Hydrogen sulfide primes diabetic wound to close through inhibition of NETosis

Diabetes-induced neutrophil NETosis impairs wound healing through neutrophil extracellular traps (NETs). Reactive oxygen species (ROS)-triggered activation of mitogen-activated protein kinase (MAPK) ERK1/2 and p38 is involved in NETosis. Hydrogen sulfide (H₂S), an endogenous signaling molecule, accelerates diabetic wound healing (DWH), and inhibits ROS production, ERK1/2 and p38 activation, while its level is decreased in diabetes. However, it remains unknown whether H₂S could accelerate DWH through inhibition of NETosis, and whether this inhibitory effect was associated with blockage of ROS-induced ERK1/2 and p38 activation. In order to solve these problems, serum NETs content was measured in diabetic foot patients and healthy individuals. Wound was created in dorsal skin of LepR^db/db and control mice and NETs content in wound tissues was tested. An in vitro NETosis model was induced by phorbol 12-myristate 13-acetate (PMA) in isolated neutrophils. Effects of H₂S in form of Na₂S on skin wound healing and NETosis were investigated both in vivo and in vitro. It was found that NETs level was highly increased in diabetic foot patients. Comparing with LepR^m+/db mice, DWH was delayed in LepR^db/db mice, accompanied with high NETs level. In PMA-induced NETosis model, peptidylarginine deiminase (PAD)-4 and citrullinated histone H₃, as well as NETs components dsDNA framework, myeloperoxidase and neutrophil elastase, were significantly increased. PMA-induced neutrophil NETosis and NETs formation were abolished by treatment with H₂S. The delayed DWH of diabetic mice was partially restored by intraperitoneal injection of H₂S, meanwhile, the highly expressed NETosis and NETs release were also down-regulated. The treatment with H₂S not only attenuated ROS production but also abolished MAPK ERK1/2 and p38 activation. Like the effects of H₂S, inhibition of MAPK ERK1/2 or p38 could decrease NETs release. These findings suggests that H₂S attenuates NETosis and primes diabetic wound to heal through blockage of ROS-mediated MAPK ERK1/2 and p38 activation.