Laboratory of Equine Reproduction and Equine Spermatology, Veterinary Teaching Hospital, University of Extremadura, Cáceres, Spain.
Facility for Innovation and Analysis in Animal Source Foodstuffs, University of Extremadura, Cáceres, Spain.
Reproduction. 2020 Dec;160(6):803-818. doi: 10.1530/REP-20-0181.
Spermatozoa are redox-regulated cells, and stallion spermatozoa, in particular, present an intense mitochondrial activity in which large amounts of reactive oxygen species (ROS) are produced. To maintain the redox potential under physiological conditions, sophisticated mechanisms ought to be present, particularly in the mitochondria. In the present study, we investigated the role of the SLC7A11 antiporter. This antiporter exchanges intracellular glutamate for extracellular cystine. In the spermatozoa, cystine is reduced to cysteine and used for GSH synthesis. The importance of the antiporter for mitochondrial functionality was studied using flow cytometry and UHPLC/MS/MS approaches. Intracellular GSH increased in the presence of cystine, but was reduced in the presence of Buthionine sulphoximine (BSO), a γ-glutamylcysteine synthetase inhibitor (P < 0.001). Inhibition of the SLC7A11 antiporter with sulfasalazine caused a dramatic drop in intracellular GSH (P < 0.001) and in the percentage of spermatozoa showing active mitochondria (P < 0.001). These findings suggest that proper functionality of this antiporter is required for the mitochondrial function of spermatozoa. We also describe that under some conditions, glutamate may be metabolized following non-conventional pathways, also contributing to sperm functionality. We provide evidences, that the stallion spermatozoa have important metabolic plasticity, and also of the relation between redox regulation and metabolic regulation. These findings may have important implications for the understanding of sperm biology and the development of new strategies for sperm conservation and treatment of male factor infertility.
精子是氧化还原调节细胞，特别是马精子，其线粒体活性很高，会产生大量的活性氧（ROS）。为了在生理条件下维持氧化还原电势，应该存在复杂的机制，特别是在线粒体中。在本研究中，我们研究了 SLC7A11 转运蛋白的作用。该转运蛋白将细胞内的谷氨酸交换为细胞外的胱氨酸。在精子中，胱氨酸被还原为半胱氨酸，并用于 GSH 合成。使用流式细胞术和 UHPLC/MS/MS 方法研究了该转运蛋白对线粒体功能的重要性。在存在胱氨酸的情况下，细胞内 GSH 增加，但在存在 Buthionine sulphoximine (BSO)（γ-谷氨酰半胱氨酸合成酶抑制剂）的情况下，GSH 减少（P < 0.001）。用柳氮磺胺吡啶抑制 SLC7A11 转运蛋白会导致细胞内 GSH 急剧下降（P < 0.001）和显示活跃线粒体的精子比例下降（P < 0.001）。这些发现表明，该转运蛋白的正常功能对于精子的线粒体功能是必需的。我们还描述了在某些条件下，谷氨酸可能会通过非传统途径代谢，这也有助于精子功能。我们提供的证据表明，马精子具有重要的代谢可塑性，以及氧化还原调节和代谢调节之间的关系。这些发现可能对理解精子生物学和开发新的精子保存策略以及治疗男性因素不孕具有重要意义。
