Peritoneal neutrophil extracellular traps contribute to septic AKI via peritoneal IL-17A and distant organ CXCL-1/ CXCL-2 pathway in abdominal sepsis

There are no specific treatments for Sepsis-associated acute kidney injury (AKI). We previously reported that Il-17a-knockout mice had dramatically improved survival after cecal ligation and puncture (CLP). Neutrophil extracellular traps (NETs) induce IL-17A, which causes harm in some diseases, but this pathway is poorly understood in sepsis. We found that knockout of Pad4 (Peptidyl Arginine Deiminase 4), an enzyme essential for NET formation, improved survival and AKI, and suppressed neutrophil infiltration into remote organs, involving a peritoneal IL-17A/distant organ CXCL-1/CXCL-2 pathway after CLP. NETs were detected in the peritoneal cavity, and not in plasma or distant organs. Adoptive transfer of peritoneal WT neutrophils restored the IL-17A/CXCL-1/CXCL-2 pathway in Pad4KO mice, leading to neutrophil infiltration and damage to remote organs. These results revealed a pathway from peritoneal NET formation to remote organ injury/inflammation via production of IL-17A at the infectious site and distant organ CXCL-1/CXCL-2. While NETs promoted intraperitoneal IL-17A production, we also showed that conversely, peritoneal IL-17A or CXCL-1/CXCL-2 promoted intraperitoneal NET formation after CLP. This peritoneal vicious cycle that includes NET formation, IL-17A, CXCL-1/CXCL-2 that may amplify sepsis-associated organ injury. Breaking this vicious cycle by inhibiting NET formation and/or IL-17A might be a promising therapeutic target for sepsis treatment.