Targeted deletion of neuropeptide Y (NPY) modulates experimental colitis.
BACKGROUND
Neurogenic inflammation plays a major role in the pathogenesis of inflammatory bowel disease (IBD). We examined the role of neuropeptide Y (NPY) and neuronal nitric oxide synthase (nNOS) in modulating colitis.


METHODS
Colitis was induced by administration of dextran sodium sulphate (3% DSS) or streptomycin pre-treated Salmonella typhimurium (S.T.) in wild type (WT) and NPY (NPY(-/-)) knockout mice. Colitis was assessed by clinical score, histological score and myeloperoxidase activity. NPY and nNOS expression was assessed by immunostaining. Oxidative stress was assessed by measuring catalase activity, glutathione and nitrite levels. Colonic motility was assessed by isometric muscle recording in WT and DSS-treated mice.


RESULTS
DSS/S.T. induced an increase in enteric neuronal NPY and nNOS expression in WT mice. WT mice were more susceptible to inflammation compared to NPY(-/-) as indicated by higher clinical & histological scores, and myeloperoxidase (MPO) activity (p<0.01). DSS-WT mice had increased nitrite, decreased glutathione (GSH) levels and increased catalase activity indicating more oxidative stress. The lower histological scores, MPO and chemokine KC in S.T.-treated nNOS(-/-) and NPY(-/-)/nNOS(-/-) mice supported the finding that loss of NPY-induced nNOS attenuated inflammation. The inflammation resulted in chronic impairment of colonic motility in DSS-WT mice. NPY -treated rat enteric neurons in vitro exhibited increased nitrite and TNF-alpha production.


CONCLUSIONS
NPY mediated increase in nNOS is a determinant of oxidative stress and subsequent inflammation. Our study highlights the role of neuronal NPY and nNOS as mediators of inflammatory processes in IBD.
Division of Digestive Diseases, Emory University, Atlanta, Georgia, United States of America.
Bindu
B
Chandrasekharan
Vanitha
V
Bala
Vasantha L
VL
Kolachala
Matam
M
Vijay-Kumar
Dean
D
Jones
Andrew T
AT
Gewirtz
Shanthi V
SV
Sitaraman
Shanthi
S
Srinivasan
D000818:Animals; D002374:Catalase / Q000032:analysis / Q000378:metabolism; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D016264:Dextran Sulfate / Q000633:toxicity; D004195:Disease Models, Animal; D017353:Gene Deletion; D005978:Glutathione / Q000032:analysis / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D015212:Inflammatory Bowel Diseases / Q000378:metabolism / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009478:Neuropeptide Y / Q000235:genetics* / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism*; D009573:Nitrites / Q000032:analysis / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D009195:Peroxidase / Q000032:analysis / Q000378:metabolism
D009478:Neuropeptide Y; D009573:Nitrites; D016264:Dextran Sulfate; D002374:Catalase; D009195:Peroxidase; D052248:Nitric Oxide Synthase Type I; D005978:Glutathione