PPAR-γ agonist GW1929 but not antagonist GW9662 reduces TBBPA-induced neurotoxicity in primary neocortical cells

Evaluation of the protective effect of losartan in acetaminophen-induced liver and kidney damage in mice

Acetaminophen is widely used among humans as an antipyretic and analgesic. In this study, the protective effect of losartan in hepatotoxicity and nephrotoxicity induced by acetaminophen in mice was investigated owing to its anti-inflammatory and antioxidant effects. An injection of a single dose of 500 mg/kg (i.p.) acetaminophen was administered to induce hepatotoxicity and nephrotoxicity in Groups VI-X. Losartan at doses of 1 mg/kg (Group VII), 3 mg/kg (Group VIII), and 10 mg/kg (Groups III, V, IX, and X) was injected intraperitoneally twice, at 1 and 12 h after the acetaminophen injection. Additionally, a 4 mg/kg dose of GW9662 (peroxisome proliferator-activated receptor gamma (PPAR-γ) antagonist) was injected intraperitoneally 30 min before the losartan injections in Groups V and X. At the end of 24 h, the mice were euthanized, and blood, liver, and kidney tissue samples were collected. Levels of AST, ALT, creatinine, and oxidative stress markers including TBARS, SOD, CAT, GPx, TAS, TOS, GSH, and GSSG, along with pro-inflammatory cytokines IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α, were measured using ELISA kits. Additionally, a histological evaluation of the tissue samples was performed. Acetaminophen causes increases in the levels of AST, ALT, creatinine, TBARS, TOS, GSSG, IL-1β, IL-6, IL-8, IL-10, IL-17, and TNF-α in serum, liver, and kidney tissue. Meanwhile, it led to a decrease in the levels of SOD, CAT, GPx, TAS, and GSH. Losartan injection reversed oxidative and inflammatory damage induced by acetaminophen. Histopathological changes in liver and kidney tissue were alleviated by losartan. The substance GW9662 increased the protective effect of losartan. In light of all the data obtained from our study, it can be said that losartan has a protective effect on liver and kidney damage induced by acetaminophen due to its antioxidant and anti-inflammatory effects. In terms of the study, losartan was found to be an alternative substance that could protect people from the harmful effects of acetaminophen.

Update of the scientific opinion on tetrabromobisphenol A (TBBPA) and its derivatives in food

The European Commission asked EFSA to update its 2011 risk assessment on tetrabromobisphenol A (TBBPA) and five derivatives in food. Neurotoxicity and carcinogenicity were considered as the critical effects of TBBPA in rodent studies. The available evidence indicates that the carcinogenicity of TBBPA occurs via non-genotoxic mechanisms. Taking into account the new data, the CONTAM Panel considered it appropriate to set a tolerable daily intake (TDI). Based on decreased interest in social interaction in male mice, a lowest observed adverse effect level (LOAEL) of 0.2 mg/kg body weight (bw) per day was identified and selected as the reference point for the risk characterisation. Applying the default uncertainty factor of 100 for inter- and intraspecies variability, and a factor of 3 to extrapolate from the LOAEL to NOAEL, a TDI for TBBPA of 0.7 μg/kg bw per day was established. Around 2100 analytical results for TBBPA in food were used to estimate dietary exposure for the European population. The most important contributors to the chronic dietary LB exposure to TBBPA were fish and seafood, meat and meat products and milk and dairy products. The exposure estimates to TBBPA were all below the TDI, including those estimated for breastfed and formula-fed infants. Accounting for the uncertainties affecting the assessment, the CONTAM Panel concluded with 90%-95% certainty that the current dietary exposure to TBBPA does not raise a health concern for any of the population groups considered. There were insufficient data on the toxicity of any of the TBBPA derivatives to derive reference points, or to allow a comparison with TBBPA that would support assignment to an assessment group for the purposes of combined risk assessment.

RNA-Seq analysis offers insight into the TBBPA-DHEE-induced endocrine-disrupting effect and neurotoxicity in juvenile zebrafish (Danio rerio)

Tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) is the major TBBPA derivative. It has been detected in different environmental samples. Previous studies show that TBBPA-DHEE caused neurotoxicity in rats. In this study, juvenile zebrafish were exposed to various concentrations of TBBPA-DHEE to ascertain the potential neurotoxicity of TBBPA-DHEE, the chemical, and its possible molecular mechanism of action. Behavioral analysis revealed that TBBPA-DHEE could significantly increase the swimming distance and speed in the 1.5 mg/L group compared to the control. In contrast, the swimming distance and speed were significantly reduced in the 0.05 and 0.3 mg/L groups, affecting learning, memory, and neurodevelopment. Similarly, TBBPA-DHEE exposure caused a concentration-dependent significant increase in the levels of excitatory neurotransmitters, namely, dopamine, norepinephrine, and epinephrine, which could be attributed to the change observed in zebrafish behavior. This demonstrates the neurotoxicity of TBBPA-DHEE on juvenile zebrafish. The concentration-dependent increase in the IBR value revealed by the IBR index reveals the noticeable neurotoxic effect of TBBPA-DHEE. Transcriptomic analysis shows that TBBPA-DHEE exposure activated the PPAR signaling pathways, resulting in a disturbance of fatty acid (FA) metabolism and changes in the transcript levels of genes involved in these pathways, which could lead to lipotoxicity and hepatotoxicity. Our findings demonstrate a distinct endocrine-disrupting response to TBBPA-DHEE exposure, possibly contributing to abnormal behavioral alterations. This study provides novel insights into underlying the mechanisms and effects of TBBPA-DHEE on aquatic organisms, which may be helpful forenvironmental/human health risk assessments of the emerging pollutant.

The TFPI2-PPARγ axis induces M2 polarization and inhibits fibroblast activation to promote recovery from post-myocardial infarction in diabetic mice

BACKGROUND

Diabetes mellitus is one of the causes of poor ventricular remodelling and poor cardiac recovery after myocardial infarction (MI). We previously reported that tissue factor pathway inhibitor-2 (TFPI2) was downregulated in response to hyperglycaemia and that it played a pivotal role in extracellular matrix (ECM) degradation and cell migration. Nonetheless, the function and mechanism of TFPI2 in post-MI remodelling under diabetic conditions remain unclear. Therefore, in the present study, we investigated the role of TFPI2 in post-MI effects in a diabetic mouse model.

RESULTS

TFPI2 expression was markedly decreased in the infarcted myocardium of diabetic MI mice compared with that in non-diabetic mice. TFPI2 knockdown in the MI mouse model promoted fibroblast activation and migration as well as matrix metalloproteinase (MMP) expression, leading to disproportionate fibrosis remodelling and poor cardiac recovery. TFPI2 silencing promoted pro-inflammatory M1 macrophage polarization, which is consistent with the results of TFPI2 downregulation and M1 polarization under diabetic conditions. In contrast, TFPI2 overexpression in diabetic MI mice protected against adverse cardiac remodelling and functional deterioration. TFPI2 overexpression also inhibited MMP2 and MMP9 expression and attenuated fibroblast activation and migration, as well as excessive collagen production, in the infarcted myocardium of diabetic mice. TFPI2 promoted an earlier phenotype transition of pro-inflammatory M1 macrophages to reparative M2 macrophages via activation of peroxisome proliferator-activated receptor gamma.

CONCLUSIONS

This study highlights TFPI2 as a promising therapeutic target for early resolution of post-MI inflammation and disproportionate ECM remodelling under diabetic conditions.

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

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

Toxicity of bisphenol A (BPA) and its derivatives in divers biological models with the assessment of molecular mechanisms of toxicity

The aim of the study was to determine totoxicity of bisphenol A (BPA) and its derivatives (bisphenol S (BPS), bisphenol F (BPF), and tetrabromobisphenol A (TBBPA)) due to its high accumulation in environment. The performed analysis revealed the toxicity of the BPA, BPF, and BPS against Kurthia gibsoni, Microbacterium sp., and Brevundimonas diminuta as the most sensitive, reaching microbial toxic concentrations in the range of 0.018-0.031 mg ∙ L^-1. Moreover, the genotoxicity assay shows the ability of all tested compounds to increase in the β-galactosidase level at the concentration range 7.81-500 µM (in Escherichia coli, PQ37). In turn, the matbolic activation of tested bishpenols has caused the enhacement of the genotoxicity and cytotoxicity effect. Interestingely, the highest phytotoxicity effect was pointed for BPA and TBBPA at the concentrations of 10 mg ∙ L^-1 and 50 mg ∙ L^-1, which cause the inhibition of root growth by 58% and 45%, respectively (especially for S. alba and S. saccharatum). Furthermore, the cytotoxicity analyses show the ability of BPA, BPS, and TBBPA to significantly decrease the metabolic activity of human keratynoctes in vitro after 24 h of treatment at the micromolar concentrations. Simialry, the impact of the certain bisphenols on proliferation-, apoptosis-, and inflammation-related mRNA expression was shown in tested cell line. Summarizing, the presented results have proved that BPA and its derrivatives are able to show high negative effect on certain living orgnisms such as bacteria, plants, and human cells, which is strict related to pro-apoptotic and genotoxic mechanism of action.

A Review on Tetrabromobisphenol A: Human Biomonitoring, Toxicity, Detection and Treatment in the Environment

Tetrabromobisphenol A (TBBPA) is a known endocrine disruptor employed in a range of consumer products and has been predominantly found in different environments through industrial processes and in human samples. In this review, we aimed to summarize published scientific evidence on human biomonitoring, toxic effects and mode of action of TBBPA in humans. Interestingly, an overview of various pretreatment methods, emerging detection methods, and treatment methods was elucidated. Studies on exposure routes in humans, a combination of detection methods, adsorbent-based treatments and degradation of TBBPA are in the preliminary phase and have several limitations. Therefore, in-depth studies on these subjects should be considered to enhance the accurate body load of non-invasive matrix, external exposure levels, optimal design of combined detection techniques, and degrading technology of TBBPA. Overall, this review will improve the scientific comprehension of TBBPA in humans as well as the environment, and the breakthrough for treating waste products containing TBBPA.

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

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

Tetrabromobisphenol A and hexabromocyclododecane, brominated flame retardants, trigger endoplasmic reticulum stress and activate necroptosis signaling in PC12 cells

Tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCD) are brominated flame retardants commonly used in a variety of industrial and consumer products. In this study, we performed RNA sequencing analysis of PC12 cells to clarify the mechanisms by which TBBPA and HBCD induce neurotoxicity. Differential expression analysis demonstrated that 636 and 271 genes were differentially expressed after TBBPA and HBCD treatment, respectively. Gene Ontology (GO) enrichment analysis revealed that genes annotated with the GO term "endoplasmic reticulum unfolded protein response" were upregulated in both TBBPA- and HBCD-treated groups. Furthermore, protein expression of endoplasmic reticulum stress markers, such as HSPA5 and DDIT3, as well as cleaved caspase-3, an apoptosis marker, were induced by TBBPA and HBCD. We also found that the cytotoxicity induced by TBBPA and HBCD was blocked by necrostatin-1, a necroptosis inhibitor, indicating the contribution of necroptosis. Our findings provide new insight into the mechanisms of toxicity induced by these chemicals.

Apigenin attenuates tetrabromobisphenol A-induced cytotoxicity in neuronal SK-N-MC cells

Tetrabromobisphenol A (TBBPA) is a reactive brominated flame retardant widely used in various industrial and household products. This compound is persistent in the environment and accumulates in living organisms through the food chain, and is toxic to animals and human beings. Studies have shown that TBBPA is toxic to various human cell lines, including neuronal cells. Apigenin is a dietary flavonoid that exhibits various beneficial health effects on biological activities, including antioxidant, anti-inflammatory, and neuroprotective effects. This study investigated the cytoprotective effects of apigenin against TBBPA-mediated cytotoxicity in SK-N-MC cells. Our results demonstrated that treatment of SK-N-MC cells with apigenin increased the cell viability, which was decreased by TBBPA, and reduced apoptosis and autophagy induced by TBBPA. Although we did not observe any change in the levels of IL-1β and nitrite in cultured cells after TBBPA treatment, apigenin was found to decrease the production of these pro-inflammatory mediators. Apigenin decreased the intracellular Ca²⁺ concentration, NOX4 level, oxidative stress, and mitochondrial membrane potential loss and increased the mitochondrial biogenesis and nuclear Nrf2 levels that were reduced by TBBPA. Finally, apigenin treatment decreased Akt and ERK induction in cells exposed to TBBPA. Based on these results, apigenin could be a promising candidate for designing natural drugs to treat or prevent TBBPA-related neurological disorders.

Crosstalk between the aryl hydrocarbon receptor (AhR) and the peroxisome proliferator-activated receptor gamma (PPARγ) as a key factor in the metabolism of silver nanoparticles in neuroblastoma (SH-SY5Y) cells in vitro

The potential usefulness of silver nanoparticles (AgNPs) in anticancer therapy has been postulated for many years. However, little is known to date about the exact impact of such NPs on intracellular detoxication pathways. Therefore, the aim of this study was to determine the impact of AgNPs on the AhR-PPARγ-CYP1A1 pathway in neuroblastoma (SH-SY5Y) cells. The obtained results showed a decrease in the metabolic activity of the SH-SY5Y cells at the 50 and 100 μg/mL concentrations with an increase in caspase-3 activity. An increase in the intercellular ROS production was observed at the 1 and 10 μg/mL concentrations. The co-treatment of the AgNP-treated cells with the AhR and PPARγ inhibitors abolished the effect of the tested AgNPs in the SH-SY5Y cells. In turn, the CYP1A1 activity assay showed a decrease in this parameter in the AgNP-treated cells. Moreover, the gene expression analysis demonstrated that AgNPs were able to increase the AhR and CYP1A1 mRNA expression and decrease the PPARγ gene expression after the 6-h treatment. In turn, an increase in the AhR and PPARγ protein expression was observed after 24 h. Summarizing, the study shows for the first time that AgNPs with a 5-nm diameter size are able to exert a cytotoxic effect on SH-SH5Y cells in a ROS-dependent manner affect the AhR-PPARγ-CYP1A1 pathway inter alia by inhibiting the activity of CYP1A1. This is important due to given present research approaches using such NPs as enhancer agents in the modern PPARγ inhibitor-based anticancer therapy.

Sodium Propionate Contributes to Tumor Cell Growth Inhibition through PPAR-γ Signaling

New therapeutic approaches are needed to improve the outcome of patients with glioblastoma (GBM). Propionate, a short-chain fatty acid (SCFA), has a potent antiproliferative effect on various tumor cell types. Peroxisome proliferator-activated receptor (PPAR) ligands possess anticancer properties. We aimed to investigate the PPAR-γ/SCFAs interaction in in vitro and in vivo models of GBM. The U87 cell line was used in the in vitro study and was treated with sodium propionate (SP). U87 cells were silenced by using PPAR-γ siRNA or Ctr siRNA. In the in vivo study, BALB/c nude mice were inoculated in the right flank with 3 × 10⁶ U-87 cells. SP (doses of 30 and 100 mg/kg) and GW9662 (1 mg/kg) were administered. In vitro exposure of GBM to SP resulted in prominent apoptosis activation while the autophagy pathway was promoted by SP treatments by influencing autophagy-related proteins. Knockdown of PPAR-γ sensitized GBM cells and blocked the SP effect. In vivo, SP was able to decrease tumor growth and to resolve GBM tissue features. SP promoted apoptosis and autophagy pathways and tumor cell proliferation leading to cell cycle arrest through a PPAR-γ-dependent mechanism suggesting that the PPAR-γ/SCFAs axis could be targeted for the management of GBM.

Transcriptomic profiling and differential analysis revealed the neurodevelopmental toxicity mechanisms of zebrafish (Danio rerio) larvae in response to tetrabromobisphenol A bis(2-hydroxyethyl) ether (TBBPA-DHEE) exposure

Tetrabromobisphenol A bis(2-hydroxyetyl) ether (TBBPA-DHEE) is among the main derivatives of Tetrabromobisphenol A (TBBPA). Result from previous study showed that TBBPA-DHEE can cause neurotoxicity in rat. In this study, zebrafish larvae were used for evaluation of TBBPA-DHEE-induced developmental toxicity, apoptosis, oxidative stress and the potential molecular mechanisms of action. Our result showed that TBBPA-DHEE exposure caused a significant concentration-dependent developmental toxicity endpoints like death rate, malformation rate, growth rate. TBBPA-DHEE altered locomotor and enzymes activities of larvae and caused apoptosis within the brain indicating the potential TBBPA-DHEE-induced cardiac, brain impairment in the zebrafish larvae. Our transcriptomic analysis shows that 691 genes were differentially expressed (DEGs) (539 upregulated, 152 downregulated). The KEGG and GO enrichment pathway analysis shows that the DEGs were involved in development, immunity, enzyme activity. Our study provides novel evidence on the neurodevelopmental toxicity and toxicity mechanism of TBBPA-DHEE which are vital for assessment of the environmental toxicity and risk assessment of the chemical.

Halogenated bisphenol a analogues induce PPARγ-independent toxicity within human hepatocellular carcinoma cells

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TBBPA and TCBPA alone or as binary mixtures decreases cell viability.

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TBBPA or TCBPA alone or as a mixture enhances effects of reference PPARγ ligands.

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Overexpression of PPARγ does not mitigate nor enhance the effects of TBBPA.

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TBBPA and TCBPA induce toxicity within HepG2 cells in a PPARγ-independent manner.

Tetrabromobisphenol A (TBBPA) and tetrachlorobisphenol A (TCBPA) – both halogenated bisphenol (BPA) analogues – are suspected ligands of peroxisome proliferator-activated receptor gamma (PPARγ). While previous studies have shown that TBBPA and TCBPA activate PPARγ within cell-free assays, the downstream effects of TBBPA- and TCBPA-induced PPARγ activation on cellular transcription and physiology have not been thoroughly investigated. Therefore, the objective of this study was to determine whether exposure to TBBPA or TCBPA (either alone or in combination) alters levels of neutral lipids and fatty acid synthase (FASN) – an enzyme that catalyzes synthesis of long-chain saturated fatty acids – within intact cells in a PPARγ-dependent manner. For this study, we relied on human hepatocellular carcinoma (HepG2) cells as a model since these liver cells express basal levels of PPARγ and have been used to study lipoprotein metabolism and regulation of drug metabolizing enzymes. Although exposure to TBBPA and TCBPA alone did not affect cell viability nor neutral lipid and FASN levels in a concentration-dependent manner, exposure to binary mixtures of TBBPA and TCBPA resulted in a concentration-dependent decrease in cell viability in the absence of concentration-dependent effects on neutral lipid and FASN levels. Interestingly, exposure to TBBPA or TCBPA alone or as a mixture enhanced the effects of a reference PPARγ agonist (ciglitazone) and antagonist (GW 9662) on cell viability (but not neutral lipid levels), suggesting that these two halogenated BPA analogues may interact synergistically with ciglitazone and GW 9662 to induce cytotoxicity. However, overexpression of PPARγ did not mitigate nor enhance the effects of TBBPA – a potent PPARγ ligand predicted by ToxCast’s cell-free competitive binding assays – on cell viability, neutral lipid levels, nor the cellular transcriptome. Overall, our findings suggest that halogenated BPA analogues such as TCBPA and TBBPA induce toxicity within HepG2 cells in a PPARγ-independent manner.

Rapid debromination of tetrabromobisphenol A by Cu/Fe bimetallic nanoparticles in water, its mechanisms, and genotoxicity after treatments

Tetrabromobisphenol A (TBBPA), a widely used brominated flame retardants, has been detected in various environmental matrices and is known to cause various adverse effects on human bodies. This study examined the feasibility and effectiveness of remediating TBBPA using Cu/Fe bimetallic nanoparticles (Cu/Fe BNPs) at various environmental and operational conditions. In general, TBBPA removal rate and debromination efficiency increased with higher Cu doping, higher Cu/Fe BNPs loading, higher temperature, and lower pH. At optimal conditions, TBBPA was completed removed at a rate constant > 0.2 min^-1 where over 90% TBBPA was transformed to BPA within 30 min. The activation energy was found to be 35.6 kJ/mol, indicating that TBBPA was predominantly removed via surface-controlled reactions. Under pH 3-7 and ≥ 25 °C, debromination was the dominant removal mechanism compared to adsorption. The complete debromination pathway and the time-evolution of intermediates byproducts at different pHs were also presented. Cu/Fe BNPs can be reused for more than 6 times with performance constancy. Genotoxic tests showed that the treated solution did not find a significant hazardous potential. The byproducts can be further degraded by additional H₂O₂ through Fenton reaction. These results demonstrated the efficacy of Cu/Fe BNPs for treating TBBPA and its potential for degrading other halogenated organic compounds.

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.

Tris (2,3-Dibromopropyl) Isocyanurate (TDBP-TAZTO or TBC) Shows Different Toxicity Depending on the Degree of Differentiation of the Human Neuroblastoma (SH-SY5Y) Cell Line

Tris (2,3-dibromopropyl) isocyanurate (TDBP-TAZTO or TBC) is a heterocyclic hexabromated flame retardant. It is widely used during the production of many synthetic compounds. High concentrations of TDBP-TAZTO were found in river water, surface sediments, soil, earthworms, and carp tissues. Moreover, it has been shown that this compound can cross the blood–brain barrier and accumulate in the gut and brain of carp. The aryl hydrocarbon receptor (AhR) has been characterized as a multifunctional intracellular sensor and receptor. AhR is an activator of cytochrome P450 1A1 and 1A2, which metabolize various toxic compounds. The aim of the study was to explain how/whether TDBP-TAZTO increases the expression and/or activity of the CYP1A1 enzyme and the AhR and TUBB3 expression during SH-SY5Y cell differentiation. SH-SY5Y cells were differentiated for 7 and 14 days using retinoic acid. Cell viability, ethoxyresorufin-O-deethylase (EROD) activity, and mRNA expression of CYP1A1, AhR, and TUBB3 were assessed. Our experiment showed that, during the differentiation process, the ability of TDBP-TAZTO to induce EROD activity in SH-SY5Y cells subsequently decreased, which may have been an effect of cell differentiation into neurons. Moreover, the results suggest that TDBP-TAZTO can affect the differentiation process. Since no CYP2B6 mRNA expression was detected, the CAR receptor may not be involved in the TDBP-TAZTO mechanism of action. However, more research is needed in this field to elucidate this mechanism precisely.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

The antidiabetic drug troglitazone protects against PrP (106‑126)‑induced neurotoxicity via the PPARγ‑autophagy pathway in neuronal cells

Prion diseases, which involve the alteration of cellular prion protein into a misfolded isoform, disrupt the central nervous systems of humans and animals alike. Prior research has suggested that peroxisome proliferator-activator receptor (PPAR)γ and autophagy provide some protection against neurodegeneration. PPARs are critical to lipid metabolism regulation and autophagy is one of the main cellular mechanisms by which cell function and homeostasis is maintained. The present study examined the effect of troglitazone, a PPARγ agonist, on autophagy flux in a prion peptide (PrP) (106–126)-mediated neurodegeneration model. Western blot analysis confirmed that treatment with troglitazone increased LC3-II and p62 protein expression, whereas an excessive increase in autophagosomes was verified by transmission electron microscopy. Troglitazone weakened PrP (106–126)-mediated neurotoxicity via PPARγ activation and autophagy flux inhibition. A PPARγ antagonist blocked PPARγ activation as well as the neuroprotective effects induced by troglitazone treatment, indicating that PPARγ deactivation impaired troglitazone-mediated protective effects. In conclusion, the present study demonstrated that troglitazone protected primary neuronal cells against PrP (106–126)-induced neuronal cell death by inhibiting autophagic flux and activating PPARγ signals. These results suggested that troglitazone may be a useful therapeutic agent for the treatment of neurodegenerative disorders and prion diseases.

Induction of Cyp450 enzymes by 4-thiazolidinone-based derivatives in 3T3-L1 cells in vitro

4-Thiazolidinones and related derivatives are regarded as privileged structures in medicinal chemistry and a source of new drug-like compounds. To date it is known that thiazolidinones are able to induce CYP1A1 activity in 3T3-L1 cells. Therefore, to extend the knowledge of the mechanism of thiazolidinones in the cell, four chemically synthesized heterocycles were tested on 3T3-L1 cells. The 3T3-L1 cells were exposed to Les-2194, Les-3640, Les-5935, and Les-6166. Our study showed that 1 μM βNF, Les-2194, and Les-6166 decreased the expression of Ahr mRNA. In turn, βNF, Les-2194, and Les-3640 increased the Cyp1a1 mRNA expression at the same time interval. On the other hand, Les-5935 was found to decrease the Cyp1a1 mRNA expression. Interestingly, the expression of Cyp1a2 mRNA was activated only by βNF and Les-2194. The expression of Cyp1b1 mRNA in the 3T3 cell line increased after the βNF and Les-2194 treatment but declined after the exposure to Les-5935 and Les-6166. Moreover, the Les-2194 and Les-5935 compounds were shown to increase the activity of EROD, MROD, and PROD. Les-3640 increased the activity of EROD and decreased the activity of PROD. In turn, the treatment with Les-6166 resulted in an increase in the activity of EROD and a decrease in the activity of MROD and PROD in the 3T3-L1 cells.

Tetrabromobisphenol A (TBBPA): A controversial environmental pollutant

Tetrabromobisphenol A (TBBPA) is one of the most widely used brominated flame retardants and is extensively used in electronic equipment, furniture, plastics, and textiles. It is frequently detected in water, soil, air, and organisms, including humans, and has raised concerns in the scientific community regarding its potential adverse health effects. Human exposure to TBBPA is mainly via diet, respiration, and skin contact. Various in vivo and in vitro studies based on animal and cell models have demonstrated that TBBPA can induce multifaceted effects in cells and animals, and potentially exert hepatic, renal, neural, cardiac, and reproductive toxicities. Nevertheless, other reports have claimed that TBBPA might be a safe chemical. In this review, we re-evaluated most of the published TBBPA toxicological assessments with the goal of reaching a conclusion about its potential toxicity. We concluded that, although low TBBPA exposure levels and rapid metabolism in humans may signify that TBBPA is a safe chemical for the general population, particular attention should be paid to the potential effects of TBBPA on early developmental stages.

Mitochondrial-related effects of pentabromophenol, tetrabromobisphenol A, and triphenyl phosphate on murine BV-2 microglia cells

The predominant reliance on bromated flame retardants (BFRs) is diminishing with expanded use of alternative organophosphate flame retardants. However, exposure related issues for susceptible populations, the developing, infirmed, or aged, remain given environmental persistence and home-environment detection. In this regard, reports of flame retardant (FR)-related effects on the innate immune system suggest process by which a spectrum of adverse health effects could manifest across the life-span. As representative of the nervous system innate immune system, the current study examined changes in microglia following exposure to representative FRs, pentabromophenol (PBP), tetrabromobisphenol A (2,2',6,6',-tetrabromo-4,4'-isopropylidine diphenol; TBBPA) and triphenyl phosphate (TPP). Following 18hr exposure of murine BV-2 cells, at dose levels resulting in ≥80% viability (10 and 40 μM), limited alterations in pro-inflammatory responses were observed however, changes were observed in mitochondrial respiration. Basal respiration was altered by PBP; ATP-linked respiration by PBP and TBBPA, and maximum respiration by all three FRs. Basal glycolytic rate was altered by PBP and TBBPA and compensatory glycolysis by all three. Phagocytosis was decreased for PBP and TBBPA. NLRP3 inflammasome activation was assessed using BV-2-ASC (apoptosis-associated speck-like protein containing a CARD) reporter cells to visualize aggregate formation. PBP, showed a direct stimulation of aggregate formation and properties as a NLRP3 inflammasome secondary trigger. TBBPA showed indications of possible secondary triggering activity while no changes were seen with TPP. Thus, the data suggests an effect of all three FRs on mitochondria metabolism yet, different functional outcomes including, phagocytic capability and NLRP3 inflammasome activation.

Effects of GW1929 on uterus, ovary and bone metabolism function in perimenopause rats

This study was aimed to investigate the effect of GW1929, a novel peroxisome proliferator-activated receptors gamma (PPARγ) agonist, in perimenopause rats. Female Sprague-Dawley (SD) rats were treated with 4-vinylcyclohexene diepoxide (VCD) to induce perimenopause rat model. Then they were given GW1929 in low, middle and high dosage. Histopathology observation of uterus and ovary tissues was measured by hematoxylin and eosin staining. The levels of serum hormones, oxidative stress related factors, bone formation and bone metabolism associated factors in serum were detected by kits. Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling (TUNEL) was employed to evaluate cell apoptosis. Furthermore, the expression of PPARγ and apoptosis associated proteins were measured by western blotting. The results revealed that there was no thickening of endometrium and no mature follicular development in ovaries of model group rats. GW1929 treatment recovered endometrial function with a tendency of thickening and there were mature follicle in the ovary. In addition, GW1929 increased the expression of PPARγ in both uterus and ovary tissues. The contents of estrogen (E2) were increased, whereas follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were decreased after being intervened with GW1929 in perimenopause rats. Concurrently, GW1929 reduced the levels of oxidative stress in a dose-dependent manner. Following treatment with GW1929, cell apoptosis in uterus and ovary tissues were attenuated, accompanied by a downregulation of Bax expression and an upregulation of Bcl-2 and cleaved caspase-3 expression. Moreover, In the GW1929-treated perimenopause rats, the levels of alkaline phosphatase (ALP), osteocalcin (OCN), osteopontin (OPN), bone alkaline phosphatase (BALP) and bone mineral density (BMD) were enhanced, while tartrate-resistant acid phosphatase (TRAP) was reduced. Taken together, we conclude that GW1929 could improve uterus, ovary and bone metabolism function in perimenopause rats, which is of great significance for the treatment of perimenopause.

Telmisartan Protects Auditory Hair Cells from Gentamicin-Induced Toxicity in vitro

BACKGROUND

Telmisartan is an angiotensin II receptor blocker that has pleiotropic effects and protective properties in different cell types. Moreover, telmisartan has also shown partial agonism on the peroxisome proliferator-activated receptor γ (PPAR-γ). Auditory hair cells (HCs) express PPAR-γ, and the protective role of PPAR-γ agonists on HCs has been shown.

OBJECTIVES

The objective of this study was to investigate the effects of telmisartan on gentamicin-induced ototoxicity in vitro.

METHODS

Cochlear explants were exposed to gentamicin with or without telmisartan, and/or GW9662, an irreversible PPAR-γ antagonist.

RESULTS

Telmisartan protected auditory HCs against gentamicin-induced ototoxicity. GW9662 completely blocked this protective effect, suggesting that it was mediated by PPAR-γ signaling. Exposure to GW9662 or telmisartan alone was not toxic to auditory HCs.

CONCLUSIONS

We found that telmisartan, via PPAR-γ signaling, protects auditory HCs from gentamicin-induced ototoxicity. Therefore, telmisartan could potentially be used in the future to prevent or treat sensorineural hearing loss.

Typical halogenated flame retardants affect human neural stem cell gene expression during proliferation and differentiation via glycogen synthase kinase 3 beta and T3 signaling

2',2',4,4'-tetrabromo diphenyl ether (BDE-47), one of the most abundant congeners of commercial pentaBDE utilized as flame retardants, has been phased out of production due to its potential neural toxicity and endocrine disrupting activities, and yet still present in the environment. Several alternatives to BDE-47, including tetrabromobisphenol A (TBBPA), tetrabromobisphenol S (TBBPS), tetrachlorobisphenol A (TCBPA) and decabromodiphenyl ether (BDE-209), are presently employed without restrictions and their potential toxic effects on human neural development are still unclear. In this study, we utilized a human neural stem cell (hNSC)-based system to evaluate the potential developmental neurotoxic effects of the above-mentioned five chemicals, at environment and human exposure relevant concentrations. We found that those compounds slightly altered the expression of hNSC identity markers (SOX2, SOX3 and NES), without impairing cell viability or proliferation, in part by either modulating glycogen synthase kinase 3 beta (GSK3β) signaling (TBBPS, TCBPA and BDE-47), and slightly disturbing the NOTCH pathway (TBBPA, TBBPS and TCBPA). Moreover, the five chemicals seemed to alter hNSC differentiation by perturbing triiodothyronine (T3) cellular signaling. Thus, our findings suggest that the five compounds, especially TBBPS, TCBPA, and BDE-47, may affect hNSC self-renewal and differentiation abilities and potentially elicit neural developmental toxicity.

Tetrabromobisphenol A Promotes the Osteoclastogenesis of RAW264.7 Cells Induced by Receptor Activator of NF-kappa B Ligand In Vitro

BACKGROUND

Tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame-retardants, is a representative persistent organic pollutants group. Studies on TBBPA toxicity have been conducted using various target cells; however, few studies have investigated TBBPA toxicity in bone cells. Therefore, this study investigated the in vitro effects of TBBPA on osteoclasts, a cell type involved in bone metabolism.

METHODS

RAW264.7 cells were cultured in medium containing 50 ng/mL receptor activator of nuclear factor kappa B ligand (RANKL) and varying concentrations of TBBPA. To evaluate the effects of TBBPA on the differentiation and function of osteoclasts, osteoclast-specific gene expression, tartrate-resistant acid phosphatase (TRAP) activity, bone resorbing activity, mitochondrial membrane potential (MMP) and mitochondrial superoxide were measured.

RESULTS

The presence of 20 μ TBBPA significantly increased TRAP activity in RANKL-stimulated RAW264.7 cells, the bone resorbing activity of osteoclasts, and the gene expression of Akt2, nuclear factor of activated T-cells cytoplasmic 1, and chloride channel voltage-sensitive 7. However, TBBPA treatment caused no change in the expression of carbonic anhydrase II, cathepsin K, osteopetrosis-associated transmembrane protein 1, Src, extracellular signal-related kinase, GAB2, c-Fos, or matrix metalloproteinase 9. Furthermore, 20 μ TBBPA caused a significant decrease in MMP and a significant increase in mitochondrial superoxide production.

CONCLUSION

This study suggests that TBBPA promotes osteoclast differentiation and activity. The mechanism of TBBPA-stimulated osteoclastogenesis might include increased expression of several genes involved in osteoclast differentiation and reactive oxygen species production.

Tetrabromobisphenol A: Disposition, kinetics and toxicity in animals and humans

Tetrabromobisphenol A (TBBPA) is a nonregulated brominated flame retardant with a high production volume, and it is applied in a wide variety of consumer products. TBBPA is ubiquitous in abiotic matrices, wildlife and humans around the world. This paper critically reviews the published scientific data concerning the disposition, metabolism or kinetics and toxicity of TBBPA in animals and humans. TBBPA is rapidly absorbed and widely distributed among tissues, and is excreted primarily in the feces. In rats, TBBPA and its metabolites have limited systemic bioavailability. TBBPA has been detected in human milk in the general population. It is available to both the developing fetus and the nursing pups following maternal exposure. It has been suggested that TBBPA causes acute toxicity, endocrine disruptor activity, immunotoxicity, neurotoxicity, nephrotoxicity, and hepatotoxicity in animals. Cell-based assays have shown that TBBPA can induce reactive oxygen species in a concentration-dependent manner, and it promotes the production of inflammatory factors such as TNF α, IL-6, and IL-8. Cells exposed to high levels of TBBPA exhibit seriously injured mitochondria and a dilated smooth endoplasmic reticulum. This review will enhance the understanding of the potential risks of TBBPA exposure to ecological and human health.

Tetrabromobisphenol A-induced depolarization of rat cerebellar granule cells: ex vivo and in vitro studies

The brominated flame retardant tetrabromobisphenol A (TBBPA) is toxic to cultured brain neurons, and glutamate receptors partially mediate this effect; consequently, the depolarizing effect of TBBPA on neurons is to be expected, but it is yet to be actually demonstrated. The aim of this study was to detect TBBPA-evoked depolarization and identify the underlying mechanisms. The plasma membrane potential of rat cerebellar granule cells (CGC) in cerebellar slices or in primary cultures was measured using whole-cell current clamp recordings, or the fluorescent probe oxonol VI, respectively. The contribution of NMDA and AMPA receptors, voltage-gated sodium channels and intracellular calcium mobilization was tested using their selective antagonists or inhibitors. Direct interactions of TBBPA with NMDARs were tested by measuring the specific binding of radiolabeled NMDAR ligands to isolated rat cortical membrane fraction. TBBPA (25 μM) strongly depolarized CGC in cerebellar slices, and at ≥ 7.5 μM concentration-dependently depolarized primary CGC cultures. Depolarization of the primary CGC by 25 μM TBBPA was partly reduced when MK-801 was applied alone or in combination with either TTX or CNQX, or where bastadin 12 was applied in combination with ryanodine, whereas depolarization was completely prevented when MK-801, CNQX and TTX where combined. TBBPA had no effect on the specific binding of NMDAR radio-ligands to isolated cortical membranes. These results demonstrate the depolarizing effect of TBBPA on CGC, which is mainly mediated by ionotropic glutamate receptors, while voltage-gated sodium channels are also involved. We found no evidence for the direct activation of NMDARs by TBBPA.

TBBPA and Its Alternatives Disturb the Early Stages of Neural Development by Interfering with the NOTCH and WNT Pathways

Tetrabromobisphenol A (TBBPA), as well as its alternatives Tetrabromobisphenol S (TBBPS) and Tetrachlorobisphenol A (TCBPA), are widely used halogenated flame retardants. Their high detection rates in human breast milk and umbilical cord serum have raised wide concerns about their adverse effects on human fetal development. In this study, we evaluated the cytotoxicity and neural developmental toxicity of TBBPA, TBBPS, and TCBPA with a mouse embryonic stem cell (mESC) system, at human body fluid and environmental relevant doses. All the three compounds showed similar trends in their cytotoxic effects. However, while TBBPA and TBBPS stimulated ESC neural differentiation, TCBPA significantly inhibited neurogenesis. Mechanistically, we demonstrated that, as far as the NOTCH (positive regulator) and WNT (negative regulator) pathways were concerned, TBBPA only partially and slightly disturbed them, whereas TBBPS significantly inhibited the WNT pathway, and TCBPA down-regulated the expression of NOTCH effectors but increased the WNT signaling, actions which both inhibited neural specification. In conclusion, our findings suggest that TBBPS and TCBPA may not be safe alternatives to TBBPA, and their toxicity need to be comprehensively evaluated.

Intranasal administration of tetrabromobisphenol A bis(2-hydroxyethyl ether) induces neurobehavioral changes in neonatal Sprague Dawley rats

Tetrabromobisphenol A (TBBPA) and its derivatives are now being highly concerned due to their emerging environmental occurrence and deleterious effects on non-target organisms. Considering the potential neurotoxicity of TBBPA derivatives which has been demonstrated in vitro, what could happen in vivo is worthy of being studied. Tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE), a representative TBBPA derivative, was selected for a 21-day exposure experiment on neonatal Sprague Dawley (SD) rats through intranasal administration. The neurobehavioral, histopathological changes, and differentially expressed genes based on RNA microarray were investigated to evaluate the neurological effects of this chemical. The results indicated that TBBPA-BHEE exposure significantly compromised the motor co-ordination performance and the locomotor activities (p<0.05). The neurobehavioral phenotype could be attributed to the obvious histopathological changes in both cerebrum and cerebellum, such as neural cell swelling, microglial activation and proliferation. A total of 911 genes were up-regulated, whereas 433 genes were down-regulated. Gene set enrichment analysis showed multiple signaling pathways, including ubiquitin-mediated proteolysis and wingless-int (Wnt) signaling pathway etc. were involved due to TBBPA-BHEE exposure. The gene ontology enrichment analysis showed the basic cellular function and the neurological processes like synaptic transmission were influenced. The toxicological effects of TBBPA-BHEE observed in this study suggested the potential neuronal threaten from unintended exposure, which would be of great value in the biosafety evaluation of TBBPA derivatives.

Steroid and Xenobiotic Receptor Signalling in Apoptosis and Autophagy of the Nervous System

Apoptosis and autophagy are involved in neural development and in the response of the nervous system to a variety of insults. Apoptosis is responsible for cell elimination, whereas autophagy can eliminate the cells or keep them alive, even in conditions lacking trophic factors. Therefore, both processes may function synergistically or antagonistically. Steroid and xenobiotic receptors are regulators of apoptosis and autophagy; however, their actions in various pathologies are complex. In general, the estrogen (ER), progesterone (PR), and mineralocorticoid (MR) receptors mediate anti-apoptotic signalling, whereas the androgen (AR) and glucocorticoid (GR) receptors participate in pro-apoptotic pathways. ER-mediated neuroprotection is attributed to estrogen and selective ER modulators in apoptosis- and autophagy-related neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, stroke, multiple sclerosis, and retinopathies. PR activation appeared particularly effective in treating traumatic brain and spinal cord injuries and ischemic stroke. Except for in the retina, activated GR is engaged in neuronal cell death, whereas MR signalling appeared to be associated with neuroprotection. In addition to steroid receptors, the aryl hydrocarbon receptor (AHR) mediates the induction and propagation of apoptosis, whereas the peroxisome proliferator-activated receptors (PPARs) inhibit this programmed cell death. Most of the retinoid X receptor-related xenobiotic receptors stimulate apoptotic processes that accompany neural pathologies. Among the possible therapeutic strategies based on targeting apoptosis via steroid and xenobiotic receptors, the most promising are the selective modulators of the ER, AR, AHR, PPARγ agonists, flavonoids, and miRNAs. The prospective therapies to overcome neuronal cell death by targeting autophagy via steroid and xenobiotic receptors are much less recognized.

Altered expression of genes involved in programmed cell death in primary cultured rat cerebellar granule cells acutely challenged with tetrabromobisphenol A

In the present study, primary cultures of rat cerebellar granule cells (CGC) and the RT² Profiler PCR array were used to examine the effect of acutely applied brominated flame retardant tetrabromobisphenol A (TBBPA) on the expression of 84 genes related to the main modes of programmed cell death. CGC, at the 7th day of culture, were exposed to 10 or 25μM TBBPA for 30min. Then, 3, 6, and 24h later, the viability of the cells was examined by the staining with propidium iodide (PI) or using the calcein/ethidium homodimer (CA/ET) live/dead kit, and RNA was extracted for the evaluation of gene expression by RT-PCR. At 3, 6 and 24h after the treatment, the number of viable neurons decreased, according to the PI staining method, to 75%, 58% and 41%, respectively, and with the CA/ET method to 65%, 58% and 28%, respectively. In CGC analyzed 3h after the treatment with 25μM TBBPA or 6h after 10μM TBBPA, the only change in the gene expression was a reduction in the expression of Tnf, which is associated with autophagy and may activate some pro-apoptotic proteins. Six hours after 25μM TBBPA, only 2 genes were over-expressed, a pro-apoptotic Tnfrsf10b and Irgm, which is related to autophagy, and the genes that were suppressed included the anti-apoptotic gene Xiap, the necrosis-related Commd4, pro-apoptotic Abl1, 5 genes involved in autophagy (App, Atg3, Mapk8, Pten, and Snca) and 2 genes that participate in two metabolic pathways: Atp6v1g2 (pro-apoptotic and necrosis) and Tnf (pro-apoptotic, autophagy). Autophagy-related Snca and Tnf remained under-expressed 24h after treatment with 25μM TBBPA, which was accompanied by the over-expression of the pro-apoptotic Casp6, the anti-apoptotic Birc3, 2 genes related to autophagy (Htt and Irgm) and 2 genes (Fas and Tp53) that are involved in both apoptosis (pro-apoptotic) and autophagy. These results show a complex pattern of TBBPA-evoked changes in the expression of the genes involved in the programmed neuronal death, indicating no induction of programmed necrosis, an early suppression of the autophagy and anti-apoptotic genes, followed by a delayed activation of genes associated with apoptosis.

Apoptosis Induced by the UV Filter Benzophenone-3 in Mouse Neuronal Cells Is Mediated via Attenuation of Erα/Pparγ and Stimulation of Erβ/Gpr30 Signaling

Although benzophenone-3 (BP-3) has frequently been reported to play a role in endocrine disruption, there is insufficient data regarding the impact of BP-3 on the nervous system, including its possible adverse effects on the developing brain. Our study demonstrated that BP-3 caused neurotoxicity and activated apoptosis via an intrinsic pathway involving the loss of mitochondrial membrane potential and the activation of caspases-9 and -3 and kinases p38/MAPK and Gsk3β. These biochemical alterations were accompanied by ROS production, increased apoptotic body formation and impaired cell survival, and by an upregulation of the genes involved in apoptosis. The BP-3-induced effects were tissue-specific and age-dependent with the most pronounced effects observed in neocortical cells at 7 days in vitro. BP-3 changed the messenger RNA (mRNA) expression levels of Erα, Erβ, Gpr30, and Pparγ in a time-dependent manner. At 3 h of exposure, BP-3 downregulated estrogen receptor mRNAs but upregulated Pparγ mRNA. After prolonged exposures, BP-3 downregulated the receptor mRNAs except for Erβ mRNA that was upregulated. The BP-3-induced patterns of mRNA expression measured at 6 and 24 h of exposure reflected alterations in the protein levels of the receptors and paralleled their immunofluorescent labeling. Erα and Pparγ agonists diminished, but Erβ and Gpr30 agonists stimulated the BP-3-induced apoptotic and neurotoxic effects. Receptor antagonists caused the opposite effects, except for ICI 182,780. This is in line with a substantial reduction in the effects of BP-3 in cells with siRNA-silenced Erβ/Gpr30 and the maintenance of BP-3 effects in Erα- and Pparγ siRNA-transfected cells. We showed for the first time that BP-3-affected mRNA and protein expression levels of Erα, Erβ, Gpr30, and Pparγ, paralleled BP-3-induced apoptosis and neurotoxicity. Therefore, we suggest that BP-3-evoked apoptosis of neuronal cells is mediated via attenuation of Erα/Pparγ and stimulation of Erβ/Gpr30 signaling.

The Role of Ca2+ Imbalance in the Induction of Acute Oxidative Stress and Cytotoxicity in Cultured Rat Cerebellar Granule Cells Challenged with Tetrabromobisphenol A

Using primary cultures of rat cerebellar granule cells (CGC) we examined the role of calcium transients induced by tetrabromobisphenol A (TBBPA) in triggering oxidative stress and cytotoxicity. CGC were exposed for 30 min to 10 or 25 µM TBBPA. Changes in intracellular calcium concentration ([Ca²⁺]_i), in the production of reactive oxygen species (ROS), and in the potential of mitochondria (∆Ψm) were measured fluorometrically during the exposure. The intracellular glutathione (GSH) and catalase activity were determined after the incubation; cell viability was evaluated 24 h later. TBBPA concentration-dependently increased [Ca²⁺]_i and ROS production, and reduced GSH content, catalase activity, ∆Ψm and neuronal viability. The combination of NMDA and ryanodine receptor antagonists, MK-801 and bastadin 12 with ryanodine, respectively, prevented Ca²⁺ transients and partially reduced cytotoxicity induced by TBBPA at both concentrations. The antagonists also completely inhibited oxidative stress and depolarization of mitochondria evoked by 10 µM TBBPA, whereas these effects were only partially reduced in the 25 µM TBBPA treatment. Free radical scavengers prevented TBBPA-induced development of oxidative stress and improved CGC viability without having any effect on the rises in Ca²⁺ and drop in ∆Ψm. The co-administration of scavengers with NMDA and ryanodine receptor antagonists provided almost complete neuroprotection. These results indicate that Ca²⁺ imbalance and oxidative stress both mediate acute toxicity of TBBPA in CGC. At 10 µM TBBPA Ca²⁺ imbalance is a primary event, inducing oxidative stress, depolarization of mitochondria and cytotoxicity, whilst at a concentration of 25 µM TBBPA an additional Ca²⁺-independent portion of oxidative stress and cytotoxicity emerges.

The potential neurotoxicity of emerging tetrabromobisphenol A derivatives based on rat pheochromocytoma cells

Tetrabromobisphenol A (TBBPA) can cause diverse adverse effects including neurotoxicity. Emerging TBBPA derivatives, with high structure similarity to the parent compound, are now being concerned. In this study, the potential neurotoxicities of four TBBPA derivatives and their parent compound were studied by cell viability inhibition in rat pheochromocytoma cells (PC12) and the corresponding molecular mechanisms were investigated. The cellular toxicity was correlated with the chemical hydrophobicity. Tetrabromobisphenol A bis(2-hydroxyethyl ether) (TBBPA-BHEE) exhibited the highest cellular toxicity to PC12 due to its lowest hydrophobicity among these 5 tested compounds. Further experiments showed that TBBPA-BHEE disturbed dopamine (DA) secretion and altered acetylcholinesterase (AChE) enzymatic activity in PC12 cells. The molecular mechanism study indicated that TBBPA-BHEE induced cellular toxicity to PC12 cells through ROS-mediated caspase activation to a large extent, which was partially attenuated by the anti-oxidation of Vitamin E. Moreover, in contrast to TBBPA, the occurrence of TBBPA-BHEE toxicity to PC12 was not attributed to activation of mitogen-activated protein kinases (MAPKs) or thyroid hormone (TH) signaling pathway. These findings suggest TBBPA derivatives, especially TBBPA-BHEE, as potential neurotoxins need urgent attention.

A review of status of tetrabromobisphenol A (TBBPA) in China

Tetrabromobisphenol A (TBBPA), a currently intensively used brominated flame retardant (BFR), is employed primarily as a reactive flame retardant in printed circuit boards but also has additive applications in several types of polymers. TBBPA is a ubiquitous environmental contaminant that is observed in both abiotic and biotic matrices. This paper summarizes and critically reviews the published scientific data concerning the current pollution status of TBBPA in China. To provide an indication of the seriousness of the pollution levels of TBBPA in China, the data are compared with available existing data from other countries of the world. According to the available data, the sources of TBBPA in China are mainly derived from the primitive e-waste dismantling, TBBPA manufacturing and processing of TBBPA-based materials. The most serious cases of TBBPA pollution in China are in Guiyu, Guangdong (primitive e-waste dismantling site) with concentrations of TBBPA reaching 66,010-95,040 pg m(-3) in air, Shouguang, Shandong (TBBPA manufacturing site) with concentrations of TBBPA reaching 1.64-7758 ng g(-1) dry weight in soil, and Chaohu Lake, Anhui (industry concentration site) with concentrations of TBBPA reaching 850-4870 ng L(-1) in water. In general, China is the most polluted region as affected by TBBPA compared with other countries. The present review preliminarily reveals the research status of TBBPA in China.

The role of PPARγ in TBBPA-mediated endocrine disrupting effects in human choriocarcinoma JEG-3 cells

The goal of the present study was to investigate the action of TBBPA on PPARγ protein expression in vitro in human choriocarcinoma-derived placental JEG-3 cells. We also analyzed TBBPA for its action on placental secretion of progesterone and β-hCG, cell viability, and apoptosis. Our results showed that after TBBPA treatment at 10 nM and 10 µM, PPARγ protein expression increased in a time-dependent manner until 48 h and then slightly decreased at 72 h but was still above the control level. This alteration in PPARγ protein expression was accompanied by a decreased β-hCG level. Interestingly, co-treatment with the PPARγ antagonist GW9662 reversed the TBBPA-mediated changes in PPARγ protein expression but, according to β-hCG secretion, potentiated an inhibitory effect of TBBPA. Additionally, in our study, we assessed the ability of TBBPA to increase progesterone levels in JEG-3 cells compared with those of controls. Finally, in the present study, we demonstrated that TBBPA at all of the tested doses significantly increased caspase-3 activity compared with that of the vehicle control. The apoptotic action of TBBPA was also confirmed by Hoechst 33342 staining. These results showed the up-regulation of PPARγ protein expression after TBBPA exposure in human placental cells. Although co-treatment with antagonist of PPARγ reversed the TBBPA-mediated increase in this protein expression and restored it to the control level, it did not reverse the effect on β-hCG secretion. This indicated that the mechanism of TBBPA-induced changes in β-hCG secretion is PPARγ-independent.

Role of Ryanodine and NMDA Receptors in Tetrabromobisphenol A-Induced Calcium Imbalance and Cytotoxicity in Primary Cultures of Rat Cerebellar Granule Cells

The study assessed the role of ryanodine receptors (RyRs) and NMDA receptors (NMDARs) in the Ca²⁺ transients and cytotoxicity induced in neurons by the brominated flame retardant tetrabromobisphenol A (TBBPA). Primary cultures of rat cerebellar granule cells (CGC) were exposed to 7.5, 10, or 25 µM TBBPA for 30 min, and cell viability was assessed after 24 h. Moreover, ⁴⁵Ca uptake was measured, and changes in the intracellular Ca²⁺ concentration ([Ca²⁺]_i) were studied using the fluo-3 probe. The involvement of NMDARs and RyRs was verified using the pertinent receptor antagonists, 0.5 µM MK-801 and 2.5 µM bastadin 12, which was co-applied with 200 µM ryanodine, respectively. The results show that TBBPA concentration-dependently induces an increase in [Ca²⁺]_i. This effect was partly suppressed by the inhibitors of RyRs and NMDARs when administered separately, and completely abrogated by their combined application. A concentration-dependent activation of ⁴⁵Ca uptake by TBBPA was prevented by MK-801 but not by RyR inhibitors. Application of ≥10 µM TBBPA concentration-dependently reduced neuronal viability, and this effect was only partially and to an equal degree reduced by NMDAR and RyR antagonists given either separately or in combination. Our results directly demonstrate that both the RyR-mediated release of intracellular Ca²⁺ and the NMDAR-mediated influx of Ca²⁺ into neurons participate in the mechanism of TBBPA-induced Ca²⁺ imbalance in CGC and play a significant, albeit not exclusive, role in the mechanisms of TBBPA cytotoxicity.

Facilitation of adipocyte differentiation of 3T3-L1 cells by debrominated tetrabromobisphenol A compounds detected in Japanese breast milk

Tetrabromobisphenol A (TeBBPA) is widely used type of brominated flame retardant. In this study, we newly synthesized materials for the debrominated congeners, 2,2',6-tribromobisphenol A (TriBBPA), 2,2'-dibromobisphenol A (2,2'-DiBBPA), 2,6-dibromobisphenol A (2,6-DiBBPA), and 2-monobromobisphenol A (MoBBPA) and evaluated the actual extent of contamination with bisphenol A (BPA), TeBBPA and debrominated congeners in Japanese breast milk samples. TriBBPA was detected at higher levels than that of TeBBPA, while DiBBPA and MoBBPA were detected at lower levels than that of TeBBPA. This observation suggested that humans are exposed to debrominated congeners, which might cause adverse effects. Contamination of the congeners in breast milk was concern about risk infant health, having vulnerable defense system. As pilot study by in vitro experiment, we assessed the toxic potency of debrominated congeners by studying their effect on adipocyte differentiation in 3T3-L1 cells. We observed 2,6-DiBBPA, TriBBPA and TeBBPA elevated the lipid accumulation and adipocyte-specific protein 2 expression in a manner dependent on the number of substituted bromines. Moreover, PPARγ transcriptional activities increased in a dose-dependent manner in the presence of 2,6-DiBBPA and TriBBPA as well as TeBBPA. Our study clarified that TeBBPA and its debrominated congeners accumulated in breast milk and the debrominated congeners promoted adipocyte differentiation, showing that a comprehensive evaluation of the influences of these compounds including the debrominated congeners of TeBBPA on health in infants is necessary.

Neuroprotective action of raloxifene against hypoxia-induced damage in mouse hippocampal cells depends on ERα but not ERβ or GPR30 signalling

Raloxifene is the selective estrogen receptor modulator (SERM) currently used in clinical practice to activate estrogen receptors (ERs) in bone tissue and to antagonise ERs in breast and uterine cancers. Little is known, however, about mechanisms of action of raloxifene on hypoxia-induced neuronal cell damage. The aim of the present study was to investigate the neuroprotective potential of raloxifene against hypoxia-induced damage of mouse hippocampal cells in primary cultures, with a particular focus on raloxifene interactions with the classical nuclear ERs (ERα, ERβ) and the recently identified membrane ER G-protein-coupled receptor 30 (GPR30). In this study, 18 h of hypoxia increased hypoxia inducible factor 1 alpha (Hif1α) mRNA expression and induced apoptotic processes, such as loss of the mitochondrial membrane potential, activation of caspase-3 and fragmentation of cell nuclei based on Hoechst 33342 staining. These effects were accompanied by reduced ATPase and intracellular esterase activities as well as substantial lactate dehydrogenase (LDH) release from cells exposed to hypoxia. Our study demonstrated strong neuroprotective and anti-apoptotic caspase-3-independent actions of raloxifene in hippocampal cells exposed to hypoxia. Raloxifene also inhibited the hypoxia-induced decrease in Erα mRNA expression and attenuated the hypoxia-induced rise in Erβ and Gpr30 mRNA expression levels. Impact of raloxifene on hypoxia-affected Erα mRNA was mirrored by fluctuations in the protein level of the receptor as demonstrated by Western blot and immunofluorescent labelling. Raloxifene-induced changes in Erβ mRNA expression level were in parallel with ERβ immunofluorescent labeling. However, changes in Gpr30 mRNA level were not reflected by changes in the protein levels measured either by ELISA, Western blot or immunofluorescent staining at 24h post-treatment. Using specific siRNAs, we provided evidence for a key involvement of ERα, but not ERβ or GPR30 in neuroprotective action of raloxifene against hypoxia-induced cell damage. This study may have implications for the treatment or prevention of hypoxic brain injury and the administration of current or new generations of SERMs specific to ERα. This article is part of a Special Issue entitled "Sex steroids and brain disorders".

Identification of a proliferator-activated receptor-γ antagonist for the treatment of type 2 diabetes mellitus

In the present study, a novel antagonist of the peroxisome proliferator-activated receptor-γ (PPARγ) was screened and identified, and a cell-based evaluation of the biological activity of this PPARγ antagonist was conducted. The aim of the study was to produce results that may provide a foundation for the development of a novel compound in the treatment of type 2 diabetes mellitus. Since obesity is the main cause of insulin resistance and type 2 diabetes, identifying a new reagent that is able to inhibit adipocyte differentiation and lipid accumulation is a feasible method of developing novel anti-diabetes drugs. The PPARγ antagonist was screened using a mammalian one-hybrid system and transcriptional activation. The effects of the compound on adipocyte differentiation were investigated by staining the preadipocytes with Oil Red O. In addition, the effects of the compound on the expression levels of genes associated with lipid metabolism were detected using quantitative polymerase chain reaction on differentiated mature 3T3-L1 adipocytes. As a PPARγ antagonist, N-((1H-benzo[d]imidazol-2-yl)methyl) aniline (Compound Q) was shown to depress the transcriptional activity and coactivator recruitment of PPARγ, as well as preadipocyte differentiation, in a concentration-dependent manner. The compound was also shown to decrease the expression levels of genes associated with PPARγ-regulated lipid metabolism. In conclusion, the compound screening platform was demonstrated to be valid, and the present study identified a novel PPARγ antagonist that was shown to effectively reduce the rate of adipocyte differentiation and the expression of genes associated with lipid metabolism.

Isomer-nonspecific action of dichlorodiphenyltrichloroethane on aryl hydrocarbon receptor and G-protein-coupled receptor 30 intracellular signaling in apoptotic neuronal cells

Extended residual persistence of the pesticide dichlorodiphenyltrichloroethane (DDT) raises concerns about its long-term neurotoxic effects. Little is known, however, about DDT toxicity during the early stages of neural development. This study demonstrated that DDT-induced apoptosis of mouse embryonic neuronal cells is a caspase-9-, caspase-3-, and GSK-3β-dependent process, which involves p,p'-DDT-specific impairment of classical ERs. It also provided evidence for DDT-isomer-nonspecific alterations of AhR- and GPR30-mediated intracellular signaling, including changes in the levels of the receptor and receptor-regulated mRNAs, and also changes in the protein levels of the receptors. DDT-induced stimulation of AhR-signaling and reduction of GPR30-signaling were verified using selective ligands and specific siRNAs. Co-localization of the receptors was demonstrated with confocal microscopy, and the presence of functional GPR30 was detected by electrophysiology. This study demonstrates that stimulation of AhR-signaling and impairment of GPR30-signaling play important roles in the propagation of DDT-induced apoptosis during the early stages of neural development.

Sesamin enhances cholesterol efflux in RAW264.7 macrophages

Foam cells formation as a result of the uncontrolled cytophagy of modified cholesterol by macrophages plays a key role in the occurrence and development of atherosclerosis. Sesamin is an active constituent of Sesamum indicum which has been shown to possess multiple pharmacological activities. In this work, we investigated the effects of sesamin on foam cell formation and cholesterol efflux in RAW264.7 macrophages. Sesamin dose-dependently inhibited the enhanced cholesterol accumulation elicited by oxidized low-density lipoprotein cholesterol (oxLDL) in RAW264.7 cells. Treatment with sesamin (10 μM) significantly enhanced cholesterol efflux mediated by high-density lipoprotein (HDL). Realtime quantitative PCR and luciferase assays showed that sesamin significantly increased the mRNA levels of PPARγ, LXRα, and ABCG1, and increased the transcriptional activity of PPARγ. The stimulating effect of sesamin on cholesterol efflux was substantially inhibited by the co-treatment with GW9662, a potent inhibitor of PPARγ. These results suggest that sesamin is a new inhibitor of foam cell formation that may stimulate cholesterol efflux through upregulation of the PPARγ-LXRα-ABCG1 pathway.