2,4-Di-tert-butylphenol Induces Adipogenesis in Human Mesenchymal Stem Cells by Activating Retinoid X Receptors.

2,4-Di-tert-butylphenol (2,4-DTBP) is an important commercial antioxidant and a toxic natural secondary metabolite that has been detected in humans. However, there is scant information regarding its toxicological effects. We asked whether 2,4-DTBP is a potential obesogen. Using a human mesenchymal stem cell adipogenesis assay, we found that exposure to 2,4-DTBP led to increased lipid accumulation and expression of adipogenic marker genes. Antagonist assays revealed that 2,4-DTBP increased lipid accumulation by activating the peroxisome proliferator-activated receptor (PPAR) γ-retinoid X receptor (RXR) heterodimer. 2,4-DTBP likely activated the PPARγ/RXRα heterodimer by activating RXRα but not directly binding to PPARγ. We confirmed that 2,4-DTBP directly bound to RXRα by solving the crystal structure of this complex, then predicted and demonstrated that related compounds could also activate RXRα. Our study demonstrated that 2,4-DTBP and related chemicals could act as obesogens and endocrine disruptors via RXRs. These data showed that 2,4-DTBP belongs to a family of compounds whose endocrine-disrupting and obesogenic effects can be strongly modulated by their chemical composition. Structure-activity studies such as the present one could help guide the rational development of safer antioxidants that do not interact with important nuclear receptors having broad effects on human development and physiology.

Cytotoxicity and pro-inflammatory effect of polystyrene nano-plastic and micro-plastic on RAW264.7 cells.

Numerous studies have shown that exposure to micro- or nano-plastics led to the cell viability and function of macrophages in the intestine tissue might be one possible mechanism. This study investigated the cytotoxicity and pro-inflammatory effect of 80 nm polystyrene-nano-plastic (PS-NP) and 3 µm PS-micro-plastic (PS-MP) on mouse macrophages RAW264.7 cells. Our results showed that exposure to PS-NP or PS-MP induced apoptosis of cells at 5 or 10 µg/mL, respectively. Besides, PS-NP enhanced the secretion of inflammatory cytokines (Tumor necrosis factor-α, Interleukin-6 and Interleukin-10) with the lowest effective concentration (LOEC) of 1, 0.01, and 0.01 µg/mL, respectively. PS-MP enhanced secretion of TNF-α and IL-10 with the LOEC of 1 and 0.01 µg/mL, respectively. We further studied the possible mechanisms of the effects of PS-NP or PS-MP on RAW264.7 cells. We found they might cause cytotoxicity and inflammatory effects by producing reactive oxygen species and nitric oxide in the cells. Accordingly, our results demonstrated that PS-NP and PS-MP had cytotoxicity and pro-inflammatory effect on macrophages, which might further lead to intestinal inflammation. Moreover, we revealed that the PS-NP had more potent adverse impacts on macrophages than PS-MP.

Triclocarban and triclosan exacerbate high-fat diet-induced hepatic lipid accumulation at environmental related levels: The potential roles of estrogen-related receptors pathways.

Triclosan (TCS) and triclocarban (TCC) have become ubiquitous pollutants detected in human body with concentrations up to hundreds of nanomolar levels. Previous studies about the hepatic lipid accumulation induced by TCS and TCC were focused on pollutant itself, which showed weak or no effects. High-fat diet (HFD), as a known environmental factor contributing to lipid metabolism-related disorders, its synergistic action with environmental pollutants deserves concern. The present study aimed to demonstrate the combined effects and potential molecular mechanisms of TCS and TCC with HFD at cellular and animal levels. The in vitro studies showed that TCC and TCS alone had negligible impact on lipid accumulation in HepG2 cells but induced lipid deposition at nanomolar levels when co-exposure with fatty acid. TCC exhibited much higher induction effects than TCS, which was related to their differential regulatory roles in adipogenic-related genes expression. The in vivo studies showed that TCC had little influence on hepatic lipid accumulation in mice fed with normal diet (ND) but could exacerbate the lipid accumulation in mice fed with HFD. Meanwhile, TCC-induced dyslipidemia in mice fed with HFD was more significant than that fed with ND. Therefore, we speculated that TCC might increase the risk of nonalcoholic fatty liver disease (NAFLD) and atherosclerosis in HFD humans. Molecular mechanism studies showed that TCC and TCS could bind to and activate estrogen-related receptor α (ERRα) and ERRγ as well as regulate their expression. TCC had higher activity on ERRα and ERRγ than TCS, which explained partly the differential regulatory roles of two receptors in the lipid accumulation induced by TCC and TCS. This work revealed synergistic effects and molecular mechanisms of TCC and TCS with excessive fatty acid on the hepatic lipid metabolism, which provided a novel insight into the toxic mechanism of pollutants from the perspective of dietary habits.

[Research on the Construction of Hospital Equipment Management Information Platform].

With the deepening of China's medical reform, the scale of hospital equipment assets at all levels is also expanding. In the face of large-scale and various equipment assets, the traditional single machine statistical management method not only has a single interface, poor data accuracy and is not compatible with other systems, but also is difficult to achieve "full life cycle" management. In order to solve above problems, the Ninth People's Hospital Affiliated to Shanghai Jiao Tong University of Medicine aims to use the Internet of Things to build a medical equipment management information platform, realize the whole hospital area, whole subject and whole process management of medical materials, and achieve the objectives of business linkage, information connectivity and data sharing between management departments and clinical departments.

Benzotriazole Ultraviolet Stabilizers Promote Breast Cancer Cell Proliferation via Activating Estrogen-Related Receptors α and γ at Human-Relevant Levels.

Benzotriazole ultraviolet stabilizers (BUVSs) are ubiquitous emerging pollutants that have been reported to show estrogenic disruption effects through interaction with the classic estrogen receptors (ERs) in the fashion of low activity. The present study aims at revealing the potential disruption mechanism via estrogen-related receptors α and γ (ERRα and ERRγ) pathways. By the competitive binding assay, we first found that BUVSs bond to ERRγ ligand binding domain (ERRγ-LBD) with Kd ranging from 0.66 to 19.27 µM. According to the results of reporter gene assays, the transcriptional activities of ERRα and ERRγ were promoted by most tested BUVSs with the lowest observed effective concentrations (LOEC) from 10 to 100 nM, which are in the range of human exposure levels. At 1 µM, most tested BUVSs showed higher agonistic activity toward ERRγ than ERRα. The most effective two BUVSs promoted the MCF-7 proliferation dependent on ERRα and ERRγ with a LOEC of 100 nM. The molecular dynamics simulation showed that most studied BUVSs had lower binding free energy with ERRγ than with ERRα. The structure-activity relationship analysis revealed that molecular polarizability, electron-donating ability, ionization potential, and softness were the main structural factors impacting the binding of BUVSs with ERRγ. Overall, our results provide novel insights into the estrogenic disruption effects of BUVSs.

Binding and Activity of Tetrabromobisphenol A Mono-Ether Structural Analogs to Thyroid Hormone Transport Proteins and Receptors.

BACKGROUND: Tetrabromobisphenol A (TBBPA) mono-ether structural analogs, identified as the by-products or transformation products of commercial TBBPA bis-ether derivatives, have been identified as emerging widespread pollutants. However, there is very little information regarding their toxicological effects. OBJECTIVE: We aimed to explore the potential thyroid hormone (TH) system-disrupting effect of TBBPA mono-ether structural analogs. METHODS: The binding potencies of chemicals toward human TH transport proteins [transthyretin (TTR) and thyroxine-binding globulin (TBG)] and receptors [TRα ligand-binding domain (LBD) and TRß-LBD] were determined by fluorescence competitive binding assays. Molecular docking was used to simulate the binding modes of the chemicals with the proteins. The cellular TR-disrupting potencies of chemicals were assessed by a GH3 cell proliferation assay. The intracellular concentrations of the chemicals were measured by high-performance liquid chromatography and mass spectrometry. RESULTS: TBBPA mono-ether structural analogs bound to TTR with half maximal inhibitory concentrations ranging from 0.1µM to 1.0µM but did not bind to TBG. They also bound to both subtypes of TR-LBDs with 20% maximal inhibitory concentrations ranging from 4.0µM to 50.0µM. The docking results showed that the analogs fit into the ligand-binding pockets of TTR and TR-LBDs with binding modes similar to that of TBBPA. These compounds likely induced GH3 cell proliferation via TR [with the lowest effective concentrations (LOECs) ranging from 0.3µM to 2.5µM] and further enhanced TH-induced GH3 cell proliferation (with LOECs ranging from 0.3µM to 1.2µM). Compared with TBBPA, TBBPA-mono(2,3-dibromopropyl ether) showed a 4.18-fold higher GH3 cell proliferation effect and 105-fold higher cell membrane transportation ability. CONCLUSION: This study provided a possible mechanism underlying the difference in TTR or TR binding by novel TBBPA structural analogs. These compounds might exert TH system-disrupting effects by disrupting TH transport in circulation and TR activity in TH-responsive cells. https://doi.org/10.1289/EHP6498.

Agrochemicals and obesity.

Obesity has become a very large concern worldwide, reaching pandemic proportions over the past several decades. Lifestyle factors, such as excess caloric intake and decreased physical activity, together with genetic predispositions, are well-known factors related to obesity. There is accumulating evidence suggesting that exposure to some environmental chemicals during critical windows of development may contribute to the rapid increase in the incidence of obesity. Agrochemicals are a class of chemicals extensively used in agriculture, which have been widely detected in human. There is now considerable evidence linking human exposure to agrochemicals with obesity. This review summarizes human epidemiological evidence and experimental animal studies supporting the association between agrochemical exposure and obesity and outlines possible mechanistic underpinnings for this link.

Perfluoroalkyl Substances Stimulate Insulin Secretion by Islet ß Cells via G Protein-Coupled Receptor 40.

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 ß 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 ß cells (ß-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 ß 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.

Estrogen-related receptor γ is a novel target for Lower-Chlorinated Polychlorinated Biphenyls and their hydroxylated and sulfated metabolites.

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.

Investigation of binding and activity of perfluoroalkyl substances to the human peroxisome proliferator-activated receptor ß/δ.

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 PPARß/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 PPARß/δ, and further revealed the structure-binding and structure-activity relationship between PFASs and PPARß/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 PPARß/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 PPARß/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 PPARß/δ with a binding geometry similar to a fatty acid.

Comparative in Vitro and in Vivo Evaluation of the Estrogenic Effect of Hexafluoropropylene Oxide Homologues.

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 ERß-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 17ß-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.

Binding and activity of polybrominated diphenyl ether sulfates to thyroid hormone transport proteins and nuclear receptors.

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 TRß) 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.

Binding and activity of sulfated metabolites of lower-chlorinated polychlorinated biphenyls towards thyroid hormone receptor alpha.

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.

Activation of the PP2A catalytic subunit by ivabradine attenuates the development of diabetic cardiomyopathy.

Hyperglycemia-induced apoptosis plays a critical role in the pathogenesis of diabetic cardiomyopathy (DCM). Our previous study demonstrated that ivabradine, a selective If current antagonist, significantly attenuated myocardial apoptosis in diabetic mice, but the underlying mechanisms remained unknown. This study investigated the underlying mechanisms by which ivabradine exerts anti-apoptotic effects in experimental DCM. Pretreatment with ivabradine, but not ZD7288 (an established If current blocker), profoundly inhibited high glucose-induced apoptosis via inactivation of nuclear factor (NF)-κB signaling in neonatal rat cardiomyocytes. The effect was abolished by transfection of an siRNA targeting protein phosphatase 2A catalytic subunit (PP2Ac). In streptozotocin-induced diabetic mice, ivabradine treatment significantly inhibited left ventricular hyperpolarization-activated cyclic nucleotide-gated channel 2 (HCN2) and HCN4 (major components of the If current), activated PP2Ac, and attenuated NF-κB signaling activation and apoptosis, in line with improved histological abnormalities, fibrosis, and cardiac dysfunction without affecting hyperglycemia. These effects were not observed in diabetic mice with virus-mediated knockdown of HCN2 or HCN4 after myocardial injection, but were alleviated by knockdown of PP2Acα. Molecular docking and phosphatase activity assay confirmed direct binding of ivabradine to, and activation of, PP2Ac. In conclusion, ivabradine may directly activate PP2Ac, leading to inhibition of NF-κB signaling activation, myocardial apoptosis, and fibrosis, and eventually improving cardiac function in experimental DCM. Taken together, the present findings suggest that ivabradine may be a promising drug for treatment of DCM.

Adipogenic Activity of Oligomeric Hexafluoropropylene Oxide (Perfluorooctanoic Acid Alternative) through Peroxisome Proliferator-Activated Receptor γ Pathway.

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.

[comIdiopathic scrotal calcinosis: A report of 10 cases and review of the literature].

OBJECTIVE: To investigate the clinical features, pathogenesis, diagnosis and scrotal reconstruction in the treatment of idiopathic scrotal calcinosis (ISC). METHODS: From March 2007 to October 2018, 10 ISC patients, aged 28－79 (mean 45) years and with a disease course of 6－497 (mean 128.4) months, were treated in our hospital. We retrospectively analyzed their clinical data and reviewed related literature. RESULTS: All the patients underwent physical examination and biochemical and parathyroid function tests. None of them had a history of endocrine or metabolic disease, or trauma, or a family member with similar diseases, and none had subjective symptoms except local pruritus in 1 case. All were treated surgically and post-operative follow-up revealed no recurrence. Histopathological examination of the excised lesion confirmed it to be ISC. CONCLUSIONS: ISC is a rare localized benign disease, of which surgery seems an effective option for the definite diagnosis and treatment. Occasionally scrotal reconstruction may be required in case of extensive involvement of the scrotal skin.

Exogenous hydrogen sulfide attenuates the development of diabetic cardiomyopathy via the FoxO1 pathway.

BACKGROUND: Previous studies have suggested that exogenous hydrogen sulfide can alleviate the development of diabetic cardiomyopathy (DCM) by inhibiting oxidative stress, inflammation, and apoptosis. However, the underlying mechanism is not fully understood. Nuclear expression and function of the transcription factor Forkhead box protein O (FoxO1) have been associated with cardiovascular diseases, and thus, the importance of FoxO1 in DCM has gained increasing attention. This study was designed to investigate the interactions between hydrogen sulfide (H2 S) and nuclear FoxO1 in DCM. METHODS: Diabetes was induced in adult male C57BL/6J mice by intraperitoneal injection of streptozotocin and was treated with H2 S donor sodium hydrosulfide for 12 weeks. The H9C2 cardiomyoblast cell line and neonatal rat cardiomyocytes (NRCMs) were treated with the slow-releasing H2 S donor GYY4137 before high-glucose (HG) exposure with or without pretreatment with the Akt inhibitor MK-2206 2HCl. Changes in FoxO1 protein phosphorylation and subcellular localization were determined in H9C2 cells, NRCMs, and cardiac tissues from normal and diabetic mice. Cardiac structure and function in the diabetic mice were evaluated by echocardiography and histological analysis and compared with those in control animals. RESULTS: The echocardiographic and histopathological data indicated that exogenous H2 S improved cardiac function and attenuated cardiac hypertrophy and myocardial fibrosis in diabetic mice. H2 S also improved HG-induced oxidative stress and apoptosis in cardiac tissue and NRCMs. In addition, H2 S induced FoxO1 phosphorylation and nuclear exclusion in vitro and in vivo, and this function was not inhibited by MK-2206 2HCl. Alanine substitution mutation of three sites in FoxO1-enhanced FoxO1 transcriptional activity, and subsequent treatment with exogenous H2 S could not prevent HG-induced nuclear retention. CONCLUSIONS: Our data indicate that H2 S is a novel regulator of FoxO1 in cardiac cells and provide evidence supporting the potential of H2 S in inhibiting the progression of DCM.

Chlorinated Polyfluoroalkylether Sulfonates Exhibit Similar Binding Potency and Activity to Thyroid Hormone Transport Proteins and Nuclear Receptors as Perfluorooctanesulfonate.

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.

Structure-Dependent Activity of Polybrominated Diphenyl Ethers and Their Hydroxylated Metabolites on Estrogen Related Receptor γ: in Vitro and in Silico Study.

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 Kd values ranging from 0.13-13.61 µM. The OH-PBDEs showed much higher binding potency than their parent PBDEs. A quantitative structure-activity relationship (QSAR) model was developed to analyze the chemical binding potencies in relation to their structural and chemical characteristics. The QSAR model indicated that the molecular size, relative ratios of aromatic atoms, and hydrogen bond donors and acceptors were crucial factors for PBDEs/OH-PBDEs binding. By using a reporter gene assay, we found that most of the low-brominated PBDEs/OH-PBDEs exerted agonistic activity toward ERRγ, while high-brominated PBDEs/OH-PBDEs had no effect on the basal ERRγ activity. The docking results showed that the low-brominated PBDEs/OH-PBDEs tended to take an agonistic binding mode while the high-brominated ones tended to take an antagonistic binding mode. Overall, our results suggest ERRγ to be a potential novel target for PBDEs/OH-PBDEs.