Molecular mechanisms of irradiation-induced impairment eNOS expression

我们研究了自由基清除剂依达拉奉对兔中央动脉内皮依赖性松弛和内皮型一氧化氮合酶（eNOS）表达变化的治疗效果，在暴露于45 Gy（钴^<60>单位）辐射2周后。对于依达拉奉治疗，从照射前一天开始，每天给药，肠内剂量为10 mg/kg，每天两次。对乙酰胆碱的内皮依赖性松弛反应在辐照血管中明显受损。依达拉奉治疗将反应提高到未辐照对照血管中观察到的水平。使用免疫组织化学和Western blot技术，我们发现辐照血管中eNOS的蛋白表达减少到对照组的50%左右，依达拉奉治疗使其恢复到几乎完整的水平。通过RT-PCR分析，发现辐照后eNOS基因表达比对照水平降低了47%。依达拉奉治疗几乎完全阻止了辐照血管中eNOS mRNA的减少。这些结果表明依达拉奉对辐照后血管eNOS表达降低及其相关内皮细胞功能障碍具有保护作用。因此，我们假设氧自由基可能与辐照诱导的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.