Hisakazu Fuji

Delayed effects of sublethal ischemia on the acquisition of tolerance to ischemia.

The infarct-limiting effect of ischemic preconditioning is believed to be a transient phenomenon. We examined the delayed effects of repetitive brief ischemia on limiting infarct size in an open-chest dog model by an occlusion (90 minutes) of the left anterior descending coronary artery (LAD) followed by reperfusion (5 hours). The dogs were preconditioned with four brief repeated ischemic episodes induced by 5-minute LAD occlusions with subsequent reperfusion. The size of infarcts initiated by a sustained occlusion immediately or 24 hours after preconditioning was significantly smaller when compared with infarcts in sham-operated dogs (for the immediate occlusion, 14.4 +/- 2.0% versus 39.0 +/- 3.7%, respectively [p < 0.01]; and for the delayed occlusion, 18.8 +/- 3.4% versus 35.1 +/- 4.6%, respectively [p < 0.05]); however, when the infarction was induced 3 hours (31.2 +/- 3.7% versus 37.5 +/- 4.2%, respectively) or 12 hours (25.4 +/- 4.8% versus 35.0 +/- 5.3%, respectively) after repetitive ischemia, the infarct size did not differ. No differences were seen in regional myocardial blood flow or rate-pressure products between the two groups. These results indicate that an infarct-limiting effect of brief repeated ischemia can be observed 24 hours after sublethal preconditioning.

Detection of oxygen-derived free radical generation in the canine postischemic heart during late phase of reperfusion.

To define the relation between oxygen-derived free radical (oxy-radical) generation in the reperfused ischemic myocardium and the progression of myocardial damage, we measured oxy-radical generation in the ischemic myocardium and the propagating infarct size in a model of canine coronary occlusion (90 minutes) and reperfusion. We used electron paramagnetic resonance spin-trapping techniques (5,5-dimethyl-1-pyrroline N-oxide [DMPO]) to detect oxy-radicals in the rapidly frozen myocardial samples taken by needle biopsy. There was no detectable generation of DMPO adducts in the normal myocardium before or after reperfusion. In the reperfused ischemic myocardium, electron paramagnetic resonance signals of DMPO-OOH (superoxide anion) and DMPO-OH (hydroxyl radical) were detected, with peak concentrations at 1 hour after reperfusion for DMPO-OOH and at 3 hours after reperfusion for DMPO-OH, respectively. These DMPO adducts were also detected during the early phase (15 seconds) of reperfusion, but the concentrations of these signals were much less than those during the late phase of reperfusion. Treatment with human recombinant superoxide dismutase (2.5 mg/kg/hr) and catalase (2.5 mg/kg/hr) during the course of experiments abolished DMPO-OOH formation but had little effect on DMPO-OH formation. Infarct size (percent of risk area infarcted), quantified by a dual staining method with Evans blue dye and triphenyltetrazolium chloride, was 18.3 +/- 4.8% (mean +/- SEM) at 90 minutes of occlusion. After 5 hours of reperfusion, infarct size increased to 43.6 +/- 7.2%. These results indicate that a greater magnitude of oxy-radical generation was sustained in the ischemic myocardial tissue during the late phase (1-3 hours) of reperfusion, associated with the progression of myocardial infarction. The concurrent appearance of oxy-radicals and progressive infarction may support the view that a chain reaction of oxy-radicals contributes to the propagation of myocardial cell damage in the postischemic heart.

Comparison of myocardial contrast echocardiography and coronary angiography for assessing the acute protective effects of collateral recruitment during occlusion of the left anterior descending coronary artery at the time of elective angioplasty

To assess the immediate change in collateral flow distribution within the occluded myocardium and the acute protective effects on myocardial ischemia after coronary occlusion, myocardial contrast echocardiography (MCE) was performed in 15 patients with normal left ventricular function undergoing elective coronary angioplasty of the left anterior descending artery, and the results were compared with those obtained from coronary angiography (CA). The sonicated or nonsonicated contrast material was injected into the right coronary artery before and during coronary occlusion and collaterals were graded on a 4-point scale (none = 0 to good = 3). Development of subjective anginal symptoms, ST-segment shift and wall motion abnormality during coronary occlusion were graded on a 4-point scale (none = 0 to severe = 3). Both MCE and CA detected a significant development in collateral flow during coronary occlusion. There was no significant correlation between MCE and CA collateral grades before or during coronary occlusion. The collateral flow assessed with MCE was inversely but significantly correlated with development of subjective anginal symptoms (r(s) = -0.70, p <0.01), ST-segment shift (r(s) = -0.78, p < 0.005) or wall motion abnormality (r(s) = -0.91, p < 0.001) during coronary occlusion. In contrast, the angiographic collateral flow was not correlated with development of anginal symptoms (r(s) = -0.46, p = 0.10), ST-segment shift (r(s) = -0.41, p = 0.14), or wall motion abnormality (r(s) = -0.26, p = 0.35). The present study suggested that the acute protective effects of coronary collaterals during coronary occlusion were closely associated with myocardial perfusion rather than the angiographic epicardial collateral vessel filling, and thus MCE was useful in assessing the acute protective effects of coronary collaterals during coronary occlusion.

Brief myocardial ischemia affects free radical generating and scavenging systems in dogs

SummaryThis study examined whether brief repeated myocardial ischemia altered free radical generating and scavenging activity in a dog model. In dogs preconditioned with four 5-min left anterior descending coronary artery (LAD) occlusions and reperfusions, we examined transcardiac changes in both the function of neutrophils, cells which are major free radical generators, and in myocardial antioxidant enzyme activity, as an indication of free radical scavenging. Neutrophil function was assessed by determining luminol-enhanced whole blood chemiluminescence (CL) induced by zymosan. Blood was taken simultaneously from the carotid artery and the cardiac vein running along the occluded LAD. Preconditioning with sublethal ischemia significantly reduced whole blood CL in the cardiac vein compared with the carotid artery after the first and fourth 5-min reperfusions, while there was no difference in neutrophil count between these sampling sites. Immediately after brief repeated ischemia and reperfusion, manganese-superoxide dismutase (SOD) activity was significantly enhanced, and glutathione reductase activity was markedly reduced in the ischemic, compared with the non-ischemic, myocardium. There were no differences in the myocardial activities of copper, zinc-SOD, glutathione peroxidase, and glutathione S-transferase between the ischemic and non-ischemic regions. Also, no difference was observed between the reduced myocardial glutathione levels in these regions, although the oxidized glutathione level was significantly higher in the ischemic regions of the subepicardial and subendocardial areas. We demonstrated that brief repeated ischemia affects free radical generating and scavenging systems in the ischemic myocardium.

Usefulness of Plasma Brain Natriuretic Peptide After Acute Myocardial Infarction in Predicting Left Ventricular Dilatation Six Months Later

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) are synthesized and secreted from the ventricular myocardium after the onset of myocardial infarction (MI), and plasma concentrations of ANP and BNP are significantly correlated with hemodynamic variables and residual left ventricular (LV) function. 1‐4 Furthermore, plasma concentrations of these peptides may be used as simple biochemical predictors of prognosis after MI. 5,6 LV dilatation after MI may occur due to expansion of the infarct site, 7 hypertrophy of noninfarcted myocardium, or maladaptive LV “ remodeling.” 8,9 We hypothesized that plasma natriuretic peptide concentration correlated with LV remodeling. We studied the relation between plasma natriuretic peptide concentrations 1 month after the onset of MI and LV dilatation.

Polymorphonuclear leukocytes-induced injury in hypoxic cardiac myocytes

Growing evidence suggests that free radicals derived from polymorphonuclear leukocytes (PMNs) play an important role in myocardial ischemia-reperfusion injury. To elucidate the cellular mechanism by which activated PMNs exacerbate ischemic myocardial damage, we investigated the extent of cell injury, assessed by the morphological deterioration, free radical generation, and lipid peroxidation in mouse embryo myocardial cells coincubated with activated PMNs. The generation of PMN-derived free radicals was related to the extent of myocardial cell injury. When myocardial cell sheets were subjected to hypoxia and glucose-free media, myocardial cells were injured (cristalysis in the mitochondria and disruption of the sarcolemma) after adding various PMN activators, and the injury extended to the adjacent cells. Chemiluminescent emission and production of thiobarbituric acid-reactive substances in the coincubated cells increased markedly compared with myocardial cells or PMNs alone. The augmented lipid peroxidation coincided with the progression of myocardial cell injury. Catalase inhibited the myocardial cell injury by 52%, the chemiluminescence by 46%, and lipid peroxidation by 50%, whereas superoxide dismutase exhibited less pronounced inhibition. These results indicate that a chain reaction of lipid peroxidation in myocardial cells induced by PMN-derived free radicals closely correlates with membrane damage and contributes to the propagation of irreversible myocardial cell damage.

Comparison of time of reperfusion during anterior wall acute myocardial infarction to left ventricular volume one month and 20 months later.

We studied 95 patients with a first anterior wall acute myocardial infarction who received successful reperfusion within 72 hours after the onset. The patients were divided into 4 groups based on the time required to achieve reperfusion; <3 hours (n = 23), 3 to 6 hours (n = 42), 6 to 24 hours (n = 17), and >24 to 72 hours (n = 13). The infarct size, as evaluated by thallium-201 single-photon emission computed tomography, at 1 month after the infarct was significantly larger (p <0.05) in >24 to 72 hours (1,593 +/- 652 U) than that in <3 hours (749 +/- 650 U), but was not significantly different from that at 3 to 6 hours (1,353 +/- 770 U) or 6 to 24 hours (1,371 +/- 561 U). The end-diastolic volume index at 1 month did not differ among the 4 groups. However, the end-diastolic volume index during the follow-up period (20 +/- 8 months) in >24 to 72 hours (93 +/- 23 ml/m(2)) was significantly larger than that in the other 3 groups (<3 hours [65 +/- 21 ml/m(2)], 3 to 6 hours [65 +/- 22 ml/m(2)], and 6 to 24 hours [70 +/- 25 ml/m(2)]). Similar findings were observed in end-systolic volume index. In conclusion, although infarct size reduction was not observed by late reperfusion, left ventricular volumes at 1 month were comparable among patients with successful reperfusion within 3 and up to >24 hours. Left ventricular volumes 2 years after acute myocardial infarction were significantly larger in patients who did not under reperfusion for >24 hours.

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.

Sex-Related Differences in Left Ventricular Diastolic Function and Arterial Elastance during Admission in Patients with Heart Failure with Preserved Ejection Fraction: The PURSUIT HFpEF study

We previously reported that an index of afterload‐related left ventricular diastolic function, operant diastolic elastance (Ed)/effective arterial elastance (Ea) = E/e’/(0.9 × systolic blood pressure), was significantly higher in elderly hypertensive women. We aimed to determine sex‐related differences in the E/e’‐related indices for left ventricular diastolic function and their related factors during admission in patients with heart failure with preserved ejection fraction (HFpEF).

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.