Pulmonary oxidant stress in murine sepsis is due to inflammatory cell nitric oxide.
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.
Razavi
Habib M
HM
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.
Wang
Lefeng
L
Weicker
Sean
S
Quinlan
Greg J
GJ
Mumby
Sharon
S
McCormack
David G
DG
Mehta
Sanjay
S
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
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