Reoxygenation-Induced Heart Microvasculature Endothelial Cell Injury and Neutrophil Hyperreaction: Role of Arachidonate Lipoxygenase Metabolism

Summary

In order to clarify the mechanism by which neutrophils are activated in the reperfused coronary vasculature, we investigated intercellular actions between endothelial cells and neutrophils under hypoxia followed by reoxygenation. We cultured canine coronary endothelial cells and neutrophils under hypoxia (<1 torr:45min)—reoxygenation (100 torr:5h). Adhesion and diapedesis of neutrophils was measured by counting the cells which adhered on the endothelial cells and infiltrated under the endothelial cell monolayer. Arachidonate lipoxygenase metabolites, hydroxyeicosatetraenoic acids (HETE), and oxygen-free radicals were assayed by high pressure liquid chromatography (HPLC) and 5,5-dimethyl-l-pyrroline-N-oxide (DMPO) spin trapping, respectively. Under sustained hypoxia, there was no increase in neutrophil function, free radical generation, or HETE production. After reoxygenation, diapedesis and chemotaxis of the leukocytes were markedly enhanced. Under this condition, the production of 12-, 5-, and 15-HETE was markedly increased. Potent signals of the DMPO radical adducts were also detected after reoxygenation. DMPO-OOH generation was peaked at lh after reoxygenation and DMPO-OH production was peaked at 3 h after reoxygenation. The pre-treatment of endothelial cells with AA-861 (a lipoxygenase inhibitor) or CV-3611 (a radical scavenger) markedly attenuated the re-oxygenation-induced cell injury and free radical generation, resulting in the suppression of neutrophil hyperreaction. There was a close correlation between HETE production and neutrophil function. These results indicate that augmented lipoxygenase metabolism in the reoxygenated endothelial cells may serve to enhance neutrophil function, and that augmented free-radical generation from the cocultured system may enhance microvasculature endothelial cell injury under hypoxia-reoxygenation.