Deregulation of the IL-1ß axis in chronic recurrent multifocal osteomyelitis.

BACKGROUND: This study aims to investigate the inflammasome response in peripheral blood mononuclear cells (PBMCs) and the expression of inflammasome components in bone biopsies from patients with chronic recurrent multifocal osteomyelitis (CRMO). METHODS: The expression of inflammasome components mRNAs was evaluated in PBMCs isolated from 15 CRMO patients and 13 healthy controls by quantitative real-time PCR. The Interleukin (IL)-1ß released in the medium of PBMC cultures after treatment with lipopolysaccharides (LPS) alone or LPS and ATP was measured by ELISA. Immunohistochemical staining for Apoptosis-associated Speck-like protein (ASC), caspase-1 (CASP-1), Nod-like receptor protein-3 (NLRP3) and IL-1ß expression was performed in bone biopsies from CRMO patients. RESULTS: mRNA levels of ASC, CASP-1 and IL-1ß were significantly higher in freshly isolated PBMCs from CRMO patients in active disease than in healthy controls. CASP-1 and IL-1ß transcript levels were significantly higher also in PBMCs from CRMO patients in remission compared to healthy controls. PBMCs from CRMO patients in active disease stimulated in vitro with LPS showed a significant increase in IL-1ß release compared to healthy control cells. Immunohistochemistry staining of bone tissue revealed the expression of inflammasome components in CRMO osteoclasts. CONCLUSIONS: Our data suggest that an abnormal regulation of IL-1ß axis may be involved in CRMO pathogenesis.

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.

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-1ß, 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.