Effects of extracellular adenosine 5'-triphosphate on human sperm motility

Influence of extracellular ATP on mammalian sperm physiology

In addition to its central role in cellular metabolism, adenosine 5'-triphosphate (ATP) is an important extracellular signalling molecule involved in various physiological processes. In reproduction, extracellular ATP participates in both autocrine and paracrine paths regulating gametogenesis, gamete maturation and fertilisation. This review focusses on how extracellular ATP modulates sperm physiology with emphasis on the mammalian acrosome reaction. The presence of extracellular ATP in the reproductive tract is primarily determined by the ion channels and transporters that influence its movement within the cells comprising the tract. The main targets of extracellular ATP in spermatozoa are its own transporters, particularly species-specific sperm purinergic receptors. We also discuss notable phenotypes from knock-out mouse models and human Mendelian inheritance related to ATP release mechanisms, along with immunological, proteomic, and functional observations regarding sperm purinergic receptors and their involvement in sperm signalling.

l-carnitine enhances the kinematics and protects the sperm membranes of chilled and frozen-thawed Peruvian Paso horse spermatozoa

l-carnitine (LC) transports fatty acids to the mitochondria for energy production, reducing lipid availability for peroxidation through β-oxidation. This research examines the effect of LC supplementation to two skimmed milk-based extenders on the cryosurvival of chilled (5°C) and frozen-thawed Peruvian Paso horse spermatozoa .An initial experiment determined the optimal LC concentration (0, 1, 5, 10, 25, and 50 mM) when added to INRA-96® and UHT (skimmed milk + 6% egg yolk) extenders, using nine ejaculates from three stallions chilled for up to 96 h. Subsequently, the effect of 25 mM LC supplementation (the optimal concentration) on chilling (INRA-96) and freezing (INRA-Freeze®) extenders was evaluated using eight pooled samples from sixteen ejaculates (2 ejaculates/pool) from four stallions. Results indicated that all LC concentrations produced significantly higher values (P<0.05) for kinematic variables (total [TM] and progressive motilities, curvilinear [VCL] and straight-line [VSL] velocity, and beat-cross frequency [BCF]), and the integrity of plasma/acrosome membranes (IPIA) compared to non-supplemented chilled sperm samples for up to 96 h with both extenders. Moreover, the use of 25 mM LC was more efficient (P<0.05) in preserving the post-chilled values of velocity, BCF, and IPIA for the long term than lower LC concentrations (1-10 mM). Post-thaw values of total motility, the amplitude of lateral head displacement (ALH), and IPIA were significantly improved (P<0.05) when INRA-Freeze extender was supplemented with 25 mM LC. In conclusion, supplementation of l-carnitine to skimmed milk-based extenders enhanced kinematic variables and protected the membrane integrity in chilled and frozen-thawed Peruvian Paso horse spermatozoa.

The multifaceted role of extracellular ATP in sperm function: From spermatogenesis to fertilization

Extracellular adenosine 5'-triphosphate (ATP) is a vital signaling molecule involved in various physiological processes within the body. In recent years, studies have revealed its significant role in male reproduction, particularly in sperm function. This review explores the multifaceted role of extracellular ATP in sperm function, from spermatogenesis to fertilization. We discuss the impact of extracellular ATP on spermatogenesis, sperm maturation and sperm-egg fusion, highlighting the complex regulatory mechanisms and potential clinical applications in the context of male infertility. By examining the latest research, we emphasize the crucial role of extracellular ATP in sperm function and propose future research directions to further.

Synergistic effect of extracellular adenosine triphosphate and quercetin on post-thaw quality and fertilization potential of Lohi ram sperm

This study determined the individual and combined effects of extracellular adenosine triphosphate (ATP) and quercetin (QUE) on the quality of post-thawed sperm and the fertilization potential of Lohi rams. In experiment 1, semen samples from four Lohi rams were pooled and extended with different concentrations of ATP or QUE (control; no ATP or QUE, 1 or 2 mM ATP and 10 or 20 μM QUE). In experiment 2, pooled semen samples were extended with various combinations of ATP and QUE (control; no ATP and QUE, 1 mM ATP + 10 μM QUE, 1 mM ATP + 20 μM QUE, 2 mM ATP + 10 μM QUE and 2 mM ATP + 20 μM QUE). All samples in both experiments were cryopreserved and analyzed for post-thawed sperm quality. In experiment 3, the best combination of ATP and QUE from experiment 2 was to extend semen, which was then used for laparoscopic insemination in estrus-synchronized ewes (n = 83). The results of experiment 1 showed that 1 mM ATP and 20 μM QUE treatments resulted in higher total motility, progressive motility, viability, plasma membrane intactness (PMI), and motion kinetics (VCL, VSL, VAP, LIN, and STR) compared to other treatments (p < 0.05). In experiment 2, the 1 mM ATP +10 μM QUE-treated group exhibited significantly higher total and progressive motility, PMI, and motion kinetics (VSL, VCL, VAP, STR, and BCF) compared to the control group (p < 0.05). In experiment 3, the fertilizing potential of sperms treated with 1 mM ATP +10 μM QUE was greater than that of untreated controls (58.1% vs. 27.5%, respectively, p-value = 0.012). In conclusion, the quality of post-thawed ram semen is enhanced when the extender is supplemented with extracellular 1 mM ATP and 20 μM QUE, whether used separately or in combination with 1 mM ATP and 10 μM QUE. Furthermore, the inclusion of 1 mM ATP and 10 μM QUE together in the extender significantly improves in vivo fertility in Lohi ram.

Purinergic Signaling in Spermatogenesis

Adenosine triphosphate (ATP) serves as the essential source of cellular energy. Over the last two decades, however, ATP has also attracted increasing interest as an extracellular signal that activates purinergic plasma membrane receptors of the P2 family. P2 receptors are divided into two types: ATP-gated nonselective cation channels (P2X) and G protein-coupled receptors (P2Y), the latter being activated by a broad range of purine and pyrimidine nucleotides (ATP, ADP, UTP, and UDP, among others). Purinergic signaling mechanisms are involved in numerous physiological events and pathophysiological conditions. Here, we address the growing body of evidence implicating purinergic signaling in male reproductive system functions. The life-long generation of fertile male germ cells is a highly complex, yet mechanistically poorly understood process. Given the relatively sparse innervation of the testis, spermatogenesis relies on both endocrine control and multi-directional paracrine communication. Therefore, a detailed understanding of such paracrine messengers, including ATP, is crucial to gain mechanistic insight into male reproduction.⁠.

Human Sperm Remain Motile After a Temporary Energy Restriction but do Not Undergo Capacitation-Related Events

To acquire fertilization competence, mammalian sperm must undergo several biochemical and physiological modifications known as capacitation. Despite its relevance, the metabolic pathways that regulate the capacitation-related events, including the development of hyperactivated motility, are still poorly described. Previous studies from our group have shown that temporary energy restriction in mouse sperm enhanced hyperactivation, in vitro fertilization, early embryo development and pregnancy rates after embryo transfer, and it improved intracytoplasmic sperm injection results in the bovine model. However, the effects of starvation and energy recovery protocols on human sperm function have not yet been established. In the present work, human sperm were incubated for different periods of time in medium containing glucose, pyruvate and lactate (NUTR) or devoid of nutrients for the starving condition (STRV). Sperm maintained in STRV displayed reduced percentages of motility and kinematic parameters compared to cells incubated in NUTR medium. Moreover, they did not undergo hyperactivation and showed reduced levels of ATP, cAMP and protein tyrosine phosphorylation. Similar to our results with mouse sperm, starvation induced increased intracellular Ca2+ concentrations. Starved human sperm were capable to continue moving for more than 27 h, but the incubation with a mitochondrial uncoupler or inhibitors of oxidative phosphorylation led to a complete motility loss. When exogenous nutrients were added back (sperm energy recovery (SER) treatment), hyperactivated motility was rescued and there was a rise in sperm ATP and cAMP levels in 1 min, with a decrease in intracellular Ca2+ concentration and no changes in sperm protein tyrosine phosphorylation. The finding that human sperm can remain motile for several hours under starvation due to mitochondrial use of endogenous metabolites implies that other metabolic pathways may play a role in sperm energy production. In addition, full recovery of motility and other capacitation parameters of human sperm after SER suggests that this treatment might be used to modulate human sperm fertilizing ability in vitro.

Sperm Cryopreservation in American Flamingo (Phoenicopterus Ruber): Influence of Cryoprotectants and Seminal Plasma Removal

The American flamingo is a useful model for the development of successful semen cryopreservation procedures to be applied to threatened related species from the family Phoenicopteridae, and to permit genetic material banking. Current study sought to develop effective sperm cryopreservation protocols through examining the influences of two permeating cryoprotectants and the seminal plasma removal. During two consecutive years (April), semen samples were collected and frozen from American flamingos. In the first year, the effect of two permeating cryoprotectants, DMA (dimethylacetamide) (6%) or Me2SO (dimethylsulphoxide) (8%), on frozen-thawed sperm variables were compared in 21 males. No differences were seen between DMA and Me2SO for sperm motility, sperm viability, and DNA fragmentation after thawing. In the second year, the role of seminal plasma on sperm cryoresistance was investigated in 31 flamingos. Sperm samples were cryopreserved with and without seminal plasma, using Me2SO (8%) as a cryoprotectant. The results showed that samples with seminal plasma had higher values than samples without seminal plasma for the following sperm variables: Straight line velocity (22.40 µm/s vs. 16.64 µm/s), wobble (75.83% vs. 69.40%), (p < 0.05), linearity (62.73% vs. 52.01%) and straightness (82.38% vs. 73.79%) (p < 0.01); but acrosome integrity was lower (55.56% vs. 66.88%) (p < 0.05). The cryoresistance ratio (CR) was greater in samples frozen with seminal plasma than without seminal plasma for CR-progressive motility (138.72 vs. 54.59), CR-curvilinear velocity (105.98 vs. 89.32), CR-straight line velocity (152.77 vs. 112.58), CR-average path velocity (122.48 vs. 98.12), CR-wobble (111.75 vs. 102.04) (p < 0.05), CR-linearity (139.41 vs. 113.18), and CR-straightness (124.02 vs. 109.97) (p < 0.01). This research demonstrated that there were not differences between Me2SO and DMA to successful freezing sperm of flamingos; seminal plasma removal did not provide a benefit for sperm cryopreservation.

Extracellular ATPs produced in seminal plasma exosomes regulate boar sperm motility and mitochondrial metabolism

Artificial insemination using diluted semen with reduced presence of seminal plasma has been applied worldwide. Sperm stored in seminal plasma rather than diluted or removed show improvement in survival and motility. However, the link between seminal plasma and sperm remains poorly understood. This study focuses on the effect of extracellular adenosine triphosphate (exATP) produced by boar seminal plasma exosomes on sperm motility, as well as the underlying molecular mechanisms. The seminal plasma exosomes had an average diameter of 86.6 nm and showed universal exosome markers, such as heat shock protein 70 (HSP70) and CD63. Production of net ATP increased when exosomes were incubated with glucose and partly inhibited by a glycolytic inhibitor such as iodoacetate. Fresh boar sperm incubated with exATP significantly increased sperm motility and reduced apoptotic rate. Ser21 phosphorylation of glycogen synthase kinase 3α (inactivation) also significantly increased, consistent with the increase in mitochondrial transmembrane potential in the exATP-treated sperm. Moreover, exATP treatment increased the intracellular ATP (inATP) concentration and decreased the ADP/ATP ratio in boar sperm. Lactate content in the incubation medium was decreased, whereas lactate dehydrogenase activity in sperm was increased. This finding suggested that exATP could prompt lactate to produce inATP in order to sustain motility. The combined results indicate that exATP produced in seminal plasma exosomes may finely modulate mitochondrial metabolism to control sperm motility. The results can provide insights into semen dilution and artificial insemination.

Comparing Human Sperm Quality Preserved at Two Different Temperatures; Effect of Trolox, Coenzyme Q10 and Extracellular Adenosine Triphosphate

Cooling method was proposed to maintain the sperm quality for several days. Nevertheless, during this procedure, sperm is encountered to "cold shock", and its quality decreases time-dependently. This study was designed to improve the in vitro sperm preservation methods. Thirty normal semen samples were examined in Shiraz, Iran, 2017. Fifteen samples were incubated at 22-27 °C and 15 samples were cooled moderately to 4 °C. Each sample was divided into five subgroups; control, solvent, 200 μM Trolox, 40 μM Coenzyme Q10, and 10 mM ATP. ATP was added only 15 minutes before the analysis. Assessments of motility parameters and sperm viability were done every 24 hours. Statistical analysis was performed using SPSS 16 software. The differences between two main groups and subgroups were compared by t test and one-way ANOVA, respectively. The effect of time was analyzed by repeated measurement test. Sperm motility and viability were the same in both groups until 24 hours, except the straight line velocity was greater in the cold group. Even after 48 hours, progressive motility and sperm velocity, but not viability, were still the same. The greatest reduction in progressive motility occurred on the second day; and after 72 hours, sperm quality was better preserved in 22-27 °C. Treatment with Trolox, coenzyme-Q10, and extracellular ATP did not have effect on sperm quality. Cold temperature is recommended for in-vitro sperm preservation up to 24 hours, and 22-27 °C is preferred for longer time storage. The sperm does not need antioxidant therapy for quality maintenance, but the extender media must be supplied with nutrients and antibiotics.

Molecular Basis of Human Sperm Capacitation

In the early 1950s, Austin and Chang independently described the changes that are required for the sperm to fertilize oocytes in vivo. These changes were originally grouped under name of “capacitation” and were the first step in the development of in vitro fertilization (IVF) in humans. Following these initial and fundamental findings, a remarkable number of observations led to characterization of the molecular steps behind this process. The discovery of certain sperm-specific molecules and the possibility to record ion currents through patch-clamp approaches helped to integrate the initial biochemical observation with the activity of ion channels. This is of particular importance in the male gamete due to the fact that sperm are transcriptionally inactive. Therefore, sperm must control all these changes that occur during their transit through the male and female reproductive tracts by complex signaling cascades that include post-translational modifications. This review is focused on the principal molecular mechanisms that govern human sperm capacitation with particular emphasis on comparing all the reported pieces of evidence with the mouse model.

Beneficial effect of extracellular adenosine 5'-triphosphate treatment on the Indochinese leopard (Panthera pardus delacouri) sperm quality after cryopreservation

The Indochinese leopard (Panthera pardus delacouri) population, included in CITES Appendix I, has been declining for decades. Proper gamete preservation condition is critical for breeding programme management using artificial insemination or in vitro fertilization (IVF). The present study aimed at investigating the impact of post-thawing treatment of leopard semen with extracellular adenosine 5'-triphosphate (ATPe) on sperm quality (including morphological traits and ability to fertilize an oocyte). Semen from six adult male leopards was collected by electroejaculation (one ejaculation per cat). After the evaluation of the fresh sample quality, the semen was cryopreserved (10 × 10⁶ cells per straw; two straws per cat). After thawing, the sperm sample from the first straw of each cat was divided into three aliquots: control (no ATPe), supplemented with 1.0 or 2.5 mM ATPe that were evaluated for sperm quality at 10, 30 min and 3 hr post-thawing. The sperm sample from the second straw, supplemented with 0, 1.0 or 2.5 mM ATPe for 30 min, was assessed for IVF with domestic cat oocytes. Sperm quality (all metrics) was negatively affected by the cryopreservation process (p ≤ .05). However, the percentage of sperm motility, level of progressive motility and percentage of plasma membrane integrity did not differ (p > .05) among post-thawing groups. The sperm mitochondrial membrane potential was enhanced (p ≤ .05) by ATPe treatment (1.0 and 2.5 mM; 10 min to 3 hr of incubation). Furthermore, incubation of ATPe (1.0 and 2.5 mM) for 30 min could promote sperm velocity patterns (curvilinear velocity; VCL and straight line velocity; VSL) (p ≤ .05). The percentage of pronuclear formation and cleaved embryos was increased (p ≤ .05) after 1.0 ATPe treatment (49.8 ± 2.8; 45.9 ± 1.5) compared to 0 mM (41.4 ± 3.3; 38.9 ± 0.5) whereas the number of sperm binding/oocyte did not significantly differ among groups. In summary, we suggest that ATPe activated the velocity of Indochinese leopard sperm motility that may lead to faster sperm/oocyte binding and sperm penetration (factors of successful embryo development).

New Approaches to Boar Semen Evaluation, Processing and Improvement

The improvement of boar reproductive performance may be the next frontier in reproductive management of swine herd in Unites States, facilitated by better understanding of boar sperm function and by the introduction of new advanced instrumentation in the andrology field. Objective single ejaculate evaluation and individual boar fertility prediction may be possible by introducing automated flow cytometric semen analysis with vital stains (e.g. acrosomal integrity and mito-potential), DNA fragmentation analysis and biomarkers (ubiquitin, PAWP, ALOX15, aggresome) associated with normal or defective sperm phenotypes. Measurement of sperm-produced reactive oxygen species (ROS) is a helpful indicator of normal semen sample. Semen ROS levels could be managed by the addition of ROS-scavenging antioxidants. Alternative energy regeneration substrates and sperm stimulants such as inorganic pyrophosphate and caffeine could increase sperm lifespan in extended semen and within the female reproductive system. Such technology could be combined with timed sperm release in the female reproductive system after artificial insemination. Sperm phenotype analysis by the image-based flow cytometry will go hand in hand with the advancement of swine genomics, linking aberrant sperm phenotype to the fertility influencing gene polymorphisms. Finally, poor-quality ejaculates could be rescued and acceptable ejaculates improved by semen purification methods such as the nanoparticle-based semen purification and magnetic-activated sperm sorting. Altogether, these scientific and technological advances could benefit swine industry, provided that the challenges of new technology adoption, dissemination and cost reduction are met.

Involvement of a P2X7 Receptor in the Acrosome Reaction Induced by ATP in Rat Spermatozoa

The acrosome reaction (AR) is the exocytosis of the acrosomal vesicle in response to different physiological and non-physiological stimuli. Particularly in mammals, the AR is needed for sperm to fuse with the oocyte plasma membrane, and it occurs only in capacitated sperm. Previous evidence in the literature indicates that extracellular ATP induces the AR in capacitated human and bovine spermatozoa, but its receptor has not yet been identified. The aim of this work was to define a putative ATP receptor in rat spermatozoa using pharmacological and biochemical approaches. We found that ATP induced the AR only in capacitated rat spermatozoa, which was inhibited in the presence of two general inhibitors of ATP receptors (P2 receptors), Suramin, and oxidized ATP (oATP), and one inhibitor of P2X receptor (pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid [PPADS]). In addition, the AR induced by ATP in capacitated rat spermatozoa was inhibited by brilliant blue-G (BB-G) and 17-β-oestradiol, two blockers of P2X7 receptors. Moreover, the ATP analog 2'(3')-O-(4-benzoylbenzoyl) ATP (BzATP) was almost 500 times more potent than ATP to induce the AR, which agrees with the pharmacology of a P2X7 receptor. Here, we show the presence of P2X7 receptor by Western blot and its localization in the tail and acrosome by indirect immunofluorescence. Finally, we quantify the presence of ATP in the rat oviduct during the estrous cycle. We found that the ATP concentration within the lumen of the oviduct is similar to those required to induce acrosome reaction, which agree with its role during in vivo fertilization. Therefore, our results strongly suggest that ATP induces the AR in capacitated rat spermatozoa through a P2X7 receptor, which may be functional during in vivo fertilization.

Effect of extracellular adenosine 5'-triphosphate on cryopreserved epididymal cat sperm intracellular ATP concentration, sperm quality, and in vitro fertilizing ability

Intracellular adenosine 5'-triphosphate (ATP) is essential for supporting sperm function in the fertilization process. During cryopreservation, damage of sperm mitochondrial membrane usually leads to compromised production of intracellular ATP. Recently, extracellular ATP (ATPe) was introduced as a potent activator of sperm motility and fertilizing ability. This study aimed to evaluate (1) levels of intracellular ATP in frozen-thawed epididymal cat sperm after incubation with ATPe and (2) effects of ATPe on epididymal cat sperm parameters after freezing and thawing. Eighteen male cats were included. For each replicate, epididymal sperm from two cats were pooled to one sample (N = 9). Each pooled sample was cryopreserved with the Tris-egg yolk extender into three straws. After thawing, the first and second straws were incubated with 0-, 1.0-, or 2.5-mM ATPe for 10 minutes and evaluated for sperm quality at 10 minutes, 1, 3, and 6 hours after thawing and fertilizing ability. The third straw was evaluated for intracellular ATP concentration in control and with 2.5-mM ATPe treatment. Higher concentration of intracellular sperm ATP was observed in the samples treated with 2.5-mM ATPe compared to the controls (0.339 ± 0.06 μg/2 × 10(6) sperm vs. 0.002 ± 0.003 μg/2 × 10(6) sperm, P ≤ 0.05). In addition, incubation with 2.5-mM ATPe for 10 minutes promoted sperm motility (56.7 ± 5.0 vs. 53.3 ± 4.4%, P ≤ 0.05) and progressive motility (3.1 ± 0.2 vs. 2.8 ± 0.4, P ≤ 0.05), mitochondrial membrane potential (36.4 ± 5.5 vs. 28.7 ± 4.8%, P ≤ 0.05), and blastocyst rate (36.1 ± 7.0 and 28.8 ± 7.4%, P ≤ 0.05) compared with the controls. In contrast, ATPe remarkably interfered acrosome integrity after 6 hours of postthawed incubation. In sum, the present finding that optimal incubation time of postthaw epididymal cat sperm under proper ATPe condition might constitute a rationale for the studies on other endangered wild felids regarding sperm quality and embryo development.

Nucleoside triphosphate diphosphohydrolase-1 ectonucleotidase is required for normal vas deferens contraction and male fertility through maintaining P2X1 receptor function

In this work, we report that Entpd1(-/-) mice, deficient for the ectonucleotidase nucleoside triphosphate diphosphohydrolase-1 (NTPDase1), produce smaller litters (27% reduction) compared with wild-type C57BL6 animals. This deficit is linked to reduced in vivo oocyte fertilization by Entpd1(-/-) males (61 ± 11% versus 88 ± 7% for Entpd1(+/+)). Normal epididymal sperm count, spermatozoa morphology, capacitation, and motility and reduced ejaculated sperm number (2.4 ± 0.5 versus 3.7 ± 0.4 million for Entpd1(+/+)) pointed to vas deferens dysfunction. NTPDase1 was localized by immunofluorescence in the tunica muscularis of the vas deferens. Its absence resulted in a major ATP hydrolysis deficiency, as observed in situ by histochemistry and in primary smooth muscle cell cultures. In vitro, Entpd1(-/-) vas deferens displayed an exacerbated contraction to ATP, a diminished response to its non-hydrolysable analog αβMeATP, and a reduced contraction to electrical field stimulation, suggesting altered P2X1 receptor function with a propensity to desensitize. This functional alteration was accompanied by a 3-fold decrease in P2X1 protein expression in Entpd1(-/-) vas deferens with no variation in mRNA levels. Accordingly, exogenous nucleotidase activity was required to fully preserve P2X1 receptor activation by ATP in vitro. Our study demonstrates that NTPDase1 is required to maintain normal P2X1 receptor functionality in the vas deferens and that its absence leads to impaired peristalsis, reduced spermatozoa concentration in the semen, and, eventually, reduced fertility. This suggests that alteration of NTPDase1 activity affects ejaculation efficacy and male fertility. This work may contribute to unveil a cause of infertility and open new therapeutic potentials.

Purinergic signalling in the reproductive system in health and disease

There are multiple roles for purinergic signalling in both male and female reproductive organs. ATP, released as a cotransmitter with noradrenaline from sympathetic nerves, contracts smooth muscle via P2X1 receptors in vas deferens, seminal vesicles, prostate and uterus, as well as in blood vessels. Male infertility occurs in P2X1 receptor knockout mice. Both short- and long-term trophic purinergic signalling occurs in reproductive organs. Purinergic signalling is involved in hormone secretion, penile erection, sperm motility and capacitation, and mucous production. Changes in purinoceptor expression occur in pathophysiological conditions, including pre-eclampsia, cancer and pain.

Signaling in sperm: toward a molecular understanding of the acquisition of sperm motility in the mouse epididymis

Sperm motility encompasses a wide range of events involving epididymal maturation and activation of biochemical pathways, most notably cyclic AMP (cAMP)-protein kinase A (PKA) activation. Following the discovery of guanine-nucleotide exchange factors (RAPGEFs), also known as exchange proteins activated by cAMP, we investigated the separate roles of PKA and RAPGEFs in sperm motility. RT-PCR showed the presence of Rapgef3, Rapgef4, and Rapgef5, as well as several known RAPGEF partner mRNAs, in spermatogenic cells. However, Rapgef3 and Rapgef4 appeared to be less abundant in condensing spermatids versus pachytene spermatocytes. Similarly, many of these proteins were detected by immunoblotting. RAPGEF5 was detected in germ cells and murine epididymal sperm. Indirect immunofluorescence localized SGK1, SGK3, AKT1 pT(308), and RAPGEF5 to the acrosome, while PDPK1 was found in the postacrosomal region. SGK3 was present throughout the tail, while PDPK1 and AKT1 pT(308) were in the midpiece. When motility was assessed in demembranated cauda epididymal sperm, addition of ATP and the selective ligand for RAPGEFs, 8-pCPT-2'-O-Me-cAMP, resulted in motility, but the sperm were unable to undergo hyperactivated-like motility. In contrast, when demembranated cauda epididymal sperm were incubated with ATP plus dibutyryl cAMP, sperm became motile and progressed to hyperactivated-like motility. However, no significant difference was observed when intact sperm were examined. GSK3 phosphorylation was altered in the presence of H89, a PKA inhibitor. Significantly, intact caput epididymal sperm became motile when incubated in the presence of extracellular ATP. These results provide evidence for a new pathway involved in endowing sperm with the capacity to swim.

Nutlin-3a decreases male fertility via UQCRC2

Ubiquinol-cytochrome-c reductase core protein 2 (UQCRC2) is a component of ubiquinol-cytochrome c reductase complex that is known to correlate with male fertility via spermatogenesis. Simultaneously, nutlin-3a is a small molecule antagonist of mouse double minute 2 repressor (MDM2), activate p53 and induce apoptosis responsible for spermatogenesis. To date, however there are no known effects of nutlin-3a on reproduction. Therefore, present study was designed to investigate the effect of nutlin-3a on male fertility via UQCRC2. In this in vitro trial with mice spermatozoa, we utilized CASA, CTC staining, ATP assay, western blotting, and IVF to measure the main study outcome. The short-term exposure of spermatozoa in nutlin-3a decreases sperm motion kinematics, intracellular ATP production, capacitation, the acrosome reaction, UQCRC2, and tyrosine phosphorylation (TYP) of sperm proteins in a dose-dependent manner. Notably, the decreased UQCRC2 and TYP were associated with reduced sperm kinematics, ATP production, and capacitation, which ultimately led to adverse effects on male fertility such as poor fertilization rates and embryo development. Thus, nutlin-3a may be considered as a potential male contraceptive agent due to its ability to decrease fertility secondary to changes in overall sperm physiology and embryonic development. However, the results of this preliminary study have to be confirmed by additional independent trial.

Ecto-nucleotidases distribution in human cyclic and postmenopausic endometrium

Extracellular ATP and its hydrolysis product, adenosine, acting through specific receptors collectively named purinergic receptors, regulate female fertility by influencing the endometrial fluid microenvironment. There are four major groups of ecto-nucleotidases that control the levels of extracellular ATP and adenosine and thus their availability at purinergic receptors: ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases), ecto-nucleotide pyrophosphatase/phospho-diesterases (E-NPPs), ecto-5'-nucleotidase (5'NT), and alkaline phosphatases (APs). The aim of the present work is to characterize the expression and distribution of ecto-nucleotidases in human endometrium along the menstrual cycle and after menopause, to evaluate their potential utility as fertility markers. We examined proliferative, secretory and atrophic endometria from women without endometrial pathology undergoing hysterectomy. We show that the ecto-nucleotidases are mainly present at endometrial epithelia, both luminal and glandular, and that their expression fluctuates along the cycle and also changes after menopause. An important result was identifying NPP3 as a new biological marker of tubal metaplasia. Our results emphasize the relevance of the study of purinergic signaling in human fertility.

ATP secretion in the male reproductive tract: essential role of CFTR

Extracellular ATP is essential for the function of the epididymis and spermatozoa, but ATP release in the epididymis remains uncharacterized. We investigated here whether epithelial cells release ATP into the lumen of the epididymis, and we examined the role of the cystic fibrosis transmembrane conductance regulator (CFTR), a Cl(-) and HCO(3)(-) conducting ion channel known to be associated with male fertility, in this process. Immunofluorescence labelling of mouse cauda epididymidis showed expression of CFTR in principal cells but not in other epithelial cells. CFTR mRNA was not detectable in clear cells isolated by fluorescence-activated cell sorting (FACS) from B1-EGFP mice, which express enhanced green fluorescent protein (EGFP) exclusively in these cells in the epididymis. ATP release was detected from the mouse epididymal principal cell line (DC2) and increased by adrenaline and forskolin. Inhibition of CFTR with CFTR(inh172) and transfection with CFTR-specific siRNAs in DC2 cells reduced basal and forskolin-activated ATP release. CFTR-dependent ATP release was also observed in primary cultures of mouse epididymal epithelial cells. In addition, steady-state ATP release was detected in vivo in mice, by measuring ATP concentration in a solution perfused through the lumen of the cauda epididymidis tubule and collected by cannulation of the vas deferens. Luminal CFTR(inh172) reduced the ATP concentration detected in the perfusate. This study shows that CFTR is involved in the regulation of ATP release from principal cells in the cauda epididymidis. Given that mutations in CFTR are a leading cause of male infertility, we propose that defective ATP signalling in the epididymis might contribute to dysfunction of the male reproductive tract associated with these mutations.

Identification of the inorganic pyrophosphate metabolizing, ATP substituting pathway in mammalian spermatozoa

Inorganic pyrophosphate (PPi) is generated by ATP hydrolysis in the cells and also present in extracellular matrix, cartilage and bodily fluids. Fueling an alternative pathway for energy production in cells, PPi is hydrolyzed by inorganic pyrophosphatase (PPA1) in a highly exergonic reaction that can under certain conditions substitute for ATP-derived energy. Recombinant PPA1 is used for energy-regeneration in the cell-free systems used to study the zymology of ATP-dependent ubiquitin-proteasome system, including the role of sperm-borne proteasomes in mammalian fertilization. Inspired by an observation of reduced in vitro fertilization (IVF) rates in the presence of external, recombinant PPA1, this study reveals, for the first time, the presence of PPi, PPA1 and PPi transporter, progressive ankylosis protein ANKH in mammalian spermatozoa. Addition of PPi during porcine IVF increased fertilization rates significantly and in a dose-dependent manner. Fluorometric assay detected high levels of PPi in porcine seminal plasma, oviductal fluid and spermatozoa. Immunofluorescence detected PPA1 in the postacrosomal sheath (PAS) and connecting piece of boar spermatozoa; ANKH was present in the sperm head PAS and equatorial segment. Both ANKH and PPA1 were also detected in human and mouse spermatozoa, and in porcine spermatids. Higher proteasomal-proteolytic activity, indispensable for fertilization, was measured in spermatozoa preserved with PPi. The identification of an alternative, PPi dependent pathway for ATP production in spermatozoa elevates our understanding of sperm physiology and sets the stage for the improvement of semen extenders, storage media and IVF media for animal biotechnology and human assisted reproductive therapies.

In vitro effects of α-tocopherol on teratozoospermic semen samples

A strong positive correlation exists between teratozoospermia and reactive oxygen species production, which in turn has negative effects on their in vitro fertilisation outcome. Our aim of this study was to determine potential protective effects of α-tocopherol on teratozoospermia motility, viability, acrosome reaction and DNA integrity after 1-h in vitro incubation. Teratozoospermic semen samples were obtained from 15 volunteers aged between 20 and 30 years after 3-5 days of sexual abstinence. Samples were washed, centrifuged and incubated in 37 °C and 5% CO(2) until sperm swimmed-up. Spermatozoa were counted in the supernatant and divided into four groups, each contained 2 × 10(6) sperm/ml(-1). Groups one to four were incubated for 1 h with Ham's F-10 solution as control group, 10 μm A23187, 40 μmα-tocopherol and 10 μm A23187 + 40 μmα-tocopherol respectively. The results indicated that α-tocopherol has ability to enhance teratozoospermia viability and motility, while there were no ameliorative effects on acrosome reaction and DNA fragmentation. A23187 induced acrosome reaction in teratozoospermia and α-tocopherol significantly diminished this effect. In conclusion, although α-tocopherol could improve teratozoospermia motility and viability, its effects on DNA integrity and acrosome reaction ability as supplementation IVF culture media are not obvious.

Treatment of sperm with extracellular adenosine 5'-triphosphate improves the in vitro fertility rate of inbred and genetically modified mice with low fertility

In vitro fertilization (IVF) is one of the most important techniques used for assisted reproduction in mouse colony management. As with natural mating, where mice have varying fertility indices, fertility rates of genetically modified (GM) [transgenic (Tg), knock out (KO) and congenic (Cg)] mice are influenced by their genetic background. Lines of GM mice that have poor fertility have a concomitant poor IVF outcome. Treatment of mouse sperm with extracellular adenosine 5'-triphosphate (ATPe) enhanced in vitro fertilization rates in outbred and hybrid mice. The objective of this study was to analyze the effects of using extracellular adenosine 5'-triphosphate-treated sperm for IVF of inbred wild type, and genetically modified mouse lines, for which standard IVF did not work well. The IVF was performed using the GM mice on C57BL/10SnJ, C57BL/6J, BALB/cJ and NFS/N background strains and wild type (WT) mice such as C57BL/6N, BALB/cAnN, and B6129SF1 strains. Oocytes from superovulated females were fertilized in vitro with sperm from the same background strain, and either treated or not treated with ATPe. The ATPe treatment enhanced IVF outcome in most of the GM and some WT strains, as indicated by the percentage of embryos that progressed to the two-cell stage. There was no marked difference between ATPe treated and control groups for the development rate of two-cell embryos to blastocysts in culture, or in the number of pups born after transfer of two-cell embryos into recipient females. The observed improvement of the IVF results following ATPe treatment of transgenic and KO mouse sperm were a potential solution for improving the outcome of assisted reproduction techniques used for rederivation or for gamete banking.

Comparative cryopreservation of avian spermatozoa: benefits of non-permeating osmoprotectants and ATP on turkey and crane sperm cryosurvival

A comparative approach was used to evaluate the cryosurvival of turkey and crane sperm frozen in a dimethylacetamide (DMA) cryodiluent supplemented with osmoprotectants and ATP. A range (6-26%) of DMA concentrations was used alone or in combination with ATP (30, 60 or 118mM) or one of the following osmoprotectants: (1) sucrose (turkey, 8.0%; crane, 5.0%); (2) 5.0% sucrose and 5.0% trehalose; or (3) betaine hydrochloride (0.1, 0.2 or 0.4mM). The viability of thawed sperm was assessed using the nigrosin-eosin stain and sperm motility was determined using the hanging-drop technique. For semen frozen only with DMA, post-thaw sperm motility was greatest (P<0.05) for the 6.0%, 10.0% and 18% concentrations, regardless of species. Turkey sperm frozen with the sucrose/trehalose combination had greater (P<0.05) post-thaw motility for all DMA treatments compared to DMA alone. The lowest concentration of the osmoprotectant betaine hydrochloride substantially improved turkey sperm viability post-thaw in all treatments compared to DMA alone (P<0.05). The post-thaw motility of crane sperm was improved (P<0.05) with a combination of 18.0%, 24.0% or 26.0% DMA and 30mM ATP. Moreover, in the presence of osmoprotectants, crane sperm motility decreased as the osmoprotectant concentration increased. The lowest concentration of ATP also improved crane sperm viability post-thaw, especially for DMA concentrations 18% or greater. The combination of sucrose and trehalose improved (P<0.05) crane sperm viability only with 6% and 10% DMA. These data affirm that there are avian-specific differences in sperm survival after cryopreservation and suggest that post-thaw survival can be enhanced by including species-based osmoprotectant/ATP combinations in a cryodiluent where DMA is the cryoprotectant.

Localization of plasma membrane bound NTPDases in the murine reproductive tract

Extracellular nucleotides might influence aspects of the biology of reproduction in that ATP affects smooth muscle contraction, participates in steroidogenesis and spermatogenesis, and also regulates transepithelial transport, as in oviducts. Activation of cellular nucleotide purinergic receptors is influenced by four plasma membrane-bound members of the ectonucleoside triphosphate diphosphohydrolase (E-NTPDase) family, namely NTPDase1, NTPDase2, NTPDase3, and NTPDase8 that differ in their ecto-enzymatic properties. The purpose of this study was to characterize the expression profile of the membrane-bound NTPDases in the murine female and male reproductive tracts by immunological techniques (immunolabelling, Western blotting) and by enzymatic assays, in situ and on tissue homogenates. Other than the expected expression on vascular endothelial and smooth muscle cells, NTPDase1 was also detected in Sertoli cells and interstitial macrophages in testes, in ovarian granulosa cells, and in apical cells from epididymal epithelium. NTPDase2 was largely expressed by cells in the connective tissue; NTPDase3 in secretory epithelia, and finally, NTPDase8 was not detected in any of the tissues studied here. In addition, NTPDase6 was putatively detected in Golgi-phase acrosome vesicles of round spermatids. This descriptive study suggests close regulation of extracellular nucleotide levels in the genital tract by NTPDases that may impact specific biological functions.

Extracellular adenosine 5'-triphosphate alters motility and improves the fertilizing capability of mouse sperm

Extracellular adenosine 5'-triphosphate (ATPe) treatment of human sperm has been implicated in improving in vitro fertilization (IVF) results. We used the mouse model to investigate mechanisms of action of ATPe on sperm. ATPe treatment significantly enhanced IVF success as indicated by both rate of pronuclear formation and percentage cleavage to the 2-cell stage. However, ATPe did not increase the percentage of sperm undergoing spontaneous acrosomal exocytosis nor change the pattern of protein tyrosine phosphorylation normally observed in capacitated sperm. ATPe altered sperm motility parameters; in particular, both noncapacitated and capacitated sperm swam faster and straighter. The percentage of hyperactivated sperm did not increase in capacitated ATPe-treated sperm compared to control sperm. ATPe induced a rapid increase in the level of intracellular calcium that was inhibited by two distinct P2 purinergic receptor inhibitors, confirming that these receptors have an ionotropic role in sperm function. The observed motility changes likely explain, in part, the improved fertilizing capability when ATPe-treated sperm were used in IVF procedures and suggest a mechanism by which ATPe treatment may be beneficial for artificial reproductive techniques.