Inducible nitric oxide synthase and heme oxygenase-1 in the lung during lipopolysaccharide tolerance and cross tolerance.
OBJECTIVE
Pretreatment with low-dose lipopolysaccharide protects cells/organs against a subsequent lethal Gram-negative (lipopolysaccharide tolerance) or Gram-positive (cross tolerance) stimulus. We determined whether this occurs in the rat lung. The involvement of inducible nitric oxide synthase and heme oxygenase-1 was evaluated.


METHODS
Laboratory study.


METHODS
University hospital laboratory.


METHODS
Anesthetized male Wistar rats.


METHODS
To test the hypothesis, rats received saline or lipopolysaccharide (1 mg/kg). At 2, 4, 8, 16, or 24 hrs later, blood samples and lung tissue were taken to determine messenger RNA, protein concentration, and activity of inducible nitric oxide synthase and heme oxygenase-1. In additional experiments, rats were challenged with lipopolysaccharide (1 mg/kg) and subjected to Gram-negative (lipopolysaccharide) or Gram-positive (lipoteichoic acid and peptidoglycan) shock 24 hrs later. These studies were carried out in the presence and absence of inducible nitric oxide synthase or heme oxygenase-1 inhibitors (1400W or tin protoporphyrin IX). Following 6 hrs of shock, lung tissue was taken to determine lung damage and heme oxygenase-1 concentration and activity.


RESULTS
In the rat lung, lipopolysaccharide (1 mg/kg) induced a significant increase in inducible nitric oxide synthase protein at 8 hrs with a corresponding increase in plasma nitrate/nitrite at 8-16 hrs. Simultaneously, heme oxygenase-1 messenger RNA transcripts were observed at 8-16 hrs, and maximal expression of the protein followed (24 hrs). Pretreatment with low-dose lipopolysaccharide reduced myeloperoxidase activity (neutrophil infiltration) and wet-dry ratio (pulmonary edema) in the lungs of animals subjected to Gram-negative or Gram-positive shock, demonstrating tolerance. Pretreatment with low-dose lipopolysaccharide and the selective inducible nitric oxide synthase inhibitor 1400W reduced heme oxygenase-1 protein expression, and lung protection was abolished. Tin protoporphyrin IX did not affect heme oxygenase-1 expression, but heme oxygenase activity and lung protection were significantly reduced.


CONCLUSIONS
We propose that nitric oxide (most likely inducible nitric oxide synthase derived) regulates the induction of heme oxygenase-1 in the lung, which in turn plays an important part in pulmonary protection during lipopolysaccharide tolerance and cross tolerance.
Koch
Alexander
A
Molecular Cardioprotection and Inflammation Group, Department of Anesthesia, Bristol University, Bristol, UK.
Boehm
Olaf
O
Zacharowski
Paula A
PA
Loer
Stephan A
SA
Weimann
Jörg
J
Rensing
Hauke
H
Foster
Simon J
SJ
Schmidt
Rene
R
Berkels
Reinhard
R
Reingruber
Sonja
S
Zacharowski
Kai
K
D000818:Animals; D003888:Desensitization, Immunologic; D005786:Gene Expression Regulation / Q000276:immunology; D016905:Gram-Negative Bacterial Infections / Q000276:immunology; D016908:Gram-Positive Bacterial Infections / Q000276:immunology; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D007108:Immune Tolerance / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology*; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008297:Male; D052247:Nitric Oxide Synthase Type II / Q000276:immunology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D012772:Shock, Septic / Q000276:immunology* / Q000473:pathology
D008070:Lipopolysaccharides; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1