Kazunori Kuwano

Free oxygen radicals contribute to platelet aggregation and cyclic flow variations in stenosed and endothelium-injured canine coronary arteries

OBJECTIVES The purpose of this study was to test the hypothesis that free oxygen radicals contribute to platelet aggregation and cyclic flow variations in stenosed and endothelium-injured coronary arteries. BACKGROUND Although free oxygen radicals, such as superoxide anion and hydrogen peroxide, have been shown to alter platelet function in vitro, the potential role of free oxygen radicals has not been fully described in an in vivo model of coronary artery thrombosis. METHODS Cyclic flow variations were produced in dogs by an external constrictor placed at the site of the left anterior descending coronary artery with injured endothelium. Blood flow in this artery was monitored by a pulsed Doppler flow probe. If cyclic flow variations were observed during postoperative days, dogs intravenously received superoxide dismutase plus catalase. In anesthetized dogs that did not develop an episode of cyclic flow variations, the effect of intracoronary infusion of xanthine plus xanthine oxidase or hydrogen peroxide on arterial blood flow velocity was studied. In platelet studies, the effect of free oxygen radicals and radical scavengers on platelet aggregation was examined. RESULTS In conscious dogs with cyclic flow variations, superoxide dismutase plus catalase significantly reduced cyclic flow variations (n = 7), whereas saline infusion had no effect (n = 7). The infusion of xanthine plus xanthine oxidase or hydrogen peroxide significantly induced cyclic flow variations in four of six dogs or in five of seven dogs, respectively. In vitro platelet studies showed that xanthine plus xanthine oxidase or hydrogen peroxide significantly enhanced platelet aggregation, and superoxide dismutase or catalase significantly inhibited such aggregation. CONCLUSIONS Reduction of free radical formation decreases platelet aggregation and may eliminate cyclic flow variations, whereas promotion of free radical generation enhances platelet aggregation and may induce cyclic flow variations. Thus, free oxygen radicals are an important mediator in this model.

Cyclic flow variations in a conscious dog model of coronary artery stenoses and endothelial injury correlate with acute ischemic heart disease syndromes in humans

OBJECTIVES The purpose of this study was to test the hypothesis that episodes of cyclic flow variations (CFVs) in conscious dogs with coronary stenoses and endothelial injury correlate with acute ischemic heart disease syndromes in humans. BACKGROUND Although the canine model with CFVs has proved to be a useful model of coronary thrombosis, whether CFVs progress to these syndromes has not been clearly described. METHODS Cyclic flow variations were produced by an external constrictor placed at the site of the left anterior descending coronary artery with injured endothelium. Blood flow in this artery and 24-h Holter electrocardiogram (ECG) were recorded during the 1st 5 postoperative days. RESULTS Of 41 dogs that underwent the initial operative procedure successfully, 29 developed an episode of CFVs. In five dogs in which CFVs persisted throughout the monitoring period, the left anterior descending coronary artery flow decreased until day 3 and thereafter increased through day 5. Transient coronary occlusion during CFVs induced ST segment changes that returned to baseline after reflow. In 12 dogs, CFVs progressed to persistent coronary occlusion, and histologic examination revealed thrombus formation at the stenotic site and evidence of myocardial infarction. Four of these 12 dogs died suddenly of ventricular arrhythmias during persistent coronary occlusion; another 5 dogs died of reperfusion arrhythmias during CFVs with no evidence of myocardial infarction. CONCLUSIONS Conscious dogs with CFVs closely correlated with clinical acute ischemic heart disease syndromes, suggesting them to be a useful model for investigating the complex mechanisms of cellular interactions in the pathogenesis of these syndromes.

Effects of Monoclonal Antibody to P-Selectin and Analogue of Sialyl Lewis X on Cyclic Flow Variations in Stenosed and Endothelium-Injured Canine Coronary Arteries

BACKGROUND A fundamental role of cell adhesion molecules is implicated in the disease processes of acute coronary syndromes. We have shown an increase in the soluble form of P-selectin in these syndromes, suggesting the important interaction between P-selectin and sialyl Lewis X (SLe(x)) for the pathophysiology of these syndromes. To further test this, we examined the effects of a monoclonal antibody against P-selectin (PB1.3) and a carbohydrate analogue of SLe(x) (SLe(x)-OS) on cyclic flow variations (CFVs) in stenosed and endothelium-injured canine coronary arteries. METHODS AND RESULTS Anesthetized, open-chest dogs (n = 48) were divided into six groups after CFVs were established. Dogs received intravenous normal saline, PB1.3 (1 mg/kg bolus), a low dose (5 mg/kg bolus) or a high dose (40 mg/kg bolus) of SLe(x)-OS followed by an infusion (5 mg.kg-1.h-1) for 60 minutes, a combination of PB1.3 and SLe(x)-OS (low dose), or a combination of a nonblocking antibody against P-selectin (PNB1.6, 1 mg/kg) and SLe(x)-OS (low dose). Although saline, PB1.3, SLe(x)-OS (low dose), and the combination of PNB1.6 and SLe(x)-OS (low dose) did not affect CFVs, the high dose of SLe(x)-OS and the combination of PB1.3 and SLe(x)-OS (low dose) significantly reduced CFVs. CONCLUSIONS These findings indicate that the high dose of SLe(x)-OS and the combination of PB1.3 and the low dose of SLe(x)-OS provide protection against CFVs. Thus, the adhesive interaction between P-selectin and SLe(x) may play an important role in mediating CFVs in this model.

Reconstruction of the Mitral Annulus With Porcine Pericardium

A 60-year-old man was admitted to our hospital for investigation of dyspnea and disorientation with right hemiplegia. Echocardiography showed thickened mitral valve leaflets with vegetations and severe mitral regurgitation. Blood cultures grew Staphylococcus aureus. During the operation, perforation and destruction of the mitral valve leaflets and vegetations were confirmed. Debridement of the infected tissues resulted in segmental disruption of the posterior mitral fibrous annulus. Reconstruction of the mitral annulus with porcine pericardium treated with glutaraldehyde and mitral valve replacement were successful. The patients postoperative course was complicated with metastatic cerebral and splenic abscesses. After splenectomy on the 8th postoperative day, he gradually recovered without major neurologic sequelae. We believe that reconstruction of the mitral valve annulus with pericardium, especially autologous pericardium, is reliable and useful for the treatment of patients with disruption of the mitral valve annulus.

Inhibitory Effect of Free Radical Scavengers on Cyclic Flow Variations in Unsedated Dogs with Coronary Stenosis and Endothelial Injury

Severe coronary artery stenosis with endothelial injury in the canine model induces cyclic coronary flow variations (CFVs), which are partially due to spontaneous platelet aggregation and dislodgement at the stenotic site. In the present study, we used anesthetized open-chest and unsedated closed-chest dogs with CFVs to investigate whether oxidative metabolic burst (hydrogen peroxide generation) occurred in neutrophils during CFVs and whether CFVs were attenuated by superoxide dismutase (SOD) and catalase. CFVs were produced by placing a cylindrical constrictor on the left anterior descending coronary artery (LAD). LAD blood flow was monitored by means of a Doppler flow probe placed proximally to the constrictor, and the severity of CFVs was expressed by both the frequency of CFVs and mean LAD blood flow. Hydrogen peroxide generation in neutrophils was measured by flow cytometry, using single cell analysis, and was expressed as the mean fluorescence intensity of 2’, 7’-dichlorofluorescein. Dogs received an intravenous infusion of saline (n = 8), SOD (5 mg/kg, n = 7), catalase (5mg/kg, n = 7), or a combination of SOD and catalase (same doses, n = 7). Although the mean fluorescence intensity did not change in sham-operated dogs without CFVs (61.7 ± 15.8 to 60.4 ± 11.8; NS), the intensity in the dogs with CFVs was significantly increased during CFVs (62.2 ± 13.7 to 79.8 ± 9.8; P < 0.005). These results indicate that hydrogen peroxide is generated in neutrophils.