The gut microbiota-induced kynurenic acid recruits GPR35-positive macrophages to promote experimental encephalitis

Cell Rep. 2023 Aug 29;42(8):113005. doi: 10.1016/j.celrep.2023.113005. Epub 2023 Aug 16.

Abstract

The intricate interplay between gut microbes and the onset of experimental autoimmune encephalomyelitis (EAE) remains poorly understood. Here, we uncover remarkable similarities between CD4+ T cells in the spinal cord and their counterparts in the small intestine. Furthermore, we unveil a synergistic relationship between the microbiota, particularly enriched with the tryptophan metabolism gene EC:1.13.11.11, and intestinal cells. This symbiotic collaboration results in the biosynthesis of kynurenic acid (KYNA), which modulates the recruitment and aggregation of GPR35-positive macrophages. Subsequently, a robust T helper 17 (Th17) immune response is activated, ultimately triggering the onset of EAE. Conversely, modulating the KYNA-mediated GPR35 signaling in Cx3cr1+ macrophages leads to a remarkable amelioration of EAE. These findings shed light on the crucial role of microbial-derived tryptophan metabolites in regulating immune responses within extraintestinal tissues.

Keywords: CD4(+) T cells; CP: Immunology; CP: Microbiology; GPR35; encephalomyelitis; gut microbes; immune system; kynurenic acid; macrophages; multiple sclerosis; spinal cord; tryptophan metabolites.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Encephalitis*
  • Encephalomyelitis, Autoimmune, Experimental*
  • Gastrointestinal Microbiome*
  • Kynurenic Acid
  • Macrophages
  • Tryptophan

Substances

  • Kynurenic Acid
  • Tryptophan