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Screening Bioactive Nanoparticles in Phagocytic Immune Cells for Inhibitors of Toll-like Receptor Signaling
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Mrp8 and Mrp14 are endogenous activators of Toll-like receptor 4, promoting lethal, endotoxin-induced shock

Thomas Vogl1, Klaus Tenbrock, Stephan Ludwig

  • 1Institute of Experimental Dermatology, University of Münster, D-48129 Münster, Germany.

Nature Medicine
|September 4, 2007
PubMed

Insights

Myeloid-related proteins (Mrp8/S100A8 and Mrp14/S100A9) amplify sepsis inflammation. Mice lacking these proteins are protected from lethal shock, revealing their role as endogenous TLR4 ligands.

Area of Science:

  • Immunology
  • Molecular Biology
  • Sepsis Pathophysiology

Background:

  • Sepsis involves a complex inflammatory cascade.
  • Phagocyte activation is central to sepsis pathogenesis.
  • Myeloid-related proteins Mrp8 (S100A8) and Mrp14 (S100A9) are abundant in phagocytes.

Purpose of the Study:

  • To investigate the role of Mrp8-Mrp14 complexes in sepsis.
  • To identify novel regulators of the inflammatory cascade during sepsis.
  • To elucidate the mechanism by which Mrp8-Mrp14 complexes modulate inflammation.

Main Methods:

  • Genetic knockout mouse models (Mrp8-Mrp14 deficient).
  • Induction of sepsis using endotoxin and Escherichia coli.
  • Cellular assays with phagocytes and HEK293 cells.
  • Biochemical studies including surface plasmon resonance.

Main Results:

  • Mice lacking Mrp8-Mrp14 complexes showed protection against lethal endotoxin shock and E. coli sepsis.
  • Mrp8-Mrp14 complexes are released upon phagocyte activation and amplify inflammatory responses.
  • Mrp8 acts as an endogenous ligand, directly interacting with the Toll-like receptor 4 (TLR4)-MD2 complex.
  • This interaction leads to downstream signaling, including activation of NF-kappaB and increased TNF-alpha production.

Conclusions:

  • Mrp8-Mrp14 complexes are critical amplifiers of phagocyte activation in sepsis.
  • Mrp8 functions upstream of TNF-alpha, acting as an endogenous TLR4 ligand.
  • Targeting Mrp8-Mrp14 complexes represents a potential therapeutic strategy for sepsis.

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