Cytotoxicity evaluation of three pairs of hexabromocyclododecane (HBCD) enantiomers on Hep G2 cell

Enantioselective biomarkers of maize toxicity induced by hexabromocyclododecane based on submicroscopic structure, gene expression and molecular docking

Hexabromocyclododecane (HBCD), as a monitored chemical of the Chemical Weapons Convention, the Stockholm Convention and the Action Plan for New Pollutants Treatment in China, raises significant concerns on its impact of human health and food security. This study investigated enantiomer-specific biomarkers of HBCD in maize (Zea mays L.). Upon exposure to HBCD enantiomers, the maize root tip cell wall exhibited thinning, uneven cell gaps, and increased deposition on the cell outer wall. Elevated malondialdehyde (MDA) indicated lipid peroxidation, with higher mitochondrial membrane potential (MMP) inhibition in (+)-enantiomer treatments (47.2%-57.9%) than (-)-enantiomers (14.4%-37.4%). The cell death rate significantly increased by 37.7%-108.8% in roots and 16.4%-62.4% in shoots, accompanied by the upregulation of superoxide dismutase isoforms genes. Molecular docking presenting interactions between HBCD and target proteins, suggested that HBCD has an affinity for antioxidant enzyme receptors with higher binding energy for (+)-enantiomers, further confirming their stronger toxic effects. All indicators revealed that oxidative damage to maize seedlings was more severe after treatment with (+)-enantiomers compared to (-)-enantiomers. This study elucidates the biomarkers of phytotoxicity evolution induced by HBCD enantiomers, providing valuable insights for the formulation of more effective policies to safeguard environmental safety and human health in the future.

Dynamic modeling of the occurrence, sources, and environmental behavior of polybrominated diphenyl ethers in Zhelin Bay, China

This study analyzed polybrominated diphenyl ethers (PBDEs) in Zhelin Bay, China, investigating their occurrence, sources, and environmental behavior. PBDE congeners were detected in all sampled media. The Σ13PBDE concentrations in the dissolved phase ranged from 1.04 to 41.40 ng/L, while the concentrations ranged in suspended particulate matter from 0.02 to 12.56 ng/L. In sediments, PBDE concentrations ranged from 1.41 to 8.57 ng/g. The higher proportion of PBDEs in the dissolved phase in the bay than in the estuary is attributable to the type of PBDE products used in the aquacultural process in Zhelin Bay. Moreover, correlation analysis between PBDE concentrations and environmental parameters showed that the primary factor influencing PBDE concentrations in Zhelin Bay sediments may shift from riverine inputs to aquaculture. Principal component analysis and positive matrix factorization revealed that PBDEs in the water of Zhelin Bay primarily originated from the degradation of octa-BDE, deca-BDE, and penta-BDE products employed in aquaculture. In contrast, the PBDEs in Zhelin Bay sediments mainly originated from riverine inputs. In addition, a level IV dynamic fugacity-based multimedia model was used to simulate the temporal variation of PBDE concentrations in Zhelin Bay. Modeled short-term trends showed a relatively swift transport of PBDE congeners in the water column to the atmosphere and sediments. Over the long term, sediment concentrations gradually decreased, in contrast to the less rapid declines observed in the atmosphere and water. Furthermore, this study revealed that the transport and transformation processes of PBDEs in the Zhelin Bay environment were considerably influenced by the diffusion coefficient in water, the water-side mass transfer coefficient at the water-sediment interface, the sediment resuspension rate, and the organic carbon-water partition coefficient.

Spatial distribution, source, and ecological risk of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) in Jiaozhou Bay, China

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs) are commonly found in the environment as components of brominated flame retardants. Due to their potential impact on human health and wildlife, it is imperative to closely monitor and manage their levels in the environment. This study investigated the spatial distribution, sources, and ecological risks of PBDEs and HBCDs in Jiaozhou Bay (JZB), a large bay situated on the eastern coast of China. The results showed that PBDE concentrations ranged from not detected (ND) to 7.93 ng/L in the water and ND to 65.76 ng/g in the sediment, while HBCD concentrations ranged from ND to 0.31 ng/L in the water and ND to 16.63 ng/g in the sediment. Furthermore, we observed significantly higher concentrations of PBDEs and HBCDs in the inner JZB compared to the outer JZB. Our source apportionment analysis showed that PBDEs primarily originated from the production and debromination of BDE-209, as well as the emission of commercial PeBDEs, whereas HBCDs in sediments mostly stemmed from anthropogenic activities and river input. Finally, our eco-logical risk assessment highlighted the need for continuous monitoring of PBDEs in JZB sediments. Overall, our study aims to provide valuable assistance for the environmental management of the JZB bay area, which is characterized by a complex net-work of rivers and a thriving economy.

Expanded polystyrene buoys as an important source of hexabromocyclododecanes for aquatic ecosystem: Evidence from field exposure with different substrates

The production and use of hexabromocyclododecanes (HBCDs) have been strictly limited due to their persistence, toxicity and bioaccumulation. However, the release of HBCDs from related products and wastes would continue for a long time, which may cause many environmental problems. In this study, we investigated the occurrence and distribution of HBCDs and microplastics (MPs) in aquatic organisms inhabiting different substrates. HBCDs were measurable in the seawater, sediment, expanded polystyrene (EPS) substrates and organism samples. Mostly, the concentrations of HBCDs in organisms inhabiting EPS buoys were significantly higher than those of the same species inhabiting other substrates. Meanwhile, the diastereomeric ratio (α/γ) of HBCDs in organisms inhabiting EPS buoys was closer to that in EPS buoys. The fugacity values of HBCDs in EPS buoys were much higher than those in other media, implying that HBCDs can be transferred from EPS buoys to other media. Additionally, MPs derived from EPS buoys would be mistaken as food and ingested by aquatic organisms. The transfer of HBCDs from EPS buoys to aquatic organisms can be achieved by aqueous and dietary exposures. In combination, the contribution of MP ingestion to HBCDs for aquatic organisms should be very limited. These results supported EPS buoys as an important source of HBCDs for the aquatic ecosystem. To effectively control HBCDs pollution, it is necessary to discontinue or reduce the use of EPS buoys.

Bioaccumulation and Biomagnification of Hexabromocyclododecane in Marine Biota from China: A Review

Hexabromocyclododecane (HBCD) was listed in Annex A of the Stockholm Convention on Persistent Organic Pollutants for its persistence, bioaccumulation and toxicity, and pose significant adverse effects on natural environments and human health. HBCDs are ubiquitously found in marine environments worldwide and can be biomagnified in marine organisms with a high trophic level. In the present study, we reviewed the available data on contamination of HBCDs in the marine biota from China, including mollusks, crustaceans, fish and mammals. Bioaccumulation and biomagnification of HBCDs in the marine food web were summarized as well. This study also prospected the future research of HBCDs, including the transport and fluxes of HBCDs to and within the marine environment, the biomagnification of HBCDs in different ecosystems, and the metabolism of HBCDs in different marine species.

Health toxicity effects of brominated flame retardants: From environmental to human exposure

Hexabromocyclododecane (HBCD) and Tetrabromobisphenol A (TBBP-A) are brominated flame retardants widely used in variety of industrial and consumer products (e.g., automobiles, electronics, furniture, textiles and plastics) to reduce flammability. HBCD and TBBPA can also contaminate the environment, mainly water, dust, air and soil, from which human exposure occurs. This constant exposure has raised some concerns against human health. These compounds can act as endocrine disruptors, a property that gives them the ability to interfere with hormonal function and quantity, when HBCD and TBBPA bind target tissues in the body. Studies in human and animals suggest a correlation between HBCD and TBBPA exposure and adverse health outcomes, namely thyroid disorders, neurobehavior and development disorders, reproductive health, immunological, oncological and cardiovascular diseases. However, in humans these effects are still poorly understood, once only a few data evaluated the human health effects. Thus, the purpose of this review is to present the toxicity effects of HBCD and TBBPA and how these compounds affect the environment and health, resorting to data and knowledge of 255 published papers from 1979 to 2020.

The enantiomer-selective metabolism of hexabromocyclododecanes (HBCDs) by human HepG2 cells

Although hepatic metabolism of hexabromocyclododecanes (HBCDs) played critical roles in the selective bioaccumulation of HBCDs in humans, the hepatic metabolism patterns of its enantiomers remained ambiguous. Aiming to elucidate the mechanism on hepatic metabolism of hexabromocyclododecanes (HBCDs) enantiomers, the enantiomers ((+)-α-HBCD, (-)-α-HBCD, (+)-γ-HBCD, and (-)-γ-HBCD), the diastereoisomers (α-, β-, and γ-HBCDs) and the mixed of α- and γ-HBCDs were incubated with human HepG2 cell under different exposure levels in the present study. The clearance percentages ranked as γ-HBCD enantiomers >β-HBCD enantiomers >α-HBCD enantiomers at the same exposure levels. The clearance percentages of (+)- and (-)-α-HBCDs increased when cells were exposed to racemic α-HBCD and the mixture of racemic α- and γ-HBCDs (p < 0.05). (-)-γ-HBCD was more resistant to human hepatic metabolism than (+)-γ-HBCD, leading to the enantiomer fractions (EFs) of γ-HBCD lower than 0.50. (-)-α-HBCD was slightly more metabolized when independently exposed to α-HBCD, while (+)-α-HBCD was more preferentially metabolized after exposure to α- and γ-HBCD mixtures. Hydroxylation and debromination HBCD metabolites were identified. In addition, the different EFs of HBCDs in cells and mediums suggested the selective transfer of chiral HBCDs and HBCD metabolites through the cell membrane. This study provided new insight into the enantiomer-selective metabolism of HBCDs.

Spatial distribution, source identification, and anthropogenic effects of brominated flame retardants in nationwide soil collected from South Korea

Soil samples were collected at 61 sites of the national monitoring network for persistent organic pollutants (POPs) in South Korea. The target compounds were brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), hexabromocyclododecanes (HBCDDs), and tetrabromobisphenol A (TBBPA). The mean concentrations of Σ₂₇ PBDEs, Σ₃ HBCDDs, and TBBPA in soil were 222, 17.2, and 4.4 ng/g, respectively, but PBBs were not detected. Industrial sites had statistically higher BFR concentrations than suburban sites but no significant difference compared with urban sites. The commercial deca-BDE mixtures were the most likely source of PBDE contamination in the soil samples, with the minor influence of commercial penta-BDE and octa-BDE mixtures. The profiles of HBCDDs in most soil samples differed from those in the powder types of technical HBCDD mixtures, indicating that they are affected by the HBCDDs contained in commercial products and the conversion of HBCDD diastereoisomers (γ-HBCDD to α-HBCDD) in the environment. The concentrations of Σ₂₇ PBDEs, Σ₃ HBCDDs, and TBBPA were significantly correlated with population density, gross domestic product, and the number of companies (p < 0.01), indicating a direct impact of anthropogenic activities. Significant correlations among BFRs were determined (0.63 < r < 0.74, p < 0.01), suggesting that these pollutants had similar sources. Relatively good correlations (0.44 < r < 0.98, p < 0.01) between BDE-209 and other light BDEs (except for BDE-71, -77, -126, -156, and -205) might result from the degradation of heavy BDEs under anaerobic and natural sunlight conditions. To the best of our knowledge, this study provides the most comprehensive soil monitoring data for various BFRs in South Korea. Furthermore, it is the first report on soil contamination by deca-BDE, HBCDDs, and TBBPA in South Korea.

Enantiomeric fraction of hexabromocyclododecanes in foodstuff from the Belgian market

Diet is considered a major route of human exposure to hexabromocyclododecane, a chiral environmental contaminant. A previous study reported on the occurrence of hexabromocyclododecane diastereoisomers in food items of animal origin collected in Belgium. The present study reports further results on corresponding enantiomeric fractions of the same samples. None of the samples could be considered as racemic for the α-isomer suggesting that foodstuff contamination occurred prior to death of the corresponding producing animal and was not the result of the food item being in contact with technical HBCDD. Non-racemic chiral signatures were also observed for β- and γ-isomers. We conclude that, depending on their dietary habits, different individuals might be overall exposed to non-racemic profiles. Considering that toxicological effects are enantiomer-dependent, this could modulate potential adverse effects.

Probing the Mechanism of Hepatotoxicity of Hexabromocyclododecanes through Toxicological Network Analysis

The prediction and mechanism analysis of hepatotoxicity of contaminants, because of their various phenotypes and complex mechanisms, is still a key problem in environmental research. We applied a toxicological network analysis method to predict the hepatotoxicity of three hexabromocyclododecane (HBCD) diastereoisomers (α-HBCD, β-HBCD, and γ-HBCD) and explore their potential mechanisms. First, we collected the hepatotoxicity related genes and found that those genes were significantly localized in the human interactome. Therefore, these genes form a disease module of hepatotoxicity. We also collected targets of α-, β-, and γ-HBCD and found that their targets overlap with the hepatotoxicity disease module. Then, we trained a model to predict hepatotoxicity of three HBCD diastereoisomers based on the relationship between the hepatotoxicity disease module and targets of compounds. We found that 593 genes were significantly located in the hepatotoxicity disease module (Z = 11.9, p < 0.001) involved in oxidative stress, cellular immunity, and proliferation, and the accuracy of hepatotoxicity prediction of HBCD was 0.7095 ± 0.0193 and the recall score was 0.8355 ± 0.0352. HBCD mainly affects the core disease module genes to mediate the adenosine monophosphate-activated kinase, p38MAPK, PI3K/Akt, and TNFα pathways to regulate the immune reaction and inflammation. HBCD also induces the secretion of IL6 and STAT3 to lead hepatotoxicity by regulating NR3C1. This approach is transferable to other toxicity research studies of environmental pollutants.

Inhibitory potentials of Cymbopogon citratus oil against aluminium-induced behavioral deficits and neuropathology in rats

Cymbopogon citratus is a tropical phytomedicinal plant that is widely known for its hypoglycemic, hypolipidemic, anxiolytic, sedative, antioxidative and anti-inflammatory properties. In this study, we have examined the neuroprotective effects of the essential oil (ESO) of Cymbopogon citratus, following aluminum chloride (AlCl₃)-induced neurotoxicity within the cerebellum of Wistar rats. A total of 40 adult male Wistar rats were assigned into five groups and treated orally as follows: A–phosphate-buffered saline (1 ml daily for 15 days); B–ESO (50 mg/kg daily for 15 days); C–AlCl₃ (100 mg/kg daily for 15 days); D–AlCl₃ then ESO (100 mg/kg AlCl₃ daily for 15 days followed by 50 mg/kg ESO daily for subsequent 15 days); E–ESO then AlCl₃ (50 mg/kg ESO daily for 15 days followed by 100 mg/kg AlCl₃ daily for following 15 days). To address our questions, we observed the locomotion and exploratory behavior of the rats in the open field apparatus and subsequently evaluated cerebellar oxidative redox parameters, neural bioenergetics, acetylcholinesterase levels, transferrin receptor protein, and total protein profiles by biochemical assays. Furthermore, we investigated cerebellar histomorphology and Nissl profile by H&E and Cresyl violet Nissl staining procedures. ESO treatment markedly attenuated deficits in exploratory activities and rearing behavior following AlCl₃ toxicity, indicating its anxiolytic potentials. Additionally, AlCl₃ evokedincrease in malondialdehyde and nitric oxide levels, as well as repressed cerebellar catalase, glutathione peroxidase, and superoxide dismutase profiles were normalised to baseline levels by ESO treatment. Treatment with ESO, ergo, exhibits substantial neuroprotective and modulatory potentials in response to AlCl₃ toxicity.

Assessment of Tetrabromobisphenol and Hexabromocyclododecanes exposure and risk characterization using occurrence data in foods

Tetrabromobisphenol A (TBBPA) and Hexabromocyclododecanes (HBCDs) are two of the most used BFRs and they have cumulated in the environment. TBBPA and HBCDs in food were determined and their risks were assessed. The analytical method used was validated in different food categories, and the performance parameters were acceptable based on the criteria of AOAC. Fish and cephalopods were contaminated with TBBPA higher than other foods, and fish contained higher levels of HBCDs than other foods. α-HBCD was the predominant diastereomer in fish and meat and had strong correlations with HBCDs in fish and cephalopods. HBCDs accumulated easier than TBBPA in food. People were exposed to TBBPA from 0.125 ng kg^-1 b.w. day^-1 to 0.284 ng kg^-1 b.w. day^-1 and HBCDs from 0.353 ng kg^-1 b.w. day^-1 to 1.006 ng kg^-1 b.w. day^-1 via food and air. Food mainly contributed to exposure to TBBPA and HBCDs and vegetables were the main contributors for exposure to TBBPA and HBCDs in food. MOEs for the whole population were over 100, and the risks of exposure to TBBPA and HBCDs from food and the environment were of low concern to public health.

The HBCDs biodegradation using a Pseudomonas strain and its application in soil phytoremediation

Hexabromocyclododecanes (HBCDs) are the second-most widely used brominated flame retardants. They cause inappropriate antidiuretic hormone syndrome and can induce cancer. However, little information is available about bacterial degradation of HBCDs. In this study, HBCDs (α-, β- and γ-HBCD) degrading strain Pseudomonas aeruginosa HS9 was isolated, identified, and characterized. The strain HS9 could remove 69% (± 0.05%) of 1.7 mg/L HBCDs in 14 days. Based on identification of metabolites, this bacterium could oxidize HBCDs by two pathways. In the first, HBCDs are sequentially debromized to tetrabromocyclododecene, dibromocyclododecadiene, and then debromized once more to cis, trans, trans-1, 5, 9-cyclododecatriene (CDT). After that, CDT is then oxidized to 1,2-epoxy-5,9-cyclododecadiene. The second identified pathway is a simultaneous debrominating and hydroxylating process based on the detection of 2,5,6,9,10-pentabromocyclododecanols, which were newly identified. The strain's effects on plant-maize growth were tested and bioremediation evaluation trials were performed. The addition of strain HS9 could decrease HBCDs of 4.08 mg/g (87.6% removed) and 0.1 mg/g (25% removed) in soil and plants, respectively. Microbial diversity analysis shows that the addition of strain HS9 can promote the abundance of plant-beneficial bacteria, such as Methylobacillus, Nitrosomonas, Plancoccus, Bacillus, and Rhodococcus. The results provide insights for the bioremediation of HBCDs-contaminated soils.

In vitro screening and toxic mechanism exploring of leading components with potential hepatotoxicity of Herba Epimedii extracts

Herba Epimedii is a famous Chinese edible herb, and due to its potential hepatotoxic effects, the safety associated with this herb has attracted a great deal of attention. In this study, the components of four types of the Herba Epimedii extracts were identified by HPLC-MS/MS. Among these components, 11 components that were present in all four extracts and could be obtained as reference substances were evaluated for their ability of cytotoxicity in HL-7702 and HepG2 cells, resulting in the identification of icarisid I and sagittatoside A as the most relevant with respect to the toxicity of the extracts. The targeted toxicological effects were further investigated using a series of correlated biological indicators to elucidate potentially hepatotoxic mechanisms. The results showed that the extracts and the selected compounds had varying degrees of influence on the leakage of ALT, AST and LDH; the activity of SOD, GSH and MDA; the increase in intercellular ROS; and the decrease in MMP. Among the tested substances, the ethanol extracts exhibited stronger hepatotoxicity, with icarisid I and sagittatoside A correlating with this toxic effect, and the hepatoxic mechanisms of which may be associated with damaged cell structure, increased oxidative stress and induction of apoptosis.

Distribution and diastereoisomeric profiles of hexabromocyclododecanes in air, water, soil, and sediment samples in South Korea: Application of an optimized analytical method

In this study, the levels and distribution patterns of HBCD diastereoisomers in air, water, soil, and sediment samples in South Korea were investigated after optimizing the UPLC-MS/MS analytical process. Extraction and cleanup efficiencies were tested using several different extraction solvents and adsorbents. Dichloromethane was selected as the base extraction solvent, and multi-layer silica gel (MSG) and MSG-alumina columns were selected for the removal of HBCDs from complex environmental matrices. The concentration of Ʃ₃ HBCDs was 22-133 pg/m³, 10-128 ng/g, 0.2-151 ng/L, and 0.5-552 ng/g dw for air, soil, water, and sediment samples, respectively. Relatively higher concentrations of Ʃ₃ HBCDs were observed at stations adjacent to industrial facilities (e.g., rubber and plastic, textile, chemical, fabricated metal, and wholesale trade factories) associated with the use of commercial HBCDs. The proportion of γ-HBCD in the soil (48.3-86.2%) and sediment (54.2-78.1%, except for one station) samples was similar to that found in technical and commercial HBCDs. In contrast, α-HBCD (52.3-71.2%) was dominant in all air samples, while the water samples displayed no clear trend in their diastereoisomer profiles. As the first nationwide report on HBCD diastereoisomers in the environment, this study demonstrates that most environmental compartments in South Korea are moderately contaminated with HBCDs.

Diastereoisomer-specific neurotoxicity of hexabromocyclododecane in human SH-SY5Y neuroblastoma cells

Hexabromocyclododecane (HBCD) is a widely applied brominated flame retardant (BFR) and is regarded as a persistent organic pollutant. It has been found in human tissues and has the potential to cause neurological disorders. However, our understanding of HBCD neurotoxicity at the diastereoisomer level remains lacking. Here, we investigated the neurotoxicity of three HBCD diastereoisomers, i.e., α-, β-, and γ-HBCD, in SH-SY5Y human neuroblastoma cells. Results showed that the HBCD diastereoisomers decreased cell viability, increased lactate dehydrogenase (LDH) release, and impaired cytoskeleton development. Typical morphological features and apoptosis rates showed that the HBCD diastereoisomers induced SH-SY5Y cell apoptosis. The expression levels of several cell apoptosis-related genes and proteins, including Bax, caspase-3, caspase-9, cytochrome c, Bcl-2, and X-linked inhibitor of apoptosis (XIAP), as well as the cell cycle arrest, DNA damage, adenosine triphosphate (ATP) consumption, reactive oxygen species (ROS) levels, and intracellular calcium ion (Ca²⁺) levels, were examined. Results showed that the HBCD diastereoisomer neurotoxicity was ranked β-HBCD > γ-HBCD > α-HBCD. The cell apoptosis and caspase expression levels of the three HBCD diastereoisomers followed the same order, suggesting that caspase-dependent apoptosis may be one mechanism responsible for the structure-selective HBCD diastereoisomer neurotoxicity. The levels of intracellular Ca²⁺ and ROS increased significantly. The ROS levels were ordered β-HBCD > γ-HBCD > α-HBCD, whereas those of intracellular Ca²⁺ were γ-HBCD > β-HBCD > α-HBCD. Thus, ROS may be a key factor regulating the neurotoxicity of HBCD diastereoisomers. To the best of our knowledge, this is the first study to report on the diastereoisomer-specific toxicity of HBCD in human neural cells and on the possible mechanisms responsible for the selective neurotoxicity of HBCD diastereoisomers.

Hepatic transcriptional dose-response analysis of male and female Fischer rats exposed to hexabromocyclododecane

Hexabromocyclododecane (HBCD) is a brominated flame retardant found in the environment and human tissues. The toxicological effects of HBCD exposure are not clearly understood. We employed whole-genome RNA-sequencing on liver samples from male and female Fischer rats exposed to 0, 250, 1250, and 5000 mg technical mixture of HBCD/kg diet for 28 days to gain further insight into HBCD toxicity. HBCD altered 428 and 250 gene transcripts in males and females, respectively, which were involved in metabolism of xenobiotics, oxidative stress, immune response, metabolism of glucose and lipids, circadian regulation, cell cycle, fibrotic activity, and hormonal balance. Signature analysis supported that HBCD operates through the constitutive androstane and pregnane X receptors. The median transcriptomic benchmark dose (BMD) for the lowest statistically significant pathway was within 1.5-fold of the BMD for increased liver weight, while the BMD for the lowest pathway with at least three modeled genes (minimum 5% of pathway) was similar to the lowest apical endpoint BMD. The results show how transcriptional analyses can inform mechanisms underlying chemical toxicity and the doses at which potentially adverse effects occur. This experiment is part of a larger study exploring the use of toxicogenomics and high-throughput screening for human health risk assessment.

Hexabromocyclododecane: concentrations and isomer profiles from sources to environmental sinks

Concentrations and isomer compositions of hexabromocyclododecane (HBCD) were measured in six matrices in the Czech Republic (HBCD technical mixture; consumer products; indoor and outdoor air at industrial, urban and background locations; soils; and sediments) to provide insight into changes in concentrations and isomer profiles between environmental sources and environmental sinks. A distinct gradient of air concentrations was observed, from 1600 ng/m³ in the industrial area to < 10 pg/m³ in urban and background air. Isomer profiles also showed a distinct gradient in air, from 95% γ-HBCD in industrial air to 40% γ-HBCD in background air, suggesting the influence of differential atmospheric transport and phototransformation of γ- to α-HBCD. Concentrations and isomer compositions in consumer products were highly variable and indicated differences between products with intentional addition of HBCD as a flame retardant versus those with HBCD as an impurity, e.g., from recycled plastic. Understanding the isomer-specific environmental distributions and processes remains important for risk assessment and toxicology, considering the continued use of HBCD and the isomer-specific differences in uptake, metabolism, and toxicity, and further, demonstrates the utility of isomer profiles to better understand environmental processes of HBCDs.

Enantioselectivity in biotransformation and bioaccumulation processes of typical chiral contaminants

Chirality is a critical topic in the medicinal and agrochemical fields. One quarter of all agrochemicals was chiral in 1996, and this proportion has increased remarkably with the introduction of new compounds over time. Despite scientists have made great efforts to probe the enantiomeric selectivity of chiral chemicals in the environment since early 1990s, the different behaviours of individual enantiomers in biologically mediated processes are still unclear. In the present review, we highlight state-of-the-knowledge on the stereoselective biotransformation and accumulation of chiral contaminants in organisms ranging from invertebrates to humans. Chiral insecticides, fungicides, and herbicides, polychlorinated biphenyls (PCBs), pharmaceuticals, flame retardants hexabromocyclododecane (HBCD), and perfluorooctane sulfonate (PFOS) are all included in the target compounds. Key findings included: a) Changes in the enantiomeric fractions in vitro and in vivo models revealed that enantioselectivity commonly occurs in biotransformation and bioaccumulation. b) Emerging contaminants have become more important in the field of enantioselectivity together with their metabolites in biological transformation process. c) Chiral signatures have also been regarded as powerful tools for tracking pollution sources when the contribution of precursor is unknown. Future studies are needed in order to understand not only preliminary enrichment results but also detailed molecular mechanisms in diverse models to comprehensively understand the behaviours of chiral compounds.

Taurine Alleviate Hexabromocyclododecane-Induced Cytotoxicity in PC12 Cells via Inhibiting Oxidative Stress

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant. Its adverse effects on brain had been observed. Taurine, a sulfur amino acid, take part in many brain physiological functions and exhibits protective effects on a variety of detrimental situations. In this paper, we explored the protections of taurine on cytotoxicity induced by HBCD in PC12 cells. PC12 cells were pretreated with taurine (1 mM, 3 mM and 9 mM) for 30 min before 10 μM HBCD treatment for 24 h. Then, the cell survival was assayed by the lactate dehydrogenase (LDH) release and trypan blue dyeing method. The formation of reactive oxygen species (ROS) and a collapse of mitochondrial membrane potential (MMP) were evaluated with a fluorescence microplate reader using the non-fluorescent probe 2'7'-dichlorofluorescin diacetate (DCFH-DA) and the fluorescent cationic dyestuff Rhodamine 123 (Rh 123), respectively. Further, the activity of many antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and the content of glutathione (GSH) were tested by kits. Our results displayed that taurine significantly decreased the cell death induced by HBCD, prevented ROS production and disruption of mitochondrial membrane potential, and reversed the decline of SOD, CAT, GPx activity and GSH content induced by HBCD. These results suggested that taurine could alleviate cytotoxicity induced by HBCD in PC12 cells through inhibition of oxidative stress.

Stereoisomer-Specific Trophodynamics of the Chiral Brominated Flame Retardants HBCD and TBECH in a Marine Food Web, with Implications for Human Exposure

Stereoisomers of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)-cyclohexane (TBECH) were determined in sediments and 30 marine species in a marine food web to investigate their trophic transfer. Lipid content was found to affect the bioaccumulation of ΣHBCD and ΣTBECH in these species. Elevated biomagnification of each diastereomer from prey species to marine mammals was observed. For HBCD, biota samples showed a shift from γ- to α-HBCD when compared with sediments and technical mixtures; trophic magnification potential of (-)-α- and (+)-α-HBCD were observed in the food web, with trophic magnification factors (TMFs) of 11.8 and 8.7, respectively. For TBECH, the relative abundance of γ- and δ-TBECH exhibited an increasing trend from abiotic matrices to biota samples; trophic magnification was observed for each diastereomer, with TMFs ranging from 1.9 to 3.5. The enantioselective bioaccumulation of the first eluting enantiomer of δ-TBECH in organisms at higher TLs was consistently observed across samples. This is the first report on the trophic transfer of TBECH in the food web. The estimated daily intake of HBCD for Hong Kong residents was approximately 16-times higher than that for the general population in China, and the health risk to local children was high, based on the relevant available reference dose.

The effect of zerovalent iron on the microbial degradation of hexabromocyclododecane

Hexabromocyclododecane (HBCD), a commonly used brominated flame retardant (BFR), has been listed as a persistent organic pollutant (POP). In order to remediate HBCD in the environment, the influence of microscale zerovalent iron (MZVI) on the HBCD degrading microcosm was evaluated. In the acclimated microcosm collected from river sediment, 49% of HBCD was initially removed through adsorption and then 30% of HBCD was biodegraded through non-debromination processes. In contrast to MZVI only, over 60% of HBCD was gradually degraded by MZVI through a debromination reaction. In the microcosm-MZVI combined system, the biodegradation ability of the microcosm was inhibited. The aqueous chemistry was changed by the addition of MZVI, which led to the alteration of microbial composition and biodegradation ability. These better understandings can facilitate an evaluation of the impact of MZVI on HBCD biodegradation when ZVI was used to remediate this BFR.

Biomagnification of Hexabromocyclododecane (HBCD) in a coastal ecosystem near a large producer in China: Human exposure implication through food web transfer

Hexabromocyclododecane (HBCD) is a widely used brominated flame retardant which is mainly produced in China. Many HBCD facilities are located at the coast and the released HBCD may enter into the coastal ecosystem. There is a risk that HBCD can transfer through the food web to the diet of local population. Therefore, the coastal organisms near one of the biggest HBCD facilities in China were investigated. Variation was observed for the bioaccumulation of HBCD between the detrital food chain and the grazing food chain. In the studied species, the mullet was most contaminated which may be caused by its feeding on detritus. At the same time, the transfer of HBCD along the food web was investigated, and HBCD was biomagnified from the prey to the predator in the grazing food chains. Among the three diastereoisomers, α-HBCD was biomagnified with increasing trophic levels in the food web while β- and γ-HBCD were not. To assess the human dietary exposure, the dietary intake of HBCD from seafood was estimated, and the estimated daily intake (EDI) was 5.22ng/kg/day for adults, and 16.39ng/kg/day for children. The EDI for local residents were tens of times higher than that for general population in China, but the risk through dietary intake was very low in terms of existing reference dose.

Temporal Changes and Stereoisomeric Compositions of 1,2,5,6,9,10-Hexabromocyclododecane and 1,2-Dibromo-4-(1,2-dibromoethyl)cyclohexane in Marine Mammals from the South China Sea

Stereoisomeric compositions of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) were investigated in the blubber of two species of marine mammals, finless porpoises ( Neophocaena phocaenoides) and Indo-Pacific humpback dolphins ( Sousa chinensis), from the South China Sea between 2005 and 2015. The concentrations of ΣHBCD in samples of porpoise ( n = 59) and dolphin ( n = 32) ranged from 97.2 to 6,260 ng/g lipid weight (lw) and from 447 to 45,800 ng/g lw, respectively, while those of ΣTBECH were both roughly 2 orders of magnitude lower. A significant increasing trend of ΣHBCD was found in dolphin blubber over the past decade. The diastereomeric profiles exhibited an absolute predominance of α-HBCD (mostly >90%), while the proportions of four TBECH diastereomers in the samples appeared similar. A preferential enrichment of the (-)-enantiomers of α-, β-, and γ-HBCD was found in most blubber samples. Interestingly, the body lengths of porpoises showed a significant negative correlation with the enantiomer fractions of α-HBCD. Significant racemic deviations were also observed for α-, γ-, and δ-TBECH enantiomeric pairs. This is the first report of the presence of TBECH enantiomers in the environment. The estimated hazard quotient indicates that there is a potential risk to dolphins due to HBCD exposure.

In vitro study on the joint hepatoxicity upon combined exposure of cadmium and BDE-209

Joint toxicity is an important issue during the risk assessment of environmental pollutants. Contamination of heavy metals and persistent organic pollutants (POPs) under the environmental and biological settings poses substantial health risk to humans. Although previous studies demonstrated the co-occurrence of cadmium and decabrominated diphenyl ether (BDE-209) in environmental mediums, food chains and even human body, their potentially joint toxicities remain elusive thus far. Our investigation here with respect to the hepatotoxicity in vitro clearly demonstrated that combined exposure of cadmium and BDE-209 aggravated the injuries in hepatocytes, which was evidenced by the additive effects on the induction of remarkable morphological alternations, LDH release, cell apoptosis and necrosis, impairment of mitochondrial activity and transmembrane potential. Enhanced ROS production was one of the mechanisms for cell apoptosis and death upon joint treatment. Additionally, more cadmium-treated cells underwent apoptosis than BDE-209-treated cells while more ROS was generated with BDE-209 treatment, indicating that other mechanisms might be involved in cadmium-induced apoptosis. Our results would be helpful for evaluating the joint-hepatotoxicity upon combined exposure of cadmium and BDE-209 as well as investigating the underlying mechanisms.

Fate and adverse effects of hexabromocyclododecane diastereoisomers (HBCDDs) in a soil-ryegrass pot system

This study explored the fate and adverse effects of 3 main hexabromocyclododecane diastereoisomers (α-, β-, and γ-HBCDDs) in a soil pot system planted with ryegrass (Lolium perenne L.) using a short-term (8 weeks) experiment. At the end of the experiment, soil urease activity in planted spiked soil increased and catalase activity decreased; while there was no obvious change in sucrase and peroxidase activities. HBCDDs mainly accumulated in the root of ryegrass, with root concentration factors (RCF) in the range of 1.46-4.43 and only a small part was transferred to the stem (SCF: 0.198-0.305) and leaf (LCF: 0.042-0.062). The concentration factors varied for different HBCDD diastereoisomers, being in the order of α- > β- > γ-HBCDD for all tissues, indicating preferential accumulation of α-HBCDD in ryegrass tissues. Moreover, the enantiomeric analysis revealed an enrichment of (+)-α-, (-)-β- and (+)-γ-HBCDD enantiomers in ryegrass tissues. β- and γ-HBCDDs (up to 1.90% and 4.11%, respectively) were transformed to aα-HBCDD in ryegrass, while no isomerization product from α-HBCDD was found. Hydroxylated HBCDDs metabolites, such as monoOHHBCDDs and diOHHBCDDs were found in ryegrass tissues for the first time.

Exposure to decabromodiphenyl ether (BDE-209) produces mitochondrial dysfunction in rat liver and cell death

Polybrominated diphenyl ethers (PBDE) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunctions, reproductive disorders, and hepatotoxicity. The widespread use of PBDE as flame retardants has culminated in daily exposure of humans and wildlife to these contaminants and resulted in their banned use. Thus assessment of the potential effects of each PBDE congener on living organisms has become cause for concern. The aim of this study was to (1) examine the effects of decabromodiphenyl ether (BDE)-209 on different functions of HepG2 cells and (2) investigate whether this congener is involved in mitochondrial toxicity. The use of multiple methods was employed to (i) study the influence of BDE-209 on mitochondrial permeability transition (MPT) process in mitochondria isolated from rat liver and (ii) determine the consequential cellular damage. Our results showed that BDE-209 induced matrix swelling related to MPT with 10 µM and ATP depletion with 0.1 µM. In addition, 0.5 μM BDE-209 reduced HepG2 cell viability, produced collapse of membrane potential, but increased levels of reactive oxygen species (ROS) after 48 h incubation. After 24 h with 5 μM treatment elevated levels of ROS, DNA fragmentation and cytochrome c release, accompanied by caspase 9 and caspase 3 activation was noted. Taken together, these results suggest that short-duration exposure (24 or 48 h) to 0.5 μM or 5 μM BDE-209 concentrations diminished HepG2 cell viability due to apoptosis associated with mitochondrial dysfunction.

Enantiomer-specific accumulation and depuration of α-hexabromocyclododecane (α-HBCDD) in chicken (Gallus gallus) as a tool to identify contamination sources

A LC-ESI(-)-HRMS method dedicated to the analysis of 6 HBCDD enantiomers at trace levels in animal matrices was developed, using a cellulose based stationary phase with a particle size of 2.5 μm. This method was applied to a sample set derived from a kinetic study of α-HBCDD previously conducted in fast- and slow-growing chickens (Gallus gallus domesticus, n = 49, plus controls), in order to study the enantiomer specific accumulation and depuration of α-HBCDD in various tissues. Regarding abdominal adipose tissue, muscle and liver, the average enantiomeric fractions of α-HBCDD (EF_α) for continuously exposed groups ranged between 0.434 and 0.467, with standard deviations below 0.014, showing a significant enrichment in (-)α enantiomer even accentuated for slow growing individuals during depuration with EF_α reduced by about 0.020. Similar trends were observed for pooled plasma. Then, EF_α of circulating plasma α-HBCDD appeared to closely reflect EF_α in storage tissues and liver, suggesting some equilibrium. The racemic elimination of α enantiomer in excreta during the contamination phase indicated that no preferential gastrointestinal absorption took place. By contrast, preferential excretion of (-)α-HBCDD from the circulating compartment to the intestinal lumen occurred during the depuration. Finally, the method was applied to samples collected in three chicken farms, selected for total HBCDD levels in muscle in the ng/g range, as a tool to determine whether the contamination occurred ante- or post-mortem, according to the chiral signature. Ante-mortem contamination was hypothesised for 2 farms, with feed being excluded as contamination source.

Multidirectional inhibition of cortico-hippocampal neurodegeneration by kolaviron treatment in rats

Earliest signs of neurodegenerative cascades in the course of Alzheimer's disease (AD) are seen within the prefrontal cortex (PFC) and hippocampus, with pathological evidences in both cortical structures correlating with manifestation of behavioural and cognitive deficits. Despite the enormous problems associated with AD's clinical manifestations in sufferers, therapeutic advances for the disorder are still very limited. Therefore, this study examined cortico-hippocampal microstructures in models of AD, and evaluated the possible beneficial roles of kolaviron (Kv)-a biflavonoid complex in rats. Nine groups of rats were orally exposed to sodium azide (NaN₃) or aluminium chloride (AlCl₃) solely or in different combinations with Kv. Sequel to sacrifice and transcardial perfusion (using buffered saline then 4% paraformaldehyde), PFC and hippocampal tissues were harvested and processed for: spectrophotometric assays of oxidative stress and neuronal bioenergetics parameters, histological demonstration of cytoarchitecture and immunohistochemical evaluation of astrocytes and neuronal cytoskeleton. Results showed alterations in mitochondrial functions, which led to compromised neuronal antioxidant system, dysfunctional neural bioenergetics, hypertrophic astrogliosis, cytoskeletal dysregulation and neuronal death within the PFC and hippocampus. These degenerative events were associated with NaN₃ and AlCl₃ toxicity in rats. Furthermore, Kv inhibited cortico-hippocampal degeneration through multiple mechanisms that primarily involved halting of biochemical cascades that activate proteases which destroy molecules expedient for cell survival, and others that mediate a program of cell suicide in neuronal apoptosis. In conclusion, Kv showed important neuroprotective roles within cortico-hippocampal cells through multiple mechanisms, and particularly has prominent prophylactic activity than regenerative potentials.

Matrix-specific distribution and diastereomeric profiles of hexabromocyclododecane (HBCD) in a multimedia environment: Air, soil, sludge, sediment, and fish

Hexabromocyclododecane (HBCD) contamination and its diastereomeric profile were investigated in a multi-media environment along a river at the local scale in air, soil, sludge, sediment, and fish samples. The spatial distribution of HBCD in each matrix showed a different result. The highest concentrations of HBCD in air and soil were detected near a general industrial complex; in the sediment and sludge samples, they were detected in the down-stream region (i.e., urban area). Each matrix showed the specific distribution patterns of HBCD diastereomers, suggesting continuous inputs of contaminants, different physicochemical properties, or isomerizations. The particle phases in air, sludge, and fish matrices were dominated by α-HBCD, owing to HBCD's various isomerization processes and different degradation rate in the environment, and metabolic capabilities of the fish; in contrast, the sediment and soil matrices were dominated by γ-HBCD because of the major composition of the technical mixtures and the strong adsorption onto solid particles. Based on these results, the prevalent and matrix-specific distribution of HBCD diastereomers suggested that more careful consideration should be given to the characteristics of the matrices and their effects on the potential influence of HBCD at the diastereomeric level.

Spatial and temporal distributions of hexabromocyclododecanes in the vicinity of an expanded polystyrene material manufacturing plant in Tianjin, China

To investigate the environmental fate of 3 main hexabromocyclododecane diastereoisomers (α-, β-, and γ-HBCDs), samples from various environmental media, including outdoor settled dust, soil, sediment, plant tissues (holly, cypress and pine) and marine species (shrimp, crab and fish) were obtained around an expanded polystyrene material manufacturing plant in Tianjin, China. The 3 main HBCD diastereoisomers were detected with the total concentrations ranging from 328 to 31,752 ng/g dry weight (dw), 2.91-1730 ng/g dw, 23.5-716 ng/g dw, 3.45-2494 ng/g dw, and 0.878-44.8 ng/g dw in the dust, soil, sediment, plant tissues, and marine species, respectively. This indicated that a point source of HBCDs could bring wide impact on its vicinal environment. A significant increasing trend of HBCDs concentrations was noted, as indicated by 12.9-41.6% of increasing rates in total concentrations of HBCDs at four sediment sites in the past five years. The diastereoisomer profiles were sorted into 3 groups: dust, soil and sediment, which had no statistical difference from commercial EPS-products (p > 0.05); plant tissues, which showed a moderate increase of α-isomer (22.9 ± 3.3%); and marine species, which were dominated by α-isomer (62.6 ± 2.8%). For α- and β-isomers, the results of enantiomeric analysis showed a preferential accumulation of the (+)-enantiomer in part of plant tissues and all marine organisms (p < 0.05). However, there was no enantioselectivity of the 3 isomers in dust, soil, and sediment samples (p > 0.05). Besides, marine food web magnification is observed for HBCDs, with trophic magnification factors close to 2. The daily intakes of HBCDs were estimated to be 0.058-5.84 ng/kg-bw/day for local residents through dust and soil ingestion and 0.048-8.43 ng/kg-bw/day for Tianjin citizens through seafood consumption.

Enantioselective Analytical- and Preparative-Scale Separation of Hexabromocyclododecane Stereoisomers Using Packed Column Supercritical Fluid Chromatography

Hexabromocyclododecane (HBCDD) is an additive brominated flame retardant which has been listed in Annex A of the Stockholm Convention for elimination of production and use. It has been reported to persist in the environment and has the potential for enantiomer-specific degradation, accumulation, or both, making enantioselective analyses increasingly important. The six main stereoisomers of technical HBCDD (i.e., the (+) and (−) enantiomers of α-, β-, and γ-HBCDD) were separated and isolated for the first time using enantioselective packed column supercritical fluid chromatography (pSFC) separation methods on a preparative scale. Characterization was completed using published chiral liquid chromatography (LC) methods and elution profiles, as well as X-ray crystallography, and the isolated fractions were definitively identified. Additionally, the resolution of the enantiomers, along with two minor components of the technical product (δ- and ε-HBCDD), was investigated on an analytical scale using both LC and pSFC separation techniques, and changes in elution order were highlighted. Baseline separation of all HBCDD enantiomers was achieved by pSFC on an analytical scale using a cellulose-based column. The described method emphasizes the potential associated with pSFC as a green method of isolating and analyzing environmental contaminants of concern.

Impacts of loach bioturbation on the selective bioaccumulation of HBCDD diastereoisomers and enantiomers by mirror carp in a microcosm

To assess the impacts of bioturbation at the water-sediment interface on the bioaccumulation of hexabromocyclododecane diastereoisomers (HBCDDs) by pelagic organisms and the bioisomerization and enantioselectivity therein, we built microcosms containing water, mirror carp (Cyprinus carpio), and sediment. The microcosms were sorted into two groups, with or without loach (Misgurnus anguillicaudatus) living at the water-sediment interface. A 50-d accumulation test was conducted by spiking the microcosms with the three main HBCDD diastereoisomers (α-, β-, and γ-HBCDDs) separately. The HBCDDs were mainly associated with the sediment. The dissolved organic matter and suspended particulate matter content increased due to loach bioturbation, which promoted the release of sediment-associated HBCDDs and led to enhanced HBCDD bioaccumulation in the carp. Isomerization from β- and γ-HBCDD to α-HBCDD occurred in the carp, and the amounts of isomerization did not increase proportionally with increasing bioaccumulation. Moreover, the enantioselectivity of the HBCDD diastereoisomers showed species-specific differences between mirror carp and loach, and no significant change in the enantioselectivity in the carp was observed in the presence of loach.

In vitro study on the biotransformation and cytotoxicity of three hexabromocyclododecane diastereoisomers in liver cells

In order to clarify the cytotoxicity of hexabromocyclododecane (HBCD) diastereoisomers, and to investigate the correlation of cytotoxicity and biotransformation of HBCDs, the immortalized human liver cells L02 and human hepatoma cells HepG2 were exposed to individual HBCD diastereoisomer (α-, β- and γ-HBCD). Cytotoxicity was assayed in terms of cell viability, reactive oxygen species (ROS) level and DNA damage. Metabolic rate, bioisomerization and enantiomer fractions were analyzed using the liquid chromatograph coupled to triple quadrupole mass spectrometer (LC-MS/MS). The α-, β- and γ-HBCD all had cytotoxicity in L02 and HepG2 cells with the toxicity order β-HBCD ≥ γ-HBCD > α-HBCD according to the results of proliferation assay. The cytotoxicity mechanism between the two cells seemed different: a) the stability of intracellular redox state plays an important role in inducing cell toxicity in HepG2 cells. b) DNA damage status is central to inhibit proliferation in L02 cells. The metabolic capability of HepG2 was superior to L02 for HBCD diastereoisomers, which may explain the greater toxicity of HBCDs in HepG2 cells. The bioisomerization and enantiomer enrichment were also detected in this study, although the results were inconsistent with other reports, which might result from species-specific differences in HBCDs metabolism or experimental conditions. The cytotoxicity and metabolic mechanism of individual enantiomers must be further investigated to evaluate the health risks of HBCDs.

Evaluation of Common Use Brominated Flame Retardant (BFR) Toxicity Using a Zebrafish Embryo Model

Brominated flame retardants (BFRs) are used to reduce the flammability of plastics, textiles, and electronics. BFRs vary in their chemical properties and structures, and it is expected that these differences alter their biological interactions and toxicity. Zebrafish were used as the model organism for assessing the toxicity of nine structurally-diverse BFRs. In addition to monitoring for overt toxicity, the rate of spontaneous movement, and acetylcholinesterase and glutathione-S-transferase (GST) activities were assessed following exposure. The toxicities of BFRs tested can be ranked by LC50 as tetrabromobisphenol A (TBBPA) < 4,4'-isopropylidenebis[2-(2,6-dibromophenoxyl)ethanol] (TBBPA-OHEE) < Pentabromochlorocyclohexane (PBCH) < 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) < hexabromocyclododecane (HBCD) < hexabromobenzene (HBB) < Tetrabromophthalic anhydride (PHT4). No adverse effect was observed in di(2-ethylhexyl) tetrabromophthalate (TBPH) or dibromoneopentyl glycol (DBNPG)-treated embryos. The rate of spontaneous movement was decreased in a concentration-dependent manner following exposure to four of the nine compounds. GST activity was elevated following treatment with PBCH, TBBPA, HBCD, and HBB. The results indicate that exposure to several BFRs may activate an antioxidant response and alter behavior during early development. Some of the BFRs, such as TBBPA and TBBPA-OHEE, induced adverse effects at concentrations lower than chemicals that are currently banned. These results suggest that zebrafish are sensitive to exposure to BFRs and can be used as a comparative screening model, as well as to determine alterations in behavior following exposure and probe mechanisms of action.

The "adaptive responses" of low concentrations of HBCD in L02 cells and the underlying molecular mechanisms

This study aimed to investigate the "adaptive responses" of hexabromocyclododecanes (HBCD) at environmentally relevant concentrations in human hepatocytes L02. L02 cells were pre-treated with low concentrations of HBCD (10(-13)-10(-11) M), followed by treatment with high concentrations of HBCD, α-hexachlorocyclohexane (α-HCH), polychlorinated biphenyls (PCBs), or polybrominated diphenyl ether-47 (BDE47). The results showed that the pre-treatment with low concentrations of HBCD induced "adaptive responses" to high concentrations of HBCD/α-HCH exposure (but not to PCBs and BDE47), as evidenced by attenuation of survival inhibition, reactive oxygen species (ROS) over-production, and deoxyribonucleic acid (DNA) damage induction. The "adaptive responses" induced by low concentrations of HBCD, which depended on the activation of the phosphatidylinositide 3-kinase/protein kinase B (PI3K/Akt) pathway, reduced the phosphorylation of adenosine monophosphate-activated kinase (AMPK) and enhanced the phosphorylation of p38 mitogen-activated protein kinases (p38 MAPK). The observations were further confirmed by the experiments with inhibitors. Moreover, the evaluation on the changes of metabolic enzymes revealed that HBCD and α-HCH shared a similar pattern of cytochrome P450 induction (CYP2B6), which was different from those of PCBs and BDE47 (CYP1A1 and CYP2B6). These results indicated that low concentrations of HBCD could induce "adaptive responses" to the subsequent treatment with high concentrations of HBCD/α-HCH in L02 cells, which was associated with the PI3K/Akt pathway, and AMPK and p38 MAPK signaling. The "adaptive responses" seemed to be dependent on the types of chemicals in terms of the metabolic patterns and chemical structures.

Hexabromocyclododecane (HBCD) induced changes in the liver proteome of eu- and hypothyroid female rats

Hexabromocyclododecane (HBCD) is a brominated flame retardant known for its low acute toxicity as observed in animal experiments. However, HBCD exposure can affect liver functioning and thyroid hormone (TH) status. As exact mechanisms are unknown and only limited toxicological data exists, a gel-based proteomic approach was undertaken. In a eu- and hypothyroid female rat model, rats were exposed to 3 and 30 mg/kg bw/day HBCD for 7 days via their diet, and exposure was related to a range of canonical endpoints (hormone status, body weight) available for these animals. Alterations in the liver proteome under HBCD exposure were determined in comparison with patterns of control animals, for both thyroid states. This revealed significantly changed abundance of proteins involved in metabolic processes (gluconeogenesis/glycolysis, amino acid metabolism, lipid metabolism), but also in oxidative stress responses, in both euthyroid and hypothyroid rats. The results provide a more detailed picture on the mechanisms involved in these alterations, e.g. at the protein level changes of the proposed influence of HBCD on the lipid metabolism. Present results show that proteomic approaches can provide further mechanistic insights in toxicological studies.

Diastereoisomer-specific effects of hexabromocyclododecanes on hepatic aryl hydrocarbon receptors and cytochrome P450s in zebrafish (Danio rerio)

In order to elucidate the mechanism for diastereoisomer-specific toxicity and metabolism of hexabromocyclododecanes (HBCDs) in biota, zebrafish (Danio rerio) were exposed to different concentrations of individual HBCD diastereoisomers (α-, β- and γ-HBCD) in water for 7 and 21d. We examined the gene expression of aryl hydrocarbon receptor (AHR) and cytochrome P450 (CYP), as well as ethoxyresorufin-O-deethylase (EROD) activity in zebrafish livers. Exposure to different HBCD diastereoisomers caused different expression of AHRs in zebrafish livers. For instance, 10 and 100μgL(-1) of α- and β-HBCD up-regulated the expressions of ahr1a and ahr1b in zebrafish liver, whereas 10 and 100μgL(-)(1) of γ-HBCD down-regulated them after 7d exposure. α-HBCD showed the most significant up-regulation of ahr1a and ahr1b expression, whereas γ-HBCD showed the most significant down-regulation of their expression among three HBCD diastereoisomers. Moreover, HBCDs could affect the expression of CYP1s as well as EROD activity in a gene-specific and diastereoisomer-specific manner. α-, β- and γ-HBCD inhibited cyp1a expression but enhanced the expression of cyp1b1 and cyp1c1. α-, β- and γ-HBCD showed different degrees of effect on the same CYP1 gene in a concentration-dependent way. The different effects of HBCD diastereoisomers on these genes we examined and EROD activity not only indicate diastereoisomer-specific toxic effect, but also in turn explain diastereoisomer-specific accumulation of HBCDs in zebrafish.

Review of hexabromocyclododecane (HBCD) with a focus on legislation and recent publications concerning toxicokinetics and -dynamics

In this paper, we review recent publications regarding the toxicokinetics and -dynamics of the flame retardant Hexabromocyclododecane (HBCD). HBCD has recently been listed as a persistent organic pollutant, which therefore influenced the legislation concerning its manufacturing and formulation. However, under specific circumstances it may still be used until 2024. Early toxicity studies have only focussed on HBCD itself, which is a mixture of different isomers with different physical and toxicological characteristics. Here we take a more differentiated look at the three diastereomers α-, β- and γ-HBCD. We also address the different enantiomers to give an overview of the toxicity of HBCD to identify present gaps in our knowledge about this chemical, especially with respect to its possible formulation until 2024.

Upregulation of glycolytic enzymes, mitochondrial dysfunction and increased cytotoxicity in glial cells treated with Alzheimer's disease plasma

Alzheimer's disease (AD) is a neurodegenerative disorder associated with increased oxidative stress and neuroinflammation. Markers of increased protein, lipid and nucleic acid oxidation and reduced activities of antioxidant enzymes have been reported in AD plasma. Amyloid plaques in the AD brain elicit a range of reactive inflammatory responses including complement activation and acute phase reactions, which may also be reflected in plasma. Previous studies have shown that human AD plasma may be cytotoxic to cultured cells. We investigated the effect of pooled plasma (n = 20 each) from healthy controls, individuals with amnestic mild cognitive impairment (aMCI) and Alzheimer's disease (AD) on cultured microglial cells. AD plasma and was found to significantly decrease cell viability and increase glycolytic flux in microglia compared to plasma from healthy controls. This effect was prevented by the heat inactivation of complement. Proteomic methods and isobaric tags (iTRAQ) found the expression level of complement and other acute phase proteins to be altered in MCI and AD plasma and an upregulation of key enzymes involved in the glycolysis pathway in cells exposed to AD plasma. Altered expression levels of acute phase reactants in AD plasma may alter the energy metabolism of glia.

Antiproliferative and immunostimulatory activity of a protein from Pleurotus eryngii

BACKGROUND

Currently, the use of mushrooms as functional foods, nutraceuticals or phytopharmaceuticals source has risen. In contrast, the possible cellular cytotoxicity and immunostimulatory activity of Pleurotus eryngii (DC. ex Fr.) Quel protein (PEQP) is unknown. Here we report extraction, anti-tumorigenic and immunostimulatory activity of PEQP in vitro.

RESULTS

PEQP was extracted from the dried fruiting bodies of P. eryngii, purified and characterised. Its in vitro antiproliferative activity was then evaluated in human non-small cell lung cancer A549 (NSCLC), stomach adenocarcinoma BGC-823, hepatocellular carcinoma HepG2 and gastric carcinoma HGC-27 cell lines using conventional cancer drugs (paclitaxel, doxorubicin and mitomycin C) as positive controls. The protein fractions (PEQP 1, 2, 3 and 4) obtained inhibited tumour cell proliferation dose-dependently with fraction PEQP 2 having significant (P < 0.05) toxicity in all tumour cells. PEQP had no significant toxicity on normal liver Chang cells but their proliferation was significantly inhibited by mitomycin C. Moreover, PEQP stimulated the proliferation, lysosomal enzyme activity, pinocytosis, nitric oxide and hydrogen peroxide production of RAW 264.7 cell lines dose-dependently.

CONCLUSION

Based on these results, P. eryngii protein has a potential application in functional foods as a natural anti-tumour agent with immunostimulatory activity.

Immunopotentiation of Pleurotus eryngii (DC. ex Fr.) Quel

ETHNOPHARMACOLOGICAL RELEVANCE

Pleurotus eryngii (DC. ex Fr.) Quel has been collected from the wild, cultivated and used in traditional medicines to treat various disorders and diseases since antiquity. In traditional Chinese medicine, the powdered fruiting bodies of Pleurotus eryngii were used for immunostimulation, skin-care, wound-healing, cancer and lumbago treatment. In the current study, we investigated the antiproliferative activity of Pleurotus eryngii powder on A549, BGC-823, HepG2 and HGC-27 cancer cells and its immunomodulating activity on macrophage, RAW 264.7 cells based on its active compound.

MATERIALS AND METHODS

A novel bioactive protein (PEP) was extracted from Pleurotus eryngii fruiting bodies powder and purified on DEAE-52, CM-52 and Superdex 75 column chromatographies using an ÄKTA purifier. Its cytotoxicity on A549, BGC-823, HepG2, HGC-27 and RAW 267.4 cell lines was then evaluated using MTT, alamar blue (AB), trypan blue (TB), neutral red (NR), lactate dehydrogenase (LDH), Annexin V FITC/PI and morphological change assays. Moreover, lysosomal enzyme activity, pinocytosis, nitric oxide (NO) and hydrogen peroxide (H₂O₂) production assays were used to examine immunomostimulatory activity of PEP on RAW 267.4 cells.

RESULTS

Based on high performance gel permeation chromatography (HPGPC), Fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR) analyses, the isolated protein (PEP) had a molecular weight of 63 kDa, a secondary (α-helical) structure and was mainly composed of arginine, serine and glycine. PEP significantly (P<0.05) inhibited A549, BGC-823, HepG2 and HGC-27 tumor cells proliferation dose-dependently with an IC₅₀ range of 36.5 ± 0.84 to 229.0 ± 1.24 µg/ml. Contrarily, PEP stimulated the proliferation of macrophages.

CONCLUSION

Pleurotus eryngii fruiting bodies powder has a potential application as a natural antitumor agent with immunomodulatory activity, proposedly, by targeting the lysosomes of cancerous cells and stimulating macrophage-mediated immune responses.

Hexabromocyclododecanes in limnic and marine organisms and terrestrial plants from Tianjin, China: diastereomer- and enantiomer-specific profiles, biomagnification, and human exposure

To interpret the distribution of hexabromocyclododecanes (HBCDs) in various organisms, we measured the concentrations and diastereomer and enantiomer profiles of HBCDs in 21 different species of limnic and marine cohorts from Tianjin, China. The concentration ranges of HBCDs in limnic and marine organisms were 64.3-1111 ng g(-1) lw and 85.5-989 ng g(-1) lw, respectively. Living habitat and feeding habits had important impacts on HBCD diastereomer distribution. Most of the species appeared to preferentially select (+)-α-, (-)-β- and (-)-γ-HBCD. There is a tendency that the total and α-HBCDs were magnified as trophic level increased with trophic magnification factors (TMFs) around 2. The concentrations of HBCDs in the limnic and marine fishes were highest in the liver, followed by the gill, skin, and muscle. In terrestrial plants, the highest concentrations of HBCDs were observed in the leaf, followed by the root and the rhizosphere soil. Plants showed enantioselectivity for HBCD enantiomers, which varied with plant species and organs (leaf vs. root) of the same plant. Higher estimated daily intakes (EDIs) of HBCDs were observed from fish than from wheat.