Induction of p53-mediated apoptosis in splenocytes and thymocytes of C57BL/6 mice exposed to perfluorooctane sulfonate (PFOS)

Angiotoxic effects of chlorinated polyfluorinated ether sulfonate, a novel perfluorooctane sulfonate substitute, in vivo and in vitro

Chlorinated polyfluorinated ether sulfonate (Cl-PFESA), a substitute for perfluorooctane sulfonate (PFOS), has been widely used in the Chinese electroplating industry under the trade name F-53B. The production and use of F-53B is keep increasing in recent years, consequently causing more emissions into the environment. Thus, there is a growing concern about the adverse effects of F-53B on human health. However, related research is very limited, particularly in terms of its toxicity to the vascular system. In this study, C57BL/6 J mice were exposed to 0.04, 0.2, and 1 mg/kg F-53B for 12 weeks to assess its impact on the vascular system. We found that F-53B exposure caused aortic wall thickening, collagen deposition, and reduced elasticity in mice. In addition, F-53B exposure led to a loss of vascular endothelial integrity and a vascular inflammatory response. Intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were found to be indispensable for this process. Furthermore, RNA sequencing analysis revealed that F-53B can decrease the repair capacity of endothelial cells by inhibiting their proliferation and migration. Collectively, our findings demonstrate that F-53B exposure induces vascular inflammation and loss of endothelial integrity as well as suppresses the repair capacity of endothelial cells, which ultimately results in vascular injury, highlighting the need for a more thorough risk assessment of F-53B to human health.

Structural and molecular changes in the rat myocardium following perfluoroctane sulfonate (PFOS) exposure are mitigated by quercetin via modulating HSP 70 and SERCA 2

Perfluorooctane sulfonate (PFOS) is a man-made fluorinated compound employed in a variety of industrial and civilian applications. Due to its long elimination half-life and promotion of oxidative stress and inflammation, it is one of the most abundant organic contaminants. The present study was designed to determine the cytotoxic effect of PFOS on adult male rat cardiac tissue and to assess the cardioprotective role of the flavonoid quercetin (Que), which possesses antioxidant, anti-inflammatory, and anti-apoptotic properties. Twenty-four adult male Sprague-Dawley rats were randomly divided into four equal groups: Group I (Control). Group II (Que) received Que (75 mg/kg/day for 4 weeks) by oral gavage. Group III (PFOS group): supplemented orally with PFOS (20 mg/kg/day for 4 weeks) and Group IV (PF OS/Que). The rat heart was processed for histological, immunohistochemical, and gene expression studies. The PFOS group showed histological alterations in the myocardium that were partially reversed by the administration of Que. The inflammatory biomarkers (TNF, IL-6, and IL-1), lipid profile, TSH, MDA, and serum cardiac enzymes (LDH and CK-MB) were all altered. These findings collectively suggest that PFOS had adverse effects on the cardiac muscle structure, and these effects were alleviated by quercetin, which is a promising cardioprotective flavonoid.

Alteration of hepato-lipidomic homeostasis in A/J mice fed an environmentally relevant PFAS mixture

In the present study, we have investigated liver lipid homeostasis and corresponding changes in transcript and functional product levels in A/J mice exposed to environmental relevant concentration of per- and polyfluoroalkyl substances (PFAS) mixture. Mice were fed environmentally relevant concentrations of a PFAS mixture during a period of 10 weeks. The concentrations of the 8 individual PFAS in the mixture were chosen based on measured concentrations in earthworms at a Norwegian skiing area. Our data show high liver accumulation of ∑PFAS in exposed mice, which paralleled significant elevation in body weight and hepatosomatic index (HSI) of male mice. UPC2 -MS/MS analysis in both positive and negative mode, respectively, indicated significant differences between control and exposure groups in the liver of exposed mice. Principal component analysis (PCA) of the features revealed separation of control and exposure groups in both sexes. From the significantly differential 207 lipids, only 72 were identified and shown to belong to eight different lipid classes. PCA of fatty acids (FAs) profile showed a clear separation between control and PFAS exposure groups in both female and male mice, with differential abundant levels of 5 and 4 hydrolyzed FAs, respectively. Transcript and protein analysis of genes associated with lipid homeostasis (ppar-α and β, lxr-α and β, rxr, fasn and srebp) showed that PFAS exposure produced sex- and individual response related alterations. Glutathione reductase (Gr) activity showed exposure-related changes in both female and male mice, compared with controls. Overall, the present study has demonstrated changes in lipid metabolism after PFAS exposure, showing that PFAS accumulation in the liver resulted to hepatotoxic effects, potential interference with membrane lipid profile and homeostasis, and oxidative stress. Given the structural similarity with FAs, interaction between PFAS and nuclear receptors such as PPARs may have severe consequences for general health and physiology in exposed animals and humans.

Effects of PFOS and cyclophosphamide exposure on immune homeostasis in mice

Perfluorooctane sulfonic acid (PFOS) is member of a class of molecules with fluorinated carbon chains known as polyfluoroalkyls. PFOS have been used to produce a variety of industry and comsumer uses. However, a significant concern is that it accumulates in the environment, including in animals and humans, and that it is a potential immunosuppressant. Here we analyze immune homeostasis in mice following chronic exposure to PFOS at levels up to those historically found in PFOS manufacturing workers. Mice were exposed to 0.15, 1.5, 15, or 50 µg /kg of PFOS for 28 days, after which, B cells, T cells, and granulocytes from the bone marrow, liver, spleen, lymph nodes, and thymus were evaluated. We find that at these exposures, there was no effect of PFOS on major T- or B-cell populations, macrophages, dendritic cells, basophils, mast cells, eosinophils, neutrophils, serum antibodies or select serum cytokines. By contrast, mice exposed the known immunosuppressant cyclophosphamide, which was given at 40 mg/kg for four days, exhibited depletion of several granulocyte, T- and B-cell populations of the thymus, bone marrow, and spleen, as well as circulating IgM and IgE antibodies. These data indicate that exposures of up to 50 µg /kg of PFOS for 28 days does not affect immune homeostasis in mice.

Weight of evidence evaluation for chemical-induced immunotoxicity for PFOA and PFOS: findings from an independent panel of experts

Immunotoxicity is the critical endpoint used by some regulatory agencies to establish toxicity values for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS). However, the hypothesis that exposure to certain per- and polyfluoroalkyl substances (PFAS) causes immune dysregulation is subject to much debate. An independent, international expert panel was engaged utilizing methods to reduce bias and "groupthink". The panel concluded there is moderate evidence that PFOS and PFOA are immunotoxic, based primarily on evidence from animal data. However, species concordance and human relevance cannot be well established due to data limitations. The panel recommended additional testing that includes longer-term exposures, evaluates both genders, includes other species of animals, tests lower dose levels, assesses more complete measures of immune responses, and elucidates the mechanism of action. Panel members agreed that the Faroe Islands cohort data should not be used as the primary basis for deriving PFAS risk assessment values. The panel agreed that vaccine antibody titer is not useful as a stand-alone metric for risk assessment. Instead, PFOA and PFOS toxicity values should rely on multiple high-quality studies, which are currently not available for immune suppression. The panel concluded that the available PFAS immune epidemiology studies suffer from weaknesses in study design that preclude their use, whereas available animal toxicity studies provide comprehensive dataset to derive points of departure (PODs) for non-immune endpoints. The panel recommends accounting for potential PFAS immunotoxicity by applying a database uncertainty factor to POD values derived from animal studies for other more robustly supported critical effects.

L-Carnitine reduces reactive oxygen species/endoplasmic reticulum stress and maintains mitochondrial function during autophagy-mediated cell apoptosis in perfluorooctanesulfonate-treated renal tubular cells

We previously reported that perfluorooctanesulfonate (PFOS) causes autophagy-induced apoptosis in renal tubular cells (RTCs) through a mechanism dependent on reactive oxygen species (ROS)/extracellular signal-regulated kinase. This study extended our findings and determined the therapeutic potency of l-Carnitine in PFOS-treated RTCs. l-Carnitine (10 mM) reversed the effects of PFOS (100 µM) on autophagy induction and impaired autophagy flux. Furthermore, it downregulated the protein level of p47Phox, which is partly related to PFOS-induced increased cytosolic ROS in RTCs. Moreover, l-Carnitine reduced ROS production in mitochondria and restored PFOS-impeded mitochondrial function, leading to sustained normal adenosine triphosphate synthesis and oxygen consumption and reduced proton leakage in a Seahorse XF stress test. The increased inositol-requiring enzyme 1α expression by PFOS, which indicated endoplasmic reticulum (ER) stress activation, was associated with PFOS-mediated autophagy activation that could be attenuated through 4-phenylbutyrate (5 mM, an ER stress inhibitor) and l-Carnitine pretreatment. Therefore, by reducing the level of IRE1α, l-Carnitine reduced the levels of Beclin and LC3BII, consequently reducing the level of apoptotic biomarkers including Bax and cleaving PARP and caspase 3. Collectively, these results indicate that through the elimination of oxidative stress, extracellular signal–regulated kinase activation, and ER stress, l-Carnitine reduced cell autophagy/apoptosis and concomitantly increased cell viability in RTCs. This study clarified the potential mechanism of PFOS-mediated RTC apoptosis and provided a new strategy for using l-Carnitine to prevent and treat PFOS-induced RTC apoptosis.

Immunotoxicity mechanisms of perfluorinated compounds PFOA and PFOS

Perfluorinated and polyfluorinated compounds (PFASs) are a class of synthetic chemical substances that are widely used in human production and life, such as fire-fighting foams, textiles and clothing, surfactants, and surface protective agents. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the most abundant and common perfluorinated compounds in biota and humans. Currently, PFOA and PFOS have been listed in the Stockholm Convention on Persistent Organic Pollutants, and their production has been halted in many countries. However, because the high-energy carbon-fluorine bond can make it resistant to hydrolysis, photolysis, microbial degradation, and vertebrate metabolism, PFOA and PFOS show environmental persistence and bioaccumulation and hence, are of great concern to humans and wildlife. PFOA and PFOS have toxic effects on the immune system of the body. This article reviewed the effects of PFOA and PFOS on immune organs such as the spleen, bone marrow, and thymus of mice and zebrafish, and the effects on non-specific immune functions such as the skin barrier, intestinal mucosal barrier, and humoral immunity. We also reviewed the influence of specific immune functions based on cellular immunity, and further summarized the possible immune toxicity mechanisms such as AIM2 inflammasome activation, gene dysregulation, and signal pathway disorders caused by PFOA and PFOS. The aim of this review was to provide a reference for further understanding of the immunotoxicity and the responsible mechanism of PFOA and PFOS.

Effects of an environmentally relevant PFAS mixture on dopamine and steroid hormone levels in exposed mice

In the present study, we investigated the dopaminergic and steroid hormone systems of A/J mice fed environmentally relevant concentrations of a perfluoroalkyl substance (PFAS) mixture over a period of 10 weeks. The PFAS mixture was chosen based on measured PFAS concentrations in earthworms at a Norwegian skiing area (Trondheim) and consisted of eight different PFAS. Dietary exposure to PFAS led to lower total brain dopamine (DA) concentrations in male mice, as compared to control. On the transcript level, brain tyrosine hydroxylase (th) of PFAS exposed males was reduced, compared to the control group. No significant differences were observed on the transcript levels of enzymes responsible for DA metabolism, namely - monoamine oxidase (maoa and maob) and catechol-O methyltransferase (comt). We detected increased transcript level for DA receptor 2 (dr2) in PFAS exposed females, while expression of DA receptor 1 (dr1), DA transporter (dat) and vesicular monoamine transporter (vmat) were not affected by PFAS exposure. Regarding the steroid hormones, plasma and muscle testosterone (T), 11-ketotestosterone (11-KT) and 17β-estradiol (E2) levels, as well as transcripts for estrogen receptors (esr1 and esr2), gonadotropin releasing hormone (gnrh) and aromatase (cyp19) were unaltered by the PFAS treatment. These results indicate that exposure to PFAS doses, comparable to previous observation in earthworms at a Norwegian skiing area, may alter the dopaminergic system of mice with overt consequences for health, general physiology, cognitive behavior, reproduction and metabolism.

Exposure, health effects, sensing, and remediation of the emerging PFAS contaminants - Scientific challenges and potential research directions

Per- and polyfluoroalkyl substances (PFAS) make up a large group of persistent anthropogenic chemicals which are difficult to degrade and/or destroy. PFAS are an emerging class of contaminants, but little is known about the long-term health effects related to exposure. In addition, technologies to identify levels of contamination in the environment and to remediate contaminated sites are currently inadequate. In this opinion-type discussion paper, a team of researchers from the University of Connecticut and the University at Albany discuss the scientific challenges in their specific but intertwined PFAS research areas, including rapid and low-cost detection, energy-saving remediation, the role of T helper cells in immunotoxicity, and the biochemical and molecular effects of PFAS among community residents with measurable PFAS concentrations. Potential research directions that may be employed to address those challenges and improve the understanding of sensing, remediation, exposure to, and health effects of PFAS are then presented. We hope our account of emerging problems related to PFAS contamination will encourage a broad range of scientific experts to bring these research initiatives addressing PFAS into play on a national scale.

Risk to human health related to the presence of perfluoroalkyl substances in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluoroalkyl substances (PFASs) in food. Based on several similar effects in animals, toxicokinetics and observed concentrations in human blood, the CONTAM Panel decided to perform the assessment for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS. These made up half of the lower bound (LB) exposure to those PFASs with available occurrence data, the remaining contribution being primarily from PFASs with short half-lives. Equal potencies were assumed for the four PFASs included in the assessment. The mean LB exposure in adolescents and adult age groups ranged from 3 to 22, the 95th percentile from 9 to 70 ng/kg body weight (bw) per week. Toddlers and 'other children' showed a twofold higher exposure. Upper bound exposure was 4- to 49-fold higher than LB levels, but the latter were considered more reliable. 'Fish meat', 'Fruit and fruit products' and 'Eggs and egg products' contributed most to the exposure. Based on available studies in animals and humans, effects on the immune system were considered the most critical for the risk assessment. From a human study, a lowest BMDL 10 of 17.5 ng/mL for the sum of the four PFASs in serum was identified for 1-year-old children. Using PBPK modelling, this serum level of 17.5 ng/mL in children was estimated to correspond to long-term maternal exposure of 0.63 ng/kg bw per day. Since accumulation over time is important, a tolerable weekly intake (TWI) of 4.4 ng/kg bw per week was established. This TWI also protects against other potential adverse effects observed in humans. Based on the estimated LB exposure, but also reported serum levels, the CONTAM Panel concluded that parts of the European population exceed this TWI, which is of concern.

Using Traditional Chinese Medicine to Treat Hepatocellular Carcinoma by Targeting Tumor Immunity

As the leading cause of cancer-related death, hepatocellular carcinoma (HCC) threatens human health and limited treatments are available to cure the disease efficiently and effectively. The particularly immunotolerant environment of the liver lowers the efficacy of current therapies in patients with advanced HCC. Traditional Chinese medicine (TCM) is gathering increasing interest due to the immunoregulatory properties of certain compounds. In advanced HCC, TCM can restore immunosurveillance to promote antitumor effects in several ways, including the upregulation of immunostimulatory factors and the downregulation of immunosuppressive factors. The characteristic multitarget regulation of TCM compounds may provide new insights regarding effective HCC immunotherapies. Here, we review the immunoregulatory potency of TCMs for treating HCC and explain how individual TCM drugs and complex formulas remodel the immune environment in various cell- and cytokine-dependent manners.

Perfluorooctane sulfonate induces apoptosis via activation of FoxO3a and upregulation of proapoptotic Bcl-2 proteins in PC12 cells

Perfluorooctane sulfonate (PFOS), a kind of organic pollutant widely found in the environment and biota, could alter normal brain development and produce cognitive dysfunction. For the past years, the neurotoxic effects of PFOS have been shown. Recent studies have proven that PFOS can induce neuronal apoptosis and cause neurotoxicity, but the regulatory proteins referred to the process have not been clarified. In this study, PC12 cells were used to investigate the changes of the expression of apoptosis-related proteins, forkhead box O3 (FoxO3a) and pro-apoptotic Bcl-2 proteins. We detected that the levels of cleaved caspase-3 and cleaved PARP were up-regulated obviously in PFOS-treated PC12 cells by using Western blotting, and that the apoptotic rate of PC12 cells was increased significantly by using flow cytometry, verifying that PFOS could induce neuronal apoptosis. Western blot analysis and immunofluorescence revealed obvious up-regulation of the expression of FoxO3a and proapoptotic Bcl-2 proteins. In addition, knockdown of FoxO3a gene inhibited Bim expression and apoptosis. According to the data, we believe that FoxO3a may play a crucial role in PFOS-induced neurotoxicity.

Assessing the human health risks of perfluorooctane sulfonate by in vivo and in vitro studies

The wide use of perfluorooctane sulfonate (PFOS) has led to increasing concern about its human health risks over the past decade. In vivo and in vitro studies are important and effective means to ascertain the toxic effects of PFOS on humans and its toxic mechanisms. This article systematically reviews the human health risks of PFOS based on the currently known facts found by in vivo and in vitro studies from 2008 to 2018. Exposure to PFOS has caused hepatotoxicity, neurotoxicity, reproductive toxicity, immunotoxicity, thyroid disruption, cardiovascular toxicity, pulmonary toxicity, and renal toxicity in laboratory animals and many in vitro human systems. These results and related epidemiological studies confirmed the human health risks of PFOS, especially for exposure via food and drinking water. Oxidative stress and physiological process disruption based on fatty acid similarity were widely studied mechanisms of PFOS toxicity. Future research for assessing the human health risks of PFOS is recommended in the chronic toxicity and molecular mechanisms, the application of various omics, and the integration of toxicological and epidemiological data.

Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in food. Regarding PFOS and PFOA occurrence, the final data set available for dietary exposure assessment contained a total of 20,019 analytical results (PFOS n = 10,191 and PFOA n = 9,828). There were large differences between upper and lower bound exposure due to analytical methods with insufficient sensitivity. The CONTAM Panel considered the lower bound estimates to be closer to true exposure levels. Important contributors to the lower bound mean chronic exposure were 'Fish and other seafood', 'Meat and meat products' and 'Eggs and egg products', for PFOS, and 'Milk and dairy products', 'Drinking water' and 'Fish and other seafood' for PFOA. PFOS and PFOA are readily absorbed in the gastrointestinal tract, excreted in urine and faeces, and do not undergo metabolism. Estimated human half-lives for PFOS and PFOA are about 5 years and 2-4 years, respectively. The derivation of a health-based guidance value was based on human epidemiological studies. For PFOS, the increase in serum total cholesterol in adults, and the decrease in antibody response at vaccination in children were identified as the critical effects. For PFOA, the increase in serum total cholesterol was the critical effect. Also reduced birth weight (for both compounds) and increased prevalence of high serum levels of the liver enzyme alanine aminotransferase (ALT) (for PFOA) were considered. After benchmark modelling of serum levels of PFOS and PFOA, and estimating the corresponding daily intakes, the CONTAM Panel established a tolerable weekly intake (TWI) of 13 ng/kg body weight (bw) per week for PFOS and 6 ng/kg bw per week for PFOA. For both compounds, exposure of a considerable proportion of the population exceeds the proposed TWIs.

Subchronic Hepatotoxicity Effects of 6:2 Chlorinated Polyfluorinated Ether Sulfonate (6:2 Cl-PFESA), a Novel Perfluorooctanesulfonate (PFOS) Alternative, on Adult Male Mice

The compound 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), an alternative to perfluorooctanesulfonate (PFOS) in the metal-plating industry, has been widely detected in various environmental matrices. However, its hepatotoxicity has yet to be clarified. Here, male mice were exposed to 0.04, 0.2, or 1 mg/kg/day of 6:2 Cl-PFESA for 56 days. Results demonstrated that relative liver weight increased significantly in the 0.2 and 1 mg/kg/day 6:2 Cl-PFESA groups, whereas liver lipid accumulation increased in all 6:2 Cl-PFESA groups. Serum enzyme activities of alanine transaminase and alkaline phosphatase were increased. Serum triglycerides and low-density lipoprotein cholesterol both increased, whereas serum total cholesterol and high-density lipoprotein cholesterol decreased following 6:2 Cl-PFESA exposure. A total of 264 differentially expressed proteins (127 up-regulated and 137 down-regulated), mainly involved in lipid metabolism, xenobiotic metabolism, and ribosome biogenesis, were identified by quantitative proteomics. Bioinformatics analysis highlighted the de-regulation of PPAR and PXR, which may contribute to the hepatotoxicity of 6:2 Cl-PFESA. Additionally, 6:2 Cl-PFESA induced both cell apoptosis and proliferation in the mouse liver. Compared to the overt toxicity of PFOS, 6:2 Cl-PFESA exhibited more-serious hepatotoxicity. Thus, caution should be exercised in the application of 6:2 Cl-PFESA as a replacement alternative to PFOS in industrial areas.

Environmental perfluorooctane sulfonate exposure drives T cell activation in bottlenose dolphins

Perfluoroalkyl acids (PFAAs) are highly stable compounds that have been associated with immunotoxicity in epidemiologic studies and experimental rodent models. Lengthy half-lives and resistance to environmental degradation result in bioaccumulation of PFAAs in humans and wildlife. Perfluorooctane sulfonate (PFOS), the most prevalent PFAA detected within the environment, is found at high levels in occupationally exposed humans. We have monitored the environmental exposure of dolphins in the Charleston, SC region for over 10 years and levels of PFAAs, and PFOS in particular, were significantly elevated. As dolphins may serve as large mammal sentinels to identify the impact of environmental chemical exposure on human disease, we sought to assess the effect of environmental PFAAs on the cellular immune system in highly exposed dolphins. Herein, we utilized a novel flow cytometry-based assay to examine T cell-specific responses to environmental PFAA exposure ex vivo and to exogenous PFOS exposure in vitro. Baseline PFOS concentrations were associated with significantly increased CD4⁺ and CD8⁺ T cell proliferation from a heterogeneous resident dolphin population. Further analysis demonstrated that in vitro exposure to environmentally relevant levels of PFOS promoted proinflammatory cytokine production and proliferation in a dose-dependent manner. Collectively, these findings indicate that PFOS is capable of inducing proinflammatory interferon-gamma, but not immunoregulatory interleukin-4 production in T cells, which may establish a state of chronic immune activation known to be associated with susceptibility to disease. These findings suggest that PFOS directly dysregulates the dolphin cellular immune system and has implications for health hazards. Copyright © 2017 John Wiley & Sons, Ltd.

Testosterone-Mediated Endocrine Function and TH1/TH2 Cytokine Balance after Prenatal Exposure to Perfluorooctane Sulfonate: By Sex Status

Little information exists about the evaluation of potential developmental immunotoxicity induced by perfluorooctane sulfonate (PFOS), a synthetic persistent and increasingly ubiquitous environmental contaminant. To assess potential sex-specific impacts of PFOS on immunological health in the offspring, using male and female C57BL/6 mice, pups were evaluated for developmental immunotoxic effects after maternal oral exposure to PFOS (0.1, 1.0 and 5.0 mg PFOS/kg/day) during Gestational Days 1-17. Spontaneous TH1/TH2-type cytokines, serum levels of testosterone and estradiol were evaluated in F1 pups at four and eight weeks of age. The study showed that male pups were more sensitive to the effects of PFOS than female pups. At eight weeks of age, an imbalance in TH1/TH2-type cytokines with excess TH2 cytokines (IL-4) was found only in male pups. As for hormone levels, PFOS treatment in utero significantly decreased serum testosterone levels and increased estradiol levels only in male pups, and a significant interaction between sex and PFOS was observed for serum testosterone at both four weeks of age (pinteraction = 0.0049) and eight weeks of age (pinteraction = 0.0227) and for estradiol alternation at four weeks of age (pinteraction = 0.0351). In conclusion, testosterone-mediated endocrine function may be partially involved in the TH1/TH2 imbalance induced by PFOS, and these deficits are detectable among both young and adult mice and may affect males more than females.

ROS-mediated apoptosis of HAPI microglia through p53 signaling following PFOS exposure

Perfluorooctane sulfonate (PFOS), the most extensively studied member of perfluoroalkyl and polyfluoroalkyl substances (PFASs), has been thought to be toxic to the central nervous system (CNS) of mammals. However, the neurotoxic effects of PFOS remain largely unknown. In this study, the effect of PFOS on microglial apoptosis was examined. The results showed that PFOS could significantly reduce the cell viability and mediate cell apoptosis in HAPI microglia, which was closely accompanied with ROS production and p53 overexpression. Moreover, p53 interference significantly ameliorated PFOS-triggered cytotoxic effects in HAPI microglia, including the downregulation of cleaved PARP and cleaved caspase 3. Interestingly, NAC, a ROS inhibitor, inhibited p53 expression, and decreased the apoptosis of HAPI microglia. Taken together, these findings suggest that upregulated production of ROS plays a vital role in PFOS-mediated apoptosis in HAPI microglia via the modulation of p53 signaling.

In vivo immunotoxicity of perfluorooctane sulfonate in BALB/c mice: Identification of T-cell receptor and calcium-mediated signaling pathway disruption through gene expression profiling of the spleen

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant that is used worldwide and is continuously being detected in biota and the environment, thus presenting potential threats to the ecosystem and human health. Although PFOS is highly immunotoxic, its underlying molecular mechanisms remain largely unknown. The present study examined PFOS-induced immunotoxicity in the mouse spleen and explored its underlying mechanisms by gene expression profiling. Oral exposure of male BALB/c mice for three weeks followed by one-week recovery showed that a 10 mg/kg/day PFOS exposure damaged the splenic architecture, inhibited T-cell proliferation in response to mitogen, and increased the percentages of T helper (CD3(+)CD4(+)) and cytotoxic T (CD3(+)CD8(+)) cells, despite the decrease in the absolute number of these cells. A delayed type of PFOS immunotoxicity was observed, which mainly occurred during the recovery period. Global gene expression profiling of mouse spleens and QRT-PCR analyses suggest that PFOS inhibited the expression of genes involved in cell cycle regulation and NRF2-mediated oxidative stress response, and upregulated those in TCR signaling, calcium signaling, and p38/MAPK signaling pathways. Western blot analysis confirmed that the expressions of CAMK4, THEMIS, and CD3G, which were involved in the upregulated pathways, were induced upon PFOS exposure. Acute PFOS exposure modulated calcium homoeostasis in splenocytes. These results indicate that PFOS exposure can activate TCR signaling and calcium ion influx, which provides a clue for the potential mechanism of PFOS immunotoxicity. The altered signaling pathways by PFOS treatment as revealed in the present study might facilitate in better understanding PFOS immunotoxicity and explain the association between immune disease and PFOS exposure.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: focus on the cancer hallmark of tumor angiogenesis

One of the important 'hallmarks' of cancer is angiogenesis, which is the process of formation of new blood vessels that are necessary for tumor expansion, invasion and metastasis. Under normal physiological conditions, angiogenesis is well balanced and controlled by endogenous proangiogenic factors and antiangiogenic factors. However, factors produced by cancer cells, cancer stem cells and other cell types in the tumor stroma can disrupt the balance so that the tumor microenvironment favors tumor angiogenesis. These factors include vascular endothelial growth factor, endothelial tissue factor and other membrane bound receptors that mediate multiple intracellular signaling pathways that contribute to tumor angiogenesis. Though environmental exposures to certain chemicals have been found to initiate and promote tumor development, the role of these exposures (particularly to low doses of multiple substances), is largely unknown in relation to tumor angiogenesis. This review summarizes the evidence of the role of environmental chemical bioactivity and exposure in tumor angiogenesis and carcinogenesis. We identify a number of ubiquitous (prototypical) chemicals with disruptive potential that may warrant further investigation given their selectivity for high-throughput screening assay targets associated with proangiogenic pathways. We also consider the cross-hallmark relationships of a number of important angiogenic pathway targets with other cancer hallmarks and we make recommendations for future research. Understanding of the role of low-dose exposure of chemicals with disruptive potential could help us refine our approach to cancer risk assessment, and may ultimately aid in preventing cancer by reducing or eliminating exposures to synergistic mixtures of chemicals with carcinogenic potential.

APC targeted micelle for enhanced intradermal delivery of hepatitis B DNA vaccine

Chronic hepatitis B is a serious liver disease and puts people at high risk of death from cirrhosis and liver cancer. Although DNA vaccination has been emerged as a potential immunotherapeutic strategy for the treatment of chronic hepatitis B, the efficiencies were not adequate in clinical trials. Here we describe the design, synthesis, and evaluation of mannosylated phenylalanine grafted chitosan (Man-CS-Phe) as a DNA delivery vector for direct transfection of antigen presenting cells to improve cellular and humoral immunity to plasmid-coded antigen. The cationic Man-CS-Phe micelles condense plasmid DNA into nanoscale polyplexes and provide efficient protection of complexed DNA from nuclease degradation. The mannose receptor-mediated enhanced cell uptake and high in vitro transfection efficiency of the polyplexes were demonstrated in RAW 264.7 and DC 2.4 cells using GFP-expressing plasmid DNA. Furthermore, intradermal immunization of BALB/c mice indicated that hepatitis B DNA vaccine/Man-CS-Phe polyplexes not only induced multi-fold higher serum antibody titer in comparison to all other formulations including FuGENE HD, but also significantly stimulated T-cell proliferation and skewed T helper toward Th1 polarization. These results illustrate that the Man-CS-Phe can serve as a promising DNA delivery vector to harness both cellular and humoral arms of immune system.

Perfluorooctane sulfonate induces apoptosis of hippocampal neurons in rat offspring associated with calcium overload

The purpose of this research is to investigate the effects of perfluorooctane sulfonate (PFOS) on neuronal apoptosis in the hippocampus of rat offspring, and to elucidate the underlying mechanisms associated with calcium homeostasis.

Toxicity of the azo dyes Acid Red 97 and Bismarck Brown Y to Western clawed frog (Silurana tropicalis)

Azo compounds are used in a variety of industrial applications, such as textile colorant. Azo dyes have been found to contaminate aquatic environments and it has been shown that these compounds could potentially be toxic or induce endocrine disruption in aquatic organisms. However, there are few data available on the toxicity of these dyes, specifically Acid Red 97 (AR97) and Bismarck Brown Y (BBY). The aim of this study was to determine the toxicity and the endocrine-disrupting properties of AR97 and BBY in frogs. As fugacity modeling predicted that both compounds would sorb to sediment, sediment exposures were performed using a geometric range of concentrations (0, 1, 10, 100 and 1,000 ppm). Both AR97 and BBY dyes were not lethal to Silurana tropicalis embryos; however, BBY significantly induced malformations. Gene expression analysis of oxidative stress and mutagen-related genes was performed in BBY-treated larvae. There were significant two-fold increases of the tumor-suppressing protein p53 and heat shock protein 70 mRNA at 1,000 ppm suggesting that BBY induces cellular stress in early S. tropicalis development. Transcripts of the heat shock protein 90 did not change. Furthermore, reproductive-related genes were assessed and a 2.1-fold change was observed in the mRNA of the steroidogenic acute regulatory protein while steroid 5 alpha-reductase type 2 and androgen receptor transcript levels did not vary among treatments. In conclusion, high concentrations of BBY lead to increased developmental defects in frog embryogenesis and early larval development.

Proteomic analysis of perfluorooctane sulfonate-induced apoptosis in human hepatic cells using the iTRAQ technique

Perfluorooctane sulfonate (PFOS) is one of the most commonly used perfluorinated compounds, whose environmental exposure has been associated with a number of adverse health outcomes. However, the molecular mechanisms involved in PFOS toxicity are still not well elucidated. In the present study, we applied iTRAQ labeling quantitative proteomic technology to investigate the differential protein expression profiles of non-tumor human hepatic cells (L-02) exposed to PFOS. A total of 18 proteins were differentially expressed in a dose-dependent manner in PFOS-treated cells versus the control. Among these, 11 proteins were up-regulated and 7 were down-regulated. Gene ontology analysis indicated that PFOS would exert toxic effects on L-02 cells by affecting multiple biological processes, including protein biosynthesis and degradation, mRNA processing and splicing, transcription, signal transduction and transport. Furthermore, the proteomic results especially proposed that the inhibition of HNRNPC, HUWE1 and UBQLN1, as well as the induction of PAF1 is involved in the activation of the p53 and c-myc signaling pathways, which then trigger the apoptotic process in L-02 cells exposed to PFOS. Overall, these data will aid our understanding of the mechanisms responsible for PFOS-mediated hepatotoxicity, and develop useful biomarkers for monitoring and evaluating PFOS contamination in the environment.

Gastrodin stimulates anticancer immune response and represses transplanted H22 hepatic ascitic tumor cell growth: Involvement of NF-κB signaling activation in CD4+ T cells

Gastrodia elata Blume (G. elata) is a famous restorative food in East Asia. It can be used as an auxiliary reagent in hepatocellular carcinoma (HCC) treatment. Previous studies unveiled that G. elata exhibited immunomodulatory activities. To explore the active ingredients contributing to its immunomodulatory activities, gastrodin, vanillin, and parishin B were purified from G. elata and their anti-HCC effects were assessed in vivo. Among these compounds, only gastrodin was capable of repressing transplanted H22 ascitic hepatic tumor cell growth in vivo with low toxicity. Further investigations were designed to explore the effects of gastrodin on the immune system of tumor-bearing mice and potential molecular mechanisms underlying these effects. Our data showed that gastrodin ameliorated tumor cell transplantation-induced activation of endogenous pro-apoptotic pathway in CD4+ T cells and abnormalities in serum cytokine profiles in host animals. These events enhanced cytotoxic activities of natural killer and CD8+ T cells against H22 hepatic cancer cells. Gastrodin administration specifically upregulated mRNA levels of several nuclear factor κB (NF-κB) responsive genes in CD4+ T cells but not in CD8+ T cells. Chromatin immunoprecipitation assay showed that gastrodin increased the association of NF-κB p65 subunit to the promoter regions of IL-2 and Bcl-2 encoding genes in CD4+ T cells. Our investigations demonstrated that gastrodin is the main active ingredient contributing to the anticancer immunomodulatory properties of G. elata. Promoting NF-κB-mediated gene transcription in CD4+ T cells is implicated in its immunomodulatory activity.