Resveratrol protects boar sperm in vitro via its antioxidant capacity

The Effect of κ-Carrageenan on Porcine Sperm Cryo-Survival

κ-Carrageenan is a sulfated polysaccharide from red seaweed with substantial antioxidant activities. This study aimed to investigate the effect of κ-Carrageenan treatment on frozen-thawed (FT) porcine semen quality. Therefore, the spermatozoa were diluted and cryopreserved in a freezing extender supplemented with 0 (control), 0.2, 0.4, 0.6, and 0.8 mg/mL κ-Carrageenan. Sperm kinematics were assessed immediately after thawing (AT) and post-incubation for 120 min. The viability, acrosome integrity, lipid peroxidation, mitochondrial membrane potential (MMP), and intracellular caspase activity were measured AT. The results indicated that 0.2 mg/mL κ-Carrageenan increased total and progressive motility AT and post-incubation for 120 min (p < 0.05). Moreover, the viable sperm percentage and MMP after 0.2 mg/mL treatment were higher than those after control and other κ-Carrageenan concentration treatments. The proportion of acrosome-intact spermatozoa was significantly higher after 0.2 and 0.4 mg/mL κ-Carrageenan treatment than that after control and other κ-Carrageenan concentration treatments. The intracellular caspase activity was not significantly different among the experimental groups. However, the MDA concentration after 0.2 mg/mL κ-Carrageenan treatment was lower (p < 0.05) than that after the control treatment. Taken together, adding κ-Carrageenan to the porcine semen freezing extender improved the FT sperm quality mainly by influencing membrane stability and protecting against oxidative stress.

Pyrroloquinoline Quinone Improves Ram Sperm Quality through Its Antioxidative Ability during Storage at 4 °C

Sperm motility is an important factor in the migration of sperm from the uterus to the oviduct. During sperm preservation in vitro, sperm generates excessive ROS that damages its function. This study aims to investigate whether the addition of pyrroloquinoline quinone (PQQ) to the diluted medium could improve chilled ram sperm quality, and then elucidates the mechanism. Ram semen was diluted with Tris-citric acid-glucose (TCG) medium containing different doses of PQQ (0 nM, 10 nM, 100 nM, 1000 nM, 10,000 nM), and stored at 4 °C. Sperm motility patterns, plasma membrane integrity, acrosome integrity, mitochondrial membrane potential, reactive oxygen species (ROS) levels, malondialdehyde (MDA) levels, superoxide dismutase (SOD) activity, and ATP levels were measured after preservation. Furthermore, the expressions of NADH dehydrogenase 1 (MT-ND1) and NADH dehydrogenase 6 (MT-ND6) in sperm were also detected by western blotting. In addition, sperm capacitation and the ability of sperm to bind to the zona pellucina were also evaluated. It was observed that the addition of PQQ significantly (p < 0.05) improved ram sperm motility, membrane integrity, and acrosome integrity during preservation. The percentage of sperm with high mitochondrial membrane potential in the PQQ treatment group was much higher than that in the control. In addition, supplementation of PQQ also decreased the sperm MDA and ROS levels, while increasing ATP levels. Interestingly, the levels of MT-ND1 and MT-ND6 protein in sperm treated with PQQ were also higher than that of the control. Furthermore, the addition of 100 nM PQQ to the medium decreased ROS damage in MT-ND1 and MT-ND6 proteins. The addition of 100 nM PQQ significantly (p < 0.05) increased protein tyrosine phosphorylation in ram sperm after induced capacitation. Furthermore, the value of the sperm-zona pellucida binding capacity in the 100 nM PQQ treatment group was also much higher than that of the control. Overall, during chilled ram- sperm preservation, PQQ protected ram sperm quality by quenching the ROS levels to reduce ROS damage and maintain sperm mitochondrial function, and preserved the sperm's high ability of fertilization.

The emergence of natural products as potential therapeutics for male infertility

Infertility is a major reproductive health problem. Approximately 50% of all documented cases of infertility are attributable to male factors, such as poor testicular function and semen quality. The recent significant global decline in sperm counts has serious implications for male fertility, but the armamentarium for improving testicular function and semen quality is limited. Natural products have a wide range of activities and are a major source of drugs for disease prevention and treatment. To provide ideas and a theoretical basis for the research and development of therapeutic drugs for male infertility, this review summarizes natural products (mostly monomers) that have been shown to improve testicular function and semen quality and their possible mechanisms of action. These natural products primarily improve testicular function and semen quality via antioxidant, antiapoptotic, and anti-inflammatory effects, in addition to increasing serum testosterone and reducing DNA damage in spermatozoa and testicular cells. Prospects for the application of natural products in the treatment of male infertility are discussed.

Quality and redox state of bovine sperm cryopreserved with resveratrol use of resveratrol in bovine semen

The use of antioxidants for semen preservation prevents oxidative damage caused by reactive oxygen species (ROS). One of the most promising natural antioxidants is resveratrol, a phytoalexin derived from plants, grapes, berries, peanuts and red wine. To evaluate the effect of resveratrol on the quality and redox status of cryopreserved bovine semen. Five bulls were subjected to electroejaculation to obtain 15 ejaculates. Each ejaculate was extended with a tris-egg yolk-glycerol-based medium and divided into six aliquots supplemented with 0 (control), 10, 20, 30, 40 and 50 μM of resveratrol. Semen was frozen with liquid nitrogen vapours. Post-thawing, motility and kinetics were evaluated using a computer-assisted sperm analysis (CASA) system, membrane integrity using the hypoosmotic test (HOST), morphology by staining with eosin-nigrosin, sperm vitality by fluorescence microscopy with the SYBR14/IP probes. Total antioxidant capacity (TAC) was evaluated using the ABTS•+ assay and ROS was evaluated using spectrofluorimetry with the H2 DCFDA probe. For the statistical analysis linear models were adjusted and means were compared using the Tukey test. All concentrations of resveratrol reduced post-thawed motility and kinetics of sperm. Supplementation with 40 and 50 μM of resveratrol reduced sperm kinetics, and between 30 and 50 μM of resveratrol alterations in the sperm membrane and morphology were observed. However, using resveratrol at 50 μM increased TAC and at 20 μM, it reduced ROS production of cryopreserved bovine semen. Resveratrol appears to have a dose-dependent effect in which higher doses produce greater sperm alterations, however, it can increase semen TAC during freezing. It is concluded that resveratrol can increase antioxidant capacity and reduce ROS production in cryopreserved bovine semen. However, its use between 10 and 50 μM reduces post-thawing semen quality.

Resveratrol Improves the Frozen-Thawed Ram Sperm Quality

Cryopreservation generates a substantial quantity of ROS in semen, leading to a decline in sperm quality and fertilization capacity. The objective of this study was to investigate the effects of resveratrol and its optimal concentration on ram sperm quality after cryopreservation. Ram semen was diluted with a freezing medium containing different concentrations of resveratrol (0, 25, 50, 75, and 100 μM). After thawing, various sperm parameters such as total motility, progressive motility, acrosome integrity, plasma membrane integrity, mitochondrial membrane potential, glutathione (GSH) content, glutathione synthase (GPx) activity, superoxide dismutase (SOD) activity, catalase (CAT) activity, lipid peroxidation (LPO) content, malondialdehyde (MDA) content, ROS level, SIRT1 level, DNA oxidative damage, and AMPK phosphorylation level were assessed. In addition, post-thaw sperm apoptosis was evaluated. Comparatively, the addition of resveratrol up to 75 μM significantly improved the sperm motility and sperm parameters of cryopreserved ram sperm. Specifically, 50 μM resveratrol demonstrated a notable enhancement in acrosome and plasma membrane integrity, antioxidant capacity, mitochondrial membrane potential, adenosine triphosphate (ATP) content, SIRT1 level, and AMPK phosphorylation levels compared to the control group (p < 0.05). It also significantly (p < 0.05) reduced the oxidative damage to sperm DNA. However, detrimental effects of resveratrol were observed at a concentration of 100 μM resveratrol. In conclusion, the addition of 50 μM resveratrol to the cryopreservation solution is optimal for enhancing the quality of cryopreserved ram sperm.

The Beneficial Effect of Resveratrol on the Quality of Frozen-Thawed Boar Sperm

This study aimed to determine the effect of resveratrol and its optimal concentration on the quality of frozen-thawed (FT) boar sperm. Semen ejaculates were obtained from 13 Duroc boars aged between 1.5 and 3 years. The sperm sample was separated into 7 groups based on the concentrations of resveratrol in the freezing extender, which were 0 (control), 25, 50, 75, 100, 125, and 250 µM, respectively. The sperm was frozen using liquid nitrogen vapor and thawed at 50 °C for 12 s. After thawing, total motility, progressive motility, viability, intact acrosomes, mitochondrial membrane potential and level of MDA were assessed. The supplementation of 50-100 µM resveratrol improved the sperm motility and viability of FT sperm in comparison to the control group (p < 0.05). Furthermore, the 50 µM resveratrol group was significantly more protective than the control group in terms of intact acrosome, mitochondrial membrane potential, and level of MDA (p < 0.05). Nonetheless, the detrimental effect of resveratrol was found at a concentration of 250 µM. In conclusion, the addition of 50-100 µM resveratrol to a freezing extender is the optimal concentration for enhancing the quality of cryopreserved boar sperm.

Myo-inositol improves the viability of boar sperm during liquid storage

Introduction

Liquid preservation of boar semen is a highly preferred method for semen preservation in pig production. However, oxidative stress is the main challenge during the liquid preservation of boar semen in a time dependent manner. Therefore, supplementation of sperm with antioxidants during storage to protect them from oxidative stress has been the focus of recent research. Myo-inositol (Myo-Ins), the most active form of inositol, which belongs to the vitamin (Vit.) (B1 group has been shown to improve semen quality) (1). This study aimed to investigate whether Myo-Ins supplementation protects boar sperm in liquid preservation against oxidative stress and determine the appropriate concentration of Myo-Ins to be used in this regard.

Methods

Boar sperm was diluted with a semen extender with different concentrations of Myo-Ins (2, 4, 6, and 8 mg/mL) depending on the previous studies (1, 24). Sperm motility and viability, plasma membrane and acrosome integrity, mitochondrial membrane potential (MMP), semen time survival, and gene expression were measured and analyzed on days 0, 1, 3, 5, and 7 for the different samples.

Results

Different concentrations of Myo-Ins exerted different protective effects on the boar sperm quality. The addition of 2 mg/mL Myo-Ins resulted in higher sperm motility and viability, plasma membrane and acrosome integrity, MMP, and effective survival time. Investigation of mRNA expression patterns via qRT-PCR suggested that the 2 mg/mL Myo-Ins sample had increased expression of antioxidative genes.

Conclusion

The addition of Myo-Ins to semen extender improved the boar semen quality by decreasing the effects of oxidative stress during liquid preservation at 17°C. Additionally, 2 mg/mL is the optimum inclusion concentration of Myo-Ins for semen preservation.

Antioxidants and Oxidants in Boar Spermatozoa and Their Surrounding Environment Are Associated with AMPK Activation during Liquid Storage

Activation of the AMP-activated protein kinase (AMPK) has been demonstrated to be beneficial for boar sperm quality and functionality, while the underlying mechanism of AMPK activation of boar spermatozoa remains obscure. This study aimed to explore the effect of antioxidants and oxidants in boar spermatozoa and their surrounding fluid (SF) on the activation of AMPK during the liquid storage. Ejaculates from Duroc boars, routinely used for semen production, were collected and diluted to a final concentration of 25 × 106/mL. In experiment 1, twenty-five semen samples from eighteen boars were stored at 17 °C for 7 days. In experiment 2, three pooled semen samples created from nine ejaculates of nine boars were used, and each sample was treated with 0, 0.1, 0.2, and 0.4 μM/L H2O2 and stored at 17 °C for 3 h. Sperm quality and functionality, antioxidants and oxidants in boar spermatozoa and SF, the intracellular AMP/ATP ratio, and the expression levels of the phosphorylated AMPK (Thr172) were determined. Sperm quality significantly decreased with storage time in terms of viability (p < 0.05). Antioxidant and oxidant levels were markedly affected with storage time, with a decline in the SF total antioxidant capacity (TAC) (p < 0.05), SF malondialdehyde (MDA) (p < 0.05), and the sperm’s total oxidant status (TOS), as well as a fluctuation in sperm superoxidase dismutase-like (SOD-like) activity (p < 0.05). The intracellular AMP/ATP ratio increased (p < 0.05) on day 4 and subsequently decreased to its lowest value on days 6 and 7 (p < 0.05). The phosphorylated AMPK levels increased from day 2 to day 7 (p < 0.05). Correlation analyses indicate that sperm quality during liquid storage was correlated to antioxidants and oxidants in spermatozoa and SF (p < 0.05), which were correlated to the phosphorylation of sperm AMPK (p < 0.05). Treatment with H2O2 induced damages in sperm quality (p < 0.05), a decline in antioxidant levels (SF TAC, p < 0.05; sperm SOD-like activity, p < 0.01), an increase in oxidant levels (SF MDA, p < 0.05; intracellular ROS production, p < 0.05), a higher AMP/ATP ratio (p < 0.05), and phosphorylated AMPK levels (p < 0.05) in comparison with the control. The results suggest that antioxidants and oxidants in boar spermatozoa and SF are involved in AMPK activation during liquid storage.

The relevance of sperm morphology in male infertility

This brief report concerns the role of human sperm morphology assessment in different fields of male infertility: basic research, genetics, assisted reproduction technologies, oxidative stress. One of the best methods in studying sperm morphology is transmission electron microscopy (TEM) that enables defining the concept of sperm pathology and classifying alterations in non-systematic and systematic. Non-systematic sperm defects affect head and tail in variable ratio, whereas the rare systematic defects are characterized by a particular anomaly that marks most sperm of an ejaculate. TEM analysis and fluorescence in situ hybridization represent outstanding methods in the study of sperm morphology and cytogenetic in patients with altered karyotype characterizing their semen quality before intracytoplasmic sperm injection. In recent years, the genetic investigations on systematic sperm defects, made extraordinary progress identifying candidate genes whose mutations induce morphological sperm anomalies. The question if sperm morphology has an impact on assisted fertilization outcome is debated. Nowadays, oxidative stress represents one of the most important causes of altered sperm morphology and function and can be analyzed from two points of view: 1) spermatozoa with cytoplasmic residue produce reactive oxygen species, 2) the pathologies with inflammatory/oxidative stress background cause morphological alterations. Finally, sperm morphology is also considered an important endpoint in in vitro experiments where toxic substances, drugs, antioxidants are tested. We think that the field of sperm morphology is far from being exhausted and needs other research. This parameter can be still considered a valuable indicator of sperm dysfunction both in basic and clinical research.

Effects of dietary L-leucine supplementation on testicular development and semen quality in boars

Sperm and seminal plasma are rich in leucine, and leucine can promote the protein synthesis. This property makes it an interesting amino acid to increase sperm quality of human and livestock spermatogenesis. The goal of this study was to explore the effects of dietary leucine supplementation on testicular development and semen quality in boars from weaning to 10 months of age. 30 pure-bred, weaned Duroc boars (8.0 ± 1.0 kg) were randomly divided into two groups: control group (CON; fed the basal diet) and leucine group (LEU; fed the basal diet supplemented with 1.2% leucine); then, their body weight and testicular volume were recorded every 4 weeks. Testes were collected for histological and genes expression analysis from 150-day-old boars. Semen was collected and analyzed. Amino acids contents of blood plasma, seminal plasma, sperm, and testes were determined. Dietary supplementation with leucine increased the testicular volume and weight of boars, compared with CON. Sperm viability, sperm count per ejaculation, and average curve speed of sperm in leucine-supplemented boars were increased. Furthermore, leucine supplementation increased the blood plasma and seminal plasma leucine concentrations, and enhanced the gene expressions of branch chain amino acid transaminase, protein kinase B, mammalian target of rapamycin (mTOR), and cyclinb1 in the testes. Interestingly, the expressions of the p-mTOR and mTOR proteins in the testes were also upregulated. Thus, dietary leucine supplementation increased leucine absorption and utilization in the testes, promoted testicular development, and improved semen quality of boars, partly through the mTOR signaling pathway.

Boar seminal plasma improves sperm quality by enhancing its antioxidant capacity during liquid storage at 17°C

The objective of this study was to investigate the effects of different levels of seminal plasma (SP) on boar sperm quality, antioxidant capacity and bacterial concentrations during liquid storage at 17°C. Boar sperm was diluted with Beltsville Thawing Solution (BTS) consisting of 0, 25, 50 and 75% (v/v) of SP. Total motility, progressive motility and dynamic parameters were assessed by the computer assisted sperm analysis (CASA) system. Acrosome and plasma membrane integrity were measured by FITC-PNA/DAPI and SYBR-14/PI staining, respectively. In addition, total antioxidant capacity (T-AOC), malondialdehyde (MDA) content, and reactive oxygen species (ROS) levels were detected using commercial assay kits. Bacterial concentrations were assessed by turbidimetric assay. Our results showed that 25% SP markedly improved total motility, progressive motility, sperm dynamic parameters, acrosome integrity compared with 0, 50 and 75% SP (P < 0.05). In addition, 25% SP significantly increased T-AOC but decreased MDA content and ROS levels compared with 0, and 75% SP (P < 0.05). Moreover, 25% SP significantly decreased the bacterial concentrations in extended semen compared with 50% and 75% SP, however, which was higher than with 0% SP (P < 0.05). These results suggest that 25% SP can promote boar sperm quality through enhancing its antioxidant capacity during liquid storage.

Polyamines protect boar sperm from oxidative stress in vitro

Sperm are susceptible to excessive reactive oxygen species (ROS). Spermine and spermidine are secreted in large amounts by the prostate and potent natural free radical scavengers and protect cells against redox disorder. Thus, we used boar sperm as a model to study the polyamines uptake and elucidate whether polyamines protected sperm from ROS stress. Seven mature and fertile Duroc boars (aged 15 to 30 mo) were used in this study. In experiment 1, spermine and spermidine (3.6 ± 0.3 and 3.3 ± 0.2 mmol/L, respectively) were abundant in seminal plasma, and the content of polyamine decreased (P < 0.05) after preservation at 17 °C for 7 d or incubation at 37 °C for 6 h. In experiment 2, using labeling of spermine or spermidine by conjugation with fluorescein isothiocyanate and ultra-high-performance liquid chromatography, we found that the accumulation of spermine or spermidine in sperm was inhibited by quinidine and dl-tetrahydropalmatine (THP, organic cation transporters [OCT] inhibitors, P < 0.05), but not mildronate and l-carnitine (organic cation/carnitine transporter [OCTN] inhibitors, P > 0.05). In experiment 3, the addition of spermine or spermidine (0.5 mmol/L) in the extender resulted in higher motility, plasma membrane and acrosome integrity, and lower ROS level after preservation in vitro at 17 °C for 7 d (P < 0.05). In experiment 4, in the condition of oxidative stress (treatment with H2O2 at 37 °C for 2 h), the addition of spermine (1 mmol/L) or spermidine (0.5 mmol/L) in extender increased activities of glutathione peroxidase, glutathione reductase, and glutathione S-transferase; reduced glutathione and oxidized glutathione ratio (P < 0.05); and alleviate oxidative stress-induced lipid peroxidation, DNA damage, mitochondrial membrane potential (ΔΨm) decline, adenosine triphosphate depletion, and intracellular calcium concentration ([Ca2+]i) overload (P < 0.05), thereby improving boar sperm motility, the integrity of plasma membrane and acrosome (P < 0.05) in vitro. These data suggest that spermine and spermidine alleviate oxidative stress via the antioxidant capacity, thereby improving the efficacy of boar semen preservation.

Resveratrol and lycium barbarum polysaccharide improve Qinling giant panda (Ailuropoda melanoleuca Qinlingensis) sperm quality during cryopreservation

Background

Semen cryopreservation has become an essential tool for conservation efforts of the giant panda (Ailuropoda melanoleuca); however, it is severely detrimental to sperm quality. Evidence has shown that antioxidants have the potential to reverse cryopreservation-induced damage in sperm. The purpose of this study was to screen effective antioxidants that could retain sperm quality during cryopreservation and to determine the optimal dose. Seven antioxidant groups, including resveratrol (RSV = 50 μM, RSV = 100 μM, RSV = 150 μM), lycium barbarum polysaccharide (LBP = 2 mg/mL, LBP = 4 mg/mL), laminaria japonica polysaccharides (LJP = 1 mg/mL) or combination (LBP = 2 mg/mL, LJP = 1 mg/mL and RSV = 100 μM) were assessed.

Results

RSV, LBP, LJP, or a combination of RSV, LBP, and LJP added to the freezing medium significantly improved sperm progressive motility, plasma membrane integrity, acrosome integrity, and mitochondrial activity during the cryopreservation process. Furthermore, the activities of glutathione peroxidase and superoxide dismutase were also improved. The levels of reactive oxygen species and malondialdehyde in semen were notably reduced. Hyaluronidase activity and acrosin activity were significantly increased in LBP-treated sperm. However, sperm total motility and DNA integrity were not significantly different between the groups.

Conclusions

RSV (50 μM) or LBP (2 mg/mL) are the best candidate antioxidants for inclusion in the freezing medium to improve the quality of giant panda spermatozoa during semen cryopreservation.

Role of exogenous antioxidants on the performance and function of pig sperm after preservation in liquid and frozen states: A systematic review

In situations where an excessive generation of reactive oxygen species overwhelms antioxidant capacity, a harmful effect on sperm function is exerted. Antioxidants are molecules capable of minimizing this detrimental effect, which is important in pig sperm due to the high content of polyunsaturated fatty acids in their plasma membrane. The present systematic review aims at evaluating whether supplementing semen extenders (for liquid storage at 17 °C) or freezing and/or thawing media (for cryopreservation) with antioxidants influences sperm quality and functionality parameters, and in vitro/in vivo fertility outcomes. We defined inclusion and exclusion criteria in a PICOS table according to PRISMA guidelines, and conducted a literature search through MEDLINE-PubMed in November 2020. After systematic selection, 75 studies were included: 47 focused on cryopreservation and 28 on liquid storage at 17 °C. More than 70% of the studies included in this review showed that adding semen extenders for liquid storage and/or freezing/thawing media for cryopreservation with antioxidants enhances sperm quality and functionality parameters. In addition, this supplementation improves in vivo/in vitro fertility outcomes, supporting the hypothesis that the beneficial effect observed upon sperm quality has a positive impact on reproduction outcomes.

Improving the post-thaw quality of rooster semen using the extender supplemented with resveratrol

Avian spermatozoa are highly susceptible to reactive oxygen species (ROS) produced during the cryopreservation. The aim of the current study was to investigate the antioxidant effects of resveratrol (RSV) during rooster semen cryopreservation. Changes in expression of AMP-activated protein kinase as a possible mechanism behind the beneficial effects of resveratrol were also evaluated. Semen samples were collected from ten Ross broiler breeders (52-wk) using abdominal massage, then divided into 4 equal aliquots and cryopreserved in Beltsville extender that contained different concentrations (0 µM, 0.01µM, 0.1µM, and 1µM) of RSV. higher percentage (P < 0.05) of total motility and membrane integrity was observed in RSV-0.1 compared to the other frozen groups. Moreover, higher percentage of sperm mitochondrial activity was observed in the RSV-0.01 and RSV-0.1 compared to the frozen control (P < 0.05). The lowest percentage of apoptotic like changes was found in the RSV-0.1 in comparison to the other groups (P < 0.05). RSV-0.01 and RSV-1 groups produced the lowest levels of H2O2 and O2- compared to the other frozen groups, respectively. Malondialdehyde (MDA) concentration, velocity average path (VAP), and linearity (LIN) were not affected by different concentrations of RSV (P > 0.05). We observed a dose-dependent increase in AMP-activated protein kinase expression in groups exposed to RSV. Thus, RSV-1 increased AMP-activated protein kinase phosphorylation but had no positive effects on post thaw sperm parameters. Our findings suggest that RSV-0.1 improve thawed sperm functions, and these effects might be mediated through activation of AMP-activated protein kinase.

The Role of Selected Natural Biomolecules in Sperm Production and Functionality

Emerging evidence from in vivo as well as in vitro studies indicates that natural biomolecules may play important roles in the prevention or management of a wide array of chronic diseases. Furthermore, the use of natural compounds in the treatment of male sub- or infertility has been proposed as a potential alternative to conventional therapeutic options. As such, we aimed to evaluate the effects of selected natural biomolecules on the sperm production, structural integrity, and functional activity. At the same time, we reviewed their possible beneficial or adverse effects on male reproductive health. Using relevant keywords, a literature search was performed to collect currently available information regarding molecular mechanisms by which selected natural biomolecules exhibit their biological effects in the context of male reproductive dysfunction. Evidence gathered from clinical trials, in vitro experiments and in vivo studies suggest that the selected natural compounds affect key targets related to sperm mitochondrial metabolism and motion behavior, oxidative stress, inflammation, DNA integrity and cell death. The majority of reports emphasize on ameliorative, stimulating and protective effects of natural biomolecules on the sperm function. Nevertheless, possible adverse and toxic behavior of natural compounds has been indicated as well, pointing out to a possible dose-dependent impact of natural biomolecules on the sperm survival and functionality. As such, further research leading to a deeper understanding of the beneficial or adverse roles of natural compounds is necessary before these can be employed for the management of male reproductive dysfunction.

Role of Antioxidants in Cooled Liquid Storage of Mammal Spermatozoa

Cooled preservation of semen is usually associated with artificial insemination and genetic improvement programs in livestock species. Several studies have reported an increase in reactive oxidative species and a decrease in antioxidant substances and sperm quality parameters during long-term semen storage at refrigerated temperatures. The supplementation of antioxidants in extenders before refrigeration could reduce this detrimental effect. Various antioxidants have been tested, both enzymatic, such as superoxide dismutase and catalase, and non-enzymatic, such as reduced glutathione, vitamins E and C and melatonin. However, the problem of oxidative stress in semen storage has not been fully resolved. The effects of antioxidants for semen-cooled storage have not been reviewed in depth. Therefore, the objective of the present study was to review the efficiency of the supplementation of antioxidants in the extender during cooled storage of semen in livestock species.

Protective Effect of Chlorogenic Acid on Human Sperm: In Vitro Studies and Frozen-Thawed Protocol

The study evaluated the chlorogenic acid (CGA) antioxidant potential on oxidative stress (OS) induced in vitro in human spermatozoa and during cryopreservation procedure. Swim-up selected spermatozoa were treated with 100 µM CGA, 100 µM H₂O₂ to induce lipid peroxidation (LPO), and with both compounds and the effects on mitochondrial membrane potential (MMP) by JC-1, DNA integrity by acridine orange (AO), and sperm ultrastructure by transmission electron microscopy (TEM), were evaluated. CGA antioxidant activity was assessed by measuring malondialdehyde (MDA) and F₂-isoprostanes (F₂-IsoPs) in the media. The CGA protective activity and the immunolocalization of Phospho-AMPKα (Thr172) were explored in frozen-thawed sperm. CGA was not toxic for sperm motility, DNA integrity and MMP. The increase in MDA (p < 0.05) and F₂-IsoPs (p < 0.001), DNA damage (p < 0.01) and low MMP (p < 0.01) levels after H₂O₂ treatment were reduced in presence of CGA as well as the percentage of broken plasma membranes (p < 0.01) and altered acrosomes (p < 0.01) detected by TEM. Treated frozen-thawed spermatozoa showed increased sperm motility (p < 0.01), DNA integrity (p < 0.01), MMP (p < 0.01), reduced MDA (p < 0.01) and increased sperm percentage with Phospho-AMPKα labelling in the head (p < 0.001). CGA can be used to supplement culture media during semen handling and cryopreservation where OS is exacerbated.

Resveratrol supplementation into extender protects against cryodamage in dog post-thaw sperm

Antioxidants have multiple protective roles in a variety of cells and thus can be used to protect sperm against cryo-damage during freezing, which affects fertility. The antioxidant resveratrol (3,5,4-trihydroxytrans-stilbene; RSV) has been reported to protect the animal sperm during cryopreservation, including human sperm. In this study, we assessed the protective effects of RSV supplementation on dog sperm cryopreservation. Semen was collected from four dogs and the effect of different concentrations of RSV (0, 100, 200, and 400 µM) on post-thaw sperm quality was examined. After thawing, sperm motility was assessed using computer-aided sperm analysis, and the structural integrity of the plasma membrane, acrosome, and chromatin was examined. In addition, their mitochondrial activity and gene expression were also assessed. Dog sperm cryopreserved with 200 µM RSV showed significant improvement in post-thaw sperm motility and viability compared with that of the control group (P<0.05). Moreover, RSV-supplemented samples showed significantly higher numbers of sperm with an intact plasma membrane, active mitochondria, and structural integrity of acrosomes and chromatin than that of control samples (P<0.05). Furthermore, gene expression showed that RSV supplemented samples showed lower expression of pro-apoptotic (BAX), reactive oxygen species (ROS) modulator oxidative stress-related (ROMO1) and 8-oxoguanine DNA glycosylase 1 (OGG1) whereas higher expression levels of anti‐apoptotic (BCL2), protamine-2 (PRM2), protamine-3 (PRM3) and sperm acrosome‐associated 3 (SPACA3) genes than control. Our results suggest that RSV, at its optimum concentration, can be efficiently used as an antioxidant in the cryopreservation of dog sperm.