血红素氧合酶系统对一氧化碳中毒后体外培养少突胶质细胞 Nogo-A的影响

摘要

背景：鉴于Nogo-A蛋白及其受体NgR分别表达于中枢神经系统的少突胶质细胞与神经元，而一氧化碳中毒迟发性脑病患者颅脑影像学上白质脱髓鞘突出，推测Nogo-A蛋白及NgR系统参与急性一氧化碳中毒脑损害，可能与一氧化碳中毒迟发性脑病关系密切。内源性一氧化碳(CO)是机体重要的气体信使分子之一，主要是由血红素氧合酶代谢产生的，其对Nogo-A体系的影响目前亦未见报道。目的：采用外源性CO处理体外培养少突胶质细胞，并用锌原卟啉9抑制血红素氧合酶系统活性，观察少突胶质细胞Nogo-A在mRNA及蛋白质水平的表达情况。方法：将体外培养的少突胶质细胞分为对照组、CO组和锌原卟啉9组。CO组和锌原卟啉9组细胞置于含体积分数1%CO的密封室内培养。锌原卟啉9组细胞在CO处理前，预先在培养液中加入10μmol/L锌原卟啉9。首先比较培养6，24和48 h时细胞中Nogo-A mRNA和蛋白的表达水平，检测表达水平最高时CO组和锌原卟啉9组细胞中Nogo-A mRNA和蛋白表达水平的差异。结果与结论：CO组细胞中Nogo-A mRNA和蛋白的表达水平均高于对照组，且都在培养24 h时表达水平最高。培养24 h时锌原卟啉9组细胞中Nogo-A mRNA和蛋白表达水平均高于CO组。提示排除在体情况中一氧化碳中毒所致的缺氧的影响，单纯外源性CO可诱导体外培养少突胶质细胞Nogo-A mRNA及蛋白表达水平增加；血红素氧合酶系统可抑制Nogo-A mRNA及蛋白的表达水平。%BACKGROUND:Cerebral white matter demyelination is outstanding in the images of delayed encephalopathy after acute carbon monoxide (CO) poisoning. Since Nogo-A and Nogo-receptor are expressed in onoligodendrocytes and neurons respectively, we infer that Nogo-A system is involved in brain injury after acute CO poisoning and related to delayed encephalopathy after acute CO poisoning. Endogenous CO is a gaseous messenger, which is the metabolic product of hemeoxygenase. There is no report about the CO effect on Nogo-A system til now. OBIECTIVE: To in vitro culture oligodendrocytes using endogenous CO, inhibit the activity of hemeoxygenase system using zinc protoporphyrin-IX (ZnPPIX) and observe the variation of Nogo-A in oligodendrocytes at mRNA and protein levels. METHODS: Rat oligodendrocytes cultured in vitro were divided into control, CO, ZnPPIX groups. Cels in the CO and ZnPPIX groups were treated with 1% CO directly, In the ZnPPIX group, 10 μmol/L ZnPPIX was added into the culture medium before CO treatment. The expressions of Nogo-A mRNA and protein at 6, 24, 48 hours after culture were compared. Differences in the peak levels of Nogo-A mRNA and protein between CO and ZnPPIX groups were detected using RT-PCR and immunohistochemistry respectively. RESULTS: The expression levels of Nogo-A mRNA and protein were significantly higher in the CO group than the control group and reached the peak at 24 hours of culture. Compared with the CO group, oligodendrocytes cultured with ZnPPIX showed higher expressions of Nogo-A mRNA and protein at 24 hours of culture. These findings suggest that except the influence of hypoxia occurring in CO poisoning, exogenous CO increases the expression of Nogo-A in cultured oligodendrocytes in vitro, and the heme oxygenase system can inhibit the expression of Nogo-A mRNA and protein.