Anti-inflammatory, anti-apoptotic, and antioxidant effects of obestatin on the colonic mucosa following acetic acid-induced colitis

Background: Cellular inflammatory processes, fibrogenesis, and apoptosis are the most characteristic pathologic features of colonic injury and colitis in human and experimental animals. Obestatin, a peptide derived from proghrelin, is reported to have significant protective and curative actions on many gastrointestinal tract inflammatory diseases, including ulcerative colitis. However, its exact protective mechanisms and the associated histopathological changes, are still in need of deeper exploration. This study explores the effect of obestatin on the course of acetic acid (AA)-induced colitis as an antifibrotic, anti-inflammatory, and anti-ap- optotic agent in relation to associated tissue stress parameters. Materials and methods: A total of 40 healthy male albino Wistar rats weighing 200-250 g were recruited in this study. The rats were classified into four groups (10 rats each); group I: control, group II: obestatin only treated (16 nmol/kg), group III: colitis induced group (AA 1 mL of 3.5% (v/v), and group IV: AA-induced colitis + obestatin for 14 days. Colonic samples were examined after staining haema- toxylin and eosin, Alcian blue, Masson trichrome. The expression of proliferating cell nuclear antigen (PCNA), nuclear factor kappa B (NFkB), and caspase-3 was estimated after immunohistochemical staining. Oxidative stress parameters, anti-oxidant enzymes, tissue myeloperoxidase (MPO) activity, ghrelin, and fibrogenesis markers were identified by immunoassay and colorimetric techniques. Results: Colonic mucosa of group IV exhibited mucosal healing and regeneration of the surface epithelium with the restoration of the goblet cells' function together with a decline in PCNA, NFkB, and caspase-3 immunoreactivity in comparison to group III. This was accompanied by a reduction of the expression of fibrosis markers, hydroxyproline and fibronectin. In addition, tissue antioxidant status was significantly improved with a marked reduction of tissue MPO. Ghrelin level was significantly increased in comparison to group III. Group IV exhibited significant reduction in the levels of oxidative stress markers, malondialdehyde, total oxidant status with a marked increase in the activity of antioxidant enzymes, superoxide dismutase, catalase, and total cellular total antioxidant capacity. Conclusions: The concomitant treatment of obestatin inhibits the development of AA-induced colitis. The data signify that it has both curative and protective effects via antifibrotic, antioxidant, and anti-inflammatory activities. (Folia Morphol 2023; 82, 3: 641-655)