Ischemia-Reperfusion Lung Injury Is Prevented by Apocynin, a Novel Inhibitor of Leukocyte NADPH Oxidase

Ischemia and reperfusion (IR) of isolated sheep lungs caused polymorphonuclear leukocyte (PMN) sequestration, pulmonary hypertension secondary to thromboxane (TX), edema, and increased vascular permeability.1Pearse DB Sylvester JT Vascular injury in isolated sheep lungs: role of ischemia, extracorporeal perfusion, and oxygen.Am J Respir Crit Care Med. 1996; 153: 196-202Crossref PubMed Scopus (17) Google Scholar PMN depletion attenuated this injury, suggesting that PMN-derived O2 radicals were involved.2Pearse DB Brower RG Adkinson Jr, NF et al.Spontaneous injury in isolated sheep lungs: role of perfusate leukocytes and platelets.J Appl Physiol. 1989; 66: 1287-1296Crossref PubMed Scopus (19) Google Scholar Apocynin (Apo) is a methoxy-substituted catechol that requires activation by myeloperoxidase to inhibit the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and thus prevents O2− production from activated PMN leukocytes. To determine the effect of Apo in IR injury, we subjected 20 sheep lungs to 30 min of ischemia and 180 min of reperfusion with blood. We injected 3 mM, 0.3 mM, 0.03 mM Apo, or diluent (n = 5 each) into the pulmonary artery early in ischemia and the reservoir before reperfusion. Peak pulmonary artery pressure, peak perfusate TXB2 concentration, and the reflection coefficient for albumin were measured (Table 1) . The ability of Apo to inhibit in vitro O2− production from zymosan-activated sheep PMN leukocytes was also assessed (n = 3).Table 1MeasurementsGroupReflection Coefficient for AlbuminPeak Pulmonary Artery Pressure, mm HgTXB2, ng/mLO2 InhibitionControl0.47 ± 0.1143.2 ± 9.413.52 ± 7.440%0.03 mM Apo0.48 ± 0.0537.2 ± 1.12.97 ± 2.4340 ± 20%0.3 mM Apo0.69 ± 0.06*p < 0.05 vs control.24.0 ± 4.0*p < 0.05 vs control.0.00*p < 0.05 vs control.66 ± 8%*p < 0.05 vs control.3 mM Apo0.93 ± 0.03*p < 0.05 vs control.†p < 0.05 vs 0.3 mM.12.6 ± 1.3*p < 0.05 vs control.†p < 0.05 vs 0.3 mM.0.08 ± 0.07*p < 0.05 vs control.99 ± 1%*p < 0.05 vs control.†p < 0.05 vs 0.3 mM.* p < 0.05 vs control.† p < 0.05 vs 0.3 mM. Open table in a new tab In a dose-dependent manner, Apo prevented the increased vascular permeability, pulmonary hypertension, and TX release associated with IR injury. The correlation of these effects with inhibition of O2− production from PMN leukocytes in vitro suggests that Apo protected by inhibiting leukocyte NADPH oxidase. Apo may represent a new therapeutic approach to the clinical problem of reperfusion lung injury.