Search

Heart failure is known to predispose to life-threatening ventricular tachyarrhythmias even before compromising the systemic circulation. but the underlying mechanism is not well understood. The aim of this study was to clarify the connexin43 (Cx43) gap junction remodeling and its potential role in the pathogenesis of arrhythmias during the development of heart failure. We investigated stage-dependent changes in Cx43 expression in UM-X7.1 cardiomyopathic hamster hearts and associated alterations in the electrophysiological properties using a high-resolution optical mapping system. UM-X7.1 hamsters developed left ventricular (LV) hypertrophy by ages 6-10 wk and showed a moderate reduction in LV contractility at age 20 wk. Appreciable interstitial fibrosis was recognized at these stages. LV mRNA and protein levels of Cx43 in UM-X7.1 were unaffected at age 10 wk but significantly reduced at 20 wk. The expression level of Ser255-phosphorylated Cx43 in UM-X7.1 at age 20 wk was significantly greater than that in control golden hamsters at the same age. In UM-X7.1 at age 10 wk, almost normal LV conduction was preserved, whereas the dispersion of action potential duration was significantly increased. UM-X7.1 at age 20 wk showed significant reduction of cardiac space constant, significant decrease in conduction velocity, marked distortion of activation fronts, and pronounced increase in action potential duration dispersion. Programmed stimulation resulted in sustained ventricular tachycardia or fibrillation in UM-X7.1. LV activation during polymorphic ventricular tachycardia was characterized by multiple phase singularities or wavebreaks. During the development of heart failure in the cardiomyopathic hamster, alterations of Cx43 expression and phosphorylation in concert with interstitial fibrosis may create serious arrhythmogenic substrate through an inhibition of cell-to-cell coupling. cardiomyopathy; ventricular arrhythmia; optical mapping; phosphorylation

Reactive oxygen species-scavenging enzyme Cu/Zn superoxide dismutase (SOD) regulated by peroxisome proliferator-activated receptors (PPARs) plays an important role in vascular responsiveness. However, it remains unknown whether statin restores vascular dysfunction through the activation of reactive oxygen species-scavenging enzymes in vivo. We hypothesized that pitavastatin restores vascular function by modulating oxidative stress through the activation of Cu/ZnSOD and PPAR-[gamma] in hypercholesterolemia. New Zealand White male rabbits were fed either normal chow or a 1% cholesterol (CHO) diet for 14 wk. After the first 7 wk, the CHO-fed rabbits were further divided into three groups: those fed with CHO feed only (HC), those additionally given pitavastatin, and those additionally given an antioxidant, probucol. The extent of atherosclerosis was assessed by examining aortic stiffness. When compared with the HC group, both the pitavastatin and probucol groups showed improved aortic stiffness by reducing aortic levels of reactive oxidative stress, nitrotyrosine, and collagen, without affecting serum cholesterol or blood pressure levels. Pitavastatin restored both Cu/ZnSOD activity (P < 0.005) and PPAR-[gamma] expression and activity (P < 0.01) and inhibited NAD(P)H oxidase activity (P < 0.0001) in the aorta, whereas probucol inhibited NAD(P)H oxidase activity more than did pitavastatin (P < 0.0005) without affecting Cu/ZnSOD activity or PPAR-[gamma] expression and activity. Importantly, Cu/ZnSOD activity was positively correlated with the PPAR-[gamma] activity in the aorta (P < 0.005), both of which were negatively correlated with aortic stiffness (P < 0.05). Vascular Cu/ ZnSOD and PPAR-[gamma] may play a crucial role in the antiatherogenic effects of pitavastatin in hypercholesterolemia in vivo. vascular dysfunction; atherosclerosis; pleiotropic effects; antioxidant; peroxisome proliferator-activated receptor; reactive oxygen species

It is well known that the implantation of bone marrow mononuclear cells (BM-MNCs) into ischemic hearts can induce angiogenesis and improve cardiac function after myocardial infarction, but the precise mechanisms of these actions are unclear. We hypothesize that the cytokines produced by BM-MNCs play a key role in this cell-based therapy. BM-MNCs from rats were cultured under normoxic or hypoxic (1% [O.sub.2]) conditions for 24 h, and then supernatants were collected for study. ELISA and Western blotting analysis showed that various cytokines, including VEGF, IL-1[beta], PDGF, and IGF-1, were produced from BM-MNCs, some of which were enhanced significantly under hypoxia stimulation. When compared with a control blank medium, the supernatants of BM-MNCs cultured under normoxic or hypoxic conditions inhibited apoptosis significantly and preserved the contractile capacity of isolated adult rat cardiomyocytes in vitro (P < 0.05). Using a rat model of acute myocardial infarction, we injected the supernatants of BM-MNCs or control medium intramyocardially on day 0 and then intraperitoneally on days 2, 4, and 6 after infarction. When compared with the control medium, the supernatants of BM-MNCs cultured under both normoxic or hypoxic conditions increased the microvessel density and decreased the fibrotic area in the infarcted myocardium significantly, contributing to remarkable improvement in cardiac function. Various cytokines were produced by BM-MNCs, and these cytokines contributed to functional improvement of the infarcted heart by directly preserving the contractile capacity of the myocardium, inhibiting apoptosis of cardiomyocytes, and inducing therapeutic angiogenesis of the infarcted heart. ischemia; angiogenesis; bone marrow mononuclear cell; cytokine; apoptosis doi:10.1152/ajpheart.00142.2005

During early apoptosis, adult cardiomyocytes show unusual beating, suggesting possible participation of abnormal [Ca.sup.2+] transients in initiation of apoptotic processes in this cell type. Simultaneously with the beating, these cells show dynamic structural alteration resulting from cytoskeletal disintegration that is quite rapid. Because of the specialized structure and extensive cytoskeleton of cardiomyocytes, we hypothesized that its degradation in so short a time would require a particularly efficient mechanism. To better understand this mechanism, we used serial video microscopy to observe [beta]-adrenergic stimulation-induced apoptosis in isolated adult rat cardiomyocytes while simultaneously recording intracellular [Ca.sup.2+] concentration and cell length. Trains of [Ca.sup.2+] transients and corresponding rhythmic contractions and relaxations (beating) were observed in apoptotic cells. Frequencies of [Ca.sup.2+] transients and beating gradually increased with time and were accompanied by cellular shrinkage. As the cells shrank, amplitudes of [Ca.sup.2+] transients declined and diastolic intracellular [Ca.sup.2+] concentration increased until the transients were lost. Beating and progression of apoptosis were significantly inhibited by antagonists against the L-type [Ca.sup.2+] channel (nifedipine), ryanodine receptor (ryanodine), inositol 1,4,5-trisphosphate receptor (heparin), sarco(endo)plasmic [Ca.sup.2+]-ATPase (thapsigargin), and [Na.sup.+]/[Ca.sup.2+] exchanger (KB-R7943). Electron-microscopic examination of beating cardiomyocytes revealed progressive breakdown of Z disks. Immunohistochemical analysis and Western blot confirmed that disappearance of Z disk constituent proteins ([alpha]-actinin, desmin, and tropomyosin) preceded degradation of other cytoskeletal proteins. It thus appears that, in adult cardiomyocyte apoptosis, [Ca.sup.2+] transients mediate apoptotic beating and efficient sarcomere destruction initiated by Z disk breakdown. apoptosis; calcium regulation; cardiac myocytes; sarcomere: Z disk

Abdominal aortic aneurysm (AAA) is a common disease among elderly people that, when surgical treatment is inapplicable, results in progressive expansion and rupture of the aorta with high mortality. Although nonsurgical treatment for AAA is much awaited, few options are available because its molecular pathogenesis remains elusive. Here, we identify JNK as a proximal signaling molecule in the pathogenesis of AAA. Human AAA tissue showed a high level of phosphorylated JNK. We show that JNK programs a gene expression pattern in different cell types that cooperatively enhances the degradation of the extracellular matrix while suppressing biosynthetic enzymes of the extracellular matrix. Selective inhibition of JNK in vivo not only prevented the development of AAA but also caused regression of established AAA in two mouse models. Thus, JNK promotes abnormal extracellular matrix metabolism in the tissue of AAA and may represent a therapeutic target., Author(s): Koichi Yoshimura [1]; Hiroki Aoki (corresponding author) [1]; Yasuhiro Ikeda [1]; Kozo Fujii [1]; Norio Akiyama [2]; Akira Furutani [2]; Yoshinobu Hoshii [3]; Nobuyuki Tanaka [4]; Romeo Ricci [5]; [...]

Li, Tao-Sheng, Masanori Hayashi, Ze-Lin Liu, Hiroshi Ito, Akihito Mikamo, Akira Furutani, Masunori Matsuzaki, and Kimikazu Hamano. Low angiogenic potency induced by the implantation of ex vivo expanded [CD117.sup.+] stem cells. Am J Physiol Heart Circ Physiol 286: H1236-H1241, 2004. First published December 4, 2003; 10.1152/ajpheart.00950.2003.--Ex vivo expansion of stem cells might be a feasible method of resolving the problem of limited cell supply in cell-based therapy. The implantation of expanded [CD34.sup.+] endothelial progenitor cells has the capacity to induce angiogenesis. In this study, we tried to induce angiogenesis by implanting expanded [CD117.sup.+] stem cells derived from mouse bone marrow. After 2 wk of culture with the addition of several growth factors, the [CD117.sup.+] stem cells expanded ~20-fold and had an endothelial phenotype with high expression of CD34 and vascular endothelialcadherin. However, >70% of these ex vivo expanded cells had a senescent phenotype by [beta]-galactosidase staining, and their survival and incorporation were poor after implantation into the ischemic limbs of mice. Compared with the PBS injection only, the microvessel density and the percentage of limb blood flow were significantly higher after the implantation of 2 x [10.sup.5] freshly collected [CD117.sup.+] cells (P < 0.01) but not after the implantation of 2 x [10.sup.5] expanded [CD117.sup.+] cells (P > 0.05). These data indicate that ex vivo expansion of [CD117.sup.+] stem cells has low potency for inducing therapeutic angiogenesis, which might be related to the cellular senescence during ex vivo expansion. ischemic; blood flow; senescence; differentiation

Therapeutic angiogenesis can be induced by the implantation of bone marrow mononuclear cells. We investigated the roles of mature mononuclear cell and stem cell fractions in bone marrow in this treatment. Although CD34 is the most popular marker for stem cell selection for inducing therapeutic angiogenesis, we separated CD117-positive cells (C[D117.sup.+]) from mature bone marrow mononuclear cells [CD117-negative cells (C[D117.sup.-]) from mice using the antibody to the stem cell receptor, because some of the bone marrow stem cells that express C[D117.sup.+] and C[D34.sup.-] might generate angiogenic cytokines and differentiate into endothelial cells. The angiogenic potency of C[D117.sup.+] and C[D117.sup.-] cells was investigated in vitro and in vivo. Significantly higher levels of VEGF were secreted from the C[D117.sup.+] cells than from the C[D117.sup.-] cells (P < 0.001). Most of the C[D117.sup.-] cells died, but the C[D117.sup.-] cells grew well and differentiated into endothelial cells within 14 days of culture. The C[D117.sup.+] cells survived and were incorporated in microvessels within 14 days of being implanted into the ischemic hindlimbs of mice, but the C[D117.sup.-] cells did not. The microvessel density and blood perfusion of the ischemic hindlimbs were significantly higher in the C[D117.sup.+] cell-implanted mice than in the C[D117.sup.-] cell-implanted mice (P < 0.01). The microvessel density in ischemic hindlimbs was also significantly higher in the C[D117.sup.+] cell-implanted mice than in the total bone marrow cell-implanted mice (P < 0.05). Thus C[D117.sup.+] stem cells play a key role in the therapeutic angiogenesis induced by bone marrow cell implantation. endothelial differentiation; angiogenic growth factor; blood flow; ischemia

Defective interaction between FKBP12.6 and ryanodine receptors (RyR) is a possible cause of cardiac dysfunction in heart failure (HF). Here, we assess whether the new cardioprotective agent JTV519 can correct it in tachycardia-induced HF. HF was induced in dogs by 4-wk rapid ventricular pacing, and sarcoplasmic reticulum (SR) was isolated from left ventricular muscles. In failing SR, JTV519 increased the rate of [Ca.sup.2+] release and [[sup.3]H]ryanodine binding. RyR were then labeled in a site-directed fashion with the fluorescent conformational probe methylcoumarin acetamide. In failing SR, the polylysine induced a rapid change in methylcoumarin acetamide fluorescence, presumably because the channel opening preceding the [Ca.sup.2+] release was smaller than in normal SR (consistent with a decreased rate of [Ca.sup.2+] release in failing SR), and JTV519 increased it. In conclusion, JTV519, a new 1,4-benzothiazepine derivative, corrected the defective channel gating in RyR (increase in both the rapid conformational change and the subsequent [Ca.sup.2+] release rate) in HF. sarcoplasmic reticulum; ion channel; binding protein; excitation-contraction coupling

The angiogenic effect induced by autologous bone marrow cell implantation (BMCI) was examined in the ischemic hindlimbs of diabetic and nondiabetic rats. Diabetes mellitus was induced by the systemic administration of streptozotocin. We investigated the production of angiogenic factors and endothelial differentiation from bone marrow cells and the native recovery of blood flow in the ischemic hindlimbs. To observe the angiogenic effect induced by BMCI treatment, 6 x [10.sup.7] bone marrow cells were injected intramuscularly at six points into the ischemic limbs, and regional perfusion recovery was evaluated with colored microspheres 2 wk later. No difference was found between diabetic and nondiabetic rats in the release of angiogenic factors or endothelial differentiation from bone marrow cells in vitro. The levels of nitric oxide in plasma were significantly lower, and native perfusion recovery in the ischemic hindlimbs was significantly slower in the diabetic rats than in the nondiabetic rats. However, although perfusion recovery was achieved in the ischemic hindlimbs, there was no significant increase in systemic VEGF after BMCI treatment in either the diabetic or nondiabetic rats. Therefore, therapeutic angiogenesis induced by BMCI could be a safe and effective treatment for ischemic limb disease in diabetic patients. diabetes mellitus; angiogenic factor; endothelial differentiation; colored microsphere