Recent evidence suggests that neutrophil extracellular traps (NETs) play an important role in the development of acute pancreatitis (AP). Herein, we examined the role of peptidylarginine deiminase (PAD), which has been shown to regulate NET formation, in severe AP. AP was induced by retrograde of taurocholate infusion into pancreatic duct in C57BL/6 mice. PAD was pharmacologically inhibited using Cl‐amidine, a pan‐PAD inhibitor. Pancreata were collected, and histones, citrullinated histone 3, chemokines, myeloperoxidase, and NETs were quantified. Chemokines, matrix metalloproteinase‐9 (MMP‐9), interleukin‐6 (IL‐6), and DNA‐histone complexes were determined in plasma samples. Infusion of taurocholate induced formation of NETs in pancreatic tissues of mice. Pretreatment with Cl‐amidine markedly reduced the NET formation in the inflamed pancreas. Moreover, inhibition of PAD decreased the levels of blood amylase as well as edema, acinar cell necrosis, hemorrhage, and neutrophil infiltration in the pancreas of animals with AP. Administration of Cl‐amidine attenuated the myeloperoxidase levels in the pancreas and lung of mice exposed to taurocholate. In addition, Cl‐amidine decreased pancreatic levels of CXC chemokines, plasma levels of IL‐6, and MMP‐9 in mice with severe AP. This study shows that Cl‐amidine is a potent inhibitor of NET formation in severe AP. Also, our results suggest that PAD regulates pathological inflammation and tissue damage in the inflamed pancreas. Thus, targeting PAD might be a useful strategy to treat patients with severe AP.

Following publication, the Editors became aware of irregularities in the pseudocoloring of microparticles in scanning electron microscopy images in Figures 1-4 and 6 and Supplemental Figure 7. The Editors have requested an institutional investigation into this matter, and we will inform our readers of the outcome when the investigation is complete.

Neutrophil extracellular traps (NETs)‐mediated tissue damage is a hallmark in abdominal sepsis. Under certain conditions, microRNAs (miRs) can regulate protein expression and cellular functions. The aim of this study was to investigate the role of miR‐155 in sepsis‐induced NET formation, lung inflammation, and tissue damage. Abdominal sepsis was induced in wild‐type (WT) C57BL/6 and miR‐155 gene‐deficient mice by cecal ligation and puncture (CLP). The amount of DNA–histone complex formation as well as myeloperoxidase (MPO) and citrullinated histone 3 in neutrophils isolated from bone marrow were examined by ELISA and flow cytometry. NETs were detected by electron microscopy in the septic lung. Levels of PAD4 and citrullinated histone 3 were determined by Western blot in the blood neutrophils. Lung levels of MPO, CXC chemokines, and plasma levels of DNA–histone complexes and CXC chemokines were quantified. In vitro studies revealed that neutrophils from miR‐155 gene‐deficient mice had less NETs forming ability than WT neutrophils. In the miR‐155 gene‐deficient mice, CLP yielded much less NETs in the lung tissue compared with WT control. CLP‐induced PAD4 levels, histone 3 citrullination, edema, MPO activity, and neutrophil recruitment in the lung were markedly reduced in the mice lacking miR‐155. Furthermore, tissue and plasma levels of CXCL1 and CXCL2 were significantly lower in the miR‐155 gene‐deficient mice compared with WT after induction of abdominal sepsis. Taken together, our findings suggest that miR‐155 regulates pulmonary formation of NETs in abdominal sepsis via PAD4 up‐regulation and histone 3 citrullination. Thus, targeting miR‐155 could be a useful target to reduce pulmonary damage in abdominal sepsis.