Takuro Tsukube

Oxidative stress in the pathogenesis of thoracic aortic aneurysm : Protective role of statin and angiotensin II type 1 receptor blocker

OBJECTIVE The pathogenesis of thoracic aortic aneurysms (TAA) is still unclear. A recent investigation indicated that angiotensin II, a potent activator of NADH/NADPH oxidase, plays an important role in aneurysmal formation. We investigated the potential role of p22phox-based NADH/NADPH oxidase in the pathogenesis of TAA. METHODS Human thoracic aneurysmal (n=40) and non-aneurysmal (control, n=39) aortic sections were examined, and the localization of p22phox, an essential component of the oxidase, and its expressional differences were investigated by immunohistochemistry and Western blot. In situ reactive oxygen species (ROS) generation was examined by the dihydroethidium method, and the impact of medical treatment on p22phox expression was investigated by multiple regression analysis. RESULTS In situ production of ROS and the expression of p22phox increased markedly in TAA throughout the wall, and Western blot confirmed the enhanced expression of p22phox. The expression was more intense in the regions where monocytes/macrophages accumulated. In these inflammatory regions, numerous chymase-positive mast cells and angiotensin converting enzyme-positive macrophages were present. Their localization closely overlapped the in situ activity of matrix metalloproteinase and the expression of p22phox. Multiple regression analysis revealed that medical treatment with statin and angiotensin II type 1 receptor blocker (ARB) suppressed p22phox expression in TAA. CONCLUSION Our findings indicate the role of p22phox-based NADH/NADPH oxidase and the local renin-angiotensin system in the pathogenesis of TAA. Statin and ARB might have inhibitory effects on the formation of aneurysms via the suppression of NADH/NADPH oxidase.

Mutations in a TGF-β Ligand, TGFB3, Cause Syndromic Aortic Aneurysms and Dissections

Background Aneurysms affecting the aorta are a common condition associated with high mortality as a result of aortic dissection or rupture. Investigations of the pathogenic mechanisms involved in syndromic types of thoracic aortic aneurysms, such as Marfan and Loeys-Dietz syndromes, have revealed an important contribution of disturbed transforming growth factor (TGF)-β signaling. Objectives This study sought to discover a novel gene causing syndromic aortic aneurysms in order to unravel the underlying pathogenesis. Methods We combined genome-wide linkage analysis, exome sequencing, and candidate gene Sanger sequencing in a total of 470 index cases with thoracic aortic aneurysms. Extensive cardiological examination, including physical examination, electrocardiography, and transthoracic echocardiography was performed. In adults, imaging of the entire aorta using computed tomography or magnetic resonance imaging was done. Results Here, we report on 43 patients from 11 families with syndromic presentations of aortic aneurysms caused by TGFB3 mutations. We demonstrate that TGFB3 mutations are associated with significant cardiovascular involvement, including thoracic/abdominal aortic aneurysm and dissection, and mitral valve disease. Other systemic features overlap clinically with Loeys-Dietz, Shprintzen-Goldberg, and Marfan syndromes, including cleft palate, bifid uvula, skeletal overgrowth, cervical spine instability and clubfoot deformity. In line with previous observations in aortic wall tissues of patients with mutations in effectors of TGF-β signaling (TGFBR1/2, SMAD3, and TGFB2), we confirm a paradoxical up-regulation of both canonical and noncanonical TGF-β signaling in association with up-regulation of the expression of TGF-β ligands. Conclusions Our findings emphasize the broad clinical variability associated with TGFB3 mutations and highlight the importance of early recognition of the disease because of high cardiovascular risk.

Developmental differences in cytosolic calcium accumulation associated with surgically induced global ischemia: Optimization of cardioplegic protection and mechanism of action ☆ ☆☆ ★ ★★ ♢

OBJECTIVE The effect of cardioplegic solutions with high concentrations of potassium or magnesium (or both) on cytosolic calcium accumulation was investigated with fura-2 in isolated perfused mature (n = 24) and aged (n = 24) rabbit hearts. METHODS We compared cytosolic calcium accumulation before ischemia (control), during 30 minutes of ischemia and 30 minutes of reperfusion under global ischemia, or after treatment with potassium (20 mmol/L), magnesium (20 mmol/L), or both. RESULTS Cytosolic calcium accumulation was increased during global ischemia in the mature heart (from 178.7 +/- 24.2 in the control group to 393.6 +/- 25.5 nmol/L; p < 0.005) and in the aged heart (from 187.4 +/- 18.7 in the control group to 501.0 +/- 46.1 nmol/L; p < 0.005). Potassium reduced cytosolic calcium accumulation during ischemia in both the mature and aged hearts (300.9 +/- 23.2 and 365.2 +/- 27.7 nmol/L, respectively; p < 0.05 vs global ischemia). Magnesium and potassium/magnesium completely controlled cytosolic calcium accumulation in the mature heart (198.7 +/- 27.5 nmol/L; p < 0.01 vs global ischemia and p < 0.05 vs potassium: 182.3 +/- 22.7 nmol/L; p < 0.05 vs global ischemia and potassium, respectively). Magnesium and potassium/magnesium attenuated cytosolic calcium accumulation in the aged heart (261.3 +/- 26.7, 262.3 +/- 25.2 nmol/L, respectively; p < 0.01 vs global ischemia). These changes in cytosolic calcium accumulation correlated with improved post-ischemic ventricular function. To investigate the mechanism(s) of magnesium-supplemented cardioplegic inhibition of cytosolic calcium accumulation, we performed parallel studies (n = 43) using nifedipine, ryanodine, and dimethylthiourea. Nifedipine with or without ryanodine reduced cytosolic calcium accumulation. Dimethylthiourea did not alter cytosolic calcium accumulation during global ischemia. Our results suggest that cytosolic calcium accumulation during global ischemia was mainly increased via the sarcolemmal 1-type calcium channel and the sarcoplasmic reticulum calcium-release channel. The modulating action of potassium/magnesium cardioplegia on cytosolic calcium accumulation during ischemia would appear to act through the inhibition of the myocardial 1-type calcium channel and the sarcoplasmic reticulum calcium-release channel. CONCLUSION Senescent cardiac dysfunction correlates with increased ischemia-induced cytosolic calcium accumulation. Magnesium-supplemented potassium cardioplegia ameliorates this age-related phenomenon at normothermia and may have important implications in myocardial protection in the elderly population.

Magnesium cardioplegia reduces cytosolic and nuclear calcium and DNA fragmentation in the senescent myocardium.

Previous reports have indicated that the senescent myocardium is less tolerant to surgically induced ischemia and that diminished functional recovery is associated with alterations in cytosolic calcium ([Ca2+]i) accumulation. Recently, increased [Ca2+]i has been suggested to alter nuclear calcium ([Ca2+]n) accumulation. To investigate the relation between [Ca2+]i and [Ca2+]n, we subjected mature and aged rabbit hearts to normothermic global ischemia, either without treatment or after treatment with potassium cardioplegia, magnesium cardioplegia, or a combination of potassium and magnesium cardioplegia. The relation between altered [Ca2+]n and DNA fragmentation was also investigated. Our results indicate that [Ca2+]i was increased during 30 minutes of normothermic global ischemia without treatment in both the mature and aged hearts (p < 0.05). Accumulation of [Ca2+]i during global ischemia was reduced with the use of potassium, magnesium, and a combination of potassium and magnesium cardioplegia (p < 0.05 versus untreated ischemia) in both the mature and aged hearts. Levels of [Ca2+]n were unaffected by global ischemia or cardioplegia in the mature myocardium; however, in the aged myocardium, [Ca2+]n was increased during global ischemia and with potassium cardioplegia and was associated with increased nuclear DNA fragmentation (p < 0.05). The use of magnesium and a combination of potassium and magnesium cardioplegia attenuated [Ca2+]n accumulation and nuclear DNA fragmentation (p < 0.05). Control of [Ca2+]i and [Ca2+]n was associated with enhanced functional recovery during reperfusion. These results indicate that during normothermic ischemia, there is increased [Ca2+]i and [Ca2+]n in the aged myocardium, and increased [Ca2+]n is associated with increased nuclear DNA fragmentation.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical treatment of an aneurysm in the right aortic arch with aberrant left subclavian artery

A saccular aneurysm in the right-sided aortic arch with aberrant left subclavian artery is an uncommon disease, and surgical treatment is complicated. Three patients with Edwards type III-B right aortic arch and enlargement of the Kommerells diverticulum underwent operations. Right thoracotomy was the preferred approach for this lesion and partial cardiopulmonary bypass is a safe and simple procedure when the aortic arch has mild atherosclerosis.

Transbrachial arterial insertion of aortic occlusion balloon catheter in patients with shock from ruptured abdominal aortic aneurysm.

OBJECTIVE Of 125 surgical patients with abdominal aortic aneurysm (AAA) treated from 1999, 11 patients with deep shock from ruptured AAAs who underwent aortic occlusion balloon catheter (AOBC) insertion before laparotomy were studied. METHODS With the patients under local anesthesia, the brachial artery was exposed and the balloon catheter was inserted into the thoracic aorta. The balloon was inflated halfway and pulled back gently to the orifice of the left subclavian artery, and was advanced with the aid of blood flow down to the abdominal aorta. After full inflation of the balloon, the catheter was pulled until the balloon was fixed at the proximal shoulder of the AAA. RESULTS AOBC insertion was completed within 16.1 +/- 5.1 minutes. Systolic blood pressure at presentation was 84.1 +/- 31.7 mm Hg, deteriorated to 60.9 +/- 15.4 mm Hg on arrival in the operating room, and increased significantly (P <.0001) to 123.4 +/- 25.3 mm Hg after AOBC insertion. The balloon burst in three patients. Embolic complications were observed in two patients. There were three deaths, two associated with the balloon bursting. In nine patients whose shock was successfully controlled by AOBC, operative mortality was 11%. CONCLUSION Transbrachial arterial insertion of an AOBC may be useful to ameliorate hemorrhagic shock in patients with ruptured AAAs.

Neurological Outcomes After Immediate Aortic Repair for Acute Type A Aortic Dissection Complicated by Coma

Background— Management of acute type A aortic dissection (AADA) complicated by coma remains controversial. We analyzed our experience in managing AADA complicated by coma to determine the relationship of duration of preoperative coma to postoperative neurological recovery. Methods and Results— Between September 2003 and October 2010, 181 patients with AADA were treated, including 27 presenting with coma (Glasgow Coma Scale <11) on arrival. Twenty-one patients were repaired immediately (immediate group); time from onset of symptoms to operating room was <5 hours. For brain protection, deep hypothermia with antegrade cerebral perfusion was used, and postoperative therapeutic hypothermia with magnesium treatment was performed. Six patients initially were managed medically, and 3 of them were followed by eventual repair because time from onset was >5 hours (delayed group). The preoperative National Institutes of Health Stroke Scale score was 31.4±6.6 in the immediate group and 28.3±9.5 in the delayed group. Hospital mortality was 14% in the immediate group and 67% in the delayed group. Full recovery of consciousness was achieved in 86% of patients in the immediate group and in 17% in the delayed group. In immediate group, the postoperative National Institutes of Health Stroke Scale score significantly improved to 6.4±8.4, cumulative survival rate was 71.8% in 3 years, and independence in daily activities was achieved in 52% (11/21). Conclusions— Aortic repair, if performed immediately from the onset of symptoms, showed satisfactory recovery of consciousness and neurological function in patients with AADA complicated by coma. In this patient population, immediate aortic repair is warranted.

Magnesium Cardioplegia Enhances mRNA Levels and the Maximal Velocity of Cytochrome Oxidase I in the Senescent Myocardium During Global Ischemia

BACKGROUND The aged myocardium accumulates significantly more cytosolic calcium [Ca2+]i during ischemia, and functional recovery is more severely compromised as compared with the mature heart. Cardioplegia ameliorates these phenomena. The mechanism by which increased calcium accumulation reduces functional recovery in the senescent myocardium is unknown, but it has been suggested that futile calcium cycling in the mitochondria leading to depletion of ATP stores during normothermic global ischemia may be involved. METHODS AND RESULTS To investigate the effect of cardioplegia on mitochondrial calcium ([Ca2+]mt) accumulation and the expression of cytochrome oxidase I (COX I) during global ischemia, mitochondria were isolated from mature (age, 15 to 20 weeks) and aged (age > 130 weeks) rabbit hearts after Langendorff perfusion. Five perfused heart groups were investigated: 30 minutes of global ischemia without treatment (control), with potassium (K, 20 mmol/L), magnesium (Mg, 20 mmol/L), or potassium and magnesium (K/Mg) cardioplegia. No significant difference in [Ca2+]mt was evident in mature hearts with any protocol. In aged hearts, [Ca2+]mt was increased in global ischemia but was ameliorated with Mg and K/Mg cardioplegia. COX I mRNA levels in aged hearts were lower in both control and global ischemia but were increased with cardioplegia. Maximal velocities for COX I were significantly increased with Mg cardioplegia both in the mature and the aged myocardium. CONCLUSIONS K and/or Mg cardioplegia ameliorates [Ca2+]mt accumulation in aged hearts during normothermic global ischemia and increases COX I mRNA levels to a level not significantly different from that found in mature hearts.

Impact of Controlled Pericardial Drainage on Critical Cardiac Tamponade With Acute Type A Aortic Dissection

Background— Cardiac tamponade is associated with fatal outcomes for patients with acute type A aortic dissection, and the presence of cardiac tamponade should prompt urgent aortic repair. However, treatment of the patient with critical cardiac tamponade who cannot survive until surgery remains unclear. We analyzed our experience of controlled pericardial drainage (CPD) managing critical cardiac tamponade. Methods and Results— Between September 2003 and May 2011, 175 patients with acute type A aortic dissection were treated surgically, including 43 (24.6%) who presented with cardiac tamponade on arrival. Eighteen patients, who did not respond to intravenous volume resuscitation, underwent CPD in the emergency department. An 8F pigtail drainage catheter was inserted percutaneously, and drainage volume was controlled by means of several cycles of intermittent drainage to maintain blood pressure at ≈90 mm Hg. After CPD, all of the patients were transferred to the operating room, and immediate aortic repair was performed. Systolic blood pressure before CPD was 64.3±8.2 mm Hg and elevated significantly in all of the cases after CPD. Systolic blood pressure after CPD was 94.8±10.5 mm Hg, and increase in systolic pressure was 30.5±11.7 mm Hg. Total volume of aspirated pericardial effusion was 40.1±30.6 mL, and 10 patients required only ⩽30-mL aspiration volume. All of the patients underwent aortic repair successfully. In-hospital mortality was 16.7%; however, there was no complications or mortality related to CPD. Conclusions— Preoperative pericardial drainage with control of volume is a safe and effective procedure for acute type A aortic dissection complicated by critical cardiac tamponade. In our patient population, timely controlled pericardial drainage is warranted.

Transcranial myogenic motor-evoked potentials after transient spinal cord ischemia predicts neurologic outcome in rabbits

OBJECTIVE Myogenic transcranial motor-evoked potentials (tc-MEPs) were applied to monitor spinal cord ischemia in the repairs of thoracoabdominal aortic aneurysms. We investigated whether tc-MEPs after spinal cord ischemia/reperfusion could be used to predict neurologic outcome in leporine model. METHODS Tc-MEPs were measured at 30-second intervals before, during, and after spinal cord ischemia (SCI) induced by balloon occlusion of the infrarenal aorta. Twenty rabbits were divided into five groups. Four groups (n = 4 animals in each group) had transient ischemia induced for 10, 15, 20, or 30 minutes. In fifth group, the terminal aorta at the aortic bifurcation was occluded for 30 minutes. All animals were evaluated neurologically 48 hours later, and their spinal cords were removed for histologic examination. RESULTS The tc-MEPs in each SCI group rapidly disappeared after SCI. After reperfusion, the recovery of tc-MEPs amplitude was inversely correlated to duration of SCI. Tc-MEPs amplitude at one hour after reperfusion was correlated with both neurologic score and number of neuron cells in the spinal cord 48 hours later. Logistic regression analysis demonstrated that the neurologic deficits differed significantly between animals with tc-MEPs amplitude of less than 75% of the baseline and those with an amplitude of more than 75%. CONCLUSIONS The amplitude of tc-MEPs after ischemia /reperfusion of the spinal cord showed a high correlation with durations of SCI, with neurologic deficits, and with pathologic findings of the spinal cord. Tc-MEPs, therefore, could be used to predict neurologic outcome. In particular, tc-MEPs whose amplitude recovered by less than 75% indicated a risk of paraplegia.