Oxidative damage increases with age in a variety of cell types, including sperm, which are particularly susceptible to attack by reactive oxygen species (ROS). While mitochondrial respiration is the main source of cellular ROS, the relationship between the rates of aerobic metabolism and ROS production, and how this relationship may be affected by age, both in sperm and in other cell types, is unclear. Here, we investigate in Drosophila melanogaster sperm the effects of male age on i) the level of hydrogen peroxide in the mitochondria, using a transgenic H2O2 reporter line; ii) the in-situ rate of non-H2O2 ROS production, using a novel biophysical method; and iii) metabolic rate, using fluorescent lifetime imaging microscopy. Sperm from older males had higher mitochondrial ROS levels and a higher metabolic rate but produced ROS at a lower rate. In comparison, a somatic tissue, the gut epithelium, also showed an age-related increase in mitochondrial ROS levels but a decrease in metabolic rate. These results support the idea of a tissue-specific optimal rate of aerobic respiration balancing the production and removal of ROS, with aging causing a shift away from this optimum and leading to increased ROS accumulation. Our findings also support the view that pathways of germline and somatic ageing can be uncoupled, which may have implications for male infertility treatments.

中文翻译：

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果蝇黑色素精子的代谢速率和氧自由基水平增加，但自由基产生速率降低。

在包括精子在内的多种细胞类型中，氧化损伤随着年龄的增长而增加，这些细胞特别容易受到活性氧（ROS）的攻击。线粒体呼吸是细胞ROS的主要来源，但尚不清楚有氧代谢速率与ROS产生之间的关系，以及这种关系在精子和其他细胞类型中如何受到年龄的影响。在这里，我们在果蝇的精子中研究了雄性年龄对i）转基因H2O2报告基因系线粒体中过氧化氢水平的影响；ii）采用新型生物物理方法原位产生非H2O2 ROS的速率；iii）代谢率，使用荧光寿命成像显微镜。老年男性的精子具有较高的线粒体ROS水平和较高的代谢率，但产生的ROS较低。相比之下，体细胞组织-肠上皮细胞也显示出与年龄相关的线粒体ROS水平升高，但代谢率降低。这些结果支持了组织特定的有氧呼吸最佳速率的想法，该速率平衡了ROS的产生和去除，并且衰老导致偏离该最佳值并导致ROS积累增加。我们的发现还支持种系和体细胞衰老的途径可以解偶联的观点，这可能对男性不育症治疗有影响。老化会导致偏离最佳值并导致ROS积累增加。我们的发现还支持种系和体细胞衰老的途径可以解偶联的观点，这可能对男性不育症治疗有影响。老化会导致偏离最佳值并导致ROS积累增加。我们的发现还支持种系和体细胞衰老的途径可以解偶联的观点，这可能对男性不育症治疗有影响。