title: TNF-alpha promotes cell survival through stimulation of K+ channel and NFkappaB activity in corneal epithelial cells.
abstract: Tumor necrosis factor (TNF-alpha) in various cell types induces either cell death or mitogenesis through different signaling pathways. In the present study, we determined in human corneal epithelial cells how TNF-alpha also promotes cell survival. Human corneal epithelial (HCE) cells were cultured in DMEM/F-12 medium containing 10% FBS. TNF-alpha stimulation induced activation of a voltage-gated K+ channel detected by measuring single channel activity using patch clamp techniques. The effect of TNF-alpha on downstream events included NFkappaB nuclear translocation and increases in DNA binding activities, but did not elicit ERK, JNK, or p38 limb signaling activation. TNF-alpha induced increases in p21 expression resulting in partial cell cycle attenuation in the G1 phase. Cell cycle progression was also mapped by flow cytometer analysis. Blockade of TNF-alpha-induced K+ channel activity effectively prevented NFkappaB nuclear translocation and binding to DNA, diminishing the cell-survival protective effect of TNF-alpha. In conclusion, TNF-alpha promotes survival of HCE cells through sequential stimulation of K+ channel and NFkappaB activities. This response to TNF-alpha is dependent on stimulating K+ channel activity because following suppression of K+ channel activity TNF-alpha failed to activate NFkappaB nuclear translocation and binding to nuclear DNA.
authors.affiliation: Division of Molecular Medicine, Harbor-UCLA Medical Center, David Geffen School of Medicine, University of California Los Angeles, 1124 W. Carson Street, C-2, Torrance, CA 90502, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Wang
authors.forename: Peter
authors.initials: P
authors.lastname: Reinach
authors.forename: Luo
authors.initials: L
authors.lastname: Lu
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D019573:Epithelium, Corneal / Q000187:drug effects* / Q000378:metabolism* / Q000473:pathology; D005434:Flow Cytometry; D016193:G1 Phase; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism*; D015221:Potassium Channels / Q000378:metabolism*; D021381:Protein Transport; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D016328:NF-kappa B; D015221:Potassium Channels; D014409:Tumor Necrosis Factor-alpha; D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases