metallothionein and Mercury-Poisoning

Topics: Adult; Animals; Autistic Disorder; Brain; Child; Child, Preschool; Developmental Disabilities; Female; Fishes; Food Contamination; Humans; Infant; Mercury; Mercury Poisoning; Metallothionein; Organomercury Compounds; Pilot Projects; Pregnancy; Prenatal Exposure Delayed Effects; Rats; Water Pollutants, Chemical

This article reviews the use of nuclear magnetic resonance methods of spin 1/2 metal nuclei to probe the metal binding site(s) in a variety of metalloproteins. The majority of the studies have involved native Zn(II) and Ca(II) metalloproteins where there has been isostructural substitution of these metal ions with the I = 1/2 (111/113)Cd(II) ion. Also included are recent studies that have utilized the 109Ag(I) ion to probe Cu(I) sites in yeast metallothionein and 199Hg(II) as a probe of the metal binding sites in mercury resistance proteins. Pertinent aspects for the optimal execution of these experiments along with the procedures for the metal substitution reactions are discussed together with the presentation of a 113Cd chemical shift correlation map with ligand type and coordination number. Specific examples of protein systems studied using the (111/113)Cd and 109Ag nuclei include the metallothionein superfamily of Zn(II)- and Cu(I)-binding proteins from mammalian, invertebrate, and yeast systems. In addition to the structural features revealed by these metal ion nuclear magnetic resonance studies, important new information is frequently provided about the dynamics at the active-site metal ion. In an effort for completeness, other less frequently used spin 1/2 metal nuclei are mentioned.

Topics: Accidents, Occupational; Animals; Binding Sites; Cations; Chemical Phenomena; Chemistry, Physical; Fungal Proteins; Invertebrates; Magnetic Resonance Spectroscopy; Mammals; Mercury Poisoning; Metalloproteins; Metallothionein; Metals; Methylmercury Compounds; Models, Molecular; Protein Conformation; Safety; Sensitivity and Specificity

Topics: Aging; Body Fluids; Cadmium; Cadmium Poisoning; Edetic Acid; Humans; Kidney Diseases; Kidney Glomerulus; Lead Poisoning; Mercury Poisoning; Metallothionein; Nephritis, Interstitial

Curcumin, a safe nutritional component and a highly promising natural antioxidant with a wide spectrum of biological functions, has been examined in several metal toxicity studies, but its role in protection against mercury toxicity has not been investigated. Therefore, the detoxification and antioxidant effects of curcumin were examined to determine its prophylactic/therapeutic role in rats experimentally exposed to mercury (in the from of mercuric chloride-HgCl(2), 12 micromol kg(-1) b.w. single intraperitoneal injection). Curcumin treatment (80 mg kg(-1) b.w. daily for 3 days, orally) was found to have a protective effect on mercury-induced oxidative stress parameters, namely, lipid peroxidation and glutathione levels and superoxide dismutase, glutathione peroxidase and catalase activities in the liver, kidney and brain. Curcumin treatment was also effective for reversing mercury-induced serum biochemical changes, which are the markers of liver and kidney injury. Mercury concentration in the tissues was also decreased by the pre/post-treatment with curcumin. However, histopathological alterations in the liver and kidney were not reversed by curcumin treatment. Mercury exposure resulted in the induction of metallothionein (MT) mRNA expressions in the liver and kidney. Metallothionein mRNA expression levels were found to decrease after the pre-treatment with curcumin, whereas post-treatment with curcumin further increased MT mRNA expression levels. Our findings suggest that curcumin pretreatment has a protective effect and that curcumin can be used as a therapeutic agent in mercury intoxication. The study indicates that curcumin, an effective antioxidant, may have a protective effect through its routine dietary intake against mercury exposure.

Topics: Animals; Antioxidants; Curcumin; Disinfectants; Enzyme Inhibitors; Gene Expression; Glutathione; Inactivation, Metabolic; Kidney; Lipid Peroxidation; Liver; Male; Malondialdehyde; Mercuric Chloride; Mercury Poisoning; Metallothionein; Oxidative Stress; Oxidoreductases; Rats; Rats, Wistar; RNA, Messenger

Inorganic mercury (HgCl2) exposure provokes damage in many organs, especially kidney. Inducible nitric oxide synthase (iNOS) expression, total NOS activity and the profiles of zinc (Zn), copper (Cu) and Hg as well as their distribution when bound to specific intracellular proteins, including metallothioneins (MT), were studied during HgCl2 exposure and after l-arginine treatment in C57BL/6 mouse kidney. HgCl2 exposure modulates differently iNOS expression and NOS activity, increasing iNOS expression but, conversely, decreasing total NOS activity in the mouse kidney. Moreover, during Hg exposure an increased MT production occurs. The kidney damage leads to a loss of urinary proteins, increased plasma creatinine and high Zn mobilization with consequent increased urinary Zn excretion. l-arginine treatment recovers NOS activity and induces a normalization of MT induction, plasma creatinine values and urinary proteins excretion, suggesting that l-arginine may limit kidney damages by Hg exposure.

Topics: Animals; Arginine; Chromatography, High Pressure Liquid; Copper; Creatinine; Kidney; Male; Mass Spectrometry; Mercuric Chloride; Mercury; Mercury Poisoning; Metallothionein; Mice; Mice, Inbred C57BL; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Protein Binding; Proteinuria; RNA, Messenger; Tissue Distribution

Mercury, an occupational and environmental contaminant, is a well-recognized health hazard. The thymus is a target for inorganic mercury (Hg2+); thymic function is impaired in Hg2+ intoxication and is partially restored by simultaneous L-arginine supplementation. The nitric oxide (NO)-nitric oxide synthase (NOS) pathway and metallothioneins (MTs) were studied to investigate the role of L-arginine in thymic function restoration after mercury exposure. Mice received a higher and a lower dose of inorganic mercury, with and without L-arginine supplementation. Saline-treated mice were used as controls. Thymus weight and thymulin were measured as indices of thymic function. Mice treated with Hg2+ alone displayed an accumulation of metal in the thymus, reduced NOS activity, a lower plasma nitrite plus nitrate concentration and an increased MTs expression compared with control mice. L-arginine supplementation was associated with lower Hg2+ concentrations in the organ and partial preservation of other measures. Reduced accumulation of Hg2+ in mice dosed with L-arginine was probably related to greater NO production and NO-MTs interactions.

Topics: Animals; Arginine; Male; Mercury; Mercury Poisoning; Metallothionein; Mice; Mice, Inbred BALB C; Nitric Oxide Synthase; Reverse Transcriptase Polymerase Chain Reaction; Thymus Gland

The neurobehavioral changes in wild-type and metallothionein (MT)-null mice after the cessation of long-term, low-level exposure to Hg0 were investigated. MT-null and wild-type females were continuously (24 h/day) exposed to mercury vapor (Hg0) at 0.055 mg/m3 (range: 0.043-0.073 mg/m3), which was similar to the current threshold limit value (TLV), for 29 weeks. The effects on behavior, such as locomotor activity in the open field (OPF), learning ability in the passive avoidance response (PA) and spatial learning ability in the Morris water maze (MM) were examined immediately and 12 weeks after the cessation of exposure. Immediately after the exposure had ceased, total locomotor activity in OPF was decreased in the both strain of mice, although the MT-null mice appeared to show more distinct effect. In the PA test, the exposed animals of both strains showed learning impairment as compared to un-exposed mice. Twelve weeks after the cessation of exposure, the locomotor activity in OPF was elevated in the exposed mice of both strains, while the learning ability in the PA test appeared normal in both strains. Spatial learning ability was not affected at all. Immediately after the exposure had ceased, the brain mercury concentration of the exposed wild-type mice was 1.75 microg/g, twofold of that in the MT-null mice. In 12 weeks, brain mercury levels decreased to approximately 1/20 of those in immediately after the exposure in both of the strains. These results for the first time indicated that long-term, low-level exposure to Hg0 could exert neurobehavioral effects, which were not reversible even after a long exposure-free period. Whereas the effects on learning ability were presumably transient, the effects on spontaneous behavior as evaluated in OPF were persistent. Finally, the MT-null mice seemed more susceptible to Hg0-induced neurotoxicity than the wild-type mice, confirming our previous results.

Topics: Animals; Avoidance Learning; Behavior, Animal; Brain; Female; Learning; Maze Learning; Mercury; Mercury Poisoning; Metallothionein; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity; Volatilization

Acute effects of mercury on mouse blood, kidneys, and liver were evaluated. Mice received a single dose of mercuric chloride (HgCl2, 4.6 mg/kg, subcutaneously) for three consecutive days. We investigated the possible beneficial effects of antioxidant therapy (N-acetylcysteine (NAC) and diphenyl diselenide (PhSe)2) compared with the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS), an effective chelating agent in HgCl2 exposure in mice. We also verified whether metallothionein (MT) induction might be involved in a possible mechanism of protection against HgCl2 poisoning and whether different treatments would modify MT levels and other toxicological parameters. The results demonstrated that HgCl2 exposure significantly inhibited delta-aminolevulinate dehydratase (delta-ALA-D) activity in liver and only DMPS treatment prevented the inhibitory effect. Mercuric chloride caused an increase in renal non-protein thiol groups (NPSH) and none of the treatments modified renal NPSH levels. Urea concentration was increased after HgCl2 exposure. NAC plus (PhSe)2 was partially effective in protecting against the effects of mercury. DMPS and (PhSe)2 were effective in restoring the increment in urea concentration caused by mercury. Thiobarbituric acid-reactive substances (TBARS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities and ascorbic acid levels were not modified after mercury exposure. Mercuric chloride poisoning caused an increase in hepatic and renal MT levels and antioxidant treatments did not modify this parameter. Our data indicated a lack of therapeutic effect of the antioxidants tested.

Topics: Acetylcysteine; Animals; Antioxidants; Benzene Derivatives; Body Weight; Chelating Agents; Drug Therapy, Combination; Free Radical Scavengers; Injections, Subcutaneous; Kidney; Liver; Male; Mercuric Chloride; Mercury Poisoning; Metallothionein; Mice; Organoselenium Compounds; Porphobilinogen Synthase; Sulfhydryl Compounds; Unithiol; Urea

Selected toxic and essential metals (mercury, Hg; cadmium, Cd; and zinc, Zn) were determined in the liver and in the kidney collected from 13 dolphins (Stenella coeruleoalba and Tursiops truncatus) stranded along the southern coasts of Italy from 1991 to 1999. Liver samples were also analysed for their methyl mercury (MeHg) and selenium (Se) contents. For subcellular fractionation, liver and kidney samples were homogenized in Tris-HCl buffer; after centrifugation, the supernatant (cytosol) was separated from pellets (insoluble fraction), heated at 80 degrees C for 10 min and centrifuged in order to separate the precipitate containing the thermolabile high molecular weight proteins. The cytosol heat-stable fraction, including metallothionein-like proteins (MTLPs), was then purified by gel filtration chromatography on Sephadex G-75 column. The three subcellular fractions collected (insoluble fraction, thermolabile fraction and purified heat-stable fraction) were analysed for their Hg, Cd and Zn contents. The analytical results confirm previous similar studies on toothed whales in showing that: (1) in the liver, as well as in the kidney, Hg was mainly found in the insoluble fraction, therefore, metallothioneins seem to have no role in the Hg detoxification; (2) in the liver, the molar ratio between Se and inorganic Hg was very close to 1; this suggests that the final compound of MeHg detoxification could be HgSe (tiemannite); (3) in almost all the samples, Cd and Zn were detected in the purified heat-stable fraction (including MTLPs). The mechanism of Cd detoxification and Zn homeostasis is also discussed.

Topics: Animals; Cadmium; Cadmium Poisoning; Dolphins; Female; Homeostasis; Kidney; Liver; Male; Mercury; Mercury Poisoning; Metallothionein; Mortality; Tissue Distribution; Zinc

Previously we found that exposure to mercury vapor effectively induced brain metallothionein (MT) in rats. Here, using FPLC-gel chromatography, we examined time-dependent alterations in the MT isomers, MT-I/II and MT-III, following 3 weeks of exposure. Rats were exposed to mercury vapor at 8.3 mg/m3 for 15 h in total over 5 consecutive days. Total MT levels in rat cerebrum and cerebellum increased by 65% and 155%, respectively, 24 h after the final exposure. The increased levels in both tissues remained unchanged for at least 2 weeks after termination of exposure. Interestingly, most MT in control rat cerebrum and cerebellum was accounted for by MT-III, with MT-I/II being less than 10%. Through mercury vapor exposure, MT-I/II was quickly induced to a significant extent in both tissues, reaching a level comparable to that of MT-III. The induction rate of MT-I/II in the cerebellum was somewhat higher than in the cerebrum. Chromatograms showed that the MT-I/II thus induced began to decline at an early stage in both tissues. In the cerebrum, the amount of MT-I/II on day 22 was about 30% of the maximum level on day 1. On the other hand, the induction of MT-III was not that dramatic, but it did become evident, at least in the latter stage, when MT-I/II had begun to decrease. Thus, though the induction rate of MT-III was not as high as MT-I/II, it was sustained throughout the experimental period.

Topics: Administration, Inhalation; Animals; Brain; Chromatography, Gas; Isomerism; Male; Mercury; Mercury Poisoning; Metallothionein; Rats; Rats, Wistar; Volatilization

The effects of CdCl2 and ZnCl2 pretreatments on the inhibition of delta-ALA-D (delta-aminolevulinic acid dehydratase) activity and Hg contents in liver and kidneys of suckling rats intoxicated with HgCl2 were investigated. Zn-pretreatment prevented the effects of mercury at a higher magnitude than CdCl2. Hepatic and renal delta-ALA-D activities were significantly inhibited by HgCl2 and prior exposure to CdCl2 partially prevented the renal effect of mercury but not altered the mercury levels in both tissues. Pretreatment with ZnCl2 abolished mercury-induced delta-ALA-D-inhibition in kidneys and liver and induced an increase in renal (about three times) and a decrease in hepatic (to one-third) Hg contents when compared to the group injected only with mercury. In face of zinc effects to prevent Hg-delta-ALA-D inhibition and to alter Hg-deposition levels in kidney and liver, these results suggest that these effects may be partially due to the synthesis of metallothioneins (MT). In fact, liver MT content presented by animals pretreated with zinc was significantly greater than control and Hg-treated groups, but the increase showed by renal tissue (about 60%) was not significant. Although the MT is rich in cysteine (-SH) and consequently can form a great number of MT-Hg complex, other mechanisms should be also involved in zinc protection on mercury toxicity.

Topics: Animals; Animals, Suckling; Cadmium Chloride; Chlorides; Female; Injections, Subcutaneous; Kidney; Liver; Male; Mercuric Chloride; Mercury Poisoning; Metallothionein; Organ Size; Porphobilinogen Synthase; Rats; Rats, Wistar; Tissue Distribution; Zinc Compounds

Pretreatment with Na2MoO4 protected rats from HgCl2-induced decreases in the renal concentration of amino acids, RNA, DNA, ATP and dry matter. It also reduced the mercury-induced increases in renal water, Ca and serum creatinine. Ma2MoO4 considerably elevated the RNA/DNA ratio in the renal cortex after treatment with HgCl2. In addition, subcellular distribution of mercury was markedly altered by pretreatment with Na2MoO4, specifically Na2MoO4 pretreatment decreased the mercury content in the particulate fractions such as the nuclei and mitochondria while increasing the mercury content of the cytosol. Sephadex G-75 gel filtration showed that the increase in mercury content in the cytosol of Na2MoO4-pretreated rats is due to an increase in the metal content of a metallothionein-like fraction. These results suggest that Na2MoO4-pretreatment protects against HgCl2 renal toxicity by stimulating mercury-mediated metallothionein induction in the renal cortex and renal regenerative processes.

Topics: Adenosine Triphosphate; Animals; Cations; Creatine; DNA; gamma-Glutamyltransferase; Kidney; Kidney Diseases; Mercury; Mercury Poisoning; Metallothionein; Molybdenum; Rats; Regeneration; RNA; Water

Topics: Animals; Kidney; Kidney Diseases; Male; Mercury; Mercury Poisoning; Metalloproteins; Metallothionein; Rats; Spironolactone; Zinc

Topics: Adaptation, Physiological; Animals; Eels; Gills; Mercury; Mercury Poisoning; Metalloproteins; Metallothionein; Time Factors

Topics: Animals; Drug Interactions; Female; Half-Life; Homeostasis; Kidney; Liver; Mercury; Mercury Poisoning; Metabolic Clearance Rate; Metallothionein; Mice; Protein Binding; Selenium; Spleen; Tissue Distribution

Topics: Animals; Cysteine; Liver; Male; Mercury Poisoning; Metallothionein; Rats; Zinc

Topics: Adaptation, Physiological; Amino Acids; Animals; Chromatography, Gel; Eels; Fresh Water; Liver; Mercury; Mercury Poisoning; Metalloproteins; Metallothionein; Molecular Weight; Muscles; Protein Binding; Receptors, Drug; Seawater; Spectrophotometry, Atomic; Spectrophotometry, Ultraviolet