Abstract：
The antioxidant role of mitochondrial uncoupling protein 3 (UCP3) is controversial. This work aimed to investigate the effects of UCP3 on the heart of mice housed at thermoneutral temperature, an experimental condition that avoids the effects of thermoregulation on mitochondrial activity and redox homeostasis, preventing the alterations related to these processes from confusing the results caused by the lack of UCP3. WT and KO UCP3 mice were acclimatized at 30 °C for 4 weeks and hearts were used to evaluate metabolic capacity and redox state. Tissue and mitochondrial respiration, the activities of the mitochondrial complexes, and the protein expression of mitochondrial complexes markers furnished information on mitochondrial functionality. The levels of lipid and protein oxidative damage markers, the activity of antioxidant enzymes, the reactive oxygen species levels, and the susceptibility to in vitro Fe-ascorbate-induced oxidative stress furnished information on redox state. UCP3 ablation reduced tissue and mitochondrial respiratory capacities, not affecting the mitochondrial content. In KO UCP3 mice, the mitochondrial complexes activities were lower than in WT without changes in their content. These effects were accompanied by an increase in the level of oxidative stress markers, ROS content, and in vitro susceptibility to oxidative stress, notwithstanding that the activities of antioxidant enzymes were not affected by UCP3 ablation. Such modifications are also associated with enhanced activation/phosphorylation of EIF2α, a marker of integrated stress response and endoplasmic reticulum stress (GRP778 BIP). The lack of UCP3 makes the heart more prone to oxidative insult by reducing oxygen consumption and increasing ROS. Our results demonstrate that UCP3 helps the cell to preserve mitochondrial function by mitigating oxidative stress.
摘要：
线粒体解偶联蛋白3(UCP3)的抗氧化作用存在争议。这项工作旨在研究UCP3对在热中性温度下饲养的小鼠心脏的影响，一种避免体温调节对线粒体活性和氧化还原稳态影响的实验条件，防止与这些过程相关的改变混淆由于缺乏UCP3而导致的结果。WT和KOUCP3小鼠在30°C下适应4周,并且心脏用于评估代谢能力和氧化还原状态。组织和线粒体呼吸，线粒体复合物的活性，线粒体复合物标记的蛋白质表达提供了有关线粒体功能的信息。脂质和蛋白质氧化损伤标志物的水平，抗氧化酶的活性，活性氧的水平，对体外抗坏血酸铁诱导的氧化应激的敏感性提供了氧化还原状态的信息。UCP3消融降低了组织和线粒体呼吸能力，不影响线粒体含量。在KOUCP3小鼠中，线粒体复合物活性低于WT，其含量没有变化。这些影响伴随着氧化应激标志物水平的增加，ROS含量,和体外对氧化应激的敏感性，尽管抗氧化酶的活性不受UCP3消融的影响。此类修饰也与EIF2α的增强激活/磷酸化有关，整合应激反应和内质网应激的标志物(GRP778BIP)。UCP3的缺乏通过减少氧消耗和增加ROS使心脏更容易受到氧化损伤。我们的结果表明，UCP3通过减轻氧化应激来帮助细胞保持线粒体功能。
