SOD2-mediated adaptive responses induced by low-dose ionizing radiation via TNF signaling and amifostine.
SOD2-mediated adaptive responses induced by low-dose ionizing radiation via TNF signaling and amifostine.
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DOI：
10.1016/j.freeradbiomed.2011.08.032
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发表时间：
2011-11-15
影响因子：
7.4
通讯作者：
Grdina DJ
中科院分区：
文献类型：
--
作者：
Murley JS;Baker KL;Miller RC;Darga TE;Weichselbaum RR;Grdina DJ
通过预先将细胞暴露于低剂量电离辐射 (10 cGy) 或 WR1065 (40 µM)（氨磷汀的活性硫醇形式），在 2 Gy 照射后，可以在细胞中诱导锰超氧化物歧化酶 (SOD2) 介导的适应性过程，以防止辐射诱导的微核形成。虽然这两种适应性过程均以 SOD2 酶活性水平升高而达到顶峰，但潜在途径的复杂性有所不同，肿瘤坏死因子 α (TNFα) 信号途径涉及低剂量辐射诱导的反应，但不涉及硫醇诱导的途径。本研究的目的是以微核形成为终点，表征 TNFα 受体 1 和 2 (TNFR1, 2) 对低剂量照射或硫醇暴露诱导的适应性反应的影响。具有功能性 TNFR1 和 2 的 BFS-1 野生型 (WT) 细胞在 2 Gy 剂量的电离辐射前 24 小时暴露于 10 cGy 或 40 µM 剂量的 WR1065。 TNFR1 缺陷的 BFS2C-SH02 细胞和 TNFR1 和 2 缺陷的 BFS2C-SH22 细胞也暴露在类似条件下进行比较，这些细胞是通过用鼠 TNFR2 靶向载体转染从 BFS2C-SH02 细胞产生的，并通过定量 PCR 确认为 TNFR2 缺陷。与各自未处理的对照相比，10 cGy 剂量的辐射诱导 BFS-1 (P < 0.001) 和 BFS2C-SH02 (P = 0.005) 细胞中 SOD2 活性显着升高，但 BFS2C-SH22 细胞 (P = 0.433) 没有显着升高。相比之下，WR1065 显着诱导所有三种细胞系中 SOD2 活性升高（分别为 P = 0.001；P = 0.007；P = 0.020）。当在 SOD2 活性最大升高期间暴露于 2 Gy 激发剂量的辐射时，在每个细胞系中观察到辐射诱导的微核频率显着降低。然而，如果在低剂量辐射或硫醇暴露前 24 小时用 SOD2 siRNA 转染细胞，则这种适应性效应会被完全抑制。在测试条件下，TNFR1,2 抑制会对低剂量辐射诱导的适应性反应产生负面影响，但不会对硫醇诱导的适应性反应产生负面影响，而硫醇诱导的适应性反应是由 SOD2 活性升高介导的。
Manganese superoxide dismutase (SOD2)-mediated adaptive processes that protect against radiation-induced micronuclei formation can be induced in cells following a 2 Gy exposure by previously exposing them to either low dose ionizing radiation (10 cGy) or WR1065 (40 µM), the active thiol form of amifostine. While both adaptive processes culminate with elevated levels of SOD2 enzymatic activities, the underlying pathways differ in complexity, with the tumor necrosis factor α (TNFα) signaling pathway implicated in the low dose radiation-induced response, but not in the thiol-induced pathway. The goal of this study was the characterization of the effects of TNFα receptors1 and 2 (TNFR1, 2) on the adaptive responses induced by low dose irradiation or thiol exposures using micronuclei formation as an endpoint. BFS-1 wild type (WT) cells with functional TNFR1 and 2 were exposed 24 h prior to a 2 Gy dose of ionizing radiation to either 10 cGy or a 40 µM dose of WR1065. BFS2C-SH02 cells defective in TNFR1 and BFS2C-SH22 cells defective in both TNFR1 and 2, generated from BFS2C-SH02 cells by transfection with a murine TNFR2 targeting vector and confirmed to be TNFR2 defective by quantitative PCR, were also exposed under similar conditions for comparison. A 10 cGy dose of radiation induced a significant elevation of SOD2 activity in BFS-1 (P < 0.001) and BFS2C-SH02 (P = 0.005) but not BFS2C-SH22 cells (P = 0.433) as compared to their respective untreated controls. In contrast, WR1065 significantly induced elevations in SOD2 activity in all three cell lines (P = 0.001; P = 0.007; P = 0.020; respectively). A significant reduction in the frequency of radiation-induced micronuclei was observed in each cell line when exposure to a 2 Gy challenge dose of radiation occurred during the period of maximal elevation in SOD2 activity. However, this adaptive effect was completely inhibited if the cells were transfected 24 h prior to low dose radiation or thiol exposure with SOD2 siRNA. Under the conditions tested, TNFR1,2 inhibition negatively impacted the low dose radiation-induced but not the thiol-induced adaptive responses observed to be mediated by elevations in SOD2 activity.