Protective Role of Heme Oxygenase in Ischemic Brain

中风的并发症是脑出血。 血红素加氧酶（HO）系统，它在细胞防御机制中起着关键作用，催化血红蛋白血红素氧化为生物活性分子：胆色素和CO。我们已经确定了两种活性形式的酶：HO-1和HO-2。 HO-2是一种血红素蛋白，可作为NO的“汇”，NO是炎症和免疫反应中的效应分子。 我们已经开发了过表达HO-1或HO-2的转基因（Tg）小鼠。 与nonTg小鼠相比，HO-1 Tg小鼠的脑显示增加的神经元cGMP水平和血管衬里中HO-1的表达。 而且，在pMCAo后，他们显示出脑卒中量和脂质过氧化作用的减少。 此外，Tg小鼠神经元对H2 O2和谷氨酸毒性具有抗性。 HO-2 Tg系的初步研究显示神经元HO-2表达增加，脑脂质过氧化减少。 迄今为止，没有关于HO-2过表达对卒中结局影响的数据。 然而，该基因的缺失会加剧这种损伤。此外，HO-1基因转移对CNS损伤的影响尚未得到研究。 虽然，HO-1基因表达的上调，使用腺病毒（Ad）介导的基因转移，是已知的保护免受氧化应激介导的全身组织损伤。 本研究的总体目标是进一步探讨HO同工酶在脑卒中和脑出血神经保护中的作用。 具体目标是：1）采用HO-1和HO-2转基因小鼠，研究HO基因过表达对短暂性局灶性脑缺血（tMCAo）和蛛网膜下腔注射裂解血引起的蛛网膜下腔出血（SAH）的影响。 将评价tMCAo模型的缺血性损伤进展和应激标志物：脂质过氧化和氧化还原可用铁;以及血红素和胆红素水平。 将评价SAH模型的血管痉挛和坏死/凋亡细胞死亡。2)在上述模型中评价Ad-HO-1和Ad-HO-2基因转移对脑卒中和脑出血的潜在治疗作用。 将通过CSF或颈动脉内途径递送基因，并评价相同的指标。

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.