Nitric oxide inhibits rat intestinal secretion by Clostridium difficile toxin A but not Vibrio cholerae enterotoxin.
OBJECTIVE
Intestinal inflammation is associated with increased synthesis of nitric oxide, whereas inhibition of NO synthase (NOS) reduces experimental chronic intestinal inflammation. The aim of this study was to test the effects of NO blockers and donors on acute intestinal inflammation induced by Clostridium difficile toxin A in rat ileum.


METHODS
Rats received NOS inhibitors or NO donors before measurement of toxin-mediated ileal secretion and permeability changes. Mucosal mast cell and neutrophil activity were measured by release of rat mast cell protease II and myeloperoxidase activity, respectively.


RESULTS
NOS inhibitors augmented but an NO donor inhibited toxin A-mediated ileal secretion and permeability when given before but not after toxin administration. Neither an NOS inhibitor nor an NO donor had any effect on cholera toxin-mediated secretion. Mast cell degranulation and neutrophil infiltration occurred after injection of toxin A or an NOS inhibitor, whereas the NO donor blocked both toxin A effects.


CONCLUSIONS
NOS inhibitors augmented and an NO donor blocked the intestinal effects of toxin A but not of cholera toxin. NO protects against toxin A by inhibition of intestinal mast cells and neutrophils, which are activated by toxin A, but not by cholera toxin.
Qiu
B
B
Section of Gastroenterology, Boston University Medical Center Hospital, Massachusetts, USA.
Pothoulakis
C
C
Castagliuolo
I
I
Nikulasson
Z
Z
LaMont
J T
JT
D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001427:Bacterial Toxins; D015550:Cell Degranulation / Q000187:drug effects; D053818:Chymases; D016360:Clostridioides difficile / Q000378:metabolism*; D004768:Enterotoxins / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006146:Guanidines / Q000494:pharmacology; D007082:Ileum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D010539:Permeability; D009195:Peroxidase / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012697:Serine Endopeptidases / Q000378:metabolism; D014734:Vibrio cholerae / Q000378:metabolism*
D001427:Bacterial Toxins; D004768:Enterotoxins; D004791:Enzyme Inhibitors; D006146:Guanidines; D007191:Indazoles; C037420:stN protein, Vibrio cholerae; C041348:tcdA protein, Clostridium difficile; D009569:Nitric Oxide; C024940:S-nitroso-N-acetylcysteine; D001120:Arginine; D009195:Peroxidase; D019001:Nitric Oxide Synthase; D012697:Serine Endopeptidases; C083294:chymase 2; D053818:Chymases; C004479:pimagedine; C080122:7-nitroindazole; D019331:NG-Nitroarginine Methyl Ester; D000111:Acetylcysteine