TROPISETRON DIMINISHES DEMYELINATION AND DISEASE SEVERITY IN AN ANIMAL MODEL OF MULTIPLE SCLEROSIS A. AMINIAN, a F. NOORBAKHSH, b M. GHAZI-KHANSARI, a L. KAFAMI, c S. JAVADI, a G. HASSANZADEH, d,e R. RAHIMIAN, a,f A. R. DEHPOUR a AND S. E. MEHR a * a Department of Pharmacology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran b Department of Immunology, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran c Shefa Neuroscience Research Center, Tehran, Iran d Department of Anatomy, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran e Department of Neuroscience, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran f Brain and Spinal Injury Repair Research Center, Tehran University of Medical Sciences, Tehran, Iran Abstract—Tropisetron, a selective 5-HT3 receptor (5-HT3R) antagonist, has been widely used to counteract chemother- apy-induced emesis. New investigations described the immunomodulatory properties of tropisetron which may not be 5HT3R mediated. In the present study, we assessed the potential effects of tropisetron on an animal model of multiple sclerosis (MS), experimental autoimmune encepha- lomyelitis (EAE). EAE was induced in C57BL/6 mice by mye- lin oligodendrocyte glycoprotein peptide (MOG 35-55 ) immunization. Animals were treated with tropisetron (5 mg/ kg/day); m-chlorophenylbiguanide (mCPBG), a selective 5- HT3R agonist (10 mg/kg/day); tropisetron (5 mg/kg/day) plus mCPBG (10 mg/kg/day), and granisetron (5 mg/kg/day) intra- peritoneally on days 3–35 post-immunization. Treatment with tropisetron and granisetron markedly suppressed the clinical symptoms of EAE (p < 0.001) and reduced leuko- cyte infiltration as well as demyelination in the spinal cord (p < 0.05). In addition, in vivo tropisetron, granisetron or tropisetron plus mCPBG therapy greatly reduced in vitro MOG 35-55 -stimulated proliferation of mononuclear cells from spleens, and MOG 35-55 -induced IL-2, IL-6 and IL-17 produc- tion by splenocytes isolated from EAE-induced mice (p < 0.05). Concurrent administration of tropisetron and mCPBG did not significantly alter the histological damage in the spinal cord. mCPBG had no effect on the mentioned parameters. Taken together, these findings indicate that tropisetron has considerable immunoregulatory functions in EAE and may be promising for the treatment of MS or other autoimmune and inflammatory diseases of the CNS. Furthermore, beneficial effects of tropisetron in this setting seem to be both receptor dependent and recep- tor independent in the early phase of the disease. Ó 2013 IBRO. Published by Elsevier Ltd. All rights reserved. Key words: tropisetron, 5-HT3 receptor, experimental auto- immune encephalomyelitis, multiple sclerosis. INTRODUCTION Tropisetron, a selective 5-HT3 receptor (5-HT3R) antagonist, has been widely used in preventing and treating chemotherapy-induced emesis in humans. Recently, there has been increasing evidence suggesting that 5-HT3R antagonists, particularly tropisetron might possess prominent immunomodulatory and anti- inflammatory properties (Faerber et al., 2007; Fiebich et al., 2004a; Muller et al., 2006). However, the underlying mechanisms for these effects are largely unknown. Previous data have shown that tropisetron could be clinically beneficial in patients with fibromyalgia and rheumatic diseases (Muller et al., 2006; Mu¨ ller et al., 2007). In animal studies, pretreatment with tropisetron has been reported to ameliorate ischemic brain injury in an embolic model of stroke via reducing leukocyte transmigration into the brain and also decreased TNF-a levels (Rahimian et al., 2011). Moreover, anti- inflammatory effects of tropisetron and the congener granisetron in suppressing the proinflammatory cytokines (TNF-a, IL-1b), leukocyte infiltration, neutrophil infiltration and lipid peroxidation have been shown in a rat model of colitis (Mousavizadeh et al., 2009; Fakhfouri et al., 2010). Interestingly, it has been shown that early and late events in T cell receptor (TCR)-mediated T cell activation are potently inhibited by tropisetron. Moreover, this compound inhibited not only antigen-induced proliferation and IL-2 production in human peripheral T cells, but also the transcriptional activities of the nuclear factor of activated T cells (NFAT), nuclear factor-kappa B (NF-jB) and activator protein-1 (AP-1) (Vega et al., 2005). The most striking finding in this study was that granisetron, another selective 5-HT3R antagonist, failed to elicit any beneficial effects on the mentioned parameters. Thus, it was clear that the immunosuppressive activities of tropisetron were independent of 5-HT3R signaling. 0306-4522/13 $36.00 Ó 2013 IBRO. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neuroscience.2013.06.009 * Corresponding author. Address: P.O. Box 13145-784 Tehran, Iran. Fax: +98-21-6640-2569. E-mail address: ejtemam@gmail.com (S. E. Mehr). Abbreviations: ANOVA, analysis of variance; AP-1, activator protein-1; CFA, complete Freund’s adjuvant; CNS, central nervous system; EAE, experimental autoimmune encephalomyelitis; EDTA, ethylenediaminetetraacetic acid; ELISA, enzyme-linked immunosorbent assay; H&E, hematoxylin and eosin; HT3R, HT3 receptor; IL-1b, interleukin-1b; LFB, Luxor fast blue; MBP, myelin basic protein; mCPBG, m-chlorophenylbiguanide; MOG, myelin oligodendrocyte glycoprotein; MS, multiple sclerosis; NFAT, nuclear factor of activated T cells; NF-jB, nuclear factor-kappa B; PLP, proteolipid protein; RBC, red blood cell; TCR, T cell receptor; TNF-a, tumor necrosis factor-a. Neuroscience 248 (2013) 299–306 299