Experimental Ulcerative Colitis Impairs Antioxidant Defense System in Rat Intestine N. NIETO, PhD, M.I. TORRES, PhD, M.I. FERNA ´ NDEZ, PhD, M.D. GIRO ´ N, PhD, A. RI ´ OS, PhD, M.D. SUA ´ REZ, PhD, and A. GIL, PhD Increasing attention has been given recently to the role of free radicals in the pathogenesis of ulcerative colitis, since the inflamed intestine is exposed to oxidative stress generated by infiltrating macrophages and neutrophils within the lamina propia. The overall goal of this study was to evaluate whether experimental ulcerative colitis induces significant changes in the antioxidant defense system in an experimental model induced by the intrarectal admin- istration of 2,4,6-trinitrobenzenesulfonic acid. Twenty rats were treated with 80 mg/kg body weight of trinitrobenzenesulfonic acid and 20 with the same volume of 0.9% NaCl. Rats were killed at one and two weeks after treatment to evaluate colon damage by light and electron transmission microscopy. The degree of tissue injury and inflammation was determined by measuring alkaline phosphatase, g-glutamyltranspeptidase, and myeloperoxidase activities and prostaglandin E 2 and leukotriene B 4 . Glutathione levels and the activity of the enzymes of the antioxidant defense system were determined. Enzymatic markers of colon injury showed higher activities in rats with ulcerative colitis. Concentrations of prostaglandin E 2 and leukotriene B 4 were higher in the groups treated for one week with trinitrobenzenesulfonic acid and markers decreased after two weeks of treatment. All antioxidant enzyme activities were higher at one and two weeks after treatment; however, a significant decrease in total glutathione content was also observed. In conclusion, ulcerative colitis induced by trinitro- benzenesulfonic acid damages the intestinal mucosa and is accompanied by a shift in the antioxidant enzyme activities, and low levels of glutathione. This deficiency in glutathione could be a target for new therapies to treat ulcerative colitis. KEY WORDS: trinitrobenzenesulfonic acid; ulcerative colitis; antioxidant defense system; eicosanoids; reactive oxygen species. Ulcerative colitis (UC) and Crohn’s disease are chronic inflammatory diseases of the gastrointestinal tract identified and diagnosed by a set of clinical, endoscopic, and histological features (1–3). A model of acute colitis in animals has been achieved by the intrarectal administration of toxic agents such as 2,4,6-trinitrobenzenesulfonic acid (TNBS) into rat co- lon (4 – 6). This model resembles histological features of the human UC such as transmural inflammation with granuloma and Langhans-type giant cells, skip- segment ulceration and inflammation, cobblestone- like appearance of the mucosa, mast cell and lym- phoid infiltrates, as well as crypt distortion (7, 8). The TNBS model previously described by other authors (6, 7, 9) is a good experimental model of UC that can be used to study acute and chronic mucosal damage of the colon, and the biochemical phenom- Manuscript received July 29, 1999; revised manuscript received January 28, 2000; accepted February 20, 2000. From the Departments of Biochemistry and Molecular Biology and Cell Biology, University of Granada, Granada, Spain. These studies were supported by the CI1-CT91-0078 grant from the European Union (AG). N. Nieto is currently working in the Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, One Gustave L. Levy Place, New York, New York 10029. Address for reprint requests: Prof. A ´ ngel Gil, Department of Biochemistry and Molecular Biology, Facultad de Farmacia, Uni- versidad de Granada, Campus Universitario de Cartuja s/n, 18071 Granada, Spain. Digestive Diseases and Sciences, Vol. 45, No. 9 (September 2000), pp. 1820 –1827 1820 Digestive Diseases and Sciences, Vol. 45, No. 9 (September 2000) 0163-2116/00/0900-1820$18.00/0 © 2000 Plenum Publishing Corporation