Role of nitric oxide in posthypoxic contractile dysfunction of diabetic cardiomyopathy

We investigated the role of nitric oxide synthase (NOS) in the contractile dysfunction of diabetic cardiomyopathy, comparing streptozotocin-treated (60 mg/kg) diabetic Wistar rats with matched non-diabetic controls. Isolated isovolumic heart function was studied during normoxia and in response to brief hypoxia-reoxygenation. Diabetic hearts had significantly lower left-ventricular pressure and slower isovolumic relaxation than controls (relaxation time constant, T 40.2+/-2.3 vs. 27.7+/-0.9 ms; P<0.05) and a blunted response to hypoxia. These abnormalities were unaffected by NOS inhibition. Upon reoxygenation after brief hypoxia, diabetic hearts exhibited substantial worsening of LV relaxation compared to normal hearts (T 69.1+/-3.3 vs. 56.6+/-7.9 ms; P<0.05). This post-hypoxic diastolic dysfunction was significantly attenuated either by the non-selective NOS inhibitor L-NAME, the iNOS inhibitor L-NIL, or the reactive-oxygen-species (ROS) scavenger thiourea. Only diabetic hearts expressed iNOS protein, whereas eNOS expression was similar in both groups. In conclusion, diabetic hearts exhibit markedly abnormal post-hypoxic relaxation, which is attributable to both ROS and NO derived from iNOS.     

The Role of Nitric Oxide in the Failing Heart

Nitric oxide (NO) has effects on contractility, energetics and gene expression of failing myocardium. Initial studies on isolated cardiomyocytes showed NO to reduce systolic shortening but intracoronary infusions of NO-donors or of NO synthase (NOS) inhibitors failed to elicit changes in baseline LV contractility indices such as LVdP/dt(max). Intracoronary infusions of NO-donors or of substance P, which releases NO from the coronary endothelium, however demonstrated NO to induce a downward displacement of the left ventricular (LV) diastolic pressure-volume relation, consistent with increased LV diastolic distensibility. In end-stage failing myocardium, the increased oxygen consumption is related to reduced NO production and in isolated cardiomyocytes, NO blunts the norepinephrine-induced expression of the fetal gene programme thereby preserving myocardial calcium homeostasis.In dilated cardiomyopathy, changed endomyocardial NOS gene expression has been reported. Because of lower endomyocardial NOS gene expression in patients with higher functional class and lower LV stroke work, increased endomyocardial NOS gene expression seems to be beneficial rather than detrimental for the failing heart. A beneficial effect of increased NOS gene expression could result from NO's ability to increase LV diastolic distensibility, to augment LV preload reserve, to reduce myocardial oxygen consumption and to prevent downregulation of calcium ATPase. Upregulated endomyocardial NOS gene expression has also been reported in athlete's heart and could therefore play a role in physiological LV remodeling. Reduced endomyocardial NO content because of decreased NO or increased superoxide production could lower LV diastolic distensibility and contribute to diastolic heart failure. In many conditions such as aging, hypertension, diabetes or posttransplantation, the increased incidence of diastolic heart failure is indeed paralleled by reduced endothelium-dependent vasodilation.     

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.     

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.     

Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: role of nitric oxide synthase isoforms

BACKGROUND: Hepatic encephalopathy is a complex neuropsychiatric syndrome. A previous study showed that chronic nitric oxide (NO) inhibition aggravated the severity of encephalopathy in thioacetamide (TAA)-treated rats. The present study investigated the relative contribution of NO synthase (NOS) isoforms on the severity of hepatic encephalopathy in TAA-treated rats. METHOD: Fulminant hepatic failure was induced in male Sprague-Dawley rats by intraperitoneal injection of TAA (350 mg/kg/day) for 3 days. Rats were divided into three groups to receive N(omega)-nitro-L-arginine methyl ester (L-NAME, a non-selective NOS inhibitor, 25 mg/kg/day in tap water), L-canavanine (an inducible NOS inhibitor, 100 mg/kg/day via intraperitoneal injection) or normal saline (N/S) from 2 days prior to TAA administration and lasting for 5 days. Severity of encephalopathy was assessed by the counts of motor activity. Plasma levels of tumor necrosis factor-alpha (TNF- alpha) were determined by enzyme-linked immunosorbent assay (ELISA), and total bilirubin, alanine aminotransferase (ALT) and creatinine were determined by colorimetric assay. RESULTS: Compared with L-canavanine or N/S-treated rats (0% and 4%, respectively), the mortality rate was significantly higher in rats receiving L-NAME administration (29%, P < 0.005). Inhibition of NO created detrimental effects on the counts of motor activities (P < 0.05). Rats treated with L-NAME had significantly higher plasma levels of total bilirubin, ALT, creatinine and TNF- alpha as compared with rats treated with L-canavanine or N/S (P < 0.01). CONCLUSION: Chronic L-NAME administration, but not L-canavanine, had detrimental effects on the severity of hepatic damage and motor activities in TAA-treated rats. These results suggest that constitutive NOS activities play a major protective role in rats with fulminant hepatic failure.     

Role of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal injury in neonatal rats

AIM: To investigate the dynamic change and role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in neonatal rat with intestinal injury and to define whether necrotizing enterocolitis (NEC) is associated with the levels of nitric oxide synthase (NOS) in the mucosa of the affected intestine tissue. METHODS: Wistar rats less than 24 h in age received an intraperitoneal injection with 5 mg/kg lipopolysaccharide (IPS). Ileum tissues were collected at 1, 3, 6, 12 and 24 h following LPS challenge for histological evaluation of NEC and for measurements of nNOS and iNOS. The correlation between the degree of intestinal injury and levels of NOS was determined. RESULTS: The LPS-injected pups showed a significant increase in injury scores versus the control. The expression of nNOS protein and mRNA was diminished after LPS injection. There was a negative significant correlation between the nNOS protein and the grade of median intestinal injury within 24 h. The expression of iNOS protein and mRNA was significantly increased in the peak of intestinal injury. CONCLUSION: nNOS and iNOS play different roles in LPS-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of NOS inhibitors in NEC.     

人胃癌组织中一氧化氮合酶的表达

目的探讨NOS与胃癌的关系.方法用NADPH-d组织化学法测定了正常胃组织、癌旁组织和癌组织中一氧化氮合酶(NOS)表达水平.结果正常胃组织中粘膜上皮细胞、各种有分泌功能的细胞及肌层神经纤维中均有NOS表达,测一个视野NOS阳性细胞的平均灰度,正常胃组织为112、癌旁组织为120、胃癌组织为145.各组间差异有显著意义.表明正常胃组织NOS活性最高,胃癌组织NOS活性最低.结论①正常胃组织有广泛的NOS分布,提示NO对维持正常胃功能具有重要作用;②胃粘膜细胞癌变过程中,NOS活性明显降低,提示NOS活性与胃粘膜细胞癌变有高度相关性.     

Expression of inducible nitric oxide synthase in human gastric cancer

INTRODUCTIONInduciblenitricoxidesynthase(iNOS)isanenzymethatcatalyzestheformationofnitric0xide(N0)fromL-arginine.iNOSexpressionandactivityresultsintheproduction0fhighlevelsofNO[1].ThegenerationofphysiologicallevelsofNOisimp0rtantformucosalfunctionanditalsoexertsacytoprotectiveeffectonthegastr0intestinalmucosa.However,increasediNOSexpressionhasbeenobservedinpatientswithchronicinflammatorydiseasesofthegastr0intestinaltract,suchasulcerativec0litis[2'3],andgastritis['Jandithasbeenspecul…     

外源性Apelin-13对大鼠阿霉素心力衰竭模型的影响与一氧化氮途径的关系

目的研究Apelin 13对大鼠阿霉素心力衰竭的影响与NO途径的关系。方法 SD大鼠70只,随机取10只作为对照组,其余60只采用阿霉素8次隔日腹腔注射法制备大鼠心力衰竭模型。17～20 d将造模成功的55只大鼠随机分为模型组21只,Apelin-13组16只,Apelin-13十一氧化氮合酶抑制剂组(联合组)18只;Apelin-13组给予Apelin 13,联合组预先给予LNAME.然后给予Apelin-13,2组对应的药物连续尾静脉注射1周,对照组给予同等剂量的生理盐水。1周后,左心室插管法测心功能,ELISA法测血浆B型钠尿肽(BNP)、NO浓度;HE染色法观察心脏、肺脏、肝脏的病理学变化,VG染色法观察胶原纤维变化,并计算胶原容积分数(CVF)。结果模型组死亡11只,Apelin-1 3组死亡6只,联合组死亡8只,死亡率分别为52.38%、37.50%、44.44%。与对照组比较,其余3组左心室压力最大上升和下降速率均下降,模型组下降最明显,治疗组下降不明显(P<0.05);与对照组比较,其余3组BNP、NO、CVF均升高,模型组升高最明显,治疗组升高不明显(P<0.05)。结论 Apelin-13对阿霉素心力衰竭有一定的治疗作用,一氧化氮合酶抑制剂部分抵消Apelin-13的治疗作用,可能通过NO途径发挥作用。     

内皮型一氧化氮合酶基因多态性与冠心病的关系

内皮型一氧化氮合酶(eNOS)基因被列为冠心病(CHD)的一个候选易感基因。本文对与冠心病关系较为密切的三种eNOS基因多态性:4b/a、T786C和G894T的研究进展作一综述,对进一步认识冠心病的发病机制具有重要意义。     

Subcellular distribution of nitric oxide synthase isoforms in the rat duodenum

AIM:To study the cell-type specific subcellular distribution of the three isoforms of nitric oxide synthase(NOS) in the rat duodenum.METHODS:Postembedding immunoelectronmicroscopy was performed,in which primary antibodies for neuronal NOS(nNOS),endothelial NOS(eNOS),and inducible NOS(iNOS),were visualized with protein A-gold-conjugated secondary antibodies.Stained ultrathin sections were examined and photographed with a Philips CM10 electron microscope equipped with a MEGAVIEW II camera.The specificity of t...     

内皮型一氧化氮合酶基因多态性与冠心病的研究进展

冠状动脉粥样硬化性心脏病（cronary atherosclerotic heart disease,CHD）简称冠心病,是指冠状动脉发生粥样硬化引起管腔狭窄或闭塞,导致心肌缺血缺氧或坏死引起的心脏病.吸烟、肥胖、高血压及代谢综合征等均已成为广为人知的几个冠心病重要危险因素.但也有患者没有这些危险因素存在,并且在一些个体中,常有明显的冠心病家族史,说明冠心病是环境与遗传危险因素动态相互作用所致的.目前已有诸多冠心病基因多态性研究,包括内皮型一氧化氮合酶（endothelial nitric oxide synthase,eNOS）.在近年的荟萃分析中显示,某些遗传变异可能为特定群体冠心病发病的危险因素之一.     

Role of nitric oxide in the pathophysiology of heart failure

Nitric oxide (NO) plays critical roles in the regulation of integrated cardiac and vascular function and homeostasis. An understanding of the physiologic role and relative contribution of the three NO synthase isoforms (neuronal—NOS1, inducible—NOS2, and endothelial—NOS3) is imperative to comprehend derangements of the NO signaling pathway in the failing cardiovascular system. Several theories of NO and its regulation have developed as explanations for the divergent observations from studies in health and disease states. Here we review the physiologic and pathophysiologic influence of NO on cardiac function, in a framework that considers several theories of altered NO signaling in heart failure. We discuss the notion of spatial compartmentalization of NO signaling within the myocyte in an effort to reconcile many controversies about derangements in the influences of NO in the heart and vasculature.     

NO与肝癌形成

目的研究一氧化氮(NO)在肝癌发生发展的作用。方法用免疫组化的方法对21例肝癌及癌旁组织中的3种一氧化氮合酶(NOS)及血管内皮细胞生长因子(VEGF)的表达进行原位检测和观察,结果紧邻癌细胞的肝硬化组织或慢性肝炎组织iNOS呈强阳性,远离癌组织的肝硬化组织或慢性肝炎组织多呈阴性或弥漫弱阳性;iNOS在周边癌组织及侵入纤维组织中的癌细胞呈阳性,癌组织核心多呈阴性或弥漫弱阳性。VEGF、nNOS的分布与iNOS相似。eNOS主要分布在肝癌细胞小血管壁内皮及其肌层组织。结论 NOS表达与肝组织癌变及肝癌侵润能力有关,与癌组织获得血管形成和转移表型有关。     

NO及NOS在低氧大鼠肺组织和主动脉中的差异性及其意义

目的观察低氧性肺动脉高压大鼠肺组织匀浆、主动脉匀浆及出肺血和入肺血中一氧化氮（NO）的含量、一氧化氮合酶（NOS）的活性。方法将24只雄性SD大鼠随机分成4组,即常氧2周组、常氧3周组、低氧2周组、低氧3周组。采用间断负压低氧法制备大鼠低氧性肺动脉高压模型;右心室导管法测定最高肺动脉压（PAP）;左颈总动脉插管测量左颈总动脉压代表动脉血压（Psa）;计算右心室肥厚指数[RV/（LV+S）];采用硝酸还原酶法测定各组大鼠出、入肺血及肺组织和主动脉匀浆中的NO含量;用化学比色法测定各组大鼠肺组织和主动脉匀浆中NOS的活性;应用免疫组化染色法观察各组大鼠肺组织及主动脉eNOS在蛋白质水平表达的变化。结果低氧组大鼠的PAP[（43.4±4.4）mmHg,（51.8±4.2）mmHg,1mmHg=0.133kPa],RV/（LV+S）（32.3±1.0,37.0±1.6）均高于其正常对照组[（20.8±2.4）mmHg,（21.8±3.9）mmHg;21.3±1.0,20.3±1.2,P<0.01)],且随缺氧时间延长而增高（P<0.01）,而Psa与常氧对照组比无差别。低氧组大鼠的出、入肺血及肺组织匀浆中的NO含量、NOS活性及肺组织eNOS的表达量均较其常氧对照组显著降低（P<0.01）,出肺血与入肺血的NO含量无差别;主动脉匀浆中NO含量和NOS的活性及大鼠主动脉的eNOS染色在各组间未见明显差异。结论低氧时,大鼠肺组织中NO的含量及NOS的活性均较常氧时降低,而主动脉中二者的表达在低氧和常氧时却没有差异,这种差异性可能是低氧时引起肺动脉高压却很少导致高血压的机制之一。     

Vascular effects of a heme oxygenase inhibitor are enhanced in the absence of nitric oxide

BACKGROUND: Vascular endothelium and smooth muscle express heme oxygenase (HO) that metabolizes heme to biliverdin, iron and carbon monoxide (CO). Carbon monoxide promotes endothelium-independent vasodilation, but also inhibits nitric oxide formation. This study examines the hypothesis that an inhibitor of HO promotes endothelium-independent vasoconstriction, which is attenuated in the presence of unabated nitric oxide formation. METHODS: In vivo studies were conducted in anesthetized male Sprague-Dawley (SD) rats instrumented with flow probes and arterial catheters. In vitro experiments were performed on pressurized first-order gracilis muscle arterioles isolated from male SD rats superfused with oxygenated modified Krebs buffer. RESULTS: Vascular smooth muscle and endothelium showed positive HO-1 and HO-2 immunostaining. In anesthetized rats the HO inhibitor chromium mesoporphyrin (CrMP; 45 micromol/kg intraperitoneally) had minimal effect on hindlimb resistance. However, in animals pretreated with N(omega)-nitro-L-arginine methyl ester (L-NAME; 300 mg/kg intraperitoneally), CrMP substantially increased hindlimb resistance. In contrast, in rats infused with phenylephrine to increase blood pressure and vascular tone, CrMP had no effect on hindlimb resistance. In isolated arterioles denuded of endothelium, CrMP (15 micromol/L) caused a powerful vasoconstriction, which was abolished in the presence of a functional endothelium. In arterioles with intact endothelium pretreated with L-NAME (1 mmol/L), or with L-NAME and sodium nitroprusside (10 to 30 nmol/L), CrMP promoted a similarly powerful vasoconstriction as in vessels denuded of endothelium. CONCLUSIONS: These results suggest that smooth muscle-derived CO may contribute to endothelium-independent regulation of vascular tone by providing a vasodilatory influence. Furthermore, the dilatory effects of endogenous CO are offset by a unique interaction between the CO and nitric oxide systems.