Levels of Blood Organophosphorus Flame Retardants and Association with Changes in Human Sphingolipid Homeostasis

Tributyl Phosphate Induced Male Reproductive Toxicity in Mice

Tributyl phosphate (TBP) is an emerging hazardous material that is ubiquitous in the environment. However, whether TBP affects the male reproductive system remains unknown. In this study, we exposed male ICR mice and mouse spermatocyte GC-2 cells to TBP to explore the male reproductive toxicity of TBP. The results revealed that TBP (50 and 100 mg·kg-1·day-1) decreased sperm count and motility, damaged testicular structure, and induced apoptosis in mice after 35 days of oral gavage. TBP (10, 50, and 200 μM) inhibited cell viability, induced apoptosis, and reduced the ratio of BCL2/BAX in GC-2 cells after 24 h of exposure. TBP (50 and 200 μM) triggered the buildup of reactive oxygen species and induced a reduction in the mitochondrial membrane potential within GC-2 cells. In addition, TBP led to gut microbiota dysbiosis and metabolic profile alterations and increased the abundance of Prevotellaceae, which are negatively associated with sperm motility. Furthermore, TBP caused inflammation, induced the infiltration of Th17 cells into the mouse small intestine, and stimulated IL-17A signaling in mouse testes. In conclusion, TBP induced male reproductive toxicity via the gut-testis axis, oxidative stress, and apoptosis, offering fresh perspectives on TBP's reproductive hazards in male mammals.

High-Throughput Zebrafish Screening Reveals Cardiotoxic Effects of Organophosphate Flame Retardants

The toxicity of organophosphorus flame retardants (OPFRs) remains poorly understood, despite their widespread environmental presence and potential risks to human and ecological health. This study aimed to characterize the cardiovascular developmental toxicity of OPFRs using a high-throughput zebrafish screening model. Over thirty representative OPFRs, classified into three major groups-alkyl, aryl, and halogenated-were evaluated. Our results demonstrated that aryl-substituted OPFRs, such as triphenyl phosphate (TPHP) and tris(3,5-dimethylphenyl) phosphate (TXP), exhibit significantly more potent cardiotoxic effects compared to alkyl- and halogenated-substituted OPFRs. Specifically, heart rate of zebrafish increased by 8.3% and 11.9%, and cardiac output increased by 30.8% and 39.9% for TPHP and TXP, respectively, at a concentration of 160 μg/L. Additionally, exposure to aryl-substituted compounds like TPHP resulted in notable developmental abnormalities, including pericardial edema and skeletal bending. Molecular descriptor analysis further identified a series of essential structural features, including estrogen receptor agonist activity and bioconversion rates, which are closely linked to the observed cardiotoxicity, thus providing a mechanistic explanation for these effects. These findings offer valuable insights into the molecular mechanisms underlying OPFRs toxicity, which could inform the development of safer flame retardant alternatives. Moreover, addressing the research gaps in translating zebrafish findings to other species and real-world ecological scenarios should be further concerned.

Comprehensive analysis of transplacental transfer of environmental pollutants detected in paired maternal and cord serums

Prenatal exposure to hazardous environmental pollutants is a critical global concern due to their confirmed presence in umbilical cord blood, indicating the ability of pollutants to cross the placental barrier and expose the fetus to harmful compounds. However, the transplacental transfer efficiencies (TTEs) of many pollutants remain underexplored. Herein, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to quantitatively analyze 91 environmental pollutants, including 13 bisphenols (BPs), 18 organophosphorus flame retardants (OPFRs), 7 brominated and other flame retardants (BFRs), 34 phthalates (PAEs), and 19 per- and polyfluoroalkyl substances (PFASs), in paired maternal and cord serums. 38 pollutants were detected in serums, including 5 BPs, 13 OPFRs, 2 BFRs, 4 PAEs, and 14 PFASs. Among the detected pollutants, bisphenol A (BPA) exists in the highest concentration (GM: 10.92 ng/mL in maternal serums and 12.66 ng/mL in cord serums), followed by tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), perfluorooctanoic acid (PFOA), and 4,4'-(1,3-phenylenediisopropylidene) bisphenol (BPM). The exposure concentrations of the same type of pollutants were highly correlated between maternal and cord serums. Perfluorohexanoic acid (PFHxA) had the highest TTE value (5.526), while perfluorooctane sulfonic acid (PFOS) had the lowest (0.206). TTEs of PFOS and perfluorononanoic acid (PFNA) were higher for female newborns, whereas TTEs of perfluorohexadecanoic acid (PFHxDA) and perfluorodecane sulfonic acid (PFDS) were higher for male newborns. Moreover, the expression levels of the transplacental transporters ABCA1, ABCC2, ABCC3, ABCC4, ABCG1, SLCO3A1, and SLC22A3 were associated with the transplacental transfer of triphenyl phosphate (TPHP), TDCIPP, di-n-propyl phthalate (DPRP), perfluoroundecanoic acid (PFUnDA), perfluorotridecanoic acid (PFTrDA), and PFOS. Further research is essential to unveil the mechanisms involved in the transplacental transfer of environmental pollutants, ultimately boosting our comprehension of their impact on fetal health and birth outcomes.

Prenatal Triphenyl Phosphate Exposure and Hyperlipidemia in Offspring: Role of Trophoblast-Derived Extracellular Vesicle PPARγ

Triphenyl phosphate (TPhP) is a widely used organophosphate flame retardant, the health risks of TPhP are a global concern. In this study, we found that prenatal TPhP exposure at human relevant concentration induced hyperlipidemia in male offspring, it increased serum levels of triglyceride, total cholesterol, and low-density lipoprotein cholesterol. Placental trophoblast-derived extracellular vesicles (T-EVs) could transport to the fetus through maternal-fetal circulation. TPhP significantly upregulated the protein level of peroxisome proliferator activated receptor γ (PPARγ) in T-EVs. Similar to TPhP, gestational exposure to T-EVs isolated from TPhP exposed mice placentae induced the same effects. While, gestational intervention with GW9662 (PPARγ inhibitor) or GW4869 (EVs secretion inhibitor) would alleviate the disturbed lipid metabolism induced by TPhP. Meanwhile, in vitro experiments verified that TPhP upregulated PPARγ in HTR8/SVneo cells derived EVs, and these EVs promoted adipogenesis in preadipocyte 3T3-L1 cells. Knock down of PPARγ in HTR8/SVneo could alleviate the adipogenensis effects of EVs derived from TPhP exposed HTR8/SVneo cells. These results demonstrate that TPhP exposure induces hyperlipidemia in male offspring by upregulating PPARγ in T-EVs. Our study provides new insights into the metabolic disruptive effects of TPhP, and emphasizes the mediating effects of placental T-EVs on gestational environmental stress in fetal development.

A proposed biomarker for human citric acid ester (CAE) exposure, and the potential disturbance on human lipid metabolism

Citric acid esters (CAEs), as one class of important alternative plasticizers, have been proven to be ubiquitous in the environments, leading to an increasing concern regarding their potential health risk to humans. However, information regarding the biomarkers for human CAE biomonitoring is currently unknown. In the present study, we investigated the metabolism characteristics of CAEs by use of in vitro rat liver microsomes (RLMs) and in vivo mice. We observed that CAEs would undergo a rapid metabolism in both in vitro and in vivo conditions, implying that parent CAEs could be not suitable for biomonitoring of human CAE exposure. By use of high-resolution Orbitrap mass spectrometry (MS), ten molecules were tentatively identified as CAE potential metabolites on the basis of their MS and MS/MS characteristics, and CAEs could be metabolized via multiple pathways, i.e. hydrolyzation, hydroxylation, O-dealkylation. Further MS screening in human serum samples demonstrated that most of parent CAEs were not detectable, whereas numerous CAE metabolites were detected in the same batch of analyzed samples. Especially, one of metabolites of tributyl citrate (named with TBC-M1), exhibited a high detection frequency of 73.3%. By use of TBC-M1 as the biomarker of human CAE exposure, alteration of lipid metabolism was further examined in human serum. Interestingly, we observed statistically significant correlations between TBC-M1 levels and population characteristics (i.e., age, BMI, and drinking). Beyond that, we also observed statistically significant correlation between levels of TBC-M1 and lipid molecules (phosphatidylinositol (18:0/20:4) and sphingomyelin (d34:1)). Collectively, this study underscored the property of rapid metabolism of CAEs in exposed organism, and proposed a potential biomarker that could be greatly helpful for further investigating the human CAE exposure and understanding their potential health risks.

Occurrence of legacy and emerging organophosphate flame retardants (OPFRs) on silicone wristbands: Comparison within couples

Novel organophosphate flame retardants (OPFRs) are recently identified and highly detected in indoor dusts, but their personal exposure was not clear. Here, wristband was used to estimate non-dietary exposure to emerging OPFRs in comparison with legacy OPFRs in 93 adults in Beijing, China. Comparison of studies in wristband monitoring data showed a clear difference in profiles of legacy OPFRs between China and United States, where tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) was usually the dominant OPFR in the United States, but triphenyl phosphate has the highest contribution to total OPFRs in China. Five emerging OPFRs, including diethylene glycol bis(bis(2-chloroisopropyl) phosphate) (DEGBBCPP) and bis(2-ethylhexyl) phenyl phosphate (BEHPP), were detected in above 45 % of wristbands. The median concentration of DEGBBCPP (2.2 ng/g) was about three times higher than TDCIPP (0.76 ng/g), a legacy chloro-OPFR. Both emerging and legacy OPFRs were significantly correlated within 40 pairs of couples, suggesting major exposure in their homes. Wristbands from husbands had significantly higher tris(2-butoxyethyl) phosphate (TBOEP) and DEGBBCPP, while 2-ethylhexyl diphenyl phosphate (EHDPP) was significantly higher in wives' bands, suggesting gender-related exposure sources for these OPFRs.

Occupational exposure to traditional and emerging organophosphate esters: A comparison of levels across different sources and blood distribution

Currently, there is limited knowledge regarding occupational exposure of traditional and emerging organophosphate esters (OPEs) from e-waste and automobile dismantling activities, and their distribution within the human blood. In the present study, we collected dust and urine samples from e-waste (ED) (n = 91 and 130, respectively) and automobile dismantling (AD) plants (n = 93 and 94, respectively), as well as serum-plasma-whole blood samples (sets from 128 participants) within ED areas for analyzing traditional and emerging organophosphate tri-esters (tri-OPEs) and organophosphate di-esters (di-OPEs). Median concentration of ∑tri-OPEs and ∑di-OPEs in dust (37,400 and 9,000 ng/g in ED, and 27,000 and 14,700 ng/g in AD areas, respectively) and urine samples (11.8 and 21.9 ng/mL in ED areas, and 17.2 and 15.0 ng/mL in AD areas, respectively) indicated that both e-waste and automobile dismantling activities served as important pollution source for OPEs. Dust ingestion has been evidenced to be the main exposure pathway compared to dermal absorption and inhalation. The median concentration (ng/mL) of OPEs in blood matrices descended order as follow: whole blood (13.1) > serum (11.6) > plasma (10.4) for ∑tri-OPEs, and plasma (3.51) > serum (0.36) > whole blood (0.23) for ∑di-OPEs. Concentration ratios of OPEs varied across blood matrices, depending on the compounds, suggesting that the essentiality of appropriate biomonitoring matrix for conducting comprehensive exposure assessments.

Insights into the Chemical Exposome during Pregnancy: A Non-Targeted Analysis of Preterm and Term Births

Human-made chemicals are ubiquitous, leading to chronic exposure to complex mixtures of potentially harmful substances. We investigated chemical exposures in pregnant women in New York City by applying a non-targeted analysis (NTA) workflow to 95 paired prenatal urine and serum samples (35 pairs of preterm birth) collected as part of the New York University Children's Health and Environment Study. We analyzed all samples using liquid chromatography coupled with Orbitrap high-resolution mass spectrometry in both positive and negative electrospray ionization modes, employing full scan and data-dependent MS/MS fragmentation scans. We detected a total of 1524 chemical features for annotation, with 12 chemicals confirmed by authentic standards. Two confirmed chemicals dodecyltrimethylammonium and N,N-dimethyldecylamine N-oxide appear to not have been previously reported in human blood samples. We observed a statistically significant differential enrichment between urine and serum samples, as well as between preterm and term birth (p < 0.0001) in serum samples. When comparing between preterm and term births, an exogenous contaminant, 1,4-cyclohexanedicarboxylic acid (tentative), showed a statistical significance difference (p = 0.003) with more abundance in preterm birth in serum. An example of chemical associations (12 associations in total) observed was between surfactants (tertiary amines) and endogenous metabolites (fatty acid amides).

Organophosphorus flame retardants in infant's diets from Beijing, China: Detection and risk assessment

As a group of widely used flame retardants, organophosphate esters (OPEs) and their metabolites, organophosphate diesters (di-OPEs), have been widely detected in various environmental media and human samples. However, the information on dietary exposure to OPEs for lactating infants is still limited. Here, 38 OPEs and 10 di-OPEs were monitored in 110 infant formula samples and 122 breast milk samples collected in Beijing, China. 20 OPEs (median: 49.9 ng/g, 16.5-160 ng/g) and 6 di-OPEs (median: 20.6 ng/g, 12.4-30.5 ng/g) were detected with frequency above 50% in infant formula, while 5 OPEs (median: 6.66 ng/g, 0.0566-221 ng/g) and 3 di-OPEs (median: 18.8 ng/g, 1.39-591 ng/g) had detection frequency above 50% in breast milk samples. For lactating infants, the total estimated daily intake (EDI) of ∑20OPEs (850 ng/kg bw/day) from infant formula was comparable with that of ∑5OPEs (836 ng/kg bw/day) from breast feeding, while the EDI of ∑6di-OPEs (333 ng/kg bw/day) from infant formula was significantly lower than that of ∑3di-OPEs (2456 ng/kg bw/day) from breast feeding. In summary, the results highlighted the risks of OPEs exposure from breast feeding. Further studies are warranted to evaluate the developmental toxicity of direct exposure to di-OPEs.

Organophosphorus Flame Retardants and Metabolic Disruption: An in Silico, in Vitro, and in Vivo Study Focusing on Adiponectin Receptors

BACKGROUND

Environmental chemical exposures have been associated with metabolic outcomes, and typically, their binding to nuclear hormone receptors is considered the molecular initiating event (MIE) for a number of outcomes. However, more studies are needed to understand the influence of such exposures on cell membrane-bound adiponectin receptors (AdipoRs), which are critical metabolic regulators.

OBJECTIVE

We aimed to clarify the potential interactions between AdipoRs and environmental chemicals, specifically organophosphorus flame retardants (OPFRs), and the resultant effects.

METHODS

Employing in silico simulation, cell thermal shift, and noncompetitive binding assays, we screened eight OPFRs for interactions with AdipoR1 and AdipoR2. We tested two key events underlying AdipoR modulation upon OPFR exposure in a liver cell model. The Toxicological Prioritization Index (ToxPi)scoring scheme was used to rank OPFRs according to their potential to disrupt AdipoR-associated metabolism. We further examined the inhibitory effect of OPFRs on AdipoR signaling activation in mouse models.

RESULTS

Analyses identified pi-pi stacking and pi-sulfur interactions between the aryl-OPFRs 2-ethylhexyl diphenyl phosphate (EHDPP), triphenyl phosphate (TPhP), and tricresyl phosphate (TCP) and the transmembrane cavities of AdipoR1 and AdipoR2. Cell thermal shift assays showed a > 3 ° C rightward shift in the AdipoR proteins' melting curves upon exposure to these three compounds. Although the binding sites differed from adiponectin, results suggest that aryl-OPFRs noncompetitively inhibited the binding of the endogenous peptide ligand ADP355 to the receptors. Analyses of key events underlying AdipoR modulation revealed that glucose uptake was notably lower, whereas lipid content was higher in cells exposed to aryl-OPFRs. EHDPP, TCP, and TPhP were ranked as the top three disruptors according to the ToxPi scores. A noncompetitive binding between these aryl-OPFRs and AdipoRs was also observed in wild-type (WT) mice. In db/db mice, the finding of lower blood glucose levels after ADP355 injection was diminished in the presence of a typical aryl-OPFR (TCP). WT mice exposed to TCP demonstrated lower AdipoR1 signaling, which was marked by lower phosphorylated AMP-activated protein kinase (pAMPK) and a higher expression of gluconeogenesis-related genes. Moreover, WT mice exposed to ADP355 demonstrated higher levels of pAMPK protein and peroxisome proliferator-activated receptor-α messenger RNA. This was accompanied by higher glucose disposal and by lower levels of long-chain fatty acids and hepatic triglycerides; these metabolic improvements were negated upon TCP co-treatment.

CONCLUSIONS

In silico, in vitro, and in vivo assays suggest that aryl-OPFRs act as noncompetitive inhibitors of AdipoRs, preventing their activation by adiponectin, and thus function as antagonists to these receptors. Our study describes a novel MIE for chemical-induced metabolic disturbances and highlights a new pathway for environmental impact on metabolic health. https://doi.org/10.1289/EHP14634.

A comprehensive evaluation of the endocrine-disrupting effects of emerging organophosphate esters

The ubiquitous presence of organophosphate esters (OPEs) in the environment has prompted growing concerns about their potential health risks, particularly their endocrine-disrupting effects. This study comprehensively evaluated the endocrine-disrupting properties of six emerging OPEs: five aryl-OPEs (2-ethylhexyl diphenyl phosphate (EHDPP), tris (2-biphenylyl) phosphate (TBPP), resorcinol bis (diphenyl phosphate) (RDP), 4-hydroxyphenyl diphenyl phosphate (para-OH-TPHP), and 3-hydroxyphenyl diphenyl phosphate (meta-OH-TPHP) and one alkyl-OPE, triallyl phosphate (TAP). Our findings revealed that all tested aryl-OPEs exhibited antagonistic effects on one or more hormone receptors. Importantly, para-OH-TPHP demonstrated the most potent antagonistic activity, inhibiting estrogen receptor α (ERα), thyroid hormone receptor β (TRβ), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR) with the concentration of test compounds showing 20 % relative inhibitory concentration (RIC20) value below 10-6 mol/L (M). RDP antagonized ERα and cortical receptors (GR and MR), TBPP affected TRβ and GR, while EHDPP and meta-OH-TPHP targeted MR. Regarding steroidogenesis, para-OH-TPHP significantly inhibited genes for estrogen (cyp19) and cortisol synthesis (cyp11b2), and along with meta-OH-TPHP, EHDPP, TAP, and RDP downregulated cyp11a1, a rate-limiting enzyme in hormone synthesis. All compounds caused malformations and swimming abnormalities in zebrafish embryos/larvae at concentrations of 10-7 M or higher, with para-OH-TPHP showing nearly 50 % peak induction. Furthermore, the six compounds tested influenced genes associated with the hypothalamic-pituitary-gonadal (HPG) axis in both zebrafish larvae and adult female zebrafish, in addition to affecting the reproductive behavior of zebrafish. A weighted scoring system was employed to rank the endocrine-disrupting potency of the OPEs, with para-OH-TPHP exhibiting the highest risk, followed by EHDPP, RDP, TBPP, meta-OH-TPHP, and TAP. Collectively, our results highlight the significant endocrine-disrupting effects of emerging OPEs, underscoring the urgent need for further research to assess their potential health implications.

The Role of Human Adiponectin Receptor 1 in 2-Ethylhexyl Diphenyl Phosphate Induced Lipid Metabolic Disruption

Epidemiological evidence links exposure to 2-ethylhexyl diphenyl phosphate (EHDPP) with lipid metabolic disruption, typically attributed to nuclear receptors, while the role of membrane receptors remains underexplored. This study explored the role of adiponectin receptor 1 (AdipoR1) in EHDPP-induced lipid metabolic disturbances. We examined EHDPP's binding affinity and transcriptional impact on AdipoR1. AdipoR1 knockdown (AdipoR1kd) human liver cells and coculture experiments with AdipoR1 activator (AdipoRon) were used to investigate the effect and the mechanism. EHDPP disrupted triglyceride and phospholipid synthesis and altered corresponding gene expression, mirroring effects in AdipoR1kd cells but diminishing in EHDPP-treated AdipoR1kd cells. RNA sequencing revealed that EHDPP primarily disrupted oxidative phosphorylation and insulin signaling dependent on AdipoR1. Mechanistically, EHDPP interacted with AdipoR1 and reduced AdipoR1 protein levels at 10-7 mol/L or higher, weakening the activation of the calmodulin dependent protein kinase β (CaMKKβ)/AMPK/acetyl CoA carboxylase pathway. Furthermore, EHDPP pretreatment blocked the increase in Ca2+ flux and the corresponding kinase CaMKKβ, as well as liver kinase B1 (LKB1) activation induced by AdipoRon, which is necessary for AMPK activation. Collectively, these findings demonstrate that EHDPP-induced lipid imbalance is partially dependent on AdipoR1, expanding the understanding of environmental metabolic disruptors beyond nuclear receptors.

2-Ethylhexyl Diphenyl Phosphate Induces Autism Spectrum Disorder-Like Behaviors in Offspring Mice by Disrupting Postsynaptic Development

As organophosphorus flame retardants (OPFRs) are constantly detected in human samples, the neurotoxicity of OPFRs is of concern. In this study, pregnant ICR mice were exposed to 2-ethylhexyl diphenyl phosphate (EHDPP) in drinking water from gestation to lactation to investigate its effects on autism spectrum disorder-like (ASD-like) behaviors in offspring. Serum EHDPP concentrations in dams in the 0.4, 2, and 10 mg/kg groups were 0.282 ± 0.051, 0.713 ± 0.115, and 0.974 ± 0.048 ng/mL, respectively, within the concentration range in humans. At the highest dose, EHDPP exposure induced ASD-like behaviors in both female and male offspring. Significant reductions in mature dendritic spines and structural damage to the postsynaptic density zone were noted in all but the lowest exposure groups, indicating postsynaptic membrane impairment. Mechanistically, EHDPP significantly downregulated disc large MAGUK scaffold protein 4 expression by inhibiting protein kinase B and type 1 insulin-like growth factor receptor phosphorylation. In the heterologous synapse formation assay in vivo, EHDPP significantly reduced the levels of postsynaptic density protein 95 expression in neurons at 1 μM. Overall, the study utilized in vitro and in vivo experiments to confirm that EHDPP damaged postsynaptic membrane formation and might increase the incidence of ASD in offspring.

Biotransformation, Bioaccumulation, and Bioelimination of Triphenyl Phosphate and Its Dominant Metabolite Diphenyl Phosphate In Vivo

Aryl phosphorus flame retardants (aryl-PFRs), such as triphenyl phosphate (TPHP) and diphenyl phosphate (DPHP), are widely used worldwide. Understanding the fates of aryl-PFRs in vivo is crucial to assessing their toxicity and the risks they pose. Seven TPHP metabolites, including Phase I hydrolysis and hydroxylation and Phase II glucuronidation products, were identified in C57BL/6J male mice following subacute dietary exposure to aryl-PFRs (70 μg/kg body weight (bw)/day) for 7 days. TPHP was almost completely metabolized by mice (∼97%), with DPHP the major metabolite formed (34%-58%). In addition, mice were exposed to aryl-PFRs (7 μg/kg bw/day) for 12 weeks. Both TPHP and DPHP occurred at higher concentrations in the digestive tract (intestine and stomach), liver and heart. The total concentration of DPHP in all organs was 3.55-fold greater than that of TPHP. Recovery analysis showed that the rate of TPHP elimination from mouse organs reached 38%, while only 3%-5% of DPHP was removed, suggesting that the rates of degradation and elimination of DPHP were slower than TPHP and its bioaccumulation potential was higher. These results highlight the critical role of DPHP in the biotransformation, bioaccumulation, and bioelimination of TPHP, providing valuable insights into the fate of aryl-PFRs in vivo.

Exposure levels and maternal transfer of emerging organophosphate flame retardants (OPFRs) in pregnant women: Comparison with traditional OPFRs

Prenatal exposure to organophosphorus flame retardants (OPFRs) has been linked with adverse effects on reproductive health, and new OPFRs are continually emerging. In this study, emerging OPFRs, such as bis(2-ethylhexyl) phenyl phosphate (BEHPP), triamyl phosphate (TAP), tris(4-tert-butylphenyl) phosphate (T4tBPPP), oxydi-2,1-ethanediyl phosphoric acid tetrakis(2 chloro-1-methylethyl) ester (RDT905), cresyl diphenyl phosphate (CDP), and 2-isopropylphenyl diphenyl phosphate (2IPPDPP), were detected in 84 %, 100 %, 100 %, 52 %, 40 %, and 40 % of 25 decidua samples with average concentrations of 2.36, 6.21, 1.5, 2.6, 1.07, and 0.09 ng/g of dry weight (dw), respectively. Six of the aforementioned emerging OPFRs (BEHPP, T4tBPPP, RDT905, 2IPPDPP, CDP, and TAP) were simultaneously detected in paired chorionic villus samples, and their average concentrations were 11.3, 1.77, 3.64, 0.11, 0.58, and 3.34 ng/g, which were significantly higher than and positively correlated with those in decidua samples. The geometric mean concentration ratios between chorionic villus and decidua samples for BEHPP, T4tBPPP, RDT905, 2IPPDPP, CDP, and TAP were 4.02, 1.61, 1.73, 1.48, 0.82, and 0.69, respectively, consistent with transthyretin binding-dependent behavior. Prenatal exposure to such emerging OPFRs, especially for BEHPP with relatively high concentration and maternal transfer, is of high concern from the view of women's reproductive health.

Embryonic Exposure to Organophosphate Flame Retardants (OPFRs) Differentially Induces Cardiotoxicity in Rare Minnow (Gobiocypris rarus)

Organophosphorus flame retardants (OPFRs) such as triphenyl phosphate (TPHP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were reported to impair cardiac function in fish. However, limited information is available regarding their cardiotoxic mechanisms. Using rare minnow (Gobiocypris rarus) as a model, we found that both TPHP and TDCIPP exposures decreased heart rate at 96 h postfertilization (hpf) in embryos. Atropine (an mAChR antagonist) can significantly attenuate the bradycardia caused by TPHP, but only marginally attenuated in TDCIPP treatment, suggesting that TDCIPP-induced bradycardia is independent of mAChR. Unlike TDCIPP, although TPHP-induced bradycardia could be reversed by transferring larvae to a clean medium, the inhibitory effect of AChE activity persisted compared to 96 hpf, indicating the existence of other bradycardia regulatory mechanisms. Transcriptome profiling revealed cardiotoxicity-related pathways in treatments at 24 and 72 hpf in embryos/larvae. Similar transcriptional alterations were also confirmed in the hearts of adult fish. Further studies verified that TPHP and TDCIPP can interfere with Na+/Ca2+ transport and lead to disorders of cardiac excitation-contraction coupling in larvae. Our findings provide useful clues for unveiling the differential cardiotoxic mechanisms of OPFRs and identifying abnormal Na+/Ca2+ transport as one of a select few known factors sufficient to impair fish cardiac function.

Melatonin improves mouse oocyte quality from 2-ethylhexyl diphenyl phosphate-induced toxicity by enhancing mitochondrial function

2-Ethylhexyl diphenyl phosphate (EHDPP) is a representative organophosphorus flame retardant (OPFR) that has garnered attention due to its widespread use and potential adverse effects. EHDPP exhibits cytotoxicity, genotoxicity, developmental toxicity, and endocrine disruption. However, the toxicity of EHDPP in mammalian oocytes and the underlying mechanisms remain poorly understood. Melatonin is a natural free radical scavenger that has demonstrated cytoprotective properties. In this study, we investigated the effect of EHDPP on mouse oocytes in vitro culture system and evaluated the rescue effect of melatonin on oocytes exposed to EHDPP. Our results indicated that EHDPP disrupted oocyte maturation, resulting in the majority of oocytes arrested at the metaphase I (MI) stage, accompanied by cytoskeletal damage and elevated levels of reactive oxygen species (ROS). Nevertheless, melatonin supplementation partially rescued EHDPP-induced mouse oocyte maturation impairment. Results of single-cell RNA sequencing (scRNA-seq) analysis elucidated potential mechanisms underlying these protective effects. According to the results of scRNA-seq, we conducted further tests and found that EHDPP primarily disrupts mitochondrial distribution and function, kinetochore-microtubule (K-MT) attachment, DNA damage, apoptosis, and histone modification, which were rescued upon the supplementation of melatonin. This study reveals the mechanisms of EHDPP on female reproduction and indicates the efficacy of melatonin as a therapeutic intervention for EHDPP-induced defects in mouse oocytes.

Organophosphate esters in human serum: a relatively simple and efficient liquid chromatography-mass spectrometry method

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers, which are of growing concern due to their endocrine-disrupting effects, developmental toxicity, and potential carcinogenicity. However, data on human exposure to OPEs is still scarce. In this study, a relatively simple and efficient method with less serum consumption for the detection of OPEs in human serum was developed and validated. Nine OPEs in 200 μL of human serum were extracted by an acetonitrile-formic acid system and analyzed using ultra-high-performance liquid chromatography-quadrupole tandem time-of-flight high-resolution mass spectrometry. Several experiments were conducted to optimize the chromatographic and mass spectrometric conditions as well as sample preparation to obtain a more sensitive and efficient analytical protocol. The proposed method was examined in terms of its linearity, accuracy, precision, detection limit, and matrix effect. The matrix-spiked recoveries of the target OPEs ranged from 83.3% to 111.1%, with relative standard deviations between 2.7% and 16.6%. The detection limits were within (0.002 to 0.029) ng mL-1, while the quantification limits were within (0.007 to 0.098) ng mL-1. The internal standard-corrected matrix effects varied from 82.7% to 113.9%. Finally, the method was applied to detect OPEs in actual human serum samples. All nine OPEs were detected in 269 serum samples to varying degrees, with the average concentrations ranging from (0.08 to 1.77) ng mL-1. After validation, the method was found to be simple in pretreatment, high in sensitivity, good in practicality, and suitable for exposure evaluation of OPEs in populations.

Specific human CYP enzymes-dependent mutagenicity of tris(2-butoxyethyl) phosphate (an organophosphorus flame retardant) in human and hamster cell lines

Tris(2-butoxyethyl) phosphate (TBOEP) is an organophosphorus flame retardant ubiquitously present in the environment and even the human body. TBOEP is toxic in multiple tissues, which forms dealkylated and hydroxylated metabolites under incubation with human hepatic microsomes; however, the impact of TBOEP metabolism on its toxicity, particularly mutagenicity (typically requiring metabolic activation), is left unidentified. In this study, the mutagenicity of TBOEP in human hepatoma cell lines (HepG2 and C3A) and the role of specific CYPs were studied. Through molecular docking, TBOEP bound to human CYP1A1, 1B1, 2B6 and 3A4 with energies and conformations favorable for catalyzing reactions, while the conformations of its binding with human CYP1A2 and 2E1 appeared unfavorable. In C3A cells (endogenous CYPs being substantial), TBOEP exposing for 72 h (2-cell cycle) at low micromolar levels induced micronucleus, which was abolished by 1-aminobenzotriazole (inhibitor of CYPs); in HepG2 cells (CYPs being insufficient) TBOEP did not induce micronucleus, whose effect was however potentiated by pretreating the cells with PCB126 (CYP1A1 inducer) or rifampicin (CYP3A4 inducer). TBOEP induced micronucleus in Chinese hamster V79-derived cell lines genetically engineered for stably expressing human CYP1A1 and 3A4, but not in cells expressing the other CYPs. In C3A cells, TBOEP selectively induced centromere protein B-free micronucleus (visualized by immunofluorescence) and PIG-A gene mutations, and elevated γ-H2AX rather than p-H3 (by Western blot) which indicated specific double-strand DNA breaks. Therefore, this study suggests that TBOEP may induce DNA/chromosome breaks and gene mutations in human cells, which requires metabolic activation by CYPs, primarily CYP1A1 and 3A4.

A new approach to monitoring typical organophosphorus compounds (OPs) in environmental media: From database building to suspect screening

Organophosphorus compounds (OPs) are widely used as flame retardants (FRs) and plasticizers, yet strategies for comprehensively screening of suspect OPs in environmental samples are still lacking. In this work, a neoteric, robust, and general suspect screening technique was developed to identify novel chemical exposures by use of ultra-high performance liquid chromatography-Q Exactive hybrid quadrupole-Orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS). We firstly established a suspect chemical database which had 7,922 OPs with 4,686 molecular formulas, and then conducted suspect screening in n = 50 indoor dust samples, n = 76 sediment samples, and n = 111 water samples. By use of scoring criteria such as retention time prediction models, we successfully confirmed five compounds by comparison with their authentic standards, and prioritized three OPs candidates including a nitrogen/fluorine-containing compound, that is dimethyl {1H-indol-3-yl[3-(trifluoromethyl)anilino]methyl} phosphonate (DMITFMAMP). Given that the biodegradation half-life values in water (t1/2,w) of DMITFMAMP calculated by EPI Suite is 180 d, it is considered to be potentially persistent. This strategy shows promising potential in environmental pollution assessment, and can be expected to be widely used in future research.

House dust-derived mixtures of organophosphate esters alter the phenotype, function, transcriptome, and lipidome of KGN human ovarian granulosa cells

Organophosphate esters (OPEs), used as flame retardants and plasticizers, are present ubiquitously in the environment. Previous studies suggest that exposure to OPEs is detrimental to female fertility in humans. However, no experimental information is available on the effects of OPE mixtures on ovarian granulosa cells, which play essential roles in female reproduction. We used high-content imaging to investigate the effects of environmentally relevant OPE mixtures on KGN human granulosa cell phenotypes. Perturbations to steroidogenesis were assessed using ELISA and qRT-PCR. A high-throughput transcriptomic approach, TempO-Seq, was used to identify transcriptional changes in a targeted panel of genes. Effects on lipid homeostasis were explored using a cholesterol assay and global lipidomic profiling. OPE mixtures altered multiple phenotypic features of KGN cells, with triaryl OPEs in the mixture showing higher potencies than other mixture components. The mixtures increased basal production of steroid hormones; this was mediated by significant changes in the expression of critical transcripts involved in steroidogenesis. Further, the total-OPE mixture disrupted cholesterol homeostasis and the composition of intracellular lipid droplets. Exposure to complex mixtures of OPEs, similar to those found in house dust, may adversely affect female reproductive health by altering a multitude of phenotypic and functional endpoints in granulosa cells. This study provides novel insights into the mechanisms of actions underlying the toxicity induced by OPEs and highlights the need to examine the effects of human relevant chemical mixtures.

Unlocking the genomic potential of Red Sea coral probiotics

The application of beneficial microorganisms for corals (BMC) decreases the bleaching susceptibility and mortality rate of corals. BMC selection is typically performed via molecular and biochemical assays, followed by genomic screening for BMC traits. Herein, we present a comprehensive in silico framework to explore a set of six putative BMC strains. We extracted high-quality DNA from coral samples collected from the Red Sea and performed PacBio sequencing. We identified BMC traits and mechanisms associated with each strain as well as proposed new traits and mechanisms, such as chemotaxis and the presence of phages and bioactive secondary metabolites. The presence of prophages in two of the six studied BMC strains suggests their possible distribution within beneficial bacteria. We also detected various secondary metabolites, such as terpenes, ectoines, lanthipeptides, and lasso peptides. These metabolites possess antimicrobial, antifungal, antiviral, anti-inflammatory, and antioxidant activities and play key roles in coral health by reducing the effects of heat stress, high salinity, reactive oxygen species, and radiation. Corals are currently facing unprecedented challenges, and our revised framework can help select more efficient BMC for use in studies on coral microbiome rehabilitation, coral resilience, and coral restoration.

Prenatal organophosphate esters exposure and neurodevelopment trajectory in infancy: Evidence from the Shanghai Maternal-Child Pairs Cohort

BACKGROUND

Concerns remain about the neurotoxic properties of the ubiquitous organophosphate esters (OPEs), the replacement of the toxicant polybrominated diphenyl ethers.

OBJECTIVES

We examined the associations of prenatal exposure to OPEs and their mixtures with early-life neurodevelopment trajectories.

METHODS

Totally 1276 mother-child pairs were recruited from the Shanghai Maternal-Child Pairs Cohort. A high-performance liquid chromatography-triple quadrupole mass spectrometer was used to measure the levels of 7 OPEs in cord serum. Ages and Stages Questionnaires was used to examine children's neuropsychological development at 2, 6, 12, and 24 months of age. Group-based trajectory models were applied to derive the neurodevelopmental trajectories. Multiple linear regression and logistic regression model were performed to assess the relationships between OPEs exposure and neurodevelopment and trajectories. Mixtures for widely detected OPEs (n = 4) were investigated using quantile-based g-computation.

RESULTS

Tributyl phosphate (TBP), tris (2-butoxy ethyl) phosphate (TBEP), tris(1,3-dichloro-2-propyl) phosphate (TDCPP), and 2-ethylhexyl diphenyl phosphate (EHDPP), had detection rates >50 %. TDCPP had the highest median concentration (1.02 μg/L) in cord serum. EHDPP concentrations were negatively associated with scores in most domains at 12 months of age, with effect values (β) ranging from -1.89 to -0.57. EHDPP could negatively affect the total ASQ (OR = 1.07, 95 % CI: 1, 1.15) and gross-motor (OR = 1.09, 95 % CI: 1.02, 1.17) trajectory in infancy. Joint exposure to OPEs was associated with decreased scores in the total ASQ, gross-motor, fine-motor and problem-solving domain of 12-month-old infants, with β ranging from -5.93 to -1.25. In addition, the qgcomp models indicated significant positive associations between the concentrations of OPEs mixtures and risks of the persistently low group of the total ASQ, gross-motor and fine-motor development in early childhood. The impact of OPEs was more pronounced in boys.

DISCUSSION

Our findings suggested OPEs, especially EHDPP, had a persistently negative effect on neurodevelopment during the first 2 years.

Triphenyl phosphate interferes with the synthesis of steroid hormones through the PPARγ/CD36 pathway in human trophoblast JEG-3 cells

Triphenyl phosphate (TPhP), a chemical commonly found in human placenta and breast milk, has been shown to disturb the endocrine system. Our previous study confirmed that TPhP could accumulate in the placenta and interference with placental lipid metabolism and steroid hormone synthesis, as well as induce endoplasmic reticulum (ER) stress through PPARγ in human placental trophoblast JEG-3 cells. However, the molecular mechanism underlying this disruption remains unknown. Our study aimed to identify the role of the PPARγ/CD36 pathway in TPhP-induced steroid hormone disruption. We found that TPhP increased lipid accumulation, total cholesterol, low- and high-density protein cholesterol, progesterone, estradiol, glucocorticoid, and aldosterone levels, and genes related to steroid hormones synthesis, including 3βHSD1, 17βHSD1, CYP11A, CYP19, and CYP21. These effects were largely blocked by co-exposure with either a PPARγ antagonist GW9662 or knockdown of CD36 using siRNA (siCD36). Furthermore, an ER stress inhibitor 4-PBA attenuated the effect of TPhP on progesterone and glucocorticoid levels, and siCD36 reduced ER stress-related protein levels induced by TPhP, including BiP, PERK, and CHOP. These findings suggest that ER stress may also play a role in the disruption of steroid hormone synthesis by TPhP. As our study has shed light on the PPARγ/CD36 pathway's involvement in the disturbance of steroid hormone biosynthesis by TPhP in the JEG-3 cells, further investigations of the potential impacts on the placental function and following birth outcome are warranted.

Global responses to tris(1-chloro-2-propyl) phosphate and tris(2-butoxyethyl) phosphate in Escherichia coli: Evidences from biomarkers, and metabolic disturbance using GC-MS and LC-MS metabolomics analyses

Tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-butoxyethyl) phosphate (TBEP) as pollutants of emerging concern have aroused the rising attention due to their potential risks on aquatic ecosystem and public health. Nevertheless, there is a lack of toxicological mechanisms exploration of TCPP and TBEP at molecular levels. Herein, the toxicity effects and molecular mechanism of them were fully researched and summarized on Escherichia coli (E.coli). Acute exposure to them significantly activated antioxidant defense system and caused lipid peroxidation, as proved by the changes of antioxidant enzymes and MDA. The ROS overload resulted in the drop of membrane potential as well as the downregulated synthesis of ATPase, endorsing that E. coli cytotoxicity was ascribed to oxidative stress damage induced by TCPP and TBEP. The combination of GC-MS and LC-MS based metabolomics validated that TCPP and TBEP induced metabolic reprogramming in E.coli. More specifically, the responsive metabolites in carbohydrate metabolism, lipids metabolism, nucleotide metabolism, amino acid metabolism, and organic acids metabolism were significantly disturbed by TCPP and TBEP, confirming the negative effects on metabolic functions and key bioprocesses. Additionally, several biomarkers including PE(16:1(5Z)/15:0), PA(17:1(9Z)/18:2(9Z,12Z)), PE(19:1(9Z)/0:0), and LysoPE(0:0/18:1(11Z)) were remarkably upregulated, verifying that the protection of cellular membrane was conducted by regulating the expression of lipids-associated metabolites. Collectively, this work sheds new light on the potential molecular toxicity mechanism of TCPP and TBEP on aquatic organisms, and these findings using GC-MS and LC-MS metabolomics generate a fresh insight into assessing the effects of OPFRs on target and non-target aquatic organisms.

Nontarget Identification of Novel Organophosphorus Flame Retardants and Plasticizers in Indoor Air and Dust from Multiple Microenvironments in China

The indoor environment is a typical source for organophosphorus flame retardants and plasticizers (OPFRs), yet the source characteristics of OPFRs in different microenvironments remain less clear. This study collected 109 indoor air samples and 34 paired indoor dust samples from 4 typical microenvironments within a university in Tianjin, China, including the dormitory, office, library, and information center. 29 target OPFRs were analyzed, and novel organophosphorus compounds (NOPs) were identified by fragment-based nontarget analysis. Target OPFRs exhibited the highest air and dust concentrations of 46.2-234 ng/m3 and 20.4-76.0 μg/g, respectively, in the information center, where chlorinated OPFRs were dominant. Triphenyl phosphate (TPHP) was the primary OPFR in office air, while tris(2-chloroethyl) phosphate dominated in the dust. TPHP was predominant in the library. Triethyl phosphate (TEP) was ubiquitous in the dormitory, and tris(2-butoxyethyl) phosphate was particularly high in the dust. 9 of 25 NOPs were identified for the first time, mainly from the information center and office, such as bis(chloropropyl) 2,3-dichloropropyl phosphate. Diphenyl phosphinic acid, two hydroxylated and methylated metabolites of tris(2,4-ditert-butylphenyl) phosphite (AO168), and a dimer phosphate were newly reported in the indoor environment. NOPs were widely associated with target OPFRs, and their human exposure risk and environmental behaviors warrant further study.

Behavioral toxicity of TDCPP in marine zooplankton: Evidence from feeding and swimming responses, molecular dynamics and metabolomics of rotifers

As new organic flame retardants, chlorinated organophosphate esters (Cl-OPEs) have high water solubility and structural similarity to organophosphate pesticides, posing risks to aquatic organisms. The potential neurotoxicity of Cl-OPEs has attracted attention, especially in marine invertebrates with a relatively simple nervous system. In this study, a marine rotifer with a cerebral ganglion, Brachionus plicatilis, was exposed to tris (1,3-dichloro-2-propyl) phosphate (TDCPP) (two environmental concentrations and one extreme level), and the changes in feeding and swimming behaviors and internal mechanism were explored. Exposure to 1.05 nM TDCPP did not change the filtration and ingestion rates of rotifers and average linear velocity. But 0.42 and 4.20 μM TDCPP inhibited these three parameters and reduced unsaturated fatty acid content, reproduction and population growth. All TDCPP test concentrations suppressed AChE activity, causing excessive accumulation of acetylcholine within rotifers, thereby disturbing the neural innervation of corona cilia. Molecular docking and molecular dynamics revealed that this inhibition was because TDCPP can bind to the catalytic active site of rotifer AChE through van der Waals forces and electrostatic interactions. TRP420 was the leading amino residue in the binding, and GLY207 contributed to a hydrogen bond. Nontargeted metabolomics using LC-MS and GC-MS identified differentially expressed metabolites in TDCPP treatments, mainly from lipid and lipid-like molecules, especially sphingolipids. TDCPP decreased ganglioside content but stimulated ceramide generation and the expression levels of 3 genes related to ceramide de novo synthesis. The mitochondrial membrane potential (MMP) and ATP content decreased, and the electron respiratory chain complex and TCA cycle were deactivated. An inhibitor of ceramide synthase, fumonisin, alleviated MMP and ATP, implying a critical role of ceramide in mitochondrial dysfunction. Thus, TDCPP exposure caused an energy supply deficit affecting ciliary movement and ultimately inhibiting rotifer behaviors. Overall, this study promotes the understanding of the neurotoxicity of Cl-OPEs in marine invertebrates.

Role of inflammatory lipid and fatty acid metabolic abnormalities induced by plastic additives exposure in childhood asthma

Lipid metabolism play an essential role in occurrence and development of asthma, and it can be disturbed by phthalate esters (PAEs) and organophosphate flame retardants (OPFRs). As a chronic inflammatory respiratory disease, the occurrence risk of childhood asthma is increased by PAEs and OPFRs exposure, but it remains not entirely clear how PAEs and OPFRs contribute the onset and progress of the disease. We have profiled the serum levels of PAEs and OPFRs congeners by liquid chromatography coupled with mass spectrometry, and its relationships with the dysregulation of lipid metabolism in asthmatic, bronchitic (acute inflammation) and healthy (non-inflammation) children. Eight PAEs and nine OPFRs congeners were found in the serum of children (1 - 5 years old) from Shenzhen, and their total median levels were 615.16 ng/mL and 17.06 ng/mL, respectively. Moreover, the serum levels of mono-methyl phthalate (MMP), tri-propyl phosphate (TPP) and tri-n-butyl phosphate (TNBP) were significant higher in asthmatic children than in healthy and bronchitic children as control. Thirty-one characteristic lipids and fatty acids of asthma were screened by machine-learning random forest model based on serum lipidome data, and the alterations of inflammatory characteristic lipids and fatty acids including palmitic acids, 12,13-DiHODE, 14,21-DiHDHA, prostaglandin D2 and LysoPA(18:2) showed significant correlated with high serum levels of MMP, TPP and TNBP. These results imply PAEs and OPFRs promote the occurrence of childhood asthma via disrupting inflammatory lipid and fatty acid metabolism, and provide a novel sight for better understanding the effects of plastic additives on childhood asthma.

A critical review on organophosphate esters in drinking water: Analysis, occurrence, sources, and human health risk assessment

Organophosphate esters (OPEs) are ubiquitous in the environment. Copious studies assessed OPEs in various environmental media. However, there is limited summative information about OPEs in drinking water. This review provides comprehensive data for the analytical methods, occurrence, sources, and risk assessment of OPEs in drinking water. In general, liquid-liquid extraction and solid-phase extraction are the most common methods in the extraction of OPEs from drinking water, while gas chromatography and liquid chromatography are the most commonly used instrumental methods for detecting OPEs in drinking water. On the basis of these techniques, a variety of methods on OPEs pretreatment and determination have been developed to know the pollution situation of OPEs. Studies on the occurrence of OPEs in drinking water show that the total concentrations of OPEs vary seasonally and regionally, with tris(1-chloro-2-isopropyl) phosphate and tris(2-chloroethyl) phosphate dominant among different kinds of drinking water. Source identification studies show that there are three main sources of OPEs in drinking water: 1) source water contamination; 2) residual in drinking water treatment process; 3) leakage from device or pipeline. Besides, risk assessments indicate that individual and total OPEs pose no or negligible health risk to human, but this result may be significantly underestimated. Finally, the current knowledge gaps on the research of OPEs in drinking water are discussed and some suggestions are provided for future environmental research.

Critical review on organophosphate esters in water environment: Occurrence, health hazards and removal technologies

Organophosphate esters (OPEs), which are phosphoric acid ester derivatives, are anthropogenic substances that are widely used in commerce. Nevertheless, there is growing public concern about these ubiquitous contaminants, which are frequently detected in contaminated water sources. OPEs are mostly emitted by industrial operations, and the primary routes of human exposure to OPEs include food intake and dermal absorption. Because of their negative effects on both human health and the environment, it is clear that innovative methods are needed to facilitate their eradication. In this study, we present a comprehensive overview of the existing characteristics and origins of OPEs, their possible impacts on human health, and the merits, drawbacks, and future possibilities of contemporary sophisticated remediation methods. Current advanced remediation approaches for OPEs include adsorption, degradation (advanced oxidation, advanced reduction, and redox technology), membrane filtration, and municipal wastewater treatment plants, degradation and adsorption are the most promising removal technologies. Meanwhile, we proposed potential areas for future research (appropriate management approaches, exploring the combination treatment process, economic factors, and potential for secondary pollution). Collectively, this work gives a comprehensive understanding of OPEs, providing useful insights for future research on OPEs pollution.

Organophosphate Esters in Building Materials from China: Levels, Sources, Emissions, and Preliminary Assessment of Human Exposure

Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑13OPE contents varied significantly (p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑13OPEs varied from 154 ng/m2/h (carpet) to 2760 ng/m2/h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10-7) were close to the acceptable level (1 × 10-6) and deserved special attention.

Organophosphate ester cresyl diphenyl phosphate disrupts lipid homeostasis in zebrafish embryos

As a new class of organophosphate ester, cresyl diphenyl phosphate (CDP) has been widely monitored in environmental matrices and human samples, nonetheless, its toxicity is not fully understood. Here we described an in-depth analysis of the disruptions in lipid homeostasis of zebrafish following exposure to CDP concentrations ranging from 2.0 to 313.0 μg/L. Nile red staining revealed significant alterations in lipid contents in 72 hpf zebrafish embryos at CDP concentrations of 5.3 μg/L and above. Lipidomic analysis unveiled substantial disruptions in lipid homeostasis. Notably, disruptive effects were detected in various lipid classes, including phospholipids (i.e. cardiolipin, lysophosphatidylcholine, and phosphatidylethanolamine), glycerolipids (triglycerides), and fatty acids (fatty acids (FA) and wax esters (WE)). These alterations were further supported by transcriptional changes, with remarkable shifts observed in genes associated with lipid synthesis, transport, and metabolism, encompassing phospholipids, glycerolipids, fatty acids, and sphingolipids. Furthermore, CDP exposure elicited a significant elevation in ATP content and swimming activity in embryos, signifying perturbed energy homeostasis. Taken together, the present findings underscore the disruptive effects of CDP on lipid homeostasis, thereby providing novel insights essential for advancing the health risk assessment of organophosphate flame retardants.

Cytotoxic and genotoxic effects of triphenyl phosphate on root tip cells of Allium cepa L

Triphenyl phosphate (TPhP) is a tri-ester of phosphoric acid and phenol. It is used in products such as polyvinyl chloride, hydraulic fluids, polymers, photographic films and printed circuit cards as a flame retardant. It is also widely used in consumer products like electric and electronic devices, textiles and building necessaries. TPhP can diffuse into its surrounding environment easily, because it does not form a chemical bond with polymeric materials. Therefore, bio-monitoring of such compounds is needed for possible environmental and human health effects. In this study, we evaluated genotoxicity and cytotoxicity of TPhP on Allium cepa on the cells of root tips. A 10 mg/mL stock solution of TPhP was dissolved in DMSO and dilutions of 2, 4, 6, 8 and 10 mg/mL was made in distilled water. Onion bulbs, rooted in test tubes, were exposed to these concentrations of TPhP for 24 h. Distilled water was used as a negative control, 0.7% hydrogen peroxide was used as positive control, and 0.5% DMSO was used as solvent control. Significant inhibition of onion root growth was observed following treatment with the 6, 8 and 10 mg/mL TPhP ranges in comparison with the negative and solvent control groups (p < 0.05). Furthermore, in the TPhP treatment groups, total chromosome aberration ratios were significantly high in comparison with the controls (p < 0.05). These results suggest that TPhP have cytotoxic and genotoxic effects on A. cepa root tips.

Highly sensitive and selective off-on fluorescent platform for tricresyl phosphate flame retardant based on twisted intramolecular charge transfer probe

BACKGROUND

Tricresyl phosphate (TCP), a typical organic phosphorus flame retardant (OPFR), is an emerging pollutant that causes great concern in recent years due to its high neurotoxicity and reproductive toxicity, etc. Conventional analysis methods for TCP such as gas chromatography and liquid chromatography-tandem mass spectrometry exhibit high sensitivity and accuracy. However, these techniques generally suffer from certain limitations, such as high cost, bulky equipment, time-consuming and operator-dependent properties. Therefore, the establishment of fast and efficient analytical methods for TCP still remains a great challenge.

RESULT

A "turn on" fluorescence sensing strategy for the efficient detection of TCP was established, based on a unique molecular rotor probe of 9-(2,2-dicyanovinyl)-julolidine (DCVJ). The introduction of TCP led to a significant enhancement of the fluorescence intensity of DCVJ. The results show that twisted intramolecular charge transfer (TICT) process might play an important role for this enhancement of fluorescence response via dynamic light scattering measurements and fluorescence lifetime analysis. Further investigations demonstrate that the hydrophobic interaction and conjugation effect between DCVJ and TCP constrain the molecular rotation and vibration of DCVJ, thereby regulating the TICT process, which contribute to this intriguing "turn on" behavior. In view of this, a new sensing platform with excellent performance for TCP was established, which offers quick response time, high selectivity, wide linear range (20-1200 ng mL-1, 1600-8000 ng mL-1), and low detection limit (4.82 ng mL-1).

SIGNIFICANCE

The established new sensing platform for TCP demonstrates the advantages of simplicity, high efficiency, excellent sensitivity and selectivity. The obtained results are also superior to some other previously reported fluorescence methods. This work opens up a new perspective for the efficient detection of emerging OPFRs pollutants.

Determinants of organophosphate esters exposure in pregnant women from East China

Organophosphate esters (OPEs) have been broadly used in various industrial and consumer products, resulting in global distribution and human exposure. Gestational exposure to OPEs may adversely affect the health of both pregnant women and their offspring. To better understand OPE exposure in pregnant women, our study determined eight urinary metabolites of major OPEs in pregnant women (n = 733) recruited at 12-16 weeks of gestation from Shanghai, China, and explored the determinants of OPE exposure among various sociodemographic characteristics, lifestyles, and dietary factors. Urinary metabolites of OPEs, including bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), bis (1-chloro-2-propyl) phosphate (BCIPP), dicresyl phosphate (DCP), diphenyl phosphate (DPP), dibutyl phosphate (DBP), bis (2-ethylhexyl) phosphate (BEHP), and bis (2-butoxyethyl) phosphate (BBOEP), exhibited a detection rate ranging from 69.30% to 99.32%. Multivariate linear regression models indicated that pregnant women who were multiparous, had a higher family income per capita, worked in white-collar jobs, and took nutritional supplements such as milk powder and fish oil tended to have higher urinary OPE metabolite concentrations. Besides, independent of sociodemographic characteristics and lifestyle factors, consumption of more aquatic products, soy products, pork, and puffed food, as well as drinking of purified tap water versus tap water, were associated with increased urinary OPEs metabolite concentrations. Our study demonstrated that OPE exposure was ubiquitous in pregnant women from Shanghai, and provided new insights into the potential factors influencing OPE exposure during pregnancy.

Uncovering the distribution patterns and origins of organophosphate esters (OPEs) in the Yellow River Estuary via high-resolution mass spectrometry

Limited information is available regarding the pollution status of organophosphate esters (OPEs) in the environment of the Yellow River estuary. Here, n = 51 sediment samples were collected from the Yellow River estuary in 2021, and further analyzed by using the integrated target, suspect, and feature fragment-dependent nontarget OPE screening strategy developed in our laboratory. Among the 30 target OPEs, 19 were detectable in at least one of the analyzed samples, with total concentrations (Σ19OPEs) ranging from of 41.4 to 1930 ng/g dry weight (dw). On the basis of an in-house suspect compound database, we further tentatively identified 11 suspect OPEs, and they were semi-quantified. Furthermore, four other interesting findings were observed and described as follows: 1) a statistically significant difference existed in the concentrations of OPEs in sediment samples between the lower reaches of the Yellow River (n = 5 samples), and the Yellow River estuary (n = 46 samples) (unpaired t-test, p < 0.001); 2) tris(2,4-di-tert-butylphenyl)phosphate (TDTBPP) exhibited the greatest concentrations (ranging from 30.7 to 1920 ng/g dw) among all OPEs detected in the sediment samples; 3) samples from the north of the Yellow River estuary had higher OPE concentrations than those from the south; and 4) a suspect screening strategy allowed us to identify a novel OPE structure (tert-butyl)phenyl (ethyne-oxidane) bis(2,4-di-tert-butylphenyl) phosphate (TPBDTP) that exhibited a highly positive correlation relationship with TDTBPP (r = 0.749; p < 0.001). Overall, this study provided evidence that OPEs (especially TDTBPP) were ubiquitous in the sediment environment of the Yellow River estuary; thus, we emphasize that continuous monitoring of OPE pollution should be conducted in this region.

Discovery and occurrence of organophosphorothioate esters in food contact plastics and foodstuffs from South China: Dietary intake assessment

A recent study revealed the presence of non-pesticide organothiophosphate esters (OTPEs) - precursors to organophosphate esters (OPEs) contaminants - in river water. Since OPEs have demonstrated adverse reproductive outcomes in humans, this accentuates the urgency to explore the prevalence of non-pesticide OTPEs in other potential human exposure matrices. In this study, a nontarget screening method based on high-resolution mass spectrometry was used to identify OTPEs in food contact plastic (FCP) samples collected from South China. O,O,O-triphenyl phosphorothioate (TPhPt) and O,O,O-tris(2,4-di-tert-butylphenyl) phosphorothioate (AO168 = S) were unequivocally identified (Level 1), while O,O-di(di-butylphenyl) O-methyl phosphorothioate (BDBPMPt) was tentatively identified (Level 2b, indicating probable structure based on diagnostic evidence). Among n = 70 FCP samples, AO168 = S emerged with the highest detection frequency and median concentration of 74 % and 111 ng/g, respectively. Significant Pearson correlations were observed in log-transformed peak areas of AO168 = S and TPhPt in FCPs with their respective oxons, respectively. Occurrences of AO168 = S and TPhPt were further investigated in n = 100 foodstuff samples using a market basket method. AO168 = S and TPhPt exhibited detection frequencies of 43 % and 44 % in all food items with mean concentrations of 2.17 ng/g wet weight (ww) (range: <0.53-67.8 ng/g ww) and 0.112 ng/g ww (range: <0.006-2.39 ng/g ww), respectively. The highest mean concentrations for AO168 = S and TPhPt were found in vegetables (4.62 ng/g ww) and oil (3.00 ng/g ww), respectively. The median estimated daily intakes (EDIs) of AO168 = S and TPhPt via diet were calculated as 10.4 and 1.51 ng/kg body weight/day, respectively. For AO168 = S, only meat and vegetables contributed to the median EDI, whereas for TPhPt, oil was identified as the principal contributor to the median EDI. This study for the first time evaluated human exposure to OTPEs via diet, providing new insights to overall human exposure to OPEs.

High-resolution mass spectrometry-based screening and dietary intake assessment of organophosphate esters in foodstuffs from South China

Organophosphate esters (OPEs) are a group of emerging contaminants with widespread environmental occurrence, yet research on their occurrence in foodstuffs is limited. We collected 100 foodstuff samples in South China using a market basket method, and analyzed food extracts for the presence of OPEs and organophosphite antioxidants (OPAs) by suspect and nontarget screening through high-resolution mass spectrometry. Our analysis resulted in the identification of 30 OPEs, comprised of 25 OPEs with a confidence level (CL) of 1 (unequivocal identification using standards) and five OPEs with CL = 2b (probable structure based on diagnostic evidence). Interestingly, 11 of these identified OPEs had not been previously reported in food. No OPA was identified. The occurrence of identified OPEs within the food samples was further investigated. The highest median concentration of OPEs in all food samples was reached by tris(2-chloroisopropyl) phosphate (TCPP) (1.55 ng/g ww, range < 0.74-12.0 ng/g wet weight (ww)). Cereals demonstrated the highest median concentration of the cumulative 30 OPEs. Tris(2-chloroethyl) phosphate (TCEP), TCPP, and triethyl phosphate (TEP) predominantly contributed to OPEs contamination in most food categories. Eight OPEs, namely TEP, tris(2-ethylhexyl) phosphate (TEHP), TCEP, triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP), bis(2-ethylhexyl) phenyl phosphate (BEHPP), resorcinol bis(diphenyl phosphate) (RDP), and methyl diphenyl phosphate (MDPP) exhibited significantly higher concentrations in the processed group as compared to non-processed group, suggesting that food processing may result in contamination of these OPEs. The median sum of estimated dietary intake (ΣEDI) of all OPEs was determined to be 161 ng/kg body weight/day. Cereals (38.5 %) and vegetables (23.5 %) were the predominant food categories contributing to ΣEDI, and TEP (29.0 %), TCEP (20.2 %), and TCPP (18.3 %) were three major OPEs contributing to ΣEDI. This study for the first time offered a comprehensive overview of OPE species and revealed their occurrence in foodstuffs from South China.

Unregistered Hexaphenoxycyclotriphosphazene and Its Metabolite Antagonize Retinoic Acid and Retinoic X Receptors and Cause Early Developmental Damage

Hexaphenoxycyclotriphosphazene (HPCTP), an unregistered chemical, has been used as a substitute for triphenyl phosphate in flame retardants and plasticizers. Here, we identified its metabolite, pentaphenoxycyclotriphosphazene (PPCTP) in the liver of Japanese medaka exposed to HPCTP. When sexually mature female medaka were exposed to HPCTP at 37.0, 90.4, and 465.4 ng/L for 35 days, the HPCTP concentration (642.1-2531.9 ng/g lipid weight [lw]) in the embryos considerably exceeded that (34.7-298.1 ng/g lw) in the maternal muscle, indicating remarkable maternal transfer. During 0-9 days postfertilization, the HPCTP concentration in the embryos decreased continuously, while the PPCTP concentration increased. HPCTP and PPCTP antagonized the retinoic X receptor with 50% inhibitory concentrations (IC50) of 34.8 and 21.2 μM, respectively, and PPCTP also antagonized the retinoic acid receptor with IC50 of 2.79 μM. Such antagonistic activities may contribute to eye deformity (4.7% at 465.4 ng/L), body malformation (2.1% at 90.4 ng/L and 6.8% at 465.4 ng/L), and early developmental mortality (11.6-21.7% in all exposure groups) of the embryos. HPCTP was detected in a main tributary of the Yangtze River Basin. Thus, HPCTP poses a risk to wild fish populations, given the developmental toxicities associated with this chemical and its metabolite.

Organophosphorus flame retardants and their metabolites in paired human blood and urine

Organophosphorus flame retardants (OPFRs) have been shown to be carcinogenic, neurotoxic, and endocrine disruptive, so it is important to understand the levels of OPFRs in human body as well as the modes of external exposure. In this study, we investigated the levels of 13 OPFRs and 7 phosphodiester metabolites in paired human blood and urine, as well as the influencing factors (region, age and gender), and studied the relationship between OPFRs and oxidative stress by urinary metabolites. We found that the concentrations of triphenyl phosphate (TPhP) and tris-(2-ethylhexyl) phosphate (TEHP) in the blood of urban populations were higher than those of rural populations, and that younger populations suffered higher TPhP and 2-ethylhexyl diphenyl phosphate (EHDPP) exposures than older populations. In addition, we found that tris-(2-chloroethyl) phosphate (TCEP), tributyl phosphate (TnBP), TPhP and EHDPP exposure induced oxidative stress. The results of the internal load principal component analysis indicated that dust ingestion, skin exposure, respiration and dietary intake may be the most important sources of TCEP, tris(2-butoxyethyl) phosphate (TBOEP), tri(2-chloroisopropyl) phosphate (TCIPP) and TEHP, respectively, and dust ingestion and skin exposure may be the main sources of TPhP for humans.

Plastic additive components of PM2.5 increase corrected QT interval: Screening for exposure markers based on airborne exposome

The impact of industrial chemical components of ambient fine particles (e.g. PM2.5) on cardiovascular health has been poorly explored. Our study reports for the first time the associations between human exposure to complex plastic additive (PA) components of PM2.5 and prolongation of heart rate-corrected QT (QTC) interval by employing a screening-to-validation strategy based on a cohort of 373 participants (136 in the screening set and 237 in the validation set) recruited from 7 communities across China. The high-throughput airborne exposome framework revealed ubiquitous occurrences of 95 of 224 target PAs in PM2.5, totaling from 66.3 to 555 ng m-3 across the study locations. Joint effects were identified for 9 of the 13 groups of PAs with positive associations with QTC interval. Independent effect analysis also identified and validated tris(2-chloroisopropyl) phosphate, di-n-butyl/diisobutyl adipate, and 3,5-di-tert-butyl-4-hydroxybenzaldehyde as the key exposure markers for QTC interval prolongation and changes of selected cardiovascular biomarkers. Our findings highlight the important contributions of airborne industrial chemicals to the risks of cardiovascular diseases and underline the critical need for further research on the underlying mechanisms, toxic modes of action, and human exposure risks.

Association of organophosphate flame retardants with all-cause and cause-specific mortality among adults aged 40 years and older

The longitudinal associations of urinary concentrations of diphenyl phosphate (DPHP), bis(2-chloroethyl) phosphate (BCEP), and bis(1,3-dichloro-2-propyl) phosphate (BDCPP) with all-cause, cardiovascular, and cancer mortality in a population of adults aged 40 years and older are still unclear. A total of 3238 participants were included in this cohort study. Urinary BCEP levels were positively associated with all-cause mortality and cardiovascular mortality. Specifically, a logarithmic increase in BCEP concentration was related to a 26 % higher risk of all-cause mortality and a 32 % higher risk of cardiovascular mortality. No significant associations were observed for DPHP and BDCPP in relation to mortality. Doseresponse analysis confirmed the linear associations of BCEP with all-cause and cardiovascular mortality and the nonlinear inverted U-shaped association between DPHP exposure and all-cause mortality. Notably, the economic burden associated with BCEP exposure was estimated, and it was shown that concentrations in the third tertile of BCEP exposure incurred approximately 507 billion dollars of financial burden for all-cause mortality and approximately 717 billion dollars for cardiovascular mortality. These results highlight the importance of addressing exposure to BCEP and its potential health impacts on the population. More research is warranted to explore the underlying mechanisms and develop strategies for reducing exposure to this harmful chemical.

Endoplasmic reticulum stress participates in apoptosis of HeLa cells exposed to TPHP and OH-TPHP via the eIF2α-ATF4/ATF3-CHOP-DR5/P53 signaling pathway

Purpose

Triphenyl phosphate (TPHP) is a widely used organophosphate flame retardant, which can be transformed in vivo into diphenyl phosphate (DPHP) and 4-hydroxyphenyl phosphate (diphenyl) ester (OH-TPHP) through biotransformation process. Accumulation of TPHP and its derivatives in biological tissues makes it necessary to investigate their toxicity and molecular mechanism.

Methods

The present study evaluated the cellular effects of TPHP, DPHP, and OH-TPHP on cell survival, cell membrane damage, oxidative damage, and cell apoptosis using HeLa cells as in vitro model. RNA sequencing and bioinformatics analysis were conducted to monitor the differently expressed genes, and then RT-qPCR and Western bolt were used to identify potential molecular mechanisms and key hub genes.

Results

Results showed that OH-TPHP had the most significant cytotoxic effect in HeLa cells, followed by TPHP; and no significant cytotoxic effects were observed for DPHP exposure within the experimental concentrations. Biological function enrichment analysis suggested that TPHP and OH-TPHP exposure may induce endoplasmic reticulum stress (ERS) and cell apoptosis. The nodes filtering revealed that ERS and apoptosis related genes were involved in biological effects induced by TPHP and OH-TPHP, which may be mediated through the eukaryotic translation initiation factor 2α/activating transcription factor 4 (ATF4)/ATF3- CCAAT/ enhancer-binding protein homologous protein (CHOP) cascade pathway and death receptor 5 (DR5) /P53 signaling axis.

Conclusion

Above all, these findings indicated that ERS-mediated apoptosis might be one of potential mechanisms for cytotoxicity of TPHP and OH-TPHP.

Prenatal exposure to emerging and traditional organophosphate flame retardants: Regional comparison, transplacental transfer, and birth outcomes

During gestation, organophosphate flame retardants (OPFRs) have the potential to pose health risks to fetuses due to their ability to cross the placental barrier. However, data are scarce regarding the transplacental transfer of these compounds, particularly concerning emerging OPFRs and regional variations. In this study, we analyzed 14 traditional OPFRs and 5 emerging OPFRs in maternal and cord serum samples from Mianyang and Hangzhou, two cities in eastern and western China, respectively. The results revealed marked disparities in the overall levels of OPFRs between the two cities (p < 0.05), with the average concentration in maternal serum being higher in Hangzhou (14.55 ng/mL) than in Mianyang (8.28 ng/mL). The most abundant compounds found in both cities were tris (2-chloroethyl) phosphate (TCEP), Triphenyl phosphate (TPHP), and Tri-n-butyl phosphate (TnBP). Additionally, this study marked the first detection of novel OPFRs, including resorcinol bis (diphenyl phosphate) (RDP), isodecyl diphenyl phosphate (IDDPP), cresyl diphenyl phosphate (CDP), and bisphenol A bis (diphenyl phosphate) (BPA-BDPP) in maternal and cord serum simultaneously with the detection frequencies higher than 45%. This study also found that transplacental transfer efficiencies for OPFRs varied by ester group, with Aryl-OPFRs exhibiting the highest transfer rates (0.90-1.11) and Alkyl-OPFRs exhibiting the lowest (0.66-0.83). Transfer efficiencies exhibited a positive correlation with log Kow values (p < 0.05), suggesting that hydrophobic OPFRs with higher log Kow values are more likely to permeate the placental barrier. Moreover, the exposure levels of Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), Tri (Chloropropyl) Phosphate (TCIPP), TPHP, and CDP in cord serum were negatively associated (p < 0.05) with birthweight of newborns. This research adds to our understanding of the transplacental transfer of OPFRs and the possible health risks associated with prenatal exposure.

Review on typical organophosphate diesters (di-OPEs) requiring priority attention: Formation, occurrence, toxicological, and epidemiological studies

The impact of primary metabolites of organophosphate triesters (tri-OPEs), namely, organophosphate diesters (di-OPEs), on the ecology, environment, and humans cannot be ignored. While extensive studies have been conducted on tri-OPEs, research on the environmental occurrence, toxicity, and health risks of di-OPEs is still in the preliminary stage. Understanding the current research status of di-OPEs is crucial for directing future investigations on the production, distribution, and risks associated with environmental organophosphate esters (OPEs). This paper specifically reviews the metabolization process from tri-OPEs to di-OPEs and the occurrence of di-OPEs in environmental media and organisms, proposes typical di-OPEs in different media, and classifies their toxicological and epidemiological findings. Through a comprehensive analysis, six di-OPEs were identified as typical di-OPEs that require prioritized research. These include di-n-butyl phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCIPP), and diphenyl phosphate (DPHP). This review provides new insights for subsequent toxicological studies on these typical di-OPEs, aiming to improve our understanding of their current status and provide guidance and ideas for research on the toxicity and health risks of di-OPEs. Ultimately, this review aims to enhance the risk warning system of environmental OPEs.

2-Ethylhexyl Diphenyl Phosphate Causes Obesity in Zebrafish by Stimulating Overeating via Inhibition of Dopamine Receptor D2

Obesity is a popular public health problem worldwide and is mainly caused by overeating, but little is known about the impacts of synthetic chemicals on obesity. Herein, we evaluated the obesogenic effect caused by 2-ethylhexyl diphenyl phosphate (EHDPHP) on zebrafish. Adult zebrafish were exposed to 5, 35, and 245 μg/L of EHDPHP for 21 days. Results showed that EHDPHP exposure significantly promoted the feeding behavior of zebrafish, as evidenced by shorter reaction time, increased average food intake, feeding rate, and intake frequency (p < 0.05). Transcriptomic, real-time quantitative PCR, and neurotransmitter analyses revealed that the dopamine (DA) receptor D2 (DRD2) was inhibited, which interfered with the DA neural reward regulation system, thus stimulating food addiction to zebrafish. This was further verified by the restored DRD2 after 7 days of Halo (a DRD2 agonist) treatment. A strong interaction between EHDPHP and DRD2 was identified via molecular docking. As a consequence of the abnormal feeding behavior, the exposed fish exhibited significant obesity evidenced by increased body weight, body mass index, plasma total cholesterol, triglyceride, and body fat content. Additionally, the pathways linked to Parkinson's disease, alcoholism, and cocaine addiction were also disrupted, implying that EHDPHP might cause other neurological disorders via the disrupted DA system.

Interactions of organophosphate flame retardants with human drug transporters

Organophosphate flame retardants (OPFRs) are environmental pollutants of increasing interest, widely distributed in the environment and exerting possible deleterious effects towards the human health. The present study investigates in vitro their possible interactions with human drug transporters, which are targets for environmental chemicals and actors of their toxicokinetics. Some OPFRs, i.e., tris(2-butoxyethyl) phosphate (TBOEP), tris(1,3-dichloroisopropyl) phosphate (TDCPP), tri-o-cresyl phosphate (TOCP) and triphenyl phosphate (TPHP), were found to inhibit activities of some transporters, such as organic anion transporter 3 (OAT3), organic anion transporting polypeptide (OATP) 1B1, OATP1B3, organic cation transporter 2 (OCT2) or breast cancer resistance protein (BCRP). These effects were concentration-dependent, with IC50 values ranging from 6.1 µM (for TDCPP-mediated inhibition of OCT2) to 51.4 µM (for TOCP-mediated inhibition of BCRP). OPFRs also blocked the transporter-dependent membrane passage of endogenous substrates, notably that of hormones. OAT3 however failed to transport TBOEP and TPHP. OPFRs additionally repressed mRNA expressions of some transporters in cultured human hepatic HepaRG cells, especially those of OAT2 and OCT1 in response to TOCP, with IC50 values of 2.3 µM and 2.5 µM, respectively. These data therefore add OPFRs to the expanding list of pollutants interacting with drug transporters, even if OPFR concentrations required to impact transporters, in the 2-50 µM range, are rather higher than those observed in humans environmentally or dietarily exposed to these chemicals.

Maternal transfer of resorcinol-bis(diphenyl)-phosphate perturbs gut microbiota development and gut metabolism of offspring in rats

Resorcinol-bis(diphenyl)-phosphate (RDP), an emerging organophosphate flame retardant, is increasingly used as a primary alternative for decabromodiphenyl ether and is frequently detected in global environmental matrices. However, the long-term effects of its exposure to humans remain largely unknown. To investigate its intergenerational transfer capacity and health risks, female Sprague Dawley rats were orally exposed to RDP from the beginning of pregnancy to the end of the lactation period. The RDP content, gut microbiota homeostasis, and metabolic levels were determined. RDP accumulation occurred in the livers of maternal rats and offspring and increased with exposure time. 16S rRNA gene sequencing showed that exposure to RDP during pregnancy and/or lactation significantly disrupted gut microbiota homeostasis, as evidenced by decreased abundance and diversity. In particular, the abundance of Turicibacter, Adlercreutzia, and YRC22 decreased, correlating significantly with glycollipic metabolism. This finding was consistent with the reduced levels of short-chain fatty acids, the crucial gut microbial metabolites. Meanwhile, RDP exposure resulted in changes in gut microbiome-related metabolism. Nine critical overlapping KEGG metabolic pathways were identified, and the levels of related differential metabolites decreased. Our results suggest that the significant adverse impacts of RDP on gut microbiota homeostasis and metabolic function may increase the long-term risks related to inflammation, obesity, and metabolic diseases.

Lipid metabolic disturbance induced by triphenyl phosphate and hydroxy metabolite in HepG2 cells

Triphenyl phosphate (TPHP) has been widely used as flame retardants and been detected with increasing frequency in environment. TPHP can transform into mono-hydroxylated phosphate (OH-TPHP) and diester diphenyl phosphate (DPHP) through biotransformation. So far, information on the cytotoxicity and molecular regulatory mechanisms of TPHP metabolites are still limit. This study investigated the adverse effects of TPHP, OH-TPHP, and DPHP in HepG2 cells in terms of cell proliferation, lactate dehydrogenase release, reactive oxygen species generation, and mitochondrial membrane potential. The transcriptomic changes were measured using RNA sequencing, and bioinformatics characteristics including biological functions, signal pathways and protein-protein interaction were analyzed to explore the potential molecular mechanisms. Results displayed that the order of cytotoxicity was OH-TPHP> TPHP> DPHP. The prioritized biological functions changes induced by TPHP and OH-TPHP were correlated with lipid metabolism. Significant lipid accumulation was observed as confirmed by increased total cholesterol and triglycerides contents, and enhanced oil red O staining. Enrichment of PPARα/γ and down-stream genes suggested the participation of PPARs signal pathway in lipid metabolism disorder. In addition, TPHP and OH-TPHP induced endoplasmic reticulum stress (ERS), which was further confirmed by the ERS inhibitor experiment. In general, TPHP and OH-TPHP had obvious cytotoxic effects in HepG2 cells. PPARs signal pathway and endoplasmic reticulum stress may be involved in the lipid metabolism disorder induced by TPHP and OH-TPHP.

First insight into the sex-dependent accumulation, tissue distribution and potential toxicities of 2-ethylhexyl diphenyl phosphate and its metabolites in adult zebrafish

The 2-ethylhexyl diphenyl phosphate (EHDPHP), a primary organophosphorus flame retardant used in various industrial products, is prone to biotransformation. However, there is a knowledge gap on the sex- and tissue-specific accumulation and potential toxicities of EHDPHP (M1) and its metabolites (M2-M16). In this study, adult zebrafish (Danio rerio) were exposed to EHDPHP (0, 5, 35 and 245 µg/L) for 21-day, which was followed by 7-day depuration. The bioconcentration factor (BCF) of EHDPHP in female zebrafish was 26.2 ± 7.7% lower than in males due to the lower uptake rate (k_u) while higher depuration rate (k_d) in the females. The regular ovulation and higher metabolic efficiency promoted elimination from female zebrafish, thus leading to much less (28-44%) accumulation of ∑(M1-M16) in female zebrafish. They exhibited the highest accumulation in the liver and intestine in both sexes, which might be regulated by tissue-specific transporters and histones evidenced by molecular docking results. Intestine microbiota analysis further revealed that female zebrafish were more susceptible to EHDPHP exposure, with more significant changes in phenotype number and KEGG pathways in female than male fish. Disease prediction results suggested that EHDPHP exposure might cause cancers, cardiovascular diseases as well as endocrine disorders in both sexes. These results provide a comprehensive understanding of the sex-dependent accumulation and toxicity of EHDPHP and its metabolites.