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1.
Curr Drug Targets ; 7(5): 607-627, 2006 May.
Article in English | MEDLINE | ID: mdl-16719771

ABSTRACT

The dietary group IIb metal zinc (Zn) plays essential housekeeping roles in cellular metabolism and gene expression. It regulates a number of cellular processes including mitosis, apoptosis, secretion and signal transduction as well as critical events in physiological processes as diverse as insulin release, T cell cytokine production, wound healing, vision and neurotransmission. Critical to these processes are the mechanisms that regulate Zn homeostasis in cells and tissues. The proteins that control Zn uptake and compartmentalization are rapidly being identified and characterized. Recently, the first images of sub-cellular pools of Zn in airway epithelium have been obtained. This review discusses what we currently know about Zn in the airways, both in the normal and inflamed states, and then considers how we might target Zn metabolism by developing strategies to monitor and manipulate airway Zn levels in airway disease.


Subject(s)
Asthma/drug therapy , Carrier Proteins/physiology , Zinc/physiology , Absorption , Animals , Asthma/metabolism , Bronchi/metabolism , Cation Transport Proteins/physiology , Homeostasis , Humans , Trachea/metabolism , Zinc/administration & dosage , Zinc/deficiency
2.
Immunol Cell Biol ; 79(2): 170-7, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11264713

ABSTRACT

Over the past 30 years, many researchers have demonstrated the critical role of zinc (Zn), a group IIb metal, in diverse physiological processes, such as growth and development, maintenance and priming of the immune system, and tissue repair. This review will discuss aspects of Zn physiology and its possible beneficial role in the respiratory epithelium. Here we have detailed the mechanisms by which Zn diversely acts as: (i) an anti-oxidant; (ii) an organelle stabilizer; (iii) an anti-apopototic agent; (iv) an important cofactor for DNA synthesis; (v) a vital component for wound healing; and (vi) an anti-inflammatory agent. This paper will also review studies from the authors' laboratory concerning the first attempts to map Zn in the respiratory epithelium and to elucidate its role in regulating caspase-3 activated apoptosis. We propose that Zn, being a major dietary anti-oxidant has a protective role for the airway epithelium against oxyradicals and other noxious agents. Zn may therefore have important implications for asthma and other inflammatory diseases where the physical barrier is vulnerable and compromised.


Subject(s)
Asthma/immunology , Respiratory Mucosa/immunology , Zinc/physiology , Animals , Apoptosis/immunology , Asthma/etiology , Caspases/metabolism , Enzyme Activation , Humans , Respiratory Mucosa/injuries , Respiratory System/immunology , Respiratory Tract Diseases/immunology , Respiratory Tract Diseases/physiopathology , Zinc/deficiency , Zinc/metabolism
3.
Biometals ; 14(3-4): 315-30, 2001.
Article in English | MEDLINE | ID: mdl-11831462

ABSTRACT

In addition to its diverse role in many physiological systems, zinc (Zn) has now been shown to be an important regulator of apoptosis. The purpose of this review is to integrate previously published knowledge on Zn and apoptosis with current attempts to elucidate the mechanisms of action of this biometal. This paper begins with an introduction to apoptosis and then briefly reviews the evidence relating Zn to apoptosis. The major focus of this review is the mechanistic actions of Zn and its candidate intracellular targets. In particular, we examine the cytoprotective functions of Zn which suppress major pathways leading to apoptosis, as well as the more direct influence of Zn on the apoptotic regulators, especially the caspase family of enzymes. These two mechanisms are closely related since a decline in intracellular Zn below a critical threshold level may not only trigger pathways leading to caspase activation but may also facilitate the process by which the caspases are activated. Studies by our laboratory in airway epithelial cells show that Zn is co-localized with the precursor form of caspase-3, mitochondria and microtubules, suggesting this Zn is critically placed to control apoptosis. Further understanding the different pools of Zn and how they interact with apoptotic pathways should have importance in human disease.


Subject(s)
Apoptosis/physiology , Caspases/metabolism , Zinc/metabolism , Animals , Antioxidants/metabolism , Apoptosis/drug effects , Caspase 3 , Caspase 6 , Caspase 9 , Enzyme Activation/drug effects , Epithelial Cells/cytology , Epithelial Cells/metabolism , Homeostasis , Humans , Models, Biological , Necrosis , Respiratory System/cytology , Respiratory System/metabolism , Zinc/pharmacology
4.
Am J Physiol Lung Cell Mol Physiol ; 279(6): L1172-83, 2000 Dec.
Article in English | MEDLINE | ID: mdl-11076807

ABSTRACT

The respiratory epithelium is vulnerable to noxious substances, resulting in the shedding of cells and decreased protection. Zinc (Zn), an antioxidant and cytoprotectant, can suppress apoptosis in a variety of cells. Here we used the novel Zn-specific fluorophore Zinquin to visualize and quantify labile intracellular Zn in respiratory epithelial cells. Zinquin fluorescence in isolated ciliated tracheobronchial epithelial cells and intact epithelium from sheep and pigs revealed an intense fluorescence in the apical and mitochondria-rich cytoplasm below the cilia. Zinquin fluorescence was quenched by the Zn chelator N,N,N', N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and increased by the Zn ionophore pyrithione. We also assessed whether changes in intracellular labile Zn would influence susceptibility of these cells to apoptosis by hydrogen peroxide. Our results confirm that Zn deficiency enhanced hydrogen peroxide-induced caspase activation from 1.24 +/- 0.12 to 2.58 +/- 0.53 units. microg protein(-1). h(-1) (P

Subject(s)
Apoptosis/physiology , Respiratory Mucosa/chemistry , Respiratory Mucosa/cytology , Zinc/analysis , Zinc/physiology , Adenocarcinoma, Bronchiolo-Alveolar , Animals , Apoptosis/drug effects , Bronchi/cytology , Butyrates/pharmacology , Caspase 3 , Caspases/metabolism , Chelating Agents/pharmacology , Coumarins/pharmacology , Drug Synergism , Enzyme Activation/drug effects , Epithelial Cells/chemistry , Epithelial Cells/enzymology , Epithelial Cells/ultrastructure , Ethylenediamines/pharmacology , Fluorescent Dyes , Humans , Hydrogen Peroxide/pharmacology , Lung Neoplasms , Microscopy, Electron , Microscopy, Fluorescence , Oligopeptides/pharmacology , Oxidants/pharmacology , Pulmonary Alveoli/cytology , Quinolones , Sheep , Swine , Tosyl Compounds , Trachea/cytology , Tumor Cells, Cultured/chemistry , Tumor Cells, Cultured/cytology , Tumor Cells, Cultured/enzymology
5.
J Infect Dis ; 182 Suppl 1: S85-92, 2000 Sep.
Article in English | MEDLINE | ID: mdl-11041715

ABSTRACT

To better understand the mechanisms by which zinc deficiency induces epithelial cell death, studies were done of the effects of intracellular zinc depletion induced by the zinc chelator TPEN on apoptosis-related events in human malignant epithelial cell lines LIM1215 (colonic), NCI-H292 (bronchial), and A549 (alveolar type II). In TPEN-treated cells, depletion of zinc was followed by activation of caspase-3 (as demonstrated by enzymatic assay and Western blotting), DNA fragmentation, and morphologic changes. Increase in caspase-3 activity began 12 h after addition of TPEN, suggesting that zinc may suppress a step just before the activation of this caspase. Caspase-6, a mediator of caspase-3 processing, also increased, but later than caspase-3. Effects of TPEN on apoptosis were completely prevented by exogenous ZnSO4 and partially prevented by peptide caspase inhibitors. A critical substrate of caspase-3 may be the cell cycle regulator p21Waf1/Cip1, which was rapidly cleaved in TPEN-treated cells to a 15-kDa fragment before further degradation.


Subject(s)
Apoptosis/physiology , Caspases/metabolism , Cyclins/metabolism , Cysteine Proteinase Inhibitors/pharmacology , Ethylenediamines/pharmacology , Zinc/physiology , Caspase 3 , Caspase 6 , Chelating Agents/pharmacology , Cyclin-Dependent Kinase Inhibitor p21 , DNA Fragmentation , Enzyme Inhibitors/metabolism , Epithelial Cells/cytology , Epithelial Cells/physiology , Humans , Kinetics , Tumor Cells, Cultured , Zinc/deficiency
6.
J Nutr ; 130(5S Suppl): 1459S-66S, 2000 05.
Article in English | MEDLINE | ID: mdl-10801960

ABSTRACT

The maintenance of discrete subcellular pools of zinc (Zn) is critical for the functional and structural integrity of cells. Among the important biological processes influenced by Zn is apoptosis, a process that is important in cellular homeostasis (an important cellular homeostatic process). It has also been identified as a major mechanism contributing to cell death in response to toxins and in disease, offering hope that novel therapies that target apoptotic pathways may be developed. Because Zn levels in the body can be increased in a relatively nontoxic manner, it may be possible to prevent or ameliorate degenerative disorders that are associated with high rates of apoptotic cell death. This review begins with brief introductions that address, first, the cellular biology of Zn, especially the critical labile Zn pools, and, second, the phenomenon of apoptosis. We then review the evidence relating Zn to apoptosis and address three major hypotheses: (1) that a specific pool or pools of intracellular labile Zn regulates apoptosis; (2) that systemic changes in Zn levels in the body, due to dietary factors, altered physiological states or disease, can influence cell susceptibility to apoptosis, and (3) that this altered susceptibility to apoptosis contributes to pathophysiological changes in the body. Other key issues are the identity of the molecular targets of Zn in the apoptotic cascade, the types of cells and tissues most susceptible to Zn-regulated apoptosis, the role of Zn as a coordinate regulator of mitosis and apoptosis and the apparent release of tightly bound intracellular pools of Zn during the later stages of apoptosis. This review concludes with a section highlighting areas of priority for future studies.


Subject(s)
Apoptosis/physiology , Caspases/metabolism , Homeostasis/physiology , Zinc/physiology , Animals , Apoptosis/drug effects , Apoptosis/genetics , Homeostasis/drug effects , Humans , Molecular Biology , Zinc/deficiency , Zinc/pharmacology
7.
Immunol Cell Biol ; 77(3): 272-8, 1999 Jun.
Article in English | MEDLINE | ID: mdl-10361260

ABSTRACT

Non-toxic agents that target intracellular signalling pathways in apoptosis may have potential therapeutic use in many diseases. One such agent is the transition metal Zn, a dietary cytoprotectant and anti-oxidant, which stimulates cell proliferation and suppresses apoptosis. Zn is maintained in discrete subcellular pools that are critical for the functional and structural integrity of cells. The present review initially describes the current state of knowledge on the cellular biology of Zn, especially the critical free or loosely bound (labile) pools of Zn, which are thought to regulate apoptosis. We then review the evidence relating Zn to apoptosis, including studies from our laboratory showing potent synergy between intracellular Zn deficiency and the short chain fatty acid butyrate in induction of caspase activation and the downstream events of apoptosis. Our studies have also reported the suppressive effects of micromolar concentrations of Zn on caspase-3 activation in cell-free models. Other key issues that will be discussed include the identification of the putative molecular targets of Zn and the evidence that systemic changes in labile Zn levels are sufficient to alter susceptibility to apoptosis and lead to physiopathological changes in the human body. Finally, we propose that labile Zn may serve as a coordinate regulator of mitosis and apoptosis to regulate tissue growth.


Subject(s)
Apoptosis/physiology , Zinc/physiology , Animals , Butyrates/pharmacology , Caspases/physiology , Cell Division/drug effects , Chelating Agents/pharmacology , Ethylenediamines/pharmacology , Humans , Jurkat Cells/drug effects
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