Tris (2-chloroethyl) phosphate induces senescence-like phenotype of hepatocytes via the p21Waf1/Cip1-Rb pathway in a p53-independent manner

Unveiling the mechanisms of reproductive toxicity induced by full life-cycle exposure to environmentally relevant concentrations of tris(2-chloroethyl) phosphate in male zebrafish

Tris (2-chloroethyl) phosphate (TCEP), a commonly used organophosphate flame retardant, has garnered considerable concern owing to its pervasive presence in the environment and its toxic effects on living organisms. The perpetuation of populations and species hinges on successful reproduction, yet research into the mechanisms underlying reproductive toxicity remains scant, particularly in aquatic species. In this work, zebrafish embryos were exposed to TCEP (0, 0.8, 4, 20, and 100 µg/L) for 120 days until sexual maturation, and multiple reproductive endpoints were investigated in male zebrafish. Our results showed that the body weight, body length, and gonadal-somatic index (GSI) were remarkably decreased in all TCEP treatment groups (except GSI in the 0.8 µg/L TCEP-treated group). Long-term exposure to TCEP led to reduced reproductive capacity of male zebrafish, as evidenced by decreased fertilization. Histological observation gave an indication of delayed testicular development and inhibited spermatogenesis under TCEP stress. The content of testosterone (T) was significantly elevated in all TCEP treatment group, whereas 17 β-estradiol (E2) levels remained stable. Transcriptome analysis revealed a lot of downregulated genes involved in steroid hormone biosynthesis, energy metabolism, and sperm motility, which might account for the imbalance of steroid hormone levels, retarded spermatogenesis and declined fertilization success. Overall, these findings offered a thorough understanding of the mechanisms underlying the male reproductive toxicity caused by TCEP, highlight the risk of TCEP on reproductive health of fish.

Exploring the effects of environmentally relevant concentrations of tris(2-chloroethyl) phosphate on tadpole health: A comprehensive analysis of intestinal microbiota and hepatic transcriptome

Tris(2-chloroethyl) phosphate (TCEP), a chlorinated organophosphate ester, is commonly found in aquatic environments. Due to its various toxic effects, it may pose a risk to the health of aquatic organisms. However, the potential impacts of TCEP exposure on the intestinal microbiota and hepatic function in amphibians have not been reported. This study investigated the impact of long-term exposure to environmentally relevant concentrations of TCEP (0, 3, and 90 μg/L) on the intestinal microbiota and hepatic transcriptome of Polypedates megacephalus tadpoles. The results showed that the body size of the tadpoles decreased significantly with an increase in TCEP concentration. Additionally, TCEP exposure affected the diversity and composition of the intestinal microbiota in tadpoles, leading to significant changes in the relative abundance of certain bacterial groups (the genera Aeromonas decreased and Citrobacter increased) and potentially promoting a more even distribution of microbial species, as indicated by a significant increase in the Simpson index. Moreover, the impact of TCEP on hepatic gene expression profiles in tadpoles was significant, with the majority of differentially expressed genes (DEGs) (709 out of 906 total DEGs in 3 μg/L of TCEP versus control, and 344 out of 387 DEGs in 90 μg/L of TCEP versus control) being significantly down-regulated, which were primarily related to immune response and immune system process. Notably, exposure to TCEP significantly reduced the relative abundance of the genera Aeromonas and Cetobacterium in the tadpole intestine. This reduction was positively correlated with the down-regulated expression of immune-related genes in the liver of corresponding tadpoles. In summary, these findings provide empirical evidence of the potential health risks to tadpoles exposed to TCEP at environmentally relevant concentrations.

Organophosphorus Flame Retardant TCPP Induces Cellular Senescence in Normal Human Skin Keratinocytes: Implication for Skin Aging

Tris (1-chloro-2-propyl) phosphate (TCPP) is one of the most frequently detected organophosphorus flames in the environment. Continuous daily exposure to TCPP may harm human skin. However, little is known about the adverse effects of TCPP on human skin. In this study, we first evaluated the detrimental effects and tried to uncover the underlying mechanisms of TCPP on human skin keratinocytes (HaCaT) after 24 h exposure. We found that TCPP caused a concentration-dependent decrease in HaCaT cell viability after exposure to 1.56-400 μg/mL for 24 h, with an IC₅₀ of 275 μg/mL. TCPP also promoted the generation of intracellular reactive oxygen species (ROS) and triggered DNA damage, evidenced by an increase of phosphorylated histone H2A.X (γH2A.X) in the nucleus. Furthermore, the cell cycle was arrested at the G1 phase at 100 μg/mL by upregulation of the mRNA expression of p53 and p21 and downregulation of cyclin D1 and CDK4 expression. Additionally, both the senescence-associated-β-galactosidase activity and related proinflammatory cytokine IL-1β and IL-6 were elevated, indicating that TCPP exposure caused cellular senescence may be through the p53-dependent DNA damage signal pathway in HaCaT cells. Taken together, our data suggest that flame-retardant exposure may be a key precipitating factor for human skin aging.

Probiotics protect against hepatic steatosis in tris (2-chloroethyl) phosphate-induced metabolic disorder of mice via FXR signaling

Tris (2-chloroethyl) phosphate (TCEP), the most widely useful and most frequently detective organophosphate flame retardants in environment, has been shown potential relationship with adolescent weight. Probiotics is an effective therapy for metabolic diseases such as obesity and NAFLD with gut microbiota dysregulation. This study aims to explore the protective effects of probiotics against lipid metabolic disorder induced by chronic TCEP exposure and demonstrate the mechanism of this event. The data showed that dietary complex probiotics supplement attenuated TCEP-induced obesity, hyperlipidemia, liver dysfunction, and hepatic steatosis. In addition, dietary complex probiotics suppressed TCEP-promoted ileal FXR signaling, and upregulated hepatic FXR/SHP pathway inhibited by TCEP. Moreover, dietary complex probiotics stimulated PPARα-mediated lipid oxidation and suppressed SREBP1c/PPARγ-mediated lipid synthesis via regulation of FXR signaling. Therefore, this study indicates that dietary complex probiotics could protect against hepatic steatosis via FXR-mediated signaling pathway in TCEP-induced metabolism disorder in mice, resulting in attenuation of systemic lipid accumulation.

Tris (2-chloroethyl) phosphate (TCEP) induces obesity and hepatic steatosis via FXR-mediated lipid accumulation in mice: Long-term exposure as a potential risk for metabolic diseases

Tris (2-chloroethyl) phosphate (TCEP) is the most commonly detective organophosphate flame retardant in surroundings. TCEP is also evidenced as endocrine disrupting chemicals and has potential adverse effects on metabolic diseases. In this study, we hypothesized that metabolic diseases are adverse outcomes of TCEP exposure. Adult ICR mice was daily treated with TCEP (20 mg/kg and 60 mg/kg, higher than expected level in people) by gavage administration for 9 weeks. The results demonstrate that TCEP promoted body weight gain, hypertriglyceridemia, and hepatic steatosis, consistent with upregulation of hepatic lipogenesis-related gene expression. Moreover, TCEP altered the levels of several hepatic metabolites, especially bile acids and downregulated bile acid synthesis pathways. Intriguingly, we found a marked downregulation of the bile acid nuclear reporter, FXR, in TCEP-exposed livers. Mechanistically, TCEP directly interacted with FXR at Lys335 and Lys336. Further studies in this work elucidate the mechanisms of long-term TCEP exposure on hepatic steatosis and obesity in mice via FXR-mediated lipid accumulation. Our results provide insight into the possibility of intermediate TCEP exposure in causing metabolic diseases.

Organophosphate flame retardants induce oxidative stress and Chop/Caspase 3-related apoptosis via Sod1/p53/Map3k6/Fkbp5 in NCI-1975 cells

Organophosphate flame retardants (OPFRs) have been ubiquitously detected in dust and air which could cause damage to human health through inhalation. Currently the understanding of their adverse effects and potential mechanisms on the lung are still limited. In this study, human non-small cell lung cancer cell line NCI-H1975 was used to investigate the cytotoxicity, oxidative stress, cellular apoptosis of 9 typical OPFRs with concentrations varied from 0 to 200 μM, and their toxic mechanism associated with molecular structure was compared. After 72 h, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) displayed the highest cytotoxicity, followed by 2-ethylhexyl diphenyl phosphate (EHDPP), tris(2-butoxyethyl) phosphate (TBOEP) and tris(2-chloroisopropyl) phosphate (TCIPP), while tris(2-chloroethyl) phosphate (TCEP) and tris(2-ethylhexyl) phosphate (TEHP) exhibited the least suppression on cell viability. These results indicated that the variation of cytotoxicity on OPFRs could only be partially explained by their ester linkage. Moreover, the overexpression of intracellular reactive oxygen species (ROS), free Ca²⁺ and cellular apoptosis suggested that exposure to OPFRs can lead to apoptosis related to oxidative stress. Six genes associated with oxidative stress and apoptosis were upregulated dramatically compared with the control, demonstrating OPFRs induced Chop/Caspase 3-related apoptosis by activating Sod1/p53/Map3k6/Fkbp5 expression in NCI-H1975 cells. This is the first study to investigate cytotoxicity and related mechanism on commonly-used OPFRs in NCI-H1975 cells.

Metabolomic analysis and oxidative stress response reveals the toxicity in Escherichia coli induced by organophosphate flame retardants tris(2-chloroethyl) phosphate and triphenyl phosphate

Organophosphate flame retardants (OPFRs) are emerging environmental pollutants that are increasingly being used in consumer commodities. The adverse effects on biota induced by tris(2-chloroethyl) phosphate (TCEP) and triphenyl phosphate (TPHP) have become a growing concern. Unfortunately, toxic mechanisms at the molecular level for OPFRs in organisms are still lacking. Herein, Escherichia coli (E.coli) was exposed to TCEP and TPHP for 24 and 48 h to reveal oxidative stress response and molecular toxicity mechanisms. The results indicated that promotion of ROS overload occurred at higher dosages groups. The levels of SOD and CAT were significantly elevated along with the increase of MDA attributed to lipid peroxidation. Additionally, apoptosis rates increased, accompanied by a decline in membrane potential and Na⁺/K⁺-ATPase and Ca²⁺/Mg²⁺-ATPase contents, signifying that E. coli cytotoxicity induced by TCEP and TPHP was mediated by oxidative stress. Based on metabolomic analysis, different metabolic pathways were disrupted, including glycolysis/gluconeogenesis, pentose phosphate metabolism, purine metabolism, glutathione metabolism, amino acid biosynthesis, butanoate metabolism, alanine and aspartate metabolism. Most differentially expressed metabolites were downregulated, indicating an inhibitory effect on metabolic functions and key metabolic pathways. These findings generated new insights into the potential environmental risks of OPFRs in aquatic organisms.

5,6,7,4'-Tetramethoxyflavanone attenuates NADPH oxidase 1/4 and promotes sirtuin-1 to inhibit cell stress, senescence and apoptosis in Aß25-35-mediated SK-N-SH dysfunction

Amyloidogenesis is a fundamental step of amyloid beta (Aβ) generation-induced toxicity that is commonly reported to disrupt neuronal circuits, function and survival in Alzheimer's disease (AD). The neuroprotective effect of 5,6,7,4'-tetramethoxyflavanone (TMF) from Chormolaela odorata extract on brain degeneration and amyloidogenesis has previously been demonstrated. However, the mechanistic evidence for TMF's effects is still unclear. In this study, we evaluated the neuroprotective effect of TMF in Aβ_25-35-induced toxicity in SK-N-SH neuroblastoma cells. Herein, we demonstrated that TMF exhibited potent antioxidant activity and significantly increased cell viability and decreased ROS production in a dose-dependent manner. Moreover, TMF reversed the effect of Aβ_25-35, which caused energy deprivation and apoptosis, by decreasing the ratio of Bax/Bcl-x_L and reducing mitochondrial membrane potential (Δψ_m), caspase-3 expression, apoptotic cells, and attenuating glucose transporter (Glut-3) expression. In addition, TMF protected against Aβ_25-35-induced cellular senescence by attenuating β-galactosidase, p-21 and p-53 expression and promoted the expression of Sirt-1 and p-Rb. In addition, the effects of TMF on Aβ_25-35 toxicity were related to the upregulation of phase II antioxidant and nuclear factor erythroid 2-related factor-2 (Nrf2) signaling, including superoxide dismutase (SOD), heme oxygenase (HO)-1, and nuclear translocation of Nrf2. Finally, we also found that TMF attenuated Aβ_25-35-reduced synaptic plasticity by increasing the expression of synaptophysin and PSD-95, which was correlated with a decrease in acetylcholine esterase (AChE). Importantly, we found that the protective effects of TMF on Aβ_25-35 were bidirectional, including marked inhibition of NADPH oxidase (NOX)-4 activity and partial activation of Sirt-1, which occurred prior to a reduction in the negative responses. Therefore, TMF may be useful for treating Aβ toxicity in AD.

UV/H2O2 oxidation of tri(2-chloroethyl) phosphate: Intermediate products, degradation pathway and toxicity evaluation

Tri(2-chloroethyl) phosphate (TCEP) with the initial concentration of 5 mg/L was degraded by UV/H₂O₂ oxidation process. The removal rate of TCEP in the UV/H₂O₂ system was 89.1% with the production of Cl^- and PO₄^3- of 0.23 and 0.64 mg/L. The removal rate of total organic carbon of the reaction was 48.8% and the pH reached 3.3 after the reaction. The oxidative degradation process of TCEP in the UV/H₂O₂ system obeyed the first order kinetic reaction with the apparent rate constant of 0.0025 min^-1 (R²=0.9788). The intermediate products were isolated and identified by gas chromatography-mass spectrometer. The addition reaction of HO• and H₂O and the oxidation reaction with H₂O₂ were found during the degradation pathway of 5 mg/L TCEP in the UV/H₂O₂ system. For the first time, environment risk was estimated via the "ecological structure activity relationships" program and acute and chronic toxicity changes of intermediate products were pointed out. The luminescence inhibition rate of photobacterium was used to evaluate the acute toxicity of intermediate products. The results showed that the toxicity of the intermediate products increased with the increase of reaction time, which may be due to the production of chlorine compounds. Some measures should be introduced to the UV/H₂O₂ system to remove the highly toxic Cl-containing compounds, such as a nanofiltration or reverse osmosis unit.

Tris(2-chloroethyl) Phosphate (TCEP) Elicits Hepatotoxicity by Activating Human Cancer Pathway Genes in HepG2 Cells

Tris(2-chloroethyl) phosphate (TCEP) is one of the organophosphorus flame retardants (OPFRs) used in consumer commodities and have been detected in human body fluids. Research on TCEP-induced transcriptomic alterations and toxicological consequences in liver cells is still lacking. Herein, human hepatocellular (HepG2) cells were treated with 100, 200, and 400 μM TCEP for 3 days to quantify hepatotoxicity by MTT, NRU, and comet assays. Apoptosis, mitochondrial membrane potential (ΔΨm), oxidative stress, and Ca²⁺ influx were measured by flow cytometry. A qPCR array was employed for transcriptomic analysis. MTT and NRU data showed 70.92% and 75.57% reduction in cell survival at 400 μM. In addition, 20-fold greater DNA damage was recorded at 400 μM. Cell cycle data showed 65.96% subG1 apoptotic peak in 400 μM treated cells. An elevated level of oxidative stress, esterase, Ca²⁺ influx, and ΔΨm dysfunction were recorded in TCEP-treated cells. Out of 84 genes, the qPCR array showed upregulation of 17 genes and downregulation of 10 key genes belonging to human cancer pathways. Our study endorses the fact that TCEP possesses hepatotoxic potential at higher concentrations and prolonged exposure. Hence, TCEP may act as a cancer-inducing entity by provoking the gene network of human cancer pathways.

Tris(2-chloroethyl) phosphate, a pervasive flame retardant: critical perspective on its emissions into the environment and human toxicity

Regulations and the voluntary activities of manufacturers have led to a market shift in the use of flame retardants (FRs). Accordingly, organophosphate ester flame retardants (OPFRs) have emerged as a replacement for polybrominated diphenyl ethers (PBDEs). One of the widely used OPFRs is tris(2-chloroethyl) phosphate (TCEP), the considerable usage of which has reached 1.0 Mt globally. High concentrations of TCEP in indoor dust (∼2.0 × 105 ng g-1), its detection in nearly all foodstuffs (max. concentration of ∼30-300 ng g-1 or ng L-1), human body burden, and toxicological properties as revealed by meta-analysis make TCEP hard to distinguish from traditional FRs, and this situation requires researchers to rethink whether or not TCEP is an appropriate choice as a new FR. However, there are many unresolved issues, which may impede global health agencies in framing stringent regulations and manufacturers considering the meticulous use of TCEP. Therefore, the aim of the present review is to highlight the factors that influence TCEP emissions from its sources, its bioaccessibility, threat of trophic transfer, and toxicogenomics in order to provide better insight into its emergence as an FR. Finally, remediation strategies for dealing with TCEP emissions, and future research directions are addressed.

Biochemical responses of a freshwater fish Cirrhinus mrigala exposed to tris(2-chloroethyl) phosphate (TCEP)

Freshwater fish Cirrhinus mrigala were exposed to tris(2-chloroethyl) phosphate (TCEP) with three different concentrations (0.04, 0.2, and 1 mg/L) for a period of 21 days. During the study period, thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels were significantly (p < 0.05) inhibited. The superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and lipid peroxidation (LPO) levels were increased significantly (p < 0.05) in gills, liver, and kidney tissues, whereas glutathione (GSH) and glutathione peroxidase (GPx) (except liver tissue) activities were inhibited when compared to the control group. Likewise, exposure to TCEP significantly (p < 0.05) altered the biochemical (glucose and protein) and electrolyte (sodium, potassium, and chloride) levels of fish. Light microscopic studies exhibited series of histopathological anomalies in the gills, liver, and kidney tissues. The present study reveals that TCEP at tested concentrations causes adverse effects on fish and the studied biomarkers could be used for monitoring the ecotoxicity of organophosphate esters (OPEs).

Enhancing the performance of pollution degradation through secondary self-assembled composite supramolecular heterojunction photocatalyst BiOCl/PDI under visible light irradiation

A novel n-n type inorganic/organic heterojunction of flaky-like BiOCl/PDI photocatalyst was constructed by water bath heating method. Meanwhile, a simple method - secondary self-assembly was used to prepare the BiOCl/PDI with a special band structure. The photocatalytic activities were evaluated by degrading aqueous organic pollutants under visible light (λ > 420 nm). The removal rates of 5 mg L^-1 phenol (non-ionic type), methyl orange (MO, anionic type), rhodamine B (RhB, cationic type) and 10 mg L^-1 RhB by secondary self-assembly BiOCl/PDI (BiOCl/PDI-2) were 8.0%, 3.4%, 27.8% and 78.9% higher than self-assembly BiOCl/PDI (BiOCl/PDI-1) under visible light (λ > 420 nm). The better photocatalytic activity for BiOCl/PDI-2 was attributed to the optimization of energy-band structures, which arose from different exposed surfaces, narrower interplanar spacing and stronger visible light absorption performance. Under acidic condition, BiOCl/PDI-2 showed a good photocatalytic activity, which was not affected by neutral ionic intensity and had good recycling properties. Moreover, the photocatalytic mechanism was explored by free radical capture test and electron paramagnetic resonance (EPR), and contribution of active species was calculated. The main active species of BiOCl/PDI-2 were ·O₂^-, ¹O₂ and h⁺. Our work may provide a route to design efficient inorganic/organic heterojunctions for organic pollutants degradation.

The p66shc-mediated Regulation of Hepatocyte Senescence Influences Hepatic Steatosis in Nonalcoholic Fatty Liver Disease

Background

Recent studies have suggested that hepatocyte senescence could contribute to hepatic steatosis and its progression in nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanism causing hepatocyte senescence in this pathological condition is still unclear. A thorough understanding of the mechanism could provide a new target for therapeutic intervention. The purpose of this study was to investigate the role of p66shc in hepatocyte senescence and hepatocyte damage in NAFLD progression.

Material/Methods

We examined the expression levels of hepatic p66shc and senescence markers in rats and humans with NAFLD, and we assessed the effect of p66shc knockdown or overexpression on senescence and steatosis in human liver cells.

Results

In this study, we showed that increased hepatic p66shc expression was consistent with upregulated expression of the following senescence markers in NAFLD rats: heterochromatin protein-1-beta (HP1β), p16, p21, and p53. Furthermore, senescence and steatosis could be induced in hepatoblastoma cell line (HepG2) cells when cells were stimulated with a low concentration of H₂O₂, and this effect was significantly alleviated by knockdown of p66shc. However, overexpression of p66shc could promote senescence and steatosis in L02 cells. Finally, increased hepatic p66shc protein levels correlated with enhanced expression of the senescence marker p21 and mirrored the degree of disease severity in NAFLD patients.

Conclusions

Our findings indicated that the increase in hepatocyte senescence and steatosis in NAFLD may be caused by the upregulation of p66shc expression, implying that strategies for p66shc-mediated regulation of hepatocyte senescence may provide new therapeutic tools for NAFLD.

Rosiglitazone ameliorates senescence and promotes apoptosis in ovarian cancer induced by olaparib

OBJECTIVE

Senescence mechanisms are vital to resistance to long-term olaparib maintenance treatment. Recently, peroxisome proliferator-activated receptor-γ agonists (e.g., rosiglitazone) have been reported to ameliorate the senescence-like phenotype by modulating inflammatory mediator production. This study examined synergistic effects on the anti-tumor activity of rosiglitazone combined with olaparib in ovarian cancer treatment.

METHODS

A2780 and SKOV3 mouse subcutaneous xenograft models were established for observing anti-tumor effects in living organisms and were randomly split into combination (both olaparib and rosiglitazone), rosiglitazone (10 mg/kg), olaparib (10 mg/kg), control (solvent) groups that received treatment once every 2 or 3 days (n = 6 per group). Cell counting kit-8 (CCK-8) assays were used to test the influences of rosiglitazone and olaparib on cell proliferation. PI and Annexin-V-FITC staining was used with flow cytometry to assess the cell cycle distribution and cell apoptosis. Senescence-associated β-galactosidase (SA-β-Gal) staining was used to observe cellular senescence. We performed quantitative real-time polymerase chain reaction assays to study the senescence-related secretory phenotype (SASP).

RESULTS

Olaparib and rosiglitazone were observed to synergistically retard subcutaneous ovarian cancer growth in vivo, and synergistically suppress ovarian cancer cell proliferation in vitro. Compared with olaparib alone, the percentage of positive cells expressed SA-β-gal and SASP were significantly decreased in the treatment of combination of olaparib and rosiglitazone. Furthermore, olaparib plus rosiglitazone increased the percentage of apoptosis in ovarian cancer cell compared with olaparib alone. In A2780 cells, it showed lower expression of P53, phospho-p53 (Ser15), P21, and P18 protein in combination treatment compared with olaparib alone. While, in SKOV3 cells, it showed lower expression of phosphor-retinoblastoma protein (Rb) (Ser807/811), and higher expression of cyclin D1, P21, and P16 protein in combination treatment compared with olaparib alone.

CONCLUSIONS

Rosiglitazone combined with olaparib can help manage ovarian cancer by ameliorating olaparib-induced senescence and improving anti-tumor effects.

The critical factors affecting typical organophosphate flame retardants to mimetic biomembrane: An integrated in vitro and in silico study

Organophosphate flame retardants (OPFRs) have been reported to induce cytotoxicity in a structure-dependent manner. The toxic effects may be due to the damage of biomembrane integrity and/or the interference of membrane signal pathway. In this study, the damages of fifteen typical OPFRs (chlorinated phosphates, alkyl phosphates, aryl phosphates, and alkoxy phosphates) to mimetic biomembrane were determined by the electrochemical impedance spectroscopy (EIS). The molecular structure descriptors that characterized the action mechanisms were screened by stepwise regression. The six molecular descriptors (MATS7e, DLS_05, Mor19m, Mor22v, Mor12v and MATS8m) were screened to study the actions between OPFRs and mimetic biomembrane. A quantitative structure-activity relationship (QSAR) model was developed by the partial least squares (PLS) method. Statistical results indicated that the QSAR model had good robustness and mechanism interpretability. The distribution of atomic electronegativities (MATS7e) and atomic masses in three dimensional spaces (Mor19m) were the key factors influencing the actions between OPFRs and simulated biofilms. The compounds with strong electron-withdrawing property could invade the inner layer of membrane and destroy its integrity. High levels of steric hindrance could impair the damage capacity caused by electronegativity. Moreover, drug-like index (DLS_05), spatial structures of particle (Mor22v, Mor12v) and atomic masses (MATS8m) also affected the actions. The results revealed the mechanism of the actions of OPFRs with simulated biofilms and elucidated the key structural characteristics affecting the actions of OPFRs, which could provide theoretical basis for ecological risk assessment of OPFRs.

OPFRs and BFRs induced A549 cell apoptosis by caspase-dependent mitochondrial pathway

Organophosphate flame retardants (OPFRs) and brominated flame retardants (BFRs) are frequently detected in indoor environment at high levels, posing health risks to humans. However, the potential cytotoxicity mediated by OPFRs and BFRs in relevant human cell models is limited. In current study, non-small cell lung cancer A549 cell was employed to investigate toxicity mechanisms of typical OPFRs (i.e., tris (2-chloroethyl) phosphate (TCEP), tris-(2-chloropropyl) phosphate (TCPP), tricresy phosphate (TCP), triphenyl phosphate (TPHP) and BFRs (i.e., 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 3,3', 5,5'-tetrabromobisphenol A (TBBPA)). It was found that BDE-47 exhibited the strongest cytotoxicity, followed by TBBPA, TPHP, TCP, TCPP and TCEP. OPFRs and BFRs could cause the reduction of cell viability of A549 cell in both dose- and time-dependent manner after exposure for 24 and 48 h. Simultaneously, excessive generation of reactive oxygen species (ROS), mitochondrial membrane potential (MMP) dysfunction, cell apoptosis and overload of intracellular free Ca²⁺ demonstrated that cytotoxicity induced by OPFRs and BFRs were mediated by oxidative stress. Of note, the survival rate of cell significantly increased when pretreated with Ac-DEVD-CHO, suggesting that caspase-3 dependent mitochondrial pathway may have played a primary role in the process of A549 cell apoptosis.

DNA damage and methylation induced by organophosphate flame retardants: Tris(2-chloroethyl) phosphate and tris(1-chloro-2-propyl) phosphate in human peripheral blood mononuclear cells

Phosphorus flame retardants are a group of chemicals that are used to slow or prevent the spread of fire. These compounds have been detected in different environments including human organism. In the present study, we have investigated DNA-damaging potential and effect on DNA methylation of tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCPP) in human peripheral blood mononuclear cells (PBMCs). In order to determine DNA damage and repair, the alkaline and neutral versions of the comet assay were used. The level of DNA methylation was determined with specific antibodies against methylated DNA. PBMCs were exposed to TCEP and TCPP at the concentrations in the range of 1-1000 µM for 24 h. We have observed that TCEP and TCPP induced DNA damage-DNA breaks and alkali-labile sites. All DNA damages were effectively repaired during 120-min repair incubation. The results have also shown that TCEP and TCPP decreased the level of DNA methylation in PBMCs. In the case of TCEP, this effect was observed at a very low concentration of 1 µM.

Combined effect of tris(2-chloroethyl)phosphate and benzo (a) pyrene on the release of IL-6 and IL-8 from HepG2 cells via the EGFR-ERK1/2 signaling pathway

Tris(2-chloroethyl)phosphate plus benzo (a) pyrene induced inflammatory response in HepG2 cells through the activation of EGFR-ERK1/2 signaling pathway.