Perfluorooctanesulfonate and perfluorooctanoate exacerbate airway inflammation in asthmatic mice and in vitro

Single-cell transcriptomics reveal the microenvironment landscape of perfluorooctane sulfonate-induced liver injury in female mice

Epidemic and animal studies have reported that perfluoroalkyl and polyfluoroalkyl substances (PFASs) are strongly associated with liver injury; however, to date, the effects of PFASs on the hepatic microenvironment remain largely unknown. In this study, we established perfluorooctane sulfonic acid (PFOS)-induced liver injury models by providing male and female C57BL/6 mice with water containing PFOS at varying doses for 4 weeks. Hematoxylin and eosin staining revealed that PFOS induced liver injury in both sexes. Elevated levels of serum aminotransferases including those of alanine aminotransferase and aspartate transaminase were detected in the serum of mice treated with PFOS. Female mice exhibited more severe liver injury than male mice. We collected the livers from female mice and performed single-cell RNA sequencing. In total, 36,529 cells were included and grouped into 10 major cell types: B cells, granulocytes, T cells, NK cells, monocytes, dendritic cells, macrophages, endothelial cells, fibroblasts, and hepatocytes. Osteoclast differentiation was upregulated and the T cell receptor signaling pathway was significantly downregulated in PFOS-treated livers. Further analyses revealed that among immune cell clusters in PFOS-treated livers, Tcf7+CD4+T cells were predominantly downregulated, whereas conventional dendritic cells and macrophages were upregulated. Among the fibroblast subpopulations, hepatic stellate cells were significantly enriched in PFOS-treated female mice. CellphoneDB analysis suggested that fibroblasts interact closely with endothelial cells. The major ligand-receptor pairs between fibroblasts and endothelial cells in PFOS-treated livers were Dpp4_Cxcl12, Ackr3_Cxcl12, and Flt1_complex_Vegfa. These genes are associated with directing cell migration and angiogenesis. Our study provides a general framework for understanding the microenvironment in the livers of female mice exposed to PFOS at the single-cell level.

SPIN: sex-specific and pathway-based interpretable neural network for sexual dimorphism analysis

Sexual dimorphism in prevalence, severity and genetic susceptibility exists for most common diseases. However, most genetic and clinical outcome studies are designed in sex-combined framework considering sex as a covariate. Few sex-specific studies have analyzed males and females separately, which failed to identify gene-by-sex interaction. Here, we propose a novel unified biologically interpretable deep learning-based framework (named SPIN) for sexual dimorphism analysis. We demonstrate that SPIN significantly improved the C-index up to 23.6% in TCGA cancer datasets, and it was further validated using asthma datasets. In addition, SPIN identifies sex-specific and -shared risk loci that are often missed in previous sex-combined/-separate analysis. We also show that SPIN is interpretable for explaining how biological pathways contribute to sexual dimorphism and improve risk prediction in an individual level, which can result in the development of precision medicine tailored to a specific individual's characteristics.

Association between per- and polyfluoroalkyl substances exposure and prevalence of chronic obstructive pulmonary disease: The mediating role of serum albumin

BACKGROUND

No study has examined the association between per- and polyfluoroalkyl substances (PFAS) exposure and chronic obstructive pulmonary disease (COPD) risk. This study aims to explore this relationship.

METHODS

This study enrolled 4541 individuals who had available data on PFAS, COPD, and covariates from NHANES 2007-2018. Serum PFAS including perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS) were analyzed, because of high detective rates. Considering the skew distribution of PFAS levels, the natural logarithm-transformed PFAS (Ln-PFAS) was used. Logistic regression analysis, restricted cubic spline (RCS), and weighted quantile sum (WQS) regression were performed to explore the single, nonlinear, and mixed effects. A mediating analysis was used to evaluate the mediated effects of albumin.

RESULTS

Individuals with COPD had higher levels of PFHxS, PFNA, PFOA, and PFOS compared to those without COPD. Ln-PFNA (OR males: 1.92, 95 % CI:1.31 to 2.80, P: <0.001; OR females: 1.07, 95 % CI: 0.81 to 1.40, P: 0.636) and ln-PFOA (OR males: 2.17, 95 % CI:1.38 to 3.41, P: <0.001; OR females: 1.49, 95 % CI: 1.08 to 2.05, P: 0.016) were associated with COPD risk especially in males. The interaction between PFNA exposure and sex on COPD risk was significant (P interaction: <0.001). The RCS curve demonstrated the nonlinear relationship between the ln-PFOA (P nonlinear:0.001), ln-PFNA (P nonlinear:0.045), and COPD risk in males. WQS analysis showed mixed PFAS exposure was correlated with COPD risk in males (OR: 1.44, 95 % CI:1.18 to 1.75, P: <0.001). Albumin mediated the relationship between PFOA and COPD (mediated proportion: -17.94 %).

CONCLUSION

This study concludes PFOA and PFNA are linked to a higher COPD risk in males, and serum albumin plays a mediating role in the relationship between PFOA and COPD. Thess findings are beneficial for the prevention of COPD. Further studies are required to explore potential mechanisms.

Threats of per- and poly-fluoroalkyl pollutants to susceptible populations

Environmental exposure to per- and poly-fluoroalkyl substances (PFAS) has raised significant global health concerns due to potential hazards in healthy adults. However, the impact of PFAS on susceptible populations, including pregnant individuals, newborns, the older people, and those with underlying health conditions, has been overlooked. These susceptible groups often have physiological changes that make them less resilient to the same exposures. Consequently, there is an urgent need for a comprehensive understanding of the health risks posed by PFAS exposure to these populations. In this review, we delve into the potential health risks of PFAS exposure in these susceptible populations. Equally important, we also examine and discuss the molecular mechanisms that underlie this susceptibility. These mechanisms include the induction of oxidative stress, disruption of the immune system, impairment of cellular metabolism, and alterations in gut microbiota, all of which contribute to the enhanced toxicity of PFAS in susceptible populations. Finally, we address the primary research challenges and unresolved issues that require further investigation. This discussion aims to foster research for a better understanding of how PFAS affect susceptible populations and to pave the way for strategies to minimize their adverse effects.

Inflammation and cardiometabolic diseases induced by persistent organic pollutants and nutritional interventions: Effects of multi-organ interactions

The development and outcome of inflammatory diseases are associated with genetic and lifestyle factors, which include chemical and nonchemical stressors. Persistent organic pollutants (POPs) are major groups of chemical stressors. For example, dioxin-like polychlorinated biphenyls (PCBs), per- and polyfluoroalkyl substances (PFASs), and polybrominated diphenyl ethers (PBDEs) are closely associated with the incidence of inflammatory diseases. The pathology of environmental chemical-mediated inflammatory diseases is complex and may involve disturbances in multiple organs, including the gut, liver, brain, vascular tissues, and immune systems. Recent studies suggested that diet-derived nutrients (e.g., phytochemicals, vitamins, unsaturated fatty acids, dietary fibers) could modulate environmental insults and affect disease development, progression, and outcome. In this article, mechanisms of environmental pollutant-induced inflammation and cardiometabolic diseases are reviewed, focusing on multi-organ interplays and highlighting recent advances in nutritional strategies to improve the outcome of cardiometabolic diseases associated with environmental exposures. In addition, advanced system biology approaches are discussed, which present unique opportunities to unveil the complex interactions among multiple organs and to fuel the development of precision intervention strategies in exposed individuals.

Impact of endocrine disruptors on peripheral blood mononuclear cells in vitro: role of gender

Humans can be exposed to endocrine disruptors (EDs) in numerous ways. EDs can interfere with endogenous hormones at different levels, resulting in numerous adverse human health outcomes, including immunotoxicity. In this regard, this study aimed to investigate in vitro the possible effects of EDs on immune cells and possible gender differences. Peripheral blood mononuclear cells from healthy humans, both males and females, were exposed to 6 different EDs, namely atrazine (herbicide), cypermethrin (insecticide), diethyl phthalate (plasticizer), 17α-ethynylestradiol (contraceptive drug), perfluorooctanesulfonic acid (persistent organic pollutant), and vinclozolin (fungicide). We evaluated the effect of EDs on RACK1 (receptor for activated C kinase 1) expression, considering it as a bridge between the endocrine and the immune system, and putatively used as screening tool of immunotoxic effects of EDs. The exposure to EDs resulted at different extent in alteration in RACK1 expression, pro-inflammatory activity, natural killer lytic ability, and lymphocyte differentiation, with sex-related differences. In particular, diethyl phthalate and perfluorooctanesulfonic acid resulted the most active EDs tested, with gender differences in terms of effects and magnitude. The results from our study evidenced the ability of EDs to directly affect immune cells.

C57BL/6J mice exposed to perfluorooctanoic acid demonstrate altered immune responses and increased seizures after Theiler's murine encephalomyelitis virus infection

Introduction

Neurological diseases can stem from environmental influences such as antecedent viral infections or exposure to potential toxicants, some of which can trigger immune responses leading to neurological symptoms. Theiler's murine encephalomyelitis virus (TMEV) is used to model human neurological conditions associated with prior viral infections, with outcomes partly attributable to improper induction and regulation of the immune response. Perfluorooctanoic acid (PFOA) can alter pathologies known to influence neurological disease such as inflammatory responses, cytokine expression, and glial activation. Co-exposure to TMEV and PFOA was used to test the hypothesis that early life exposure to the potential immunotoxicant PFOA would affect immune responses so as to render TMEV-resistant C57BL/6J (B6) mice susceptible to viral-induced neurological disease.

Methods

Neonate B6 mice were exposed to different treatments: non-injected, sham-infected with PBS, and TMEV-infected, with the drinking water of each group including either 70 ppt PFOA or filtered water. The effects of PFOA were evaluated by comparing neurological symptoms and changes in immune-related cytokine and chemokine production induced by viral infection. Immune responses of 23 cytokines and chemokines were measured before and after infection to determine the effects of PFOA exposure on immune response.

Results

Prior to infection, an imbalance between Th1, Th2, and Treg cytokines was observed in PFOA-exposed mice, suppressing IL-4 and IL-13 production. However, the balance was restored and characterized by an increase in pro-inflammatory cytokines in the non-infected group, and a decrease in IL-10 in the PFOA + TMEV group. Furthermore, the PFOA + TMEV group experienced an increase in seizure frequency and severity.

Discussion

Overall, these findings provide insight into the complex roles of immune responses in the pathogenesis of virus-associated neurological diseases influenced by co-exposures to viruses and immunotoxic compounds.

PFOA, PFHxA and C6O4 differently modulate the expression of CXCL8 in normal thyroid cells and in thyroid cancer cell lines

Industrial chemical PFAS are persistent pollutants. Long chain PFAS were taken out of production due to their risk for human health, however, new congeners PFAS have been introduced. The in vitro effects of the long-chain PFOA, the short-chain PFHxA and the new-generation C6O4 were evaluated in normal and in thyroid cancer cell lines in terms of cell viability and proliferation, and secretion of a pro-tumorigenic chemokine (CXCL8), both at the mRNA and at the protein level. The Nthy-ory 3-1 normal-thyroid cell line, the TPC-1 and the 8505C (RET/PTC rearranged and BRAFV600e mutated, respectively) thyroid-cancer cell lines were exposed to increasing concentrations of each PFAS in a time-course. We evaluated viability using WST-1 (confirmed by AnnexinV/PI) and proliferation using the cristal-violet test. To evaluate CXCL8 mRNA we used RT-PCR and measured CXCL8 in the supernatants by ELISA. The exposure to none PFAS did not affect thyroid cells viability (except for a reduction of 8505C cells viability after 144 h) or proliferation. Individual PFAS differently modulated CXCL8 mRNA and protein level. PFOA increased CXCL8 both at mRNA and protein level in the three cell lines; PFHxA increased CXCL8 mRNA in the three cell lines, but increased the protein only in TPC-1 cells; C6O4 increased the CXCL8 mRNA only in thyroid cancer cell lines, but never increased the CXCL8 protein. The results of the present study indicate that the in vitro exposure to different PFAS may modulate both at the mRNA and secreted protein levels of CXCL8 in normal and cancer thyroid cells. Strikingly different effects emerged according to the specific cell type and to the targeted analyte (CXCL8 mRNA or protein).

Formaldehyde exacerbates asthma in mice through the potentiation of HIF-1α-mediated pro-inflammatory responses in pulmonary macrophages

Exposure to formaldehyde (FA) has been indicated to be positively correlated with increased incidence of allergic asthma in many epidemiological and experimental studies. However, few studies have ever addressed the molecular basis of the correlation. In the present study, it was found that inhaling 2.0 mg/m³ FA for 2 weeks could exacerbate the pulmonary inflammation and mucus over-accumulation in OVA-induced murine asthmatic model. The pro-inflammatory cytokines, such as IL-1β, TNF-α, IL-6 and IL-8, were increased in lung and serum of FA-exposed asthmatic mice. The contribution of HIF-1α signaling in FA-exacerbated allergic asthma was confirmed by bioinformatic analysis. HIF-1α and its downstream proteins, which are known as mediators of glycolysis, were found to be upregulated by 50 μM FA, and the FA-enhanced of glycolysis was reversed by inhibition of HIF-1α with PX-478 in vitro and YC-1 in vivo. Furthermore, it was confirmed that inhibition of HIF-1α signaling could restrain the macrophagic inflammatory responses and asthma exacerbation induced by FA. Collectively, these results revealed that FA could exacerbate asthma through the potentiation of HIF-1α-mediated inflammatory responses in macrophages, which also indicated the universal roles of FA-triggered macrophage metabolic and functional alterations in inflammatory or allergic diseases.

Perfluoroalkyl substance exposure is associated with asthma and innate immune cell count in US adolescents stratified by sex

Exposure to perfluoroalkyl substances (PFAS) may be harmful to humans; however, previous studies have been inconsistent regarding the potential for PFAS-induced immunosuppresion. This study explored the relationship between PFAS exposure and risks of asthma, wheezing, and immunosuppression in 12-19 year-olds using the National Health and Nutrition Examination Survey (NHANES) data. Logistic regression models were used to reveal associations between serum PFAS levels and risks of asthma, wheezing, asthma attack, and emergency department visits. Pearson's correlation was used to determine the relationship between serum PFAS levels and leukocyte count. Data were also stratified by sex. We found that medium-low levels of serum perfluorooctane sulfonate (PFOS) (6.90-12.40 ng/mL) and serum perfluorooctanoic acid (PFOA) (2.43-3.60 ng/mL) were negatively related, respectively, to current asthma and wheezing in boys, and to wheezing in girls. Meanwhile, boys with medium-high levels (1.50-3.00 ng/mL) of serum perfluorohexanesulfonate (PFHxS) had a high risk of wheezing. Among asthmatic participants, both medium-high levels (3.75-5.07 ng/mL) of serum PFOA and high levels (> 3.92 ng/mL) of PFHxS correlated with asthma attacks in boys; likewise, medium-low levels (0.70-0.99 ng/mL) of serum PFNA correlated with asthma attacks in girls. Also, PFOA and PFNA levels were weakly positively correlated with basophil count, whereas PFOS levels were weakly negatively correlated with eosinophils in asthmatic boys, indicating that basophils may be important in the immune response to PFAS exposure among asthmatics.

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.

Perfluorooctane sulfonate promotes atherosclerosis by modulating M1 polarization of macrophages through the NF-κB pathway

Perfluorooctane sulfonate (PFOS) is a widely used and distributed perfluorinated compounds and is reported to be harmful to cardiovascular health; however, the direct association between PFOS exposure and atherosclerosis and the underlying mechanisms remain unknown. Therefore, this study aimed to investigate the effects of PFOS exposure on the atherosclerosis progression and the underlying mechanisms. PFOS was administered through oral gavage to apolipoprotein E-deficient (ApoE^-/-) mice for 12 weeks. PFOS exposure significantly increased pulse wave velocity (PWV) and intima-media thickness (IMT), increased aortic plaque burden and vulnerability, and elevated serum lipid and inflammatory cytokine levels. PFOS promoted aortic and RAW264.7 M1 macrophage polarization, which increased the secretion of nitric oxide synthase (iNOS) and pro-inflammatory factors (tumor necrosis factor-α [TNF-α], interleukin-6 [IL-6], and interleukin-1β [IL-1β]), and suppressed M2 macrophage polarization, which decreased the expression of CD206, arginine I (Arg-1), and interleukin-10 (IL-10). Moreover, PFOS activated nuclear factor-kappa B (NF-κB) in the aorta and macrophages. BAY11-7082 was used to inhibit NF-κB-alleviated M1 macrophage polarization and the inflammatory response induced by PFOS in RAW264.7 macrophages. Our results are the first to reveal the acceleratory effect of PFOS on the atherosclerosis progression in ApoE^-/- mice, which is associated with the NF-κB activation of macrophages to M1 polarization to induce inflammation.

Uptake, distribution, and depuration of emerging per- and polyfluoroalkyl substances in mice: Role of gut microbiota

The bioaccumulation and fate in mammals of hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide dimer acid (HFPO-DA), as major alternatives for perfluorooctanoate (PFOA), have rarely been reported. In addition, the role of gut microbiota was greatly understudied. In this study, the uptake, distribution, and depuration of HFPO-TA, HFPO-DA, and PFOA were investigated by exposure to mice for 14 days, followed by a clearance period of 7 days. The patterns of tissue distribution and depuration kinetics of HFPO-TA and PFOA were similar, but different from HFPO-DA. Liver was the main deposition organ for HFPO-TA and PFOA, making contributions of 58.8 % and 59.1 % to the total mass recovered on day 14. Depuration of HFPO-DA was more rapid than HFPO-TA and PFOA. Approximately 95.3 % of HFPO-DA in liver was eliminated on day 21 compared with day 14. While the clearance rates of HPFO-TA and PFOA were only 6.1 % and 13.9 % on day 21. The comparison between normal and pseudo germ-free mice (GM) was also conducted to investigate the effect of gut microbial on in vivo absorption of the three per- and polyfluoroalkyl substances (PFASs). Significantly higher (p < 0.05) concentrations of all the three PFASs were observed in most organs and tissues of GM compared with NC group. An analysis of gut microbiota showed that the higher absorption of PFASs in GM group may be attributed to the increase of intestinal permeability (as indicated by the decrease of tight junction protein expression), which were induced by the change of lachnospiraceae abundance. The result highlighted the importance of gut microbiota in absorption and health risk evaluation of emerging PFASs.

Electrospun UiO-66-F4/polyacrylonitrile nanofibers for efficient extraction of perfluoroalkyl and polyfluoroalkyl substances in environmental media

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) are a family of emerging contaminants which are widely present in environment. In this work, novel UiO-66-F₄/polyacrylonitrile (UiO-66-F₄/PAN) hybrid nanofibers were firstly prepared via blend electrospinning or in-situ growth method for the pipette-tip solid phase extraction of PFASs. Characterizations demonstrate the as-synthesized UiO-66-F₄/PAN nanofibers have good chemical and thermal stability, possess large surface area (248 m²/g) and mesoporous framework structure. Several extraction factors including the amount of adsorbent, pH and ionic strength of sample solution, extraction time and eluent were investigated and the optimum conditions are 20 mg of the selected sorbent, adjusting to pH 5 and adding 4% w/v NaCl to sample solution, extraction for 12 min (3 min × 4). The good adsorption affinity of UiO-66-F₄/PAN for PFASs can be attributed to the extensive adsorption sites and multiple interactions including hydrophobic interaction, hydrogen bonding and F-F interaction. Low limit of detection (0.008-0.076 µg/L), limit of quantification (0.010-0.163 µg/L) and recoveries (70.84-113.57%) for 9 PFASs with relative standard deviations < 15% were achieved. When applied in the analysis of target PFASs in lake water, tap water, beverage, and shrimp muscle samples, this method could achieve robust and accurate results with sufficient sensitivity for nine PFASs.

Prenatal and postnatal exposure to PFAS and cardiometabolic factors and inflammation status in children from six European cohorts

Developing children are particularly vulnerable to the effects of exposure to per- and polyfluoroalkyl substances (PFAS), a group of endocrine disrupting chemicals. We hypothesized that early life exposure to PFASs is associated with poor metabolic health in children. We studied the association between prenatal and postnatal PFASs mixture exposure and cardiometabolic health in children, and the role of inflammatory proteins. In 1,101 mothers-child pairs from the Human Early Life Exposome project, we measured the concentrations of PFAS in blood collected in pregnancy and at 8 years (range = 6-12 years). We applied Bayesian Kernel Machine regression (BKMR) to estimate the associations between exposure to PFAS mixture and the cardiometabolic factors as age and sex- specific z-scores of waist circumference (WC), systolic and diastolic blood pressures (BP), and concentrations of triglycerides (TG), high-density lipoprotein (HDL-C) and low-density lipoprotein (LDL-C) cholesterol. We measured thirty six inflammatory biomarkers in child plasma and examined the underlying role of inflammatory status for the exposure-outcome association by integrating the three panels into a network. Exposure to the PFAS mixture was positively associated with HDL-C and systolic BP, and negatively associated with WC, LDL-C and TG. When we examined the independent effects of the individual chemicals in the mixture, prenatal PFHxS was negatively associated with HDL-C and prenatal PFNA was positively associated with WC and these were opposing directions from the overall mixture. Further, the network consisted of five distinct communities connected with positive and negative correlations. The selected inflammatory biomarkers were positively, while the postnatal PFAS were negatively related with the included cardiometabolic factors, and only prenatal PFOA was positively related with the pro-inflammatory cytokine IL-1beta and WC. Our study supports that prenatal, rather than postnatal, PFAS exposure might contribute to an unfavorable lipidemic profile and adiposity in childhood.

Perfluoroalkyl substance pollutants activate the innate immune system through the AIM2 inflammasome

Perfluoroalkyl substances (PFAS) are widely used in various manufacturing processes. Accumulation of these chemicals has adverse effects on human health, including inflammation in multiple organs, yet how PFAS are sensed by host cells, and how tissue inflammation eventually incurs, is still unclear. Here, we show that the double-stranded DNA receptor AIM2 is able to recognize perfluorooctane sulfonate (PFOS), a common form of PFAS, to trigger IL-1β secretion and pyroptosis. Mechanistically, PFOS activates the AIM2 inflammasome in a process involving mitochondrial DNA release through the Ca2+-PKC-NF-κB/JNK-BAX/BAK axis. Accordingly, Aim2-/- mice have reduced PFOS-induced inflammation, as well as tissue damage in the lungs, livers, and kidneys in both their basic condition and in an asthmatic exacerbation model. Our results thus suggest a function of AIM2 in PFOS-mediated tissue inflammation, and identify AIM2 as a major pattern recognition receptor in response to the environmental organic pollutants.