Nitric oxide inhalation inhibits inducible nitric oxide synthase but not nitrotyrosine formation and cell apoptosis in rat lungs with meconium-induced injury.
OBJECTIVE
To investigate the effects of inhaled nitric oxide (NO) on pulmonary inflammation, apoptosis, peroxidation and protein nitration in a rat model of acute lung injury (ALI) induced by meconium.


METHODS
Twenty-four healthy male Sprague-Dawley rats were randomly devided into 3 groups (n=8): meconium-induced ALI with intratracheal instillation of 1 mL/kg saline (Mec/saline group), continuous inhalation of NO at 20 muL/L. (Mec/iNO), and the control group (control). Electromicroscopic examination was used to determine the extent of epithelial apoptosis. TUNEL was used to detect DNA fragmentation in pulmonary apoptotic cells, expressed as the apoptosis index (AI). Western blotting was used to detect pulmonary inducible NO synthase (iNOS) expression. RT-PCR was used to detect interleukin (IL)-1beta mRNA expression. Cell count in bronchoalveolar lavage (BAL), myeloperoxidase (MPO) activity, as well as malondialdehyde (MDA) and nitrotyrosine formation, the markers of toxic NO-superoxide pathway in rat lung parenchyma specimens, were also examined.


RESULTS
Expression of iNOS protein and IL-1beta mRNA were increased significantly in the Mec/saline group (both P<0.01) compared with the control group. BAL cell count, MPO activity, lung injury score, pulmonary AI, MDA level and nitrotyrosine formation were also increased significantly (all P<0.01). The meconium-induced iNOS protein and IL-1beta mRNA expression were inhibited significantly by NO inhalation when compared with the Mec/saline group (both P<0.01). BAL cell count, MPO activity and lung injury score were also decreased significantly (P<0.01 or P<0.05). However, there were no statistical differences in MDA level, nitrotyrosine formation or pulmonary AI between the Mec/saline and Mec/iNO groups. Electromicroscopic examination revealed a significant degree of epithelial apoptosis in both the Mec/saline and Mec/iNO groups.


CONCLUSIONS
Early continuous inhalation of NO 20 muL/L may protect the lungs from inflammatory injury, but does not decrease epithelial apoptosis or lung nitrotyrosine formation. Inhalation of NO alone is not associated with a detectable increase in oxidant stress.
Lu
Mei-Ping
MP
Neonatal Intensive Care Unit, Department of Pediatrics, Children's Hospital, Zhejiang University School of Medicine, Hangzhou 310003, China.
Du
Li-zhong
LZ
Gu
Wei-zhong
WZ
Chen
Xiang-xiang
XX
D000280:Administration, Inhalation; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D007375:Interleukin-1 / Q000096:biosynthesis / Q000235:genetics; D008168:Lung / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D008470:Meconium; D009569:Nitric Oxide / Q000008:administration & dosage / Q000494:pharmacology*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D012128:Respiratory Distress Syndrome / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D007375:Interleukin-1; D012333:RNA, Messenger; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D008315:Malondialdehyde; D009195:Peroxidase; D052247:Nitric Oxide Synthase Type II