Esebanmen Grace E, Langridge William H R
Department of Earth and Biological Sciences, Loma Linda University School of Medicine, Loma Linda, CA, USA; Center for Health Disparities and Molecular Medicine, Loma Linda University School of Medicine, Mortensen Hall, Loma Linda, CA, USA.
Center for Health Disparities and Molecular Medicine, Loma Linda University School of Medicine, Mortensen Hall, Loma Linda, CA, USA; Division of Biochemistry, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, USA.
Cell Immunol. 2017 Sep;319:43-52. doi: 10.1016/j.cellimm.2017.08.002. Epub 2017 Aug 21.
Cholera toxin B subunit fusion to autoantigens such as proinsulin (CTB-INS) down regulate dendritic cell (DC) activation and stimulate synthesis of DC immunosuppressive cytokines. Recent studies of CTB-INS induction of immune tolerance in human DCs indicate that increased biosynthesis of indoleamine 2,3-dioxygenase (IDO1) may play an important role in CTB-INS vaccine suppression of DC activation. Studies in murine models suggest a role for transforming growth factor beta (TGF-β) in the stimulation of IDO1 biosynthesis, for the induction of tolerance in DCs. Here, we investigated the contribution of TGF-β superfamily proteins to CTB-INS induction of IDO1 biosynthesis in human monocyte-derived DCs (moDCs). We show that CTB-INS upregulates the level of TGF-β1, activin-A and the TGF-β activator, integrin αvβ8 in human DCs. However, inhibition of endogenous TGF-β, activin-A or addition of biologically active TGF-β1, and activin-A, did not inhibit or stimulate IDO1 biosynthesis in human DCs treated with CTB-INS. While inhibition with the kinase inhibitor, RepSox, blocked SMAD2/3 phosphorylation and diminished IDO1 biosynthesis in a concentration dependent manner. Specific blocking of the TGF-β type 1 kinase receptor with SB-431542 did not arrest IDO1 biosynthesis, suggesting the involvement of a different kinase pathway other than TGF-β type 1 receptor kinase in CTB-INS induction of IDO1 in human moDCs. Together, our experimental findings identify additional immunoregulatory proteins induced by the CTB-INS fusion protein, suggesting CTB-INS may utilize multiple mechanisms in the induction of tolerance in human moDCs.
霍乱毒素B亚基与自身抗原如胰岛素原融合（CTB-INS）可下调树突状细胞（DC）的活化，并刺激DC免疫抑制细胞因子的合成。最近关于CTB-INS在人DC中诱导免疫耐受的研究表明，吲哚胺2,3-双加氧酶（IDO1）生物合成的增加可能在CTB-INS疫苗抑制DC活化中起重要作用。在小鼠模型中的研究表明，转化生长因子β（TGF-β）在刺激IDO1生物合成以及诱导DC耐受中发挥作用。在此，我们研究了TGF-β超家族蛋白对CTB-INS诱导人单核细胞来源的DC（moDC）中IDO1生物合成的作用。我们发现CTB-INS可上调人DC中TGF-β1、激活素A以及TGF-β激活剂整合素αvβ8的水平。然而，抑制内源性TGF-β、激活素A或添加生物活性TGF-β1和激活素A，均不能抑制或刺激用CTB-INS处理的人DC中IDO1的生物合成。而用激酶抑制剂RepSox抑制可阻断SMAD2/3磷酸化，并以浓度依赖的方式减少IDO1的生物合成。用SB-431542特异性阻断TGF-β1型激酶受体并不能阻止IDO1的生物合成，这表明在CTB-INS诱导人moDC中IDO1的过程中，除了TGF-β1型受体激酶外，还有其他不同的激酶途径参与其中。总之，我们的实验结果确定了CTB-INS融合蛋白诱导的其他免疫调节蛋白，表明CTB-INS可能利用多种机制在人moDC中诱导耐受。
