Enhanced NETosis generation in radiographic axial spondyloarthritis: utility as biomarker for disease activity and anti-TNF-α therapy effectiveness

Abstract

Background: Radiographic axial spondyloarthritis (r-axSpA) is a chronic inflammatory form of arthritis in which tumor necrosis factor (TNF)-α, a potent inducer of inflammatory response and a key regulator of innate immunity and of Th1 immune responses, plays a central role. NETosis is a mechanism of innate immune defense that is involved in diverse rheumatology diseases. Nevertheless, spontaneous NETosis generation in r-axSpA, its association to disease pathogenesis, and the NETosis involvement on anti-TNF-α therapy's effects has never been explored.Methods: Thirty r-axSpA patients and 32 healthy donors (HDs) were evaluated. Neutrophil extracellular trap (NET) formation, mediators of signal-transduction cascade required for NETosis induction and cell-free NETosis-derived products were quantified. An additional cohort of 15 r-axSpA patients treated with infliximab (IFX) for six months were further analyzed. In vitro studies were designed to assess the effects of IFX in NETosis generation and the inflammatory profile triggered. (Continued on next page)Results: Compared to HDs, neutrophils from r-axSpA patients displayed augmented spontaneous NET formation, elevated expression of NET-associated signaling components, nuclear peptidylarginine deiminase 4 translocation and increased citrullinated histone H3. Furthermore, patients exhibited altered circulating levels of cell-free NETosisderived products (DNA, nucleosomes and elastase). Additional studies revealed that cell-free NETosis-derived products could be suitable biomarkers for distinguish r-axSpA patients from HDs. Correlation studies showed association between cell-free NETosis-derived products and clinical inflammatory parameters. Besides, nucleosomes displayed potential as a biomarker for discriminate patients according to disease activity. IFX therapy promoted a reduction in both NETosis generation and disease activity in r-axSpA patients. Mechanistic in vitro studies further unveiled the relevance of IFX in reducing NET release and normalizing the augmented inflammatory activities promoted by NETs in mononuclear cells.Conclusions: This study reveals that NETosis is enhanced in r-axSpA patients and identifies the NETosis-derived products as potential disease activity biomarkers. In addition, the data suggests the potential role of NET generation analysis for assessment of therapeutic effectiveness in r-axSpA.

IL‐17A expressed on neutrophil extracellular traps promotes mesenchymal stem cell differentiation toward bone‐forming cells in ankylosing spondylitis

“…Here, we found that peripheral neutrophils of active AS patients are highly prone to NETosis by showing an increased rate of NET formation in serum and ex vivo. Recently, Ruiz-Limon et al also reported increased levels of circulating NETosis-derived products in active AS patients further supporting our findings [35]. From a clinical point of view, surrogates of NET formation, such as serum levels of circulating cell-free DNA and MPO-DNA complexes, could be promising candidate markers in future large-scale studies assessing AS disease activity.…”

“…This is in agreement with experimental evidence demonstrating that IL‐1β plays a significant indirect role in IL‐17‐dependent MSC osteogenic differentiation, by activating ERK1/2, AKT, and STAT3 signaling pathways [44]. In addition, recent data describe a high accumulation of activated IL‐1β‐producing neutrophils in the paw joints during experimental spondyloarthritis [48], while plasma cell‐free DNA levels are positively correlated with IL‐1β concentration in active AS patients, further supporting the role of neutrophil‐derived IL‐1β in AS [35]. Recently, we reported the key pathogenic role of neutrophil/NET‐driven IL‐1β‐mediated inflammation in ulcerative colitis, a chronic inflammatory disease overlapping with the spondyloarthritis spectrum [30].…”

The Potential for Repurposing Anti-TNF as a Therapy for the Treatment of COVID-19

“…43,46 Of relevance, anti-TNF therapy reduces NET formation in vitro as well as in murine models and patients with immune mediated disease. [47][48][49]…”

Novel immune cell phenotypes in spondyloarthritis pathogenesis

“…A buffering mechanism similar to that observed for mast cells could be therefore postulated. In line with this consideration, one of the ways by which neutrophils promptly release the IL-17 in an inflammatory fashion is NETosis, previously observed in psoriasis and more recently reported to be exaggerated in radiographic axial SpA patients [ 107 , 108 ].…”