Lefevre Sjannie, Stecyk Jonathan A W, Torp May-Kristin, Løvold Lisa Y, Sørensen Christina, Johansen Ida B, Stensløkken Kåre-Olav, Couturier Christine S, Sloman Katherine A, Nilsson Göran E
Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway
Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0371 Oslo, Norway.
J Exp Biol. 2017 Nov 1;220(Pt 21):3883-3895. doi: 10.1242/jeb.165118.
Crucian carp () survive without oxygen for several months, but it is unknown whether they are able to protect themselves from cell death normally caused by the absence, and particularly return, of oxygen. Here, we quantified cell death in brain tissue from crucian carp exposed to anoxia and re-oxygenation using the terminal deoxy-nucleotidyl transferase dUTP nick-end labelling (TUNEL) assay, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen (PCNA) as well as PCNA mRNA expression. We also measured mRNA and protein expression of the apoptosis executer protease caspase 3, in laboratory fish exposed to anoxia and re-oxygenation and fish exposed to seasonal anoxia and re-oxygenation in their natural habitat over the year. Finally, a behavioural experiment was used to assess the ability to learn and remember how to navigate in a maze to find food, before and after exposure to anoxia and re-oxygenation. The number of TUNEL-positive cells in the telencephalon increased after 1 day of re-oxygenation following 7 days of anoxia, indicating increased cell death. However, there were no consistent changes in whole-brain expression of caspase 3 in either laboratory-exposed or naturally exposed fish, indicating that cell death might occur via caspase-independent pathways or necrosis. Re-oxygenated crucian carp appeared to have lost the memory of how to navigate in a maze (learnt prior to anoxia exposure), while the ability to learn remained intact. PCNA mRNA was elevated after re-oxygenation, indicating increased neurogenesis. We conclude that anoxia tolerance involves not only protection from damage but also repair after re-oxygenation.
鲫鱼（）能够在无氧状态下存活数月，但它们是否能够保护自身免受通常因缺氧，尤其是氧的恢复所导致的细胞死亡尚不清楚。在此，我们使用末端脱氧核苷酸转移酶dUTP缺口末端标记（TUNEL）分析法对暴露于缺氧和复氧环境下的鲫鱼脑组织中的细胞死亡情况进行了量化，并通过增殖细胞核抗原（PCNA）的免疫组织化学染色以及PCNA mRNA表达来检测细胞增殖情况。我们还测量了在实验室中暴露于缺氧和复氧环境下的鱼以及在自然栖息地中经历季节性缺氧和复氧的鱼体内凋亡执行蛋白酶半胱天冬酶3的mRNA和蛋白质表达。最后，进行了一项行为实验，以评估在暴露于缺氧和复氧前后，鲫鱼学习和记忆如何在迷宫中导航以寻找食物的能力。在缺氧7天后复氧1天，端脑TUNEL阳性细胞数量增加，表明细胞死亡增加。然而，无论是实验室暴露的鱼还是自然暴露的鱼，全脑半胱天冬酶3的表达均无一致变化，这表明细胞死亡可能通过不依赖半胱天冬酶的途径或坏死发生。复氧后的鲫鱼似乎已经失去了在迷宫中导航的记忆（在缺氧暴露前学会的），而学习能力仍然完好。复氧后PCNA mRNA升高，表明神经发生增加。我们得出结论，缺氧耐受性不仅涉及免受损伤的保护，还涉及复氧后的修复。
