他克莫司通过DNA羟甲基化酶Tet1调控黑素细胞抗氧化应激在白癜风治疗中的机制研究

Vitiligo is a common skin depigmenting disorder characterized by the death of melanocytes from lesional epidermis. Despite much research, the etiology of vitiligo and the causes of melanocyte death are not yet fully understood. Recent experimental and clinical evidence suggests that oxidative stress has a pivotal role in the onset and progression of melanocytes destruction. So it is convinced that strategies resulting in reduction of oxidative stress will be a promising approach for vitiligo treatment. So far, topical application of Tacrolimus (FK506) is one of best drugs for vitiligo. Traditionally, FK506 is considered as a kind of calcineurin inhibitors, which can inhibit the activation of T lymphocytes and suppress the autoimmune against melanocytes. Further studies on other disease models suggest that FK506 possesses a powerful capacity of anti-oxidative stress besides immunesuppression. We found in previous work that FK506 indeed enhanced the tolerance of MCs to H2O2. And this protective effect was associated with the reversion of Tet1 and Bcl-2 down-regulation incuded by oxidative stress. Therefore, we hypothesized that anti-oxidative stress may be a plausible mechanism of FK506 in vitiligo treatment. In this proposal, we plan and design a set of experiments to confirm the anti-oxidative stress effect of FK506 and to clarify its molecular mechanism. This will not only provide an option for therapy optimization, but also new strategies for medication development.

白癜风是黑素细胞（MC）丢失形成的脱色性皮肤病，确切机制尚不明了，其中氧化应激被视为启动MC破坏的重要环节，这也被视为研发治疗新策略的重要靶点。他克莫司（FK506）是目前白癜风治疗的一线药物。传统观点认为，它是钙调磷酸酶抑制剂，通过抑制T细胞活化、减轻自身免疫反应来发挥疗效。近年来在多种疾病模型中发现，FK506对靶组织还有直接的抗氧应激作用。我们在前期工作中发现，FK506可以提高MC对H2O2的耐受力，且这种作用可能与DNA羟甲基化酶（Tet1）相关。另外mRNA表达谱芯片研究显示，抗凋亡基因Bcl-2可能是Tet1的下游靶点。因此我们提出这样的假说：FK506是通过逆转氧化应激对Tet1的抑制作用、维持Bcl-2表达来防止MC凋亡的。本项目旨在探索抗氧化应激是否是FK506治疗白癜风的潜在新机制，这对阐明其作用靶点有重要意义，也可为优化临床治疗方案、研发新药提供了新思路和理论依据。

【研究背景】白癜风是临床最常见的脱色素性皮肤病，国人患病率约0.1~2.9%，且逐年上升。虽然它并不影响患者个体生存，但严重损害容貌外观、妨碍正常社交活动，带来沉重的精神和经济负担，甚至威胁家庭和睦。但棘手的是，该病病因复杂、确切发病机制尚不明了，目前沿用的治疗方法效果也不完全令人满意。因此，进一步阐明白癜风发病机制对于寻找新的治疗靶点有着至关重要的意义。. 【研究内容】他克莫司（FK506）是目前白癜风治疗的一线药物。传统观点认为，它是钙调磷酸酶抑制剂，通过抑制T细胞活化、减轻自身免疫反应来发挥疗效。近年来在多种疾病模型中发现，FK506对靶组织还有直接的抗氧应激作用。本课题旨在探索FK506药理作用的新机制，明确其是否能保护黑素细胞（MC）免于氧化应激伤害。. 【关键数据】我们发现：① 在H2O2干预同时予FK506处理，可明显减轻MC的增殖抑制和凋亡，且这种抗氧化应激保护作用呈FK506剂量依赖性。② DNA羟甲基化酶Tet1在白癜风和正常皮肤中的表达有显著差异，提示其与白癜风发病相关。③ Tet1可调控MC的增殖/凋亡、迁移和氧化应激，且这种能力与其表观遗传学催化活性相关。④ 更进一步地，氧化应激干预会明显抑制MC的Tet1的表达。⑤ 另外，mRNA表达谱芯片研究显示，抗凋亡基因Bcl-2是Tet1的下游靶点。. 【重要结果】综合以上发现，我们提出这样的推论：健康状态下，Tet1使Bcl-2基因启动子去甲基化，维持Bcl-2蛋白的表达。应激状态下，ROS抑制Tet1表达，Bcl-2基因启动子不能去甲基化，随之Bcl-2表达下降，MC大量凋亡。FK506的抗氧化应激作用就在于其可以逆转ROS对Tet1的抑制作用，恢复Tet1的表达水平，维持Bcl-2的表达，防止MC凋亡。. 【科学意义】本课题的发现证实抗氧化应激是FK506治疗白癜风的潜在新机制，这对阐明其作用靶点有重要意义，也可为优化临床治疗方案、研发新药提供了新思路和理论依据。