Nebulized nitrite protects rat lung grafts from ischemia reperfusion injury

ObjectivesNebulization is a potential method for delivering therapeutic agents to lung grafts. Recent evidence suggests that nitrite may mitigate ischemia-reperfusion injury via a nitric oxide-dependent pathway.MethodsSyngeneic orthotopic left lung transplantation was performed in rats after 7 hours of cold ischemia. Sodium nitrite (3 mg) or phosphate-buffered saline (controls) was delivered before procurement via nebulization.ResultsNitrite treatment was associated with better oxygenation, lower peak airway pressure, lower wet/dry ratio, reduced myeloperoxidase level and macrophage infiltration, increased cyclic guanosine monophosphate (cGMP) levels, and decreased levels of interleukin 6, interleukin 1-β, inducible nitric oxide synthase, and intercellular adhesion molecule-1 at 2 hours after reperfusion. Treatment with 2-(4-carboxypheny)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, a nitric oxide scavenger, reversed the beneficial effects of nitrite and decreased cGMP concentration in grafts. A dose-response curve of nitrite was performed at the following doses: 0.3 mg (N0.1), 3.0 mg (N1.0), 5.25 mg (N1.75), 7.5 mg (N2.5), and 15.0 mg (N5.0). All treatments, excluding N1.0, resulted in poorer oxygenation, higher peak airway pressures, and higher wet/dry ratio. Higher dosage groups (N1.75, N2.5, and N5.0) exhibited positive immunostaining of nitrotyrosine and increased the intensity of nitrotyrosine in immunoblotting.ConclusionsThese data suggest that nebulized nitrite limits lung ischemia-reperfusion injury and may prove a clinically useful strategy but requires appropriate dosing to limit oxidative injury at high doses.