Scott M D, van den Berg J J, Repka T, Rouyer-Fessard P, Hebbel R P, Beuzard Y, Lubin B H
Children's Hospital Oakland Research Institute, California 94609.
J Clin Invest. 1993 Apr;91(4):1706-12. doi: 10.1172/JCI116380.
While red cells from individuals with beta thalassemias are characterized by evidence of elevated in vivo oxidation, it has not been possible to directly examine the relationship between excess alpha-hemoglobin chains and the observed oxidant damage. To investigate the oxidative effects of unpaired alpha-hemoglobin chains, purified alpha-hemoglobin chains were entrapped within normal erythrocytes. These "model" beta-thalassemic cells generated significantly (P < 0.001) greater amounts of methemoglobin and intracellular hydrogen peroxide than did control cells. This resulted in significant time-dependent decreases in the protein concentrations and reduced thiol content of spectrin and ankyrin. These abnormalities correlated with the rate of alpha-hemoglobin chain autoxidation and appearance of membrane-bound globin. In addition, alpha-hemoglobin chain loading resulted in a direct decrease (38.5%) in catalase activity. In the absence of exogenous oxidants, membrane peroxidation and vitamin E levels were unaltered. However, when challenged with an external oxidant, lipid peroxidation and vitamin E oxidation were significantly (P < 0.001) enhanced in the alpha-hemoglobin chain-loaded cells. Membrane bound heme and iron were also significantly elevated (P < 0.001) in the alpha-hemoglobin chain-loaded cells and lipid peroxidation could be partially inhibited by entrapment of an iron chelator. In contrast, chemical inhibition of cellular catalase activity enhanced the detrimental effects of entrapped alpha-hemoglobin chains. In summary, entrapment of purified alpha-hemoglobin chains within normal erythrocytes significantly enhanced cellular oxidant stress and resulted in pathological changes characteristic of thalassemic cells in vivo. This model provides a means by which the pathophysiological effects of excess alpha-hemoglobin chains can be examined.
虽然β地中海贫血患者的红细胞具有体内氧化升高的证据，但尚未能够直接研究过量α-血红蛋白链与观察到的氧化损伤之间的关系。为了研究未配对α-血红蛋白链的氧化作用，将纯化的α-血红蛋白链包裹在正常红细胞内。这些“模型”β地中海贫血细胞产生的高铁血红蛋白和细胞内过氧化氢量比对照细胞显著（P<0.001）增加。这导致血影蛋白和锚蛋白的蛋白质浓度随时间显著降低，硫醇含量减少。这些异常与α-血红蛋白链的自氧化速率和膜结合珠蛋白的出现相关。此外，α-血红蛋白链的加载导致过氧化氢酶活性直接降低（38.5%）。在没有外源性氧化剂的情况下，膜过氧化和维生素E水平未改变。然而，当受到外部氧化剂挑战时，α-血红蛋白链加载的细胞中脂质过氧化和维生素E氧化显著（P<0.001）增强。α-血红蛋白链加载的细胞中膜结合血红素和铁也显著升高（P<0.001），脂质过氧化可通过包裹铁螯合剂而部分受到抑制。相反，化学抑制细胞过氧化氢酶活性增强了包裹的α-血红蛋白链的有害作用。总之，将纯化的α-血红蛋白链包裹在正常红细胞内显著增强了细胞氧化应激，并导致体内地中海贫血细胞的病理变化特征。该模型提供了一种研究过量α-血红蛋白链病理生理作用的方法。
