Membrane hyperpolarization abolishes calcium oscillations that prevent induced acrosomal exocytosis in human sperm

Plasma membrane (PM) hyperpolarization, increased intracellular pH (pHi), and changes in intracellular calcium concentration ([Ca2+]i) are physiological events that occur during human sperm capacitation. These parameters are potential predictors of successful outcomes for men undergoing artificial reproduction techniques (ARTs), but methods currently available for their determination pose various technical challenges and limitations. Here, we developed a novel strategy employing time-lapse flow cytometry (TLFC) to determine capacitation-related membrane potential (Em) and pHi changes, and progesterone-induced [Ca2+]i increases. Our results show that TLFC is a robust method to measure absolute Em and pHi values and to qualitatively evaluate [Ca2+]i changes. To support the usefulness of our methodology, we used sperm from two types of normozoospermic donors: known paternity (subjects with self-reported paternity) and no-known paternity (subjects without self-reported paternity and no known fertility problems). We found relevant differences between them. The incidences of membrane hyperpolarization, pHi alkalinization, and increased [Ca2+]i were consistently high among known paternity samples (100%, 100%, and 86%, respectively), while they varied widely among no-known paternity samples (44%, 17%, and 45%, respectively). Our results indicate that TLFC is a powerful tool to analyze key physiological parameters of human sperm, which pending clinical validation, could potentially be employed as fertility predictors.

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O-228 The SSRI antidepressant Sertraline inhibits CatSper calcium channels in human sperm

Human Reproduction ◽

10.1093/humrep/deab128.052 ◽

2021 ◽

Vol 36 (Supplement_1) ◽

Author(s):

R Rahban ◽

A Rehfeld ◽

C Schiffer ◽

C Brenker ◽

D. Louise Egeberg Palme ◽

...

Keyword(s):

In Vitro Study ◽

Human Sperm ◽

Fertilization Process ◽

Acrosomal Exocytosis ◽

Depth Analysis ◽

Sperm Penetration ◽

Viscous Media ◽

Voltage Activation

Abstract Study question Do Selective Serotonin Reuptake Inhibitor (SSRI) antidepressants affect the function of human sperm? Summary answer The SSRI-antidepressant Sertraline (e.g. Zoloft) inhibits the sperm-specific Ca2+ channel CatSper and affects human sperm function in vitro. What is known already In human sperm, CatSper translates changes of the chemical microenvironment into changes of the intracellular Ca2+ concentration ([Ca2+]i) and swimming behavior. CatSper is promiscuously activated by oviductal ligands, but also by synthetic chemicals that might disturb the fertilization process. It is well known that SSRIs have off-target actions on Ca2+, Na+, and K+ channels in somatic cells. Whether SSRIs affect the activity of CatSper is, however, unknown. Study design, size, duration We studied the action of the seven drugs belonging to the most commonly prescribed class of antidepressants, SSRIs, on resting [Ca2+]i and Ca2+ influx via CatSper in human sperm. The SSRI Sertraline was selected for in-depth analysis of its action on steroid-, prostaglandin-, pH-, and voltage-activation of human CatSper. Moreover, the action of Sertraline on sperm acrosomal exocytosis and penetration into viscous media was evaluated. Participants/materials, setting, methods The activity of CatSper was investigated in sperm of healthy volunteers, using kinetic Ca2+ fluorimetry and patch-clamp recordings. Acrosomal exocytosis was investigated using Pisum sativum agglutinin (PSA) and image cytometry. Sperm penetration in viscous media was evaluated using the Kremer test. Main results and the role of chance Four SSRIs increased [Ca2+]i, two out of which also attenuated ligand-induced Ca2+ influx via CatSper. In contrast, Sertraline decreased [Ca2+]i and almost completely suppressed ligand-induced Ca2+ influx via CatSper. Remarkably, the drug was about four-fold more potent to suppress prostaglandin- versus steroid-induced Ca2+ influx. Sertraline also suppressed alkaline- and voltage-activation of CatSper, indicating that the drug directly inhibits human CatSper. Finally, Sertraline suppressed ligand-induced acrosome reaction and sperm penetration into viscous media. Limitations, reasons for caution This is an in vitro study. Future studies have to assess the physiological relevance in vivo. Wider implications of the findings The off-target action of Sertraline on CatSper in human sperm might impair the fertilization process. In a research setting, Sertraline may be used to selectively inhibit prostaglandin-induced Ca2+ influx. Trial registration number CRU326

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Discrete Dynamic Model of the Mammalian Sperm Acrosome Reaction: The Influence of Acrosomal pH and Physiological Heterogeneity

Frontiers in Physiology ◽

10.3389/fphys.2021.682790 ◽

2021 ◽

Vol 12 ◽

Author(s):

Andrés Aldana ◽

Jorge Carneiro ◽

Gustavo Martínez-Mekler ◽

Alberto Darszon

Keyword(s):

Acrosome Reaction ◽

Human Sperm ◽

Extracellular Medium ◽

Mammalian Sperm ◽

Discrete Dynamic Model ◽

Acrosomal Exocytosis ◽

Mammalian Fertilization ◽

Main Components ◽

Discrete Mathematical Model ◽

Physiological Heterogeneity

The acrosome reaction (AR) is an exocytotic process essential for mammalian fertilization. It involves diverse physiological changes (biochemical, biophysical, and morphological) that culminate in the release of the acrosomal content to the extracellular medium as well as a reorganization of the plasma membrane (PM) that allows sperm to interact and fuse with the egg. In spite of many efforts, there are still important pending questions regarding the molecular mechanism regulating the AR. Particularly, the contribution of acrosomal alkalinization to AR triggering physiological conditions is not well understood. Also, the dependence of the proportion of sperm capable of undergoing AR on the physiological heterogeneity within a sperm population has not been studied. Here, we present a discrete mathematical model for the human sperm AR based on the physiological interactions among some of the main components of this complex exocytotic process. We show that this model can qualitatively reproduce diverse experimental results, and that it can be used to analyze how acrosomal pH (pHa) and cell heterogeneity regulate AR. Our results confirm that a pHa increase can on its own trigger AR in a subpopulation of sperm, and furthermore, it indicates that this is a necessary step to trigger acrosomal exocytosis through progesterone, a known natural inducer of AR. Most importantly, we show that the proportion of sperm undergoing AR is directly related to the detailed structure of the population physiological heterogeneity.

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Optimized Protocols to Analyze Sphingosine-1-Phosphate Signal Transduction Pathways During Acrosomal Exocytosis in Human Sperm

Methods in Molecular Biology - Sphingosine-1-Phosphate ◽

10.1007/978-1-61779-800-9_9 ◽

2012 ◽

pp. 99-128 ◽

Cited By ~ 4

Author(s):

Silvia A. Belmonte ◽

Laila Suhaiman

Keyword(s):

Signal Transduction ◽

Human Sperm ◽

Signal Transduction Pathways ◽

Acrosomal Exocytosis ◽

Sphingosine 1 Phosphate

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Kinetics of human sperm acrosomal exocytosis

MHR Basic science of reproductive medicine ◽

10.1093/molehr/gau110 ◽

2014 ◽

Vol 21 (3) ◽

pp. 244-254 ◽

Cited By ~ 13

Author(s):

C.M. Sosa ◽

M.A. Pavarotti ◽

M.N. Zanetti ◽

F.C.M. Zoppino ◽

G.A. De Blas ◽

...

Keyword(s):

Human Sperm ◽

Acrosomal Exocytosis ◽

Kinetics Of

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The Role of Zinc in Male Fertility

International Journal of Molecular Sciences ◽

10.3390/ijms21207796 ◽

2020 ◽

Vol 21 (20) ◽

pp. 7796

Author(s):

Deborah Allouche-Fitoussi ◽

Haim Breitbart

Keyword(s):

Adenylyl Cyclase ◽

Sperm Motility ◽

Intracellular Signaling ◽

Male Fertility ◽

Human Sperm ◽

Zinc Ion ◽

Human Seminal Plasma ◽

Cellular Mechanisms ◽

Acrosomal Exocytosis ◽

The Impact

Several studies proposed the importance of zinc ion in male fertility. Here, we describe the properties, roles and cellular mechanisms of action of Zn2+ in spermatozoa, focusing on its involvement in sperm motility, capacitation and acrosomal exocytosis, three functions that are crucial for successful fertilization. The impact of zinc supplementation on assisted fertilization techniques is also described. The impact of zinc on sperm motility has been investigated in many vertebrate and invertebrate species. It has been reported that Zn2+ in human seminal plasma decreases sperm motility and that Zn2+ removal enhances motility. Reduction in the intracellular concentration of Zn2+ during epididymal transit allows the development of progressive motility and the subsequent hyper activated motility during sperm capacitation. Extracellular Zn2+ affects intracellular signaling pathways through its interaction with the Zn2+ sensing receptor (ZnR), also named GPR39. This receptor was found in the sperm tail and the acrosome, suggesting the possible involvement of Zn2+ in sperm motility and acrosomal exocytosis. Our studies showed that Zn2+ stimulates bovine sperm acrosomal exocytosis, as well as human sperm hyper-activated motility, were both mediated by GPR39. Zn2+ binds and activates GPR39, which activates the trans-membrane-adenylyl-cyclase (tmAC) to catalyze cAMP production. The NHE (Na+/H+-exchanger) is activated by cAMP, leading in increased pHi and activation of the sperm-specific Ca2+ channel CatSper, resulting in an increase in [Ca2+]i, which, together with HCO3−, activates the soluble adenylyl-cyclase (sAC). The increase in [cAMP]i activates protein kinase A (PKA), followed by activation of the Src-epidermal growth factor receptor-Pphospholipase C (Src-EGFR-PLC) cascade, resulting in inositol-triphosphate (IP3) production, which mobilizes Ca2+ from the acrosome, causing a further increase in [Ca2+]i and the development of hyper-activated motility. PKA also activates phospholipase D1 (PLD1), leading to F-actin formation during capacitation. Prior to the acrosomal exocytosis, PLC induces phosphadidylinositol-4,5-bisphosphate (PIP2) hydrolysis, leading to the release of the actin-severing protein gelsolin to the cytosol, which is activated by Ca2+, resulting in F-actin breakdown and the occurrence of acrosomal exocytosis.

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