Elevated Metallothionein Research Articles

Effects of ethyl acetate extract of Moringa oleifera leaf and vitamin c co-exposures on acute cadmium chloride-induced toxicopathological changes in Clarias gariepinus

Cadmium (Cd2+) is reportedly one of the most toxic metals, which is increasingly polluting our aquatic environments. The need to modify Cd2+ toxicity led to the investigation of the possible effects of ethyl acetate extract of Moringa oleifera (M. oleifera) leaf (EAEMOL) and vitamin C on cadmium chloride (CdCl2) co-exposures of adult Clarias gariepinus over a 96-hour period. The exposure involved 105 fish in five groups of seven fish each in triplicates. Group I contained the control unexposed fish, Group II contained Tween 80, and Groups III-V contained CdCl2, EAEMOL co-exposure, and the vitamin C co-exposure, respectively. A total of 52.38%, 28.57%, and 47.62% mortalities occurred in Group III, IV, and V exposed fish, respectively, with marked deterioration in fish water quality over the exposure period. Although CdCl2 exposure caused considerable lipid peroxidation, the EAEMOL and vitamin C co-exposures insignificantly (p>0.05) aggravated it rather than ameliorate it. Similarly, the co-exposures slightly elevated the recorded drop in liver metallothionein (MT) level induced by the CdCl2 exposure. Although CdCl2 exposure caused severe gill damage, only moderate gill damages occurred in both co-exposures based on the degree of tissue change protocol. Therefore, the EAEMOL and vitamin C co-exposures, as administered, ameliorated the CdCl2 toxicity in the exposed fish based on the recorded mortality and gills cellular damage as the induced biochemical changes were insignificant (p >0.05). However, the rationale behind the recorded slightly elevated serum lipid peroxidation and liver MT levels by the co-exposures need further elucidation.

Elevated metallothionein expression in long-lived species mediates the influence of cadmium accumulation on aging.

Cadmium (Cd) accumulates with aging and is elevated in long-lived species. Metallothioneins (MTs), small cysteine-rich proteins involved in metal homeostasis and Cd detoxification, are known to be related to longevity. However, the relationship between Cd accumulation, the role of MTs, and aging is currently unclear. Specifically, we do not know if long-lived species evolved an efficient metal stress response by upregulating their MT levels to reduce the toxic effects of environmental pollutants, such as Cd, that accumulate over their longer life span. It is also unknown if the number of MT genes, their expression, or both protect the organisms from potentially damaging effects during aging. To address these questions, we reanalyzed several cross-species studies and obtained data on MT expression and Cd accumulation in long-lived mouse models. We confirmed a relationship between species maximum life span in captive mammals and their Cd content in liver and kidney. We found that although the number of MT genes does not affect longevity, gene expression and protein amount of specific MT paralogs are strongly related to life span in mammals. MT expression rather than gene number may influence the high Cd levels and longevity of some species. In support of this, we found that overexpression of MT-1 accelerated Cd accumulation in mice and that tissue Cd was higher in long-lived mouse strains with high MT expression. We conclude that long-lived species have evolved a more efficient stress response by upregulating the expression of MT genes in presence of Cd, which contributes to elevated tissue Cd levels.

625-P: Metallothionein Improves Angiogenic Function of Endothelial Progenitor Cells via HIF-1α/SDF-1/Akt Pathway in Diabetic Limb Ischemia

Diabetes mellitus associated dysfunction of endothelial progenitor cells (EPCs) may contribute to dysregulation of endothelial regeneration. Metallothionein (MT) acts as an antioxidant in various pathophysiological processes. Whether MT in EPCs has positive angiogenic effects and the mechanisms involved remain unclear. Endothelial MT overexpression (JTMT) mice were made diabetic by high fat diet followed by STZ administration (HFD/STZ). Diabetic hind limb ischemia model was established by femoral artery ligation. Bone marrow derived mononuclear leucocytes (MNCs) collected from JTMT mice were transplanted into db/db mice with hind limb ischemia. Blood reperfusion was monitored and oxidative stress was measured. High glucose and hypoxia conditions in culture were adopted to mimic diabetic ischemia in vitro. MT improved blood perfusion of ischemic hind limb and promoted angiogenesis in HFD/STZ diabetes. Oxidative stress of ischemic muscles was aggravated under diabetic condition, which was reduced in JTMT mice. Compared with WT mice, the expression of HIF-1α, SDF-1, VEGF and p-Akt were all increased in JTMT mice, along with elevation of plasma SDF-1α and VEGF. Moreover, transplantation of MT overexpressed MNCs showed better therapeutic effect on db/db diabetic mice with hind limb ischemia than control or transplantation of normal MNCs. Transplantation was accompanied by elevated HIF-1α, SDF-1 and Akt signaling. Vitro studies demonstrated that MT overexpression reduced high glucose and hypoxia induced EPC dysfunction and preserved high glucose and hypoxia impaired HIF-1α, SDF-1, VEGF and Akt signaling, all of which were abolished by siRNA knockdown of HIF-1α. In conclusion, elevated MT enhances angiogenic function and therapeutic efficacy of EPCs in diabetic limb ischemia. The benefits of MT are predominantly mediated by a HIF-1α/SDF-1/Akt pathway under diabetic ischemia conditions. Disclosure K. Wang: None. X. Dai: None. J. He: None. C. Yang: None. J. Chen: None. K.A. Wintergerst: None. P.N. Epstein: None. L. Cai: None. Y. Tan: None. Funding American Diabetes Association (1-15-BS-018, 1-18-IBS-082 to L.C.); 1-13-JF-53 (to Y.T.)

Copper attenuates early and late biochemical alterations induced by inorganic mercury in young rats

ABSTRACTMercury (Hg), a divalent metal, produces adverse effects predominantly in the renal and central nervous systems. The aim of this study was to determine the effectiveness of copper (Cu) in prevention of mercuric mercury (Hg2+)-mediated toxic effects as well as the role metallothioneins (MT) play in this protective mechanism in young rats. Wistar rats were treated subcutaneously with saline (Sal) or CuCl2.2H2O (Cu 2.6 mg/kg/day) from 3 to 7 days old and with saline or HgCl2 (Hg 3.7 mg/kg/day) from 8 to 12 days old. The experimental groups were (1) Sal-Sal, (2) Cu-Sal, (3) Sal-Hg, and (4) Cu-Hg. MTs and metal contents were determined at 13 and 33 days of age. Porphobilinogen synthase (PBG-synthase) activity as well as renal and hepatic parameters were measured at 33 days. At 13 day, Hg2+ exposure increased hepatic MT, Hg, zinc (Zn) and iron (Fe) levels, in kidney elevated Cu and Hg and decreased renal Fe concentrations, accompanied by elevated blood Hg levels. At 33 days, Hg2+ exposure inhibited renal PBG-synthase activity, increased serum urea levels and lowered Fe and Mg levels. Copper partially prevented the rise in blood Hg and liver Fe noted at 13 days; and completely blocked urea rise and diminished renal PBG-synthase activity inhibition at 33 days. In 13-day-old rats, Cu exposure redistributed the Hg in the body, decreasing hepatic and blood levels while increasing renal levels, accompanied by elevated renal and hepatic MT levels in Hg2+-exposed animals. These results suggest that hepatic MT might bind to hepatic and blood Hg for transport to the kidney in order to be excreted.Abbreviations: MT: metallothioneins; PBG-synthase: porphobilinogen synthase.

Tolerance and stress response of sclerotiogenic Aspergillus oryzae G15 to copper and lead.

Aspergillus oryzae G15 was cultured on Czapek yeast extract agar medium containing different concentrations of copper and lead to investigate the mechanisms sustaining metal tolerance. The effects of heavy metals on biomass, metal accumulation, metallothionein (MT), malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) were evaluated. Cu and Pb treatment remarkably delayed sclerotial maturation and inhibited mycelial growth, indicating the toxic effects of the metals. Cu decreased sclerotial biomass, whereas Pb led to an increase in sclerotial biomass. G15 bioadsorbed most Cu and Pb ions on the cell surface, revealing the involvement of the extracellular mechanism. Cu treatment significantly elevated MT level in mycelia, and Pb treatment at concentrations of 50-100mg/L also caused an increase in MT content in mycelia. Both metals significantly increased MDA level in sclerotia. The variations in MT and MDA levels revealed the appearance of heavy metal-induced oxidative stress. The activities of SOD, CAT, and POD varied with heavy metal concentrations, which demonstrated that tolerance of G15 to Cu and Pb was associated with an efficient antioxidant defense system. In sum, the santioxidative detoxification system allowed the strain to survive in high concentrations of Cu and Pb. G15 depended mostly on sclerotial differentiation to defend against Pb stress.

A baseline study of the metallothioneins induction and its reversibility in Neohelice granulata from the Bahía Blanca Estuary (Argentina)

Contamination by heavy metals causes serious effects in marine systems. Nowadays, the combination of chemical and biological data is recommended in monitoring programs. Metallothioneins (MT) are early-warning signals of metal exposure and are widely used in biomonitoring. The present research evaluates the heavy metals levels in sediments and the MT synthesis in the crab Neohelice granulata from the Bahía Blanca Estuary (BBE). Then, the recovery capabilities of N. granulata followed by a depuration phase are assessed. Results demonstrate a slow decline in the level of metals in the study area. In relation to MT, female crabs showed elevated MT when compared to males. Furthermore, MT synthesis diminished after the depuration phase. These data constitute the first MT information in organisms from the BBE and may be considered as baseline for future studies in this matter. Although pollution level found was low, further biomonitoring considering both types of data is recommended.

Metallothioneins in the lung cancer.

Metallothioneins (MTs) are low weight proteins involved in several key cellular processes such as metal ions homeostasis, detoxification and scavenging of free radicals. Four groups of MTs are distinguished: MT-1, MT-2, MT-3 and MT-4. Regardless of the type, MTs are characterized by high content of cysteine, responsible for their biological properties such as binding of relevant zinc and copper ions, as well as toxic ions such as lead and cadmium. MTs were additionally shown to protect cells against oxidative stress damage and participate in differentiation, proliferation and/or apoptosis of normal and cancer cells. Many studies of different neoplasms showed association of elevated MTs levels with occurrence of chemo- and radiotherapy resistance and poor patients' outcome. In this review, we summarize and discuss the potential mechanism of action of metallotioneins in lung physiology and pathology.

Metal, metallothionein and glutathione levels in blue crab (Callinectes sp.) specimens from southeastern Brazil

Metal concentrations (Cu, Pb, Zn and Cd) were determined in muscle, gills, soft tissues and eggs in male, non-ovigerous and ovigerous female Callinectes sp. specimens from a reference site in Southeastern Brazil. Metallothionein (MT) and reduced glutathione (GSH) levels were also determined. Results demonstrate that sex has a significant influence on metal, MT and GSH concentrations. Significant maternal transfer of Pb and Zn from ovigerous females to eggs was verified, while female crabs, both ovigerous and non-ovigerous, showed elevated GSH and MT in viscera when compared to males, indicating possible MT role in excreting metals to eggs in ovigerous females of this species. Several strong statistical correlations between metals and MT indicate MTs role in detoxification of both toxic and essential elements in different organs. Pb and Zn were significantly correlated to GSH, indicating oxidative stress caused by the former and a direct link between Zn and GSH in maintaining homeostasis. Regarding human consumption, metal concentrations were lower than the maximum permissible levels established by international and Brazilian regulatory agencies, indicating that this species is safe for human consumption concerning this parameter. The presence of metals in Callinectes sp., however, is still of importance considering that this is a key species within the studied ecosystem and, therefore, plays a major role in the transference of pollutants to higher trophic levels. In addition, the presence of significant metal concentrations found in eggs must be considered in this context, since crab eggs are eaten by several other species, such as shorebirds, seabirds, and fish. Also, to the best of our knowledge, this is the first study regarding both MT and GSH levels in Callinectes sp. eggs and is of interest in the investigation of molecular mechanisms regarding metal exposure in these crustaceans. Data reported in this study support the conclusions from previous reports, provide mechanistic insights regarding metal exposure, metallothionein and oxidative stress induction in this species and also present novel data regarding eggs.

Increased Metallothionein Expression Reflects Steroid Resistance in Renal Allograft Recipients

Steroid-refractory acute rejection is a risk factor for inferior renal allograft outcome. We aimed to gain insight into the mechanisms underlying steroid resistance by identifying novel molecular markers of steroid-refractory acute rejection. Eighty-three kidney transplant recipients (1995–2005), who were treated with methylprednisolone during a first acute rejection episode, were included in this study. Gene expression patterns were investigated in a discovery cohort of 36 acute rejection biopsies, and verified in a validation cohort of 47 acute rejection biopsies. In the discovery set, expression of metallothioneins (MT) was significantly (p < 0.000001) associated with decreased response to steroid treatment. Multivariate analysis resulted in a predictive model containing MT-1 as an independent covariate (AUC = 0.88, p < 0.0000001). In the validation set, MT-1 expression was also significantly associated with steroid resistance (p = 0.029). Metallothionein expression was detected in macrophages and tubular epithelial cells. Parallel to the findings in patients, in vitro experiments of peripheral blood mononuclear cells from 11 donors showed that nonresponse to methylprednisolone treatment is related to highly elevated MT levels. High expression of metallothioneins in renal allografts is associated with resistance to steroid treatment. Metallothioneins regulate intracellular concentrations of zinc, through which they may diminish the zinc-requiring anti-inflammatory effect of the glucocorticoid receptor.

EROD and metallothionein in Limnodrilus profundicola (Oligochaeta: Tubifi cidae) as an indicator of pollution exposure in the Curuksu stream of Menderes river, Denizli–Turkey

In this study, pollution in Curuksu Stream of Menderes River has been followed by measuring the chemical and biological parameters on five predetermined stations for about 20 mon. Our previous studies have shown that Limnodrilus profundicola, Eristalis sp. and Chironomus thummi taxa are valuable bioindicators for the Curuksu stream and Limnodrilus profundicola Metallo-Thionein (MT) and EthoxyResorufi n-O-deEthylase (EROD) levels are valuable and useful biomarkers for biomonitoring heavy metals and PAHs pollutions, respectively. Cu-, Cr-, Cd- and Pb-type pollution was detected in all sediment samples taken from all of the stations, including reference station. Pollution source of these heavy metals are considered to be industrial wastewater, atmosphere and soil. Similarly, PAHs level was found to be considerably higher for Curuksu and Guzelkoy stations than other stations. These heavy metal- and PAHs-pollution were also confirmed with elevated MT and EROD levels measured with Limnodrilus profundicola sampl...

Detection of elemental mercury in abdominal wall soft tissue

A 19-year-old male with an unremarkable medical history presented with his father, who requested an evaluation of a pathology specimen from a reported "lump" under the skin in the middle of the son's lower abdomen. The lump had been excised by a surgeon approximately 3 months prior, per parental request. Upon gross inspection, the specimen appeared to contain small metallic droplets. The patient denied self-injection of any metals, including mercury, despite the results of a 24-hour urine heavy-metal screen (without chelation) that revealed an elevated concentration of mercury (87.6 microg/g creatinine; reference range for nonexposed adults: <4 microg/g creatinine). Confirmatory analysis of the tissue sample included gross and microscopic examination, electron microscopy using secondary and backscattered electron imaging modes, and energy dispersive x-ray spectrum analysis of isolated tissue particles. Grossly, the tissue had small silver spherules suggestive of elemental mercury; these droplets were identified histologically with associated foreign body reaction. Numerous smooth, round-to-oval particles scattered randomly throughout the tissue were identified ultrastructurally, which produced an x-ray energy spectrum corresponding to mercury. Elemental mercury is liquid at room temperature and may be injected into the body for recreational, psychiatric, and other purposes. Isolated cases of mercury injection following accidents with broken thermometers have been reported, as well as cases of elevated metallothionein concentration following human gingival amalgam tattoos. In cases of surreptitious injection, histology and ultrastructural evidence may be used to confirm the presence of mercury.

Histological Expression of Metallothionein in the Developing Rat Placenta

In order to clarify the metallothionein (MT) localization in the developing placenta, we histologically investigated the sequential MT expression in placentas and fetal livers using pregnant rats during gestation days (GDs) 9 - 21. The placentas were sampled and weighed on GDs 9, 11, 13, 15, 17, 19 and 21. In the early post implantation period, the expression of MT was slightly detected in the yolk sac and the primary decidual zone around the embryo. MT was then mainly present in the deciduas parietalis and yolk sac. After the deciduas parietalis ruptured, MT was subsequently detected in the yolk sac and deciduas basalis. MT continued to be detected in the yolk sac until GD 21, but it was reduced in the deciduas basalis in accordance with development of the fetal liver with elevated MT expression. In conclusion, the main expression site of MT changes from the maternal placenta to the fetal placenta, and then to the fetal liver in accordance with the fetal development. However, we speculate that the MT-positive cells in the placenta are positioned between the maternal and embryonic environments throughout the gestation period and always surround the embryo/fetus.

PROTECTION OF GLYCOLYTIC ENZYMES BY METALLOTHIONEINS FROM OXIDATIVE DAMAGE IN THE DIGESTIVE GLAND OF GREEN LIPPED MUSSEL PERNA VIRIDIS

We evaluated the capacity of metallothioneins (MT) in maintaining anaerobic metabolism in the green lipped mussel Perna viridis during experimentally induced oxidative stress. Mussels were exposed to 50 mg/L of cadmium during seven days, followed by recuperation in the sea during 35 days. Other groups of cadmium pre-exposed organisms and their respective controls were exposed to 200 and 500 mM of ferric iron/100 mM ascorbate to promote the formation of reactive oxygen species (ROS) by the Fenton reaction. Oxidative damage was evidenced by the malondialdehyde (MDA) production through thiobarbituric acid reactive substances (TBARS). The activities of the enzymes, hexokinase (HK), piruvate kinase (PK), and glucose-6-P dehydrogenase (G6PDH) in the digestive gland and the survival during anoxia were evaluated. Exposure of organisms to cadmium led to a significant bioaccumulation of this metal with concomitant high MT levels. Survival during prolonged periods of anoxia was reduced only in the iron/ascorbate exposed organisms, which exhibited an increase in MDA concentration; however, the cadmium-preexposed and control organisms showed similar resistance to anoxia. The iron/ ascorbate-exposed organisms showed a decrease in the activities of HK in the cytosol and HK, PK, and G6PDH of the particulate fraction. In comparison with the control group, the cadmium pre-exposed/iron-exposed organisms did not show significant differences in lipid peroxidation, associated with elevated MT levels. In conclusion, the data obtained suggest that of the glycolytic enzymes, HK and PK and G6PDH are targets to the attack by ROS and that the MT can protect molecules against these effects. MT appears to protect against ROS induced injury, allowing maintenance of metabolic control by glycolytic enzymes that are important during anaerobic metabolism.

Cell proliferation and hepatocarcinogenesis in rat initiated by diethylnitrosamine and promoted by phenobarbital: Potential roles of early DNA damage and liver metallothionein expression

Cell proliferation plays an important role in multistage chemical carcinogenesis. Again, several reports demonstrated that upregulation of metallothionein (MT) expression is associated with increased cell proliferation that may contribute to the pathogenesis of preneoplastic phenotype to frank malignancy. In this study, we evaluated the roles of early DNA damage, altered expressions of liver MT and Ki-67 nuclear antigen, and altered hepatic levels of zinc (Zn) and copper (Cu) on cell proliferation and the progression of hepatocarcinogenesis through premalignant, late premalignant and malignant transformation phases in male Sprague–Dawley rats. We have further studied the association between MT expression and cell proliferation in hepatocarcinogenesis. There was substantial induction of DNA single-strand breaks (SSBs) ( P < 0.001) and development of hepatocellular premalignant lesions along with significant decrease in hepatic levels of Zn and increase in Cu content following a single, necrogenic, intraperitoneal (i.p.) injection (200 mg/Kg body weight) of diethylnitrosamine (DEN) at week 4 of the experimental protocol. Moreover, DEN + phenobarbital (PB)-treatment significantly elevated MT-, Ki-67-, and BrdU-immunoexpressions along with their immunolabeling indices. Furthermore, positive correlations between MT- and Ki-67- labeling ( P = 0.0006) at various time intervals, as well as, between MT immunoreactivity and 5’-bromo-2’-deoxyuridine-labeling index (BrdU-LI) ( P = 0.0007) indicate that, MT expression might be associated with Ki-67 expression and cell proliferation thereby. The study suggests that DEN treatment may lead to alteration of Zn and Cu levels resulting in early DNA damage along with elevation of MT expression that may ultimately lead to hepatic cell proliferation. The results thus provide evidence in support of the role of MT as a potential positive regulator of cell growth during the early stages of hepatocellular transformation in rats.

Nuclear metallothionein expression correlates with cisplatin resistance of ovarian cancer cells and poor clinical outcome

Elevated metallothionein (MT) expression in ovarian cancers treated with cisplatin-based schemes represents an unfavorable prognostic index. MT expression is significantly higher in tumor samples obtained after chemotherapy. The present study aimed at examining MT expression in ovarian carcinoma cells sensitive (A2780) or resistant (A2780RCIS) against platinum drug treatment as well as examining effects of exposure to cisplatin on MT expression. Subcellular expression of MT was evaluated also in samples originating from 73 ovarian tumors. Cisplatin-resistant A2780RCIS cells were exposed to increasing cisplatin concentrations, and the subcellular expression of MT was determined by immunocytochemistry. The studies demonstrated that cisplatin-resistant A2780RCIS cells exposed to cisplatin typically manifested a nuclear MT expression. The study demonstrated also that exposure to cisplatin was paralleled by growing MT expression in cell nuclei. The nuclear expression of MT was also found to be specific for ovarian cancers of poor clinical outcome. No relationship could be demonstrated between cytoplasmic expression of MT and clinical variables. Nuclear MT expression is induced by cisplatin and seems to protect DNA in the cells from toxic effects of the drug.

Concurrent repletion of iron and zinc reduces intestinal oxidative damage in iron- and zinc-deficient rats

To understand the interactions between iron and zinc during absorption in iron- and zinc-deficient rats, and their consequences on intestinal oxidant-antioxidant balance. Twenty-four weanling Wistar-Kyoto rats fed an iron- and zinc-deficient diet (< 6.5 mg Fe and 4.0 mg Zn/kg diet) for 4 wk were randomly divided into three groups (n = 8, each) and orally gavaged with 4 mg iron, 3.3 mg zinc, or 4 mg iron + 3.3 mg zinc for 2 wk. At the last day of repletion, 3 h before the animals were sacrificed, they received either 37 mBq of (55)Fe or (65)Zn, to study their localization in the intestine, using microautoradiography. Hemoglobin, iron and zinc content in plasma and liver were measured as indicators of iron and zinc status. Duodenal sections were used for immunochemical staining of ferritin and metallothionein. Duodenal homogenates (mitochondrial and cytosolic fractions), were used to assess aconitase activity, oxidative stress, functional integrity and the response of antioxidant enzymes. Concurrent repletion of iron- and zinc-deficient rats showed reduced localization of these minerals compared to rats that were treated with iron or zinc alone; these data provide evidence for antagonistic interactions. This resulted in reduced formation of lipid and protein oxidation products and better functional integrity of the intestinal mucosa. Further, combined repletion lowered iron-associated aconitase activity and ferritin expression, but significantly elevated metallothionein and glutathione levels in the intestinal mucosa. The mechanism of interactions during combined supplementation and its subsequent effects appeared to be due to through modulation of cytosolic aconitase, which in turn influenced the labile iron pool and metallothionein levels, and hence reduced intestinal oxidative damage. Concurrent administration of iron and zinc corrects iron and zinc deficiency, and also reduces the intestinal oxidative damage associated with iron supplementation.

Alteration of dissolved cadmium and zinc uptake kinetics by metal pre‐exposure in the black sea bream (Acanthopagrus schlegeli)

We first examined the uptake kinetics of Cd and Zn in the juvenile marine black sea bream (Acanthopagrus schlegeli) over a wide range of ambient Cd and Zn concentrations, and the relationships with metal accumulation (uptake rate and amount of nonexchangeable surface binding) were established for different fish tissues. Both Cd and Zn accumulation in the body increased linearly with exposure time after the initial metal surface binding. The dissolved Cd and Zn uptake rate constants were 2.64 and 6.50 L/kg/d, respectively, and the kinetics followed a first-order process. No evidence of biphasic transport was found, in contrast to the situation in freshwater fish. Viscera were the most important sites of metal uptake, and gills were the second most important sites. The black sea breams were then acclimated at different Cd or Zn concentrations from either waterborne or dietary source for one week, and the alteration of metal uptake kinetics or subcellular distribution and metallothionein (MT) induction were further quantified. The Cd body burden was enhanced up to 8.6- and 49-fold after waterborne and dietary Cd pre-exposure, respectively. Cadmium pre-exposure also altered the tissue-specific subcellular Cd distribution and significantly elevated tissue MT levels. In contrast, the black sea breams were able to regulate Zn accumulation, and waterborne or dietary Zn pre-exposure had only weak influences on Zn body burden and redistribution. Both Cd and Zn pre-exposures enhanced the metal uptake rate constants, whereas the nonexchangeable surface bindings were less impacted by these pre-exposures. We demonstrated a positive relationship between the Cd uptake rate and Cd or MT concentration in the fish. Pre-exposure to metals may substantially modify the kinetics of metal uptake.

A Gene Expression Signature of Genetic Instability in Colon Cancer

Genetic instability plays a central role in the development and progression of human cancer. Two major classes of genetic instability, microsatellite instability (MSI) and chromosome instability (microsatellite stable; MSS), are best understood in the context of colon cancer, where MSI tumors represent approximately 15% of cases, and compared with MSS tumors, more often arise in the proximal colon and display favorable clinical outcome. To further explore molecular differences, we profiled gene expression in a set of 18 colon cancer cell lines using cDNA microarrays representing approximately 21,000 different genes. Supervised analysis identified a robust expression signature distinguishing MSI and MSS samples. As few as eight genes predicted with high accuracy the underlying genetic instability in the original and in three independent sample sets, comprising 13 colon cancer cell lines, 61 colorectal tumors, and 87 gastric tumors. Notably, the MSI signature was retained despite genetically correcting the underlying instability, suggesting the signature reflects a legacy of the tumor having arisen from MSI, rather than sensing the ongoing state of MSI. Our findings support a model in which MSI and MSS preferentially target different genes and pathways in cancer. Further, among the MSI signature genes, our findings implicate a role of elevated metallothionein expression in the clinical behavior of MSI cancers.

Elevated metallothionein (MT) expression in invasive ductal breast cancers predicts tamoxifen resistance.

Elevated expression of the low molecular weight metallothionein (MT) proteins can be found typically in breast cancer cases with less favourable prognosis. The MT gene has been described to be potentially down-regulated by estrogen receptor alpha. The present study is aimed at examining the predictive value of MT expression for results of tamoxifen treatment in breast cancer in relation to steroid receptor status. Sixty patients with primary invasive ductal breast cancers with post-operative tamoxifen treatment were enrolled in the study. In paraffin sections of the studied tumours immmunohistochemical reactions were performed using antibodies directed against MT, estrogen receptors (ER) and progesterone receptors (PgR). Results of the immunohistochemical reactions and of clinical observations were analysed using multivariate progression analysis based on the Cox proportional hazard model. Elevated MT expression was demonstrated to be typical for cases with documented relapse of the disease (P<0.001) or terminated by death (P=0.03). Decreased ER expression was found to be typical for cases of a higher grade (P=0.02) and cases terminated by death (P=0.006). The multivariate analysis showed that elevated MT expression was characteristic for cases with shorter overall survival time (P=0.04). The data showed that MT carried an independent, and also independent from ER status, unfavourable predictive value as far as results of tamoxifen treatment were concerned.

Metallothionein mediates leukocyte chemotaxis

BackgroundMetallothionein (MT) is a cysteine-rich, metal-binding protein that can be induced by a variety of agents. Modulation of MT levels has also been shown to alter specific immune functions. We have noticed that the MT genes map close to the chemokines Ccl17 and Cx3cl1. Cysteine motifs that characterize these chemokines are also found in the MT sequence suggesting that MT might also act as a chemotactic factor.ResultsIn the experiments reported here, we show that immune cells migrate chemotactically in the presence of a gradient of MT. This response can be specifically blocked by two different monoclonal anti-MT antibodies. Exposure of cells to MT also leads to a rapid increase in F-actin content. Incubation of Jurkat T cells with cholera toxin or pertussis toxin completely abrogates the chemotactic response to MT. Thus MT may act via G-protein coupled receptors and through the cyclic AMP signaling pathway to initiate chemotaxis.ConclusionThese results suggest that, under inflammatory conditions, metallothionein in the extracellular environment may support the beneficial movement of leukocytes to the site of inflammation. MT may therefore represent a "danger signal"; modifying the character of the immune response when cells sense cellular stress. Elevated metallothionein produced in the context of exposure to environmental toxicants, or as a result of chronic inflammatory disease, may alter the normal chemotactic responses that regulate leukocyte trafficking. Thus, MT synthesis may represent an important factor in immunomodulation that is associated with autoimmune disease and toxicant exposure.