K+Efflux-Independent NLRP3 Inflammasome Activation by Small Molecules Targeting Mitochondria.
Imiquimod is a small-molecule ligand of Toll-like receptor-7 (TLR7) that is licensed for the treatment of viral infections and cancers of the skin. Imiquimod has TLR7-independent activities that are mechanistically unexplained, including NLRP3 inflammasome activation in myeloid cells and apoptosis induction in cancer cells. We investigated the mechanism of inflammasome activation by imiquimod and the related molecule CL097 and determined that K+efflux was dispensable for NLRP3 activation by these compounds. Imiquimod and CL097 inhibited the quinone oxidoreductases NQO2 and mitochondrial Complex I. This induced a burst of reactive oxygen species (ROS) and thiol oxidation, and led to NLRP3 activation via NEK7, a recently identified component of this inflammasome. Metabolic consequences of Complex I inhibition and endolysosomal effects of imiquimod might also contribute to NLRP3 activation. Our results reveal a K+efflux-independent mechanism for NLRP3 activation and identify targets of imiquimod that might be clinically relevant.
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Christina J
CJ
Groß
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Ritu
R
Mishra
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Katharina S
KS
Schneider
Chair of Proteomics and Bioanalytics, TUM, 85354 Freising, Germany.
Guillaume
G
Médard
Genzentrum, Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, and Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
Jennifer
J
Wettmarshausen
Chair and Institute of Environmental Medicine, UNIKA-T, TUM, 86156 Augsburg, and Helmholtz Zentrum München, 85764 Neuherberg, Germany.
Daniela C
DC
Dittlein
Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Hexin
H
Shi
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Oliver
O
Gorka
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Paul-Albert
PA
Koenig
Fachgruppe Analytische Chemie, Department of Chemistry, TUM, 85748 Garching, Germany.
Stephan
S
Fromm
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Giovanni
G
Magnani
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Tamara
T
Ćiković
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Lara
L
Hartjes
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany.
Joachim
J
Smollich
Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4067, Australia.
Avril A B
AAB
Robertson
Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4067, Australia.
Matthew A
MA
Cooper
Department of Hematology and Oncology, Klinikum rechts der Isar, TUM, 81675 Munich, Germany; TranslaTUM: Zentralinstitut für translationale Krebsforschung, TUM, 81675 Munich, Germany.
Marc
M
Schmidt-Supprian
Fachgruppe Analytische Chemie, Department of Chemistry, TUM, 85748 Garching, Germany.
Michael
M
Schuster
Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4067, Australia.
Kate
K
Schroder
Focal Area Infection Biology, Biozentrum, University of Basel, 4003 Basel, Switzerland.
Petr
P
Broz
Chair and Institute of Environmental Medicine, UNIKA-T, TUM, 86156 Augsburg, and Helmholtz Zentrum München, 85764 Neuherberg, Germany.
Claudia
C
Traidl-Hoffmann
Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Bruce
B
Beutler
Chair of Proteomics and Bioanalytics, TUM, 85354 Freising, Germany; Center for Integrated Protein Science Munich (CIPSM), 81377 Munich, Germany.
Bernhard
B
Kuster
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany; TranslaTUM: Zentralinstitut für translationale Krebsforschung, TUM, 81675 Munich, Germany.
Jürgen
J
Ruland
Department of Chemistry, TUM, 85748 Garching, Germany; Center for Integrated Protein Science Munich (CIPSM), 81377 Munich, Germany.
Sabine
S
Schneider
Genzentrum, Department of Biochemistry, Ludwig-Maximilians-Universität München, 81377 Munich, and Institute of Human Genetics, Helmholtz Zentrum München, 85764 Neuherberg, Germany.
Fabiana
F
Perocchi
Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München (TUM), 81675 Munich, Germany; TranslaTUM: Zentralinstitut für translationale Krebsforschung, TUM, 81675 Munich, Germany. Electronic address: olaf.gross@tum.de.
Olaf
O
Groß
D000818:Animals; D042967:Electron Transport Complex I / Q000378:metabolism; D058847:Inflammasomes / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D000072379:NIMA-Related Kinases / Q000378:metabolism; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011808:Quinone Reductases / Q000378:metabolism; D012342:RNA, Small Nuclear / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D051199:Toll-Like Receptor 7 / Q000378:metabolism
D058847:Inflammasomes; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C492716:Nlrp3 protein, mouse; D012342:RNA, Small Nuclear; D017382:Reactive Oxygen Species; D051199:Toll-Like Receptor 7; C419642:NRH - quinone oxidoreductase2; D011808:Quinone Reductases; D000072379:NIMA-Related Kinases; D042967:Electron Transport Complex I; D011188:Potassium