title: Non-invasive measurements of exhaled NO and CO associated with methacholine responses in mice.
abstract: BACKGROUND
  Nitric oxide (NO) and carbon monoxide (CO) in exhaled breath are considered obtainable biomarkers of physiologic mechanisms. Therefore, obtaining their measures simply, non-invasively, and repeatedly, is of interest, and was the purpose of the current study.
  
  
  METHODS
  Expired NO (ENO) and CO (ECO) were measured non-invasively using a gas micro-analyzer on several strains of mice (C57Bl6, IL-10-/-, A/J, MKK3-/-, JNK1-/-, NOS-2-/- and NOS-3-/-) with and without allergic airway inflammation (AI) induced by ovalbumin systemic sensitization and aerosol challenge, compared using independent-sample t-tests between groups, and repeated measures analysis of variance (ANOVA) within groups over time of inflammation induction. ENO and ECO were also measured in C57Bl6 and IL-10-/- mice, ages 8-58 weeks old, the relationship of which was determined by regression analysis. S-methionyl-L-thiocitrulline (SMTC), and tin protoporphyrin (SnPP) were used to inhibit neuronal/constitutive NOS-1 and heme-oxygenase, respectively, and alter NO and CO production, respectively, as assessed by paired t-tests. Methacholine-associated airway responses (AR) were measured by the enhanced pause method, with comparisons by repeated measures ANOVA and post-hoc testing.
  
  
  RESULTS
  ENO was significantly elevated in naïve IL-10-/- (9-14 ppb) and NOS-2-/- (16 ppb) mice as compared to others (average: 5-8 ppb), whereas ECO was significantly higher in naïve A/J, NOS-3-/- (3-4 ppm), and MKK3-/- (4-5 ppm) mice, as compared to others (average: 2.5 ppm). As compared to C57Bl6 mice, AR of IL-10-/-, JNK1-/-, NOS-2-/-, and NOS-3-/- mice were decreased, whereas they were greater for A/J and MKK3-/- mice. SMTC significantly decreased ENO by ~30%, but did not change AR in NOS-2-/- mice. SnPP reduced ECO in C57Bl6 and IL-10-/- mice, and increased AR in NOS-2-/- mice. ENO decreased as a function of age in IL-10-/- mice, remaining unchanged in C57Bl6 mice.
  
  
  CONCLUSIONS
  These results are consistent with the ideas that: 1) ENO is associated with mouse strain and knockout differences in NO production and AR, 2) alterations of ENO and ECO can be measured non-invasively with induction of allergic AI or inhibition of key gas-producing enzymes, and 3) alterations in AR may be dependent on the relative balance of NO and CO in the airway.
authors.affiliation: Division of Allergy, Pulmonary, Immunology, Critical Care and Sleep Division, Department of Internal Medicine, University of Texas Medical Branch, Galveston TX 77755-1083, USA. jmsethi@upmc.edu
authors.forename: Jigme M
authors.initials: JM
authors.lastname: Sethi
authors.forename: Augustine M K
authors.initials: AM
authors.lastname: Choi
authors.forename: William J
authors.initials: WJ
authors.lastname: Calhoun
authors.forename: Bill T
authors.initials: BT
authors.lastname: Ameredes
mesh_terms: D000818:Animals; D001944:Breath Tests; D016085:Bronchoconstrictor Agents / Q000009:adverse effects*; D002245:Carbon Dioxide / Q000378:metabolism*; D045853:Exhalation; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism; D048371:MAP Kinase Kinase 3 / Q000235:genetics / Q000378:metabolism; D008297:Male; D016210:Methacholine Chloride / Q000009:adverse effects*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D048055:Mitogen-Activated Protein Kinase 8 / Q000235:genetics / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III; D011014:Pneumonia / Q000139:chemically induced* / Q000378:metabolism*; D012044:Regression Analysis
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D016753:Interleukin-10; D002245:Carbon Dioxide; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496317:Nos2 protein, mouse; C496315:Nos3 protein, mouse; D006419:Heme Oxygenase (Decyclizing); D048055:Mitogen-Activated Protein Kinase 8; D048371:MAP Kinase Kinase 3; C482531:Map2k3 protein, mouse