Rey Benjamin, Dégletagne Cyril, Bodennec Jacques, Monternier Pierre-Axel, Mortz Mathieu, Roussel Damien, Romestaing Caroline, Rouanet Jean-Louis, Tornos Jeremy, Duchamp Claude
Université de Lyon, Université Lyon 1, CNRS - Laboratoire de Biométrie et Biologie Evolutive, Villeurbanne, France; Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Université de Lyon; Université Lyon 1, CNRS - Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, Villeurbanne Cedex, France.
Free Radic Biol Med. 2016 Aug;97:577-587. doi: 10.1016/j.freeradbiomed.2016.07.015. Epub 2016 Jul 19.
Repeated deep dives are highly pro-oxidative events for air-breathing aquatic foragers such as penguins. At fledging, the transition from a strictly terrestrial to a marine lifestyle may therefore trigger a complex set of anti-oxidant responses to prevent chronic oxidative stress in immature penguins but these processes are still undefined. By combining in vivo and in vitro approaches with transcriptome analysis, we investigated the adaptive responses of sea-acclimatized (SA) immature king penguins (Aptenodytes patagonicus) compared with pre-fledging never-immersed (NI) birds. In vivo, experimental immersion into cold water stimulated a higher thermogenic response in SA penguins than in NI birds, but both groups exhibited hypothermia, a condition favouring oxidative stress. In vitro, the pectoralis muscles of SA birds displayed increased oxidative capacity and mitochondrial protein abundance but unchanged reactive oxygen species (ROS) generation per g tissue because ROS production per mitochondria was reduced. The genes encoding oxidant-generating proteins were down-regulated in SA birds while mRNA abundance and activity of the main antioxidant enzymes were up-regulated. Genes encoding proteins involved in repair mechanisms of oxidized DNA or proteins and in degradation processes were also up-regulated in SA birds. Sea life also increased the degree of fatty acid unsaturation in muscle mitochondrial membranes resulting in higher intrinsic susceptibility to ROS. Oxidative damages to protein or DNA were reduced in SA birds. Repeated experimental immersions of NI penguins in cold-water partially mimicked the effects of acclimatization to marine life, modified the expression of fewer genes related to oxidative stress but in a similar way as in SA birds and increased oxidative damages to DNA. It is concluded that the multifaceted plasticity observed after marine life may be crucial to maintain redox homeostasis in active tissues subjected to high pro-oxidative pressure in diving birds. Initial immersions in cold-water may initiate an hormetic response triggering essential changes in the adaptive antioxidant response to marine life.
对于像企鹅这样的用肺呼吸的水生觅食者来说，反复进行深度潜水是极具促氧化作用的事件。因此，在羽翼初丰时，从严格的陆地生活方式向海洋生活方式的转变可能会引发一系列复杂的抗氧化反应，以防止未成熟企鹅出现慢性氧化应激，但这些过程仍未明确。通过将体内和体外方法与转录组分析相结合，我们研究了适应海洋环境（SA）的未成熟帝企鹅（Aptenodytes patagonicus）与未离巢且从未接触过水（NI）的幼鸟相比的适应性反应。在体内，将实验对象浸入冷水中时，SA企鹅比NI企鹅表现出更高的产热反应，但两组都出现了体温过低的情况，而体温过低有利于氧化应激的发生。在体外，SA企鹅的胸肌显示出氧化能力和线粒体蛋白丰度增加，但每克组织的活性氧（ROS）生成量未变，因为每个线粒体的ROS产生量减少了。在SA企鹅中，编码产生活性氧蛋白的基因被下调，而主要抗氧化酶的mRNA丰度和活性则上调。编码参与氧化DNA或蛋白质修复机制以及降解过程的蛋白质的基因在SA企鹅中也上调。海洋生活还增加了肌肉线粒体膜中脂肪酸的不饱和度，导致对ROS的内在敏感性更高。SA企鹅中蛋白质或DNA的氧化损伤减少。将NI企鹅反复实验性浸入冷水中部分模拟了适应海洋生活的效果，改变了较少与氧化应激相关基因的表达，但方式与SA企鹅相似，并增加了对DNA的氧化损伤。可以得出结论，在海洋生活后观察到的多方面可塑性对于维持潜水鸟类中承受高促氧化压力的活跃组织中的氧化还原稳态可能至关重要。初次浸入冷水中可能引发一种应激反应，触发对海洋生活的适应性抗氧化反应的本质变化。
