Respiratory Nitric Oxide Research Articles

The Role of Exhaled Nitric Oxide Fraction in Sarcoidosis Patients

Nitric oxide is a molecule that has important roles in various biological processes such as apoptosis, angiogenesis and endothelial permeability and therefore its disorder plays a role in the pathogenesis of various disorders. We aimed to investigate fractional exhaled nitric oxide values in sarcoidosis, a multi-systemic non-caseified granulomatous disease that commonly affects all organs, especially the pulmonary system. A total of 107 individuals, including 54 sarcoidosis patients and 53 healthy controls were included in this study. Data were analyzed retrospectively. Gender, age, body mass index, exhaled nitric oxide fraction values, respiratory function parameters, diagnostic methods and additional disease states were recorded. Exhaled nitric oxide fraction values in sarcoidosis patients and the control group were measured using Bedfont NObreath (UK) device, respiratory function parameters were measured using ZAN GPI.3.00 (Germany) device and the results were recorded. Sarcoidosis patients were graded as stage 0, 1, 2, 3, 4 according to chest x-ray findings. Exhaled nitric oxide fraction values detected in sarcoidosis patients and fractional exhaled nitric oxide values detected in the control group were compared. The sensitivity and specificity of exhaled nitric oxide fraction values in sarcoidosis were investigated. The relationship between respiratory function parameters and exhaled nitric oxide fraction values was examined. There was a significant difference between the exhaled nitric oxide fraction values detected in sarcoidosis patients and the exhaled nitric oxide fraction values detected in the control group and the specificity and sensitivity of the exhaled nitric oxide fraction value was found to be high in patients with and sarcoidosis. There was no relationship between respiratory function parameters and exhaled nitric oxide fraction values. Exhaled nitric oxide fraction values, which have been studied in very few studies in sarcoidosis patients, may be a biomarker that can be used in the evaluation of pulmonary parenchymal involvement of sarcoidosis.

Non-heme Fe cofactor insertion into respiratory nitric oxide reductase from Paracoccus denitrificans

Non-heme Fe cofactor insertion into respiratory nitric oxide reductase from Paracoccus denitrificans

Analysis of multiple haloarchaeal genomes suggests that the quinone-dependent respiratory nitric oxide reductase is an important source of nitrous oxide in hypersaline environments.

Microorganisms, including Bacteria and Archaea, play a key role in denitrification, which is the major mechanism by which fixed nitrogen returns to the atmosphere from soil and water. While the enzymology of denitrification is well understood in Bacteria, the details of the last two reactions in this pathway, which catalyse the reduction of nitric oxide (NO) via nitrous oxide (N2 O) to nitrogen (N2 ), are little studied in Archaea, and hardly at all in haloarchaea. This work describes an extensive interspecies analysis of both complete and draft haloarchaeal genomes aimed at identifying the genes that encode respiratory nitric oxide reductases (Nors). The study revealed that the only nor gene found in haloarchaea is one that encodes a single subunit quinone dependent Nor homologous to the qNor found in bacteria. This surprising discovery is considered in terms of our emerging understanding of haloarchaeal bioenergetics and NO management.

Evaluation of the Effect of Mesenchymal Stem Cells pulsed with Caffeine on the Function of the Peritoneal Macrophages of Rat

Introduction: Pervious studies indicated that the mesenchymal stem cells (MSCs) produce adenosine and express adenosine receptors. Moreover, produced adenosine has biological effect on these cells. On the other hand, MSCs have a wide relationship with macrophages in tissues and bone marrow. The aim of the present study was to determine the effects of the MSCs treated with caffeine, as an adenosine antagonist, on the peritoneal macrophages isolated from rats. Materials & methods: After isolation of mesenchymal stem cells from bone marrow of rats, these cells pulsed with different concentration of caffeine (0, 0.1, 0.5 and 1 mM) for 48h. Then, MSCs were co-cultured with macrophages for 1 day. Then, the level of nitric oxide production and respiratory burst of macrophages after challenge with N-formylmethionine-leucyl-phenylalanine (f-MLP) or opsonized yeast were evaluated. Findings: It seems that MSCs pulsed with caffeine or without it could significantly decrease the respiratory burst and nitric oxide production of co-cultured macrophages more prominent than macrophages alone after unspecific challenged with fMLP. Although, pervious treatment of MSCs with caffeine could decrease the respiratory burst and nitric oxide production of macrophages challenged with f-MLP more prominent than MSCs without treatment. However, the potential of nitric oxide production and respiratory burst of various group after challenge with opsonized yeast didnt show any significant differences. Discussion & conclusions: Collectively, these data may offer new insight into the potential mechanisms underlying the immunomodulatory and anti-inflammatory effects of caffeine.

Nitrous oxide production and consumption: regulation of gene expression by gas-sensitive transcription factors

Several biochemical mechanisms contribute to the biological generation of nitrous oxide (N(2)O). N(2)O generating enzymes include the respiratory nitric oxide (NO) reductase, an enzyme from the flavo-diiron family, and flavohaemoglobin. On the other hand, there is only one enzyme that is known to use N(2)O as a substrate, which is the respiratory N(2)O reductase typically found in bacteria capable of denitrification (the respiratory reduction of nitrate and nitrite to dinitrogen). This article will briefly review the properties of the enzymes that make and consume N(2)O, together with the accessory proteins that have roles in the assembly and maturation of those enzymes. The expression of the genes encoding the enzymes that produce and consume N(2)O is regulated by environmental signals (typically oxygen and NO) acting through regulatory proteins, which, either directly or indirectly, control the frequency of transcription initiation. The roles and mechanisms of these proteins, and the structures of the regulatory networks in which they participate will also be reviewed.

Bronquiolitis obliterante. Evolución a medio plazo

BackgroundBronchiolitis obliterans is a chronic obstructive lung disease that follows a severe insult to the lower respiratory tract. Severity and outcome are different depending on the geographic area. The aim of this study was to communicate the results of our sample. MethodsA retrospective study was performed in a sample of boys and girls with a medical diagnosis of bronchiolitis obliterans (BO) between December 1994 and February 2011. The diagnosis was made by high-resolution computed tomography (HRCT) scan and lung function. Lung biopsy was performed in one case. Pulmonary function testing included; forced spirometry (≥ 3 years old), plethysmography (≥ 5 years), bronchodilator tests (BDT), single-breath determination of carbon monoxide uptake in the lung (DLCO) (≥ 6 years) and measurement of exhaled lower respiratory nitric oxide (FENO). Quantitative variables were; age at diagnosis, respiratory morbidity before the diagnosis, time from the start of the symptomatology until the diagnosis, follow-up time, respiratory morbidity after the diagnosis, airway specific resistance (sReff), airway specific conductance (sGeff), residual volume, total lung capacity, thoracic gas volume, FEV1, FVC, FEV1/FVC, FEF25-75, DLCO and FENO. Qualitative variables were; sex, reason for consulting, viral infections, atopy, smoke exposure, HRCT scan and current treatment. Descriptive analysis was performed and pulmonary function before and after BDT was studied using paired-sample Wilcoxon and Student́s t-test. ResultsWe studied a cohort of 22 cases, 10 (45.4%) boys and 12 (54.5%) girls. The mean age at the diagnosis was 4.87±3, 27 years old. The follow-up period was 5 years (range 1 to 8 years). Related virus were; influenza 2 (9.09%), parainfluenza 2 (9.09%), adenovirus 3 (13.69%), syncytial respiratory virus 1 (4.5%) and rhinovirus 1 (4.54%). HRCT scan: mosaic pattern of lung attenuation 22 (100%) and bronchiectasis 8 (36.36%). Lung function at diagnosis showed fixed airflow obstruction and increased lung volumes. The global analysis showed a progressive decrease in FEV1, FVC, FVC/FEV1, FEF25-75 and increase in sReff and residual volume with decrease in sGeff. Individually, there was a tendency to stabilise the lung function comparing with initial values at diagnosis. Respiratory morbidity was low after the diagnosis. ConclusionsIn most cases, fixed air-flow obstruction and lung function stability with low respiratory morbidity were observed. HRCT scan and lung function testing supported the diagnosis.

Low-Spin Heme b3 in the Catalytic Center of Nitric Oxide Reductase from Pseudomonas nautica

Respiratory nitric oxide reductase (NOR) was purified from membrane extract of Pseudomonas (Ps.) nautica cells to homogeneity as judged by polyacrylamide gel electrophoresis. The purified protein is a heterodimer with subunits of molecular masses of 54 and 18 kDa. The gene encoding both subunits was cloned and sequenced. The amino acid sequence shows strong homology with enzymes of the cNOR class. Iron/heme determinations show that one heme c is present in the small subunit (NORC) and that approximately two heme b and one non-heme iron are associated with the large subunit (NORB), in agreement with the available data for enzymes of the cNOR class. Mössbauer characterization of the as-purified, ascorbate-reduced, and dithionite-reduced enzyme confirms the presence of three heme groups (the catalytic heme b(3) and the electron transfer heme b and heme c) and one redox-active non-heme Fe (Fe(B)). Consistent with results obtained for other cNORs, heme c and heme b in Ps. nautica cNOR were found to be low-spin while Fe(B) was found to be high-spin. Unexpectedly, as opposed to the presumed high-spin state for heme b(3), the Mössbauer data demonstrate unambiguously that heme b(3) is, in fact, low-spin in both ferric and ferrous states, suggesting that heme b(3) is six-coordinated regardless of its oxidation state. EPR spectroscopic measurements of the as-purified enzyme show resonances at the g ∼ 6 and g ∼ 2-3 regions very similar to those reported previously for other cNORs. The signals at g = 3.60, 2.99, 2.26, and 1.43 are attributed to the two charge-transfer low-spin ferric heme c and heme b. Previously, resonances at the g ∼ 6 region were assigned to a small quantity of uncoupled high-spin Fe(III) heme b(3). This assignment is now questionable because heme b(3) is low-spin. On the basis of our spectroscopic data, we argue that the g = 6.34 signal is likely arising from a spin-spin coupled binuclear center comprising the low-spin Fe(III) heme b(3) and the high-spin Fe(B)(III). Activity assays performed under various reducing conditions indicate that heme b(3) has to be reduced for the enzyme to be active. But, from an energetic point of view, the formation of a ferrous heme-NO as an initial reaction intermediate for NO reduction is disfavored because heme [FeNO](7) is a stable product. We suspect that the presence of a sixth ligand in the Fe(II)-heme b(3) may weaken its affinity for NO and thus promotes, in the first catalytic step, binding of NO at the Fe(B)(II) site. The function of heme b(3) would then be to orient the Fe(B)-bound NO molecules for the formation of the N-N bond and to provide reducing equivalents for NO reduction.

A mathematical model for breath gas analysis of volatile organic compounds with special emphasis on acetone

Recommended standardized procedures for determining exhaled lower respiratory nitric oxide and nasal nitric oxide (NO) have been developed by task forces of the European Respiratory Society and the American Thoracic Society. These recommendations have paved the way for the measurement of nitric oxide to become a diagnostic tool for specific clinical applications. It would be desirable to develop similar guidelines for the sampling of other trace gases in exhaled breath, especially volatile organic compounds (VOCs) which may reflect ongoing metabolism. The concentrations of water-soluble, blood-borne substances in exhaled breath are influenced by: (i) breathing patterns affecting gas exchange in the conducting airways, (ii) the concentrations in the tracheo-bronchial lining fluid, (iii) the alveolar and systemic concentrations of the compound. The classical Farhi equation takes only the alveolar concentrations into account. Real-time measurements of acetone in end-tidal breath under an ergometer challenge show characteristics which cannot be explained within the Farhi setting. Here we develop a compartment model that reliably captures these profiles and is capable of relating breath to the systemic concentrations of acetone. By comparison with experimental data it is inferred that the major part of variability in breath acetone concentrations (e.g., in response to moderate exercise or altered breathing patterns) can be attributed to airway gas exchange, with minimal changes of the underlying blood and tissue concentrations. Moreover, the model illuminates the discrepancies between observed and theoretically predicted blood-breath ratios of acetone during resting conditions, i.e., in steady state. Particularly, the current formulation includes the classical Farhi and the Scheid series inhomogeneity model as special limiting cases and thus is expected to have general relevance for a wider range of blood-borne inert gases. The chief intention of the present modeling study is to provide mechanistic relationships for further investigating the exhalation kinetics of acetone and other water-soluble species. This quantitative approach is a first step towards new guidelines for breath gas analyses of volatile organic compounds, similar to those for nitric oxide.

Carboxyhemoglobin Formation Secondary to Nitric Oxide Therapy in the Setting of Interstitial Lung Disease and Pulmonary Hypertension

Carbon monoxide (CO) has been widely recognized as an exogenous poison, although endogenous mechanisms for its formation involve heme-oxygenase (HO) isoforms, more specifically HO-1, in the setting of oxidative stress such as acute respiratory distress syndrome, sepsis, trauma, and nitric oxide use have been studied. In patients with refractory hypoxemia, inhaled nitric oxide (iNO) therapy is used to selectively vasodilate the pulmonary vasculature and improve ventilation-perfusion match. Inhaled nitric oxide is rapidly inactivated on binding to hemoglobin in the formation of nitrosyl- and methemoglobin in the pulmonary vasculature. Hence, inhaled nitric oxide has minimal systemic dissemination. Several experimental design studies involving lab rats have demonstrated increased levels of carboxyhemoglobin and exhaled CO as a result of nitric oxide HO-1 induction.

Exercise but not mannitol provocation increases urinary Clara cell protein (CC16) in elite swimmers

Elite swimmers have an increased risk of developing asthma, and exposure to chloramine is believed to be an important trigger factor. The aim of the present study was to explore pathophysiological mechanisms behind induced bronchoconstriction in swimmers exposed to chloramine, before and after swim exercise provocation as well as mannitol provocation. Urinary Clara cell protein (CC16) was used as a possible marker for epithelial stress. 101 elite aspiring swim athletes were investigated and urinary samples were collected before and 1h after completed exercise and mannitol challenge. CC16, 11β-prostaglandin (PG)F(2α) and leukotriene E(4) (LTE(4)) were measured. Urinary levels of CC16 were clearly increased after exercise challenge, while no reaction was seen after mannitol challenge. Similar to CC16, the level of 11β-PGF(2α) was increased after exercise challenge, but not after mannitol challenge, while LTE(4) was reduced after exercise. There was no significant difference in urinary response between those with a negative compared to positive challenge, but a tendency of increased baseline levels of 11β-PGF(2α) and LTE(4) in individuals with a positive mannitol challenge. The uniform increase of CC16 after swim exercise indicates that CC16 is of importance in epithelial stress, and may as such be an important pathogenic factor behind asthma development in swimmers. The changes seen in urinary levels of 11β-PGF(2α) and LTE(4) indicate a pathophysiological role in both mannitol and exercise challenge.

The bacterial respiratory nitric oxide reductase

The two-subunit cytochrome bc complex (NorBC) isolated from membranes of the model denitrifying soil bacterium Paracoccus denitrificans is the best-characterized example of the bacterial respiratory nitric oxide reductases. These are members of the super-family of haem-copper oxidases and are characterized by the elemental composition of their active site, which contains non-haem iron rather than copper, at which the reductive coupling of two molecules of nitric oxide to form nitrous oxide is catalysed. The reaction requires the presence of two substrate molecules at the active site along with the controlled input of two electrons and two protons from the same side of the membrane. In the present paper, we consider progress towards understanding the pathways of electron and proton transfer in NOR and how this information can be integrated with evidence for the likely modes of substrate binding at the active site to propose a revised and experimentally testable reaction mechanism.

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.

Exhaled nitric oxide measurements: Correction equation to compare hand-held device to stationary analyzer

Exhaled nitric oxide (FE(NO)) is a reliable non-invasive marker of airway inflammation. In 2003 FE(NO) chemiluminescence analyzer (NIOX; Aerocrine AB, Solna, Sweden) was approved by U.S. Food and Drug Administration for monitoring asthma therapy. Recently, the same company developed a portable device using electrochemical sensors (NIOX-MINO; Aerocrine AB). The aim of our study was to compare NIOX-MINO FE(NO) values to those obtained by NIOX and to calculate a correction equation. Two adequate measurements obtained by NIOX and NIOX-MINO were recorded in 32 subjects (16 females, mean age 41 years). FE(NO) values measured by NIOX-MINO were systematically higher than those obtained by NIOX (47.1ppb, IC 95% 35.2-59.1 and 36.9ppb, IC 95% 25.0-49.0, respectively). There was a significant correlation (r=0.998, p<0.001) between FE(NO) measured by the two analyzers and the following conversion equation was calculated as: FE(NO(NIOX))=-1.656(SE=0.61)+0.808(SE=0.009)x FE(NO(NIOX-MINO)) DISCUSSION: FE(NO) values measured by the portable nitric oxide analyzer are reliable and strongly correlated with values obtained by the standard stationary device, with a systematic difference observed between the two instruments' values that can be described by the conversion equation we provided. This equation will help clinicians and researchers to compare data obtainable by the two analyzers.

Defining the Proton Entry Point in the Bacterial Respiratory Nitric-oxide Reductase

The bacterial respiratory nitric-oxide reductase (NOR) is a member of the superfamily of O(2)-reducing, proton-pumping, heme-copper oxidases. Even although nitric oxide reduction is a highly exergonic reaction, NOR is not a proton pump and rather than taking up protons from the cytoplasmic (membrane potential-negative) side of the membrane, like the heme-copper oxidases, NOR derives its substrate protons from the periplasmic (membrane potential-positive) side of the membrane. The molecular details of this non-electrogenic proton transfer are not yet resolved, so in this study we have explored a role in a proposed proton pathway for a conserved surface glutamate (Glu-122) in the catalytic subunit (NorB). The effect of substituting Glu-122 with Ala, Gln, or Asp on a single turnover of the reduced NOR variants with O(2), an alternative and experimentally tractable substrate for NOR, was determined. Electron transfer coupled to proton uptake to the bound O(2) is severely and specifically inhibited in both the E122A and E122Q variants, establishing the importance of a protonatable side chain at this position. In the E122D mutant, proton uptake is retained but it is associated with a significant increase in the observed pK(a) of the group donating protons to the active site. This suggests that Glu-122 is important in defining this proton donor. A second nearby glutamate (Glu-125) is also required for the electron transfer coupled to proton uptake, further emphasizing the importance of this region of NorB in proton transfer. Because Glu-122 is predicted to lie near the periplasmic surface of NOR, the results provide strong experimental evidence that this residue contributes to defining the aperture of a non-electrogenic "E-pathway" that serves to deliver protons from the periplasm to the buried active site in NOR.

Chlorinated Pools and the Risk of Asthma

In a recent article, Bernard et al. (2006) presented data that led them to conclude that the use of chlorinated pools, especially by young children, interacts with atopic status to promote the development of childhood asthma. I question these conclusions for several reasons. First, this finding is not consistent with the authors’ recent publication from this same group of children (Nickmilder et al. 2005) concluding that children living in a home cleaned with chlorine bleach had a lower prevalence of asthma. It is difficult to understand how occasional exposure to chlorinated compounds at indoor swimming pools could cause asthma if more frequent and longer exposures at home were actually protective. Second, the data presented by Bernard et al. (2006) do not fully support their conclusion. For example, the exposure metric they used to describe the children’s exposure to chlorinated pools is the lifetime cumulative swimming pool attendance (CPA) given in hours. The CPA data are based on lifetime exposure derived from questionnaires that the parents of these 11- to 12-year-old children completed at home [American Thoracic Society, European Respiratory Society (ATS/ERS) 2005] and is thus subject to their understanding and interpreting the question, as well as to recall bias. In addition, systematic bias is introduced by using a lifetime cumulative measure like CPA to relate exposure to asthma prevalence. Lifetime cumulative exposure is obviously dependent on the age of the child; because asthma prevalence also increases during this same time, the child’s age becomes a confounder that cannot be dealt with adequately in the analysis used by Bernard et al. (2006). Third, the data presented to relate the dose response between CPA and asthma prevalence are confusing. In Table 2 of Bernard et al. (2006), the relationship is not significant, while in Figure 1 it is significant in a subgroup. In their Figure 1A, a dose response is suggested between CPA and the prevalence of doctor-diagnosed and total asthma, but only in those children whose total IgE is > 100 IU/mL. The subgroups in this figure are small; from data in Table 1 and the text, it appears that only 14 children had both IgE > 100 IU/mL and doctor-diagnosed asthma, and only 20 had total asthma with a high IgE concentration. Because Figure 1 (Bernard et al. 2006) divides all 341 children into approximately equal quartiles of CPA, it seems impossible to allocate the 14–20 children with asthma in such a way that would result in an asthma prevalence of 12–35% within each quartile. I suggest that the figure is drawn incorrectly and that the correct relationship is shown in their Table 2. Fourth, insufficient information is available to address the uncertainties in the outcome measures of Bernard et al. (2006). The data in their Table 2 demonstrate that swimming pool attendance was associated with the prevalence of an elevated exhaled nitric oxide (eNO); neither doctor-diagnosed asthma nor total asthma was significantly related to swimming pool attendance unless combined with eNO measures. Although eNO is associated with asthma, it has been used primarily to measure the state of airway inflammation in asthma; the use of eNO is less certain as a diagnostic tool (ATS/ERS 2005). In fact, elevated eNO levels have been associated with viral respiratory tract infections, allergic rhinitis, and sinusitis (ATS/ERS 2005). These conditions were not included in the health questionnaire described by Bernard et al. (2006) in their “Materials and Methods.” Indeed, only 20 of the 29 children with an elevated eNO (> 30 ppb) had doctor-diagnosed asthma. In addition, the study was conducted during winter months when viral respiratory infections are common; therefore, the presence of these infections could have produced outcome misclassification. Finally, inhaled steroid medications markedly reduce eNO, and use by these children could have introduced yet another reason for outcome misclassification. To summarize, the uncertainty in both the exposure estimates and the outcome measures, coupled with the conflicting outcomes with home exposure to chlorine bleach, make it difficult to accept the strong conclusions reached by Bernard et al. (2006) in their article.

The role of Bradyrhizobium japonicum nitric oxide reductase in nitric oxide detoxification in soya bean root nodules

The identification of nitric oxide-bound leghaemoglobin within soya bean nodules has led to the question of how Bradyrhizobium japonicum bacteroids overcome the toxicity of this nitric oxide. It has previously been shown that one candidate for nitric oxide detoxification, the respiratory nitric oxide reductase, is expressed in soya bean nodules from plants supplied with nitrate. In this paper, the role of this enzyme in nitric oxide detoxification is assessed and discussion is provided on other possible B. japonicum nitric oxide detoxification systems.

Protective effect of aprotinin against lung damage in patients undergoing CABG surgery

Objective — We investigated the protective effects of aprotinin, administered in the pulmonary artery, on lung damage after cardiopulmonary bypass (CPB).Methods — A total of 20 patients undergoing elective coronary artery bypass grafting operations was included in the study and divided into two groups. In the aprotinin group (study group) (n = 10) the drug was administered in the pulmonary artery (15,000 KIU/min) via the pulmonary artery catheter. The control group (n = 10) received only placebo. Blood gas measurements, respiratory function tests, malondialdehyde (MDA), nitric oxide (NO), C4 and leukocyte counts were determined as parameters. Blood samples were taken before and after cross clamping. Lung biopsies were taken before and after CPB.Results — In the aprotinin group, forced expiratory volume (FEV1) and paCO2 values were better than in the control group.The postclamping MDA value in the study group was 20.6 ± 8.7 jmol/ml and in the control group 37.5 ± 9.6 jmol/ml. The post clamping NO value in the study group was 261.9 μmol/l and in the control group 147.20 ± 27.6 μmol/l. C4 levels were found to be better in the study group than in the control group: reduced levels of C4 were found to be statistically significant (study group postclamping: 12.98 ± 2.63 mg/dl vs. control group 20.6 ± 11.81 mg/dl).The increase in leukocyte count was found to be statistically significant (12.63 ± 3.83 ≈ 103 vs. 7.27 ± 1.72 ≈ 103. The difference between the preoperative and postoperative FEV1 in the control group was statistically significant. A statistically significant difference was found in the postoperative FEV1 in both groups.Conclusion — Aprotinin administered in the pulmonary artery during CPB had a protective effect against lung damage after open-heart surgery.

Electron/Proton Coupling in Bacterial Nitric Oxide Reductase during Reduction of Oxygen

The respiratory nitric oxide reductase (NOR) from Paracoccus denitrificans catalyzes the two-electron reduction of NO to N(2)O (2NO + 2H(+) + 2e(-) --> N(2)O + H(2)O), which is an obligatory step in the sequential reduction of nitrate to dinitrogen known as denitrification. NOR has four redox-active cofactors, namely, two low-spin hemes c and b, one high-spin heme b(3), and a non-heme iron Fe(B), and belongs to same superfamily as the oxygen-reducing heme-copper oxidases. NOR can also use oxygen as an electron acceptor; this catalytic activity was investigated in this study. We show that the product in the steady-state reduction of oxygen is water. A single turnover of the fully reduced NOR with oxygen was initiated using the flow-flash technique, and the progress of the reaction monitored by time-resolved optical absorption spectroscopy. Two major phases with time constants of 40 micros and 25 ms (pH 7.5, 1 mM O(2)) were observed. The rate constant for the faster process was dependent on the O(2) concentration and is assigned to O(2) binding to heme b(3) at a bimolecular rate constant of 2 x 10(7) M(-)(1) s(-)(1). The second phase (tau = 25 ms) involves oxidation of the low-spin hemes b and c, and is coupled to the uptake of protons from the bulk solution. The rate constant for this phase shows a pH dependence consistent with rate limitation by proton transfer from an internal group with a pK(a) = 6.6. This group is presumably an amino acid residue that is crucial for proton transfer to the catalytic site also during NO reduction.

ATS/ERS Recommendations for Standardized Procedures for the Online and Offline Measurement of Exhaled Lower Respiratory Nitric Oxide and Nasal Nitric Oxide, 2005

ATS/ERS Recommendations for Standardized Procedures for the Online and Offline Measurement of Exhaled Lower Respiratory Nitric Oxide and Nasal Nitric Oxide, 2005

Redox-dependent Open and Closed Forms of the Active Site of the Bacterial Respiratory Nitric-oxide Reductase Revealed by Cyanide Binding Studies

The bacterial respiratory nitric-oxide reductase (NOR) catalyzes the respiratory detoxification of nitric oxide in bacteria and Archaea. It is a member of the well known super-family of heme-copper oxidases but has a [heme Fe-non-heme Fe] active site rather than the [heme Fe-Cu(B)] active site normally associated with oxygen reduction. Paracoccus denitrificans NOR is spectrally characterized by a ligand-to-metal charge transfer absorption band at 595 nm, which arises from the high spin ferric heme iron of a micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site. On reduction of the nonheme iron, the micro-oxo bridge is broken, and the ferric heme iron is hydroxylated or hydrated, depending on the pH. At present, the catalytic cycle of NOR is a matter of much debate, and it is not known to which redox state(s) of the enzyme nitric oxide can bind. This study has used cyanide to probe the nature of the active site in a number of different redox states. Our observations suggest that the micro-oxo-bridged [heme Fe(III)-O-Fe(III)] active site represents a closed or resting state of NOR that can be opened by reduction of the non-heme iron.