Up-regulation of Program Death Ligand-1 in CD11c Cells is One of the Protective Mechanism of 5-Aza-2`-deoxycytidine Treatment in Experimental Autoimmune Encephalomyelitis mice

• Main Authors: Kai-Hsu Yang, 楊開旭
• Other Authors: Wu, Shu-Fen
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/fh6627

碩士 === 國立中正大學 === 生命科學系生物醫學研究所 === 106 === Multiple sclerosis (MS) is a chronic autoimmune disease caused by type 1 T helper cells (Th1) and type 17 T helper cells (Th17), not only a single gene but also environmental factors can cause MS diseases. Experimental autoimmune encephalomyelitis (EAE) is an animal model commonly used in the study of multiple sclerosis. The myelin sheath and central nervous system in MS patient are destroyed causing by activated T helper cells that stimulate by antigen presenting cells (APC) present myelin antigens, promoting T cells to release inflammatory mediators and cytokines. Previous studies in our laboratory showed that EAE mice pretreated with 5-Aza-2'-deoxycytidine (5-Aza), a methyltransferase inhibitor, could suppress the disease by increasing the expression of CD4+Foxp3+ regulatory T cells. In addition to regulatory helper T cells (Treg), other immunosuppressive pathways have not been explored in detail. Previous literatures had mentioned that the programmed pathway of apoptosis (PD-1/PD-L1), in addition to playing an important role in autoimmune diseases, also affects the differentiation and function of regulatory T helper cells. Therefore, we will investigate whether 5-Aza will up-regulate PD-1/PD-L1 or other T cell’s inhibitory pathways. First we used PD-L1 knockout mice to induce EAE production and treated with 5-Aza. We found that PD-L1 knockout mice had the effect of suppressing disease only during the treatment period. From the results of the tissue section, it was observed that the myelin sheath of PD-L1 knockout mice in the 5-Aza group had no cell infiltration and damage during the treatment, but it was still onset about 10 days after the end of the treatment, showing that 5- Aza has only a short-term protective effect on PD-L1 knockout mice. Next, we selected the immunosuppressive pathways on regulatory T helper cells and CD4 T cells including Fas, Foxp3, and TIGIT, which are regulated by of gene methylation. Comparing the expressions of peripheral receptors/ligands in peripheral blood cells before and after treatment, we found that Fas and Foxp3 expression levels were significantly higher in the 5-Aza treatment group; there was no significant difference in FasL. From the co-culture experiments, we found that the presence or absence of PD-L1 or the level of TIGIT did not affect the suppressive function of regulatory T helper cells. However, the expression of PD-L1 on the CD11c+ antigen-presenting cells increased significantly with 5-Aza treatment. The results of co-culture showed that CD11c+ antigen-presenting cells in the absence of PD-L1, the activation of activated CD4 T cells were significantly inhibited. In conclusion, the role of PD-L1 in the inhibition of EAE by 5-Aza is important, as well as regulatory CD4 T helper cells. Although antigen-presenting cells have numerous immunosuppressive pathways, the lack of PD-L1 causes severe inhibition of EAE. From the available data, we can only speculate that 5-Aza treatment can up-regulate PD-L1 expression to inhibit EAE progression, and other inhibitory factor Fas or Foxp3 can also be up-regulated by 5-Aza. As to why B6 mice still maintain resistance to EAE after treatment, further studies are needed.