Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.
Mutagenesis. 2013 Jul;28(4):427-32. doi: 10.1093/mutage/get018. Epub 2013 Apr 29.
DNA damage is commonly measured at the level of individual cells using the so-called comet assay (single-cell gel electrophoresis). As the frequency of DNA breaks increases, so does the fraction of the DNA extending towards the anode, forming the comet tail. Comets with almost all DNA in the tail are often referred to as 'hedgehog' comets and are widely assumed to represent apoptotic cells. We review the literature and present theoretical and empirical arguments against this interpretation. The level of DNA damage in these comets is far less than the massive fragmentation that occurs in apoptosis. 'Hedgehog' comets are formed after moderate exposure of cells to, for example, H2O2, but if the cells are incubated for a short period, 'hedgehogs' are no longer seen. We confirm that this is not because DNA has degraded further and been lost from the gel, but because the DNA is repaired. The comet assay may detect the earliest stages of apoptosis, but as it proceeds, comets disappear in a smear of unattached DNA. It is clear that 'hedgehogs' can correspond to one level on a continuum of genotoxic damage, are not diagnostic of apoptosis and should not be regarded as an indicator of cytotoxicity.
DNA 损伤通常在单个细胞水平上使用所谓的彗星试验（单细胞凝胶电泳）进行测量。随着 DNA 断裂频率的增加，DNA 向阳极延伸的部分也会增加，形成彗星尾巴。几乎所有 DNA 都在尾巴中的彗星通常被称为“刺猬”彗星，并被广泛认为代表凋亡细胞。我们回顾了文献，并提出了理论和经验论据来反对这种解释。这些彗星中的 DNA 损伤水平远低于凋亡中发生的大量片段化。“刺猬”彗星是在细胞受到例如 H2O2 的适度暴露后形成的，但如果细胞短时间孵育，则不再观察到“刺猬”彗星。我们证实这不是因为 DNA 进一步降解并从凝胶中丢失，而是因为 DNA 已被修复。彗星试验可能会检测到凋亡的最早阶段，但随着其进行，彗星会在未附着的 DNA 中消失。很明显，“刺猬”彗星可以对应于遗传毒性损伤连续体上的一个水平，不是凋亡的诊断指标，不应被视为细胞毒性的指标。
