title: Neutrophil elastase inhibitor reduces ventilation-induced lung injury via nuclear factor-κB and NF-κB repressing factor in mice.
abstract: Mechanical ventilation used in patients with acute lung injury can damage pulmonary epithelial cells through production of inflammatory cytokines, oxygen radicals, and neutrophil infiltration, termed ventilator-induced lung injury. Neutrophil elastase, nuclear factor-κB (NF-κB), and NF-κB repressing factor (NRF) have previously been shown to participate in the regulation of macrophage inflammatory protein-2 (MIP-2) during airway inflammation. However, the mechanisms regulating interactions among mechanical ventilation, neutrophil influx, and NF-κB/NRF remain unclear. Thus, we hypothesized that neutrophil elastase inhibitor attenuated ventilation-induced neutrophil recruitment and MIP-2 production through inhibition of the NF-κB/NRF pathway. Male C57BL/6 mice were exposed to low-tidal-volume (6 mL/kg) or high-tidal-volume (30 mL/kg) mechanical ventilation using room air with or without 2 µg/g NF-κB inhibitor SN50 or 6 µg/g NRF short interfering RNA or 100 µg/g neutrophil elastase inhibitor administration. Nonventilated mice served as a control group. Evan blue dye, lung wet-to-dry weight ratio, free radicals, myeloperoxidase, histopathologic grading of lung tissue, inflammatory cytokines, Western blot of NF-κB and NRF, and gene expression of NRF were measured to establish the extent of lung injury. Neutrophil elastase inhibitor ameliorated high-tidal-volume ventilation-induced lung injury, neutrophil influx, production of MIP-2 and malondialdehyde, activation of NF-κB and NRF, apoptotic epithelial cell death, and disruption of bronchial microstructure in mice. Mechanical stretch-augmented acute lung injury was also attenuated through pharmacological inhibition of NF-κB activity by SN50 and NRF expression by NRF short interfering RNA. Our data suggest that neutrophil elastase inhibitor attenuates high-tidal-volume mechanical ventilation-induced neutrophil influx, oxidative stress, and production of MIP-2, at least partly, through inhibition of NF-κB/NRF pathway. Understanding the protective effects of neutrophil elastase inhibitor associated with the reduction of MIP-2 allow clarification of the pathophysiological mechanisms regulating severe lung inflammation and development of possible therapeutic strategies involved in acute lung injury.
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan 333, Taiwan Department of Respiratory Therapy, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
authors.forename: Li-Fu
authors.initials: LF
authors.lastname: Li
authors.affiliation: Department of Respiratory Therapy, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan Graduate Institute of Clinical Medical Sciences and Department of Respiratory Care, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan.
authors.forename: Yi-Ting
authors.initials: YT
authors.lastname: Lai
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan 333, Taiwan.
authors.forename: Chih-Hao
authors.initials: CH
authors.lastname: Chang
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung 833, Taiwan.
authors.forename: Meng-Chih
authors.initials: MC
authors.lastname: Lin
authors.affiliation: Chest Department, Taipei Veterans General Hospital, Taipei 112, Taiwan Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei 112, Taiwan.
authors.forename: Yung-Yang
authors.initials: YY
authors.lastname: Liu
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan 333, Taiwan Department of Respiratory Therapy, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
authors.forename: Kuo-Chin
authors.initials: KC
authors.lastname: Kao
authors.affiliation: Department of Medicine, Division of Pulmonary and Critical Care Medicine, Chang Gung Memorial Hospital and Chang Gung University, Taoyuan 333, Taiwan Department of Respiratory Therapy, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan chestmed@adm.cgmh.org.tw.
authors.forename: Ying-Huang
authors.initials: YH
authors.lastname: Tsai
keywords: Acute respiratory distress syndrome; neutrophils; ventilator-induced lung injury