基于PI3K-Akt-mTOR通路探讨白癜风调节性T细胞对CD8+T细胞抑制功能的调节及芹黄素的干预作用

Vitiligo is an intractable skin diseases. It's mechanism is not yet clear and lacking of effective treatment of drugs. Autoimmune play an important role in the pathogenesis of vitiligo. We previously have revealed decreased frequency of regulatory T cells (Treg) in patients with vitiligo and defective inhibition function of Treg on autologous CD8+CLA+T cells. We also found that Apigenin can reduce dopamine induced apoptosis of melanocyte by inhibiting the activity of Akt.Recently, studies have shown that PI3K-Akt-mTOR pathway can regulate Treg and CD8+T cell differentiation and their dynamic balance. Besides, levels of PI3K and Akt are abnormal in vitiligo skin. Based on these studies, we suggest that mTOR pathway may play a key role in decreased frequency of Treg and weakened inhibition function of Treg on autoreactive CD8+T cells, and apigenin may restore the balance of Treg and CD8+T cells by regulating mTOR pathway. To verify the hypothesis, in this study we will use Treg and CD8+T cells isolated from peripheral blood of vitiligo patients and autoimmunal mouse model of vitiligo to investigate the regulatory function of PI3K-Akt-mTOR pathway on effects of Treg on proliferation and function of CD8+T cell as well as the intervention mechanism of apigenin. This will be helpful to find new targets and medicine for treatment of vitiligo and to provide new idea in treatment of vitiligo by traditional Chinese medicine.

白癜风为难治性皮肤病，发病机制尚未明了，缺少有效治疗药物。自身免疫在白癜风发病中起重要作用，但调控机制不清。课题组前期发现白癜风患者调节性T细胞（Treg）数目和功能异常，对CD8+CLA+T细胞的抑制能力降低，芹黄素可通过抑制Akt活性减轻多巴胺诱导黑素细胞的凋亡。有研究显示PI3K-Akt-mTOR通路可调节Treg和CD8+T细胞的分化及动态平衡，且PI3K及Akt在白癜风表皮中表达异常。由此推测PI3K-Akt-mTOR通路异常可能是白癜风Treg数量减少、功能减弱、对自身反应性CD8+T细胞抑制失控的原因之一，芹黄素对此通路可能有调节作用。本项目拟通过体外培养白癜风患者外周血Treg和CD8+T细胞及免疫小鼠白癜风模型，探讨PI3K-Akt-mTOR通路对Treg和CD8+T细胞增殖和功能的调节作用及芹黄素的干预机制，以寻求治疗的新靶点和药物，为中医药治疗白癜风提供新思路。

白癜风易诊难治，临床上缺少安全有效的药物治疗。自身免疫在白癜风发病中起重要作用，但调控机制不清。研究显示白癜风Tregs数量减少和功能下降减弱了对CD8+T细胞的抑制，导致免疫耐受失衡而引发自身免疫反应。PI3K-Akt-mTOR通路可调节Treg和CD8+T细胞的分化及动态平衡，且PI3K及Akt在白癜风表皮中表达异常。由此推测PI3K-Akt-mTOR通路异常参与了白癜风的免疫发病机制。芹黄素具有抗炎、抗氧化及免疫调节等生物学作用，可通过调节Th1型/Th2型细胞因子平衡而发挥作用，推测芹黄素对此通路可能具有调节作用。本课题研究显示白癜风患者外周血CD8+T细胞中PTEN表达降低，AKT、mTOR磷酸化蛋白水平及mRNA水平表达升高，存在PI3K-Akt-mTOR信号通路的异常。加入PI3K-Akt-mTOR通路抑制剂后，CD8+T功能相关的表面分子（CXCR3、CD107a）和杀伤因子（IFN-γ、穿孔素和颗粒酶B）均有所降低。课题组成功建立自身免疫性白癜风小鼠模型，发现白癜风小鼠脾脏CD8+T细胞PTEN蛋白及mRNA水平明显降低，AKT、mTOR磷酸化蛋白水平及mRNA水平显著升高。白癜风患者和小鼠模型均证实了PI3K-Akt-mTOR通路参与了白癜风的免疫发病机制。基于自身免疫性白癜风小鼠模型，研究芹黄素对小鼠免疫相关指标的影响，发现芹黄素可以调节自身免疫小鼠模型的免疫细胞和炎症因子的失衡，说明芹黄素可能成为治疗白癜风的有效药物。