RESUMO
Worldwide, millions of people are co-exposed to arsenic and cadmium. Environmental exposure to both metals is linked with a higher risk of atherosclerosis. While studies have characterized the pro-atherosclerotic effects of arsenic and cadmium as single agents, little is known about the potential effects of metal mixtures, particularly at low doses. Here, we used a combination of in vitro and in vivo models to assess the effects of low-dose metals individually and as mixtures on early events and plaque development associated with atherosclerosis. In vitro, we investigated early pro-atherogenic changes in macrophages and endothelial cells with metal treatments. The combined cytotoxic effects of both metals at low concentrations were dose interactive, specifically, synergistic in macrophages, but antagonistic in endothelial cells. Despite this differential behavior across cell types, the mixtures did not initiate early pro-atherogenic events: neither reactive oxygen species generation in macrophages nor adhesion molecule expression on endothelial cells. In vivo, we utilized the well-characterized hyperlipidemic apolipoprotein E knock-out (ApoE-/-) mouse model. Previously, we have shown that low concentrations of arsenic (down to 10 ppb) enhance atherosclerosis in ApoE-/- mice. This model has also been used with cadmium to demonstrate pro-atherogenic effects, although at concentrations above human-relevant exposures. In both sexes, there are some small increases in atherosclerotic lesion size, but very few changes in plaque constituents in the ApoE-/- mouse model. Together, these results suggests that low-dose metal mixtures are not significantly more pro-atherogenic than either metal alone.
Assuntos
Arsênio , Aterosclerose , Placa Aterosclerótica , Masculino , Feminino , Humanos , Animais , Camundongos , Arsênio/toxicidade , Cádmio/toxicidade , Células Endoteliais/metabolismo , Aterosclerose/metabolismo , Placa Aterosclerótica/induzido quimicamente , Metais , Apolipoproteínas E/genéticaRESUMO
Arsenic is world-wide contaminant to which millions of people are exposed. The health consequences of arsenic exposure are varied, including cancer, cardiometabolic disease, and respiratory disorders. Arsenic is also toxic to the immune system, which may link many of the pathologies associated with arsenic exposure. The immune system can be classified into two interconnected arms: the innate and the adaptive immune responses. Herein, we discuss the effects of arsenic on key cell types within each of these arms, highlighting both in vitro and in vivo responses. These cells include macrophages, neutrophils, dendritic cells, and both B and T lymphocytes. Furthermore, we will explore data from human populations where altered immune status is implicated in disease and identify several data gaps where research is needed to complete our understanding of the immunotoxic effects of arsenic.
Assuntos
Arsênio , Arsênio/toxicidade , Humanos , Imunidade Humoral , Imunidade Inata , Macrófagos , NeutrófilosRESUMO
BACKGROUND: Organophosphate esters (OPEs) are flame retardants and plasticizers used in consumer products. OPEs are found ubiquitously throughout the environment with high concentrations in indoor house dust. Exposure to individual OPEs is associated with immune dysfunction, particularly in macrophages. However, OPEs exist as complex mixtures and the effects of environmentally relevant mixtures on the immune system have not been investigated. OBJECTIVES: The objectives of this study were to evaluate the toxicity of an environmentally relevant mixture of OPEs that models Canadian house dust on macrophages using phenotypic and functional assessments in vitro. METHODS: High-content live-cell fluorescent imaging for phenotypic biomarkers of toxicity in THP-1 macrophages treated with the OPE mixture was undertaken. We used confocal microscopy and cholesterol analysis to validate and expand on the observed OPE-induced lipid phenotype. Then, we used flow cytometry and live-cell imaging to conduct functional tests and uncover mechanisms of OPE-induced phagocytic suppression. Finally, we validated our THP-1 findings in human primary peripheral blood mononuclear cells (hPBMC) derived macrophages. RESULTS: Exposure to non-cytotoxic dilutions of the OPE mixture resulted in higher oxidative stress and disrupted lysosome and lipid homeostasis in THP-1 and primary macrophages. We further observed that phagocytosis of apoptotic cells in THP-1 and primary macrophages was lower in OPE-exposed cells vs. controls. In THP-1 macrophages, phagocytosis of both Gram-positive and Gram-negative bacteria was also lower in OPE-exposed cells vs. controls. Additionally, the OPE mixture altered the expression of phagocytic receptors linked to the recognition of phosphatidylserine and pathogen-associated molecular patterns. DISCUSSION: The results of this in vitro study suggested that exposure to an environmentally relevant mixture of OPEs resulted in higher lipid retention in macrophages and poor efferocytic response. These effects could translate to enhanced foam cell generation resulting in higher cardiovascular mortality. Furthermore, bacterial phagocytosis was lower in OPE-exposed macrophages in an in vitro setting, which may indicate the potential for reduced bacterial clearance in models of infections. Taken together, our data provide strong evidence that mixtures of OPEs can influence the biology of macrophages and offer new mechanistic insights into the impact of OPE mixtures on the immune system. https://doi.org/10.1289/EHP13869.
Assuntos
Ésteres , Macrófagos , Organofosfatos , Macrófagos/efeitos dos fármacos , Humanos , Organofosfatos/toxicidade , Retardadores de Chama/toxicidade , Estresse Oxidativo/efeitos dos fármacos , Fenótipo , Poeira , Células THP-1 , Fagocitose/efeitos dos fármacosRESUMO
Arsenic exposure is correlated with atherosclerosis in epidemiological studies and in animal models. We have previously shown that arsenic exposure enhanced the atherosclerotic plaque size, increased the plaque lipid content, and decreased the plaque smooth muscle cell and collagen contents in the apolipoprotein E knockout (apoE-/-) mice. However, the percentage of plaque-resident macrophages, the primary drivers of atherosclerosis remained unchanged. Therefore, we hypothesized that although arsenic does not change the quantity of macrophages, it alters the macrophage transcriptome towards a proatherogenic state. To test this hypothesis, we used bone marrow-derived macrophages, polarized them to either interferon-γ (IFN-É£) stimulated, proinflammatory or interleukin-4 (IL-4) stimulated, alternatively activated macrophages in the presence or absence of 0.67 µM (50 ppb) arsenic and performed RNA sequencing. Arsenic exposure altered the gene expression of the macrophages in a subtype-specific manner. Most differentially expressed genes (88%) were altered specifically in either IFN-É£- or IL-4-stimulated macrophages, whereas in the remaining 12% of genes that changed in both cell types, did so in opposite directions. In IL-4-stimulated macrophages, arsenic significantly downregulated the genes involved in cholesterol biosynthesis and the chemokines CCL17/CCL22, whereas in IFN-É£-stimulated macrophages, the genes associated with the liver X receptor (LXR) pathway were downregulated by arsenic. Using a bone marrow transplant experiment, we validated that the deletion of LXRα from the hematopoietic compartment rescued arsenic-enhanced atherosclerosis in the apoE-/- mouse model. Together, these data suggest that arsenic modulates subtype-specific transcriptomic changes in macrophages and further emphasize the need to define macrophage heterogeneity in atherosclerotic plaques in order to evaluate the proatherogenic role of arsenic.