Benefit of nicorandil using an immunologic murine model of experimental colitis

Inflammatory bowel disease (IBD) is a chronic inflammatory condition with an unknown etiology. Nicorandil, a potassium channel opener, has been used for many years for the treatment of angina. Recently, it has been shown that nicorandil possesses some novel traits such as anti-apoptotic, gastroprotective, free radical scavenging, and anti-inflammatory properties. Therefore, we set out to examine the possible beneficial effect of nicorandil in a rat model of IBD. Colitis was induced by rectal administration of 2,4,6-trintrobenzene sulphonic acid (TNBS) into rats. Groups of animals used in this study were sham, control, and exposure to dexamethasone, nicorandil, glibenclamid (a pure adenosine triphosphate sensitive potassium channel (KATP) blocker), or nicorandil plus glibenclamid. Drugs were administered by gavage and animals were sacrificed after 7 days. Biochemical markers, including TNF-α and IL-1β, ferric reducing/antioxidant power (FRAP), myeloperoxidase (MPO) activity and thiobarbitoric acid-reactive substance (TBARS), were measured in the homogenate of colonic tissue. Results indicate that nicorandil significantly reduces macroscopic and histological damage induced by TNBS. Nicorandil diminishes MPO activity and levels of TBARS, TNF-∢, and IL-1β in damaged colonic tissue with a concomitant increase in FRAP value (P<0.01). These effects were not reversed by coadministration of glibenclamide. In conclusion, nicorandil is able to ameliorate experimental IBD with a dose in which it does not show any anti-hypertensive effect, and the mechanism of which is partially or totally independent from KATP channels. It is hypothesized that nitric oxide donation and free-radical scavenging properties of nicorandil upregulate endothelial nitric oxide synthase may be responsible for this phenomenon. These findings suggest that nicorandil can be useful in treatment of IBD, although further investigations are needed to elucidate the mechanisms involved.