Lipopolysaccharide activation of the MEK-ERK1/2 pathway in human monocytic cells mediates tissue factor and tumor necrosis factor alpha expression by inducing Elk-1 phosphorylation and Egr-1 expression

Mausumee Guha, Maria A. O'Connell, Rafal Pawlinski, Angela Hollis, Patricia McGovern, Shi-Fang Yan, David Stern, Nigel Mackman

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315 Citations (Scopus)

Abstract

Lipopolysaccharide (LPS) induces human monocytes to express many proinflammatory mediators, including the procoagulant molecule tissue factor (TF) and the cytokine tumor necrosis factor alpha (TNIF-alpha). The TF and TNF-alpha genes are regulated by various transcription factors, including nuclear factor (NF)-kappaB/Rel proteins and Egr-1. In this study, the role of the MEK-ERK1/2 mitogen-activated protein kinase (MAPK) pathway in LIPS induction of TF and TNF-alpha gene expression in human monocytic cells was investigated. The MAPK kinase (MEK)1 inhibitor PD98059 reduced LPS induction of TF and TNIF-alpha expression in a dose-dependent manner. PD98059 did not affect LPS-induced nuclear translocation of NF-kappaB/Rel proteins and minimally affected LPS induction Of KB-dependent transcription. In contrast, PD98059 and dominant-negative mutants of the Ras-Raf1-MEK-ERK (extacellular signal-regulated kinase) pathway strongly inhibited LPS induction of Egr-1 expression. In kinetic experiments LPS induction of Egr-1 expression preceded induction of TF expression. In addition, mutation of the Egr-1 sites in the TF and TNF-alpha promoters reduced expression of these proinflammatory genes. It was demonstrated that LPS induction of the Egr-1 promoter was mediated by 3 SRE sites, which bound an LIPS-Inducible complex containing serum response factor and Elk-1. LPS stimulation transiently induced phosphorylation of Elk-1 and increased the functional activity of a GAL4-Elk-1TA chimeric protein via the MEK-ERK1/2 pathway. The data indicate that LPS induction of Egr-1 gene expression is required for maximal induction of the TNF-alpha and TF genes in human monocytic cells. (C) 2001 by The American Society of Hematology.
Original languageEnglish
Pages (from-to)1429-1439
Number of pages11
JournalBlood
Volume98
Issue number5
DOIs
Publication statusPublished - 2001

Keywords

  • ACTIVATION
  • FACTOR MESSENGER-RNA
  • TRANSCRIPTIONAL
  • FACTOR GENE-EXPRESSION
  • BINDING PROTEINS
  • SERUM RESPONSE ELEMENTS
  • TERNARY COMPLEX FACTORS
  • C-JUN
  • EPITHELIAL-CELLS
  • FACTOR-KAPPA-B
  • BACTERIAL LIPOPOLYSACCHARIDE

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