Assessment of arsenic and polycyclic aromatic hydrocarbon (PAH) exposures on immune function among males in Bangladesh

Humoral immunosuppression of exposure to polycyclic aromatic hydrocarbons and the roles of oxidative stress and inflammation

Previous studies have indicated adverse health effects of exposure to polycyclic aromatic hydrocarbons (PAHs), but evidence on the association between PAH exposure and immunity is scarce and its underlying mechanism is largely unknown. This study assessed human exposure to PAHs by determining the concentrations of PAHs in serum and their metabolites in paired urine. The oxidative stress and inflammation levels were evaluated by urinary DNA damage biomarker 8-hydroxydeoxyguanosine, white blood cell counts and C-reaction protein. We investigated the relationship between PAH exposure and seven immunological components, and explored the indirect roles of oxidative stress and inflammation by mediation and moderation analysis. Multivariate regression analysis revealed that 1-hydroxynaphthalene and 2-hydroxyfluorene were negatively associated with immunoglobulin A, and 3-hydroxyphenanthrene was negatively correlated with complement component 3. Restricted cubic spline analysis demonstrated nonlinear relationships between some individual PAHs or their metabolites with immunological components. Bayesian kernel machine regression and quantile g-computation revealed significant associations of higher PAH exposure with decreased immunoglobulin G and kappa light chain levels. Phenanthrene was the compound that contributed the most to reduced immunoglobulin G. Mediation analysis demonstrated significant indirect effects of 8-hydroxydeoxyguanosine and white blood cell counts on the association between higher PAH exposure and decreased immunological components. Moderation analysis revealed that PAH exposure and decreased immunological components are significantly associated with higher levels of C-reaction protein and white blood cell counts. The results demonstrated significant immunosuppression of PAH exposure and highlighted the indirect roles of oxidative stress and inflammation. Interventions to reduce systemic inflammation may mitigate the adverse immune effects of PAH exposure.

Arsenic exposure is associated with alterations to multiple red blood cell parameters among adults in rural Bangladesh

Chronic arsenic exposures are associated with multiple hematologic disturbances, including anemia. The goal of this study was to evaluate associations between arsenic exposures and hematological parameters among men and women who are chronically exposed to elevated levels of arsenic from drinking water. Hematologic analyses were performed on blood collected from 755 participants (45% male and 54% female) in the Health Effects of Arsenic Longitudinal Study (HEALS) cohort, Bangladesh. Herein, we used linear regression models to estimate associations between red blood cell (RBC) parameters (i.e., RBC counts, hematocrit (HCT), hemoglobin (Hgb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC)) and measurements of arsenic exposure (urinary arsenic and urinary arsenic metabolites). Arsenic exposures showed trending associations with decreased RBC counts in both men and women, a positive association with MCV in males, and an inverse association with MCHC among males, but not among non-smoking females. Among men, those who smoked had stronger associations between arsenic exposures and MCHC than non-smoking males. Collectively, our results show that arsenic exposures affect multiple RBC parameters and highlight potentially important sex differences in arsenic-induced hematotoxicity.

The single and mixed impacts of cadmium, cobalt, lead, and PAHs on systemic immunity inflammation index in male and female

Background

Studies on the association between mixed exposure to common pollutants such as cadmium (Cd), cobalt (Co), lead (Pb), and polycyclic aromatic hydrocarbons (PAHs) with Systemic Immune Inflammatory Index (SII), a novel hemocyte-based inflammatory marker, have not been reported. This study explored the relationship between co-exposure to Cd, Co, Pb, PAHs, and SII.

Methods

In this study, we used data from the National Health and Nutrition Examination Survey and enrolled adults with complete information on Cd, Co, Pb, PAHs, and SII. The linear regression was used to analyze the association of single pollutants with SII. Furthermore, a Bayesian Kernel Machine Regression analysis and a generalized weighted quantile sum regression analysis were used to analyze the association between mixed exposure to Cd, Co, Pb, and six PAHs and SII. We also separated males and females and analyzed the different effects of pollutants on SII, respectively.

Results

5,176 participants were included in the study. After adjusting for age, gender, race, education, smoking, drinking, physical activity, and sedentary, Cd, Co, 1-OHN, 2-OHN and 2-OHF were positive with SII in the total population. Compared with the 50th percentile, the joint effect of pollutants on SII was positive. In the total population, males, and females, the top contaminant with the highest effect weights on SII were Co, Cd, and 1-OHN, respectively. The result of interaction analysis showed that the low concentrations of Cd had an elevation effect on SII in males.

Conclusion

This study found a positive association of mixed exposure to Cd, Co, Pb, and six PAHs with SII, which occurred mainly in females.

Polycyclic aromatic hydrocarbons (PAHs): Updated aspects of their determination, kinetics in the human body, and toxicity

Polycyclic aromatic hydrocarbons (PAHs) are legacy pollutants of considerable public health concern. Polycyclic aromatic hydrocarbons arise from natural and anthropogenic sources and are ubiquitously present in the environment. Several PAHs are highly toxic to humans with associated carcinogenic and mutagenic properties. Further, more severe harmful effects on human- and environmental health have been attributed to the presence of high molecular weight (HMW) PAHs, that is PAHs with molecular mass greater than 300 Da. However, more research has been conducted using low molecular weight (LMW) PAHs). In addition, no HMW PAHs are on the priority pollutants list of the United States Environmental Protection Agency (US EPA), which is limited to only 16 PAHs. However, limited analytical methodologies for separating and determining HMW PAHs and their potential isomers and lack of readily available commercial standards make research with these compounds challenging. Since most of the PAH kinetic data originate from animal studies, our understanding of the effects of PAHs on humans is still minimal. In addition, current knowledge of toxic effects after exposure to PAHs may be underrepresented since most investigations focused on exposure to a single PAH. Currently, information on PAH mixtures is limited. Thus, this review aims to critically assess the current knowledge of PAH chemical properties, their kinetic disposition, and toxicity to humans. Further, future research needs to improve and provide the missing information and minimize PAH exposure to humans.

Bibliometric analysis of global research on polycyclic aromatic hydrocarbons and health risk between 2002 and 2021

During the last 20 years, the association between polycyclic aromatic hydrocarbons (PAHs) and health risk has become one of the hotspots in the fields of public health and the environment. A bibliometric study of 1392 research articles retrieved from the Web of Science Core Collection (WoSCC) published between 2002 and 2021 was performed to give an in-depth statistical evaluation of research progress and future trends on PAHs and health risk (PHR). According to the findings, the annual output of significant scientific papers increased exponentially. China ranked first among the 86 nations in terms of the number of publications (NP), followed by the USA and India. Logistic regression analysis showed that there was a positive relationship between the second tertile of 180-day usage count (AOR = 1.62; 95% CI: 1.16-2.26) and increased odds of open access publishing after adjustment for the confounders, indicating that open access papers on PHR were more preferred over the preceding 6 months than non-open access articles. The most popular terms were "PAHs," "risk assessment," and "source identification." According to the bibliometric study, the research hotspots that require more exploration include identifying PAH sources in media such as soil, water, dust, and food and evaluating their linkages to health hazards using appropriate risk models. Understanding the environmental behavior, bioavailability, and health concerns of PAHs and their derivatives in various media is critical for environmental and public health protection. This paper provides an overview of current research status and future perspectives for PHR research.

Effect of polycyclic aromatic hydrocarbons on immunity

Nearly a quarter of the total number of deaths in the world are caused by unhealthy living or working environments. Therefore, we consider it significant to introduce the effect of a widely distributed component of air/water/food-source contaminants, polycyclic aromatic hydrocarbons (PAHs), on the human body, especially on immunity in this review. PAHs are a large class of organic compounds containing two or more benzene rings. PAH exposure could occur in most people through breath, smoke, food, and direct skin contact, resulting in both cellular immunosuppression and humoral immunosuppression. PAHs usually lead to the exacerbation of autoimmune diseases by regulating the balance of T helper cell 17 and regulatory T cells, and promoting type 2 immunity. However, the receptor of PAHs, aryl hydrocarbon receptor (AhR), appears to exhibit duality in the immune response, which seems to explain some seemingly opposite experimental results. In addition, PAH exposure was also able to exacerbate allergic reactions and regulate monocytes to a certain extent. The specific regulation mechanisms of immune system include the assistance of AhR, the activation of the CYP-ROS axis, the recruitment of intracellular calcium, and some epigenetic mechanisms. This review aims to summarize our current understanding on the impact of PAHs in the immune system and some related diseases such as cancer, autoimmune diseases (rheumatoid arthritis, type 1 diabetes, multiple sclerosis, and systemic lupus erythematosus), and allergic diseases (asthma and atopic dermatitis). Finally, we also propose future research directions for the prevention or treatment on environmental induced diseases.

Human Variation in DNA Repair, Immune Function, and Cancer Risk

DNA damage constantly threatens genome integrity, and DNA repair deficiency is associated with increased cancer risk. An intuitive and widely accepted explanation for this relationship is that unrepaired DNA damage leads to carcinogenesis due to the accumulation of mutations in somatic cells. But DNA repair also plays key roles in the function of immune cells, and immunodeficiency is an important risk factor for many cancers. Thus, it is possible that emerging links between inter-individual variation in DNA repair capacity and cancer risk are driven, at least in part, by variation in immune function, but this idea is underexplored. In this review we present an overview of the current understanding of the links between cancer risk and both inter-individual variation in DNA repair capacity and inter-individual variation in immune function. We discuss factors that play a role in both types of variability, including age, lifestyle, and environmental exposures. In conclusion, we propose a research paradigm that incorporates functional studies of both genome integrity and the immune system to predict cancer risk and lay the groundwork for personalized prevention.

Exposure to arsenic and level of Vitamin D influence the number of Th17 cells and production of IL-17A in human peripheral blood mononuclear cells in adults

There is limited evidence on the effects of environmental exposure to arsenic (As) on the immune system in adults. In a population-based study, we have found that urinary As (UAs), and its metabolites [inorganic As (InAs), monomethylated arsenicals (MMA^+3/+5), and dimethylated arsenicals (DMA^+3/+5)] modulate or influence the number of T-helper 17 (Th17) cells and IL-17A cytokine production. In non-smoking women, we observed that UAs and DMA^+3/+5 were associated with changes in Th17 cell numbers in a nonlinear fashion. In smoking males, we found that UAs was associated with a significant decrease of Th17 cell numbers. Similar association was observed among non-smoking males. Likewise, UAs, DMA^+3/+5 and MMA^+3/+5 were associated with diminished production of IL-17A among non-smoking males. When stratified by Vitamin D levels defined as sufficient (≥20 ng/ml) and insufficient (<20 ng/ml), we found a substancial decrease in Th17 cell numbers among those with insufficient levels. Individuals with sufficient VitD levels demonstrated significant inhibition of IL-17A production in non-smoking males. Collectively, we find that exposure to As via drinking water is associated with alterations in Th17 numbers and IL-17A production, and that these associations may be modified by Vitamin D status. Our findings have significance for health outcomes associated with As exposure.

Potential value and mechanism of Rosa roxburghii tratt juice on pro-inflammatory responses in peripheral blood of patients with arsenic poisoning

Increasing evidence supports the role of arsenic in dysregulated immune and inflammation responses, while, safe and effective treatments have not been fully examined. Rosa roxburghii Tratt (RRT), a traditional Chinese edible fruit with potential immunoregulatory activities, was considered as a dietary supplement to explore its protective effects and possible mechanism in arsenic-induced dysregulated inflammation responses. We enrolled 209 arsenicosis patients and 41 controls to obtain baseline data, including the degree of arsenic poisoning prior to the RRT juice (RRTJ) intervention. Then, based on criteria of inclusion and exclusion and the principle of voluntary participation, 106 arsenicosis patients who volunteered to receive treatment were divided into RRTJ (n = 53) and placebo (n = 53) groups randomly. After three months follow-up, 89 subjects (46 and 43 of the RRTJ and placebo groups, respectively) completed the study and were examined for the effects and possible mechanisms of RRTJ on the Th17 cells-related pro-inflammatory responses in peripheral blood mononuclear cells (PBMCs). The PBMCs had higher levels of Th17 and Th17-related inflammatory cytokines IL-17, IL-6, and RORγt. Furthermore, the gene expressions of STAT3 and SOCS3 in PBMCs increased and decreased, respectively. Conversely, RRTJ decreased the number of Th17 cells, secretion of IL-17, IL-6, RORγt, and relative mRNA levels of STAT3, and increased the transcript levels of SOCS3. This study provides limited evidence that possible immunomodulatory effects of RRTJ on the critical regulators, IL-6 and STAT3, of the Th17 cells in arsenicosis patients, which indicated that IL-6/STAT3 pathway might appear as a potential therapeutic target in arsenicosis.

Polycyclic Aromatic Hydrocarbons and the Risk of Kidney Stones in US Adults: An Exposure-Response Analysis of NHANES 2007-2012

Background

Polycyclic aromatic hydrocarbons (PAHs) exposure may cause various diseases. However, the association between PAHs exposure and kidney stones remains unclear. The purpose of this study was to examine the relationship between PAHs and the risk of kidney stones in the US population.

Methods

The study included a total of 30,442 individuals (≥20 years) from the 2007–2012 National Health and Nutrition Examination Survey (NHANES). Nine urinary PAHs were included in this study. Logistic regression and dose–response curves were used to evaluate the association between PAHs and the risk of kidney stones.

Results

We selected 4385 participants. The dose–response curves showed a significant positive association between total PAHs, 2-hydroxynaphthalene, 1-hydroxyphenanthrene, 2-hydroxyphenanthrene, 9-hydroxyfluorene and the risk of kidney stones after adjusting for confounding factors. Compared with the low group, an increased risk of kidney stones was observed in the high group of total PAHs [OR (95% CI), 1.32 (1.06–1.64), P=0.013], 2-hydroxynaphthalene [OR (95% CI), 1.37 (1.10–1.71), P=0.005], 1-hydroxyphenanthrene [OR (95% CI), 1.24 (1.00–1.54), P=0.046] and 9-hydroxyfluorene [OR (95% CI), 1.36 (1.09–1.70), P=0.007].

Conclusion

High levels of PAHs were positively associated with the risk of kidney stones in the US population.

Urinary polycyclic aromatic hydrocarbons concentrations and hepatitis B antibody serology in the United States (NHANES, 2003-2014)

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that are hepatotoxic and immunotoxic. PAH exposure may modulate hepatitis B immunology.

OBJECTIVE

We used data from 6 cycles of the National Health and Nutrition Examination Survey (2003-2014) to evaluate the associations between urinary PAH metabolites and hepatitis B serology.

METHODS

This analysis included individuals who self-reported receiving ≥3 doses of hepatitis B vaccine and urinary PAH metabolites (i.e. 1-napthol, 2-napthol, 3-fluorene, 2-fluorene, 1-phenanthrene, 1-pyrene, and total PAH [sum of all metabolites]). Separate logistic regression models assessed the association between hepatitis B vaccination status (i.e. individuals who were immune due to vaccination or susceptible) and tertiles of urinary PAH. Models were adjusted for age, gender, race/ethnicity, survey cycle, family income to poverty ratio, BMI, country of birth, serum cotinine, and urinary creatinine.

RESULTS

Among participants who reported receiving ≥3 doses of vaccine and had no antibodies indicating a history of hepatitis B infection and/or current hepatitis B infection, dose-response relationships were observed where individuals with the lowest odds of serology indicating a response to the hepatitis B vaccine (i.e., anti-HBs⁺, anti-HBc^-, and HBsAg^-) were in the highest tertile of 2-Napthol (adjusted Odds Ratio [aOR]: 0.70, 95% confidence interval [CI]: 0.54, 0.91), 3-Napthol (aOR: 0.68, 95% CI: 0.53, 0.87), 2-Fluorene (aOR: 0.61, 95% CI: 0.54, 0.86), 1-Phenanthrene (aOR: 0.79, 95% CI: 0.65, 0.97), 1-Pyrene (aOR): 0.68, 95% CI: 0.55, 0.83), and total PAH (aOR: 0.73, 95% CI: 0.56, 0.95) had the compared to the lowest tertile.

CONCLUSION

This cross-sectional study supports a hypothesis that PAH exposures experienced by the general US population may modulate hepatitis B vaccine induced immunity. Given the ubiquity of PAH exposures in the US, additional research is warranted to explore the effects of chronic PAH exposures on hepatitis B related humoral immunity.

The Preliminary Study on the Association Between PAHs and Air Pollutants and Microbiota Diversity

The purpose of this study was to investigate the association among polycyclic aromatic hydrocarbons (PAHs) exposure and air pollutants and the diversity of microbiota. Daily average concentrations of six common air pollutants were obtained from China National Environmental Monitoring Centre. The PAHs exposure levels were evaluated by external and internal exposure detection methods, including monitoring atmospheric PAHs and urinary hydroxyl-polycyclic aromatic hydrocarbon (OH-PAH) metabolite levels. We analyzed the diversity of environmental and commensal bacterial communities with 16S rRNA gene sequencing and performed functional enrichment with Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Correlation analysis and logistic regression modeling were conducted to evaluate the relationship of PAHs levels with air pollutants and microbial diversity. Correlation analysis found that the concentrations of atmospheric PAHs were significantly positively correlated with those of PM₁₀, NO₂, and SO₂. There also was a positive correlation between the abundance of the genus Micrococcus (Actinobacteria) and high molecular weight PAHs, and Bacillus, such as genera and low molecular weight PAHs in the atmosphere. Logistic regression showed that the level of urinary 1-OHPyrene was associated with childhood asthma after sex and age adjustment. The level of urinary 1-OHPyrene was significantly positively correlated with that of PM_2.5 and PM₁₀. In addition, the level of 1-OHPyrene was positively correlated with oral Prevotella-7 abundance. Functional enrichment analysis demonstrated that PAHs exposure may disturb signaling pathways by the imbalance of commensal microbiota, such as purine metabolism, pyrimidine metabolites, lipid metabolism, and one carbon pool by folate, which may contribute to public health issues. Our results confirmed that atmospheric PAHs and urinary 1-OHPyrene were correlated with part of six common air pollutants and indicated that PAHs pollution may alter both environmental and commensal microbiota communities associated with health-related problems. The potential health and environmental impacts of PAHs should be further explored.

Exposures to uranium and arsenic alter intraepithelial and innate immune cells in the small intestine of male and female mice

Human exposures to environmental metals, including uranium (U) and arsenic (As) are a global public health concern. Chronic exposures to U and As are linked to many adverse health effects including, immune suppression and autoimmunity. The gastrointestinal (GI) tract is home to many immune cells vital in the maintenance of systemic immune health. However, very little is known about the immunotoxicity of U and As at this site. The present study examined the burden of U and As exposure in the GI tract as well as the resultant immunotoxicity to intraepithelial lymphocytes (IELs) and innate immune cells of the small intestine following chronic drinking water exposures of male and female mice to U (in the form of uranyl acetate, UA) and As (in the form of sodium arsenite, As3+). Exposure to U or As3+ resulted in high levels of U or As in the GI tract of male and female mice, respectively. A reduction of small intestinal CD4+ IELs (TCRαβ+, CD8αα+) was found following As3+ exposure, whereas U produced widespread suppression of CD4- IEL subsets (TCRαβ+ and TCRγδ+). Evaluation of innate immune cell subsets in the small intestinal lamina propria revealed a decrease in mature macrophages, along with a corresponding increase in immature/proinflammatory macrophages following As3+ exposures. These data show that exposures to two prevalent environmental contaminants, U and As produce significant immunotoxicity in the GI tract. Collectively, these findings provide a critical framework for understanding the underlying immune health issues reported in human populations chronically exposed to environmental metals.

DNMT1-mediated Foxp3 gene promoter hypermethylation involved in immune dysfunction caused by arsenic in human lymphocytes

Growing evidence indicates that arsenic can cause long-lasting and irreversible damage to the function of the human immune system. It is known that forkhead box protein 3(Foxp3), which is specifically expressed in regulatory T cells (Tregs), plays a decisive role in immunoregulation and is regulated by DNA methylation. While evidence suggests that epigenetic regulated Foxp3 is involved in the immune disorders caused by arsenic exposure, the specific mechanism remains unclear. In this study, after primary human lymphocytes were treated with different doses of NaAsO₂, our results showed that arsenic induced the high expression of DNMT1 and Foxp3 gene promoter methylation level, thereby inhibiting the expression levels of Foxp3, followed by decreasing Tregs and reducing related anti-inflammatory cytokines, such as interleukin 10 (IL-10) and interleukin 10 (IL-35), and increasing the ratio of CD4⁺/CD8⁺ T cells in lymphocytes. Treatment with DNA methyltransferase inhibitor 5-Aza-CdR can notably inhibit the expression of DNMT1, effectively restoring the hypermethylation of the Foxp3 promoter region in primary human lymphocytes and upregulating the expression levels of Foxp3, balancing the ratio of CD4⁺/CD8⁺ T cells in lymphocytes. It also activates the secretion of anti-inflammatory cytokines and restores the immune regulatory functions of Tregs. In conclusion, our study provides limited evidence that DNMT1-mediated Foxp3 gene promoter hypermethylation is involved in immune dysfunction caused by arsenic in primary human lymphocytes. The study can provide a scientific basis for further understanding the arsenic-induced immune dysfunction in primary human lymphocytes.

Arsenic exposure associated T cell proliferation, smoking, and vitamin D in Bangladeshi men and women

There are limited data examining the consequences of environmental exposure to arsenic on the immune system in adults, particularly among smokers. Smoking has been shown to exacerbate or contribute to impaired immune function in men chronically exposed to arsenic. In contrast, vitamin D (VitD) is known to have a positive influence on innate and adaptive immune responses. The effect of circulating VitD on arsenic-associated immune dysfunction is not known. Here we examine the relationship of arsenic exposure and T cell proliferation (TCP), a measure of immune responsiveness, and circulating VitD among adult men and women in Bangladesh. Arsenic exposure was assessed using total urinary arsenic as well as urinary arsenic metabolites all adjusted for urinary creatinine. TCP was measured ex vivo in cryopreserved peripheral blood mononuclear cells from 614 adult participants enrolled in the Bangladesh Health Effects of Arsenic Longitudinal Study; serum VitD was also evaluated. The influence of cigarette smoking on arsenic-induced TCP modulation was assessed only in males as there was an inadequate number of female smokers. These studies show that arsenic suppressed TCP in males. The association was significantly strong in male smokers and to a lesser extent in male non-smokers. Interestingly, we found a strong protective effect of high/sufficient serum VitD levels on TCP among non-smoking males. Furthermore, among male smokers with low serum VitD (⊔20 ng/ml), we found a strong suppression of TCP by arsenic. On the other hand, high VitD (>20 ng/ml) was found to attenuate effects of arsenic on TCP among male-smokers. Overall, we found a strong protective effect of VitD, when serum levels were >20 ng/ml, on arsenic-induced inhibition of TCP in men, irrespective of smoking status. To our knowledge this is the first large study of immune function in healthy adult males and females with a history of chronic arsenic exposure.

Elevated expression of AhR and NLRP3 link polycyclic aromatic hydrocarbon exposure to cytokine storm in preschool children

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs), as a group of persistent organic pollutants, are linked to impaired immune function and low-grade inflammation in adults and children. However, the potential of PAHs to lead to a cytokine storm associated with AhR (aryl hydrocarbon receptor) and NLRP3 (NLR family pyrin domain containing 3) in humans has been poorly studied.

OBJECTIVES

We aimed to investigate the associations between PAH exposure, AhR and NLRP3 expression, and cytokines associated with a cytokine storm in healthy preschoolers.

METHODS

Basic demographic surveys and physical examinations were conducted on 248 preschoolers from an electronic waste (e-waste) recycling area (Guiyu, n = 121) and a reference area (Haojiang, n = 127). Ten urinary PAH metabolite (OH-PAH) concentrations were measured. We also measured the expression levels of AhR and NLRP3 and seventeen serum cytokine levels.

RESULTS

The concentrations of multiple OH-PAHs were significantly higher in the exposed group than those in the reference group, especially 1-hydroxynaphthalene (1-OH-Nap) and 2-hydroxynaphthalene (2-OH-Nap). PAH exposure was closely related to a child's living environment and hygiene habits. Expression levels of AhR and NLRP3 were significantly higher in the exposed group than in the reference group. Similarly, serum IL-1β, IL-4, IL-5, IL-10, IL-12p70, IL-13, IL-17A, IL-18, IL-22, IL-23, and IFN-γ levels were notably higher in the e-waste-exposed children than in the reference children. After adjusting for age, gender, BMI, family income, parental education level, and second-hand smoke exposure, we found that increased PAH exposure was associated with higher AhR and NLRP3 expression and elevated IL-4, IL-10, IL-12p70, IL-18, IL-22, IL-23, TNF-α, and IFN-γ levels. The associations between PAH exposure and IL-1β, IL-18, IFN-γ, and TNF-β were mediated by NLRP3 expression, and the relationships between PAH exposure and IL-4, IL-10, IL-12p70, IL-22, IL-23, and TNF-α were mediated by AhR expression.

CONCLUSIONS

Our findings suggest that the association between PAH exposure and a cytokine storm may be mediated by AhR and NLRP3 expression among preschoolers.

An increase in circulating B cells and B cell activation markers in peripheral blood is associated with cigarette smoking in a male cohort in Bangladesh

In a cohort of approximately 200 Bangladeshi men, equally divided into smokers and non-smokers and equally divided by exposure to high and low levels of drinking water arsenic, we examined ex vivo a series of immune markers and immune function tests in peripheral blood mononuclear cells (PBMC). These immune parameters included PBMC cell surface markers (CSM) for B, T, monocytes, and NK cells, activated T and B cell markers, cytokine production in vitro, and analysis of CD4 subsets (Th1, Th2, Treg, and Th17 cells). We found that the effects of cigarette smoke were quite different than those associated with arsenic or polycyclic aromatic hydrocarbon (PAH)-DNA adducts. Cigarette smoking was associated with a significant increase in the number of PAH-DNA adducts as well as an increase in urinary levels of 1-hydropxypyrene (1-OHP). After correcting for arsenic exposure and PAH-DNA adducts, we found that cigarette smoking was associated with an increase in the percentage of CD19+ B cells, as well as the percentage of activated B cells (CD19+, HLA-DRbright cells) found in PBMC. These findings demonstrate activation of the immune system during chronic exposure to cigarette smoke, which is a known risk factor for autoimmune diseases.

Exposure to low-dose arsenic in early life alters innate immune function in children

Early-life exposure to arsenic (As) increases risks of respiratory diseases/infections in children. However, data on the ability of the innate immune system to combat bacterial infections in the respiratory tracts of As-exposed children are scarce. To evaluate whether persistent low-dose As exposure alters innate immune function among children younger than 5 years-of-age, mothers and participating children (N = 51) that were members of the Health Effects of Arsenic Longitudinal Study (HEALS) cohort in rural Bangladesh were recruited. Household water As, past and concurrent maternal urinary As (U-As) as well as child U-As were all measured at enrollment. In addition, U-As metabolites were evaluated. Innate immune function was examined via measures of cathelicidin LL-37 in plasma, ex vivo monocyte-derived-macrophage (MDM)-mediated killing of Streptococcus pneumoniae (Spn), and serum bactericidal antibody (SBA) responses against Haemophilus influenzae type b (Hib). Cyto-/chemokines produced by isolated peripheral blood mononuclear cells (PBMC) were assayed using a Multiplex system. Multivariable linear regression analyses revealed that maternal (p < 0.01) and child (p = 0.02) U-As were positively associated with plasma LL-37 levels. Decreased MDM-mediated Spn killing (p = 0.05) and SBA responses (p = 0.02) were seen to be each associated with fractions of mono-methylarsonic acid (MMA; a U-As metabolite) in the children. In addition, U-As levels were seen to be negatively associated with PBMC formation of fractalkine and IL-7, and positively associated with that for IL-13, IL-17 and MIP-1α. These findings suggested that early-life As exposure may disrupt the innate host defense pathway in these children. It is possible that such disruptions may have health consequences later in life.

Changes in human peripheral blood mononuclear cell (HPBMC) populations and T-cell subsets associated with arsenic and polycyclic aromatic hydrocarbon exposures in a Bangladesh cohort

Exposures to environmental arsenic (As) and polycyclic aromatic hydrocarbons (PAH) have been shown to independently cause dysregulation of immune function. Little data exists on the associations between combined exposures to As and PAH with immunotoxicity in humans. In this work we examined associations between As and PAH exposures with lymphoid cell populations in human peripheral blood mononuclear cells (PBMC), as well as alterations in differentiation and activation of B and T cells. Two hundred men, participating in the Health Effects of Arsenic Longitudinal Study (HEALS) in Bangladesh, were selected for the present study based on their exposure to As from drinking water and their cigarette smoking status. Blood and urine samples were collected from study participants. We utilized multiparameter flow cytometry in PBMC to identify immune cells (B, T, monocytes, NK) as well as the T-helper (Th) cell subsets (Th1, Th2, Th17, and Tregs) following ex vivo activation. We did not find evidence of interactions between As and PAH exposures. However, individual exposures (As or PAH) were associated with changes to immune cell populations, including Th cell subsets. Arsenic exposure was associated with an increase in the percentage of Th cells, and dose dependent changes in monocytes, NKT cells and a monocyte subset. Within the Th cell subset we found that Arsenic exposure was also associated with a significant increase in the percentage of circulating proinflammatory Th17 cells. PAH exposure was associated with changes in T cells, monocytes and T memory (Tmem) cells and with changes in Th, Th1, Th2 and Th17 subsets all of which were non-monotonic (dose dependent). Alterations of immune cell populations caused by environmental exposures to As and PAH may result in adverse health outcomes, such as changes in systemic inflammation, immune suppression, or autoimmunity.