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1. Tumour necrosis factor alpha regulates iron transport and transporter expression in human intestinal epithelial cells

Author

Phillip A. Sharp, Deborah M. Johnson, Surjit K. S. Srai, J. P. Tennant, Kelly L Johnston, and Henry K. Bayele

Subjects
Iron, medicine.medical_treatment, Iron regulated transporter, Biophysics, Biochemistry, Intestinal mucosa, Structural Biology, Hepcidin, Iron-Binding Proteins, Receptors, Transferrin, Genetics, medicine, Humans, Interferon gamma, RNA, Messenger, Iron transport, Promoter Regions, Genetic, Cation Transport Proteins, Molecular Biology, biology, Tumor Necrosis Factor-alpha, Membrane Transport Proteins, Biological Transport, Epithelial Cells, Transporter, Cell Biology, Molecular biology, Transport protein, Intestines, Cytokine, Gene Expression Regulation, Caco-2, Divalent metal transporter, Ferritins, biology.protein, Tumor necrosis factor alpha, Caco-2 Cells, medicine.drug
Abstract

TNFalpha has dramatic effects on iron metabolism contributing to the generation of hypoferraemia in the anaemia of chronic disease. Interestingly, TNFalpha is also synthesised and released within the intestinal mucosa, suggesting that this pro-inflammatory cytokine may play a role in regulating dietary iron absorption. To investigate this possibility, we stimulated intestinal Caco-2 cells with TNFalpha (10 ng/ml). In TNFalpha-treated cells, apical iron uptake was significantly decreased and this was accompanied by a reduction in divalent metal transporter protein and mRNA expression. Our data suggest that TNFalpha could regulate dietary iron absorption and that the apical transport machinery is the target for these actions.

Published
2004

2. Simple shifts in redox/thiol balance that perturb blood coagulation

Author

K. John Pasi, Paul J. Murdock, Henry K. Bayele, and David J. Perry

Subjects
Oxidant, Antioxidant, medicine.medical_treatment, Biophysics, Thiol–disulphide interchange, Dithionitrobenzoic Acid, Biochemistry, Redox, chemistry.chemical_compound, Tissue factor, Structural Biology, Genetics, medicine, Humans, Sulfhydryl Compounds, Molecular Biology, Blood Coagulation, chemistry.chemical_classification, Clotting factor, Fibrin, Coagulation, Glutathione Disulfide, Sulfhydryl Reagents, Cell Biology, Glutathione, Oxidants, Redox equilibrium, chemistry, Thiol, Partial Thromboplastin Time, Oxidation-Reduction, Tenase
Abstract

The biological chemistry that underlies and regulates the blood coagulation cascade is not fully understood. To begin to understand this, we performed clotting assays under various redox conditions. By varying the amount of oxidant and/or antioxidant in these assays, we observed that both the intrinsic/tenase complex and the extrinsic pathways were susceptible to shifts in the thiol/redox balance. We established a dichotomy where blood clotting via the intrinsic pathway was sensitive to oxidation whereas the tissue factor or extrinsic pathway was more sensitive to reduction. These differential inhibitory effects present a conceptual mechanism for selective modulation of the activities of clotting factors specific for the respective pathways. These data also suggest that blood clotting may be influenced by unidentified redox or thiol equilibria.

Published
2002

3. Divalent metal-dependent regulation of hepcidin expression by MTF-1

Author

Henry K. Bayele, Surjit K. S. Srai, Harry J. McArdle, Sara Balesaria, and Bala Ramesh

Subjects
inorganic chemicals, congenital, hereditary, and neonatal diseases and abnormalities, Transcription, Genetic, Cations, Divalent, Iron, Blotting, Western, Biophysics, Hepcidin, Electrophoretic Mobility Shift Assay, Peptide, Plasma protein binding, Response Elements, Transfection, Biochemistry, chemistry.chemical_compound, Hepcidins, Structural Biology, Transcription (biology), Cell Line, Tumor, hemic and lymphatic diseases, Genetics, Humans, Metallothionein, MRE-binding transcription factor-1, Electrophoretic mobility shift assay, Luciferases, Promoter Regions, Genetic, Molecular Biology, chemistry.chemical_classification, Metal response element, Messenger RNA, Binding Sites, biology, Reverse Transcriptase Polymerase Chain Reaction, nutritional and metabolic diseases, Cell Biology, DNA-Binding Proteins, Zinc, Gene Expression Regulation, chemistry, Metals, Mutation, biology.protein, Xenobiotic, Antimicrobial Cationic Peptides, Protein Binding, Transcription Factors
Abstract

Hepcidin is a small acute phase peptide that regulates iron absorption. It is induced by inflammation and infection, but is repressed by anaemia and hypoxia. Here we further reveal that hepcidin transcription also involves interactions between functional metal response elements (MREs) in its promoter, and the MRE-binding transcription factor-1. Analysis of hepcidin mRNA and protein levels in hepatoma cells suggests that its expression may be regulated by divalent metal ions, with zinc inducing maximal effects on hepcidin levels. These data suggest that this peptide may be a pleiotropic sensor of divalent metals, some of which are xenobiotic environmental toxins.

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