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Signaling pathways of the TREM-1- and TLR4-mediated neutrophil oxidative burst

Philipp Haselmayer1, Martin Daniel, Christine Tertilt

  • 1Institute for Immunology, Johannes Gutenberg University, Mainz, Germany.

Journal of Innate Immunity
|April 9, 2010
PubMed

Insights

Triggering receptor expressed on myeloid cells 1 (TREM-1) and Toll-like receptor 4 (TLR4) synergistically activate human neutrophils. Key signaling molecules like PI3K, PLC, and p38MAPK mediate this response, offering insights into inflammatory conditions.

Area of Science:

  • Immunology
  • Cellular Biology
  • Molecular Medicine

Background:

  • The triggering receptor expressed on myeloid cells 1 (TREM-1) plays a crucial role in innate immunity during microbial infections.
  • TREM-1 activation in polymorphonuclear neutrophils (PMN) often occurs alongside Toll-like receptors (TLRs), such as TLR4, but the underlying molecular mechanisms are not fully understood.

Purpose of the Study:

  • To elucidate the molecular pathways mediating the synergistic activation of human PMN by TREM-1 and TLR4.
  • To identify key intracellular signaling molecules involved in the oxidative burst induced by TREM-1 and TLR4.

Main Methods:

  • Utilized pharmacological inhibitors to block specific signaling pathways.
  • Employed Western blot analysis to assess protein activation and phosphorylation patterns.
  • Investigated the oxidative burst response in human PMN upon stimulation of TREM-1 and TLR4.

Main Results:

  • Phosphatidyl inositide 3-kinase (PI3K), phospholipase C (PLC), and p38 mitogen-activated protein kinase (p38MAPK) were identified as essential for the TREM-1- and TLR4-induced oxidative burst.
  • Distinct phosphorylation patterns of protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) were observed upon single or co-ligation of TREM-1 and TLR4, indicating separate activation pathways.
  • Demonstrated synergistic activation of human PMN through the combined engagement of TREM-1 and TLR4.

Conclusions:

  • Provided novel insights into the molecular mechanisms underlying TREM-1 and TLR4 interaction and synergistic activation in PMN.
  • Highlighted the critical roles of PI3K, PLC, and p38MAPK in mediating the innate inflammatory response.
  • These findings may inform the development of therapeutic strategies for severe inflammatory conditions like sepsis.

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