Modifiers of hepcidin expression as new therapies for iron overload

描述(申请人提供)：铁超载综合征仍然是地中海贫血或遗传性血色沉着症患者心脏和肝脏衰竭的重要原因，这是世界上常见的遗传性疾病。目前对这些疾病的治疗方法包括连续静脉切开术(血色素沉着症)或螯合疗法(地中海贫血)，这两种方法都与患者依从性差有关，因为不便和显著的副作用。地中海贫血和遗传性血色沉着症都与海普西丁水平过低有关，海普西丁是肠道铁吸收和细胞铁储存的关键调节因子，导致饮食中铁吸收过多。组织铁负荷和炎症反应时产生的海普西丁与铁出口蛋白1结合，导致这两种蛋白质内化，减少了从肠细胞到循环和从巨噬细胞到其他组织的铁释放。我们假设，提高海普西丁的表达将通过减少饮食中铁的吸收和促进网状内皮系统中铁的储存来增强地中海贫血的螯合治疗的疗效，并可以消除血色素沉着患者的静脉切开治疗的需要。我们先前已经证明，在斑马鱼中，铁蛋白1是铁输出和通过肠细胞和巨噬细胞的铁循环所必需的。我们还证明了斑马鱼胚胎中海普西丁的表达调控类似于在哺乳动物系统中观察到的，因为它对转铁蛋白结合的铁和BMP途径做出反应。最近，我们还发现，用植物雌激素金雀异黄素处理后，斑马鱼胚胎和人类肝细胞中海普西丁的转录水平增加。我们建议通过在斑马鱼胚胎中进行化学筛选来筛选调节海普西丁表达的额外小分子。为了阐明筛选中识别的分子的作用机制，我们将表征调节剂对哺乳动物细胞铁运输、染色质免疫沉淀、RNA表达和信号通路的影响。最好的候选调节剂将在地中海贫血和血色素沉着症的小鼠模型中进行评估，以确定它们对铁超载和红细胞生成的影响。这些研究将导致分子和途径的确定，这些分子和途径可能适用于地中海贫血或遗传性血色素沉着症患者的治疗。

DESCRIPTION (provided by applicant): Iron overload syndromes remain important causes of heart and liver failure in patients with thalassemia or hereditary hemochromatosis, which are common genetic diseases worldwide. Current therapy for these conditions includes serial phlebotomy (hemochromatosis) or chelation therapy (thalassemia), both of which are associated with poor patient compliance because of inconvenience and significant side effects. Both thalassemia and hereditary hemochromatosis are associated with inappropriately low levels of hepcidin, the key regulator of intestinal iron absorption and cellular iron storage, resulting in excessive dietary iron absorption. Hepcidin, produced in response to tissue iron loading and inflammation, binds the iron exporter ferroportin1, causing internalization of both proteins and reduced iron release from enterocytes to the circulation and from macrophages to other tissues. We hypothesize that raising hepcidin expression will enhance the efficacy of chelation therapy in thalassemia by reducing dietary iron absorption and promoting storage of iron in the reticuloendothelial system and could eliminate the need for phlebotomy treatment in patients with hemochromatosis. We have previously demonstrated that ferroportin1 is required for iron export and iron cycling through enterocytes and macrophages in zebrafish. We have also demonstrated that the regulation of hepcidin expression in zebrafish embryos resembles that observed in mammalian systems, in that it is responsive to transferrin-bound iron and the BMP pathway. Recently, we have also discovered that treatment with the phytoestrogen, genistein, results in increased hepcidin transcript levels in zebrafish embryos and in human hepatocytes. We propose to screen for additional small molecules that regulate hepcidin expression by conducting a chemical screen in zebrafish embryos. To elucidate the mechanism of action of molecules identified in the screen, we will characterize the modulators' effects on mammalian cellular iron transport, chromatin immunoprecipitation, RNA expression, and signaling pathways. The best candidate regulators will be evaluated in mouse models of thalassemia and hemochromatosis for their effects on iron overload and erythropoiesis. These studies will lead to the identification of molecules and pathways that may be adapted to generate treatments for patients with thalassemia or hereditary hemochromatosis.