Circulating neutrophil extracellular trap-forming neutrophils in rheumatoid arthritis exacerbation are majority dual endothelin-1/signal peptide receptor+ subtype
Andrew Cross, Helen L. Wright, Jacqueline J. Choi, Steven W. Edwards, Nelson Ruiz‐Opazo, Victoria L. M. Herrera
Abstract
Neutrophil extracellular traps (NETs) are associated with rheumatoid arthritis pathogenesis and severity. Since homeostatic NET-forming neutrophils [NET+Ns] have beneficial roles in defense against pathogens, their distinction from pro-injury [NET+N] subtypes is important, especially if they are to be therapeutically targeted. Having identified circulating, pro-injury DEspR+CD11b+[NET+Ns] in patients with neutrophilic secondary tissue injury, we determined whether DEspR+[NET+Ns] are present in rheumatoid arthritis (RA) flares. Whole blood samples of patients with RA flares on maintenance therapy (n = 6) were analyzed by flow cytometry (FCM) and immunofluorescence cytology followed by semi-automated quantitative confocal microscopy (qIFC). We assessed clinical parameters, levels of neutrophils and [NET+Ns], and plasma S100A8/A9. qIFC detected circulating DEspR+CD11b+neutrophils and [NET+Ns] in RA-flare patients but not healthy controls. DEspR+[NET+Ns] were positive for citrullinated histone H3 (citH3+), extruded DNA, decondensed but recognizable polymorphic nuclei, and [NET+N] doublet interactions in mostly non-ruptured NET-forming neutrophils. Circulating DNA+/DEspR+/CD11b+/citH3+microvesicles (netMVs) were observed. FCM detected increased %DEspR+CD11b+neutrophils and DEspR+ cell-cell doublets whose levels trended with DAS28 scores, as did plasma S100A8/A9 levels. This study identifies circulating DEspR+/CD11b+neutrophils and [NET+Ns] in RA-flare patients on maintenance therapy. Detection of circulating DEspR+citH3+[NET+Ns] and netMVs indicate a systemic neutrophilic source of citH3-antigen concordant with multi-joint RA pathogenesis. Increased S100A8/A9 alarmin levels are associated with cell injury and released upon NET-formation. As a ligand for TLR4, S100A8/A9 forms a positive feedback loop for TLR4-induced DEspR+neutrophils. These data identify DEspR+neutrophils and [NET+Ns] in RA pathogenesis as a potential biomarker and/or therapeutic target.