Neutrophil extracellular trap (NET) formation is a key feature in sepsis. The aim of the present study was to examine the role of the actin cytoskeleton in regulating the expulsion of NETs. Actin-related protein 2/3 (Arp 2/3) complex is an important regulator of F-actin polymerization. Coincubation with CK666, a specific Arp 2/3 inhibitor, decreased 12-phorbol 13-myristate acetate-induced NET formation in vitro. CK666 not only abolished F-actin polymerization but also caused intracellular retention of NETs. Inhibition of Arp 2/3 reduced NET formation on circulating neutrophils and in the bronchoalveolar space in mice undergoing cecal ligation and puncture (CLP). Notably, treatment with CK666 attenuated CLP-induced neutrophil recruitment, edema formation, and tissue damage in the lungs. Moreover, Arp 2/3 inhibition decreased levels of C-X-C motif chemokine ligand 1 (CXCL-1) and interleukin-6 in the lung and plasma of septic animals. Taken together, this study shows that expulsion of NETs is regulated by the actin cytoskeleton and that inhibition of Arp 2/3-dependent F-actin polymerization not only decreases NET formation but also protects against pathological inflammation and tissue damage in septic lung injury. Thus, we suggest that targeting NET release is a novel and useful way to ameliorate lung damage in abdominal sepsis.
Keywords: cytoskeleton; infection; inflammation; leukocyte; sepsis; tissue injury.