Gibb Zamira, Aitken Robert J, Sheridan Alecia R, Holt Brandan, Waugh Stephanie, Swegen Aleona
School of Environmental and Life Sciences, College of Engineering, Science and Environment The University of Newcastle Callaghan New South Wales Australia.
Faculty of Health, School of Biomedical Sciences Queensland University of Technology Brisbane Queensland Australia.
FASEB Bioadv. 2024 May 3;6(6):143-158. doi: 10.1096/fba.2023-00051. eCollection 2024 Jun.
The in vitro storage of stallion spermatozoa for use in artificial insemination leads to oxidative stress and imbalances in calcium homeostasis that trigger the formation of the mitochondrial permeability transition pore (mPTP), resulting in premature cell death. However, little is understood about the dynamics and the role of mPTP formation in mammalian spermatozoa. Here, we identify an important role for mPTP in stallion sperm Ca homeostasis. We show that stallion spermatozoa do not exhibit "classical" features of mPTP; specifically, they are resistant to cyclosporin A-mediated inhibition of mPTP formation, and they do not require exogenous Ca to form the mPTP. However, chelation of endogenous Ca prevented mPTP formation, indicating a role for intracellular Ca in this process. Furthermore, our findings suggest that this cell type can mobilize intracellular Ca stores to form the mPTP in response to low Ca environments and that under oxidative stress conditions, mPTP formation preceded a measurable increase in intracellular Ca, and vice versa. Contrary to previous work that identified mitochondrial membrane potential (MMP) as a proxy for mPTP formation, here we show that a loss of MMP can occur independently of mPTP formation, and thus MMP is not an appropriate proxy for the detection of mPTP formation. In conclusion, the mPTP plays a crucial role in maintaining Ca and reactive oxygen species homeostasis in stallion spermatozoa, serving as an important regulatory mechanism for normal sperm function, thereby contraindicating the in vitro pharmacological inhibition of mPTP formation to enhance sperm longevity.
用于人工授精的种马精子体外储存会导致氧化应激和钙稳态失衡，从而触发线粒体通透性转换孔（mPTP）的形成，导致细胞过早死亡。然而，对于mPTP在哺乳动物精子中的动态变化及其作用了解甚少。在此，我们确定了mPTP在种马精子钙稳态中的重要作用。我们发现种马精子不表现出mPTP的“经典”特征；具体而言，它们对环孢菌素A介导的mPTP形成抑制具有抗性，并且它们形成mPTP不需要外源钙。然而，内源性钙的螯合阻止了mPTP的形成，表明细胞内钙在这一过程中发挥作用。此外，我们的研究结果表明，这种细胞类型可以动员细胞内钙库，以响应低钙环境形成mPTP，并且在氧化应激条件下，mPTP的形成先于细胞内钙的可测量增加，反之亦然。与之前将线粒体膜电位（MMP）作为mPTP形成替代指标的研究不同，我们在此表明MMP的丧失可能独立于mPTP的形成而发生，因此MMP不是检测mPTP形成的合适替代指标。总之，mPTP在维持种马精子中的钙和活性氧稳态方面起着关键作用，是正常精子功能的重要调节机制，因此不建议对mPTP形成进行体外药理学抑制以提高精子寿命。
