Sirtuin 1 is an endogenous NETosis inhibitor that becomes dysfunctional in diabetes

Neutrophils release their chromatin with toxic granular proteins as neutrophil extracellular traps (NETs) when activated. Diabetes exacerbates NET formation (NETosis), resulting in tissue damage and diabetic complications such as nonhealing wounds. How diabetes predisposes neutrophils to NETosis remains unclear. Herein, we found that pharmacological inhibition or siRNA knockdown of sirtuin 1 (SIRT1) increased NETosis in neutrophils of healthy humans and mice, unveiling SIRT1 as an endogenous suppressor of NETosis. In contrast, SIRT1 inhibition did not cause further increase in NETosis in neutrophils of humans and mice with diabetes, indicative of SIRT1 dysfunction in a disease state. Indeed, SIRT1 deacetylase activity was significantly lower in neutrophils of individuals with diabetes, accompanied by a concomitant increase in the activity of peptidylarginine deiminase 4 (PAD4), a key enzyme that mediates NETosis. PAD4 was codetected with SIRT1 immunoprecipitated from neutrophils isolated from healthy individuals and HL-60-derived neutrophils (dHL-60) cultured in basal glucose; such co-immunoprecipitation was absent in neutrophils of individuals with diabetes and dHL-60 cells treated with high levels of glucose, suggesting that hyperglycemia disrupts the SIRT1-PAD4 interaction. SIRT1 activators restored the SIRT1-PAD4 interaction and normalized the exacerbated NETosis and PAD4 activity in diabetes and hyperglycemia, culminating in improved diabetic wound healing. This study reveals a novel regulatory role of SIRT1 on PAD4 activity. Revitalizing SIRT1 can be a new preventive or therapeutic strategy for combating NET-mediated inflammation in diabetes and beyond.