Inhaled nitric oxide prevents 3-nitrotyrosine formation in the lungs of neonatal mice exposed to >95% oxygen.
Inhaled nitric oxide is being evaluated as a preventative therapy for patients at risk for bronchopulmonary dysplasia (BPD). Nitric oxide (NO), in the presence of superoxide, forms peroxynitrite, which reacts with tyrosine residues on proteins to form 3-nitrotyrosine (3-NT). However, NO can also act as an antioxidant and was recently found to improve the oxidative balance in preterm infants. Thus, we tested the hypothesis that the addition of a therapeutically relevant concentration (10 ppm) of NO to a hyperoxic exposure would lead to decreased 3-NT formation in the lung. FVB mouse pups were exposed to either room air (21% O(2)) or >95% O(2) with or without 10 ppm NO within 24 h of birth. In the first set of studies, body weights and survival were monitored for 7 days, and exposure to >95% O(2) resulted in impaired weight gain and near 100% mortality by 7 days. However, the mortality occurred earlier in pups exposed to >95% O(2) + NO than in pups exposed to >95% O(2) alone. In a second set of studies, lungs were harvested at 72 h. Immunohistochemistry of the lungs at 72 h revealed that the addition of NO decreased alveolar, bronchial, and vascular 3-NT staining in pups exposed to both room air and hyperoxia. The lung nitrite levels were higher in animals exposed to >95% oxygen + NO than in animals exposed to >95% oxygen alone. The protein levels of myeloperoxidase, monocyte chemotactic protein-1, and intracellular adhesion molecule-1 were assessed after 72 h of exposure and found to be greatest in the lungs of pups exposed to >95% O(2). This hyperoxia-induced protein expression was significantly attenuated by the addition of 10 ppm NO. We propose that in the presence of >95% O(2), peroxynitrite formation results in protein nitration; however, adding excess NO to the >95% O(2) exposure prevents 3-NT formation by NO reacting with peroxynitrite to produce nitrite and NO(2). We speculate that the decreased protein nitration observed with the addition of NO may be a potential mechanism limiting hyperoxic lung injury.
Pulmonary Hypertension Group, Center for Perinatal Research, The Research Institute at Nationwide Children's Hospital, 700 Children's Drive, Columbus, OH 43205, USA. Michael.Stenger@nationwidechildrens.org
Michael R
MR
Stenger
Melissa J
MJ
Rose
Mandar S
MS
Joshi
Lynette K
LK
Rogers
Louis G
LG
Chicoine
John Anthony
JA
Bauer
Leif D
LD
Nelin
D000818:Animals; D018932:Chemokine CCL2 / Q000032:analysis; D018496:Hyperoxia / Q000378:metabolism / Q000473:pathology; D018799:Intercellular Adhesion Molecule-1 / Q000032:analysis; D008168:Lung / Q000187:drug effects / Q000473:pathology; D055370:Lung Injury / Q000139:chemically induced / Q000473:pathology / Q000517:prevention & control*; D051379:Mice; D009569:Nitric Oxide / Q000008:administration & dosage*; D010100:Oxygen / Q000009:adverse effects; D009195:Peroxidase / Q000032:analysis; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000096:biosynthesis
D018932:Chemokine CCL2; D018799:Intercellular Adhesion Molecule-1; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D009195:Peroxidase; D010100:Oxygen