Phosphatidylinositol 3-kinase is involved in Toll-like receptor 4-mediated cytokine expression in mouse macrophages

Eur J Immunol. 2003 Mar;33(3):597-605. doi: 10.1002/eji.200323376.


Recent evidence suggests a role for phosphatidylinositol (PI) 3-kinase in various inflammatory responses. In this study, the consequences of LPS-induced PI 3-kinase activation on cytokine and chemokine expression and the intracellular mechanisms of inflammatory activation were examined in mouse macrophages. LPS stimulation induced a complex formation between PI 3-kinase and myeloid differentiation factor 88 (MyD88), which was followed by an induction of IL-1beta, tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein (MIP)-2. The induction of IL-1beta, but not of MIP-2 or TNF-alpha, was blocked by the PI 3-kinase inhibitors LY294002 and wortmannin. The nuclear factor-kappaB (NF-kappaB) inhibitor pyrrolidinedithiocarbamate (PDTC) blocked the induction of IL-1beta and TNF-alpha, but had no effect on MIP-2 expression. Inhibition of PI 3-kinase decreased the LPS-induced transcriptional activity of NF-kappaB, but it had no effect on the nuclear DNA binding activity of NF-kappaB. These findings suggest that, while NF-kappaB nuclear localization and DNA binding are necessary, they are not sufficient for transcriptional activation of the IL-1beta gene in the absence of PI 3-kinase activity. Taken together, our results demonstrate that activation of Toll-like receptor (TLR)-4 results in PI 3-kinase-MyD88 complex formation, and that PI 3-kinase activity selectively leads to cytokine induction downstream of TLR4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing
  • Animals
  • Antigens, Differentiation / physiology
  • Cells, Cultured
  • Cytokines / biosynthesis*
  • Cytokines / genetics
  • Drosophila Proteins*
  • Lipopolysaccharides / pharmacology
  • Macrophages / immunology*
  • Membrane Glycoproteins / physiology*
  • Mice
  • Myeloid Differentiation Factor 88
  • NF-kappa B / physiology
  • Phosphatidylinositol 3-Kinases / physiology*
  • Protein Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / physiology
  • Proto-Oncogene Proteins c-akt
  • RNA, Messenger / analysis
  • Receptors, Cell Surface / physiology*
  • Receptors, Immunologic / physiology
  • Toll-Like Receptor 4
  • Toll-Like Receptors


  • Adaptor Proteins, Signal Transducing
  • Antigens, Differentiation
  • Cytokines
  • Drosophila Proteins
  • Lipopolysaccharides
  • Membrane Glycoproteins
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • NF-kappa B
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Receptors, Cell Surface
  • Receptors, Immunologic
  • Toll-Like Receptor 4
  • Toll-Like Receptors
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt