Iadecola C, Zhang F, Xu S, Casey R, Ross M E
Department of Neurology, University of Minnesota, Minneapolis 55455, USA.
J Cereb Blood Flow Metab. 1995 May;15(3):378-84. doi: 10.1038/jcbfm.1995.47.
Cerebral ischemia is followed by a local inflammatory response that is thought to participate in the extension of the tissue damage occurring in the postischemic period. However, the mechanisms whereby the inflammation contributes to the progression of the damage have not been fully elucidated. In models of inflammation, expression of the inducible isoform of nitric oxide synthase (iNOS) is responsible for cytotoxicity through the production of large amounts of nitric oxide (NO). In this study, therefore, we sought to establish whether iNOS is expressed in the ischemic brain. Rats were killed 6 h to 7 days after occlusion of the middle cerebral artery. iNOS expression in the ischemic area was determined by reverse-transcription polymerase chain reaction. Porphobilinogen deaminase mRNA was detected in the same sample and used for normalization. In the ischemic brain, there was expression of iNOS mRNA that began at 12 h, peaked at 48 h, and returned to baseline at 7 days (n = 3/time point). iNOS mRNA expression paralleled the time course of induction of iNOS catalytic activity, determined by the citrulline assay (17.4 +/- 4.4 pmol citrulline/micrograms protein/min at 48 h; mean +/- SD; n = 5 per time point). iNOS immunoreactivity was seen in neutrophils at 48-96 h after ischemia. The data provide molecular, biochemical, and immunocytochemical evidence of iNOS induction following focal cerebral ischemia. These findings, in concert with our recent demonstration that inhibition of iNOS reduces infarct volume in the same stroke model, indicate that NO production may play an important pathogenic role in the progression of the tissue damage that follows cerebral ischemia.
脑缺血后会伴随局部炎症反应，这种反应被认为参与了缺血后时期发生的组织损伤的扩展。然而，炎症导致损伤进展的机制尚未完全阐明。在炎症模型中，诱导型一氧化氮合酶（iNOS）的表达通过产生大量一氧化氮（NO）而导致细胞毒性。因此，在本研究中，我们试图确定iNOS是否在缺血脑中表达。在大脑中动脉闭塞后6小时至7天处死大鼠。通过逆转录聚合酶链反应测定缺血区域的iNOS表达。在同一样本中检测到胆色素原脱氨酶mRNA并用于标准化。在缺血脑中，iNOS mRNA的表达在12小时开始，在48小时达到峰值，并在7天时恢复到基线水平（每个时间点n = 3）。iNOS mRNA表达与通过瓜氨酸测定法确定的iNOS催化活性的诱导时间进程平行（48小时时为17.4±4.4 pmol瓜氨酸/微克蛋白质/分钟；平均值±标准差；每个时间点n = 5）。在缺血后48 - 96小时，在中性粒细胞中可见iNOS免疫反应性。这些数据提供了局灶性脑缺血后iNOS诱导的分子、生化和免疫细胞化学证据。这些发现，与我们最近证明抑制iNOS可减少同一中风模型中的梗死体积的结果一致，表明NO的产生可能在脑缺血后组织损伤的进展中起重要的致病作用。
