Sympathetic control of cerebral arteries: specialization in receptor type, reserve, affinity, and distribution

The sympathetic neuroeffector system in the mammalian cerebral circulation has a number of distinctive features that reflect its specialized role in this vascular bed: 1) there is limited alpha-adrenoceptor-mediated contraction in large vessels that becomes progressively less important with branching; 2) contraction is limited by receptor number; small branches often seem to have no functional alpha adrenoceptors; 3) adrenoceptor affinity for norepinephrine is low and so is sensitivity; and 4) the dominant alpha-adrenoceptor subtype differs in different species and may have unique characteristics in some. There is a mechanism of non-alpha-adrenoceptor-mediated contraction involving low-affinity receptor sites--extraceptors--activated by sympathetic nerves. The pig has a seemingly atypical sympathetic mechanism. On the basis of current information the sympathetic neuroeffector mechanisms of the rabbit seem most clearly related to the human. The size, pattern, and distribution of sympathetic control suggest that the role of the sympathetic nerves is to protect the smaller pial arteries against the consequences of sudden increases in sympathetic adrenal discharge. It is not an important mechanism of controlling cerebral blood flow.     

Elevated expression of activated Na+/H+ exchanger protein induces hypertrophy in isolated rat neonatal ventricular cardiomyocytes

The plasma membrane protein the Na(+)/H(+) exchanger isoform1 (NHE1) has been implicated in various cardiac pathologies including ischemia/reperfusion damage to the myocardium and cardiac hypertrophy. Levels of NHE1 protein and activity are elevated in cardiac disease; however, the mechanism by which these factors contribute to the accompanying hypertrophy in the myocardium is still not clear. To investigate the mechanism of NHE1-induced hypertrophy in the myocardium we constructed two adenoviral vectors expressing either wild type NHE1 protein or a constitutively active NHE1 protein. Infection of neonatal rat ventricular cardiomyocytes (NRVM) resulted in elevated expression of both wild type NHE1 or constitutively active NHE1. Only expression of activated NHE1 protein resulted in an increase in cell size and in an increase in protein synthesis in isolated cardiomyocyte cells. The results demonstrate that expression of activated NHE1 promotes cardiac hypertrophy in isolated cardiac cells and that simple elevation of levels of wild type NHE1 protein does not have a significant hypertrophic effect in NRVM. The results suggest that regulation of NHE1 activity is a critical direct effector of the hypertrophic effect induced in the myocardium by the NHE1 protein.     

Tbx20 regulation of cardiac cell proliferation and lineage specialization during embryonic and fetal development in vivo

TBX20 gain-of-function mutations in humans are associated with congenital heart malformations and myocardial defects. However the effects of increased Tbx20 function during cardiac chamber development and maturation have not been reported previously. CAG-CAT-Tbx20 transgenic mice were generated for Cre-dependent induction of Tbx20 in myocardial lineages in the developing heart. βMHCCre-mediated overexpression of Tbx20 in fetal ventricular cardiomyocytes results in increased thickness of compact myocardium, induction of cardiomyocyte proliferation, and increased expression of Bmp10 and pSmad1/5/8 at embryonic day (E) 14.5. βMHCCre-mediated Tbx20 overexpression also leads to increased expression of cardiac conduction system (CCS) genes Tbx5, Cx40, and Cx43 throughout the ventricular myocardium. In contrast, Nkx2.5Cre mediated overexpression of Tbx20 in the embryonic heart results in reduced cardiomyocyte proliferation, increased expression of a cell cycle inhibitor, p21(CIP1), and decreased expression of Tbx2, Tbx5, and N-myc1 at E9.5, concomitant with decreased phospho-ERK1/2 expression. Together, these analyses demonstrate that Tbx20 differentially regulates cell proliferation and cardiac lineage specification in embryonic versus fetal cardiomyocytes. Induction of pSmad1/5/8 at E14.5 and inhibition of dpERK expression at E9.5 are consistent with selective Tbx20 regulation of these pathways in association with stage-specific effects on cardiomyocyte proliferation. Together, these in vivo data support distinct functions for Tbx20 in regulation of cardiomyocyte lineage maturation and cell proliferation at embryonic and fetal stages of heart development.     

Cardiac sympathetic activation in patients with pulmonary arterial hypertension

Patients with congestive heart failure (CHF) due to left ventricular (LV) dysfunction have sympathetic activation specifically directed to the myocardium. Although pulmonary arterial hypertension (PAH) is associated with increased systemic sympathetic activity, its impact on sympathetic drive to ventricular myocardium is unknown. Fifteen patients with PAH (9 women; 54 ± 12 years) were studied: 10 with idiopathic PAH and 5 with a connective tissue disorder. We measured hemodynamics, as well as radiolabeled and endogenous concentrations of arterial and coronary sinus norepinephrine (NE). These measures were repeated after inhaled nitric oxide (NO). Measurement of transcardiac NE concentrations and the cardiac extraction of radiolabeled NE allowed calculation of the corrected transcardiac gradient of NE (CTCG of NE). Comparative data were collected from 15 patients (9 women: 55 ± 12 yr) with normal LV function and 15 patients with CHF (10 women; 53 ± 12 yr). PAH patients had elevated arterial NE concentrations compared with those with normal LV function but were similar to those with CHF. The CTCG of NE was higher in those with PAH than in the normal LV group (3.6 ± 2.2 vs. 1.5 ± 0.9 pmol/ml; P < 0.01) but similar to that seen in those with CHF (3.3 ± 1.4; P = NS). Inhaled NO, which reduced pulmonary artery pressure and increased cardiac output, had no effect on cardiac sympathetic activity. Therefore, cardiac sympathetic activation occurs in PAH. The mechanism of this activation remains uncertain but does not involve elevations in left heart filling pressure.     

CIRBP-OGFR axis safeguards against cardiomyocyte apoptosis and cardiotoxicity induced by chemotherapy

Cold-inducible RNA-binding protein (CIRBP) is documented to be required for maintaining cardiac function, however, its role in chemotherapy-induced cardiotoxicity remains obscured. Herein, we report that CIRBP decreases cardiomyocyte apoptosis and attenuates cardiotoxicity through disrupting OGF-OGFR signal. CIRBP deficiency is involved in diverse chemotherapeutic agents induced cardiomyocyte apoptosis. Delivery of exogenous CIRBP to the mouse myocardium significantly mitigated doxorubicin-induced cardiac apoptosis and dysfunction. Specifically, OGFR was identified as a downstream core effector responsible for chemotherapy-induced cardiomyocyte apoptosis. CIRBP was shown to interact with OGFR mRNA and to repress OGFR expression by reducing mRNA stability. CIRBP-mediated cytoprotection against doxorubicin-induced cardiac apoptosis was demonstrated to largely involve OGFR repression by CIRBP. NTX as a potent antagonist of OGFR successfully rescued CIRBP ablation-rendered susceptibility to cardiac dyshomeostasis upon exposure to doxorubicin, whereas another antagonist ALV acting only on opioid receptors did not. Taken together, our results demonstrate that CIRBP confers myocardium resistance to chemotherapy-induced cardiac apoptosis and dysfunction by dampening OGF/OGFR axis, shedding new light on the mechanisms of chemo-induced cardiotoxicity and providing insights into the development of an efficacious cardioprotective strategy for cancer patients.     

Quick adaptation of the myocardium and autonomic nervous regulation of the cardiac rhythm in 10- to 11-year-old children operating a computer

A study of quick adaptation of the myocardium of subjects operating a computer, depending on the adaptive capacities of the body, was conducted in 100 children with ages varying between 10 and 11 years using the electrocardiography method for the analysis of heart rate variability. Significant differences in the bioelectrical processes in the myocardium and autonomic nervous regulation of the cardiac rhythm (CR) were found in children with different adaptive capacities of the body. Quick adaptation to the operator activity in children with a good adaptive capacity is characterized by intensification of atrial activity and metabolic processes in the myocardium, as well as by a shortened duration of the cardiac cycle due to a shorter diastolic time, determined by increased sympathetic influences on the CR. In children with a decreased adaptive capacity, a decrease in the atrial excitability and myocardial metabolism, an increase in the systolic time, a decrease in the diastolic time, and an increase in parasympathetic influences on the CR are observed.     

T-type calcium channel expression and function in the diseased heart

The regulation of intracellular Ca (2+) is essential for cardiomyocyte function, and alterations in proteins that regulate Ca (2+) influx have dire consequences in the diseased heart. Low voltage-activated, T-type Ca (2+) channels are one pathway of Ca (2+) entry that is regulated according to developmental stage and in pathological conditions in the adult heart. Cardiac T-type channels consist of two main types, Cav3.1 (α1G) and Cav3.2 (α1H), and both can be induced in the myocardium in disease and injury but still, relatively little is known about mechanisms for their regulation and their respective functions. This article integrates previous data establishing regulation of T-type Ca (2+) channels in animal models of cardiac disease, with recent data that begin to address the functional consequences of cardiac Cav3.1 and Cav3.2 Ca (2+) channel expression in the pathological setting. The putative association of T-type Ca (2+) channels with Ca (2+) dependent signaling pathways in the context of cardiac hypertrophy is also discussed.     

Norepinephrine transporter（NET）is expressed in cardiac sympathetic ganglia of adult rat

INTRODUCTIONThe sympathetic nervous system (SNS) plays animportant role in regulating cardiac function in bothhealth and disease through releasing neurotransmit-ter norepinephrine (NE). 1n central nervous sys-tem (CNS), the neurotransmission of NE is terminated tbIough reuptaxe of released neurotransndt-ter by Na , Cl---dependent norepineplirine trans-porter (NET) on pre--synaPtic membrane[1, 2]. ALthough the NE uptake was well studied in heaxt, butthe molecular basis fOr that is s…     

Brain-Derived Neurotrophic Factor Regulates TRPC3/6 Channels and Protects Against Myocardial Infarction in Rodents

Background: Brain-derived neurotrophic factor (BDNF) is associated with coronary artery diseases. However, its role and mechanism in myocardial infarction (MI) is not fully understood.Methods: Wistar rat and Kunming mouse model of MI were induced by the ligation of left coronary artery. Blood samples were collected from MI rats and patients. Plasma BDNF level, protein expression of BDNF, tropomyosin-related kinase B (TrkB) and its downstream transient receptor potential canonical (TRPC)3/6 channels were examined by enzyme-linked immunosorbent assay and Western blot. Infarct size, cardiac function and cardiomyocyte apoptosis were measured after intra-myocardium injection with recombinant human BDNF. Protective role of BDNF against cardiomyocyte apoptosis was confirmed by BDNF scavenger TrkB-Fc. The regulation of TRPC3/6 channels by BDNF was validated by pretreating with TRPC blocker (2-Aminoethyl diphenylborinate, 2-APB) and TRPC3/6 siRNAs.Results: Circulating BDNF was significantly enhanced in MI rats and patients. Protein expression of BDNF, TrkB and TRPC3/6 channels were upregulated in MI. 3 days post-MI, BDNF treatment markedly reduced the infarct size and serum lactate dehydrogenase activity. Meanwhile, echocardiography indicated that BDNF significantly improved cardiac function of MI mice. Furthermore, BDNF markedly inhibited cardiomyocyte apoptosis by upregulating Bcl-2 expression and downregulating caspase-3 expression and activity in ischemic myocardium. In neonatal rat ventricular myocytes, cell viability was dramatically increased by BDNF in hypoxia, which was restored by TrkB-Fc. Furthermore, protective role of BDNF against hypoxia-induced apoptosis was reversed by 2-APB and TRPC3/6 siRNAs.Conclusion: BDNF/TrkB alleviated cardiac ischemic injury and inhibited cardiomyocytes apoptosis by regulating TRPC3/6 channels, which provides a novel potential therapeutic candidate for MI.     

Hsp70 may protect cardiomyocytes from stress-induced injury by inhibiting Fas-mediated apoptosis

Expression of Hsp70 is an endogenous mechanism by which living cells adapt to stress and the protection of Hsp70 may interfere with the apoptotic machinery in a variety of ways. Here, we observed the change of Hsp70 expression in rat myocardium under stress and explored the protective effect of Hsp70 on the Fas-mediated pathway to cardiomyocyte apoptosis. The results showed that restraint stress led to cardiac dysfunction and structural damage of the myocardium, as well as activation of the Fas pathway. A similar increase in the Fas expression level, caspase-8/3 activity, and the apoptotic rate of the cardiomyocyte also were found, which indicated that Fas-mediated apoptosis of cardiomyocytes might be one of the mechanisms of cardiomyocyte injury induced by stress. Changes in Hsp70 levels and distribution occurred during the stress process, which correlated with the severity of myocardium injury. Heat preconditioning induced the upregulation of Hsp70 synthesis, which in turn may have mitigated subsequent restraint stress-induced damage, including electrocardiography (ECG) abnormality, myocardium damage, and cell death. Moreover, Hsp70 overexpression induced by heat preconditioning had no effect on Fas expression in the cardiomyocyte, but could inhibit activation of caspase-8/3 induced by the Fas signaling pathway and, as a result, prevent cell apoptosis. These results suggest that Hsp70 is capable of protecting the cardiomyocyte from stress-induced injury by inhibiting Fas-mediated apoptosis, and Hsp70 could be considered a target in future drugs to prevent cardiovascular injury caused by stress.     

迷走神经功能调节与心肌缺血保护

心血管系统的生理活动受自主神经系统(autonomic nervous system,ANS)调节.已有研究表明,自主神经功能紊乱,尤其是迷走神经功能低下,与心血管疾病(cardiovascular disease,CVD)的发生、发展及预后密切相关.本文结合国内外研究现状,就本研究室在迷走神经对心脏不同部位的调控及其对心肌的保护作用机制方面的研究成果进行阐述.通过收缩功能检测及标准玻璃微电极细胞内记录技术,发现迷走神经递质--乙酰胆碱对哺乳动物心室肌有直接作用,可抑制细胞收缩力及动作电位时程;通过组织化学染色及分子生物学方法进一步证明心室有毒蕈碱受体分布;通过膜片钳技术显示在部分动物心室肌上存在乙酰胆碱激活的内向整流钾通道(acetylcholine-activated potassium channel,KACh),并且其电流(IK·ACh)和心房肌一样具有衰减现象.前期研究证明心房肌IK·ACh的衰减与毒蕈碱受体、G蛋白或钾通道磷酸化有关;而心室肌的IK·ACh还有待于进一步研究.我们建立了相关动物模型,结合心率变异性分析等自主神经评价方法,探讨ANS在健康和疾病状态下的变化情况,证明了迷走神经对心脏调节的增龄性改变及代偿效应.通过提高迷走张力(乙酰胆碱缺血预/后适应、有氧运动、β受体阻断剂),研究改善自主神经平衡对缺血心肌的保护作用以及胆碱能抗炎通路防御缺血,再灌注诱导的炎症损伤机制.综合评价心脏自主神经调节,改善交感和迷走张力平衡,将为CVD防治的基础研究提供重要的理论依据.     

Granulocyte colony-stimulating factor treatment enhances the efficacy of cellular cardiomyoplasty with transplantation of embryonic stem cell-derived cardiomyocytes in infarcted myocardium

We tested the hypothesis that granulocyte colony-stimulating factor (G-CSF) administration would enhance the efficacy of cellular cardiomyoplasty with embryonic stem (ES) cell-derived cardiomyocytes in infarcted myocardium. Three weeks after myocardial infarction by cryoinjury, Sprague-Dawley rats were randomized to receive either an injection of medium, ES cell-derived cardiomyocyte transplantation, G-CSF administration, or a combination of G-CSF administration and ES cell-derived cardiomyocyte transplantation. Eight weeks after treatment, the cardiac tissue formation, neovascularization, and apoptotic activity in the infarct regions were evaluated by histology and immunohistochemistry. The left ventricular (LV) dimensions and function of the treated heart were evaluated by echocardiography. Transplanted ES cell-derived cardiomyocytes survived and participated in the myocardial regeneration in the infarcted heart. A combination of G-CSF treatment and ES cell-derived cardiomyocyte transplantation significantly promoted angiogenesis and reduced the infarct area and cell apoptosis in the infarcted myocardium compared with ES cell-derived cardiomyocyte transplantation alone. The combination therapy also attenuated LV dilation, as compared with ES cell-derived cardiomyocyte transplantation alone. G-CSF treatment can enhance the efficacy of cellular cardiomyoplasty by ES cell-derived cardiomyocyte transplantation to treat myocardial infarction.     

Aligned human cardiac syncytium for in vitro analysis of electrical,structural, and mechanical readouts

Human pluripotent stem cell‐derived cardiomyocytes (hPSC‐CMs) have emerged as an exciting new tool for cardiac research and can serve as a preclinical platform for drug development and disease modeling studies. However, these aspirations are limited by current culture methods in which hPSC‐CMs resemble fetal human cardiomyocytes in terms of structure and function. Herein we provide a novel in vitro platform that includes patterned extracellular matrix with physiological substrate stiffness and is amenable to both mechanical and electrical analysis. Micropatterned lanes promote the cellular and myofibril alignment of hPSC‐CMs while the addition of micropatterned bridges enable formation of a functional cardiac syncytium that beats synchronously over a large two‐dimensional area. We investigated the electrophysiological properties of the patterned cardiac constructs and showed they have anisotropic electrical impulse propagation, as occurs in the native myocardium, with speeds 2x faster in the primary direction of the pattern as compared to the transverse direction. Lastly, we interrogated the mechanical function of the pattern constructs and demonstrated the utility of this platform in recording the strength of cardiomyocyte contractions. This biomimetic platform with electrical and mechanical readout capabilities will enable the study of cardiac disease and the influence of pharmaceuticals and toxins on cardiomyocyte function. The platform also holds potential for high throughput evaluation of drug safety and efficacy, thus furthering our understanding of cardiovascular disease and increasing the translational use of hPSC‐CMs.     

血红素氧合酶-1/一氧化碳通路参与辛伐他汀抗高血压诱发的大鼠心肌肥厚

为了探讨他汀类药物抑制心肌肥厚的作用机制,本研究应用一氧化氮合酶抑制剂左旋硝基精氨酸[N-nitro-L-arginine, L-NNA,15 mg／(kg·d)]制备大鼠高血压心肌肥厚模型,并分别给予不同剂量辛伐他汀[5或30 mg／(kg·d)进行干预。6周后测大鼠左心室功能、左心室重量指数(left ventricular mass index,LVMI)、心肌脑钠素(brain natriuretic peptide,BNP)含量、心肌羟脯氨酸含量和心肌血红素氧合酶(heme oxygenase,HO)活性。在体外培养的新生大鼠心肌细胞中,观察辛伐他汀对血管紧张素Ⅱ(angiotensin Ⅱ,Ang Ⅱ)引起的心肌细胞肥大的抑制作用与细胞血红素氧合酶-1(HO-1)表达、HO活性及CO生成间的关系。结果表明,辛伐他汀干预明显减轻L-NNA处理大鼠的心肌肥厚(LVMI值、心肌BNP和羟脯氨酸含量均显著低于单纯L-NNA处理组),改善左心室舒张功能,而且心肌HO活性显著升高。在离体培养的原代乳鼠心肌细胞,辛伐他汀浓度依赖性地抑制Ang Ⅱ引起的细胞肥大(3H-亮氨酸掺入),并相应增加HO-1 mRNA表达、HO活性和CO生成量。应用HO抑制剂锌卟啉能有效抑制辛伐他汀抗Ang Ⅱ诱导的心肌肥大作用。结果提示:辛伐他汀上调HO-1／CO通路是其抗高血压诱发的心肌肥厚的机制之一。     

Adult stem cell therapy for the heart

The purpose of this review is to summarize current data leading to and arising from recent clinical application of cellular therapy for acute myocardial infarct (heart attack) and congestive heart failure. We specifically focus on use of adult stem cells and compare and contrast bone marrow and adipose tissue; two different sources from which stem cells can be harvested in substantial numbers with limited morbidity. Cellular therapy is the latest in a series of strategies applied in an effort to prevent or mitigate the progressive and otherwise irreversible loss of cardiac function that frequently follows a heart attack. Unlike surgical, pharmacologic, and gene transfer approaches, cellular therapy has the potential to restore cardiac function by providing cells capable of regenerating damaged myocardium and/or myocardial function. Skeletal muscle myoblast expansion and transfer allows delivery of cells with contractile function, albeit without any evidence of cardiomyogenesis or electrical coupling to remaining healthy myocardium. Delivery of endothelial progenitor cells (EPCs) which drive reperfusion of infarct zone tissues is also promising, although this mechanism is directed at halting ongoing degeneration rather than initiating a regenerative process. By contrast, demonstration of the ability of adult stem cells to undergo cardiomyocyte differentiation both in vitro and in vivo suggests a potential for regenerative medicine. This potential is being examined in early clinical studies.