body clearance in males than in females 24 h after treatment and preferences for biliary and renal excretion of the pesticide in male and female rats, respectively. A high degradation rate was found for vanisulfane in the plasma; thus, the metabolites of vanisulfane were investigated using liquid chromatography-quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) combined with ¹⁴C labeling. One glucuronic acid conjugate and two oxidation metabolites were detected, supporting the monitoring of vanisulfane in vivo. Additionally, rats exposed to vanisulfane exhibited hepatic steatosis in both sexes, along with mild gonadal effects in males. This research offers an effective method for conducting environmental behavioral research and provides new insights for evaluating the potential risks of novel pesticides in mammals from a sex perspective.

Decabromodiphenyl ether initiates mitochondria-dependent apoptosis by disrupting calcium homeostasis in mice livers

Decabromodiphenyl ether (BDE-209) tends to accumulate in lipid-rich tissues and targets the liver since its high lipophilicity. This study aimed to investigate the effects of BDE-209 on mouse liver and reveal the underlying toxicological mechanisms. Here we firstly confirmed that treatment of BDE-209 could lead to an imbalance of redox and promote apoptosis with a mitochondria-dependent manner in mice livers. Next, the transmission electron microscope (TEM) image revealed BDE-209 induced changes in mitochondrial morphology and increased endoplasmic reticulum (ER) - mitochondrial contact. ER stress was involved in the apoptosis process, which was displayed by the enhancive ER stress makers . Finally, from the increased abundance of cellular pivotal Ca²⁺ signals transducer CaM, activating Ca²⁺ release channel Sig-1R and IP3R1, and the stronger fluorescence density of mitochondria-specifically Ca²⁺ labeled probe Rhod-2 in vitro, we summarized that there was overloaded mitochondrial Ca²⁺ in hepatocytes of BDE-209 treated mice. In conclusion, these results partly illustrated evidence to reveal a potential mechanism of BDE-209-induced hepatoxicity, where oxidative stress-induced-ER stress led to the over-release of Ca²⁺, followed by the overloaded mitochondrial Ca²⁺, and cell apoptosis initiated. Our findings provided a theoretical basis for further studying.

Reduced mitochondrial DNA copy number in occupational workers from brominated flame retardants manufacturing plants

Decabrominated diphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are two flame retardants that have similar structure and are widely used in various industrial products. The accumulation and potential toxicity of them to human health have already aroused attention, and some research showed that they may affect mitochondrial function. Therefore, this study focused on the population with high exposure to brominated flame retardants (BFRs) and the related changes in mtDNA copy number (mtDNAcn) in whole blood. 334 blood samples were collected from three groups of people in Shandong Province, including 42 BDE-209 occupational exposure workers from the BDE-209 manufacturing plant, 131 DBDPE occupational exposure workers from the DBDPE manufacturing plant, and 161 non-BFRs occupational exposure residents from the BFRs contaminated area. We measured the levels of BDE-209, DBDPE in serum sample, and the mtDNAcn in whole blood sample and analyzed these data by multiple linear regression. The average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in BDE-209 occupational workers were 3510, 639 and 4600 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in DBDPE occupational workers were 229, 4040 and 4470 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in non-BFRs occupational exposure residents were 66.3, 45.7 and 137 ng/g lw, respectively. The relative mtDNAcn was 0.823 in BDE-209 occupational workers, 0.845 in DBDPE occupational workers and 0.989 in non-BFRs occupational exposure residents. A 10-fold increase in BDE-209, DBDPE concentrations was separately associated with a 0.068 and 0.063 decrease in mtDNAcn. Therefore, our study implied that BFRs may affect mitochondrial function. As increasing BFRs exposure has emerged in recent years, the relationship between BFRs exposure and mitochondrial function needs further study.

Biodegradation of decabromodiphenyl ethane (DBDPE) by white-rot fungus Pleurotus ostreatus: Characteristics, mechanisms, and toxicological response

Decabromodiphenyl ethane (DBDPE) can pose a potential toxic threat to human beings and the environment. P. ostreatus, as one of the typical white-rot fungi, can effectively degrade various refractory pollutants. The biodegradable characteristics of DBDPE by P. ostreatus, as well as the mechanisms, and toxicological response were investigated in this study. The removal rate reached 47.73% and 43.20%, respectively, for 5 and 20 mg/L DBDPE after 120-h degradation by P. ostreatus. As a coexisting substance, Pb could inhibit the biodegradation. It is found that both the intracellular enzyme (P450) and extracellular enzymes (manganese peroxidase (MnP), lignin peroxidase (LiP), and laccase (Lac)) played a very important role in the biodegradation of DBDPE, of which Lac dominated the degradation. The toxic response was monitored during the degradation. The activities of SOD and CAT were enhanced to eliminate excess ROS in P. ostreatus triggered by DBDPE. In addition, debromination, hydroxylation, and oxidation were inferred as the main degradation pathways preliminarily. The findings provide a theoretical basis for the application of microbial degradation of DBDPE contamination.

Decabromodiphenyl Ethane Mainly Affected the Muscle Contraction and Reproductive Endocrine System in Female Adult Zebrafish

The novel brominated flame retardant decabromodiphenyl ethane (DBDPE) has become a widespread environmental pollutant. However, the target tissue and toxicity of DBDPE are still not clear. In the current study, female zebrafish were exposed to 1 and 100 nM DBDPE for 28 days. Chemical analysis revealed that DBDPE tended to accumulate in the brain other than the liver and gonad. Subsequently, tandem mass tag-based quantitative proteomics and parallel reaction monitoring verification were performed to screen the differentially expressed proteins in the brain. Bioinformatics analysis revealed that DBDPE mainly affected the biological process related to muscle contraction and estrogenic response. Therefore, the neurotoxicity and reproductive disruptions were validated via multilevel toxicological endpoints. Specifically, locomotor behavioral changes proved the potency of neurotoxicity, which may be caused by disturbance of muscular proteins and calcium homeostasis; decreases of sex hormone levels and transcriptional changes of genes related to the hypothalamic-pituitary-gonad-liver axis confirmed reproductive disruptions upon DBDPE exposure. In summary, our results suggested that DBDPE primarily accumulated in the brain and evoked neurotoxicity and reproductive disruptions in female zebrafish. These findings can provide important clues for a further mechanism study and risk assessment of DBDPE.

Exogenous melatonin protects preimplantation embryo development from decabromodiphenyl ethane-induced circadian rhythm disorder and endogenous melatonin reduction

Decabromodiphenyl ethane (DBDPE) is a novel flame retardant that is widely used in plastics, electronic products, building materials and textiles. Our previous studies have revealed the oocyte toxicity of DBDPE, but the effect of DBDPE on preimplantation embryo development has not been reported. Here, we investigated whether and how DBDPE exposure affects preimplantation embryo development. Adult female mice were orally exposed to DBDPE (0, 5, 50, 500 μg/kg bw/day) for 14 days. First, we found that after DBDPE exposure, mice showed obvious circadian rhythm disorder. Moreover, the development of preimplantation embryos was inhibited in DBDPE-exposed mice after pregnancy. Then, we further explored and revealed that DBDPE exposure reduced the endogenous melatonin (MLT) level during pregnancy, thereby inhibiting the development of preimplantation embryos. Furthermore, we discovered that exogenous MLT supplementation (15 mg/kg bw/day) rescued the inhibition of preimplantation embryo development induced by DBDPE, and a mechanistic study demonstrated that exogenous MLT inhibited the overexpression of ROS and DNA methylation at the 5-position of cytosine (5-mC) in DBDPE-exposed preimplantation embryos. Simultaneously, MLT ameliorated the DBDPE-induced mitochondrial dysfunction by increasing the mitochondrial membrane potential (MMP), ATP, and Trp1 expression. Additionally, MLT restored DBDPE-induced changes in zona pellucida (ZP) hardness and trophectoderm (TE) cortical tension. Finally, the protective effect of MLT on embryos ameliorated the adverse reproductive outcomes (dead fetus, fetus with abnormal liver, fetal weight loss) induced by DBDPE. Collectively, DBDPE induced preimplantation embryo damage leading to adverse reproductive outcomes, and MLT has emerged as a potential tool to rescue adverse reproductive outcomes induced by DBDPE.

High-fat diet exacerbated decabromodiphenyl ether-induced hepatocyte apoptosis via intensifying the transfer of Ca2+ from endoplasmic reticulum to mitochondria

Polybrominated diphenyl ether (PBDE) as the flame retardant is heavily used in daily necessities, causing adverse health effects on humans. This study aimed to evaluate the hepatotoxicity of decabromodiphenyl ether (BDE-209), the most widely used PBDE, in lean and high-fat diet (HFD)-treated obese mice and elucidate the underlying mechanism. Firstly, the increasing levels of TG and proinflammatory factors in the liver and ALT and AST in serum demonstrated the hepatic damage caused by BDE-209 and further exacerbated by HFD. Tunel image revealed that BDE-209 induced more severe hepatocyte apoptosis with the assistant of HFD. Next, the mechanism analysis showed that the pro-apoptotic action of BDE-209 was in an endoplasmic reticulum (ER)/Ca²⁺ flux/mitochondria-dependent manner, concluded from the impairment of mitochondrial membrane potential, the enhancive protein expression of p-PERK/PERK, p-IRE1/IRE1, ATF6, CHOP, Bax/Bcl-2, cleaved caspase-3/caspase-3, IP3R1 and Sig-1R, and the over-transfer of Ca²⁺ from ER to mitochondria. Such proposed mechanism was further confirmed by the IP3R1 siRNA transfection cell experiment, where apoptotic rate was reduced in parallel with the reduced mitochondrial Ca²⁺ level. Finally, the higher expression of PACS-2 protein and the expanded ER contributed to the enriched ER-mitochondria interaction, reflected by the closer distance between ER and mitochondria visually displayed in the TEM image in HFD groups. This change was conducive to the rapid delivery of apoptosis signals via Ca²⁺, as proven, mechanically explaining the strengthening effect of HFD on BDE-209 hepatotoxicity. These findings detailedly explained the mechanism of BDE-209 hepatotoxicity and clarified the auxiliary effect of HFD, providing a theoretical basis for further studying other analogs.

Oxidative stress and endoplasmic reticulum stress contributed to hepatotoxicity of decabromodiphenyl ethane (DBDPE) in L-02 cells

Decabromodiphenyl ethane (DBDPE) is one of the most commonly used novel brominated flame retardants (NBFRs), and its mass production and widespread application have caused health threats to the human being. Existing studies have shown that DBDPE has hepatotoxicity. And we have found that DBDPE could change cytochrome P450 3A (CYP3A) expression levels in rat livers, whereas the mechanism is unclear. In this study, we exposed human normal hepatocyte (L-02) to DBDPE to further study the effect and mechanism of DBDPE on hepatocellular injury and liver metabolic enzyme CYP3A changes in vitro. The results showed that DBDPE caused L-02 cell viability decrease, lactate dehydrogenase (LDH) and transaminase release, ultrastructural damage, and apoptosis. Moreover, DBDPE exposure induced oxidative stress (i.e., increased ROS generation and MDA levels and decreased GSH content, SOD activity, and mitochondrial membrane potential) and endoplasmic reticulum (ER) stress in L-02 cells as evidenced by the elevated PERK and IRE-1α expression levels. These results confirmed that DBDPE is toxic to hepatocytes. Besides, the CYP3A expression level was decreased in DBDPE exposed L-02 cells. However, pretreatment of L-02 cells with antioxidant N-Acetyl-l-cysteine (NAC) and endoplasmic reticulum stress inhibitor 4-PBA inhibited DBDPE-induced oxidative stress, endoplasmic reticulum stress, CYP3A expression decrease, and apoptosis. Therefore, we demonstrated that DBDPE could exert toxic effects and decrease CYP3A expression on L-02 cells by inducing ER stress and oxidative stress.