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Ag, SiO2 and TiO2 nanoparticles and food-grade TiO2 impact antagonistic activity of oral bacteria cultivated in artificial saliva.

Toxicity screening and risk assessment of an overwhelmingly large and ever-increasing number of chemicals are vitally essential for ecological safety and human health. Genotoxicity is particularly important because of its association with mutagenicity, carcinogenicity and cancer. Phosphorylated histone H2AX (γH2AX) is an early sensitive genotoxic biomarker. It is therefore highly desirable to develop analytical methods for the detection of trace γH2AX to enable screening and assessment of genotoxicity. Here, we developed a novel cathodic photoelectrochemical (PEC) immunoassay with dual signal amplification for the rapid and ultrasensitive detection of γH2AX in cell lysates. A sandwich immuno-reaction targeting γH2AX was first carried out on a 96-well plate, using a secondary antibody/gold nanoparticle/glucose oxidase conjugate as the labeled detection antibody. The conjugate increased the production of H

This study provides a comprehensive compilation of published toxicological and environmental data further used to assess the ecological risks of six antifouling biocides, including tributyltin (TBT), Irgarol 1051, Diuron, Chlorothalonil, 4,5-Dichloro-N-octyl-3(2H)-isothiazolone (DCOIT), and Dichlofluanid. The standard maximum concentration and standard continuous concentration of antifouling biocides were derived by the species susceptibility distribution method. Following that, the ecological risk assessment of antifouling biocides in the aquatic environment was conducted using the hazard quotient, margin of safety, joint probability curve, and Monte Carlo random sampling method. The following is a concise list of the antifouling biocide dangers associated with acute and chronic risks: Irgarol 1051 TBT DiuronDCOITChlorothalonilDichlofluanid. It is strongly advised that systematic and ongoing monitoring of these biocides in coastal areas take place, as well as the creation of acceptable and efficient environmental protection measures, to safeguard the coastal environment's services and functions.

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.

Ionic liquids play multi-functions in synthesizing catalysts for HER such as electrolytes/electrolyte additives, reaction solvents, precursors, single/dual ion sources, binders, or morphological structure/phase structure directing agents.

Antibiotics are emerging environmental contaminants with wide attention due to their high consumption and pseudo-persistence in the environment. They have been shown to induce obesity or obesity-related metabolic diseases in experimental animals, but the underlying toxicological mechanisms remain unclear. Here, the disruptive effects of four commonly used antibiotics, namely doxycycline (DC), enrofloxacin (ENR), florfenicol (FF) and sulfamethazine (SMT) on lipid metabolism were investigated in zebrafish (Danio rerio) larvae and murine preadipocyte cell line. Triglyceride (TG) content was reduced after 1 ng/L DC or ENR exposure but was increased at higher concentrations up to 100 mg/L. FF increased and SMT reduced TG content but did not show any concentration dependence. None of the antibiotics had any significant effect on total cholesterol (TC) content in zebrafish except 100 μg/L SMT. Expression levels of 8 lipid metabolism-related genes were also quantified. SMT was most disruptive by up-regulating six genes, followed by FF which up-regulated four genes and down-regulated one gene, whereas DC and ENR both up-regulated one gene. In 3T3-L1 preadipocytes, ENR, FF, and SMT in general increased TG content, while 100 mg/L FF reduced TG substantially. DC did not show any effect up to 10 mg/L, at which TG increased significantly. FF and SMT increased TC slightly at low concentrations but reduced it at high concentrations, whereas TC, DC and ENR had no effect at any tested concentrations. Gene expression measurement also indicated that SMT was most disruptive, followed by FF, DC, and ENR. Reporter gene assays showed that only SMT inhibited the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ). The above experimental results and clustering analysis demonstrate that the four antibiotics exerted disruption on lipid metabolism through different mechanisms, and one of the mechanisms for SMT may be inhibition of PPARγ transcriptional activity.

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 attracted widespread attention recently due to their environmental ubiquity and high potential for bioaccumulation and toxicity. In the present study, a set of in vivo mouse and in vitro mouse testicular Sertoli TM4 cell experiments were employed to explore the male reproductive toxicity and underlying mechanisms of HFPO homologues on blood-testis barrier. Tissue and permeability analyses of mice testes after 28-day treatment with 5 mg/kg/day HFPO-DA or PFOA, or 0.05 mg/kg/day HFPO-TA or HFPO-TeA indicated that there was an increase in the degradation of TJ protein occludin in mice with a disrupted blood-testis barrier (BTB). Following exposure to 100 μM HFPO-DA, HFPO-TA or 10 μM PFOA, HFPO-TeA, transepithelial electrical resistance measurements of TM4 cells also indicated BTB disruption. Additionally, as a result of the exposure, matrix metalloproteinase-9 expression was enhanced through activation of p38 MAPK, which promoted the degradation of occludin. On the whole, the results indicated HFPO homologues and PFOA induced BTB disruption through upregulation of p-p38/p38 MAPK/MMP-9 pathway, which promoted the degradation of TJ protein occludin and caused the disruption of TJ.

Sensitive detection of phosphorylated histone H2AX (γH2AX) in cells as a biomarker of DNA double-strand breaks has great significance in the field of molecular toxicology and life science research. However, current γH2AX detection methods require labor- and time-consuming steps. Here, for the first time, we designed a simple electrochemiluminescence (ECL) immunoassay integrated with a microplate-based sensor array to realize sensitive and high-throughput detection of γH2AX in cell lysates. Under the optimized conditions, this ECL immunosensor array could linearly respond to γH2AX concentrations in the range from 2 × 102 to 1 × 105 pg/mL. In addition, our approach possessed excellent specificity and satisfactory reproducibility, and its practicality was verified in real cell lysates. The whole process including instrumental and manual operation was completed in no more than 3 h. This study provides a convenient and rapid alternative method for the sensitive quantification of γH2AX, which shows promising application in high-throughput screening of genotoxic chemicals and drug candidates.

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.

Photocatalytic reduction of hexavalent chromium (Cr (VI)) has received widespread attention due to its high toxicity, in which the interfacial electrons generation and transfer on the conduction of the semiconductor surface was the key factor. Herein, Polydopamine (PDA) as hole scavengers and eco-benign polymer, was modified on the TiO2 surface which can not only enhance the hole-electron separation and then generate more long-lived electrons for Cr (VI) reduction but also harvest visible light. Different coated thickness of TiO2/PDA has systematically been investigated for the effect on the electrons generation and reduction treatment ability of Cr (VI), the results showed that TiO2/PDA-15 exhibited the more localized electron, making it advantageous for Cr (VI) removal. The reduction kinetics of Cr (VI) by electrons exhibited two distinct phases: an initial fast reduction and then slow decay removal due to the deposition of Cr (OH)3 solids on the synthesized TiO2 surface in neutral or alkali conditions. While, in the acidic solution, fast removal of Cr (VI) was obtained only within 3 min. A wastewater treatment and a preliminary in vivo study on Daphnia magna experiment suggested that treatment with the TiO2/PDA-15 can effectively remove Cr (VI) and significantly reduce its lethality.

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.

Reactive oxygen species (ROS) play an essential role in TiO2 photocatalysis. They arise from the transfer of light-initiated carriers to the TiO2 surface and react with oxygen or water, in which th...

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.

The mechanism of environmental pollution promoting gastric cancer incidence and difficulty of treatment is not fully understood. In the present article, perfluorodecanoic acid (PFDA), a common persistent environmental pollutant, was used to treat the gastric cell lines and mice to test its genotoxicity. The γ-H2AX immunoblot and plasmid fragment PCR results showed that PFDA had a promotion effect on the DNA double-strand breaks (DSBs) in human and mouse cells. Subsequent results showed that PFDA significantly altered the sensitivity of cells to chemotherapy. Microarray data showed that the expressions of some important DNA repair genes were changed. Further investigation discovered that PFDA inhibition of DNA repair was mediated by X-ray repair cross complementing 4 (XRCC4). The cells deficient in XRCC4 generally exhibited reduced proliferation and premature aging in culture; however, our results indicated that PFDA induced p53 inhibition rescued cells from the apoptosis that was triggered by nonhomologous end-joining (NHEJ) inactivation, and overexpression of p53 expression in PFDA-treated cells enhanced their apoptosis. Finally, T-cell specific factor 4 was suggested by the results as an upstream regulator of XRCC4. This article revealed for the first time that perfluorinated chemicals affect chemotherapeutic sensitivity and the NHEJ pathway, and p53 reduction rescues cells from death.

Graphene quantum dots (GQDs) possess great potential in various applications due to their superior physicochemical properties and wide array of available surface modifications. However, the toxicity of GQDs has not been systematically assessed, thus hindered their further development; especially, the risk of surface modifications of GQDs is largely unknown. In this study, we employed a lung carcinoma A549 cells as the model to investigate the cytotoxicity and autophagy induction of three types GQDs, including cGQDs (COOH-GQDs), hGQDs (OH-GQDs), and aGQDs (NH2-GQDs). The results showed hGQDs was the most toxic, as significant cell death was induced at the concentration of 100 μg/mL, determining by WST-1 assay as well as Annexin-V-FITC/PI apoptosis analysis, whereas cGQDs and aGQDs were non-cytotoxic within the measured concentration. Autophagy detection was performed by TEM examination, LC3 fluorescence tracking, and Western-blot. Both aGQDs and hGQDs induced cellular autophagy to various degrees except for cGQDs. Further analysis on autophagy pathways indicated all GQDs significantly activated p-p38MAPK; p-ERK1/2 was inhibited by aGQDs and hGQDs but activated by cGQDs. p-JNK was inhibited by aGQDs and cGQDs, while activated by hGQDs. Simultaneously, Akt was activated by hGQDs but inhibited by aGQDs. Inhibition of autophagy by 3-MA significantly increased the cytotoxicity of GQDs, suggesting that autophagy played a protective role against the toxicity of GQDs. In conclusion, cGQDs showed excellent biocompatibility and may be considered for biological applications. Autophagy induction may be included in the health risk assessment of GQDs as it reflects the stress status which may eventually lead to diseases.

Several studies have indicated metabolic function disruption effects of bisphenol analogues through peroxisome proliferator-activated receptor (PPAR) alpha and gamma pathways. In the present study, we found for the first time that PPARβ/δ might be a novel cellular target of bisphenol analogues. By using the fluorescence competitive binding assay, we found seven bisphenol analogues could bind to PPARβ/δ directly, among which tetrabromobisphenol A (TBBPA, 18.38-fold) and tetrachlorobisphenol A (TCBPA, 12.06-fold) exhibited stronger binding affinity than bisphenol A (BPA). In PPARβ/δ-mediated luciferase reporter gene assay, the seven bisphenol analogues showed transcriptional activity toward PPARβ/δ. Bisphenol AF (BPAF), bisphenol F (BPF) and bisphenol B (BPB) even showed higher transcriptional activity than BPA, while TBBPA and TCBPA showed comparable activity with BPA. Moreover, in human liver HL-7702 cells, the bisphenol analogues promoted the expression of two PPARβ/δ target genes PDK4 and ANGPTL4. Molecular docking simulation indicated the binding potency of bisphenol analogues to PPARβ/δ might depend on halogenation and hydrophobicity and the transcriptional activity might depend on their binding affinity and hydrogen bond interactions. Overall, the PPARβ/δ pathway may provide a new mechanism for the metabolic function disruption of bisphenol analogues, and TBBPA and TCBPA might exert higher metabolic disruption effects than BPA via PPARβ/δ pathway.

Per- and polyfluoroalkyl substances (PFAS) are found to have multiple adverse outcomes on human health. Recently, epidemiological and toxicological studies showed that exposure to PFAS had adverse impacts on pancreas and showed association with insulin abnormalities. To explore how PFAS may contribute to diabetes, we studied impacts of perfluorooctane sulfonate (PFOS) on cell viability and insulin release capacity of pancreatic β cells by using in vivo and in vitro methods. We found that 28-day administration with PFOS (10 mg/(kg body weight•day)) caused reductions of pancreas weight and islet size in male mice. PFOS administration also led to lower serum insulin level both in fasting state and after glucose infusion among male mice. For cell-based in vitro bioassay, we used mouse β-TC-6 cancer cells and found 48-hr exposure to PFOS decreased the cell viability at 50 μmol/L. By measuring insulin content in supernatant, 48-hr pretreatment of PFOS (100 μmol/L) decreased the insulin release capacity of β-TC-6 cells after glucose stimulation. Although these concentrations were higher than the environmental concentration of PFOS, it might be reasonable for high concentration of PFOS to exert observable toxic effects in mice considering mice had a faster removal efficiency of PFOS than human. PFOS exposure (50 μmol/L) to β-TC-6 cells induced intracellular accumulation of reactive oxidative specie (ROS). Excessive ROS induced the reactive toxicity of cells, which eventually invoke apoptosis and necrosis. Results in this study provide evidence for the possible causal link of exposure to PFOS and diabetes risk.

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.

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

A formation model of O2˙− produced in TiO2 photocatalysis was established, and then a custom built continuous flow chemiluminescence (CFCL) system was used to confirm the model's reliability by monitoring the O2˙− formation process. This model may give deeper insights into O2˙− formation for TiO2 and other photocatalysts.

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.

Pentachlorophenol (PCP), a highly toxic halogenated aromatic compound, and its direct photolysis or TiO

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.

Interface engineering in heterogeneous catalysis is fascinating because of the modulation of charge-transfer processes and catalytic activity. Herein, by constructing Fe(III)–TiO2 systems with diff...

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...

Heterogeneous catalytic reactions usually proceed at the surfaces of materials, where many intermediates, such as free radicals, usually were believed to be short-lived. Herein, surface long-lived superoxide radicals (O2˙−) were identified in UV-irradiated aqueous suspensions of TiO2 and other metal oxide nanoparticles using an online chemiluminescence system. From the decay dynamics process of O2˙−, a long-lived O2˙− radical was observed on anatase TiO2 at pH = 12. After separation of the photo-excited suspension via filtration, CL was detected from the particles but not the filtrate, thus confirming O2˙− surface adsorption. The unusual stability of O2˙− was also verified using density functional theory (DFT) calculations. The lifetimes of the radicals were estimated on the different kinds of semiconductor surface according to the decay dynamics curves, and followed the order: TiO2 > ZnO > SnO2 > CeO2 > Fe2O3. Furthermore, the function of surface long-lived O2˙− in TiO2 suspensions with regards to photochemical conversion was investigated using NBT as a chemical model; it was found that half of the molecules were reduced by the surface-adsorbed O2˙−. The finding of surface-stabilized, long-lived superoxide radicals may have important implications in relation to the chemistry, biology and toxicology of these radicals.

Exosomes are a type of nano-scale biofilm-enclosed vesicles involved in intercellular communications, which are actively secreted by almost all eukaryotes and have been suggested to play an important role in various biological and physiological processes. Since exosomes carry biological contents informative of the original cells and can be easily harvested from body fluids, they are regarded as an emerging and promising biomarker bank for liquid biopsy. Conventional exosome detection methods such as transmission electron microscopy, nanoparticle tracking analysis, and Western blotting are cumbersomely conducted with partial information and limited in sensitivity and specificity. Thus new analytical approaches are urgently needed to facilitate exosome-based in vitro early diagnosis of diseases. Herein, we summarized recent advances in the development of immunoassay-based technologies for rapid exosome detection which have sparked huge interest in the last few years. A brief introduction of exosomes and general principles of immunoassays was first presented. We then described in some detail the studies on four major types of immunoassay technologies incorporated with specific configurations for exosome quantification as well as surface protein profiling, including single immunosensors, immunosensor arrays, immunoassays integrated with microfluidics, and paper-based immunoassays. Challenges and future research perspectives were also discussed in the field of exosome immunoassay detection.