“炎症堵疏兼治介质”LXA4通过TET2对银屑病炎症过程的表观遗传调控研究

Our research group found in prophase work that pro-resolving mediator --lipoxin A4 (LXA4) can significantly inhibit the release of inflammatory mediators during the course of psoriasis，and has a dual effect of anti-inflammation and pro-resolution. Furthermore, in the mice’s psoriasis-like animal model, LXA4 can up-regulate at both inflammatory-initiating stage and resolving stage the expression of TET2, which is a classic methylation-regulated enzymes --DNA Methylation Hydroxylase 2 (TET2). In September 2015, Nature reported for the first time the mechanism of “epigenetic regulation” in “inflammation resolution”: TET2 has an unmethylation-regulated effect in inflammation resolution, which is closely related to psoriasis and has attracted considerable attention at present. Our research group proposes a hypothesis that LXA4 may play a role of epigenetic regulation during the initiating phase and resolving phase by up-regulate TET2. More specifically, TET2 may mediate methylation of psoriasis-related-DNA at inflammatory-initiating stage and inhibit the transcription of IL-6 by inducing the deacetylation of histone at inflammation-resolving stage. Methylation of psoriatic lesion and the laws of TET2’expression would be detected, and then intervention to psoriasis will be given with exogenous LXA4 to find the effects of LXA4 and TET2 on p16 gene, Treg cells and Th17 cells at different inflammatory phase, thus to gain an in-depth understanding of the pathogenesis of psoriasis from two perspectives: a combination of “dual action of anti-inflammation and pro-resolution” and “epigenetic regulation”, which might offer a new tactics for “precise control of inflammation” in treatment of psoriasis.

我们前期研究发现“促炎症消退”介质LXA4可显著抑制银屑病中炎症介质的释放，起到“抗炎”及“促炎症消退”双重作用。此外，银屑病样小鼠模型中LXA4在炎症“启动”和“消退”阶段均可上调DNA甲基羟化酶2（TET2）的表达。2015年9月《Nature》首次报道“炎症消退”过程中的“表观遗传调控”机制：TET2在该过程中起到非甲基化调控作用，该机制目前备受关注且与银屑病联系密切。我们提出LXA4可能通过TET2发挥表观遗传调控作用的假说：TET2介导炎症“启动”阶段相关基因启动子DNA去甲基化和炎症“消退”阶段组蛋白去乙酰化而抑制IL-6的转录。拟通过检测银屑病皮损甲基化状态、TET2表达规律，外源性补充LXA4，探讨LXA4和TET2在炎症不同阶段对p16基因、Treg细胞、Th17细胞的调节，从“炎症堵疏兼治”和“表观遗传调控”两方面来认识银屑病的发病机制，为“炎症精准控制”提供新策略。

银屑病的发病与炎症反应密切相关，可能同时存在炎症活化过度与炎症消退不足，导致炎症反应失控，进而形成顽固性皮损。前期我们研究了一系列的“促炎症消退”介质对银屑病样皮炎的改善效果及作用机制，包括脂氧素A4（LXA4）、消退素E1和消退素D1，这类生物活性脂质小分子均展现出强大的“抗炎”及“促炎症消退”的双重效应，其中LXA4被证明能够上调TET2的表达，并且在既往的文献中已证实TET2通过去甲基化和介导的组蛋白去乙酰化作用，可调控细胞周期、Treg细胞和Th17细胞的分化及功能、以及抑制促炎因子IL-6及IL-1β的表达，这提示LXA4发挥治疗银屑病的作用可能与表观遗传有关。.在此基础上，本项目通过收集银屑病患者和健康志愿者的皮肤，构建咪喹莫特诱导的银屑病样皮损动物模型，及TET2过表达或敲低的细胞系，从各个层面研究银屑病中TET2、5hmc的表达规律，研究银屑病发病过程中LXA4作为“炎症堵疏兼治介质”对TET2及其下游分子的调节作用，以及TET2对细胞周期、炎性细胞分化，及与银屑病发病密切相关的炎症分子如IL-17、IL-23、CCL20等的调控机制。.结果显示，与正常人皮肤相比，银屑病患者皮损中存在显著异常的甲基化基因，5hmC水平显著增加。在咪喹莫特诱导的小鼠银屑病样皮损中也发现了TET2和5hmC的高表达，敲低TET2表达可减轻小鼠模型中银屑病样皮炎的严重程度，下调CD4+T细胞向Th17细胞的分化，降低促炎细胞因子如IL-17A、IL-17F、IFN-γ和趋化因子CXCL1的表达水平。这可能与某些银屑病相关基因启动子DNA去甲基化和介导炎症“消退”阶段组蛋白去乙酰化有关，提示TET2在银屑病发病机理中可能通过调控银屑病致病的关键基因的转录和蛋白修饰参与银屑病的发病，强调了TET2在银屑病发病机理中的关键作用。.通过这些研究，“促炎症消退”介质脂痒素A4可从“炎症疏堵兼治”和“表观遗传调控”两个方面为银屑病的“炎症精准控制”提供新策略。