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Oxidative stress is a unifying mechanism relating to the adverse effects induced by atmospheric particulate matter (PM). Owing to complex compositions, the role of PM constituents in triggering oxidative stress remains unclear. We employed synthetic particle suspensions with controlled sizes and compositions as PM surrogates to identify the key contributors to oxidative stress. The suspensions consisted of carbon black (CB) particles, polycyclic aromatic hydrocarbon adsorbed on CB, and dissolved metal ions. After the exposure of A549 or BEAS-2B cells to CB particles, the reactive oxygen species (ROS) level increased in a manner that was dependent on the size and concentration of the particles, in the order of 14 nm > 56 nm > 260 nm. Benzo[a]pyrene-coated CB also increased the ROS level, but not as much as the naked CB, and the benzo[a]pyrene-dione coating had no effect. The co-exposure of CB with one of the eight metal ions did not lead to any additional ROS increase. The results indicate that among the three major constituents, CB particles, and the small-sized ones in particular, contributed most to ROS generation. In mechanistic studies, damaged mitochondria cristae were observed, suggesting that mitochondria are one of the target organelles. Both naked and BaP-coated CB decreased the mitochondrial membrane potential and changed the mRNA expression of fusion/fission proteins. ROS inhibition experiments suggest that complex I of the mitochondria was involved, but complex III and the NADPH oxidase (NOX) system were not. It was thus postulated that small-sized particles could enter cells and disrupt the mitochondria, particularly complex I, leading to the elevated generation of ROS. Our work calls for more attention to be paid to the toxicity of the ultrafine fractions of PM.

In in vitro cell assays, nominal concentrations of a test chemical are most frequently used in the description of its dose-response curves. Although the biologically effective concentration (BEC) is considered as the most relevant dose metric, in practice, it is very difficult to measure. In this work, we attempted to determine the BEC of long-chain perfluoroalkyl carboxylic acids (PFCAs) in peroxisome proliferator-activated receptor γ (PPARγ) activity assays. In both adipogenesis and transcriptional activity assays with human and mouse cells, PPARγ activity of 7 PFCAs first increased and then decreased with their carbon chain length. The binding affinity of these PFCAs with the ligand-binding domain of PPARγ was measured by fluorescence competitive binding assay and showed very poor correlation with their receptor activity (r2 = 0.002-0.047). Internal concentrations of the PFCAs in the cells were measured by LC-MS/MS. Although their correlation with the receptor activity increased significantly, it is still low (r2 = 0.41-0.82). Using the binding affinity constant, internal concentration, and PPARγ concentration measured by immunoassays, concentrations of receptor-bound PFCAs in cells were calculated, which exhibited excellent correlation with PPARγ activity in both adipogenesis and transcriptional activity assays (r2 = 0.91-0.93). These results demonstrate that the concentration of receptor-bound PFCA is the BEC that dictates its activity on human and mouse PPARγ in cell assays. In the absence of any direct detection method, our approach can be used to calculate the target-site concentration of other ligands.

Despite many studies on the toxicity of nanoplastic particles (NPPs) to aquatic invertebrates, the effects of ecological constituents such as humic substances (HSs) are often neglected. In our study, Daphnia magna was used to evaluate the effects of three HSs, natural organic matter (NOM), fulvic acid (FA), and humic acid (HA), on NPP toxicity and corona formation. Acute toxicities of NPPs were reduced by all HSs at environmentally relevant concentrations. NPPs elicited the upregulation of all genes related to detoxification, oxidative stress, and endocrine activity after 7 days of exposure. The presence of NOM or HA resulted in the mitigation of gene expression, whereas significantly higher upregulation of all of the genes was observed with FA. The presence of FA led to increased protein adsorption on NPPs in D. magna culture medium (eco-corona, EC) and homogenates (protein corona, PC), while there was less adsorption in the presence of HA. The highly abundant proteins identified in EC are involved in immune defense, cell maintenance, and antipredator response, while those in PC are responsible for lipid transport, antioxidant effects, and estrogen mediation. Our findings revealed the key influence of HSs on the toxicity of NPPs and provide an analytical and conceptual foundation for future study.

The growing evidence of the microbiome's crucial role in human health and disease has prompted research on understanding the impacts of engineered nanomaterials (ENMs) on commensal microorganisms. Accordingly, the number of studies addressing the ENM effects on intestinal microbiota has been rapidly increasing over the past few years. The focus on the gut microbiota is justified due to established metabolic and immunological functions of gut microbes, however, respiratory tract and skin microbiota also play important roles in host health and immunity. Here we review the composition and functions of microbiota inhabiting the major human organs that are prone to ENM exposure – skin, respiratory and digestive tract. We discuss the mechanisms of ENM actions relevant to physiological conditions and microbiota, and describe recently developed in vitro models for elucidating the ENM impacts on the gut microbiota. We find that studies pertinent to the oxygen levels prevailing in the digestive tract, are still limited. Finally, we analyze the results of in vivo studies conducted in vertebrate models – zebrafish, mice and rats – exposed to ENMs via ingestion. The relative abundances of bacterial phyla indicate that ENMs have a potential to modulate intestinal microbiota and induce harmful or beneficial effects in the host. Future perspectives include identification of the factors driving ENM-caused dysbiosis and the ENM impacts on microbiota with deviated composition, e.g., under compromised health conditions. Understanding the interplay between ENMs and the human microbiota is crucial for the continued development of nanomedicine and protection of human health against accidental exposure to hazardous ENMs.

There has been long-standing evidence that the lower-chlorinated polychlorinated biphenyls (LC-PCBs) can be metabolized to hydroxylated metabolites (OH-PCBs), which play important roles in the LC-PCBs induced toxicity. Recently, multiple studies have demonstrated the further metabolic transformation of OH-PCBs to LC-PCB sulfates in vitro and in vivo. Several studies found LC-PCB sulfates could bind with thyroid hormone (TH) transport proteins in the serum, indicating the potential relevance of these metabolites in the TH system disruption effects. However, the interaction of LC-PCB sulfates with the TH nuclear receptor (TR), another kind of important functional protein in the TH system, has not been explored. Here, by using a fluorescence competitive binding assay, we demonstrated that LC-PCB sulfates could bind with TRα. Moreover, the LC-PCB sulfates had higher binding potency than their corresponding OH-PCB precursors. By using a luciferase reporter gene assay, we found the LC-PCB sulfates showed agonistic activity towards the TRα signaling pathway. Molecular docking simulation showed all the tested LC-PCB sulfates could fit into the ligand binding pocket of the TRα. The LC-PCB sulfates formed hydrogen bond interaction with arginine 228 residue of TRα by their sulfate groups, which might facilitate the TR binding and agonistic activity. The present study suggests that interaction with the TR might be another possible mechanism by which LC-PCB sulfate induce TH system disruption effects.

As alternatives to perfluorooctanoic acid (PFOA), hexafluoropropylene oxide (HFPO) homologues, including hexafluoropropylene oxide dimer acid (HFPO-DA), hexafluoropropylene oxide trimer acid (HFPO-TA), and hexafluoropropylene oxide tetramer acid (HFPO-TeA), have been used in the fluoropolymer industry for a long period of time. These compounds have attracted widespread attention in recent years due to their environmental ubiquity and high bioaccumulation capability, as well as their toxicity. In our study, we evaluated the potential estrogenic effects of HFPOs in comparison to PFOA by ligand binding, transcriptional activity, and in vivo assays. Fluorescence ligand binding assays showed that both HFPO-TA and HFPO-TeA exhibited higher binding affinity to estrogen receptor ligand binding domains (ER-LBDs) than PFOA, with 2.5- and 57.5-fold higher affinity to ERα-LBD and 2.6- and 41.8-fold higher affinity to ERβ-LBD, respectively, whereas HFPO-DA exhibited weaker binding affinity than PFOA. Unlike PFOA, HFPO-TA and HFPO-TeA exhibited antagonistic activity toward the ERs' signaling pathway, with HFPO-TeA displaying the strongest potency. In silico study revealed that while PFOA binds with ERs in a similar fashion as 17β-estradiol, the HFPOs display an antagonistic binding mode. Using a zebrafish model, we further found that exposure to HFPO homologues significantly altered the levels of sex steroid hormones and vitellogenin. In general, both in vivo and in vitro results indicate that HFPO homologues might exert higher estrogenic effects than PFOA.

Pentachlorophenol (PCP) caused water quality problems owe to its past widespread application and stability, harmful to human health. Photocatalysis, which was mainly involved in the reactive oxygen species (ROS) reaction, has large potential as water treatment process. However, the roles of ROS on the degradation process of PCP are not yet clearly defined. The main objectives of this work were to investigate the roles of ROS involved in the whole degradation of PCP and main toxic intermediates and elucidate the degradation mechanisms. Tetrachloro-1,4-benzo/hydroquinone (TCBQ/TCHQ), trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) and 2,5-dichloro-3,6-dihydroxy-1,4-benzoquinone (OH-DCBQ) were identified as main intermediates. The roles of generated ROS including OH, O2- and H2O2 were systematically explored for the degradation of PCP and its main intermediates using radical quenchers. The results showed that, OH played the dominant role for the degradation of PCP, O2- played more contributing roles for the degradation of TCBQ, H2O2 exhibited major contribution for the degradation of OH-TrCBQ and OH-DCBQ. These results offered us an insight into the degradation mechanism of PCP involved with ROS. It can also serve as the basis for controlling and blocking the generation of highly toxic substances through regulating the ROS generation during the PCP degradation.

Parabens are one of the most widely used preservatives in food, pharmaceuticals and personal care products (PCPs) because of their advantageous properties and low toxicity based on the early assessments. However, recent research indicates that parabens may act as endocrine-disrupting chemicals (EDCs) and thus, are considered as chemicals of emerging concern that have adverse human health effects. To provide the basis for future human health studies, we reviewed relevant literature, published between 2005 and 2020, regarding the levels of parabens in the consumer products (pharmaceuticals, PCPs and food), environmental matrices and humans, including susceptible populations, such as pregnant women and children. The analysis showed that paraben detection rates in consumer products, environmental compartments and human populations are high, while the levels vary greatly by country and paraben type. The concentrations of parabens reported in pregnant women (~20–120 μg/L) were an order of magnitude higher than in the general population. Paraben concentrations in food and pharmaceuticals were at the ng/g level, while the levels in PCPs reached mg/g levels. Environmental concentrations ranged from ng/L–μg/L in surface waters to tens of μg/g in wastewater and indoor dust. The levels of human exposure to parabens appear to be higher in the U.S. and EU countries than in China and India, which may change with the increasing production of parabens in the latter countries. The review provides context for future studies to connect paraben exposure levels with human health effects.

Many environmental chemicals have been found to exert estrogenic effects in cells and experimental animals by activating nuclear receptors such as estrogen receptors and estrogen-related receptors. These compounds include bisphenols, pesticides, polybrominated diphenyl ethers (PBDEs), organophosphate flame retardants, phthalates and metalloestrogens. G protein-coupled estrogen receptor (GPER) exists widely in numerous cells/tissues of human and other vertebrates. A number of studies have demonstrated that GPER plays a vital role in mediating the estrogenic effects of environmental pollutants. Even at very low concentrations, these chemicals may activate GPER pathways, thus affect many aspects of cellular functions including proliferation, metastasis and apoptosis, resulting in cancer progression, cardiovascular disorders, and reproductive dysfunction. This review summarized the environmental occurrence and human exposure levels of these pollutants, and integrated current experimental evidence toward revealing the underlying mechanisms of pollutant-induced cellular dysfunction via GPER. The GPER mediated rapid non-genomic actions play an important role in the process leading to the adverse effects observed in experimental animals and even in human beings.

Interfacial interactions between TiO2 nanocrystals and the surrounding environmental media play a critical role in dictating their environmental behaviors. Here two specific-faceted TiO2 crystals, {101} facet and {001} facet, were adopted to investigate facet-mediated aggregation kinetics in aquatic environments. In pristine electrolyte solution (NaCl and CaCl2), {001} TiO2 exhibited higher stability than {101} TiO2 due to the abundant –OH groups on the {001} facet surface. The presence of Suwannee river humic acid (SRHA) significantly improved the stability of TiO2 nanocrystals in a facet dependent manner, in which {101} TiO2 exhibited a more remarkable improvement in stability than {001} TiO2. At a high SRHA concentration (10 mg L−1), both faceted TiO2 displayed comparable stability. The adsorption experiments and attenuated total reflectance Fourier transformation infrared spectroscopy demonstrated that {101} TiO2 induced more pronounced adsorption of SRHA molecules than {001} TiO2, probably driven by the efficient bidentate coordination of –COO– groups in SRHA on the {101} facet. This facet-affected colloidal stability behavior would deepen our understanding on nanomaterial transport and exposure in natural waters.

With worldwide environmental accumulation of plastics and their recognized degradation into smaller particles, attention to their impacts on ecological systems and humans has been increasing recently. However, environmental factors and their impacts are seldom considered during their eco-toxicity evaluation. In this study, D. magna neonates were used to assess and compare the acute toxicities of polystyrene microplastic particles (MPPs) and nanoplastic particles (NPPs) in the absence and presence of humic acids (HAs), an important environmental factor in aquatic systems. Four stress response and detoxification genes (CAT, GST, HSP70, and P-GP) were used to characterize the toxic response of the neonates to the exposure. Our results showed that NPPs were much more toxic than MPPs in that 10 mg L−1 NPPs induced over 70% of death in 96 h but MPPs (as high as 400 mg L−1) caused no mortality under all tested conditions. More importantly, we revealed a potent protective role of HA against NPP toxicity at environmentally relevant concentrations. The effect was concentration dependent, as 50 mg L−1 HA subdued the NPP (400 mg L−1) toxicity effect completely. NPPs elicited the up-regulation of all examined genes while HA diminished the change appreciably, further confirming its detoxifying role against NPP toxicity. Through fluorescence and dynamic light scattering measurements, we found that HA was adsorbed on NPPs and formed a corona, without causing agglomeration or precipitation, but changed NPP distribution in the D. magna neonates in a way similar to that of MPPs, leading to alleviated toxicity. Our results suggest that it is essential to consider environmental factors in evaluating and monitoring NPP toxicity as this presents a more relevant exposure state.

Chlorinated polyfluoroalkylether sulfonates (Cl-PFAESs) have been used as perfluorooctanesulfonate (PFOS) alternatives in the chrome plating industry for years. Although Cl-PFAESs have become ubiquitous environmental contaminants, knowledge on their toxicological mechanism remains very limited. We compared potential thyroid hormone (TH) disruption effects of Cl-PFAESs and PFOS via the mechanisms of competitive binding to TH transport proteins and activation of TH receptors (TRs). Fluorescence binding assays revealed that 6:2 Cl-PFAES, 8:2 Cl-PFAES and F-53B (a mixture of 6:2 and 8:2 Cl-PFAES) all interacted with a TH transport protein transthyretin (TTR), with 6:2 Cl-PFAES showing the highest affinity. It was also found that the chemicals interacted with TRs, with the affinity following the order of 6:2 Cl-PFAES > PFOS > 8:2 Cl-PFAES. In reporter gene assays the chemicals exhibited agonistic activity toward TRs, with the potency of 6:2 Cl-PFAES comparable to that of PFOS. The chemicals also promoted GH3 cell proliferation, with 6:2 Cl-PFAES displaying the highest potency. Molecular docking and molecular dynamic simulation revealed that both Cl-PFAESs fit into the ligand binding pockets of TTR and TRs with the binding modes similar to PFOS. Collectively, our results demonstrate that Cl-PFAESs might cause TH disruption effects through competitive binding to transport proteins and activation of TRs.

Wide application of perfluoroalkyl acids (PFAAs) has raised great concerns on their side-effects on human health. PFAAs have been shown to accumulate mainly in the liver and cause hepatotoxicity. However, PFAAs can also deposit in lung tissues through air-borne particles and cause serious pulmonary toxicity. But the underlying mechanisms are still largely unknown. Autophagy is a type of programmed cell death parallel to necrosis and apoptosis, and may be involved in the lung toxicity of PFAAs. In this study, lung cancer cells, A549, were employed as the model to investigate the effects of three PFAAs with different carbon chain lengths on cell autophagy. Through Western blot analysis on LC3-I/II ratio of cells exposed to non-cytotoxic concentration (200 µM) and cytotoxic concentration (350 µM), we found concentration-dependent increase of autophagosomes in cells, which was further confirmed by TEM examination on ultra-thin section of cells and fluorescence imaging on autophagosomes in live cells. The abundance of p62 increased with the PFAAs concentration indicating the blockage of autophagy flux. Furthermore, we identified the mitochondrial autophagy (mitophagy) and endoplasmic reticulum autophagy (ER-phagy) morphologically as the major types of autophagy, suggesting the disruption on mitochondria and ERs. These organelle damages were confirmed by the overgeneration of ROS, hyperpolarization of mitochondrial membrane potential, as well as the up-regulation of ER-stress-related proteins, ATF4 and p-IRE1. Further analysis on the signaling pathways showed that PFAAs activated the MAPK pathways and inhibited the PI3K/Akt pathway, with potencies following the order of PFDA > PFNA > PFOA. Anti-oxidant (NAC) treatment did not rescue cells from death, indicating that oxidative stress is not the reason of cytotoxicity. Inhibition of autophagy by Atg5 siRNA and chloroquine even increased the toxicity of PFAAs, suggesting that PFAAs-autophagy was induced as the secondary effects of organelle damages and played a protective role during cell death.

Estrogen-related receptor γ (ERRγ) is an orphan nuclear receptor having functional cross-talk with classical estrogen receptors. Here, we investigated whether ERRγ is a potential target of polybrominated diphenyl ethers (PBDEs) and their hydroxylated metabolites (OH-PBDEs). By using a fluorescence competitive binding method established in our laboratory, the binding potencies of 30 PBDEs/OH-PBDEs with ERRγ were determined for the first time. All of the tested OH-PBDEs and some PBDEs bound to ERRγ with K

Organophosphate flame retardants (OPFRs), as alternatives of brominated flame retardants, can cause neurodevelopmental effects similar to organophosphate pesticides. However, the molecular mechanisms underlying the toxicity remain elusive. O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) regulates numerous neural processes through the O-GlcNAcylation modification of nuclear and cytoplasmic proteins. In this study, we aimed to investigate the molecular mechanisms accounting for the developmental neurotoxicity of OPFRs by identifying potential targets of OPFRs and the attendant effects. Twelve OPFRs were evaluated for inhibition of OGT activity using an electrochemical biosensor. Their potency differed with substituent groups. The alkyl group substituted OPFRs had no inhibitory effect. Instead, the six OPFRs substituted with aromatic or chlorinated alkyl groups inhibited OGT activity significantly, with tri-m-cresyl phosphate (TCrP) being the strongest. The six OPFRs (0–100 μM exposure) also inhibited OGT activity in PC12 cells and decreased protein O-GlcNAcylation level. Inhibition of OGT by OPFRs might be involved in the subsequent toxic effects, including intracellular reactive oxygen species (ROS), calcium level, as well as cell proliferation and autophagy. Molecular docking of the OGT/OPFR complexes provided rationales for the difference in their structure-dependent inhibition potency. Our findings may provide a new biological target of OPFRs in their neurotoxicological actions, which might be a major molecular mechanism of OPFRs developmental neurotoxicity.

The wide use of the alternatives to bisphenol A (BPA) has raised concerns about their potential toxicities. Considering the disrupting activity of BPA on thyroid hormone (TH) signaling, we investigated whether bisphenol S (BPS) and bisphenol F (BPF), two leading alternatives, could interfere with TH signaling pathway using a series of assays in vitro and in vivo. In the fluorescence competitive binding assay, we found BPS and BPF, like BPA, bound to TH receptors (TRα and TRβ), with the binding potencies an order of magnitude lower than BPA (BPA > BPF > BPS). Molecular docking data also show their binding potencies to TRs. In the coactivator recruitment assay, BPS and BPF recruited coactivator to TRβ but not TRα, with weaker potencies than BPA. Correspondingly, agonistic actions of the three bisphenols in the absence or presence of T3 were observed in the TR-mediated reporter gene transcription assay. Also, all the three bisphenols induced TH-dependent GH3 cell proliferation, whereas BPA and BPF inhibited T3 induction in the presence of T3. As for in vivo assay, the three bisphenols like T3 induced TH-response gene transcription in Pelophylax nigromaculatus tadpoles, but in the presence of T3 altered T3-induced gene transcription in a biphasic concentration-response manner. These results for the first time demonstrate that BPS and BPF, like BPA, have potential to interfere with TH signaling pathway, i.e., they generally activate TH signaling in the absence of T3, but in the presence of TH, display agonistic or/and antagonistic actions under certain condition. Our study highlights the potential risks of BPS and BPF as BPA alternatives.

Chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are the alternative products of perfluorooctanesulfonate (PFOS) in the metal plating industry in China. The similarity in chemical structures between Cl-PFAESs and PFOS makes it reasonable to assume they possess similar biological activities. In the present study, we investigated whether Cl-PFAESs could induce cellular effects through peroxisome proliferator-activated receptors (PPARs) signaling pathways like PFOS. By using fluorescence competitive binding assay, we found two dominant Cl-PFAESs (6:2 Cl-PFAES and 8:2 Cl-PFAES) bound to PPARs with affinity higher than PFOS. Based on the luciferase reporter gene transcription assay, the two Cl-PFAESs also showed agonistic activity toward PPARs signaling pathways with potency similar to (6:2 Cl-PFAES) or higher than (8:2 Cl-PFAES) PFOS. Molecular docking simulation showed the two Cl-PFAESs fitted into the ligand binding pockets of PPARs with very similar binding mode as PFOS. The cell function results showed Cl-PFAESs promoted the process of adipogenesis in 3T3-L1 cells with potency higher than PFOS. Taken together, we found for the first time that Cl-PFAESs have the ability to interfere with PPARs signaling pathways, and current exposure level of 6:2 Cl-PFAES in occupational workers has exceeded the margin of safety. Our study highlights the potential health risks of Cl-PFAESs as PFOS alternatives.

Organophosphate esters (OPEs) have been reported to induce endocrine disruption effects, and several well-known nuclear receptors have been investigated as cellular targets of OPEs in their mode of action. Here, we demonstrated for the first time that an orphan nuclear receptor estrogen-related receptor γ (ERRγ) is another possible target of OPEs. Using the fluorescence competitive binding assays that we established, we measured the binding affinity of nine OPEs with different substitution groups, including aromatic rings, chlorinated alkyl chains, and alkyl chains. Seven of the OPEs were found to bind to ERRγ, with tri-m-cresyl phosphate (TCrP) showing the highest binding affinity (Kd, 0.34 μM). By using an ERRγ-mediated luciferase reporter gene assay, we found seven OPEs showed inhibitory effects toward ERRγ. Both the binding affinity and the inhibitory effect of the OPEs correlate positively with the hydrophobicity of their substitution groups in the following rank order: aromatic rings > chlorinated a...

Numerous studies have indicated estrogenic disruption effects of bisphenol A (BPA) analogues. Previous mechanistic studies were mainly focused on their genomic activities on nuclear estrogen receptor pathway. However, their nongenomic effects through G protein-coupled estrogen receptor (GPER) pathway remain poorly understood. Here, using a SKBR3 cell-based fluorescence competitive binding assay, we found six BPA analogues bound to GPER directly, with bisphenol AF (BPAF) and bisphenol B (BPB) displaying much higher (∼9-fold) binding affinity than BPA. Molecular docking also demonstrated the binding of these BPA analogues to GPER. By measuring calcium mobilization and cAMP production in SKBR3 cells, we found the binding of these BPA analogues to GPER lead to the activation of subsequent signaling pathways. Consistent with the binding results, BPAF and BPB presented higher agonistic activity than BPA with the lowest effective concentration (LOEC) of 10 nM. Moreover, based on the results of Boyden chamber and wound-healing assays, BPAF and BPB displayed higher activity in promoting GPER mediated SKBR3 cell migration than BPA with the LOEC of 100 nM. Overall, we found two BPA analogues BPAF and BPB could exert higher estrogenic effects than BPA via GPER pathway at nanomolar concentrations.

Ecotoxicity of engineered nanoparticles (NPs) has become the focus of considerable attention because of their wide applications. Reactive oxygen species (ROS) play important roles in the toxicity mechanisms of engineered metal oxide NPs. This work aimed to understand quantitatively the contribution of photogenerated ROS on metal oxide NPs to their toxicity. The dynamic generation of O2•–, •OH, and H2O2 in aqueous suspensions of photoilluminated metal oxide nano- and bulk particles (TiO2, ZnO, V2O5, CeO2, Fe2O3, and Al2O3) was measured by a continuous-flow chemiluminescence (CFCL) detection system. Superoxides were generated on all six nanoparticles as well as bulk TiO2 and ZnO, with nano TiO2 producing the highest concentration (180 nM). Hydroxyl radicals were detected on both nano- and bulk TiO2 and ZnO, whereas H2O2 was detected only on TiO2 and ZnO nanoparticles. The generation of ROS can in general be interpreted by the electronic structures and surface defects of the NPs and the ROS redox potentials....

// Tianyi Dong 1, 2, * , Yanping Peng 1, * , Ning Zhong 3 , Fengyan Liu 3 , Hanyu Zhang 1 , Mengchen Xu 4 , Rutao Liu 4 , Mingyong Han 5 , Xingsong Tian 2 , Jihui Jia 1 , Lap Kam Chang 1 , Liang-Hong Guo 6 and Shili Liu 1 1 School of Medicine, Shandong University, Jinan, Shandong, 250012, China 2 Department of Breast Thyroid Surgery, Shandong Provincial Hospital, Shandong University, Jinan, Shandong, 250021, China 3 Department of Gastroenterology, Qilu Hospital of Shandong University, Jinan, Shandong, 250012, China 4 School of Environmental Science and Engineering, Shandong University, Jinan, Shandong, 250100, China 5 Cancer Therapy and Research Center, Shandong Provincial Hospital, Shandong university, Jinan, Shandong 250021, China 6 State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China * These authors contributed equally to this work Correspondence to: Liang-Hong Guo, email: lhguo@rcees.ac.cn Shili Liu, email: liushili@sdu.edu.cn Keywords: PFDA, proliferation, sPLA2-IIA, TCF4 Received: September 06, 2016 Accepted: April 05, 2017 Published: April 20, 2017 ABSTRACT The association of perfluorodecanoicacid (PFDA) with tumor promotion and associated effects is not clear. Given that PDFA is mostly consumed with food and drinking water, we evaluated the effects of PFDA on a gastric cell line. When added to cell cultures, PFDA significantly increased growth rate and colony forming ability compared with control treatment. We found that suppression of cell senescence, but not apoptosis or autophagy was associated with PFDA-induced promotion of cell amount. To determine the molecular mechanism that was involved, DNA microarray assays was used to analyze changes in gene expression in response to PFDA treatment. Data analysis demonstrated that the vascular endothelial growth factor signaling pathway had the lowest p -value, with sPLA2-IIA ( pla2g2a ) exhibits the most altered expression pattern within the pathway. Moreover, sPLA2-IIA and its transcription factor TCF4, known as a direct target and a binding partner of Wnt/β-catenin signaling in gastric cells respectively, were the third and second most varied genes globally. Cells transfected with expression plasmids pENTER- tcf4 and pENTER- pla2g2a show reduced cell proliferation by more than 60% and 30% respectively. Knockdown with sPLA2-IIA siRNA provided additional evidence that sPLA2-IIA was a mediator of PFDA-induced cell senescence suppression. The results suggest for the first time that PFDA induced suppression of cell senescence through inhibition of sPLA2-IIA protein expression and might increased the proliferative capacity of an existing tumor.

The potential causal relationship between exposure to environmental contaminants and diabetes is troubling. Exposure of perfluoroalkyl substances (PFASs) is found to be associated with hyperinsulinemia and the enhancement of insulin secretion by islet β cells in humans, but the underlying mechanism is still unclear. Here, by combining in vivo studies with both wild type and gene knockout mice and in vitro studies with mouse islet β cells (β-TC-6), we demonstrated clearly that 1 h exposure of perfluorooctanesulfonate (PFOS) stimulated insulin secretion and intracellular calcium level by activating G protein-coupled receptor 40 (GPR40), a vital free fatty acid regulated membrane receptor on islet β cells. We further showed that the observed effects of PFASs on the mouse model may also exist in humans by investigating the molecular binding interaction of PFASs with human GPR40. We thus provided evidence for a novel mechanism for how insulin-secretion is disrupted by PFASs in humans.

Chlorinated polyfluoroalkylether sulfonic acids (Cl-PFESAs) have been shown to have potential thyroid hormone (TH) disruption effects. Here, we further investigated their estrogenic effects and underlying mechanisms. In vivo results revealed that exposure of zebrafish to Cl-PFESAs induced disorder of sex hormones during the early embryonic stages and caused histopathological lesions in the gonads of adult zebrafish relative to control groups. To find out whether the estrogen receptor is the molecular target of Cl-PFESAs, the binding interaction between Cl-PFESAs and ERs was investigated using a series of in vitro assays. We found that all tested chemicals could bind directly to ERs and exhibit relatively weak agonistic activity toward ERs, suggesting that the ER-mediated signaling pathway is directly involved in the estrogenic effects of Cl-PFESAs. The internal dose of 8:2 Cl-PFESA was significantly higher than the others, which explained why it obviously displayed an ER agonistic effect despite its weak ER binding affinity. Taken together, these results uncover that, in addition to the TH disruption effect, Cl-PFESAs might also cause estrogenic effects by activating ER pathways.

Microplastic (MP) accumulation in the environment has become an issue of human and environmental importance. Great efforts were made recently to identify the sources of MP exposure to humans and their release into the environment. Here, we employed spectroscopic techniques to identify and characterize MP in consumer plastic food containers that are, in huge quantity, used for food delivery and disposable plastic cups for daily drinking. We determined the average weight of isolated MP per pack to be 12 ± 5.12 mg, 38 ± 5.29 mg, and 3 ± 1.13 mg for the round-shaped, rectangular-shaped plastic container and disposable plastic cups, respectively, with various morphological features including cubic, spherical, rod-like as well as irregular shapes, which may either be consumed by humans or released into the environment. This study demonstrates that new plastic containers can be an important source of direct human and environmental exposure to microplastics. Most importantly, our results indicated that necessary attention must be given to morphological features of realistic MPs when evaluating their risks to humans and the environment.

Previously, perfluoroalkyl substances (PFASs) have been found to be associated with many adverse effects mediated by the peroxisome proliferator-activated receptor α (PPARα) and PPARγ. Here, we found another subtype of the peroxisome proliferator-activated receptors (PPARs); the PPARβ/δ mediated pathway might also be a potential adverse outcome pathway for PFASs. We investigated the direct binding and transcriptional activity of PFASs toward human PPARβ/δ, and further revealed the structure-binding and structure–activity relationship between PFASs and PPARβ/δ. The receptor binding experiment showed that their binding potency was dependent on the carbon chain length and the terminal functional group. For twelve perfluoroalkyl carboxylic acids (PFCAs), an inverted U-shaped relationship existed between the PPARβ/δ binding potency and the carbon chain length, with perfluorododecanoc acid (C12) showing the highest binding potency. The three perfluoroalkane sulfonic acids (PFSAs) exhibited a stronger binding potency than their PFCA counterparts. The two fluorotelomer alcohols (FTOHs) showed no binding potency. In receptor transcriptional activity assays, they enhanced the PPARβ/δ transcriptional activity. Their transcriptional activity was also related to the carbon chain length and the terminal functional group. Molecular docking analysis showed the PFASs fitted into the ligand binding pocket of PPARβ/δ with a binding geometry similar to a fatty acid.

Polybrominated diphenyl ethers (PBDEs) can be metabolized to hydroxylated PBDEs (OH-PBDEs), which play important roles in their disruption effects on the thyroid hormone (TH) system. Recently, multiple in vitro studies suggested that OH-PBDEs might be further metabolically transformed to PBDE sulfates. However, information about the bioactivity of PBDE sulfate metabolites is limited. In the present study, we explored the possible disruption effects of PBDE sulfates to the TH system by studying their binding and activity towards TH transport proteins and nuclear receptors. We found PBDE sulfates could bind to two major TH transport proteins (thyroxine-binding globulin and transthyretin). Besides, PBDE sulfates could also bind to two subtypes of TH nuclear receptors (TRα and TRβ) and showed agonistic activity towards the subsequent signaling pathway. Moreover, the PBDE sulfates showed higher binding potency to TH transport proteins and TRs compared with their corresponding OH-PBDE precursors. Molecular docking results showed that replacement of hydroxyl groups with sulfate groups might lead to more hydrogen bond interactions with these proteins. Overall, our study suggested that PBDE sulfates might disturb the TH system by binding to TH transport proteins or TRs. Our finding indicated a possible mechanism for the TH system disruption effects of PBDEs through their sulfate metabolites.

Bisphenol analogues including bisphenol A and its derivatives are ubiquitous environmental contaminants and have been linked to adverse neurodevelopment effects on animals and humans. Most toxicological research focused on estrogen receptor mediated pathways and did not comprehensively clarify the observed toxicity. O-GlcNAcase (OGA), the highest level in brain, plays a critical role in controlling neuronal functions at multi-levels from molecule to animal behaviors. In this work, we intend to investigate the underlying molecular mechanisms for the neurotoxicity of bisphenol analogues by identifying their cellular targets and the resultant effects. The inhibitory actions of seven bisphenol analogues on the OGA activity at molecular level were investigated by our developed electrochemical biosensor. We found that their potency varied with substituent groups, in which tetrabromo bisphenol A (TBBPA) was the strongest. The seven bisphenol analogues (0–100 μM exposure) significantly inhibited OGA activity and up-regulated protein O-GlcNAcylation level in PC12 cells. Inhibition of OGA by bisphenol analogues further induced intracellular calcium, ROS, inflammation, repressed proliferation, interfered with cell cycle, induced apoptosis. And especially, 10 μM tetrabromo bisphenol A (TBBPA) exposure could impair the growth and development of neurite in human neural stem cells (hNSCs). Molecular docking for OGA/bisphenol analogue complexes revealed the hydrophobicity-dominated inhibition potency. OGA, as a new cellular target of bisphenol analogues, would illuminate the molecular mechanism of bisphenol analogues neurotoxicity.

Coexistence of nanomaterials and environmental pollutants requires in-depth understanding of combined toxicity and underlying mechanism. In this work, we found that coexposure to the mixture of noncytotoxic level of single-walled carbon nanotubes (SWCNTs) (10 μg/mL) and Ni2+ (20 μM) induced significant cytotoxicity in macrophages. However, almost equal amount of intracellular Ni2+ was detected after Ni2+/SWCNT coexposure or Ni2+ single exposure, indicating no enhanced cellular uptake of Ni2+ occurred. SDS-PAGE analysis revealed 50% more SWCNTs retained in Ni2+/SWCNT exposed cells than that with SWCNT exposure alone, regardless of the exposure sequence (coexposure, Ni2+ pre- or post-treatment), suggesting inhibited SWCNT exocytosis by Ni2+. The increased cellular dose of SWCNTs could quantitatively account for the elevated toxicity of Ni2+/SWCNT mixture to cells. It was then found that agonist (ATP) and antagonist (o-ATP) of P2X7R could regulate intracellular SWCNT amount and the cytotoxicity accordingly. ...

The environmental behavior of engineered nanomaterials is complex due to their photochemical transformation and interactions with the surrounding aquatic environment. In this report, the aggregation of UV-irradiated TiO2 nanoparticles under different aquatic conditions (ionic strength, ionic composition, and humic acids) was investigated. With increased UV irradiation time and elevated ionic strength, TiO2 aggregation was remarkably accelerated due to the suppression of the electrostatic repulsion between the nanoparticles. Humic acids normally stabilize nanoparticle suspensions in salt solutions by the steric hindrance effect. But the change of TiO2 surface chemistry induced by UV irradiation reduced their adsorption capacity toward humic acids and thus weakened their stabilizing effect. In a simulated aquatic solution with 450 mM NaCl and 10 mg L− 1 SRHA, aggregation rate a TiO2 nanoparticle suspension increased from 5.8 nm min− 1 before UV irradiation to 26.7 nm min− 1 after 40 h irradiation. These results demonstrate the critical role of light irradiation in mediating the environmental behaviors of nanomaterials in aquatic environments.

Pentachlorophenol (PCP), a highly toxic halogenated aromatic compound, and its direct photolysis or TiO2 photocatalysis may generate toxic intermediates and induce secondary pollution in the environment. It is urgently needed to design a strategy to inhibit the toxic intermediates in the photodegradation of PCP. To achieve this, polydopamine (PDA), a non-toxic substance, modified TiO2 (P25/PDA) nanoparticles were synthesized and used to improve the PCP photodegradation process. The dynamic tracking of toxic intermediates tetrachloro-1,4-benzoquinone (TCBQ) and trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) produced in the PCP photodegradation process were obtained by continuous flow chemiluminescence. Combined with reactive oxygen species (ROS) measurements, P25/PDA could approximatively depress 70 % TCBQ and 40 % OH-TrCBQ generation through the regulation of ROS especially the generation of a fairly large amount of H2O2 (about 30 μM) and O2- (about 20 μM) on the surface of the P25/PDA. The toxicity evaluation showed that the photodegradation of PCP by P25/PDA was a safer and green approach. Therefore, it was instructive to inhibit the formation of highly toxic intermediates in the photodegradation of environmental contaminants by regulating the ROS generated on the surface of the photocatalysts.

The design and synthesis of antibacterial nanomaterials (NM) with improved efficiency, stability, fouling resistance, biocompatibility and recyclability is a fast-developing field. Here we review the recent research directions in the antibacterial NM development for potential applications in the environmental and consumer products, with the focus on the antibacterial mechanisms and novel material synthesis approaches. We identify the major application areas for antibacterial NMs and the types of NMs under research and already in use in the consumer products. The main synthetic approaches for preparation of antibacterial NMs range from surfaces coated with vertically aligned 2D NMs, photocatalytic membranes with extended photoactivation range and composite materials for solar-to-thermal energy conversion to layered nanocomposites and metal-organic frameworks for controlled release of antibacterial compounds. The strategies for increasing antibacterial efficiency of NMs include contact-mediated damage via the edges of 2D NMs, efficient generation of reactive oxygen species (ROS) by photocatalytic composite NMs with or without concurrent mechanical entrapment of bacteria, photothermal damage, and synergistic action of photocatalysts and metal ion release. For the research in antibacterial NM synthesis to successfully progress into the product development phase it is crucial to incorporate NM safety assessment into all steps of the research and development process. Based on the synthesis approaches and antibacterial mechanisms of NMs reviewed herein we discuss considerations for safe-by-design strategies for antibacterial NMs, crucial for the sustainable development of nano-enabled products in the environmental and consumer applications.

As a class of widely used ultraviolet filters, hydroxylated benzophenones (BPs) have been detected in various environmental and human samples, raising concerns about their ecological and health effects. BPs were found to impair reproductive functions, and their disruption effects on estrogen receptor, G protein-coupled estrogen receptor, and androgen receptor were investigated as possible mechanisms of action. In the present study, we investigated the binding and activation of estrogen related receptor γ (ERRγ) as an alternative mechanism of BPs reproductive toxicity. In competitive fluorescence binding assays, all of the 8 tested BPs were found to bind to the ligand-binding domain of ERRγ but with varying binding affinity. Molecular dock analysis indicated that binding of BPs to ERRγ in the agonistic conformation is preferred. In luciferase reporter gene assays in HepG2 cells, all the 8 BPs activated the transcription of ERRγ in a concentration-dependent manner in the range of 3–100 μM,consistent with the docking result. Hazard quotient calculation revealed a high risk on the BP-type personal care products users. The combined in vitro and in silico results suggest that binding and activation of ERRγ might be the molecular initiating events of an alternative mechanism of BPs endocrine disruption toxicity.

Hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide dimer acid (HFPO-DA) have been used as perfluorooctanoic acid (PFOA) alternatives in the fluoropolymer industry for years. Their widespread environmental distribution, high bioaccumulation capability, and human exposure have caused great concern. Nevertheless, their potential toxicity and health risk remain largely unknown. In the present study, we compared potential disruption effects of HFPO-TA, HFPO-DA, and PFOA on peroxisome proliferator-activated receptor γ (PPARγ) via the investigation of receptor binding, receptor activity, and cell adipogenesis effects. The receptor binding experiment showed HFPO-TA exhibited 4.8-7.5 folds higher binding affinity with PPARγ than PFOA, whereas HFPO-DA exhibited weaker binding affinity than PFOA. They also showed agonistic activity toward PPARγ signaling pathway in HEK 293 cells in the order of HFPO-TA > PFOA > HFPO-DA. Molecular docking simulation indicated HFPO-TA formed more hydrogen bonds than PFOA, whereas HFPO-DA formed fewer hydrogen bonds than PFOA. HFPO-TA promoted adipogenic differentiation and lipid accumulation in both mouse and human preadipocytes with potency higher than PFOA. Adipogenesis in human preadipocytes is a more sensitive end point than mouse preadipocytes. Collectively, HFPO-TA exerts higher binding affinity, agonistic activity, and adipogenesis activity than PFOA. The potential health risk of HFPO-TA should be of concern.

Background: Numerous studies have indicated the estrogenic effects of polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDEs (OH-PBDEs). However, the previous mechanistic studies focused on ...

Background: Numerous studies have indicated the estrogenic effects of polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDEs (OH-PBDEs). However, the previous mechanistic studies focused on their estrogenic effects through genomic transcriptional activation of estrogen receptors. Objective: The present study aimed to investigate the estrogenic effects of PBDEs and OH-PBDEs via nongenomic G protein–coupled estrogen receptor (GPER) pathways. Methods: The binding affinities of 12 PBDEs and 18 OH-PBDEs with GPER were determined by a fluorescence competitive binding assay in a human breast cancer cell line (SKBR3). Molecular docking was performed to simulate the interactions. Their activities on GPER pathways were investigated by detecting calcium mobilization and cyclic adenosine monophosphate (cAMP) accumulation in SKBR3 cells. The effects on SKBR3 cell migration were investigated using Boyden chamber and wound-healing assays. Results: Our results showed that 11 of the OH-PBDEs but none of the PBDEs bound to GPER directly. Relative binding affinities ranged from 1.3% to 20.0% compared to 17β-estradiol. Docking results suggested that the hydroxyl group played an essential role in the binding of OH-PBDEs to GPER by forming hydrogen bond interactions. Most of the OH-PBDEs activated subsequent GPER signaling pathways. Among them, 4ʹ-OH-BDE-049, 5ʹ-OH-BDE-099, and 3ʹ-OH-BDE-154 displayed the highest activity with lowest effective concentrations (LOECs) of 10–100 nM. These three OH-PBDEs also promoted SKBR3 cell migration via GPER pathways with LOECs of 0.1–1μM. Conclusion: OH-PBDEs could bind to GPER, activate the subsequent signaling pathways, and promote SKBR3 cell migration via GPER pathways. OH-PBDEs might exert estrogenic effects by a novel nongenomic mechanism involving the activation of GPER at nanomolar concentrations. https://doi.org/10.1289/EHP2387

Biotransformation of 8:2 fluorotelomer alcohol (8:2 FTOH) can form potentially more toxic metabolites. However, the responsible cytochrome P450 (CYP) isoform(s) and phase II metabolism have not been studied in humans. Here, we characterized the in vitro metabolism of 8:2 FTOH by recombinant human CYPs, human liver microsomes, and human liver cytosol. The results showed that among the 11 isoforms investigated, CYP2C19 was the only enzyme capable of catalyzing 8:2 FTOH with Km and Vmax values of 18.8 μM and 8.52 pmol min−1 pmol−1 P450, respectively. The phase I metabolite was identified as 8:2 fluorotelomer aldehyde (8:2 FTAL). HLMs also catalyzed 8:2 FTOH transformation, with the Vmax and intrinsic clearance (CLint) values similar to those of CYP2C19 after the protein content is taken into account. Molecular docking showed that the hydroxyl group of 8:2 FTOH accesses the heme iron-oxo of CYP2C19 in an energetically favored orientation. 8:2 FTOH was also transformed by phase II enzymes to form O-glucuronide and O-sulfate conjugates. The CLint values follow the order of sulfation > oxidation > glucuronidation, suggesting that conjugation is the major metabolic pathway, which explains the low yield of perfluoroalkyl acids (PFCAs). These results provide new insight into fluorotelomer alcohol biotransformation and indirect human exposure to PFCAs.

Photocatalytic degradation is a powerful technique for the decomposition of pollutants. However, toxic intermediates might be generated which have become a great concern recently. In the present work, a continuous flow chemiluminescence (CFCL) method was developed for dynamic monitoring of toxic intermediates generated in the photocatalytic degradation of pentachlorophenol (PCP). Among the main intermediates, tetrachloro-1,4-benzoquinone (TCBQ) and trichlorohydroxy-1,4-benzoquinone (OH-TrCBQ) showed higher or similar toxicity to PCP. As both TCBQ and OH-TrCBQ can produce chemiluminescence (CL) in the presence of H2O2, a CFCL system was established for the dynamic tracking of the two toxic intermediates. A PCP/TiO2 suspension was irradiated in a photoreactor, pumped continuously into a detection cell, and mixed with H2O2 to produce CL. The time-dependent CL response displayed two distinctive peaks at pH 7, which were attributed to the generation of OH-TrCBQ and TCBQ, respectively, by comparing with their c...

Airborne lower-chlorinated PCBs are vulnerable to metabolization to PCB sulfates through further sulfation of the hydroxylated metabolites (OH-PCBs). However, studies on the toxic effects and mechanisms of PCB sulfates are still very limited. Here, we investigated for the first time the potential endocrine disruption effects of PCB sulfates through estrogen-related receptor γ (ERRγ) in comparison with their OH-PCBs precursors and PCB parent compounds. The binding affinity of thirteen PCBs/OH-PCBs/PCB sulfates was measured by using fluorescence competitive binding assays based on fluorescence polarization (FP). All of the tested chemicals could bind to ERRγ with the Kd (dissociation constant) values ranging from not available (NA) to 3.2 μM 4′–OH–PCB 12 showed the highest binding affinity with Kd value of 3.2 μM, which was comparable to that of a synthetic ERRγ agonist GSK4716. The effects of the thirteen chemicals on the ERRγ transcriptional activity were determined by using the luciferase reporter gene assay. We found the PCBs/OH-PCBs/PCB sulfates acted as agonists for ERRγ, with the lowest observed effective concentration reaching 3 μM. The binding affinity and agonistic activity of PCBs towards ERRγ were both enhanced after hydroxylation, while further sulfation of OH-PCBs decreased the activity instead. Molecular docking simulation showed that OH-PCBs had lower binding energy than the corresponding PCBs and PCB sulfates, indicating that OH-PCBs had higher binding affinity theoretically. In addition, OH-PCBs could form hydrogen bonds with amino acids Glu316 and Arg247 while PCBs and PCB sulfates could not, which might be the main factor impacting the binding affinity and agonistic activity. Overall, ERRγ is a novel target for lower-chlorinated PCBs and their metabolites.

Perfluoroalkyl substances (PFASs) have been shown to cause abnormal levels of thyroid hormones (THs) in experimental animals, but the molecular mechanism is poorly understood. Here, a fluorescence displacement assay was used to determine the binding affinities of 16 PFASs with two major TH transport proteins, transthyretin (TTR) and thyroxine-binding globulin (TBG). Most of the tested PFASs bound TTR with relative potency (RP) values of 3×10(-4) to 0.24 when compared with that of the natural ligand thyroxine, whereas fluorotelomer alcohols did not bind. Only perfluorotridecanoic acid and perfluorotetradecanoic acid bound TBG, with RP values of 2×10(-4) when compared with that of thyroxine. Based on these results, it was estimated that displacement of T4 from TTR by perfluorooctane sulfonate and perfluorooctanoic acids would be significant for the occupationally exposed workers but not the general population. Structure-binding analysis revealed that PFASs with a medium chain length and a sulfonate acid group are optimal for TTR binding, and PFASs with lengths longer than 12 carbons are optimal for TBG binding. Three mutant proteins were prepared to examine crucial residues involved in the binding of PFASs to TH transport proteins. TTR with a K15G mutation and TBG with either a R378G or R381G mutation showed decreased binding affinity to PFASs, indicating that these residues play key roles in the interaction with the compounds. Molecular docking showed that the PFASs bind to TTR with their acid group forming a hydrogen bond with K15 and the hydrophobic chain towards the interior. PFASs were modeled to bind TBG with their acid group forming a hydrogen bond with R381 and the hydrophobic chain extending towards R378. The findings aid our understanding of the behavior and toxicity of PFASs on the thyroid hormone system.

Perfluoroalkyl acids (PFAAs) are widespread environmental contaminants which have been detected in humans and linked to adverse health effects. Previous toxicological studies mostly focused on nuclear receptor-mediated pathways and did not support the observed toxic effects. In this study, we aimed to investigate the molecular mechanisms of PFAA toxicities by identifying their biological targets in cells. Using a novel electrochemical biosensor, 16 PFAAs were evaluated for inhibition of protein tyrosine phosphatase SHP-2 activity. Their potency increased with PFAA chain length, with perfluorooctadecanoic acid (PFODA) showing the strongest inhibition. Three selected PFAAs, 25 μM perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid, and PFODA, also inhibited SHP-2 activity in HepG2 cells and increased paxillin phosphorylation level. PFOA was detected in the immunoprecipitated SHP-2 from the cells exposed to 250 μM PFOA, providing unequivocal evidence for the direct binding of PFOA with SHP-2 in the cell. Molecular docking rationalized the formation of PFAA/SHP-2 complex and chain length-dependent inhibition potency. Our results have established SHP-2 as a new cellular target of PFAAs.

Previous animal experiments have implied that organophosphate esters (OPEs) have a disruption effect on the thyroid endocrine system. However, knowledge of the toxicological mechanism remains limited. In this study, the activities of four OPEs have been characterized against the thyroid hormone (TH) nuclear receptor (TR) using two in vitro models, with the aim of evaluating their toxicity mechanisms towards the TR. The results of a TH-dependent cell proliferation assay showed that tris(2-chloro-1-(chloromethyl)ethyl)phosphate (TDCPP) could induce cell growth, while the other three OPEs had no effect. The results of a luciferase reporter gene assay revealed that all four of the OPEs tested in the current study showed agonistic activity towards TRβ, with TDCPP being the most potent one. Moreover, molecular docking revealed that all the tested OPEs could fit into the ligand binding pocket of TRβ, with TDCPP binding more effectively than the other three OPEs. Taken together, these data suggest that OPEs might disrupt the thyroid endocrine system via a mechanism involving the activation of TR.