TLR costimulation causes oxidative stress with unbalance of proinflammatory and anti-inflammatory cytokine production.
IL-1β acts in concert with anti-inflammatory cytokines, in particular, IL-1R antagonist (IL-1Ra), to ensure the correct development and outcome of the inflammation: imbalance in the IL-1β/IL-1Ra ratio is implicated in many human diseases and may lead to dramatic consequences. In this article, we show that single TLR engagement induces IL-1β and, with a little delay, IL-1Ra. Differently, costimulation of TLR2, TLR4, and TLR7/8 enhances IL-1β secretion but severely inhibits IL-1Ra production. The IL-1β/IL-1Ra unbalance after activation of multiple TLRs depends on the insurgence of oxidative stress, because of enhanced production of reactive oxygen species and failure of the antioxidant systems. Increased reactive oxygen species levels increase ATP externalization by monocytes, resulting in enhanced inflammasome activation and IL-1β secretion. Oxidative stress then induces cell responses to stress, including inhibition of protein synthesis, which, in turn, is responsible for the impaired production of IL-1Ra. IL-1Ra secretion is restored by exogenous antioxidants that oppose oxidative stress. Similar effects are evident also on other cytokines: TNF-α is induced, whereas IL-6 is inhibited by costimulation. Our findings provide a molecular basis to the imbalance between proinflammatory and regulatory cytokine circuits that occur in various pathologic conditions, and suggest new strategies for controlling inflammation.
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy.
Rosa
R
Lavieri
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy.
Patrizia
P
Piccioli
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy.
Sonia
S
Carta
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy.
Laura
L
Delfino
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy.
Patrizia
P
Castellani
Unità di Biologia Cellulare, IRCCS Azienda Ospedaliera Universitaria San Martino, IST Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy anna.rubartelli@hsanmartino.it.
Anna
A
Rubartelli
D000893:Anti-Inflammatory Agents / Q000276:immunology*; D016207:Cytokines / Q000276:immunology; D005260:Female; D006801:Humans; D058847:Inflammasomes / Q000276:immunology; D018836:Inflammation Mediators / Q000276:immunology*; D053590:Interleukin 1 Receptor Antagonist Protein / Q000276:immunology*; D008297:Male; D018384:Oxidative Stress / Q000276:immunology*; D017382:Reactive Oxygen Species / Q000276:immunology; D051193:Toll-Like Receptors / Q000819:agonists / Q000276:immunology*
D000893:Anti-Inflammatory Agents; D016207:Cytokines; C507763:IL1RN protein, human; D058847:Inflammasomes; D018836:Inflammation Mediators; D053590:Interleukin 1 Receptor Antagonist Protein; D017382:Reactive Oxygen Species; D051193:Toll-Like Receptors