Ionizing radiation produces reactive oxygen species (ROS) leading to cellular DNA damage. Therefore, patients undergoing radiation therapy or first responders in radiological accident scenarios could both benefit from the identification of specifically acting pharmacological radiomitigators. The synthetic triterpenoid bardoxolone-methyl (CDDO-Me) has previously been shown to exert antioxidant, anti-inflammatory and anticancer activities in several cell lines, in part by enhancing the DNA damage response. In our study, we examined the effect of nanomolar concentrations of CDDO-Me in human peripheral blood mononuclear cells (PBMC). We observed increased cellular levels of the antioxidative enzymes heme oxygenase-1 (HO-1), NAD(P)H dehydrogenase (quinone1) and mitochondrial superoxide dismutase 2 by immunoblotting. Surprisingly, we found increased intracellular ROS-levels using imaging flow-cytometry. However, the radiation-induced DNA double-strand break (DSB) formation using the γ-H2AX + 53BP1 DSB focus assay and the cytokinesis-block micronucleus assay both revealed, that nanomolar CDDO-Me pre-treatment of PBMC for 2 h or 6 h ahead of X irradiation with 2 Gy did neither significantly affect γ-H2AX + 53BP1 DSB foci formation nor the frequency of micronuclei. CDDO-Me treatment also failed to alter the nuclear division index and the frequency of IR-induced PBMC apoptosis as investigated by Annexin V-labeled live-cell imaging. Our results indicate that pharmacologically increased cellular concentrations of antioxidative enzymes might not necessarily exert radiomitigating short-term effects in IR-exposed PBMC. However, the increase of antioxidative enzymes could also be a result of a defensive cellular mechanism towards elevated ROS levels.

中文翻译：

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三萜类CDDO-Me可诱导ROS生成并上调细胞抗氧化酶的水平，而不会诱导人外周血单核细胞中的DSB。

电离辐射产生活性氧（ROS），导致细胞DNA受损。因此，在放射意外情况下接受放射治疗的患者或第一反应者均可受益于确定具有特殊作用的药理放射减轻剂。合成三萜类Bardoxolone-methyl（CDDO-Me）先前已显示在几种细胞系中发挥抗氧化，抗炎和抗癌活性，部分是通过增强DNA损伤反应来实现的。在我们的研究中，我们检查了人外周血单核细胞（PBMC）中纳摩尔浓度CDDO-Me的作用。我们通过免疫印迹观察到了细胞水平的抗氧化酶血红素加氧酶-1（HO-1），NAD（P）H脱氢酶（quinone1）和线粒体超氧化物歧化酶2的细胞水平增加。出奇，我们发现使用成像流式细胞仪可增加细胞内ROS水平。然而，使用γ-H2AX+ 53BP1 DSB聚焦测定和胞质阻滞微核测定的放射诱导DNA双链断裂（DSB）形成均显示，PBMC的纳摩尔CDDO-Me预处理2 h或6 X射线在2 Gy照射之前1 h既不显着影响γ-H2AX+ 53BP1 DSB灶的形成，也不显着影响微核的频率。膜联蛋白V标记的活细胞成像研究表明，CDDO-Me治疗也未能改变核分裂指数和IR诱导的PBMC凋亡的频率。我们的结果表明，药理学上增加的抗氧化酶的细胞浓度不一定会在IR暴露的PBMC中发挥放射缓解的短期作用。然而，