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Cole TR, Igumenova TI. Reactivity of Thiol-Rich Zn Sites in Diacylglycerol-Sensing PKC C1 Domain Probed by NMR Spectroscopy. Front Mol Biosci 2021; 8:728711. [PMID: 34447788 PMCID: PMC8382798 DOI: 10.3389/fmolb.2021.728711] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2021] [Accepted: 07/27/2021] [Indexed: 11/13/2022] Open
Abstract
Conserved homology 1 (C1) domains are peripheral zinc finger domains that are responsible for recruiting their host signaling proteins, including Protein Kinase C (PKC) isoenzymes, to diacylglycerol-containing lipid membranes. In this work, we investigated the reactivity of the C1 structural zinc sites, using the cysteine-rich C1B regulatory region of the PKCα isoform as a paradigm. The choice of Cd2+ as a probe was prompted by previous findings that xenobiotic metal ions modulate PKC activity. Using solution NMR and UV-vis spectroscopy, we found that Cd2+ spontaneously replaced Zn2+ in both structural sites of the C1B domain, with the formation of all-Cd and mixed Zn/Cd protein species. The Cd2+ substitution for Zn2+ preserved the C1B fold and function, as probed by its ability to interact with a potent tumor-promoting agent. Both Cys3His metal-ion sites of C1B have higher affinity to Cd2+ than Zn2+, but are thermodynamically and kinetically inequivalent with respect to the metal ion replacement, despite the identical coordination spheres. We find that even in the presence of the oxygen-rich sites presented by the neighboring peripheral membrane-binding C2 domain, the thiol-rich sites can successfully compete for the available Cd2+. Our results indicate that Cd2+ can target the entire membrane-binding regulatory region of PKCs, and that the competition between the thiol- and oxygen-rich sites will likely determine the activation pattern of PKCs.
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Affiliation(s)
- Taylor R Cole
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, United States
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Cell organelles as targets of mammalian cadmium toxicity. Arch Toxicol 2020; 94:1017-1049. [PMID: 32206829 DOI: 10.1007/s00204-020-02692-8] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 02/25/2020] [Indexed: 02/07/2023]
Abstract
Ever increasing environmental presence of cadmium as a consequence of industrial activities is considered a health hazard and is closely linked to deteriorating global health status. General animal and human cadmium exposure ranges from ingestion of foodstuffs sourced from heavily polluted hotspots and cigarette smoke to widespread contamination of air and water, including cadmium-containing microplastics found in household water. Cadmium is promiscuous in its effects and exerts numerous cellular perturbations based on direct interactions with macromolecules and its capacity to mimic or displace essential physiological ions, such as iron and zinc. Cell organelles use lipid membranes to form complex tightly-regulated, compartmentalized networks with specialized functions, which are fundamental to life. Interorganellar communication is crucial for orchestrating correct cell behavior, such as adaptive stress responses, and can be mediated by the release of signaling molecules, exchange of organelle contents, mechanical force generated through organelle shape changes or direct membrane contact sites. In this review, cadmium effects on organellar structure and function will be critically discussed with particular consideration to disruption of organelle physiology in vertebrates.
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Cole TR, Erickson SG, Morales KA, Sung M, Holzenburg A, Igumenova TI. Cd(II)- and Pb(II)-Induced Self-Assembly of Peripheral Membrane Domains from Protein Kinase C. Biochemistry 2019; 58:509-513. [PMID: 30584764 DOI: 10.1021/acs.biochem.8b01235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cd2+ and Pb2+ are xenobiotic heavy metal ions that use ionic mimicry to interfere with the cellular function of biomacromolecules. Using a combination of SAXS, electron microscopy, FRET, and solution NMR spectroscopy, we demonstrate that treatment with Cd2+ and Pb2+ causes self-assembly of protein kinase C regulatory domains that peripherally associate with membranes. The self-assembly process successfully competes with ionic mimicry and is mediated by conserved protein regions that are distinct from the canonical Ca2+-binding motifs of protein kinase C. The ability of protein oligomers to interact with anionic membranes is enhanced compared to the monomeric species. Our findings suggest that metal-ion-dependent peripheral membrane domains can be utilized for generating protein-metal-ion nanoclusters and serve as biotemplates for the design of sequestration agents.
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Affiliation(s)
- Taylor R Cole
- Department of Biochemistry and Biophysics , Texas A&M University , 300 Olsen Boulevard , College Station , Texas 77843 , United States
| | - Samuel G Erickson
- Department of Biochemistry and Biophysics , Texas A&M University , 300 Olsen Boulevard , College Station , Texas 77843 , United States
| | - Krystal A Morales
- Department of Biochemistry and Biophysics , Texas A&M University , 300 Olsen Boulevard , College Station , Texas 77843 , United States
| | - MinWoo Sung
- Department of Biology , Texas A&M University , College Station , Texas 77843 , United States
| | - Andreas Holzenburg
- School of Medicine , University of Texas Rio Grande Valley , Harlingen , Texas 78550 , United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics , Texas A&M University , 300 Olsen Boulevard , College Station , Texas 77843 , United States
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Cao X, Lin H, Muskhelishvili L, Latendresse J, Richter P, Heflich RH. Tight junction disruption by cadmium in an in vitro human airway tissue model. Respir Res 2015; 16:30. [PMID: 25851441 PMCID: PMC4352288 DOI: 10.1186/s12931-015-0191-9] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2014] [Accepted: 02/10/2015] [Indexed: 02/01/2023] Open
Abstract
Background The cadmium (Cd) present in air pollutants and cigarette smoke has the potential of causing multiple adverse health outcomes involving damage to pulmonary and cardiovascular tissue. Injury to pulmonary epithelium may include alterations in tight junction (TJ) integrity, resulting in impaired epithelial barrier function and enhanced penetration of chemicals and biomolecules. Herein, we investigated mechanisms involved in the disruption of TJ integrity by Cd exposure using an in vitro human air-liquid-interface (ALI) airway tissue model derived from normal primary human bronchial epithelial cells. Methods ALI cultures were exposed to noncytotoxic doses of CdCl2 basolaterally and TJ integrity was measured by Trans-Epithelial Electrical Resistance (TEER) and immunofluorescence staining with TJ markers. PCR array analysis was used to identify genes involved with TJ collapse. To explore the involvement of kinase signaling pathways, cultures were treated with CdCl2 in the presence of kinase inhibitors specific for cellular Src or Protein Kinase C (PKC). Results Noncytotoxic doses of CdCl2 resulted in the collapse of barrier function, as demonstrated by TEER measurements and Zonula occludens-1 (ZO-1) and occludin staining. CdCl2 exposure altered the expression of several groups of genes encoding proteins involved in TJ homeostasis. In particular, down-regulation of select junction-interacting proteins suggested that a possible mechanism for Cd toxicity involves disruption of the peripheral junctional complexes implicated in connecting membrane-bound TJ components to the actin cytoskeleton. Inhibition of kinase signaling using inhibitors specific for cellular Src or PKC preserved the integrity of TJs, possibly by preventing occludin tyrosine hyperphosphorylation, rather than reversing the down-regulation of the junction-interacting proteins. Conclusions Our findings indicate that acute doses of Cd likely disrupt TJ integrity in human ALI airway cultures both through occludin hyperphosphorylation via kinase activation and by direct disruption of the junction-interacting complex.
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Abstract
Rapid advances in redox systems biology are creating new opportunities to understand complexities of human disease and contributions of environmental exposures. New understanding of thiol-disulfide systems have occurred during the past decade as a consequence of the discoveries that thiol and disulfide systems are maintained in kinetically controlled steady states displaced from thermodynamic equilibrium, that a widely distributed family of NADPH oxidases produces oxidants that function in cell signaling and that a family of peroxiredoxins utilize thioredoxin as a reductant to complement the well-studied glutathione antioxidant system for peroxide elimination and redox regulation. This review focuses on thiol/disulfide redox state in biologic systems and the knowledge base available to support development of integrated redox systems biology models to better understand the function and dysfunction of thiol-disulfide redox systems. In particular, central principles have emerged concerning redox compartmentalization and utility of thiol/disulfide redox measures as indicators of physiologic function. Advances in redox proteomics show that, in addition to functioning in protein active sites and cell signaling, cysteine residues also serve as redox sensors to integrate biologic functions. These advances provide a framework for translation of redox systems biology concepts to practical use in understanding and treating human disease. Biological responses to cadmium, a widespread environmental agent, are used to illustrate the utility of these advances to the understanding of complex pleiotropic toxicities.
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Affiliation(s)
- Young-Mi Go
- Division of Pulmonary, Allergy and Critical Care Medicine, Department of Medicine, Emory University, Atlanta, GA 30322, USA
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Li R, Zhou Y, Wang L, Ren G. Low-molecular-weight-chitosan ameliorates cadmium-induced toxicity in the freshwater crab, Sinopotamon yangtsekiense. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2011; 74:1164-1170. [PMID: 21392824 DOI: 10.1016/j.ecoenv.2011.02.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2011] [Revised: 02/15/2011] [Accepted: 02/20/2011] [Indexed: 05/30/2023]
Abstract
Cadmium (Cd) has been shown to induce oxidative stress. Low-molecular-weight-chitosan (LMWC) has been demonstrated to exhibit potent antioxidant effects. We investigated the regulation role in Cd²⁺-induced oxidative damage in the hepatopancreas of the freshwater crab Sinopotamon yangtsekiense and the protective effect of LMWC. The results showed that Cd²⁺ significantly increased the hepatopancreatic metallothionein (MT) mRNA levels and protein kinase C (PKC) activity while decreasing the activities of Na⁺,K⁺-ATPase and Ca²⁺-ATPase in crabs relative to the control group. Co-treatment with LMWC suppressed the levels of MT and PKC but raised the activities of Na⁺,K+-ATPase and Ca²⁺-ATPase in hepatopancreatic tissues compared with the crabs exposed to Cd²⁺ alone. We postulate that LMWC may exert its protective effect through regulating the expressions of MT, PKC, Na⁺,K⁺-ATPase and Ca²⁺-ATPase, thereby enhancing antioxidant defense. These observations suggest that LMWC may be beneficial because of its ability to alleviate the Cd²⁺-induced damages to the crabs.
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Affiliation(s)
- Ruijin Li
- School of Life Science, Shanxi University, Taiyuan 030006, Shanxi Province, PR China
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Pan Y, Yuan D, Zhang J, Xu P, Chen H, Shao C. Cadmium-Induced Adaptive Response in Cells of Chinese Hamster Ovary Cell Lines with Varying DNA Repair Capacity. Radiat Res 2009; 171:446-53. [DOI: 10.1667/rr1491.1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Martin P, Boulukos KE, Poggi MC, Pognonec P. Long-term extracellular signal-related kinase activation following cadmium intoxication is negatively regulated by a protein kinase C-dependent pathway affecting cadmium transport. FEBS J 2009; 276:1667-79. [DOI: 10.1111/j.1742-4658.2009.06899.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Prozialeck WC, Edwards JR. Cell adhesion molecules in chemically-induced renal injury. Pharmacol Ther 2007; 114:74-93. [PMID: 17316817 PMCID: PMC1913814 DOI: 10.1016/j.pharmthera.2007.01.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2007] [Accepted: 01/05/2007] [Indexed: 01/15/2023]
Abstract
Cell adhesion molecules are integral cell-membrane proteins that maintain cell-cell and cell-substrate adhesion and in some cases act as regulators of intracellular signaling cascades. In the kidney, cell adhesion molecules, such as the cadherins, the catenins, the zonula occludens protein-1 (ZO-1), occludin and the claudins are essential for maintaining the epithelial polarity and barrier integrity that are necessary for the normal absorption/excretion of fluid and solutes. A growing volume of evidence indicates that these cell adhesion molecules are important early targets for a variety of nephrotoxic substances including metals, drugs, and venom components. In addition, it is now widely appreciated that molecules, such as intracellular adhesion molecule-1 (ICAM-1), integrins, and selectins play important roles in the recruitment of leukocytes and inflammatory responses that are associated with nephrotoxic injury. This review summarizes the results of recent in vitro and in vivo studies indicating that these cell adhesion molecules may be primary molecular targets in many types of chemically-induced renal injury. Some of the specific agents that are discussed include cadmium (Cd), mercury (Hg), bismuth (Bi), cisplatin, aminoglycoside antibiotics, S-(1,2-dichlorovinyl)-l-cysteine (DCVC), and various venom toxins. This review also includes a discussion of the various mechanisms, by which these substances can affect cell adhesion molecules in the kidney.
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Affiliation(s)
- Walter C Prozialeck
- Department of Pharmacology, Midwestern University, 555 31st Street, Downers Grove, IL 60515, United States.
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10
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The vascular endothelium as a target of cadmium toxicity. Life Sci 2006; 79:1493-506. [PMID: 16765992 DOI: 10.1016/j.lfs.2006.05.007] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 04/18/2006] [Accepted: 05/10/2006] [Indexed: 12/16/2022]
Abstract
Cadmium (Cd) is an important industrial and environmental pollutant that can produce a wide variety of adverse effects in humans and animals. A growing volume of evidence indicates that the vascular endothelium may be one of the primary targets of Cd toxicity in vivo. Studies over the past 20 years have shown that Cd, at relatively low, sublethal concentrations, can target vascular endothelial cells at a variety of molecular levels, including cell adhesion molecules, metal ion transporters and protein kinase signaling pathways. The purpose of this review is to summarize the results of these recent studies and to discuss the implications of these findings with regard to the mechanisms of Cd toxicity in specific organs including the lung, liver, kidney, testis and heart. In addition the possible roles of the vascular endothelium in mediating the tumor promoting and anticarcinogenic effects of Cd are discussed.
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Matsumoto ST, Mantovani MS, Malaguttii MIA, Dias AL, Fonseca IC, Marin-Morales MA. Genotoxicity and mutagenicity of water contaminated with tannery effluents, as evaluated by the micronucleus test and comet assay using the fish Oreochromis niloticus and chromosome aberrations in onion root-tips. Genet Mol Biol 2006. [DOI: 10.1590/s1415-47572006000100028] [Citation(s) in RCA: 190] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Dong J, Song MO, Freedman JH. Identification and characterization of a family of Caenorhabditis elegans genes that is homologous to the cadmium-responsive gene cdr-1. ACTA ACUST UNITED AC 2005; 1727:16-26. [PMID: 15652154 DOI: 10.1016/j.bbaexp.2004.11.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2004] [Revised: 11/03/2004] [Accepted: 11/09/2004] [Indexed: 11/16/2022]
Abstract
Six Caenorhabditis elegans genes that are homologous to the novel, cadmium-responsive gene cdr-1 have been identified and characterized. Nucleotide and amino acid sequence comparisons among the CDR family, which includes cdr-1, cdr-2, cdr-3, cdr-4, cdr-5, cdr-6, and cdr-7, reveals a high degree of identity among the seven members in this family. There are high levels of amino acid and nucleotide sequence similarity in the lengths of the open reading frames, predicted sizes, and protein characteristics. The seven proteins are predicted to be extremely hydrophobic, and are classified as integral membrane proteins. Structural analysis of the predicted proteins suggests that they may have similar biological functions. In response to cadmium exposure, cdr-1, cdr-2, cdr-3, and cdr-4 transcription significantly increases. In contrast, the levels of cdr-5, cdr-6, and cdr-7 transcription are not significantly affected or inhibited by cadmium exposure. Further, in non-exposed C. elegans, cdr-2, cdr-4, cdr-6, and cdr-7 are constitutively expressed. When CDR-1 expression was inhibited using RNAi, numerous fluid droplets were observed throughout the nematode body cavity. This phenotype became more pronounced in the presence of hypotonic stress. This suggests that CDR-1 may function in osmoregulation to maintain salt balance in C. elegans.
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Affiliation(s)
- Jie Dong
- Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA
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13
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Abstract
Cadmium is a heavy metal, which is widely used in industry, affecting human health through occupational and environmental exposure. In mammals, it exerts multiple toxic effects and has been classified as a human carcinogen by the International Agency for Research on Cancer. Cadmium affects cell proliferation, differentiation, apoptosis and other cellular activities. Cd2+ does not catalyze Fenton-type reactions because it does not accept or donate electrons under physiological conditions, and it is only weakly genotoxic. Hence, indirect mechanisms are implicated in the carcinogenicity of cadmium. In this review multiple mechanisms are discussed, such as modulation of gene expression and signal transduction, interference with enzymes of the cellular antioxidant system and generation of reactive oxygen species (ROS), inhibition of DNA repair and DNA methylation, role in apoptosis and disruption of E-cadherin-mediated cell-cell adhesion. Cadmium affects both gene transcription and translation. The major mechanisms of gene induction by cadmium known so far are modulation of cellular signal transduction pathways by enhancement of protein phosphorylation and activation of transcription and translation factors. Cadmium interferes with antioxidant defense mechanisms and stimulates the production of reactive oxygen species, which may act as signaling molecules in the induction of gene expression and apoptosis. The inhibition of DNA repair processes by cadmium represents a mechanism by which cadmium enhances the genotoxicity of other agents and may contribute to the tumor initiation by this metal. The disruption of E-cadherin-mediated cell-cell adhesion by cadmium probably further stimulates the development of tumors. It becomes clear that there exist multiple mechanisms which contribute to the carcinogenicity of cadmium, although the relative weights of these contributions are difficult to estimate.
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Affiliation(s)
- Michael Waisberg
- Department of Land Resource Science, University of Guelph, Guelph, Ont., Canada.
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Han TK, Derby M, Martin DF, Wright SD, Dao ML. Effects of brevetoxins on murine myeloma SP2/O cells: aberrant cellular division. Int J Toxicol 2003; 22:73-80. [PMID: 12745987 DOI: 10.1080/10915810305095] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Massive deaths of manatees (Trichechus manatus latirostris) during the red tide seasons have been attributed to brevetoxins produced by the dinoflagellate Karenia brevis (formerly Ptychodiscus breve and Gymnodinium breve). Although these toxins have been found in macrophages and lymphocytes in the lung, liver, and secondary lymphoid tissues of these animals, the molecular mechanisms of brevetoxicosis have not yet been identified. To investigate the effects of brevetoxins on immune cells, a murine myeloma cell line (SP2/O) was used as a model for in vitro studies. By adding brevetoxins to cultures of the SP2/O cells at concentrations ranging from 20 to 600 ng/ml, an apparent increase in proliferation was observed at around 2 hours post challenge as compared to the unchallenged cell cultures. This was followed by a drop in cell number at around 3 hours, suggesting an aberrant effect of brevetoxins on cellular division, the cells generated at 2 hours being apparently short-lived. In situ immunochemical staining of the SP2/O cells at 1 and 2 hour post challenge showed an accumulation of the toxins in the nucleus. A 21-kDa protein was subsequently isolated from the SP2/O cells as having brevetoxin-binding properties, and immunologically identified as p21, a nuclear factor known to down-regulate cellular proliferation through inhibition of cyclin-dependent kinases. These data are the first on a possible effect of brevetoxins on the cell cycle via binding to p21, a phenomenon that needs to be further investigated and validated in normal immune cells.
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Affiliation(s)
- Thomas K Han
- Department of Biology, University of South Florida, Tampa, Florida 33620-5150, USA
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Wätjen W, Haase H, Biagioli M, Beyersmann D. Induction of apoptosis in mammalian cells by cadmium and zinc. ENVIRONMENTAL HEALTH PERSPECTIVES 2002; 110 Suppl 5:865-7. [PMID: 12426148 PMCID: PMC1241262 DOI: 10.1289/ehp.110-1241262] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
In various mammalian cells, two group IIb metals, cadmium and zinc, induce several morphological and biochemical effects that are salient features of programmed cell death. In C6 rat glioma cells, cadmium caused externalization of phosphatidylserine, breakdown of the mitochondrial membrane potential, activation of caspase-9, internucleosomal DNA fragmentation, chromatin condensation, and nuclear fragmentation. In NIH3T3 murine fibroblasts, cadmium-induced apoptosis was inhibited by overexpression of the antiapoptotic protein Bcl-2. Cadmium-induced DNA fragmentation in C6 cells was independent of inhibition of protein kinase A (PKA), protein kinase C (PKC), mitogen-activated protein kinase (MAPK), phosphatidylinositol-3-kinase, Ca-calmodulin-dependent protein kinase, and protein kinase G. Zinc at moderate concentrations (10-50 microM) protected against programmed cell death induced by cadmium, whereas deprivation of zinc by the membrane-permeable chelator N,N,N',N-terakis-(2-pyridylmethyl)ethylenediamine (TPEN) caused cell death with features characteristic of apoptosis. On the other hand, at elevated extracellular levels (150-200 microM), zinc alone caused programmed cell death in C6 cells. Zinc-induced apoptosis was independent of inhibition of PKA, PKC, guanylate cyclase and MAPK, but it was suppressed in the presence of 100 microM lanthanum chloride.
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Affiliation(s)
- Wim Wätjen
- Department of Biology and Chemistry, University of Bremen, D-28334 Bremen, Germany
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Wätjen W, Haase H, Biagioli M, Beyersmann D. Induction of apoptosis in mammalian cells by cadmium and zinc. ENVIRONMENTAL HEALTH PERSPECTIVES 2002; 110 Suppl 5:865-867. [PMID: 12426148 DOI: 10.1289/ehp.02110s5865] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
In various mammalian cells, two group IIb metals, cadmium and zinc, induce several morphological and biochemical effects that are salient features of programmed cell death. In C6 rat glioma cells, cadmium caused externalization of phosphatidylserine, breakdown of the mitochondrial membrane potential, activation of caspase-9, internucleosomal DNA fragmentation, chromatin condensation, and nuclear fragmentation. In NIH3T3 murine fibroblasts, cadmium-induced apoptosis was inhibited by overexpression of the antiapoptotic protein Bcl-2. Cadmium-induced DNA fragmentation in C6 cells was independent of inhibition of protein kinase A (PKA), protein kinase C (PKC), mitogen-activated protein kinase (MAPK), phosphatidylinositol-3-kinase, Ca-calmodulin-dependent protein kinase, and protein kinase G. Zinc at moderate concentrations (10-50 microM) protected against programmed cell death induced by cadmium, whereas deprivation of zinc by the membrane-permeable chelator N,N,N',N-terakis-(2-pyridylmethyl)ethylenediamine (TPEN) caused cell death with features characteristic of apoptosis. On the other hand, at elevated extracellular levels (150-200 microM), zinc alone caused programmed cell death in C6 cells. Zinc-induced apoptosis was independent of inhibition of PKA, PKC, guanylate cyclase and MAPK, but it was suppressed in the presence of 100 microM lanthanum chloride.
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Affiliation(s)
- Wim Wätjen
- Department of Biology and Chemistry, University of Bremen, D-28334 Bremen, Germany
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Daniels PJ, Bittel D, Smirnova IV, Winge DR, Andrews GK. Mammalian metal response element-binding transcription factor-1 functions as a zinc sensor in yeast, but not as a sensor of cadmium or oxidative stress. Nucleic Acids Res 2002; 30:3130-40. [PMID: 12136095 PMCID: PMC135752 DOI: 10.1093/nar/gkf432] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2002] [Revised: 05/24/2002] [Accepted: 05/24/2002] [Indexed: 11/12/2022] Open
Abstract
The zinc finger protein, metal response element-binding transcription factor-1 (MTF-1) regulates the expression of genes in response to metal ions and oxidative stress. The precise mechanisms by which this occurs are not understood. To further examine this problem, mouse MTF-1 was expressed in Saccharomyces cerevisiae and tested for the ability to activate metal response element-driven reporter gene expression. Zinc was an effective inducer of reporter gene expression. In general, the magnitude of zinc induction was dependent on the concentration of zinc in the culture medium, but independent of the amount of MTF-1 expression. Zinc induction also occurred with either integrated or episomal reporter plasmids containing the native mouse metallothionein-I proximal promoter. Deletion of fingers 5 and 6 of MTF-1, which function in a zinc-dependent manner to stabilize the DNA-binding activity of the protein in vitro, did not diminish the zinc induction of either episomal or integrated promoters. However, a Gal4 DNA-binding domain- MTF-1 fusion protein, which binds constitutively to the Gal4-responsive promoter, was not zinc inducible but caused constitutive activation of reporter gene expression. This suggests that zinc activation of the DNA-binding activity of MTF-1 is the rate limiting step in its metalloregulatory function in yeast. In contrast, MTF-1 was not responsive to either cadmium or hydrogen peroxide, suggesting that distinct co-activators or signal transduction cascades not found in yeast are required to mediate MTF-1 activation of gene expression by this toxic metal and by oxidative stress.
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Affiliation(s)
- Patrick J Daniels
- Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, KS 66160-7421, USA
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Jeon SH, Cho MH, Cho JH. Effects of cadmium on gap junctional intercellular communication in WB-F344 rat liver epithelial cells. Hum Exp Toxicol 2001; 20:577-83. [PMID: 11926612 DOI: 10.1191/096032701718620855] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Cadmium has been associated with a number of tumors but its role in tumor promotion has not been elucidated clearly or the results obtained from various studies have been conflicting. This study was designed to investigate the effects of cadmium on the gap junctional intercellular communication (GJIC), number of gap junctions per cell, and cell proliferation in WB-F344 rat liver epithelial cells from the viewpoint of tumor promotion. GJIC was monitored by counting the cells stained with Lucifer yellow CH dye, using the scrape-loading and dye-transfer method. The numbers of gap junctions per cell were visually quantitated after an indirect immunostaining for gap junction protein using an antibody to connexin 43. Cell proliferation was assayed by direct counting of the living cells using the trypan blue dye exclusion method. In the time course study, cells treated with 200 microM CdCl2 showed rapid and nearly complete inhibition of GJIC (approximately 14% of the control) and a decrease in the number of gap junctions per cell (approximately 21% of the control) at 30 min, and the decrease continued up to 4 h without any changes in the cell viability. Treatment with CdCl2 (7.4-200 microM) for 4 h resulted in the decrease of GJIC and gap junction numbers per cell in a dose-response pattern without changes in the cell viability. In the long-term (14 days) exposure studies at doses of 0.01-7.4 microM CdCl2, an increase in cell proliferation was observed at low doses of 0.03-2.5 microM CdCl2, with GJIC also decreasing. These data demonstrate that cadmium inhibits GJIC, reduces the number of gap junctions per cell, and induces cell proliferation while decreasing the function of the gap junction.
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Affiliation(s)
- S H Jeon
- National Veterinary Research and Quarantine Service, Anyang, South Korea
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Calevro F, Campani S, Ragghianti M, Bucci S, Mancino G. Tests of toxicity and teratogenicity in biphasic vertebrates treated with heavy metals (Cr3+, Al3+, Cd2+). CHEMOSPHERE 1998; 37:3011-3017. [PMID: 9839411 DOI: 10.1016/s0045-6535(98)00342-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Developmental toxicity of chromium(III), aluminium(III) and cadmium(II) were evaluated by examining abnormalities and mortality in embryos belonging to different species of amphibians. Cr(III) and Al(III) are lethal at 1.5 mM concentration, and seriously affect the differentiation of central nervous system, skeleton and eye, and cause cephalic and trunk oedemas at lower concentrations, being aluminium significantly more harmful than chromium. Cd(II), tested only in P. waltl, is highly toxic: embryos exposed to concentrations ranging from 0.18 to 50 microM display malformations, delay and arrest of development in a dose dependent manner.
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Affiliation(s)
- F Calevro
- Dipartimento di Fisiologia e Biochimica, Università di Pisa, Ghezzano (PI), Italy
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Yang JL, Chao JI, Lin JG. Reactive oxygen species may participate in the mutagenicity and mutational spectrum of cadmium in Chinese hamster ovary-K1 cells. Chem Res Toxicol 1996; 9:1360-7. [PMID: 8951241 DOI: 10.1021/tx960122y] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The molecular nature of mutations induced by Cd was investigated in this study to elucidate the role of Cd in the initiation of carcinogenesis. Exposing Chinese hamster ovary (CHO)-K1 cells to cadmium acetate markedly decreased the colony-forming ability of cells and induced mutation frequency in the hypoxanthine (guanine) phosphoribosyltransferase (hprt) gene. The mutation frequency induced by Cd at LD30-LD20 doses was approximately 20 times that of untreated cells. D-Mannitol, a scavenger of reactive oxygen species (ROS), significantly protects cells against Cd cytotoxicity and mutagenicity. Furthermore, non-cytotoxic doses of 3-amino-1,2,4-triazole, a catalase inhibitor, potentiates Cd cytotoxicity and mutagenicity. The cellular Cd uptake ability was not altered by the combined treatment with either D-mannitol or 3-amino-1,2,4-triazole. The GSH level and the activities of GSH peroxidase, GSSG reductase, and catalase in cells treated with Cd (4 microM, 4 h) decreased to 78%, 47%, 40%, and 22% of the untreated cells, respectively. Those enzymatic activities recovered to normal levels 8 h after removing Cd. Polymerase chain reaction and DNA sequencing analysis of 54 independent Cd mutants revealed Cd-induced base substitutions, splice mutations, and large genomic deletions. All six types of base substitutions were observed; however, base transversions (22/27; 81%) occurred more frequently than transitions (5/27; 19%). The frequencies of mutations occurring at T.A or G.C base pairs were roughly equal. Results in this study strongly suggest that Cd mutagenicity in CHO-K1 cells is ROS-dependent. Moreover, the unique mutational spectrum induced by Cd implies that specific DNA adducts generated through the interaction of Cd-DNA and ROS may play a role in the mutational specificity.
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Affiliation(s)
- J L Yang
- Department of Life Sciences, National Tsing Hua University, Taiwan, Republic of China.
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Abshire MK, Buzard GS, Shiraishi N, Waalkes MP. Induction of c-myc and c-jun proto-oncogene expression in rat L6 myoblasts by cadmium is inhibited by zinc preinduction of the metallothionein gene. JOURNAL OF TOXICOLOGY AND ENVIRONMENTAL HEALTH 1996; 48:359-77. [PMID: 8691507 DOI: 10.1080/009841096161258] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Certain proto-oncogenes transfer growth regulatory signals from the cell surface to the nucleus. These genes often show activation soon after cells are exposed to mitogenic stimulation but can also be activated as a nonmitogenic stress response. Cadmium (Cd) is a carcinogenic metal in humans and rodents and, though its mechanism of action is unknown, it could involve activation of such proto-oncogenes. Metallothionein (MT), a metal-inducible protein that binds Cd, can protect against many aspects of Cd toxicity, including genotoxicity and possibly carcinogenesis. Thus, the effects of Cd on expression of c-myc and c-jun in rat L6 myoblasts, and the effect of preactivation of the MT gene by Zn treatment on such oncogene expression, were studied. MT protein levels were determined by the Cd-heme assay, and MT, c-myc, and c-jun mRNA levels were measured using oligonucleotide hybridization and standardized to beta-actin levels. Cd (5 microM CdCl2, 0-30 h) stimulated both c-myc and c-jun mRNA expression. An initial peak of activation of c-myc expression occurred 2 h after initiation of Cd exposure, and levels remained elevated throughout the assessment period. Zn pretreatment markedly reduced the activation of c-myc expression by Cd compared to cells not receiving Zn pretreatment. Cd treatment increased c-jun mRNA levels by up to 3.5-fold. Again, Zn pretreatment markedly reduced Cd-induced activation of c-jun expression as minimal increases occurred with Cd exposures of < or = 1 h, but otherwise the Zn pretreatment prevented activation of c-jun. The Zn pretreatment elevated MT protein levels > 5-fold over control at the point of Cd exposure, but Cd exposure did not further elevate these Zn-induced MT levels. Similarly, Zn pretreatment did not result in increased relative MT mRNA levels above Cd exposure alone at various time points after Cd exposure. Therefore, Zn pretreatment, possibly by providing elevated MT protein levels at the point of Cd exposure, inhibited the Cd-induced c-myc and c-jun proto-oncogene expression. The extent of Cd-induced proto-oncogene activation thus may be limited by the presence of cellular MT.
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Affiliation(s)
- M K Abshire
- Inorganic Carcinogenesis Section, National Cancer Institute, Frederick Cancer Research and Development Center, Maryland 21702, USA
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