NETosis Delays Diabetic Wound Healing in Mice and Humans

Abstract

Upon activation, neutrophils undergo histone citrullination by protein arginine deiminase (PAD)4, exocytosis of chromatin and enzymes as neutrophil extracellular traps (NETs), and death. In diabetes, neutrophils are primed to release NETs and die by NETosis. Although this process is a defense against infection, NETosis can damage tissue. Therefore, we examined the effect of NETosis on the healing of diabetic foot ulcers (DFUs). Using proteomics, we found that NET components were enriched in nonhealing human DFUs. In an independent validation cohort, a high concentration of neutrophil elastase in the wound was associated with infection and a subsequent worsening of the ulcer. NET components (elastase, histones, neutrophil gelatinase-associated lipocalin, and proteinase-3) were elevated in the blood of patients with DFUs. Circulating elastase and proteinase-3 were associated with infection, and serum elastase predicted delayed healing. Neutrophils isolated from the blood of DFU patients showed an increased spontaneous NETosis but an impaired inducible NETosis. In mice, skin PAD4 activity was increased by diabetes, and FACS detection of histone citrullination, together with intravital microscopy, showed that NETosis occurred in the bed of excisional wounds. PAD4 inhibition by Cl-amidine reduced NETting neutrophils and rescued wound healing in diabetic mice. Cumulatively, these data suggest that NETosis delays DFU healing.

The Neutrophil Extracellular Traps: The Missed Link between Microvascular Inflammation and Diabetes?

“…Neutrophils that are isolated from the blood of diabetics have been shown an increased spontaneous NETosis, but an impaired inducible exaggerated NETosis response might be a leading cause of tissue damage in diabetics with healing, such as diabetic food. Moreover, NET components (elastase, histones, NGAL, and proteinase-3) were enriched in non-healing human with diabetes [19]. In was found that the finely tuned balance of NETosis required protecting the human body from microorganisms yet avoiding self-damage seems to be lost in diabetes.…”

“…However, the role of spontaneous NERosis in dysmetabolic states including diabetes mellitus is not fully established. In fact, in diabetes, neutrophils are primed to release NETs and die by NETosis [19]. Neutrophils that are isolated from the blood of diabetics have been shown an increased spontaneous NETosis, but an impaired inducible exaggerated NETosis response might be a leading cause of tissue damage in diabetics with healing, such as diabetic food.…”

Is the neutrophil extracellular trap-driven microvascular inflammation essential for diabetes vasculopathy?

“…Neutrophils that are isolated from the blood of diabetics have been shown an increased spontaneous NETosis, but an impaired inducible exaggerated NETosis response might be a leading cause of tissue damage in diabetics with healing, such as diabetic food. Moreover, NET components (elastase, histones, NGAL, and proteinase-3) were enriched in nonhealing human with diabetes (Fadini et al, 2016a). Wong SL et al (2015) have been suggested that diabetes may not only activate neutrophils to overproduce PAD4 and NETs, but NETs are as a key factor delaying wound healing.…”

Neutrophil extracellular traps as the main source of eDNA

“…It should be assumed that the physicochemical characteristics of DNA/F-actin aggregates formed at the surface of mucosal membranes differ from that formed within tissues because assembly of negatively charged PEs is governed by local ion composition and the presence of a bundling factor (polycations), such as most cationic antibacterial peptides. Additionally the NET composition might vary based on mechanisms activating NETosis [13,18,23]. The composition of DNA-protein complexes that accumulate in airway sputum of CF patients is consistent with NETosis and joins a similar proteomic signature, indicating that the majority of the DNA in sputum is NET derived.…”

“…Another outcome of neutrophil accumulation leading to build-up of polyelectrolytes into the extracellular space is proteolytic action of neutrophil proteases (elastase, cathepsin G protease, and proteinase-3) that are released as both free and as a part of the NET component and are very destructive within the surrounding tissue [13,14]. In effect, DNA and F-actin gathering at infectious sites originate from neutrophils and broken host cells.…”