Protective Role of Heme Oxygenase in Ischemic Brain

中风的一个并发症是脑出血。血红素加氧酶(HO)系统在细胞防御机制中起着关键作用，它催化血红素氧化成具有生物活性的分子：胆色素和CO。我们已经鉴定了该酶的两种活性形式：HO-1和HO-2。HO-2是一种血红素蛋白，可能是炎症和免疫反应中的效应分子NO的“接收器”。我们已经开发出过表达HO-1或HO-2的转基因(TG)小鼠。与非Tg鼠相比，HO-1Tg鼠脑组织中神经元cGMP水平和血管衬里中HO-1的表达均增加。而且，在pMCAo后，他们显示出脑卒中体积和脂质过氧化的减少。此外，TG小鼠的神经元对过氧化氢和谷氨酸毒性具有抵抗力。对HO-2 TG系的初步研究表明，神经元HO-2表达增加，脑组织脂质过氧化减少。到目前为止，还没有关于HO-2过度表达对卒中预后的影响的数据。然而，该基因的缺失会加剧这种伤害。此外，HO-1基因转移在中枢神经系统损伤中的作用也未见报道。虽然，通过腺病毒(Ad)介导的基因转移上调HO-1基因的表达，已知可保护氧化应激介导的系统性组织损伤。这项建议的总体目标是进一步探讨HO同工酶在预防中风和脑出血的神经元保护中的作用。1)利用HO-1和HO-2TG小鼠，研究HO基因过表达对短暂性局灶性脑缺血(TMCAo)转归的影响，以及对蛛网膜下腔注射溶血所致蛛网膜下腔出血(SAH)的影响。TMCAo模型将评估缺血性损伤的进展和应激的标志：脂质过氧化和氧化还原有效铁；以及血红素和胆红素水平。SAH模型将评估血管痉挛和坏死性/凋亡性细胞死亡。2)评价Ad-HO-1和Ad-HO-2基因转移对卒中和脑出血的潜在治疗作用。基因将通过脑脊液或颈动脉途径传递，相同的指征将被评估。

A complication of stroke is cerebral hemorrhage. The heme oxygenase (HO) system, which plays a key role in cellular defense mechanisms, catalyses oxidation of hemoglobin heme to biologically active molecules: bile pigments and CO. We have identified two active forms of the enzyme: HO-1 and HO-2. HO-2 is a hemoprotein and may function as a "sink" for NO, an effector molecule in inflammation and immune response. We have developed transgenic (Tg) mice that overexpress HO-1 or HO-2. HO-1 Tg mice brain, when compared with nonTg mice, show increased neuronal cGMP levels and expression of HO-1 in the lining of blood vessels. And, after pMCAo, they show decreases in brain stroke volume and in lipid peroxidation. Also, Tg mice neurons are resistant to H2O2 and glutamate toxicity. Initial studies with the HO-2 Tg line show increase in neuronal HO-2 expression and decrease in brain lipid peroxidation. To date, no data are available on the effect of HO-2 overexpression on the outcome of stroke. Deletion of the gene, however, exacerbates such injury. Also, the effect of HO-1 gene transfer on CNS injury has not been examined. Although, upregulation of HO-1 gene expression, using adenovirus (Ad)-mediated gene transfer, is known to protect against oxidative stress-mediated systemic tissue injury. The overall objective of this proposal is to further explore the role of HO isozymes in neuronal protection against stroke and cerebral hemorrhage. Specific aims are: 1) Using the HO-1 and HO-2 Tg mice to investigate the effect of HO gene overexpression on the outcome of transient focal ischemia (tMCAo), and on subarachnoid hemorrhage (SAH) caused by injection of lysed blood into the subarachnoid space. The tMCAo model will be evaluated for progression of ischemic injury and markers of stress: lipid peroxidation and redox available iron; also, for heme and bilirubin levels. The SAH model will be evaluated for vasospasm and necrotic/ apoptotic cell death. 2) To evaluate in the above models the potential therapeutic benefits of Ad-HO-1 and Ad-HO-2 gene transfer in stroke and cerebral hemorrhage. Genes will be delivered by CSF or by intracarotid route and the same indeces will be evaluated.