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

Developmental toxicity and skin sensitization potential of synthetic phenolic antioxidants and butylated hydroxytoluene transformation products: Insights from human embryonic stem cell models

Synthetic phenolic antioxidants (SPAs) are commonly used in food, cosmetics, and other products for their antioxidant properties and stability. However, increasing evidence links excessive SPA use to adverse effects, including developmental issues in animals. Given the widespread use of SPAs in cosmetics, there is a growing need to assess their potential health risks, particularly whether safe to be used during pregnancy. This study investigates the early developmental toxicity of SPAs using a human embryonic stem cell (hESC) monolayer differentiation model. Results show that SPAs and butylated hydroxytoluene transformation products (BHT-TPs) up-regulated neural ectoderm and neural crest genes while down-regulated surface ectoderm and primitive streak genes during differentiation. Furthermore, in a skin-specific differentiation model, SPAs and BHT-TPs disrupted keratinocyte differentiation, inhibiting the differentiation of keratinocyte progenitors into more mature keratinocytes. They also led to the up-regulation of genes associated with psoriasis, pro-inflammatory cytokines, and chemokines, suggesting the potential of SPAs to act as skin sensitizers. These findings suggest that SPAs may affect early embryonic development at an early germ layer specification stage, as well as during skin development, potentially increasing skin sensitivity. Thus, excessive SPA use in cosmetics could pose risks to fetal development and adult skin health.

Consumer products are important reservoirs and sources of organophosphate tri-esters and di-esters: Characteristics, mass inventory, and implication for waste management

Numerous studies documented the occurrence of organophosphate tri-esters (tri-OPEs) and di-esters (di-OPEs) in the environment. Little information is available on their occurrence in waste consumer products, reservoirs and sources of these chemicals. This study collected and analyzed 92 waste consumer products manufactured from diverse polymers, including polyurethane foam (PUF), polystyrene (PS), acrylonitrile butadiene styrene (ABS), polypropylene (PP), and polyethylene (PE) to obtain information on the occurrence and profiles of 16 tri-OPEs and 10 di-OPEs. Total concentrations of di-OPEs (18-370,000 ng/ g, median 1,700 ng/g) were one order of magnitude lower than those of tri-OPEs (94-4,500,000 ng/g, median 5,400 ng/g). The concentrations of both tri- and di-OPEs in products made of PUF, PS, and ABS were orders of magnitude higher than those made of PP and PE. The compositional patterns of OPEs varied among different polymer types but were generally dominated by bisphenol A bis(diphenyl phosphate), triphenyl phosphate, tris(1-chloro-2-propyl) phosphate, di-phenyl phosphate (DPHP), and bis (2-ethylhexyl) phosphate. Two industrially applied di-OPEs (di-n-butyl phosphate and DPHP) exhibited higher levels than their respective tri-OPEs, contrary to their production volumes. Some non-industrially applied chlorinated di-OPEs were also detected, with concentrations up to 97,000 ng/g. These findings suggest that degradation of tri-OPEs during the manufacturing and use of products is an important source of di-OPEs. The mass inventories of tri-OPEs and di-OPEs in consumer products were estimated at 3,100 and 750 tons/year, respectively. This study highlights the importance of consumer products as emission sources of a broad suite of OPEs.

TDCPP promotes apoptosis and inhibits the calcium signaling pathway in human neural stem cells

Tris (1, 3-dichloro-2-propyl) phosphate (TDCPP) is an extensively used organophosphorus flame retardant (OFR). Previous studies have suggested that it has neurotoxic effects, but the neurotoxicity mechanism is still unclear. Neural stem cells are an important in vitro model for studying the neurotoxicity mechanism of pollutants. In this study, we investigated the neurotoxic effects and molecular mechanisms of TDCPP by using human induced pluripotent stem cells (hiPSCs)-derived neural stem cells. We found that TDCPP inhibited the viability of human neural stem cells (hNSCs), stimulated the generation of ROS, arrested the cell cycle in the S phase, and promoted apoptosis. A total of 387 differentially expressed genes were screened out by transcriptome sequencing analysis, and KEGG enrichment analysis showed that the "calcium signaling pathway" was the most significantly enriched. Further studies on the calcium signaling pathway showed that TDCPP disrupted intracellular calcium homeostasis and inhibited the activation of the Ca2+/CALM/CaN/CAMK signaling pathway and the expression levels of NFATC2 and GSK3β. In conclusion, TDCPP has significant toxicity on the calcium signaling pathway of human neural stem cells, which may affect the development process of the human nervous system.

Sex steroid hormones mediate the association between neonicotinoids and obesity among children and adolescents

BACKGROUND

Neonicotinoids are the most widely used insecticide worldwide. Toxicological and epidemiological studies suggest that exposure to neonicotinoid may be linked to the development of childhood obesity. However, the evidence is limited.

OBJECTIVE

To investigate the association between neonicotinoid exposure and obesity among U.S. children and adolescents and to explore underlying mechanism mediated by serum sex steroid hormones in these associations.

METHODS

Data from the 2015-2016 National Health and Nutrition Examination Survey were used for the analysis. Generalized linear regression was used to investigate the association between detectable neonicotinoids and ten measures of obesity. The interaction effects of multiple neonicotinoids were determined by Chi-squared Automatic Interaction Detection method. Mediation analysis was used to assess potential mediators of sex steroid hormones, including testosterone (T), estradiol (E2), T/E2, sex hormone-binding globulin (SHBG), and free androgen index (FAI).

RESULTS

Clothianidin (β = -0.29, 95 % CI: -0.57, -0.01) and N-desmethyl-acetamiprid (β = -0.19, 95 % CI: -0.35, -0.03) were associated with reduced VFI z-score. After stratification, 5-hydroxy-imidacloprid was positively associated with the risk of general obesity in males (OR=2.24, 95 % CI: 1.20, 4.20) with a probability of 52.5 %. FAI mediated 15 % of the association between neonicotinoid exposure and reduced risk of obesity, and SHBG mediated 30 % of the association between neonicotinoid exposure and increased risk of obesity.

CONCLUSION

Neonicotinoids showed associations with obesity, but the results were mixed and sex-specific. Sex steroid hormones may play a role in mediating the effects of neonicotinoids on obesity.

Development of a TBXT-EGFP iPS cell model for screening the early developmental toxicity of typical environmental pollutants

In our daily lives, we are inevitably exposed to a variety of environmental pollutants in numerous ways. Fortunately, recent years have witnessed significant advancements in the field of stem cell toxicology, which have provided new opportunities for research in environmental toxicology. Applying stem cell technology to environmental toxicology, overcomes some of the limitations of traditional screening methods and we can more accurately predict the toxicity of environmental pollutants. However, there are still several aspects of stem cell toxicology models that require improvement, such as increasing the throughput of detection and simplifying detection methods. Consequently, we developed an environmental pollutant toxicity detection model based on TBXT-EGFP iPS cells and screened the developmental toxicity of 38 typical environmental pollutants. Our results indicate that TBBPA-BDBPE, TBBPA-BHEE, DG, and AO2246 may interfere with the expression of TBXT, a critical marker gene for early human embryo development, implying that these environmental pollutants could lead to developmental abnormalities.

Neonicotinoid residues in fruits and vegetables in Shenzhen: Assessing human exposure and health risks

The extensive use of neonicotinoids (NEOs) in agricultural production has led to their pervasive presence in various environmental matrices, including human samples. Given the central role of fruits and vegetables in daily human diets, it is crucial to evaluate the levels of NEOs residues and their potential health risks. In this study, 3104 vegetable samples and 1567 fruit samples from the Shenzhen city were analyzed. Using the relative potency factor (RPF) method, the residue levels of six representative neonicotinoids, including imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (THM), dinotefuran (DIN), clothianidin (CLO), thiacloprid (THI), were systematically evaluated. The estimated daily intake (EDI), hazard quotient (HQ), and hazard index (HI) for both children and adults were calculated to gauge the prevalence and potential health risks of NEOs in fruits and vegetables. Acetamiprid (ACE) was the most frequently detected NEO in vegetables (69.4%) and fruits (73.9%), making it the predominant contributor to total residues. Further analyses indicated notably higher levels of imidacloprid-equivalent total neonicotinoids (IMIRPF) in root and tuber vegetables (3025 μg/kg) and other fruits (243 μg/kg). A significant strong positive correlation (r = 0.748, P < 0.05) was observed between thiamethoxam (THM) and clothianidin (CLO), possibly due to their shared metabolic pathways. Although the mean HI values for adults and children from daily fruit (adults: 0.02, children: 0.01) and vegetable (adults: 0.02, children: 0.03) intake were generally below safety thresholds, some maximum HI values exceeded these limits, indicating that the potential health risks associated with NEOs exposure should not be overlooked.

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

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

Human health risk assessment associated with the reuse of treated wastewater in arid areas

Qatar produces more than 850,000 m3/day of highly treated wastewater. The present study aims at characterizing the effluents coming out of three central wastewater treatment plants (WWTPs) of chemical pollutants including metals, metalloids and antibiotics commonly used in the country. Additionally, the study is assessing human health risks associated with the exposure to the treated wastewater (TWW) via dermal and ingestion routes. Although the origin of domestic wastewater is desalinated water (the only source of fresh water), the results show that the targeted parameters in TWW were within the international standards. Concentrations of Cl, F, Br, NO3, NO2, SO4 and PO4, were 389, <0.1, 1.2, 25, <0.1, 346, and 2.8 mg/L, respectively. On the other hand, among all cations, metals and metalloids, only boron (B) was 2.1 mg/L which is higher than the Qatari guidelines for TWW reuse in irrigation of 1.5 mg/L. Additionally, strontium (Sr) and thallium (Tl) were detected with relatively high concentrations of 30 mg/L and 12.5 μg/L, respectively, due to their natural and anthropogenic sources. The study found that the low concentrations of all tested metals and metalloids do not pose any risk to human health. However, Tl presents exposure levels above the 10 % of oral reference dose (HQ = 0.4) for accidental oral ingestion of TWW. The results for antibiotics show that exposure for adults and children to TWW are far below the admissible daily intakes set using minimum therapeutic dose and considering uncertainty factors. Treated wastewater of Qatar can be used safely for irrigation. However, further investigations are still needed to assess microbiological quality.

Typical neonicotinoids and organophosphate esters, but not their metabolites, adversely impact early human development by activating BMP4 signaling

Recent studies have highlighted the presence of potentially harmful chemicals, such as neonicotinoids (NEOs) and organophosphate esters (OPEs), in everyday items. Despite their potential threats to human health, these dangers are often overlooked. In a previous study, we discovered that NEOs and OPEs can negatively impact development, but liver metabolism can help mitigate their harmful effects. In our current research, our objective was to investigate the toxicity mechanisms associated with NEOs, OPEs, and their liver metabolites using a human embryonic stem cell-based differentiation model that mimics early embryonic development. Our transcriptomics data revealed that NEOs and OPEs significantly influenced the expression of hundreds of genes, disrupted around 100 biological processes, and affected two signaling pathways. Notably, the BMP4 signaling pathway emerged as a key player in the disruption caused by exposure to these pollutants. Both NEOs and OPEs activated BMP4 signaling, potentially impacting early embryonic development. Interestingly, we observed that treatment with a human liver S9 fraction, which mimics liver metabolism, effectively reduced the toxic effects of these pollutants. Most importantly, it reversed the adverse effects dependent on the BMP4 pathway. These findings suggest that normal liver function plays a crucial role in detoxifying environmental pollutants and provides valuable experimental insights for addressing this issue.

Organophosphate esters in the urban atmosphere of Thessaloniki city, Greece

The occurrence of organophosphate esters (OPEs) in the atmosphere of the urban area of Thessaloniki city, Greece was studied. OPEs were determined in particulate matter (PM2.5) and precipitation during the period 2020-2021. ∑OPEs in rainwater ranged from 520 to 4719 ng L-11 (mean: 1662 ng L-1) with tris (2-butoxyethyl) phosphate (TBOEP) and tris (1-chloro-2-propyl) phosphate (TClPP) being the most abundant compounds. TBOEP and TClPP as well as triphenylphosphine oxide (TPPO) and tris (chloroethyl) phosphate (TCEP) were the dominant OPEs in PM2.5. Concentrations of ∑OPEs in PM2.5ranged from 2.82 to 13.3 ng m-3 (mean: 5.93 ng m-3). Wet deposition fluxes of OPEs were estimated and air mass back trajectories were used to elucidate possible source profiles. An overall low health risk for local population via inhalation of OPEs was revealed.

Long-lasting developmental effects in rat offspring after maternal exposure to acetamiprid in the drinking water during gestation

Neonicotinoids (NNTs) are a class of insecticides proposed to be safe for pest control in urban, suburban, and agricultural applications. However, little is known about their developmental effects after repeated low-dose exposures during gestation. Here, we tested a dose considered subthreshold for maternal toxicity in rats (6 mg/kg/day) by assessing several morphological, biochemical, and neurobehavioral features in preterm fetuses and developing pups after maternal administration of the NTT acetamiprid (ACP) dissolved in the drinking water during gestational days (GD) 2-19. The exploratory evaluation included monitoring maternal body weight gain, fetal viability, body weight and sex ratio, cephalic length, neonatal body weight and sex ratio, metabolic enzymes in the placenta, maternal blood and fetal liver, and anogenital distance and surface righting response during infancy. We also used the circling training test to study the integrity of the associative-spatial-motor response in adolescence. Results showed no consistent findings indicating maternal, reproductive or developmental toxicity. However, we found ACP effects on maternal body weight gain, placental butyrylcholinesterase activity, and neurobehavioral responses, suggestive of a mild toxic action. Thus, our study showed a trend for developmental susceptibility at a dose so far considered subtoxic. Although the ACP concentration in environmental samples of surface water and groundwater has been mostly reported to be much lower than that used in our study, our results suggest that the ACP point of departure used in current guidelines aimed to prevent developmental effects may need to be verified by complementary sensitive multiple-endpoint testing in the offspring.