NADPH Oxidase 4 Signaling in a Ventilator-Induced Lung Injury Mouse Model

Abstract

BackgroundFor patients with acute respiratory distress syndrome (ARDS), a ventilator is essential to supply oxygen to tissues, but it may also cause lung damage. In this study, we investigated the role of NOX4 in lung injury using NOX4 knockout (KO) mice and NOX4 inhibitors in a ventilator-induced lung injury (VILI) model.MethodsWild-type male C57BL/6J mice and NOX4 KO male mice were divided into five groups: (1) control group: wild-type (WT) mice + non-ventilator; (2) high tidal ventilation (HTV) group: WT mice + HTV; (3) NOX4 KO group: NOX4 KO + non-ventilator; (4) NOX4 KO with HTV group: NOX4 KO mice + HTV; (5) NOX4 inhibitor group: WT mice + HTV + post-treatment (anti-GKT 137831 inhibitor). In the VILI model, the supine position was maintained at 24 mL/kg volume, 0 cm H2O PEEP, 100/min respiratory rate, and 0.21 inspired oxygen fraction. In the NOX4 inhibitor group, 50 μL anti-GKT 137831 inhibitor was injected intraperitoneally, 2 h after ventilator use. After 5 h of HTV, mice in the ventilator group were euthanized, and their lung tissues were obtained for further analysis. In addition, the relationship between EphA2 (which is related to lung injury) and NOX4 was investigated using EphA2 KO mice, and NOX4 levels in the bronchoalveolar lavage fluid (BALF) of 38 patients with pneumonia were examined.ResultsCell counts from BALFs were significantly lower (p<0.01) in the NOX4 KO with HTV group compared to that in the HTV group. In the NOX4 inhibitor group, cell counts and protein concentrations were significantly lower than those in the HTV group (both, p<0.001). In the NOX4 KO mouse group and the NOX4 inhibitor group, EphA2 levels were significantly lower than those in the HTV group (both, p<0.001). In patients with respiratory disease, NOX4 levels were significantly higher in patients with pneumonia and patients who received ventilator treatment in the intensive care unit.ConclusionsIn the VILI model, NOX4 expression is significantly associated with Eph-ephrin signaling. It may be possible to block VILI using NOX4 antibodies.