A critical role for MAPK signalling pathways in the transcriptional regulation of toll like receptors

PLoS One. 2013;8(2):e51243. doi: 10.1371/journal.pone.0051243. Epub 2013 Feb 6.

Abstract

Toll-like Receptors (TLR) are phylogenetically conserved transmembrane proteins responsible for detection of pathogens and activation of immune responses in diverse animal species. The stimulation of TLR by pathogen-derived molecules leads to the production of pro-inflammatory mediators including cytokines and nitric oxide. Although TLR-induced events are critical for immune induction, uncontrolled inflammation can be life threatening and regulation is a critical feature of TLR biology. We used an avian macrophage cell line (HD11) to determine the relationship between TLR agonist-induced activation of inflammatory responses and the transcriptional regulation of TLR. Exposure of macrophages to specific TLR agonists induced upregulation of cytokine and nitric oxide pathways that were inhibited by blocking various components of the TLR signalling pathways. TLR activation also led to changes in the levels of mRNA encoding the TLR responsible for recognising the inducing agonist (cognate regulation) and cross-regulation of other TLR (non-cognate regulation). Interestingly, in most cases, regulation of TLR mRNA was independent of NFκB activity but dependent on one or more of the MAPK pathway components. Moreover, the relative importance of ERK, JNK and p38 was dependent upon both the stimulating agonist and the target TLR. These results provide a framework for understanding the complex pathways involved in transcriptional regulation of TLR, immune induction and inflammation. Manipulation of these pathways during vaccination or management of acute inflammatory disease may lead to improved clinical outcome or enhanced vaccine efficacy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Birds
  • Cell Line
  • Cytokines / genetics
  • Cytokines / metabolism
  • Inflammation / genetics
  • Inflammation / metabolism
  • MAP Kinase Signaling System / genetics*
  • Macrophages / metabolism
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Nitric Oxide / genetics
  • Nitric Oxide / metabolism
  • RNA, Messenger / genetics
  • Signal Transduction
  • Toll-Like Receptors / biosynthesis*
  • Toll-Like Receptors / genetics*
  • Toll-Like Receptors / metabolism
  • Transcription, Genetic
  • Up-Regulation
  • p38 Mitogen-Activated Protein Kinases / genetics
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Cytokines
  • NF-kappa B
  • RNA, Messenger
  • Toll-Like Receptors
  • Nitric Oxide
  • p38 Mitogen-Activated Protein Kinases

Grants and funding

This work was supported by Department for Environment, Food and Rural Affairs project number OD0547 with further funds from the Institute for Animal Health doctoral training account and the University of Oxford (John Fell Fund and the Jenner Institute). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.