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Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions.

ABSTRACT: Systemic juvenile idiopathic arthritis (sJIA) has long been recognized as unique among childhood arthritides, because of its distinctive clinical and epidemiological features, including an association with macrophage activation syndrome. Here, we summarize research into sJIA pathogenesis. The triggers of disease are unknown, although infections are suspects. Once initiated, sJIA seems to be driven by innate proinflammatory cytokines. Endogenous Toll-like receptor ligands, including S100 proteins, probably synergize with cytokines to perpetuate inflammation. These and other findings support the hypothesis that sJIA is an autoinflammatory condition. Indeed, IL-1 is implicated as a pivotal cytokine, but the source of excess IL-1 activity remains obscure and the role of IL-1 in chronic arthritis is less clear. Another hypothesis is that a form of hemophagocytic lymphohistiocytosis underlies sJIA, with varying degrees of its expression across the spectrum of disease. Alternatively, sJIA with MAS might be a genetically distinct subtype. Yet another hypothesis proposes that inadequate downregulation of immune activation is central to sJIA, supporting evidence for which includes 'alternative activation' of monocyte and macrophages and possible deficiencies in IL-10 and T regulatory cells. Some altered immune phenotypes persist during clinically inactive disease, which suggests that this stage might represent compensated inflammation. Despite much progress being made, many questions remain, providing fertile ground for future research.

SUBMITTER: Mellins ED

PROVIDER: S-EPMC4180659 | biostudies-literature | 2011 Jun

REPOSITORIES: biostudies-literature

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Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions.

Mellins Elizabeth D ED Macaubas Claudia C Grom Alexei A AA

Nature reviews. Rheumatology 20110607 7

Systemic juvenile idiopathic arthritis (sJIA) has long been recognized as unique among childhood arthritides, because of its distinctive clinical and epidemiological features, including an association with macrophage activation syndrome. Here, we summarize research into sJIA pathogenesis. The triggers of disease are unknown, although infections are suspects. Once initiated, sJIA seems to be driven by innate proinflammatory cytokines. Endogenous Toll-like receptor ligands, including S100 proteins ...[more]

PMID: 21647204

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Project description:Background: Systemic-Onset Juvenile Idiopathic Arthritis (SJIA) is a rare disease associated with dysregulated interleukin (IL)-1 activity. Objectives: To assess the efficacy and safety of Anakinra, an IL-1 receptor antagonist in SJIA and its effects on gene expression profiling. Methods: We conducted a multicenter, randomized, double-blind placebo-controlled trial. The primary objective was to compare the efficacy of a one-month treatment with anakinra (2 mg/kg subcutaneoulsy daily, maximum 100 mg) to a placebo between 2 groups of 12 SJIA patients each. Response was defined by a 30% improvement of the pediatric American College of Rheumatology criteria for JIA, resolution of systemic symptoms and a decrease of at least 50% of both C-reactive protein and erythrocyte sedimentation rate compared to baseline. An intention-to-treat analyze was performed. After Month 1 (M1), patients taking placebo were switched to Anakinra. Secondary objectives included tolerance and efficacy assessment for 12 months. Results: At M1, concluding the randomized trial, there was a significant difference in the response rate between patients treated with Anakinra (8/12 responders) and placebo (1/12) (p=0.003). The number of adverse events, mainly pain to injections, was similar between both groups. Ten patients from the placebo group switched to Anakinra at M1; nine were responders at M2. Between M1 and M12, six patients stopped treatment for an adverse event (Crohn’s disease, hepatitis), a lack of efficacy or a disease flare (2 cases each). Blood gene expression profiling at enrollment and upon follow-up allowed us to identify one set of dysregulated genes that reverted to normal values in the clinical responders and a second set, including interferon-inducible genes, that was induced by Anakinra. Conclusion: Anakinra is an effective treatment of SJIA. Its effect is associated with normalization of blood gene expression profiles in clinical responders and de novo induction of an interferon signature. (Clinical trials registration number: NCT00339157)

Project description:Systemic juvenile idiopathic arthritis (SJIA) is a chronic childhood arthropathy with features of autoinflammation. Early inflammatory SJIA is associated with expansion and activation of neutrophils with a sepsis-like phenotype, but neutrophil phenotypes present in longstanding and clinically inactive disease (CID) are unknown. The objective of this study was to examine activated neutrophil subsets, S100 alarmin release, and gene expression signatures in children with a spectrum of SJIA disease activity. Methods: Highly-purified neutrophils were isolated using a two-step procedure of density-gradient centrifugation followed by magnetic-bead based negative selection prior to flow cytometry or cell culture to quantify S100 protein release. Whole transcriptome gene expression profiles were compared in neutrophils from children with both active SJIA and CID. Results: Patients with SJIA and active systemic features demonstrated a higher number of CD16+CD62Llo neutrophil population compared to controls. This neutrophil subset was not seen in patients with CID or patients with active arthritis not exhibiting systemic features. Using imaging flow cytometry, CD16+CD62Llo neutrophils from patients with active SJIA and features of macrophage activation syndrome (MAS) had increased nuclear hypersegmentation compared to CD16+CD62L+ neutrophils. Serum levels of S100A8/A9 and S100A12 were strongly correlated with peripheral blood neutrophil counts. Neutrophils from active SJIA patients did not show enhanced resting S100 protein release; however, regardless of disease activity, neutrophils from SJIA patients did show enhanced S100A8/A9 release upon PMA stimulation compared to control neutrophils. Furthermore, whole transcriptome analysis of highly purified neutrophils from children with active SJIA identified 214 differentially expressed genes compared to neutrophils from healthy controls. The most significantly upregulated gene pathway was Immune System Process, including AIM2, IL18RAP, and NLRC4. Interestingly, this gene set showed intermediate levels of expression in neutrophils from patients with long-standing CID yet persistent serum IL-18 elevation. Indeed, all patient samples regardless of disease activity demonstrated elevated inflammatory gene expression, including inflammasome components and S100A8. Conclusion: We identify features of neutrophil activation in SJIA patients with active disease and CID, including a proinflammatory gene expression signature, reflecting persistent innate immune activation. Taken together, these studies expand understanding of neutrophil function in chronic autoinflammatory disorders such as SJIA.

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Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions.

Publications

Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions.

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