The phosphatidylinositol 3-kinase-Akt pathway limits lipopolysaccharide activation of signaling pathways and expression of inflammatory mediators in human monocytic cells

J Biol Chem. 2002 Aug 30;277(35):32124-32. doi: 10.1074/jbc.M203298200. Epub 2002 Jun 6.

Abstract

Monocytes and macrophages express cytokines and procoagulant molecules in various inflammatory diseases. In sepsis, lipopolysaccharide (LPS) from Gram-negative bacteria induces tumor necrosis factor-alpha (TNF-alpha) and tissue factor (TF) in monocytic cells via the activation of the transcription factors Egr-1, AP-1, and nuclear factor-kappa B. However, the signaling pathways that negatively regulate LPS-induced TNF-alpha and TF expression in monocytic cells are currently unknown. We report that inhibition of the phosphatidylinositol 3-kinase (PI3K)-Akt pathway enhances LPS-induced activation of the mitogen-activated protein kinase pathways (ERK1/2, p38, and JNK) and the downstream targets AP-1 and Egr-1. In addition, inhibition of PI3K-Akt enhanced LPS-induced nuclear translocation of nuclear factor-kappa B and prevented Akt-dependent inactivation of glycogen synthase kinase-beta, which increased the transactivational activity of p65. We propose that the activation of the PI3K-Akt pathway in human monocytes limits the LPS induction of TNF-alpha and TF expression. Our study provides new insight into the inhibitory mechanism by which the PI3K-Akt pathway ensures transient expression of these potent inflammatory mediators.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Cell Line
  • DNA-Binding Proteins / metabolism
  • Early Growth Response Protein 1
  • Escherichia coli
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / immunology
  • Humans
  • Immediate-Early Proteins / metabolism
  • Inflammation / physiopathology*
  • Lipopolysaccharides / pharmacology*
  • Monocytes / drug effects
  • Monocytes / enzymology
  • Monocytes / physiology*
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Protein Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Thromboplastin / genetics
  • Transcription Factor AP-1 / metabolism
  • Transcription Factors / metabolism
  • Transcription, Genetic / drug effects*
  • Tumor Necrosis Factor-alpha / genetics*
  • Zinc Fingers

Substances

  • DNA-Binding Proteins
  • EGR1 protein, human
  • Early Growth Response Protein 1
  • Immediate-Early Proteins
  • Lipopolysaccharides
  • Proto-Oncogene Proteins
  • Transcription Factor AP-1
  • Transcription Factors
  • Tumor Necrosis Factor-alpha
  • Thromboplastin
  • AKT1 protein, human
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt