Effect of volatile anesthetics on hydrogen peroxide-induced injury in aortic and pulmonary arterial endothelial cells

Background: Oxidant damage to endothelial cells occurs during inflammation and reperfusion after ischemia, mediated in part by endogenously produced hydrogen peroxide (H ₂O ₂). Previous studies have established a role for increased cytosolic calcium in the mechanism of endothelial oxidant injury, and have suggested that volatile anesthetics may exacerbate oxidant injury in pulmonary endothelium. However, the effect of volatile anesthetics on oxidant injury to systemic arterial endothelial cells, and their effect on oxidant- related changes in cytosolic calcium homeostasis, have not been reported previously. Methods: Primary cultures of human aortic and pulmonary arterial endothelial cells were studied. The rate of cell death after H ₂O ₂ exposure was determined in cell suspension bypropidium iodide fluorimetry and lactate dehydrogenase release. The final extent of cell death 24 h after H ₂O ₂ exposure was determined in monolayer cultures by methyl thiazolyl tetrazolium reduction. Cytosolic calcium and cell death were determined in single cells using fura-2 and propidium iodide imaging with digitized, multiparameter, fluorescent video microscopy. Results: In aortic endothelial cells, clinical concentrations of halothane (1.0%) and isoflurane (1.5%) decreased both the rate of cell death and the final extent of cell death after H ₂O ₂ exposure, with halothane being more protective. Supraclinical concentrations of halothane (2.7%) and isoflurane (4.0%) were less protective. In pulmonary arterial endothelial cells, halothane and isoflurane had essentially no effect on H ₂O ₂-mediated cell death. The protective effect of anesthetic in aortic endothelial cells was not due to an enhanced removal of H ₂O ₂ by endogenous enzymes. Hydrogen peroxide exposure caused a large increase in cytosolic calcium well before cell death, and this was moderated by anesthetic treatment. Conclusions: The effect of volatile anesthetics on oxidant injury to endothelial cells may differ between cells derived from systemic and pulmonary vascular beds. Halothane, and to a lesser extent, isoflurane, protects against oxidant injury in aortic endothelial cells. The mechanism of protection may involve modulation of the interaction of H ₂O ₂ with vital cellular constituents, and/or amelioration of the toxic increase in cytosolic calcium that follows such interaction.