AIM The aim of this study was to provide a systematic approach to characterize DNA damage induction and repair in isolated peripheral blood mononuclear cells (PBMCs) after internal ex vivo irradiation with [131I]NaI. In this approach, we tried to mimic ex vivo the irradiation of patient blood in the first hours after radioiodine therapy. MATERIAL AND METHODS Blood of 33 patients of two centres was collected immediately before radioiodine therapy of differentiated thyroid cancer (DTC) and split into two samples. One sample served as non-irradiated control. The second sample was exposed to ionizing radiation by adding 1 ml of [131I]NaI solution to 7 ml of blood, followed by incubation at 37 °C for 1 h. PBMCs of both samples were isolated, split in three parts each and (i) fixed in 70% ethanol and stored at - 20 °C directly (0 h) after irradiation, (ii) after 4 h and (iii) 24 h after irradiation and culture in RPMI medium. After immunofluorescence staining microscopically visible co-localizing γ-H2AX + 53BP1 foci were scored in 100 cells per sample as biomarkers for radiation-induced double-strand breaks (DSBs). RESULTS Thirty-two of 33 blood samples could be analysed. The mean absorbed dose to the blood in all irradiated samples was 50.1 ± 2.3 mGy. For all time points (0 h, 4 h, 24 h), the average number of γ-H2AX + 53BP1 foci per cell was significantly different when compared to baseline and the other time points. The average number of radiation-induced foci (RIF) per cell after irradiation was 0.72 ± 0.16 at t = 0 h, 0.26 ± 0.09 at t = 4 h and 0.04 ± 0.09 at t = 24 h. A monoexponential fit of the mean values of the three time points provided a decay rate of 0.25 ± 0.05 h-1, which is in good agreement with data obtained from external irradiation with γ- or X-rays. CONCLUSION This study provides novel data about the ex vivo DSB repair in internally irradiated PBMCs of patients before radionuclide therapy. Our findings show, in a large patient sample, that efficient repair occurs after internal irradiation with 50 mGy absorbed dose, and that the induction and repair rate after 131I exposure is comparable to that of external irradiation with γ- or X-rays.

中文翻译：

---

用 131I 对患者血液进行体内离体照射后外周血单个核细胞的 DNA 损伤和修复。

目的 本研究的目的是提供一种系统的方法来表征用 [131I]NaI 进行离体内部照射后分离的外周血单个核细胞 (PBMC) 中 DNA 损伤的诱导和修复。在这种方法中，我们试图在放射性碘治疗后的最初几个小时内模拟离体患者血液的照射。材料与方法 在放射性碘治疗分化型甲状腺癌（DTC）前立即采集两个中心的33例患者的血液，并分成两个样本。一份样品作为未辐照对照。通过向 7 ml 血液中加入 1 ml [131I] NaI 溶液，将第二个样品暴露于电离辐射，然后在 37 °C 下孵育 1 h。分离两个样品的 PBMC，分别分成三部分，(i) 固定在 70% 乙醇中，辐照后直接储存在 - 20 °C (0 h)，(ii) 4 小时后和 (iii) 在 RPMI 培养基中照射和培养 24 小时后。在免疫荧光染色后，显微镜下可见的共定位 γ-H2AX + 53BP1 病灶在每个样品的 100 个细胞中进行评分，作为辐射诱导的双链断裂 (DSB) 的生物标志物。结果 可以分析 33 份血液样本中的 32 份。在所有辐照样品中，血液的平均吸收剂量为 50.1 ± 2.3 mGy。对于所有时间点（0 小时、4 小时、24 小时），与基线和其他时间点相比，每个细胞的 γ-H2AX + 53BP1 病灶的平均数显着不同。照射后每个细胞的辐射诱导病灶 (RIF) 的平均数量在 t = 0 小时时为 0.72 ± 0.16，在 t = 4 小时时为 0.26 ± 0.09，在 t = 24 小时时为 0.04 ± 0.09。三个时间点的平均值的单指数拟合提供了 0.25 ± 0.05 h-1 的衰减率，这与从外部用 γ 射线或 X 射线辐照获得的数据非常一致。结论 本研究提供了关于放射性核素治疗前患者体内照射 PBMC 的体外 DSB 修复的新数据。我们的研究结果表明，在大量患者样本中，50 mGy 吸收剂量的内部照射后发生有效修复，并且 131I 暴露后的诱导和修复率与 γ 射线或 X 射线的外部照射相当。