A20 Is Critical for the Induction of Pam3CSK4-tolerance in Monocytic THP-1 Cells

PLoS One. 2014 Jan 28;9(1):e87528. doi: 10.1371/journal.pone.0087528. eCollection 2014.

Abstract

A20 functions to terminate Toll-like receptor (TLR)-induced immune response, and play important roles in the induction of lipopolysacchride (LPS)-tolerance. However, the molecular mechanism for Pam3CSK4-tolerance is uncertain. Here we report that TLR1/2 ligand Pam3CSK4 induced tolerance in monocytic THP-1 cells. The pre-treatment of THP-1 cells with Pam3CSK4 down-regulated the induction of pro-inflammatory cytokines induced by Pam3CSK4 re-stimulation. Pam3CSK4 pre-treatment also down-regulated the signaling transduction of JNK, p38 and NF-κB induced by Pam3CSK4 re-stimulation. The activation of TLR1/2 induced a rapid and robust up-regulation of A20, suggesting that A20 may contribute to the induction of Pam3CSK4-tolerance. This hypothesis was proved by the observation that the over-expression of A20 by gene transfer down-regulated Pam3CSK4-induced inflammatory responses, and the down-regulation of A20 by RNA interference inhibited the induction of tolerance. Moreover, LPS induced a significant up-regulation of A20, which contributed to the induction of cross-tolerance between LPS and Pam3CSK4. A20 was also induced by the treatment of THP-1 cells with TNF-α and IL-1β. The pre-treatment with TNF-α and IL-1β partly down-regulated Pam3CSK4-induced activation of MAPKs. Furthermore, pharmacologic inhibition of GSK3 signaling down-regulated Pam3CSK4-induced A20 expression, up-regulated Pam3CSK4-induced inflammatory responses, and partly reversed Pam3CSK4 pre-treatment-induced tolerance, suggesting that GSK3 is involved in TLR1/2-induced tolerance by up-regulation of A20 expression. Taken together, these results indicated that A20 is a critical regulator for TLR1/2-induced pro-inflammatory responses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • DNA-Binding Proteins / physiology*
  • Down-Regulation
  • Immune Tolerance*
  • Interleukin-1beta / pharmacology
  • Intracellular Signaling Peptides and Proteins / physiology*
  • Lipopeptides / immunology*
  • Monocytes / immunology*
  • Nuclear Proteins / physiology*
  • Receptors, Pattern Recognition / immunology
  • Signal Transduction
  • Tumor Necrosis Factor alpha-Induced Protein 3
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • DNA-Binding Proteins
  • Interleukin-1beta
  • Intracellular Signaling Peptides and Proteins
  • Lipopeptides
  • Nuclear Proteins
  • Pam(3)CSK(4) peptide
  • Receptors, Pattern Recognition
  • Tumor Necrosis Factor-alpha
  • TNFAIP3 protein, human
  • Tumor Necrosis Factor alpha-Induced Protein 3

Grant support

This work was supported by National Science and Technology Major Project (2013ZX10005004). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.