Molecular mechanisms of irradiation-induced impairment eNOS expression

我们观察了自由基清除剂依达拉奉对45Gy60Co照射后2周兔中央动脉内皮依赖性松弛和内皮型一氧化氮合酶(ENOS)表达的影响。对于依达拉奉治疗，从照射前一天开始每天给动物注射依达拉奉，每日两次，每次10毫克/公斤。受照血管对乙酰胆碱的内皮依赖性松弛反应明显受损。依达拉奉治疗改善了对未照射对照血管中观察到的水平的反应。应用免疫组织化学和Western印迹技术，我们发现照射后血管中eNOS的蛋白表达减少到对照的50%左右，依达拉奉治疗使其恢复到几乎完整的水平。RT-PCR分析eNOS基因表达，发现照射后eNOS基因表达较对照水平下降47%。依达拉奉治疗后，照射血管中enos基因表达的减少几乎完全被阻止。这些结果提示依达拉奉对照射后血管eNOS表达减少及其相关的内皮细胞功能障碍具有保护作用。因此，我们推测氧自由基可能与辐射引起的eNOS基因调控紊乱密切相关。

We investigated the therapeutic effect of edaravone, a free radical scavenger, on alterations in endothelium-dependent relaxation and endothelial nitric oxide synthase (eNOS) expression in the rabbit central artery at 2 weeks after exposure to a dose of 45 Gy radiation with a cobalt^<60> unit. For treatment with edaravone, edaravone was given daily to the animals from the day before irradiation at an intrapenetreal dose of 10 mg/kg twice a day. The endothelium-dependent relaxant response to acetylcholine was markedly impaired in irradiated vessels. Edaravone treatment improved the response to the level observed in nonirradiated control vessels. Using immunohistochemical and Western blot techniques, we showed that protein expression of eNOS in irradiated vessels was reduced to about 50% of control and that edaravone treatment restored it nearly to intact levels. Gene expression of eNOS, analyzed by RT-PCR, was found to be reduced from the control level by 47% following irradiation. The reduction in eNOS mRNA observed in irradiated vessels was almost completely prevented by edaravone treatment. These results suggest that edaravone has a protective effect on the reduced expression of eNOS and its associated endothelial cell dysfunction in the vessels following irradiation. We thus assume that oxygen free radicals may be closely related to the irradiation-induced derangement of the eNOS gene regulation.