HEMOGLOBIN MEDIATED DAMAGE IN THALASSEMIC ERYTHROCYTES

地中海贫血是由于珠蛋白链合成不平衡引起的 贝塔和阿尔法血红蛋白基因的缺失或突变。AS 其结果是，未配对的α-或β-血红蛋白链(α-和 β链)存在于地中海贫血红细胞(RBC)内。 这些不成对的链条被认为是导致无效的 地中海贫血患者的红细胞生成和红细胞存活期缩短。 令人惊讶的是，尽管地中海贫血的红细胞异常很好 目前，人们对未配对的阿尔法-阿尔法的机制知之甚少 而Beta链则会伤害细胞。我们对此缺乏了解 地中海贫血细胞的细胞病理学是由于：1)发病和 细胞病理学的发展在体内发生得相当快；以及2) 受影响最严重的红细胞会迅速在两根骨头中被破坏 骨髓或外周血中。因此，它并没有 有可能直接研究未配对的阿尔法- 而Beta链则会损害RBC。为了绕过这些问题，我有 开发了阿尔法和贝塔地中海贫血红细胞的模型。这些模型 细胞，通过包裹纯化的α-链和β-链在正常 RBC的功能和结构变化与这些变化几乎相同 可见于地中海贫血患者的红细胞。使用地中海贫血模型RBC，in 结合患者样本，现在可以在实验上 研究未配对的血红蛋白链介导细胞的机制 损坏。重要的是，地中海贫血模型细胞还提供了一种独特的 对可能的治疗药物进行实验评估的手段。它是 这一提议的假设是未配对的人固有的不稳定性 珠蛋白链导致活性氧物种的产生和 球蛋白、游离血红素和铁的释放以及这些物质的基础 地中海贫血红细胞的病理生理学。此外，通过确定 未配对的珠蛋白链损伤红细胞的直接机制， 可以设计治疗干预措施来防止细胞损伤。 基于这些假设，研究提案的具体目标是 A)阐明血红素和铁的直接作用机制 从未配对的阿尔法链和贝塔链中释放；B)决定 珠蛋白来源于血红素和铁，并随后识别特定的 红细胞损伤的部位、机制和病理后果； 和c)评估干预措施(例如，抗氧化剂和螯合剂) 减少或阻止未配对的阿尔法链和贝塔链造成的伤害。结果是 这些研究将为我们提供对 地中海贫血细胞的病理生理学及实验证据 用于可能改善体内红细胞生成和红细胞的治疗药物 生死存亡。

The thalassemias arise from unbalanced globin chain synthesis due to deletions of, or mutations to, the Beta- and alpha-hemoglobin genes. As a consequence, unpaired alpha- or Beta-hemoglobin chains (alpha- and Beta-chains) are present within the thalassemic red blood cell (RBC). These unpaired chains are thought to contribute to the ineffective erythropoiesis and shortened RBC survival noted in the thalassemias. Surprisingly, while the RBC abnormalities in thalassemic are well characterized, little is known of the mechanisms by which unpaired alpha- and Beta-chains injure the cell. Our lack of knowledge regarding the cellular pathology of the thalassemic cell is due to: 1) the onset and development of cellular pathology occur quite rapidly in vivo; and 2) the most severely affected RBC are swiftly destroyed in either the bone marrow or in the peripheral blood. Consequently, it has not been possible to directly investigate the mechanism by which unpaired alpha- and Beta-chains damage the RBC. To circumvent these problems, I have developed models of the alpha and Beta thalassemic RBC. These model cells, made by entrapment of purified alpha- and Beta-chains in normal RBC, develop functional and structural changes almost identical to those seen in thalassemic patient RBC. Using the model thalassemic RBC, in conjunction with patient samples, it is now possible to experimentally examine the mechanisms by which unpaired hemoglobin chains mediate cell damage. Importantly, the model thalassemic cells also provide a unique means to experimentally evaluate possible therapeutic agents. It is the hypothesis of this proposal that the inherent instability of the unpaired globin chains results in the generation of reactive oxygen species and the release of globin free heme and iron and that these agents underlie the pathophysiology of the thalassemic RBC. Furthermore, by determining the direct mechanisms by which unpaired globin chains injure the RBC, therapeutic interventions can be designed that prevent cell damage. Based on these hypotheses, the specific aims of the research proposal are to: A) elucidate the direct mechanisms by which heme and iron are released from unpaired alpha- and Beta-chains; B) determine the fate of the globin derived heme and iron and, subsequently, identify the specific sites, mechanisms, and pathological consequences of damage to the RBC; and C) evaluate interventions (e.g., antioxidants and chelators) that diminish or block damage by unpaired alpha- and Beta-chains. The results of these studies will provide significant new insights into the pathophysiology of the thalassemic cell and give experimental evidence for therapeutic agents that might improve in vivo erythropoiesis and RBC survival.