Neutrophil extracellular trap‐microparticle complexes trigger neutrophil recruitment via high‐mobility group protein 1 (HMGB1)‐toll‐like receptors(TLR2)/TLR4 signalling

Abstract

Background and Purpose Recent data suggest that neutrophil extracellular traps (NETs) form aggregates with microparticles (MPs) upon activation of neutrophils although the functional role of NET‐MP complexes remain elusive. The objective of this study was to examine the role of NET‐MP aggregates in leukocyte recruitment in vivo. Experimental Approach PMA stimulation of murine bone marrow neutrophils generated NET‐MP complexes and pretreatment with caspase and calpain inhibitors resulted in the formation of NETs depleted of MPs. Leukocyte–endothelium interactions were studied by using intravital microscopy of the mouse cremaster microcirculation. Key Results Intrascrotal injection of NET‐MP aggregates dose‐dependently increased leukocyte recruitment. In contrast, leukocyte responses were markedly reduced after administration of NETs depleted of MPs. Neutrophil depletion abolished intravascular and extravascular leukocytes in response to challenge with NET‐MP complexes. Electron microscopy revealed that NET‐associated MPs express HMGB1. Notably, immunoneutralization of HMGB1 markedly decreased NET‐MP complex‐induced neutrophil accumulation. Moreover, inhibition of TLR2 and TLR4 significantly reduced neutrophil recruitment in response to NET‐MP aggregates. Conclusions and Implications These data show that NET‐MP complexes are potent inducers of neutrophil recruitment, which is dependent on HMGB1 expressed on MPs and mediated via TLR2 and TLR4. Blocking MP binding to NETs or downstream inhibition of the HMGB1‐TLR2/TLR4 axis might provide useful targets to attenuating NET‐dependent tissue damage in acute inflammation.

NETosis as a Pathogenic Factor for Heart Failure

“…By contrast, antagonistic HMGB1 box A, miR-129-5p, and the natural product HMGB1 inhibitor glycyrrhizic acid reduce infarct size and tissue damage of the heart; inhibit oxidative stress and inflammatory response; and prevent pressure overload-induced cardiac hypertrophy, heart fibrosis, and failure [ 144 – 147 ]. Importantly, HMGB1 promotes NETs and exacerbates tissue damage [ 148 , 149 ]. Furthermore, soluble FN-EDA is a valuable biomarker in cardiac remodeling, and in patients with HF, the serum FN-EDA level was significantly elevated [ 150 ].…”

Pre-treatment with compound Danshen dripping pills prevents lipid infusion-induced microvascular dysfunction in mice

“…Leukocyte flux and leukocyte endothelium interactions (rolling and adhesion) analysis was conducted as described by Wang et al. ( 2019 ). Briefly, rolling leukocyte flux was measured at indicated time points by counting the number of rolling leukocytes per 20 s passing a reference point in the microvessel and expressed as cells/min.…”

“…Quantification of microvascular blood flow velocity in cremaster and leukocyte adhesion in venules were completed by Image-Pro Plus 6.0 software (Media Cybernetic, Rockville, MD) (Zhang et al 2019). Leukocyte flux and leukocyte endothelium interactions (rolling and adhesion) analysis was conducted as described by Wang et al (2019). Briefly, rolling leukocyte flux was measured at indicated time points by counting the number of rolling leukocytes per 20 s passing a reference point in the microvessel and expressed as cells/min.…”

COVID‑19 and ischemic stroke: Mechanisms of hypercoagulability (Review)

“…1 ) ( 41 ). In addition, Wang et al found that neutrophil extracellular trap-MP complexes can promote the intrinsic pathway of coagulation in a sepsis mouse model; t hey subsequently found that neutrophil extracellular trap-MP complexes can trigger inflammation by mediating neutrophil aggregation through HMGB1-TLR2/TLR4 signaling ( 42 , 43 ). Damaged endothelial cells and epithelial cells are also found to release MPs in a number of respiratory diseases, such as chronic obstructive pulmonary disease, asthma, pulmonary fibrosis and pulmonary hypertension ( 44 ).…”