TLR-stimulated IRAKM activates caspase-8 inflammasome in microglia and promotes neuroinflammation

J Clin Invest. 2018 Dec 3;128(12):5399-5412. doi: 10.1172/JCI121901. Epub 2018 Oct 29.

Abstract

NLRP3 inflammasome plays a critical spatiotemporal role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE). This study reports a mechanistic insight into noncanonical NLRP3 inflammasome activation in microglia for the effector stage of EAE. Microglia-specific deficiency of ASC (apoptosis-associated speck-like protein containing a C-terminal caspase-activation and recruitment [CARD] domain) attenuated T cell expansion and neutrophil recruitment during EAE pathogenesis. Mechanistically, TLR stimulation led to IRAKM-caspase-8-ASC complex formation, resulting in the activation of caspase-8 and IL-1β release in microglia. Noncanonical inflammasome-derived IL-1β produced by microglia in the CNS helped to expand the microglia population in an autocrine manner and amplified the production of inflammatory cytokines/chemokines. Furthermore, active caspase-8 was markedly increased in the microglia in the brain tissue from patients with multiple sclerosis. Taken together, our study suggests that microglia-derived IL-1β via noncanonical caspase-8-dependent inflammasome is necessary for microglia to exert their pathogenic role during CNS inflammation.

Keywords: Autoimmune diseases; Autoimmunity; Inflammation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caspase 8 / genetics
  • Caspase 8 / metabolism*
  • Encephalomyelitis, Autoimmune, Experimental / enzymology*
  • Encephalomyelitis, Autoimmune, Experimental / genetics
  • Encephalomyelitis, Autoimmune, Experimental / pathology
  • Female
  • Humans
  • Inflammation / genetics
  • Inflammation / metabolism
  • Inflammation / pathology
  • Interleukin-1 Receptor-Associated Kinases / genetics
  • Interleukin-1 Receptor-Associated Kinases / metabolism*
  • Interleukin-1beta / genetics
  • Interleukin-1beta / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Microglia / metabolism*
  • Microglia / pathology
  • Multiple Sclerosis / enzymology*
  • Multiple Sclerosis / genetics
  • Multiple Sclerosis / pathology
  • Signal Transduction*
  • Toll-Like Receptors / genetics
  • Toll-Like Receptors / metabolism

Substances

  • IL1B protein, human
  • IL1B protein, mouse
  • Interleukin-1beta
  • Toll-Like Receptors
  • IRAK3 protein, human
  • Interleukin-1 Receptor-Associated Kinases
  • Irak3 protein, mouse
  • CASP8 protein, human
  • Casp8 protein, mouse
  • Caspase 8