Ascorbate removes key precursors to oxidative damage by cell-free haemoglobin in vitro and in vivo
Ascorbate removes key precursors to oxidative damage by cell-free haemoglobin in vitro and in vivo
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DOI：
10.1042/bj20060341
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发表时间：
2006-11-01
影响因子：
4.1
通讯作者：
Cooper, Chris E.
中科院分区：
文献类型：
--
作者：
Dunne, Jacqueline;Caron, Alexis;Cooper, Chris E.
血红蛋白引发自由基化学反应。特别是，过氧化物与血红蛋白的三价铁 (met) 物质相互作用产生两种强氧化剂：铁和蛋白质结合的自由基。我们在兔子模型中研究了对这种反应化学的内源性防御，该模型在用稳定在四聚体形式的无细胞血红蛋白进行 20% 换血后[通过与双-(3,5-二溴水杨基)富马酸酯交联]。输血含有95%氧合血红蛋白、5%高铁血红蛋白和25μM游离铁。 EPR 光谱显示，输血中的游离铁通过与转铁蛋白快速结合而失去氧化还原活性。高铁血红蛋白通过较慢的过程（t1/2 = 1 小时）还原为氧合血红蛋白。血浆中未检测到球蛋白结合自由基。这些氧化还原防御完全归因于血浆抗坏血酸在消除氧化损伤的关键前体方面的新型多功能作用。抗坏血酸能有效降低血浆高铁血红蛋白、铁血红蛋白和球蛋白自由基。形成的抗坏血酸自由基被红细胞膜结合还原酶（其本身使用红细胞内抗坏血酸作为电子供体）有效地重新还原。除了与基于血红蛋白的氧载体的毒性相关之外，这些发现对于血红蛋白存在于保护性细胞环境之外的情况也有影响，例如，溶血性贫血、蛛网膜下腔出血、横纹肌溶解症。
Haemoglobin initiates free radical chemistry. In particular, the interactions of peroxides with the ferric (met) species of haemoglobin generate two strong oxidants: ferryl iron and a protein-bound free radical. We have studied the endogenous defences to this reactive chemistry in a rabbit model following 20% exchange transfusion with cell-free haemoglobin stabilized in tetrameric form [via cross-linking with bis-(3,5-dibromosalicyl)fumarate]. The transfusate contained 95% oxyhaemoglobin, 5% methaemoglobin and 25 mu M free iron. EPR spectroscopy revealed that the free iron in the transfusate was rendered redox inactive by rapid binding to transferrin. Methaemoglobin was reduced to oxyhaemoglobin by a slower process (t1/2 = 1 h). No globin-bound free radicals were detected in the plasma. These redox defences could be fully attributed to a novel multifunctional role of plasma ascorbate in removing key precursors of oxidative damage. Ascorbate is able to effectively reduce plasma methaemoglobin, ferryl haemoglobin and globin radicals. The ascorbyl free radicals formed are efficiently re-reduced by the erythrocyte membranebound reductase (which itself uses intra-erythrocyte ascorbate as an electron donor). As well as relating to the toxicity of haemoglobin-based oxygen carriers, these findings have implications for situations where haem proteins exist outside the protective cell environment, e.g. haemolytic anaemias, subarachnoid haemorrhage, rhabdomyolysis.