Endurance training enhances vasodilation induced by nitric oxide in human skin.

Résumé Il a été démontré que l'exercice physique modifiait le contrôle de la thermorégulation cutané, ce qui se manifeste par une augmentation de la perfusion de la microcirculation de la peau. Pour une même augmentation de température, ce phénomène est plus important chez les sportifs d'endurance que chez les sujets sédentaires. Dans cette étude, nous posons l'hypothèse qu'une composante de cette adaptation peut provenir d'une plus haute capacité des vaisseaux sanguins à répondre à un stimulus vasodilatateur. Pour la tester, nous avons recruté des hommes sains, non fumeurs, soit entraînés (surtout sport d'endurance) ou sédentaires que nous avons partagé en deux classes d'âges (18-35 ans [jeunes] et >50 ans[âgés]). Le flux sanguin cutané était mesuré par un laser-Doppler au niveau de la peau de l'avant-bras. Nous avons alors mesuré la vasodilatation obtenue par les stimuli suivant : Iontophorèse à l'acétylcholine (ACh, un vasodilatateur dépendant de l'endothélium), iontophorèse au nitroprussiate de sodium (SNP, un donneur d'oxyde nitrique) et par libération d'une interruption momentanée du flux artériel huméral (hyperémie réactive). Chez les sujets entraînés, l'effet de l'hyperémie réactive et de l'ACh n'ont pas montré de différence. Par contre, l'augmentation de la perfusion, suivant la iontophorèse de SNP, exprimé en unité de perfusion (PU), était plus importante chez les sujets entraînés que chez les sujets sédentaires (jeunes: 398±54 vs 350±87, p<0.05; âgés: 339±72 vs 307±66, p<0.05). Pour conclure, l'entraînement d'endurance augmente l'effet vasodilatateur de l'oxyde nitrique de la microcirculation cutanée humaine, au moins au niveau de la peau de l'avant-bras. Ces observations ont un intérêt physiologique considérable au vu des résultats d'études récentes qui montrent que le NO sert d'intermédiaire dans la vasodilatation cutanée produite par un stress thermique. Donc, l'augmentation de la bioactivité du NO dans la microcirculation cutanée pourrait être un des mécanismes par lequel l'entraînement physique modifierait le contrôle de la thermorégulation du flux sanguin cutané. Abstract Endurance training modifies the thermoregulatory control of skin blood flow, as manifested by a greater augmentation of skin perfusion for the same increase in core temperature in athletes, in comparison with se-dentary subjects. In this study, we tested the hypothesis that a component of this adaptation might reside in a higher ability of cutaneous blood vessels to respond to vasodilatory stimuli. We recruited healthy nonsmoking males, either endurance trained or sedentary, in two different age ranges (18-35 y and >50 y). Skin blood flow was measured in the forearm skin, using a laser Doppler imager, allowing to record the vasodilatory responses to the following stimuli: iontophoresis of acetylcholine (an endothelium-dependent vasodilator), iontophoresis of sodium nitroprusside (a nitric oxide donor), and release of a temporary interruption of arterial inflow (reactive hyperemia). There was no effect of training on reactive hyperemia or the response to acetylcholine. In contrast, the increase in perfusion following the iontophoresis of sodium nitroprusside, ex-pressed in perfusion units, was larger in trained than in sedentary subjects (younger: 398±54 vs 350±87, p<0.05; older 339±72 vs 307±66, p<0.05). In conclusion, endurance training enhances the vasodilatory effects of nitric oxide in the human dermal microcirculation, at least in forearm skin. These observations have considerable physiologic interest in view of recent data indicating that nitric oxide mediates in part the cutaneous vasodilation induced by heat stress in humans. Therefore, the augmentation of nitric oxide bioactivity in the dermal microcirculation might be one mechanism whereby endurance training modifies the thermoregulatory control of skin blood flow.

L-canavanine, an inhibitor of inducible nitric oxide synthase, improves venous return in endotoxemic rats.

OBJECTIVE: To investigate the hemodynamic effects of L-canavanine (an inhibitor of inducible, but not of constitutive, nitric oxide synthase) in endotoxic shock. DESIGN: Controlled, randomized, experimental study. SETTING: Animal laboratory. SUBJECTS: Wistar rats. INTERVENTIONS: Rats were anesthetized with pentobarbital, and hemodynamically monitored. One hour after an intravenous challenge with 5 mg/kg of Escherichia coli endotoxin, the rats were randomized to receive a continuous infusion of either L-canavanine (20 mg/kg/hr; n = 8) or vehicle only (isotonic saline, n = 11). In all animals, the infusion was given over 5 hrs at a rate of 2 mL/kg/hr. These experiments were repeated in additional rats challenged with isotonic saline instead of endotoxin (sham experiments). MEASUREMENTS AND MAIN RESULTS: Arterial blood pressure, heart rate, thermodilution cardiac output, central venous pressure, mean systemic filling pressure, urine output, arterial blood gases, blood lactate concentration, and hematocrit were measured. In sham experiments, hemodynamic stability was maintained throughout and L-canavanine had no detectable effect. Animals challenged with endotoxin and not treated with L-canavanine developed progressive hypotension and low cardiac output. After 6 hrs of endotoxemia, both central venous pressure and mean systemic filling pressure were significantly below their baseline values, indicating relative hypovolemia as the main determinant of reduced cardiac output. In endotoxemic animals treated with L-canavanine, hypotension was less marked, while cardiac output, central venous pressure, and mean systemic filling pressure were maintained throughout the experiment. L-canavanine had no effect on the time-course of hematocrit. L-canavanine significantly increased urine output and reduced the severity of lactic acidosis. CONCLUSIONS: Six hours after an endotoxin challenge in rats, low cardiac output develops, which appears to be primarily related to relative hypovolemia. L-canavanine, a selective inhibitor of the inducible nitric oxide synthase, increases the mean systemic filling pressure, thereby improving venous return, under these conditions.

Partial gene deletion of endothelial nitric oxide synthase predisposes to exaggerated high-fat diet-induced insulin resistance and arterial hypertension.

Nitric oxide (NO) plays a major role in the regulation of cardiovascular and metabolic homeostasis, as evidenced by insulin resistance and arterial hypertension in endothelial NO synthase (eNOS) null mice. Extrapolation of these findings to humans is difficult, however, because eNOS gene deficiency has not been reported. eNOS gene polymorphism and impaired NO synthesis, however, have been reported in several cardiovascular disease states and could predispose to insulin resistance. High-fat diet induces insulin resistance and arterial hypertension in normal mice. To test whether partial eNOS deficiency facilitates the development of insulin resistance and arterial hypertension during metabolic stress, we examined effects of an 8-week high-fat diet on insulin sensitivity (euglycemic clamp) and arterial pressure in eNOS(+/-) mice. When fed a normal diet, these mice had normal insulin sensitivity and were normotensive. When fed a high-fat diet, however, eNOS(+/-) mice developed exaggerated arterial hypertension and had fasting hyperinsulinemia and a 35% lower insulin-stimulated glucose utilization than control mice. The partial deletion of the eNOS gene does not alter insulin sensitivity or blood pressure in mice. When challenged with nutritional stress, however, partial eNOS deficiency facilitates the development of insulin resistance and arterial hypertension, providing further evidence for the importance of this gene in linking metabolic and cardiovascular disease.

Induced sputum versus exhaled nitric oxide for the evaluation of airway inflammation in allergic paediatric asthma patients treated with omalizumab

Our purpose is to determine the inflammatory changes in the airways of allergic paediatric asthma patients treated with omalizumab, measured by the percentage of eosinophils in induced sputum and exhaled nitric oxide (FENO). We observed a progressive and statistically significant decrease of eosinophil count in the induced sputum meanwhile FENO, although very sensible, was a less reproducible and thus a less reliable method to evaluate chronic airway inflammation in this population. Induced sputum seems to be a better method to monitor chronic inflammation and thus the response to chronic omalizumab treatment while FENO measurement would be more useful to monitor acute events preceding exacerbations.

Long-term swimming exercise does not modulate the Akt-dependent endothelial nitric oxide synthase phosphorylation in healthy mice.

Molecular mechanisms by which exercise exerts cardiovascular benefits are poorly understood. Exercise-induced increase of endothelial NO synthase (eNOS) phosphorylation through the protein kinase Akt has been shown to be a key mechanism underlying the beneficial effect of exercise in coronary artery disease patients. We examined whether this protective pathway might also be activated in long-term-exercised healthy mice. C57BL/6 wild-type mice swam for 24 weeks. A group of sedentary animals were used as controls. Aortic levels of total protein kinase Akt (protein kinase B), phosphorylated Akt at ser473 (p-Akt), total eNOS, phosphorylated eNOS at Ser1177 (p-eNOS), and PECAM-1 (platelet endothelial cell adhesion molecule-1) were assessed by Western blotting. Protein expressions of Akt, p-Akt, eNOS, p-eNOS, and PECAM-1 were not modulated by 24 weeks of exercise. The Akt-dependent eNOS phosphorylation did not seem to be a primary molecular adaptation in response to long-term exercise in healthy mice.

Nitric oxide mediates the blood pressure response to mental stress in humans.

OBJECTIVE: Nitric oxide (NO) regulates arterial pressure by modulating peripheral vascular tone and sympathetic vasoconstrictor outflow. NO synthesis is impaired in several major cardiovascular disease states. Loss of NO-induced vasodilator tone and restraint on sympathetic outflow could result in exaggerated pressor responses to mental stress. METHODS: We, therefore, compared the sympathetic (muscle sympathetic nerve activity) and haemodynamic responses to mental stress performed during saline infusion and systemic inhibition of NO-synthase by NG-monomethyl-L-arginine (L-NMMA) infusion. RESULTS: The major finding was that mental stress which during saline infusion increased sympathetic nerve activity by ~50 percent and mean arterial pressure by ~15 percent had no detectable sympathoexcitatory and pressor effect during L-NMMA infusion. These findings were not related to a generalised impairment of the haemodynamic and/or sympathetic responsiveness by L-NMMA, since the pressor and sympathetic nerve responses to immersion of the hand in ice water were preserved during L-NMMA infusion. CONCLUSION: Mental stress causes pressor and sympathoexcitatory effects in humans that are mediated by NO. These findings are consistent with the new concept that, in contrast to what has been generally assumed, under some circumstances, NO has a blood pressure raising action in vivo.

Nitric oxide activity through guanylate cyclase and phosphodiesterase modulation is impaired in fetal lambs with congenital diaphragmatic hernia.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is associated with pulmonary hypertension and death. Administration of nitric oxide (NO) alone remains ineffective in CDH cases. We investigated in near full-term lambs with and without CDH the role of guanylate cyclase (GC), the enzyme activated by NO in increasing cyclic 3'-5'-guanylosine monophosphate, and the role of phosphodiesterase (PDE) 5, the enzyme-degrading cyclic 3'-5'-guanylosine monophosphate. METHODS: Congenital diaphragmatic hernia was surgically created in fetal lambs at 85 days of gestation. Pulmonary hemodynamics were assessed by means of pressure and blood flow catheters (135 days). In vitro, we tested drugs on rings of isolated pulmonary vessels. RESULTS: In vivo, sodium nitroprusside, a direct NO donor, and methyl-2(4-aminophenyl)-1,2-dihydro-1-oxo-7-(2-pyridinylmethoxy)-4-(3,4,5 trimethoxyphenyl)-3-isoquinoline carboxylate sulfate (T-1032) and Zaprinast, both PDE 5 blockers, reduced pulmonary vascular resistance in CDH and non-CDH animals. The activation of GC by sodium nitroprusside and the inhibition of PDE 5 by T-1032 were less effective in CDH animals. In vitro, the stimulation of GC by 3(5'hydroxymethyl-2'furyl)-1-benzyl indazole (YC-1) (a benzyl indazole derivative) and the inhibition of PDE 5 by T-1032 were less effective in pulmonary vascular rings from CDH animals. The YC-1-induced vasodilation in rings from CDH animals was higher when associated with the PDE 5 inhibitor T-1032. CONCLUSIONS: Guanylate cyclase and PDE 5 play a role in controlling pulmonary vascular tone in fetal lambs with or without CDH. Both enzymes seem to be impaired in fetal lambs with CDH.

Ventricular but not atrial electro-mechanical delay of the embryonic heart is altered by anoxia-reoxygenation and improved by nitric oxide.

BACKGROUND/AIM: Excitation-contraction coupling is modulated by nitric oxide (NO) which otherwise has either beneficial or detrimental effects on myocardial function during hypoxia-reoxygenation. This work aimed at characterizing the variations of electromechanical delay (EMD) induced by anoxia-reoxygenation within the developing heart and determining whether atrial and ventricular EMD are modulated by NO to the same extent. METHODS: Hearts of 4 or 4.5-day-old chick embryos were excised and submitted in vitro to normoxia (45 min), anoxia (30 min) and reoxygenation (60 min). Electrocardiogram and atrial and ventricular contractions were simultaneously recorded throughout experiment. Anoxia-reoxygenation-induced chrono-, dromo-and inotropic disturbances and changes in EMD in atrium (EMDa) and ventricle (EMDv) were investigated in control hearts and in hearts exposed to 0.1, 1, 10, 50 and 100 microM of DETA-NONOate (a NO donating agent) or to 50 microM of L-NAME (a NOS inhibitor). RESULTS: Under normoxia, heart rate, PR interval, ventricular shortening velocity, EMDa and EMDv were similar in control, L-NAME-treated and DETA-NONOate-treated hearts. Under anoxia, cardiac activity became markedly erratic within less than 10 min in all groups. At the onset of reoxygenation, EMDv was increased by about 300% with respect to the preanoxic value while EMDa did not vary significatively. Compared to control conditions, L-NAME or DETA-NONOate had no influence on the negative chrono-, dromo- and inotropic effects induced by anoxia-reoxygenation. However, L-NAME prolonged EMDv during anoxia and delayed EMDv recovery during reoxygenation while 100 microM DETA-NONOate had the opposite effects. EMDa was neither affected by NOS inhibitor nor NO donor. At the end of reoxygenation, all the investigated parameters returned to their basal values. CONCLUSION: This work provides evidence that a NO-dependent pathway is involved in regulation of the ventricular excitation-contraction coupling in the anoxic-reoxygenated developing heart.

Defecto en la homeostasis del oxido nítrico. Mecanismo común subyacente de la insulino-resistencia, la hiperactividad simpática y la morbi-mortalidad cardiovascular [Defective nitric oxide homeostasis. Common underlying mechanism between insulin resistance, sympathetic overactivity and cardiovascular morbidity and mortality]

Obesity, insulin resistance and associated cardiovascular complications are reaching epidemic proportions worldwide and represent a major public health problem. Over the past decade, evidence has accumulated indicating that insulin administration, in addition to its metabolic effects, also has important cardiovascular actions. The sympathetic nervous system and the L-arginine-nitric oxide pathway are the central players in the mediation of insulin's cardiovascular actions. Based on recent animal and human research, we demonstrate that both defective and augmented NO synthesis represent a central defect triggering many of the metabolic, vascular and sympathetic abnormalities characteristic of insulin-resistant states. These observations provide the rationale for the use of pharmaceutical drugs releasing small and physiological amounts of NO and/or inhibitors of NO overproduction as a future treatment for insulin resistance and associated comorbidities.

Reduction of corneal edema in endotoxin-induced uveitis after application of L-NAME as nitric oxide synthase inhibitor in rats by iontophoresis.

PURPOSE: To investigate the involvement of the cornea during endotoxin-induced uveitis (EIU) in the rat and the effect of Ngamma-nitro-L-arginine methyl ester (L-NAME) as nitric oxide synthase (NOS) inhibitor, administered by iontophoresis. METHODS: EIU was induced in Lewis rats that were killed at 8 and 16 hours after lipopolysaccharide (LPS) injection. The severity of uveitis was evaluated clinically at 16 hours, and nitrite levels were evaluated in the aqueous humor at 8 hours. Corneal thickness was measured, 16 hours after LPS injection, on histologic sections using an image analyzer. Transmission electron microscopy (TEM) was used for fine analysis of the cornea. Transcorneoscleral iontophoresis of L-NAME (100 mM) was performed either at LPS injection or at 1 and 2 hours after LPS injection. RESULTS: At 16 hours after LPS injection, mean corneal thickness was 153.7+/-5.58 microm in the group of rats injected with LPS (n=8) compared with 126.89+/-11.11 microm in the saline-injected rats (n=8) (P < 0.01). TEM showed stromal edema and signs of damage in the endothelial and epithelial layers. In the group of rats treated by three successive iontophoreses of L-NAME (n=8), corneal thickness was 125.24+/-10.36 microm compared with 146.76+/-7.52 microm in the group of rats treated with iontophoresis of saline (n=8), (P=0.015). TEM observation showed a reduction of stromal edema and a normal endothelium. Nitrite levels in the aqueous humor were significantly reduced at 8 hours by L-NAME treatment (P=0.03). No effect on corneal edema was observed after a single iontophoresis of L-NAME at LPS injection (P=0.19). Iontophoresis of saline by itself induced no change in corneal thickness nor in TEM structure analysis compared with normal rats. CONCLUSIONS: Corneal edema is observed during EIU. This edema is significantly reduced by three successive iontophoreses of L-NAME, which partially inhibited the inflammation. A role of nitric oxide in the corneal endothelium functions may explain the antiedematous effect of L-NAME.

Both the Fas ligand and inducible nitric oxide synthase are needed for control of parasite replication within lesions in mice infected with Leishmania major whereas the contribution of tumor necrosis factor is minimal.

Following infection with the protozoan parasite Leishmania major, C57BL/6 mice develop a small lesion that heals spontaneously. Resistance to infection is associated with the development of CD4(+) Th1 cells producing gamma interferon (IFN-gamma) and tumor necrosis factor (TNF), which synergize in activating macrophages to their microbicidal state. We show here that C57BL/6 mice lacking both TNF and Fas ligand (FasL) (gld TNF(-/-) mice) infected with L. major neither resolved their lesions nor controlled Leishmania replication despite the development of a strong Th1 response. Comparable inducible nitric oxide synthase (iNOS) activities were detected in lesions of TNF(-/-), gld TNF(-/-), and gld mice, but only gld and gld TNF(-/-) mice failed to control parasite replication. Parasite numbers were high in gld mice and even more elevated in gld TNF(-/-) mice, suggesting that, in addition to iNOS, the Fas/FasL pathway is required for successful control of parasite replication and that TNF contributes only a small part to this process. Furthermore, FasL was shown to synergize with IFN-gamma for the induction of leishmanicidal activity within macrophages infected with L. major in vitro. Interestingly, TNF(-/-) mice maintained large lesion size throughout infection, despite being able to largely control parasite numbers. Thus, IFN-gamma, FasL, and iNOS appear to be essential for the complete control of parasite replication, while the contribution of TNF is more important in controlling inflammation at the site of parasite inoculation.

Pulmonary-artery pressure and exhaled nitric oxide in Bolivian and Caucasian high altitude dwellers.

There is evidence that high altitude populations may be better protected from hypoxic pulmonary hypertension than low altitude natives, but the underlying mechanism is incompletely understood. In Tibetans, increased pulmonary respiratory NO synthesis attenuates hypoxic pulmonary hypertension. It has been speculated that this mechanism may represent a generalized high altitude adaptation pattern, but direct evidence for this speculation is lacking. We therefore measured systolic pulmonary-artery pressure (Doppler chocardiography) and exhaled nitric oxide (NO) in 34 healthy, middle-aged Bolivian high altitude natives and in 34 age- and sex-matched, well-acclimatized Caucasian low altitude natives living at high altitude (3600 m). The mean+/-SD systolic right ventricular to right atrial pressure gradient (24.3+/-5.9 vs. 24.7+/-4.9 mmHg) and exhaled NO (19.2+/-7.2 vs. 22.5+/-9.5 ppb) were similar in Bolivians and Caucasians. There was no relationship between pulmonary-artery pressure and respiratory NO in the two groups. These findings provide no evidence that Bolivian high altitude natives are better protected from hypoxic pulmonary hypertension than Caucasian low altitude natives and suggest that attenuation of pulmonary hypertension by increased respiratory NO synthesis may not represent a universal adaptation pattern in highaltitude populations.

Local transient myocardial liposomal gene transfer of inducible nitric oxide synthase does not aggravate myocardial function and fibrosis and leads to moderate neovascularization in chronic myocardial ischemia in pigs.

Microcirculation (2010) 17, 69-78. doi: 10.1111/j.1549-8719.2010.00002.x Abstract Background: This study was designed to explore the effect of transient inducible nitric oxide synthase (iNOS) overexpression via cationic liposome-mediated gene transfer on cardiac function, fibrosis, and microvascular perfusion in a porcine model of chronic ischemia. Methods and Results: Chronic myocardial ischemia was induced using a minimally invasive model in 23 landrace pigs. Upon demonstration of heart failure, 10 animals were treated with liposome-mediated iNOS-gene-transfer by local intramyocardial injection and 13 animals received a sham procedure to serve as control. The efficacy of this iNOS-gene-transfer was demonstrated for up to 7 days by reverse transcriptase-polymerase chain reaction in preliminary studies. Four weeks after iNOS transfer, magnetic resonance imaging showed no effect of iNOS overexpression on cardiac contractility at rest and during dobutamine stress (resting ejection fraction: control 27%, iNOS 26%; P = ns). Late enhancement, infarct size, and the amount of fibrosis were similar between groups. Although perfusion and perfusion reserve in response to adenosine and dobutamine were not significantly modified by iNOS-transfer, both vessel number and diameter were significantly increased in the ischemic area in the iNOS-treated group versus control (point score: control 15.3, iNOS 34.7; P < 0.05). Conclusions: Our findings demonstrate that transient iNOS overexpression does not aggravate cardiac dysfunction or postischemic fibrosis, while potentially contributing to neovascularization in the chronically ischemic heart.

Respiratory nitric oxide and pulmonary artery pressure in children of aymara and European ancestry at high altitude.

Invasive studies suggest that healthy children living at high altitude display pulmonary hypertension, but the data to support this assumption are sparse. Nitric oxide (NO) synthesized by the respiratory epithelium regulates pulmonary artery pressure, and its synthesis was reported to be increased in Aymara high-altitude dwellers. We hypothesized that pulmonary artery pressure will be lower in Aymara children than in children of European ancestry at high altitude, and that this will be related to increased respiratory NO. We therefore compared pulmonary artery pressure and exhaled NO (a marker of respiratory epithelial NO synthesis) between large groups of healthy children of Aymara (n = 200; mean +/- SD age, 9.5 +/- 3.6 years) and European ancestry (n = 77) living at high altitude (3,600 to 4,000 m). We also studied a group of European children (n = 29) living at low altitude. The systolic right ventricular to right atrial pressure gradient in the Aymara children was normal, even though significantly higher than the gradient measured in European children at low altitude (22.5 +/- 6.1 mm Hg vs 17.7 +/- 3.1 mm Hg, p < 0.001). In children of European ancestry studied at high altitude, the pressure gradient was 33% higher than in the Aymara children (30.0 +/- 5.3 mm Hg vs 22.5 +/- 6.1 mm Hg, p < 0.0001). In contrast to what was expected, exhaled NO tended to be lower in Aymara children than in European children living at the same altitude (12.4 +/- 8.8 parts per billion [ppb] vs 16.1 +/- 11.1 ppb, p = 0.06) and was not related to pulmonary artery pressure in either group. Aymara children are protected from hypoxic pulmonary hypertension at high altitude. This protection does not appear to be related to increased respiratory NO synthesis.