Beneficial Effects of Nitric Oxide on Cardiac Diastolic Function: 'The Flip Side of the Coin'

Modulation by NO of systolic myocardial function received widespread attention but most studies focused on potential negative inotropic properties of NO. The very original observations on the effects of NO on myocardial contraction already provided evidence that NO modified myocardial contractile performance mainly through a relaxation-hastening effect (i.e. earlier onset of relaxation) and through an increase in myocardial distensibility. The present review discusses the relaxation hastening and distensibility-increasing effects of NO in experimental preparations, in the normal human heart, in left ventricular hypertrophy of aortic stenosis, in the human allograft and in dilated nonischemic cardiomyopathy. This diastolic flip side of the myocardial effects of NO appears to be beneficial especially for patients who are dependent on the LV Frank-Starling response to maintain cardiac output.     

一氧化氮合酶/一氧化氮系统与心血管疾病

一氧化氮在心血管疾病中发挥了重要作用；一氧化氮是在一氧化氮合酶催化下生成的。三种不同的一氧化氮合酶在心血管疾病中的作用各不相同，通过对一氧化氮合酶的干预将成为心血管疾病治疗的新策略。现就国内外在一氧化氮合酶／一氧化氮系统与心血管疾病方面的主要研究进展进行综述。     

Role of Nitric Oxide in the Regulation of Substrate Metabolism in Heart Failure

Solid experimental evidence indicates that nitric oxide (NO) inhibits oxygen utilization in vitro and in vivo. The role played by NO in cellular metabolism is likely extended to the control of substrate utilization. Studies performed in normal hearts show that NO inhibits glucose uptake and that a reduced synthesis of NO impairs free fatty acid consumption. Interestingly, we found also that myocardial free fatty acid utilization decreases while glucose consumption is enhanced in end stage heart failure, when cardiac NO production falls dramatically. This phenomenon led us to the hypothesis that the reduced synthesis of NO could be at least in part responsible for myocardial metabolic alterations occurring in severe heart failure. The present review mentions some of the seminal studies that defined the function of NO as metabolic modulator. A particular emphasis is put on available data suggesting a role for NO in the control of cardiac substrate utilization in normal and failing hearts.     

Myocardial contractile effects of nitric oxide

Recent experimental and clinical research solved some of the controversies surrounding the myocardial contractile effects of NO. These controversies were: (1) does NO exert a contractile effect at baseline? (2) is NO a positive or a negative inotrope? (3) Are the contractile effects of NO similar when NO is derived from NO-donors or from the different isoforms of NO synthases (NOS)? (4) Does NO exert the same effects in hypertrophied, failing or ischemic myocardium? Transgenic mice with cardioselective overexpression of NOS revealed NO to produce a small reduction in basal developed LV pressure and a LV relaxation-hastening effect mainly through myofilamentary desensitization. Similar findings had previously been reported during intracoronary infusions of NO-donors in isolated rodent hearts and in humans. The LV relaxation hastening effect was accompanied by increased diastolic LV distensibility, which augmented LV preload reserve especially in heart failure patients. This beneficial effect on diastolic LV function always overrode the small NO-induced attenuation in LV developed pressure in terms of overall LV performance. In most experimental and clinical conditions, contractile effects of NO were similar when NO was derived from NO-donors or produced by the different isoforms of NOS. Because expression of inducible NOS (NOS2) is frequently accompanied by elevated oxidative stress, NO produced by NOS2 can lead to peroxynitrite-induced contractile impairment as observed in ischemic or septic myocardium. Finally, shifts in isoforms or in concentrations of myofilaments can affect NO-mediated myofilamentary desensitization and alter the myocardial contractile effects of NO in hypertrophied or failing myocardium.     

Nitric Oxide and its Role in Blastocyst Implantation

Reviews in Endocrine and Metabolic Disorders -     

Interactions Between Cytokines and Neurohormonal Systems in the Failing Heart

The prognosis for patients with congestive heart failure (CHF) has been improved as a result of the use of angiotensin converting enzyme inhibitors and -adrenergic receptor blockers. The success of these therapies underscores the pathogenic role of neurohormonal activation in CHF. Clinical and experimental evidence supports a pathophysiologic role for pro-inflammatory cytokines and nitric oxide (NO) in the effects of angiotensin II and norepinephrine in CHF. Potential mechanism(s) responsible for the effects of these immunomodulators can be explained on the basis of established principles of myocardial excitation contraction coupling (E-C). A novel hypothesis is proposed that cytokines and NO-mediated alterations in E-C coupling contribute to the reversible myocardial depression and -adrenergic desensitization observed in a diverse group of clinical conditions that activate host inflammatory responses, including CHF. Basic studies into cytokine signaling pathways in cardiac myocytes have the potential to provide important new insights relevant to the design of new management strategies for the treatment of congestive heart failure patients.     

The Antagonism of Aldosterone Receptor Prevents the Development of Hypertensive Heart Failure Induced by Chronic Inhibition of Nitric Oxide Synthesis in Rats

Summary Aldosterone promotes cardiovascular inflammation and remodeling, both of which are characteristic changes in hypertensive and failing hearts. Since chronic inhibition of nitric oxide (NO) synthase with N^ω-nitro-L-arginine methyl ester (L-NAME) induces systemic hypertension associated with cardiovascular inflammation and remodeling, we examined the potential role of aldosterone in this process using eplerenone, a selective aldosterone receptor antagonist. Ten-week-old male Wistar-Kyoto rats were randomly divided into 3 groups: the control group (no treatment), the L-NAME group (received L-NAME 1 g/L in drinking water), and the L-NAME+Eplerenone group (L-NAME plus eplerenone at 100 mg/kg/day). After 8 weeks of the treatment, the L-NAME group showed significantly higher systolic blood pressure than the control group (198 ± 7 vs. 141 ± 3 mmHg, P < 0.05). Eplerenone did not affect the increase in blood pressure caused by L-NAME (189 ± 12 mmHg). Chronic inhibition of NO synthesis increased the plasma aldosterone concentration and CYP11B2 mRNA in adrenal glands. Cardiac inflammation and fibrosis were detected in the L-NAME group, while both changes were completely prevented by eplerenone. Cardiac hypertrophy was induced in L-NAME group, but was partially prevented by eplerenone. In the L-NAME group, left ventricular fractional shortening (LVFS: 27 ± 2 vs. 38 ± 1%) and E/A ratio (1.7 ± 0.1 vs. 2.1 ± 0.1) were significantly lower and LV end-diastolic pressure (LVEDP) was higher (4.9 ± 0.6 vs. 13.9 ± 0.5 mmHg) without LV enlargement, compared with those in the control group (P < 0.05). Eplerenone completely normalized LVFS (36 ± 2%), E/A ratio (2.2 ± 0.1), and LVEDP (6.2 ± 0.7 mmHg). These results suggest that chronic inhibition of NO synthesis induces cardiac inflammation and dysfunction via an aldosterone receptor-dependent mechanism.     

吸入NO在心肺疾病中的应用

现综述NO的生物学效应、毒副作用以及在心肺疾病中的应用。     

Nitric oxide: not just a negative inotrope

Nitric oxide (NO) appears to play a role in modulating cardiac function in both health and disease. Early studies in isolated rodent cardiac myocytes demonstrated a depressant effect of NO supplied by NO donors (exogenous) as well as NO generated within myocytes (endogenous). There is increasing evidence for a functional NO generating system within the human myocardium, which appears upregulated in certain disease states. Induction of the high output nitric oxide synthase isoform (iNOS) has been demonstrated in the failing myocardium, though its functional significance remains unproven. More recently published data have contradicted the notion that NO acts solely as a negative inotrope demonstrating positive inotropy in both isolated rodent and human ventricular myocytes in response to a range of NO donors. Different NO donors have different NO release kinetics and generate a range of NO species (NO., NO+ and NO-) which may interact at a number of subcellular targets. The observed response of any cardiac preparation to an NO donor represents the net effect of activation of different effector targets and may explain the contradictory reported effects of NO. To realise the therapeutic potential of NO will require specific targeting at a subcellular level.     

一氧化氮与先天性心脏病合并肺动脉高压

一氧化氮是一种脂溶性气体,它具有独特的理化性质和生物学活性,主要由血管内皮产生,在先天性心脏病合并肺动脉高压的发生、发展过程中起到了重要作用。吸入一氧化氮气体,可选择性扩张肺血管,降低肺动脉阻力和肺动脉压。现主要综述一氧化氮与先天性心脏病合并肺动脉高压的相互作用关系及一氧化氮在治疗上的研究进展。     

诱导型一氧化氮合酶在心肌缺血/再灌注损伤中的研究进展

采用溶栓疗法、动脉搭桥术、冠状动脉血管成形术等技术,使缺血组织和器官重新恢复血流,挽救了众多危急重病人的生命,然而,缺血器官及组织在恢复血流的同时,均伴随着缺血/再灌注损伤,是目前临床上亟待解决的问题。在对心血管疾病的研究过程中,随着心肌保护研究的不断深入,如何减轻心肌缺血/再灌注损伤成为心肌保护问题的关键。越来越多的研究表明,心肌缺血/再灌注损伤与诱导型一氧化氮合酶表达过量一氧化氮紧密相关。研究表明,诱导型一氧化氮合酶既有心肌保护作用,也有促心肌损伤作用,而通过对诱导型一氧化氮合酶抑制剂的应用,有望减轻心肌损伤的进展,保护损伤心肌。     

高血压患者血浆一氧化氮浓度的变化

探讨一氧化氮（ＮＯ）与高血压的发病关系及其临床意义。方法用重氮法检测５０例高血压患者治疗前后和３６例正常对照组血浆ＮＯ浓度的变化。结果（１）高血压患者ＮＯ浓度（１４．９１±２．１８μｍｏｌ／Ｌ）较正常对照组明显地降低（Ｐ＜０．０１）；降压治疗后高血压患者血浆ＮＯ浓度有明显地增高（Ｐ＜０．０１），但仍明显低于正常对照组（Ｐ＜０．０１）。（２）高血压患者血浆ＮＯ浓度Ⅰ期最高，Ⅱ期居中，Ⅲ期最低，各期之间比较差异有显著性（Ｆ＝６７．５８，Ｐ＜０．０１）。（３）重度患者血浆ＮＯ浓度明显地低于轻度、中度患者（Ｐ＜０．０１）；中度明显低于轻度（Ｐ＜０．０１）。（４）并发心力衰竭组血浆ＮＯ浓度明显低于无心力衰竭组（Ｐ＜０．０１）。结论ＮＯ参与高血压的发生和发展，并与病情有关。检测血浆ＮＯ浓度可作为判断高血压患者病情的指标     

The Role of Anti-Cytokine Therapy in the Failing Heart

The understanding of the role of neurohormones in the progression of heart failure has led to the utilization of agents that antagonize the activation of neurohormonal systems as effective therapy in patients with heart failure. As more evidence emerges linking proinflammatory cytokines to disease progression in heart failure, there is an increasing interest in developing anti-cytokine strategies that might be used as adjunctive therapy in patients with heart failure. Accordingly, the focus of the present review is to summarize the experimental and clinical studies that have attempted to modulate the effects of cytokines in heart failure. Strategies have been employed to either suppress cytokine production or to prevent their toxic effects by interfering with the binding of cytokines to their cognate receptors.     

Nitric Oxide Inhibitors Ameliorate Indomethacin-Induced Enteropathy in Rats

The role of nitric oxide (NO) synthase inhibitors in indomethacin (INDO) -induced enteropathy was investigated in male Sprague-Dawley rats. Rats were subcutaneously administered 5% sodium bicarbonate (controls), two doses of INDO 7.5 mg/kg, and three different inducible NO synthase (iNOS) inhibitors at various concentrations 24 hr, apart; aminoguanidine (AG), guanidinoethyldisulfide (GED), and n-(3-aminomethyl)benzylacetamidine (1400W). Rats were killed four days after the initial injection and small intestinal mucosa was assayed for myeloperoxidase (MPO) activity and iNOS expression by western blot analysis. Serum nitrite/nitrate (NO_x) concentration was measured colorimetrically. INDO produced acute ulcers along the mesenteric border from the ileum to proximal jejunum. Rats treated with AG (25 and 50 mg/kg), GED (2.5 mg/kg), and 1400W (0.1 mg/kg) showed decreased total ulcer length and MPO activity by 51, 72, 53, and 61% and by 58, 88, 68, and 70%, respectively, compared to INDO alone. All inhibitors similarly reduced INDO-enhanced serum NO_x concentrations to its basal levels. Significant iNOS expression was detected in INDO-treated rats, but the inhibitors did not alter iNOS expression. Our data suggest that NO derived from iNOS may be a key factor in the pathogenesis of acute INDO-induced enteropathy in rats.     

芪红合剂含药血清对体外培养人外周血内皮祖细胞NO及NOS的影响

目的观察芪红合剂含药血清对人外周血内皮祖细胞(EPCs)一氧化氮(NO)、一氧化氮合酶(NOS)的影响,探讨其对人外周血内皮祖细胞的保护机制。方法12只雄性Wistar大鼠随机分为芪红合剂组(低剂量组、中剂量组、高剂量组)和对照组,制备含药血清和空白血清。采集健康成人外周血,分离单核细胞,体外培养7d后,收集贴壁细胞,激光共聚焦显微镜及流式细胞仪鉴定正在分化的EPCs,加入含不同浓度芪红合剂药物血清及空白血清的M199培养基孵育24h,将其在倒置荧光显微镜下计数,硝酸还原酶法测定NO,化学比色法测定NOS。结果芪红合剂药物组的血清NO水平和NOS活性明显高于空白血清对照组(P0.05),并且呈剂量依赖性。结论芪红合剂可能通过增加EPCsNOS活性,促进NO分泌,防止血管内皮损伤及动员血管内皮祖细胞修复损伤血管来发挥血管内皮保护作用。     

血红素加氧酶和一氧化氮合酶在缺血性脑损伤时的保护作用

内源性一氧化氮(NO)和一氧化碳(CO)是先后发现的2种气体信号分子,NO合酶(NOS)和血红素加氧酶(HO)分别是生成NO和CO的氧合酶。研究表明,NOS/NO系统和HO/CO系统均与缺血性脑损伤的发生发展密切相关,而且两者之间还存在着错综复杂的相互作用,对其作用机制的深入了解有助于探索缺血性脑损伤的临床治疗途径。