Department of Biology, Colgate University, 13 Oak Drive, Hamilton, NY 13346, USA.
Department of Biology, Hamilton College, 198 College Hill Road, Clinton, NY 13323, USA.
Integr Comp Biol. 2019 Oct 1;59(4):953-969. doi: 10.1093/icb/icz017.
As part of mitonuclear communication, retrograde and anterograde signaling helps maintain homeostasis under basal conditions. Basal conditions, however, vary across phylogeny. At the cell-level, some mitonuclear retrograde responses can be quantified by measuring the constitutive components of oxidative stress, the balance between reactive oxygen species (ROS) and antioxidants. ROS are metabolic by-products produced by the mitochondria that can damage macromolecules by structurally altering proteins and inducing mutations in DNA, among other processes. To combat accumulating damage, organisms have evolved endogenous antioxidants and can consume exogenous antioxidants to sequester ROS before they cause cellular damage. ROS are also considered to be regulated through a retrograde signaling cascade from the mitochondria to the nucleus. These cellular pathways may have implications at the whole-animal level as well. For example, birds have higher basal metabolic rates, higher blood glucose concentration, and longer lifespans than similar sized mammals, however, the literature is divergent on whether oxidative stress is higher in birds compared with mammals. Herein, we collected literature values for whole-animal metabolism of birds and mammals. Then, we collected cellular metabolic rate data from primary fibroblast cells isolated from birds and mammals and we collected blood from a phylogenetically diverse group of birds and mammals housed at zoos and measured several parameters of oxidative stress. Additionally, we reviewed the literature on basal-level oxidative stress parameters between mammals and birds. We found that mass-specific metabolic rates were higher in birds compared with mammals. Our laboratory results suggest that cellular basal metabolism, total antioxidant capacity, circulating lipid damage, and catalase activity were significantly lower in birds compared with mammals. We found no body-size correlation on cellular metabolism or oxidative stress. We also found that most oxidative stress parameters significantly correlate with increasing age in mammals, but not in birds; and that correlations with reported maximum lifespans show different results compared with correlations with known aged birds. Our literature review revealed that basal levels of oxidative stress measurements for birds were rare, which made it difficult to draw conclusions.
作为线粒体-核通讯的一部分，逆行和顺行信号有助于在基础条件下维持体内平衡。然而，基础条件在系统发育上有所不同。在细胞水平上，一些线粒体逆行反应可以通过测量氧化应激的组成成分来量化，即活性氧 (ROS) 和抗氧化剂之间的平衡。ROS 是线粒体产生的代谢副产物，通过结构性改变蛋白质和诱导 DNA 突变等过程，可以破坏大分子。为了对抗积累的损伤，生物体已经进化出内源性抗氧化剂，并可以消耗外源性抗氧化剂，在 ROS 造成细胞损伤之前将其隔离。ROS 也被认为是通过从线粒体到细胞核的逆行信号级联来调节的。这些细胞途径在整体动物水平上也可能具有重要意义。例如，鸟类的基础代谢率、血糖浓度和寿命比相似大小的哺乳动物高，然而，关于氧化应激是否在鸟类中比在哺乳动物中更高，文献存在分歧。在此，我们收集了鸟类和哺乳动物整体动物代谢的文献值。然后，我们从鸟类和哺乳动物分离的原代成纤维细胞中收集细胞代谢率数据，并从动物园饲养的具有系统发育多样性的鸟类和哺乳动物中采集血液，测量氧化应激的几个参数。此外，我们回顾了哺乳动物和鸟类之间基础水平氧化应激参数的文献。我们发现鸟类的比质量代谢率高于哺乳动物。我们的实验室结果表明，与哺乳动物相比，鸟类的细胞基础代谢、总抗氧化能力、循环脂质损伤和过氧化氢酶活性显著降低。我们没有发现细胞代谢或氧化应激与体型大小的相关性。我们还发现，大多数氧化应激参数在哺乳动物中与年龄的增加显著相关，但在鸟类中则不然；与报告的最大寿命的相关性与与已知的老年鸟类的相关性不同。我们的文献综述表明，鸟类氧化应激测量的基础水平很少，这使得难以得出结论。
