Youngjoon Kim

Attenuation of neutrophil function by inhibitors of arachidonate metabolism reduces the extent of canine myocardial infarction

To assess the role of neutrophils and arachidonate metabolites in evolving myocardial infarction, the effect of inhibitors of arachidonate metabolism on the extent of myocardial damage and neutrophil function was examined in a 90-minute occlusion/5-hour reperfusion model of canine myocardial infarction. A thromboxane A2 synthetase inhibitor, CV-4151, and a lipoxygenase inhibitor, AA-861, greatly reduced the infarct size. They also attenuated the production of chemoattractant leukotriene B4 and chemotactic activity of neutrophils isolated from peripheral circulation. Under these conditions, both the increases in peripheral leukocyte count and neutrophil infiltration in ischemic myocardium were inhibited. These results indicate that the inhibition of 2 pathways of arachidonate metabolism may decrease infiltration of activated neutrophils in ischemic myocardium by attenuating chemotactic function of neutrophils, resulting in reduction of the extent of myocardial infarction.

Transcardiac alteration of neutrophil function before and after coronary thrombolysis in human myocardial infarction

We examined function of isolated neutrophils taken from aorta and coronary sinus before and after thrombolytic reperfusion in 17 patients whose infarct-related coronary arteries were totally occluded. Before reperfusion in left coronary artery disease, free radical generation by activated neutrophils in coronary sinus, assessed by ferricytochrome c reduction (phorbol myristate acetate, 10 ng/ml) and luminol-enhanced chemiluminescence (A23187, 2 microM), was reduced by 20% (P less than 0.05) and 30% (P less than 0.05), respectively, compared with those in aorta. Neutrophil aggregation (A23187, 10 microM) and chemotactic activity (formyl-methionyl-leucyl-phenylalanine, 5 microM) were also reduced in coronary sinus by 21% and 20%. After reperfusion the extent of such neutrophil function in coronary sinus recovered and was similar to that in aorta. There were no significant differences between neutrophil counts in aorta and coronary sinus before and after reperfusion. In right coronary artery disease, no significant changes were seen in these functions of neutrophils of aorta and coronary sinus before and after reperfusion. These results indicate that function of neutrophils passing through coronary circulation fluctuated significantly in association with reperfusion, suggesting (1) factor(s) that depress neutrophil function are produced in coronary circulation during myocardial ischemia and their effects are overcome after reperfusion or (2) activated neutrophils, trapped in the ischemic coronary bed, are washed out to coronary sinus after reperfusion.

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

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.