Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Background/Purpose: Reduction of adenosine deaminase 2 (ADA2) activity due to autosomal recessive loss of function mutations in the CECR1 gene results in a systemic illness known as DADA2 characterized in part by early-onset stroke, vasculitis, and clinical response to TNF-inhibitors. Adenosine, which is extracellularly degraded by ADA2, modulates inflammation via four different adenosine receptors (ARs). Neutrophils and a subset of neutrophils known as low-density granulocytes (LDGs) have been implicated in the pathogenesis of small-vessel vasculitis through the formation of neutrophil extracellular traps (NETs). The study objective was to determine whether neutrophils and NETs play a pathogenic role in DADA2.
Methods: Neutrophils and LDGs were isolated from healthy volunteers, patients with DADA2, and their family members. NETs were quantified and visualized by fluorescence microscopy. Immunofluorescence was performed against citrullinated-histone H4 and macrophage markers to detect NETs and macrophages in affected tissue from a patient with DADA2. Neutrophils were incubated with adenosine +/- ADA2 enzyme and resultant NET formation was quantified. Pharmacologic approaches were utilized to determine the specific receptor(s) and pathways that mediate NET formation by adenosine. ELISA quantified TNF-alpha release in supernatants from macrophages incubated with NETs.
Results: An abundance of circulating LDGs prone to spontaneous NET formation were observed during active disease in DADA2 and were significantly reduced after remission induction by anti-TNF therapies. Increased circulating LDGs were identified in unaffected heterozygous carriers of CECR1 mutations. In vivo evidence demonstrated NETs and macrophages in affected gastrointestinal tissue in a patient with DADA2. Adenosine triggered NET formation by engaging A1 and A3 adenosine receptors and through ROS- and PAD4- dependent pathways. Adenosine-induced NETosis was inhibited in the presence of recombinant ADA2, A1/A3 AR antagonists, or an A2A agonist. M1 macrophages incubated with NETs from patients with DADA2 released significantly increased amounts of TNF-alpha. Treatment with IL-1Ra (anakinra) or an A2A AR agonist decreased nuclear translocation of NFkB and pro-inflammatory cytokines-induced by NETs in macrophages.
Conclusion: Neutrophils may play a pathogenic role in DADA2. LDGs and NETs are observed during active disease. Adenosine can trigger NET formation, and deficiency of ADA2 may enhance adenosine-mediated NETosis. M1 macrophages produce TNF-alpha when exposed to NETs from patients with DADA2, potentially explaining the efficacy of anti-TNF therapies in this disease. Modulation of adenosine-mediated NET formation may constitute a novel and directed therapeutic approach in the treatment of DADA2.
To cite this abstract in AMA style:Carmona-Rivera C, Shwin KW, irizarry-Caro JA, Khaznadar SS, Liu Y, Jacobson KA, Ombrello A, Stone DL, Tsai WL, Gadina MG, Kastner DL, Aksentijevich I, Kaplan MJ, Grayson PC. Neutrophil Extracellular Traps Are Induced By Adenosine and Stimulate Release of TNF Alpha from Macrophages in Deficiency of Adenosine Deaminase 2 (DADA2) [abstract]. Arthritis Rheumatol. 2017; 69 (suppl 10). https://acrabstracts.org/abstract/neutrophil-extracellular-traps-are-induced-by-adenosine-and-stimulate-release-of-tnf-alpha-from-macrophages-in-deficiency-of-adenosine-deaminase-2-dada2/. Accessed September 28, 2021.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/neutrophil-extracellular-traps-are-induced-by-adenosine-and-stimulate-release-of-tnf-alpha-from-macrophages-in-deficiency-of-adenosine-deaminase-2-dada2/