Health surveillance in the population living in a methyl mercury-polluted area over a long period

Harmonization of Mangiferin on methylmercury engendered mitochondrial dysfunction

Mangiferin (MGN), a C-glucosylxanthone abundantly found in mango plants, was studied for its potential to ameliorate methylmercury (MeHg) induced mitochondrial damage in HepG2 (human hepatocarcinoma) cell line. Cell viability experiments performed using 3-[4,5-dimethylthiazol-2-yl]-2,5- diphenyltetrazolium bromide (MTT) showed protective property of MGN in annulling MeHg-induced cytotoxicity. Conditioning the cells with optimal dose of MGN (50 µM) lowered MeHg-induced oxidative stress, calcium influx/efflux, depletion of mitochondrial trans-membrane potential and prevented mitochondrial fission as observed by decrease in Mitotracker red fluorescence, expression of pDRP1 (serine 616), and DRP1 levels. MGN pre-treated cells demonstrated elevation in the activities of glutathione (GSH), Glutathione-S-transferase (GST), Glutathione peroxidase (GPx), Glutathione reductase (GR), reduced levels of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) and mitochondrial electron transport chain (ETC) enzyme complexes. In addition, the anti-apoptotic effect of MGN was clearly indicated by the reduction in MeHg-induced apoptotic cells analyzed by flowcytometric analysis after Annexin V-FITC/propidium iodide staining. In conclusion, the present work demonstrates the ability of a dietary polyphenol, MGN to ameliorate MeHg-mediated mitochondrial dysfunction in human hepatic cells in vitro. This hepatoprotective potential may be attributed predominantly to the free radical scavenging/antioxidant property of MGN, by facilitating the balancing of cellular Ca²⁺ ions, maintenance of redox homeostasis and intracellular antioxidant activities, ultimately preserving the mitochondrial function and cell viability after MeHg intoxication. As MeHg intoxication occurs over a period of time, continuous consumption of such dietary compounds may prove to be very useful in promoting human health. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 630-644, 2017.

Environmental toxins, a potential risk factor for diabetes among Canadian Aboriginals

OBJECTIVES

To review the current literature to determine if there is a case for examining the presence of toxins in traditional foods and the environment as a possible risk factor for type 2 diabetes in Canadian Aboriginal populations.

STUDY DESIGN

Literature review. METHODS. The scientific literature on possible causes of type 2 diabetes in Aboriginal populations in Canada was reviewed. Potential exposure through food and water to environmental toxins such as methylmercury, arsenic, persistent organic pollutants (POPs), including bisphenol A and phthalates, as well as Aboriginal lifestyle and composition of the traditional diet is discussed. RESULTS. There is growing evidence to suggest that environmental toxins may be associated with noninsulin-dependent diabetes mellitus (type 2 diabetes), which many consider to be endemic worldwide. In Canada, diabetes has reached epidemic proportions, especially among Aboriginal populations. Based on both molecular and pathological findings, some toxins found in the environment interfere with the functioning of the pancreas' islets of Langerhans cells, and consequently they affect insulin production. In addition, there is new evidence suggesting that obesity may be linked to endocrine disruptors, thus increasing the likelihood that obesity in itself may not be a chief risk factor for diabetes.

CONCLUSIONS

Diabetes prevalence rates among First Nations, Inuit and Métis populations are 3-5 times higher than the general population. Accepted risk factors such as diet, lifestyle and genetics do not fully explain this phenomenon. However, as many environmental toxins bioaccumulate in the food chain and are found in wild game and fish traditionally harvested and consumed by Aboriginal peoples, these chemicals could present health risks not yet fully explored. As there is not enough evidence to rule out this possibility, further studies are suggested. If correct, such environmental risk factors, especially if they are encountered early in life, would have implications on Aboriginal public health.

The removal of mercury from water by open chain ligands containing multiple sulfurs

Mercury pollution is a serious challenge faced by environmental chemists over the world. For several years now, our group has been developing new compounds to precipitate and thereby remove mercury from water. In this paper, we present a new family of alkyl thiol mercury chelates to add to the aromatic ligands we have previously reported. These new compounds are effective at precipitating mercury from water and with an excess of the best compound, removal is quantitative. Furthermore, the precipitates are stable and released little to no mercury back into solution during leaching studies.

Mercury content of hair in different populations relative to fish consumption

Hair has been used in many studies as a bioindicator of mercury exposure for human populations. At the time of hair formation, mercury from the blood capillaries penetrates into the hair follicles. As hair grows approximately 1 cm each month, mercury exposure over time is recapitulated in hair strands. Mercury levels in hair closest to the scalp reflect the most recent exposure, while those farthest from the scalp are representative of previous blood concentrations. Sequential analyses of hair mercury have been useful for identifying seasonal variations over time in hair mercury content, which may be the result of seasonal differences in bioavailability of fish and differential consumption of piscivorous and herbivorous fish species. Knowledge of the relation between fish-eating practices and hair mercury levels is particularly important for adequate mitigation strategies. Methyl mercury is well absorbed, and because the biological half-life is long, the body burden in humans may reach high levels. People who frequently eat contaminated seafood can acquire mercury concentrations that are potentially dangerous to the fetus in pregnant women. The dose-response relationships have been extensively studied, and the safe levels of exposure have tended to decline. Individual methyl mercury exposure is usually determined by analysis of mercury in blood and hair. The objective of the present review was to examine variations in hair mercury levels from different populations with respect to fish-eating practices.

Predictors of Blood Mercury Levels in Older Urban Residents

OBJECTIVE

The objective of this study was to describe the distribution and predictors of blood mercury levels in an adult population.

METHODS

This was a cross-sectional analysis of first-visit data (2001-2002) on a random sample of 474 subjects from the Baltimore Memory Study.

RESULTS

After adjustment for race/ethnicity, education, assets, and diabetes, persons in the highest quartile of fish consumption had median mercury levels 1.82 times above the levels in the lowest quartile, while those in the highest education category had median mercury levels 1.57 times higher than levels in the lowest category. Nine percent of subjects were above the reference dose recommended by the Environmental Protection Agency, which is high compared with that found by the Centers for Disease Control and Prevention in women of childbearing age.

CONCLUSIONS

These findings offer guidance for targeted education and possible new insights regarding the kinetics of mercury.

The role of phosphoinositide 3-kinase/Akt signaling in low-dose mercury-induced mouse pancreatic beta-cell dysfunction in vitro and in vivo

The relationship between oxidation stress and phosphoinositide 3-kinase (PI3K) signaling in pancreatic beta-cell dysfunction remains unclear. Mercury is a well-known toxic metal that induces oxidative stress. Submicromolar-concentration HgCl(2) or methylmercury triggered reactive oxygen species (ROS) production and decreased insulin secretion in beta-cell-derived HIT-T15 cells and isolated mouse islets. Mercury increased PI3K activity and its downstream effector Akt phosphorylation. Antioxidant N-acetyl-l-cysteine (NAC) prevented mercury-induced insulin secretion inhibition and Akt phosphorylation but not increased PI3K activity. Inhibition of PI3K/Akt activity with PI3K inhibitor or by expressing the dominant-negative p85 or Akt prevented mercury-induced insulin secretion inhibition but not ROS production. These results indicate that both PI3K and ROS independently regulated Akt signaling-related, mercury-induced insulin secretion inhibition. We next observed that 2- or 4-week oral exposure to low-dose mercury to mice significantly caused the decrease in plasma insulin and displayed the elevation of blood glucose and plasma lipid peroxidation and glucose intolerance. Akt phosphorylation was shown in islets isolated from mercury-exposed mice. NAC effectively antagonized mercury-induced responses. Mercury-induced in vivo effects and increased blood mercury were reversed after mercury exposure was terminated. These results demonstrate that low-dose mercury-induced oxidative stress and PI3K activation cause Akt signaling-related pancreatic beta-cell dysfunction.

Cases of mercury exposure, bioavailability, and absorption

Mercury is a unique element that, unlike many metals, has no essential biological function. It is liquid at room temperature and is 13.6 times heavier than water. Its unique physical properties have been exploited for a variety of uses such as in mercury switches, thermostats, thermometers, and other instruments. Its ability to amalgamate with gold and silver are used in mining these precious metals and as a dental restorative. Its toxic properties have been exploited for medications, preservatives, antiseptics, and pesticides. For these reasons there have been many industrial uses of mercury, and occupational exposures of workers and industrial emissions and effluents contaminating air, water, soil, and ultimately food chains have long been a matter of great public health concern. This paper examines briefly six cases representing various forms of exposure to different species of mercury, and indicates the methodological issues in estimating exposure, bioavailability and absorption; these cases include Minamata disease in Japan, organic mercury poisoning in Iraq, methylmercury (MeHg) exposure in the Amazon, dimethylmercury (PMM) in the laboratory, an elemental mercury spill in Cajamarca, Peru, and a mercury-contaminated building in Hoboken, NJ, USA. Other scenarios that are not described include occupational exposure to mercury salts, mercurial preservatives in vaccines, cultural and ritualistic uses of mercury, and mercury in dental amalgams.

Recent advances in recognition of low-level methylmercury poisoning

Clinically evident neurologic damage from methylmercury exposure was well described following poisoning episodes in Japan and Iraq several decades ago. Paresthesias have been considered to be an early effect; however, additional data raise questions about whether this is the most sensitive adverse effect among adults. Fetuses are considered the most sensitive subpopulation because of the vulnerability of the developing nervous system. Over the past 5 years questions have been raised about what is an appropriate level of exposure for sensitive groups. A recent evaluation by a committee for the US National Research Council found that 0.1 microg/kg body weight per day is a scientifically justified level of methylmercury exposure for maternal-fetal pairs. The conclusions of this report and other issues are discussed in the present review. Because of anthropogenic release of mercury into the environment, methylmercury exposure from fish consumption is a pathway that is of increasing concern.