NLRP3 activation induced by neutrophil extracellular traps sustains inflammatory response in the diabetic wound

Abstract

Persistent inflammatory response in the diabetic wound impairs the healing process, resulting in significant morbidity and mortality. Mounting evidence indicate that the activation of Nod-like receptor protein (NLRP) 3 inflammasome in macrophages (MΦ) contributes to the sustained inflammatory response and impaired wound healing associated with diabetes. However, the main trigger of NLRP3 inflammasome in the wounds is not known. Neutrophils, as sentinels of the innate immune system and key stimulators of MΦ, are immune cells that play the main role in the early phase of healing. Neutrophils release extracellular traps (NETs) as defense against pathogens. On the other hand, NETs induce tissue damage. NETs have been detected in the diabetic wound and implicated in the impaired healing process, but the mechanism of NETs suspend wound healing and its role in fostering inflammatory dysregulation are elusive. Here, we report that NLRP3 and NETs production are elevated in human and rat diabetic wounds. NETs overproduced in the diabetic wounds triggered NLRP3 inflammasome activation and IL-1β release in MΦ. Furthermore, NETs up-regulated NLRP3 and pro-IL-1β levels via the TLR-4/TLR-9/NF-κB signaling pathway. They also elicited the generation of reactive oxygen species, which facilitated the association between NLRP3 and thioredoxin-interacting protein, and activated the NLRP3 inflammasome. In addition, NET digestion by DNase I alleviated the activation of NLRP3 inflammasome, regulated the immune cell infiltration, and accelerated wound healing in diabetic rat model. These findings illustrate a new mechanism by which NETs contribute to the activation of NLRP3 inflammasome and sustained inflammatory response in the diabetic wound.

DNase I improves corneal epithelial and nerve regeneration in diabetic mice

“…Moreover, DNase I also promoted the transition of M1 to M2 macrophage phenotype, which improved the clearance of inflammatory products and thereby the healing rate of corneal wound in diabetic mice. Similarly, previous study had confirmed that DNase I promoted wound repair in diabetic rats by alleviating the activation of NLRP3 inflammasome, 44 suggesting that DNase I can not only reduce the inflammatory response of neutrophils, but also that of macrophages.…”

“…As a characteristic of inflammation resolution, the transition impairment of M1 to M2 macrophage phenotype was involved in the impaired wound healing in diabetic condition 44‐46 . Immunofluorescence staining results showed the enhanced staining of anti‐F4/80 (a macrophage marker) and anti‐CD206 (a M2 macrophage marker) in diabetic cornea, whereas topical application of DNase I remarkably reduced the infiltration of M1 macrophages and increased the proportion of M2 macrophages in diabetic cornea at 48 hours after injury (Figure 3A).…”

The Red Blood Cell—Inflammation Vicious Circle in Sickle Cell Disease

“…It has also been suggested that NETs could promote vessel occlusion by providing a scaffold for platelets, RBCs and pro-coagulant molecules (48). Recent studies also demonstrated that NETs induced the activation of the NLRP3 inflammasome in macrophages through TLR4/TLR9 signaling pathways, leading to higher production of IL-1β in the context of diabetes and atherosclerosis (49,50). Indeed, one may suspect a role of NETs in SCD pathogenesis through an activation of the immune innate system (15).…”

Effect and Mechanism of the Bruton Tyrosine Kinase (Btk) Inhibitor Ibrutinib on Rat Model of Diabetic Foot Ulcers

“…TLRs are one of the pattern recognition receptors involved in innate immunity, a class of important protein molecules that link natural immunity with specific immunity. TLR2 and TLR4, as members of the TLRs family, play an important role in inflammation, bacterial infection, and autoimmune diseases [23]. The regulation of VEGF expression can improve the microvascular lesions in diabetes, resulting in insufficient local blood perfusion, and thus regulates the progression of diabetic foot disease [24].…”