Inhibition of Na-K-Cl cotransporter isoform 1 reduces lung injury induced by ischemia-reperfusion.

OBJECTIVES: Ischemia-reperfusion acute lung injury is characterized by increased vascular permeability, lung edema, and neutrophil sequestration. Ischemia-reperfusion acute lung injury occurs in lung transplantation and other major surgical procedures. Effective regulation of alveolar fluid balance is critical for pulmonary edema. Sodium-potassium-chloride co-transporter regulates alveolar fluid and is associated with inflammation. We hypothesized that sodium-potassium-chloride co-transporter is important in ischemia-reperfusion acute lung injury. Bumetanide, a sodium-potassium-chloride co-transporter inhibitor, is used to treat pulmonary edema clinically. We studied the effect of bumetanide in ischemia-reperfusion acute lung injury. METHODS: Isolated perfusion of mouse lungs in situ was performed. The main pulmonary artery and left atrium were catheterized for lung perfusion and effluent collection for recirculation, respectively, with perfusate consisting of 1 mL blood and 9 mL physiologic solution. Ischemia-reperfusion was induced by 120 minutes of ischemia (no ventilation or perfusion) and reperfused for 60 minutes. Wild-type, SPAK knockout (SPAK-/-), and WNK4 knockin (WNK4D561A/+) mice were divided into control, ischemia-reperfusion, and ischemia-reperfusion + bumetanide groups (n = 6 per group). Bumetanide was administered via perfusate during reperfusion. Measurements were taken of lung wet/dry weight, microvascular permeability, histopathology, cytokine concentrations, and activity of the nuclear factor-κB pathway. RESULTS: In wild-type mice, ischemia-reperfusion caused lung edema (wet/dry weight 6.30 ± 0.36) and hyperpermeability (microvascular permeability, 0.29 ± 0.04), neutrophil sequestration (255.0 ± 55.8 cells/high-power field), increased proinflammatory cytokines, and nuclear factor-κB activation (1.33 ± 0.13). Acute lung injury was more severe in WNK4 mice with more lung edema, permeability, neutrophil sequestration, and nuclear factor-κB activation. Severity of acute lung injury was attenuated in SPAK-/-mice. Bumetanide decreased pulmonary edema (wild-type: wet/dry weight 5.05 ± 0.44, WNK4: wet/dry weight 5.13 ± 0.70), neutrophil sequestration (wild-type: 151.7 ± 27.8 cells/high-power field, WNK4: 135.3 ± 19.1 cells/high-power field), permeability (wild-type: 0.19 ± 0.01, WNK4: 0.21 ± 0.03), cytokines, and nuclear factor-κB activation after ischemia-reperfusion. CONCLUSIONS: Functional reduction of sodium-potassium-chloride co-transporter by genetic or pharmacologic treatment to inhibit sodium-potassium-chloride co-transporter resulted in lower severity of acute lung injury induced by ischemia-reperfusion. Sodium-potassium-chloride co-transporter may present a promising target for therapeutic interventions in a clinical setting.