Enhanced TLR4 reactivity following injury is mediated by increased p38 activation

Adrian A. Maung, Satoshi Fujimi, Marissa L. Miller, Malcolm P. MacConmara, John A. Mannick, James A. Lederer

Research output: Contribution to journalArticle

68 Citations (Scopus)

Abstract

Severe injury primes the innate-immune system for increased Toll-like receptor 4 (TLR4)-induced proinflammatory cytokine production by macrophages. In this study, we examined changes in TLR4 signaling pathways in splenic macrophages from burn-injured or sham mice to determine the molecular mechanism(s) responsible for the increased TLR4 responsiveness. Using flow cytometry and specific antibodies, we first looked for injury-induced changes in the expression levels of several TLR-associated signaling molecules. We found similar levels of myeloid differentiation primary-response protein 88 (MyD88) and interleukin-1 receptor-associated kinase-M (IRAK-M) and somewhat lower levels of total p38, extracellular signal-regulated kinase (ERK), and stress-activated protein kinase (SAPK)/c-jun N-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) in burn compared with sham macrophages. However, with the use of antibodies specific for the phosphorylated (activated) forms of the three MAPKs, we found that macrophages from burn mice showed a twofold increase in purified lipopolysaccharide (LPS)-stimulated p38 activation as compared with cells from sham mice on days 1 and 7 post-injury, whereas ERK and SAPK/JNK activation was increased by burn injury only on day 1. Using the specific p38 inhibitor (SB203580), we confirmed that the increase in tumor necrosis factor α production by LPS-stimulated burn macrophages requires p38 activation. Although we demonstrated that injury increases macrophage TLR4 mRNA expression and intracellular expression of TLR4-myeloid differentiation protein-2 (MD-2) protein, macrophage cell-surface expression of TLR4-MD-2 was not changed by burn injury. Our results suggest that the injury-induced increase in TLR4 reactivity is mediated, at least in part, by enhanced activation of the p38 signaling pathway.

Original languageEnglish (US)
Pages (from-to)565-573
Number of pages9
JournalJournal of Leukocyte Biology
Volume78
Issue number2
DOIs
StatePublished - Aug 2005

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Toll-Like Receptor 4
Macrophages
Wounds and Injuries
JNK Mitogen-Activated Protein Kinases
Extracellular Signal-Regulated MAP Kinases
Heat-Shock Proteins
Mitogen-Activated Protein Kinases
Protein Kinases
Lipopolysaccharides
Interleukin-1 Receptor-Associated Kinases
Myeloid Differentiation Factor 88
Antibodies
Burns
Immune System
Flow Cytometry
Membrane Proteins
Proteins
Tumor Necrosis Factor-alpha
Cytokines
Messenger RNA

Keywords

  • Inflammation
  • Macrophages
  • Monocytes
  • Signal transduction

ASJC Scopus subject areas

  • Cell Biology

Cite this

Enhanced TLR4 reactivity following injury is mediated by increased p38 activation. / Maung, Adrian A.; Fujimi, Satoshi; Miller, Marissa L.; MacConmara, Malcolm P.; Mannick, John A.; Lederer, James A.

In: Journal of Leukocyte Biology, Vol. 78, No. 2, 08.2005, p. 565-573.

Research output: Contribution to journalArticle

Maung, Adrian A. ; Fujimi, Satoshi ; Miller, Marissa L. ; MacConmara, Malcolm P. ; Mannick, John A. ; Lederer, James A. / Enhanced TLR4 reactivity following injury is mediated by increased p38 activation. In: Journal of Leukocyte Biology. 2005 ; Vol. 78, No. 2. pp. 565-573.
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