Analysis On The Regulation Of Cimetidine On Immune Response

Balanced immunity is critical in host immune system. Regulatory T cell (de Vries et al.) mainly involves in peripheral immune tolerance and negatively regulates immune responses. After the elimination of pathogenic microorganisms, inflammatory responses should be self-regulated to avoid disease causing over-reactions. Cimetidine (CIM), a H2-histamine receptor antagonist, was widely used to treat peptic and other gastric ulcers. Our lab previously study had demonstrated that CIM could enhance the adaptive immune response as a vaccine adjuvant to inhibiting the Treg cell function. However, no direct evidence to explain the interaction between CIM and Treg cells. Our first study find the mechanism of CIM regulates the Treg by the means of molecular biology technique, and the second part is mainly about CIM inhibits the inflammation degree in innate immune system.The first study focuses on if such direct interaction occurs between CIM and hTreg. After human CD4+CD25+Treg cells and Jurkat T cells were stimulated with CIM, the level of Foxp3, a master regulator for the development and function of Treg, was monitored. We observed that effects of CIM on level of Foxp3 protein. Furthermore, knocking down the expression of E3 ligase Stubl leads to CIM failed to reduce Foxp3, suggesting that CIM could activate the Stub1-mediated Foxp3 proteosomal degradation pathway. Finally, by blocking PI3K-Akt-mTOR pathway with LY294002, the Foxp3 were also reduced, suggesting that CIM induced Foxp3 reduction is dependent on the activation of PI3K-Akt-mTOR pathway. In summary, CIM could reduce Foxp3 expression in Treg cells through E3 ligase Stubl-mediated proteosomal degradation, which lead to down regulate the function of Treg cells, in turn, elevate the adaptive immune response.The second part study I focus on the IBD (inflammatory bowel disease), which is a group of inflammatory conditions of the colon and small intestine, caused by gut microbes pathogenic bacteria and inflammation. IBD is a complex disease and difficult to cure entirely, and IBD patients are more likely to have colon cancer than healthy people. It is reported that CIM could inhibit innate immune response inflammatory cytokines production in gastric ulcer and gastrointestinal ulcers. To find whether CIM could exacerbate the inflammation bowel disease (IBD) via enhancing immune response, we used TNBS to induce mouse IBD model with or without CIM treatments. CIM could effectively protect animals from IBD, which was opposite to our expectation. Further results from the H&E and immunohistochemical detections indicated CIM could reduce macrophage infiltrated in the gut tissue and decrease the release of TNF-α and other inflammatory cytokines. And then we simulated the macrophage activation on the cell level, mouse bone marrow derived macrophage (BMDM) was separated and stimulated with CIM and LPS. The Western Blot testCIM inhibited the LPS-induced NF-κB signal pathway which promote several inflammatory cytokines expression besides TNF-α in BMDM. We also found that CIM could inhibit the transcription of TNF-α, IL-6, IL-1β and the expression of TNF-α. Moreover, macrophage transfer and real-time PCR results explained CIM may effect macrophage migration to colon during the early period of IBD.As conclusion, our results indicated that CIM could affect the immune system in different ways. On the one hand, it inhibit the function of Treg cell which negative regulate the adaptive immune response, on the other hand, CIM could inhibit the inflammation response in the early stage of ulcerative IBD. CIM mainly reduce the inflammatory cytokines by inhibition of NF-κB signal pathway, as a consequence, CIM could help mouse survive from TNBS-induced IBD.