Mitophagy as Potential Target in Sickle Cell Disease

镰状细胞病(SCD)是一种遗传性血液疾病，影响着全球数百万人。在美国 美国有大约10万人患有这种疾病，美国的医疗费用估计为11亿美元 独自一人。它是由γ-珠蛋白基因的突变引起的，导致谷氨酸被缬氨酸取代。 正因为如此，当脱氧时，血红蛋白能够聚合，导致红色形状变化 血细胞(RBC)，RBC溶解，以及无数其他并发症，包括急性和慢性疼痛，慢性 贫血，多系统器官损伤，以及预期寿命大大缩短。 这些症状在出生后不久就会出现，此时胎儿的血红蛋白(HBF)水平会下降，并被 成人镰状血红蛋白。由于这一观察结果，人们花了很多精力来诱导胎儿血红蛋白。 在SCD患者中的水平。羟基脲是FDA批准的唯一治疗SCD的药物，不幸的是 仅在约50%的服用者中有效，其机制尚不清楚。因此，我们的实验室正在调查 SCD小鼠模型中SCD的替代治疗。 人们认为，红细胞(RBC)是人体内最常见的细胞。为了维持一个正常的 携带氧气和排出二氧化碳的血红蛋白量，成年人超过200万 红血球一秒钟！这是一个高度精心策划的计划的结果。成人的红细胞生成 起源于骨髓，遵循从祖细胞到前体再到成熟红细胞的路径。他们 遵循原红细胞的发育方案，然后是嗜碱性红细胞， 先是多染红细胞，然后是正染红细胞。接下来是网织红细胞， 它们被去核，失去细胞器，并从骨髓迁移到外周循环。 它们通常占所有红细胞的0.5%到1.5%，在那些贫血的人中，这一比例会增加。 网织红细胞被发现有大的空泡包涵体，这些包涵体标记着内质 网状结构、高尔基体和线粒体。据认为，这些空泡通过胞吐作用和 自噬。已知PGCα1可诱导有丝分裂和线粒体呼吸调节。最新研究 在基因敲除(Nix-/-)小鼠上也证明了缺乏有丝分裂导致我们的红细胞寿命短 来自未经处理的镰状细胞小鼠的初步数据显示，成熟的红细胞保持较高的线粒体 级别高于控件。循环血液中富含线粒体的网织红细胞数量较多可能 促进体内活性氧水平升高、氧代谢改变和细胞溶解 在疾病中。 SCD导致红细胞线粒体增多的分子机制尚不清楚。 哺乳动物雷帕霉素靶标(m-TOR)依赖和非依赖调控有丝分裂 有丝分裂途径。这项提案寻求提供将异常有丝分裂与镰状细胞联系起来的试点数据。 病理学，并开发使用吞噬修复药物治疗SCD的新策略。 我们的目标是获得初步数据，即减少线粒体在红细胞中的滞留将提供安全的 并对SCD小鼠进行有效治疗。

Sickle cell disease (SCD) is an inherited blood disorder that affects millions of people worldwide. In the United States, approximately 100,000 people have it, with heath care costs estimated to be $1.1 billion in the US alone. It is caused by a mutation in the γ-globin gene, causing glutamic acid to be substituted by valine. Because of this, when deoxygenated, the hemoglobin is able to polymerize, causing shape change of the red blood cell (RBC), RBC lysis, and innumerable other complications including acute and chronic pain, chronic anemia, multisystem organ damage, and a much shortened life expectancy. The symptoms appear shortly after birth, when fetal hemoglobin (HbF) levels decline, and are replaced by adult sickle hemoglobin. Because of this observation, much effort has been placed to induce fetal hemoglobin levels in those with SCD. Hydroxyurea, the only FDA approved drug for the treatment of SCD, is unfortunately effective in only about 50% of those who take it, and its mechanism is not clear. Therefore, our lab investigates alternate treatments for SCD in the SCD mouse model. It is believed that the red blood cell (RBC) is the most common cell in the body. In order to maintain a normal amount of hemoglobin to carry oxygen and remove carbon dioxide, adult humans, make more than 2 million red blood cells a second! This is the result of a highly orchestrated plan. Erythropoiesis in adult humans originates in the bone marrow and follows a path from progenitor to precursor to mature red blood cells. They follow the developmental scheme of the proerythroblast, followed by the basophilic erythroblast, the polychromatophilic erythroblast, and then the orthochromatic erythroblast. These are followed by reticulocytes, which are enucleated, and lose their organelles, and migrate from the marrow to the peripheral circulation. They normally account for 0.5 to 1.5% of all red blood cells, in those who are anemic, the percent increases. Reticulocytes have been found to have large vacuolar inclusions, which label for markers of the endoplasmic reticulum, Golgi, and mitochondria. It is thought that these vacuoles are eliminated by exocytosis and autophagy. PGCα1 is known to induce regulators of mitophagy and mitochondrial respiration. Recent studies on a knockout (Nix -/-) mouse also demonstrated the lack of mitophagy led to the short life span of RBCs Our preliminary data from untreated sickle cell mice show mature red blood cells retain mitochondria at a higher level than controls. The higher number of mitochondria rich reticulocytes in circulating blood could potentially promote the elevated levels of reactive oxygen species, changes in oxygen metabolism and the cell lysis seen in the disease. The molecular mechanism of increased mitochondria in red blood cells associated with SCD is not clear. Mitophagy regulated through the mammalian Target of Rapamycin (m-TOR) dependent and independent mitophagy pathway. This proposal seeks to provide pilot data that will link aberrant mitophagy with sickle cell pathology and develop new strategies for the treatment of SCD using mitophagy restoration drugs. Our goal is to obtain preliminary data that the reductions of mitochondrial retention in RBC will provide safe and effective therapy in SCD mouse.