MECHANISMS AND PREVENTION OF HEMOGLOBIN NEUROTOXICITY

基于血红蛋白的化合物正在开发作为血液替代品， 用于外科或急诊医学，但放置的后果 与CNS组织直接接触的基于血红蛋白的化合物是未知的。 这些研究将继续开发一种细胞培养模型， 用于评估血红蛋白或基于血红蛋白的化合物对 CNS。此外，该模型可用于识别和测试 治疗血红蛋白介导的 细胞损伤 先前的研究结果表明血红蛋白具有神经毒性。血氧 会引起脑血管痉挛，皮质内注射血红蛋白 被用来制作癫痫的动物模型。初步实验 证明了血红蛋白和血红蛋白氧 载体对培养的鼠神经元具有浓度依赖性毒性 时尚.这种毒性随着时间的推移而发展，甚至在 除去血红蛋白。所有检测的血红蛋白溶液 似乎对鼠神经胶质细胞有毒。 目前的建议将解决血红蛋白介导的损伤文化 大鼠小脑神经元，皮质神经元，纯星形胶质细胞，和共- 星形胶质细胞和小胶质细胞的培养物。浓度依赖性和 将描述血红蛋白介导的损伤的时间过程。具体 血浆蛋白将作为保护剂进行评价，强调蛋白质 结合并促进血红蛋白或血红素的清除--结合珠蛋白 或血红素结合蛋白。其他可能具有治疗潜力的化合物 将评价血红蛋白介导的损伤的治疗。这些化合物 将包括抗氧化剂（如Trolox，α生育酚和21- 氨基类固醇）、螯合剂（如去铁胺和一种新的去铁胺 衍生物），以及阻断钙进入神经元的药物 (NMDA、红藻氨酸盐/AMPA和代谢型受体拮抗剂和钙离子拮抗剂 通道阻断剂）。将进行额外的实验以测试 假设抗坏血酸和血红蛋白依赖性神经毒性是 通过类似的机制介导，抗坏血酸可能加剧 血红蛋白介导的损伤。最后，热休克的表达 将在神经元中检测蛋白HSP 70和血红素氧合酶-1， 星形胶质细胞在血红蛋白和抗坏血酸依赖性 损伤这些被认为具有保护作用的蛋白质， 在不同的细胞中有差异，部分解释了 神经元和星形胶质细胞对血红蛋白的敏感性。

Hemoglobin-based compounds are being developed as blood substitutes to be used in surgery or emergency medicine, yet the consequences of placing hemoglobin-based compounds in direct contact with CNS tissue are unknown. These studies will continue to develop a cell culture model that can be used to assess the toxicity of hemoglobin or hemoglobin-based compounds to the CNS. Additionally, this model can be utilized to identify and test possible therapeutic approaches for the treatment of hemoglobin-mediated cellular injury. Previous results suggest that hemoglobin is neurotoxic. Oxyhemoglobin causes cerebral vasospasm, and intracortical injections of hemoglobin have been used to generate animal models of epilepsy. Preliminary experiments have demonstrated that both hemoglobin and a hemoglobin-based oxygen carrier are toxic to cultured murine neurons in a concentration-dependent fashion. This toxicity developed over time and progressed even after hemoglobin was removed. None of the hemoglobin solutions tested have appeared to be toxic to murine glial cells. The current proposal will address hemoglobin-mediated injury in cultures of rat cerebellar neurons, cortical neurons, pure astrocytes, and co- cultures of astrocytes and microglia. The concentration dependence and time course of hemoglobin-mediated injury will be delineated. Specific plasma proteins will be evaluated as protectants, emphasizing proteins that bind and facilitate the clearance of hemoglobin or heme--haptoglobin or hemopexin. Other compounds that may have therapeutic potential for the treatment of hemoglobin-mediated injury will be evaluated. These compounds will include antioxidants (such as Trolox, alpha tocopherol, and the 21- aminosteroids), chelators (such as deferoxamine and a novel deferoxamine derivative), as well as drugs that block the calcium entry into neurons (NMDA, kainate/AMPA, and metabotropic receptor antagonists and calcium channel blockers). Additional experiments will be conducted to test the hypotheses that ascorbate- and hemoglobin-dependent neurotoxicity are mediated through similar mechanisms and that ascorbate may exacerbate hemoglobin-mediated injury. Finally, the expression the of heat shock proteins HSP7O and heme oxygenase- l will be examined in neurons and astrocytes during the course of hemoglobin- and ascorbate-dependent injury. These proteins, which are thought to be protective, may be induced differently in different cells, partially explaining the differential sensitivity of neurons and astrocytes to hemoglobin.