Mercury and Atherosclerosis: Cell Biology, Pathophysiology, and Epidemiological Studies

In vivo chronic exposure to inorganic mercury worsens hypercholesterolemia, oxidative stress and atherosclerosis in the LDL receptor knockout mice

Heavy metal exposure leads to multiple system dysfunctions. The mechanisms are likely multifactorial and involve inflammation and oxidative stress. The aim of this study was to evaluate markers and risk factors for atherosclerosis in the LDL receptor knockout mouse model chronically exposed to inorganic mercury (Hg) in the drinking water. Results revealed that Hg exposed mice present increased plasma levels of cholesterol, without alterations in glucose. As a major source and target of oxidants, we evaluated mitochondrial function. We found that liver mitochondria from Hg treated mice show worse respiratory control, lower oxidative phosphorylation efficiency and increased H2O2 release. In addition, Hg induced mitochondrial membrane permeability transition. Erythrocytes from Hg treated mice showed a 50% reduction in their ability to take up oxygen, lower levels of reduced glutathione (GSH) and of antioxidant enzymes (SOD, catalase and GPx). The Hg treatment disturbed immune system cells counting and function. While lymphocytes were reduced, monocytes, eosinophils and neutrophils were increased. Peritoneal macrophages from Hg treated mice showed increased phagocytic activity. Hg exposed mice tissues present metal impregnation and parenchymal architecture alterations. In agreement, increased systemic markers of liver and kidney dysfunction were observed. Plasma, liver and kidney oxidative damage indicators (MDA and carbonyl) were increased while GSH and thiol groups were diminished by Hg exposure. Importantly, atherosclerotic lesion size in the aorta root of Hg exposed mice were larger than in controls. In conclusion, in vivo chronic exposure to Hg worsens the hypercholesterolemia, impairs mitochondrial bioenergetics and redox function, alters immune cells profile and function, causes several tissues oxidative damage and accelerates atherosclerosis development.

Association Between Multiple Heavy Metal Exposures and Cholesterol Levels in Residents Living Near a Smelter Plant in Korea

BACKGROUND

Considering the interactions between heavy metals, a comprehensive evaluation of the effects of exposure to various types of co-interacting heavy metals on health is required. This study assessed the association between dyslipidemia markers and blood mercury, lead, cadmium, iron, zinc, and nickel levels in residents of an abandoned refinery plant.

METHODS

A total of 972 individuals (exposed group: 567, control group: 405) living near the Janghang refinery plant in the Republic of Korea were included. Blood mercury, lead, cadmium, iron, zinc, nickel, cholesterol, and triglyceride levels were measured. The combined effect of the six heavy metals on dyslipidemia markers was evaluated using a Bayesian kernel machine regression (BKMR) model and compared with the results of a linear regression analysis. The BKMR model results were compared using a stratified analysis of the exposed and control groups.

RESULTS

In the BKMR model, the combined effect of the six heavy metals was significantly associated with total cholesterol (TC) levels both below the 45th percentile and above the 55th percentile in the total population. The combined effect range between the 25th and 75th percentiles of the six metals on TC levels was larger in the exposed group than that in the total population. In the control group, the combined effects of the changes in concentration of the six heavy metals on the TC concentration were not statistically significant.

CONCLUSION

These results suggest that the cholesterol levels of residents around the Janghang refinery plant may be elevated owing to exposure to multiple heavy metals.

The Association Between Blood Mercury and Lipid Biomarkers in US Hypertensive Adults

Mercury (Hg) is detrimental to human health, but its impact on lipid biomarkers remains a subject of controversy. This study sought to delineate a clear link between blood Hg and lipid biomarkers correlated with cardiovascular disease (CVD), including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG), in hypertensive adults in the USA.

METHODS

This cross-sectional research gathered data from a total of 4415 participants sourced from the National Health and Nutrition Examination Survey (NHANES). The Holm-Bonferroni stepdown procedure was utilized to control the type I error rate in multiple comparisons. We employed multivariable linear regression models to assess the correlation between blood Hg and lipid biomarkers. Subsequently, subgroup analyses were conducted, categorized by both gender and race. Additionally, we used smooth curve fittings and generalized additive models to confirm the presence of non-linear relationships. When non-linearity was detected, we applied a recursive algorithm to calculate the inflection points. Finally, we established a weighted two-piecewise linear regression model to illustrate the associations on either side of the inflection point.

RESULTS

In our multivariable linear regression models, clear associations emerged. Specifically, positive correlations were observed between blood mercury and TC (β = 0.025; 95% CI 0.009 to 0.041; corrected P = 0.011), LDL-C (β = 0.022; 95% CI 0.007 to 0.036; corrected P = 0.012), and HDL-C (β = 0.007; 95% CI 0.001 to 0.013; corrected P = 0.058). However, there was no significant correlation with TG (β =  - 0.007; 95% CI - 0.018 to 0.004; corrected P = 0.526). Notably, it has been demonstrated that distinct inverted U-shaped and U-shaped curves exist when stratified by gender in our analysis.

CONCLUSIONS

Blood Hg exhibited a positive correlation with TC, LDL-C, and HDL-C in hypertensive adults in the USA. Nonetheless, no significant association was observed with TG.

Contaminant Metals and Cardiovascular Health

A growing body of research has begun to link exposure to environmental contaminants, such as heavy metals, with a variety of negative health outcomes. In this paper, we sought to review the current research describing the impact of certain common contaminant metals on cardiovascular (CV) health. We reviewed ten metals: lead, barium, nickel, chromium, cadmium, arsenic, mercury, selenium, zinc, and copper. After a literature review, we briefly summarized the routes of environmental exposure, pathophysiological mechanisms, CV health impacts, and exposure prevention and/or mitigation strategies for each metal. The resulting article discloses a broad spectrum of pathological significance, from relatively benign substances with little to no described effects on CV health, such as chromium and selenium, to substances with a wide-ranging and relatively severe spectrum of CV pathologies, such as arsenic, cadmium, and lead. It is our hope that this article will provide clinicians with a practical overview of the impact of these common environmental contaminants on CV health as well as highlight areas that require further investigation to better understand how these metals impact the incidence and progression of CV diseases.

Free Radicals and Obesity-Related Chronic Inflammation Contrasted by Antioxidants: A New Perspective in Coronary Artery Disease

We are surrounded by factors called free radicals (FR), which attach to the molecules our body is made of, first among them the endothelium. Even though FR are to a certain extent a normal factor, nowadays we face an escalating increase in these biologically aggressive molecules. The escalating formation of FR is linked to the increased usage of man-made chemicals for personal care (toothpaste, shampoo, bubble bath, etc.), domestic laundry and dish-washer detergents, and also an ever wider usage of drugs (both prescription and over the counter), especially if they are to be used long-term (years). In addition, tobacco smoking, processed foods, pesticides, various chronic infectious microbes, nutritional deficiencies, lack of sun exposure, and, finally, with a markedly increasing impact, electromagnetic pollution (a terribly destructive factor), can increase the risk of cancer, as well as endothelial dysfunction, owing to the increased production of FR that they cause. All these factors create endothelial damage, but the organism may be able to repair such damage thanks to the intervention of the immune system supported by antioxidants. However, one other factor can perpetuate the state of inflammation, namely obesity and metabolic syndrome with associated hyperinsulinemia. In this review, the role of FR, with a special emphasis on their origin, and of antioxidants, is explored from the perspective of their role in causing atherosclerosis, in particular at the coronary level.

Hair mercury is associated with dyslipidemia and cardiovascular risk: An anthropometric, biochemical and genetic cross-sectional study of Amazonian vulnerable populations

This cross-sectional study evaluated the association between human exposure to mercury and cardiovascular risk using lipid profile (including apolipoproteins) and genetic analysis of Amazonian riverine population. Anthropometric data (gender, age, height, weight, blood pressure, and neck and waist circumferences) of the participants were recorded. Total mercury and methylmercury (MeHg) content were quantified in hair by ICP-MS and GC-pyro-AFS system. Polymorphisms rs662799, rs693, rs429358 and rs7412 (of genes of apolipoproteins A-V, B, and E at positions 112 and 158, respectively) were genotyped by real-time PCR. The population presented a dyslipidemia profile significantly correlated with high mercury levels. The apolipoprotein B/apolipoprotein A-I (ApoB/ApoA-I) index was also positively correlated with mercury, supporting a possible causal relationship. Allelic distributions were similar to those described in other populations, suggesting that genetic susceptibility may not have a significant role in the lipid alterations found in this work. This study demonstrated for the first time: i) the relationship between mercury exposure and cardiovascular risk-related apolipoproteins in humans, ii) the ApoB levels and the ApoB/ApoA-I index as the risk factors more strongly associated to the mercury-related dyslipidemia in humans, and iii) the prevalence of high/moderate risk of acute myocardial infarction in the vulnerable and chronically exposed-populations of the Amazon, in addition to the genotypic profile of the three most frequent polymorphisms in apolipoproteins of relevance for cardiovascular risk. This early detection of lipid alterations is essential to prevent the development of cardiovascular diseases (CVD), especially in chronically exposed populations such as those found in the Amazon. Therefore, in addition to provide data for the Minamata Convention implementation, our work is in line with the efforts joined by all members of the World Health Organization committed to reducing premature deaths originating from non-communicable diseases by 25% in 2025, including CVD.

Mercury remediation potential of mercury-resistant strain Rheinheimera metallidurans sp. nov. isolated from a municipal waste dumping site

A novel mercury-resistant bacterium, designated strain DCL_24^T, was isolated from the legacy waste at the Daddu Majra dumping site in Chandigarh, India. It showed resistance up to 300 µM of inorganic mercury (mercuric chloride). The isolate was found to be a Gram-negative, facultative anaerobic, motile, and rod-shaped bacterium that can grow at 4 - 30 °C (optimum 25 °C), pH 6.0 - 12.0 (optimum 7.0), and 0 - 4.0 % (w/v) NaCl (optimum 0.5 - 2.0 %). The 16 S rRNA gene-based phylogenetic analysis showed that DCL_ 24 ^T shared a 97.53 % similarity with itsºlosest type strain Rheinheimera muenzenbergensis E-49^T. Insilico DNA-DNA hybridization and average nucleotide identity values were found to be 18.60 % and 73.77 %, respectively, between the genomes of DCL_24^T and R. muenzenbergensis E-49^T. The strain DCL_24^T has 44.33 DNA G+C content (mol %). Based on the phenotypic, chemotaxonomic, and genotypic data, the strain DCL_24^T represents a novel species within the genus Rheinheimera, for which the name Rheinheimera metallidurans sp. nov is proposed. The type strain is DCL_24^T (MTCC13203^T = NBRC115780^T = JCM 35551 ^T). The isolate was found to volatilize and remove mercury efficiently, as demonstrated by X-ray film and dithizone-based colorimetric methods. Around 92 % of mercury removal was observed within 48 h. The mercury-resistant determinant mer operon consisting of merA, encoding the mercuric reductase enzyme, and transport and regulatory genes (merT, merP, merD, and merR) were found in the isolate. Relative expression analysis of merA at increasing concentrations of HgCl₂ was confirmed by quantitative real-time PCR. These data indicate the merA-mediated reduction of toxic Hg²⁺ into a non-toxic volatile Hg⁰. The phytotoxicity assay performed using Arabidopsis thaliana seeds further demonstrated the mercury toxicity reduction potential of DCL_24^T. The study shows that this novel isolate, DCL_24^T, is an interesting candidate for mercury bioremediation. However, further studies are required to assess the bioremediation efficacy of the strain under the harsh environmental conditions prevailing in polluted sites.

The association of trace elements with arthritis in US adults: NHANES 2013-2016

BACKGROUND

Arthritis is a common chronic disease, and is a major cause of disability and chronic pain in adults. Considering inflammatory responses is closely related with trace elements (TEs), the role of TEs in arthritis has attracted much attention. This study aimed to assess the association between TEs and arthritis.

METHODS

Concentrations of TEs in whole blood [cadmium (Cd), lead (Pb), mercury (Hg), selenium (Se), and manganese (Mn)] and serum [copper (Cu) and zinc (Zn)] were measured in adults who participated in the US National Health and Nutrition Examination Survey. Logistic regression model and Bayesian kernel machine regression model were used to explore the association between TEs and arthritis.

RESULTS

The levels of five TEs (Pb, Hg, Cd, Se, and Cu) in the arthritis group changed significantly. Three TEs were found to be associated with an increased risk of arthritis: Pb [OR (95% CI): 2.96 (2.18, 4.03), p-value for trend (P-t) < 0.001], Cd [OR (95% CI): 2.28 (1.68, 3.11), P-t < 0.001], Cu [OR (95% CI): 2.05 (1.53, 2.76), P-t < 0.001]. The Relative Excess Risk of Interaction was 0.35 (95% CI: 0.06-0.65) and 0.38 (95% CI: 0.11-0.64), respectively, suggesting that Hg ions and Se ions have positive additional interactions with alcohol consumption, which reduced the risk of arthritis. Subgroup analysis showed that Pb ions and Cd ions were significantly correlated with osteoarthritis and rheumatoid arthritis.

CONCLUSION

Elevated concentrations of Pb, Cd, and Cu were associated with increased risk of arthritis. Drinking with high levels of Hg or Se may be a protective factor for arthritis. Future studies are warranted to validate these findings in prospective studies.

Association of Blood Heavy Metal Exposure with Atherosclerotic Cardiovascular Disease (ASCVD) Among White Adults: Evidence from NHANES 1999-2018

Cardiovascular diseases (CVD) are main public health concerns highly prevalent in industrialized societies where human health is threatened by a series of environmental pollutants, particularly heavy metal contaminants. We aimed to find out if blood heavy metals are associated with the 10-year risk of atherosclerotic cardiovascular disease (ASCVD) in a nationally representative sample of US adults. We analyzed the cross-sectional data on blood heavy metals of 3268 non-Hispanic white participants aged 40-79 years from the National Health and Nutrition Examination Survey (NHANES) 1999-2018. We introduced a risk estimation algorithm, namely the 2013 Pooled Cohort Equations (PCE), to assess the risk for ASCVD over a 10-year period. The 10-year risk for ASCVD was categorized as either reduced risk (< 7.5% risk) or elevated risk (≥ 7.5% risk). Blood lead, cadmium, and mercury were distributed into four quartiles. We used weighted multivariate logistic regression models and restricted cubic spline (RCS) regression to detect the association of blood heavy metal exposure with 10-year ASCVD risk. Following the adjustment of covariates, the adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for elevated 10-year ASCVD risk for participants from the highest quartiles were 4.50 (2.88-7.02), 2.59 (1.68-4.00), and 1.06 (0.66-1.71) for blood cadmium, lead, and mercury compared to the lowest quartiles, respectively. The RCS plot demonstrated that blood cadmium was linearly and positively associated with 10-year ASCVD risk (P for nonlinearity = 0.112). According to our findings, non-Hispanic whites aged 40-79 years had a greater 10-year ASCVD risk as their blood lead and cadmium levels increased. Consequently, when establishing approaches for ASCVD prevention, blood heavy metals should be considered.

Misuse of Cardiac Lipid upon Exposure to Toxic Trace Elements-A Focused Review

Heavy metals and metalloids like cadmium, arsenic, mercury, and lead are frequently found in the soil, water, food, and atmosphere; trace amounts can cause serious health issues to the human organism. These toxic trace elements (TTE) affect almost all the organs, mainly the heart, kidney, liver, lungs, and the nervous system, through increased free radical formation, DNA damage, lipid peroxidation, and protein sulfhydryl depletion. This work aims to advance our understanding of the mechanisms behind lipid accumulation via increased free fatty acid levels in circulation due to TTEs. The increased lipid level in the myocardium worsens the heart function. This dysregulation of the lipid metabolism leads to damage in the structure of the myocardium, inclusive fibrosis in cardiac tissue, myocyte apoptosis, and decreased contractility due to mitochondrial dysfunction. Additionally, it is discussed herein how exposure to cadmium decreases the heart rate, contractile tension, the conductivity of the atrioventricular node, and coronary flow rate. Arsenic may induce atherosclerosis by increasing platelet aggregation and reducing fibrinolysis, as exposure interferes with apolipoprotein (Apo) levels, resulting in the rise of the Apo-B/Apo-A1 ratio and an elevated risk of acute cardiovascular events. Concerning mercury and lead, these toxicants can cause hypertension, myocardial infarction, and carotid atherosclerosis, in association with the generation of free radicals and oxidative stress. This review offers a complete overview of the critical factors and biomarkers of lipid and TTE-induced cardiotoxicity useful for developing future protective interventions.

Effects of e-waste exposure on biomarkers of coronary heart disease (CHD) and their associations with level of heavy metals in blood

Excess heavy metals increase the risk of various diseases. Electronic waste (e-waste) is a potential route to heavy metal exposure, and Taizhou is a large e-waste dismantling area in China. In this study, we acquire blood samples from residents living near an e-waste recycling area (exposed group) and other residents in a selected reference area (reference group) for a comparative study in Taizhou in December 2017. Seven heavy metals, including cobalt (Co), nickel (Ni), cadmium (Cd), tin (Sn), copper (Cu), zinc (Zn), and lead (Pb), are quantitatively determined in all blood samples. It is discovered that the levels of Co, Ni, Sn, and Pb in the exposed group are higher than those in the reference group. Additionally, two crucial biomarkers of coronary heart disease (CHD), i.e., troponin (Tn) and myeloperoxidase (MPO), and two biomarkers of oxidative stress, i.e., malondialdehyde (MDA) and 8-isoprostane (8-I), are measured. We discovered that the levels of these indicators in the exposed group are significantly higher than those in the reference group. Meanwhile, both the Spearman correlation and multiple linear regression analysis show that Ni is positively correlated with Tn, MPO, 8-I, and MDA. Hence, we hypothesize that exposure to e-waste increases the risk of CHD and that Ni is an important contributor to the initiation of the disease.

New strategy for clinical etiologic diagnosis of acute ischemic stroke and blood biomarker discovery based on machine learning

Acute ischemic stroke (AIS) is a syndrome characterized by high morbidity, prevalence, mortality, recurrence and disability. The longer the delay before proper treatment of a stroke, the greater the likelihood of brain damage and disability. Computed tomography and nuclear magnetic resonance are the primary choices for fast diagnosis of AIS in the early stage, which can provide certain information about infarction location and degree, and even the vascular distribution of lesions responsible for strokes. However, this is quite difficult to achieve in small clinics or at-home diagnoses. Hematology tests could quickly obtain a large number of pathology-related indicators, and offer an effective method for rapid AIS diagnosis when combined with the machine learning technique. To explore a reliable, predictable method for early clinical etiologic diagnosis of AIS, a retrospective study was deployed on 456 AIS patients at the early stage and 28 reference subjects without the symptoms of AIS, by means of the selected significant traits amongst 64 clinical and blood traits in conjunction with powerful machine learning strategies. Five representative biomarkers were closely related to cardioembolic (CE), 22 to large artery atherosclerosis (LAA), and 15 to small vessel occlusion (SVO) strokes, respectively. With these biomarkers, different etiologic subtypes of stroke patients were determined with high accuracy of >0.73, sensitivity of >0.73, and specificity of >0.70, which was comparable to the accuracy obtained in the emergency department by clinical diagnosis. The proposed method may offer an alternative strategy for the etiologic diagnosis of AIS at the early stage when integrating significant blood traits into machine learning.

A rapid and safe strategy was proposed for clinical etiologic diagnosis of acute ischemic stroke at the early stage using clinical hematology traits and machine learning. Blood biomarkers were effectively identified.

Random Forests Highlight the Combined Effect of Environmental Heavy Metals Exposure and Genetic Damages for Cardiovascular Diseases

Heavy metals are a dangerous source of pollution due to their toxicity, permanence in the environment and chemical nature. It is well known that long-term exposure to heavy metals is related to several chronic degenerative diseases (cardiovascular diseases, neoplasms, neurodegenerative syndromes, etc.). In this work, we propose a machine learning framework to evaluate the severity of cardiovascular diseases (CVD) from Human scalp hair analysis (HSHA) tests and genetic analysis and identify a small group of these clinical features mostly associated with the CVD risk. Using a private dataset provided by the DD Clinic foundation in Caserta, Italy, we cross-validated the classification performance of a Random Forests model with 90 subjects affected by CVD. The proposed model reached an AUC of 0.78 ± 0.01 on a three class classification problem. The robustness of the predictions was assessed by comparison with different cross-validation schemes and two state-of-the-art classifiers, such as Artificial Neural Network and General Linear Model. Thus, is the first work that studies, through a machine learning approach, the tight link between CVD severity, heavy metal concentrations and SNPs. Then, the selected features appear highly correlated with the CVD phenotype, and they could represent targets for future CVD therapies.

Association between Dyslipidemia and Mercury Exposure in Adults

Background-Dyslipidemia is one of the prominent risk factors for cardiovascular disease, which is the leading cause of death worldwide. Dyslipidemia has various causes, including metabolic capacity, genetic problems, physical inactivity, and dietary habits. This study aimed to determine the association between dyslipidemia and exposure to heavy metals in adults. Methods-Using data from the seventh Korean National Health and Nutrition Examination Survey (2016-2017), 5345 participants aged ≥20 years who were tested for heavy metal levels were analyzed in this study. Multiple logistic regression was conducted to assess the factors affecting the prevalence of dyslipidemia. Results-The risks of dyslipidemia among all and male participants with mercury (Hg) levels of ≥2.75 μg/L (corresponding to the Korean average level) were 1.273 and 1.699 times higher than in those with levels of <2.75 μg/L, respectively. The factors that significantly affected the dyslipidemia risk were age, household income, body mass index, and subjective health status in both males and females. Conclusions-In adult males, exposure to Hg at higher-than-average levels was positively associated with dyslipidemia. These results provide a basis for targeted prevention strategies for dyslipidemia using lifestyle guidelines for reducing Hg exposure and healthy behavioral interventions.

Transcriptomic-based toxicological investigations of ethanol to human umbilical vein endothelial cells

Ethanol has a complex effect on the cardiovascular system in humans, but the systemic effects of ethanol to endothelial cells were rarely investigated. In this study, we exposed human umbilical vein endothelial cells (HUVECs) to 5- or 50-mM ethanol and performed transcriptomics to investigate the systemic effects of ethanol. While these concentrations of ethanol did not significantly affect HUVEC viability, 5-mM ethanol significantly upregulated and downregulated 59 and 73 genes, respectively, whereas 50-mM ethanol significantly upregulated and downregulated 50 and 80 genes, respectively. Totally, 37 genes were shared by the two concentrations of ethanol. The most significantly altered gene ontology (GO) term and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway after 5-mM ethanol treatment were nucleic acid binding (GO:0003676) and Herpes simplex virus 1 infection (ko05168), respectively, whereas the most significantly altered GO term and KEGG pathway by 50-mM ethanol treatment were aryl sulfotransferase activity (GO:0004062) and chemical carcinogenesis (ko05204). We further verified that ethanol treatment downregulated the mRNA levels of CD38 molecule (CD38), ORAI calcium release-activated calcium modulator 2 (ORAI2), cysteinyl leukotriene receptor 2 (CYSLTR2), key genes involved in calcium signaling pathway (ko04020), as well as integrin subunit alpha 2 (ITGA2), and cAMP responsive element binding protein 3 like 2 (CREB3L2), key genes involved in PI3K-Akt signaling pathway (ko04151). The results from this study suggested that ethanol could induce systemic effects and alter signaling pathways in HUVECs.