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。本研究旨在探讨血红素加氧酶-1 （HO-1）在脊髓损伤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。细胞外血红素来源于肺实质内出血和垂死细胞释放的血红素蛋白。尽管出血和持续的细胞死亡都是损伤脊髓的特征，但对于血红素如何促进早期和延迟损伤知之甚少。一般的假设是HO-1对损伤脊髓中血红素的解毒至关重要。下面的实验将检验三个主要假设：假设：1。小胶质细胞通过代谢血红素和区隔游离铁（血红素代谢的产物），在损伤的脊髓中提供重要的防线。实验：(1)我们将比较HO-1敲除（KO）和野生型（WT）小鼠的小胶质细胞反应，并确定HO-1和铁蛋白表达的急性诱导是否发生在铁积聚和出血区域。假设2。在小胶质细胞/巨噬细胞中诱导HO-1通过减少氧化应激/损伤促进伤口愈合和运动恢复。实验：(1)我们将测量HO-1 WT和KO动物的氧化应激/损伤指标，评估血运重建、白质损伤和运动恢复。(2)在脊髓损伤小鼠中，使用鞘内血红蛋白（一种优先诱导神经胶质中HO-1的策略）进行预处理，将评估类似的结果。假设3。损伤前在脊髓血管中诱导HO-1，稳定血脊髓屏障，减弱早期诱导的血管粘附分子和炎症细胞浸润，促进功能恢复。实验：我们将确定损伤前全身给药血红素（一种优先诱导内皮细胞HO-1的策略）是否会限制屏障对蛋白质的破坏，通过调节血管粘附分子限制中性粒细胞的浸润，并促进运动恢复。总之，这些研究反映了脊髓损伤后出血、氧化应激和功能结局之间的联系，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.