Reversal of perfluorooctanesulfonate-induced immunotoxicity by a glucan-resveratrol-vitamin C combination

Per- and polyfluoroalkyl substances alter innate immune function: evidence and data gaps

Per- and polyfluoroalkyl substances (PFASs) are a large class of compounds used in a variety of processes and consumer products. Their unique chemical properties make them ubiquitous and persistent environmental contaminants while also making them economically viable and socially convenient. To date, several reviews have been published to synthesize information regarding the immunotoxic effects of PFASs on the adaptive immune system. However, these reviews often do not include data on the impact of these compounds on innate immunity. Here, current literature is reviewed to identify and incorporate data regarding the effects of PFASs on innate immunity in humans, experimental models, and wildlife. Known mechanisms by which PFASs modulate innate immune function are also reviewed, including disruption of cell signaling, metabolism, and tissue-level effects. For PFASs where innate immune data are available, results are equivocal, raising additional questions about common mechanisms or pathways of toxicity, but highlighting that the innate immune system within several species can be perturbed by exposure to PFASs. Recommendations are provided for future research to inform hazard identification, risk assessment, and risk management practices for PFASs to protect the immune systems of exposed organisms as well as environmental health.

Immune cell profiles associated with human exposure to perfluorinated compounds (PFAS) suggest changes in natural killer, T helper, and T cytotoxic cell subpopulations

Per- and polyfluoroalkyl substances (PFAS) constitutes a group of highly persistent man-made substances. Recent evidence indicates that PFAS negatively impact the immune system. However, it remains unclear how different PFAS are associated with alterations in circulating leukocyte subpopulations. More detailed knowledge of such potential associations can provide better understanding into mechanisms of PFAS immunotoxicity in humans. In this exploratory study, associations of serum levels of common PFAS (perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexane sulfonic acid (PFHxS)) and immune cell profiles of peripheral blood mononuclear cells, both with and without immunostimulation, were investigated. High-dimensional single cell analysis by mass cytometry was done on blood leukocytes from fifty participants in the Norwegian human biomonitoring EuroMix study. Different PFAS were associated with changes in various subpopulations of natural killer (NK), T helper (Th), and cytotoxic T (Tc) cells. Broadly, PFAS concentrations were related to increased frequencies of NK cells and activated subpopulations of NK cells. Additionally, increased levels of activated T helper memory cell subpopulations point to Th2/Th17 and Treg-like skewed profiles. Finally, PFAS concentrations were associated with decreased frequencies of T cytotoxic cell subpopulations with CXCR3+ effector memory (EM) phenotypes. Several of these observations point to biologically plausible mechanisms that may contribute to explaining the epidemiological reports of immunosuppression by PFAS. Our results suggest that PFAS exposures even at relatively low levels are associated with changes in immune cell subpopulations, a finding which should be explored more thoroughly in a larger cohort. Additionally, causal relationships should be confirmed in experimental studies. Overall, this study demonstrates the strength of profiling by mass cytometry in revealing detailed changes in immune cells at a single cell level.

Immune response to COVID-19 vaccination in a population with a history of elevated exposure to per- and polyfluoroalkyl substances (PFAS) through drinking water

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) has been linked to lower vaccine-induced antibody concentrations in children, while data from adults remains limited and equivocal. Characteristics of PFAS exposure and age at vaccination may modify such effects.

OBJECTIVE

We used the mass administration of novel COVID-19 vaccines to test the hypothesis that prior exposure to environmentally-relevant concentrations of PFAS affect antibody response to vaccines in adolescents and adults.

METHODS

Between April and June 2021, 226 participants aged 12-90 years with a history of exposure to PFAS in drinking water and who received an mRNA COVID-19 vaccine participated in our prospective cohort study. SARS-CoV-2 anti-spike and anti-nucleocapsid antibodies (IgG) were quantified before the first and second vaccine doses and again at two follow-ups in the following months (up to 103 days post dose 1). Serum PFAS concentrations (n = 39 individual PFAS) were measured once for each participant during baseline, before their first vaccination. The association between PFAS exposure and immune response to vaccination was investigated using linear regression and generalized estimating equation (GEE) models with adjustment for covariates that affect antibody response. PFAS mixture effects were assessed using weighted quantile sum and Bayesian kernel machine regression methods.

RESULTS

The geometric mean (standard deviation) of perfluorooctane sulfonate and perfluorooctanoic acid serum concentrations in this population was 10.49 (3.22) and 3.90 (4.90) µg/L, respectively. PFAS concentrations were not associated with peak anti-spike antibody response, the initial increase in anti-spike antibody response following vaccination, or the waning over time of the anti-spike antibody response. Neither individual PFAS concentrations nor their evaluation as a mixture was associated with antibody response to mRNA vaccination against COVID-19.

IMPACT STATEMENT

Given the importance of understanding vaccine response among populations exposed to environmental contaminants and the current gaps in understanding this relationship outside of early life/childhood vaccinations, our manuscript contributes meaningful data from an adolescent and adult population receiving a novel vaccination.

Consideration of pathways for immunotoxicity of per- and polyfluoroalkyl substances (PFAS)

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) are of public health concern, because of their ubiquitous and extremely persistent occurrence, and depending on their structure, their bio-accumulative, mobile and toxic properties. Human health effects associated with exposure to PFAS include adverse effects on the immune system. In 2020, EFSA (the European Food Safety Authority) defined adverse effects on the immune system as the most critical effect for human health risk assessment, based on reduced antibody responses to childhood vaccines and similar effects observed in experimental animal studies. Likewise, the U.S. EPA (Environmental Protection Agency) considers PFAS-induced immunotoxicity, especially in children, as the critical effect for risk assessment. However, the mechanisms by which antibody concentrations are impacted are not completely understood. Furthermore, other targets of the immune system functions have been reported in the literature.

OBJECTIVE

The aim of this review is to explore PFAS-associated immune-related effects. This includes, relevant mechanisms that may underlie the observed effects on the immune system, immunosuppression as well as immunoenhancement, such as i) modulation of cell signalling and nuclear receptors, such as NF-κB and PPARs; ii) alteration of calcium signalling and homoeostasis in immune cells; iii) modulation of immune cell populations; iv) oxidative stress and v) impact on fatty acid metabolism & secondary effects on the immune system.

METHODS

A literature research was conducted using three databases (Web of Science, PubMed, and Scopus), which were searched in July 2021 for relevant studies published in the time frame from 2018 to 2021. In total, 487 publications were identified as potentially eligible and following expert-based judgement, articles relevant for mechanisms of PFAS induced immunotoxicity are discussed.

CONCLUSIONS

Taken together, we show that there is substantial evidence from both in vitro and in vivo experimental as well as epidemiological studies, supporting that various PFAS, not only PFOA and PFOS, affect multiple aspects of the immune system. Timing of exposure is critical, because the developing immune system is especially vulnerable to toxic insults, resulting in a higher risk of particularly adverse immune effects but also other organs later in life.

Perfluorooctanoic acid and perfluorooctanesulfonic acid induce immunotoxicity through the NF-κB pathway in black-spotted frog (Rana nigromaculata)

Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are widely detected in the environment and wild animals, thus posing a threat to wildlife and public health; however, knowledge about their immunotoxicity and the underlying mechanism remains limited. In the present study, male black-spotted frogs (Rana nigromaculata) were exposed to environmentally relevant concentrations (0, 1, and 10 μg/L) of PFOA or PFOS for 21 days; subsequently, biochemical analysis, molecular docking, and gene expression determination were conducted. The results indicated that exposure to 10 μg/L PFOA decreased the serum levels of immunoglobulin A. PFOS exposure significantly increased the hepatic levels of interleukin-1β, interleukin-6, tumor necrosis factor-α, interferon-γ, and nitric oxide; but PFOA significantly increased the levels of only tumor necrosis factor-α. Furthermore, PFOA and PFOS exposure significantly decreased the activity of inducible nitric oxide synthase and total nitric oxide synthase. IBRv2 analysis indicated that PFOA and PFOS had a similar effect on these immune indicators, but PFOS was more toxic than PFOA. Molecular docking revealed that PFOA and PFOS can bind to nuclear factor-κB (NF-κB) by forming stable hydrogen bonds. PFOA and PFOS exposure upregulated the gene expression of NF-κB and its downstream genes. Significant correlations between the expression of genes involved in the NF-κB pathway and immune-related indicators suggests that PFOA- and PFOS-induced immunotoxicity was associated with the activation of NF-κB. Our findings provide novel insights into the potential role of NF-κB in immunotoxicity induced by PFOA and PFOS in frogs.

Internal relative potency factors based on immunotoxicity for the risk assessment of mixtures of per- and polyfluoroalkyl substances (PFAS) in human biomonitoring

Relative potency factors (RPFs) for per- and polyfluoroalkyl substances (PFAS) have previously been derived based on liver effects in rodents for the purpose of performing mixture risk assessment with primary input from biomonitoring studies. However, in 2020, EFSA established a tolerable weekly intake for four PFAS assuming equal toxic potency for immune suppressive effects in humans. In this study we explored the possibility of deriving RPFs for immune suppressive effects using available data in rodents and humans. Lymphoid organ weights, differential blood cell counts, and clinical chemistry from 28-day studies in male rats from the National Toxicology Program (NTP) were combined with modeled serum PFAS concentrations to derive internal RPFs by applying dose-response modelling. Identified functional studies used diverse protocols and were not suitable for derivation of RPFs but were used to support immunotoxicity of PFAS in a qualitative manner. Furthermore, a novel approach was used to estimate internal RPFs based on epidemiological data by dose-response curve fitting optimization, looking at serum antibody concentrations and key cell populations from the National Health and Nutrition Examination Survey (NHANES). Internal RPFs were successfully derived for PFAS based on rat thymus weight, spleen weight, and globulin concentration. The available dose-response information for blood cell counts did not show a significant trend. Immunotoxic potency in serum was determined in the order PFDA > PFNA > PFHxA > PFOS > PFBS > PFOA > PFHxS. The epidemiological data showed inverse associations for the sum of PFOA, PFNA, PFHxS, and PFOS with serum antibody concentrations to mumps and rubella, but the data did not allow for deduction of reliable internal RPF estimates. The internal RPFs for PFAS based on decreased rat lymphoid organ weights are similar to those previously established for increased rat liver weight, strengthening the confidence in the overall applicability of these RPFs.

Perfluoroalkyl substances (PFASs) decrease the expression of recombination-activating genes (RAG1 and RAG2) in human B lymphoma Namalwa cells

Per- and polyfluoroalkyl substances (PFASs) are omnipresent and have been shown to induce a wide range of adverse effects, including hepatotoxicity, developmental toxicity and immunotoxicity. So far, little information is available about the mechanisms underlying the toxicity of PFASs, including those related to their immunotoxicity. Reported immunotoxic effects of PFASs include decreased antibody responses in experimental animals and humans, indicating that PFASs may, among others, affect B cell function. In the present study, we first assessed the effects of PFOA on the transcriptome of the human Namalwa B cell line using RNA seq analysis. Gene expression changes, analyzed using Ingenuity Pathway Analysis, pointed to various cellular processes affected by PFOA, including 'B cell development' and 'Primary immunodeficiency signaling'. Interestingly, PFOA decreased the expression of RAG1 and RAG2, genes involved in immunoglobulin and T cell receptor V(D)J recombination. As a next step, time- and concentration-dependent changes in the expression of RAG1 and RAG2 upon exposure to PFOA, PFNA, PFHxS and PFOS were studied through RT-qPCR analysis. Analysis with the concentration-response modeling software PROAST resulted in the following potency ranking: PFNA > PFOA > PFOS > PFHxS. Altogether, the present in vitro study provides insights into the effects of selected PFASs on B cells, identifying RAG1 and RAG2 expression as possible relevant targets that may play a role in the immunotoxicity of PFASs.

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.

Effect of Perfluorooctanesulfonic acid (PFOS) on immune cell development and function in mice

Perfluoroctanesulfonate (PFOS) belongs to a larger family of compounds known as Per- and polyfluoroalkyl substances (PFAS). The strength of the carbon-fluorine bond makes PFOS extremely resistant to environmental degradation. Due to its persistent nature, research has been directed to elucidating possible health effects of PFOS on humans and laboratory animals. Here we have explored the effects of PFOS exposure on immune development and function in mice. We exposed adult mice to 3 and 1.5 μg/kg/day of PFOS for 2 and 4 weeks, respectively, and examined the effects of PFOS exposure on populations of T cells, B cells, and granulocytes. These doses of PFOS resulted in serum levels of approximately 100 ng/mL with no weight loss during exposure. We find that PFOS does not affect T-cell development during this time. However, while PFOS exposure reduced immune cell populations in some organs, it also led to an increase in the numbers of cells in others, suggesting possible relocalization of cells. We also examined the effect of PFOS on the response to influenza virus infection. We find that exposure to PFOS at 1.5 μg/kg/day of PFOS for 4 weeks does not affect weight loss or survival, nor is viral clearance affected. Analysis of antibody and T cell specific antiviral responses indicate that at this concentration, PFOS does not suppress the immune cell development or antigen specific immune response.

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.

Application of the Key Characteristics of Carcinogens to Per and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) constitute a large class of environmentally persistent chemicals used in industrial and consumer products. Human exposure to PFAS is extensive, and PFAS contamination has been reported in drinking water and food supplies as well as in the serum of nearly all people. The most well-studied member of the PFAS class, perfluorooctanoic acid (PFOA), induces tumors in animal bioassays and has been associated with elevated risk of cancer in human populations. GenX, one of the PFOA replacement chemicals, induces tumors in animal bioassays as well. Using the Key Characteristics of Carcinogens framework for cancer hazard identification, we considered the existing epidemiological, toxicological and mechanistic data for 26 different PFAS. We found strong evidence that multiple PFAS induce oxidative stress, are immunosuppressive, and modulate receptor-mediated effects. We also found suggestive evidence indicating that some PFAS can induce epigenetic alterations and influence cell proliferation. Experimental data indicate that PFAS are not genotoxic and generally do not undergo metabolic activation. Data are currently insufficient to assess whether any PFAS promote chronic inflammation, cellular immortalization or alter DNA repair. While more research is needed to address data gaps, evidence exists that several PFAS exhibit one or more of the key characteristics of carcinogens.

Exposure to per-fluoroalkyl and polyfluoroalkyl substances leads to immunotoxicity: epidemiological and toxicological evidence

In this perspective, we evaluate key and emerging epidemiological and toxicological data concerning immunotoxicity of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) and seek to reconcile conflicting conclusions from two reviews published in 2016. We summarize ways that immunosuppression and immunoenhancement are defined and explain how specific outcomes are used to evaluate immunotoxicity in humans and experimental animals. We observe that different approaches to defining immunotoxicological outcomes, particularly those that do not produce clinical disease, may lead to different conclusions from epidemiological and toxicological studies. The fundamental point that we make is that aspects of epidemiological studies considered as limitations can be minimized when data from toxicological studies support epidemiological findings. Taken together, we find that results of epidemiological studies, supported by findings from toxicological studies, provide strong evidence that humans exposed to PFOA and PFOS are at risk for immunosuppression.

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.

Anti-stress action of an orally-given combination of resveratrol, β-glucan, and vitamin C

Stress has repeatedly been found to reduce the abilities of the immune system to fight against individual attacks. The current dissatisfaction with classical medications has led to more attention being focused on natural molecules. As recent studies have suggested that some bioactive molecules can have synergistic effects in stimulation of immune system and reduction of stress, we have evaluated the stress-reducing effects of the resveratrol-β-glucan-vitamin C combination. We found that compared to its individual components, this combination was the strongest reducer of stress-related symptoms, including corticosterone levels and IL-6, IL-12 and IFN-γ production.

Effects of β-glucan on some environmental toxins: An overview

BACKGROUND

Beta-glucans are naturally occurring polysaccharides and constituents of the cell wall of certain pathogenic bacteria and fungi. They have proven healing and immunostimulating properties, linked to enhanced macrophage and natural killer cell function which likely involves specific interaction with several cell surface receptors, such as lactosylceramide, selected scavenger receptors, and dectin-1 (betaGR). In particular, glucan reduces the immunosuppressive effects of a number of agents including chemo therapy and radiation. More recent studies suggest a positive function for glucan in the immunosuppression caused by toxic agents in the environment.

AIM

An overview of the effects of glucan on the mycotoxin, aflotoxin and other environmental toxins (mercury-thimerosal, depleted uranium).

CONCLUSION

Glucan is effective as a natural immunomodulator and could be used as an inexpensive solution to reducing the adverse effects of some environmental toxins.