Protective Effect of Inhaled Rho-Kinase Inhibitor on Lung Ischemia-Reperfusion Injury

Background Rho-kinase, an intracellular serine/threonine kinase, is a key regulator of cytoskeletal dynamics. Recent studies have demonstrated that Rho-kinase is involved in the ischemia-reperfusion injury (IRI) pathogenesis of many organs; however, its involvement with lung IRI remains unclear. This study assessed the association of Rho-kinase with lung IRI and evaluated the protective effect of inhaled Rho-kinase inhibitors in lung IRI. Methods The study included isolated rat lung perfusion models, divided into three groups: sham, Rho-kinase inhibitor, and warm ischemia (n = 6 each). The lungs were exposed to 60 minutes of warm ischemia by perfusion cessation. At the onset of ischemia, nebulized fasudil, a novel Rho-kinase inhibitor, and saline were inhaled in the Rho-kinase inhibitor and warm ischemia groups, respectively. Perfusion was restarted after the ischemic period, and physiologic data were collected for 90 minutes. Lungs in the sham group were continuously perfused without ischemia or drug administrations. Protein expression in tissue specimens related to the Rho-kinase pathway was evaluated by Western blotting. Results Warm ischemia and subsequent reperfusion enhanced Rho-kinase activity, and this was suppressed by fasudil inhalation. Fasudil inhalation significantly attenuated IRI pathophysiology, including pulmonary vascular contraction, dynamic compliance, lung edema, and oxygenation. Molecular analysis showed that Rho-kinase suppressed myosin phosphatase and endothelial nitric oxide synthase activities, suggesting these are downstream targets of Rho-kinase during lung IRI pathogenesis. Conclusions The present study suggests that Rho-kinase activation is involved in lung IRI pathogenesis and that inhaled Rho-kinase inhibitors may attenuate this pathogenesis.