Mrp8 and Mrp14 are endogenous activators of Toll-like receptor 4, promoting lethal, endotoxin-induced shock

T Vogl, K Tenbrock, S Ludwig, N Leukert, C Ehrhardt… - Nature medicine, 2007 - nature.com
T Vogl, K Tenbrock, S Ludwig, N Leukert, C Ehrhardt, MAD Van Zoelen, W Nacken, D Foell…
Nature medicine, 2007nature.com
To identify new components that regulate the inflammatory cascade during sepsis, we
characterized the functions of myeloid-related protein-8 (Mrp8, S100A8) and myeloid-related
protein-14 (Mrp14, S100A9), two abundant cytoplasmic proteins of phagocytes. We now
demonstrate that mice lacking Mrp8-Mrp14 complexes are protected from endotoxin-
induced lethal shock and Escherichia coli–induced abdominal sepsis. Both proteins are
released during activation of phagocytes, and Mrp8-Mrp14 complexes amplify the endotoxin …
Abstract
To identify new components that regulate the inflammatory cascade during sepsis, we characterized the functions of myeloid-related protein-8 (Mrp8, S100A8) and myeloid-related protein-14 (Mrp14, S100A9), two abundant cytoplasmic proteins of phagocytes. We now demonstrate that mice lacking Mrp8-Mrp14 complexes are protected from endotoxin-induced lethal shock and Escherichia coli–induced abdominal sepsis. Both proteins are released during activation of phagocytes, and Mrp8-Mrp14 complexes amplify the endotoxin-triggered inflammatory responses of phagocytes. Mrp8 is the active component that induces intracellular translocation of myeloid differentiation primary response protein 88 and activation of interleukin-1 receptor–associated kinase-1 and nuclear factor-κB, resulting in elevated expression of tumor necrosis factor-α (TNF-α). Using phagocytes expressing a nonfunctional Toll-like receptor 4 (TLR4), HEK293 cells transfected with TLR4, CD14 and MD2, and by surface plasmon resonance studies in vitro, we demonstrate that Mrp8 specifically interacts with the TLR4-MD2 complex, thus representing an endogenous ligand of TLR4. Therefore Mrp8-Mrp14 complexes are new inflammatory components that amplify phagocyte activation during sepsis upstream of TNFα–dependent effects.
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