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Objective: Sepsis causes millions of deaths on a global scale annually. Activation of peptidylarginine deiminase (PAD) enzymes in sepsis causes citrullination of histones, which results in neutrophil extracellular trap formation and sepsis progression. This study evaluates pan-PAD inhibitor, Cl-amidine, in a model of lipopolysaccharide (LPS)-induced endotoxic shock in rabbits. We hypothesized that Cl-amidine would improve survival and attenuate kidney injury. Methods: In the survival model, rabbits were injected injected intravenously with 1 mg/kg of LPS, and then randomly assigned either to receive dimethyl sulfoxide (DMSO; 1 mcL/g) or Cl-amidine (10 mg/kg diluted in 1 mcL/g DMSO). They were then monitored for 14 days to evaluate survival. In the non-survival experiment, the same insult and treatment were administered, however; the animals were euthanized 12 hours after LPS injection for kidney harvest. Acute kidney injury (AKI) scoring was performed by a histopathologist who was blinded to the group assignment. Serial blood samples were also collected and compared. Results: Rabbits that received Cl-amidine had a higher survival (72%) compared with the rabbits that received DMSO (14%; p < 0.05). Cl-amidine-treated rabbits had lower (p < 0.05) histopathologic AKI scores, as well as plasma creatinine and blood urea nitrogen (BUN) levels 12 hours after insult. Conclusions: Pan-PAD inhibitor Cl-amidine improves survival and attenuates kidney injury in LPS-induced endotoxic shock in rabbits. [ABSTRACT FROM AUTHOR]

Immune cell death caused by neutrophil extracellular traps (NETs), referred to as NETosis, can contribute to the pathogenesis of endotoxemia and organ damage. Although the mechanisms by which infection induces NETosis and how that leads to organ dysfunction remain largely unknown, NET formation is often found following citrullination of histone H3 (CitH3) by peptidylarginine deiminase (PAD). We hypothesized that lipopolysaccharide (LPS)-induced activation of PAD and subsequent CitH3-mediated NET formation increases endothelial permeability and pulmonary dysfunction and, therefore, that inhibition of PAD can mitigate damage and improve survival in lethal endotoxemia. Here, we showed that treatment with YW3–56, a PAD2/PAD4 inhibitor, significantly diminished PAD activation, blocked LPS-induced pulmonary vascular leakage, alleviated acute lung injury, and improved survival in a mouse model of lethal LPS-induced endotoxemia. We found CitH3 in the bloodstream 30 min after intraperitoneal injection of LPS (35 mg/kg) into mice. Additionally, CitH3 production was induced in cultured neutrophils exposed to LPS, and NETs derived from these LPS-treated neutrophils increased the permeability of endothelial cells. However, YW3–56 reduced CitH3 production and NET formation by neutrophils following LPS exposure. Moreover, treatment with YW3–56 decreased the levels of circulating CitH3 and abolished neutrophil activation and NET formation in the lungs of mice with endotoxemia. These data suggest a novel mechanism by which PAD-NET-CitH3 can play a pivotal role in pulmonary vascular dysfunction and the pathogenesis of lethal endotoxemia. [ABSTRACT FROM AUTHOR]