Amelioration of experimental colitis by Na-H exchanger-1 inhibitor amiloride is associated with reversal of IL-1ss and ERK mitogen-activated protein kinase.
OBJECTIVE
Na-H exchanger-1 (NHE-1) is induced in experimental colitis. It has not yet been established whether its inhibition ameliorates colitis. The effects of amiloride, an inhibitor of NHE-1, on colitis were examined in this study. Levels of mitogen-activated protein (MAP) kinases ERK, p38 and interleukin 1ss which participate in intestinal inflammation were also examined in the colonic smooth muscle of rats with colitis.


METHODS
Colitis was induced in Sprague-Dawley male rats by intrarectal administration of trinitrobenzenesulphonic acid (TNBS) and treated daily with amiloride (3, 5, and 10 mg/kg b.w. (body-weight), orally) starting 1 h before induction of colitis. The animals were sacrificed on day 5 post-TNBS. Controls received phosphate buffered saline in a similar manner.


RESULTS
The highest dose of amiloride (10 mg/kg) was lethal. The lowest dose (3 mg/kg) was tolerated and was used in this study. Amiloride significantly reversed the colitis-reduced contractility and induction of MPO activity, NHE-1, IL-1ss and ERK, but not of p38 in inflamed colonic smooth muscle. Splenomegaly, increased colonic mass and decreased sodium pump activity were significantly reversed by amiloride treatment. There was no recovery of b.w. loss in the treated colitic animals. Urine output was increased, whereas food and water intake remained unchanged following amiloride treatment.


CONCLUSIONS
These findings suggest that the beneficial effects of NHE-1 inhibition in experimental colitis are mediated through IL-1ss and ERK MAP kinase.
Khan
Islam
I
Department of Biochemistry, Kuwait University. Islam@hsc.edu.kw
Oriowo
Mabayoje A
MA
Anim
Jehoram T
JT
D000584:Amiloride / Q000627:therapeutic use*; D000818:Animals; D015153:Blotting, Western; D003092:Colitis / Q000139:chemically induced / Q000188:drug therapy*; D004232:Diuretics / Q000627:therapeutic use*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D007375:Interleukin-1 / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000378:metabolism; D009195:Peroxidase / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism; D014302:Trinitrobenzenesulfonic Acid; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D004232:Diuretics; D007375:Interleukin-1; D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride; D014302:Trinitrobenzenesulfonic Acid; D009195:Peroxidase; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases