Pathophysiology of Hypertension in the Absence of Nitric Oxide/Cyclic GMP Signaling

The nitric oxide (NO)-cyclic guanosine monophosphate (cGMP) signaling system is a well-characterized modulator of cardiovascular function, in general, and blood pressure, in particular. The availability of mice mutant for key enzymes in the NO-cGMP signaling system facilitated the identification of interactions with other blood pressure modifying pathways (e.g. the renin-angiotensin-aldosterone system) and of gender-specific effects of impaired NO-cGMP signaling. In addition, recent genome-wide association studies identified blood pressure-modifying genetic variants in genes that modulate NO and cGMP levels. Together, these findings have advanced our understanding of how NO-cGMP signaling regulates blood pressure. In this review, we will summarize the results obtained in mice with disrupted NO-cGMP signaling and highlight the relevance of this pathway as a potential therapeutic target for the treatment of hypertension.     

Nitric oxide signaling in the cardiovascular system: implications for heart failure

PURPOSE OF REVIEW: The role played by nitric oxide (NO) in cardiovascular physiology remains highly controversial. Following the discovery that NO is the prototypic endothelium-derived relaxing factor, this signaling molecule was implicated as possessing many other biological actions within the cardiovascular system, including effects on cardiac contraction, relaxation, and energetics. Here, we discuss new concepts regarding NO signaling, its effector pathways, and interactions between NO and the redox milieu within a framework of cardiac physiology and pathophysiology. RECENT FINDINGS: Major recent insights that have advanced understanding of the mechanisms of NO bioactivity include the following. (1) NO acts in subcellular signaling compartments or modules. (2) S-nitrosylation (covalent modification of cysteine thiol moieties) of proteins represents a prototypic second messenger signaling mode in biologic systems. (3) Reactive oxygen and nitrogen species work together to facilitate signaling. (4) Disruption of physiologic signaling can occur by either increased formation of reactive oxygen species or decreased production of reactive nitrogen species, a situation of nitroso-redox imbalance. SUMMARY: These insights, which challenge classically held views that NO acts as a freely diffusible molecule regulated primarily by concentration and exerting signaling primarily through cyclic GMP production, offer a new perspective on the pathophysiology and treatment of congestive heart failure.     

Beta 3-adrenoreceptor regulation of nitric oxide in the cardiovascular system

The presence of a third β-adrenergic receptor (β3-AR) in the cardiovascular system has challenged the classical paradigm of sympathetic regulation by β1- and β2-adrenergic receptors. While β3-AR's role in the cardiovascular system remains controversial, increasing evidence suggests that it serves as a “brake” in sympathetic overstimulation — it is activated at high catecholamine concentrations, producing a negative inotropic effect that antagonizes β1- and β2-AR activity. The anti-adrenergic effects induced by β3-AR were initially linked to nitric oxide (NO) release via endothelial NO synthase (eNOS), although more recently it has been shown under some conditions to increase NO production in the cardiovascular system via the other two NOS isoforms, namely inducible NOS (iNOS) and neuronal NOS (nNOS). We summarize recent findings regarding β3-AR effects on the cardiovascular system and explore its prospective as a therapeutic target, particularly focusing on its emerging role as an important mediator of NO signaling in the pathogenesis of cardiovascular disorders.     

Nitric oxide down-regulates brain-derived neurotrophic factor secretion in cultured hippocampal neurons

The regulation of neurotrophin (NT) secretion is critical for many aspects of NT-mediated neuronal plasticity. Neurons release NTs by activity-regulated secretion pathways, initiated either by neurotransmitters and/or by existing NTs by a positive-feedback mechanism. This process depends on calcium release from intracellular stores. Little is known, however, about potential pathways that down-regulate NT secretion. Here we demonstrate that nitric oxide (NO) induces a rapid down-regulation of brain-derived neurotrophic factor (BDNF) secretion in cultured hippocampal neurons. Similar effects occur by activating a downstream target of intracellular NO, the soluble guanylyl cyclase, or by increasing the levels of its product, cGMP. Furthermore, down-regulation of BDNF secretion is mediated by cGMP-activated protein kinase G, which prevents calcium release from inositol 1,4,5-trisphosphate-sensitive stores. Our data indicate that the NO/cGMP/protein kinase G pathway represents a signaling mechanism by which neurons can rapidly down-regulate BDNF secretion and suggest that, in hippocampal neurons, NT secretion is finely tuned by both stimulatory and inhibitory signals.     

Mechanical activation of signaling pathways in the cardiovascular system

Mechanical forces are constantly exerting stress upon the tissues and cells of the cardiovascular system. To influence the biology of cells, these stimuli, which exist in the physical domain, must be converted into signals in the biochemical language of the cells. This process has been referred to as mechano-chemical signal transduction, or mechanotransduction. Although a great deal is known about which aspects of cardiovascular biology are influenced or dictated by physical forces, a great deal of uncertainty exists about which of the many signaling pathways that respond in cardiovascular cells to mechanical stimuli specifically regulate mechanosensitive aspects of the "cardiovascular phenotype". Even less is known regarding the identity and function of structures and catalysts that operate at the physical-biochemical interface and act to convert physical energy into signals of biological relevance. This article presents what is known regarding signaling pathways in cells of the cardiovascular system, which have been shown empirically to respond to mechanical stimuli, and what can be inferred from biochemical and pharmacological studies in cultured cardiovascular cells regarding the potential for certain signaling pathways to be involved in the manifestation of mechanically responsive phenotypes in the cardiovascular system.     

再灌注损伤挽救激酶和生存活化因子增强信号通路在心肌缺血再灌注损伤中的研究进展

经皮冠状动脉介入治疗、溶栓治疗可以使心肌梗死患者明显获益并且改善预后,但是由此引起的心肌缺血再灌注损伤问题也凸显出来,心肌缺血再灌注损伤涉及到多个靶点通路,不同信号通路之间的关系错综复杂。近几年医学家提出的再灌注损伤挽救激酶和生存活化因子增强两个促存活激酶信号通路成为了再灌注干预治疗的新靶点,从而成为心血管疾病甚至其他血管性疾病的新的切入点。本文拟阐述这两条信号通路对缺血再灌注后心肌保护的作用机制,为心肌梗死新药研发提供新思路。     

Targeting cardiac sympatho-vagal imbalance using gene transfer of nitric oxide synthase

Heightened sympathetic excitation and diminished parasympathetic suppression of heart rate, cardiac contractility and vascular tone are all associated with cardiovascular diseases such as hypertension and ischemic heart disease. This phenotype often exists before these disease states have been established and is a strong correlate of mortality in the population. However, the causal role of the autonomic phenotype in the development and maintenance of hypertension and myocardial ischemia remains a subject of debate, as are the mechanisms responsible for regulating sympathovagal balance. Emerging evidence suggests oxidative stress and reactive oxygen species (such as nitric oxide (NO) and superoxide) play important roles in the modulation of autonomic balance, but so far the most important sites of action of these ubiquitous signaling molecules are unclear. In many cases, these mediators have opposing effects in separate tissues rendering conventional pharmacological approaches non-efficacious. Novel techniques have recently been used to augment these signaling pathways experimentally in a targeted fashion to central autonomic nuclei, cardiac neurons, and myocytes using gene transfer of NO synthase. This review article discusses these recent advances in the understanding of the roles of NO and its oxidative metabolites on autonomic imbalance in models of cardiovascular disease.     

Mechanisms of the pro- and anti-oxidant actions of nitric oxide in atherosclerosis

The association of nitric oxide (NO) with cardiovascular disease has long been recognized and the extensive research on this topic has revealed both pro- and anti-atherosclerotic effects. While these contradictory findings were initially perplexing recent studies offer molecular mechanisms for the integration of these data in the context of our current understanding of the biochemistry of NO. The essential findings are that the biochemical properties of NO allow its exploitation as both a cell signaling molecule, through its interaction with redox centers in heme proteins, and an extremely rapid reaction with other biologically relevant free radicals. The direct reaction of NO with free radicals can have either pro- or antioxidant effects. In the cell, antioxidant properties of NO can be greatly amplified by the activation of signal transduction pathways that lead to the increased synthesis of endogenous antioxidants or down regulate responses to pro-inflammatory stimuli. These findings will be discussed in the context of atherosclerosis.     

Modulatory Role of Nitric Oxide/cGMP System in Endothelin-1-Induced Signaling Responses in Vascular Smooth Muscle Cells

Nitric oxide (NO) is an important vasoprotective molecule that serves not only as a vasodilator but also exerts antihypertrophic and antiproliferative effects in vascular smooth muscle cells (VSMC). The precise mechanism by which the antihypertrophic and antiproliferative responses of NO are mediated remains obscure. However, recent studies have suggested that one of the mechanisms by which this may be achieved includes the attenuation of signal transduction pathways responsible for inducing the hypertrophic and proliferative program in VSMC. Endothelin-1 is a powerful vasoconstrictor peptide with mitogenic and growth stimulatory properties and exerts its effects by activating multiple signaling pathways which include ERK 1/2, PKB and Rho-ROCK. Both cGMP-dependent and independent events have been reported to mediate the effect of NO on these pathways leading to its vasoprotective response. This review briefly summarizes some key studies on the modulatory effect of NO on these signaling pathways and discusses the possible role of cGMP system in this process.     

Multi-tasking RGS proteins in the heart: the next therapeutic target?

Regulator of G-protein-signaling (RGS) proteins play a key role in the regulation of G-protein-coupled receptor (GPCR) signaling. The characteristic hallmark of RGS proteins is a conserved approximately 120-aa RGS region that confers on these proteins the ability to serve as GTPase-activating proteins (GAPs) for G(alpha) proteins. Most RGS proteins can serve as GAPs for multiple isoforms of G(alpha) and therefore have the potential to influence many cellular signaling pathways. However, RGS proteins can be highly regulated and can demonstrate extreme specificity for a particular signaling pathway. RGS proteins can be regulated by altering their GAP activity or subcellular localization; such regulation is achieved by phosphorylation, palmitoylation, and interaction with protein and lipid-binding partners. Many RGS proteins have GAP-independent functions that influence GPCR and non-GPCR-mediated signaling, such as effector regulation or action as an effector. Hence, RGS proteins should be considered multifunctional signaling regulators. GPCR-mediated signaling is critical for normal function in the cardiovascular system and is currently the primary target for the pharmacological treatment of disease. Alterations in RGS protein levels, in particular RGS2 and RGS4, produce cardiovascular phenotypes. Thus, because of the importance of GPCR-signaling pathways and the profound influence of RGS proteins on these pathways, RGS proteins are regulators of cardiovascular physiology and potentially novel drug targets as well.     

硝基化修饰蛋白质在心血管内皮功能障碍中的作用

内皮功能障碍作为多种心血管疾病共同的特征之一,与过量表达的活性氧(ROS)/活性氮(RNS)密切相关。超氧阴离子与一氧化氮(NO)反应可以生成氧化能力更强的过氧亚硝酸盐,可以通过氧化多种蛋白质耗竭NO,导致内皮收缩与舒张功能障碍,在多种心血管疾病中发挥了重要的作用。该文通过综述硝基化修饰蛋白质产生的途径及其在心血管疾病中促进内皮功能紊乱的可能机制,讨论了ROS/RNS介导的硝基化修饰与内皮功能障碍之间相互促进,共同推动心血管疾病进程的关系。该文还讨论了清除过氧亚硝酸盐、抑制ROS产生途径以及直接增强内皮细胞功能的治疗策略在内皮功能障碍相关的心血管疾病中的应用,可以为进一步研究蛋白质硝基化修饰这一蛋白质翻译后修饰作为干预靶点在心血管疾病中的作用提供参考。     

eNOS/NO 信号通路与心血管疾病关系的研究进展

一氧化氮（nitric oxide,NO）作为一种信号分子,在生理活动中起着重要作用,包括血压调节、血管张力维持、免疫系统调控等,尤其在心血管系统中发挥重要作用。NO产生异常是多种心血管疾病的诱因。内皮型一氧化氮合酶（endothelial nitric oxide synthase,eNOS）作为诱导合成NO的限速酶,主要在血管壁的调节中发挥重要作用,因此,其与心血管的正常生理活动密切相关。本文综述了eNOS的基本结构与功能、NO的理化性质,以及eNOS/NO信号通路与心血管系统疾病的关系。     

Nitric oxide signaling in vascular biology

Nitric oxide (NO) research has expanded rapidly in the past 20 years, and the role of NO in physiology and pathology has been extensively studied. This review focuses on the pathways of NO synthesis and metabolism in vascular biological systems. Healthy vascular homeostasis is dependent on the integrity of the endothelium, which is a very large dynamic autocrine and paracrine organ with vasodilator, anti-inflammatory, and antithrombotic properties. The importance and relevance of NO signaling is stressed in this review. The potential role of nitrotyrosine formation with vascular pathological conditions is discussed. The use of pharmacologic, biochemical, and molecular biological approaches to characterize, purify, and reconstitute these regulatory pathways should lead to the development of new therapies for various pathological conditions that are characterized by an insufficient production of NO. With more than 77,000 publications in the field of NO signaling, this brief review can only focus on some aspects of the field as it applies to vascular biology. Many molecular targets have been identified for drug development dealing with NO and cyclic guanosine monophosphate formation, metabolism, and function. Many agents have been identified that are in pre-clinical evaluation or in clinical trials. Certainly, many should prove to be important therapeutic additions during the next decade.     

Angiotensin II and oxidative stress

PURPOSE OF REVIEW: Angiotensin II regulates vasoconstriction, homeostasis of salt and water, and cardiovascular hypertrophy and remodeling. Angiotensin II is a potent activator of NAD(P)H oxidase in the cardiovascular system, and augments production of reactive oxygen species. Numerous signaling pathways in response to angiotensin II are mediated by reactive oxygen species and oxidative stress is deeply associated with the progression of cardiovascular disease. The purpose of this review is to discuss the mechanism of reactive oxygen species formation and the pathophysiological effects of angiotensin II in the cardiovascular system. RECENT FINDINGS: Recent studies have demonstrated novel molecular mechanisms of reactive oxygen species generation by angiotensin II and signaling pathways including cell proliferation, hypertrophy and apoptosis. In spite of these findings that strongly suggest the benefits of angiotensin II inhibition for cardiovascular disease, the clinical effects of angiotensin II-induced reactive oxygen species on the cardiovascular system are still controversial. SUMMARY: We focus on the effects of angiotensin II-induced oxidative stress on cardiovascular function and remodeling after discussing the source of reactive oxygen species and novel signaling pathways in response to reactive oxygen species.     

Cyclic GMP-dependent protein kinases and the cardiovascular system: insights from genetically modified mice

Signaling cascades initiated by nitric oxide (NO) and natriuretic peptides (NPs) play an important role in the maintenance of cardiovascular homeostasis. It is currently accepted that many effects of these endogenous signaling molecules are mediated via stimulation of guanylyl cyclases and intracellular production of the second messenger cGMP. Indeed, cGMP-elevating drugs like glyceryl trinitrate have been used for more than 100 years to treat cardiovascular diseases. However, the molecular mechanisms of NO/NP signaling downstream of cGMP are not completely understood. Recent in vitro and in vivo evidence identifies cGMP-dependent protein kinases (cGKs) as major mediators of cGMP signaling in the cardiovascular system. In particular, the analysis of conventional and conditional knockout mice indicates that cGKs are critically involved in regulating vascular remodeling and thrombosis. Thus, cGKs may represent novel drug targets for the treatment of human cardiovascular disorders.     

Statins,Nitric Oxide and Neovascularization

Several landmark clinical trials suggest that 3‐hydroxyl‐3‐methylglutaryl coenzyme A reductase inhibitors (statins) have additional cardiovascular protective activity that may function independently of their ability to lower serum cholesterol. The cardiovascular protective effects of statins are partly caused by the activation of postnatal neovascularization. At therapeutic doses, statins promote proliferation, migration and survival of endothelial cells, induce mobilization and differentiation of bone marrow‐derived endothelial progenitor cells by stimulating the serine/threonine protein kinase Akt (also known as protein kinase B) and nitric oxide (NO) signal pathway. However, at excessive doses, statins may decrease protein isoprenylation as well as inhibit endothelial cell growth and migration. NO is an important signaling molecule that regulates a wide range of physiological and pathological processes in different tissues. There is substantial evidence that effective neovascularization requires endothelium‐derived NO. Statins have pleiotropic effects on the expression and activity of endothelial nitric oxide synthase (eNOS) and lead to improved NO bioavailability. NO plays an important role in the effects of statins on neovascularization. In this review, we focus on the effects of statins on neovascularization and highlight specific novel targets, such as endothelial progenitor cells and NO.     

The mammalian tribbles homolog TRIB3, glucose homeostasis, and cardiovascular diseases

Insulin signaling plays a physiological role in traditional insulin target tissues controlling glucose homeostasis as well as in pancreatic β-cells and in the endothelium. Insulin signaling abnormalities may, therefore, be pathogenic for insulin resistance, impaired insulin secretion, endothelial dysfunction, and eventually, type 2 diabetes mellitus (T2DM) and cardiovascular disease. Tribbles homolog 3 (TRIB3) is a 45-kDa pseudokinase binding to and inhibiting Akt, a key mediator of insulin signaling. Akt-mediated effects of TRIB3 in the liver, pancreatic β-cells, and skeletal muscle result in impaired glucose homeostasis. TRIB3 effects are also modulated by its direct interaction with other signaling molecules. In humans, TRIB3 overactivity, due to TRIB3 overexpression or to Q84R genetic polymorphism, with R84 being a gain-of-function variant, may be involved in shaping the risk of insulin resistance, T2DM, and cardiovascular disease. TRIB3 overexpression has been observed in the liver, adipose tissue, skeletal muscle, and pancreatic β-cells of individuals with insulin resistance and/or T2DM. The R84 variant has also proved to be associated with insulin resistance, T2DM, and cardiovascular disease. TRIB3 direct effects on the endothelium might also play a role in increasing the risk of atherosclerosis, as indicated by studies on human endothelial cells carrying the R84 variant that are dysfunctional in terms of Akt activation, NO production, and other proatherogenic changes. In conclusion, studies on TRIB3 have unraveled new molecular mechanisms underlying metabolic and cardiovascular abnormalities. Additional investigations are needed to verify whether such acquired knowledge will be relevant for improving care delivery to patients with metabolic and cardiovascular alterations.