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

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.

Nano titanium dioxide alleviates the toxic effects of tris (2-chloropropyl) phosphate on the digestive gland and hemolymph of thick-shell mussel Mytilus coruscus

In the marine environment, nanoparticles play a role in adsorbing and catalytically degrading organic pollutants, thereby mitigating their toxic effects on aquatic organisms. This study aimed to investigate the impact of nano titanium dioxide (nTiO2) and tris (2-chloropropyl) phosphate (TCPP) on the hemolymph and digestive function of the thick-shell mussel Mytilus coruscus. Mussels were divided into a control group, a group exposed to TCPP alone, a group exposed to a combination of TCPP and 0.5 mg/L nTiO2, and a group exposed to a combination of TCPP and 1 mg/L nTiO2. After 14 days of exposure, oxidative stress responses, including superoxide dismutase (SOD) activity and malondialdehyde (MDA) content, immune defense responses, including acid phosphatase (ACP) and alkaline phosphatase (AKP) activities, and gene expression, including HSP70 expression, were measured in the hemolymph and digestive glands of the mussels. Compared to the control group, mussels solely exposed to 100 μg/L TCPP exhibited a significant reduction in SOD activity in the hemolymph. When TCPP was co-exposed with 0.5 mg/L nTiO2, there were significant increases in MDA content and AKP activity in both the digestive gland and hemolymph compared to the control group. Upon co-exposure of TCPP with 1 mg/L nTiO2, MDA content and AKP activity in the digestive gland significantly decreased, while SOD, ACP, and AKP activity in the hemolymph significantly increased and MDA content significantly decreased, returning to the control group levels. Furthermore, in the combined exposure, HSP70 gene expression significantly decreased as the nTiO2 concentration increased from 0.5 mg/L to 1 mg/L. In summary, TCPP impacted the hemolymph and digestive function of mussels, whereas a concentration of 1 mg/L nTiO2 effectively alleviated the toxic effects of TCPP. This study is crucial for assessing the ecological risks of nanoparticles and emerging organic pollutants in marine environments, and provides new insights into the interaction between nTiO2 and TCPP, as well as the influence of nTiO2 concentration on mitigating TCPP toxicity.

Effect of nitrogen oxides and sulfur oxides to triphenyl phosphate degradation and cytotoxicity on surface of different transition metal salts

Nitrogen oxides and sulfur oxides, as the dominant toxic gases in the atmosphere, can induce severe human health problems under the composite pollutant conditions. Currently the effect of nitrogen or sulfur oxides in atmospheric environment to the degradation and cytotoxicity of triphenyl phosphate (TPhP) on atmospheric particle surfaces still remain poorly understood. Hence, laboratory simulation methods were used in this study to investigate the effect and related mechanism. First, particle samples were prepared with the TPhP coated on MnSO4, CuSO4, FeSO4 and Fe2(SO4)3 surface. The results showed that, when nitrogen or sulfur oxides were present, more significant TPhP degradation on all samples can be observed under both light and dark conditions. The results proved nitrogen oxides and sulfur oxides were the vital influence factors to the degradation of TPhP, which mainly promoted the OH generation in the polluted atmosphere. The mechanism study indicated that diphenyl hydrogen phosphate (DPhP) and OH-DPhP were two main stable degradation products. These degradation products originated from the phenoxy bond cleavage and hydroxylation of TPhP caused by hydroxyl radicals. In addition, no TPhP related organosulfates (OSs) or organic nitrates (ON) formation were observed. Regarding the cytotoxicity, all the particles can induce more significant cellular injury and apoptosis of A549 cells, which may be relevant to the adsorbed nitrogen oxides or sulfur oxides on particles surfaces. The superfluous reactive oxygen species (ROS) generation was the possible reason of cytotoxicity. This research can supply a comprehensive understanding of the promoting effect of nitrogen and sulfur oxides to TPhP degradation and the composite cytotoxicity of atmospheric particles.

Effects of organophosphorus flame retardant EHDPP on mouse retinal photoreceptor cells: Oxidative stress, apoptosis, and proinflammatory response

2-Ethylhexyl diphenyl phosphate (EHDPP) is a frequently utilized organophosphorus flame retardant (OPFR) and has been extensively detected in environmental media. Prolonged daily exposure to EHDPP has been linked to potential retinal damage, yet the adverse impacts on the retina are still generally underexplored. In this research, we explored oxidative stress, inflammation, and the activating mechanisms initiated by EHDPP in mouse retinal photoreceptor (661 W) cells following a 24 h exposure period. Our research demonstrated that EHDPP led to a decline in cell viability that was directly proportional to its concentration, with the median lethal concentration (LC50) being 88 µM. Furthermore, EHDPP was found to elevate intracellular and mitochondrial levels of reactive oxygen species (ROS), trigger apoptosis, induce cell cycle arrest at the G1 phase, and modulate the expression of both antioxidant enzymes (Nrf2, HO-1, and CAT) and pro-inflammatory mediators (TNF-α, IL-1β, and IL-6) within 661 W cells. These findings indicate that retinal damage triggered by EHDPP exposure could be mediated via the Nrf2/HO-1 signaling pathway in these cells. Collectively, our investigation revealed that oxidative stress induced by EHDPP is likely a critical factor in the cytotoxic response of 661 W cells, potentially leading to damage in retinal photoreceptor cells.

Investigation of alkyl, aryl, and chlorinated OPFRs in sediments from estuarine systems: Seasonal variation, spatial distribution and ecological risks assessment

Estuaries in South Africa are very important for biodiversity conservation and serve as focal points for leisure and tourism activities. The organophosphate flame retardants (OPFRs) levels in these aquatic systems haven't been documented in any studies as of yet. Due to the negative effects of persistent organic pollutants in South African estuaries, we examined the occurrence of eight OPFRs in sediments of two estuaries by studying their spatiotemporal distribution, season variation, and ecological risks. The Sundays Estuary (SDE), a semi-urbanized agricultural surrounding system, recorded an ∑8OPFR concentration in sediments that ranged from 0.71 to 22.5 ng/g dw, whereas Swartkops Estuary, a largely urbanized system, recorded a concentration that ranged from 0.61 to 119 ng/g dw. Alkyl-OPFRs were the prevalent homologue in both estuaries compared to the chlorinated and aryl groups. While TBP, TCPP, and TCrP were the most abundant compounds among the homologue groups. There was no distinct seasonal trend of ∑8OPFR concentration in either estuary, with summer and autumn seasons recording the highest concentrations in SDE and SWE, respectively. Ecological risks in the majority of the study sites for the detected compounds were at low (RQ < 0.1) and medium levels (0.1 ≤ RQ < 1) for certain species of fish, Daphnia magna and algae. However, the cumulative RQs for all the compounds had ∑RQs ≥1 for most sites in both estuaries, indicating that these organisms, if present in both estuaries, may be exposed to potential ecological concerns due to accumulated OPFR chemicals. The scope of future studies should be broadened to include research areas that are not only focus on the bioaccumulation patterns of these compounds but also find sustainable ways to reduce them from these estuarine environments.

EGFR and Hippo signaling pathways are involved in organophosphate esters-induced proliferation and migration of triple-negative breast cancer cells

The widespread application of organophosphate flame retardants has led to pervasive exposure to organophosphate esters (OPEs), prompting considerable concerns regarding their potential health risk to humans. Despite hints from previous research about OPEs' association with breast cancer, their specific effects and underlying mechanisms of triple-negative breast cancer (TNBC) remain unclear. In this study, we investigated the effects of four representative OPEs on cell proliferation, cell cycle regulation, migration, and the expression of genes and proteins associated with the epidermal growth factor receptor (EGFR) and Hippo signaling pathways in TNBC (MDA-MB-231) cells. Our findings revealed that treatment with 1-25 μM triphenyl phosphate (TPHP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) induced TNBC cell proliferation and accelerated cell cycle progression, with upregulation in MYC, CCND1, and BRCA1 mRNA. Moreover, exposure to 1-25 μM TPHP, 10-25 μM TDCIPP, and 1-10 μM tris (2-chloroethyl) phosphate (TCEP) induced MMP2/9 mRNA expression and enhanced migratory capacity, except for 2-ethylhexyl diphenyl phosphate (EHDPP). Mechanistically, four OPEs treatments activated the EGFR-ERK1/2 and EGFR-PI3K/AKT signaling pathways by increasing the transcript of EGFR, ERK1/2, PI3K, and AKT mRNA. OPEs treatment also suppressed the Hippo signaling pathway by inhibiting the expression of MST1 mRNA and phosphorylation of LATS1, leading to the overactivation of YAP1 protein, thereby promoting TNBC cell proliferation and migration. In summary, our study elucidated that activation of the EGFR signaling pathway and suppression of the Hippo signaling pathway contributed to the proliferation, cell cycle dysregulation, and migration of TNBC cells following exposure to OPEs.

Degradation, transformation and cytotoxicity of triphenyl phosphate on surface of different transition metal salts in atmospheric environment

Triphenyl phosphate (TPhP) and transition metal elements have been ubiquitously detected in the atmosphere, which can participate in atmospheric chemical reactions and induce damage to human health. Currently the understanding of TPhP degradation, transformation and cytotoxicity on atmospheric particles surface are still limited. Therefore, this study used laboratory simulation methods to investigate the influence of irradiation time, transition metal salts, relative humidity (RH) to TPhP degradation, transformation and relative cytotoxicity. TPhP was coated on particle surfaces of four transition metal salts (MnSO4, CuSO4, FeSO4 and Fe2(SO4)3) in the experiment. Within 12 h irradiation, the significant TPhP photodegradation can be observed on all particles surface. Among these influence factors, the irradiation and RH were the crucial aspects to TPhP degradation, which primarily affect the OH concentration in the atmosphere. The transition metal elements only exhibited slightly catalytic effect to TPhP degradation. The mechanism study indicated that the major degradation products of TPhP are diphenyl hydrogen phosphate (DPhP) and OH-DPhP, which originated from the phenoxy bond cleavage and hydroxylation of TPhP induced by OH. As for the cytotoxicity to A549 cells, all the transition metal particles coated with TPhP can cause cellular injury, which was chiefly induced by the transition metal salt. The possible cytotoxicity mechanism of these particles to A549 cells can be attributed to the excessive reactive oxygen species (ROS) production. This study may provide a further understanding of TPhP degradation and related cytotoxicity with the coexistent transition metal salts in the atmosphere.

The neurotoxicity of organophosphorus flame retardant tris (1,3-dichloro-2-propyl) phosphate (TDCPP): Main effects and its underlying mechanisms

As a major alternative to the brominated flame retardants, the production and use of organophosphorus flame retardants (OPFRs) are increasing. And tris (1,3-dichloro-2-propyl) phosphate (TDCPP), one of the most widely used OPFRs, is now commonly found in a variety of products, such as building materials, furniture, bedding, electronic equipment, and baby products. TDCPP does not readily degrade in the water and tends to accumulate continuously in the environment. It has been detected in indoor dust, air, water, soil, and human samples. Considered as an emerging environmental pollutant, increasing studies have demonstrated its adverse effects on environmental organisms and human beings, with the nerve system identified as a sensitive target organ. This paper systematically summarized the progress of TDCPP application and its current exposure in the environment, with a focus on its neurotoxicity. In particular, we highlighted that TDCPP can be neurotoxic (including neurodevelopmentally toxic) to humans and animals, primarily through oxidative stress, neuroinflammation, mitochondrial damage, and epigenetic regulation. Additionally, this paper provided an outlook for further studies on neurotoxicity of TDCPP, as well as offered scientific evidence and clues for rational application of TDCPP in daily life and the prevention and control of its environmental impact in the future.

Perfluorooctanoic acid induces Leydig cell injury via inhibition of autophagosomes formation and activation of endoplasmic reticulum stress

Perfluorooctanoic acid (PFOA) is a man-made chemical broadly distributed in various ecological environment and human bodies, which poses potential health risks. Its toxicity, especially the male reproduction toxicity has drawn increasing attention due to declining birth rates in recent years. However, how PFOA induces male reproductive toxicity remains unclear. Here, we characterize PFOA-induced cell injury and reveal the underlying mechanism in mouse Leydig cells, which are critical to spermatogenesis in the testes. We show that PFOA induces cell injury as evidenced by reduced cell viability, cell morphology changes and apoptosis induction. RNA-sequencing analysis reveals that PFOA-induced cell injury is correlated with compromised autophagy and activated endoplasmic reticulum (ER) stress, two conserved biological processes required for regulating cellular homeostasis. Mechanistic analysis shows that PFOA inhibits autophagosomes formation, and activation of autophagy rescues PFOA-induced apoptosis. Additionally, PFOA activates ER stress, and pharmacological inhibition of ER stress attenuates PFOA-induced cell injury. Taken together, these results demonstrate that PFOA induces cell injury through inhibition of autophagosomes formation and induction of ER stress in Leydig cells. Thus, our study sheds light on the cellular mechanisms of PFOA-induced Leydig cell injury, which may be suggestive to human male reproductive health risk assessment and prevention from PFOA exposure-induced reproductive toxicity.

Tris(1,3-dichloro-2-propyl) phosphate disrupts cellular metabolism within human embryonic kidney (HEK293) cells

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is a widely used, additive flame retardant that migrates from end-use products, leading to ubiquitous exposure of humans around the world. However, little is known about whether TDCIPP disrupts the physiology of human embryonic cells. Therefore, the objective of this study was to determine whether TDCIPP alters cell viability, cellular metabolism, cytosine methylation, and reactive oxygen species (ROS) levels within human embryonic kidney (HEK293) cells. Relative to vehicle controls, TDCIPP (0.015-0.1225 µM) resulted in a concentration-dependent increase in cell viability, a finding that was driven by an increase in relative ATP abundance. Interestingly, TDCIPP (0.061-0.98 µM) increased the rate of glycolysis - an adaptive mechanism consistent with the Warburg effect exhibited by tumorigenic cells. Moreover, relative to vehicle-treated cells, TDCIPP (0.245-15.63 µM) exposure for 48 h (but not 24 h) resulted in a significant, concentration-dependent decrease in ROS in situ, and TDCIPP (0.245 µM) exposure significantly increased carnosine within the histidine metabolism pathway. However, TDCIPP did not affect global 5-methylcytosine (5-mC) methylation (0.015-15.63 µM), cell membrane integrity (0.061-0.98 µM), nor the abundance of mitochondria (0.061-1.95 µM). Overall, our findings with TDCIPP point to a novel mechanism of action that may be relevant to human embryonic stem cells.

N-acetylcysteine alleviated tris(2-chloroisopropyl) phosphate-induced sperm motility decline and functional dysfunction in mice through reversing oxidative stress and DNA damage

The decline in male fertility caused by environmental pollutants has attracted worldwide attention nowadays. Tris(2-chloroisopropyl) phosphate (TCPP) is a chlorine-containing organophosphorus flame retardant applied in many consumer products and has multiple side effects on health. However, whether TCPP impairs spermatogenesis remains unclear. In this study, we found that TCPP reduced the sperm motility and blastocyst formation, inhibited proliferation and induced apoptosis in mice testes and spermatocyte cell line GC-2. Moreover, TCPP induced imbalance of oxidant and anti-oxidant, DNA damage and mitochondrial dysfunction, thus induced abnormal spermatogenesis. In this process, p53 signaling pathway was activated and N-acetylcysteine treatment partially alleviated the side effects of TCPP, including decrease of sperm motility, activation of p53 signaling pathway and DNA damage. Finally, our study verified that TCPP elevated reactive oxygen species (ROS), decreased mitochondrial membrane potential and induced apoptosis in human semen samples. Overall, ROS mediated TCPP-induced germ cell proliferation inhibition and apoptosis, which finally led to the decline of sperm motility.

Multigenerational effects and mutagenicity of three flame retardants on germ cells in Caenorhabditis elegans

Flame retardants (FRs) have raised public concerns because of their environmental persistence and negative impacts on human health. Recent evidence has revealed that many FRs exhibit reproductive toxicities and transgenerational impacts, whereas the toxic effects of FRs on germ cells remain barely explored. Here we investigated the multigenerational effects of three flame retardants (TBBPA, TCEP and TCPP) on germ cell development in Caenorhabditis elegans, and examined the germ cell mutagenicity of these FRs by using whole genome sequencing. Parental exposure to three FRs markedly increased germ cell apoptosis, and impeded oogenesis in F1-F6 offspring. In addition, the double-increased mutation frequencies observed in progeny genomes uncover the mutagenic actions of FRs on germ cells. Analysis of mutation spectra revealed that these FRs predominantly induced point mutations at A:T base pairs, whereas both small and large indels were almost unaffected. These results revealed the long-term effects of FRs on development and genomic stability of germ cells, which may pose risks to environmental organisms and human reproductive health. Taken together, our findings suggest that germ cell mutagenicity should be carefully examined for the environmental risk assessment of FRs and other emerging pollutants.

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.

Effects of TCPP and TCEP exposure on human corneal epithelial cells: Oxidate damage, cell cycle arrest, and pyroptosis

Tris(2-chloroisopropyl) phosphate (TCPP) and Tris(2-chloroethyl) phosphate (TCEP) are the widely used organophosphorus flame retardants indoors and easily accessible to the eyes as the common adhesive components of dust and particle matter, however, hardly any evidence has demonstrated their corneal toxicity. In this study, the adverse effects of TCPP, TCEP, and TCPP + TCEP exposure on human corneal epithelial cells (HCECs) were investigated. The cell viability and morphology, intracellular reactive oxygen species (ROS), cell cycle, and the expressions of cell cycle and pyroptosis-related genes were assessed to explain the underlying mechanisms. Compared to individual exposure, co-exposure to TCPP₂₀+TCEP₂₀ showed higher cytotoxicity with a sharp decrease of >30% in viability and more serious oxidative damage by increasing ROS production to 110.92% compared to the control group. Furthermore, the cell cycle arrested at the S phase (36.20%) was observed after combined treatment, evidenced by the upregulation of cyclin D1, CDK2, CDK4, CDK6, p21, and p27. Interestingly, pyroptosis-related genes GSDMD, Caspase-1, NLRP3, IL-1β, IL-18, NLRP1, and NLRC4 expressions were promoted with cell swelling and glowing morphology. Oxidative stress and cell cycle arrest probably acted as a key role in TCPP₂₀+TCEP₂₀-induced cytotoxicity and pyroptosis in HCECs. Our results suggested that TCPP₂₀+TCEP₂₀ co-exposure induced severer corneal damage, further illustrating its significance in estimating indoor health hazards to humans.

Association between Organophosphate Ester Exposure and Insulin Resistance with Glycometabolic Disorders among Older Chinese Adults 60-69 Years of Age: Evidence from the China BAPE Study

BACKGROUND

Organophosphate esters (OPEs) are common endocrine-disrupting chemicals, and OPE exposure may be associated with type 2 diabetes (T2D). However, greater knowledge regarding the biomolecular intermediators underlying the impact of OPEs on T2D in humans are needed to understand biological etiology.

OBJECTIVES

We explored the associations between OPE exposure and glycometabolic markers among older Chinese adults 60-69 years of age to elucidate the underlying mechanisms using a multi-omics approach.

METHODS

This was a longitudinal panel study comprising 76 healthy participants 60-69 years of age who lived in Jinan city of northern China. The study was conducted once every month for 5 months, from September 2018 to January 2019. We measured a total of 17 OPEs in the blood, 11 OPE metabolites in urine, and 4 glycometabolic markers (fasting plasma glucose, glycated serum protein, fasting insulin, and homeostatic model assessment for insulin resistance). The blood transcriptome and serum/urine metabolome were also evaluated. The associations between individual OPEs and glycometabolic markers were explored. An adverse outcome pathway (AOP) was established to determine the biomolecules mediating the associations.

RESULTS

Exposure to five OPEs and OPE metabolites (trimethylolpropane phosphate, triphenyl phosphate, tri-iso-butyl phosphate, dibutyl phosphate, and diphenyl phosphate) was associated with increased levels of glycometabolic markers. The mixture effect analysis further indicated the adverse effect of OPE mixtures. Multi-omics analyses revealed that the endogenous changes in the transcriptional and metabolic levels were associated with OPE exposure. The putative AOPs model suggested that triggers of molecular initiation events (e.g., insulin receptor and glucose transporter type 4) with subsequent key events, including disruptions in signal transduction pathways (e.g., phosphatidylinositol 3-kinase/protein kinase B and insulin secretion signaling) and biological functions (glucose uptake and insulin secretion), may constitute the diabetogenic effects of OPEs.

DISCUSSION

OPEs are associated with the elevated risk of T2D among older Chinese adults 60-69 years of age. Implementing OPE exposure reduction strategies may help reduce the T2D burden among these individuals, if the relationship is causal. https://doi.org/10.1289/EHP11896.

Environmentally relevant concentrations of butyl benzyl phthalate triggered oxidative stress and apoptosis in adult zebrafish (Danio rerio) liver: Combined analysis at physiological and molecular levels

Butyl benzyl phthalate (BBP), a typical phthalate plasticizer, is frequently detected in aquatic environments, but its possible effects on fish liver are unknown. In this study, adult zebrafish were exposed to 5-500 μg/L BBP and cultured for 28 days. The toxicity mechanism of environmentally relevant concentrations of BBP in the liver was explored using integrated biomarker response (IBR), molecular docking, and histopathological analysis, based on the tests of oxidative stress, apoptosis, and tissue damage, respectively. The results revealed that exposure to 500 μg/L BBP caused lipid peroxidation and DNA damage and induced inflammatory responses in the liver and intestinal tissues. The accumulation of reactive oxygen species (ROS) is the primary manifestation of BBP toxicity and is accompanied by changes in the activities of antioxidant and detoxification enzymes. Notably, the pro-apoptotic genes (p53 and caspase-3) were still significantly upregulated in the 50 μg/L and 500 μg/L treatment groups on day 28. Moreover, BBP interfered with apoptosis by forming a stable complex with apoptosis proteins (P53 and Caspase-3). Our findings are helpful for understanding the toxicity mechanisms of BBP, which could further promote the assessment of the potential environmental risks of BBP.

Aryl-, halogenated- and alkyl- organophosphate esters induced oxidative stress, endoplasmic reticulum stress and NLRP3 inflammasome activation in HepG2 cells

Organophosphate esters (OPEs) are a group of extensively used man-made chemicals with diverse substituents that are ubiquitously detected in human-related samples including serum, breastmilk, food and house dust. The understanding of their toxicological effects and potential mechanisms on hepatocytes is still limited. In this study, nine most frequently detected OPEs were selected and divided into three subgroups (aryl-, halogenated- and alkyl-OPEs) based on their substituents. The cytotoxicity, apoptosis, oxidative stress, endoplasmic reticulum (ER) stress and NLRP3 inflammasome activation induced by OPEs were evaluated in human hepatocellular carcinomas HepG2 cells. All OPEs induced apoptosis likely through a caspase-dependent apoptotic pathway. The activities of anti-oxidative enzyme SOD and CAT exhibited sensitive responses after OPEs treatment for 6 h. The OPEs induced ROS overproduction, DNA damage, endoplasmic reticulum (ER) stress and NLRP3 inflammasome activation varied among aryl-, halogenated- and alkyl-OPEs. Halogenated- and alkyl- OPEs induced overproduction of ROS and DNA damage, and elevated ER stress and NLRP3 inflammasome activation are observed aryl-OPEs induced cytotoxicity.

Parental whole life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) disrupts embryonic development and thyroid system in zebrafish offspring

Tris (2-chloroethyl) phosphate (TCEP), an emerging environmental pollutant, has been frequently detected in natural waters. The objective of this study was to investigate possible parental transfer of TCEP and transgenerational effects on the early development and thyroid hormone homeostasis in F1 larvae following parental whole life-cycle exposure to TCEP. To this end, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations (0.8, 4, 20 and 100 μg/L) of TCEP for 120 days until sexual maturation. Parental exposure to TCEP resulted in significant levels of TCEP, developmental toxicity including decreased survival and final hatching rates, accelerated heart rate and elevated malformation rate, as well as induction of oxidative stress and cell apoptosis in F1 offspring. In F1 eggs, declined thyroxin (T4) levels were observed, consistent with those in plasma of F0 adult females, indicating the maternal transfer of thyroid endocrine disruption to the offspring. In addition, mRNA levels of several genes along the hypothalamic-pituitary-thyroid (HPT) axis were significantly modified in F1 larvae, which could be linked to transgenerational developmental toxicity and thyroid hormone disruption. For the first time, we revealed that the parental exposure to environmentally relevant levels of TCEP could cause developmental toxicity and thyroid endocrine disruption in subsequent unexposed generation.

Association of organophosphate ester exposure with cardiovascular disease among US adults: Cross-sectional findings from the 2011-2018 National Health and Nutrition Examination Survey

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers worldwide. Therefore, the potentially deleterious effect of OPE on human beings deserves extensive attention. The primary objective of this present study was to untangle the relationship between OPE exposure and cardiovascular disease (CVD) among general population. Detailed information about participants' baseline characteristics, involving socioeconomic data, demographic data and key covariates was obtained from National Health and Nutrition Examination Survey (NHANES) 2011-2018. Multivariate logistic regression models with adjustment for prior-determined covariates were utilized to examine the relationship between various OPEs and CVD among US adults and calculate odd ratios (ORs) and corresponding confidence intervals (CIs). Two multi-pollutant statistical strategies (weighted quantile sum regression and Bayesian kernel machine regression) were employed to investigate the joint effect of OPE mixture on CVD. A total of 5067 participants were included in this study. In completely-adjusted logistic model, the highest tertiles of OPE metabolites were positively associated with CVD risk, while the relationships did not reach statistical significance. The weighted quantile sum (WQS) index was significantly correlated with increased prevalence of CVD (adjusted OR: 1.25; CI: 1.02, 1.53, p value = 0.032) and Diphenyl phosphate (DPHP) was the greatest contributor (31.38%). The BKMR also indicated that mixed OPE exposure associated with an increased risk of CVD. Taken together, the present study demonstrated that there were possible links between OPE exposures and increased risk of CVD, while the relationships did not reach statistical significance. Our study provided the suggestive evidence that cumulative effect of OPE mixtures on CVD. DPHP may be a major driver of this positive association. Given the limitation of cross-sectional design and relatively limited kinds of OPE metabolites, further studies are warranted to longitudinally evaluate the potential effect of a wider range of OPEs on CVD or cardiac metabolism.

Paeoniflorin Protects H9c2 Cardiomyocytes against Hypoxia/Reoxygenation Induced Injury via Regulating the AMPK/Nrf2 Signaling Pathway

Myocardial ischemia/reperfusion (MIR) injury contributes to the exacerbation of heart disease by causing cardiac arrhythmias, myocardial infarction, and even sudden death. Studies have found that paeoniflorin (PF) has a protective effect on coronary artery disease (CAD). However, the mechanism of PF in MIR has not been fully investigated. The purpose of this study was to investigate the functional role of PF in H9c2 cells subjected to hypoxia/reoxygenation (H/R). Here, PF treatment enhanced cell viability in H/R-stimulated H9c2 cells. In H9c2 cells, PF treatment reduced the formation of reactive oxygen species (ROS) induced by H/R. In H/R-stimulated H9c2 cells, PF also increased the activity of antioxidant enzymes such as superoxide dismutase and glutathione peroxidase. Furthermore, PF protected H9c2 cells against H/R-induced apoptosis, as demonstrated by increased Bcl-2 expression, decreased Bax expression, and decreased caspase-3 activity. Furthermore, PF increased the levels of p-AMPK and nuclear Nrf2 expression in response to H/R stimulation. AMPK inhibition, on the other hand, abolished the PF-mediated increase in Nrf2 signaling and the cardiac-protective effect in H9c2 cells exposed to H/R. These data suggest that PF protected H9c2 cells against H/R-induced oxidative stress and apoptosis through modulating the AMPK/Nrf2 signaling pathway. Our findings support the therapeutic potential of PF in myocardial I/R damage.

Triclocarban evoked neutrophil extracellular trap formation in common carp (Cyprinus carpio L.) by modulating SIRT3-mediated ROS crosstalk with ERK1/2/p38 signaling

Triclocarban (TCC), an antimicrobial ingredient in personal care products, is associated with immunosuppression and physiological dysfunctions of aquatic organisms. The aim of this study was to investigate whether TCC can induce common carp NETosis (neutrophil death by neutrophil extracellular trap (NET) release) and then to attempt to identify the potential molecular mechanisms. Herein, scanning electron microscopy and flow cytometric assays showed that revealed that TCC triggers DNA-containing web-like structures and increases extracellular DNA content. In the proteomic analysis, we observed that NET-related proteins, extracellular regulated protein kinase (Mapk1, Mapk14, Jak2) and apoptotic protein (caspase3) were significantly increased, and defender against cell death 1 (Dad1) was significantly decreased after TCC treatments. Meanwhile, we confirmed that TCC stress can trigger NETosis in common carp by activating the reactive oxygen species (ROS)/ERK1/2/p38 signaling. We think that the upregulated NDUFS1 expression is closely related to oxidative stress induced by TCC. Importantly, we discovered that SIRT3 expression was significantly decreased in the process of TCC-induced NETs. Importantly, pretreatment with the SIRT3 agonist honokiol (HKL) effectively suppressed TCC-induced NET release. In contrast, the SIRT3 antagonist 3-TYP escalated TCC-induced NET formation. Mechanistically, SIRT3 degradation serves as a potential mediator for regulating oxidative stress crosstalk between ERK1/2/p38 signals in the process of TCC-induced NET formation. These findings unveil new insights into the TCC-evoked health risk of fish and other aquatic organisms and suggest that SIRT3 is a potential pharmacological intervention target to alleviate TCC-induced common carp NETosis.

Cyto-Genotoxic and Transcriptomic Alterations in Human Liver Cells by Tris (2-Ethylhexyl) Phosphate (TEHP): A Putative Hepatocarcinogen

Tris (2-ethylhexyl) phosphate (TEHP) is an organophosphate flame retardant (OPFRs) which is extensively used as a plasticizer and has been detected in human body fluids. Contemporarily, toxicological studies on TEHP in human cells are very limited and there are few studies on its genotoxicity and cell death mechanism in human liver cells (HepG2). Herein, we find that HepG2 cells exposed to TEHP (100, 200, 400 µM) for 72 h reduced cell survival to 19.68%, 49.83%, 58.91% and 29.08%, 47.7% and 57.90%, measured by MTT and NRU assays. TEHP did not induce cytotoxicity at lower concentrations (5, 10, 25, 50 µM) after 24 h and 48 h of exposure. Flow cytometric analysis of TEHP-treated cells elevated intracellular reactive oxygen species (ROS), nitric oxide (NO), Ca⁺⁺ influx and esterase levels, leading to mitochondrial dysfunction (ΔΨm). DNA damage analysis by comet assay showed 4.67, 9.35, 13.78-fold greater OTM values in TEHP (100, 200, 400 µM)-treated cells. Cell cycle analysis exhibited 23.1%, 29.6%, and 50.8% of cells in SubG1 apoptotic phase after TEHP (100, 200 and 400 μM) treatment. Immunofluorescence data affirmed the activation of P53, caspase 3 and 9 proteins in TEHP-treated cells. In qPCR array of 84 genes, HepG2 cells treated with TEHP (100 µM, 72 h) upregulated 10 genes and downregulated 4 genes belonging to a human cancer pathway. Our novel data categorically indicate that TEHP is an oxidative stressor and carcinogenic entity, which exaggerates mitochondrial functions to induce cyto- and genotoxicity and cell death, implying its hepatotoxic features.