Department of General Psychiatry I, PZN-Wiesloch, Teaching Hospital of Ruprecht-Karls-University Heidelberg, Heidelberger Str. 1a, Wiesloch 69168, Germany.
Radiat Oncol. 2012 Apr 20;7:61. doi: 10.1186/1748-717X-7-61.
To investigate whether different conditions of DNA structure and radiation treatment could modify heterogeneity of response. Additionally to study variance as a potential parameter of heterogeneity for radiosensitivity testing.
Two-hundred leukocytes per sample of healthy donors were split into four groups. I: Intact chromatin structure; II: Nucleoids of histone-depleted DNA; III: Nucleoids of histone-depleted DNA with 90 mM DMSO as antioxidant. Response to single (I-III) and twice (IV) irradiation with 4 Gy and repair kinetics were evaluated using %Tail-DNA. Heterogeneity of DNA damage was determined by calculation of variance of DNA-damage (V) and mean variance (Mvar), mutual comparisons were done by one-way analysis of variance (ANOVA).
Heterogeneity of initial DNA-damage (I, 0 min repair) increased without histones (II). Absence of histones was balanced by addition of antioxidants (III). Repair reduced heterogeneity of all samples (with and without irradiation). However double irradiation plus repair led to a higher level of heterogeneity distinguishable from single irradiation and repair in intact cells. Increase of mean DNA damage was associated with a similarly elevated variance of DNA damage (r = +0.88).
Heterogeneity of DNA-damage can be modified by histone level, antioxidant concentration, repair and radiation dose and was positively correlated with DNA damage. Experimental conditions might be optimized by reducing scatter of comet assay data by repair and antioxidants, potentially allowing better discrimination of small differences. Amount of heterogeneity measured by variance might be an additional useful parameter to characterize radiosensitivity.
研究不同的 DNA 结构和辐射处理条件是否可以改变反应异质性。此外，还研究了方差作为放射敏感性测试异质性的潜在参数。
每个健康供体样本的 200 个白细胞分为四组。I：完整的染色质结构；II：组蛋白耗尽的 DNA 核小体；III：组蛋白耗尽的 DNA 核小体，用 90mM DMSO 作为抗氧化剂。使用 %Tail-DNA 评估单次（I-III）和两次（IV）照射 4Gy 的反应和修复动力学。通过计算 DNA 损伤的方差（V）和平均方差（Mvar）来确定 DNA 损伤的异质性，通过单向方差分析（ANOVA）进行组间比较。
无组蛋白时，初始 DNA 损伤的异质性（I，0 分钟修复）增加（II）。抗氧化剂的加入平衡了组蛋白的缺失（III）。所有样本的修复均降低了异质性（有或没有照射）。然而，双照射加修复导致的异质性水平高于完整细胞中单照射和修复的水平。平均 DNA 损伤的增加与 DNA 损伤方差的类似升高相关（r=+0.88）。
DNA 损伤的异质性可以通过组蛋白水平、抗氧化剂浓度、修复和辐射剂量进行修饰，并且与 DNA 损伤呈正相关。通过修复和抗氧化剂减少彗星试验数据的分散，可以优化实验条件，从而有可能更好地区分微小差异。通过方差测量的异质性量可能是一个额外有用的参数来表征放射敏感性。
