The effects of intra-rectal and intra-peritoneal application of Origanum onites L. essential oil on 2,4,6-trinitrobenzenesulfonic acid-induced colitis in the rat.

The aim of the present study is to investigate the treatment efficiency of intra-rectal (IR) and intra-peritoneal (IP) application of Origanum onites essential oil (OOEO), which is a well-known antioxidant, in the colitis model induced by 2,4,6-trinitrobenzenesulfonic acid (TNBS) and ethanol (E) in comparison with dexamethasone therapy through the morphologic damage score. Monoclonal antibodies against intercellular adhesion molecule-1 (ICAM-1, CD54), anti-rat granulocytes, and myeloperoxidase (MPO), were also investigated immunohistochemically. There was a significant difference in terms of ulceration, mucus cell depletion, inflammatory cell infiltration, vascular dilatation (p<0.001), crypt abscesses (p<0.01), and edema (p<0.05) between OOEO-1mg/kg-IR and control colitis groups. A significant difference was encountered in terms of mucus cell depletion, crypt abscesses, inflammatory cell infiltration, vascular dilatation (p<0.01), and ulceration (p<0.05) between the OOEO-0.1mg/kg-IR and control colitis groups. A significant difference was noticed in terms of ulceration, inflammatory cell infiltration, mucus cell depletion (p<0.001), vascular dilatation (p<0.01), and mucosal atrophy (p<0.05) between the OOEO-1mg/kg-IP and control colitis groups. There was a significant difference in terms of ulceration, mucus cell depletion, inflammatory cell infiltration (p<0.001), crypt abscesses, vascular dilatation (p<0.01), and mucosal atrophy (p<0.05) between the OOEO-0.1mg/kg-IP and control colitis groups. No significant difference was determined in terms of ulceration, inflammatory cyst, mucosal atrophy, edema, and vascular dilatation between the dexamethazone and control colitis groups (p>0.05). Under the present conditions, we concluded that IR and IP OOEO treatment, applied at the dosage of 0.1 or 1mg/kg/day, have a significant protective effect on the colonic injury.