Oroboros trace flie.DLD

Aim: It is well-established that adult vertebrates acclimatising to hypoxic environments undergo mitochondrial remodelling to enhance oxygen delivery, maintain ATP balance, and limit oxidative stress. However, many vertebrates also encounter oxygen deprivation during embryonic development. The effects of hypoxia on mitochondrial function are likely to be more profound during embryonic development because environmental stress during early life can lead to permanent physiological and morphological changes that can sometimes be inherited by subsequent generations. To this end, we investigated the long-term effects of developmental hypoxia on mitochondrial function in a species that regularly encounters oxygen deprivation during development; the common snapping turtle (Chelydra serpentina). Methods: Common snapping turtle eggs were incubated in 21% or 10% oxygen from 20% of embryonic development until hatching. Once hatched, turtles were reared in 21% oxygen for up to one year, and ventricular mitochondria were isolated by differential centrifugation. Mitochondrial respiration and reactive oxygen species (ROS) production were measured with an Oroboros microrespirometer. Results: Compared to their normoxic counterparts, juvenile turtles from hypoxic incubations had lower levels of Leak respiration, higher P:O ratios, improved oxygen affinity, and reduced rates of ROS production. Interestingly, these same attributes occur in adult vertebrates that acclimatise to high-altitude hypoxia. Conclusions: Developmental hypoxia remodelled turtle mitochondria, leading to improvements in mitochondrial efficiceny, oxygen delivery, and ROS management. We speculate that these adjustments permanently improve snapping turtle mitochondrial hypoxia tolernace, which would be beneficial for this species during breath-hold diving and overwintering in anoxic environments.

研究目的：成年脊椎动物适应低氧环境时会发生线粒体重塑，以增强氧递送、维持ATP稳态并减轻氧化应激，这一点已得到广泛证实。然而，众多脊椎动物在胚胎发育阶段也会遭遇缺氧。由于生命早期的环境应激可引发永久性的生理与形态改变，且此类改变有时可遗传给后代，因此缺氧对胚胎发育阶段线粒体功能的影响可能更为深远。为此，本研究以一种在发育过程中常经历缺氧的物种——普通鳄龟（Chelydra serpentina）为对象，探究发育阶段缺氧对其线粒体功能的长期影响。
研究方法：将普通鳄龟的卵在21%或10%氧浓度环境中孵化，孵化时段覆盖胚胎发育20%阶段至幼龟破壳。幼龟破壳后，在21%氧浓度环境中饲养最长达1年，随后通过差速离心法分离心室线粒体。采用奥罗博罗斯微量呼吸仪（Oroboros microrespirometer）测定线粒体呼吸活性与活性氧（reactive oxygen species, ROS）生成量。
研究结果：与常氧对照组幼龟相比，低氧孵化组幼龟表现出更低的质子漏呼吸（Leak respiration）水平、更高的磷氧比（P:O ratio）、更优的氧亲和力以及更低的ROS生成速率。值得注意的是，这些特征同样见于适应高原低氧环境的成年脊椎动物。
研究结论：发育阶段的缺氧重塑了鳄龟的线粒体，使其线粒体效率、氧递送能力与ROS调控能力均得到提升。我们推测，此类调整可永久性增强普通鳄龟的线粒体低氧耐受能力，这对该物种在屏息潜水以及在缺氧环境中越冬时具有积极意义。