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Trypsin inhibits lipopolysaccharide signaling in macrophages via toll-like receptor 4 accessory molecules

Hiroyuki Komatsu1, Akihiro Shimose, Takashi Shimizu

  • 1Laboratory of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Yamaguchi University, Japan.

Life Sciences
|July 10, 2012
PubMed
Abstract

Insights

Trypsin inhibits lipopolysaccharide (LPS) immune responses in macrophages by degrading CD14, independent of protease-activated receptors (PARs). This finding clarifies trypsin's role in the immune response, particularly in acute pancreatitis.

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • Macrophages play a crucial role in the innate immune response.
  • Lipopolysaccharide (LPS) is a potent activator of macrophages via Toll-like receptor 4 (TLR4) complex.
  • Protease-activated receptors (PARs) are involved in various cellular processes, including inflammation.

Purpose of the Study:

  • To investigate the role of trypsin in macrophage immune responses.
  • To determine if protease-activated receptors (PARs) mediate trypsin's effects on macrophages.
  • To elucidate the mechanism by which trypsin influences LPS signaling.

Main Methods:

  • Utilized RAW264.7 cells and primary macrophages from wild-type and PAR2 knockout mice.
  • Stimulated macrophages with LPS, trypsin, thrombin, and PAR-specific agonists.
  • Quantified macrophage activation via nitric oxide production and inflammatory mediator expression (iNOS, IL-1β, IL-6).
  • Assessed the expression of TLR4 and its accessory molecules (MD-2, CD14).
  • Investigated trypsin's direct effect on recombinant CD14 protein.

Main Results:

  • Trypsin significantly inhibited LPS-induced nitric oxide production and inflammatory mediator expression.
  • These inhibitory effects were observed in both wild-type and PAR2 knockout macrophages, indicating a PAR-independent mechanism.
  • Trypsin decreased the expression of soluble CD14 (sCD14), membrane-bound CD14 (mCD14), and soluble MD-2 (sMD-2).
  • Trypsin directly degraded recombinant CD14 protein.
  • Other PAR agonists did not replicate trypsin's inhibitory effects.

Conclusions:

  • Trypsin inhibits LPS signaling in a PAR-independent manner.
  • The mechanism involves the degradation of TLR4 accessory molecules, specifically CD14.
  • This study enhances understanding of the complex immune responses in conditions like acute pancreatitis.

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