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

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

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

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.

Cresyl Diphenyl Phosphate exposure induces reproductive functional defects in men and male mice

Cresyl Diphenyl Phosphate (CDP), as a novel organophosphate esters (OPEs), achieves widely used and exposed in multiple industries. However, its male reproductive toxicity and underlying mechanism remains unclear. In vivo, male mice were gavaged with CDP (0, 4, 20, or 100 mg/kg/d) for 8 weeks. And we treated TM3, TM4 and GC-2 cells with 0, 10, 25, and 50 μM CDP for 24 h to detect its reproductive toxicity effect in vitro. In our study, we revealed that CDP inhibited proliferation and induced apoptosis in mice testis and GC-2 cells, thereby leading to the decreased sperm quality. In mechanism, CDP trigger the oxidative stress and ROS production, thus partially causing DNA damage and cell apoptosis. Moreover, CDP exposure causes injury to Ledyig cells and Sertoli cells, thus disturbing the testicular microenvironment and inhibiting spermatogonia proliferation. In conclusion, this research reveals multiple adverse impacts of CDP on the male reproductive system and calls for further study of the toxicological effects of CDP on human health.

Organophosphate esters (OPEs) and novel brominated flame retardants (NBFRs) in indoor dust: A systematic review on concentration, spatial distribution, sources, and human exposure

In recent years, the indoor exposure of organophosphate esters (OPEs) and novel brominated flame retardants (NBFRs) has received widespread attention worldwide. Using published data on 6 OPEs in 23 countries (n = 1437) and 2 NBFRs in 18 countries (n = 826) in indoor dust, this study systematically reviewed the concentrations, spatial distribution, sources and exposure risk of 8 flame retardants (FRs) worldwide. Tris(chloroisopropyl)phosphate (TCIPP) is the predominant FR with a median concentration of 1050 ng g-1 ΣCl-OPEs are significantly higher than Σnon-Cl-OPEs (p < 0.05). ΣOPEs in indoor dust from industrially-developed countries are higher than those from the countries lacking industrial development. Household appliances, electronics and plastic products are the main sources of non-Cl-OPEs and NBFRs, while interior decorations and materials contribute abundant Cl-OPEs in indoor dust. The mean hazard index (HI) of TCIPP for children is greater than 1, possibly posing non-cancer risk for children in some countries. The median ILCRs for 3 carcinogenic OPEs are all less than 10-6, suggesting no cancer risk induced by these compounds for both adults and children. This review helps to understand the composition, spatial pattern and human exposure risk of OPEs and NBFRs in indoor dust worldwide.

Probing the molecular mechanism of interaction between polystyrene nanoplastics and catalase by multispectroscopic techniques

Nanoplastics are emerging pollutants that pose a potential threat to the environment and organisms and are widely distributed in environmental samples and food chains. The accumulation of polystyrene nanoplastics (PS-NPs) in an organism can cause oxidative stress. Currently, toxicity studies of PS-NPs mainly focus on the individual and cellular levels, whereas few studies have been conducted on the molecular mechanisms of the interaction between PS-NPs and catalase (CAT). Based on this, CAT was chosen as the target receptor for molecular toxicity research to reveal the interaction mechanism at the molecular level between PS-NPs and CAT by using various spectroscopic means and enzyme activity detection methods. The results indicated that PS-NPs destroyed the secondary structure of CAT, causing its protein skeleton to loosen and unfold, increasing the content of α-helices, decreasing the content of β-sheets, and exposing the position of the heme group. After exposure to PS-NPs, the internal fluorophore of CAT underwent fluorescence sensitization, resulting in a micelle-like structure, which enhanced the hydrophobicity of aromatic amino acids but did not change their polarity. In addition, the aggregation state of CAT was altered upon binding to PS-NPs, and the volume was further increased. Finally, these structural changes led to a gradual decrease in CAT activity. This study presents a comprehensive assessment of the toxicity of PS-NPs at the molecular level, which can provide more experimental support for the study of the biotoxicological efficacy of PS-NPs.

The Organophosphate Esters Used as Flame Retardants and Plasticizers Affect H295R Adrenal Cell Phenotypes and Functions

Adverse effects associated with exposure to brominated flame retardants have led to regulations for their use and their replacement with organophosphate esters (OPEs). However, little is known about the impact of OPEs on the adrenal, a vital endocrine gland. Here, we used a high-content screening approach to elucidate the effects of OPEs on H295R human adrenal cell phenotypic endpoints and function. The effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), a legacy brominated flame retardant, on H295R cell cytotoxicity, oxidative stress, mitochondria, lysosomes, and lipid droplets were compared with those of 6 OPEs. Most OPEs reduced oxidative stress, increased the numbers of mitochondria, decreased lysosomes, and increased lipid droplets. Two potency ranking approaches, the lowest benchmark concentration/administered equivalent dose methods and Toxicological Prioritization Index analyses, revealed that the triaryl-OPEs (isopropylated triphenyl phosphate [IPPP], tris(methylphenyl) phosphate [TMPP], and triphenyl phosphate [TPHP]) and 1 nontriaryl OPE (tris(1,3-dichloro-2-propyl) phosphate [TDCIPP]) were more potent than BDE-47. The steroidogenic activity of adrenal cells in the presence or absence of forskolin, a steroidogenic stimulus, was determined after exposure to triaryl-OPEs. The basal production of cortisol and aldosterone was increased by IPPP but decreased by TPHP or TMPP exposure; the response to forskolin was not affected by these OPEs. All 3 triaryl OPEs altered the expression of rate-limiting enzymes involved in cholesterol and steroid biosynthesis; CYP11B1 and CYP11B2 were the most prominently affected targets. The OPE chemical-specific effects on cortisol and aldosterone production were best explained by alterations in STAR expression. Thus, the adrenal may be an important target for these endocrine-disrupting chemicals.

Replacement Flame-Retardant 2-Ethylhexyldiphenyl Phosphate (EHDPP) Disrupts Hepatic Lipidome: Evidence from Human 3D Hepatospheroid Cell Culture

The present study aims to evaluate the effects of repeated exposure to 2-ethylhexyldiphenyl phosphate (EHDPP) on human liver cells. In vitro three-dimensional (3D) hepatospheroid cell culture was utilized to explore the potential mechanisms of EHDPP-mediated metabolic disruption through morphological, transcriptional, and biochemical assays. Lipidomics analysis was performed on the individual hepatospheroids to investigate the effects on intracellular lipid profiles, followed by hepatospheroid morphology, growth, functional parameters, and cytotoxicity evaluation. The possible mechanisms were delineated using the gene-level analysis by assessing the expression of key genes encoding for hepatic lipid metabolism. We revealed that exposure to EHDPP at 1 and 10 μM for 7 days alters the lipid profile of human 3D hepatospheroids. Dysregulation in several lipid classes, including sterol lipids (cholesterol esters), sphingolipids (dihydroceramide, hexosylceramide, ceramide, sphingomyelin), glycerolipids (triglycerides), glycerophospholipids, and fatty acyls, was noted along with alteration in genes including ACAT1, ACAT2, CYP27A1, ABCA1, GPAT2, PNPLA2, PGC1α, and Nrf2. Our study brings a novel insight into the metabolic disrupting effects of EHDPP and demonstrates the utility of hepatospheroids as an in vitro cell culture model complemented with omics technology (e.g., lipidomics) for mechanistic toxicity studies.