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Prolonged tumor necrosis factor ? primes fibroblast-like synoviocytes in a gene-specific manner by altering chromatin.

ABSTRACT: During the course of rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) are chronically exposed to an inflammatory milieu. The purpose of this study was to test the hypothesis that prolonged exposure of FLS to tumor necrosis factor ? (TNF?) augments inflammatory responses to secondary stimuli (priming effect).FLS obtained from RA patients were exposed to TNF? for 3 days and were then stimulated with interferons (IFNs). Expression of IFN target genes was measured by real-time quantitative reverse transcription-polymerase chain reaction analysis and enzyme-linked immunosorbent assay. Total STAT-1 protein and IFN-mediated STAT-1 activation were evaluated by Western blotting. Total histone levels, histone acetylation, and NF-?B p65 and RNA polymerase II (Pol II) recruitment were measured at the CXCL10 promoter (encodes IFN?-inducible 10-kd protein [IP-10]) by chromatin immunoprecipitation assays.Prolonged pre-exposure of FLS to TNF? enhanced the magnitude and extended the kinetics of CXCL10/IP-10, CXCL9, and CXCL11 production upon subsequent IFN stimulation. This phenotype was retained over a period of days, even after the removal of TNF?. Prolonged TNF? exposure decreased histone levels, increased acetylation of the remaining histones, and heightened recruitment of NF-?B p65 and Pol II to the CXCL10 promoter. In parallel, an increase in intracellular STAT-1 led to amplification of IFN-induced STAT-1 activation.Our study reveals a novel pathogenic function of TNF?, namely, prolonged and gene-specific priming of FLS for enhanced transcription of inflammatory chemokine genes due to the priming of chromatin, the sustained activation of NF-?B, and the amplification of STAT-1 activation downstream of IFNs. These data also suggest that FLS gain an "inflammatory memory" upon prolonged exposure to TNF?.

SUBMITTER: Sohn C

PROVIDER: S-EPMC4455921 | biostudies-literature | 2015 Jan

REPOSITORIES: biostudies-literature

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Prolonged tumor necrosis factor α primes fibroblast-like synoviocytes in a gene-specific manner by altering chromatin.

Sohn Christopher C Lee Angela A Qiao Yu Y Loupasakis Konstantinos K Ivashkiv Lionel B LB Kalliolias George D GD

Arthritis & rheumatology (Hoboken, N.J.) 20150101 1

<h4>Objective</h4>During the course of rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) are chronically exposed to an inflammatory milieu. The purpose of this study was to test the hypothesis that prolonged exposure of FLS to tumor necrosis factor α (TNFα) augments inflammatory responses to secondary stimuli (priming effect).<h4>Methods</h4>FLS obtained from RA patients were exposed to TNFα for 3 days and were then stimulated with interferons (IFNs). Expression of IFN target genes w ...[more]

PMID: 25199798

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Project description:Aseptic loosening of total joint replacements is driven by a macrophage-mediated inflammatory reaction to implant-derived wear particles. Phagocytosis of implant debris has been suggested to activate the NLRP3 inflammasome leading to secretion of interleukin (IL)-1β. However, factors and molecular mechanisms driving the particle-induced inflammasome activation are yet to be fully elucidated. In this study, we investigated the inflammasome response of human primary macrophages to titanium, chromium, and molybdenum particles in vitro. We observed that particles alone were not sufficient to induce IL-1β secretion, but an additional priming signal-such as bacterial lipopolysaccharide (LPS)-was required to license the inflammasome activation. By using specific inhibitors against the inflammasome signaling pathway, we demonstrate that the particle-induced IL-1β secretion depended upon activation of the NLRP3 inflammasome. We further hypothesized that tumor necrosis factor (TNF) could substitute for LPS as a priming signal, and found that particle stimulation together with preceding TNF treatment resulted in inflammasome-dependent IL-1β production as well. Our results show that the NLRP3 inflammasome mediates wear particle responses in human primary macrophages, and its activation does not necessarily require the presence of bacterial components, but can be induced under aseptic conditions by TNF priming. STATEMENT OF SIGNIFICANCE: This study was conducted to elucidate the molecular mechanisms of metal particle-induced IL-1β secretion in human primary macrophages. Production of this pro-inflammatory mediator from wear particle-activated macrophages has been associated with increased bone loss around total joint replacements-a condition eventually requiring revision surgery. Our results confirm that together with a co-stimulatory priming signal, particles of common implant metals elicit macrophage-mediated IL-1β secretion through activation of the NLRP3 inflammasome pathway. We also present a concept of TNF priming in this context, demonstrating that the particle-related IL-1β secretion can take place in a truly sterile environment. Thus, inhibition of inflammasome signaling appears a means to prevent wear particle-induced inflammation and development of peri‑prosthetic osteolysis.

Dataset Information

Prolonged tumor necrosis factor ? primes fibroblast-like synoviocytes in a gene-specific manner by altering chromatin.

Publications

Prolonged tumor necrosis factor α primes fibroblast-like synoviocytes in a gene-specific manner by altering chromatin.

Similar Datasets

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