Inorganic arsenic (iAs) is a known carcinogen and immunotoxicant that contaminates groundwater used for drinking, food production, and irrigation, exposing an estimated 200 million people worldwide to levels above the World Health Organization safe drinking water limit of 10 μg/L. Classified as a known carcinogen classified by the International Agency for Research on Cancer (IARC), iAs alsond causes increasesd susceptibility to infectious diseases, highlighting its role as an immunotoxicant. This study elucidates the effects of arsenic on macrophages using in vitro exposure models. Bone marrow-derived macrophages (BMDMs) were cultured from adult male and female C57BL/6 mice. Naïve macrophages ("M0" BMDMs) were exposed to a non-cytotoxic dose of iAs during the 7-day differentiation period and stimulated for 24 h with LPS and IFNγ, or IL-4 and IL-13, to induce "M1" or "M2" activation, respectively. In parallel, RAW 264.7 (RAW) macrophages were chronically exposed to iAs for 70 days, and activated in the last 24 h s. Culture supernatant analysis indicated reduced nitric oxide production in "M1" RAW macrophages, but not BMDMs upon iAs exposure; whereas BMDMs displayed predominantly suppressed cytokine/chemokine profiles, albeit with notable sex-dependent differences across activation states. Flow cytometry confirmed these sex- and stimulation-dependent changes in macrophage polarization, with "M2" markers being upregulated upon iAs exposure, whereas the functional markers iNOS and MHCII were reduced in male BMDMs only. Increased lipid droplet formation and altered lipidomic and metabolomic profiles further suggested iAs exposure induces a pro-tumorigenic microenvironment. Accordingly, iAs-exposed macrophages displayed increased migration toward cancer cell-conditioned media and promoted cancer cell proliferation. Collectively, these results provide phenotypic and mechanistic insights that iAs not only suppresses immune function but also skews macrophage polarization and immunometabolism towards tumor promoting phenotypes.

Cardiovascular disease is the leading cause of death globally, yet cardiovascular risks from environmental pollutants remain under-recognized and are not considered a stand-alone hazard trait. Growing evidence shows that industrial and environmental chemicals, including air pollutants, metals, solvents, pesticides and other chemicals, may be hazardous to human cardiovascular health. Indeed, many human and animal studies demonstrate that environmental chemicals can act through oxidative stress, inflammation, and endothelial dysfunction, potentially causing hypertension, arrhythmias, and other cardiovascular conditions. This commentary reviews the state of the science for recognizing chemical cardiotoxicity under the Organisation for Economic Co-operation and Development (OECD) Working Party on Hazard Assessment project [ENV/CBC/HA(2024)13]. New approach methodologies (NAMs) provide organizing principles for assembling mechanism-based data on cardiovascular toxicants and evaluating potential cardiovascular hazards. Case studies demonstrate how broad toxicity testing programs like ToxCast and cardiovascular-specific NAMs can assess hazards and risks for environmental chemical cardiovascular toxicity. The pharmaceutical industry's approach and strategies for de-risking cardiovascular toxicities serve as an example of regulatory applicability of a tiered context-of-use-focused approach consisting of in silico, in vitro and targeted animal and human studies. Overall, a framework for integrating clinical, animal, and NAMs data to support decisions regarding potential chemical cardiovascular toxicity is proposed.

Over 100,000 people were exposed to arsenic-contaminated drinking water in Antofagasta, Chile from 1958-1970. Individuals born during this high exposure period have elevated rates of cancer, lung and cardiovascular disease, and hypertension. However, the mechanisms of long-term arsenic toxicity remain unclear. We investigated whether early-life arsenic exposure was associated with altered glucocorticoid levels in adulthood. This study included 114 individuals born in Antofagasta during the high exposure period and 118 individuals born elsewhere. Arsenic exposure metrics were constructed based on residential histories and included: concentration at birth, peak and highest 5-year average between ages 0-10 years, and highest lifetime 5-year average, and lifetime cumulative exposure. Morning plasma cortisol concentrations were measured using a cell-based bioassay. Individuals in the highest quartile of highest lifetime 5-year average of arsenic exposure had approximately 11% lower mean log cortisol levels than those in the lowest quartile of exposure (β = -0.116; 95% CI: -0.229, -0.003). In sex-stratified analyses, associations were stronger among females. For example, females in the highest quartile of cumulative exposure had 22.0% lower cortisol levels compared to those in the lowest quartile (β = -0.248; 95% CI: -0.444, -0.053) and the test for interaction by sex was statistically significant (p = 0.036). This study is the first to show that early-life arsenic exposure may have lasting effects on cortisol. These findings highlight endocrine disruption as a mechanism contributing to long-term health effects of early arsenic exposure.

Supplementary Data from B-Cell NHL Subtype Risk Associated with Autoimmune Conditions and PRS

A critical component of evaluating whether a chemical can cause human neurotoxicity is hazard identification, which typically involves a comprehensive literature search to identify and synthesize epidemiological, animal, and mechanistic data for the chemical of interest. The key characteristics (KCs) concept has proven to be a useful tool for searching, organizing, and evaluating mechanistic data for hazard identification. KCs are the established chemical and biological properties of known human neurotoxic agents based on understanding of their mechanisms of neurotoxicity. KCs were originally developed for carcinogens but have now also been published for endocrine- and metabolism-disruptors and various organ-selective toxic chemicals. To identify KCs associated with neurotoxic chemicals, an expert committee was convened to consider current mechanistic understanding of chemicals known to be neurotoxic in humans with the goal of identifying established molecular and cellular actions of neurotoxic chemicals. After extensive discussion, the committee reached consensus on 10 KCs. Here, we describe the 10 proposed KCs and provide chemical-related examples to support their inclusion. Several important considerations emerged from the committee’s deliberations including: (1) a mechanistic action need not be unique to neurotoxicity to be considered a KC of neurotoxic chemicals; (2) many, if not most, neurotoxic chemicals exhibit multiple KCs, and the relative importance of any specific KC and/or its causal relationship to other KCs may vary depending on life stage at the time of exposure and/or the exposure paradigm; and (3) data indicating a chemical exhibits one or more KCs of neurotoxic chemicals suggests that the chemical poses a neurotoxic hazard but does not necessarily identify the risk that the chemical presents to humans. These considerations, as well as potential applications of KCs in neurotoxicology, are discussed. The committee also strongly recommended that the list of proposed KCs of neurotoxic chemicals be viewed as a “living document” that is reviewed and revised in response to emerging insights on mechanisms of neurotoxicity, as well as lessons learned from the application of these proposed KCs, including but not limited to their use as a tool for the systemic identification and review of mechanistic data for assessment of neurotoxic hazards.

In evaluating whether a chemical can cause cancer or another adverse outcome, three lines of evidence are typically considered: epidemiology, animal bioassays and mechanistic evidence. The key characteristics (KCs) form the basis of a uniform approach for searching, organizing, and evaluating mechanistic evidence to support hazard identification. KCs are the established properties of the toxicants themselves and are generated from our understanding of mechanisms of toxicity. KCs have been published for carcinogens, endocrine disruptors and reproductive, liver immune and cardiovascular toxicants. We noted that several KCs were common to different types of toxicants, whereas others were highly specific. Hence, there may be overlapping umbrella KCs for potentially hazardous bioactive chemicals that could be used in predictive toxicology. There are, however, also clearly unique KCs for chemicals that primarily target a specific organ and these unique KCs could be especially important to predicting target organ toxicity. It is possible that in silico approaches, in vitro tests, and in vivo biomarkers could be developed, which predict the "umbrella" and "unique" KCs of hazardous chemicals. However, given the significance of human evidence, the development of a set of biomarkers that could be used to measure the KCs in molecular epidemiology studies is also important.

The potential for food contact chemicals to disrupt genetic programs in development and metabolism raises concerns. Nuclear receptors (NRs) control many of these programs, and the retinoid-X receptor (RXR) is a DNA-binding partner for one-third of the NRs. RXR disruption could generate adverse outcomes in several NR pathways. We used machine learning and other in silico methods to identify RXR-interacting candidates from a list of over 57,000 chemicals. Butylphenols comprised the largest, high-probability, structural group (58 compounds); several are food contact chemicals with widespread commercial use. In vitro ToxCast data suggested that bulky, aliphatic substitution at C4 of 2,6-di-tert-butylphenol facilitated RXR activation. We tested six butylphenols with increasing bulk at C4 in vivo for their ability to disrupt thyroid hormone receptor (TR) signaling, using an integrated luciferase reporter driven by TR-RXR binding and quantifiable morphological changes in a Xenopus laevis precocious metamorphosis assay. Three tert-butylphenols potentiated TH action at nanomolar concentrations. Molecular modeling showed the three positives formed more frequent, stable interactions with RXRα, and bulkiness at C4 increased steric complementarity with the RXR ligand-binding pocket. Our findings establish a paradigm for machine learning coupled with a convenient, in vivo validation approach to identify chemicals interacting with RXR-NR-controlled genetic pathways.

In many regions around the world, including the United States, inorganic arsenic (iAs) contaminates groundwater used for drinking, food production, and irrigation. Although the World Health Organization has set a safety limit of 10 μg/L for arsenic in drinking water, an estimated 200 million people worldwide are still exposed to arsenic concentrations above this threshold. Eliciting a broad range of adverse health effects, arsenic is a known carcinogen classified by the International Agency for Research on Cancer (IARC) and causes increased susceptibility to infectious diseases, highlighting its role as an immunotoxicant. The purpose of this study is to elucidate the effects of arsenic on the innate immune system, namely macrophages, using in vitro exposure models. Bone marrow-derived macrophages (BMDMs) were cultured from adult male and female C57/BL6 mice. These naïve macrophages ("M0" BMDMs) were exposed in vitro to a non-cytotoxic dose of iAs (0.1 μM sodium (meta)arsenite) during the 7 day period of macrophage differentiation and stimulated for 24 hrs with LPS and IFNγ (to induce "M1" pro-inflammatory activation) or IL-4 and IL-13 (to induce "M2" anti-inflammatory activation). In a parallel chronic exposure model, RAW 264.7 (RAW) macrophages were cultured in vitro with iAs for 70 days. Culture supernatant analysis for nitric oxide and cytokine secretion revealed sex-dependent differences in immune response between exposure models, as well as between iAs-exposed and nonexposed macrophages, with and without stimulation. Additionally, iAs-exposed macrophages exhibited increased lipid droplet formation and altered lipidomic and metabolomic profiles, as determined by LC/MS. Flow cytometric analysis further revealed changes in macrophage polarization markers in a sex- and stimulation-dependent manner, with M2-related markers being upregulated in iAs-exposed conditions. Finally, to assess the effects of iAs on macrophages in the context of cancer, we demonstrated that iAs-exposed macrophages displayed increased migration toward cancer cell-conditioned media, and promoted cancer cell proliferation. These results suggest that dysregulated macrophage polarization due to iAs exposure could impact susceptibility to diseases. This research contributes to our understanding of the full spectrum of adverse health effects of iAs exposure and may aid in the development of therapeutics for iAs-induced diseases, including cancer.

Benzene is a ubiquitous environmental pollutant that induces blood cancers via its complex metabolism. Since cancer risks to the general public involve toxic benzene metabolites derived from the inhalation of benzene at ppb air concentrations, questions remain regarding low-dose metabolism. Using previously published data from 389 Chinese workers, we fit Michaelis–Menten-like models to predict urinary concentrations of E,E-muconic acid (the most discriminating urinary metabolite) as functions of urinary benzene levels between 0.0001 μM and 54 μM, equivalent to benzene air concentrations between 0.1 ppb and more than 100 ppm. When we compared models having either one or two metabolic pathways, weights of evidence favoring two pathways were essentially 100 percent for nonsmoking males and females and 58 percent for smoking males. At ppb exposure levels, metabolic rates for the high-affinity pathway were 43-fold greater than those for the low-affinity pathway in nonsmoking males, 6.5-fold greater in nonsmoking females, and 4.9-fold greater in smoking males. Thus, the high-affinity pathway is most efficient in nonsmoking males and is inhibited by smoking. The characteristics of the two-pathway model implicate lung metabolism of benzene via CYP2A13 and/or CYP2F1 at ppb air levels and liver metabolism by CYP2E1 above one ppm. Since ambient benzene concentrations are typically less than 10 ppb, blood-cancer risks predicted from workers exposed to above 1 ppm likely underestimate risks to the general public by many fold, and these risks may be modulated by smoking. Also, since the lung is the site of initial metabolism upon inhalation, the respiratory bioactivation of benzene could contribute to lung-cancer incidence, including that for lung adenomas in never smokers.

AbstractBackground: A previous International Lymphoma Epidemiology (InterLymph) Consortium evaluation of joint associations between five immune gene variants and autoimmune conditions reported interactions between B-cell response-mediated autoimmune conditions and the rs1800629 genotype on risk of B-cell non–Hodgkin lymphoma (NHL) subtypes. Here, we extend that evaluation using NHL subtype-specific polygenic risk scores (PRS) constructed from loci identified in genome-wide association studies of three common B-cell NHL subtypes. Methods: In a pooled analysis of NHL cases and controls of Caucasian descent from 14 participating InterLymph studies, we evaluated joint associations between B-cell–mediated autoimmune conditions and tertile (T) of PRS for risk of diffuse large B-cell lymphoma (DLBCL; n = 1,914), follicular lymphoma (n = 1,733), and marginal zone lymphoma (MZL; n = 407), using unconditional logistic regression. Results: We demonstrated a positive association of DLBCL PRS with DLBCL risk [T2 vs. T1: OR = 1.24; 95% confidence interval (CI), 1.08–1.43; T3 vs. T1: OR = 1.81; 95% CI, 1.59–2.07; P-trend (Ptrend) < 0.0001]. DLBCL risk also increased with increasing PRS tertile among those with an autoimmune condition, being highest for those with a B-cell–mediated autoimmune condition and a T3 PRS [OR = 6.46 vs. no autoimmune condition and a T1 PRS, Ptrend < 0.0001, P-interaction (Pinteraction) = 0.49]. Follicular lymphoma and MZL risk demonstrated no evidence of joint associations or significant Pinteraction. Conclusions: Our results suggest that PRS constructed from currently known subtype-specific loci may not necessarily capture biological pathways shared with autoimmune conditions. Impact: Targeted genetic (PRS) screening among population subsets with autoimmune conditions may offer opportunities for identifying those at highest risk for (and early detection from) DLBCL.

The key characteristics (KCs) of carcinogens are the properties common to known human carcinogens that can be used to search for, organize, and evaluate mechanistic data in support of hazard identification. A limiting factor in this approach is that relevant in vitro and in vivo assays, as well as corresponding biomarkers and endpoints, have been only partially documented for each of the 10 KCs (Smith MT, Guyton KZ, Kleinstreuer N et al. The key characteristics of carcinogens: relationship to the hallmarks of cancer, relevant biomarkers, and assays to measure them. Cancer Epidemiol Biomarkers Prev 2020;29:1887-903. https://doi.org/10.1158/1055-9965.EPI-19-1346). To address this limitation, a comprehensive database is described that catalogues these previously described methods and endpoints/biomarkers pertinent to the 10 KCs of carcinogens as well as those referenced as supporting evidence for each KC in the International Agency of Research on Cancer Monograph Volumes 112-131. Our comprehensive mapping of KCs to assays and endpoints can be used to facilitate mechanistic data searches, presents a useful tool for searching for assays and endpoints relevant to the 10 KCs, and can be used to create a roadmap for utilizing data to evaluate the strength of the evidence for each KC. The KC-Assay database is available to the public on the web at https://kcad.cchem.berkeley.edu and acts as a 'living document', with the ability to be updated and refined. Database URL: https://kcad.cchem.berkeley.edu.

Per- and poly-fluoroalkyl substances (PFASs) are persistent, toxic chemicals that pose significant hazards to human health and the environment. Screening large numbers of chemicals for their ability to act as endocrine disruptors by modulating the activity of nuclear receptors (NRs) is challenging because of the time and cost of in vitro and in vivo experiments. For this reason, we need computational approaches to screen these chemicals and quickly prioritize them for further testing. Here, we utilized molecular modeling and machine-learning predictions to identify potential interactions between 4545 PFASs with ten different NRs. The results show that some PFASs can bind strongly to several receptors. Further, PFASs that bind to different receptors can have very different structures spread throughout the chemical space. Biological validation of these in silico findings should be a high priority.

Metabolism-disrupting agents (MDAs) are chemical, infectious or physical agents that increase the risk of metabolic disorders. Examples include pharmaceuticals, such as antidepressants, and environmental agents, such as bisphenol A. Various types of studies can provide evidence to identify MDAs, yet a systematic method is needed to integrate these data to help to identify such hazards. Inspired by work to improve hazard identification of carcinogens using key characteristics (KCs), we developed 12 KCs of MDAs based on our knowledge of processes underlying metabolic diseases and the effects of their causal agents: (1) alters function of the endocrine pancreas; (2) impairs function of adipose tissue; (3) alters nervous system control of metabolic function; (4) promotes insulin resistance; (5) disrupts metabolic signalling pathways; (6) alters development and fate of metabolic cell types; (7) alters energy homeostasis; (8) causes inappropriate nutrient handling and partitioning; (9) promotes chronic inflammation and immune dysregulation in metabolic tissues; (10) disrupts gastrointestinal tract function; (11) induces cellular stress pathways; and (12) disrupts circadian rhythms. In this Consensus Statement, we present the logic that revealed the KCs of MDAs and highlight evidence that supports the identification of KCs. We use chemical, infectious and physical agents as examples to illustrate how the KCs can be used to organize and use mechanistic data to help to identify MDAs.

Abstract Introduction Occupational exposure to formaldehyde (FA) has been linked to hematopoietic and nasopharyngeal cancers. Methods To further evaluate the biological effects of exposure to FA in humans, we used comprehensive untargeted liquid chromatography with high resolution mass spectrometry (LC-HRMS) to characterize the plasma metabolome of workers (n=43) exposed to relatively high levels of FA [median 8-h time-weighted air level average exposure: 1.3 parts-per-million (ppm) of air] and comparable controls (n=51). Metabolite features associated with FA exposure were identified using a metabolome- wide association study that tested for relationships between metabolite feature intensity and occupational exposure to FA. Results and discussion Metabolic pathway enrichment analysis highlighted multiple pathways associated with FA exposure, with significant changes in the carnitine shuttle and in arachidonic acid, fatty acid, nucleic acid, amino acid, steroid, and prostaglandin metabolism. These results suggest possible changes or perturbations from FA exposure in fatty acid uptake, oxidative stress, and pathways related to mitochondrial dysfunction, immune system disorders, and altered cell proliferation, several of which are consistent with previous experimental and human studies. Taken together, our results suggest that occupational exposure to FA was associated with alterations in a number of systemic metabolic processes. Conclusion Further study is needed with larger sample sizes to replicate and extend these findings.

Supplementary Figure S4A and S4B: Comparison of Designs 0/1A/1B and Designs 0/3A/3B

Glyphosate was classified as a probable human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC) partially due to strong mechanistic evidence in 2015. Since then, numerous studies of glyphosate and its formulations (GBF) have emerged. These studies can be evaluated for cancer hazard identification with the newly described ten key characteristics (KC) of carcinogens approach. Our objective was to assess all in vivo, ex vivo, and in vitro mechanistic studies of human and experimental animals (mammals) that compared exposure to glyphosate/GBF with low/no exposure counterparts for evidence of the ten KCs. A protocol with our methods adhering to PRISMA guidelines was registered a priori (INPLASY202180045). Two blinded reviewers screened all in vivo, ex vivo, and in vitro studies of glyphosate/GBF exposure in humans/mammals reporting any KC-related outcome available in PubMed before August 2021. Studies that met inclusion criteria underwent data extraction conducted in duplicate for each KC outcome reported along with key aspects of internal/external validity, results, and reference information. These data were used to construct a matrix that was subsequently analyzed in the program R to conduct strength of evidence and quality assessments. Of the 2537 articles screened, 175 articles met inclusion criteria, from which we extracted >50,000 data points related to KC outcomes. Data analysis revealed strong evidence for KC2, KC4, KC5, KC6, KC8, limited evidence for KC1 and KC3, and inadequate evidence for KC7, KC9, and KC10. Notably, our in-depth quality analyses of genotoxicity (KC2) and endocrine disruption (KC8) revealed strong and consistent positive findings. For KC2, we found: 1) studies conducted in humans and human cells provided stronger positive evidence than counterpart animal models; 2) GBF elicited a stronger effect in both human and animal systems when compared to glyphosate alone; and 3) the highest quality studies in humans and human cells consistently revealed strong evidence of genotoxicity. Our analysis of KC8 indicated that glyphosate's ability to modulate hormone levels and estrogen receptor activity is sensitive to both exposure concentration and formulation. The modulations observed provide clear evidence that glyphosate interacts with receptors, alters receptor activation, and modulates the levels and effects of endogenous ligands (including hormones). Our findings strengthen the mechanistic evidence that glyphosate is a probable human carcinogen and provide biological plausibility for previously reported cancer associations in humans, such as non-Hodgkin lymphoma. We identified potential molecular interactions and subsequent key events that were used to generate a probable pathway to lymphomagenesis.

Supplementary Figure S2A and S2B: miR qPCR Assay Comparison

Due to their persistence and toxicity, perfluoroalkyl and polyfluoroalkyl substances (PFASs) constitute significant hazards to human health and the environment. Their effects include immune suppression, altered hormone levels, and osteoporosis. Recently, the most studied PFAS, perfluorooctanoic acid (PFOA), was shown to competitively binding to the Vitamin D receptor (VDR). VDR plays a crucial role in regulating genes involved in maintaining immune, endocrine, and calcium homeostasis, suggesting it may be a target for at least some of the health effects of PFAS. Hence, this study examined the potential binding of 5206 PFASs to VDR using molecular docking, molecular dynamics, and free energy binding calculations. We identified 14 PFAS that are predicted to interact strongly with VDR, similar to the natural ligands. We further investigated the interactions of VDR with 256 PFASs of established commercial importance. Eighty-three (32%) of these 256 commercially important PFAS were predicted to be stronger binders to VDR than PFOA. At least 16 PFASs of regulatory importance, because they have been identified in water supplies and human blood samples, were also more potent binders to VDR than PFOA. Further, PFASs are usually found together in contaminated drinking water and human blood samples, which raises the concern that multiple PFASs may act together as a mixture on VDR function, potentially producing harmful effects on the immune, endocrine, and bone homeostasis.

Background: Impairment of the hematopoietic system is one of the primary adverse health effects from exposure to benzene. We previously have shown that exposure to benzene at low levels (<1 ppm) affects the blood forming system and that these effects were proportionally stronger at lower versus higher levels of benzene exposure. This observation is potentially explained by saturation of enzymatic systems. Methods: Here we extend these analyses by detailed modeling of the exposure response association of benzene and its major metabolites (i.e. catechol, muconic acid, phenol, and hydroquinone) on peripheral white blood cell (WBC) counts and its major cell-subtypes (i.e. granulocytes, lymphocytes, and monocytes) using two previously published cross-sectional studies among occupationally exposed Chinese workers. Results: Supra-linear exposure response associations were observed between air benzene concentrations (range similar to 0.1 - 100 ppm) and WBC counts and its cell-subtypes, with a larger than proportional decrease in cell counts at lower than at higher levels of benzene exposure. The hematotoxicity associations were largely similar in shape when the analyses were repeated with benzene urinary metabolites suggesting that enzymatic saturation is not a full explanation of the observed non-linearity with WBC endpoints. Discussion: We hypothesize that the flattening of the exposure response curve especially at higher benzene exposure levels may reflect a response by the bone marrow to maintain hematopoietic homeostasis. Toxicity to the bone marrow and an induced hyper-proliferative response could both contribute to risk of subsequently developing a hematopoietic malignancy. Additional work is needed to explore this hypothesis.