Fumie Nishizaki

Matrix metalloprotein-9 activation under cell-to-cell interaction between endothelial cells and monocytes: possible role of hypoxia and tumor necrosis factor-α

Matrix metalloproteinase (MMP)-9 plays an important role in cardiovascular events. However, the mechanisms underlying in vivo activation of MMP-9 are largely unknown. We investigated the secretion and activation of MMP-9 under a cell-to-cell interaction, and the effects of hypoxia and cytokine. Human umbilical vein endothelial cell (HUVEC) and THP-1 (human monocyte cell line) were cultured individually, or cocultured under normoxic and hypoxic conditions. In a coculture of HUVEC and THP-1, proMMP-9 secretion was increased twofold compared with individual culture of HUVEC and THP-1, whereas MMP-2 secretion was unchanged. The increase in proMMP-9 secretion was suppressed by antiadhesion molecule antibodies and mitogen-activated protein kinase inhibitors, PD98059 (MAPK/ERK kinase1 inhibitor) and SP600125 (Jun N-terminal kinase inhibitor). ProMMP-9 secretion was increased by tumor necrosis factor (TNF)-α at 50 ng/ml (P < 0.05) but was not activated under normoxic (20%) conditions. ProMMP-9 in coculture was activated under hypoxic (<1%) conditions, and was potentiated by TNF-α (both P < 0.05). To further investigate the mechanism of hypoxia-induced MMP-9 activation, heat shock protein (Hsp)90, which was suggested to be related to MMP-9 activation, was measured by Western blot analysis. The ratio of Hsp90 to glyceraldehyde-3-phosphate dehydrogenase was increased in hypoxic (<1%) coculture conditions with TNF-α (P < 0.05). Treatment with geldanamycin and 17-DMAG (Hsp90 inhibitor) suppressed the active form of MMP-9. Cell-to-cell interaction between endothelial cells and monocytes promotes proMMP-9 synthesis and secretion. Hypoxia and inflammation are suggested to play an important role in activating proMMP-9, presumably via Hsp90.

Estrogen attenuates coupling factor 6-induced salt-sensitive hypertension and cardiac systolic dysfunction in mice

In male coupling factor 6 (CF6)-overexpressing transgenic (TG) mice, a high-salt diet induces hypertension and cardiac systolic dysfunction with excessive reactive oxygen species generation. However, the role of gender in CF6-mediated pathophysiology is unknown. We investigated the effects of ovariectomy and estrogen replacement on hypertension, cardiac dysfunction and Rac1 activity, which activates radical generation and the mineralocorticoid receptor, in female TG mice. Fifteen-week-old male and female TG and wild-type (WT) mice were fed a normal- or high-salt diet for 60 weeks. Systolic and diastolic blood pressures were higher in the TG mice fed a high-salt diet than in those fed a normal-salt diet at 20–60 weeks in males but only at 60 weeks in females. The blood pressure elevation under high-salt diet conditions was concomitant with a decrease in left ventricular fractional shortening. In the WT mice, neither blood pressure nor cardiac systolic function was influenced by a high-salt diet. In the female TG mice, bilateral ovariectomy induced hypertension with cardiac systolic dysfunction 8 weeks after the initiation of a high-salt diet. The ratios of Rac1 bound to guanosine triphosphate (Rac1-GTP) to total Rac1 in the heart and kidneys were increased in the ovariectomized TG mice, and estrogen replacement abolished the CF6-mediated pathophysiology induced under the high-salt diet conditions. The overexpression of CF6 induced salt-sensitive hypertension, complicated by systolic cardiac dysfunction, but its onset was delayed in females. Estrogen has an important role in the regulation of CF6-mediated pathophysiology, presumably via the downregulation of Rac1.

Potential roles of the wearable cardioverter-defibrillator in acute phase care of patients at high risk of sudden cardiac death: A single-center Japanese experience

BACKGROUND The wearable cardioverter-defibrillator (WCD) has been expected to play a role as an effective bridge therapy to implantable cardioverter-defibrillator (ICD) implantation in patients at high risk of ventricular tachyarrhythmias (VA). Although WCD has been available since April 2014 in Japan, its usefulness remains unclear. METHODS AND RESULTS During the early period after hospitalization, patients at high risk of VA after excluding some elderly patients were prescribed WCD. The consecutive 50 patients with WCD use (median age 56 years, 38 for secondary prevention) were studied. We analyzed clinical efficacy and safety of WCD, and examined its potential roles. Of the 50 patients, 38 used WCD only during hospitalization. During WCD use [median 16 (IQR 8-33) days], all patients wore WCD for 98% of a day regardless of in or out-of-hospital use. Sustained VA was detected in 4 patients (8%; for primary prevention in 1) with 7 episodes, and 6 of 7 episodes required shock therapy. Of the 6 shock therapies, 4 were for sustained ventricular tachycardia with the median rate of 236beats/min (IQR 203-250), and the other 2 for ventricular fibrillation. Subsequently, only 27 patients (54%) of all underwent ICD implantation following the WCD use, because of reduced risk of VA after optimal pharmacological therapy or improvement in the left ventricular function. CONCLUSIONS The WCD use for the acute phase care of patients at high risk of VA can be safe and effective, and may be useful for evaluating indication of ICD implantation.

Re-elevation of T-wave from day 2 to day 4 after successful percutaneous coronary intervention predicts chronic cardiac systolic dysfunction in patients with first anterior acute myocardial infarction

This study evaluates the clinical significance of re-elevation of T-wave in patients with ST segment elevation acute myocardial infarction (STEMI) undergoing successful percutaneous coronary intervention (PCI). Resolution of ST elevation within 24 h after reperfusion is associated with better outcome. However, little is known about the serial electrocardiography (ECG) changes and their significance. Seventy-five patients (52 men; 66 ± 1 years) with the first anterior STEMI in whom 12-lead ECG was recorded every day from day 0 to day 8 after PCI were studied. JT interval was quartered (points 1–5), and the deviations from isoelectric line at each point were analyzed in leads V2, V3, and V4. Serial ECG showed ST resolution and T-wave inversion within 2 days after PCI in all patients at the middle of JT interval (point 3), and subsequent re-elevation of T-wave on day 4 in 73 patients (97.3 %). The patients were divided into two groups: Group A (n = 37) with less JT deviation changes (<0.25 mV) from day 2 to day 4 at point 3; and Group B (n = 38) with greater JT deviation changes (≥0.25 mV). Group B had less retrograde collateral flow and longer JT interval in the acute phase, and lower left ventricular ejection fraction (LVEF), worse regional contractility, and higher plasma brain natriuretic peptide levels at 6 months after the onset than Group A (all P < 0.05). The JT deviation change was negatively correlated with and an independent predictor for LVEF in the chronic phase. Re-elevation ≥0.25 mV of T-wave at the middle of JT interval after successful PCI predicts chronic cardiac systolic dysfunction in patients with first anterior STEMI.

Coronary Plaque Characteristics Associated With Reduced TIMI (Thrombolysis in Myocardial Infarction) Flow Grade in Patients With ST-Segment–Elevation Myocardial Infarction: A Combined Optical Coherence Tomography and Intravascular Ultrasound Study

Background—Previous studies reported that reduced TIMI (Thrombolysis in Myocardial Infarction) flow grade before procedure was associated with worse clinical outcomes in patients with ST-segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention. The aim of this study was to identify specific morphological characteristics of the culprit plaque associated with poor TIMI flow grade at baseline in patients with ST-segment–elevation myocardial infarction using both optical coherence tomography and intravascular ultrasound. Methods and Results—A total of 111 ST-segment–elevation myocardial infarction patients who underwent percutaneous coronary intervention within 24 hours of symptom onset were included. Both optical coherence tomography and intravascular ultrasound were performed after thrombectomy. Patients were divided into 2 groups according to preprocedural TIMI flow grade (TIMI 0–1 [n=82] and TIMI 2–3 [n=29]). Patients with preprocedural TIMI 0 to 1 had a greater lipid arc (P=0.037), a longer lipid length (P=0.021), and a greater lipid index (P=0.007) determined by optical coherence tomography and a larger external elastic membrane cross-sectional area (P=0.030) and plaque plus media cross-sectional area (P=0.030) determined by intravascular ultrasound, compared with patients with preprocedural TIMI 2 to 3. Conclusions—ST-segment–elevation myocardial infarction patients with reduced TIMI flow grade at baseline have greater lipid burden, larger vessel sizes, and larger plaque areas.

Coupling factor 6 enhances the spontaneous microaggregation of platelets by decreasing cytosolic cAMP irrespective of antiplatelet therapy

The spontaneous microaggregation of platelets (SMAPs) is a marker for the prognosis of patients with cardiovascular diseases. Coupling factor 6 (CF6) binds to the plasma membrane ATP synthase and functions as a pro-atherogenic molecule in the cardiovascular system. However, the role of CF6 in SMAPs and stroke remains unknown. In 650 consecutive patients, including those with acute-onset stroke, and 20 control subjects, platelet-rich plasma (PRP) was obtained, and SMAP was measured using a laser light-scattering aggregometer. The cytosolic cyclic adenosine monophosphate (cAMP) concentration in platelets was measured using an enzyme-linked immunosorbent assay. CF6 increased SMAPs in patients and control subjects to a similar degree by binding to the α- and β-subunits of ATP synthase and inducing intracellular acidosis. It was abolished by PRP pretreatment with antibodies against CF6, and the α- or β-subunit of the plasma membrane ATP synthase, and the ATP synthase inhibitor efrapeptin. CF6 increased SMAPs in patient groups with and without antiplatelet therapy to a similar degree, and no difference was found among the subgroups taking aspirin, thienopyridine or cilostazol. The cytosolic cAMP concentration in platelets was decreased by CF6 in the presence of the direct adenylate cyclase activator forskolin. Pretreatment of PRP with the Gs activator cholera toxin blocked the decrease, whereas the Gi inactivator pertussis toxin and cilostazol had no influence. The CF6-induced acceleration of SMAPs was suppressed by cholera toxin but not by cilostazol or pertussis toxin. CF6 enhanced SMAPs by decreasing cytosolic cAMP. Because it was observed irrespective of antiplatelet agents, CF6 appears to be a novel target for antiplatelet therapy.

Acute myocardial infarction caused by a floating thrombus in the ascending aorta: A role of CD34-positive endothelial cells

A 49-year-old woman was transferred to our hospital with acute-onset chest pain. Her electrocardiogram showed complete atrioventricular block and bradycardia with ST-segment elevation in the inferior leads, and she presented with cardiogenic shock. She was diagnosed with inferior acute myocardial infarction (AMI), and subsequent emergency cardiac catheterization was performed. Selective coronary angiography showed neither stenosis nor obstruction in any of the coronary arteries. Left ventriculography showed a large floating object located on the ascending aortic wall above the ostium of the right coronary artery (RCA). Chest enhanced computed tomography confirmed the floating object in the ascending aorta. These findings suggested that the floating object was associated with the RCA occlusion. To remove the floating object, emergency surgery was performed. The floating object was a large thrombus derived from the localized atheromatous plaque in the ascending aorta. Specialized immunostaining for surface antigen CD34 revealed that regenerated endothelial cells were present on the erosion, along the stalk, and on the floating thrombus. These findings indicate that the CD34-positive endothelial precursor cells strayed into the surface and/or inside of the thrombus, and consequently the floating thrombus supported by these regenerated endothelial cells occluded the RCA, causing AMI. <Learning objective: A free floating thrombus formed in the ascending aorta can cause obstruction of the coronary artery ostium, leading to AMI. This unusual cause of AMI mostly occurs in females, and shows high mortality rates. Although the risk factors are known to be current smoking, oral hormone therapy, and hypercoagulable state such as pregnancy, the underlying mechanism of thrombus formation is still unclear. This report describes a possible role of CD-34 positive regenerated endothelial cells in thrombus formation.>.

Deeply reinverted T wave at 14 days after the onset of first anterior acute myocardial infarction predicts improved left ventricular function at 6 months.

Changes in electrocardiogram (ECG), especially in the ST segment and T wave, have been recognized as a noninvasive diagnostic tool for coronary flow or myocardial injury.