Effects Of Mycophenolate Mofetil On Inflammatory Boweldisease And On Cytokine Production

Inflammatory bowel disease(IBD), is a chronic, relapsing inflammatory disorder of the digestive tract that, comprises Crohn’s disease(CD) and ulcerative colitis(UC). It is characterized by dysregulated immune responses, altered cytokine production, and cellular inflammation, which ultimately lead to damage of the distal small intestine and the colonic mucosa. Currently, the exact etiology of IBD is complicated and remains unknown, but it is related to many factors such as immunity, heredity, intestinal environment, and bacterial infection. Specifically, immunological factors have been found to play particularly important roles in the pathogenesis and sustainable development of inflammatory bowel disease. Recently, the hypothesis that an imbalance of the CD4+ T subtypes(Thl/Th2) cells leads to pro-inflammatory/anti-inflammatory cytokine disproportionality and immune abnormalities was widely accepted to play an important role in the pathogenesis of IBD.Mycophenolate mofetil(MMF), the 2,4-morpholino ethyl ester of mycophenolic acid, is a new immunosuppressive drug that has demonstrated considerable efficacy in allograft transplant recipients and in patients with a variety of autoimmune disorders. In the liver, MMF is converted into mycophenolic acid(MPA), which is active form of MMF. Mycophenolic acid is a non-competitive reversible inhibitor of type-2 inosine monophosphate dehydrogenase, which is a key enzyme in the de novo pathway of purine synthesis. Mycophenolate mofetil can alternatively suppress the proliferation of both B and T cells because unlike other cell types that can recycle uncleotides via a salvage pathway, B and T lymphocytes depend solely on de novo nucleotide synthesis. Therefore, the action of MMF is thought to suppress proliferation of this specific cell group. The use of MMF in IBD patients especially in those who are steroid-dependent, refractory, or intolerant of more conventional therapies has been documented. Moreover, MMF has a low toxicity. However, the precise mechanism of immune suppression by MMF is still poorly understood.In my study, the BALB/c mice were randomly divided into five groups, namely the normal group, control group, TNBS group, gavage group and intraperitoneal injection group. IBD model mice were induced by trinitrobenzene sulfonic acid(TNBS), and then colitic mice was treated with an intraperitoneal injection and gavage of different concentrations(1 or 2 mg per mouse) of MMF on days-1, 0, 1, 2, and 7. The change of body weight and mortality in mice were recorded for 10 days. All mice were sacrificed either 3 or 10 days after TNBS administration, collecting the blood and colon tissue of mice. The changes of related cytokines(IFN-γ, TNF-α, IL-12, IL-6, IL-1β and IL-10) in serum and colon tissue were detected by RT-PCR and ELISA methods. The changes of histologic score, myeloperoxidase(MPO) activity and histological damage were observed. Splenic lymphocytes of mice in the experimental group and Spleen lymphocytes of normal mice stimulated by MPA in vitro were collected, and the effect of MMF on the differentiation of murine splenic lymphocytes, especially CD4+T cells, was detected by flow cytometry in vivo and in vitro. Through the above experiments, the immune suppression mechanism of MMF in IBD was expected to clearly define.The results show that MMF treatment not only significantly ameliorated diarrhea, and loss of body weight but also abrogated the histopathologic severity and inflammatory response of inflammatory colitis, and increased the survival rate of TNBS-induced colitic mice. Additionally, MMF significantly inhibited m RNA expression of pro-inflammatory cytokines IFN-γ, TNF-α, IL-12, IL-6, and IL-1β in mice with TNBS-induced colitis; however, MMF did not inhibit the expression of IL-10 m RNA. ELISA showed that the serum levels of IFN-γ, TNF-α, IL-12, IL-6, and IL-1β were down-regulated in a TNBS model of colitis. Flow cytometric analysis showed MMF markedly reduced the percentages of Th1 and Th2 splenocytes in the IBD Model Mouse. Mycophenolic acid(MPA) also significantly decreased the percentages of splenic Th1 and Th2 cells in vitro. These results suggest that treatment with MMF may improve experimental colitis and induce inflammatory response remission of IBD by down-regulation of pro-inflammatory cytokines via modulation of the differentiation of Th1/Th2 cells.