Effects of taurine and hypotaurine supplementation and ionophore concentrations on post-thaw acrosome reaction of dog spermatozoa

A Combination of Taurine and Caffeine in Stallion Semen Extender Positively Affects the Spermatozoa Parameters

This study was aimed to determine the impact of different taurine and caffeine combinations on the motility, viability, and oxidative markers of chilled stallion spermatozoa. Each stallion semen sample was diluted in a ratio of 1:2, with various taurine and caffeine concentrations (2.5-7.5 mg/mL taurine + 0.625-1.25 mg/mL caffeine) dissolved in a conventional extender. The control samples (CON) were prepared by diluting ejaculate only using the conventional extender. The motility was analyzed using a CASA system at different time intervals (0, 6, 12, 24, and 30 h) and the viability was evaluated using a mitochondrial toxicity test (MTT) performed at the end of the incubation at 5 °C. The liquid part of experimental samples was separated by centrifugation after 30 h of incubation and underwent the evaluation of oxidative stress via the quantification of markers ferric reducing ability of plasma (FRAP) and total oxidant status (TOS). The samples that were treated with a combination of taurine and caffeine significantly improved the motility parameters, mainly after 12, 24, and 30 h of incubation. Samples extended with combination of taurine and caffeine neither compromise viability nor alterations of redox status. The results of this study describe the combination of taurine and caffeine as an optimal supplement for improving the quality of stallion semen during chilled storage.

The role of taurine in male reproduction: Physiology, pathology and toxicology

Taurine, a sulfur-containing amino acid, has a wide range of biological effects, such as bile salt formation, osmotic regulation, oxidative stress inhibition, immunomodulation and neuromodulation. Taurine has been proved to be synthesized and abundant in male reproductive organs. Recently, accumulating data showed that taurine has a potential protective effect on reproductive function of male animals. In physiology, taurine can promote the endocrine function of the hypothalamus-pituitary-testis (HPT) axis, testicular tissue development, spermatogenesis and maturation, delay the aging of testicular structure and function, maintain the homeostasis of the testicular environment, and enhance sexual ability. In pathology, taurine supplement may be beneficial to alleviate pathological damage of male reproductive system, including oxidative damage of sperm preservation in vitro, testicular reperfusion injury and diabetes -induced reproductive complications. In addition, taurine acts as a protective agent against toxic damage to the male reproductive system by exogenous substances (e.g., therapeutic drugs, environmental pollutants, radiation). Related mechanisms include reduced oxidative stress, increased antioxidant capacity, inhibited inflammation and apoptosis, restored the secretory activity of the HPT axis, reduced chromosomal variation, enhanced sperm mitochondrial energy metabolism, cell membrane stabilization effect, etc. Therefore, this article reviewed the protective effect of taurine on male reproductive function and its detailed mechanism, in order to provide reference for further research and clinical application.

Taurine as a Natural Antioxidant: From Direct Antioxidant Effects to Protective Action in Various Toxicological Models

Natural antioxidants have received tremendous attention over the last 3 decades. At the same time, the attitude to free radicals is slowly changing, and their signalling role in adaptation to stress has recently received a lot of attention. Among many different antioxidants in the body, taurine (Tau), a sulphur-containing non-proteinogenic β-amino acid, is shown to have a special place as an important natural modulator of the antioxidant defence networks. Indeed, Tau is synthesised in most mammals and birds, and the Tau requirement is met by both synthesis and food/feed supply. From the analysis of recent data, it could be concluded that the direct antioxidant effect of Tau due to scavenging free radicals is limited and could be expected only in a few mammalian/avian tissues (e.g., heart and eye) with comparatively high (>15-20 mM) Tau concentrations. The stabilising effects of Tau on mitochondria, a prime site of free radical formation, are characterised and deserve more attention. Tau deficiency has been shown to compromise the electron transport chain in mitochondria and significantly increase free radical production. It seems likely that by maintaining the optimal Tau status of mitochondria, it is possible to control free radical production. Tau's antioxidant protective action is of great importance in various stress conditions in human life, and is related to commercial animal and poultry production. In various in vitro and in vivo toxicological models, Tau showed AO protective effects. The membrane-stabilizing effects, inhibiting effects on ROS-producing enzymes, as well as the indirect AO effects of Tau via redox balance maintenance associated with the modulation of various transcription factors (e.g., Nrf2 and NF-κB) and vitagenes could also contribute to its protective action in stress conditions, and thus deserve more attention.

Beneficial effects of hypotaurine supplementation in preparation and freezing media on human sperm cryo-capacitation and DNA quality

BACKGROUND

Although widely used, slow freezing considerably modifies the functions of human spermatozoa. Cryopreservation induces nuclear sperm alterations and cryo-capacitation, reducing the chances of pregnancy. Hypotaurine is naturally present in the male and female genital tracts and has capacitating, osmolytic and anti-oxidant properties. The analysis were performed on surplus semen of men with normal (n = 19) or abnormal (n = 14) sperm parameters. Spermatozoa were selected by density gradient centrifugation before slow freezing. For each sample, these steps were performed in parallel with ("H+" arm) or without ("H-" arm) hypotaurine supplementation. After thawing, we measured total and progressive mobility, vitality, acrosome integrity, markers of capacitation signaling pathway and nuclear quality. For the latter, we focused on sperm chromatin packaging, DNA fragmentation and the presence of vacuoles in the sperm nucleus.

RESULTS

Post-thaw spermatozoa selected and frozen in the presence of hypotaurine had a higher vitality (+ 16.7%, p < 0.001), progressive and total motility (+ 39.9% and +  21.6% respectively, p < 0.005) than spermatozoa from the control "H-" arm. Hypotaurine also reduced the non-specific phosphorylation of the capacitation protein markers P110 and P80 (p < 0.01), indicating a decrease in cryo-capacitation. Hypotaurine supplementation reduced chromatin decondensation, measured by chromomycin A3 (- 16.1%, p < 0.05), DNA fragmentation (- 18.7%, p < 0.05) and nuclear vacuolization (- 20.8%, p < 0.05).

CONCLUSION

Our study is the first to demonstrate beneficial effects of hypotaurine supplementation in preparation and freezing procedures on human spermatozoa sperm fertilization capacity and nucleus quality. Hypotaurine supplementation limited cryo-capacitation, increased the proportion of live and progressively motile spermatozoa and reduces the percentage of spermatozoa showing chromatin decondensation, DNA fragmentation and nuclear vacuolation.

TRIAL REGISTRATION

Clinical Trial, NCT04011813 . Registered 19 May 2019 - Retrospectively registered.

Overview on the Antioxidants, Egg Yolk Alternatives, and Mesenchymal Stem Cells and Derivatives Used in Canine Sperm Cryopreservation

Sperm cryopreservation is a widely used assisted reproductive technology for canine species. The long-term storage of dog sperm is effective for the breeding of dogs living far apart, scheduling the time of artificial insemination that suits the female, and preventing diseases of the reproductive tract. However, spermatozoa functions are impaired during the freeze-thaw processes, which may decrease reproductive performance. Numerous attempts have been made to restore such impairments, including the use of cryoprotectants to prevent the damage caused by ice crystal formation, and supplementation of antioxidants to reduce reactive oxygen species generation due to osmotic stress during the procedure. Egg yolk derivatives, antioxidants, and, more recently, mesenchymal stem cells (MSCs) and their derivatives have been proposed in this research field. This review article will summarize the current literature available on the topic.

The Effect of L-Carnitine, Hypotaurine, and Taurine Supplementation on the Quality of Cryopreserved Chicken Semen

The objective of this study was to investigate the effect of L-carnitine (LC), hypotaurine (HT), and taurine (T) on the quality of frozen-thawed chicken semen. Pooled semen samples were divided into seven aliquots (control, 1 mM LC, 5 mM LC, 1 mM HT, 10 mM HT, 1 mM T, and 10 mM T) and subjected to cryopreservation. Postthaw sperm motility was determined by IVOS system and sperm characteristics were assessed with fluorochromes and flow cytometry. The highest sperm motility and the highest percentage of viable sperm were in the HT1 group (P < 0.01 and P < 0.05) following cryopreservation. After thawing, we observed a higher percentage of sperm without apoptosis and membrane reorganization changes in the LC1 and T1 group when compared to the control (P < 0.05). There was a higher percentage of live sperm without lipid peroxidation (LPO) in all treatments (P < 0.01; P < 0.05), when compared to the control group. The percentage of sperm with high mitochondrial potential significantly increased with LC1, T1, and T10 (P < 0.05). Supplementation of the diluent with LC1, LC5, and T1 significantly (P < 0.05) reduced DNA susceptibility to fragmentation, compared to the control and HT1 groups. These results indicate that the addition of examined antioxidants improves the quality of cryopreserved chicken semen.

Density gradient centrifugation prior to cryopreservation and hypotaurine supplementation improve post-thaw quality of sperm from infertile men with oligoasthenoteratozoospermia

STUDY QUESTION

Can selection of spermatozoa by density gradient centrifugation prior to cryopreservation and/or hypotaurine supplementation improve the post-thaw quality of sperm from infertile men with oligoasthenoteratozoospermia?

SUMMARY ANSWER

Sperm selection by density gradient centrifugation before freezing and supplementation of the media by hypotaurine is beneficial for the cryopreservation of semen samples of patients with oligoasthenoteratozoospermia.

WHAT IS KNOWN ALREADY

Sperm from men with oligoasthenoteratozoospermia are more susceptible than normal to cryoinjury. Density gradient centrifugation before sperm freezing may allow the selection of a subpopulation of spermatozoa more resistant to cryopreservation. Hypotaurine is an antioxidant with a protective effect on sperm functions.

STUDY DESIGN, SIZE, DURATION

The experiment was carried out according to a factorial design involving two binary factors resulting in four treatment combinations which were randomly allocated in oligoasthenoteratozoospermia sperm samples from 64 patients recruited between January 2009 and June 2010.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Semen was provided by 64 men undergoing evaluation for infertility at the Centre for Reproductive Medicine of the University Hospital in Clermont-Ferrand, France, between January 2009 and June 2010. Four treatment combinations were tested: sperm freezing before selection without (F-S/H-; n = 16) and with hypotaurine supplementation (F-S/H+; n = 16); sperm selection before freezing without (S-F/H-; n = 16) and with hypotaurine supplementation (S-F/H+; n = 16). Measurements of sperm recovery rates and markers of apoptosis (externalization of phosphatidylserine (PS), mitochondrial membrane potential and DNA fragmentation) were compared in recovered spermatozoa after each procedure.

MAIN RESULTS AND THE ROLE OF CHANCE

Higher recovery rates of progressive and total motile spermatozoa were observed when sperm selection was performed before freezing (P < 0.05). The protective effect of hypotaurine was only observed on the percentage of live spermatozoa with PS externalization among total live spermatozoa (AN+ PI-/((AN+ PI-) + (AN- PI-)) when the sperm selection by density gradient centrifugation was performed before freezing (S-F/H+ versus S-F/H-: 6.8 ± 1.09 versus 11.8 ± 2.03%, P = 0.04). The percentage of mitochondrial membrane potential (DiOC6(3) (high)) spermatozoa was higher (P = 0.001) when sperm selection was done before freezing compared with procedures in which sperm selection was done after sperm freezing with (S-F/H+ versus F-S/H+: 58.1 ± 3.50 versus 46.7 ± 5.48%) or without (S-F/H- versus F-S/H-: 57.0 ± 5.18 versus 35.4 ± 4.99%) hypotaurine supplementation. The percentages of TUNEL+ spermatozoa were significantly lower (P = 0.001) when sperm selection was done before sperm freezing compared with procedures in which sperm selection was done after sperm freezing with (S-F/H+ versus F-S/H+: 38.6 ± 9.59 versus 55.7 ± 5.88%) or without hypotaurine supplementation (S-F/H- versus F-S/H-: 37.2 ± 7.91 versus 71.0 ± 5.66%).

LIMITATIONS, REASONS FOR CAUTION

The ICSI outcomes were not assessed and the fertility of the spermatozoa remains unknown.

WIDER IMPLICATIONS OF THE FINDINGS

Sperm selection by density gradient centrifugation before freezing and hypotaurine supplementation could improve the cryopreservation of sperm from oligoasthenoteratozoospermic men and make a larger number of functional spermatozoa available for ICSI.

STUDY FUNDING/COMPETING INTERETS(S)

This work was supported by a hospital grant (Projet Hospitalier Recherche Clinique, CHU Clermont Ferrand, France). None of the authors has any conflict of interest to declare.

Assessment of intracellular Ca2+, cAMP and 1,2-diacylglycerol in cryopreserved buffalo (Bubalus bubalis) spermatozoa on supplementation of taurine and trehalose in the extender

In mammalian spermatozoa, intracellular calcium plays a major role in sperm functions like motility and capacitation. Cryopreservation-induced modifications to sperm membrane result in an influx of intracellular calcium affecting calcium-dependent intracellular signalling pathways. Intracellular calcium activates adenyl cyclase to produce cAMP that activates phospholipase A(2) (PLA(2) ) and phospholipase C (PLC) generating lysophosphatidyl choline, 1,2-diacylglycerol (DAG) and IP(3) , acting as intracellular secondary messengers required for sperm capacitation. Present study was designed to determine levels of intracellular calcium, cAMP and DAG in fresh and frozen-thawed buffalo spermatozoa cryopreserved in the presence and absence of taurine or trehalose. A total number of nine ejaculates from three randomly chosen buffalo bulls were cryopreserved in Tris-based egg yolk extender and thawed in warm water at 37°C. The cAMP was measured by enzyme immuno assay, and intracellular calcium was quantified using fluorescent dye FURA 2-AM. Total lipid was extracted from spermatozoa, and DAG was estimated using thin layer chromatography followed by spectrophotometric analysis. Intracellular calcium, cAMP and DAG levels in spermatozoa were significantly (p < 0.01) increased following cryopreservation as compared to fresh ejaculate. Addition of taurine or trehalose to the freezing medium significantly decreased (p < 0.01) the levels of intracellular calcium and cAMP in frozen-thawed spermatozoa. 1,2-diacylglycerol content was also decreased significantly (p < 0.01) in spermatozoa cryopreserved in presence of additives. Moreover, significant (p < 0.01) improvement in post-thaw motility, viability and membrane integrity of spermatozoa on addition of taurine or trehalose clearly indicated the reduced level of capacitation-like changes in buffalo spermatozoa.

Effect of incorporation of additives in tris-based egg yolk extender on buffalo (Bubalus bubalis) sperm tyrosine phosphorylation during cryopreservation

Phosphorylation of tyrosine residues on sperm protein is a known indicator of capacitation and a major intracellular signalling event. There is evidence that sperm cryopreservation promotes tyrosine phosphorylation and is associated with reduced fertility of spermatozoa. Under this study, cryoprotective role of different additives namely taurine, trehalose, catalase and 4-bromophenacyl bromide on buffalo sperm quality was evaluated. Buffalo semen was cryopreserved in tris-based egg yolk extender supplemented with additives like taurine (50 mm) or trehalose (100 mm) or 4-bromophenacyl bromide (200 μm) or catalase (100 U/ml) and used for assessment of levels of tyrosine phosphorylation in frozen-thawed spermatozoa. The results obtained were compared with the level of protein tyrosine phosphorylation of semen cryopreserved in tris-based egg yolk extender without additives. Proteins were extracted from a total number of nine ejaculates from three individual buffalo bulls chosen at random and analysed for tyrosine phospho-proteins using SDS-PAGE followed by immunoblotting. Monoclonal anti-phosphotyrosine antibody (Clone pT-154) was used as primary antibody followed by treatment with HRP-conjugated secondary antibody. Signals were detected on X-ray film using chemiluminescence. Nine proteins (p20, p30, p32, p38, p49, p56, p59, p72 and p86) were found to be tyrosine phosphorylated in cryopreserved spermatozoa. Supplementation of additives significantly (p<0.05) reduced the level of protein tyrosine phosphorylation in spermatozoa. Moreover, this study showed improved (p<0.05) post-thaw motility, viability and membrane integrity of spermatozoa on addition of these additives. The results obtained clearly indicate reduced level of capacitation like changes on supplementation of additives in terms of protein tyrosine phosphorylation.