Enhanced neuronal expression of the oxidoreductase - biliverdin reductase - after permanent focal cerebral ischemia
Enhanced neuronal expression of the oxidoreductase - biliverdin reductase - after permanent focal cerebral ischemia
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DOI：
10.1016/s0006-8993(99)01726-6
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发表时间：
1999-12-11
期刊：
影响因子：
2.9
通讯作者：
Maines, MD
中科院分区：
文献类型：
--
作者：
Panahian, N;Huang, TJ;Maines, MD
这是缺血性脑损伤后神经元胆绿素还原酶（BVR）水平升高的第一篇报道。BVR是一种氧化还原酶，在迄今为止已知的所有酶中，它具有双重pH/双重辅因子需求- NADH和NADPH分别为6.7和8.7。BVR催化血红素代谢途径的最后一步，将血红素降解产物胆绿素还原为胆红素。胆红素既可以是神经毒物，也可以是抗氧化剂，这取决于它与蛋白质的比例和浓度。胆红素也有免疫调节作用。其他具有生物活性的血红素降解产物是铁和一氧化碳。本研究评估了永久性大脑中动脉闭塞（MCAo）后BVR水平的时间依赖性变化。并探讨了BVR表达变化与缺血性组织损伤指标表现的相关性。在氟烷麻醉和常温条件下，对72只DNX近交系小鼠进行MCAo。缺血性病变的时间扩大在24小时观察并测量了55 + / - 5毫米(3)在6 h, 63 + / - 6.7 mm3 12 h和73 + / - 5 mm3在MCAo后24 h。六个小时,增加免疫反应性BVR指出在神经元peri-ischemic地区,intraischemic皮质层3和5,以及神经元在遥远地区的边界MCA的血管分布,如在黑质,小脑浦肯野层和下丘中央核。MCAo 24小时后，缺血周围区域BVR的免疫反应性仍然升高。各时间点缺血核区BVR染色均下降。在24 h时间点，病变周缘Fe染色增加，病变边缘脂质过氧化Schiff染色增加。原位杂交分析显示，缺血周围区神经元中BVR mRNA标记的时间依赖性增加。在缺血半球，与对侧半球相比，pH为6.7时未观察到可测量的BVR mRNA或总蛋白水平的降低，也未观察到nadh依赖性BVR活性的降低。通过Northern和Western blots和活性分析判断，尽管缺血核心的BVR明显减少，并且在缺血周围区域BVR增加，但与对侧半球相比，缺血半球催化胆绿素还原的总体能力在整个实验过程中没有变化。如果在缺血的情况下，条件有利于胆红素的抗氧化活性，那么我们认为BVR在缺血半暗区表达的增加可能存在一种针对自由基介导的神经元损伤的细胞防御机制。此外，我们认为BVR在缺血半球的表达明显受到严格调控，是防止胆红素神经毒性的重要因素。数据提示，BVR表达的药理调控可能是保护神经元免受缺血损伤和氧化应激的新方向。(C) 1999 Elsevier Science B.V.版权所有
This is the first report on increased neuronal levels of biliverdin reductase (BVR) in response to ischemic brain injury. BVR is an oxidoreductase, and is unique among all enzymes characterized to date in having dual pH/dual cofactor requirements - NADH and NADPH at 6.7 and 8.7, respectively. BVR catalyses the final step in the heme metabolic pathway and reduces the heme degradation product, biliverdin, to bilirubin. Bilirubin can be both a neurotoxicant and an antioxidant depending on its ratio to protein and concentration. Bilirubin also has immunomodulatory activity. Other biologically active heme degradation products are iron and CO. This study assessed time-dependent changes in the level of BVR, following permanent middle cerebral artery occlusion (MCAo). It also examined correlation of the change in BVR expression with display of indices of ischemic tissue injury. Under halothane anesthesia and normothermic conditions, 72 DNX inbred mice were subjected to MCAo. A time-dependent enlargement of an ischemic lesion over the course of 24 h was observed and measured 55 +/- 5 mm(3) at 6 h, 63 +/- 6.7 mm3 at 12 h, and 73 +/- 5 mm3 at 24 h. Six hours after MCAo, increased immunoreactivity for BVR was noted in neurons in the peri-ischemic areas, intraischemic cortical layers 3 and 5, as well as in neurons in regions distant from the borders of vascular distribution of the MCA, such as those in substantia nigra, in the Purkinje layer of the cerebellum and in the central nucleus of inferior colliculus. Twenty-four hours after MCAo, immunoreactivity for BVR remained increased in the peri-ischemia areas. At all time points staining for BVR was decreased in the ischemic core. At the 24 h time point there was an increase in Fe staining in the perimeter of the lesion and an increase in Schiff's staining for lipid peroxidation at the rim of the lesion. In situ hybridization analysis demonstrated a time dependent increase in BVR mRNA labeling in neurons of the peri-ischemic area. In the ischemic hemisphere, when compared with the contralateral hemisphere, neither measurable decreases in BVR mRNA or total protein levels nor a decrease in NADH-dependent BVR activity at pH 6.7 were observed. As judged by Northern and Western blots and activity analysis, despite the apparent loss of BVR from the ischemic core, and its increase in the peri-ischemic region, when compared with the contralateral hemisphere, the overall capacity of the ischemic hemisphere to catalyze the reduction of biliverdin was unchanged throughout the experiment. Should, in the case of ischemia, the conditions favor the antioxidant activity of bilirubin, then we suggest that increase in BVR expression in ischemic penumbra may present a cellular defense mechanism against free radical-mediated neuronal damage. Furthermore, we interpret the apparent tightly regulated expression of BVR in the ischemic hemisphere as an important factor in protection against bilirubin neurotoxicity. Data suggest that pharmacological modulation of BVR expression is a possible new direction for protecting neurons against ischemic injury and oxidative stress. (C) 1999 Elsevier Science B.V. All rights reserved.