Seligman Judith, Newton Gerald L, Fahey Robert C, Shalgi Ruth, Kosower Nechama S
Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel-Aviv University, Tel Aviv 69978, Israel.
J Androl. 2005 Sep-Oct;26(5):629-37; discussion 638-40. doi: 10.2164/jandrol.05040.
Sperm thiol oxidation during sperm maturation is important for sperm component stabilization, the acquisition of sperm motility, and fertilizing ability. A correct degree of oxidation is required, since spermatozoa are very susceptible to oxidative damage. The pathways involved in physiologic sperm thiol oxidation in the epididymis are not completely understood. The nonprotein thiol glutathione (GSH), in addition to playing a major role as an antioxidant and in eliminating toxic compounds, has been implicated in prooxidation processes in various cells, via gamma-glutamyl-transpeptidase (gamma-GT)-dependent catabolism. Little information is available on the dynamics of nonprotein thiols (NPSHs) and disulfides (NPSSNPs) in spermatozoa and epididymal fluid (EF) during sperm passage in the epididymis. It is not clear whether NPSHs and NPSSNPs are involved in sperm protein thiol (PSH) oxidation or whether GSH catabolism in the epididymis can serve as a pathway for sperm PSH oxidation. In the present study, we used the thiol fluorescence labeling agent monobromobimane to analyze NPSHs and nonprotein disulfides (NPSSRs) (R, nonprotein or protein) in spermatozoa and EF in the rat caput and cauda epididymis. NPSH levels are shown to be significantly higher in the caput than in the cauda (spermatozoa and fluid). GSH in the caput lumen is subject to high gamma-GT activity. A marked loss of sperm GSH and a shift to an oxidized state (resulting in a significantly higher concentration of glutathione disulfides [GSSRs] than GSH) occur during the passage of spermatozoa from the caput to the cauda epididymis. Caput EF and extracellular NPSSNPs induce sperm thiol oxidation. The results suggest that epididymal NPSH/NPSSNP participates in sperm PSH oxidation and that some reactions of GSH in the gamma-GT pathway (in the epididymis) provide oxidizing power, leading to physiologic sperm thiol oxidation.
精子成熟过程中的硫醇氧化对于精子成分的稳定、精子运动能力的获得以及受精能力都很重要。由于精子极易受到氧化损伤，因此需要正确的氧化程度。附睾中生理性精子硫醇氧化所涉及的途径尚未完全明确。非蛋白质硫醇谷胱甘肽（GSH）除了作为抗氧化剂和清除有毒化合物发挥主要作用外，还通过γ-谷氨酰转肽酶（γ-GT）依赖性分解代谢参与各种细胞的促氧化过程。关于精子在附睾中通过时精子和附睾液（EF）中非蛋白质硫醇（NPSHs）和二硫化物（NPSSNPs）的动态变化，目前所知甚少。尚不清楚NPSHs和NPSSNPs是否参与精子蛋白硫醇（PSH）氧化，以及附睾中GSH分解代谢是否可作为精子PSH氧化的途径。在本研究中，我们使用硫醇荧光标记剂单溴化双硫腙来分析大鼠附睾头和附睾尾精子及EF中的NPSHs和非蛋白质二硫化物（NPSSRs）（R为非蛋白质或蛋白质）。结果显示，附睾头中的NPSH水平显著高于附睾尾（精子和液体中均如此）。附睾头管腔中的GSH具有较高的γ-GT活性。在精子从附睾头向附睾尾通过的过程中，精子GSH显著减少并转变为氧化状态（导致谷胱甘肽二硫化物[GSSRs]的浓度显著高于GSH）。附睾头EF和细胞外NPSSNPs可诱导精子硫醇氧化。结果表明，附睾NPSH/NPSSNP参与精子PSH氧化，并且γ-GT途径（在附睾中）中GSH的一些反应提供了氧化能力，导致生理性精子硫醇氧化。
