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Journal of Biomedicine & Biotechnology 2012Methylmercury (MeHg) mediated cytotoxicity is associated with loss of intracellular calcium (Ca²⁺) homeostasis. The imbalance in Ca²⁺ physiology is believed to be... (Review)
Review
Methylmercury (MeHg) mediated cytotoxicity is associated with loss of intracellular calcium (Ca²⁺) homeostasis. The imbalance in Ca²⁺ physiology is believed to be associated with dysregulation of Ca²⁺ intracellular stores and/or increased permeability of the biomembranes to this ion. In this paper we summarize the contribution of glutamate dyshomeostasis in intracellular Ca²⁺ overload and highlight the mitochondrial dysfunctions induced by MeHg via Ca²⁺ overload. Mitochondrial disturbances elicited by Ca²⁺ may involve several molecular events (i.e., alterations in the activity of the mitochondrial electron transport chain complexes, mitochondrial proton gradient dissipation, mitochondrial permeability transition pore (MPTP) opening, thiol depletion, failure of energy metabolism, reactive oxygen species overproduction) that could culminate in cell death. Here we will focus on the role of oxidative stress in these phenomena. Additionally, possible antioxidant therapies that could be effective in the treatment of MeHg intoxication are briefly discussed.
Topics: Animals; Antioxidants; Calcium; Cell Death; Homeostasis; Humans; Methylmercury Compounds; Mitochondria
PubMed: 22927718
DOI: 10.1155/2012/248764 -
Environment International Aug 2023The plant microbiota can affect plant health and fitness by promoting methylmercury (MeHg) production in paddy soil. Although most well-known mercury (Hg) methylators...
The plant microbiota can affect plant health and fitness by promoting methylmercury (MeHg) production in paddy soil. Although most well-known mercury (Hg) methylators are observed in the soil, it remains unclear how rice rhizosphere assemblages alter MeHg production. Here, we used network analyses of microbial diversity to identify bulk soil (BS), rhizosphere (RS) and root bacterial networks during rice development at Hg gradients. Hg gradients greatly impacted the niche-sharing of taxa significantly relating to MeHg/THg, while plant development had little effect. In RS networks, Hg gradients increased the proportion of MeHg-related nodes in total nodes from 37.88% to 45.76%, but plant development enhanced from 48.59% to 50.41%. The module hub and connector in RS networks included taxa positively (Nitrososphaeracea, Vicinamibacteraceae and Oxalobacteraceae) and negatively (Gracilibacteraceae) correlating with MeHg/THg at the blooming stage. In BS networks, Deinococcaceae and Paludibacteraceae were positively related to MeHg/THg, and constituted the connector at the reviving stage and the module hub at the blooming stage. Soil with an Hg concentration of 30 mg kg increased the complexity and connectivity of root microbial networks, although microbial community structure in roots was less affected by Hg gradients and plant development. As most frequent connector in root microbial networks, Desulfovibrionaceae did not significantly correlate with MeHg/THg, but was likely to play an important role in the response to Hg stress.
Topics: Methylmercury Compounds; Oryza; Soil; Environmental Monitoring; Soil Pollutants; Mercury; Bacteria
PubMed: 37399771
DOI: 10.1016/j.envint.2023.108066 -
MSystems Feb 2023Methylmercury (MeHg) is a notorious neurotoxin, and its production and degradation in the environment are mainly driven by microorganisms. A variety of microbial MeHg...
Methylmercury (MeHg) is a notorious neurotoxin, and its production and degradation in the environment are mainly driven by microorganisms. A variety of microbial MeHg producers carrying the gene pair and degraders carrying the gene have been separately reported in recent studies. However, surprisingly little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat, and no studies have been performed to explore to what extent these two contrasting microbial groups correlate with MeHg accumulation in the habitat of interest. Here, we collected 86 acid mine drainage (AMD) sediments from an area spanning approximately 500,000 km in southern China and profiled the sediment-borne putative MeHg producers and degraders using genome-resolved metagenomics. 46 metagenome-assembled genomes (MAGs) containing and 93 MAGs containing were obtained, including those from various taxa without previously known MeHg-metabolizing microorganisms. These diverse MeHg-metabolizing MAGs were formed largely via multiple independent horizontal gene transfer (HGT) events. The putative MeHg producers from Deltaproteobacteria and as well as MeHg degraders from were closely correlated with MeHg accumulation in the sediments. Furthermore, these three taxa, in combination with two abiotic factors, explained over 60% of the variance in MeHg accumulation. Most of the members of these taxa were characterized by their metabolic potential for nitrogen fixation and copper tolerance. Overall, these findings improve our understanding of the ecology of MeHg-metabolizing microorganisms and likely have implications for the development of management strategies for the reduction of MeHg accumulation in the AMD sediments. Microorganisms are the main drivers of MeHg production and degradation in the environment. However, little attention has been paid to the simultaneous investigation of the diversities of microbial MeHg producers and degraders in a given habitat. We used genome-resolved metagenomics to reveal the vast phylogenetic and metabolic diversities of putative MeHg producers and degraders in AMD sediments. Our results show that the diversity of MeHg-metabolizing microorganisms (particularly MeHg degraders) in AMD sediments is much higher than was previously recognized. Via multiple linear regression analysis, we identified both microbial and abiotic factors affecting MeHg accumulation in AMD sediments. Despite their great diversity, only a few taxa of MeHg-metabolizing microorganisms were closely correlated with MeHg accumulation. This work underscores the importance of using genome-resolved metagenomics to survey MeHg-metabolizing microorganisms and provides a framework for the illumination of the microbial basis of MeHg accumulation via the characterization of physicochemical properties, MeHg-metabolizing microorganisms, and the correlations between them.
Topics: Methylmercury Compounds; Bacteria; Phylogeny; Metagenome; Firmicutes
PubMed: 36507660
DOI: 10.1128/msystems.00736-22 -
Environmental Health Perspectives Jan 2008
Topics: Acetylcysteine; Animals; Antidotes; Biomarkers; Chelating Agents; Environmental Pollutants; Methylmercury Compounds; Rats
PubMed: 18197288
DOI: 10.1289/ehp.116-a36a -
International Journal of Circumpolar... Dec 2021Indigenous Arctic Canadians have a higher prevalence of gastric neoplasms relative to North Americans of European ancestry. We investigated the hypothesis that low-dose...
Indigenous Arctic Canadians have a higher prevalence of gastric neoplasms relative to North Americans of European ancestry. We investigated the hypothesis that low-dose methylmercury exposure from eating fish/whale increases the risk of gastric cancer in Arctic communities. We used intermediate endpoints from an established model of gastric carcinogenesis: intestinal metaplasia, atrophy, and severe chronic gastritis. During 2008-2012, we obtained gastric biopsies from participants of community-driven projects in 3 communities. In 2016, we collected hair samples to measure methylmercury levels and interviewed them about diet. In cross-sectional analysis, logistic regression estimated odds ratios for the estimated effect of hair-methylmercury concentration on the prevalence of each pathology outcome stratified by selenium intake. Among 80 participants, prevalence of intestinal metaplasia, atrophy and severe chronic gastritis was 17, 29 and 38%, respectively. Adjusted Odds of severe chronic gastritis and atrophy were highest at hair-methylmercury concentrations ≥1μg/g when estimated selenium intake was 0, and approached 0 for all methylmercury levels as estimated selenium intake increased. Gastric pathology increased with methylmercury exposure when selenium intake was low. Though limited by small numbers, these findings suggest selenium ingested by eating fish/whale may counter harmful effects of methylmercury exposure in Arctic populations.
Topics: Animals; Canada; Cross-Sectional Studies; Dietary Exposure; Helicobacter Infections; Helicobacter pylori; Humans; Methylmercury Compounds; Outcome Assessment, Health Care
PubMed: 33646085
DOI: 10.1080/22423982.2021.1889879 -
Nutricion Hospitalaria Nov 2014The beneficial effects of fish consumption are well- known. Nevertheless, there is worldwide concern regard methylmercury concentrations in fish, which is why many... (Review)
Review
The beneficial effects of fish consumption are well- known. Nevertheless, there is worldwide concern regard methylmercury concentrations in fish, which is why many countries such as the United States, Australia, New Zealand, Canada and numerous European countries have made fish consumption recommendations for their populations, particularly vulnerable groups, in order to México methylmercury intake. Blood and hair are the best biological samples for measuring methylmercury. The most widely-used method to analyse methylmercury is cold vapor atomic absorption spectrometry, although there are also direct methods based on the thermal decomposition of the sample. In recent years, the number of laboratories that measure mercury by inductively coupled plasma mass spectrometry has increased. In addition, the different kinds of mercury can be distinguished by coupling chromatography methods of separation. Laboratories that analyse mercury in biological samples need to participate in external quality control programmes. Even if mercury emissions are reduced, mercury may remain in the environment for many years, so dietary recommendations are fundamental in order to reduce exposure. It is necessary to propose public health measures aimed at decreasing mercury exposure and to evaluate the benefits of such measures from the economic and social standpoints.
Topics: Animals; Cost-Benefit Analysis; Fishes; Food Contamination; Humans; Methylmercury Compounds
PubMed: 25561094
DOI: 10.3305/nh.2015.31.1.8316 -
International Journal of Molecular... Nov 2022Methylmercury (MeHg) is highly toxic to the human brain. Although much is known about MeHg neurotoxic effects, less is known about how chronic MeHg affects hippocampal...
Methylmercury (MeHg) is highly toxic to the human brain. Although much is known about MeHg neurotoxic effects, less is known about how chronic MeHg affects hippocampal amino acids and other neurochemical markers in adult mice. In this study, we evaluated the MeHg effects on systemic lipids and inflammation, hippocampal oxidative stress, amino acid levels, neuroinflammation, and behavior in adult male mice. Challenged mice received MeHg in drinking water (2 mg/L) for 30 days. We assessed weight gain, total plasma cholesterol (TC), triglycerides (TG), endotoxin, and TNF levels. Hippocampal myeloperoxidase (MPO), malondialdehyde (MDA), acetylcholinesterase (AChE), amino acid levels, and cytokine transcripts were evaluated. Mice underwent open field, object recognition, Y, and Barnes maze tests. MeHg-intoxicated mice had higher weight gain and increased the TG and TC plasma levels. Elevated circulating TNF and LPS confirmed systemic inflammation. Higher levels of MPO and MDA and a reduction in IL-4 transcripts were found in the hippocampus. MeHg-intoxication led to increased GABA and glycine, reduced hippocampal taurine levels, delayed acquisition in the Barnes maze, and poor locomotor activity. No significant changes were found in AChE activity and object recognition. Altogether, our findings highlight chronic MeHg-induced effects that may have long-term mental health consequences in prolonged exposed human populations.
Topics: Animals; Humans; Male; Mice; Acetylcholinesterase; Amino Acids; Hippocampus; Inflammation; Methylmercury Compounds; Weight Gain; Mice, Inbred C57BL
PubMed: 36430321
DOI: 10.3390/ijms232213837 -
Environmental Science & Technology Oct 2022Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of...
Anoxic conditions within reservoirs related to thermal stratification and oxygen depletion lead to methylmercury (MeHg) production, a key process governing the uptake of mercury in aquatic food webs. Once formed within a reservoir, the timing and magnitude of the biological uptake of MeHg and the relative importance of MeHg export in water versus biological compartments remain poorly understood. We examined the relations between the reservoir stratification state, anoxia, and the concentrations and export loads of MeHg in aqueous and biological compartments at the outflow locations of two reservoirs of the Hells Canyon Complex (Snake River, Idaho-Oregon). Results show that (1) MeHg concentrations in filter-passing water, zooplankton, suspended particles, and detritus increased in response to reservoir destratification; (2) zooplankton MeHg strongly correlated with MeHg in filter-passing water during destratification; (3) reservoir anoxia appeared to be a key control on MeHg export; and (4) biological MeHg, primarily in zooplankton, accounted for only 5% of total MeHg export from the reservoirs (the remainder being aqueous compartments). These results improve our understanding of the role of biological incorporation of MeHg and the subsequent downstream release from seasonally stratified reservoirs and demonstrate that in-reservoir physical processes strongly influence MeHg incorporation at the base of the aquatic food web.
Topics: Environmental Monitoring; Food Chain; Humans; Hypoxia; Mercury; Methylmercury Compounds; Oxygen; Rivers; Water; Water Pollutants, Chemical
PubMed: 36107858
DOI: 10.1021/acs.est.2c03958 -
Experimental Biology and Medicine... Jul 2008Mercury is a major toxic metal ranked top in the Toxic Substances List. Cinnabar, which contains mercury sulfide, has been used in Chinese traditional medicines for... (Comparative Study)
Comparative Study Review
Mercury is a major toxic metal ranked top in the Toxic Substances List. Cinnabar, which contains mercury sulfide, has been used in Chinese traditional medicines for thousands of years as an ingredient in various remedies, and 40 cinnabar-containing traditional medicines are still used today. Little is known about toxicology profiles or toxicokinetics of cinnabar and cinnabar-containing traditional medicines, and the high mercury content in these Chinese medicines raises justifiably escalations of public concern. This minireview, by searching the available database of cinnabar and by comparing cinnabar with common mercurials, discusses differences in their bioavailability, disposition, and toxicity. The analysis showed that cinnabar is insoluble and poorly absorbed from the gastrointestinal tract. Absorbed mercury from cinnabar is mainly accumulated in the kidneys, resembling the disposition pattern of inorganic mercury. Heating cinnabar results in release of mercury vapor, which in turn can produce toxicity similar to inhalation of these vapors. The doses of cinnabar required to produce neurotoxicity are 1000 times higher than methyl mercury. Following long-term use of cinnabar, renal dysfunction may occur. Dimercaprol and succimer are effective chelation therapies for general mercury intoxication including cinnabar. Pharmacological studies of cinnabar suggest sedative and hypnotic effects, but the therapeutic basis of cinnabar is still not clear. In summary, cinnabar is chemically inert with a relatively low toxic potential when taken orally. In risk assessment, cinnabar is less toxic than many other forms of mercury, but the rationale for its inclusion in traditional Chinese medicines remains to be fully justified.
Topics: Dose-Response Relationship, Drug; Humans; Medicine, Chinese Traditional; Mercuric Chloride; Mercury; Mercury Compounds; Methylmercury Compounds
PubMed: 18445765
DOI: 10.3181/0712-MR-336 -
The Journal of Toxicological Sciences 2023Granule cell-selective toxicity of methylmercury in the cerebellum is one of the main unresolved issues in the pathogenesis of Minamata disease. Rats were orally...
Granule cell-selective toxicity of methylmercury in the cerebellum is one of the main unresolved issues in the pathogenesis of Minamata disease. Rats were orally administered methylmercury chloride (10 mg/kg/day) for 5 consecutive days, and their brains were harvested on days 1, 7, 14, 21, or 28 after the last administration for histological examination of the cerebellum. It was found that methylmercury caused a marked degenerative change to the granule cell layers but not to the Purkinje cell layers. The generative change of the granule cell layer was due to cell death, including apoptosis, which occurred at day 21 and beyond after the methylmercury administration. Meanwhile, cytotoxic T-lymphocytes and macrophages had infiltrated the granule cell layer. Additionally, granule cells are shown to be a cell type susceptible to TNF-α. Taken together, these results suggest that methylmercury causes small-scale damage to granule cells, triggering the infiltration of cytotoxic T-lymphocytes and macrophages into the granule cell layer, which secrete tumor necrosis factor-α (TNF-α) to induce apoptosis in granule cells. This chain is established based on the susceptibility of granule cells to methylmercury, the ability of cytotoxic T lymphocytes and macrophages to synthesize and secrete TNF-α, and the sensitivity of granule cells to TNF-α and methylmercury. We propose to call the pathology of methylmercury-induced cerebellar damage the "inflammation hypothesis."
Topics: Rats; Animals; Methylmercury Compounds; Tumor Necrosis Factor-alpha; Cerebellum; Neurons; Apoptosis
PubMed: 37394656
DOI: 10.2131/jts.48.429