PubMed Health⌕ Search

Biomedical subjects

B Gaston

Publications and source records attributed to B Gaston.

At least 19 recordsLinked to original sources
PubMed2001

S-nitrosothiols signal the ventilatory response to hypoxia.

Increased ventilation in response to hypoxia has been appreciated for over a century, but the biochemistry underlying this response remains poorly understood. Here we define a pathway in which increased minute ventilation (&Vdot;E ) is signalled by deoxyhaemoglobin-derived S-nitrosothiols (SNOs). Specifically, we demonstrate that S-nitrosocysteinyl glycine (CGSNO) and S-nitroso-l-cysteine (l-CSNO)-but not S-nitroso-d-cysteine (d-CSNO)-reproduce the ventilatory effects of hypoxia at the level of the nucleus tractus solitarius (NTS). We show that plasma from deoxygenated, but not from oxygenated, blood produces the ventilatory effect of both SNOs and hypoxia. Further, this activity is mediated by S-nitrosoglutathione (GSNO), and GSNO activation by gamma-glutamyl transpeptidase (gamma-GT) is required. The normal response to hypoxia is impaired in a knockout mouse lacking gamma-GT. These observations suggest that S-nitrosothiol biochemistry is of central importance to the regulation of breathing.

Animals↗
PubMed2001

S-Nitrosylation of mitochondrial caspases.

Caspase-3 is a cysteine protease located in both the cytoplasm and mitochondrial intermembrane space that is a central effector of many apoptotic pathways. In resting cells, a subset of caspase-3 zymogens is S-nitrosylated at the active site cysteine, inhibiting enzyme activity. During Fas-induced apoptosis, caspases are denitrosylated, allowing the catalytic site to function. In the current studies, we sought to identify the subpopulation of caspases that is regulated by S-nitrosylation. We report that the majority of mitochondrial, but not cytoplasmic, caspase-3 zymogens contain this inhibitory modification. In addition, the majority of mitochondrial caspase-9 is S-nitrosylated. These studies suggest that S-nitrosylation plays an important role in regulating mitochondrial caspase function and that the S-nitrosylation state of a given protein depends on its subcellular localization.

Caspase 3↗
PubMed2001

Accelerated s-nitrosothiol breakdown by amyotrophic lateral sclerosis mutant copper,zinc-superoxide dismutase.

Mutations in copper,zinc-superoxide dismutase (SOD) have been implicated in familial amyotrophic lateral sclerosis (FALS). We have investigated the breakdown of S-nitrosothiols by wild-type (WT) SOD and two common FALS mutants, alanine-4 valine (A4V) SOD and glycine-37 arginine (G37R) SOD. In the presence of glutathione, A4V SOD and G37R SOD catalyzed S-nitrosoglutathione breakdown three times more efficiently than WT SOD. Indeed, A4V SOD catabolized GSNO more efficiently than WT SOD throughout the physiological range of GSH concentrations. Moreover, a variety of additional S-nitrosothiols were catabolized more readily by A4V SOD than by WT SOD. Initial rate data for fully reduced WT SOD and A4V SOD, and data using ascorbic acid as the reductant, suggest that FALS mutations in SOD may influence the efficiency of reduction of the copper center by glutathione. We have identified a potentially toxic gain of function of two common FALS mutations that may contribute to neurodegeneration in FALS.

Amyotrophic Lateral Sclerosis↗
PubMed2001

S-nitrosoglutathione increases cystic fibrosis transmembrane regulator maturation.

Endogenous S-nitrosoglutathione (GSNO) is known to increase the expression of certain proteins at concentrations present in the normal human airway. We hypothesized that GSNO would increase expression and maturation of the cystic fibrosis transmembrane conductance regulator (CFTR). Cells expressing DeltaF508 and wild type CFTR were exposed to GSNO and analyzed for expression and maturation by Western blot analysis. Physiologically relevant concentrations of GSNO resulted in dose- and time-dependent increases in expression. The GSNO-induced increases were eliminated by cycloheximide, suggesting a posttranscriptional effect. Unlike proteasome inhibitors, GSNO resulted in an increase CFTR maturation. The GSNO effect could be reversed by dithiothreitol and inhibited by acivicin, a gamma glutamyl transpeptidase inhibitor. These observations suggest that GSNO leads to maturation of mutated DeltaF508 CFTR, a process associated with restoration of CFTR function. Because endogenous levels of GSNO are low in the cystic fibrosis (CF) airway, these results raise the possibility that GSNO replacement therapy could be an effective treatment for CF.

Animals↗
PubMed2001

NO chemical events in the human airway during the immediate and late antigen-induced asthmatic response.

A wealth of evidence supports increased NO (NO.) in asthma, but its roles are unknown. To investigate how NO participates in inflammatory airway events in asthma, we measured NO. and NO. chemical reaction products [nitrite, nitrate, S-nitrosothiols (SNO), and nitrotyrosine] before, immediately and 48 h after bronchoscopic antigen (Ag) challenge of the peripheral airways in atopic asthmatic individuals and nonatopic healthy controls. Strikingly, NO(3)(-) was the only NO. derivative to increase during the immediate Ag-induced asthmatic response and continued to increase over 2-fold at 48 h after Ag challenge in contrast to controls [P < 0.05]. NO(2)(-) was not affected by Ag challenge at 10 min or 48 h after Ag challenge. Although SNO was not detectable in asthmatic airways at baseline or immediately after Ag, SNO increased during the late response to levels found in healthy controls. A model of NO. dynamics derived from the current findings predicts that NO. may have harmful effects through formation of peroxynitrite, but also subserves an antioxidant role by consuming reactive oxygen species during the immediate asthmatic response, whereas nitrosylation during the late asthmatic response generates SNO, safe reservoirs for removal of toxic NO. derivatives.

Adult↗
PubMed2000

Endogenous nitric oxide in allergic airway disease.

There has been intense research into the role nitric oxide (NO) plays in physiologic and pathologic mechanisms. The presence of NO in exhaled breath and the high concentrations in nasal airways stimulated many studies examining exhaled and nasal NO as potential markers of airway inflammation, enabling repeated monitoring of airway inflammation not possible with invasive tests (eg, bronchoscopy). In airway inflammation, NO is not merely a marker but may have anti-inflammatory and proinflammatory effects. Nasal NO measurement may be used in the noninvasive diagnosis and monitoring of nasal disease. This review was compiled by speakers who gave presentations on NO at the annual meeting of the American Academy of Allergy, Asthma, and Immunology in 1999 on exhaled and nasal NO, in vitro studies of NO, the chemistry of airway NO formation, and standardized measurement of exhaled mediators.

Asthma↗
PubMed2000

Elevated nitric oxide metabolite levels in chronic sinusitis.

Decreased exhaled nitric oxide (NO) is found in chronic sinusitis. NO metabolites (nitrates, nitrites, and S-nitrosothiols) were measured in sinus lavages with a rabbit model of chronic sinusitis. NO metabolite levels (mean +/- SD) were 3.0+/-1.6 micromol/L in uninfected rabbits, 10.7+/-11.4 micromol/L in infected animals, and 7.6+/-5.4 micromol/L in postantrostomy recovering animals. Infected sinuses had elevated levels of NO metabolites that were statistically significant (P<0.01) when compared with uninfected sinuses. Mucociliary transport velocity was measured in uninfected (16.0+/-5.7 mm/minute), infected (5.2+/-1.3 mm/minute), and recovery phases (3.0 mm/minute). Endoscopic appearance, light and electron microscopy, and bacterial cultures improved during recovery. Elevated levels of NO metabolites were found during chronic sinusitis and began to return to normal levels during recovery. The possible link between NO in epithelial autotoxicity and host defense mechanisms warrants further investigation.

Animals↗
PubMed2000

Airway nitrogen oxide measurements in asthma and other pediatric respiratory diseases.

Markers for airway inflammation that can be measured noninvasively in expired air may be helpful in treating patients with asthma. For example, levels of nitric oxide are high in the breath of children with asthma exacerbations and decrease with anti-inflammatory therapy. Expired nitric oxide testing has now been standardized and may be useful for children with recurring wheezing that is diagnostically or therapeutically challenging. However, the results may be influenced by several biochemical and anatomic variables and must therefore be interpreted with caution.

Asthma↗
PubMed2000

Normoxic stabilization of hypoxia-inducible factor-1 expression and activity: redox-dependent effect of nitrogen oxides.

Hypoxia-inducible factor-1 (HIF-1) is an essential transcription factor involved in the oxygen-dependent regulation of gene expression. Thiol groups in HIF-1 or in proteins that modify HIF-1 are conventional targets for regulation by nitric oxide (NO). Moreover, NO delivery to tissue by hemoglobin appears to be oxygen dependent. Therefore, the role NO plays in regulating HIF-1 activity and expression was examined. The 1-substituted diazen-1-ium-1, 2-diolate NOC-18 induced HIF-1 DNA-binding activity in normoxic bovine pulmonary artery endothelial cells and rat aortic smooth muscle cells in a time- and dose-dependent manner. Induction of HIF-1-binding activity was consistent with an increased expression of HIF-1 subunit proteins HIF-1alpha and HIF-1beta. The effect of NOC-18 on HIF-1 activity was blocked by cycloheximide, consistent with a post-transcriptional effect. NOC-18 induction of HIF-1 DNA-binding activity was not blocked with oxyhemoglobin, nor was it related to the rate of NO evolution, arguing against NO-mediation of the effect. Additionally, the effect of NOC-18 could not be mimicked by Angeli's salt, arguing against nitroxyl mediation. However, the NOC-18 effect could be reproduced by S-nitrosoglutathione (GSNO), an endogenous nitrosonium donor formed in the presence of deoxyhemoglobin. Furthermore, the GSNO effect could be reversed by dithiothreitol as well as acivicin, an inhibitor of GSNO bioactivation. Taken together, these results suggest that an S-nitrosylation reaction stabilizes HIF-1 protein expression and activity. We speculate that one signaling mechanism by which deoxyhemoglobin may activate HIF-1 involves NO.

Animals↗
PubMed2000

S-nitrosoglutathione breakdown prevents airway smooth muscle relaxation in the guinea pig.

Airway levels of the endogenous bronchodilator S-nitrosoglutathione (GSNO) are low in children with near-fatal asthma. We hypothesized that GSNO could be broken down in the lung and that this catabolism could inhibit airway smooth muscle relaxation. In our experiments, GSNO was broken down by guinea pig lung homogenates, particularly after ovalbumin sensitization (OS). Two lung protein fractions had catabolic activity. One was NADPH dependent and was more active after OS. The other was NADPH independent and was partially inhibited by aurothioglucose. Guinea pig lung tissue protein fractions with GSNO catabolic activity inhibited GSNO-mediated guinea pig tracheal ring relaxation. The relaxant effect of GSNO was partially restored by aurothioglucose. These observations suggest that catabolism of GSNO in the guinea pig 1) is mediated by lung proteins, 2) is partially upregulated after OS, and 3) may contribute to increased airway smooth muscle tone. We speculate that enzymatic breakdown of GSNO in the lung could contribute to asthma pathophysiology by inhibiting the beneficial effects of GSNO, including its effect on airway smooth muscle tone.

Animals↗
PubMed2000

Endogenous airway acidification. Implications for asthma pathophysiology.

Airway concentrations of many reactive nitrogen and oxygen species are high in asthma. The stability and bioactivities of these species are pH-dependent; however, the pH of the airway during acute asthma has not previously been studied. As with gastric and urinary acidification, asthmatic airway acidification could be expected dramatically to alter the concentrations and bioactivities/cytotoxicities of endogenous nitrogen oxides. Here, we demonstrate that the pH of deaerated exhaled airway vapor condensate is over two log orders lower in patients with acute asthma (5.23 +/- 0.21, n = 22) than in control subjects (7.65 +/- 0.20, n = 19, p < 0. 001) and normalizes with corticosteroid therapy. Values are highly reproducible, unaffected by salivary or therapeutic artifact, and identical to samples taken directly from the lower airway. Further, at these low pH values, the endogenous airway compound, nitrite, is converted to nitric oxide (NO) in quantities sufficient largely to account for the concentrations of NO in asthmatic expired air, and eosinophils undergo accelerated necrosis. We speculate that airway pH may be an important determinant of expired NO concentration and airway inflammation, and suggest that regulation of airway pH has a previously unsuspected role in asthma pathophysiology.

Acid-Base Equilibrium↗
PubMed1999

Nitric oxide and thiol groups.

S-Nitroso(sy)lation reactions have recently been appreciated to regulate protein function and mediate 'nitrosative' stress. S-Nitrosothiols (SNOs) have been identified in a variety of tissues, and represent a novel class of signaling molecules which may act independently of homolytic cleavage to NO - and, indeed, in a stereoselective fashion - or be metabolized to other bioactive nitrogen oxides. It is now appreciated that sulfur-NO interactions have critical physiological relevance to mammalian neurotransmission, ion channel function, intracellular signaling and antimicrobial defense. These reactions are promising targets for the development of new medical therapies.

Animals↗
PubMed1999

Decreased levels of nitrosothiols in the lower airways of patients with cystic fibrosis and normal pulmonary function.

Airway S-nitrosothiols (SNOs) are naturally occurring bronchodilators. SNOs, nitrate, and nitrite were measured in bronchoalveolar lavage fluid of 23 patients with cystic fibrosis (CF) and mild pulmonary disease (aged 6-16 years) and 13 healthy children (aged 8-15 years). Concentrations of SNOs were decreased in the lower airways of patients with CF and mild pulmonary disease (median, range: 0, 0-320 nmol/L vs 80, 0-970 nmol/L) despite normal levels of the inert nitric oxide metabolites nitrate and nitrite (mean +/- SEM: 3.7 +/- 0.5 micromol/L vs 4.8 +/- 0.9 micromol/L). S-nitrosolation- mediated bioreactivities may be impaired by depletion of the CF airway SNO reservoir.

Adolescent↗
PubMed1999

Vital capacity reservoir and online measurement of childhood nitrosopnea are linearly related. Clinical implications.

Hypernitrosopnea, a robust marker for childhood asthma, is measured reproducibly in mixed vital capacity (VC) expirates. Recent guidelines for measurement of expired nitric oxide (NO) in adults have favored use of an online (OL), flow-dependent technique. We compared VC and OL NO measurements in 14 asthmatic and 11 control children 5 through 18 yr of age. After spirometry, subjects breathed both into an open-ended reservoir (20 cm H2O resistance) and into a tedlar bag (VC maneuver). End-expiratory pressure > 5 cm H2O was continuously maintained during VC measurements, and the velum remained shut. Eight additional children (24% of total number of subjects) were unable reproducibly to perform the OL measurement at constant flow (six asthmatics; two control children). For subjects able to perform the OL technique, OL and VC NO measurements were linearly related (r2 = 0.88). In children, VC NO assays are reproducible, sensitive in identifying asthma, and portable. Additionally, we have shown that (1) not all children are able to perform OL measurements, and (2) VC measurements vary linearly with OL measurements. These findings suggest that there may not be compelling reason to favor OL over VC measurements for hypernitrosopnea in children with asthma.

Adolescent↗
PubMed1998

Umbilical arterial S-nitrosothiols in stressed newborns: role in perinatal circulatory transition.

S-Nitrosothiols are potent endogenous vasodilators recently found to be in greater concentrations in fetal umbilical venous than arterial blood. We hypothesized that neonatal increases in SNOs may be involved in the normal human perinatal circulatory transition. Paired human umbilical artery and vein plasma samples were collected after birth. S-Nitrosothiol concentrations were measured as NO after photolysis--and NO3- after reduction in vanadium chloride--by chemiluminescence. Normal umbilical arterial serum SNO levels were nearly twice those of matched venous samples but were low in infants who did not transition normally to neonatal circulation. There was no difference in the concentration of NO3- between the normal and depressed infants. The parallel failure of some fetuses to switch both to a normal arteriovenous SNO relationship and a normal clinical post-partum state suggests that SNOs may be involved in the perinatal circulatory transition.

Blood Circulation↗
PubMed1998

Reductive assays for S-nitrosothiols: implications for measurements in biological systems.

Bioactive SNOs are found in many tissues. We speculated SNOs might be misidentified in conventional assays which reduce NO-3 to NO. S-Nitrosothiols were exposed to saturated VCl3 in HCl, 1% KI in acetic acid, photolysis, or CuCl and CSH in He; NO was measured by chemiluminescence. S-Nitrosothiols were readily detected in VCl3 but not in KI. Reduction in CuCl/cysteine was linear (r2 = 1.0, n = 6), sensitive to 10 pmol, and eliminated by HgCl2; it did not detect NO-2, NO-3, or 3-nitrotyrosine. S-Nitrosothiols represented approximately 2.9% of NOx assayed by VCl3 in human serum, of which <5% were low-mass species. In summary, (i) conventional assays may misidentify NO-3, but not NO-2, as SNOs; and (ii) chemiluminescence/reduction systems may be sensitive and specific as SNO assays. We suggest that assay of the SNO fraction in biological NOx may be more relevant and feasible than is now appreciated.

Chromatography, High Pressure Liquid↗
PubMed1998

Bronchodilator S-nitrosothiol deficiency in asthmatic respiratory failure.

BACKGROUND: Nitric oxide (NO) gas concentrations are high in the expired air of individuals with asthma, but not consistently so in the expired air of people with pneumonia. S-nitrosothiols are naturally occurring bronchodilators, the concentrations of which are raised in the airways of patients with pneumonia. Airway S-nitrosothiols have not been studied in asthma. METHODS: Tracheal S-nitrosothiol concentrations from eight asthmatic children in respiratory failure were compared with those of 21 children undergoing elective surgery. RESULTS: Mean S-nitrosothiol concentrations in asthmatic children were lower than in normal children (65 [SD 45] nmol/L vs 502 [SD 429] nmol/L) and did not vary with inspired oxygen concentration or airway thiol concentration. INTERPRETATION: Severe asthma is associated with low concentrations of airway S-nitrosothiols. This is the first reported deficiency of an endogenous bronchodilator in the human asthmatic airway lining fluid. We suggest that S-nitrosothiol metabolism may be a target for the development of new asthma therapies.

Acute Disease↗