Effect of the NADPH oxidase inhibitor apocynin on ischemia-reperfusion lung injury.
Apocynin (4-hydroxy-3-methoxy-acetophenone) inhibits NADPH oxidase in activated polymorphonuclear (PMN) leukocytes, preventing the generation of reactive oxygen species. To determine if apocynin attenuates ischemia-reperfusion lung injury, we examined the effects of apocynin (0.03, 0.3, and 3 mM) in isolated in situ sheep lungs. In diluent-treated lungs, reperfusion with blood (180 min) after 30 min of ischemia (ventilation 28% O(2), 5% CO(2)) caused leukocyte sequestration in the lung and increased vascular permeability [reflection coefficient for albumin (sigma(alb)) 0.47 +/- 0.10, filtration coefficient (K(f)) 0.14 +/- 0.03 g. min(-1). mmHg(-1). 100 g(-1)] compared with nonreperfused lungs (sigma(alb) 0.77 +/- 0. 03, K(f) 0.03 +/- 0.01 g. min(-1). mmHg(-1). 100 g(-1); P < 0.05). Apocynin attenuated the increased protein permeability at 0.3 and 3 mM (sigma(alb) 0.69 +/- 0.05 and 0.91 +/- 0.03, respectively, P < 0. 05); K(f) was decreased by 3 mM apocynin (0.05 +/- 0.01 g. min(-1). mmHg(-1). 100 g(-1), P < 0.05). Diphenyleneiodonium (DPI, 5 microM), a structurally unrelated inhibitor of NADPH oxidase, worsened injury (K(f) 0.32 +/- 0.07 g. min(-1). mmHg(-1). 100 g(-1), P < 0.05). Neither apocynin nor DPI affected leukocyte sequestration. Apocynin and DPI inhibited whole blood chemiluminescence and isolated PMN leukocyte-induced resazurin reduction, confirming NADPH oxidase inhibition. Apocynin inhibited pulmonary artery hypertension and perfusate concentrations of cyclooxygenase metabolites, including thromboxane B(2). The cyclooxygenase inhibitor indomethacin had no effect on the increased vascular permeability, suggesting that cyclooxygenase inhibition was not the explanation for the apocynin results. Apocynin prevented ischemia-reperfusion lung injury, but the mechanism of protection remains unclear.
Dodd-O
J M
JM
Department of Anesthesia and Critical Care and Medicine, The Johns Hopkins Medical Institutions, Baltimore, Maryland 21224, USA.
Pearse
D B
DB
D000098:Acetophenones / Q000494:pharmacology*; D000975:Antioxidants / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D008163:Luminescent Measurements; D008168:Lung / Q000098:blood supply* / Q000187:drug effects / Q000473:pathology; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors*; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D009861:Onium Compounds / Q000494:pharmacology; D010078:Oxazines; D010084:Oxidation-Reduction; D011652:Pulmonary Circulation / Q000187:drug effects / Q000502:physiology*; D015427:Reperfusion Injury / Q000473:pathology / Q000503:physiopathology*; D014966:Xanthenes
D000098:Acetophenones; D000975:Antioxidants; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D009861:Onium Compounds; D010078:Oxazines; D014966:Xanthenes; C005843:resazurin; C007517:diphenyleneiodonium; C056165:acetovanillone; D019255:NADPH Oxidases