Effects of monocrotaline on endothelial nitric oxide synthase expression and sulfhydryl levels in rat lungs

The nitric oxide-cyclic guanosine monophosphate signal-transduction mechanism plays a key role in the regulation of vascular tone and structure. Monocrotaline-induced pulmonary hypertension is associated with low bioavailability of nitric oxide. To characterize the mechanism(s) involved in this dysfunction, rats received a single subcutaneous injection of monocrotaline, normal saline (control), or monocrotaline plus daily L-arginine, a precursor of nitric oxide, in drinking water. Pulmonary artery pressure and right ventricular hypertrophy were assessed 2 weeks later. In addition, the authors evaluated the expression of endothelial nitric oxide synthase messenger RNA, endothelial nitric oxide synthase protein, cyclic guanosine monophosphate, and sulfhydryl levels in the lungs. Sulfhydryls are needed for the dynamic modulation of soluble guanylate cyclase by nitric oxide, which results in cyclic guanosine monophosphate formation. L-arginine treatment did not attenuate monocrotaline-induced pulmonary hypertension or right ventricular hypertrophy. Monocrotaline did not alter the expression of endothelial nitric oxide synthase messenger RNA or endothelial nitric oxide synthase protein in the lungs. Protein-bound sulfhydryls (28 +/- 5 vs. 75 +/- 16 pmol/microg protein) and cyclic guanosine monophosphate (0.63 +/- 0.05 vs. 1.06 +/- 0.017 pmol/microg protein) levels in the monocrotaline group were significantly low compared with controls. The low sulfhydryl levels, an indicator of oxidant stress, may account for the impaired availability of bioactive nitric oxide and low cyclic guanosine monophosphate levels. These results suggest that oxidative stress may, in part, contribute to the pathogenesis of pulmonary hypertension in the monocrotaline model.     

Multimodal imaging in the congenital pulmonary lymphangiectasia-congenital chylothorax-hydrops fetalis continuum

We report on three infants with congenital chylothorax (CC) and congenital pulmonary lymphangiectasia (CPL). CPL appears to be a characteristic pathological finding in CC. Through the use of lymphoscintigraphy and computed tomography, this study suggests that CC and CPL are strongly correlated entities and that the dysplasia of the lymphatic system results in a pulmonary lymphatic obstruction sequence. The initial microscopic dilatation of the lymph channels may lead to progressive weeping of lymphatics and, consequently, to pleural effusion. Non-Immune Hydrops Fetalis (NIHF) may be the final consequence of impaired systemic venous return and may help to explain pleural-pulmonary involvement in this generalized lymph-vessel malformation syndrome.     

Impaired lymphatic contraction associated with immunosuppression

To trigger an effective immune response, antigen and antigen-presenting cells travel to the lymph nodes via collecting lymphatic vessels. However, our understanding of the regulation of collecting lymphatic vessel function and lymph transport is limited. To dissect the molecular control of lymphatic function, we developed a unique mouse model that allows intravital imaging of autonomous lymphatic vessel contraction. Using this method, we demonstrated that endothelial nitric oxide synthase (eNOS) in lymphatic endothelial cells is required for robust lymphatic contractions under physiological conditions. By contrast, under inflammatory conditions, inducible NOS (iNOS)-expressing CD11b(+)Gr-1(+) cells attenuate lymphatic contraction. This inhibition of lymphatic contraction was associated with a reduction in the response to antigen in a model of immune-induced multiple sclerosis. These results suggest the suppression of lymphatic function by the CD11b(+)Gr-1(+) cells as a potential mechanism of self-protection from autoreactive responses during on-going inflammation. The central role for nitric oxide also suggests that other diseases such as cancer and infection may also mediate lymphatic contraction and thus immune response. Our unique method allows the study of lymphatic function and its molecular regulation during inflammation, lymphedema, and lymphatic metastasis.     

Chronic liver injury alters basal and stimulated nitric oxide production and 3H-thymidine incorporation in cultured sinusoidal endothelial cells from rats.

BACKGROUND/AIM: Under pathological conditions the nitric oxide synthase (NOS)-mediated nitric oxide production of sinusoidal endothelial cells might be altered. Therefore, studies were performed to evaluate the nitrite formation by cultured sinusoidal endothelial cells from rat livers chronically injured by thioacetamide and the effect of endogenously or exogenously generated nitric oxide on their proliferative activity. METHODS: Basal and stimulated nitrite formation, expression of NOS and DNA synthesis were examined in sinusoidal endothelial cells isolated and cultivated from livers with incipient or advanced chemically-induced cirrhosis. RESULTS: Cultured sinusoidal endothelial cells from injured livers exhibited a reduced basal and an increased lipopolysaccharide-stimulated nitrite production when compared with controls. Western blot analysis revealed a markedly reduced protein expression of endothelial NOS (eNOS) and inducible NOS (iNOS) in sinusoidal endothelial cells from both experimental groups when compared with controls. Lipopolysaccharide stimulated iNOS expression in sinusoidal endothelial cells from control livers only marginally, and from those with cirrhosis more strongly. There was no clear correlation between the amount of enzyme and nitrite formation. Cultured sinusoidal endothelial cells from livers with incipient cirrhosis showed a higher proliferative activity than controls. Endogenously-produced nitric oxide inhibited DNA synthesis in all groups in a cGMP-independent way. Exogenously-generated nitric oxide affected DNA synthesis differently in sinusoidal endothelial cells from controls and injured livers. CONCLUSION: The results provide evidence that cultured sinusoidal endothelial cells from controls and livers with incipient or advanced cirrhosis differ with respect to basal and lipopolysaccharide-stimulated nitrite production. The data can be taken as evidence that in sinusoidal endothelial cells from livers chronically injured by thioacetamide, eNOS and iNOS are aberrantly expressed and differently regulated.     

Analysis of pulmonary heme oxygenase-1 and nitric oxide synthase alterations in experimental hepatopulmonary syndrome

BACKGROUND & AIMS: Cirrhosis and portal hypertension due to chronic common bile duct ligation reproduce the features of human hepatopulmonary syndrome, whereas portal hypertension alone due to partial portal vein ligation does not. Nitric oxide contributes to experimental hepatopulmonary syndrome, but the nitric oxide synthase forms involved remain controversial. Recently, increased pulmonary heme oxygenase-1 expression and carbon monoxide production have also been found after common bile duct ligation. Our aim was to explore the role of the heme oxygenase-1/carbon monoxide pathway in the pathogenesis of experimental hepatopulmonary syndrome. METHODS: Pulmonary heme oxygenase-1 expression and distribution were assessed in sham; 3-week partial portal vein ligation; and 1-, 2-, 3-, 4-, and 5-week common bile duct ligation animals by Northern, Western and immunohistochemical analysis relative to endothelial and inducible nitric oxide synthase levels and to hepatopulmonary syndrome development. In vivo heme oxygenase enzyme inhibition with tin protoporphyrin IX in common bile duct ligation animals was used to define effects on intrapulmonary vasodilatation and arterial blood gases. RESULTS: Heme oxygenase-1 expression in pulmonary intravascular monocytes/macrophages and arterial carboxyhemoglobin levels increased progressively from 3 to 5 weeks after common bile duct ligation relative to controls (5-week protein levels were 15.94 +/- 1.75-fold those of sham animals; P < 0.001). Inducible nitric oxide synthase increased transiently in pulmonary intravascular monocytes/macrophages in 3-week common bile duct ligation animals, whereas pulmonary microvascular endothelial nitric oxide synthase increases began at 2 weeks and correlated with the onset of hepatopulmonary syndrome. Tin protoporphyrin treatment normalized carboxyhemoglobin and improved arterial blood gases and intrapulmonary vasodilatation, reflecting partial reversal of hepatopulmonary syndrome. CONCLUSIONS: The heme oxygenase-1/carbon monoxide system is an important contributor to the progression of experimental hepatopulmonary syndrome in addition to alterations in the endothelial nitric oxide synthase/nitric oxide pathway.     

The role of endothelin-1 and the endothelin B receptor in the pathogenesis of hepatopulmonary syndrome in the rat

Endothelin-1 (ET-1) stimulation of endothelial nitric oxide synthase (eNOS) via pulmonary endothelial endothelin B (ET(B)) receptors and pulmonary intravascular macrophage accumulation with expression of inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) are implicated in experimental hepatopulmonary syndrome (HPS) after common bile duct ligation (CBDL). Our aim was to evaluate the role of ET-1 in the development of experimental HPS. The time course of molecular and physiological changes of HPS and the effects of selective endothelin receptor antagonists in vivo were assessed after CBDL. Effects of ET-1 on intralobar pulmonary vascular segment reactivity and on eNOS expression and activity in rat pulmonary microvascular endothelial cells (RPMVECs) were also evaluated. Hepatic and plasma ET-1 levels increased 1 week after CBDL in association with a subsequent increase in pulmonary microvascular eNOS and ET(B) receptor levels and the onset of HPS. Selective ET(B) receptor inhibition in vivo significantly decreased pulmonary eNOS and ET(B) receptor levels and ameliorated HPS. CBDL pulmonary artery segments had markedly increased ET(B) receptor mediated, nitric oxide dependent vasodilatory responses to ET-1 compared with controls and ET-1 triggered an ET(B) receptor dependent stimulation of eNOS in RPMVECs. Pulmonary intravascular macrophages also accumulated after CBDL and expressed HO-1 and iNOS at 3 weeks. Selective ET(B) receptor blockade also decreased macrophage accumulation and iNOS production. In conclusion, ET-1 plays a central role in modulating pulmonary micovascular tone in experimental HPS.     

Endothelial nitric oxide synthase variants in cystic fibrosis lung disease

Variants in the genes encoding for the nitric oxide synthases may act as disease modifier loci in cystic fibrosis, affecting both an individual's nitric oxide level and pulmonary function. In this study, the 894G/T variant in exon 7 of the endothelial nitric oxide synthase gene was related to exhaled nitric oxide and pulmonary function in 70 cystic fibrosis patients who were aged 14.8 +/- 6.9 years (mean +/- SD), with a FEV1 of 69.4 +/- 24.8% predicted. Although there was no association between endothelial nitric oxide synthase genotypes and exhaled nitric oxide in males, nitric oxide levels were significantly higher in female cystic fibrosis patients with an 894T mutant allele, compared with female patients homozygous for the 894G wild-type allele (7.0 +/- 4.4 versus 3.6 +/- 1.9 parts per billion, p = 0.02). Furthermore, in female patients, colonization of airways with Pseudomonas aeruginosa was significantly (p < 0.05) less frequent when carrying an 894T mutant allele as compared with wild type. These data suggest that the 894T variant in the endothelial nitric oxide synthase gene is associated with increased airway nitric oxide formation in female cystic fibrosis patients, possibly affecting colonization of airways with P. aeruginosa.     

Effects of mitral regurgitation on the reflex diuresis to pulmonary lymphatic obstruction in rabbits

Increasing the extravascular fluid of the airways acutely by obstructing pulmonary lymph drainage causes a reflex diuresis mediated by neuronal nitric oxide synthase in the renal medulla. The authors examined this reflex in rabbits with a chronic increase in extravascular fluid of the airways resulting from surgically induced mitral regurgitation. Intact rabbits served as controls. Renal neuronal (nNOS) and endothelial (eNOS) nitric oxide synthase expressions were also examined. The reflex was absent in rabbits with mitral regurgitation. There were significant increases in medullary and cortical nNOS mRNA compared to controls. The observed changes in mRNA levels correlated with nNOS protein levels. eNOS mRNA was unaffected.     

Inhibiting long chain fatty Acyl CoA synthetase increases basal and agonist-stimulated NO synthesis in endothelium

OBJECTIVES: Endothelial nitric oxide synthase (eNOS) activation/deactivation is associated with cyclic depalmitoylation/repalmitoylation of specific Cys residues. The mechanism of depalmitoylation has been identified recently, but repalmitoylation remains undefined. We hypothesized that long chain fatty acyl CoA synthetase (LCFACoAS) modulates endothelial nitric oxide synthase repalmitoylation by limiting palmitoyl CoA availability. METHODS: Human coronary endothelial cells were treated with triacsin-C, an inhibitor of long chain fatty acyl CoA synthetase, for 24 h. Media nitrite accumulation, eNOS activity, and eNOS palmitoylation were measured. Methacholine-induced NO synthesis or vascular relaxation were measured in endothelium-intact rat aortae in the presence and absence of triacsin-C. RESULTS: Triacsin-C significantly reduced incorporation of [3H] palmitate into immunoreactive endothelial nitric oxide synthase and over a concentration range of 0.1 to 10 microM, increased media nitrite accumulations 2- to 2.5-fold over baseline. Total in vitro catalytic activity of nitric oxide synthase in triacsin-C treated cells did not differ significantly from control. Triacsin-C significantly increased methacholine-induced NO synthesis in the isolated rat aorta, and significantly enhanced methacholine-induced relaxation of rat aortic rings. CONCLUSIONS: These data are consistent with the interpretation that inhibition of palmitoylation increases endothelial nitric oxide synthase activity without changing endothelial nitric oxide synthase expression, suggesting that inhibiting palmitoylation increases the catalytically active fraction of endothelial nitric oxide synthase.     

Simvastatin inhibits cigarette smoking-induced emphysema and pulmonary hypertension in rat lungs

RATIONALE: In cigarette smoking-induced chronic obstructive pulmonary disease, structural and functional derangements are characterized by parenchymal destruction and pulmonary hypertension. Statins are 3-hydroxy-3-methyl-glutaryl-coenzyme-A reductase inhibitors that have been used as lipid-lowering agents. These drugs also have additional pharmacologic properties, including antiinflammation, scavenging reactive oxygen species, restoring endothelial function, and antithrombogenesis, all of which can counteract the harmful effects of cigarette smoking. OBJECTIVE: We performed assays to determine whether simvastatin could attenuate lung damage induced by chronic cigarette smoking in rats. METHODS: In Sprague-Dawley rats exposed to cigarette smoke for 16 weeks, morphologic changes in the lungs and pulmonary arterial pressure were examined. MAIN RESULTS: Simvastatin inhibited lung parenchymal destruction and development of pulmonary hypertension, and also inhibited peribronchial and perivascular infiltration of inflammatory cells and induction of matrix metalloproteinase-9 activity in lung tissue. Simvastatin additionally prevented pulmonary vascular remodeling and the changes in endothelial nitric oxide synthase expression induced by smoking. In human lung microvascular endothelial cells, simvastatin increased expression of endothelial nitric oxide synthase mRNA. CONCLUSIONS: Simvastatin ameliorated the structural and functional derangements of the lungs caused by cigarette smoking, partly by suppressing inflammation and matrix metalloproteinase-9 induction and preventing pulmonary vascular abnormality. These findings indicate that statins may play a role in the treatment of cigarette smoking-induced chronic obstructive pulmonary disease.     

Differential expression of pulmonary nitric oxide synthase isoforms after intestinal ischemia-reperfusion

BACKGROUND/AIMS: Nitric oxide has been implicated in both attenuating and aggravating ischemia-reperfusion injury in most organs. This study aimed to investigate the role of nitric oxide produced by the two principal isoforms of nitric oxide synthase in the lung during post-ischemic reperfusion of the intestine. METHODOLOGY: Rats were randomized into four groups of 6 animals: Group A: laparotomy and superior mesenteric artery dissection without occlusion and maintenance for 2 h (control group at 2 h). Group B: laparatomy and superior mesenteric artery occlusion for 30 min and reperfusion of the intestine for 2 h (ischemia-reperfusion group at 2 h). Group C: control animals at 6 h. Group D: ischemia-reperfusion animals at 6 h. Arterial blood pressure was monitored throughout the procedure. Animals were euthanazed at the end of the experiment, and lungs were harvested for histological assessment of injury and for immunohistochemical examination of nitric oxide synthase isoforms and nitrotyrosine. RESULTS: In all animals subjected to intestinal ischemia a period of systemic hypotension occurred immediately upon reperfusion. Histological evidence of lung injury was limited to those animals subjected to an intestinal reperfusion insult. Compared to control animals, pulmonary endothelial nitric oxide synthase expression was diminished at 2 h (p = 0.002), while expression of inducible nitric oxide synthase (p = 0.002) and nitrotyrosine (p = 0.02) was increased at 6 h. CONCLUSIONS: Following intestinal ischemia-reperfusion, early pulmonary damage is associated with decreased endothelial nitric oxide synthase expression in the lung. Expression of inducible nitric oxide synthase occurs during the later stages of reperfusion; this leads to overproduction of nitric oxide with consequent nitrosylation of protein tyrosine residues and thus aggravated pulmonary injury.     

Enhanced blood pressure variability in eNOS knockout mice.

It has been shown previously that endogenous nitric oxide can buffer arterial blood pressure variability in dogs and rats. In these former studies, all isoforms of the nitric oxide synthase were blocked pharmacologically and an increased blood pressure variability was observed. Thus the question as to which isoform of the nitric oxide synthase is responsible for the blood pressure buffering effect of endogenous nitric oxide remains unraveled. In the present study, we therefore compared blood pressure variability in knockout mice that lack specifically the gene for endothelial nitric oxide synthase with their respective wild-type controls. One day after carotid artery cannulation, blood pressure was recorded in these conscious mice. During resting conditions, blood pressure variability was markedly enhanced in knockout mice compared with wild-type mice (10.5+/-1.5 mm Hg2 vs 6.0+/-0.8 mm Hg2, P<0.05). Power spectral analysis revealed that this increase in blood pressure variability is manifested at low frequencies that range from 0.05 to 0.40 s-1 (Hz) (5.1+/-1.0 mm Hg2 vs 2.5+/-0.5 mm Hg2, P<0.05). On the basis of these results, we conclude that the blood pressure buffering effect of endogenous nitric oxide is mediated by the endothelial isoform of the nitric oxide synthase. In addition, endothelial nitric oxide is most effective in buffering blood pressure oscillations at frequencies that range from 0.05 to 0.40 s-1 (Hz) in conscious mice.     

Lipopolysaccharide and interleukin 1 augment the effects of hypoxia and inflammation in human pulmonary arterial tissue.

The combined effects of hypoxia and interleukin 1, lipopolysaccharide, or tumor necrosis factor alpha on the expression of genes encoding endothelial constitutive and inducible nitric oxide synthases, endothelin 1, interleukin 6, and interleukin 8 were investigated in human primary pulmonary endothelial cells and whole pulmonary artery organoid cultures. Hypoxia decreased the expression of constitutive endothelial nitric oxide synthase (NOS-3) mRNA and NOS-3 protein as compared with normoxic conditions. The inhibition of expression of NOS-3 corresponded with a reduced production of NO. A combination of hypoxia with bacterial lipopolysaccharide, interleukin 1 beta, or tumor necrosis factor alpha augmented both effects. In contrast, the combination of hypoxia and the inflammatory mediators superinduced the expression of endothelin 1, interleukin 6, and interleukin 8. Here, we have shown that inflammatory mediators aggravate the effect of hypoxia on the down-regulation of NOS-3 and increase the expression of proinflammatory cytokines in human pulmonary endothelial cells and whole pulmonary artery organoid cultures.     

Genistein, a phytoestrogen, attenuates monocrotaline-induced pulmonary hypertension

BACKGROUND: Pulmonary hypertension is characterized by high pulmonary blood pressure, vascular remodeling, and right ventricular hypertrophy. Although recent studies suggest that an imbalance between endothelial mediators on pulmonary vasculature may contribute to the development of pulmonary hypertension, the pathogenesis is not fully understood and the treatment of pulmonary hypertension is still unresolved. OBJECTIVE: The purpose of this study was to investigate whether genistein, a phytoestrogen derived from soybean, would prevent the development of monocrotaline (MCT)-induced pulmonary hypertension in rats. Hemodynamic parameters of catheterized rats and morphological feature of lungs were evaluated among MCT-treated rats receiving or not receiving genistein. Furthermore, examination of expression in endothelial nitric oxide synthase and endothelin-1 peptide level was performed. METHODS: Daily supplementation with either genistein (0.2 mg/kg) or vehicle was started 2 days prior to a single-dose injection of MCT (60 mg/kg). On day 28, rats underwent catheterization, and right ventricular hypertrophy and morphological features were assessed. Furthermore, endothelial nitric oxide synthase and endothelin-1 were examined by Western blot analysis and radioimmunoassay, respectively, in homogenated lungs. RESULTS: In rats that received daily supplementation of genistein, mean pulmonary arterial pressure was significantly reduced, whereas mean systemic arterial pressure and heart rate were unaltered compared with MCT control rats on day 28 after MCT injection. Right ventricular hypertrophy, medial wall thickness of pulmonary arteries corresponding to the terminal bronchioles, and the degree of neo-muscularization of more distal arteries were less severe in genistein-treated rats. Genistein supplementation improved MCT-induced downregulation of expression of endothelial nitric oxide synthase in the lungs. However, endothelin-1 peptide levels did not differ among all groups of lungs. CONCLUSIONS: We conclude that daily supplementation of genistein potently attenuates MCT-induced pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular remodeling in rats. The underlying mechanism responsible for this effect may be partly related to the restoration of a decreased expression of endothelial nitric oxide synthase.     

The effects of hypoxia on the cells of the pulmonary vasculature.

Pulmonary hypertension is associated with remodelling of pulmonary vessels. Chronic hypoxia is a common cause of pulmonary hypertension and pulmonary vascular remodelling. Vascular remodelling is characterised largely by fibroblast, smooth muscle and endothelial cell proliferation, which results in lumen obliteration. Chronic hypoxia elicits expression of mitogens, growth factors and cytokines by fibroblasts and endothelial cells, and also the suppression of endothelial nitric oxide synthase. Although hypoxic pulmonary vascular remodelling is associated with medial hypertrophy, many in vitro studies have found that hypoxia does not lead to a direct increase in smooth muscle cell proliferation. This paradox is not well understood and this review aims to examine the various reasons why this might be so. The present authors reviewed data from in vitro studies and also considered whether hypoxia could act on adjacent cells such as fibroblasts and endothelial cells to trigger smooth muscle cell proliferation. It is possible that hypoxia is sensed by fibroblasts, endothelial cells, or both, and relayed to adjacent pulmonary artery smooth muscle cells by intercellular signalling, causing proliferation. The present article reviews the data from in vitro studies of hypoxia on the three cellular components of the pulmonary vascular wall, namely endothelial cells, smooth muscle cells and fibroblasts.     

Variation of endothelial nitric oxide synthase synthesis in the median eminence during the rat estrous cycle: an additional argument for the implication of vascular blood vessel in the control of GnRH release

Recent studies from our laboratory suggested that the vascular endothelium of the median eminence was involved via nitric oxide secretion in the modulation of GnRH release during the estrous cycle. To further investigate that issue, we studied the variations of endothelial nitric oxide synthase protein and mRNA in the median eminence of female rats killed at different time points of the day and/or of the estrous cycle. Endothelial nitric oxide synthase protein levels were measured by Western blot, and endothelial nitric oxide synthase mRNA analysis was performed with semiquantitative RT-PCR (for each time point, n = 4). The results revealed that endothelial nitric oxide synthase synthesis varied markedly across the estrous cycle. Indeed, endothelial nitric oxide synthase protein (n = 20) and mRNA (n = 16) levels increase significantly on 0800 h and 1600 h proestrus compared with 1400 h diestrus II. In a second step, quantification analysis were made in median eminence obtained from ovariectomized and ovariectomized, E2 benzoate primed rat. The results show a significant increase in expression of endothelial nitric oxide synthase protein as well as endothelial nitric oxide synthase mRNA in ovx-E2 primed rat median eminence. Concurrently, the levels of the cav-1 protein, a specific endogenous inhibitor of endothelial nitric oxide synthase, were measured in median eminence during estrous cycle and in ME from ovx and ovx-E2 primed rats. A significant decrease of median eminence cav-1 was noted on 1600 h proestrus and in ovx-E2 primed rats when compared with 1400 h diestrus II and ovx, respectively. Altogether, these results strongly suggest that high NO release from median eminence observed on proestrus may be due to an increase of endothelial nitric oxide synthase expression and a decrease of the cav-1 protein levels. These findings demonstrate that E2 is able to modulate endothelial nitric oxide synthase and cav-1 expression both during the estrous cycle and in experimental conditions and consequently reinforce the idea that nitric oxide acting on GnRH release, is essentially endothelial in origin. These results may also imply that variations of endothelial nitric oxide synthase expression are essential for the pulsatile/cyclic nitric oxide median eminence release observed in a previous study.     

Increased eNO and pulmonary iNOS expression in eNOS null mice.

Nitric oxide (NO) is a major regulatory molecule of the cardiovascular system; however, measurement of vascular NO synthesis in vivo represents a major challenge. NO stemming from the lower respiratory tract has been used as a marker of vascular endothelial function. Experimental evidence for this concept is lacking. Therefore, the aim of the present study was to investigate this relationship. Lower respiratory tract exhaled NO concentration, together with systemic and pulmonary artery pressure, was measured in endothelial nitric oxide synthase (NOS) (eNOS) null mice (eNOS-/-). Similar studies were performed in inducible NOS (iNOS) null mice (iNOS-/-). Defective endothelial NO synthesis in eNOS-/- mice (evidenced by systemic and pulmonary hypertension) was associated with augmented exhaled NO levels (12.5 +/- 1.9 versus 9.8 +/- 1.2 parts per billion (ppb), eNOS-/- versus wild type), whereas normal endothelial NO synthesis in iNOS-/- mice was associated with decreased exhaled NO levels (4.3 +/- 1.5 ppb). Augmented exhaled NO levels in eNOS-/- mice were associated with upregulation of iNOS expression in the lung. These results indicate that inducible nitric oxide synthase is a major determinant of gaseous nitric oxide production in the lung, and lower respiratory tract exhaled nitric oxide does not always represent a marker of vascular endothelial nitric oxide synthesis.     

Pulmonary lymphangiectasis in an asymptomatic adult

Pulmonary lymphangiectasis is a rare anomaly in infancy that is characterized by dilatation of pulmonary lymphatic vessels resulting in fetal respiratory distress. Pulmonary lymphangiectasis is considered to occur exclusively in young children and neonates, and very few survive beyond an early age. We herein present an asymptomatic adult case of localized pulmonary lymphangiectasis with multiple nodules. A 27-year-old asymptomatic female presented with multiple nodules on chest computed tomogram images. An exploratory video-assisted thoracoscopy revealed multiple yellowish cysts on the visceral pleura, which were histologically diagnosed as lymphangiectasis. In the present study, the pathogenesis and clinical characteristics are discussed.     

Low NO bioavailability in CCl<Subscript>4</Subscript>cirrhotic rat livers might result from low NO synthesis combined with decreased superoxide dismutase activity allowing superoxide-mediated NO breakdown: A comparison of two portal hypertensive rat models with healthy controls

Background  

In cirrhotic livers, the balance of vasoactive substances is in favour of vasoconstrictors with relatively insufficient nitric oxide. Endothelial dysfunction has been documented in cirrhotic rat livers leading to a lower activity of endothelial nitric oxide synthase but this might not be sufficient to explain the low nitric oxide presence. We compared the amount of all nitric oxide synthase isoforms and other factors that influence nitric oxide bioavailability in livers of two portal hypertensive rat models: prehepatic portal hypertension and carbon tetrachloride induced cirrhosis, in comparison with healthy controls.     

Increased vascular expression of iNOS at day but not at night in asthmatic subjects with increased nocturnal airway obstruction.

Nitric oxide production by endothelial cells may have important consequences for the development of airway inflammation as well as for airway obstruction. The present study investigated whether the expression of vascular inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) in human bronchi differs between asthmatic and healthy subjects, and whether it shows a circadian rhythm, especially in subjects with increased nocturnal airway obstruction. Bronchial biopsy samples were taken at 16:00 and 04:00 h from 13 healthy and 25 asthmatic subjects, 18-45 yrs. Biopsy samples were snap-frozen and double-immunostained for iNOS and eNOS in combination with a common vascular antigen (CD31). The degree of immunopositivity was expressed as a percentage of CD31-positive vessels encountered in complete biopsy sections. Asthmatic subjects showed greater iNOS expression than healthy controls: 23+/-15 versus 7+/-17% (mean+/-SD) at 16:00 h (p<0.001) and 19+/-15 versus 8+/-11% at 04:00 h (p<0.05). Asthmatic subjects with a fall in forced expiratory volume in one second of >10% of the predicted value between 16:00 and 04:00 h showed greater iNOS expression at 16:00 than at 04:00 h: 32+/-16 versus 20+/-13% (p<0.05). eNOS expression did not differ between healthy controls and asthmatic patients, nor did it differ between 16:00 and 04:00 h. It is suggested that asthmatic subjects with increased nocturnal airway obstruction demonstrate increased activation of inducible nitric oxide synthase during the day. The resulting nitric oxide production might protect against airway obstruction during the day. However, at night, nitric oxide production is probably insufficient to counterbalance the bronchoconstricting forces.