In Vitro Immunotoxicity of Organophosphate Flame Retardants in Human THP-1-Derived Macrophages

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

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

Assessment of immunomodulatory effects of five commonly used parabens on human THP-1 derived macrophages: Implications for ecological and human health impacts

Parabens are widely used as broad-spectrum anti-microbials and preservatives in food, cosmetics, pharmaceuticals, and personal care products. Studies suggest that the utilization of parabens has substantially increased over the past years, particularly during the global pandemic of coronavirus disease 2019 (COVID-19). Although parabens are generally recognized as safe by the U.S. FDA, some concerns have been raised regarding the potential health effects of parabens associated with immunotoxicity. Herein, we comprehensively investigated several key characteristics of immunotoxicants of five commonly used parabens (methyl-, ethyl-, propyl-, butyl-, and benzyl parabens) in human THP-1 derived macrophages, which are effector cells serving as a first line of host defense against pathogens and tumor immunosurveillance. The results indicate parabens, at concentrations found in humans and biota, significantly dampened macrophage chemotaxis and secretion of major pro-inflammatory cytokines (TNF-α and IL-6) and anti-inflammatory cytokine (IL-10), corroborating the mRNA expression profile. Furthermore, some parabens were found to markedly alter macrophage adhesion and cell surface expression of costimulatory molecules, CD80+ and CD86+, and significantly increase macrophage phagocytosis. Collectively, these findings heighten awareness of potential immunotoxicity posed by paraben exposure at biologically relevant concentrations, providing implications for human health and ecological risks associated with immune dysfunctions.

Physiological and transcriptomic changes of zebrafish (Danio rerio) in response to Isopropylate Triphenyl Phosphate (IPPP) exposure

Isopropylate Triphenyl Phosphate (IPPP), a novel organophosphorus flame retardant, has become a widespread environmental pollutant. However, the toxic effects and mechanisms of IPPP remain unclear. In this study, we evaluated the neurodevelopmental toxicity effects of IPPP on zebrafish embryonic development, neurobehavior, and physiological and transcriptomic changes. The results showed that IPPP induced adverse developments such as low survival rates and hatching rates, decreased body length and eye distance, and also led to increased heart rates and embryonic malformation rates. The developmental defects mainly included typical pericardial edema, eye deformities, and a reduction in the number of newborn neurons. Mitochondrial energy metabolism disorders and apoptosis of cardiomyocytes may be responsible for heart malformation. Behavioral results showed that IPPP caused abnormal changes in swimming speed, total swimming distance and trajectory, and showed a low-dose effect. In addition, the decreased activity of neurotransmitters such as acetylcholinesterase (AchE) and dopamine (DA), and the changes in genes related to the central nervous system (CNS) and metabolism pathway may be the causes of neurodevelopmental toxicity of IPPP. Meanwhile, IPPP induced oxidative stress and apoptosis, and changed the ATPase activity of zebrafish larvae by altering nuclear factor erythroid2-related factor 2 (Nrf2) and mitochondrial signaling pathways, respectively. Transcriptome sequencing results indicated that Cytochrome P450 and drug metabolism, Energy metabolism-related pathways, Glutathione metabolism, Retinoid acid (RA) and REDOX signaling pathways were significantly enriched, and most of the genes in these pathways were up-regulated after IPPP treatment, which may be new targets for IPPP-induced neurodevelopment. In summary, the results of this study provide an important reference for a comprehensive assessment of the toxic effects and health risks of the new pollutant IPPP.

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

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

Phenotypic and Functional Outcomes in Macrophages Exposed to an Environmentally Relevant Mixture of Organophosphate Esters in Vitro

BACKGROUND

Organophosphate esters (OPEs) are flame retardants and plasticizers used in consumer products. OPEs are found ubiquitously throughout the environment with high concentrations in indoor house dust. Exposure to individual OPEs is associated with immune dysfunction, particularly in macrophages. However, OPEs exist as complex mixtures and the effects of environmentally relevant mixtures on the immune system have not been investigated.

OBJECTIVES

The objectives of this study were to evaluate the toxicity of an environmentally relevant mixture of OPEs that models Canadian house dust on macrophages using phenotypic and functional assessments in vitro.

METHODS

High-content live-cell fluorescent imaging for phenotypic biomarkers of toxicity in THP-1 macrophages treated with the OPE mixture was undertaken. We used confocal microscopy and cholesterol analysis to validate and expand on the observed OPE-induced lipid phenotype. Then, we used flow cytometry and live-cell imaging to conduct functional tests and uncover mechanisms of OPE-induced phagocytic suppression. Finally, we validated our THP-1 findings in human primary peripheral blood mononuclear cells (hPBMC) derived macrophages.

RESULTS

Exposure to non-cytotoxic dilutions of the OPE mixture resulted in higher oxidative stress and disrupted lysosome and lipid homeostasis in THP-1 and primary macrophages. We further observed that phagocytosis of apoptotic cells in THP-1 and primary macrophages was lower in OPE-exposed cells vs. controls. In THP-1 macrophages, phagocytosis of both Gram-positive and Gram-negative bacteria was also lower in OPE-exposed cells vs. controls. Additionally, the OPE mixture altered the expression of phagocytic receptors linked to the recognition of phosphatidylserine and pathogen-associated molecular patterns.

DISCUSSION

The results of this in vitro study suggested that exposure to an environmentally relevant mixture of OPEs resulted in higher lipid retention in macrophages and poor efferocytic response. These effects could translate to enhanced foam cell generation resulting in higher cardiovascular mortality. Furthermore, bacterial phagocytosis was lower in OPE-exposed macrophages in an in vitro setting, which may indicate the potential for reduced bacterial clearance in models of infections. Taken together, our data provide strong evidence that mixtures of OPEs can influence the biology of macrophages and offer new mechanistic insights into the impact of OPE mixtures on the immune system. https://doi.org/10.1289/EHP13869.

E-waste: mechanisms of toxicity and safety testing

Currently, information on the toxicity profile of the majority of the identified e-waste chemicals, while extensive and growing, is admittedly fragmentary, particularly at the cellular and molecular levels. Furthermore, the toxicity of the chemical mixtures likely to be encountered by humans during and after informal e-waste recycling, as well as their underlying mechanisms of action, is largely unknown. This review paper summarizes state-of-the-art knowledge of the potential underlying toxicity mechanisms associated with e-waste exposures, with a focus on toxic responses connected to specific organs, organ systems, and overall effects on the organism. To overcome the complexities associated with assessing the possible adverse outcomes from exposure to chemicals, a growing number of new approach methodologies have emerged in recent years, with the long-term objective of providing a human-based and animal-free system that is scientifically superior to animal testing, more effective, and acceptable. This encompasses a variety of techniques, typically regarded as alternative approaches for determining chemical-induced toxicities and holds greater promise for a better understanding of key events in the metabolic pathways that mediate known adverse health outcomes in e-waste exposure scenarios. This is crucial to establishing accurate scientific knowledge on mixed e-waste chemical exposures in shorter time frames and with greater efficacy, as well as supporting the need for safe management of hazardous chemicals. The present review paper discusses important gaps in knowledge and shows promising directions for mechanistically anchored effect-based monitoring strategies that will contribute to the advancement of the methods currently used in characterizing and monitoring e-waste-impacted ecosystems.

Developmental toxicity assessment of neonicotinoids and organophosphate esters with a human embryonic stem cell- and metabolism-based fast-screening model

In recent years, neonicotinoids (NEOs) and organophosphate esters (OPEs) have been widely used as substitutes for traditional pesticides and brominated flame-retardants, respectively. Previous studies have shown that those compounds can be frequently detected in environmental and human samples, are able to penetrate the placental barrier, and are toxic to animals. Thus, it is reasonable to speculate that NEOs and OPEs may have potential adverse effects in humans, especially during development. We employed a human embryonic stem cell differentiation- and liver S9 fraction metabolism-based fast screening model to assess the potential embryonic toxicity of those two types of chemicals. We show that four NEO and five OPE prototypes targeted mostly ectoderm specification, as neural ectoderm and neural crest genes were down-regulated, and surface ectoderm and placode markers up-regulated. Human liver S9 fraction's treatment could generally reduce the effects of the chemicals, except in a few specific instances, indicating the liver may detoxify NEOs and OPEs. Our findings suggest that NEOs and OPEs interfere with human early embryonic development.

Triphenyl phosphate exposure impairs colorectal health by altering host immunity and colorectal microbiota

Colorectal diseases such as colorectal cancer (CRC) and inflammatory bowel disease (IBD) have become one of the most common public health concerns worldwide due to the increasing incidence. Environmental factors are one of the important causes of colorectal diseases, as they can affect the intestinal barrier function, immune response and microbiota, causing intestinal inflammation and tumorigenesis. Triphenyl phosphate (TPHP), a widely used organophosphorus flame retardant that can leach and accumulate in various environmental media and biota, can enter the human intestine through drinking water and food. However, the effects of TPHP on colorectal health have not been well understood. In this study, we investigated the adverse influence of TPHP exposure on colorectal cells (in vitro assay) and C57BL/6 mice (in vivo assay), and further explored the potential mechanism underlying the association between TPHP and colorectal disease. We found that TPHP exposure inhibited cell viability, increased apoptosis and caused G1/S cycle arrest of colorectal cells. Moreover, TPHP exposure damaged colorectal tissue structure, changed immune-related gene expression in the colorectal transcriptome, and disrupted the composition of colorectal microbiota. Importantly, we found that TPHP exposure upregulated chemokine CXCL10, which was involved in colorectal diseases. Our study revealed that exposure to TPHP had significant impacts on colorectal health, which may possibly stem from alterations in host immunity and the structure of the colorectal microbial community.

Toxicity of TPhP on the gills and intestines of zebrafish from the perspectives of histopathology, oxidative stress and immune response

As an organophosphate ester (OPE), triphenyl phosphate (TPhP) has been frequently detected in aquatic environments, and its environmental risk has been widely studied. The gills and intestines are the most important part of the mucosal immune barrier in fish as the first line of defense against the invasion of harmful substances. TPhP is more abundant in the gill and intestine of fish. However, knowledge of the toxic effects and potential mechanisms of TPhP on the intestine and gill is limited. Herein, the adverse effects of TPhP (0.01, 0.1 and 1 mg/L) on the gills and intestines of zebrafish after 75 days of exposure were investigated from the perspectives of histology, oxidative stress and immune level. The histological results of exposed zebrafish showed that TPhP caused significant damage to gills and intestines. TPhP significantly increased the activities of the antioxidant enzymes catalase (CAT) and glutathione s-transferase (GST), inducing oxidative damage to lipids, proteins, and DNA. Meanwhile, the immune function of the gills and intestines was significantly influenced by TPhP, as evidenced by the upregulation of the expression of interleukin-1β (IL-1β) and interleukin-6 (IL-6), upregulation of the content of complement 3 (C3) and complement 4 (C4), and downregulation of the activity of lysozyme (LZM) and the content of immunoglobulin M (IgM). Oxidative stress and the immune response were more severe in the gills. These findings indicate that TPhP, a typical OPE, caused tissue damage in aquatic organisms by inducing oxidative stress and immune damage and has strong environmental toxicity.

Comprehensive analysis of the impact of emerging flame retardants on prostate cancer progression: The potential molecular mechanisms and immune infiltration landscape

Emerging flame retardants have been used to replace traditional flame retardants, but their potential impact on cancer, especially prostate cancer, is not well understood. Our study aimed to explore the link between flame retardants and prostate cancer, and identify potential carcinogenic mechanisms among populations exposed to emerging flame retardants. We screened flame retardant interacting genes differentially expressed in prostate cancer patients and identified hub genes by protein-protein interaction (PPI) analysis based on the STRING database. Univariate and multivariate Cox regression analyses were performed to construct risk models and identify flame retardant-related prognostic genes. We calculated the proportion of immune cell infiltration to explore the potential mechanism of the prognostic gene, and verified the target cell population of the prognostic gene in the single-cell transcriptome dataset. Our study revealed a significant link between emerging flame retardants and prostate cancer. We constructed a risk model with good predictive ability for prostate cancer prognosis using TCGA dataset, and identified six flame retardant-related prognostic genes validated in the GSE70769 dataset. We found that the expression of M2 macrophages was up-regulated in patients with high expression of prognostic genes, and the single-cell dataset confirmed the expression of prognostic genes in macrophages. Our study confirms the link between emerging flame retardants and prostate cancer, and highlights the role of immune-related pathways in the high-risk population exposed to these flame retardants.

Examining the immunotoxicity of oil sands process affected waters using a human macrophage cell line

Oil sands process affected water (OSPW) is produced during the surface mining of the oil sands bitumen deposits in Northern Alberta. OSPW contains variable quantities of organic and inorganic components causing toxic effects on living organisms. Advanced Oxidation Processes (AOPs) are widely used to degrade toxic organic components from OSPW including naphthenic acids (NAs). However, there is no established biological procedure to assess the effectiveness of the remediation processes. Our previous study showed that human macrophage cells (THP-1) can be used as a bioindicator system to evaluate the effectiveness of OSPW treatments through examining the proinflammatory gene transcription levels. In the present study, we investigated the immunotoxicological changes in THP-1 cells following exposure to untreated and AOP-treated OSPW. Specifically, using proinflammatory cytokine protein secretion assays we showed that AOP treatment significantly abrogates the ability of OSPW to induce the secretion of IL-1β, IL-6, IL-8, TNF-α, IL-1Ra and MCP-1. By measuring transcriptional activity as well as surface protein expression levels, we also showed that two select immune cell surface markers, CD40 and CD54, were significantly elevated following OSPW exposure. However, AOP treatments abolished the immunostimulatory properties of OSPW to enhance the surface expression of these immune proteins. Finally, a transcriptome-based approach was used to examine the proinflammatory effects of OSPW as well as the abrogation of immunotoxicity following AOP treatments. Overall, this research shows how a human macrophage cell-based biomonitoring system serves as an effective in vitro tool to study the immunotoxicity of OSPW samples before and after targeted remediation strategies.

Cellular and physiological mechanisms of halogenated and organophosphorus flame retardant toxicity

Flame retardants (FRs) are chemical substances used to inhibit the spread of fire in numerous industrial applications, and their abundance in modern manufactured products in the indoor and outdoor environment leads to extensive direct and food chain exposure of humans. Although once considered relatively non-toxic, FRs are demonstrated by recent literature to have disruptive effects on many biological processes, including signaling pathways, genome stability, reproduction, and immune system function. This review provides a summary of research investigating the impact of major groups of FRs, including halogenated and organophosphorus FRs, on animals and humans in vitro and/or in vivo. We put in focus those studies that explained or referenced the modes of FR action at the level of cells, tissues and organs. Since FRs are highly hydrophobic chemicals, their biophysical and biochemical modes of action usually involve lipophilic interactions, e.g. with biological membranes or elements of signaling pathways. We present selected toxicological information about these molecular actions to show how they can lead to damaging membrane integrity, damaging DNA and compromising its repair, changing gene expression, and cell cycle as well as accelerating cell death. Moreover, we indicate how this translates to deleterious bioactivity of FRs at the physiological level, with disruption of hormonal action, dysregulation of metabolism, adverse effects on male and female reproduction as well as alteration of normal pattern of immunity. Concentrating on these subjects, we make clear both the advances in knowledge in recent years and the remaining gaps in our understanding, especially at the mechanistic level.

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

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

Organophosphate esters concentrations in human serum and their associations with Sjögren syndrome

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers due to their excellent properties. The interference of OPEs on immune function has been proven, but the epidemiological data on OPEs exposure to related immune function diseases, such as sjögren syndrome (SjS), is limited. In cross-sectional study, 283 serum samples were collected from healthy individuals (n = 145) and patients with SjS (n = 138) in Hangzhou, China. Eight OPEs, triethyl phosphate (TEP), tributyl phosphate (TBP), tris (2-chloroethyl) phosphine (TCEP), triphenyl phosphate (TPHP), tri (1-chloro-2-propyl) phosphate (TCIPP), 2-ethylhexyldi-phenyl phosphate (EHDPP), tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), and tri (2-butoxyethyl) phosphate (TBOEP), were frequently measured in serum samples. In addition, we explored the associations between the serum OPEs concentration and the risk of SjS. Results showed that TEP (mean controls 2.17 and cases 3.63 ng/mL) was the most abundant OPEs in the serum samples of the control and case groups, followed by TCIPP (mean controls 0.54 and cases 0.78 ng/mL). Serum TEP, TPHP, and EHDPP concentrations were positively correlated with SjS [odds ratio (OR): 1.97, 1.96, and 2.42, respectively; 95% confidence interval (CI):1.34-2.89, 1.34-2.87, and 1.34-2.87, respectively] in the adjusted model, and a negative correlation of TBP concentrations with SjS in the adjusted model (OR: 0.35, 95% CI: 0.17-0.70) was observed. Compared with the lowest quartile concentrations, the ORs of SjS at the highest quartile concentrations of TEP (OR: 4.93, 95% CI: 2.24-10.82) and TPHP (OR: 4.75, 95% CI:1.89-11.94) were significantly higher. This study suggests that human exposure to OPEs may increase the risk of SjS.

Investigation on the immunotoxicity induced by Emamectin benzoate on THP-1 macrophages based on metabolomics analysis

Emamectin benzoate (EMB) is an insecticide extensively used in agricultural area. Assessing the toxic effects of EMB in mammals or humans and its endogenous metabolites alteration are the appropriate means of evaluating its risks to human health. In the study, THP-1 macrophage, a human immune model, was applied to investigate the immunotoxicity of EMB. A global metabolomics approach was developed to analyze metabolic perturbation on macrophages and discover the potential biomarkers of EMB-induced immunotoxicity. The results indicated that EMB could inhibit immune functions of macrophages. Based on metabolomics analysis, our results illustrated that EMB caused significant alterations in metabolic profiles on macrophages. 22 biomarkers associated with immune response were screened by pattern recognition and multivariate statistical analysis. Furthermore, pathway analysis identified purine metabolism was the most relevant pathway in the metabolic process and the abnormal conversion of AMP to xanthosine regulated by NT5E might be a potential mechanism of immunotoxicity induced by EMB. Our study provides important insights for understanding and underlying mechanism of immunotoxicity exposed to EMB.

The potential immunotoxicity of emamectin benzoate on the human THP-1 macrophages

Emamectin benzoate (EMB) as one of the typical biological pesticides has a wide range of applications in agriculture. However, the immune toxic effects of EMB in human received limited attention. In our study, THP-1 macrophage as an in vitro model was used to evaluate immune functions exposed to EMB. We observed that EMB inhibited phagocytic activity and respiratory burst capacity of macrophages without inducing cellular toxicity, implying the potential immunosuppression. Besides, EMB disturbed the cytokines balance embodied in the increase of TNF-α, IL-1β, IL-6, CCL27, CXCL8 mRNA expression and the decrease of IL-4, IL-13, IL-10 mRNA expression. EMB could exhibit pro-inflammatory responses in macrophages and promote the conversion of macrophages to M1 phenotype. Moreover, NF-κB pathway involved in regulating immune function from KEGG pathway analysis. EMB exposure could activate the NF-κB pathway in THP-1 macrophages by exploring the critical proteins. This research provided insights on immunotoxicity evaluation and clarified EMB-induced immunotoxicity was related to NF-κB pathway activation.

In vitro neurotoxic potential of emerging flame retardants on neuroblastoma cells in an acute exposure scenario

Since 2004, some legacy flame retardants (FRs) were restricted or removed from the European markets due to their concern on human health. Both organophosphorus FRs (OPFRs) and novel brominated FRs (NBFRs) have replaced them because they are presumably safer and less persistent emerging FRs (EFRs) and their exposure is currently occurring in indoor environments at high levels. Little is known about the neurotoxic potential risk of these EFRs in humans. The present study was aimed at assessing the acute neurotoxicity potential of Tris(1, 3-dichloro-2-propyl)phosphate (TDCPP), triphenyl phosphate (TPhP), Bis(2-ethylhexyl)tetrabromophthalate (BEH-TEBP) and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB) on human neuroblastoma cells (SH-SY5Y). SH-SY5Y were exposed to these EFRs at low concentrations -ranging 2.5-20 μM. during 2-24 h. We investigated viability, mitochondrial function, oxidative stress, inflammatory response, as well as neural plasticity and development. The results have demonstrated that selected EFRs (TDCPP, TPhP, EH-TBB and BEH-TBP) did not impair neural function on SH-SY5Y as acute response. To the best of our knowledge, this has been the first study focused on evaluating the neural affection of TPhP on SH-SY5Y cells and of EH-TBB and BEH-TBP on neural cells. We also assessed for the first time almost all endpoints after FR exposure on neural cell lines.

Spleen Toxicity of Organophosphorus Flame Retardant TDCPP in Mice and the Related Mechanisms

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphorus flame retardant that has been utilized in recent years as a primary replacement for polybrominated diphenyl ethers (PBDEs) in a wide variety of fire-sensitive applications. However, the impact of TDCPP on the immune system has not been fully determined. As the largest secondary immune organ in the body, the spleen is considered to be an important study endpoint for determining immune defects in the body. The aim of this study is to investigate the effect of TDCPP toxicity on the spleen and its possible molecular mechanisms. In this study, for 28 consecutive days, TDCPP was administered intragastrically (i.g), and we assessed the general condition of mice by evaluating their 24 h water and food intake. Pathological changes in spleen tissues were also evaluated at the end of the 28-day exposure. To measure the TDCPP-induced inflammatory response in the spleen and its consequences, the expression of the critical players in the NF-κB pathway and mitochondrial apoptosis were detected. Lastly, RNA-seq was performed to identify the crucial signaling pathways of TDCPP-induced splenic injury. The results showed that TDCPP intragastric exposure triggered an inflammatory response in the spleen, likely through activating the NF-κB/IFN-γ/TNF-α/IL-1β pathway. TDCPP also led to mitochondrial-related apoptosis in the spleen. Further RNA-seq analysis suggested that the TDCPP-mediated immunosuppressive effect is associated with the inhibition of chemokines and the expression of their receptor genes in the cytokine-cytokine receptor interaction pathway, including four genes of the CC subfamily, four genes of the CXC subfamily, and one gene of the C subfamily. Taken together, the present study identifies the sub-chronic splenic toxicity of TDCPP and provides insights on the potential mechanisms of TDCPP-induced splenic injury and immune suppression.

Immunotoxicity In Vitro Assays for Environmental Pollutants under Paradigm Shift in Toxicity Tests

With the outbreak of COVID-19, increasingly more attention has been paid to the effects of environmental factors on the immune system of organisms, because environmental pollutants may act in synergy with viruses by affecting the immunity of organisms. The immune system is a developing defense system formed by all metazoans in the course of struggling with various internal and external factors, whose damage may lead to increased susceptibility to pathogens and diseases. Due to a greater vulnerability of the immune system, immunotoxicity has the potential to be the early event of other toxic effects, and should be incorporated into environmental risk assessment. However, compared with other toxicity endpoints, e.g., genotoxicity, endocrine toxicity, or developmental toxicity, there are many challenges for the immunotoxicity test of environmental pollutants; this is due to the lack of detailed mechanisms of action and reliable assay methods. In addition, with the strong appeal for animal-free experiments, there has been a significant shift in the toxicity test paradigm, from traditional animal experiments to high-throughput in vitro assays that rely on cell lines. Therefore, there is an urgent need to build high-though put immunotoxicity test methods to screen massive environmental pollutants. This paper reviews the common methods of immunotoxicity assays, including assays for direct immunotoxicity and skin sensitization. Direct immunotoxicity mainly refers to immunosuppression, for which the assays mostly use mixed immune cells or isolated single cells from animals with obvious problems, such as high cost, complex experimental operation, strong variability and so on. Meanwhile, there have been no stable and standard cell lines targeting immune functions developed for high-throughput tests. Compared with direct immunotoxicity, skin sensitizer screening has developed relatively mature in vitro assay methods based on an adverse outcome pathway (AOP), which points out the way forward for the paradigm shift in toxicity tests. According to the experience of skin sensitizer screening, this paper proposes that we also should seek appropriate nodes and establish more complete AOPs for immunosuppression and other immune-mediated diseases. Then, effective in vitro immunotoxicity assay methods can be developed targeting key events, simultaneously coordinating the studies of the chemical immunotoxicity mechanism, and further promoting the paradigm shift in the immunotoxicity test.

Chlorinated Polycyclic Aromatic Hydrocarbons Induce Immunosuppression in THP-1 Macrophages Characterized by Disrupted Amino Acid Metabolism

Frequent chlorinated polycyclic aromatic hydrocarbon (Cl-PAH) occurrence in environmental samples and emerging detection in human serum have warned of their underestimated risks. Studies showed that some Cl-PAHs exhibit dioxin-like properties, implying immunotoxic potential but lacking direct evidence and specific mechanisms. Here, we integrated a high-content screening (HCS) system and high-resolution mass spectrometry to investigate the immune dysfunction and metabolic disruption induced by Cl-PAHs and their parent PAHs (PPAHs) in THP-1 macrophages. Both 9-chloroanthracene and 2,7-dichlorofluorene exerted clear immunosuppression on THP-1 mφs, while their PPAHs exhibited different immune disturbances. Interestingly, Cl-PAH/PPAHs induced complex alterations in the multicytokine/chemokine network, including biphasic alterations with initial inhibition and later enhancement. Furthermore, the protein-protein interaction results revealed that inflammatory cytokines are the core of this complicated network regulation. Connecting immune phenotypes and metabolomics, amino acid metabolism reprogramming was identified as a potential cause of Cl-PAH/PAH-induced immunotoxicity. Phytosphingosine and l-kynurenine were proposed as candidate immunosuppression biomarkers upon Cl-PAH exposure. This article provides direct immunotoxicity evidence of Cl-PAHs without activating AhR for the first time and discusses the contribution of metabolites to Cl-PAH/PPAH-induced immune responses in macrophages, highlighting the potential of developing new methods based on immunometabolism mechanisms for toxic risk evaluation of environmental chemicals.

Organophosphate esters cause thyroid dysfunction via multiple signaling pathways in zebrafish brain

Organophosphate esters (OPEs) are widespread in various environmental media, and can disrupt thyroid endocrine signaling pathways. Mechanisms by which OPEs disrupt thyroid hormone (TH) signal transduction are not fully understood. Here, we present in vivo-in vitro-in silico evidence establishing OPEs as environmental THs competitively entering the brain to inhibit growth of zebrafish via multiple signaling pathways. OPEs can bind to transthyretin (TTR) and thyroxine-binding globulin, thereby affecting the transport of TH in the blood, and to the brain by TTR through the blood-brain barrier. When GH3 cells were exposed to OPEs, cell proliferation was significantly inhibited given that OPEs are competitive inhibitors of TH. Cresyl diphenyl phosphate was shown to be an effective antagonist of TH. Chronic exposure to OPEs significantly inhibited the growth of zebrafish by interfering with thyroperoxidase and thyroglobulin to inhibit TH synthesis. Based on comparisons of modulations of gene expression with the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, signaling pathways related to thyroid endocrine functions, such as receptor-ligand binding and regulation of hormone levels, were identified as being affected by exposure to OPEs. Effects were also associated with the biosynthesis and metabolism of lipids, and neuroactive ligand-receptor interactions. These findings provide a comprehensive understanding of the mechanisms by which OPEs disrupt thyroid pathways in zebrafish.

Solar-activated zinc oxide photocatalytic treatment of real oil sands process water: Effect of treatment parameters on naphthenic acids, polyaromatic hydrocarbons and acute toxicity removal

Oil sands process water (OSPW) is an industrial process effluent that contains organic compounds such as naphthenic acids (NAs) and polyaromatic hydrocarbons (PAHs), as well as large quantities of inorganic compounds in its mixture. OSPW requires effective treatment for successful reclamation and water reuse. This study investigated the impact of solar-activated zinc oxide (ZnO) photocatalysis on the degradation and removal of NAs and PAHs in OSPW, as well as the elimination of its acute toxicity. With catalyst particles suspended in the effluent (at 1 g/L) under simulated solar radiation of steady irradiance of ~278 W/m², more than 99% removal of NAs was achieved after 4 h of treatment, while nearly all PAHs were simultaneously oxidized within the same reaction time. The photocatalytic treatment appeared to selectively convert classical NAs faster than oxidized NAs. Additionally, NAs with higher double-bond equivalents (DBEs) and higher carbon numbers seemed more susceptible to photocatalytic destruction than others. An overall pseudo first-order rate constant of 1.14 × 10^-2 min^-1, and a fluence-based rate constant of 6.81 × 10^-1 m²/MJ were recorded in apparently hydroxyl radicals (OH) and superoxide (O₂^-) radicals mediated NAs degradation mechanisms. Assessment of the toxicity levels in raw and treated OSPW samples by using Microtox® bioassay indicated that the photocatalytic treatment resulted in ~50% reduction in acute toxicity. Furthermore, we showed that by monitoring the expression levels of key proinflammatory genes using qPCR that treated OSPW significantly reduced the ability of raw OSPW to activate the inflammatory response of immune cells. This indicates that at acute sub-lethal exposure doses, photocatalytic treatment also reduces immunotoxicity. Overall, our results suggest that the ZnO-based photocatalytic degradation of these NAs and PAHs in OSPW could be a significant treatment process aimed at detoxifying OSPW.

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

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

Immunotoxicity induced by Ivermectin is associated with NF-κB signaling pathway on macrophages

Ivermectin (IVM) has been widely used as a highly effective and broad-spectrum biopesticide in animal husbandry and agriculture. Considering the frequent environmental and occupational exposure, the various toxic effects caused by IVM should be paid more attention. The immune system is a common target of toxins due to its complexity and sensitivity. The toxicity effect of the immune system may lead to increased susceptibility to infections, with potentially fatal consequences. The immunotoxicity of IVM has received little attention, which poses a challenge to the systematic assessment of safety risks. The purpose of this study was to assess the immunotoxicity of the IVM using in vitro cellular assays. We proved that IVM could inhibit the cell viability, induce DNA damage and enhance apoptosis. In addition to the induction of cytotoxicity, IVM has also been shown to reduce the phagocytic capacity and significantly increase the mRNA expression levels of proinflammatory cytokines IL-6, IL-1 β and TNF-α. Intracellular biochemical assay indicated that activation of the NF-κB signaling pathway, overproduction of reactive oxygen species (ROS), release of cytochrome C, DNA double strand damage. These results indicate that IVM can induce immunotoxicity through induction of immune dysfunction and cytotoxicity. In conclusion, this study supports that IVM can be immunotoxic to macrophages in different ways, and draw attention to the potential immunotoxicity of IVM.

ERK/p38/ROS burst responses to environmentally relevant concentrations of diphenyl phosphate-evoked neutrophil extracellular traps formation: Assessing the role of autophagy

Organophosphorus compounds were proposed to impair immune surveillance and increase the total burden of pathogens. However, scarce attention has been paid to the effects of organophosphate flame retardants (OPFRs) on neutrophils. Previous literature outlined that neutrophil extracellular traps (NETs) death (NETosis) is associated with autophagy-related signaling. Here we found that 20 μM diphenyl phosphate (DPHP) could promote NETs formation via assessing markers of NETs and the morphological changes. Concurrently, flow cytometry and western blot analysis revealed that DPHP-triggered NETs formation was associated with reactive oxygen species (ROS) burst and activation of extracellular signal-regulated kinase (ERK) and p38. Additionally, the results revealed that autophagy occurred in DPHP-triggered NETs formation, manifested as enhanced LC3B protein expressions and reduced p62 protein expressions. Mechanism dissection revealed that inhibition of autophagy by 3-methyladenine (3-MA) alleviated the ROS burst and subsequent NETosis caused by DPHP. Conversely, autophagy enhancer Rapamycin (Rapa) augmented the above effects of DPHP, including the generation of ROS and NETosis. Collectively, these data suggested ERK/p38 signaling and ROS burst might be an important cause of DPHP-triggered NETs formation, while suppression of excessive autophagy could rescue these actions. These observations provided a theoretical basis for the treatment and prevention of OPFRs-induced immunotoxicity.

Establishment of baseline cytology metrics in nestling American kestrels (Falco sparverius): Immunomodulatory effects of the flame retardant isopropylated triarylphosphate isomers

Avian populations must mount effective immune responses upon exposure to environmental stressors such as avian influenza and xenobiotics. Although multiple immune assays have been tested and applied to various avian species, antibody-mediated immune responses in non-model avian species are not commonly reported due to the lack of commercially available species-specific antibodies. The objectives of the present study were to advance methods for studying wild bird immune responses and to apply these to the evaluation of cytological responses after exposure of American kestrels, Falco sparverius, to a commercial flame retardant mixture containing isopropylated triarylphosphate isomers (ITP). Hatchlings were gavaged daily with safflower oil or 1.5 ug/g bw/day of ITP suspended in safflower oil, then bled on days 9, 17, and 21. The ITP treatment group (n = 18) and a subset of controls (Poly I:C treatment group; n = 10) were injected on days 9 and 15 with a synthetic analog of viral double-stranded RNA, polyinosinic:polycytidylic acid (Poly I:C), a toll-like receptor ligand and synthetic viral mimic, and responses compared to a sham injected control group (n = 8). The hypotheses tested whether kestrels showed immunological differences among treatment groups, genetic sex, and/or white blood cell (WBC) subpopulation type over time. A flow cytometry (FCM) gating strategy categorized heterophils (H), lymphocytes (L), and monocytes (M) and their proportions, and measured relative fluorescence in response to anti-chicken CD4 binding. Fluorescent cell surfaces and some granular/vacuolar inclusions were visualized by epifluorescence microscopy. A fourth subpopulation with higher levels of granularity than M but less than H became increasingly apparent with time and was gated along with the H subpopulation; its frequency of occurrence was lowest in the ITP group (P = 0.0023). The percentages of cells differed among treatment groups, days, and sexes (P = 0.0001). For both sexes, percentages of H and L were higher than M in control and Poly I:C. In the ITP group, L percentages were higher than H and M (P = 0.0457), and H and L were higher than M on days 9 and 21 (P = 0.0001). The ratios of H:L and H:WBC, indicators of robust immunity, were also higher on days 9 and 21 than on 17 (P = 0.0079). For each sex, the highest levels of activity measured by FCM geometric means (GEO) of fluorescence (indicative of antibody binding) were observed on day 9 (P = 0.0001 female, and P = 0.0011 male) in H over both L and M (P < 0.0001 for each). In males, GEO of the Poly I:C group was higher than that of the ITP group (P = 0.0374), with no difference observed among females over all days. By using a FCM algorithm for population comparisons of fluorescence to investigate binding within H, the T(x) scores indicated higher fluorescence in control and Poly I:C groups over ITP (P = 0.0001). Unlike chickens, Gallus gallus, which express CD4 primarily on L, kestrels bound the commercial antibody primarily within the gated H subpopulation, suggesting an immunophenotypic difference between taxa, despite a ~60% identity of Falco CD4 amino acid sequences with chicken CD4. The emergent cell subset within the gated H presented dendritic-like cell (DLC) morphological and functional properties, apparently serving as an effector cell. This study adds interpretive context to ecological investigations of infection and of potential immunomodulation by emerging compounds, whereby the early innate responses are mediated by the various cell subsets serving as useful quantitative markers of immunological condition. Data showed that dietary exposure to ITP was immunosuppressive for male and female kestrels over the course of the experiment, reducing DLC frequency compared to the Poly I:C controls. Heterophils and DLC were important in facilitating innate immunological responses.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)-induced suppression of immunity in THP-1-derived macrophages and the possible mechanisms

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a well-known immunotoxic environmental pollutant. However, most immunotoxicology studies of TCDD were based on the animal models and the inner mechanisms have just focused on a few genes/proteins. In this study, the immune functions of THP-1-derived macrophages was measured with in-vitro bioassays after 24-h exposure of TCDD including environmentally relevant concentrations. RNA-seq and Weighted Gene Co-expression Network Analysis were used to characterize the immunotoxicity molecular mechanisms. Our study is the first report on the TCDD-induced effects of cell adhesion, morphology, and multiple cytokines/chemokines production on THP-1 macrophages. After TCDD treatment, we observed an inhibited cell adherence, probably attributed to the suppressed mRNA levels of adhesion molecules ICAM-1, VCAM-1 and CD11b, and a decrease in cell pseudopodia and expression of F-actin. The inflammatory cytokines TNF-α, IL-10 and other 8 cytokines/chemokines regulating granulocytes/T cells and angiogenesis were disrupted by TCDD. Alternative splicing event was found to be a sensitive target for TCDD. Using WGCNA, we identified 10 hub genes (TNF, SRC, FGF2, PTGS2, CDH2, GNG11, BDNF, WNT5A, CXCR5 and RUNX2) highly relevant to these observed phenotypes, suggesting AhR less important in the effects TCDD have on THP-1 macrophages than in other cells. Our findings broaden the understanding of TCDD immunotoxicity on macrophages and provide new potential targets for clarifying the molecular mechanisms.

Proteomic analysis using isobaric tags for relative and absolute quantification technology reveals mechanisms of toxic effects of tris (1,3-dichloro-2-propyl) phosphate on RAW264.7 macrophage cells

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is one of the most commonly used organophosphorus flame retardants. Immuno-toxicity induced by TDCIPP is becoming of increasing concern. However, effects of TDCIPP on immune cells and mechanisms resulting in those effects are poorly understood. In this study, it was determined, for the first time, by use of isobaric tags for relative and absolute quantification (iTRAQ) based proteomic techniques expression of global proteins in RAW264.7 cells exposed to 10 μM TDCIPP. A total of 180 significantly differentially expressed proteins (DEPs) were identified. Of these, 127 were up-regulated and 53 were down-regulated. The DEPs associated with toxic effects of TDCIPP were then screened by use of Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes for enrichment analysis. Results showed that these DEPs were involved in a number of pathways including apoptosis, DNA damage, cell cycle arrest, immune-toxicity, and signaling pathways, such as the Toll-like receptor, PPAR and p53 signaling pathways. The complex regulatory relationships between different DEPs, which might play an important role in cell death were also observed in the form of a protein-protein interaction network. Meanwhile, mitochondrial membrane potential (MMP) in RAW264.7 cells after TDCIPP treatment was also analyzed, the collapse of the MMP was speculated to play an important role in TDCIPP induced apoptosis. Moreover, some of the important regulator proteins discovered in this study, such as Chk1, Aurora A, would provide novel insight into the molecular mechanisms involved in toxic responses to TDCIPP.

Flame Retardants-Mediated Interferon Signaling in the Pathogenesis of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a growing concern worldwide, affecting 25% of the global population. NAFLD is a multifactorial disease with a broad spectrum of pathology includes steatosis, which gradually progresses to a more severe condition such as nonalcoholic steatohepatitis (NASH), fibrosis, cirrhosis, and eventually leads to hepatic cancer. Several risk factors, including exposure to environmental toxicants, are involved in the development and progression of NAFLD. Environmental factors may promote the development and progression of NAFLD by various biological alterations, including mitochondrial dysfunction, reactive oxygen species production, nuclear receptors dysregulation, and interference in inflammatory and immune-mediated signaling. Moreover, environmental contaminants can influence immune responses by impairing the immune system’s components and, ultimately, disease susceptibility. Flame retardants (FRs) are anthropogenic chemicals or mixtures that are being used to inhibit or delay the spread of fire. FRs have been employed in several household and outdoor products; therefore, human exposure is unavoidable. In this review, we summarized the potential mechanisms of FRs-associated immune and inflammatory signaling and their possible contribution to the development and progression of NAFLD, with an emphasis on FRs-mediated interferon signaling. Knowledge gaps are identified, and emerging pharmacotherapeutic molecules targeting the immune and inflammatory signaling for NAFLD are also discussed.

In vitro metabolic kinetics of cresyl diphenyl phosphate (CDP) in liver microsomes of crucian carp (Carassius carassius)

Cresyl diphenyl phosphate (CDP), as a kind of aryl substituted organophosphate esters (OPEs), is commonly used as emerging flame retardants and plasticizers detected in environmental media. Due to the accumulation of CDP in organisms, it is very important to discover the toxicological mechanism and metabolic process of CDP. Hence, liver microsomes of crucian carps (Carassius carassius) were prepared for in vitro metabolism kinetics assay to estimate metabolism rates of CDP. After 140 min incubation, the depletion of CDP accounted for 58.1%-77.1% (expect 0.5 and 2 μM) of the administrated concentrations. The depletion rates were best fitted to the Michaelis-Menten model (R² = 0.995), where maximum velocity (V_max) and Michaelis-Menten constant (K_m) were 12,700 ± 2120 pmol min^-1·mg^-1 protein and 1030 ± 212 μM, respectively. Moreover, the in vitro hepatic clearance (C_Lint) of CDP was 12.3 μL min^-1·mg^-1 protein. Log K_ow and bioconcentration factor (BCF) of aryl-OPEs were both higher than those of alkyl- and chlorinated-OPEs, indicating that CDP may easily accumulate in aquatic organisms. The results made clear that the metabolism rate of CDP was greater than those of other OPEs detected in liver microsomes in previous research. This paper was first of its kind to comprehensively investigate the in vitro metabolic kinetics of CDP in fish liver microsomes. The present study might provide useful information to understand the environmental fate and metabolic processes of these kinds of substances, and also provide a theoretical basis for the ecological risk assessment of emerging contaminants.

Immunotoxic role of organophosphates: An unseen risk escalating SARS-CoV-2 pathogenicity

Consistent gathering of immunotoxic substances on earth is a serious global issue affecting people under pathogenic stress. Organophosphates are among such hazardous compounds that are ubiquitous in nature. They fuel oxidative stress to impair antiviral immune response in living entities. Aside, organophosphates promote cytokine burst and pyroptosis in broncho-alveolar chambers leading to severe respiratory ailments. At present, we witness COVID-19 outbreak caused by SARS-CoV-2. Infection triggers cytokine storm coupled with inflammatory manifestations and pulmonary disorders in patients. Since organophosphate-exposure promotes necroinflammation and respiratory troubles hence during current pandemic situation, additional exposure to such chemicals can exacerbate inflammatory outcome and pulmonary maladies in patients, or pre-exposure to organophosphates might turn-out to be a risk factor for compromised immunity. Fortunately, antioxidants alleviate organophosphate-induced immunosuppression and hence under co-exposure circumstances, dietary intake of antioxidants would be beneficial to boost immunity against SARS-CoV-2 infection.

Effects of an Environmentally Relevant Mixture of Organophosphate Esters Derived From House Dust on Endochondral Ossification in Murine Limb Bud Cultures

Organophosphate esters (OPEs) are used widely as flame retardants and plasticizers but much remains unknown about their potential toxicity. Previously, we reported that 4 individual OPEs suppress endochondral ossification in murine limb bud cultures. However, real-life exposure is to complex OPE mixtures. In the present study, we tested the hypothesis that a Canadian household dust-based OPE mixture will affect endochondral ossification in gestation day 13 CD1 mouse embryo limb buds expressing fluorescent markers for the major cell populations involved in the process: collagen type II alpha 1-enhanced cyan fluorescent protein (proliferative chondrocytes), collagen type X alpha 1-mCherry (hypertrophic chondrocytes), and collagen type I alpha 1-yellow fluorescent protein (osteoblasts). Limbs were cultured for 6 days in the presence of vehicle or dilutions of the OPE mixture (1/1 000 000, 1/600 000, and 1/300 000). All 3 OPE mixture dilutions affected cartilage template development and the progression of endochondral ossification, as indicated by the fluorescent markers. The expression of Sox9, the master regulator of chondrogenesis, was unchanged, but the expression of Runx2 and Sp7, which drive chondrocyte hypertrophy and osteoblastogenesis, was dilution-dependently suppressed. RNA-seq revealed that exposure to the 1/300 000 dilution of the OPE mixture for 24 h downregulated 153 transcripts and upregulated 48 others by at least 1.5-fold. Downregulated transcripts were enriched for those related to the immune system and bone formation. In contrast, upregulated transcripts were enriched for those with stress response functions known to be regulated by ATF4 activation. Thus, exposure to the mixture of OPEs commonly found in house dust may have adverse effects on bone formation.

A highly selective and recyclable sensor for the electroanalysis of phosphothioate pesticides using silver-doped ZnO nanorods arrays

Silver-doped ZnO nanorods (Ag/ZnO) arrays have in-situ grown onto indium tin oxide (ITO) via the one-pot hydrothermal route towards a highly selective and recyclable electroanalysis of phosphothioate pesticides (PTs) with phoxim (Phox) as a model. It was discovered that the Ag/ZnO arrays-modified electrode could obtain a steady and sharp electrochemical output of solid-state Ag/AgCl at a low potential (i.e., 0.12 V). More importantly, the achieved Ag/AgCl signals could decrease selectively induced by sulfide (S)-containing Phox by the specific Cl-S displacement reaction, which would trigger AgCl into non-electroactive Ag-Phox complex. The Ag/ZnO arrays-modified sensors present a linear range from 0.050 to 700.0 μM for the detection of Phox, with a limit of detection down to 0.010 μM. The practical applicability of the developed electroanalysis strategy was successfully employed to detect Phox in the tap water and cabbage samples. Moreover, the photocatalytic performances of the Ag/ZnO arrays were subsequently verified for the degradation of Phox, displaying the higher photocatalytic efficiency than pure ZnO nanorods. Besides, the as-developed sensor can allow for the recyclable detection of Phox by the Ag/ZnO-photocatalyzed removal of Phox after each of the detection cycles. Therefore, the sensors platform based on Ag/ZnO arrays can be expected to have potential for the electrochemical monitoring and photocatalytic degradation of toxic pesticides in the food and environmental fields.