title: A quantitative study of NF-kappaB activation by H2O2: relevance in inflammation and synergy with TNF-alpha.
abstract: Although the germicide role of H(2)O(2) released during inflammation is well established, a hypothetical regulatory function, either promoting or inhibiting inflammation, is still controversial. In particular, after 15 years of highly contradictory results it remains uncertain whether H(2)O(2) by itself activates NF-kappaB or if it stimulates or inhibits the activation of NF-kappaB by proinflammatory mediators. We investigated the role of H(2)O(2) in NF-kappaB activation using, for the first time, a calibrated and controlled method of H(2)O(2) delivery--the steady-state titration--in which cells are exposed to constant, low, and known concentrations of H(2)O(2). This technique contrasts with previously applied techniques, which disrupt cellular redox homeostasis and/or introduce uncertainties in the actual H(2)O(2) concentration to which cells are exposed. In both MCF-7 and HeLa cells, H(2)O(2) at extracellular concentrations up to 25 microM did not induce significantly per se NF-kappaB translocation to the nucleus, but it stimulated the translocation induced by TNF-alpha. For higher H(2)O(2) doses this stimulatory role shifts to an inhibition, which may explain published contradictory results. The stimulatory role was confirmed by the observation that 12.5 microM H(2)O(2), a concentration found during inflammation, increased the expression of several proinflammatory NF-kappaB-dependent genes induced by TNF-alpha (e.g., IL-8, MCP-1, TLR2, and TNF-alpha). The same low H(2)O(2) concentration also induced the anti-inflammatory gene coding for heme oxygenase-1 (HO-1) and IL-6. We propose that H(2)O(2) has a fine-tuning regulatory role, comprising both a proinflammatory control loop that increases pathogen removal and an anti-inflammatory control loop, which avoids an exacerbated harmful inflammatory response.
authors.affiliation: Grupo de Bioquímica dos Oxidantes e Antioxidantes, Centro de Química e Bioquímica, Faculty of Sciences, University of Lisbon, Lisbon, Portugal. vmmarques@fc.ul.pt
authors.forename: Virgínia
authors.initials: V
authors.lastname: de Oliveira-Marques
authors.forename: Luísa
authors.initials: L
authors.lastname: Cyrne
authors.forename: H Susana
authors.initials: HS
authors.lastname: Marinho
authors.forename: Fernando
authors.initials: F
authors.lastname: Antunes
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects / Q000276:immunology; D002467:Cell Nucleus / Q000276:immunology / Q000378:metabolism*; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000276:immunology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D006367:HeLa Cells; D051547:Heme Oxygenase-1; D006706:Homeostasis / Q000187:drug effects / Q000276:immunology; D006801:Humans; D006861:Hydrogen Peroxide / Q000819:agonists / Q000276:immunology / Q000494:pharmacology*; D007249:Inflammation / Q000276:immunology / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis / Q000276:immunology; D016209:Interleukin-8 / Q000096:biosynthesis / Q000276:immunology; D016328:NF-kappa B / Q000276:immunology / Q000378:metabolism*; D016877:Oxidants / Q000819:agonists / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D051195:Toll-Like Receptor 2 / Q000096:biosynthesis / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000819:agonists / Q000276:immunology / Q000494:pharmacology*
chemical_list: C111835:CCL2 protein, human; C508606:CXCL8 protein, human; D018932:Chemokine CCL2; C508600:IL6 protein, human; D015850:Interleukin-6; D016209:Interleukin-8; D016328:NF-kappa B; D016877:Oxidants; C495342:TLR2 protein, human; D051195:Toll-Like Receptor 2; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide; D051547:Heme Oxygenase-1