Abstract：
Epicatechin (EPC) is a flavonoid belonging to the family of catechins; it has been described as a powerful scavenger of a wide spectrum of reactive oxygen species (ROS) and a modulator of ex vivo sperm vitality. In this study, we assessed the potential protective abilities of EPC on cryopreserved bovine spermatozoa. We focused on conventional quality parameters, as well as the oxidative profile of spermatozoa alongside capacitation patterns, and expression profiles of proteins involved in the process of capacitation. Semen samples were cryopreserved in the presence of 25, 50 or 100 μmol/L EPC and compared to native semen (negative control) as well as ejaculates frozen in the absence of EPC (positive control). A dose-dependent improvement of conventional sperm quality parameters was observed following EPC administration, particularly in case of the sperm motility, membrane, acrosome and DNA integrity in comparison to the positive control. Experimental groups exposed to all EPC doses presented with a significantly lower proportion of capacitated spermatozoa as opposed to the positive control. While no significant effects of EPC were observed in cases of superoxide production, a significant decrease in the levels of hydrogen peroxide and hydroxyl radical were recorded particularly in the experimental groups supplemented with 50 and 100 μmol/L EPC. Western blot analysis revealed that supplementation of particularly 100 μmol/L EPC to the semen extender prevented the loss of the cation channel of sperm (CatSper) isoforms 1 and 2, sodium bicarbonate cotransporter (NBC) and protein kinase A (PKA), which play important roles in the process of sperm capacitation. In summary, we may hypothesize that EPC is particularly effective in the stabilization of the sperm membrane during the freeze-thaw process through its ability to quench ROS involved in damage to the membrane lipids and to prevent the loss of membrane channels crucial to initiate the process of sperm capacitation. These attributes of EPC provide an additional layer of protection to spermatozoa exposed to low temperatures, which may be translated into a higher post-thaw structural integrity and functional activity of male gametes.
摘要：
表儿茶素（EPC）是属于儿茶素家族的类黄酮；它已被描述为广谱活性氧（ROS）的强大清除剂和离体精子活力的调节剂。在这项研究中,我们评估了EPC对冷冻保存的牛精子的潜在保护能力。我们专注于常规质量参数，以及精子的氧化特征和获能模式，和参与获能过程的蛋白质的表达谱。将精液样品在25、50或100μmol/LEPC的存在下冷冻保存,并与天然精液(阴性对照)以及在不存在EPC的情况下冷冻的射精(阳性对照)进行比较。EPC给药后观察到常规精子质量参数的剂量依赖性改善，特别是在精子运动的情况下，膜,与阳性对照相比,顶体和DNA完整性。与阳性对照相比，暴露于所有EPC剂量的实验组的获能精子比例明显较低。虽然在超氧化物产生的情况下没有观察到EPC的显著影响，过氧化氢和羟基自由基水平显着下降，特别是在补充了50和100μmol/LEPC的实验组中。Westernblot分析显示，向精液延伸剂补充特别是100μmol/LEPC可以防止精子（CatSper）亚型1和2，碳酸氢钠协同转运蛋白（NBC）和蛋白激酶A（PKA）的阳离子通道丢失，在精子获能过程中起着重要作用。总之,我们可以假设EPC在冻融过程中对精子膜的稳定特别有效，因为它能够淬灭与膜脂质损伤有关的ROS，并防止对启动精子获能过程至关重要的膜通道的丢失。EPC的这些属性为暴露于低温的精子提供了额外的保护层，这可以转化为更高的解冻后结构完整性和雄性配子的功能活性。
