Role of inducible nitric oxide synthase expression and peroxynitrite formation in guinea pig ileitis.
OBJECTIVE
Inflammatory bowel disease is characterized by increased synthesis of nitric oxide. The aim of this study was to determine if inducible NO synthase (iNOS) was responsible for tissue injury, potentially via peroxynitrite formation, in the guinea pig model of gut inflammation.


METHODS
Inflammation was induced in guinea pig ileum by intraluminal administration of the hapten trinitrobenzene sulfonic acid in 50% ethanol. iNOS gene expression was assessed by reverse-transcriptase polymerase chain reaction and Western blotting, immunohistochemistry was determined by its localization, and activity was inhibited with the specific inhibitor aminoguanidine administered via the drinking water for 7 days. Nitration of tyrosines was assessed by immunohistochemistry.


RESULTS
In control animals, iNOS gene expression was minimal to absent, whereas, in hapten, inflammation-marked iNOS gene expression was evident from day 1 to 7. Nitrotyrosine and iNOS immunohistochemistry were colocalized, and positive staining was most intense in epithelia and neurons. Inhibition of NO formation prevented nitrotyrosine formation. Aminoguanidine inhibited the inflammatory response and restored morphology.


CONCLUSIONS
The colocalization of tyrosine nitration with iNOS immunoreactivity suggests that iNOS may be responsible for tissue injury and the formation of NO-dependent nitrating species, potentially peroxynitrite. Inhibition of iNOS may afford a new therapeutic approach to the treatment of inflammatory bowel disease.
Miller
M J
MJ
Department of Pediatrics, Louisiana State University Medical Center, New Orleans, USA.
Thompson
J H
JH
Zhang
X J
XJ
Sadowska-Krowicka
H
H
Kakkis
J L
JL
Munshi
U K
UK
Sandoval
M
M
Rossi
J L
JL
Eloby-Childress
S
S
Beckman
J S
JS
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004195:Disease Models, Animal; D004790:Enzyme Induction; D005260:Female; D015870:Gene Expression; D006146:Guanidines / Q000494:pharmacology; D006168:Guinea Pigs; D007079:Ileitis / Q000201:enzymology*; D007150:Immunohistochemistry; D008297:Male; D008969:Molecular Sequence Data; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000037:antagonists & inhibitors / Q000235:genetics*; D009573:Nitrites / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
D006146:Guanidines; D009573:Nitrites; D014443:Tyrosine; D019001:Nitric Oxide Synthase; C004479:pimagedine