Neutrophil extracellular traps mediate joint hyperalgesia induced by immune inflammation

Abstract

Objective To evaluate the role of neutrophil extracellular traps (NETs) in the genesis of joint hyperalgesia using an experimental model of arthritis and transpose the findings to clinical investigation. Methods C57BL/6 mice were subjected to antigen-induced arthritis (AIA) and treated with Pulmozyme (PLZ) to degrade NETs or Cl-amidine to inhibit NET production. Oedema formation, the histopathological score and mechanical hyperalgesia were evaluated. NETs were injected intra-articularly in wild type (WT), Tlr4−/−, Tlr9−/−, Tnfr1−/− and Il1r−/− mice, and the levels of cytokines and Cox2 expression were quantified. NETs were also quantified from human neutrophils isolated from RA patients and individual controls. Results AIA mice had increased NET concentration in joints, accompanied by increased Padi4 gene expression in the joint cells. Treatment of AIA mice with a peptidyl arginine deiminase 4 inhibitor or with PLZ inhibited the joint hyperalgesia. Moreover, the injection of NETs into joints of naïve animals generated a dose-dependent reduction of mechanical threshold, an increase of articular oedema, inflammatory cytokine production and cyclooxygenase-2 expression. In mice deficient for Tnfr1, Il1r, Tlr4 and Tlr9, joint hyperalgesia induced by NETs was prevented. Last, we found that neutrophils from RA patients were more likely to release NETs, and the increase in synovial fluid NET concentration correlated with an increase in joint pain. Conclusion The findings indicate that NETs cause hyperalgesia possibly through Toll-like receptor (TLR)-4 and TLR-9. These data support the idea that NETs contribute to articular pain, and this pathway can be an alternative target for the treatment of pain in RA.

Targeting Neutrophils Extracellular Traps (NETs) reduces multiple organ injury in a COVID-19 mouse model

“…The literature describes that NETs can present direct cytotoxic effects on different mammalian cell types, including epithelial and endothelial cells, inducing apoptosis or necrosis (12, 46). Moreover, NETs could also activate different PRR receptors, such as toll-like receptor (TLR)-4 and 9, which mediate the release of inflammatory mediators; in turn, amplifying the direct effects of NETs (35). In this context, during COVID-19, apoptosis of lung epithelial was previously observed.…”

“…Besides their microbicidal ability, NETs mediate lesions observed in several inflammatory diseases, including rheumatoid arthritis, lupus, diabetes, and sepsis (8,10,(35)(36)(37)(38)(39). In fact, inhibition of NETs production prevented lung, heart and liver lesions observed in experimental sepsis (38)(39)(40).…”

Protective Effect of Methyl gallate on Murine Antigen-Induced Arthritis by Inhibiting Inflammatory Process and Bone Erosion

“…This model is trigger primarily by immune processes and presents several characteristics of RA. Among others, a marked synovial-lining hyperplasia, proliferation of subliming cells, in ltration of in ammatory cells, local chemokine and cytokine production, pannus formation, (Schneider et al 2020). It is interesting to note that MG can also inhibit in ammatory pain and cell signaling induced by Toll-like receptor ligands (Correa et al 2020).…”

Potential Neuroimmune Interaction in Chronic Pain: A Review on Immune Cells in Peripheral and Central Sensitization

“…Furthermore, in the CCI model, IL-18 can feedback control its expression and regulate the other mediators involved in neuroinflammation, such as causing an up-regulation of MCP-1/CCL2, IL-4, or a down-regulation of IFN-γ ( 14 ). In patients with rheumatoid arthritis (RA), neutrophil extracellular traps (NETs) induced hyperalgesia by acting on Toll-like receptors (TLR-4 and TLR-9), and the production of NETs was positively correlated with the degree of pain ( 15 ). Other studies also reported that neutrophils infiltrated around the affected DRG release leukocyte elastase (LE) and played a role in the maintenance of chronic neuropathic pain in a diabetic neuropathic pain model.…”