Several studies demonstrated that polarization click here of Th17 cells, in addition to Th1 cells, can profoundly accelerate the perpetuation of IBD.[18] On the contrary, switching of a Th1/Th17 profile to the enhancement of Treg cells or inhibition

of Th17 polarization is beneficial for restraining immune response and ameliorating intestinal inflammation.[19-21] The immunophilin ligand sirolimus, a macrolide antibiotic produced by Streptomyces hygroscopicus, exhibits potent immunosuppressive properties and is used therapeutically in countering autoimmunity and preventing allograft rejection.[22, 23] Specific inhibition by sirolimus of the serine/threonine protein kinase mammalian target of rapamycin (mTOR) in T cells blocks co-stimulation and cytokine-induced signalling but allows T-cell receptor-mediated signal transduction.[24] Consequently, sirolimus promotes T-cell anergy and deletion.[25, 26] Unlike other commonly used immunosuppressants, such as cyclosporine A and FK506, sirolimus does not appear to interfere with tolerance induction[27, 28] and permits the in vitro proliferation and suppressive function of Treg cells.[29, 30] Whether sirolimus influences the imbalance between Th17 and Treg cells in the development of IBD, however, has not been fully elucidated. In this study, we investigated the immunomodulatory effect of sirolimus in a 2,4,6-trinitrobenzene

BYL719 supplier sulphonic acid (TNBS) -induced murine colitis model. We also explored the potential mechanisms involved, especially in the balance of Treg and Th17 cells. Male BALB/c mice (8–10 weeks old) were purchased from the Center of Experimental Animals of Guangdong Province, and maintained at an animal facility under pathogen-free conditions. All studies involving mice were approved by the Guangdong Pharmaceutical University Animal Care and Use Committee. Colitis was induced by administration of TNBS in mice at day 0 as described previously.[31] In brief, mice were anaesthetized lightly, and a 3·5-F catheter was inserted intrarectally to 4 cm proximal to the anus. To

induce colitis, 120 μl 2·5 mg TNBS (Sigma-Aldrich, St Louis, MO) in 50% ethanol was injected slowly into the lumen via the catheter. Control PDK4 mice received the same volume of 50% ethanol alone. To study the therapeutic effect of sirolimus, 1·25 mg/kg sirolimus (LC Laboratories, Woburn, MA) was administered intraperitoneally for three consecutive days starting at day 0 after TNBS administration. Animals were monitored daily for appearance of diarrhoea, loss of body weight and survival. The disease activity index was used to assess the grade of colitis based on a previously published scoring system by Reinecke et al.[31] All of the mice were killed at the indicated time after administration of TNBS. Colonic morphology was evaluated as a gross indicator of colitis.