Subacute oral toxicity of BDE-15, CDE-15, and HODE-15 in ICR male mice: assessing effects on hepatic oxidative stress and metals status and ascertaining the protective role of vitamin E

Alpha-Tocopherol Levels in Patients With Dentigerous Cysts: A Cross-Sectional Study

Background Dentigerous cysts (DC) form due to fluid accumulation between the crown of the tooth and the reduced enamel epithelium. Due to the diverse clinical characteristics, such as ambiguity concerning their biological origins and the significance of timely diagnosis and detection of these lesions, researchers are presently motivated to undertake further investigations. The aim of the present study was to assess the amount of serum alpha-tocopherol in patients with DC and compare it with that of normal, healthy individuals. Methods A total sample size of n=34 was included in the current study. Group A, designated as the control group, comprised 17 randomly selected healthy subjects, while Group B, the DC diagnostic group, consisted of 17 patients. Blood samples were collected, and the concentration of vitamin E or alpha-tocopherol was evaluated and expressed in mg/mL. Results Compared to the mean vitamin E level in healthy controls (12.08 ± 1.92 mg/mL), patients with DC showed a statistically significant (p<0.0001) reduction in mean vitamin E levels (5.29 ± 1.01 mg/mL). Conclusion Patients with DC have lower levels of vitamin E than healthy individuals. The reduced concentration of vitamin E can have a role in the extension of cystic volume and thus have an impact on the aggressiveness of pathologic lesions. The therapeutic benefits of vitamin E supplementation in reducing the aggressiveness of DC should be evaluated in future research.

A prioritization strategy for functional alternatives to bisphenol A in food contact materials

The use of bisphenol A (BPA), a substance of very high concern, is proposed to be banned in food contact materials (FCMs) in the European Union. To prevent regrettable substitution of BPA by alternatives with similar or unknown hazardous properties, it is of importance to gain the relevant toxicological information on potential BPA alternative substances and monitor them adequately. We created an inventory of over 300 substances mentioned as potential BPA alternatives in regulatory reports and scientific literature. This study presents a prioritization strategy to identify substances that may be used as an alternative to BPA in FCMs. We prioritized 20 potential BPA alternatives of which 10 are less familiar. We subsequently reviewed the available information on the 10 prioritized less familiar substances regarding hazard profiles and migration potential obtained from scientific literature and in silico screening tools to identify a possible risk of the substances. Major data gaps regarding the hazard profiles of the prioritized substances exist, although the scarce available data give some indications on the possible hazard for some of the substances (like bisphenol TMC, 4,4-dihydroxybenzophenone, and tetrachlorobisphenol A). In addition, very little is known about the actual use and exposure to these substances. More toxicological research and monitoring of these substances in FCMs are, therefore, required to avoid regrettable substitution of BPA in FCM.

Occurrence, physicochemical properties and environmental behavior of polychlorinated dibenzothiophenes: A comprehensive review and future perspectives

Polychlorinated dibenzothiophenes (PCDTs) are a form of emerging pollutant that has attracted great attention due to their structural resemblance to dioxins, which cast detrimental influence on the ecosystem and human health. This review shows the current status of research on PCDTs, focusing on their environmental occurrence, physicochemical properties, environmental behavior, and toxicity. Studies have suggested that the steps leading to the formation of PCDTs resemble those generating polychlorinated dibenzo-p-dioxin/dibenzofurans (PCDD/Fs), indicating their probable origin from the same sources. Furthermore, they may undergo a dechlorination process as a result of their photodegradation in the environment and metabolic reaction occurring within organisms, which could result in the conversion of these substances into additional pollutants like dibenzothiophene. PCDTs exist widely in the environmental media and have high logKOW values (>4.0), indicating their tendency to bioaccumulate. Moreover, the prediction results of EPI (Estimation Program Interface) Suite demonstrated a strong accumulation capacity for tetra-CDTs in fish compared to other chlorinated PCDTs. The biotransformation half-life of PCDTs would prolong with an increasing number of substituted Cl atoms in fish. A limited number of studies have also suggested that PCDTs can cause damage to the liver and immune system in living organisms, and the toxicity of PCDTs depends on the number and position of substituted Cl atoms. Future studies should be conducted on processes causing PCDT toxicity as well as their behavior and fate in actual 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.

Advanced electrocatalytic redox processes for environmental remediation of halogenated organic water pollutants

Halogenated organic compounds are widespread, and decades of heavy use have resulted in global bioaccumulation and contamination of the environment, including water sources. Here, we introduce the most common halogenated organic water pollutants, their classification by type of halogen (fluorine, chlorine, or bromine), important policies and regulations, main applications, and environmental and human health risks. Remediation techniques are outlined with particular emphasis on carbon-halogen bond strengths. Aqueous advanced redox processes are discussed, highlighting mechanistic details, including electrochemical oxidations and reductions of the water-oxygen system, and thermodynamic potentials, protonation states, and lifetimes of radicals and reactive oxygen species in aqueous electrolytes at different pH conditions. The state of the art of aqueous advanced redox processes for brominated, chlorinated, and fluorinated organic compounds is presented, along with reported mechanisms for aqueous destruction of select PFAS (per- and polyfluoroalkyl substances). Future research directions for aqueous electrocatalytic destruction of organohalogens are identified, emphasizing the crucial need for developing a quantitative mechanistic understanding of degradation pathways, the improvement of analytical detection methods for organohalogens and transient species during advanced redox processes, and the development of new catalysts and processes that are globally scalable.

Cadmium (Cd) and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) co-exposure induces acute kidney injury through oxidative stress and RIPK3-dependent necroptosis

Environmental pollution is complex, and co-exposure can accurately reflect the true environmental conditions that are important for assessment of human health. Cadmium (Cd) is a widespread toxicant that can cause acute kidney injury (AKI), while its combined effect with 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) is not fully understood. Thus, we used an in vivo model where C57BL/6J mice were treated with low dietary intake of Cd (5 mg/kg/day) and/or BDE-47 (1 mg/kg/day) for 28 days to examine AKI, and in vitro experiments to investigate the possible mechanism. Results showed that Cd or BDE-47 caused pathological kidney damage, accompanied by elevated urea nitrogen (BUN) and urinary creatinine, as well as increased interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and reduced IL-10 in kidney tissues. In vitro Cd or BDE-47 exposure decreased cell viability and induced cell swelling and blebbing of human embryonic kidney 293 (HEK-293) and renal tubular epithelial cell lines (HKCs), and changes in co-exposure was larger than that in Cd and BDE-47 treatment. Oxidative stress indicators of the reactive oxygen species (ROS) and malondialdehyde (MDA) were elevated, while the antioxidant superoxide dismutase (SOD) was decreased. Necrosis occurred with increased lactate dehydrogenase (LDH) release and propidium iodide (PI) staining, which was attenuated by the ROS scavenger N-acetyl-L-cysteine (NAC). Furthermore, necroptotic genes of receptor-interacting protein kinase-3 (RIPK3), classical mixed lineage kinase domain-like protein-dependent (MLKL), IL-1β and TNF-α were up-regulated, whereas RIPK1 was down-regulated, which was attenuated by the RIPK3 inhibitor GSK872. These findings demonstrate that Cd or BDE-47 alone produces kidney toxicities, and co-exposure poses an additive effect, resulting in AKI via inducing oxidative stress and regulating RIPK3-dependent necroptosis, which offers a further mechanistic understanding for kidney damage, and the combined effect of environmental pollutants should be noticed.

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.

A descriptive analysis of first trimester urinary concentrations of 14 bisphenol analogues in the MIREC Canadian pregnancy cohort

BACKGROUND

Concern over the health effects of BPA, particularly for the developing fetus, has led to an increasing use of bisphenol analogues in industrial and consumer products, which may be as hormonally active as BPA. Biomonitoring data for many bisphenol analogues, especially in pregnant populations, are limited.

METHODS

We measured concentrations of 14 bisphenol analogues in 1st trimester urine samples (n = 1851) from the Maternal-Infant Research on Environmental Chemicals (MIREC) Canadian pregnancy cohort (2008-2011). We examined patterns of exposure according to sociodemographic and sampling characteristics as well as occupation and frequency of consumption of canned fish within the previous 3 months.

RESULTS

BPA was detected in 89% of participants with a specific gravity standardized geometric mean concentration of 0.990 μg/L. Biphenol 4,4' (BP 4,4'), 4,4'-dihydroxydiphenyl ether (DHDPE), and bisphenol E (BPE) were detected in >97% of participants. Bisphenol F (BPF) and bisphenol S (BPS) were detected in >60% of participants. Specific gravity standardized geometric mean concentrations of these 5 compounds ranged from 0.024 to 0.564 μg/L. Nine bisphenol analogues were detected in <9% of participants. Concentrations of BP 4,4', DHDPE, and BPE were higher in younger women and those with higher pre-pregnancy BMI, lower household income, lower education, and among smokers. We found a similar pattern of differences in BPF for age, education, and smoking status while BPS similarly differed across categories of pre-pregnancy BMI. Participants who were unemployed or working in the service industry had higher molar sum of 7 bisphenol analogues than those working in healthcare, education, or an office setting. Canned fish consumption was not related to bisphenol analogue concentrations.

CONCLUSION

BP 4,4', DHDPE, BPE, BPF, and BPS were highly detected in 1st trimester urine samples in this large pan-Canadian pregnancy cohort. This suggests widespread exposure to these analogues around 2008-2011 and warrants further investigation into associations with health outcomes.

Bioaccumulation, Trophic Transfer, and Biotransformation of Polychlorinated Diphenyl Ethers in a Simulated Aquatic Food Chain

Polychlorinated diphenyl ethers (PCDEs) are detected in aquatic environments and demonstrate adverse effects in aquatic organisms. However, data regarding the environmental behavior of PCDEs in aquatic ecosystems are lacking. In the present study, a simulated aquatic food chain (Scenedesmus obliquus-Daphnia magna-Danio rerio) was constructed in a lab setting, and the bioaccumulation, trophic transfer, and biotransformation of 12 PCDE congeners were quantitatively investigated for the first time. The log-transformed bioaccumulation factors (BCFs) of PCDEs in S. obliquus, D. magna, and D. rerio were in the range of 2.94-3.77, 3.29-4.03, and 2.42-2.89 L/kg w.w., respectively, indicating the species-specific bioaccumulation of PCDE congeners. The BCF values increased significantly with the increasing number of substituted Cl atoms, with the exception of CDE 209. The number of Cl atoms at the para and meta positions were found to be the major positive contributing factors for BCFs in the case of the same number of substituted Cl. The lipid-normalized biomagnification factors (BMFs) of S. obliquus to D. magna, D. magna to D. rerio, and the whole food chain for the 12 PCDE congeners ranged at 1.08-2.27, 0.81-1.64, and 0.88-3.64, respectively, suggesting that some congeners had BMFs comparable to PBDEs and PCBs. Dechlorination was the only metabolic pathway observed for S. obliquus and D. magna. For D. rerio, dechlorination, methoxylation, and hydroxylation metabolic pathways were observed. ¹H nuclear magnetic resonance (NMR) experiments and theoretical calculations confirmed that methoxylation and hydroxylation occurred at the ortho position of the benzene rings. In addition, reliable quantitative structure-property relationship (QSPR) models were constructed to qualitatively describe the relationships between molecular structure descriptors and BCFs for PCDEs. These findings provide insights into the movement and transformation of PCDEs in aquatic ecosystems.

The low prevalence rate of vitamin E deficiency in urban adults of Wuhan from central China: findings from a single-center, cross-sectional study

Background

Vitamin E is an essential nutrient in human body famous for its antioxidant and non-antioxidant functions. However, little is known about vitamin E deficiency status in urban adults of Wuhan from central China. Our aim is to describe the distribution of both circulating and lipid-adjusted serum vitamin E concentration in urban adults of Wuhan.

Methods

We hypothesized that the prevalence rate of vitamin E deficiency would be low in Wuhan in consideration of the Chinese food composition. A cross-sectional study with 846 adults was performed in a single-center. Concentrations of vitamin E were measured by liquid chromatography coupled with tandem mass spectrometry (LC–MS/MS).

Results

The median (interquartile range, IQR) of serum vitamin E concentration was 27.40 (22.89–33.20) μmol/L while that of serum vitamin E concentration adjusted by total cholesterol or the sum of cholesterol (TC) and triglyceride (TG) (the sum of cholesterol and triglyceride, TLs) were 6.20 (5.30–7.48) and 4.86 (4.10–5.65) mmol/mol, respectively. No significant difference of the circulating and TC-adjusted vitamin E concentration was found between male and female except for vitamin E/TLs. However, concentrations of vitamin E increased significantly (r = 0.137, P < 0.001) with age, but lipid-adjusted concentrations of vitamin E did not. On analysis of risk factors, the subjects characterized by hypercholesterolemia are more likely to exhibit higher circulating but lower lipid-adjusted vitamin E level due to adequacy of the serum carriers for delivery of vitamin E. Only 0.47% of the population were below 12 μmol/L of vitamin E defined as functional deficiency.

Conclusion

The prevalence rate of vitamin E deficiency in urban adults of Wuhan is low, which is important and useful to clinicians for clinical decision-making in public health practice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40001-023-01103-9.

Polychlorinated Diphenyl Ethers in the Environment: A Review and Future Perspectives

Polychlorinated diphenyl ethers (PCDEs) are a class of synthetic halogenated aromatic compounds, which have gradually attracted widespread attention due to potential environmental risks to humans and ecosystems. This paper presents a literature review of research on PCDEs using PubMed, Web of Science and Google Scholar as search engines/databases with no constraints on publishing year or number. A total of 98 publications on the sources, environmental levels, environmental behavior and fate, synthesis and analysis and toxicology of PCDEs were retrieved. Existing studies have shown that PCDEs widely exist in the environment with the ability of long-range transport, bioaccumulation and biomagnification, which are almost comparable to polychlorinated biphenyls. They can elicit adverse effects including hepatic oxidative stress, immunosuppression, endocrine disorders, growth retardation, malformations, reduced fertility and increased mortality in organisms, among which some seem to be related to the activation of the aryl hydrocarbon receptor. PCDEs can be metabolized into other organic pollutants, such as hydroxylated and methoxylated PCDEs and even polychlorinated dibenzo-p-dioxins and furans through biotransformation, photolysis and pyrolysis reactions in the environment. Compared with reviews on PCDEs published previously, some new information and findings are summarized in this review, such as new sources, current environmental exposure levels, main metabolism pathways in aquatic organisms, acute toxicity data for more species and relationships between structural parameters and toxicity and bioaccumulation potentials of PCDE congeners. Finally, current research deficiencies and future research perspectives are proposed to facilitate the assessment of health and ecological risks of PCDEs.

An Insight into the Sorption Behavior of 2,3,7,8-Tetrachlorodibenzothiophene on the Sediments and Paddy Soil from Chaohu Lake Basin

Considering the frequent detection of polychlorinated dibenzothiophenes (PCDTs) in various environmental matrices and the potential ecological health risks, the environmental behavior of such compounds needs to be elucidated further. In this work, the sorption behavior of 2,3,7,8-tetrachlorodibenzothiophene (2,3,7,8-TCDT) onto three sediments and paddy soil from Chaohu Lake were investigated via batch equilibration experiments. From the perspective of sorption kinetics and isotherms, the sorption characteristics and mechanism of 2,3,7,8-TCDT on the above four carriers were compared, and the relationship between their structural characteristics and soil sorption capacity was discussed. Results suggested that rapid sorption played the primary role during the sorption process of 2,3,7,8-TCDT and the corresponding sorption isotherms were well fitted using the Freundlich logarithmic model. Moreover, the effects of pH and dissolved organic matter (DOM) on the sorption of 2,3,7,8-TCDT were investigated. The maximum sorption capacity of 2,3,7,8-TCDT on sediment was under acidic pH condition (pH = 4.0). Meanwhile, DOM at a low level promoted the sorption capacity of sediment toward 2,3,7,8-TCDT, while the high concentration of DOM inhibited this effect. In addition, the values of logK_oc were obtained using high-performance liquid chromatography (HPLC) and did not show any significant correlation with organic carbon (OC) contents, thereby indicating that the partition effect was the dominating influencing factor for the sorption of 2,3,7,8-TCDT both on sediments and soil. This work provides useful data to understand the sorption behavior of 2,3,7,8-TCDT on sediments and soil and assess its potential environmental risk.

Biomarker Responses, Gene Expression Alterations, and Histological Changes in Zebrafish (Danio rerio) After In Vivo Exposure to Polychlorinated Diphenyl Ethers

Polychlorinated diphenyl ethers (PCDEs) have been detected in various aquatic matrices, which pose potential threats to aquatic ecosystem security. In this work, both micro and macro analysis methods were used to assess the toxicity of PCDEs to zebrafish. Results indicated that after in vivo PCDE exposure, the oxidative stress and related gene of Danio rerio were significantly changed. The higher concentration or longer exposure time could cause more severe oxidative stress in zebrafish tissues. Compared with among the five tested compounds, more obvious changes in the level of oxidative biomarkers of lower chlorinated PCDEs’ (4-mono-CDE and 4,4′-di-CDE) exposure groups were observed. The integrated biomarker response analysis and gene expression results also indicate a similar trend. Histopathological observation suggested that 4,4′-di-CDE could render liver nuclei enlargement and necrosis, hepatocyte vacuolation, and the development inhibition of ovarian cells. Transmission electron microscope photos showed that 4,4′-di-CDE caused organelle damage in the liver and ovary, including the rupture of the endoplasmic reticulum, swelling of mitochondria, and condensation of chromatin in the liver and mitochondria disappeared significantly in the ovary. The degree of damage is enhanced with the increasing exposure doses. In addition, PCDEs also significantly altered vitellogenin content and related gene (vtg1) expression, suggesting that PCDEs may be estrogen endocrine disruptors. Overall, these results provided some valuable toxicological data of PCDEs on aquatic species.

Effects of diisononyl phthalate exposure on the oxidative stress and gut microorganisms in earthworms (Eisenia fetida)

Phthalate esters (PAEs) are widely used as plasticizers and can be ubiquitously detected in environment. However, the toxic effects and mechanisms of diisononyl phthalate (DINP) on earthworms are still poorly understood. In this study, earthworms (Eisenia fetida) were exposed to DINP at various doses (0, 300, 600, 1200, and 2400 mg/kg) to investigate their subchronic toxicity. The results demonstrated that the reactive oxygen species (ROS) levels displayed an "increase-decrease" trend with the increasing DINP doses after DINP exposure on days 7, 14, 21, and 28. The malondialdehyde (MDA) content increased with increasing DINP doses on days 7, 14, and then decreased on days 21, 28. The values of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) showed similar variation patterns and reached a maximum level on 21 d. Moreover, on day 28, the SOD and CAT gene expression levels were upregulated, while the GST gene expression levels were downregulated. Meanwhile, 16S rRNA genes of E. fetida gut bacteria and surrounding soil bacteria were measured after 28 days of exposure to DINP. The Chao index of E. fetida gut bacteria decreased when the treatment with the highest concentration (2400 mg/kg) was applied. At the phylum level, the abundance of Chloroflexi was significantly lower in the gut of E. fetida. In addition, the abundance of Proteobacteria at the phylum level and Ottowia at the genus level significantly increased in the surrounding soil. Overall, our results shed light on the toxic mechanism of DINP at biochemical, molecular, and omics levels, and contributed to a better understanding of the ecotoxicity of DINP.

Acute toxicity of polychlorinated diphenyl ethers (PCDEs) in three model aquatic organisms (Scenedesmus obliquus, Daphnia magna, and Danio rerio) of different trophic levels

The frequent detection of polychlorinated diphenyl ethers (PCDEs) in aquatic systems has aroused widespread concerns, however, their potential hazard to aquatic ecosystems has been poorly understood. Here the acute toxicity of 12 PCDE congeners was evaluated in three model aquatic organisms representing different trophic levels following OECD test guidelines, including green algae (Scenedesmus obliquus), water flea (Daphnia magna), and zebrafish (Danio rerio). Dose-dependent increases in growth inhibition and mortality were observed for all tested PCDE congeners. Most of the PCDE congeners, in particular 3,3',4,4'-tetra-CDE, were highly toxic to the three aquatic organisms with EC₅₀ or LC₅₀ values below 1 mg L^-1. Their toxicities were generally comparable with those of certain polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). Moreover, D. magna was the most sensitive species among the three aquatic organisms. In addition, the EC₅₀ or LC₅₀ values had an extremely significant correlation with the n-octanol-water partition coefficient (logK_ow) of the PCDE congeners. The established quantitative structure-property relationship (QSPR) models indicated that the molecular polarizability (α) could significantly influence the acute toxicity of PCDEs on Daphnia magna and Danio rerio, and the energy of the lowest unoccupied molecular orbital (E_LUMO) is the key factor of the acute toxicity of PCDEs in Scenedesmus obliquus. In addition, even at environmental levels, 3,3',4,4'-tetra-CDE could induced seveve oxidative damages in the three aquactic species. These findings would contribute to the understanding of adverse effects of PCDEs in aquatic organisms.

Brain γ-Tocopherol Levels Are Associated with Presynaptic Protein Levels in Elderly Human Midfrontal Cortex

BACKGROUND

Higher vitamin E intake has been widely related to lower risks of cognitive decline and dementia. Animal models suggest that this relationship might be (partially) explained by the protection of vitamin E against presynaptic protein oxidation.

OBJECTIVE

In this cross-sectional study, we aimed to examine the associations between brain tocopherols and presynaptic protein levels in elderly humans.

METHODS

We examined associations of α- and γ-tocopherol brain levels with presynaptic protein levels in 113 deceased participants (age 88.5±6.0 years, 45 (40%) female) from the prospective Memory and Aging project. Three distinct presynaptic proteins, a SNARE protein composite, a synaptotagmin synaptophysin composite and the protein-protein interaction between synaptosomal-associated protein 25 (SNAP-25), and syntaxin were measured in two cortical brain regions. Linear regression models assessed associations of brain tocopherols with presynaptic protein levels.

RESULTS

Higher brain γ-tocopherol levels were associated with higher levels of the SNARE protein composite, complexin-I, complexin-II, the synaptotagmin synaptophysin composite, and septin-5 in the midfrontal cortex (B(SE) = 0.272 to 0.412 (0.084 to 0.091), p < 0.001 to 0.003). When additionally adjusted for global Alzheimer's disease pathology, cerebral infarcts, and Lewy body disease pathology, these associations remained largely similar. No associations were found between α-tocopherol and presynaptic protein levels.

CONCLUSION

In this cross-sectional study, we found higher brain γ-tocopherol levels were associated with presynaptic protein levels in the midfrontal cortex. These results are consistent with a proposed role of vitamin E to maintain presynaptic protein levels.

Bioaccumulation, Metabolism, and Biomarker Responses in Hyriopsis cumingii Exposed to 4-Mono-Chlorinated Dibenzothiophene

Polychlorinated dibenzothiophenes (PCDTs) are sulfur analogues of polychlorinated dibenzofurans with prevalent occurrence in aquatic environments and potential ecological risks. However, data on the behavior and toxicity of PCDTs in aquatic organisms remain scarce. In the present study, the bioaccumulation, metabolism, and oxidative damage of 4-mono-chlorinated dibenzothiophene (4-mono-CDT) in freshwater mussel (Hyriopsis cumingii) were investigated after exposure to 4-mono-CDT in semistatic water. The uptake rates, depuration rates, half-lives, and bioconcentration factors of 4-mono-CDT in hepatopancreas, gill, and muscle tissues ranged from 0.492 to 1.652 L d^-1  g^-1 dry weight, from 0.117 to 0.308 d^-1 , from 2.250 to 5.924 d, and from 2.903 to 8.045 × 10³  L kg^-1 dry weight, respectively. A dechlorinated metabolite (dibenzothiophene) was detected in hepatopancreas tissue, indicating that dechlorination was the main metabolic pathway of 4-mono-CDT. As the exposure time increased, the activities of superoxide dismutase, catalase, and glutathione peroxidase were induced or inhibited in the different experimental groups. The malondialdehyde content increased with increasing 4-mono-CDT dose and exposure time. A higher concentration of 4-mono-CDT corresponded to a greater integrated biomarker response in each tissue and greater oxidative damage. The antioxidant enzymes in hepatopancreas were more sensitive to 4-mono-CDT than those in gill. The results provide useful information on the behavior and ecotoxicity of PCDTs in freshwater mussels. Environ Toxicol Chem 2021;40:1873-1882. © 2021 SETAC.

Emerging contaminant 1,3,6,8-tetrabromocarbazole induces oxidative damage and apoptosis during the embryonic development of zebrafish (Danio rerio)

Since polyhalogenated carbazoles (PHCs) have been widely detected at high concentrations in multiple environmental media in recent years, the health risk of exposure to these compounds has drawn increasing attention. Most studies have mainly focused on their dioxin-like toxicity, which is induced through the AhR pathway, because PHCs have structures similar to those of polychlorinated dibenzofurans (PCDFs). In addition, most xenobiotic compounds induce oxidative stress in organisms, which is a more common mechanism of toxicity induction. However, there is limited information regarding the oxidative stress and damage induced by PHCs in vivo. The PHC 1,3,6,8-tetrabromocarbazole (1368-TBCZ) is detected at high concentration and frequency. In the present study, the toxic effects (acute toxicity, developmental toxicity, oxidative stress, and apoptosis) induced by 1368-TBCZ at three different concentrations were investigated using zebrafish embryos. It was concluded that the 96 h median lethal concentration (LC₅₀) of 1368-TBCZ for zebrafish embryos was greater than 2.0 mg L^-1. The results showed that 1368-TBCZ had little effect on the hatching rate of zebrafish embryos. However, 1368-TBCZ at 0.5 and 2.0 mg L^-1 inhibited skeletal and cardiac development. It promoted ROS production, CAT enzyme activity, lipid peroxidation, DNA damage, and apoptosis, even at the lowest dose (0.1 mg L^-1). In addition, 1368-TBCZ influenced oxidative stress-related gene expression, upregulating the expression of caspase 3 and p53 at 2.0 mg L^-1 and inhibiting the expression of caspase 9, FoxO3b, and Bcl-2/Bax. The present study comprehensively evaluated 1368-TBCZ-induced toxicity in zebrafish, providing valuable data for better evaluation of the potential risks posed by this PHC.

Evaluation of the oxidative stress in liver of crucian carp (Carassius auratus) exposed to 3,4,4'-tri-CDE, 2-MeO-3',4,4'-tri-CDE, and 2-HO-3',4,4'-tri-CDE

Polychlorinated diphenyl ethers (PCDEs) are a class of potential persistent organic contaminants, which have been widely detected in aquatic environment. In the present study, the effects of 3,4,4'-tri-CDE and its two possible metabolites (2-MeO-3',4,4'-tri-CDE and 2-HO-3',4,4'-tri-CDE) on oxidative stress biomarkers in liver of Carassius auratus were evaluated. The fish were treated with these three compounds at different doses (0.1, 1, and 10 μg/L) via semi-static water exposure. The liver samples were individually taken at 3, 7, and 21 days for analysis of oxidative stress indicators, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), and malondialdehyde (MDA). Compare to the control group, the hepatic antioxidant enzyme activity and GSH contents showed significant decreases (p < 0.05) at high-dose treatment (10 μg/L) and prolonged exposure time (21 days) in most of the toxicant-treated groups, indicating the occurrence of oxidative stress in fish liver. However, no consistent trend of the variations of antioxidant parameters was observed at low doses (0.1 and 1 μg/L). Meanwhile, the lipid peroxidation was significantly induced with extending exposure time and increasing dose. In addition, the toxicity order of three compounds was discussed using the integrated biomarker response (IBR) index. Notably, 2-HO-3',4,4'-tri-CDE was indicated to cause the most severe hepatic oxidative stress.

Polychlorinated diphenyl ethers (PCDEs) in surface sediments, suspended particulate matter (SPM) and surface water of Chaohu Lake, China

Polychlorinated diphenyl ethers (PCDEs) are typical halogenated aromatic pollutants that have shown various toxicological effects on organisms. However, the contamination status of PCDEs in the fresh water lakes of China remains poorly researched. In this study, the levels of 15 congeners of PCDEs in the sediments, suspended particulate matter (SPM) and water of Chaohu Lake were determined. The results showed that the ranges of concentrations of total PCDEs (ΣPCDEs) in the sediment, SPM and water were 0.279 ng g^-1 dry weight (d.w.)-2.474 ng g^-1 d.w., 0.331 ng g^-1 d.w.-2.013 ng g^-1 d.w. and 0.351 ng L^-1-2.021 ng L^-1, respectively. The most abundant congeners found in sediments, SPM and water were 3,3',4,4'-tetra-CDE, deca-CDE and 2,4,6-tri-CDE, with average contributive ratios of 17.36%, 15.48% and 20.63%, respectively. The medium and higher chlorinated PCDEs (e.g., penta- and deca-CDEs) were the dominant congeners in sediments and SPM. The percentages of lower chlorinated PCDEs (e.g., tri-CDEs) in the water were higher than those in the sediments. The combined input of ΣPCDEs from the eight main tributaries to Chaohu Lake was estimated at 6.94 kg y^-1. Strong linear correlations between the concentrations of ΣPCDEs and organic carbon (OC) contents in three type samples from Chaohu Lake suggested OC could influence the distribution of PCDEs in Chaohu Lake substantially. In addition, the calculated average organic carbon normalized partition coefficients (logK_oc) of 15 PCDEs between water and SPM were in the range of 4.55-5.45 mL g^-1. This study confirmed that Chaohu Lake is contaminated by PCDEs.

The efficacy of microemulsion-based delivery to improve vitamin E properties: evaluation of the antinociceptive, antioxidant, antidepressant- and anxiolytic-like activities in mice

Objectives

A microemulsion-based delivery system was designed to improve vitamin E (VE) properties, and its antinociceptive, antioxidant, antidepressant- and anxiolytic-like activities in mice were evaluated.

Methods

Male Swiss mice received, by intragastric route, canola oil (20 ml/kg), blank microemulsion (B-ME) (20 ml/kg), VE free (VE-F) (200 mg/kg) or VE microemulsion (VE-ME) (200 mg/kg). In acute treatment, a single dose of treatments was administrated and 30 min after behavioural tests were performed. In the subchronic treatment, mice received such treatments, once a day, for 8 days. On the eighth day, behavioural tests were performed.

Key findings

In the subchronic treatment, VE-ME increased entries and spent time in the open arms in the elevated plus-maze test and decreased the immobility time in the tail suspension test, but no change was found after acute treatment. Acute and subchronic treatments with VE-ME increased response latency to thermal stimulus in the hot-plate test. VE-ME decreased the thiobarbituric acid reactive species levels in the acute and subchronic protocols. Additionally, in subchronic treatment, VE-ME increased renal catalase activity, but VE-F reduced its activity.

Conclusions

Vitamin E-microemulsions showed antioxidant, antinociceptive, antidepressant- and anxiolytic-like actions; thus, ME-based delivery improved pharmacological properties of VE.

QSPR modeling of the logKow and logKoc of polymethoxylated, polyhydroxylated diphenyl ethers and methoxylated-, hydroxylated-polychlorinated diphenyl ethers

In the present study, the structural parameters of 209 types of polymethoxylated diphenyl ethers (PMeODEs), 209 types of polyhydroxylated diphenyl ethers (PHODEs), seven types of methoxylated-polychlorinated diphenyl ethers (MeO-PCDEs) and seven types of hydroxylated-polychlorinated diphenyl ethers (HO-PCDEs) were calculated using the Gaussian 09 program at the B3LYP/6-311G** level. Using structural and positional parameters as descriptors, quantitative structure-property relationships (QSPR) models for the prediction of n-octanol/water partition coefficient (logK_ow) and soil sorption coefficient normalized to organic carbon (logK_oc) were established and verified. The position parameters N₂₍₆₎, N₃₍₅₎ and N₄ were the main positional factors influencing logK_ow and logK_oc of PMeODEs and PHODEs. The molecular polarizability α was entered into the QSPR models of the logK_ow and logK_oc of PMeODEs, PHODEs and MeO/HO-PCDEs, indicating that the molecular volume could influence the two environment-related properties of DEs significantly. All of the established QSPR models showed good goodness-of-fit, robustness, and predictive ability. The two models for all of the tested DEs are slightly inferior compared with the models for only a class of compounds. In addition, application domain analysis indicated that the models reliably predicted the logK_ow and logK_oc of the mon- to hexa-DEs.

Toxicity evaluation of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus: growth inhibition, change in pigment content, and oxidative stress

Polychlorinated diphenyl sulfides and polychlorinated diphenyl ethers are two types of dioxin-like pollutants, which are prevalent in aquatic environments. However, to date, limited information is available regarding their toxicity to green algae. In this study, growth inhibition, effect on pigment content, and oxidative stress potentials of 4,4'-di-CDPS and 4,4'-di-CDE on green algae Scenedesmus obliquus were investigated. The results indicate that the EC₅₀ values of 4,4'-di-CDPS after 24, 48, 72, and 96 h of exposure were 1.736, 1.172, 0.994, and 0.820 mg/L, while the corresponding values for 4,4'-di-CDE were 0.697, 1.087, 0.833, and 0.327 mg/L. As compared to the control group, most of the measured pigment content in algal cells significantly decreased after 96-h exposure to these two chemicals, suggesting their suppressive capability on the photosynthesis process in algal cells. Additionally, oxidative stress occurred as demonstrated by the significantly inhibited activities of the antioxidant enzymes (total superoxide dismutase (T-SOD), catalase (CAT), and glutathione peroxidase (GPx)), and high increases in malondialdehyde (MDA) content in all 4,4'-di-CDE-treated groups and some moderate-dose and high-dose treatments with 4,4'-di-CDPS. Acute toxicity tests and biochemical analysis showed that 4,4'-di-CDE was more toxic than 4,4'-di-CDPS on S. obliquus.

Vitamin E: Emerging aspects and new directions

The discovery of vitamin E will have its 100th anniversary in 2022, but we still have more questions than answers regarding the biological functions and the essentiality of vitamin E for human health. Discovered as a factor essential for rat fertility and soon after characterized for its properties of fat-soluble antioxidant, vitamin E was identified to have signaling and gene regulation effects in the 1980s. In the same years the cytochrome P-450 dependent metabolism of vitamin E was characterized and a first series of studies on short-chain carboxyethyl metabolites in the 1990s paved the way to the hypothesis of a biological role for this metabolism alternative to vitamin E catabolism. In the last decade other physiological metabolites of vitamin E have been identified, such as α-tocopheryl phosphate and the long-chain metabolites formed by the ω-hydroxylase activity of cytochrome P-450. Recent findings are consistent with gene regulation and homeostatic roles of these metabolites in different experimental models, such as inflammatory, neuronal and hepatic cells, and in vivo in animal models of acute inflammation. Molecular mechanisms underlying these responses are under investigation in several laboratories and side-glances to research on other fat soluble vitamins may help to move faster in this direction. Other emerging aspects presented in this review paper include novel insights on the mechanisms of reduction of the cardiovascular risk, immunomodulation and antiallergic effects, neuroprotection properties in models of glutamate excitotoxicity and spino-cerebellar damage, hepatoprotection and prevention of liver toxicity by different causes and even therapeutic applications in non-alcoholic steatohepatitis. We here discuss these topics with the aim of stimulating the interest of the scientific community and further research activities that may help to celebrate this anniversary of vitamin E with an in-depth knowledge of its action as vitamin.

Experimental investigation on the soil sorption properties and hydrophobicity of polymethoxylated, polyhydroxylated diphenyl ethers and methoxylated-, hydroxylated-polychlorinated diphenyl ethers

In the present study, twenty-six types of polymethoxylated diphenyl ethers (PMeODEs), twenty types of polyhydroxylated diphenyl ethers (PHODEs), seven types of methoxylated-polychlorinated diphenyl ethers (MeO-PCDEs) and seven types of hydroxylated-polychlorinated diphenyl ethers (HO-PCDEs) were synthesized. The logKow and logKoc values of all of the synthesized compounds were then determined using HPLC. The soil sorption properties of five types of selected substituted diphenyl ethers (DEs) were investigated. Sorption behavior studies suggested that rapid sorption played a primary role in the sorption process of the selected DEs and their sorption isotherms were fitted the Freundlich logarithmic model. For PMeODEs and PHODEs, with the increase in the number of substituents, both logKow and logKoc values exhibited linearly decreasing trends. Unlike PMeODEs and PHODEs, both logKow and logKoc values of MeO/HO-PCDEs were decreased linearly with the increasing number of chlorine atoms. The reason maybe that both methoxy and hydroxyl are hydrophilic groups, whereas the chlorine atom is hydrophobic group. Linear relationships were observed for the logKow and logKoc of all studied DEs. Moreover, the logKow of PMeODEs, PHODEs, MeO- and HO-PCDEs and their corresponding PCDEs showed good linearity.

Calorimetric evidence of interaction of brominated flame retardants with membrane model

The presence of polybrominated flame retardants in the environment seems to be increasing in the past decade. Considering the toxic effects of these pollutants, it is important evaluating the potential interaction with biological membranes for a risk assessment. In this study low and high brominated biphenyls and biphenyl ethers were used to investigate their interaction with biological membrane models constituted by liposomes, using differential scanning calorimetry (DSC) technique. The medium influence on membrane absorption was also assessed. The findings indicate that membrane interaction is controlled by compound structural characteristics. The membrane absorption is allowed by lipophilic medium; instead hydrophilic medium prevents membrane permeation.

Evaluation of HODE-15, FDE-15, CDE-15, and BDE-15 toxicity on adult and embryonic zebrafish (Danio rerio)

Diphenyl ether and its derivatives are widely used in the industry of spices, dyes, agrochemicals, and pharmaceuticals. Following the previous study, we selected 4,4'-dihydroxydiphenyl ether, 4,4'-difluorodiphenyl ether, 4,4'-dichlorodiphenyl ether, and 4,4'-dibromodiphenyl ether as research objects. The LC50 (96 h) values for these compounds in adult zebrafish were determined with the acute test. Also, developmental toxicities of the four substances to zebrafish embryos were observed at 24, 48, 72, and 96 hpf. All the LC50 (96 h) values of these compounds were between 1 and 10 mg/L, suggesting that they all had moderate toxicity to adult zebrafish. The embryonic test demonstrated that with increasing doses, 4,4'-dihydroxydiphenyl ether decreased the hatching rate, while 4,4'-difluorodiphenyl ether, 4,4'-dichlorodiphenyl ether, and 4,4'-dibromodiphenyl ether delayed the hatching time but had little effect on final hatchability at 96 hpf. All of these compounds inhibited larval growth, especially 4,4'-dihydroxydiphenyl ether. Exposure to these chemicals induced embryo yolk sac and pericardial edema. Spine deformation was visible in hatched larvae after 96 hpf 4,4'-dihydroxydiphenyl ether exposure, while tail curvature was observed for the halogenated compounds. The overall results indicated that 4,4'-dihydroxydiphenyl ether, 4,4'-difluorodiphenyl ether, 4,4'-dichlorodiphenyl ether, and 4,4'-dibromodiphenyl ether all had significant toxicity on adult and embryonic zebrafish.

Hepatic oxidative status and metal homeostasis disturbance of 2-hydroxylated dioxin in ICR mice

In the present study, the toxic effects of the oral exposure of 2-hydroxylated dioxin (2-HODD) in ICR male mice were examined. The mice were administered different doses (0.2, 2.0 and 20.0mg/kg) of 2-HODD. After 14 days of exposure, the oxidative stress (OS) indicator levels and the essential metal concentrations in the mouse livers were determined. The results showed that the superoxide dismutase (SOD) and the glutathione peroxidase (GPx) activities were increased in the 0.2mg/kg group, whereas they were significantly decreased in the 2.0 and 20.0mg/kg groups. Decreases in the catalase (CAT) activity and the glutathione (GSH) levels, accompanied by increases in the malondialdehyde (MDA) contents, were recorded in all of the 2-HODD-treated groups. The hepatic iron, copper and zinc levels increased in all of the 2-HODD-treated groups. The histological examination of the livers demonstrated swollen cells and inflammation. Dose-dependent changes in both the OS indicators and the hepatic metal levels were observed. In conclusion, a single low dose of 2-HODD significantly perturbed the hepatic OS status and metals homeostasis in the mice.