Type 2 nitric oxide synthase and protein nitration in chronic lung infection

• Published in: The Journal of pathology Vol. 199; no. 1; pp. 122 - 129
• Main Authors: Hopkins, Natalie, Cadogan, Elaine, Giles, Shay, Bannigan, John, McLoughlin, Paul
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2003; Wiley
• Subjects: Animals; Biological and medical sciences; Bronchoalveolar Lavage Fluid; Cell Count; Chronic Disease; Fluorescent Antibody Technique; Lung - enzymology; Lung - metabolism; Lung - pathology; Lung Diseases - enzymology; Lung Diseases - metabolism; Lung Diseases - pathology; Male; Medical sciences; nitrate; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; nitrite; nitrosothiols; Pneumology; Pseudomonas Infections - enzymology; Pseudomonas Infections - metabolism; Pseudomonas Infections - pathology; pulmonary vascular resistance; Rats; Rats, Sprague-Dawley; Respiratory system : syndromes and miscellaneous diseases; Tyrosine - analogs & derivatives; Tyrosine - analysis; Immunohistochemistry; Rat; Lung; nitrate; nitrosothiols; Lung disease; Nitration; Biochemical analysis; Respiratory disease; Enzyme; Rodentia; Inflammation; Nitric-oxide synthase; Protein; Infection; Pathology; Vertebrata; Chronic; Experimental disease; Mammalia; nitrite; Animal; Bacteriosis; Oxidoreductases; pulmonary vascular resistance; Immunofluorescence
• ISSN: 0022-3417; 1096-9896
• DOI: 10.1002/path.1256

Inflammation in the lung can lead to increased expression of inducible nitric oxide synthase (iNOS) and enhanced NO production. It has been postulated that the resultant highly reactive NO metabolites may have an important role in host defence, although they might also contribute to tissue damage. However, in a number of inflammatory lung diseases, including bronchiectasis, iNOS expression is increased but no elevation of airway NO can be detected. A potential explanation for this finding is that NO is rapidly scavenged by reaction with superoxide radicals, forming peroxynitrite, which is preferentially metabolized via nitration and nitrosation reactions. To test this hypothesis, anaesthetized, specific pathogen-free rats were inoculated with Pseudomonas aeruginosa incorporated into agar beads (chronically infected group) or sterile agar beads (control group). Ten to 15 days later, the lungs were isolated and fixed. Pseudomonas organisms were isolated from the lungs of the chronically infected group. These lungs showed extensive inflammatory cell infiltration and tissue damage, which were not observed in control lungs. Expression of iNOS was increased in the chronically infected group when compared with the control group. However, the mean number of cells staining for nitrotyrosine in the chronically infected group was not significantly different from that in the controls, nor was there an excess of nitrotyrosine, nitrate, nitrite or nitrosothiol concentrations in the infected lungs. Thus, no evidence was found of increased NO metabolites in chronically infected lungs, including products of the peroxynitrite pathway. These findings suggest that chronic infection does not cause increased iNOS activity in the lung, despite increased expression of iNOS.