The Intestinal Anti-inflammatory Activity of UR-12746S on Reactivated Experimental Colitis Is Mediated Through Downregulation of Cytokine Production *Julio Ga ´lvez, *Margarita Garrido, *Maria Elena Rodrı ´guez-Cabezas, †Isabel Ramis, *Fermı ´n Sa ´nchez de Medina, †Manuel Merlos, and *Antonio Zarzuelo *Department of Pharmacology, University of Granada, Granada, Spain; †Department of Pharmacology, J. Uriach & Cia S.A., Palau-solita ` i Plegamans, Barcelona, Spain Summary: Background: UR-12746S (dersalazine sodium) is cleaved by colonic bacteria delivering the PAF antagonist UR- 12715 and 5-ASA. This study describes the anti-inflammatory activity of UR-12746S in an experimental model of reactivated colitis and its effects on cytokine production. Methods: Rats were initially rendered colitic by a colonic instillation of 10 mg of trinitrobenzenesulphonic acid (TNBS) dissolved in 0.25 ml of 50 % ethanol, and colitis was reactivated two weeks after by a second administration of the same dose of TNBS. Two groups of colitic rats received UR-12746S (25 and 50 mg/kg daily, p.o.) and colonic damage was evaluated every week for 4 weeks. Different biochemical markers of colonic inflammation were assayed: MPO activity and cytokine (IL-1 and TNF) levels. Also, the in vitro effects of UR-12715 and 5-ASA on cytokine production were assayed. Results: UR-12746S showed anti-inflammatory effect in reactivated colitis in rats, as evidenced by a significant reduction in MPO activity. Both doses of UR-12746S decreased IL-1 production, while only the highest dose assayed inhibited TNF production. In vitro studies revealed that UR-12715 or 5-ASA (from 10 -6 to 10 -4 M) inhibited IL-8 production (30–40 %) in HT-29 cells when incubated with LPS. This inhibitory effect was enhanced when both compounds were administered simultaneously at 10 -4 M. In addition, UR-12715 inhibited IL-1 or TNF production in THP-1 or U937 cells, respectively, when these cells were stimulated by PMA and LPS; whereas 5-ASA only showed a weak effect in inhibiting IL-1 production. Conclusion: UR- 12746S was able to prevent relapse in experimental colitis and inhibition of proinflammatory cytokine production participates in the intestinal anti-inflammatory activity exerted by this com- pound. Key Words: Rat experimental colitis—UR-12746S (dersalazine sodium)—IL-1–TNF—IL-8 INTRODUCTION Chronic inflammatory bowel diseases (IBD), mainly ulcerative colitis and Crohn’s disease, are naturally re- mitting and recurring conditions of the digestive tract. These are probably related to an abnormal exacerbated immune response to otherwise innocuous stimuli which is not properly abrogated by the feedback system that normally downregulates the mucosal response to luminal factors (1). As a consequence, increased numbers of in- flammatory cells are found in areas of the intestine with chronic inflammation. This results in an overproduction of a variety of proinflammatory mediators, such as eico- sanoids, platelet activating factor (PAF), reactive oxygen metabolites and cytokines, thus influencing mucosal in- tegrity and leading to excessive tissue injury (2,3). More- over, most of these mediators can induce the biosynthesis and release of others, generating a “vicious cycle” that may result in the propagation and perpetuation of the inflammatory response. At present, a specific causal treatment of IBD is still not available, and for this reason the best chance to effectively counteract the exacerbated immune response that characterizes IBD may be to in- terfere with multiple stages of the inflammatory cascade, preferably with a unique drug treatment (4). The phar- macological profile of UR-12746S (sodium salt of UR- 12746) makes it a good candidate to be developed for the treatment of IBD. Through an azo bond, this compound Received July 9, 2002; accepted April 2, 2003. Address correspondence to Dr. J. Gálvez, Department of Pharma- cology, School of Pharmacy, University of Granada, Campus Univer- sitario “La Cartuja” s/n, 18071 Granada, Spain. E-mail: jgalvez@ugr.es Sources of support: Instituto de Salud ‘Carlos III’ (FIS 01/0936 and PI021732), Spanish Ministry of Science and Technology (Project SAF2002-02592, and through the Program of Fomento de la Investi- gación Técnica del Plan Nacional de Investigación Científica, Desa- rrollo e Innovación Tecnológica 2000–2003) and J. Uriach & Cia. S.A. Inflammatory Bowel Diseases 9(6):363–371 © 2003 Crohn’s & Colitis Foundation of America, Inc. 363