Endogenous reactive oxygen metabolites mediate sublethal endothelial cell dysfunction during reoxygenation

Purpose: Endothelial cells (EC) secrete vasoactive eicosanoids, which maintain organ blood flow. Because EC are a major source of eicosanoids, we studied the effects of reoxygenation on EC prostacyclin production. Methods: Bovine aortic EC cultures were exposed to 2 hours of normoxia, then 1 hour of hypoxia (PO₂ = 10 ± 3.5 mm Hg), followed by 1.5 hours of reoxygenation in either normal medium or medium plus either superoxide dismutase (SOD, 300 units/ml), catalase (1200 units/ml), allopurinol (5.0 x 10^-4 mol/L), or dinitrophenol (10^-4 mol/L). Results: Prostacyclin production decreased to 40% (p < 0.05) of basal prostacyclin production after 1 hour of hypoxia. EC reoxygenated with control medium recovered to 48% of basal prostacyclin production. EC reoxygenated in SOD resulted in recovery (p < 0.05) to 154% of basal prostacyclin production after 60 minutes. Catalase treatment resulted in recovery to 105% (p < 0.05) of basal prostacyclin production within 30 minutes of reoxygenation. Allopurinol treatment resulted in 77% recovery (p < 0.05) of basal prostacyclin production only during 30 minutes of reoxygenation. Dinitrophenol treatment resulted in significant (≥85%, p < 0.05) sustained recovery of basal prostacyclin production at 30, 60, and 90 minutes of experimental reperfusion. Conclusions: The hypoxia-induced decrease in EC prostacyclin does not recover during reoxygenation. Catalase/SOD allowed return to baseline prostacyclin production during reoxygenation, implicating reactive oxygen metabolites as mediators of decreased eicosanoid biosynthesis. Recovery of prostacyclin production after 60 minutes reoxygenation with dinitrophenol but not allopurinol suggests a mitochondrial origin of the oxygen metabolites responsible for decreased prostacyclin biosynthesis.