PGE2/EP通路在黑素细胞黏附、丝状伪足形成及胞吐黑素中的作用机制

Prostaglandin E2(PGE2) is an effective way to treatment of vitiligo. However the mechanism is not clear now.Our ancient NSFC foundation research have found that PGE2 promote the long dendrite and filopodia formation of human epidermal melanocytes. It remindes us that PGE2 might play a important role on melanosome releasing or melanosome transfer. On such basis, we raised the scientific hypothesis: PGE2 combinded with the EP receptor which promote the melanosome releasing or transfer in human melanocytes, the downstream signal transduction pathway such as second messager (ca2+,cAMP,IP3), PKA,PKC,MAPKs et al and small molecular GTPases which associated with movement of cytoskeleton protein might play a important role in such above process. Our research will firstly investigate the influence of PGE2/EP on melanocytic adhension, filopodia formation and exocytosis in order to explore the main target of melanosome transfer induced by PGE2. As we known, PGE2 has four different EP receptor which bind with PGE2 would induce different biological role. So the main EP signaling pathway on the role of melanosome releasing will also be determined.Secondly, we observe the changes of second messager(ca2+,cAMP,IP3)and downstream signal transduction pathway（such as PKA,PKC,MAPKs etc）after EP activation. The downstream signaling pathway of EP receptor will be determined by antagon intervention on melanocytic filopodia formation and exocytosis. Finally, we will compare the activity of GTPases(Rho,Rab family) after and before EP activation. At the same time,the influence of melanotic filopodia formation and exocytosis induced by knockdown GTPases expression on condition of EP receptor activation will also be detected. The detailed mechanism of melanosome releasing will be fully mapped out after the research finishing. The research will further providing some interesting information on prevention and therapy of pigmented skin disease.

临床发现PGE2治疗白癜风有效，但具体机制不明。我们前一个国家自然科学基金课题研究中发现PGE2可促MC树突延长、丝状伪足形成，提示PGE2具有潜在促MC传递黑素的作用。基于此，我们提出科学假说：PGE2与其特异性EP受体结合促进了MC传递黑素，第二信使、PKA、PKC、MAPKs等下游信号通路以及多种细胞骨架蛋白运动相关小分子GTP酶对此过程有重要的调节作用。本课题拟研究PGE2及其4种EP受体对MC黏附、丝状伪足形成、胞吐黑素等的影响，以探讨PGE2/EP信号促MC传递黑素的可能靶点，明确主要的EP受体通路；观察EP受体激活前后MC内cAMP、Ca2+水平以及PKC、MAPKs等磷酸化水平变化以明确下游信号转导通路；检测EP受体激活前后多种细胞骨架运动相关小分子GTP酶（Rho,Rab）的活性变化，以阐明PGE2/EP促黑素传递的深层分子机制，为临床色素障碍性皮肤病的防治提供理论依据。

308准分子光(MEL)、热疗以及前列腺素E2在临床白癜风治疗上均有明显的效果，但具体的机制不明，我们既往的研究发现这三种治疗方式均与PGE2/EP通路相关。基于此，我们对上述三种干预方式分别从细胞水平、动物模型水平进行了系列相关研究。发现：MEL可促进纯化培养的角质形成细胞分泌PGE2和α-MSH，以及黑素细胞表面高表达EP1-EP3，并激活豚鼠表皮中PGE2及其EP1和EP3受体的表达，热疗结合UVB辐射可促进黑素细胞的黑素合成功能增加，并激活角质形成细胞PGE2的表达促进黑素传递。进一步的超微结构研究显示PGE2主要通过促进黑素细胞表面丝状伪足生成和增加胞吐的方式促进黑素传递，同时还促进了角质形成细胞表面粗糙度增加以及与吞噬相关的棘突的形成。初步的相关分子机制研究也证实PGE2主要通过激活EP1/JNK/p38和EP3/PKA/ERK/p38这两条通路发挥促黑素传递的作用，其促角质形成细胞吞噬作用可能与PAR-2的激活有关。MEL的促黑素传递作用主要与激活PGE2/EP1/EP3通路有关。我们从上一个国科金所筛选的美白植物单体中进一步筛选出了鞣花酸的卓越美白效应，发现其美白机制主要与下调PGE2诱导的黑素合成和黑素传递有关。这些研究结果表明PGE2/EP通路在黑素细胞黑素合成和黑素传递中都具有重要的作用，对其进行深入的研究有助于我们更好的认识和治疗色素相关性皮肤病。另外，研究小组首次发现羟氯喹对泛发性白癜风具有很好的治疗效应，其系统的抗白作用可能与抑制血液中白癜风相关自身抗体与皮肤黑素细胞膜抗原的结合，并有效降低了抗体介导的细胞毒反应相关。