Amplification of the response to toll-like receptor ligands by prolonged exposure to interleukin-6 in mice: Implication for the pathogenesis of macrophage activation syndrome

Raffaele Strippoli, Francesco Carvello, Roberta Scianaro, Loredana De Pasquale, Marina Vivarelli, Stefania Petrini, Luisa Bracci-Laudiero, Fabrizio De Benedetti

Research output: Contribution to journalArticle

Abstract

Objective To investigate whether prolonged exposure to interleukin-6 (IL-6) affects the inflammatory response induced by Toll-like receptor (TLR) ligands. Methods IL-6-transgenic mice and wild-type mice were stimulated with different TLR ligands; survival rates, blood cell counts, and biochemical parameters were analyzed. Murine splenic mononuclear cells and peritoneal macrophages were stimulated with lipopolysaccharide (LPS), lipoteichoic acid, poly(I-C), or CpG. Human macrophages were cultured for 4 days in the presence of IL-6 and then stimulated with LPS. Inflammatory cytokine expression was measured by enzyme-linked immunosorbent assay or reverse transcription-polymerase chain reaction. Activation of STAT-3, ERK-1/2 (MAPK), and p65 NF-κB was evaluated by Western blotting or confocal analysis. Results Treatment of IL-6-transgenic mice with TLR ligands led to an increased fatality rate and elevated levels of IL-1β, tumor necrosis factor α (TNFα), IL-6, and IL-18. Macrophages from IL-6-transgenic mice produced increased levels of inflammatory cytokines, which were associated with increased phosphorylation of STAT-3 and ERK-1/2 and with increased NF-κB nuclear translocation. Human macrophages treated with IL-6 and then stimulated with LPS showed elevated levels of cytokines and similarly elevated signaling pathway activation. After LPS administration, IL-6-transgenic mice showed an increase in ferritin and soluble CD25 levels, as well as a decrease in platelet and neutrophil counts and in hemoglobin levels compared to wild-type mice. Conclusion Our findings indicate that prolonged exposure to IL-6 in vivo and in vitro leads to an exaggerated inflammatory response to TLR ligands. Hematologic and biochemical abnormalities in IL-6-transgenic mice treated with LPS show striking similarities to macrophage activation syndrome.

Original languageEnglish
Pages (from-to)1680-1688
Number of pages9
JournalArthritis and Rheumatism
Volume64
Issue number5
DOIs
Publication statusPublished - May 2012

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ASJC Scopus subject areas

  • Immunology
  • Immunology and Allergy
  • Rheumatology
  • Pharmacology (medical)

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