Nitric oxide: therapeutic opportunities

Fifteen years after the discovery of nitric oxide as a biological mediator how close are new therapies? This article describes the roles of nitric oxide, illustrates how its discovery is altering the way in which certain established drugs are being used and reviews new therapeutic developments.     

Nasal nitric oxide concentration is decreased in heart failure patients receiving nitrates

Summary— Nitric oxide (NO) is a free radical gas and a short-lived messenger which has many paracrine functions. Direct assessment of NO production is very difficult in vivo. However, the paranasal cavities generate a high amount of NO which diffuses in the nasal cavity where it can be easily measured. Several studies have suggested alterations of the NO production in heart failure. Thus, we assessed nasal NO concentration in normal subjects and in heart failure patients. The nasal NO concentration averaged 227 ± 10 ppb in the control group (n = 20), and 210 ± 10, 198 ± 20 and 159 ± 54 ppb in New York Heart Association (NYHA) class II (n = 30), III (n = 28) and IV (n = 7) patients, respectively (mean ± standard error [SE], not significant using analysis of variance [ANOVA]). Nasal NO level was not influenced by age, sex or etiology of the heart failure or by treatment with frusemide, angiotensin-converting enzyme inhibitor or digoxin. However, treatment with NO-releasing drugs (nitrates or molsidomine) significantly decreased the nasal NO level in heart failure patients. A two-way ANOVA revealed that treatment with a NO-releasing drug influenced nasal NO concentration (P = 0.0005), whereas NYHA class did not (P = 0.23), with a trend towards an interaction between the two parameters (P = 0.09): the inhibitory effect of NO-releasing drug on nasal NO concentration was more pronounced in severe heart failure. In an additional group of 12 patients (NYHA class II or III), the nasal NO concentration was 174 ± 19 ppb during NO-releasing drug treatment and increased to 231 ± 27 ppb 3 days after withdrawal of the nitrates (P = 0.0007 using paired t-test). Conversely, the nasal NO concentration in another group of seven patients (NYHA class II or III) was 219 ± 32 ppb without nitrate treatment and decreased to 188 ± 28 ppb 7 days after nitrate addition (P = 0.02 using paired (test). In contrast, the nasal NO concentration in another group of ten ischemic patients without heart failure was 203 ± 25 ppb without nitrate treatment and was similar (207 ± 28 ppb) 7 days after nitrate addition (not significant using paired t-test). In conclusion, nasal NO production is normal in heart failure, except in patients receiving NO-releasing drugs. Nasal NO concentration could be useful for investigating the mechanism(s) by which exogenous NO donors decrease endogenous NO production.     

失眠障碍的药物治疗

失眠障碍是睡眠障碍中最常见的一类,其临床诊疗对临床医生而言是个严峻的挑战。本文将对临床常用于治疗失眠障碍的药物进行介绍。     

Nitric oxide and the control of renin secretion

Summary— Research during recent years has established nitric oxide as a unique signaling molecule that plays important roles in the regulation of the cardiovascular, nervous, renal, immune and other systems. Nitric oxide has also been implicated in the control of the secretion of hormones by the pancreas, hypothalamus, pituitary and other endocrine glands, and evidence is accumulating that it contributes to the regulation of the secretion of renin by the kidneys. The enzyme nitric oxide synthetase is present in vascular and tubular elements of the kidney, particularly in cells of the macula densa , a structure that plays an important role in the control of renin secretion. Guanylyl cyclase, a major target for nitric oxide, is also present in the kidney and is responsive to changes in nitric oxide levels. Drugs that inhibit nitric oxide synthesis generally suppress renin release in vivo and in vitro , suggesting a stimulatory role for the L-arginine-nitric oxide pathway in the control of renin secretion. Under some conditions, however, blockade of nitric oxide synthesis increases renin secretion. Recent studies indicate that nitric oxide not only contributes to the regulation of basal renin secretion, but also participates in the renin secretory responses to activation of the renal baroreceptor, macula densa and beta adrenoceptor mechanisms that regulate renin secretion. Future research should clarify the mechanisms by which nitric oxide regulates the secretion of renin and establish the physiological significance of this regulation.     

脑梗死患者一氧化氮合酶基因多态性及其对一氧化氮的影响

目的观察脑梗死患者内皮型一氧化氮合酶(eNOS)基因多态性及一氧化氮(NO)变化情况。方法采用前瞻性病例对照研究,脑梗死组193例,均为发病2周内经头颅CT或MRI证实存在颈内动脉分布区梗死灶者,对照组103例为正常体检者。对两组eNOS基因4号内含子多态性进行测定,并采用Griess重氮化反应法和酶标法分别检测血清NO含量、NOS活性。结果脑梗死组eNOS基因4号内含子a等位基因(eNOS4a)携带者48例,对照组为12例,携带频率有显著性差异(χ2=8.86,P=0.003);经Logistic回归分析,eNOS4a携带是脑梗死的独立危险因素(P=0.032);脑梗死组NO产物浓度中位数为6.04(3.83～11.49)μmol/L,低于对照组6.89(4.64～12.43)μmol/L(P=0.022)。eNOS4a携带者NO产物浓度中位数为5.07(3.18～7.62)μmol/L,低于非携带者6.86(4.39～11.76)μmol/L(P=0.001)。脑梗死组NOS活性为(2.97±1.47)U/ml,对照组(3.16±1.46)U/ml,无显著性差异(P=0.517)。eNOS4a携带者NOS活性(2.77±1.13)U/ml,与非携带者(3.12±1.54)U/ml无显著性差异(P=0.100)。结论eNOS4a携带可能通过减少NO生成而在脑梗死发生过程中发挥作用。     

精神分裂症患者一氧化氮合酶活性与发病机制相关性

目的通过测定首发精神分裂症患者和正常人的血清一氧化氮合酶(NOS)活性，比较和分析他们之间的差异，探讨NOS活性以及一氧化氮(NO)能神经系统的功能变化与精神分裂症的关系。方法采用比色法分别测定首发未用抗精神病药的精神分裂症患者(研究组)、临床症状缓解的精神分裂症患者(缓解组)和正常对照者的血清NOS活性。结果研究组的血清NOS活性为6.3665±1.2260(n=39)，明显高于症状缓解组(4.1204±0.9908，n=27，P<0.01)和正常对照组(3.2660±1.0320，n=27，P<0.01)；症状缓解组的NOS活性也明显高于正常对照组(P<0.01)。结论精神分裂症患者血清NOS活性明显增高，L-精氨酸-NO神经通路功能的紊乱可能是精神分裂症的发病机制之一，也可能成为一个新的治疗靶系统。     

Nitric oxide in vascular biology

Summary.  Nitric oxide is a highly versatile heterodiatomic molecule that effects a variety of actions in the vasculture. Originally identified as a principal determination of vascular tone, nitric oxide has since been recognized to exert anti thrombotic, antiproliferative, and anti-inflammatory effects in the vasculture. At higher concentrations and in the setting of other oxidants, nitric oxide can promote vascular pathology. In this review, we summarize the molecular mechanisms of nitric oxides actions in vascular biology and pathology.     

Nitric oxide synthase gene therapy: progress and prospects

NOS gene therapy has been the focus of extensive research as dysfunction of this enzyme has been implicated in several cardiovascular diseases. Research has concentrated on comparing the effect of gene delivery of NOS isoforms (eNOS, iNOS and nNOS) in healthy and diseased animal models on intimal hyperplasia, restenosis, vascular tone and ischemia-reperfusion injury. Most results demonstrate therapeutic benefits following vascular gene delivery of all NOS in pre-clinical models of cardiovascular disease. eNOS has been shown to have particular promise as it promotes re-endothelialisation and inhibits intimal hyperplasia in injured blood vessels. The ultimate goal is to translate the benefit of NOS gene therapy in animal models into clinical practise. To develop NOS gene therapy for clinical use further work needs to be undertaken to improve delivery systems and vectors to minimise detrimental side-effects and enhance positive treatment outcomes. This review focuses on current research on NOS gene therapy in cardiovascular disease and identifies the next steps that would be necessary to lead to clinical trials.     

Nitric oxide in the human uterine cervix: Endogenous ripening factor

The human uterine cervix can produce nitric oxide (NO), a free radical with an ultra‐short half‐life. The release of NO changes during pregnancy and is increased in early nonviable pregnancies compared to normal uncomplicated pregnancies. This review concentrates on the role of NO release in cervical ripening in pregnant women. Also some suggestions on future aspects are discussed.     

Haemodynamic correlates of early and delayed responses to sublingual administration of isosorbide dinitrate in migraine patients: a transcranial Doppler study

In normal subjects or migraine patients, nitrates induce a non-specific early headache caused by vasodilation of intracranial arteries. In migraineurs a delayed headache response to nitrates may have a typical clinical profile of a spontaneous migraine attack. The cerebral vasomotor changes of this delayed response require further study. Isosorbide dinitrate (IDN), an exogenous nitric oxide (NO) donor, was given at a dose of 5 mg sublingually and a bilateral transcranial Doppler device was used to monitor bilateral mean velocity (Vm) changes at the middle cerebral artery (MCA) after IDN administration and until delayed headache occurred. Spontaneous migraine-like headache occurred only in migraine patients during the delayed phase after IDN and was accompanied by a prolonged arterial vasodilation compared to normal subjects. This vasomotor response was more evident on the customary side of the head pain of a spontaneous migraine attack. Our findings suggest a particular vasomotor response to nitrates in migraine patients. This response is associated with the nitrate-induced headache and it is not evident in healthy pain-free controls during the delayed phase after administration of an NO donor. Owing to the short half-life of NO, the neurotransmitter released by IDN, and because of the late onset of headache, we believe the mechanism is unlikely to be vascular in origin, but may have a neurogenic component.     

Nitric oxide, a double edged sword in cancer biology: searching for therapeutic opportunities

Nitric oxide (NO) is a pleiotropic molecule critical to a number of physiological and pathological processes. The last decade has witnessed major advances in dissecting NO biology and its role in cancer pathogenesis. However, the complexity of the interactions between different levels of NO and several aspects of tumor development/progression has led to apparently conflicting findings. Furthermore, both anti-NO and NO-based anticancer strategies appear effective in several preclinical models. This paradoxical dichotomy is leaving investigators with a double challenge: to determine the net impact of NO on cancer behavior and to define the therapeutic role of NO-centered anticancer strategies. Only a comprehensive and dynamic view of the cascade of molecular and cellular events underlying tumor biology and affected by NO will allow investigators to exploit the potential antitumor properties of drugs interfering with NO metabolism. Available data suggest that NO should be considered neither a universal target nor a magic bullet, but rather a signal transducer to be modulated according to the molecular makeup of each individual cancer and the interplay with conventional antineoplastic agents.     

Human endothelial cells bioactivate organic nitrates to nitric oxide: implications for the reinforcement of endothelial defence mechanisms

Abstract. Although in therapeutic use for more than a century, the mode of cellular action of organic nitrates remains incompletely understood. Despite ample experimental evidence from animal studies to show that nitrates are metabolized to NO in the vascular smooth muscle, direct demonstration of such an activity in human vascular cells is still lacking. Moreover, the role of the endothelium in modulating the pharmacodynamic action of nitrates is far from clear. We therefore aimed to investigate whether or not human endothelial cells are capable of bioactivating these drugs to NO and whether the amounts generated are sufficient to elicit any biological effects. Using cultured human umbilical vein endothelial cells (HUVECs) as an established model system a combination of three different methods was used to address this issue: (1) quantification of NO formation upon endothelial nitrate metabolism using the oxyhaemo-globin technique; (2) evaluation of the second messenger response using radioimmunoassay for cGMP; and (3) assessment of mechanism and extent of potentiation of the anti-aggregatory effect of nitrates in the presence of endothelial cells as a relevant bioassay. We now show that superfusion of cultured human endothelial cells on microcarrier beads with either glyceryl trinitrate (GTN) or isosorbide dinitrate (ISDN; both at 01.100 μmol L^-1) results in a concentration-dependent formation of NO. NO generation from isosorbide 5-mononitrate (IS-5-N) was below the detection limit. The amounts of NO produced (maximally 2–97 ± 0.98 pmoles NO min^-1 x mg protein with 100μmol L^-1 GTN; n= 8) were similar to those elicited upon challenge of the cells with 100nM bradykinin. NO formation from either organic nitrate was accompanied, in a concentration-dependent and methylene blue-inhibitable manner, by stimulation of endothelial soluble guany-lyl cyclase with consequent increases in the intracel-lular level of cGMP (maximally 32-fold over basal levels with ISDN), a significant portion of which was released into the extracellular space. Upon continuous 30 min superfusion or repeated application of high concentrations of GTN (100μmol L^-1) nitrate bioac-tivation to NO was subject to partial tachyphylaxis. Co-incubation of washed human platelets with HUVECs potentiated the anti-aggregatory action of nitrates in a cell number dependent and oxyhaemo-globin-sensitive manner and this effect, too, was accompanied by increases in intraplatelet cGMP levels. The potentiating effect was largely inhibited after blockade of sulfhydryl groups by pre-incubadon of HUVECs with N-ethylmaleimide and completely abrogated after pretreatment of cells with the tissue fixative glutaraldehyde. These results demonstrate that human endothelial cells are capable of bioactivating organic nitrates to NO by an enzymatic, apparently thiol-sensitive pathway, in quantities sufficient to influence endothelial and platelet function. Besides the well known vasorelaxant action of organic nitrates, which is mainly due to their metabolism in the smooth muscle compartment, these drugs may therefore be endowed with a hitherto underestimated potential to directly influence endothelial functions via the NO/ cGMP pathway. Through specific bioactivation in the endothelium itself organic nitrates can thus mimic and reinforce protective functions normally served by a functional endothelium such as the modulation of blood cell/vessel wall interactions and inhibition of cell proliferation.     

Nitric Oxide: Biological Mediator,Modulator and Effector

Nitric oxide (NO) is synthesized from L-arginine by at least three isoforms of NO synthase enzyme (NOS). Once generated NO can interact with a number of molecular targets including haem proteins, enzymes, DNA, thiols, oxygen and superoxide. These reactions determine the profile of NO as a major biological mediator, modulator and effector molecule.     

Nitric oxide: an ubiquitous messenger

Summary— During the last decade, a multitude of experimental arguments have led to the concept that EDRF is nitric oxide (NO), a messenger not only involved in the control of vasomotor tone but also in vascular homeostasis, neuronal and immunological functions. Regardless of its origin, endogenous NO is produced through the conversion of L-arginine to L-citrulline by NO-synthase (NOS) from which several isoforms have recently been isolated, purified and cloned. NOS-type I (isolated from brain) and type III (isolated from endothelial cells) are termed “constitutive-NOS” and produce picomolar levels of NO from which only a small fraction elicits physiological responses. These isoforms are regulated by Ca²⁺-calmodulin with NADPH, FAD/FMN and tetrahydrobiopterin as co-factors and reveal a high degree of homology with the amino-acid sequence of cytochrome P450 reductase within the C-terminal domain. Functionally, neuronal-NOS type I is important in neurotransmission (modulation of NMDA receptor), the central control of vascular homeostasis and possibly learning and memory. In the peripheral nervous system, NOS appears to be linked to nonadrenergic noncho-linergic (NANC) neuronal pathways. Endothelial-NOS type III is essential for the control of vascular tone in response to the release of endogenous mediators, although shear stress is the major trigger of endothelial-NOS activity under physiological conditions. NOS-type III also contributes to the prevention of abnormal platelet aggregation. NOS-types II and IV (isolated from macrophages) are Ca²⁺-calmodulin independent and are termed “inducible-NOS” since their activation is only promoted under pathophysiological situations where macrophages exert cytotoxic effects in response to cytokines. In contrast with NOS-types I and III, activation of NOS-type II in these cells induces the formation of nanomolar levels of NO which act as a defense mechanism of the immune system. Dysfunctions of the L-arginine-NO pathway have been characterized in multiple diseases (atherosclerosis, hypertension, diabete, sepsis, cerebral ischemia, etc) and the design of more selective activators/inhibitors of NOS isoforms is a new challenge for the understanding of their pathophysiology and treatment.     

Nitric oxide and nursing: a review

Aims and objectives. This paper, therefore, aimed to review published literature in this area of pharmacological exploitation, to look at the therapeutic applications and clinical relevance and, by so doing, provide an accessible source for nurses to gain insight into the role of nitric oxide in the clinical setting. Background. Nitric oxide is a chemical mediator fundamental in the maintenance of adequate tissue perfusion and effective cardiovascular function; a major endogenous regulator of vascular tone. The use of nitrates are well established as pharmacological agents but it is only recently that it has been recognized that they act as a source of nitric oxide. Although widely addressed within the medical literature, there appears to be a paucity of nursing literature that explores either its physiological action, or its relevance to nursing practice. Conclusions. This literature review provides an overview of the use of nitric oxide and its implications for nursing practice and patient outcomes. Relevance to clinical practice. Knowledge of nitric oxide and its action is pertinent to nurses across diverse specialities. It helps in understanding the principles of many nitrogen‐derived medications which nurses administer to their patients on a daily basis. In terms of oral medication, this is demonstrated by greater insights into the action of nitrates, the appreciation of surprising developments in medications such as sildenafil and the development of new drug opportunities such as nitric oxide–non‐steroidal anti‐inflammatory drugs. Equally, the use of inhaled nitric oxide therapy in adult and neonatal critical care units appears to be an increasingly valuable source of treatment. A particular research challenge is found in the attempt at nitric oxide inhibition in the management of septic shock. The authors argue that understanding such esoteric areas of therapeutic developments is increasingly to be part of the repertoire of knowledge and skills for nurses in the 21st century.     

Nitroglycerin-induced headache is not dependent on histamine release: support for a direct nociceptive action of nitric oxide

The molecular mechanisms of migraine pain have not yet been clarified. Monoamine and the peptide neurotransmitters involved in neurogenic inflammation do not cause significant head pain. Our previous studies of glyceryl trinitrate (GTN) and histamine-induced headaches have suggested that nitric oxide (NO) is the causative molecule in migraine pain. We furthermore suggest that substances capable of inducing experimental vascular headache do so via a common mediator which is NO. Finally, it is suggested that drugs exert their antimigraine activity by inhibiting NO or subsequent steps in the cascade of intracellular reactions triggered by NO. These novel observations change current views on vascular headache mechanisms and the importance of NO as an initiator of the migraine attacks dictates new approaches to the pharmacological treatment of migraine and other vascular headaches.     

Exhaled Nitric Oxide Levels during Acute Asthma Exacerbation

Objectives: Fractional exhaled nitric oxide (FE_NO) has been shown in laboratory settings and trials of patients with stable asthma to correlate with the degree of airway inflammation. The authors hypothesized that the technique of measuring FE_NO would be reproducible in the setting of acute asthma in the emergency department (ED) and that the FE_NO results during ED visits would potentially predict disposition, predict relapse following discharge, and correlate with the National Institutes of Health (NIH) asthma severity scale and peak expiratory flow measurements. Methods: The authors prospectively measured FE_NO in a convenience sample of ED patients with acute exacerbations of asthma, both at the earliest possible opportunity and then one hour later. Each assessment point included triplicate measurements to assess reproducibility. The authors also performed spirometry and classified asthma severity using the NIH asthma severity scale. Discharged patients were contacted in 72 hours to determine whether their asthma had relapsed. Results: The authors discontinued the trial (n= 53) after a planned interim analysis demonstrated reproducibility (coefficient of variation, 15%) substantially worse than our a priori threshold for precision (4%). There was no association between FE_NO response and corresponding changes in spirometry or clinical scores. Areas under the receiver operating characteristic curves for the prediction of hospitalization and relapse were poor (0.579 and 0.713, respectively). Conclusions: FE_NO measurements in ED patients with acute asthma exacerbations were poorly reproducible and did not correlate with standard measures of asthma severity. These results suggest that using existing technology, FE_NO is not a useful marker for assessing severity, response to treatment, or disposition of acute asthmatic patients in the ED.     

血吸虫病人血一氧化氮测定意义探讨

目的 :探讨血吸虫病人血一氧化氮测定的意义。方法 :分别测定 32例慢性血吸虫病人 ,11例晚期血吸虫病人和 30例正常人血一氧化氮 ,并进行统计分析。结果 :晚期血吸虫病人和慢性血吸虫病人血一氧化氮显著高于正常人 (P <0 .0 5 ) ,晚期血吸虫病人的血一氧化氮水平也非常显著地高于慢性血吸虫病人 (P <0 .0 1)。结论 :血一氧化氮水平与血吸虫病关系密切 ,动态观察血一氧化氮水平的变化对掌握血吸虫病情的发展有重要意义     

血清中一氧化氮浓度与精子活动度关系的分析

目的探讨个体血清一氧化氮浓度对精子运动能力的影响。方法用721分光光度计测定血清中一氧化氮浓度,用OLYMPUS显微摄影系统等自动分析精子的运动情况。结果一氧化氮浓度在60~93μmol／L之间时显著促进精子的运动,一氧化氮浓度过高(>93μmol／L)和过低(≤59μmol／L)都会抑制精子的运动。结论精子运动能力与个体血清中一氧化氮浓度有关。