Tris(2-chloroethyl) phosphate (TCEP) and tris(2-chloropropyl) phosphate (TCPP) induce locomotor deficits and dopaminergic degeneration in Caenorhabditis elegans

Integrated biomarker-based ecological risks assessment of tadpole responses to tris(2-chloroethyl) phosphate, tris(1-chloro-2-propyl) phosphate, and their combined environmental exposure

Tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCPP) are common chlorinated organophosphorus flame retardants (OPFRs) used in industry. They have been frequently detected together in aquatic environments and associated with various hazardous effects. However, the ecological risks of prolonged exposure to these OPFRs at environmentally relevant concentrations in non-model aquatic organisms remain unexplored. This study investigated the effects of long-term exposure (up to 25 days) to TCEP and TCPP on metamorphosis, hepatic antioxidants, and endocrine function in Polypedates megacephalus tadpoles. Exposure concentrations were set at 3, 30, and 90 μg/L for each substance, conducted independently and in equal-concentration combinations, with a control group included for comparison. The integrated biomarker response (IBR) method developed an optimal linear model for predicting the overall ecological risks of TCEP and TCPP to tadpoles in potential distribution areas of Polypedates species. Results showed that: (1) Exposure to environmentally relevant concentrations of TCEP and TCPP elicited variable adverse effects on tadpole metamorphosis time, hepatic antioxidant enzyme activity and related gene expression, and endocrine-related gene expression, with their combined exposure exacerbating these effects. (2) The IBR value of TCEP was consistently greater than that of TCPP at each concentration, with an additive effect observed under their combined exposure. (3) The ecological risk of tadpoles exposed to the combined presence of TCEP and TCPP was highest in China's Taihu Lake and Vietnam's Hanoi than in other distribution locations. In summary, prolonged exposure to environmentally relevant concentrations of TCEP and TCPP presents potential ecological risks to amphibian tadpoles, offering insights for the development of policies and strategies to control TCEP and TCPP pollution in aquatic ecosystems. Furthermore, the methodology employed in establishing the IBR prediction model provides a methodological framework for assessing the overall ecological risks of multiple OPFRs.

Tris (2-chloroethyl) phosphate presence inhibits methane production from anaerobic digestion: Alterations in organic matter transformation, cell physiological status, and microbial community

Organophosphate flame retardants (OPFRs) are widely used in consumer products, leading to their unavoidable release into the environment, especially accumulation in anaerobic environments and posing potential risks. This study focused on Tris(2-chloroethyl) phosphate (TCEP), a representative OPFR, to investigate its effects on carbon transformation and methane production in anaerobic digestion. Increasing TCEP concentrations from control to 16 mg/L resulted in decreased cumulative methane yield (from 235.4 to 196.3 mL/g COD) and maximum daily methane yield (from 40.8 to 16.17 mL/(g COD·d)), along with an extended optimal anaerobic digestion time (from 15 to 20 days). Mechanistic analysis revealed TCEP binding to tyrosine-like proteins in extracellular polymeric substances, causing cell membrane integrity impairment. The TCEP-caused alteration of the physiological status of cells was demonstrated to be a significant contribution to the inhibited bioprocesses including acidogenesis, acetogenesis, and methanogenesis. Illumina Miseq sequencing showed TCEP decreasing the relative abundance of acidogens (58.8 % to 46.0 %) and acetogens (7.1 % to 5.0 %), partly shifting the methanogenesis pathway from acetoclastic to hydrogenotrophic methanogenesis. These findings enhance understanding of TCEP's impact on anaerobic digestion, emphasizing the environmental risk associated with its continued accumulation.

Organophosphate flame retardants tris (2-butoxyethyl) phosphate (TBEP) and tris (2-chloroethyl) phosphate (TCEP) disrupt human motor neuron development by differentially affecting their survival and differentiation

Mounting evidence in animal experiments proves that early life stage exposure to organophosphate flame retardants (OPFRs) affects the locomotor behavior and changes the transcriptions of central nervous system genes. Unfortunately, their effect on human motor neuron (MN) development, which is necessary for body locomotion and survival, has not yet characterized. Here, we utilized a spinal cord MN differentiation model from human embryonic stem cells (ESCs) and adopted this model to test the effects of two typical OPFRs tris (2-butoxyethyl) phosphate (TBEP) and tris (2-chloroethyl) phosphate (TCEP), on MN development and the possible mechanisms underlying. Our findings revealed TBEP exerted a much more inhibitory effect on MN survival, while TCEP exhibited a stronger stimulatory effect on ESCs differentiation into MN, and thus TBEP exhibited a stronger inhibition on MN development than TCEP. RNA sequencing analysis identified TBEP and TCEP inhibited MN survival mainly by disrupting extracellular matrix (ECM)-receptor interaction. Focusing on the pathway guided MN differentiation, we found both TBEP and TCEP activated BMP signaling, whereas TCEP simultaneously downregulated Wnt signaling. Collectively, this is the first study demonstrated TBEP and TCEP disrupted human MN development by affecting their survival and differentiation, thereby raising concern about their potential harm in causing MN disorders.

2-Butoxytetrahydrofuran, Isolated from Holothuria scabra, Attenuates Aggregative and Oxidative Properties of α-Synuclein and Alleviates Its Toxicity in a Transgenic Caenorhabditis elegans Model of Parkinson's Disease

Aggregative α-synuclein and incurring oxidative stress are pivotal cascading events, leading to dopaminergic (DAergic) neuronal loss and contributing to clinical manifestations of Parkinson's disease (PD). Our previous study demonstrated that 2-butoxytetrahydrofuran (2-BTHF), isolated from Holothuria scabra (H. scabra), could inhibit amyloid-β aggregation and its ensuing toxicity, which leads to Alzheimer's disease. In the present study, we found that 2-BTHF also attenuated the aggregative and oxidative activities of α-synuclein and lessened its toxicity in a transgenic Caenorhabditis elegans (C. elegans) PD model. Such worms treated with 100 μM of 2-BTHF showed substantial reductions in α-synuclein accumulation and DAergic neurodegeneration. Mechanistically, 2-BTHF, at this concentration, significantly decreased aggregation of monomeric α-synuclein and restored locomotion and dopamine-dependent behaviors. Molecular docking exhibited potential bindings of 2-BTHF to HSF-1 and DAF-16 transcription factors. Additionally, 2-BTHF significantly increased the mRNA transcripts of genes encoding proteins involved in proteostasis, including the molecular chaperones hsp-16.2 and hsp-16.49, the ubiquitination/SUMOylation-related ubc-9 gene, and the autophagy-related genes atg-7 and lgg-1. Transcriptomic profiling revealed an additional mechanism of 2-BTHF in α-synuclein-expressing worms, which showed upregulation of PPAR signaling cascades that mediated fatty acid metabolism. 2-BTHF significantly restored lipid deposition, upregulated the fat-7 gene, and enhanced gcs-1-mediated glutathione synthesis in the C. elegans PD model. Taken together, this study demonstrated that 2-BTHF could abrogate aggregative and oxidative properties of α-synuclein and attenuate its toxicity, thus providing a possible therapeutic application for the treatment of α-synuclein-induced PD.

OPFR removal by white rot fungi: screening of removers and approach to the removal mechanism

The persistent presence of organophosphate flame retardants (OPFRs) in wastewater (WW) effluents raises significant environmental and health concerns, highlighting the limitations of conventional treatments for their remotion. Fungi, especially white rot fungi (WRF), offer a promising alternative for OPFR removal. This study sought to identify fungal candidates (from a selection of four WRF and two Ascomycota fungi) capable of effectively removing five frequently detected OPFRs in WW: tributyl phosphate (TnBP), tributoxy ethyl phosphate (TBEP), trichloroethyl phosphate (TCEP), trichloro propyl phosphate (TCPP) and triethyl phosphate (TEP). The objective was to develop a co-culture approach for WW treatment, while also addressing the utilization of less assimilable carbon sources present in WW. Research was conducted on carbon source uptake and OPFR removal by all fungal candidates, while the top degraders were analyzed for biomass sorption contribution. Additionally, the enzymatic systems involved in OPFR degradation were identified, along with toxicity of samples after fungal contact. Acetate (1.4 g·L-1), simulating less assimilable organic matter in the carbon source uptake study, was eliminated by all tested fungi in 4 days. However, during the initial screening where the removal of four OPFRs (excluding TCPP) was tested, WRF outperformed Ascomycota fungi. Ganoderma lucidum and Trametes versicolor removed over 90% of TnBP and TBEP within 4 days, with Pleorotus ostreatus and Pycnoporus sanguineus also displaying effective removal. TCEP removal was challenging, with only G. lucidum achieving partial removal (47%). A subsequent screening with selected WRF and the addition of TCPP revealed TCPP's greater susceptibility to degradation compared to TCEP, with T. versicolor exhibiting the highest removal efficiency (77%). This observation, plus the poor degradation of TEP by all fungal candidates suggests that polarity of an OPFR inversely correlates with its susceptibility to fungal degradation. Sorption studies confirmed the ability of top-performing fungi of each selected OPFR to predominantly degrade them. Enzymatic system tests identified the CYP450 intracellular system responsible for OPFR degradation, so reactions of hydroxylation, dealkylation and dehalogenation are possibly involved in the degradation pathway. Finally, toxicity tests revealed transformation products obtained by fungal degradation to be more toxic than the parent compounds, emphasizing the need to identify them and their toxicity contributions. Overall, this study provides valuable insights into OPFR degradation by WRF, with implications for future WW treatment using mixed consortia, emphasizing the importance of reducing generated toxicity.

Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (-0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Novel method for rapid monitoring of OPFRs by LLE and GC-MS as a tool for assessing biodegradation: validation and applicability

Organophosphate flame retardants (OPFRs) are high-production volume chemicals widely present in environmental compartments. The presence of water-soluble OPFRs (tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBEP), tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCPP), and triethyl phosphate (TEP)) in water compartments evidences the struggle of conventional wastewater treatment plants (WWTPs) to effectively eliminate these toxic compounds. This study reports for the first time the use of white-rot fungi as a promising alternative for the removal of these OPFRs. To accomplish this, a simple and cost-efficient quantification method for rapid monitoring of these contaminants' concentrations by GC-MS while accounting for matrix effects was developed. The method proved to be valid and reliable for all the tested parameters. Sample stability was examined under various storage conditions, showing the original samples to be stable after 60 days of freezing, while post-extraction storage techniques were also effective. Finally, a screening of fungal degraders while assessing the influence of the glucose regime on OPFR removal was performed. Longer chain organophosphate flame retardants, TBP and TBEP, could be easily and completely removed by the fungus Ganoderma lucidum after only 4 days. This fungus also stood out as the sole organism capable of partially degrading TCEP (35% removal). The other chlorinated compound, TCPP, was more easily degraded and 70% of its main isomer was removed by T. versicolor. However, chlorinated compounds were only partially degraded under nutrient-limiting conditions. TEP was either not degraded or poorly degraded, and it is likely that it is a transformation product from another OPFR's degradation. These results suggest that degradation of chlorinated compounds is dependent on the concentration of the main carbon source and that more polar OPFRs are less susceptible to degradation, given that they are less accessible to radical removal by fungi. Overall, the findings of the present study pave the way for further planned research and a potential application for the degradation of these contaminants in real wastewaters.

Chronic neurotoxicity of Tetrabromobisphenol A: Induction of oxidative stress and damage to neurons in Caenorhabditis elegans

Tetrachlorobisphenol A (TCBPA) has been used as an alternative flame retardant in various fields. However, the long-term effects of TCBPA on the nervous system remain unclear. Thus, Caenorhabditis elegans (L4 larvae) were selected as a model animal to investigate the neurotoxic effects and underlying mechanisms after 10 d of TCBPA exposure. Exposure to TCBPA (0.01-100 μg/L) decreased locomotive behavior in a concentration-dependent manner. In addition, reactive oxygen species (ROS) formation and lipofuscin accumulation were significantly increased, and the expression of sod-3 was upregulated in the exposed nematodes, indicating that TCBPA exposure induced oxidative damage. Furthermore, 100 μg/L TCBPA exposure caused a reduction in dopamine and serotonin levels, and damage in dopaminergic and serotoninergic neurons, which was further confirmed by the downregulated expression of related genes (e.g., dop-1, dop-3, cat-1, and mod-1). Molecular docking analysis demonstrated the potential of TCBPA to bind to the neurotransmitter receptor proteins DOP-1, DOP-3, and MOD-1. These results indicate that chronic exposure to TCBPA induces neurotoxic effects on locomotive behavior, which is associated with oxidative stress and damage to dopaminergic and serotoninergic neurons.

Impaired Physiological Responses and Neurotoxicity Induced by a Chlorpyrifos-Based Formulation in Caenorhabditis elegans are not Solely Dependent on the Active Ingredient

The current massive and indiscriminate agrochemicals usage, which is inexorably linked to the toxic consequences to the environment and people, represents a great concern. Our work aimed to compare the toxicity induced by chlorpyrifos in its pure form (CPF) with that of a commercial formulation containing allegedly inert ingredients (CBCF) using Caenorhabditis elegans as in vivo model. After a 48h exposure period, CBCF was 14 times more lethal than CPF; Hatching, brood size, body length and motor-related behavioral parameters were decreased, but these effects were significantly higher in CBCF-exposed worms. Additionally, CBCF induced significant morphological changes in cholinergic neurons, which are associated with the motor-related behavioral parameters. Finally, by analyzing the CBCF, were detected the presence of potentially-toxic metals that were not specified in the label. The presented results highlight the toxicological relevance of components present in the commercial formulations of pesticides, which have been claimed as inert compounds.

Activation of FGF signal in germline mediates transgenerational toxicity of polystyrene nanoparticles at predicted environmental concentrations in Caenorhabditis elegans

Nanoplastics in the environment could cause the ecological and health risks. Recently, the transgenerational toxicity of nanoplastic has been observed in different animal models. In this study, using Caenorhabditis elegans as an animal model, we aimed to examine the role of alteration in germline fibroblast growth factor (FGF) signal in mediating the transgenerational toxicity of polystyrene nanoparticle (PS-NP). Exposure to 1-100 μg/L PS-NP (20 nm) induced transgenerational increase in expressions of germline FGF ligand/EGL-17 and LRP-1 governing FGF secretion. Germline RNAi of egl-17 and lrp-1 resulted in resistance to transgenerational PS-NP toxicity, indicating the requirement of FGF ligand activation and secretion in formation of transgenerational PS-NP toxicity. Germline overexpression of EGL-17 increased expression of FGF receptor/EGL-15 in the offspring, and RNAi of egl-15 at F1 generation (F1-G) inhibited transgenerational toxicity of PS-NP exposed animals overexpressing germline EGL-17. EGL-15 functions in both the intestine and the neurons to control transgenerational PS-NP toxicity. Intestinal EGL-15 acted upstream of DAF-16 and BAR-1, and neuronal EGL-15 functioned upstream of MPK-1 to control PS-NP toxicity. Our results suggested the important role of activation in germline FGF signal in mediating the induction of transgenerational toxicity in organisms exposed to nanoplastics in the range of μg/L.

Enhanced toxicity of 2,2-bis(chloromethyl) trimethylene bis[bis(2-chloroethyl) phosphate] (V6) by nanopolystyrene particles towards HeLa cells

2,2-bis(chloromethyl) trimethylene bis[bis(2-chloroethyl) phosphate] (V6) has been widely used as an additive in a variety of plastics due to its extremely low toxicity. However, we showed in the study that once mixed with nanopolystyrene particles (NPs), the nontoxic V6 could exhibit significant toxicity to HeLa cells. The enhanced toxicity was much higher than the toxicity of NPs alone and was related to the size of NPs. The mixture of V6 and small polystyrene NPs (10 nm and 15 nm in radius) showed obvious toxicity to HeLa cells. The toxicity increased with the concentrations of both V6 and NPs. On the contrary, the mixture of V6 and larger NPs (25 nm, 50 nm, 100 nm, and 500 nm in radius) showed almost no toxicity even at extremely high concentrations (NPs: 100 mg/L; V6: 50 mg/L). The small NPs could enter the cells and accumulated in cytoplasm. However, the larger NPs did not distribute inside the cells. NPs efficiently adsorbed V6 on the surface. The mechanism of the enhanced toxicity was attributed to the increased intracellular reactive oxygen species (ROS) production and the regulation of gene expression concerning apoptosis and ROS scavenging. Our study not only showed that a safe chemical V6 could be turned to be toxic by NPs, but also pointed out a potential risk caused by the joint toxicity of 'safe' chemicals and plastic particles with small size.

Human exposure to organophosphate esters in water and packed beverages

Drinks are an essential part of human diet, which makes them a source of human exposure to plasticizers such as organophosphate esters (OPEs). The current study provides new information about sixteen OPE levels in 75 different samples (tap water, packed water, cola drinks, juice, wine and hot drinks). Tap water mean levels (40.9 ng/L) were statistically higher than packed water mean levels (4.82 ng/L), mainly due to the contribution of tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2-butoxyethyl) phosphate (TBOEP) that may come from PVC water pipes. Over 90% of samples presented at least one OPE, where regular cola drinks had the highest mean concentrations (2876 ng/L). There was a significantly higher presence of OPEs in added sugar beverages than sugar free drinks, especially for 2-ethylhexyl diphenyl phosphate (EHDPP), which might be related not only to packaging materials but to the added sugar content. Estimated daily intakes (EDIs) in normal and high-exposure scenarios were 2.52 ng/kg bw/day and 7.43 ng/kg bw/day, respectively. Human risk associated with beverages ingestion showed regular cola drinks, juice and tap water as the groups with the highest hazard quotients (HQs). Although OPE exposure was below to safety limits, it should be noted that EHDPP values for regular cola group must be cause of concern, and other routes of exposure such as food ingestion or air inhalation should be also considered.

nTiO2 alleviates the toxic effects of TCPP on mussels by adjusting respiratory metabolism and gut microbiota

As a good carrier of contaminants, nanotitanium dioxide (nTiO₂) can absorb organic pollutants, producing toxicological effects on organisms. However, the complex effects of nTiO₂ with contaminants on marine mussels are still unclear. In this study, we exposed mussels to tris (2-chloropropyl) phosphate (TCPP) 100 μg/L (T1), 0.5 mg/L nTiO₂ + 100 μg/L TCPP (T2), 1.0 mg/L nTiO₂ + 100 μg/L TCPP (T3) and control (0 nTiO₂ + 0 μg/L TCPP) treatments, and assessed the combined effects of TCPP with nTiO₂ on the thick-shelled mussel Mytilus coruscus by detecting the activities of gill pyruvate kinase (PK), hexokinase (HK), lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH), also gill acetylcholine (Ach) and muscle lactic acid (LD) contents and gut microbiota after 14-d exposure. Compared with the control group, PK activity was increased significantly, but SDH, LDH activities and LD content were decreased significantly in T1, with the addition of nTiO₂, there were not significantly different in T3. However, Ach content in T3 was significantly higher than the control and T1. Moreover, KEGG of the gut microbiota via 16 s rRNA sequencing showed that most pathways returned to the control level in T3. The results showed that TCPP affected the respiratory metabolism of mussels, changed the community structure of intestinal microflora in mussels, and nTiO₂ alleviated the toxicity of TCPP. Our study provides new insights for ecological risk assessment of TCPP in bivalves in the complex aquatic environment and the novel role of nTiO₂ in regulating the toxicity of TCPP.

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

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

Glutamatergic transmission associated with locomotion-related neurotoxicity to lindane over generations in Caenorhabditis elegans

Organochlorine pesticide lindane in the environment and biota results in the potential risks on ecosystem and human health. Lindane can adversely affect the locomotion and nervous system, yet the potential neurotoxicity of lindane over generations remains uncertain. In this study, the neurotoxicity and underlying mechanisms in Caenorhabditis elegans (C. elegans) were investigated after parental (P0) exposure to lindane at environmentally relevant concentrations over generations. Exposure to lindane at concentrations of 10-100 ng/L significantly decreased body bends and head thrashes in P0 generation. Significant decrease of fluorescence labeled different neurotransmitters, and clear morphological changes by exposure to lindane at 10-100 ng/L suggested that lindane could induce the neuronal damage in C. elegans. During the transgenerational process, decreased locomotive behaviors were also observed in F1-F3 generations, and head thrashes returned to normal levels in F4 generation. Moreover, lindane exposure down-regulated the expression of dat-1, dop-1, glr-1 and mod-1genes, while up-regulated unc-30 gene in P0 generation, which recovered to normal levels in F4 generation. Interestingly, eat-4 continued to be regulated from inhibition to stimulation in P0-F4 generations, suggesting that glutamatergic transmission may more contribute to the neurotoxicity of lindane over generations.

Induction of lipid metabolism dysfunction, oxidative stress and inflammation response by tris(1-chloro-2-propyl)phosphate in larval/adult zebrafish

As an important organophosphate flame retardant, tris(1-chloro-2-propyl)phosphate (TCPP) is ubiquitous in the environment leading to inevitable human exposure. However, there is a paucity of information regarding its acute/chronic effects on obesity, lipid homeostasis, and hepatocellular carcinoma, especially regarding the underlying molecular mechanisms in humans. Herein, we investigated the effects of TCPP exposure (5-25 mg/L) on lipid homeostasis in larval and adult zebrafish (Danio rerio). TCPP exposure caused remarkable lipid-metabolism dysfunction, which was reflected in obesity and excessive lipid accumulation in zebrafish liver. Mechanistically, TCPP induced the over-expression of adipogenesis genes and suppressed the expression of fatty-acid β-oxidation genes. Consequently, excess lipid synthesis and deficient expenditure triggered oxidative damage and an inflammation response by disrupting the antioxidant system and over-expressing proinflammatory cytokine. Based on high-throughput transcriptome sequencing, we found that TCPP exposure led to enrichment of several pathways involved in lipid metabolism and inflammation, as well as several genes related to pathways of cancer. Notably, increasing expressions of Ki-67 and 53BP1 proteins, which are reliable biomarkers for recognition and risk prediction of cellular proliferation in cancer cells, were observed in liver tissues of adult zebrafish. These results imply that chronic TCPP exposure triggers a potential risk of hepatocellular carcinogenesis (HCC) progression. Collectively, these findings offer new insights into our mechanistic understanding for the health effects of organophosphorus flame retardants on humans.

Effects of lanthanum nitrate on behavioral disorder, neuronal damage and gene expression in different developmental stages of Caenorhabditis elegans

Rare earth elements (REEs) are widely used in the industry, agriculture, biomedicine, aerospace, etc, and have been shown to pose toxic effects on animals, as such, studies focusing on their biomedical properties are gaining wide attention. However, environmental and population health risks of REEs are still not very clear. Also, the REEs damage to the nervous system and related molecular mechanisms needs further research. In this study, the L1 and L4 stages of the model organism Caenorhabditis elegans were used to evaluate the effects and possible neurotoxic mechanism of lanthanum(III) nitrate hexahydrate (La(NO₃)₃·6H₂O). For the L1 and L4 stage worms, the 48-h median lethal concentrations (LC₅₀s) of La(NO₃)₃·6H₂O were 93.163 and 648.0 mg/L respectively. Our results show that La(NO₃)₃·6H₂O induces growth inhibition and defects in behavior such as body length, body width, body bending frequency, head thrashing frequency and pharyngeal pumping frequency at the L1 and L4 stages in C. elegans. The L1 stage is more sensitive to the toxicity of lanthanum than the L4 stage worms. Using transgenic strains (BZ555, EG1285 and NL5901), we found that La(NO₃)₃·6H₂O caused the loss or break of soma and dendrite neurons in L1 and L4 stages; and α-synuclein aggregation in L1 stage, indicating that Lanthanum can cause toxic damage to dopaminergic and GABAergic neurons. Mechanistically, La(NO₃)₃·6H₂O exposure inhibited or activated the neurotransmitter transporters and receptors (glutamate, serotonin and dopamine) in C. elegans, which regulate behavior and movement functions. Furthermore, significant increase in the production of reactive oxygen species (ROS) was found in the L4 stage C. elegans exposed to La(NO₃)₃·6H₂O. Altogether, our data show that exposure to lanthanum can cause neuronal toxic damage and behavioral defects in C. elegans, and provide basic information for understanding the neurotoxic effect mechanism and environmental health risks of rare earth elements.

Tris (1-chloro-2-propyl) phosphate exposure to zebrafish causes neurodevelopmental toxicity and abnormal locomotor behavior

The organophosphate flame retardant, tris (1-chloro-2-propyl) phosphate (TCPP), is ubiquitous in environmental matrices; however, there is a paucity of information concerning its systemic toxicity. Herein, we investigated the effects of TCPP exposure on zebrafish neurodevelopment and swimming behavior to elucidate the underlying molecular mechanisms of neurotoxicity. Under TCPP gradient concentration exposure, the hatching rates were declined by up to 33.3% in 72 hpf, and the malformation rates increased from 15% to 50%. Meanwhile, TCPP led to abnormal behaviors including decreased locomotive activity in the dark and slow/insensitive responses to sound and light stimulation of larvae. TCPP caused excessive apoptosis and ROS accumulation in early embryonic development, with hair cell defects and structural deformity of neuromast. Abnormal expression of neurodevelopment (pax6a, nova1, sox11b, syn2a, foxo3a and robo2) and apoptosis-related genes (baxa, bcl2a and casp8) revealed molecular mechanisms regarding abnormal behavioral and phenotypic symptoms. Chronic TCPP exposure led to anxiety-like behavior and excessive panic, lower capacity for discrimination and risk avoidance, and conditioned place preference in adults. Social interaction tests demonstrated that long-term TCPP stress resulted in unsociable, eccentric, lonely and silent behaviors in adults. Zebrafish memory and cognitive function were severely reduced as concluded from T-maze tests. Potential mechanisms triggering behavioral abnormality were attributed to histopathological injury of diencephalon, abnormal changes in nerve-related genes at transcription and expression levels, and inhibited activity of AChE by TCPP stress. These findings provide an important reference for risk assessment and early warning to TCPP exposure, and offer insights for prevention/mitigation of pollutant-induced nervous system diseases.

Organophosphorus flame-retardant tris(1-chloro-2-propyl)phosphate is genotoxic and apoptotic inducer in human umbilical vein endothelial cells

Tris(1-chloro-2-propyl)phosphate (TCPP) is a chlorinated organophosphorus flame retardant (OPFR) widely used in consumer goods after the phaseout of brominated flame retardants (BFRs). TCPP can percolate into the indoor and outdoor dusts, leading to its detection in the human body fluids (urine, breast milk) and placenta. However, TCPP has not been studied so far for its toxicity in the human vascular system. Hence, we have used human umbilical vein endothelial cells (HUVECs) and exposed them to TCPP ranging from low to high (5-400 μM) concentrations for 24 h. Cytotoxicity analysis by MTT and NRU assays exhibited 15.27% and 20.56%, 21.67%, and 48.67% survival decline of cells only at 200 and 400 μM. Comet assay data showed DNA damage from 50 to 400 μM with Olive tail moment (OTM) values between 1.03 and 35.59, respectively. TCPP-exposed HUVECs exhibited 1.09 and 1.39-fold greater intracellular reactive oxygen species (ROS) at 25 and 400 μM, indicating oxidative stress. HUVEC mitochondrial membrane potential (ΔΨm) measurements showed 1.16 and 1.48-fold higher fluorescence of Rh123 dye at 25 and 400 μM, confirming mitochondrial dysfunction. Flow cytometric data demonstrated 5.1%-58.8% cells in SubG1 apoptotic phase at 5 and 400 μM TCPP. Our novel data revealed that TCPP is a genotoxic and apoptotic inducer, which may trigger alike responses in human vascular system. Overall, detailed in vivo studies are warranted on the transcriptional and translations effects of TCPP.

Embryotoxicity characterization of the flame retardant tris(1-chloro-2-propyl)phosphate (TCPP) in the invertebrate chordate Ciona intestinalis

Tris(1-chloro-2-propyl)phosphate (TCPP) is the most common chlorinated organophosphorus flame retardant in seawater. Due to its chemical features and abundance, TCPP has been classified as a high hazard, and restrictions of use have been set in multiple countries. Despite TCPP being highly present in the marine environment, only a few studies have explored the TCPP impact on the development of marine invertebrates. Ascidians are important invertebrate members of benthic marine communities and reliable model systems for ecotoxicological research. The aim of this study was to assess the adverse effects of TCPP exposure on the embryogenesis of the ascidian Ciona intestinalis. Our results showed that this pollutant affected both muscles and nervous system development. Malformations appeared similar to those reported in other animal models for other flame retardants, suggesting that these molecules could share a common mechanism of action and induce a mixture effect when simultaneously present in the aquatic environment even at sub-teratogenic concentrations.

Neurodevelopmental Toxicity of Polystyrene Nanoplastics in Caenorhabditis elegans and the Regulating Effect of Presenilin

As one of the most widely used materials, plastic polymer fragments can abrasively degrade into microplastic (MP) and smaller nanoplastic (NP) particles. The present study aimed to investigate the influence of particle size on neurodevelopmental toxicity induced by polystyrene nanoplastics (PS-NPs) in Caenorhabditis elegans and to explore the underlying potential mechanism. C. elegans were exposed to different concentrations of PS-NPs with various sizes (25, 50, and 100 nm) for 72 h. Our results showed that all of these PS-NPs could dose-dependently induce an increase in reactive oxygen species production and mitochondrial damage in C. elegans, resulting in inhibition of body length, head thrashes, body bending, and dopamine (DA) contents. A weaker neurotoxicity was found in 25 nm PS-NPs compared to 50 and 100 nm PS-NPs, which might be due to preferential cellular distribution and greater polymerization capability of the smaller particles. In addition, all these PS-NPs could induce lipofuscin accumulation and apoptosis independent of particle size, suggesting that oxidative damage and mitochondrial dysfunction may not be the only way responsible for NP-induced neurotoxic effects. Furthermore, the mutant test targeting two presenilin genes (sel-12 and hop-1) showed that sel-12 and hop-1 were involved in regulation of PS-NP-induced neurodevelopmental toxicity and mitochondrial damage. In conclusion, PS-NPs could induce neurodevelopmental toxicity dependent on particle sizes mediated by mitochondrial damage and DA reduction. Enhanced expression of presenilin plays a role in PS-NP-induced oxidative stress and neurodevelopmental toxicity.

Proteomic analysis revealed gender-specific responses of mussels (Mytilus galloprovincialis) to trichloropropyl phosphate (TCPP) exposure

Trichloropropyl phosphate (TCPP) is a halogenated organophosphate ester that is widely used as flame retardants and plasticizers. In this study, gender-specific accumulation and responses in mussel Mytilus galloprovincialis to TCPP exposure were focused and highlighted. After TCPP (100 nmol L^-1) exposure for 42 days, male mussels showed similar average bioaccumulation (37.14 ± 6.09 nmol g^-1 fat weight (fw)) of TCPP with that in female mussels (32.28 ± 4.49 nmol g^-1 fw). Proteomic analysis identified 219 differentially expressed proteins (DEPs) between male and female mussels in control group. There were 52 and 54 DEPs induced by TCPP in male and female mussels, respectively. Interestingly, gender-specific DEPs included 37 and 41 DEPs induced by TCPP in male and female mussels, respectively. The proteomic differences between male and female mussels were related to protein synthesis and degradation, energy metabolism, and functions of cytoskeleton and motor proteins. TCPP influenced protein synthesis, energy metabolism, cytoskeleton functions, immunity, and reproduction in both male and female mussels. Protein-protein interaction (PPI) networks indicated that protein synthesis and energy metabolism were the main biological processes influenced by TCPP. However, DEPs involved in these processes and their interaction patterns were quite different between male and female mussels. Basically, twelve ribosome DEPs which directly or indirectly interacted were found in protein synthesis in TCPP-exposed male mussels, while only 3 ribosome DEPs (not interacted) in TCPP-exposed female mussels. In energy metabolism, only 4 DEPs (with the relatively simple interaction pattern) mainly resided in fatty acid metabolism, butanoate/propanoate metabolism and glucose metabolism were discovered in TCPP-exposed male mussels, and more DEPs (with multiple interactions) functioned in TCA cycle and pyruvate/glyoxylate/dicarboxylate metabolism were found in TCCP-exposed female mussels. Taken together, TCPP induced gender-specific toxicological effects in mussels, which may shed new lights on further understanding the toxicological mechanisms of TCPP in aquatic organisms.

Global responses to tris(1-chloro-2-propyl)phosphate (TCPP) in rockfish Sebastes schlegeli using integrated proteomic and metabolomic approach

As alternatives of brominated flame retardants, organophosphate flame retardants (OPFRs) can be detected in multiple marine environmental media. Tris(1-chloro-2-propyl)phosphate (TCPP) was one of the most frequently and abundantly detected OPFRs in the Bohai Sea. Exposure to TCPP has been shown to induce abnormal behavior in zebrafish as well as neurotoxicity in Caenorhabditis elegans. However, there is a lack of mechanism investigations on the toxic effects of TCPP at molecular levels. In this work, proteomics and metabolomics were integrated to analyze the proteome and metabolome responses in rockfish Sebastes schlegeli treated with TCPP (10 and 100 nM) for 15 days. A total of 143 proteins and 8 metabolites were significantly altered in rockfish following TCPP treatments. The responsive proteins and metabolites were predominantly involved in neurotransmission, neurodevelopment, signal transduction, cellular transport, cholesterol metabolism, bile acid synthesis, and detoxification. Furthermore, a hypothesized network of proteins, metabolites, and pathways in rockfish was summarized based on the combination of proteomic and metabolomic results, showing some key molecular events in response to TCPP. Overall, the present study unraveled the molecular responses at protein and metabolite levels, which provided a better understanding of toxicological effects and mechanisms of TCPP in marine teleost.

Neurotoxicity and related mechanisms of flame retardant TCEP exposure in mice

Objective: To explore the neurotoxicity and mechanism of tris(2-chloroethyl) phosphate (TCEP) exposure in mice.Methods: Total 30 adult Kunming mice were randomly divided into normal control group (0 mg/kg·d), low-dose TCEP group (10 mg/kg·d), and high-dose TCEP group (100 mg/kg·d), and administered continuously by gavage for 30 days.Results: Compared with the control group, the water intake of high-dose TCEP group was declined significantly (p < 0.05), and the organ index of liver and spleen were increased significantly (p < 0.05). In addition, the escape latency of TCEP exposed mice were longer than that in the control group in water maze test (p < 0.05), while the total swimming course of high-dose TCEP group was elevated and the swimming time in target quadrant was obviously shortened compared with the control group (p < 0.05). The serum levels of total-triiodothyronine (TT3) and free triiodothyronine (FT3) were significantly higher in the high-dose TCEP group than in the control group (p＜0.05). Compared with the control group, the activities of glutathione transferase (GST) and super oxide dismutase (SOD) in the high-dose TCEP group were increased, and GST in the low-dose TCEP group were decreased, while the content of malonaldehyde (MDA) in both groups was increased (p＜0.05). In the CCK8 assay, the viability of PC12 cells decreased with an increase of TCEP concentration, indicating a concentration dependent neurotoxicity.Conclusion: TCEP exposure can cause neurotoxicity by increasing thyroid hormones and inducing oxidative damage in mice.

Effects of tris (2-chloroethyl) phosphate (TCEP) on growth, reproduction and gene transcription in the protozoan Tetrahymena thermophila

As a typical organophosphorus flame retardant, tris (2-chloroethyl) phosphate (TCEP) has been widely detected in various environmental media. Toxicity of TCEP to vertebrates have been investigated, but potential effects on lower trophic level species were unknown to date. In this study, toxic effects and molecular mechanisms of toxic actions of TCEP on the aquatic protozoan Tetrahymena thermophila were evaluated by use of phenotypic observations, transcriptome sequencing analysis and real-time quantitative PCR detection. Exposure to 0.044, 0.411 or 4.26 mg/L TCEP for 5 days decreased the theoretical population, cell viability, number of cilia and cell size of Tetrahymena thermophila in a time- and dose-dependent manner. Meanwhile, RNA-Seq analysis indicated that exposure to 4.26 mg/L TCEP significantly changed expression of 2932 genes (up-regulation: 1228; down-regulation: 1704). Of these, expressions of 9, 10 and 17 genes that were enriched in soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) interaction in vesicular transport, proteasome and endocytosis pathway respectively were down-regulated. Data collected during this study suggested that exposure to high concentrations of TCEP might affect growth and reproduction of Tetrahymena thermophila through down-regulating transcriptional levels of genes encoding proteins associated with vesicle trafficking, proteasome and endocytosis.

Performance Comparison of Different Constructed Wetlands Designs for the Removal of Personal Care Products

This research investigates the performance of four types of constructed wetlands (CWs): free water surface CW (FWSCW), horizontal flow CW (HFCW), vertical flow CW (VFCW), and hybrid CW (HCW) for the removal of 20 personal care products (PCPs), based on secondary data compiled for 137 CWs reported in 39 peer reviewed journal papers. In spite of considerable variation in the re-moval efficiency of PCPs, CWs prove to be a promising treatment technology. The average removal efficiency of 15 widely studied PCPs ranged from 9.0% to 84%. Although CWs effectively reduced the environmental risks caused by many PCPs, triclosan was still classified under high risk category based on effluent concentration. Five other PCPs were classified under medium risk category (triclocarban > methylparaben > galaxolide > oxybenzone > methyl dihydrojasmonate). In most of the examined PCPs, adsorption and/or sorption is the most common removal mechanism followed by biodegradation and plant uptake. The comparatively better performance of HCW followed by VFCW, HFCW, and FWSCW might be due to the co-existence of aerobic and anaerobic conditions, and longer hydraulic retention time enhancing the removal of PCPs (e.g., triclosan, methyl dihydro-jasmonate, galaxolide, tonalide, and oxybenzone), which are removed under both conditions and by adsorption/sorption processes.

Toxicological assessment and underlying mechanisms of tetrabromobisphenol A exposure on the soil nematode Caenorhabditis elegans

The widespread use of tetrabromobisphenol A (TBBPA) in industries has resulted in its frequent detection in environmental matrices, and the mechanisms of its associated hazards need further investigation. In this study, the nematode Caenorhabditis elegans (C. elegans) was exposed to environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, 200 μg/L) to determine its effects. At TBBPA concentrations above 1 μg/L, the number of head thrashes, as the most sensitive physiological indicator, decreased significantly. Using the Illumina HiSeq™ 2000 sequencer, differentially expressed genes (DEGs) were determined, and 52 were down regulated and 105 were up regulated in the 200 μg/L TBBPA treatment group versus the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis demonstrated that dorso-ventral axis formation is related to neurotoxicity; metabolism of xenobiotics by Cytochrome P450 (CYP450) and glutathione-S-transferase (GST) was found to be the vital metabolic mechanisms and were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). GST was ascribed to the augmentation because mutations in cyp-13A7 were constrained under TBBPA exposure. Additionally, oxidative stress indicators accumulated in a dose-dependent relationship. These results will help understand the molecular basis for TBBPA-induced toxicity in C. elegans and open novel avenues for facilitating the exploration of more efficient strategies against TBBPA toxicity.

Trans-generational effect of neurotoxicity and related stress response in Caenorhabditis elegans exposed to tetrabromobisphenol A

Tetrabromobisphenol A (TBBPA), one of the most common brominated flame retardants, has been associated with immunotoxicity, neurotoxicity, and reproductive toxicity. However, little attention has been focused on understanding the trans-generational effects of TBBPA. The present study used the Caenorhabditis elegans (C. elegans) animal model to evaluate the trans-generational effects of neurotoxicity induced by environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, and 1000 µg/L). Multiple indicators including physiological effects (body length, brood size, head thrashes, body bends, and crawling trajectory), degree of neuronal damage (dopamine, GABAergic, and glutamatergic neurons), oxidative stress-related biochemical indicators (superoxide dismutase [SOD] activity, catalase [CAT] enzyme, malondialdehyde [MDA] production, and reactive oxygen species [ROS] accumulation), and stress-related gene expressions have been evaluated in the exposed parental C. elegans generation (G₁) and their progeny (G₂) under TBBPA-free conditions. The results showed that TBBPA exposure induced adverse effects on physiological endpoints, among which body bends and head thrashes were the most sensitive ones, detected above 1 µg/L in G₁ and 100 µg/L in G₂ nematodes, respectively. After contaminant exposure, the three neurons revealed damage related to neurobehavioral endpoints, with no hereditary effects in the progeny. The oxidative stress-related biochemical endpoints demonstrated that when the exposure concentrations were above 1 µg/L in maternal worms, impairment can be detected in both generations, but the progeny recovered at low toxicity concentration (1-100 µg/L). The integrated target gene expression profiles were clearly altered in G₁ and G₂ worms at concentrations between 1 and 1000 µg/L, and a more significant difference existed in two generations of nematodes at low levels (1-10 µg/L) of TBBPA. Studing trans-generational neurotoxicity and the underlying mechanism can generate a precise evaluation of the environmental risk of TBBPA.

Degradation mechanism, intermediates and toxicology assessment of tris-(2-chloroisopropyl) phosphate using ultraviolet activated hydrogen peroxide

Organophosphate flame retardants (OPFRs), one kind of emerging flame retardants, have received prevalent attention owing to their ubiquity in aquatic matrices and their characteristics of being refractory to biodegradation. In current research, the degradation mechanism of tris-(2-chloroisopropyl) phosphate (TCPP), one of OPFRs, and its toxicological evaluation using UV-driven hydroxyl radical oxidation were investigated. A pseudo-first order reaction was fitted with an apparent rate constant (K_obs) of 0.1328 min^-1 on transformation of TCPP in the case of CH₂O₂ 0.1 mM, pH 6.6-7.1 and 4.7 mW cm^-2 UV irradiation. High resolution mass spectroscopy analyses identified nine degradation products (eg., C₆H₁₃Cl₂O₄P (m/z 251.0002), C₉H₁₇Cl₂O₅P (m/z 307.0266), C₉H₁₇Cl₂O₆P (m/z 323.0217), C₉H₁₈Cl₃O₅P (m/z 343.0033)) during transformation of TCPP. The removal efficiency dropped by inhibitory effect of natural organic matters and anions, implying that the complete mineralization of TCPP may be difficult in actual water treatment process. The toxicity assessment has shown an decrease in reactive oxygen species (ROS) and apoptosis, membrane potential (MP) elevation of Escherichia coli, and biological molecular function revision (eg., metabolism and DNA biosynthesis), indicating that toxicity of degradation products were conspicuously decreased in comparison with intact TCPP. To sum up, effective detoxification of TCPP can be realized by a UV driving radical-based oxidation, which will provide an alternative safe treatment method to control TCPP in water matrix.

Oxidation degradation of tris-(2-chloroisopropyl) phosphate by ultraviolet driven sulfate radical: Mechanisms and toxicology assessment of degradation intermediates using flow cytometry analyses

Organophosphate flame retardants (OPFRs) were frequently detected in biotic and abiotic matrix owing to their persistence and recalcitrant degradation. Some specific OPFRs, such as tris-(2-chloroisopropyl) phosphate (TCPP), pose a significant potential risk to human health due to their high water solubility. Therefore, an environmentally sound and high efficient technique is in urgent need of controlling TCPP. This research is focused on degrading TCPP using ultraviolet-persulfate (UV/PS) technique. The degradation reaction of TCPP followed a pseudo-first order kinetics with an apparent rate constant (k_obs) at 0.1653 min^-1. As the photocatalytic reaction proceeded, TCPP was transformed to twelve degradation intermediates via the selective electron-transfer reactions induced by activated sulfate radical. Anions existence and pH value significantly inhibited the degradation efficiency, implying that it was hard for TCPP to reach up to complete mineralization in actual water treatment process. Additionally, toxicological assessment of degradation intermediate mixture was conducted using Flow cytometry (FCM) analyses, and the result showed that the intracellular reactive oxygen species (ROS) and cell apoptotic rates significantly declined, and membrane potential (MP) increased in comparison with original TCPP. On the other hand, the negative impacts of these degradation products on DNA biosynthesis in Escherichia coli were weakened based on cell cycle analysis, all of which indicated that toxicity of these degradation intermediates was obviously reduced via UV/PS treatment. To summarize, an appropriate mineralization is effective for TCPP detoxification, suggesting the feasibility of TCPP control using UV/PS treatment in water matrix.

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

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

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

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

Neurotoxicity of nonylphenol exposure on Caenorhabditis elegans induced by reactive oxidative species and disturbance synthesis of serotonin

The present study was performed to evaluate the neurobehavioural deficit induced by nonylphenol (NP), a well-known xenobiotic chemical. The neurotoxic mechanism from oxidative stress and serotonin-related progress was also investigated. Caenorhabditis elegans was exposed at different levels of NP ranging from 0 to 200 μg L^-1 for 10 days. The results revealed that from a relatively low concentration (i.e., 10 μg L^-1), significant effects including decreased head thrashes, body bends and forging behaviour could be observed, along with impaired learning and memory behaviour plasticity. The level of reactive oxygen species (ROS) in head was significantly elevated with the increase of NP concentrations from 10 to 200 μg L^-1. Through antioxidant experiment, the oxidative damage caused by NP restored to some extent. At a NP concentration of 200 μg L^-1, the significant increased expression of stress-related genes, including sod-1, sod-3, ctl-2, ctl-3 and cyp-35A2 gene, was observed from integrated gene expression profiles. In addition, in comparison with wild-type N2 worms, the ROS accumulation was increased significantly with the mutation of sod-3. Tryptophan hydroxylase (TPH) in ADF and NSM neurons sharply decreased at the concentrations of 10-200 μg L^-1. The transcription of TPH synthesis-related genes and serotonin-related genes were both suppressed, including tph-1, cat-1, cat-4, ser-1, and mod-5. Overall, these results indicated that NP could induce neurotoxicity on Caenorhabditis elegans through excessive induction of ROS and disturbance synthesis of serotonin. The conducted research opened up new avenues for more effective exploration of neurotoxicity caused by NP.

Mutation of hop-1 and pink-1 attenuates vulnerability of neurotoxicity in C. elegans: the role of mitochondria-associated membrane proteins in Parkinsonism

Mitochondrial dysfunction is considered as a critical mechanism in the pathogenesis of Parkinson's disease (PD). Increasing evidence supports the notion of mitochondria-associated membranes (MAMs) in mitochondrial dysfunction; yet little is known about the role of MAMs-related proteins in the pathogenesis of PD. Herein we exposed the nematode Caenorhabditis elegans to 0.5-10.0 μM rotenone (RO) or 0.2-1.6 mM paraquat (PQ) for 3 days. Our results showed that both RO and PQ induced similar Parkinsonism including motor deficits and dopaminergic degeneration. RO/PQ caused mitochondrial damages characterized by the increase of vacuole areas and autophagy vesicles, but the decrease of mitochondrial cristae. RO/PQ-impacted mitochondrial function was also demonstrated by the decrease of ATP level and mitochondrial membrane potential. Additionally, the attachment or surrounding of endoplasmic reticulum to the damaged mitochondria indicates ultrastructural alterations in MAMs. Using fluorescently labeled transgenic nematodes, we further found that the expression of tomm-7 and genes of Complex I, II and III was reduced, whereas the expression of pink-1 was increased in the exposed animals. To determine MAMs in toxicity toward PD, we investigated the mutants of hop-1 and pink-1, encoding presenilin and PTEN-induced putative kinase 1 (PINK1) in mitochondria-associated membranes, respectively. Results demonstrated that the mutation of both hop-1 and pink-1 reduced the vulnerability of lethal, behavioral, and mitochondrial toxicity induced by RO/PQ. These findings suggest that presenilin and PINK1 play important roles in the RO/PQ-induced neurotoxicity through the mechanisms involved in mitochondria-associated membranes.

Metabolites of organophosphate ester flame retardants in urine from Shanghai, China

The metabolites of nine organophosphate ester (OPE) flame retardants were measured in 180 urine samples collected from a population (including adults and children) in western Shanghai, China, using liquid chromatography-tandem spectrometry (LC-MS/MS). The total urinary concentrations of nine OPE metabolites ranged 100-23800 pg/mL, with a geometric mean (GM) value of 1450 pg/mL. The concentrations of alkyl-OPE metabolites (879 pg/mL) were approximately an order of magnitude higher than those of aryl-OPE (53.7 pg/mL) and chlorinated-OPE metabolites (52.7 pg/mL). Diphenyl phosphate (DPHP), diethyl phosphate (DEP), di-n-butyl phosphate (DNBP), bis(2-ethylhexyl) phosphate (BEHP), and bis(2-butoxyethyl) phosphate (BBOEP) were the dominant OPE metabolites found in urine. The results showed that an increase in age was associated with a significant decrease in urinary DPHP (r = -0.278, p < 0.01) and DNBP (r = -0.314, p < 0.01) concentrations. The highest concentrations of DPHP (GM = 80.7 pg/mL) and DNBP (GM = 16.9 pg/mL) were found in urine from people living in homes that were less than 10 years old. The urinary DNBP concentration was significantly associated with self-reported symptoms of allergy. Our result establishes baseline value for OPE exposure in a population in China for comparison in future studies.

Microplastic particles cause intestinal damage and other adverse effects in zebrafish Danio rerio and nematode Caenorhabditis elegans

Microplastics have been frequently detected in aquatic environments, and there are increasing concerns about potential effects on biota. In this study, zebrafish Danio rerio and nematode Caenorhabditis elegans were used as model organisms for microplastic exposure in freshwater pelagic (i.e. water column) and benthic (i.e. sediment) environments. We investigated the toxic effects of five common types of microplastics: polyamides (PA), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC) and polystyrene (PS) particles. Results showed no or low lethality in D. rerio after exposure for 10d at 0.001-10.0mgL^-1 microplastics. The PA, PE, PP and/or PVC microplastics with ~70μm size caused intestinal damage including cracking of villi and splitting of enterocytes. Exposure to 5.0mgm^-2 microplastics for 2d significantly inhibited survival rates, body length and reproduction of C. elegans. Moreover, exposure to microplastics reduced calcium levels but increased expression of the glutathione S-transferase 4 enzyme in the intestine, which indicates intestinal damage and oxidative stress are major effects of microplastic exposure. Among 0.1, 1.0 and 5.0μm sizes of fluorescently labeled PS, 1.0μm particles caused the highest lethality, the maximum accumulation, the lowest Ca²⁺ level in the intestine and the highest expression of glutathione S-transferase 4 in nematodes. Taken together, these findings suggest that intestinal damage is a key effect of microplastics; and that the toxicity of microplastics is closely dependent on their size, rather than their composition.

Behavioral deficits and neural damage of Caenorhabditis elegans induced by three rare earth elements

Rare earth elements (REEs) are widely used in industry, agriculture, medicine and daily life in recent years. However, environmental and health risks of REEs are still poorly understood. In this study, neurotoxicity of trichloride neodymium, praseodymium and scandium were evaluated using nematode Caenorhabditis elegans as the assay system. Median lethal concentrations (48 h) were 99.9, 157.2 and 106.4 mg/L for NdCl₃, PrCl₃ and ScCl₃, respectively. Sublethal dose (10-30 mg/L) of these trichloride salts significantly inhibited body length of nematodes. Three REEs resulted in significant declines in locomotor frequency of body bending, head thrashing and pharyngeal pumping. In addition, mean speed and wavelength of crawling movement were significantly reduced after chronic exposure. Using transgenic nematodes, we found NdCl₃, PrCl₃ and ScCl₃ resulted in loss of dendrite and soma of neurons, and induced down-expression of dat-1::GFP and unc-47::GFP. It indicates that REEs can lead to damage of dopaminergic and GABAergic neurons. Our data suggest that exposure to REEs may cause neurotoxicity of inducing behavioral deficits and neural damage. These findings provide useful information for understanding health risk of REE materials.

Behavioral Phenotyping and Pathological Indicators of Parkinson's Disease in C. elegans Models

Parkinson's disease (PD) is a neurodegenerative disorder with symptoms that progressively worsen with age. Pathologically, PD is characterized by the aggregation of α-synuclein in cells of the substantia nigra in the brain and loss of dopaminergic neurons. This pathology is associated with impaired movement and reduced cognitive function. The etiology of PD can be attributed to a combination of environmental and genetic factors. A popular animal model, the nematode roundworm Caenorhabditis elegans, has been frequently used to study the role of genetic and environmental factors in the molecular pathology and behavioral phenotypes associated with PD. The current review summarizes cellular markers and behavioral phenotypes in transgenic and toxin-induced PD models of C. elegans.