Inhibitory effect of methylmercury on migration and tube formation by cultured human vascular endothelial cells

Mercury-induced toxicity: Mechanisms, molecular pathways, and gene regulation

Mercury is a well-known neurotoxicant for humans and wildlife. The epidemic of mercury poisoning in Japan has clearly demonstrated that chronic exposure to methylmercury (MeHg) results in serious neurological damage to the cerebral and cerebellar cortex, leading to the dysfunction of the central nervous system (CNS), especially in infants exposed to MeHg in utero. The occurrences of poisoning have caused a wide public concern regarding the health risk emanating from MeHg exposure; particularly those eating large amounts of fish may experience the low-level and long-term exposure. There is growing evidence that MeHg at environmentally relevant concentrations can affect the health of biota in the ecosystem. Although extensive in vivo and in vitro studies have demonstrated that the disruption of redox homeostasis and microtube assembly is mainly responsible for mercurial toxicity leading to adverse health outcomes, it is still unclear whether we could quantitively determine the occurrence of interaction between mercurial and thiols and/or selenols groups of proteins linked directly to outcomes, especially at very low levels of exposure. Furthermore, intracellular calcium homeostasis, cytoskeleton, mitochondrial function, oxidative stress, neurotransmitter release, and DNA methylation may be the targets of mercury compounds; however, the primary targets associated with the adverse outcomes remain to be elucidated. Considering these knowledge gaps, in this article, we conducted a comprehensive review of mercurial toxicity, focusing mainly on the mechanism, and genes/proteins expression. We speculated that comprehensive analyses of transcriptomics, proteomics, and metabolomics could enhance interpretation of "omics" profiles, which may reveal specific biomarkers obviously correlated with specific pathways that mediate selective neurotoxicity.

Association of Combined Metals and PFAS with Cardiovascular Disease Risk

This study sought to investigate the impact of exposure to metals and per- and polyfluoroalkyl substances (PFASs) on cardiovascular disease (CVD)-related risk. PFASs, including PFOA, PFOS, PFNA, and PFHxS, as well as metals such as lead (Pb), cadmium (Cd), and mercury (Hg), were analyzed to elucidate their combined effects on CVD risk.

METHODS

Utilizing data from the National Health and Nutrition Examination Survey (NHANES) spanning from 2007 to 2014, this investigation explored the effects of PFASs and metals on CVD risk. A spectrum of individual CVD markers, encompassing systolic blood pressure (SBP), diastolic blood pressure (DBP), high-density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol, and triglycerides, was examined. Additionally, comprehensive CVD risk indices were evaluated, namely the Overall Cardiovascular Biomarkers Index (OCBI), including the Framingham Risk Score and an Overall Cardiovascular Index. Linear regression analysis was employed to probe the relationships between these variables. Furthermore, to assess dose-response relationships between exposure mixtures and CVD while mitigating the influence of multicollinearity and potential interaction effects, Bayesian Kernel Machine Regression (BKMR) was employed.

RESULTS

Our findings indicated that exposure to PFAS and metals in combination increased CVD risk, with combinations occurring with lead bringing forth the largest impact among many CVD-related markers.

CONCLUSIONS

This study finds that combined exposure to metals and PFASs significantly elevates the likelihood of CVD risk. These results highlight the importance of understanding the complex interplay between multipollutant exposures and their potential implications for cardiovascular health.

Transition metals in angiogenesis - A narrative review

The aim of this paper is to offer a narrative review of the literature regarding the influence of transition metals on angiogenesis, excluding lanthanides and actinides. To our knowledge there are not any reviews up to date offering such a summary, which inclined us to write this paper. Angiogenesis describes the process of blood vessel formation, which is an essential requirement for human growth and development. When the complex interplay between pro- and antiangiogenic mediators falls out of balance, angiogenesis can quickly become harmful. As it is so fundamental, both its inhibition and enhancement take part in various diseases, making it a target for therapeutic treatments. Current methods come with limitations, therefore, novel agents are constantly being researched, with metal agents offering promising results. Various transition metals have already been investigated in-depth, with studies indicating both pro- and antiangiogenic properties, respectively. The transition metals are being applied in various formulations, such as nanoparticles, complexes, or scaffold materials. Albeit the increasing attention this field is receiving, there remain many unanswered questions, mostly regarding the molecular mechanisms behind the observed effects. Notably, approximately half of all the transition metals have not yet been investigated regarding potential angiogenic effects. Considering the promising results which have already been established, it should be of great interest to begin investigating the remaining elements whilst also further analyzing the established effects.

Associations between toxic elements and blood pressure parameters in adolescents

BACKGROUND

Both exposure to toxic elements and hypertension (HT) are a global health problem. We planned to examine the associations between some toxic elements in urine, and blood pressure (BP) and its diurnal changes in adolescents.

METHODS

In this cross-sectional study, 48 adolescents who were newly diagnosed with HT and 38 adolescents with age-appropriate BP and normal physical examination were included. Anthropometric measurements, urinary toxic elements, carotid intima media thickness (cIMT), and office and 24-hour ambulatory BP measurements (ABPM) of participants were taken. Urinary elements levels were studied with ICP-MS. Elements were grouped in tertiles according to urinary levels. Logistic regression analyses were performed to show the interactions.

RESULTS

Urinary cadmium, mercury, lead, and arsenic were found to be at detectable level in 90.7%, 69.8%, 91.9% and 100% of the participants, respectively. Univariate analyses showed that elevated daytime systolic and/or diastolic BP was associated with urinary cadmium and mercury. No association between urinary toxic elements and nighttime BP was found. When height and body mass index z-scores adjusted for, age, gender, and all four urinary creatinine-corrected toxic elements analyzed, multiple logistic regression revealed that there was an association between mercury (high vs. low; AOR:3.85) and office HT, and mercury (high vs. low; AOR:6.18) and cadmium (middle vs. low; AOR: 13.38) were associated with "elevated 24-hour systolic BP and/or diastolic BP", and "elevated 24-hour mean arterial BP" in ABPM.

CONCLUSION

There are complex relationships between toxic elements and BP parameters in adolescents, and more studies are needed to define the evolution of these relations.

Cardiometabolic risk factors and mercury content in hair of women from a territory distant from mercury-rich geochemical zones (Cherepovets city, Northwest Russia)

For the first time in the Russian Federation, a study was conducted to determine the level of mercury in the hair of young and middle-aged women with or without metabolic syndrome (MS) and the Association of mercury content in hair with cardiometabolic risk factors. The studied cohort consisted of 387 women (204 with metabolic syndrome and 183 without metabolic syndrome as controls). The mercury content in the hair was determined by atomic absorption pyrolysis. The relationship between mercury in hair and cardiometabolic risk factors was evaluated using linear regression. Calculation of the odds ratio (OR) of the risk of metabolic syndrome among quartiles of mercury content in the hair was performed by multiple logistic regression. Hg concentrations in hair were higher in women with metabolic syndrome than without metabolic syndrome (Mean - 520; median - 360; versus Mean - 330; median - 260 µg/kg, P < 0.001). There is an increased risk of developing cardiometabolic syndrome in women, whose hair contain over 544 µg/kg of mercury. The results of this study indicate that the intake of Hg in the human body can be one of the factors that can increase the development of cardiometabolic risk.

Erythrocytes as a Model for Heavy Metal-Related Vascular Dysfunction: The Protective Effect of Dietary Components

Heavy metals are toxic environmental pollutants associated with severe ecological and human health risks. Among them is mercury (Hg), widespread in air, soil, and water, due to its peculiar geo-biochemical cycle. The clinical consequences of Hg exposure include neurotoxicity and nephrotoxicity. Furthermore, increased risk for cardiovascular diseases is also reported due to a direct effect on cardiovascular tissues, including endothelial cells, recently identified as important targets for the harmful action of heavy metals. In this review, we will discuss the rationale for the potential use of erythrocytes as a surrogate model to study Hg-related toxicity on the cardiovascular system. The toxic effects of Hg on erythrocytes have been amply investigated in the last few years. Among the observed alterations, phosphatidylserine exposure has been proposed as an underlying mechanism responsible for Hg-induced increased proatherogenic and prothrombotic activity of these cells. Furthermore, following Hg-exposure, a decrease in NOS activity has also been reported, with consequent lowering of NO bioavailability, thus impairing endothelial function. An additional mechanism that may induce a decrease in NO availability is the generation of an oxidative microenvironment. Finally, considering that chronic Hg exposure mainly occurs through contaminated foods, the protective effect of dietary components is also discussed.

Downregulation of lncRNA MIR181A2HG by high glucose impairs vascular endothelial cell proliferation and migration through the dysregulation of the miRNAs/AKT2 axis

Endothelial dysfunction and diabetic vascular disease induced by chronic hyperglycemia involve complex interactions among high glucose, long non-coding RNAs (lncRNAs), microRNAs (miRNAs or miRs) and the Ser/Thr kinase AKT. However, the molecular mechanisms under-lying the regulatory crosstalk between these have not yet been completely elucidated. Thus, the present study aimed to explore the molecular mechanisms whereby high glucose (HG)-induced lncRNA MIR181A2HG modulates human umbilical vein endothelial cell (HUVEC) proliferation and migration by regulating AKT2 expression. The persistent exposure of HUVECs to HG resulted in MIR181A2HG down-regulation and thus reduced its ability to sponge miR-6832-5p, miR-6842-5p and miR-8056, subsequently leading to an increase in miR-6832-5p, miR-6842-5p and miR-8056 levels. Mechanistically, miR-6832-5p, miR-6842-5p and miR-8056 were found to target the 3′UTR of AKT2 mRNA in HUVECs, and the increase in their levels led to a decreased expression of AKT2. Thus, this also led to the suppression of HUVEC proliferation and migration, and the formation of capillary-like structures. Moreover, the suppression of HUVEC proliferation and migration induced by MIR181A2HG downregulation was accompanied by changes in glucose metabolism. On the whole, the present study demonstrates that the downregulation of lncRNA MIR181A2HG by HG impairs HUVEC proliferation and migration by dysregulating the miRNA/AKT2 axis. The MIR181A2HG/miRNA/AKT2 regulatory axis may thus be a potential therapeutic target for HG-induced endothelial dysfunction.

Chronic Mercury Exposure in Prehypertensive SHRs Accelerates Hypertension Development and Activates Vasoprotective Mechanisms by Increasing NO and H2O2 Production

Mercury is a heavy metal associated with cardiovascular diseases. Studies have reported increased vascular reactivity without changes in systolic blood pressure (SBP) after chronic mercury chloride (HgCl₂) exposure, an inorganic form of the metal, in normotensive rats. However, we do not know whether individuals in the prehypertensive phase, such as young spontaneously hypertensive rats (SHRs), are susceptible to increased arterial blood pressure. We investigated whether chronic HgCl₂ exposure in young SHRs accelerates hypertension development by studying the vascular function of mesenteric resistance arteries (MRAs) and SBP in young SHRs during the prehypertensive phase. Four-week-old male SHRs were divided into two groups: the SHR control group (vehicle) and the SHR HgCl₂ group (4 weeks of exposure). The results showed that HgCl₂ treatment accelerated the development of hypertension; reduced vascular reactivity to phenylephrine in MRAs; increased nitric oxide (NO) generation; promoted vascular dysfunction by increasing the production of reactive oxygen species (ROS), such as hydrogen peroxide (H₂O₂); increased Gp91Phox protein levels and in situ levels of superoxide anion (O₂^·-); and reduced vasoconstrictor prostanoid production compared to vehicle treatment. Although HgCl₂ accelerated the development of hypertension, the HgCl₂-exposed animals also exhibited a vasoprotective mechanism to counterbalance the rapid increase in SBP by decreasing vascular reactivity through H₂O₂ and NO overproduction. Our results suggest that HgCl₂ exposure potentiates this vasoprotective mechanism against the early establishment of hypertension. Therefore, we are concluding that chronic exposure to HgCl₂ in prehypertensive animals could enhance the risk for cardiovascular diseases.

Heavy Metal-Induced Cerebral Small Vessel Disease: Insights into Molecular Mechanisms and Possible Reversal Strategies

Heavy metals are considered a continuous threat to humanity, as they cannot be eradicated. Prolonged exposure to heavy metals/metalloids in humans has been associated with several health risks, including neurodegeneration, vascular dysfunction, metabolic disorders, cancer, etc. Small blood vessels are highly vulnerable to heavy metals as they are directly exposed to the blood circulatory system, which has comparatively higher concentration of heavy metals than other organs. Cerebral small vessel disease (CSVD) is an umbrella term used to describe various pathological processes that affect the cerebral small blood vessels and is accepted as a primary contributor in associated disorders, such as dementia, cognitive disabilities, mood disorder, and ischemic, as well as a hemorrhagic stroke. In this review, we discuss the possible implication of heavy metals/metalloid exposure in CSVD and its associated disorders based on in-vitro, preclinical, and clinical evidences. We briefly discuss the CSVD, prevalence, epidemiology, and risk factors for development such as genetic, traditional, and environmental factors. Toxic effects of specific heavy metal/metalloid intoxication (As, Cd, Pb, Hg, and Cu) in the small vessel associated endothelium and vascular dysfunction too have been reviewed. An attempt has been made to highlight the possible molecular mechanism involved in the pathophysiology, such as oxidative stress, inflammatory pathway, matrix metalloproteinases (MMPs) expression, and amyloid angiopathy in the CSVD and related disorders. Finally, we discussed the role of cellular antioxidant defense enzymes to neutralize the toxic effect, and also highlighted the potential reversal strategies to combat heavy metal-induced vascular changes. In conclusion, heavy metals in small vessels are strongly associated with the development as well as the progression of CSVD. Chelation therapy may be an effective strategy to reduce the toxic metal load and the associated complications.

Vascular Dysfunction Induced by Mercury Exposure

Methylmercury (MeHg) causes severe damage to the central nervous system, and there is increasing evidence of the association between MeHg exposure and vascular dysfunction, hemorrhage, and edema in the brain, but not in other organs of patients with acute MeHg intoxication. These observations suggest that MeHg possibly causes blood-brain barrier (BBB) damage. MeHg penetrates the BBB into the brain parenchyma via active transport systems, mainly the l-type amino acid transporter 1, on endothelial cell membranes. Recently, exposure to mercury has significantly increased. Numerous reports suggest that long-term low-level MeHg exposure can impair endothelial function and increase the risks of cardiovascular disease. The most widely reported mechanism of MeHg toxicity is oxidative stress and related pathways, such as neuroinflammation. BBB dysfunction has been suggested by both in vitro and in vivo models of MeHg intoxication. Therapy targeted at both maintaining the BBB and suppressing oxidative stress may represent a promising therapeutic strategy for MeHg intoxication. This paper reviews studies on the relationship between MeHg exposure and vascular dysfunction, with a special emphasis on the BBB.

MARCKS is involved in methylmercury-induced decrease in cell viability and nitric oxide production in EA.hy926 cells

Methylmercury (MeHg) is a persistent environmental contaminant that has been reported worldwide. MeHg exposure has been reported to lead to increased risk of cardiovascular diseases; however, the mechanisms underlying the toxic effects of MeHg on the cardiovascular system have not been well elucidated. We have previously reported that mice exposed to MeHg had increased blood pressure along with impaired endothelium-dependent vasodilation. In this study, we investigated the toxic effects of MeHg on a human endothelial cell line, EA.hy926. In addition, we have tried to elucidate the role of myristoylated alanine-rich C kinase substrate (MARCKS) in the MeHg toxicity mechanism in EA.hy926 cells. Cells exposed to MeHg (0.1-10 µM) for 24 hr showed decreased cell viability in a dose-dependent manner. Treatment with submaximal concentrations of MeHg decreased cell migration in the wound healing assay, tube formation on Matrigel and spontaneous nitric oxide (NO) production of EA.hy926 cells. MeHg exposure also elicited a decrease in MARCKS expression and an increase in MARCKS phosphorylation. MARCKS knockdown or MARCKS overexpression in EA.hy926 cells altered not only cell functions, such as migration, tube formation and NO production, but also MeHg-induced decrease in cell viability and NO production. These results suggest the broad role played by MARCKS in endothelial cell functions and the involvement of MARCKS in MeHg-induced toxicity.

Effect of mercury vapor inhalation on rat ovary: Stereology and histopathology

AIM

Mercury, an environmental contaminant, is a risk factor for health in whole living organisms. In this study, we investigated whether mercury vapor (HgO) inhalation has an effect on rat ovary.

METHODS

Twelve Wistar albino rats were divided equally into experimental (Hg) and control groups (n = 6). Animals in the Hg group were exposed to HgO for 45 days at a dose 1 mg/m(3)/day, after which, histological and stereological assessment were carried out.

RESULTS

Ovaries exposed to HgO had histo-morphometric alterations. HgO inhalation resulted in reduction of the total number of primordial, primary and Graaf follicles. Also, mean volume of ovary, medulla and cortex, corpus luteum (c. luteum) and Graaf follicles was decreased in the Hg group. Moreover, there was a significant increase in total volume of the atretic follicles. On light microscopy, thickening of tunica albuginea, increase of fibrils within the connective tissue, congestion of the capillaries and venous vessels, thinned walls and fibrin deposition in some large blood vessels, and edema were seen. Also, irregular follicle and oocyte borders, and hydropic degeneration in follicular granulosa cells were detected.

CONCLUSION

Structural alterations could be attributed to the toxic influence of HgO on rat ovary. The use of Hg should therefore be more controlled to minimize its toxic effect.

Functional role of inorganic trace elements in angiogenesis part III: (Ti, Li, Ce, As, Hg, Va, Nb and Pb)

Many essential elements exist in nature with significant influence on human health. Angiogenesis is vital in developmental, repair, and regenerative processes, and its aberrant regulation contributes to pathogenesis of many diseases including cancer. Thus, it is of great importance to explore the role of these elements in such a vital process. This is third in a series of reviews that serve as an overview of the role of inorganic elements in regulation of angiogenesis and vascular function. Here we will review the roles of titanium, lithium, cerium, arsenic, mercury, vanadium, niobium, and lead in these processes. The roles of other inorganic elements in angiogenesis were discussed in part I (N, Fe, Se, P, Au, and Ca) and part II (Cr, Si, Zn, Cu, and S) of these series. The methods of exposure, structure, mechanisms, and potential activities of these elements are briefly discussed. An electronic search was performed on the role of these elements in angiogenesis from January 2005 to April 2014. These elements can promote and/or inhibit angiogenesis through different mechanisms. The anti-angiogenic effect of titanium dioxide nanoparticles comes from the inhibition of angiogenic processes, and not from its toxicity. Lithium affects vasculogenesis but not angiogenesis. Nanoceria treatment inhibited tumor growth by inhibiting angiogenesis. Vanadium treatment inhibited cell proliferation and induced cytotoxic effects through interactions with DNA. The negative impact of mercury on endothelial cell migration and tube formation activities was dose and time dependent. Lead induced IL-8 production, which is known to promote tumor angiogenesis. Thus, understanding the impact of these elements on angiogenesis will help in development of new modalities to modulate angiogenesis under various conditions.

Toxic effects of chronic mercury exposure on the retinal nerve fiber layer and macular and choroidal thickness in industrial mercury battery workers

Background

The aim of this study was to evaluate the toxic effects of mercury on retinal nerve fiber layer thickness (RNFLT), macular thickness (MT), and choroidal thickness (CT) by using spectral-domain optical coherence tomography (SD-OCT) in battery industry workers who had been chronically exposed to mercury.

Material/Methods

Battery factory workers (n=31) and healthy non-factory employee controls (n=15) participated in the study. Participants were divided into 3 groups: Group 1 (n=15) was factory workers who had worked for more than 5 years in a mercury battery factory; Group 2 (n=16) was factory worker who had worked for less than 5 years in a mercury battery factory; and Group 3 (n=15) was healthy non-employees. Systemic symptoms were recorded. Ophthalmic examination included best-corrected visual acuity test, color vision test, full ophthalmologic examination, and SD-OCT of the RNLF, macula, and choroid. To determine mercury exposure, venous blood samples were collected and mercury levels were assessed.

Results

In our study group the most common systemic symptoms were insomnia (67.7%) and fatigue (67.7%). There were no significant differences between Group 1 and Group 2, but there were significant differences between Group 3 and both Group 1 and Group 2 in best-corrected visual acuity values (1=2<3), color vision scores, blood mercury levels, and duration (mean ±SD, range) of mercury exposure(1>2>3). OCT values of RNFLTs, MTs, and CTs of all 3 groups were statistically different from each another (1<2<3).

Conclusions

SD-OCT can be useful for evaluating the toxic effects of chronic exposure to mercury.

Hair mercury level in smokers and its influence on blood pressure and lipid metabolism

OBJECT

Smoking is a major risk factor for the development and progression of cardiovascular disease and cigarettes contain a slight amount of mercury. Mercury has been causally linked to cardiovascular diseases. This study evaluated the mercury content in hair according to smoking exposure status and the influence of the mercury level on blood pressure and lipid metabolism.

METHODS

We examined mercury concentration in the hair samples from 236 healthy people 16-75-years-of-age who had visited the health promotion center of a university hospital from January 2004 to January 2007. Self-reported cigarette smoking status and baseline health information were obtained using a questionnaire. Blood pressure and serum lipid level according to the mercury concentration were assessed.

RESULTS

The mean systolic blood pressure in the smoking exposure group and non-exposure group were 123.2±15.4mmHg and 117.2±15.9mmHg, respectively (p=0.005). The mean diastolic pressure in the smoking exposure group and non-exposed group were 80.2±10.9mmHg and 75.1±11.3mmHg, respectively (p<0.001). Mercury concentration had a positive relationship with systolic and diastolic blood pressure. Compared with the normal and high mercury groups, the normal mercury group demonstrated lower blood pressure, lower triglyceride, and lower smoking amount, but higher high density lipoprotein cholesterol than the high mercury group. There was an increase of mercury concentration in the smoking exposure group. The 20-29 packyear group showed significantly increased odds ratio of mercury content, compared with the non-exposure group (14.00, 95% confidence interval, 5.03-38.96).

CONCLUSIONS

Smoking is positively associated with mercury accumulation, and high mercury concentration is associated with increased blood pressure and abnormal lipid metabolism.

Role of mercury toxicity in hypertension, cardiovascular disease, and stroke

Mercury has a high affinity for sulfhydryl groups, inactivating numerous enzymatic reactions, amino acids, and sulfur-containing antioxidants (N-acetyl-L-cysteine, alpha-lipoic acid, L-glutathione), with subsequent decreased oxidant defense and increased oxidative stress. Mercury binds to metallothionein and substitute for zinc, copper, and other trace metals, reducing the effectiveness of metalloenzymes. Mercury induces mitochondrial dysfunction with reduction in adenosine triphosphate, depletion of glutathione, and increased lipid peroxidation. Increased oxidative stress and reduced oxidative defense are common. Selenium and fish containing omega-3 fatty acids antagonize mercury toxicity. The overall vascular effects of mercury include increased oxidative stress and inflammation, reduced oxidative defense, thrombosis, vascular smooth muscle dysfunction, endothelial dysfunction, dyslipidemia, and immune and mitochondrial dysfunction. The clinical consequences of mercury toxicity include hypertension, coronary heart disease, myocardial infarction, cardiac arrhythmias, reduced heart rate variability, increased carotid intima-media thickness and carotid artery obstruction, cerebrovascular accident, generalized atherosclerosis, and renal dysfunction, insufficiency, and proteinuria. Pathological, biochemical, and functional medicine correlations are significant and logical. Mercury diminishes the protective effect of fish and omega-3 fatty acids. Mercury inactivates catecholaminei-0-methyl transferase, which increases serum and urinary epinephrine, norepinephrine, and dopamine. This effect will increase blood pressure and may be a clinical clue to mercury-induced heavy metal toxicity. Mercury toxicity should be evaluated in any patient with hypertension, coronary heart disease, cerebral vascular disease, cerebrovascular accident, or other vascular disease. Specific testing for acute and chronic toxicity and total body burden using hair, toenail, urine, and serum should be performed.

Evaluation of the cardiovascular effects of methylmercury exposures: current evidence supports development of a dose-response function for regulatory benefits analysis

BACKGROUND

The U.S. Environmental Protection Agency (U.S. EPA) has estimated the neurological benefits of reductions in prenatal methylmercury (MeHg) exposure in past assessments of rules controlling mercury (Hg) emissions. A growing body of evidence suggests that MeHg exposure can also lead to increased risks of adverse cardiovascular impacts in exposed populations.

DATA EXTRACTION

The U.S. EPA assembled the authors of this article to participate in a workshop, where we reviewed the current science concerning cardiovascular health effects of MeHg exposure via fish and seafood consumption and provided recommendations concerning whether cardiovascular health effects should be included in future Hg regulatory impact analyses.

DATA SYNTHESIS

We found the body of evidence exploring the link between MeHg and acute myocardial infarction (MI) to be sufficiently strong to support its inclusion in future benefits analyses, based both on direct epidemiological evidence of an MeHg-MI link and on MeHg's association with intermediary impacts that contribute to MI risk. Although additional research in this area would be beneficial to further clarify key characteristics of this relationship and the biological mechanisms that underlie it, we consider the current epidemiological literature sufficiently robust to support the development of a dose- response function.

CONCLUSIONS

We recommend the development of a dose- response function relating MeHg exposures with MIs for use in regulatory benefits analyses of future rules targeting Hg air emissions.

Hair tissue mineral analysis and metabolic syndrome

Deficiency of minerals causes functional abnormality of enzymes, frequently resulting in metabolic disturbance. We investigated possible relationship between minerals and metabolic syndrome by analysis of hair tissue minerals. We selected 848 subjects older than 20 years of age at Ajou University Hospital from May 2004 to February 2007. We excluded the subjects who had cancers, steroid and thyroid medication, and incomplete record from the study. Finally, 343 subjects were eligible. We performed cross-sectional analysis for the relationship between minerals and metabolic syndrome. The contents of calcium, magnesium, and copper in the metabolic syndrome group were significantly lower than those of the normal group, whereas the amounts of sodium, potassium, and mercury in the metabolic syndrome group were significantly higher than those of the normal group. By dividing the subjects into quartile with the level of calcium, magnesium, and mercury concentrations, we carried out logistic regression analysis to study the subjects and found that the subjects in the third quartile of calcium and magnesium concentrations had significantly lower odds ratio (OR) of the metabolic syndrome compared with that of the lowest quartile group [OR = 0.30, confidence interval (CI) = 0.10-0.89; OR = 0.189, CI = 0.063-0.566] and that the subjects in the highest mercury quartile had significantly higher OR of the metabolic syndrome compared with that of the lowest mercury quartile group (OR = 7.35, CI = 1.73-31.1). As part of the metabolic syndrome, the optimal calcium and magnesium concentrations in hair tissue may reflect decreased risk of metabolic syndrome, whereas high mercury concentration in hair tissue may indicate increased risk of metabolic syndrome.

Mercury as a risk factor for cardiovascular diseases

Mercury is a heavy metal that exists naturally in the environment. Major sources include the burning of fossil fuels (especially coal) and municipal waste incineration. Mercury can exist in several forms, with the most hazardous being organic methylmercury. In waterways (lakes, rivers, reservoirs, etc.), mercury is converted to methylmercury, which then accumulates in fish, especially in large predatory fish. Fish and fish products are the major--if not the only--source of methylmercury in humans. Mercury has long been recognized as a neurotoxin for humans, but in the last 10 years, its potentially harmful effects on cardiovascular diseases (CVD) have raised a cause for concern, mostly due to the proposed role of mercury in oxidative stress propagation. Some epidemiological studies have indeed found an association between increased levels of mercury in the body and risk of CVD. There are several plausible mechanisms to explain the association; these are discussed in this review. We also review the epidemiological studies that have investigated the association between mercury and CVD.

Mercury, fish oils, and risk of acute coronary events and cardiovascular disease, coronary heart disease, and all-cause mortality in men in eastern Finland

OBJECTIVE

Mercury has been suggested to have negative effects on cardiovascular health. We investigated the effects of high mercury content in hair on the risk of acute coronary events and cardiovascular and all-cause mortality in men from eastern Finland.

METHODS AND RESULTS

The population-based prospective Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD) cohort of 1871 Finnish men aged 42 to 60 years and free of previous coronary heart disease (CHD) or stroke at baseline was used. During an average follow-up time of 13.9 years, 282 acute coronary events and 132 cardiovascular disease (CVD), 91 CHD, and 525 all-cause deaths occurred. Men in the highest third of hair mercury content (>2.03 microg/g) had an adjusted 1.60-fold (95% CI, 1.24 to 2.06) risk of acute coronary event, 1.68-fold (95% CI, 1.15 to 2.44) risk of CVD, 1.56-fold (95% CI, 0.99 to 2.46) risk of CHD, and 1.38-fold (95% CI, 1.15 to 1.66) risk of any death compared with men in the lower two thirds. High mercury content in hair also attenuated the protective effects of high-serum docosahexaenoic acid plus docosapentaenoic acid concentration.

CONCLUSIONS

High content of mercury in hair may be a risk factor for acute coronary events and CVD, CHD, and all-cause mortality in middle-aged eastern Finnish men. Mercury may also attenuate the protective effects of fish on cardiovascular health.

Mercury, fish oils, and the risk of myocardial infarction

BACKGROUND

It has been suggested that mercury, a highly reactive heavy metal with no known physiologic activity, increases the risk of cardiovascular disease. Because fish intake is a major source of exposure to mercury, the mercury content of fish may counteract the beneficial effects of its n-3 fatty acids.

METHODS

In a case-control study conducted in eight European countries and Israel, we evaluated the joint association of mercury levels in toenail clippings and docosahexaenoic acid (C22:6n-3, or DHA) levels in adipose tissue with the risk of a first myocardial infarction among men. The patients were 684 men with a first diagnosis of myocardial infarction. The controls were 724 men selected to be representative of the same populations.

RESULTS

The average toenail mercury level in controls was 0.25 microg per gram. After adjustment for the DHA level and coronary risk factors, the mercury levels in the patients were 15 percent higher than those in controls (95 percent confidence interval, 5 to 25 percent). The risk-factor-adjusted odds ratio for myocardial infarction associated with the highest as compared with the lowest quintile of mercury was 2.16 (95 percent confidence interval, 1.09 to 4.29; P for trend=0.006). After adjustment for the mercury level, the DHA level was inversely associated with the risk of myocardial infarction (odds ratio for the highest vs. the lowest quintile, 0.59; 95 percent confidence interval, 0.30 to 1.19; P for trend=0.02).

CONCLUSIONS

The toenail mercury level was directly associated with the risk of myocardial infarction, and the adipose-tissue DHA level was inversely associated with the risk. High mercury content may diminish the cardioprotective effect of fish intake.