Shandong Provincial Key Laboratory of Animal Biotechnology and Disease Control and Prevention, College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an City, 271018, P. R. China.
Cell Death Dis. 2018 Feb 22;9(3):308. doi: 10.1038/s41419-018-0368-5.
Mechanisms for post-maturation oocyte aging (PMOA) are not fully understood, and whether autophagy plays any role in PMOA is unknown. To explore the role of autophagy in PMOA, expression of autophagosomes and effects of the autophagy (macro-autophagy) activity on PMOA were observed in mouse oocytes. Oocyte activation rates and active caspase-3 levels increased continuously from 0 to 18 h of in vitro aging. While levels of microtubule-associated protein light chain 3 (LC3)-II increased up to 12 h and decreased thereafter, contents of p62 decreased from 0 to 12 h and then elevated to basal level by 18 h. However, the LC3-II/I ratio remained unchanged following aging in different media or for different times. During in vitro aging up to 12 h, upregulating autophagy with rapamycin or lithium chloride decreased activation susceptibility, cytoplasmic calcium, p62 contents, oxidative stress, caspase-3 activation and cytoplasmic fragmentation while increasing developmental competence, LC3-II contents, LC3-II/I ratio, mitochondrial membrane potential, spindle/chromosome integrity and normal cortical granule distribution. Downregulating autophagy with 3-methyladenine (3-MA) produced opposite effects on all these parameters except cytoplasmic fragmentation. After 12 h of aging culture, however, regulating autophagy with either rapamycin/lithium chloride or 3-MA had no impact on oocyte activation susceptibility. It is concluded that autophagy plays an important role in regulating PMOA. Thus, during the early stage of PMOA, autophagy increases as an adaptive response to prevent further apoptosis, but by the late stage of PMOA, the activation of more caspases blocks the autophagic process leading to severer apoptosis.
卵母细胞成熟后老化（PMOA）的机制尚不完全清楚，自噬是否在 PMOA 中发挥作用也尚不清楚。为了探讨自噬在 PMOA 中的作用，观察了小鼠卵母细胞中自噬体的表达和自噬（巨自噬）活性对 PMOA 的影响。卵母细胞激活率和活性 caspase-3 水平从体外老化 0 至 18 小时持续升高。虽然微管相关蛋白轻链 3（LC3）-II 的水平在 12 小时内升高，随后降低，但 p62 的含量从 0 小时到 12 小时减少，然后在 18 小时恢复到基础水平。然而，在不同的培养基中或在不同的时间内老化后，LC3-II/I 比值保持不变。在体外老化至 12 小时内，用雷帕霉素或氯化锂上调自噬会降低激活敏感性、细胞质钙、p62 含量、氧化应激、caspase-3 激活和细胞质碎片化，同时提高发育能力、LC3-II 含量、LC3-II/I 比值、线粒体膜电位、纺锤体/染色体完整性和正常皮质颗粒分布。用 3-甲基腺嘌呤（3-MA）下调自噬会对所有这些参数产生相反的影响，除了细胞质碎片化。然而，在 12 小时的老化培养后，用雷帕霉素/氯化锂或 3-MA 调节自噬对卵母细胞激活敏感性没有影响。综上所述，自噬在调节 PMOA 中起重要作用。因此，在 PMOA 的早期阶段，自噬增加作为一种适应性反应，以防止进一步的细胞凋亡，但在 PMOA 的晚期阶段，更多的半胱天冬酶的激活阻断了自噬过程，导致更严重的细胞凋亡。
