Modifiers of hepcidin expression as new therapies for iron overload

描述（由申请人提供）：铁超载综合征仍然是地中海贫血或遗传性血色素沉着症患者心脏和肝功能衰竭的重要原因，这是世界范围内常见的遗传性疾病。目前对这些疾病的治疗包括连续静脉切开术（血色素沉着症）或螯合治疗（地中海贫血），这两种方法都与患者依从性差有关，因为不便和明显的副作用。地中海贫血和遗传性血色素沉着症都与hepcidin（肠道铁吸收和细胞铁储存的关键调节因子）水平过低有关，从而导致过量的膳食铁吸收。Hepcidin是在组织铁负荷和炎症反应中产生的，与铁输出蛋白铁转运蛋白（ferroportin1）结合，导致这两种蛋白的内化，减少铁从肠细胞向循环和从巨噬细胞向其他组织的释放。我们假设，提高hepcidin表达将通过减少饮食中铁的吸收和促进铁在网状内皮系统中的储存来增强螯合治疗地中海贫血的疗效，并可能消除血色素沉着症患者对静脉切开术治疗的需要。我们之前已经证明，铁转运蛋白1是斑马鱼肠细胞和巨噬细胞铁输出和铁循环所必需的。我们还证明了斑马鱼胚胎中hepcidin表达的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铁和BMP通路有反应。最近，我们还发现用植物雌激素染料木素处理，导致斑马鱼胚胎和人肝细胞中hepcidin转录水平升高。我们建议通过在斑马鱼胚胎中进行化学筛选来筛选调节hepcidin表达的其他小分子。为了阐明筛选中发现的分子的作用机制，我们将描述调节剂对哺乳动物细胞铁转运、染色质免疫沉淀、RNA表达和信号通路的影响。最佳候选调节因子将在地中海贫血和血色素沉着症小鼠模型中评估其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鉴定，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方法。

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.