FoxO1 regulates Tlr4 inflammatory pathway signalling in macrophages

EMBO J. 2010 Dec 15;29(24):4223-36. doi: 10.1038/emboj.2010.268. Epub 2010 Nov 2.

Abstract

The macrophage-mediated inflammatory response is a key etiologic component of obesity-related tissue inflammation and insulin resistance. The transcriptional factor FoxO1 is a key regulator of cell metabolism, cell cycle and cell death. Its activity is tightly regulated by the phosphoinositide-3-kinase-AKT (PI3K-Akt) pathway, which leads to phosphorylation, cytoplasmic retention and inactivation of FoxO1. Here, we show that FoxO1 promotes inflammation by enhancing Tlr4-mediated signalling in mature macrophages. By means of chromatin immunoprecipitation (ChIP) combined with massively parallel sequencing (ChIP-Seq), we show that FoxO1 binds to multiple enhancer-like elements within the Tlr4 gene itself, as well as to sites in a number of Tlr4 signalling pathway genes. While FoxO1 potentiates Tlr4 signalling, activation of the latter induces AKT and subsequently inactivates FoxO1, establishing a self-limiting mechanism of inflammation. Given the central role of macrophage Tlr4 in transducing extrinsic proinflammatory signals, the novel functions for FoxO1 in macrophages as a transcriptional regulator of the Tlr4 gene and its inflammatory pathway, highlights FoxO1 as a key molecular adaptor integrating inflammatory responses in the context of obesity and insulin resistance.

Publication types

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

MeSH terms

  • Animals
  • Cell Line
  • Chromatin Immunoprecipitation
  • DNA / metabolism
  • Enhancer Elements, Genetic
  • Forkhead Box Protein O1
  • Forkhead Transcription Factors / metabolism*
  • Gene Expression Regulation*
  • Inflammation Mediators / metabolism
  • Macrophages / immunology*
  • Mice
  • Protein Binding
  • Sequence Analysis, DNA
  • Signal Transduction*
  • Toll-Like Receptor 4 / biosynthesis*

Substances

  • Forkhead Box Protein O1
  • Forkhead Transcription Factors
  • Foxo1 protein, mouse
  • Inflammation Mediators
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4
  • DNA