氧化应激活化IRE1α-XBP1-IL-15信号调控白癜风黑素细胞免疫损伤新机制

Vitiligo is an autoimmune skin disease, characterized by epidermal melanocytes (MCs) loss. Oxidative stress, which can stimulate T lymphocyte immune response, plays an important role in MCs death in vitiligo, but regulatory mechanism is still unknown. It has been reported that IL-15 can mediate the activation of T cells, which is the key step to enhance the cytotoxicity of CD8+T cells. We recently identified that oxidative stress can induce keratinocytes (KCs) to produce IL-15. Moreover, IL-15 can promote the cell-killing effects of CD8+T cells on MCs significantly in vitiligo, but the underlying mechanism is still unclear. In addition, we also found that the IRE1α-XBP1 pathway was activated under oxidation stress in KCs, and our bioinformatics analyses indicated that there are binding site of XBP1 in IL-15 gene promoter. Based on these data, we hypothesize that the IRE1α-XBP1 pathway is activated by oxidation stress in KCs, and this process can mediate proliferation and activation of CD8+T cells to kill MCs, and finally lead to vitiligo. To test this hypothesis, we will firstly confirm the previous observation in vitiligo clinical samples, and then explore the underlying mechanism of IL-15 produced by KCs under oxidative stress in cellular level; finally we will illustrate the molecular mechanisms in the process of CD8+T cells proliferation and activation mediated by IL-15. All these researches are expected to enrich the immune pathogenesis of vitiligo, and provide new target for clinical treatment.

白癜风是一种自身免疫性皮肤病，氧化应激引起T细胞免疫应答是白癜风黑素细胞（MC）死亡的重要原因，但其调控机制不明。文献表明，IL-15可介导T细胞激活，并能显著增强CD8+T细胞的杀伤活性。我们发现氧化应激诱导角质形成细胞（KC）产生IL-15，且IL-15可显著促进白癜风CD8+T细胞对MC的杀伤作用，但IL-15产生机制及其作用机理不清。我们发现，氧化应激下KC中IRE1α-XBP1通路激活，且生物信息学分析显示 IL-15启动子区存在XBP1结合位点。据此我们提出，氧化应激活化KC中IRE1α-XBP1途径诱导IL-15表达，从而介导CD8+T细胞增殖与活化，杀伤黑素细胞，引发白癜风。为验证这一假说，本项目拟在临床样本中确立现象，在原代KC中阐明氧化应激诱导IL-15表达的机制，并验证其介导白癜风CD8+T细胞杀伤MC的功能，预期结果将丰富白癜风免疫发病机制，为临床治疗提供新的靶点。

白癜风是一种自身免疫性皮肤病，氧化应激引起T细胞免疫应答是白癜风黑素细胞（MC）死亡的重要原因，但其调控机制不明。文献表明IL-15可介导T细胞激活，是促进CD8+T细胞杀伤作用的关键环节。IL-15是一种多效细胞因子，主要调控记忆CD8+T细胞、NK细胞等多种免疫细胞的活化、增殖、生存以及功能。我们发现氧化应激诱导角质形成细胞（KC）产生IL-15，且IL-15可显著促进白癜风CD8+T细胞对MC的杀伤作用，但IL-15产生机制及其作用机理不清，本项目对此进行了深入研究。我们首先进行了氧化应激促进NHEKs细胞IL-15表达和反向呈递的现象研究；进一步进行氧化应激促进NHEKs细胞IL-15表达和反向呈递的机制研究；随后进行氧化应激NHEKs细胞活化CD8+TEMs细胞的现象研究；最后进行氧化应激NHEKs细胞IL-15反向呈递活化CD8+TEMs细胞的分子机制研究。通过本项目的研究，发现氧化应激可以诱导NHEKs细胞IL-15 mRNA和蛋白表达以及细胞膜IL-15表达，促进IL-15反向呈递，在体证实了白癜风氧化应激微环境中IL-15-IL-15Rα复合体的形成。揭示了氧化应激激活NHEKs细胞NF-κB p65信号上调IL-15和IL-15Rα表达，从而促进IL-15反向呈递的具体分子机制。证实了反向呈递的IL-15通过CD122-JAK-STAT信号轴活化CD8+TEMs细胞，从而参与启动白癜风的异常免疫应答。明确了阻断IL-15-JAK-STAT信号可抑制CD8+TEM细胞活化和效应分子表达。因此，本研究率先揭示了角质形成细胞来源IL-15是氧化应激微环境介导白癜风CD8+TEMs细胞活化的关键桥梁分子，为白癜风氧化应激启动自身免疫反应的机制研究提供了新的证据，也为白癜风临床治疗提供了新的思路和靶点。