Serum polychlorinated biphenyls and their hydroxylated metabolites are associated with demographic and behavioral factors in children and mothers

Maternal exposure to polychlorinated biphenyls in indoor air and asthma, allergic rhinitis, atopic eczema, and respiratory tract infections in childhood

Polychlorinated biphenyls (PCBs) are industrial chemicals commonly found in food and building materials. PCBs are immunotoxic and may disturb the fetal programming of the immune and respiratory systems. We evaluated the association between maternal PCB exposure in indoor air and asthma, allergic rhinitis, atopic eczema, and respiratory infections in the offspring in the Health Effects of PCBs in Indoor Air (HESPAIR) cohort. This register-based study examined 7982 children born to mothers residing in two partially PCB contaminated residential areas in Greater Copenhagen before and/or during pregnancy. Children were included if their mothers at any point had lived in a contaminated or uncontaminated apartment in the period from 3.6 years prior to conception until the date of birth. PCB exposure was defined as mothers' number of years in an apartment prior to birth of the child multiplied with the PCB concentration in indoor air based on air measurements. Information on the outcomes was retrieved from the Danish health registers from 1977 to 2018. We estimated adjusted hazard ratios using Cox regression. Our main analyses revealed no association between maternal exposure to PCBs in indoor air and any of the studied allergic and respiratory outcomes. Findings of sensitivity analyses were consistent with main analyses. While these findings may appear reassuring for the considerable number of people living or working in PCB contaminated indoor environments, they should be interpreted with caution due to the indirect measure of exposure, incomplete registration of diagnoses, and lack of supporting evidence from comparable studies.

Indoor environment, physiological factors, and diet as predictors of halogenated flame retardant levels in stool and plasma of children from a Canadian cohort

Exposure to halogenated flame retardants (HFRs) has been associated with various adverse effects on human health. Human exposure to HFRs mainly occurs through diet, ingesting contaminated dust, and inhaling contaminated air. Understanding and characterizing the variables linked to these exposure pathways is essential for developing effective risk assessment and mitigation strategies. We investigated indoor environment quality, physiological factors, and diet as potential predictors of HFRs concentration in children's plasma and stool. A selected number of HFRs, including polybrominated diphenyl ethers (PBDEs), Dechlorane-like compounds, and emerging halogenated flame retardants, were measured in children from eastern Quebec (Canada). Information on indoor environment quality, physiological factors, and diet was obtained through self-report questionnaires. Our results show that lower brominated compounds, which are more volatile, were primarily correlated to indoor environment quality. Notably, the use of air purifiers was associated with lower BDE47 and BDE100 levels in blood and newer residential buildings were associated with higher concentrations of BDE47. A significant seasonal variation was found in stool samples, with higher levels of lower brominated PBDEs (BDE47 and BDE100) in samples collected during summer. No association between household income or maternal education degree and HFRs was found. Among emerging compounds, Dec602 and Dec603 were associated with the most variables, including the use of air dehumidifiers, air conditioning, and air purifiers, and the child's age and body fat percentage.

Disposition and metabolomic effects of 2,2',5,5'-tetrachlorobiphenyl in female rats following intraperitoneal exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Disposition and Metabolomic Effects of 2,2',5,5'-Tetrachlorobiphenyl in Female Rats Following Intraperitoneal Exposure

The disposition and toxicity of lower chlorinated PCBs (LC-PCBs) with less than five chlorine substituents have received little attention. This study characterizes the distribution and metabolomic effects of PCB 52, an LC-PCB found in indoor and outdoor air, three weeks after intraperitoneal exposure of female Sprague Dawley rats to 0, 1, 10, or 100 mg/kg BW. PCB 52 exposure did not affect overall body weight. Gas chromatography-tandem mass spectrometry (GC-MS/MS) analysis identified PCB 52 in all tissues investigated. Hydroxylated, sulfated, and methylated PCB metabolites, identified using GC-MS/MS and nontarget liquid chromatography-high resolution mass spectrometry (Nt-LCMS), were primarily found in the serum and liver of rats exposed to 100 mg/kg BW. Metabolomic analysis revealed minor effects on L-cysteine, glycine, cytosine, sphingosine, thymine, linoleic acid, orotic acid, L-histidine, and erythrose serum levels. Thus, the metabolism of PCB 52 and its effects on the metabolome must be considered in toxicity studies.

Highlights

PCB 52 was present in adipose, brain, liver, and serum 3 weeks after PCB exposureLiver and serum contained hydroxylated, sulfated, and methylated PCB 52 metabolitesMetabolomics analysis revealed minor changes in endogenous serum metabolitesLevels of dopamine and its metabolites in the brain were not affected by PCB 52.

Hydroxylation markedly alters how the polychlorinated biphenyl (PCB) congener, PCB52, affects gene expression in human preadipocytes

Polychlorinated biphenyls (PCBs) accumulate in adipose tissue and are linked to obesity and diabetes. The congener, PCB52 (2,2',5,5'-tetrachorobiphenyl), is found at high levels in school air. Hydroxylation of PCB52 to 4-OH-PCB52 (4-hydroxy-2,2',5,5'-tetrachorobiphenyl) may increase its toxicity. To understand PCB52's role in causing adipose dysfunction, we exposed human preadipocytes to PCB52 or 4-OH-PCB52 across a time course and assessed transcript changes using RNAseq. 4-OH-PCB52 caused considerably more changes in the number of differentially expressed genes as compared to PCB52. Both PCB52 and 4-OH-PCB52 upregulated transcript levels of the sulfotransferase SULT1E1 at early time points, but cytochrome P450 genes were generally not affected. A set of genes known to be transcriptionally regulated by PPARα were consistently downregulated by PCB52 at all time points. In contrast, 4-OH-PCB52 affected a variety of pathways, including those involving cytokine responses, hormone responses, focal adhesion, Hippo, and Wnt signaling. Sets of genes known to be transcriptionally regulated by IL17A or parathyroid hormone (PTH) were found to be consistently downregulated by 4-OH-PCB52. Most of the genes affected by PCB52 and 4-OH-PCB52 were different and, of those that were the same, many were changed in an opposite direction. These studies provide insight into how PCB52 or its metabolites may cause adipose dysfunction to cause disease.

Networks of placental DNA methylation correlate with maternal serum PCB concentrations and child neurodevelopment

BACKGROUND

Gestational exposure to polychlorinated biphenyls (PCBs) has been associated with elevated risk for neurodevelopmental disorders. Placental epigenetics may serve as a potential mechanism of risk or marker of altered placental function. Prior studies have associated differential placental DNA methylation with maternal PCB exposure or with increased risk of autism spectrum disorder (ASD). However, sequencing-based placental methylomes have not previously been tested for simultaneous associations with maternal PCB levels and child neurodevelopmental outcomes.

OBJECTIVES

We aimed to identify placental DNA methylation patterns associated with maternal PCB levels and child neurodevelopmental outcomes in the high-risk ASD MARBLES cohort.

METHODS

We measured 209 PCB congeners in 104 maternal serum samples collected at delivery. We identified networks of DNA methylation from 147 placenta samples using the Comethyl R package, which performs weighted gene correlation network analysis for whole genome bisulfite sequencing data. We tested placental DNA methylation modules for association with maternal serum PCB levels, child neurodevelopment, and other participant traits.

RESULTS

PCBs 153 + 168, 170, 180 + 193, and 187 were detected in over 50% of maternal serum samples and were highly correlated with one another. Consistent with previous findings, maternal age was the strongest predictor of serum PCB levels, alongside year of sample collection, pre-pregnancy BMI, and polyunsaturated fatty acid levels. Twenty seven modules of placental DNA methylation were identified, including five which significantly correlated with one or more PCBs, and four which correlated with child neurodevelopment. Two modules associated with maternal PCB levels as well as child neurodevelopment, and mapped to CSMD1 and AUTS2, genes previously implicated in ASD and identified as differentially methylated regions in mouse brain and placenta following gestational PCB exposure.

CONCLUSIONS

Placental DNA co-methylation modules were associated with maternal PCBs and child neurodevelopment. Methylation of CSMD1 and AUTS2 could be markers of altered placental function and/or ASD risk following maternal PCB exposure.

Profiles and determinants of dicofol, endosulfans, mirex, and toxaphenes in breast milk samples from 10 prefectures in Japan

Human exposure to persistent organic pollutants (POPs) is reflected by POP concentrations in breast milk. Many studies of POPs in breast milk have been performed in Japan, but insufficient information is available about some legacy POPs (e.g., mirex and toxaphenes, included in the Stockholm Convention in 2001) and novel POPs (e.g., dicofol and endosulfans, included in the Stockholm Convention in 2019 and 2011, respectively). In this study, dicofol, endosulfan, mirex, and toxaphene concentrations in breast milk from 10 prefectures in Japan were determined. The samples were collected between 2005 and 2010, before Stockholm Convention restrictions on endosulfans and mirex were implemented. Common POPs (e.g., polychlorinated biphenyls) were also analyzed to allow the contamination statuses to be compared. The α-endosulfan and β-endosulfan concentrations were 0.26-13 and 0.012-0.82 ng/g lipid, respectively. The toxaphene #26 and #50 concentrations were <0.08-5.6 and < 0.1-8.5 ng/g lipid, respectively. The dicofol concentrations were <0.01-4.8 ng/g lipid. The mirex concentrations were <0.2-3.5 ng/g lipid. The α- and β-endosulfan concentrations on a lipid weight basis negatively correlated with the lipid contents of the milk samples (ρ = -0.65, p < 0.01 for α-endosulfan; ρ = -0.58, p < 0.01 for β-endosulfan). The toxaphene concentrations positively correlated with the lipid contents. The mirex concentrations positively correlated with the maternal age but negatively correlated with the maternal body mass index. No correlations between the dicofol concentrations and the factors were found. Principal component analysis divided the data into four groups, (1) chlordanes, dichlorodiphenyltrichloroethanes and related compounds, hexachlorobenzene, hexachlorocyclohexanes, hexachloroethane, and polychlorinated biphenyls, (2) endosulfans, (3) dicofol, dieldrin, and toxaphenes, and (4) bromodiphenyl ether 47. This indicated that bromodiphenyl ether 47, dicofol, endosulfans, and toxaphenes have different exposure routes or different kinetics to the other legacy POPs.

Metabolism of 3-Chlorobiphenyl (PCB 2) in a Human-Relevant Cell Line: Evidence of Dechlorinated Metabolites

Lower chlorinated polychlorinated biphenyls (LC-PCBs) and their metabolites make up a class of environmental pollutants implicated in a range of adverse outcomes in humans; however, the metabolism of LC-PCBs in human models has received little attention. Here we characterize the metabolism of PCB 2 (3-chlorobiphenyl), an environmentally relevant LC-PCB congener, in HepG2 cells with in silico prediction and nontarget high-resolution mass spectrometry. Twenty PCB 2 metabolites belonging to 13 metabolite classes, including five dechlorinated metabolite classes, were identified in the cell culture media from HepG2 cells exposed for 24 h to 10 μM or 3.6 nM PCB 2. The PCB 2 metabolite profiles differed from the monochlorinated metabolite profiles identified in samples from an earlier study with PCB 11 (3,3'-dichlorobiphenyl) under identical experimental conditions. A dechlorinated dihydroxylated metabolite was also detected in human liver microsomal incubations with monohydroxylated PCB 2 metabolites but not PCB 2. These findings demonstrate that the metabolism of LC-PCBs in human-relevant models involves the formation of dechlorination products. In addition, untargeted metabolomic analyses revealed an altered bile acid biosynthesis in HepG2 cells. Our results indicate the need to study the disposition and toxicity of complex PCB 2 metabolites, including novel dechlorinated metabolites, in human-relevant models.

Assessment of Polychlorinated Biphenyls and Their Hydroxylated Metabolites in Postmortem Human Brain Samples: Age and Brain Region Differences

Exposure to polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) has been implicated in neurodevelopmental disorders. However, the distribution of PCBs and OH-PCBs in the human brain has not been characterized. This study investigated the age-, sex-, and brain region-specific distribution of all 209 PCBs using gaschromatography-tandem mass spectrometry (GC-MS/MS) in neonatal (N = 7) and adult (N = 7) postmortem brain samples. OH-PCB analyses were performed by GC-MS/MS (as methylated derivatives) and, in a subset of samples, by nontarget liquid chromatography high-resolution mass spectrometry (Nt-LCMS). Fourteen higher chlorinated PCB congeners were observed with a detection frequency >50%. Six lower chlorinated PCBs were detected with a detection frequency >10%. Higher chlorinated PCBs were observed with higher levels in samples from adult versus younger donors. PCB congener profiles from adult donors showed more similarities across brain regions and donors than younger donors. We also assess the potential neurotoxicity of the PCB residues in the human brain with neurotoxic equivalency (NEQ) approaches. The median ΣNEQs, calculated for the PCB homologues, were 40-fold higher in older versus younger donors. Importantly, lower chlorinated PCBs made considerable contributions to the neurotoxic potential of PCB residues in some donors. OH-PCBs were identified for the first time in a small number of human brain samples by GC-MS/MS and Nt-LCMS analyses, and all contained four or fewer chlorine.

Developmental polychlorinated biphenyl (PCB) exposure alters voiding physiology in young adult male and female mice

The impact of developmental exposure to environmental chemicals on lower urinary tract function is not well understood, despite the fact that these chemicals could contribute to etiologically complex lower urinary tract symptoms (LUTS). Polychlorinated biphenyls (PCBs) are environmental toxicants known to be detrimental to the central nervous system, but their impact on voiding function in mouse models is not known. Therefore, we test whether developmental exposure to PCBs is capable of altering voiding physiology in young adult mice. C57Bl/6J female mice received a daily oral dose of the MARBLES PCB mixture for two weeks prior to mating and through gestation and lactation. The mixture mimics the profile of PCBs found in a contemporary population of pregnant women. Voiding function was then tested in young adult offspring using void spot assay, uroflowmetry and anesthetized cystometry. PCB effects were sex and dose dependent. Overall, PCBs led to increases in small size urine spots in both sexes with males producing more drop-like voids and greater peak pressure during a voiding cycle while females displayed decreases in void duration and intervoid interval. Together, these results indicate that developmental exposure to PCBs are capable of altering voiding physiology in young adult mice. Further work to identify the underlying mechanisms driving these changes may help develop more effective preventative or therapeutic strategies for LUTS.

In vitro effects of polychlorinated biphenyls and their hydroxylated metabolites on the synthesis and metabolism of iodothyronines in the chicken (Gallus domesticus) thyroid gland

To assess the effect of polychlorinated biphenyls (PCBs) and their hydroxylated metabolites (OH-PCBs) on thyroid hormone [TH: thyroxine (T₄) and triiodothyronine (T₃)] secretion, the concentrations of iodothyronine deiodinases (DIO1, DIO2, DIO3), and mRNA expression of genes involved in TH synthesis (TSHR, NIS, TPO, TG), metabolism (DIO1, DIO2, DIO3), and transport (OATP1C1, MCT8, MCT10, LAT1), chicken thyroid explants were incubated in medium supplemented with TSH (250 mU/ml), PCB118, PCB153, 4-OH-PCB107, and 3-OH-PCB153 (0.5 × 10^-8 M), and TSH together with each PCB and OH-PCB. The results of the in vitro experiment revealed that, except for 4-OH-PCB107, all applied PCBs and OH-PCBs inhibited basal and TSH-stimulated T₄ secretion. Moreover, they increased basal and reduced TSH-stimulated T₃ secretion. PCBs and OH-PCBs decreased the TSH-stimulated TSHR expression. Following PCB and OH-PCB exposure, significant changes in mRNA expression of NIS, TPO, and TG were observed. PCBs and OH-PCBs affected DIO1 and DIO3 transcript levels and protein abundances of each DIO. Furthermore, PCB-dependent effects on OATP1C1, MCT8, and MCT10 mRNA expression were found. In conclusion, both PCB118 and PCB153 and their OH-PCBs affect TH synthesis and deiodination processes in the chicken thyroid gland and influence TH transport across the thyrocyte membrane. In addition, the effects of PCBs and OH-PCBs depended mainly on the type of PCB congener and the exposure time. These results indicate that not only parental PCBs but also OH-PCBs are hazardous for the thyroid gland and may disrupt its endocrine function. Further studies are necessary to explain a mechanism of PCB and OH-PCB action in the avian thyroid gland.

BMI modifies the association between dietary intake and serum levels of PCBs

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants that are carcinogenic, neurotoxic, and endocrine disrupting in humans. Although diet is the primary source of exposure, there is no consensus on the association between dietary intake and serum PCBs. Additionally, body mass index (BMI) - with its inverse association with serum PCBs - may play a role in the association, which has never been studied. Therefore, we aimed to examine the association between dietary intake and serum levels of PCBs, and whether the association was modified by BMI. We used data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004, including 1531 participants. We estimated dietary intake of PCBs using the 24-hour diet recall, USDA Food Composition Intake Database, and PCB content in foods from the Canada Total Diet Study. Serum PCBs were measured by high-resolution gas chromatography-mass spectrometry (HRGC-HRMS). We used linear regression to examine the associations of dietary PCB intake with serum levels of seven PCB congeners and six PCB metrics. Further, we explored the role of BMI in the associations. We found that participants who were older and non-Hispanic tended to have a higher serum level of ∑37-PCB. In addition, we observed positive associations between dietary intake and serum PCBs for: PCB 105, 118, 126, 138 + 158, and 153 (P value ranges 0.005-0.03); seven PCB indicators (P value = 0.03) and the sum of 37 PCBs (P value = 0.04). Furthermore, we observed an effect modification by BMI (P for interaction = 0.01 for ∑37-PCBs), with stronger associations in underweight or normal-weight individuals, and no association in overweight and obese individuals. In conclusion, within a cross-sectional, nationally representative sample of the US population, dietary PCB intake was positively associated with serum PCBs and the association was modified by BMI. Additional studies are warranted to replicate and confirm this effect modification.

Room-to-Room Variability of Airborne Polychlorinated Biphenyls in Schools and the Application of Air Sampling for Targeted Source Evaluation

Airborne polychlorinated biphenyl (PCB) concentrations are higher indoors than outdoors due to their historical use in building materials and their presence in modern paints and surface treatments. For some populations, including school children, PCB levels indoors result in inhalation exposures that may be greater than or equivalent to exposure through diet. In a school, PCB exposure may come from multiple sources. We hypothesized that there are both Aroclor and non-Aroclor sources within a single school and that PCB concentration and congener profiles differ among rooms within a single building. To evaluate this hypothesis and to identify potential localized sources, we measured airborne PCBs in nine rooms in a school. We found that schoolroom concentrations exceed outdoor air concentrations. Schoolroom concentrations and congener profiles also varied from one room to another. The concentrations were highest in the math room (35.75 ng m-3 ± 8.08) and lowest in the practice gym (1.54 ng m-3 ± 0.35). Rooms in the oldest wing of the building, originally constructed between 1920 and 1970, had the highest concentrations. The congener distribution patterns indicate historic use of Aroclor 1254 as well as modern sources of non-Aroclor congeners associated with paint pigments and surface coatings. Our findings suggest this noninvasive source identification method presents an opportunity for targeted source testing for more cost-effective prioritization of materials remediation in schools.

Effect of prevalent polychlorinated biphenyls (PCBs) food contaminant on the MCF7, LNCap and MDA-MB-231 cell lines viability and PON1 gene expression level: proposed model of binding

BACKGROUND

Polychlorinated biphenyls (PCBs) are a group of synthetic organic chlorine compounds known as an organic pollutant in food sources, which play important roles in malignancies. The present study aimed to investigate the direct effects of prevalent PCBs in food in hormone-responsive and non-responsive cell lines.

METHODS

In the current study, MCF-7, LNCap, and MDA-MB231 cell lines were treated with serial concentrations (0.001-100 μM) of PCBs for 48 h and cell viability assessment was performed using MTT assay. The best concentration then applied and the expression level of PON1 was evaluated using real-time PCR. Besides, molecular docking was performed to determine the binding mechanism and predicted binding energies of PBCs compounds to the AhR receptor.

RESULTS

Unlike MCF-7 and LNCap cells, the viability of MDA-MB231 cells did not significantly change by different concentrations of PCBs. Meanwhile, quantitative gene expression analysis showed that the PON1 was significantly more expressed in MCF-7 and LNCap lines treated with PCB28 and PCB101. However, the expression level of this gene in other groups and also MDA-MB231cells did not demonstrate any significantly change. Also, the results of molecular docking showed that PBCs had steric interaction with AhR receptor.

CONCLUSIONS

Current results showed that despite of hormone non-responsive cells the PCBs have a significant positive effect on hormone-responsive cell. Therefore, and regarding to the existence of PCBs contamination in food there should be serious concern about their impact on the prevalence of different malignancies which certainly should result in a standard limit for this material. This study aimed to investigate the direct effects of prevalent PCBs in food in hormone-responsive and non-responsive cell lines. Cell lines were treated with serial concentrations of PCBs and cell viability assessment was performed using MTT assay. The expression level of PON1 was evaluated using real-time PCR. Molecular docking was performed to determine the binding mechanism and predicted binding energies of PBCs compounds to the AhR receptor. PCBs contamination in food there should be serious concern about their impact on the prevalence of different malignancies which certainly should result in a standard limit for this material.

Non-dioxin-like polychlorinated biphenyl neurotoxic equivalents found in environmental and human samples

Non-dioxin like polychlorinated biphenyls (NDL PCB) are recognized neurotoxicants with implications on altered neurodevelopment and neurodegeneration in exposed organisms. NDL PCB neurotoxic relative potency schemes have been developed for a single mechanism, namely activity toward the ryanodine receptor (RyR), or combined mechanisms including, but not limited to, alterations of RyR and dopaminergic pathways. We compared the applicability of the two neurotoxic equivalency (NEQ) schemes and applied each scheme to PCB mixtures found in environmental and human serum samples. A multiple mechanistic NEQ predicts higher neurotoxic exposure concentrations as compared to a scheme based on the RyR alone. Predictions based on PCB ortho categorization, versus homologue categorization, lead to a higher prediction of neurotoxic exposure concentrations, especially for the mMOA. The application of the NEQ schemes to PCB concentration data suggests that PCBs found in fish from US lakes represent a considerable NEQ exposure to fish consuming individuals, that indoor air of schools contained high NEQ concentrations representing an exposure concern when inhaled by children, and that levels already detected in the serum of adults and children may contribute to neurotoxicity. With further validation and in vivo exposure data the NEQ scheme would help provide a more inclusive measure of risk presented by PCB mixtures.

Detection and Quantification of Polychlorinated Biphenyl Sulfates in Human Serum

Polychlorinated biphenyls (PCBs) are persistent toxic chemicals with both legacy sources (e.g., Aroclors) and new sources (e.g., unintentional contaminants in some pigments and varnishes). PCB sulfates are derived from further metabolism of hydroxylated PCBs (OH-PCBs), which are oxidative metabolites of PCBs. While OH-PCBs and PCB sulfates are implicated in multiple toxicological effects, studies of PCB sulfates in human serum have been limited by available analytical procedures. We have now developed a method for extraction of PCB sulfates from serum followed by differential analysis with, and without, sulfatase-catalyzed hydrolysis to OH-PCBs. A sulfatase from Helix pomatia was purified by affinity chromatography, and it displayed broad specificity for PCB sulfates without contaminant glucuronidase activity. Following sulfatase-catalyzed hydrolysis of the PCB sulfates extracted from serum, the corresponding OH-PCBs were derivatized to methoxy-PCBs and quantitated by GC-MS/MS. In a pooled sample of human serum, we identified 10 PCB sulfates, with three PCB sulfate congeners exhibiting the highest concentrations from 1200 to 3970 pg/g of serum. In conclusion, we have developed a sensitive and specific method for the determination of PCB sulfates in human serum.

Concentration of polychlorinated biphenyls in serum from New Jersey biomonitoring study: 2016-2018

The first statewide New Jersey Biomonitoring (NJBM) of serum polychlorinated biphenyls (PCBs) was conducted from 2016 to 2018. Forty ortho-substituted PCBs were measured in serum samples collected from 920 NJ residents in compliance with the CDC method. The lipid adjusted geometric mean (GM) of ∑₄₀PCB concentration for all the 920 measured subjects was 65.5 ng/g lipid (95% CIs: 56.9-75.4 ng/g lipid). Age stratified serum concentration showed that the lowest GM (33.3 ng/g lipid) was observed in the 20-39 years age group (n = 282), followed by a concentration of 76.05 ng/g lipid (n = 382) in the 40-59 years age group, and the highest GM (168.4 ng/g lipid) was found in the 60-74 years age group (n = 256). A survey regression model revealed that ∑₄₀PCBs was significantly associated with age, moderately associated with geographic region, and not significantly associated with sex. The comparison of serum PCB levels in NJBM with the sequential National Health and Nutrition Examination Survey (NHANES) data suggested that the serum PCBs in NJ adults declined 52-59% at all age groups over the last decade. Positive Matrix Factorization (PMF) suggests that ongoing and recent exposure to lower molecular weight PCBs contributes about 15% to total serum PCB levels and more in younger subjects, while higher molecular weight PCBs contribute 52% of the total serum PCB levels and more in older subjects.

Cardiovascular Effects of Polychlorinated Biphenyls and Their Major Metabolites

BACKGROUND

Xenobiotic metabolism is complex, and accounting for bioactivation and detoxification processes of chemicals remains among the most challenging aspects for decision making with in vitro new approach methods data.

OBJECTIVES

Considering the physiological relevance of human organotypic culture models and their utility for high-throughput screening, we hypothesized that multidimensional chemical-biological profiling of chemicals and their major metabolites is a sensible alternative for the toxicological characterization of parent molecules vs. metabolites in vitro.

METHODS

In this study, we tested 25 polychlorinated biphenyls (PCBs) [PCB 3, 11, 52, 126, 136, and 153 and their relevant metabolites (hydroxylated, methoxylated, sulfated, and quinone)] in concentration-response (10 nM-100μM) for effects in human induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs) and endothelial cells (ECs) (iPSC-derived and HUVECs). Functional phenotypic end points included effects on beating parameters and intracellular Ca2+ flux in CMs and inhibition of tubulogenesis in ECs. High-content imaging was used to evaluate cytotoxicity, mitochondrial integrity, and oxidative stress.

RESULTS

Data integration of a total of 19 physicochemical descriptors and 36 in vitro phenotypes revealed that chlorination status and metabolite class are strong predictors of the in vitro cardiovascular effects of PCBs. Oxidation of PCBs, especially to di-hydroxylated and quinone metabolites, was associated with the most pronounced effects, whereas sulfation and methoxylation of PCBs resulted in diminished bioactivity.

DISCUSSION

Risk characterization analysis showed that although in vitro derived effective concentrations exceeded the levels measured in the general population, risks cannot be ruled out due to the potential for population variability in susceptibility and the need to fill data gaps using read-across approaches. This study demonstrated a strategy for how in vitro data can be used to characterize human health risks from PCBs and their metabolites. https://doi.org/10.1289/EHP7030.

Sex-Dependent Effects of 2,2',3,5',6-Pentachlorobiphenyl on Dendritic Arborization of Primary Mouse Neurons

Early life exposures to environmental contaminants are implicated in the pathogenesis of many neurodevelopmental disorders (NDDs). These disorders often display sex biases, but whether environmental neurotoxicants act in a sex-dependent manner to modify neurodevelopment is largely unknown. Since altered dendritic morphology is associated with many NDDs, we tested the hypothesis that male and female primary mouse neurons are differentially susceptible to the dendrite-promoting activity of 2,2',3,5',6-pentachlorobiphenyl (PCB 95). Hippocampal and cortical neuron-glia co-cultures were exposed to vehicle (0.1% dimethylsulfoxide) or PCB 95 (100 fM-1 μM) from day in vitro 7-9. As determined by Sholl analysis, PCB 95-enhanced dendritic growth in female but not male hippocampal and cortical neurons. In contrast, both male and female neurons responded to bicuculline with increased dendritic complexity. Detailed morphometric analyses confirmed that PCB 95 effects on the number and length of primary and nonprimary dendrites varied depending on sex, brain region and PCB concentration, and that female neurons responded more consistently with increased dendritic growth and at lower concentrations of PCB 95 than their male counterparts. Exposure to PCB 95 did not alter cell viability or the ratio of neurons to glia in cultures of either sex. These results demonstrate that cultured female mouse hippocampal and cortical neurons are more sensitive than male neurons to the dendrite-promoting activity of PCB 95, and suggest that mechanisms underlying PCB 95-induced dendritic growth are sex-dependent. These data highlight the importance of sex in neuronal responses to environmental neurotoxicants.

PCB 95 promotes dendritic growth in primary rat hippocampal neurons via mTOR-dependent mechanisms

Polychlorinated biphenyls (PCBs), and in particular non-dioxin-like (NDL) congeners, continue to pose a significant risk to the developing nervous system. PCB 95, a prevalent NDL congener in the human chemosphere, promotes dendritic growth in rodent primary neurons by activating calcium-dependent transcriptional mechanisms that normally function to link activity to dendritic growth. Activity-dependent dendritic growth is also mediated by calcium-dependent translational mechanisms involving mechanistic target of rapamycin (mTOR), suggesting that the dendrite-promoting activity of PCB 95 may also involve mTOR signaling. Here, we test this hypothesis using primary neuron-glia co-cultures derived from the hippocampi of postnatal day 0 Sprague Dawley rats. PCB 95 (1 nM) activated mTOR in hippocampal cultures as evidenced by increased phosphorylation of mTOR at ser2448. Pharmacologic inhibition of mTOR signaling using rapamycin (20 nM), FK506 (5 nM), or 4EGI-1 (1 µM), and siRNA knockdown of mTOR, or the mTOR complex binding proteins, raptor or rictor, blocked PCB 95-induced dendritic growth. These data identify mTOR activation as a novel molecular mechanism contributing to the effects of PCB 95 on dendritic arborization. In light of clinical data linking gain-of-function mutations in mTOR signaling to neurodevelopmental disorders, our findings suggest that mTOR signaling may represent a convergence point for gene by environment interactions that confer risk for adverse neurodevelopmental outcomes.

Organohalogens Naturally Biosynthesized in Marine Environments and Produced as Disinfection Byproducts Alter Sarco/Endoplasmic Reticulum Ca2+ Dynamics

Contemporary sources of organohalogens produced as disinfection byproducts (DBPs) are receiving considerable attention as emerging pollutants because of their abundance, persistence, and potential to structurally mimic natural organohalogens produced by bacteria that serve signaling or toxicological functions in marine environments. Here, we tested 34 organohalogens from anthropogenic and marine sources to identify compounds active toward ryanodine receptor (RyR1), known toxicological targets of non-dioxin-like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). [3H]Ryanodine ([3H]Ry) binding screening (≤2 μM) identified 10 highly active organohalogens. Further analysis indicated that 2,3-dibromoindole (14), tetrabromopyrrole (31), and 2,3,5-tribromopyrrole (34) at 10 μM were the most efficacious at enhancing [3H]Ry binding. Interestingly, these congeners also inhibited microsomal sarcoplasmic/endoplasmic reticulum (SR/ER) Ca2+ ATPase (SERCA1a). Dual SERCA1a inhibition and RyR1 activation triggered Ca2+ efflux from microsomal vesicles with initial rates rank ordered 31 > 34 > 14. Hexabromobipyrroles (25) enhanced [3H]Ry binding moderately with strong SERCA1a inhibition, whereas pyrrole (24), 2,3,4-tribromopyrrole (26), and ethyl-4-bromopyrrole-2-carboxylate (27) were inactive. Of three PBDE derivatives of marine origin active in the [3H]Ry assay, 4'-hydroxy-2,3',4,5',6-pentabromodiphenyl ether (18) was also a highly potent SERCA1a inhibitor. Molecular targets of marine organohalogens that are also DBPs of emerging environmental concern are likely to contribute to their toxicity.

Determination of phenolic organohalogens in human serum from a Belgian population and assessment of parameters affecting the human contamination

Many in vitro or in vivo studies highlighted the potential deleterious effects of phenolic organohalogenated compounds (POHs) on the health, particularly on the thyroid system homeostasis, however few large scale human epidemiological studies have been carried out, especially in Europe. Further studies monitoring the human contamination by POHs, the sources of exposure and the influence of these compounds on thyroid health are still needed. Therefore we determined the concentrations of 16 POHs (pentachlorophenol (PCP), tetrabromobisphenol A (TBBPA), 4 bromophenols (BPs), 3 hydroxy-polybromodiphenylethers (OH-PBDEs) and 7 hydroxy-polychlorobiphenyls (OH-PCBs)) in serum from 274 people aged from 18 to 76years old living in Liege (Belgium) and the surrounding area. A questionnaire about their alimentary habits, life style and home environment was also administered to the volunteers. The predominant compound measured in the population was PCP (median concentration of 593.0pgmL^-1). 4-OH-CB 107, 4-OH-CB 146 and 4-OH-CB 187 were detected in all samples and contributed for 75% of the sum of OH-PCBs (ΣOH-PCBs). The median measured in our population for ΣOH-PCBs was 143.7pgmL^-1. TBBPA and 2,4,6-tribromophenol were detected in 31% and 63.8% of the samples respectively while the detection frequency observed for the other BPs and the OH-PBDEs was close to zero. We computed multivariate regression models in order to assess the influence of demographic and lifestyle parameters on the PCP and ΣOH-PCBs contamination levels. Significant correlation was found between the PCP concentration and sex, smoker status, sea fish consumption and level of education, although the model seemed to be a poor (R²=0.14) predictor of the PCP concentration. The model computed for ΣOH-PCBs was more explanatory (R²=0.61) and involved age, BMI and sea fish consumption. Finally, we assessed the parameters affecting the ΣOH-PCBs/ΣPCBs ratio. The model proposed involved age, BMI, smoker status and parent PCB level, and explained 41% of the variability of the ΣOH-PCBs/ΣPCBs ratio.

Airborne PCBs and OH-PCBs Inside and Outside Urban and Rural U.S. Schools

PCBs appear in school air because many school buildings were built when PCBs were still intentionally added to building materials and because PCBs are also present through inadvertent production in modern pigment. This is of concern because children are especially vulnerable to the toxic effects of PCBs. Here we report indoor and outdoor air concentrations of PCBs and OH-PCBs from two rural schools and four urban schools, the latter near a PCB-contaminated waterway of Lake Michigan in the United States. Samples (n = 108) were collected as in/out pairs using polyurethane foam passive air samplers (PUF-PAS) from January 2012 to November 2015. Samples were analyzed using GC/MS-MS for all 209 PCBs and 72 OH-PCBs. Concentrations inside schools were 1-2 orders of magnitude higher than outdoors and ranged from 0.5 to 194 ng/m³ (PCBs) and from 4 to 665 pg/m³ (OH-PCBs). Congener profiles were similar within each sampling location across season but different between schools and indicated the sources as Aroclors from building materials and individual PCBs associated with modern pigment. This study is the first cohort-specific analysis to show that some children's PCB inhalation exposure may be equal to or higher than their exposure through diet.

Identification of a sulfate metabolite of PCB 11 in human serum

Despite increasing evidence for a major role for sulfation in the metabolism of lower-chlorinated polychlorinated biphenyls in vitro and in vivo, and initial evidence for potential bioactivities of the resulting sulfate ester metabolites, the formation of PCB sulfates in PCB exposed human populations had not been explored. The primary goal of this study was to determine if PCB sulfates, and potentially other conjugated PCB derivatives, are relevant classes of PCB metabolites in the serum of humans with known exposures to PCBs. In order to detect and quantify dichlorinated PCB sulfates in serum samples of 46 PCB-exposed individuals from either rural or urban communities, we developed a high-resolution mass spectrometry-based protocol using 4-PCB 11 sulfate as a model compound. The method also allowed the preliminary analysis of these 46 human serum extracts for the presence of other metabolites, such as glucuronic acid conjugates and hydroxylated PCBs. Sulfate ester metabolites derived from dichlorinated PCBs were detectable and quantifiable in more than 20% of analyzed serum samples. Moreover, we were able to utilize this method to detect PCB glucuronides and hydroxylated PCBs, albeit at lower frequencies than PCB sulfates. Altogether, our results provide initial evidence for the presence of PCB sulfates in human serum. Considering the inability of previously employed analytical protocols for PCBs to extract these sulfate ester metabolites and the concentrations of these metabolites observed in our current study, our data support the hypothesis that total serum levels of PCB metabolites in exposed individuals may have been underestimated in the past.