Regulation of TLR2-mediated tolerance and cross-tolerance through IRAK4 modulation by miR-132 and miR-212

J Immunol. 2013 Feb 1;190(3):1250-63. doi: 10.4049/jimmunol.1103060. Epub 2012 Dec 21.

Abstract

Innate immune response is the first defense against pathogens via recognition by various conserved pattern recognition receptors, such as TLRs, to initiate a rapid and strong cytokine alarm. TLR signaling-mediated cytokine production must be properly regulated to prevent pathological conditions deriving from overproduction of cytokines. In this study, the role of specific microRNAs in TLR-signaling pathway was investigated to reveal the cross-interaction and -regulation in the MyD88 pathway. In peptidoglycan (PGN)/TLR2-stimulated THP-1 monocytes, PBMCs, and primary macrophages showed rapid and dramatic miR-132 and miR-212 (miR-132/-212) upregulation. This newly identified response appeared earlier in time than the characteristic miR-146a response in LPS-TLR4 stimulation. The rapid induction of miR-132/-212 was transcription factor CREB dependent, and the sustained expression of miR-132/-212 was responsible for inducing tolerance to subsequent PGN challenge. Cross-tolerance was observed by TLR5 ligand flagellin and heat-killed or live bacteria resulting from miR-132/-212 upregulation. Mechanistically, IRAK4 was identified and validated as a target of miR-132/-212 by luciferase reporter assay and seed-sequence mutagenesis of the reporter. Transfection of miR-132 or miR-212 alone mimicked PGN tolerance in monocytes, whereas transfected specific miRNA inhibitors tampered the tolerance effect. During bacterial infection, PGN-mediated TLR2 signaling induces miR-132/-212 to downregulate IRAK4, an early component in the MyD88-dependent pathway, whereas LPS/TLR4-induced miR-146a downregulates downstream components of the same MyD88-dependent pathway. The identification of miR-132/-212 and miR-146a together to prevent damaging consequences from the overproduction of proinflammatory cytokines by targeting a common signaling pathway is significant and will provide insights into future design and development of therapeutics.

Publication types

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

MeSH terms

  • Animals
  • Bacterial Proteins / immunology
  • Cells, Cultured / immunology
  • Cyclic AMP Response Element-Binding Protein / immunology
  • Female
  • Flagellin / immunology
  • Flagellin / pharmacology
  • Gene Expression Regulation
  • Genes, Reporter
  • Immune Tolerance / immunology*
  • Interleukin-1 Receptor-Associated Kinases / immunology*
  • Lipopolysaccharides / immunology
  • Lipoproteins / pharmacology
  • Macrophage Activation
  • Macrophages, Peritoneal / immunology*
  • Mice
  • Mice, Inbred C57BL
  • MicroRNAs / antagonists & inhibitors
  • MicroRNAs / biosynthesis
  • MicroRNAs / genetics
  • MicroRNAs / immunology*
  • Monocytes / immunology*
  • Myeloid Differentiation Factor 88 / immunology
  • Peptidoglycan / immunology*
  • RNA, Small Interfering / pharmacology
  • Signal Transduction / immunology*
  • Toll-Like Receptor 2 / immunology*
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Bacterial Proteins
  • CREB1 protein, human
  • Creb1 protein, mouse
  • Cyclic AMP Response Element-Binding Protein
  • Lipopolysaccharides
  • Lipoproteins
  • MIRN132 microRNA, human
  • MIRN132 microRNA, mouse
  • MIRN212 microRNA, human
  • MIRN212 microRNA, mouse
  • MYD88 protein, human
  • MicroRNAs
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Peptidoglycan
  • RNA, Small Interfering
  • TLR2 protein, human
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • Tumor Necrosis Factor-alpha
  • Flagellin
  • IRAK4 protein, human
  • Interleukin-1 Receptor-Associated Kinases
  • Irak4 protein, mouse