Showing papers on "Zinc toxicity published in 2012"
TL;DR: The different molecular mechanisms of nutritional (Zn) and non-nutritional (Cd) metal homeostasis between metal-sensitive and metal-adapted species are compared to provide a comprehensive overview on how plants cope with Zn/Cd stress at the molecular level.
Abstract: When plants are subjected to high metal exposure, different plant species take different strategies in response to metal-induced stress. Largely, plants can be distinguished in four groups: metal-sensitive species, metal-resistant excluder species, metal-tolerant non-hyperaccumulator species, and metal-hypertolerant hyperaccumulator species, each having different molecular mechanisms to accomplish their resistance/tolerance to metal stress or reduce the negative consequences of metal toxicity. Plant responses to heavy metals are molecularly regulated in a process called metal homeostasis, which also includes regulation of the metal-induced reactive oxygen species (ROS) signaling pathway. ROS generation and signaling plays an important duel role in heavy metal detoxification and tolerance. In this review, we will compare the different molecular mechanisms of nutritional (Zn) and non-nutritional (Cd) metal homeostasis between metal-sensitive and metal-adapted species. We will also include the role of metal-induced ROS signal transduction in this comparison, with the aim to provide a comprehensive overview on how plants cope with Zn/Cd stress at the molecular level.
532 citations
TL;DR: It is confirmed that sublethal waterborne zinc is an oxidative stressor in fish, and the important protective role of higher salinities in ameliorating the oxidative stress associated with zinc toxicity in this model estuarine teleost is highlighted.
114 citations
TL;DR: This study suggests the Si-assisted Zn tolerance of rice is mainly due to the reduction of uptake and translocation of excess Zn, and a stronger binding of Zn in the cell wall of less bioactive tissues might also contribute to some degree.
Abstract: Background and aims Silicon (Si) was suggested to enhance plant resistance to toxic elements, and its beneficial role was mainly based on external and internal plant mechanisms. This work aimed at investigating the internal effect of Si on zinc (Zn) detoxification to rice (Oryza sativa L., cv. Tian You 116) seedlings. Methods In a hydroponic experiment, we examined the uptake, xylem loading and localization of Zn in rice seedlings under the condition of 200 μ MZ n contamination with the additional silicate supply at three levels ( 0, 0.5 and 1.8 mM). Results The silicate addition significantly increased the seedling biomass, and decreased Zn concentration in both root and shoot of seedlings and in xylem sap flow. Zinpyr-1 fluorescence test and Energy-dispersive X-ray spectroscopy analysis showed the concentration of biologically active Zn 2+ decreased, and Zn and Si co-localized in the cell wall of metabolically less active tissues, especially in sclerenchyma of root. The fractionation analysis further supported silicate supply increased about 10% the cell wall bound fraction of Zn. Conclusions This study suggests the Si-assisted Zn tolerance of rice is mainly due to the reduction of uptake and translocation of excess Zn, and a stronger binding of Zn in the cell wall of less bioactive tissues might also contribute to some degree.
102 citations
TL;DR: Investigation of accumulation, tissue and intracellular localization, and toxic effects of cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) in three aquatic macrophytes showed that they could be considered good candidates for wastewaters remediation purpose.
Abstract: A comprehensive understanding of the uptake, tolerance, and transport of heavy metals by plants will be essential for the development of phytoremediation technologies. In the present paper, we investigated accumulation, tissue and intracellular localization, and toxic effects of cadmium (Cd), lead (Pb), zinc (Zn), and copper (Cu) in three aquatic macrophytes (the angiosperms Lemna minor and Elodea canadensis, and the moss Leptodictyum riparium). We also tested and compared their capacity to absorb heavy metal from water under laboratory conditions. Our data showed that all the three species examined could be considered good bioaccumulators for the heavy metals tested. L. riparium was the most resistant species and the most effective in accumulating Cu, Zn, and Pb, whereas L. minor was the most effective in accumulating Cd. Cd was the most toxic metal, followed by Pb, Cu, and Zn. At the ultrastructural level, sublethal concentrations of the heavy metals tested caused induced cell plasmolysis and alteration...
94 citations
TL;DR: This study revealed that heavy metals partially exert toxicity by disturbing the nutrient balance and modifying enzyme activities that induce damage in plants, however, P. americana has evolved hyper accumulating mechanisms to maintain elemental balance and redox homeostasis under excess Mn.
82 citations
TL;DR: It is found that Ang II-induced senescence is a zinc-dependent pathway mediated by the downregulation of the zinc transporters ZnT3 and ZnNT10, which work to reduce cytosolic zinc and might also affect other ROS-dependent processes induced by Ang II, such as hypertrophy and migration of smooth muscle cells.
Abstract: Senescence, a hallmark of mammalian aging, is associated with the onset and progression of cardiovascular disease. Angiotensin II (Ang II) signaling and zinc homeostasis dysfunction are increased with age and are linked to cardiovascular disease, but the relationship among these processes has not been investigated. We used a model of cellular senescence induced by Ang II in vascular smooth muscle cells (VSMCs) to explore the role of zinc in vascular dysfunction. We found that Ang II-induced senescence is a zinc-dependent pathway mediated by the downregulation of the zinc transporters ZnT3 and ZnT10, which work to reduce cytosolic zinc. Zinc mimics Ang II by increasing reactive oxygen species (ROS), activating NADPH oxidase activity and Akt, and by downregulating ZnT3 and ZnT10 and inducing senescence. Zinc increases Ang II-induced senescence, while the zinc chelator TPEN, as well as overexpression of ZnT3 or ZnT10, decreases ROS and prevents senescence. Using HEK293 cells, we found that ZnT10 localizes in recycling endosomes and transports zinc into vesicles to prevent zinc toxicity. Zinc and ZnT3/ZnT10 downregulation induces senescence by decreasing the expression of catalase. Consistently, ZnT3 and ZnT10 downregulation by siRNA increases ROS while downregulation of catalase by siRNA induces senescence. Zinc, siZnT3 and siZnT10 downregulate catalase by a post-transcriptional mechanism mediated by decreased phosphorylation of ERK1/2. These data demonstrate that zinc homeostasis dysfunction by decreased expression of ZnT3 or ZnT10 promotes senescence and that Ang II-induced senescence is a zinc and ROS-dependent process. Our studies suggest that zinc might also affect other ROS-dependent processes induced by Ang II, such as hypertrophy and migration of smooth muscle cells.
77 citations
TL;DR: The unified zinc BLM, developed by objectively averaging the biotic ligand binding constants for zinc and competing cations from existing BLMs, performed better in predicting toxicity to a diverse set of organisms than any individual existing BLM.
Abstract: The United States Environmental Protection Agency's (U.S. EPA) current ambient water quality criteria (AWQC) for zinc in freshwater are hardness-based and were last updated in 1995. The acute and chronic freshwater toxicity databases have since expanded substantially and the U.S. EPA's minimum phylogenetic diversity requirements for chronic zinc toxicity are now met (an acute:chronic ratio was previously required). Additionally, several acute and chronic biotic ligand models (BLMs) for zinc have since been developed and validated for freshwater organisms. Using the expanded toxicity database and existing BLMs, we developed a unified zinc BLM that could efficiently predict both acute and chronic toxicity over a wide range of zinc bioavailabilities. The unified BLM, developed by objectively averaging the biotic ligand binding constants for zinc (Zn2+) and competing cations (Ca2+, Mg2+, Na+, H+) from existing BLMs, performed better in predicting toxicity to a diverse set of organisms than any individual existing BLM. Performance of the unified BLM was further improved by optimizing the biotic ligand binding constant for the ZnOH+ species. The updated freshwater zinc toxicity database and unified BLM were then used to estimate the fifth percentiles of the acute and chronic species sensitivity distributions following the U.S. EPA guidelines for AWQC development. Environ. Toxicol. Chem. 2012;31:1264–1272. © 2012 SETAC
63 citations
TL;DR: Comparative metallo-genomics has begun to explore not only the putative zinc proteome, but also specific protein families predicted to have an involvement in zinc homeostasis, including sensors for excess and limitation, uptake systems (ZnuABC), putative intracellular zinc chaperones, and efflux pumps (ZiaA and its homologs).
Abstract: Zinc is a recognized essential element for the majority of organisms, and is indispensable for the correct function of hundreds of enzymes and thousands of regulatory proteins. In aquatic photoautotrophs including cyanobacteria, zinc is thought to be required for carbonic anhydrase and alkaline phosphatase, although there is evidence that at least some carbonic anhydrases can be cambialistic, i.e., are able to acquire in vivo and function with different metal cofactors such as Co2+ and Cd2+. Given the global importance of marine phytoplankton, zinc availability in the oceans is likely to have an impact on both carbon and phosphorus cycles. Zinc concentrations in seawater vary over several orders of magnitude, and in the open oceans adopt a nutrient-like profile. Most studies on zinc handling by cyanobacteria have focused on freshwater strains and zinc toxicity; much less information is available on marine strains and zinc limitation. Several systems for zinc homeostasis have been characterized in the freshwater species Synechococcus sp. PCC 7942 and Synechocystis sp. PCC 6803, but little is known about zinc requirements or zinc handling by marine species. Comparative metallo-genomics has begun to explore not only the putative zinc proteome, but also specific protein families predicted to have an involvement in zinc homeostasis, including sensors for excess and limitation (SmtB and its homologs as well as Zur), uptake systems (ZnuABC), putative intracellular zinc chaperones (COG0523) and metallothioneins (BmtA), and efflux pumps (ZiaA and its homologs).
56 citations
TL;DR: Heavy metals concentrations in roots always exceeded those in stem and leaves, with a lower translocation from roots to shoots, suggesting a strategy of sunflower to compartmentalise the potentially toxic elements in physiologically less active parts in order to preserve younger tissues.
Abstract: We investigated the effects on physiological response, trace elements and nutrients accumulation of sunflower plants grown in soil contaminated with: 5 mg kg−1 of Cd; 5 and 300 mg kg−1 of Cd and Zn
49 citations
TL;DR: The role of the excitotoxic influx and accumulation of zinc, the mechanisms responsible for its cytotoxicity, and a number of disorders of the central nervous system that have been linked to these neuronal ion channels and zinc toxicity are discussed.
Abstract: Ionotropic glutamate receptors, such as NMDA, AMPA and kainate receptors, are ligand-gated ion channels that mediate much of the excitatory neurotransmission in the brain Not only do these receptors bind glutamate, but they are also regulated by and facilitate the postsynaptic uptake of the trace metal zinc This paper discusses the role of the excitotoxic influx and accumulation of zinc, the mechanisms responsible for its cytotoxicity, and a number of disorders of the central nervous system that have been linked to these neuronal ion channels and zinc toxicity including ischemic brain injury, traumatic brain injury, and epilepsy
49 citations
TL;DR: The findings show that a genetically based zinc toxicosis situation can be therapeutically treated or exacerbated by modifications to the diet, providing a sensitized background for future, more detailed studies of Zip/ZnT function.
Abstract: The heavy metal zinc is an essential component of the human diet and is incorporated as a structural component in up to 10% of all mammalian proteins. The physiological importance of zinc homeostasis at the cellular level and the molecular mechanisms involved in this process have become topics of increasing interest in recent years. We have performed a systematic functional characterization of the majority of the predicted Drosophila Zip (zinc/iron regulated transporter-related protein) and ZnT genes, using the Gal4-UAS system to carry out both ubiquitous and targeted over-expression and suppression studies for 13 of the 17 putative zinc transport genes identified to date. We found that six of these 13 genes may be essential for fly viability and that three of the remaining seven demonstrate over-expression phenotypes. Our findings reaffirm the previously proposed function of dZnT63C (CG17723: FBgn005432) as an important zinc efflux protein and indicate that the fly homolog of hZip1, dZip42C.1 (CG9428: FBgn0033096), is a strong zinc importer in Drosophila. By combining over-expression of dZip42C.1 with suppression of dZnT63C we were able to produce easily identifiable zinc toxicosis phenotypes, which can be rescued or worsened by modifying dietary zinc content. Our findings show that a genetically based zinc toxicosis situation can be therapeutically treated or exacerbated by modifications to the diet, providing a sensitized background for future, more detailed studies of Zip/ZnT function.
TL;DR: A two-compartment toxicokinetic-toxicodynamic model for metals in a freshwater cladoceran, Daphnia magna, is developed and can help improve ecological risk assessments for metals.
Abstract: Relating the toxicity of metals to their internal concentration is difficult due to complicated detoxification processes within organisms. Only the metabolically available metals are potentially toxic to organisms, while metals in the detoxified form are toxicologically irrelevant. Accordingly, we developed a two-compartment toxicokinetic–toxicodynamic model for metals in a freshwater cladoceran, Daphnia magna. The toxicokinetics simulated the bioaccumulation processes, while the toxicodynamics quantitatively described the corresponding processes of toxicity development. Model parameters were estimated for D. magna and three metals, i.e., cadmium, zinc, and mercury, by fitting the literature data on metal bioaccumulation and toxicity. A range of crucial information for toxicity prediction can be readily derived from the model, including detoxification rate, no-effect concentration, threshold influx rate for toxicity, and maximum duration without toxicity. This process-based model is flexible and can help ...
TL;DR: The loss of cell viability and the significant increases of lignification in response to the highest Zn concentration may be associated with the remarkable reduction of root growth in wheat seedlings.
TL;DR: It is indicated that ZnT-1 enhances the activity of CaV3.1 and CaV 3.1 channels in a PD-98059-sensitive manner through activation of Ras-ERK signaling, which is associated with enhanced trafficking of the channel to the plasma membrane.
Abstract: Zinc transporter-1 (ZnT-1) is a putative zinc transporter that confers cellular resistance from zinc toxicity. In addition, ZnT-1 has important regulatory functions, including inhibition of L-type ...
TL;DR: Application of the metal salts and the combined solutions on cucumber seedlings revealed similar consequences for total soluble protein level, dry weight and ultimately in inhibitory rates as well, concluding that molecular marker assays can be applied in combination with population parameters to measure genotoxic effects of heavy metals on plants.
Abstract: Contamination of plants with heavy metals could result in damage in DNA, such as mutations and cross-links with proteins. These altered DNA profiles may become visible in changes such as the appearance of a new band, or loss of an existing band, in the random amplified polymorphic DNA (RAPD) assay. In this study, various concentrations of copper and zinc salts were applied to cucumber seedlings during germination. Results displayed abnormalities in germination and also changes in root elongation, dry weight and total soluble protein level. All treatment concentrations (40, 80, 160, 240, 320, and 640mg/L) used in the study caused a decrease/delay in germination of the cucumbers to different extents. Inhibition or activation of root elongation was considered to be the first effect of metal toxicity in the tested plants. Application of the metal salts and the combined solutions on cucumber (Cucumis sativus L.) seedlings revealed similar consequences for total soluble protein level, dry weight and ultimately in inhibitory rates as well. The data obtained from RAPD band-profiles and genomic template stability (GTS) showed results that were consistent with the population parameters. In this regard, we conclude that molecular marker assays can be applied in combination with population parameters to measure genotoxic effects of heavy metals on plants.
TL;DR: Both the bioavailability assessment and the sequential extraction analysis demonstrated that the immobilization of zinc was highly dependent on the physico-chemical properties of soils and showed that the lability of zinc decreased over time.
Journal Article•
TL;DR: In this paper, the effects of various concentrations of Zn on biomass, chlorophyll content, and Zn contents of Sorghum bicolor and Chenopodium album were studied at research field of Urmia University, Urmia, Iran.
Abstract: Zinc (Zn) as a heavy metal plays an important role in many biochemical functions of plants.
However, the excess amount of zinc is one of the most important growth limiting factors in soils. In the
present study, the effects of various concentrations of Zn on biomass, chlorophyll content, and Zn contents of
Sorghum bicolor and Chenopodium album were studied at research field of Urmia University, Urmia, Iran, in
2011. The plants were grown in pots over a 3 month period in soils containing zinc concentration varying
between 100.7, 300.7, 500.7, 900.7, 1300.7 and 2100.7 mgzii/kgsoil. At the end of growing season, plant height,
chlorophyll a, b, and total chlorophyll content, biomass, Zn concentration in the plants and bio-available Zn of
the soils were measured. Results indicated that, generally, with increasing Zn concentration in soil, plant
height, content of a, b, and total chlorophyll and biomass were decreased significantly (r0.05). With an
increase in soil Zn concentration, Zn in Common lambsquarter was increased up to a maximum of 1213
mg/kg (in concentration 2100 mgziiLkgsoil). The maximum Zn concentration in sorghum was 2538 mg/kg (in
concentration 500 mgz1 /kgs01). In addition, there was significant correlation between NH4NO3- extractable soil
Zn and response of plants to Zn pollution
TL;DR: The data suggests that nanoparticles act to interrupt cell membranes thereby causing cell death rather than exerting a strictly toxic effect, and identifies potentially useful genes to serve as biomarkers of membrane disruption in toxicogenomic studies with nanoparticles or to engineer biosensor organisms.
Abstract: Synthetic metal oxide nanomaterials exert toxicity via two general mechanisms: release of free ions at concentrations which exert toxic effects upon the target cell, or specific surface-mediated physicochemical processes leading to the formation of hydroxyl free radicals and other reactive oxygen species which act to disrupt cell membranes and organelles. From a regulatory standpoint this presents a potential problem since it is not trivial to detect free metal ions in the presence of nanoparticles in biological or natural media. This makes efforts to identify the route of uptake difficult. Although in vitro studies of zinc oxide nanoparticles suggest that toxicity to the soil bacterium Cupriavidus necator is exerted in a similar manner to zinc acetate, we found no free Zn ion is associated with nanoparticle suspensions. The proteome of cells subjected to equal concentrations of either the nanoparticle or zinc acetate suggest that the mode of toxicity is quite different for the two forms of Zn, with a number of membrane-associated proteins up-expressed in response to nanoparticle exposure. Our data suggests that nanoparticles act to interrupt cell membranes thereby causing cell death rather than exerting a strictly toxic effect. We also identify potentially useful genes to serve as biomarkers of membrane disruption in toxicogenomic studies with nanoparticles or to engineer biosensor organisms.
TL;DR: Cu sequestration within molt-cycle calcium storage granules is described, as both MTLP concentrations and granule formation in crustaceans are affected upon by molting, and it is hypothesized that detoxification might impact upon this existing process.
Abstract: To negate the toxicity of labile intracellular metals, some aquatic organisms partition metals into specific subcellular locations for detoxification, namely the soluble heat-stable cytosol and insoluble metal-rich granules. The aim of the present study was to characterise these subcellular storage sites in the freshwater crustacean Gammarus pulex (Linnaeus) following in situ exposures upstream (Drym, low metal) and downstream (Relubbus, elevated metal) of copper- and zinc-rich inflows into the River Hayle (Cornwall, UK). In the cytosol of gammarids exposed at Relubbus, copper and zinc associated to a 7.5-kDa metallothionein-like protein (MTLP) that was largely absent from gammarids prior to exposure. Exposure at Relubbus caused MTLP concentrations to increase 4- to 5-fold between days 2 and 4, indicating an induction response to increased labile intracellular metal. On day 16, spherical calcium-rich granules (0.5-2.5 μmol l(-1)) were visualised and analysed in the posterior caeca of gammarids exposed at both sites. Following exposure at Relubbus, granules contained trace amounts of copper, but zinc was absent. Granules in gammarids exposed at Drym contained no detectable copper or zinc. Granule formation appeared to be independent of exposure. Within the posterior caeca, granules have been associated with calcium storage during the crustacean molt, rather than in detoxification of trace metals. However, the granular copper burden appeared to follow environmental Cu availabilities. Thus, we describe Cu sequestration within molt-cycle calcium storage granules. As both MTLP concentrations and granule formation in crustaceans are affected upon by molting, we hypothesise that detoxification might impact upon this existing process.
TL;DR: Overall, a chemical measure was the best predictor of toxicity to each organism compared with biological measures, although the exact measure was dependent on organism and end point.
Abstract: The soil-contact exposure pathway can be the main driver of ecological risk assessments. There is currently no standard method to measure bioavailability of metals in soil to ecological receptors, yet the influence of metal bioavailability on toxicity has been known for decades and is a major factor influencing risk to ecological receptors. Bioavailability is to a large degree governed by varying soil characteristics within and among sites, yet ecological screening benchmarks are often derived on a total-concentration basis. We compared a calcium chloride (CaCl2) extraction, cyclodextrin extraction, simulated earthworm gut (SEG) test, earthworm kinetic bioaccumulation test, and metal residues in plant tissues with a battery of invertebrate and toxicity tests using mining soils consisting of high organic-matter content cocontaminated with copper (Cu) and zinc (Zn). Earthworm (Eisenia andrei) tissue concentrations of Cu and Zn were regulated and were not predictive of invertebrate toxicity. All chemical measures of bioavailability correlated with several biological responses; however, CaCl2-extractable Cu and SEG-extractable Cu and Zn best predicted effects to E. andrei. Total Cu concentrations in soil best correlated with effects to plants. Overall, a chemical measure was the best predictor of toxicity to each organism compared with biological measures, although the exact measure was dependent on organism and end point. Chemical-extraction techniques provide relatively quick, inexpensive indicators of essential metal bioavailability compared with biological measures; however, no single measure was indicative of all effects to all organisms.
TL;DR: The results indicate that oysters are sensitive to acute zinc toxicity but are only moderately affected by a mild zinc concentration, and an increase of MT mRNA is observed in these tissues.
TL;DR: It is demonstrated that ionophoric zinc can induce cytotoxicity in cancer cells by globally regulating posttranscriptional events.
Abstract: Zinc at cytotoxic concentrations has been shown to regulate gene transcription in cancer cells, though zinc's involvement in posttranscriptional regulation is less characterized. In this study, we investigated the involvement of cytotoxic zinc in the posttranscriptional steps of gene expression. Clioquinol, a well-established zinc ionophore, was used to raise intracellular zinc to reported cytotoxic levels. The MCF-7 human cancer cell line was applied as a cell model system. Several parameters were used as indictors of posttranscriptional regulation, including p-body formation, microRNA profiling, expression level of proteins known to regulate mRNA degradation, microRNA processing, and protein translation. p-body formation was observed in MCF-7 cells using several molecules known as p-body components. Clioquinol plus zinc enhanced p-body assembly in MCF-7 cells. This enhancement was zinc-specific and could be blocked by a high affinity zinc chelator. The enhancement does not seem to be due to a stress response, as paclitaxel, a commonly used chemotherapeutic, did not cause enhanced p-body formation at a highly cytotoxic concentration. microRNA profiling indicated that clioquinol plus zinc globally down-regulates microRNA expression in this model system, which is associated with the reduced expression of Dicer, an enzyme key to microRNA maturation, and Ago2, a protein essential for microRNA stability. This study demonstrates that ionophoric zinc can induce cytotoxicity in cancer cells by globally regulating posttranscriptional events.
TL;DR: The utility of polydentate chelators in the remediation of metal-contaminated systems is demonstrated and it is demonstrated that although the application of a chelator to metal contaminants may be effective, binding alone cannot be used to predict the level of remediation.
TL;DR: The results suggest that primary antioxidative response originates in leaves of Lablab, while roots are involved in direct uptake of heavy metals and are not adept in extrusion.
Abstract: Zinc toxicity to plants occurs in soils contaminated by mining and smelting activities, in agricultural soils treated with sewage sludge, and in urban and peri-urban soils enriched by anthropogenic inputs of Zn. Zinc-induced stress in Hyacinth bean (Lablab purpureus) was investigated by growing seedlings in hydroponics, supplemented with Zinc (0-600 µM), under controlled growth conditions. Changes in growth parameters, enzyme activities and other stress response factors, as a function of Zn uptake are directly or indirectly related to the cellular free radical scavenging systems. These parameters were studied in 10-day old Lablab seedlings over 72 h of exposure. Relative to leaves, roots accumulated ~12-fold higher amounts of Zn. Oxidative stress markers, H 2 O 2 , malondialdehyde, ascorbate, proline, soluble sugars, putrescine and spermidine were elevated in both tissues, whereas, glutathione and spermine levels showed a steady decline. Total phenol increased in roots, but decreased in leaves. Zn-stress enhanced antioxidant enzymes, guaiacol peroxidase, glutathione reductase, and polyphenol oxidase in concentration and time dependent manner in leaves, but showed an inverse relationship in roots. Catalase decreased in both leaves and roots. Metabolic enzymes β-amylase and acid phosphatase increased in both tissues. Invertase increased in leaves but declined drastically in roots. The results suggest that primary antioxidative response originates in leaves of Lablab, while roots are involved in direct uptake of heavy metals and are not adept in extrusion. Also, lower concentrations of Zn (up to 100 µM) stimulate growth of Lablab, but higher concentrations proved detrimental to the plant.
01 Mar 2012
TL;DR: The evident dualism of zinc's effects depends primarily on the energetic state of the particular cell and the efficacy of ion pumps; on genetically conditioned mechanisms regulating Zn efflux from cells and Zn sequestration inside the cell; and on the concentration of extracellular free Zn.
Abstract: Zinc plays an important role in the functioning of all cells, including neurons. The precise mechanisms responsible for its neurotoxic and neuroprotective effects remain unclear despite extensive investigations. Similar Zn(+2) effects can also be observed in cells outside the nervous system, and their lower sensitivity to hypoxia prolongs the cytotoxic effect of excess zinc. The evident dualism of zinc's effects depends primarily on the energetic state of the particular cell and the efficacy of ion pumps; on genetically conditioned mechanisms regulating Zn efflux from cells and Zn sequestration inside the cell; and on the concentration of extracellular free Zn.
TL;DR: The results suggest that the GDI1protein is involved in Zn efflux via small vesicle trafficking and contributes to the control of cytoplasmic Zn content, allowing yeast to survive in the presence of toxic Zn.
Abstract: The GDI1 protein related vesicle transport system was studied to investigate the possibility that an exclusion of toxic zinc (Zn) from the cytoplasm ameliorates Zn toxicity in Saccharomyces cerevisiae (yeast). A temperature-sensitive gdi1 mutant (originally called sec19), in which the GDP dissociation inhibitor becomes inactive at the non-permissive temperature (37 °C), was more sensitive to Zn than its parental GDI1 strain at 32 °C (a moderately non-permissive temperature). The relative efflux of cytoplasmic Zn in the gdi1 mutant was lower than that in the control strain. Treatment with a vesicle transport-specific inhibitor, Brefeldin A, caused an increase of Zn sensitivity and a decrease of Zn efflux in these strains. It is therefore suggested that the GDI1-related vesicle transport system contributes to Zn tolerance in yeast. Furthermore, changes in the number of Zn-specific fluorescent granules (zincosomes) were observed by zinquin staining in the mutant cells under Zn treatment at 32 °C and 37 °C. We concluded that the GDI1 protein is implicated in control of vesicle numbers. Collectively, the results suggest that the GDI1protein is involved in Zn efflux via small vesicle trafficking and contributes to the control of cytoplasmic Zn content, allowing yeast to survive in the presence of toxic Zn. Copyright © 2011 John Wiley & Sons, Ltd.
TL;DR: Simultaneous treatment of CGNs with kainate and zinc chloride caused the swelling of neuronal mitochondria and consequent intensive neuronal death, which was totally prevented by NBQX or ruthenium red.
TL;DR: The authors investigated integrated biological endpoints that would account for the apparent general health of the animals as well as molecular markers showing more subtle effects that could potentially go unnoticed at a biologically integrated level.
Abstract: The marine coastal environment is exposed to a mixture of environmental pollutants of anthropogenic origin, resulting in chronic low concentrations of contaminants. As a consequence, most coastal marine species are exposed to low doses of such pollutants during their entire life. Many marine species live for years in their natural environment, whereas they do not under laboratory exposure conditions. Using early stages of development in laboratory work allows animals to be chronically exposed from an early age over a reasonable experiment period. In the present study, the authors investigated the effect of chronic exposure to zinc in spats of the Pacific oyster (Crassostrea gigas), from metamorphosis up to 10 weeks. The authors investigated integrated biological endpoints that would account for the apparent general health of the animals as well as molecular markers showing more subtle effects that could potentially go unnoticed at a biologically integrated level. The authors measured in parallel both growth and the transcriptional level of target stress genes. Growth was monitored by image analysis of large samples to avoid high variability and ensure statistical robustness. A dose-response relationship was derived from growth data, yielding a median effective concentration (EC50) of 7.55 µM. Stress genes selected on the basis of available RNA sequences in C. gigas included genes involved in chaperone proteins, oxidative stress, detoxification, and cell cycle regulation. Out of nine stress target genes, only metallothionein displayed overexpression in response to high levels of zinc.
TL;DR: It is shown that zinc has a dual effect on ICaT, blocking it acutely while causing its long‐term upregulation, providing a possible explanation to the mechanism of epileptogenesis induced by pathological conditions associated with enhanced release of zinc, such as SE.
Abstract: Extracellular zinc can induce numerous acute and persistent physiological and toxic effects in neurons by acting at their plasma membrane or intracellularly following permeation or uptake into them. Zinc acutely and reversibly blocks T-type voltage-gated calcium current (I(CaT)), but the long-term effect of zinc on this current has not been studied. Because chemically induced status epilepticus (SE) results in the release of zinc into the extracellular space, as well as in a long-lasting increase in I(CaT) in CA1 pyramidal cells, we hypothesized that zinc may play a causative role in I(CaT) upregulation. We tested this hypothesis by monitoring for 18 days the effects of zinc and ibotenic acid (a neurotoxic agent serving as control for zinc), injected into the right lateral ventricle, on I(CaT) in rat CA1 pyramidal cells. Both zinc and ibotenic acid caused marked hippocampal lesions on the side of injection, but only minor damage to contralateral hippocampi. Zinc, but not ibotenic acid, caused upregulation of a nickel-sensitive I(CaT) in a subset of contralateral CA1 pyramidal cells, appearing 2 days after injection and lasting for about 2 weeks thereafter. In contrast, acute application of zinc to CA1 pyramidal cells promptly blocked I(CaT). These data indicate that extracellular zinc has a dual effect on I(CaT), blocking it acutely while causing its long-term upregulation. Through the latter effect, zinc may regulate the intrinsic excitability of principal neurons, particularly in pathological conditions associated with enhanced release of zinc, such as SE.
TL;DR: Resemblance of protective reactions of wheat plants affected by SA and NO appeared as the alteration of energy and antioxidant balance of studied plants was identified and the resemblance possibly evidences of common signaling pathway for SA andNO caused by effect of toxic concentrations of heavy metals.
Abstract: This article studies the effect of salicylic acid (SA) and nitric oxide (NO) on Triticum aestivum L. wheat plants exposed to the influence of high concentrations of copper and zinc compounds. It is shown that heavy metals (HMs) caused a decrease in the growth parameters in the overground and underground plant parts and contributed to a sharp deterioration in the energy balance and the situation regarding oxidative stress. SA and NO exerted a protective effect, which was expressed in the increased ability to accumulate shoot and root mass, stabilize the energy balance, and reduced lipid peroxidation.