Heme Oxygenase and Spinal Cord Injury

脊髓损伤后的功能恢复归因于介导早期和延迟细胞损伤的继发性致病事件。这项拟议的研究考察了血红素氧合酶-1(HO-1)在创伤脊髓早期和迟发性损伤中的作用。血红素加氧酶是唯一能将促氧化剂血红素代谢成胆汁色素、铁和一氧化碳的酶。细胞外的血红素来源于实质内出血和死亡细胞释放的血红素蛋白。虽然出血和持续的细胞死亡都是损伤脊髓的特征，但人们对血红素如何导致早期和延迟损伤知之甚少。S的普遍假设是，HO-1对于损伤脊髓中的血红素的解毒至关重要。以下实验将验证三个主要假说：假设：1.小胶质细胞通过代谢血红素和区划血红素代谢产物游离铁，为损伤脊髓提供一条重要的防线。实验：(1)我们将比较HO-1基因敲除(KO)和野生型(WT)小鼠的小胶质细胞反应，并确定在铁积累和出血区域是否发生HO-1和铁蛋白在小胶质细胞中的急性诱导表达。假设2.在小胶质细胞/巨噬细胞中诱导HO-1可通过减少氧化应激/损伤来促进伤口愈合和运动恢复。实验：(1)测定氧化应激/损伤指标，评估HO-1 WT和KO动物的血运重建、白质损伤和运动恢复。(2)类似的结果措施将在脊髓损伤小鼠中进行评估，用鞘内血红蛋白进行预处理，这是一种优先诱导胶质细胞HO-1的策略。假设3.损伤前在脊髓血管中诱导HO-1可以稳定血脊髓屏障，减轻早期诱导的血管黏附分子和炎症细胞的浸润，促进功能恢复。实验：我们将确定在损伤前全身给予血红素是否会限制对蛋白质的屏障破坏，通过调节血管黏附分子来限制中性粒细胞的渗透，并促进运动恢复。综上所述，这些研究反映了将脊髓损伤后出血、氧化应激和功能结果联系起来的集中努力，并将确定HO-1是保护还是损害细胞，调节血脊髓屏障功能和伤口愈合，并影响运动恢复。

Functional recovery after spinal cord injury is attributed to secondary pathogenic events that mediate early and delayed cell injury. The proposed studies examine the role of heme oxygenase-1 (HO-1) in both early and delayed injury in the traumatized spinal cord. Heme oxygenases are the only enzymes that metabolize the pro-oxidant heme to bile pigments, iron, and carbon monoxide. Extracellular heme is derived from intraparenchymal hemorrhage and heme proteins released from dying cells. Although both hemorrhage and ongoing cell death are features of the injured spinal cord, little is known about how heme contributes to early and delayed injury. The general hypothesis s that HO-1 is crucial for the detoxification of heme in the traumatized cord. The following experiments will test three major hypothesis: Hypothesis: 1. Microglia provide an important line of defense in the traumatized cord by metabolizing heme and compartmentalizing free iron, a product of heme metabolism. Experiments: (1) We will compare the microglial response in HO-1 knockout (KO) and wildtype (WT) mice and will determine if acute induction of HO-1 and ferritin expression in microglia occur in regions of iron accumulation and hemorrhage. Hypothesis 2. Induction of HO-1 in microglia/macrophages promotes wound healing and locomotor recovery by reducing oxidative stress/injury. Experiments: (1) We will measure indicators of oxidative stress/injury and evaluate revascularization, white matter injury, and locomotor recovery in HO-1 WT and KO animals. (2) Similar outcome measures will be evaluated in spinal cord injured mice, pretreated with intrathecal hemoglobin, a strategy that preferentially induces HO-1 in glia. Hypothesis 3. Induction of HO-1 in spinal cord blood vessels, prior to injury, stabilizes the blood-spinal cord barrier, attenuates the early induction of vascular adhesion molecules and infiltration of inflammatory cells, and promotes functional recovery. Experiments: We will determine if systemic administration of heme prior to injury, a strategy which preferentially induces HO-1 in endothelium, will restrict barrier disruption to proteins, limit the infiltration of neutrophils through the modulation of vascular adhesion molecules, and promote locomotor recovery. In summary, these studies reflect a focused effort to link hemorrhage, oxidative stress and functional outcome after spinal cord injury and will determine if HO-1 protects or harm cells, modulates blood-spinal cord barrier function and wound healing, and influences locomotor recovery.