Data from: The loss of hemoglobin and myoglobin does not minimize oxidative stress in Antarctic icefishes

The unusual pattern of expression of hemoglobin (Hb) and myoglobin (Mb) among Antarctic notothenioid fishes provides an exceptional model system for assessing the impact of these proteins on oxidative stress. We tested the hypothesis that the lack of oxygen-binding proteins may reduce oxidative stress. Levels and activity of pro-oxidants, small-molecule and enzymatic antioxidants, and levels of oxidized lipids and proteins in liver, oxidative skeletal muscle, and heart ventricle were quantified in five species of notothenioid fishes differing in the expression of Hb and Mb. Levels of ubiquitinated proteins and rates of protein degradation by the 20S proteasome were also quantified. Although levels of oxidized proteins and lipids, ubiquitinated proteins, and antioxidants are higher in red-blooded fishes than in Hb-less icefishes in some tissues, this pattern does not persist across all tissues. Expression of Mb is not associated with oxidative damage in heart ventricle, whereas the activity of citrate synthase and contents of heme are positively correlated with oxidative damage in most tissues. Despite some tissue differences in levels of protein carbonyls among species, rates of degradation by the 20S proteasome are not markedly different, suggesting either alternative pathways for eliminating oxidized proteins or redox tone varies among species. Together, our data indicate that the loss of Hb and Mb does not correspond with a clear pattern of either reduced oxidative defense or oxidative damage.

南极鱼亚目（Notothenioidei）鱼类中血红蛋白（hemoglobin, Hb）与肌红蛋白（myoglobin, Mb）的异常表达模式，为评估这两类蛋白对氧化应激的影响提供了绝佳的模型体系。我们验证了“缺失氧结合蛋白可缓解氧化应激”这一假说。针对5种Hb与Mb表达模式各异的南极鱼亚目鱼类，我们对其肝脏、氧化型骨骼肌及心室中的促氧化剂水平与活性、小分子及酶类抗氧化剂水平，以及氧化型脂质与氧化型蛋白质的含量进行了定量检测，同时还定量了泛素化蛋白水平及20S蛋白酶体（20S proteasome）介导的蛋白质降解速率。尽管在部分组织中，带红细胞鱼类的氧化型蛋白质、脂质、泛素化蛋白及抗氧化剂水平均高于无Hb的冰鱼，但该趋势并未在所有组织中保持一致。Mb的表达与心室的氧化损伤并无关联，而柠檬酸合酶活性与血红素含量在多数组织中均与氧化损伤呈正相关。尽管不同物种间的蛋白质羰基水平存在组织特异性差异，但20S蛋白酶体的降解速率并无显著差异，这提示要么存在清除氧化型蛋白质的替代通路，要么不同物种间的氧化还原基调存在差异。综上，本研究数据表明，Hb与Mb的缺失并未呈现出清晰的氧化防御能力降低或氧化损伤加剧的对应模式。