Effect of Exogenous Progesterone on Post-thaw Capacitation and Acrosome Reaction of Bovine Spermatozoa

The Modulation of Functional Status of Bovine Spermatozoa by Progesterone

Simple Summary

Progesterone is an endogenous steroid hormone, which can induce capacitation and/or acrosome reactions in semen of certain mammalian species. Our study aimed to investigate the effect of progesterone on the functional status of fresh bovine spermatozoa using a chlortetracycline fluorescent probe. Results showed that heparin induced capacitation in spermatozoa incubated with or without progesterone. The destruction of microfilaments by an inhibitor of cytochalasin D blocked the stimulating effect of heparin. Steroid hormone in mixture with prolactin stimulated the acrosome reaction in spermatozoa, which was blocked by an inhibitor of microtubule polymerization (nocodazole). At the acrosome stage, prolactin provided the undergoing of acrosome reaction in male gametes. This effect was noted both in the presence and absence of progesterone and inhibited by nocodazole. The supplementation of dibutyryl cyclic adenosine monophosphate during the acrosome reaction to progesterone-untreated spermatozoa did not cause changes in proportion of acrosome-reacted cells. However, when progesterone was added during capacitation, a significant increase in the proportion of capacitated cells was noted, which was inhibited by nocodazole. Thus, progesterone under the action of prolactin and dibutyryl cyclic adenosine monophosphate determines the functional status of fresh spermatozoa, which indicates progesterone-modulating effect on the indicators of post-ejaculatory maturation of male gametes.

Abstract

The aim of this study is to identify the effects of progesterone (PRG) on the capacitation and the acrosome reaction in bovine spermatozoa. The fresh sperm samples were incubated with and without capacitation inductors (heparin, dibutyryl cyclic adenosine monophosphate (dbcAMP)), hormones (prolactin (PRL), PRG), inhibitors of microfilaments (cytochalasin D) and microtubules (nocodazole) during capacitation and acrosome reactions. The functional status of spermatozoa was examined using the chlortetracycline assay. Supplementation of heparin stimulated capacitation in the presence and absence of PRG. Cytochalasin D blocked the stimulating effect of heparin on capacitation. The addition of PRL during capacitation (without PRG) did not affect the functional status of spermatozoa, while in PRG-treated cells PRL stimulated the acrosome reaction. PRL (with and without PRG) increased the acrosome reaction in capacitated cells. These PRL-dependent effects were inhibited by nocodazole. During the acrosome reaction, in presence of dbcAMP, PRG decreased the proportion of acrosome-reacted cells compared to PRG-untreated cells. This effect in PRG-treated cells was canceled in the presence of nocodazole. In conclusion, PRG under the action of PRL and dbcAMP determines the changes in the functional status of native sperm cells, which indicates PRG modulating effect on the indicators of post-ejaculatory maturation of spermatozoa.

Astaxanthin Improves Human Sperm Capacitation by Inducing Lyn Displacement and Activation

Astaxanthin (Asta), a photo-protective red pigment of the carotenoid family, is known for its multiple beneficial properties. In this study, the effects of Asta on isolated human sperm were evaluated. Capacitation involves a series of transformations to let sperm acquire the correct features for potential oocyte fertilization, including the generation of a controlled amount of reactive oxygen species (ROS), cholesterol depletion of the sperm outer membrane, and protein tyrosine phosphorylation (Tyr-P) process in the head region. Volunteers, with normal spermiogram values, were divided in two separate groups on the basis of their ability to generate the correct content of endogenous ROS. Both patient group (PG) and control group (CG) were analysed for Tyr-phosphorylation (Tyr-P) pattern and percentages of acrosome-reacted cells (ARC) and non-viable cells (NVC), in the presence or absence of Asta. In addition, the involvement of ROS on membrane reorganization and the presence of Lyn, a Src family kinase associated with lipid rafts, were investigated. Results show that Lyn is present in the membranes of human sperm, mainly confined in midpiece in resting conditions. Following capacitation, Lyn translocated to the head concomitantly with raft relocation, thus allowing the Tyr-P of head proteins. Asta succeeded to trigger Lyn translocation in PG sperm thus bypassing the impaired ROS-related mechanism for rafts and Lyn translocation. In this study, we showed an interdependence between ROS generation and lipid rafts and Lyn relocation leading the cells to undergo the successive acrosome reaction (AR). Asta, by ameliorating PG sperm functioning, may be utilised to decrease male idiopathic infertility.

Capacitation and acrosome reaction differences of bovine, mouse and porcine spermatozoa in responsiveness to estrogenic compounds

Background

Endocrine disruptors are exogenous substance, interfere with the endocrine system, and disrupt hormonal functions. However, the effect of endocrine disruptors in different species has not yet been elucidated. Therefore, we investigated the possible effects of 17ß-estradiol (E2), progesterone (P4), genistein (GEN) and 4-tert-octylphenol (OP), on capacitation and the acrosome reaction in bovine, mouse, and porcine spermatozoa. In this in vitro trial, spermatozoa were incubated with 0.001-100 μM of each chemical either 15 or 30 min and then assessed capacitation status using chlortetracycline staining.

Results

E2 significantly increased capacitation and the acrosome reaction after 30 min, while the acrosome reaction after 15 min incubation in mouse spermatozoa. Simultaneously, capacitation and the acrosome reaction were induced after 15 and 30 min incubation in porcine spermatozoa, respectively. Capacitation was increased in porcine spermatozoa after 15 min incubation at the lowest concentration, while the acrosome reaction was increased in mouse spermatozoa after 30 min (P <0.05). E2 significantly increased the acrosome reaction in porcine spermatozoa, but only at the highest concentration examined (P <0.05). P4 significantly increased the acrosome reaction in bovine and mouse spermatozoa treated for 15 min (P <0.05). The same treatment significantly increased capacitation in porcine spermatozoa (P <0.05). P4 significantly increased capacitation in mouse spermatozoa treated for 30 min (P <0.05). GEN significantly increased the acrosome reaction in porcine spermatozoa treated for 15 and 30 min and in mouse spermatozoa treated for 30 min (P <0.05). OP significantly increased the acrosome reaction in mouse spermatozoa after 15 min (P <0.05). Besides, when spermatozoa were incubated for 30 min, capacitation and the acrosome reaction were higher than 15 min incubation in E2 or GEN. Furthermore, the responsiveness of bovine, mouse and porcine spermatozoa to each chemical differed.

Conclusions

In conclusion, all chemicals studied effectively increased capacitation and the acrosome reaction in bovine, mouse, and porcine spermatozoa. Also we found that both E2 and P4 were more potent than environmental estrogens in altering sperm function. Porcine and mouse spermatozoa were more responsive than bovine spermatozoa.

Effect of astaxanthin on human sperm capacitation

In order to be able to fertilize oocytes, human sperm must undergo a series of morphological and structural alterations, known as capacitation. It has been shown that the production of endogenous sperm reactive oxygen species (ROS) plays a key role in causing cells to undergo a massive acrosome reaction (AR). Astaxanthin (Asta), a photo-protective red pigment belonging to the carotenoid family, is recognized as having anti-oxidant, anti-cancer, anti-diabetic and anti-inflammatory properties and is present in many dietary supplements. This study evaluates the effect of Asta in a capacitating buffer which induces low ROS production and low percentages of acrosome-reacted cells (ARC). Sperm cells were incubated in the presence or absence of increasing concentrations of Asta or diamide (Diam) and analyzed for their ROS production, Tyr-phosphorylation (Tyr-P) pattern and percentages of ARC and non-viable cells (NVC). Results show that Asta ameliorated both sperm head Tyr-P and ARC values without affecting the ROS generation curve, whereas Diam succeeded in enhancing the Tyr-P level but only of the flagellum without increasing ARC values. It is suggested that Asta can be inserted in the membrane and therefore create capacitation-like membrane alteration which allow Tyr-P of the head. Once this has occurred, AR can take place and involves a higher numbers of cells.

Xenoestrogenic chemicals effectively alter sperm functional behavior in mice

Xenoestrogenic compounds (XCs) can disrupt endogenous hormone function and affect sperm function by binding to receptors on sperm membrane. Albeit spermatozoa are potentially a useful model for screening estrogenic activities of endocrine disruptors, high-quality in vitro test system that examination of the XCs effects on sperm function is required. The objective of this study was to compare the effects of XCs (genistein and 4-tert-octylphenol) to those of steroids (estrogen and progesterone) and heparin on in vitro capacitation and acrosome reaction (AR) in mouse spermatozoa. Mouse spermatozoa were incubated with various concentrations (0.001-100 μM) of each chemical for 15 or 30 min, and then capacitation and AR were assessed using chlortetracycline. All chemicals studied effectively alter capacitation and/or AR in mouse spermatozoa with different manner. Therefore, we believed that our system will provide a good in vitro model system to characterize the physiological effect of XCs especially when compared with steroids.

Endogenous reactive oxygen species content and modulation of tyrosine phosphorylation during sperm capacitation

Generation of controlled amounts of reactive oxygen species (ROS) and phosphorylation of protein tyrosine (Tyr) residues are two main cellular changes involved in sperm capacitation. This study examined the relationship between tyrosine-phosphorylation (Tyr-P) and endogenous ROS production during sperm capacitation, and correlated them with both sperm motility and functionality expressed as acrosome-reacted cells. Immediate ROS generation was observed to peak after a 45-min incubation, followed by a rapid decrease in ROS content and successive regeneration of the ROS peak in 3 h and later. These two peaks were directly correlated with both the Tyr-P process involving sperm heads and tails, and the acrosome reaction (69 ± 8% and 65 ± 4%, respectively). The period of low-ROS content resulted in low Tyr-P patterns, located exclusively in the cell midpiece, and drastic reduction in acrosome-reacted cells. Ascorbic acid addition inhibited both Tyr-P patterns and acrosome reactions, whereas NADPH induced high ROS generation, with Tyr-P patterns located only on sperm tails, and prevented the acrosome reaction. Sperm hyperactivation was insensitive to ROS content. This is an important parameter for evaluation of sperm capacitation, which is achieved only when both ROS generation reaches a peak and Tyr-P involves the sperm head.

Involvement of cholesterol, calcium and progesterone in the induction of capacitation and acrosome reaction of mammalian spermatozoa

The aim of this paper was to review the effects of some important substances involved in the induction of sperm plasma membrane changes referred to as acrosome reaction, namely cholesterol (C), calcium (Ca(2+)) and progesterone (P(4)). For this purpose, mechanisms of capacitation and acrosome reaction (AR) as well as the processes, C, Ca(2+) and P(4) are involved in, are described. Subsequently, to get a better insight into possible beneficial and detrimental effects on sperm function, the occurrence of these molecules in semen extenders is discussed.

Effect of progesterone and oestradiol on sperm-zona binding and acrosome reaction in bovine spermatozoa after thawing

This study was conducted assess spermatozoa binding capacity to the oocyte in the presence of 0.1 or 0.5 microg/ml progesterone (P4) or a combination of 0.5 microg/ml P4 with 0.1 microg/ml oestradiol (OE). The number of oocyte-bound spermatozoa in the presence of progesterone was significantly higher (p < 0.05 to p < 0.001) when compared with the control samples, that were incubated in the absence of P4. Spermatozoa binding to the zona pellucida (ZP) of the oocyte were concentration-dependent - significantly higher numbers of spermatozoa were bound in the presence of 0.5 microg/ml P4, when compared with that of 0.1 microg/ml P4. Oestradiol at 0.1 microg/ml concentration used impaired the effect of progesterone-mediated sperm-oocyte binding. The incidences of acrosome-reacted (AR) spermatozoa bound to the ZP - following 0, 60, 120 and 180 min. incubation in the presence and absence of 1 microg/ml progesterone was also assessed. Only at 180 min of incubation a higher (p < 0.001) incidence of the AR-spermatozoa was found in sperm-ZP complexes incubated in the presence or absence of progesterone, being 56.5 +/- 11.1 and 43.2 +/- 8.8 % respectively. In conclusion, progesterone enhances the sperm-ZP binding capacity. Progesterone affects the incidences of AR on zona-bound spermatozoa only after prolonged co-culture.

The effect of oestradiol, progesterone and heparin on bovine spermatozoa function after thawing

The present experiment was designed to determine the effects of various biologically active substances, such as oestradiol (OE), progesterone (P4) and heparin (Hep) alone or in combination on sperm plasma membrane scrambling, capacitation and acrosome reaction (AR) of post-thaw bovine spermatozoa. Spermatozoa were incubated for 180 min in capacitation medium supplemented with (i) 1 mug/ml OE; (ii) 1 mug/ml P4; (iii) 1 mug/ml OE and 1 mug/ml P4; (iv) 1 mug/ml OE and 5 mug/ml Hep; (v) 1 mug/ml P4 and 5 mug/ml Hep; (vi) 1 mug/ml OE, 1 mug/ml P4 and 5 mug/ml Hep. At predetermined time intervals aliquots were taken to assess sperm plasma membrane scrambling, or capacitation (AR induced by lysophosphatidylcholine) in spermatozoa. The second experiment was aimed to study the effects of OE, P4 and OE/P4 as potential inducers of AR in Hep-capacitated spermatozoa. Plasma membrane scrambling was assessed by a flow cytometer, using Merocyanine staining. Acrosomal status and viability of spermatozoa were evaluated under epifluorescence microscope with Ethidium homodimer-1/peanut agglutinin fluorescein isothiocyanate staining method (EthD-1/PNA-FITC). The results show that OE, P4 and a combination of OE/P4 at concentrations used did not affect sperm viability. Heparin significantly (p < 0.001) increased sperm plasma membrane scrambling of OE and P4-treated spermatozoa. P4 significantly affected the rate of sperm capacitation (p < 0.001) and AR (p < 0.05), but OE expressed membrane-stabilizing properties (p < 0.05). It can be concluded that in frozen-thawed bovine spermatozoa OE presents plasma membrane stabilizing properties that can be abolished by Hep, but not by P4. Progesterone possesses capacitating and AR-inducing properties in frozen-thawed bovine spermatozoa that can be alleviated by OE.