Decreased basal production of nitric oxide in patients with heart disease

Reactive Vasodilation Predicts Mortality in Primary Systemic Light-Chain Amyloidosis

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Cardiac involvement and hypotension dominate the prognosis of light-chain amyloidosis (AL). Evidence suggests that there is also peripheral vascular involvement in AL but its prognostic significance is unknown.

Cholesterol Regulation of Pulmonary Endothelial Calcium Homeostasis

Cholesterol is a key structural component and regulator of lipid raft signaling platforms critical for cell function. Such regulation may involve changes in the biophysical properties of lipid microdomains or direct protein-sterol interactions that alter the function of ion channels, receptors, enzymes, and membrane structural proteins. Recent studies have implicated abnormal membrane cholesterol levels in mediating endothelial dysfunction that is characteristic of pulmonary hypertensive disorders, including that resulting from long-term exposure to hypoxia. Endothelial dysfunction in this setting is characterized by impaired pulmonary endothelial calcium entry and an associated imbalance that favors production vasoconstrictor and mitogenic factors that contribute to pulmonary hypertension. Here we review current knowledge of cholesterol regulation of pulmonary endothelial Ca²⁺ homeostasis, focusing on the role of membrane cholesterol in mediating agonist-induced Ca²⁺ entry and its components in the normal and hypertensive pulmonary circulation.

Value of Exhaled Nitric Oxide (FeNO) And Eosinophilia During the Exacerbations of Chronic Obstructive Pulmonary Disease Requiring Hospital Admission

The aim of this study was to analyze whether FeNO levels in acute exacerbation of COPD (AECOPD) with hospital admission have better diagnostic value than eosinophilia in blood, and to evaluate its usefulness in predicting a better clinical response. An observational prospective study of patients with AECOPD was carried out. FeNO determinations were made on arrival at the emergency room (ER), at discharge and during stability 3-6 months after discharge. Co-morbidities, bronchodilators, inhaled (IGC) and systemic (SGC) glucocorticoids, eosinophils, systemic inflammation markers (procalcitonin, C-reactive protein), eosinophil cationic protein, and total IgE were collected. Fifty consecutive patients (92% men, mean age 75 ± 6 years) were included in this study. Phenotypes were 26% Asthma-COPD Overlap Syndrome (ACOS), 42% chronic bronchitis (CB) and 32% emphysema. ACOS patients showed significantly higher levels of FeNO (73 ppb) and eosinophils (508 cells/mm³) than the rest (CB: 23 ppb, 184 cells/mm³, emphysema: 27 ppb, 159 cells/mm³; p < 0.05). A significant correlation between FeNO levels measured in ER and eosinophils was observed (r = 0.7; p < 0.001), but not at discharge or in stable phase. No significant association was found with parameters of systemic inflammation and mean stay. In conclusion, the determination of FeNO in AECOPD does not offer advantages over the evaluation of eosinophilia. These parameters rise at arrival in ER, descend at discharge, and remain unchanged in the stable phase. Both present similar diagnostic utility and are able to better identify the ACOS phenotype, which helps select a population that could benefit from a glucocorticoids therapy.

Review of biomarkers to assess the effects of switching from cigarettes to modified risk tobacco products

Context: One approach to reducing the harm caused by cigarette smoking, at both individual and population level, is to develop, assess and commercialize modified risk alternatives that adult smokers can switch to. Studies to demonstrate the exposure and risk reduction potential of such products generally involve the measuring of biomarkers, of both exposure and effect, sampled in various biological matrices.Objective: In this review, we detail the pros and cons for using several biomarkers as indicators of effects of changing from conventional cigarettes to modified risk products.Materials and methods: English language publications between 2008 and 2017 were retrieved from PubMed using the same search criteria for each of the 25 assessed biomarkers. Nine exclusion criteria were applied to exclude non-relevant publications.Results: A total of 8876 articles were retrieved (of which 7476 were excluded according to the exclusion criteria). The literature indicates that not all assessed biomarkers return to baseline levels following smoking cessation during the study periods but that nine had potential for use in medium to long-term studies.Discussion and conclusion: In clinical studies, it is important to choose biomarkers that show the biological effect of cessation within the duration of the study.

Exercise and NO production: relevance and implications in the cardiopulmonary system

This article reviews the existing knowledge about the effects of physical exercise on nitric oxide (NO) production in the cardiopulmonary system. The authors review the sources of NO in the cardiopulmonary system; involvement of three forms of NO synthases (eNOS, nNOS, and iNOS) in exercise physiology; exercise-induced modulation of NO and/or NOS in physiological and pathophysiological conditions in human subjects and animal models in the absence and presence of pharmacological modulators; and significance of exercise-induced NO production in health and disease. The authors suggest that physical activity significantly improves functioning of the cardiovascular system through an increase in NO bioavailability, potentiation of antioxidant defense, and decrease in the expression of reactive oxygen species-forming enzymes. Regular physical exercises are considered a useful approach to treat cardiovascular diseases. Future studies should focus on detailed identification of (i) the exercise-mediated mechanisms of NO exchange; (ii) optimal exercise approaches to improve cardiovascular function in health and disease; and (iii) physical effort thresholds.

Social support as a predictor exhaled nitric oxide in healthy individuals across time

Psychosocial factors such as social support and depression have long been associated with health outcomes. Elevated depressive symptoms are usually associated with worse health outcomes, whereas social support has been related to improvements in health. Nitric oxide levels are an important marker of both cardiovascular health and immune function. Research suggests that exhaled nitric oxide is affected by stress, negative affect, and depression; however, the effect of social support has not been previously explored. Thus, we sought to examine the association of social support, negative affect, and depression with exhaled nitric oxide in a group of 35 healthy individuals (10 males and 25 females) with a mean age of 20.5years across five weekly assessments. Results showed that changes in social support within individuals were positively associated with levels of exhaled nitric oxide independent of other psychosocial factors. Further exploration of the health implications of this positive relationship between airway nitric oxide and social support is necessary.

The NO/ONOO-cycle as the central cause of heart failure

The NO/ONOO-cycle is a primarily local, biochemical vicious cycle mechanism, centered on elevated peroxynitrite and oxidative stress, but also involving 10 additional elements: NF-κB, inflammatory cytokines, iNOS, nitric oxide (NO), superoxide, mitochondrial dysfunction (lowered energy charge, ATP), NMDA activity, intracellular Ca(2+), TRP receptors and tetrahydrobiopterin depletion. All 12 of these elements have causal roles in heart failure (HF) and each is linked through a total of 87 studies to specific correlates of HF. Two apparent causal factors of HF, RhoA and endothelin-1, each act as tissue-limited cycle elements. Nineteen stressors that initiate cases of HF, each act to raise multiple cycle elements, potentially initiating the cycle in this way. Different types of HF, left vs. right ventricular HF, with or without arrhythmia, etc., may differ from one another in the regions of the myocardium most impacted by the cycle. None of the elements of the cycle or the mechanisms linking them are original, but they collectively produce the robust nature of the NO/ONOO-cycle which creates a major challenge for treatment of HF or other proposed NO/ONOO-cycle diseases. Elevated peroxynitrite/NO ratio and consequent oxidative stress are essential to both HF and the NO/ONOO-cycle.

Academic exam stress and depressive mood are associated with reductions in exhaled nitric oxide in healthy individuals

Nitric oxide (NO) has beneficial effects on cardiovascular and immune health. Stress and depression have been linked to a reduction in serum NO. In this study, we examined the effect of academic exam stress on the fraction of NO in exhaled air (FeNO) and spirometric lung function in 41 healthy college students. Participants completed assessments at mid-semester as well as in the early and late phase of an academic exam period. Negative affect, depressive mood, and salivary cortisol were elevated during exams, whereas FeNO and lung function decreased. Higher depressive mood was associated with lower FeNO, whereas higher negative affect was associated higher FeNO across time. These findings provide initial evidence that depression and prolonged stress can alter FeNO and lung function in healthy individuals, which could have adverse consequences for cardiovascular, airway, and immune health.

Exhaled nitric oxide (FENO) in non-pulmonary diseases

Exhaled nitric oxide (F(E)NO) represents the only exhaled biomarker that has reached clinical practice even in primary care settings, due to the non-invasiveness of its assessment and ease of repeat measurements, even in patients with severe airflow obstruction. While F(E)NO has been suggested as a readily determined biomarker that can aid in the diagnosis and management of asthma, its potential role in pathophysiology of non-pulmonary diseases is less clear and therefore remains to be established. The purpose of the present review is to highlight the current literature investigating the use of F(E)NO in the diagnosis and management of non-pulmonary diseases.

Nitric oxide-dependent inhibition of alveolar fluid clearance in hydrostatic lung edema

Formation of cardiogenic pulmonary edema in acute left heart failure is traditionally attributed to increased fluid filtration from pulmonary capillaries and subsequent alveolar flooding. Here, we demonstrate that hydrostatic edema formation at moderately elevated vascular pressures is predominantly caused by an inhibition of alveolar fluid reabsorption, which is mediated by endothelial-derived nitric oxide (NO). In isolated rat lungs, we quantified fluid fluxes into and out of the alveolar space and endothelial NO production by a two-compartmental double-indicator dilution technique and in situ fluorescence imaging, respectively. Elevation of hydrostatic pressure induced Ca(2+)-dependent endothelial NO production and caused a net fluid shift into the alveolar space, which was predominantly attributable to impaired fluid reabsorption. Inhibition of NO production or soluble guanylate cyclase reconstituted alveolar fluid reabsorption, whereas fluid clearance was blocked by exogenous NO donors or cGMP analogs. In isolated mouse lungs, hydrostatic edema formation was attenuated by NO synthase inhibition. Similarly, edema formation was decreased in isolated mouse lungs of endothelial NO synthase-deficient mice. Chronic heart failure results in endothelial dysfunction and preservation of alveolar fluid reabsorption. These findings identify impaired alveolar fluid clearance as an important mechanism in the pathogenesis of hydrostatic lung edema. This effect is mediated by endothelial-derived NO acting as an intercompartmental signaling molecule at the alveolo-capillary barrier.

Significance of plasma nitric oxide/endothelial-1 ratio for prediction of coronary artery disease

Vascular tone is regulated by vasodilators and vasoconstrictors. Endothelin-1 (ET-1) is the predominant vasoconstrictor peptide that constricts vascular smooth muscle, whereas nitric oxide (NO) is the primary vasodilator peptide that relaxes vascular smooth muscle. In this study, the authors examined whether NO/ET-1 ratio is a useful marker for detecting coronary artery disease (CAD), by comparison with evaluation based on vascular endothelial (VE) function. They measured plasma NOX and ET-1 by using ENO-200 and radioimmunoassay, in 38 subjects with normal (NL) coronary arteries (NL group; mean age, 60 +/-12 years) and 25 subjects with CAD (CAD group; mean age, 69 +/- 6 years). VE function (randomized endothelium-dependent [D] and endothelium-independent [I] VE function) was assessed by measuring brachial artery (BA) diameter by using high-resolution ultrasound (7.5 MHz). Soon after these procedures, symptom-limited exercise testing was performed. There were no statistically significant differences in serum lipid concentrations or VED function between the groups. However, the CAD group had a significantly lower NO/ET-1 ratio (1.2 +/- 1.1 vs 2.7 +/- 2.2, p < 0.01) and BA diameter after sublingual nitroglycerin (VEID function: 6 +/- 7% vs 10 +/- 4%, p < 0.05). As expected, the ST segment and treadmill exercise duration were significantly lower in the CAD group. Sensitivity and specificity for detecting CAD by plasma NO/ET-1 ratio (> or =2 .0) were 90% and 85%, respectively; sensitivity and specificity for detecting CAD by ST depression (> or =1 mm) were 80% and 78%, respectively. The present results suggest that plasma NO/ET-1 ratio is a useful biological marker for predicting CAD.

Vascular endothelial dysfunction and mortality risk in patients with chronic heart failure

BACKGROUND

Endothelial function is known to be impaired in subjects with chronic heart failure (CHF), but the association between endothelial function and subsequent mortality risk in CHF has not been previously reported.

METHODS AND RESULTS

Biomarkers of endothelial function in the systemic arterial circulation (flow-mediated dilation [FMD] in the brachial artery) and the pulmonary circulation (exhaled nitric oxide [NO] production during submaximal exercise) were prospectively assessed in 259 subjects with New York Heart Association class II-III CHF. In subjects with FMD measurements (n=149), there were 12 deaths and 5 urgent transplantations over a median follow-up period of 841 days. In subjects with exhaled NO production measurements (n=110), there were 18 deaths and 1 urgent transplantation over a median follow-up period of 396 days. Both decreased FMD and decreased exhaled NO production were associated with increased risk of death or urgent transplantation after adjustment for other known CHF prognostic factors (age, etiology of CHF, functional class, left ventricular ejection fraction) in Cox multivariate proportional-hazards models (adjusted hazard ratio [HR] estimate for a 1% decrease in FMD=1.20; 95% confidence interval [CI], 1.03 to 1.45; P=0.027; adjusted HR estimate for a 1-ppb/min decrease in exhaled NO production=1.31, 95% CI, 1.01 to 1.69, P=0.04).

CONCLUSIONS

Endothelial dysfunction in CHF, as assessed by FMD in the brachial artery and exhaled NO production during submaximal exercise, is associated with an increased mortality risk in subjects with both ischemic and nonischemic CHF.

Repeated Sauna Therapy Increases Arterial Endothelial Nitric Oxide Synthase Expression and Nitric Oxide Production in Cardiomyopathic Hamsters

BACKGROUND

Vascular endothelial dysfunction is involved in the pathophysiology of chronic heart failure (CHF). It has been reported that sauna therapy, which allows thermal vasodilation, improves vascular endothelial dysfunction in patients with CHF. The present study investigates the mechanisms through which sauna therapy improves endothelial dysfunction induced by CHF.

METHODS AND RESULTS

Normal control and male TO-2 cardiomyopathic hamsters were used. Thirty-week-old TO-2 hamsters were treated daily with an experimental far infrared-ray dry sauna system for 15 min at 39 degrees C followed by 20 min at 30 degrees C. This procedure raised the rectal temperatures by about 1 degrees C. Arterial endothelial nitric oxide (NO) synthase (eNOS) mRNA and protein expressions were examined, and serum concentrations of nitrate were measured. The expression of eNOS mRNA in the aortas of normal controls did not change, whereas those of the TO-2 hamsters decreased with age. Four weeks of sauna therapy significantly increased eNOS mRNA expression in the aortas of TO-2 hamsters compared with those that did not undergo sauna therapy. Sauna therapy also upregulated aortic eNOS protein expression. Serum nitrate concentrations of the TO-2 hamsters were increased by 4 weeks of sauna therapy compared with those that did not undergo sauna.

CONCLUSION

Repeated sauna therapy increases eNOS expression and NO production in cardiomyopathic hamsters with heart failure.

Exercise-induced changes in exhaled nitric oxide in heart failure

BACKGROUND

In heart failure abnormalities of pulmonary function are frequently observed as shown by hyperpnea, reduced lung compliance, reduced alveolar-capillary gas diffusion, positive methacholine challenge and, during exercise, early expiratory flow limitation. Nitric oxide (NO) might be related to all the above abnormalities.

AIMS

We evaluated whether a correlation between exhaled NO (eNO) and lung function exists at rest and during exercise in heart failure.

METHODS

We studied 33 chronic heart failure patients and 11 healthy subjects with: (a) standard pulmonary function, (b) lung diffusion for carbon monoxide (DLco) including its subcomponents, capillary volume and membrane resistance and eNO both at rest and during light exercise, (c) maximal cycloergometer cardiopulmonary exercise test.

RESULTS

Forced expiratory volume in 1 s (FEV(1)) was reduced in heart failure patients (83+/-17% of predicted), as was DLco (75+/-18% of predicted) due to reduced membrane resistance (32.6+/-10.3 ml mmHg(-1) min(-1) vs. 39.9+/-6.9 in patients vs. controls, P<0.02). Exhaled NO was lower in patients vs. controls (9.7+/-5.4 ppm vs. 14.4+/-6.4, P<0.05) and was, during exercise, constant in patients and reduced in controls. No significant correlation was found between eNO and lung function. Vice-versa eNO changes during exercise were correlated with peak exercise oxygen consumption (r=0.560, P<0.001).

CONCLUSIONS

The hypothesis of a link between eNO and lung function in heart failure was not proved. The correlation between eNO changes during exercise and peak V(O(2)) might be due to hemoglobin oxygenation, which binds NO to hemoglobin.

Exhaled nitric oxide and exercise performance in heart failure

BACKGROUND

In heart failure abnormalities of pulmonary function are frequently observed particularly during exercise, which is characterized by hyperpnea, low tidal volume, early expiratory flow limitation and reduced lung compliance. Exhaled nitric oxide (NO) is increased in asthma. We evaluated whether a correlation between exhaled NO and lung mechanics exists during exercise in heart failure.

METHODS

We studied 33 chronic heart failure patients and 11 healthy subjects with: a) standard pulmonary function, b) lung diffusion for carbon monoxide (DLCO) including its subcomponents, capillary volume and membrane resistance and eNO both at rest and during light exercise, c) maximal cycloergometer cardiopulmonary exercise test.

RESULTS

Forced expiratory volume in 1 second (FEV1) was reduced in heart failure patients (83 +/- 17% of predicted) as was DLCO (75 +/- 18% of predicted) due to reduced membrane resistance (32.6 +/- 10.3 ml/mmHg/min vs. 39.9 +/- 6.9 in patients vs. controls, p < 0.02). eNO was lower in patients vs. controls (9.7 +/- 5.4 ppm vs. 14.4 +/- 6.4, p < 0.05) and was, during exercise, constant in patients and reduced in controls. No significant correlation was found between eNO and lung function. Vice-versa eNO changes during exercise were correlated with peak exercise oxygen consumption (r = 0.560, p < 0.001).

CONCLUSIONS

The hypothesis of a link between eNO and lung function in heart failure was not proved. The correlation between eNO changes during exercise and peak VO2 might be due to hemoglobin oxygenation which binds NO to hemoglobin.

Exhaled nitric oxide during exercise and dobutamine stress echocardiography in patients with mitral stenosis

BACKGROUND: Pulmonary hypertension (PH) is an important limiting factor of exercise tolerance in patients with mitral stenosis (MS). We wished to investigate the relationship between respiratory nitric oxide (NO), a potent vasodilator, and exercise tolerance in patients with moderate MS. In the same patients, we wondered whether acute change in pulmonary hemodynamics could affect respiratory NO. METHODS: Ten patients with moderate MS (valve area 1.4+/-0.2 cm(2)) were studied at rest, during incremental cycle ergometry exercise, and during dobutamine stress echocardiography (DSE). The concentration of NO in exhaled air (FE(NO)) and NO output (V'(NO)) were measured at baseline, at the end of exercise, and at the end of DSE. Eight healthy subjects served as normal controls for NO output during exercise. RESULTS: During exercise, FE(NO) decreased both in patients and in controls, while V'(NO) increased in both. At the end of exercise, both VO(2) max and V'(NO) were significantly higher in controls than in patients. The increase in V'(NO) during exercise was significantly correlated with VO(2) max, both in patients and in controls. During DSE, cardiac output (CO), pulmonary artery pressure (PAP), and mitral valve gradient increased. No changes in mean FE(NO), V'(NO), or ventilation were observed during DSE. There was a significant inverse correlation between FE(NO) and mitral valve gradient at the end of DSE. CONCLUSIONS: In patients with moderate MS, exercise performance is correlated with respiratory NO output. In the same patients, during DSE, the increase in CO, which is not accompanied by an increase in ventilation, is not associated with an increase in respiratory V'(NO).

Exhaled nitric oxide: a marker of pulmonary hemodynamics in heart failure

OBJECTIVES

We sought to test the hypothesis that patients with decompensated heart failure (HF) lose a compensatory process whereby nitric oxide (NO) maintains pulmonary vascular tone.

BACKGROUND

Exhaled nitric oxide (eNO) partially reflects vascular endothelial NO release. Levels of eNO are elevated in patients with compensated HF and correlate inversely with pulmonary artery pressures (PAP), reflecting pulmonary vasodilatory activity.

METHODS

We measured the mean mixed expired NO content of a vital-capacity breath using chemiluminescence in patients with compensated HF (n = 30), decompensated HF (n = 7) and in normal control subjects (n = 90). Pulmonary artery pressures were also measured in patients with HF. The eNO and PAP were determined sequentially during therapy with intravenous vasodilators in patients with decompensated HF (n = 7) and in an additional group of patients with HF (n = 13) before and during administration of milrinone.

RESULTS

The eNO was higher in patients with HF than in control subjects (9.9 +/- 1.1 ppb vs. 6.2 +/- 0.4 ppb, p = 0.002) and inversely correlated with PAP (r = -0.81, p < 0.00001). In marked contrast, patients with decompensated HF exhibited even higher levels of eNO (20.4 +/- 6.2 ppb) and PAP, but there was a loss of the inverse relationship between these two variables. During therapy (7.3 +/- 6 days) with sodium nitroprusside and diuresis, hemodynamics improved, eNO concentrations fell (11.2 +/- 1.2 ppb vs. before treatment, p < 0.05), and the relationship between eNO and PAP was restored. After milrinone, eNO rose proportionally with decreased PAP (p < 0.05).

CONCLUSIONS

Elevated eNO may reflect a compensatory circulatory mechanism in HF that is lost in patients with clinically decompensated HF. The eNO may be an easily obtainable and quantifiable measure of the response to therapy in advanced HF.

Increased nitric oxide output from alveolar origin during liver cirrhosis versus bronchial source during asthma

The aim of this study was to assess the usefulness of nitric oxide (NO) output measurement at multiple expiratory flow rates during diseases characterized by increased exhaled NO (FE(NO)) that could come from alveolar (liver cirrhosis) or bronchial (asthma) sources. It has been proposed that NO output measurements expressed as a function of expiratory flow allow alveolar NO concentration (FA(NO)) and maximal bronchial NO output (Qbr,max (NO)) to be computed. In 36 healthy nonsmoking subjects, we found that maximal bronchial NO output (37 +/- 3 nl/min) was correlated with the height of the subjects (p = 0.02). Alveolar NO concentration was 5.1 +/- 0.3 (SEM) ppb, which represented 31 +/- 2% and 61 +/- 3% of FE(NO) at 50 and 200 ml/s expiratory flow rate, respectively. Nonsmoking subjects with asthma (n = 28) were characterized by an increase in Qbr,max (NO) (133 +/- 14 nl/min) as compared with healthy nonsmoking subjects (p < 0.0001). FE(NO)50, FE(NO)200, and Qbr,max (NO) were equally efficient in differentiating subjects with asthma from healthy subjects. Patients with liver cirrhosis (n = 26, 14 smokers and 12 nonsmokers) had an increased FA(NO) compared with healthy subjects (cirrhosis: 8.3 +/- 0.9 ppb, healthy nonsmokers [n = 36] and smokers [n = 20], n = 56: 4.7 +/- 0.3 ppb, p < 0.05), which was correlated with the alveolar-arterial oxygen difference (p = 0.007). FA(NO) and FE(NO)200, but not FE(NO)50 values, allowed patients with liver cirrhosis to be differentiated from healthy subjects. These results suggest that a two-compartment model for NO output allows the increase in FE(NO) from alveolar sources to be differentiated from the increase from bronchial sources.

Exhaled nitric oxide in patients with PiZZ phenotype-related alpha1-anti-trypsin deficiency

There is no report of exhaled NO (eNO) in subjects with different phenotypes of alpha1-anti-trypsin (AAT) deficiency. Exhaled nitric oxide was evaluated by means of single-breath chemiluminescence analysis (fractional exhaled concentration at the plateau level [plFE(NO)]) in 40 patients with AAT deficiency. Patients were divided according to the protease inhibitor (Pi) phenotype: PiMZ/MS, n = 25; PiSZ n = 6; PiZZ, n = 9. Nineteen healthy subjects served as controls. Levels of eNO in PiZZ patients were also compared with those of subjects, without AAT deficiency (PiMM), matched for diagnosis, sex, age, smoking habit and forced expiratory volume in 1 sec (FEV1). In AAT deficiency subjects airway hyper-responsiveness to methacholine (PD20 FEV1) was also assessed. plFE(NO) was significantly lower in the PiZZ group (4.5+/-1.4 ppb) than in matched PiMM subjects (8.2+/-3.8 ppb), in healthy controls (9.3+/-2.8 ppb) and in patients of other phenotypes. Dynamic lung volumes and DL(CO) were significantly lower in PiZZ than in other AAT-deficient patients. Bronchial hyper-responsiveness was not different among AAT phenotypes. These results suggest that eNO may be significantly reduced in PiZZ as compared to healthy control subjects and to AAT subjects with other phenotypes, independent of the level of airway obstruction. Whether, at least potentially, eNO may be considered as an early marker of lung involvement in AAT deficiency must be confirmed with studies on larger number of subjects.

Plasma nitrate accumulation during the development of pacing-induced dilated cardiac myopathy in conscious dogs is due to renal impairment

Heart failure is associated with an increase in plasma nitrate and nitrite (NOx). To date there is still some controversy regarding the causes of nitrate accumulation during the development of heart failure. The goal of this study was to analyze the underlying mechanisms that cause accumulation of plasma nitrates during the development of heart failure in dogs. Dogs were chronically instrumented for measurement of hemodynamics and renal function. Hearts were paced initially at 210 bpm for 3 weeks and then at 240 until the development of heart failure. Hemodynamics, renal function, renal blood flow, arterial blood gases, hemoglobin, plasma and urine NOx levels, and creatinine levels were measured weekly. Heart failure was assessed by hemodynamic alterations, physical signs such as lethargy, ascites, cachexia, and postmortem evidence of cardiac hypertrophy. LVSP (from 127 +/- 3 to 106 +/- 3 mmHg), LV dP/dt (from 2658 +/- 173 to 1439 +/- 217 mmHg/s), MAP (from 101 +/- 1.9 to 83 +/- 1.8 mmHg) fell, whereas LVEDP tripled (from 6.4 +/- 0.9 to 20 +/- 2.6 mmHg), and heart rate rose (from 101 +/- 4.2 to 117 +/- 6.3 bpm), all changes P < 0.05. RBF (from 146 +/- 10 to 96 +/- 9.9 ml/min), urine output (V) (from 0.26 +/- 0.02 to 0.16 +/- 0.02 ml/min), GFR (from 63 +/- 1.8 to 49 +/- 2 ml/min), and Na excretion (from 45 +/- 4.5 to 14 +/- 4.6 microEq/min) all decreased (P < 0.05), whereas RVR increased (from 0.68 +/- 0.05 to 0.94 +/- 0.1 mmHg/ml/min). These changes took place during a rise in plasma NOx (from 3.7 +/- 0.5 to 16+/-3.3 microM), a decrease in urine NOx (from 33 +/- 9.9 to 8.1 +/- 4.9 microM), and a concurrent increase in NOx reabsorption (from 221 +/- 31 to 818 +/- 166 nmol/min). There was a direct correlation between the increase in plasma NOx levels and an increase in filtered load (r(2) = 0.97, P = 0.02), a negative correlation between NOx levels and NOx excretion (r(2) = 0.65 P < 0.09), and a direct correlation between plasma NOx levels and NOx reabsorption (r(2) = 0.97, P = 0.02). These results indicate that elevated plasma NOx during heart failure are most likely the result of an impairment of the renal function and not increased NOx production. Furthermore, without knowing changes in renal function the measurement of plasma NOx in and of itself is a meaningless index of NO formation.

Increased nitric oxide in exhaled air in patients with rheumatic heart disease

BACKGROUND

Endogenous production of nitric oxide and its presence in exhaled air was observed in humans. Prior studies have yielded contrasting information about the production of nitric oxide in patients with heart failure.

AIMS

The aim of this study was to measure nitric oxide in the exhaled air of patients with chronic rheumatic heart disease with and without pulmonary hypertension.

METHODS

Seventy-four patients (6 patients had isolated mitral stenosis; 13 patients had combined mitral stenosis and mitral regurgitation; 1 patient had isolated mitral regurgitation; 54 patients had combined mitral and aortic valve disease) and 27 healthy subjects were entered in the study. The nitric oxide concentration in exhaled air was determined with a chemiluminescence analyser. Echocardiography was performed in all patients to assess the severity of the valve disease and for the measurement of pulmonary artery pressure.

RESULTS

The level of exhaled nitric oxide was significantly greater in patients with rheumatic heart disease than in controls. The value of nitric oxide concentration in exhaled air was significantly increased in patients with pulmonary hypertension, as compared with patients who had normal pulmonary artery systolic pressure.

CONCLUSION

We found increased nitric oxide in the exhaled air in patients with rheumatic heart disease, especially in those with pulmonary hypertension, compared with healthy patients.

Effect of enalapril on exhaled nitric oxide in normotensive and hypertensive subjects

We investigated whether an angiotensin-converting enzyme (ACE) inhibitor increases the production of nitric oxide (NO) in exhaled air in normotensive and hypertensive subjects. In study 1, 8 normotensive male subjects received a single oral dose of enalapril (5 mg) or nitrendipine (10 mg) in a crossover manner. Exhaled air was collected at baseline, and at 2, 4, and 8 hours after administration of the drug. In study 2, 10 normotensive subjects (6 men and 4 women) and 10 hypertensive subjects (6 men and 4 women) received a single oral dose of enalapril (5 mg). Exhaled air was collected at baseline and at 2 and 4 hours after administration of the drug. In study 1, enalapril significantly increased the NO release rate from the lung in normotensive subjects (36.9+/-5.1 pmol/s at baseline versus 58.3+/-7.3 pmol/s at 4 hours, P<0.01). Nitrendipine did not change the NO release rate. In study 2, enalapril significantly increased the release of NO from the lung in normotensive subjects (40.4+/-6.0 pmol/s at baseline versus 70. 3+/-11.4 pmol/s at 4 hours, P<0.01) but not in hypertensive subjects. ACE inhibition increased NO production from the lung in normotensive subjects but not in hypertensive patients. The reduction of angiotensin II production and/or the accumulation of bradykinin in the pulmonary tissue may be responsible for increased NO production in components of the lung, such as the pulmonary vascular endothelium, bronchial epithelial cells, macrophages, nasopharyngeal cells, and neurons. However, the effects of ACE inhibition on NO production from the lung differ between hypertensive subjects and normotensive subjects.

Production of endogenous nitric oxide in chronic obstructive pulmonary disease and patients with cor pulmonale. Correlates with echo-Doppler assessment

Exhaled nitric oxide (NO) production in stable chronic obstructive pulmonary disease (COPD) has been loosely related to the severity of illness, being significantly reduced in the most severe cases. Pulmonary hypertension is associated with lower NO output from the lung. In this study expired NO was measured in patients with severe stable COPD with or without cor pulmonale (CP). Echocardiographic estimates of right heart function, lung function, diffusion capacity, respiratory muscle strength, and arterial blood gases were obtained in 34 consecutive patients with stable COPD (mean age, 68 +/- 7 yr). Expired NO was measured by chemiluminiscence to obtain fractional exhaled concentrations at peak (FENOp) and at plateau (FENOpl) points of the single-breath curve and resting NO output (V NO). All measurements of expired NO output, FENOp, FENOpl and V NO showed a negative correlation with both systolic pulmonary artery pressure (Pspa) (r = -0.51, -0.63, and -0.63, respectively, p < 0.01 for all) and right ventricle wall dimension (r = -0.41, -0.59, and -0.43, respectively, p < 0.05 for all), but not with any measurement of lung function. When the patients were divided according to the Pspa using a cutoff limit of 35 mm Hg, those subjects with CP showed lower FENOp (13.2 +/- 4.0 versus 36.7 +/- 30.8 ppb, p < 0.05), FENOpl (5.7 +/- 1.9 versus 8.9 +/- 4.7 ppb, p < 0.05), and V NO (69. 2 +/- 5.6 versus 107.6 +/- 14.6 nl/ min, p = 0.02) than did those with a normal resting Pspa. NO production from the airways was significantly lower and inversely related to development of CP in patients with severe COPD. Impaired endothelial release may account for the reduced levels of expired NO.

Relationship between decreased oxyhaemoglobin saturation and exhaled nitric oxide during exercise

Decreases in oxyhaemoglobin saturation (SaO2) are frequently observed in highly trained male endurance athletes during heavy work and has been termed exercise-induced hypoxaemia (EIH). Ventilation perfusion (VA/Q) mismatching and diffusion limitations are thought to be responsible. Nitric oxide (NO), a potent vasodilator, is present in the exhaled air of resting and exercising humans. Endogenously produced NO is thought to play a role in VA/Q matching and maintenance of low pulmonary vascular resistance. The purpose of this study was to determine the relationship between exhaled NO and EIH. It was hypothesized that athletes with EIH would have lower NO levels compared with non-EIH athletes. Eighteen highly trained male cyclists (VO2max=67.7 +/- 5.2 mL kg-1 min-1, mean +/- SD) were divided into normal (NORM, n=12, SaO2= 93.9 +/- 0.8) or low (LOW, n=6, SaO2=90.3 +/- 1.0) group, based on significantly different peak exercise SaO2 values (P < 0.05). All other descriptive and physiological characteristics were similar between the groups. Subjects performed a ramped cycle test to exhaustion breathing NO-free gas. The concentration (CNO) and production rate (VNO) of NO were determined from mixed gas samples at rest and during exercise at 100, 200, 250, 300, 350, 400 and 450 W using a chemiluminescent analyser. CNO remained unchanged from resting values in all subjects. VNO increased significantly during exercise in all subjects but was not different between LOW and NORM groups. The correlation between change in SaO2 and VNO from rest to maximal exercise was not significant (r=-0.12, P > 0.05). Collectively, these data suggest that exhaled NO is not related to decreased SaO2 during heavy exercise in highly trained male cyclists.

Endogenous nitric oxide in patients with chronic heart failure (CHF): relation to functional impairment and nitrate-containing therapies

We assessed the levels of exhaled nitric oxide (eNO) in patients with chronic heart failure (CHF) according to the functional impairment and the use of nitrate-containing agents. Forty patients (age 55+/-9 years) were classified according to the NYHA classes I-II (n=18, group 1) and classes III-IV (n=22, group 2), and to the use of nitrate-containing drugs (Nitrate+, Nitrate-). Twenty-two healthy age-related subjects served as controls (group 3). Respiratory function, symptom-limited incremental cycloergometry and resting eNO concentration at peak (FENOp) or plateau (FENOpl) of the single-breath exhalation curve were assessed in all subjects. FENOpl was significantly lower in patients than in controls (7.8+/-2.7 and 10.6+/-2.8 ppb, respectively, P<0.005) and lower in most severe CHF patients (7.1+/-2.6 and 8.8+/-2.7 ppb in group 2 and group 1, respectively, P<0.05). A significant correlation between peak V'O(2), Watts and FENOpl (r=0.42, P<0.013 and r=0.46, P=0.008, respectively) was found. Independent of NYHA class, Nitrate+ showed higher FENOp levels than Nitrate- patients (36.9+/-15.7 vs. 28. 1+/-15.1 ppb, P<0.05). Resting eNO was lower in the most compromised CHF patients and was significantly related to exercise capacity. Nitrate-containing agents might influence the levels of eNO in these patients.

Exhaled nitric oxide and exercise in stable COPD patients

STUDY OBJECTIVE

To evaluate exhaled nitric oxide (eNO) during exercise in patients with stable COPD.

SETTING

Outpatient evaluation in a rehabilitation center.

PATIENTS

Eleven consecutive male patients with stable COPD (age, 65 +/- 6 years; FEV(1), 56 +/- 10% predicted). Eight healthy (six men; age, 51 +/- 16 years) nonsmoking, nonatopic volunteers served as control subjects.

METHODS

In each subject, a symptom-limited cycle ergometry test was performed by monitoring eNO with the tidal-breath method to assess eNO concentration (FENO) and output (VNO) at rest, peak exercise, and recovery time.

RESULTS

Resting FENO (9.8 +/- 5.1 and 14.1 +/- 6.3 parts per billion, respectively) and VNO (4.2 +/- 2.0 and 5.9 +/- 3.4 nmol/min, respectively) were lower, although not significantly, in COPD patients than in control subjects. In both groups, FENO significantly decreased whereas VNO significantly increased during exercise. Both variables returned to baseline during the recovery time. Peak exercise VNO, but not FENO, was significantly lower in COPD patients than in control subjects (7.9 +/- 5.4 and 12.7 +/- 6.0 nmol/min, respectively, p < 0.05). The rise in VNO was weakly correlated to oxygen consumption VO(2)) both in control subjects (r = 0.31, p = 0. 002) and in COPD patients (r = 0.22, p = 0.03). FENO showed an inverse correlation to VO(2) in both groups (r = -0.53, p = 0.000; r = -0.31, p = 0.003 in control subjects and COPD patients, respectively).

CONCLUSIONS

In patients with mild and moderate COPD, eNO during exercise parallels that observed in normal control subjects. VNO, but not FENO, is significantly reduced at peak exercise in COPD patients as compared with control subjects. The long-term effects of exercise training on eNO has to be evaluated by further studies.

Exhaled nitric oxide during incremental and constant workload exercise in chronic cardiac failure

BACKGROUND

Nitric oxide (NO) is present in exhaled breath and produced by the pulmonary vascular endothelium as a potent vasodilator. Exercise is normally associated with pulmonary vasodilatation and a decrease in pulmonary vascular resistance to accommodate the increase in cardiac output. If production of NO is impaired in patients with chronic congestive cardiac failure (CCF), this might contribute to their exercise intolerance.

PATIENTS AND METHODS

We quantified NO production (V NO) in 12 patients with chronic stable CCF and 12 controls, at rest and during incremental cardiopulmonary exercise on a treadmill, and at a later date during constant workload exercise.

RESULTS

Patients had reduced V NO compared with controls during incremental exercise [381 (180) vs. 777 (275) nL min-1; mean (SD); P < 0.0001] but at constant workload V NO was similar between the two groups [353 (124) vs. 389 (189) nL min-1; P = 0.25]. Plasma levels of nitrate, the stable end-product of NO production, were significantly higher in patients [resting value 46.1 (21.6) vs. 23.0 (10.0) microM; P = 0.004] and were not influenced by exercise.

CONCLUSION

Impaired NO-mediated pulmonary vasodilatation does not appear to contribute to exercise limitation in CCF. Alternatively, the lower NO production observed during maximal exercise in the patient group compared with controls may reflect a reduced incremental response of a system that is already abnormally activated in heart failure.

Interactions between angiotensin II and nitric oxide during exercise in normal and heart failure rats

We hypothesized that nitric oxide (NO) opposes ANG II-induced increases in arterial pressure and reductions in renal, splanchnic, and skeletal muscle vascular conductance during dynamic exercise in normal and heart failure rats. Regional blood flow and vascular conductance were measured during treadmill running before (unblocked exercise) and after 1) ANG II AT(1)-receptor blockade (losartan, 20 mg/kg ia), 2) NO synthase (NOS) inhibition [N(G)-nitro-L-arginine methyl ester (L-NAME); 10 mg/kg ia], or 3) ANG II AT(1)-receptor blockade + NOS inhibition (combined blockade). Renal conductance during unblocked exercise (4.79 +/- 0.31 ml x 100 g(-1) x min(-1) x mmHg(-1)) was increased after ANG II AT(1)-receptor blockade (6.53 +/- 0.51 ml x 100 g(-1) x min(-1) x mmHg(-1)) and decreased by NOS inhibition (2.12 +/- 0.20 ml x 100 g(-1) x min(-1) x mmHg(-1)) and combined inhibition (3.96 +/- 0.57 ml x 100 g(-1) x min(-1) x mmHg(-1); all P < 0.05 vs. unblocked). In heart failure rats, renal conductance during unblocked exercise (5.50 +/- 0.66 ml x 100 g(-1) x min(-1) x mmHg(-1)) was increased by ANG II AT(1)-receptor blockade (8.48 +/- 0.83 ml x 100 g(-1) x min(-1) x mmHg(-1)) and decreased by NOS inhibition (2.68 +/- 0.22 ml x 100 g(-1) x min(-1) x mmHg(-1); both P < 0.05 vs. unblocked), but it was unaltered during combined inhibition (4.65 +/- 0.51 ml x 100 g(-1) x min(-1) x mmHg(-1)). Because our findings during combined blockade could be predicted from the independent actions of NO and ANG II, no interaction was apparent between these two substances in control or heart failure animals. In skeletal muscle, L-NAME-induced reductions in conductance, compared with unblocked exercise (P < 0.05), were abolished during combined inhibition in heart failure but not in control rats. These observations suggest that ANG II causes vasoconstriction in skeletal muscle that is masked by NO-evoked dilation in animals with heart failure. Because reductions in vascular conductance between unblocked exercise and combined inhibition were less than would be predicted from the independent actions of NO and ANG II, an interaction exists between these two substances in heart failure rats. L-NAME-induced increases in arterial pressure during treadmill running were attenuated (P < 0.05) similarly in both groups by combined inhibition. These findings indicate that NO opposes ANG II-induced increases in arterial pressure and in renal and skeletal muscle resistance during dynamic exercise.