Cl-Amidine Prevents Histone 3 Citrullination and Neutrophil Extracellular Trap Formation, and Improves Survival in a Murine Sepsis Model

Sepsis refers to the presence of a serious infection that correlates with systemic and uncontrolled immune activation. Posttranslational histone modification plays an important role in chromatin decondensation, which is regulated by citrullination. Citrullinated histone H3 (H3cit) has been identified as a component of neutrophil extracellular traps (NETs), which are released into the extracellular space as part of the neutrophil response to infection. The conversion of arginine to citrulline residues on histones is catalyzed by peptidylarginine deiminase 4 (PAD4). This study's goals were to characterize the presence of PAD4-catalyzed H3cit and NET formation during the onset of sepsis and elucidate the effects on the immune response when this mechanism of action is blocked. Adult C57BL/6 male mice were treated with Cl-amidine, an inhibitor of PAD4, 1 h prior to sepsis induced by cecal ligation and puncture (CLP). Twenty-four hours after CLP, cytokine levels, H3cit protein expression, neutrophil counts, and NET production were evaluated in the peritoneal cavity. Survival studies were also performed. Here we demonstrate that Cl-amidine treatment prior to CLP improves overall survival in sepsis and the abrogation of PAD4 has minimal effects on the proinflammatory immune response to sepsis, while it has no effect on overall neutrophil migration to the peritoneum.