受精和生精过程中的氧化还原调节

Redox regulation of fertilisation and the spermatogenic process

氧化应激是男性不育的重要原因之一，它可以损害生精细胞、生精过程以及精子功能。最新的氧化还原生物学研究揭示了细胞所产生的活性氧（ROS）的信号作用。虽然羟自由基等高活性氧化剂有大量的有害作用，但由于过氧化氢为中等应激并有膜渗透性，而且只能氧化有限数量的生物分子功能团，所以过氧化氢可以作为一个信号调停者切实发挥作用。氨基酸支链最敏感的氧化部位是半胱氨酸的巯基，这也是一些常见酶参与催化反应的部位。虽然半胱氨酸的巯基化反应性在普通蛋白质中并不高，但一些磷酸酶在催化中心具有高反应性的巯基组，从而可通过细胞外刺激并在一定的环境条件下暂时升高过氧化氢水平而被氧化灭活。相应的，过氧化还原酶有中等的过氧化氢还原活性，而磷酸酶受到保护以免被氧化灭活，能调节过氧化还原酶在普通细胞中的由活性氧介导的信号转导调节作用，这已经受到越来越多的关注。虽然目前我们关于活性氧在男性生殖系统的信号作用知之甚少，但其重要意义正逐渐成为一个焦点问题。因此，本文把睾丸中过氧化氢作为新兴信号的作用加以综述。

Oxidative stress is one of the major causes of male infertility; it damages spermatogenic cells, the spermatogenic process and sperm function. Recent advances in redox biology have revealed the signalling role of reactive oxygen species （ROS） that are generated by cells. While highly reactive oxidants, such as the hydroxyl radical, exert largely deleterious effects, hydrogen peroxide can feasibly serve as a signal mediator because it is moderately reactive and membrane permeable and because it can oxidize only limited numbers of functional groups of biological molecules. The amino acid side chain most sensitive to oxidation is cysteine sulphydryl, which is commonly involved in the catalysis of some enzymes. Although the reactivity of cysteine sulphhydryl is not very high in ordinary proteins, some phosphatases possess a highly reactive sulphydryl group at their catalytic centre and are thereby oxidatively inactivated by transiently elevated hydrogen peroxide levels after extracellular stimuli and under certain environmental conditions. Peroxiredoxins, in turn, show moderate hydrogen peroxide-reducing activity, and their role in the modulation of ROS-mediated signal transduction in ordinary cells, mediated by protecting phosphatases from oxidative inactivation, has attracted much attention. Although knowledge of the signalling role of ROS in the male reproductive system is limited at present, its significance is becoming a focal issue. Here, we present a review of the emerging signalling role of hydrogen peroxide in testes.