The influence of tissue-specific heme oxygenase-1 (HO-1) deficiency on neuronal damage induced by subarachnoid hemorrhage in mice: the role of carbon monoxide (CO)

血红素加氧酶1 （HO-1）内源性产生一氧化碳（CO）是一种重要的细胞保护机制。内源性CO生产的重要性被以下事实所强调：人类缺乏HO-1可导致严重的疾病状态和过早死亡，2。经典的HO-1基因敲除会导致动物寿命明显缩短。HO-1的过表达或诱导以及CO的外源应用在多种疾病模型中都具有保护作用。我们的实验室最近表明，通过CO释放分子（CO- rm）的吸入或全身途径外源性应用CO具有神经保护作用。两个重要方面仍不清楚：1。细胞特异性HO-1表达的独特作用是什么？2. 外源CO的施用是否与HO-1诱导产生的内源性CO具有同等的保护作用？为了回答这些问题，我们将使用一个完善的脑损伤模型（蛛网膜下腔出血，SAH），其中HO-1表达上调，并已被证明具有保护作用。对于HO-1敲除小鼠，无论是内皮细胞、神经元细胞还是小胶质细胞，都存在全局HO-1缺陷或条条性组织特异性HO-1缺陷，我们想要表征HO-1表达在这些细胞中所发挥的独特保护作用。因此，我们将研究以下假设：HO-1表达可改善SAH后的神经元损伤。目的1：评价HO-1缺失对SAH后神经元细胞损伤的影响。2. 内皮特异性HO-1对sah诱导的小鼠脑血管痉挛和内皮功能障碍具有保护作用。具体目的2：评估内皮HO-1缺乏对SAH后神经元细胞死亡的贡献。3. 神经元特异性HO-1可预防小鼠SAH后的细胞死亡。特异性目的3：评价组织特异性神经元HO-1敲除对SAH后神经元细胞死亡的影响。4. 小胶质细胞特异性HO-1调节血红素去除和sah诱导的神经炎症反应。特异性目的4：评估小胶质细胞特异性HO-1敲除对SAH后神经元细胞死亡的贡献。5. 在上述全球和组织特异性HO-1敲除小鼠中，CO可以弥补内源性CO产生的不足。具体目的5：研究外源性CO（以气体形式吸入或通过CO释放分子ALF186）对HO-1缺陷小鼠SAH后神经元损伤的潜在保护作用。

Endogenous production of carbon monoxide (CO) by heme oxygenase 1 (HO-1) represents an essential cellular protection mechanism. The importance of endogenous CO production is underlined by the facts that 1. deficiency of HO-1 in humans leads to a severe disease state with premature death, 2. classical genetic knockout of HO-1 in animals results in markedly reduced life span, 3. overexpression or induction of HO-1 and exogenous application of CO exerts protective effects in various disease models. Our lab has recently shown that exogenous application of CO, either inhalative or via systemic routes by a CO releasing molecule (CO-RM) exerts neuroprotective effects. Two important aspects remain unclear: 1. What is the distinct role of cell-specific HO-1 expression? 2. Does exogenous CO application equal endogenously generated CO by HO-1 induction regarding its protective effects? To answer these questions, we will use a well established model of cerebral injury (subarachnoid hemorrhage, SAH), in which HO-1 is upregulated and has been shown to be protective. With HO-1 knockout mice either with global HO-1 deficiency or conditional tissue-specific HO-1 deficiency in either endothelial, neuronal or microglial cells, we want to characterize the distinct protective role exerted by HO-1 expression in these cells. We therefore will study the following hypotheses: 1. HO-1 expression ameliorates neuronal injury after SAH. Specific aim 1: To evaluate the effect of global HO-1 deficiency on neuronal cell injury following SAH. 2. Endothelial-specific HO-1 is protective in SAH-induced cerebral vasospasm and endothelial dysfunction in mice. Specific aim 2: To evaluate the contribution of endothelial HO-1 deficiency to neuronal cell death following SAH. 3. Neuron-specific HO-1 prevents cell death following SAH in mice. Specific aim 3: To evaluate the effect of tissue-specific neuronal HO-1 knockout on neuronal cell death following SAH. 4. Microglia-specific HO-1 modulates heme removal and the SAH-induced neuroinflammatory response. Specific aim 4: To evaluate the contribution of microglia-specific HO-1 knockout to neuronal cell death following SAH. 5. CO can compensate for the deficiency of endogenous CO production in the above-described global and tissue-specific HO-1 knockout mice. Specific aim 5: To investigate the potentially protective effect of exogenous application of CO, either inhaled as gas or through the CO releasing molecule (CO-RM) ALF186 on neuronal damage after SAH in HO-1 deficient mice.