title: Pulmonary oxidant stress in murine sepsis is due to inflammatory cell nitric oxide.
abstract: OBJECTIVE
  Pulmonary oxidant stress is an important pathophysiologic feature of acute lung injury. It is unclear whether nitric oxide contributes to this oxidant stress. Thus, we examined the role of inducible nitric oxide synthase (iNOS) in pulmonary oxidant stress in murine sepsis and the differential contribution of different cellular sources of iNOS.
  
  
  METHODS
  Randomized, controlled animal study.
  
  
  METHODS
  Research laboratory of an academic institution.
  
  
  METHODS
  Male iNOS+/+, iNOS-/- C57Bl/6 mice, and bone-marrow transplanted iNOS chimeric mice: +to- (wild-type iNOS+/+ donor bone-marrow transplanted into iNOS-/- recipient mice) and the reciprocal -to+ chimeras.
  
  
  METHODS
  Animals were randomized to sepsis (n = 264), induced by cecal ligation and perforation, vs. naive groups (n = 138).
  
  
  RESULTS
  In septic iNOS-/- vs. wild-type iNOS+/+ mice, sepsis-induced pulmonary oxidant stress (33 +/- 11 [mean +/- sem] vs. 365 +/- 48 pg 8-isoprostane/mg protein, p < .01) and nitrosative stress (0.0 +/- 0.0 vs. 0.9 +/- 0.4 micromol 3-nitrotyrosine/mmol para-tyrosine, p < .05) were abolished, despite similar septic increases in pulmonary myeloperoxidase activity in both (86 +/- 20 vs. 83 +/- 12 mU/mg protein, p = .78). In +to- iNOS chimeric mice (iNOS localized only to donor bone-marrow-derived inflammatory cells), cecal ligation and perforation resulted in significant pulmonary oxidant stress (368 +/- 81 pg 8-isoprostane/mg protein) and nitrosative stress (0.6 +/- 0.2 micromol 3-nitrotyrosine/mmol para-tyrosine), similar in degree to septic wild-type mice. In contrast, pulmonary oxidant and nitrosative stresses were absent in septic -to+ iNOS chimeras (iNOS localized only to recipient parenchymal cells), similar to iNOS-/- mice.
  
  
  CONCLUSIONS
  In murine sepsis-induced acute lung injury, pulmonary oxidant stress is completely iNOS dependent and is associated with tyrosine nitration. Moreover, pulmonary oxidant stress and nitrosative stress were uniquely dependent on the presence of iNOS in inflammatory cells (e.g., macrophages and neutrophils), with no apparent contribution of iNOS in pulmonary parenchymal cells. iNOS inhibition targeted specifically to inflammatory cells may be an effective therapeutic approach in sepsis and acute lung injury.
authors.affiliation: Centre for Critical Illness Research, Lawson Health Research Institute, Division of Respirology, London Health Sciences Center and Department of Medicine, University of Western Ontario, London, ON, Canada.
authors.forename: Habib M
authors.initials: HM
authors.lastname: Razavi
authors.forename: Lefeng
authors.initials: L
authors.lastname: Wang
authors.forename: Sean
authors.initials: S
authors.lastname: Weicker
authors.forename: Greg J
authors.initials: GJ
authors.lastname: Quinlan
authors.forename: Sharon
authors.initials: S
authors.lastname: Mumby
authors.forename: David G
authors.initials: DG
authors.lastname: McCormack
authors.forename: Sanjay
authors.initials: S
authors.lastname: Mehta
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016026:Bone Marrow Transplantation; D002678:Chimera; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000201:enzymology; D016676:Macrophages, Alveolar / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D018384:Oxidative Stress; D011897:Random Allocation; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*; D018805:Sepsis / Q000503:physiopathology*; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C075750:8-epi-prostaglandin F2alpha; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D015237:Dinoprost; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse