title: A quantitative study of the cell-type specific modulation of c-Rel by hydrogen peroxide and TNF-α.
abstract: Hydrogen peroxide (H2O2) at moderate steady-state concentrations synergizes with TNF-α, leading to increased nuclear levels of NF-κB p65 subunit and to a cell-type specific up-regulation of a limited number of NF-κB-dependent genes. Here, we address how H2O2 achieves this molecular specificity. HeLa and MCF-7 cells were exposed to steady-state H2O2 and/or TNF-α and levels of c-Rel, p65, IκB-α, IκB-β and IκB-ε were determined. For an extracellular concentration of 25 µM H2O2, the intracellular H2O2 concentration is 3.7 µM and 12.5 µM for respectively HeLa and MCF-7 cells. The higher cytosolic H2O2 concentration present in MCF-7 cells may be a contributing factor for the higher activation of NF-κB caused by H2O2 in this cell line, when compared to HeLa cells. In both cells lines, H2O2 precludes the recovery of TNF-α-dependent IκB-α degradation, which may explain the observed synergism between H2O2 and TNF-α concerning p65 nuclear translocation. In MCF-7 cells, H2O2, in the presence of TNF-α, tripled the induction of c-Rel triggered either by TNF-α or H2O2. Conversely, in HeLa cells, H2O2 had a small antagonistic effect on TNF-α-induced c-Rel nuclear levels, concomitantly with a 50 % induction of IκB-ε, the preferential inhibitor protein of c-Rel dimers. The 6-fold higher c-Rel/IκB-ε ratio found in MCF-7 cells when compared with HeLa cells, may be a contributing factor for the cell-type dependent modulation of c-Rel by H2O2. Our results suggest that H2O2 might have an important cell-type specific role in the regulation of c-Rel-dependent processes, e.g. cancer or wound healing.
authors.affiliation: Grupo de Biologia Redox, Centro de Química e Bioquímica and Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, C8, 1749-016 Lisboa, Portugal.
authors.forename: Virgínia
authors.initials: V
authors.lastname: Oliveira-Marques
authors.forename: Teresa
authors.initials: T
authors.lastname: Silva
authors.forename: Filipa
authors.initials: F
authors.lastname: Cunha
authors.forename: Gonçalo
authors.initials: G
authors.lastname: Covas
authors.forename: H Susana
authors.initials: HS
authors.lastname: Marinho
authors.forename: Fernando
authors.initials: F
authors.lastname: Antunes
authors.forename: Luísa
authors.initials: L
authors.lastname: Cyrne
mesh_terms: D006367:HeLa Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism*; D020672:I-kappa B Proteins / Q000378:metabolism; D061986:MCF-7 Cells; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020569:Proto-Oncogene Proteins c-rel / Q000378:metabolism*; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: C083487:I kappa B beta protein; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C105627:NFKBIE protein, human; D011518:Proto-Oncogene Proteins; D020569:Proto-Oncogene Proteins c-rel; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D006861:Hydrogen Peroxide
keywords: GPx, glutathione peroxidase; H2O2 gradient; H2O2, hydrogen peroxide; HeLa cells; Inflammation; IκB-α, inhibitory protein α of NF-κB; IκB-β, inhibitory protein β of NF-κB; IκB-ε, inhibitory protein ε of NF-κB; MCF-7 cells; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NF-κB; NF-κB, nuclear factor-kappa B; Steady-state; TNF-α, tumor necrosis factor-alpha
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