TET2调控Foxp3 DNA去甲基化在变应性鼻炎中的作用及机制研究

The incidence of allergic rhinitis (AR) has been increasing in recent decades, which could be attributed to the epigenetic modifications. Our previous study has showed that hypermethylation of Foxp3 was the key factor resulting in the down-regulated Treg in AR, but the mechanism was unclear. Recent articles manifested that TET was involved in the active demethylation of Foxp3 DNA. Our preliminary work revealed that the decrease of TET2 mRNA expression in Treg cells of AR mice was associated with the hypermethylation of Foxp3 DNA. So it is reasonable to speculate that TET2 may be a regulator of Foxp3 DNA demethylation and has a key role in the immune disorder of AR. Our research plans to investigate the role and mechanism of TET2-mediated Foxp3 DNA demethylation in AR, by constructing AR model using Tet2-/-mice, with the methods of plasmids transfection, adoptive transfer immunization, and the techniques of FACS, oxBS-Seq and IPCh to detect expression of TET2, demethylation of Foxp3 DNA, and change of allergic inflammation. This study would enhance the understanding of epigenetic mechanism in AR and provide tractable target for therapeutic intervention.

变应性鼻炎（allergic rhinitis，AR）发病率持续增高，表观遗传调控在其中的作用备受关注。本项目组既往研究显示Foxp3高甲基化是导致AR中Treg细胞功能下降的重要因素，但具体机制不明。新近报道TET家族参与Foxp3DNA主动去甲基化过程，同时我们发现AR小鼠Treg细胞TET2表达显著降低，且与Foxp3高甲基化相关，据此推测TET2可能通过调控Treg细胞Foxp3去甲基化而在AR免疫平衡调节中发挥关键作用。本课题拟应用Tet2-/-小鼠构建AR模型，通过过继免疫和质粒转染等技术，运用FACS、oxBS-Seq及PICh等方法，检测TET2表达、Foxp3去甲基化状态及变应性炎症改变，从临床、动物和细胞水平探讨TET2调控Foxp3去甲基化在AR发病机制中的作用，并深入研究其调控机制，为通过表观遗传学手段恢复Treg细胞功能从而治疗AR提供理论依据。

变应性鼻炎（allergic rhinitis，AR）是一种常见的变应性疾病，其高发病率及所造成的社会经济负担，以及对生活质量的严重影响已引起全球广泛关注和高度重视。目前AR尚缺乏快速有效的根治方法，其根本原因在于AR的发病机制复杂，发病源头尚不明确。近年来研究提示表观遗传调控在气道变应性炎症的发生中发挥了重要作用。本项目首次探讨在AR这一特定的病理状态下TET2调控的DNA甲基化的作用，发现TET2与CD4+T细胞的甲基化水平及Th细胞免疫平衡密切相关，TET2可通过调控FOXP3 TSDR区的DNA甲基化，影响Treg细胞的数目，从而参与AR的免疫调控。TET2敲除进一步加重了OVA致敏AR小鼠模型的变应性炎症，表现为症状的加重，鼻粘膜炎性细胞浸润更加明显，Th1/Th2和Treg/Th17细胞免疫失衡更加严重， IL-4、IL-5、IL-13、IL-17A等细胞因子和转录因子Foxp3的异常表达加剧；其机制可能为TET2缺失进一步扰乱了CD4+T细胞DNA甲基化调控和基因表达，最终加重了Th细胞免疫失衡。而IL-2可通过促进p-STAT5与TET2的结合，从而促进FOXP3的表达，上调Treg细胞功能从而减轻AR的变应性炎症。该项目的顺利开展将为以TET2为靶点的AR表观遗传学治疗提供重要理论基础。未来通过TET2干预表观遗传修饰恢复相关基因的正常表达，从源头上治疗变应性疾病，可能具有重大的应用前景。