School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
Free Radic Biol Med. 2011 Apr 15;50(8):963-70. doi: 10.1016/j.freeradbiomed.2011.01.013. Epub 2011 Jan 19.
Increased reactive oxygen species (ROS) are a feature of aging cells, but little is known about when ROS generation begins as cells age. Here we show how ROS change in Saccharomyces cerevisiae cells throughout their early replicative life span using the fluorescent ROS indicator dihydroethidium (DHE), which has some specificity for the superoxide anion. Cells in a particular age range were heterogeneous with respect to their ROS burden. Surprisingly, some cells as young as 5-7 generations acquired a greatly increased level of ROS detected by DHE relative to virgin cells. By 12 generations 50% of cells had a substantial ROS burden despite being only halfway through their life span. In contrast to the wild type, cells of a sir2 mutant had lower levels of ROS reacting with DHE. Daughters from older mothers had low ROS levels, and this asymmetric distribution of ROS was SIR2-independent. Mitochondrial fragmentation also began to occur in cells after 4 generations and increased markedly as cells aged. Daughter cells regenerated normal tubular mitochondria despite the fragmentation of mitochondria in the mother cells, whereas daughters of the sir2 mutant had fragmented mitochondria at all ages.
活性氧（ROS）的增加是衰老细胞的一个特征，但对于细胞衰老时 ROS 的产生何时开始，人们知之甚少。在这里，我们使用荧光 ROS 指示剂二氢乙啶（DHE）展示了酿酒酵母细胞在其早期复制寿命过程中 ROS 如何变化，DHE 对超氧阴离子具有一定的特异性。在特定的年龄范围内，细胞在 ROS 负担方面存在异质性。令人惊讶的是，一些年轻的细胞（5-7 代）相对于原始细胞获得了大大增加的 DHE 检测到的 ROS 水平。到 12 代时，尽管仅完成了一半的寿命，但 50%的细胞具有大量的 ROS 负担。与野生型相比，sir2 突变体的细胞中与 DHE 反应的 ROS 水平较低。来自较老母亲的子细胞具有较低的 ROS 水平，这种 ROS 的不对称分布与 SIR2 无关。线粒体碎片化也在 4 代后开始发生，并随着细胞老化而显著增加。尽管母细胞中的线粒体发生了碎片化，但子细胞仍能再生正常的管状线粒体，而 sir2 突变体的子细胞在所有年龄段都有碎片化的线粒体。
