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 (H2 S), 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 H2 S 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 LepRdb/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 H2 S in form of Na2 S on skin wound healing and NETosis was investigated both in vivo and in vitro. It was found that NETs level was highly increased in diabetic foot patients. Comparing with LepRm+/db mice, DWH was delayed in diabetic LepRdb/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 H2 S. The delayed DWH of diabetic mice was partially restored by intraperitoneal injection of H2 S, meanwhile, the highly expressed NETosis and NETs release was also down-regulated. The treatment with H2 S not only attenuated ROS production but also abolished MAPK ERK1/2 and p38 activation. Like the effects of H2 S, inhibition of MAPK ERK1/2 or p38 could also decrease NETs release. These findings suggests that H2 S attenuates NETosis and primes diabetic wound to heal through blockage of ROS-mediated MAPK ERK1/2 and p38 activation.