Cysteine protects rabbit spermatozoa against reactive oxygen species-induced damages

Vibration Emissions Reduce Boar Sperm Quality via Disrupting Its Metabolism

Artificial insemination (AI) with liquid-preserved semen has recently become common in pig breeding. The semen doses are produced in a centralized manner at the boar stud and then subsequently distributed and transported to sow farms. However, vibration emissions during transportation by logistic vehicles may adversely affect the quality of boar sperm. Therefore, this study aimed to explore the impact of vibration-induced emissions on sperm quality and function under simulated transportation conditions. Each time, ejaculates from all 15 boars were collected and then pooled together to minimize individual variations, and the sample was split using an extender for dilution. Different rotational speeds (0 rpm, 80 rpm, 140 rpm, 200 rpm) were utilized to simulate varying intensities of vibration exposure using an orbital shaker, considering different transportation times (0 h, 3 h, and 6 h). Subsequently, evaluations were conducted regarding sperm motility, plasma membrane integrity, acrosome integrity, mitochondrial function, adenosine triphosphate (ATP) levels, mitochondrial reactive oxygen species (ROS) levels, pH, glycolytic pathway enzyme activities, and capacitation following exposure to vibration emissions. Both vibration time and intensity impact sperm motility, plasma membrane integrity, and acrosomal integrity. Vibration exposure significantly reduced sperm ATP levels, mitochondrial membrane potential, and the levels of mitochondria-encoded proteins (MT-ND1, MT-ND6) (p < 0.05). After vibration emission treatment, the pH value and mitochondrial ROS levels significantly increased (p < 0.05). Inhibition of sperm glycolysis was observed, with reduced activities of hexokinase (HK), pyruvate kinase (PK), and lactate dehydrogenase (LDH), along with decreased lactate levels (p < 0.05). Additionally, sperm tyrosine phosphorylation levels were significantly reduced by vibration emissions compared to the control group (p < 0.05). After the vibration emission treatment, the number of sperm bound to each square millimeter of oviduct explants decreased significantly compared to the control group (p < 0.05). Similarly, compared to the control group, using semen subjected to vibration stress for AI results in significantly reduced pregnancy rates, total born litter size, live-born litter size, and healthy born litter size (p < 0.05).

Sperm freezing damage: the role of regulated cell death

Substantial progress in research on sperm cryopreservation has occurred since the twentieth century, especially focusing on improving sperm freezing procedures and optimizing semen extenders. However, the cellular biological mechanisms of sperm freezing damage are still unclear, which greatly restricts the promotion and development of sperm cryopreservation. An essential component of sperm freezing damage is the occurrence of cell death. Considering the existence of multiple types of cell death pathways, this review discusses connections between characteristics of regulated cell death (e.g., apoptosis and ferroptosis), and accidental cell death (e.g., intracellular ice crystals) with sperm freezing damage and explores possible future research directions in this field.

Extender Supplementation with Glutathione (GSH) and Taurine Improves In Vitro Sperm Quality and Antioxidant Status of New Zealand Rabbits during Chilled Storage for up to 72 hours

This study assessed the influence of supplementing the rabbit semen extender with various concentrations of glutathione (GSH) and taurine at 24, 48, and 72 h postchilling at 5°C. Semen samples were collected from 20 New Zealand bucks, and ejaculates with standard color, motility (>85%), about 0.5 mL volume, and ∼400 × 106/mL concentration were used and diluted with extenders supplemented with 0.5, 1, and 2 mM of GSH and 1, 5, and 10 mM of taurine and chilled at 5°C. Nonsupplemented samples were used as a control. Sperm's progressive motility, acrosome reaction, and extracellular oxidative stress biomarkers such as MDA contents and GPx, SOD, and CAT concentrations and intracellular transcriptomic levels of SOD and CAT genes were assessed. GSH and taurine supplementation improved the sperm's kinetics by reducing cooling-associated stress, which was ascertained by lowering MDA concentration and increasing SOD, CAT, and GPx concentrations (P < 0.05). Increasing the levels of antioxidant enzymes in the extender was due to the increasing mRNA copies of the SOD and CAT genes (P < 0.05). Furthermore, GSH and taurine maintained the fructose levels in the extender and lowered the GPT levels, which implies sperm membrane stability is maintained through GSH and taurine supplementation. GSH and taurine supplementation to the extender had protective influences on the in vitro rabbit semen quality during chilled storage for up to 72 h, which were remarkable with increasing supplementation dose and cooling time at 5°C.

Determination of Ram (Ovis aries) Sperm DNA Damage Due to Oxidative Stress: 8-OHdG Immunodetection Assay vs. SCSA®

Conventional DNA analysis techniques can hardly detect DNA damage in ruminant spermatozoa due to high DNA compaction in these cells. Furthermore, these techniques cannot discriminate whether the damage is due to oxidative stress. The main purpose of this study was to evaluate the efficacy of two techniques for determining DNA damage in ovine sperm when the source of that damage is oxidative stress. Semen samples from twenty Manchega rams (Ovis aries) were collected and cryopreserved. After thawing, the samples were subjected to different levels of oxidative stress, and DNA oxidation was quantified using an 8-hydroxy-2′-deoxyguanosine (8-OHdG) immunodetection assay and Sperm Chromatin Structure Assay (SCSA®). For this purpose, we evaluated five different concentrations of an oxidation solution (H2O2/FeSO4•7H2O) on ram sperm DNA. Our study with the 8-OHdG immunodetection assay shows that there are higher values for DNA oxidation in samples that were subjected to the highest oxidative stress (8 M H2O2/800 µM FeSO4•7H2O) and those that were not exposed to high oxidative stress, but these differences were not significant (p ≥ 0.05). The two SCSA® parameters considered, DNA fragmentation index (DFI %) and high DNA stainability (HDS %), showed significant differences between samples that were subjected to high concentrations of the oxidation agent and those that were not (p < 0.05). We can conclude that the 8-OHdG immunodetection assay and SCSA® detect DNA damage caused by oxidative stress in ovine sperm under high oxidative conditions; SCSA® is a more straightforward method with more accurate results. For these reasons, an oxidative-stress-specific assay such as 8-OHdG immunodetection is not needed to measure DNA damage caused by oxidative stress in ram sperm samples.

Beneficial Effect of Proline Supplementation on Goat Spermatozoa Quality during Cryopreservation

Sperm cryopreservation contributes to the extensive utilization of artificial insemination (AI) in the daily livestock industry. However, due to the presence of few sperm with good biological function in post-thaw goat sperm, its use has been limited for AI purposes. Hence, its improvement has been the focus of many research studies. This study aimed to investigate the effects of proline supplementation of the freezing medium on goat sperm. The goat semen was cryopreserved with freezing medium supplementation of different concentrations of proline (0, 0.5, 1, 2 and 4 mM). The post-thaw sperm motility patterns, membrane integrity, acrosome integrity, lipid peroxidation (LPO) levels, malondialdehyde (MDA) levels, total antioxidant capacity (T-AOC), proline dehydrogenase (PRODH) activity, superoxide dis-mutase (SOD) activity, glutathione (GSH) levels and GSH/GSSG were evaluated. Likewise, the expression and immunofluorescent localization of PRODH in post-thaw goat sperm was also detected. It was observed that addition of 2 mM proline to the freezing medium significantly enhanced post-thaw goat sperm total motility, progressive motility, straight-linear velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), straightness (STR), linearity (LIN), membrane integrity and acrosome integrity. Interestingly, PRODH was expressed in post-thaw goat sperm, especially in the post-acrosome and sperm tail. Addition of 2 mM proline also significantly increased the post-thaw sperm PRODH activity compared to the control. Moreover, post-thaw goat sperm LPO levels and MDA levels were reduced by supplementation of 2 mM proline. Furthermore, compared to the control, the values of post-thaw goat sperm T-AOC, SOD activity, GSH level and GSH/GSSG were also significantly increased in 2 mM proline treatment. Reduction of post-thaw goat sperm apoptosis in 2 mM proline treatment was also observed as the levels of Caspase3 and Caspase9 were decreased by the supplementation with 2 mM proline. These observations suggest that the addition of 2 mM proline to the freezing medium increased post-thaw goat sperm quality by reducing oxidative stress during cryopreservation. These findings also provide novel insights into the use of proline as an efficient additive to enhance post-thaw goat sperm quality during cryopreservation.

Cysteine protected cells from H2O2-induced damage and promoted long-chain fatty acids synthesis in vivo to improve γ-aminobutyric acid production in Levilactobacillus brevis

Levilactobacillus brevis NPS-QW-145 isolated from kimchi is deficient in glutamate dehydrogenase-encoding gene (gdhA) to form glutamate, hence it required exogenous supplementation of glutamate/monosodium glutamate (MSG) for decarboxylation reaction to produce γ-aminobutyric acid (GABA). However, GABA conversion rate from MSG was relatively low. The individual effect of 20 amino acids on regulating GABA biosynthesis was investigated. Cysteine was selected to significantly improve GABA production from MSG. It was found that Lb. brevis was capable of producing H₂O₂, cysteine protected Lb. brevis against H₂O₂-induced oxidative damage to increase cell viability for the enhancement of GABA production. Moreover, cysteine promoted glucose consumption to produce acetyl-CoA for synthesizing long-chain fatty acids to significantly up-regulate GABA biosynthesis. These findings deciphered antioxidative capability of cysteine in Lb. brevis 145 and provided a theoretical basis for fatty acids synthesis-mediated GABA synthesis in Lb. brevis 145, and possibly in other lactic acid bacteria.

Effects of dietary supplementation with selenium yeast and jujube powder on mitochondrial oxidative damage and apoptosis of chicken

The main objective of this study was to explore the effects of dietary selenium yeast and jujube powder on mitochondrial oxidative damage and cell apoptosis of broilers during postmortem aging, chicken breasts of broilers fed diets supplemented with different concentrations of selenium yeast and jujube powder were used as research subjects. With the prolongation of postmortem aging time, the levels of reactive oxygen species (ROS), carbonyl content, mitochondrial permeability transition pore (MPTP) openness, and mitochondrial membrane permeability increased significantly (P < 0.05). The contents of the sulfhydryl, mitochondrial membrane potential, shear force, and cytochrome C (Cyt-c) reduction level decreased significantly (P < 0.05). The activity of Caspase-3 and Caspase-9 increased from 0 to 24 h postmortem but fell from 24 to 72 h postmortem. Compared with the control group, dietary selenium yeast and jujube powder significantly reduced mitochondrial oxidative damage. They greatly increased the shear force, mitochondrial membrane potential, and Cyt-c reduction levels (P < 0.05). Among them, the combination group of high-dose selenium yeast and jujube powder had more significant effects on ROS scavenging, reducing cell membrane permeability, protecting cell membrane integrity, and increasing Cyt-c reduction level (P < 0.05). In conclusion, cell apoptosis intensifies during the chicken breast's aging time, and muscle tenderness continues. Still, different doses of dietary selenium yeast and jujube powder can inhibit mitochondrial oxidation to various degrees. The combined group of selenium yeast and jujube powder with 0.6 mg·kg⁻¹ has the best effect. This study is of great significance for applying natural antioxidant ingredients such as selenium yeast and jujube powder in the development and utilization of poultry feed.

Use of Purslane (Portulaca oleracea) Extracts and Cysteine in Diluents to Improve the Cryopreserved Quality of Goat Sperm

Highlights Using cysteine and purslane extracts in extenders improved significantly the post-thaw sperm characteristics. Sperm viability, DNA integrity, and mitochondrial activity demonstrate an improvement in post-thaw sperm. Malondialdehyde production was decreased based on the positive effects of treated extenders. The obtained results demonstrate that supplementation of 50 μg/mL of purslane methanolic extract with cysteine to freezing extenders was significantly superior compared with other treatments.

Cysteine improves boar sperm quality via glutathione biosynthesis during the liquid storage

Objective

Sperm are particularly susceptible to reactive oxygen species (ROS) stress. Glutathione (GSH) is an endogenous antioxidant that regulates sperm redox homeostasis. However, it is not clear whether boar sperm could utilize cysteine for synthesis GSH to protect sperm quality from ROS damage. Therefore, the present study was undertaken to elucidate the mechanism of how cysteine is involved in protecting boar sperm quality during liquid storage.

Methods

Sperm motility, membrane integrity, lipid peroxidation, 4-hydroxyIlonenal (4-HNE) modifications, mitochondrial membrane potential, as well as the levels of ROS, GSH and, ATP were evaluated. Moreover, the enzymes (GCLC: glutamate cysteine ligase; GSS: glutathione synthetase) that are involved in glutathione synthesis from cysteine precursor were detected by western blotting.

Results

Compared to the control, addition of 1.25 mM cysteine to the liquid storage significantly increased boar sperm progressive motility, straight-line velocity (VSL), curvilinear velocity (VCL), beat-cross frequency (BCF), membrane integrity, mitochondrial membrane potential, ATP level, acrosome integrity, activities of superoxide dismutase (SOD) and catalase, and GSH level, while reducing the ROS level, lipid peroxidation and 4-HNE modifications. It was also observed that the GCLC and GSS were expressed in boar sperm. Interestingly, when we used menadione to induce sperm with ROS stress, the menadione associated damages were observed to be reduced by the cysteine supplementation. Moreover, compared to the cysteine treatment, the γ-GCS activity, GSH level, mitochondrial membrane potential, ATP level, membrane integrity and progressive motility in boar sperm were decreased by supplementing with an inhibitor of GSH synthesis, buthionine sulfoximine (BSO).

Conclusion

These data suggest that boar sperm could biosynthesize the GSH from cysteine in vitro. Therefore, during storage, addition of cysteine improves boar sperm quality via enhancing the GSH synthesis to resist ROS stress.

Strategies for Highly Efficient Rabbit Sperm Cryopreservation

The rabbit is a valuable animal for both the economy and biomedical sciences. Sperm cryopreservation is one of the most efficient ways to preserve rabbit strains because it is easy to collect ejaculate repeatedly from a single male and inseminate artificially into multiple females. During the cooling, freezing and thawing process of sperms, the plasma membrane, cytoplasm and genome structures could be damaged by osmotic stress, cold shock, intracellular ice crystal formation, and excessive production of reactive oxygen species. In this review, we will discuss the progress made during the past years regarding efforts to minimize the cell damage in rabbit sperms, including freezing extender, cryoprotectants, supplements, and procedures.

Metabonomic Insights into the Sperm Activation Mechanisms in Ricefield Eel (Monopterus albus)

In fish, sperm motility activation is one of the most essential procedures for fertilization. Previous studies have mainly focused on the external environmental effects and intracellular signals in sperm activation; however, little is known about the metabolic process of sperm motility activation in fish. In the present study, using ricefield eel (Monopterus albus) sperm as a model, metabonomics was used to analyze the metabolic mechanism of the sperm motility activation in fish. Firstly, 529 metabolites were identified in the sperm of ricefield eel, which were clustered into the organic acids, amino acids, nucleotides, benzene, and carbohydrates, respectively. Among them, the most abundant metabolites in sperm were L-phenylalanine, DL-leucine, L-leucine, lysolecithin choline 18:0, L-tryptophan, adenine, hypoxanthine, 7-Methylguanine, shikimic acid, and L-tyrosine. Secondly, compared to pre-activated sperm, the level of S-sulfo-L-cysteine and L-asparagine were both increased in the post-activated sperm. Ninety-two metabolites were decreased in the post-activated sperm, including quinic acid, acetylsalicylic acid, 7,8-dihydro L-biopterin, citric acid, glycylphenylalanine, and dihydrotachysterol (DHT). Finally, basing on the pathway analysis, we found that the changed metabolites in sperm motility activation were mainly clustered into energy metabolism and anti-oxidative stress. Fish sperm motility activation would be accompanied by the release of a large amount of energy, which might damage the genetic material of sperm. Thus, the anti-oxidative stress function is a critical process to maintain the normal physiological function of sperm.

Proline Protects Boar Sperm against Oxidative Stress through Proline Dehydrogenase-Mediated Metabolism and the Amine Structure of Pyrrolidine

Simple Summary

Reactive oxygen species that accumulate during liquid storage of boar semen lead to oxidative stress to sperm. In this study, we found that proline significantly improved boar sperm quality and protected sperm against oxidative damages during liquid storage at 17 °C. Using the model of artificially induced oxidative stress, we found that proline exerted an antioxidative role by modulating redox homeostasis in boar sperm. The secondary amine structure of proline and proline dehydrogenase-mediated metabolism are involved in the antioxidative role. We suggest that addition of proline to the extender would be beneficial to improve boar sperm quality.

Abstract

Proline was reported to improve sperm quality in rams, stallions, cynomolgus monkeys, donkeys, and canines during cryopreservation. However, the underlying mechanism remains unclear. The aim of this study was to investigate the effect of proline on boar semen during liquid storage at 17 °C and explore the underlying mechanism. Freshly ejaculated boar semen was supplemented with different concentrations of proline (0, 25, 50, 75, 100, 125 mM) and stored at 17 °C for nine days. Sperm motility patterns, membrane integrity, ATP (adenosine triphosphate), reactive oxygen species (ROS), and GSH (glutathione) levels, and the activities of catalase (CAT) and superoxide dismutase (SOD) were evaluated after storage for up to five days. It was observed that boar sperm quality gradually decreased with the extension of storage time, while the ROS levels increased. Addition of 75 mM proline not only significantly improved sperm membrane integrity, motility, and ATP levels but also maintained the redox homeostasis via increasing the GSH levels and activities of CAT and SOD. When hydrogen peroxide (H₂O₂) was used to induce oxidative stress, addition of proline significantly improved sperm quality and reduced ROS levels. Moreover, addition of proline also improved sperm quality during the rapid cooling process. Notably, addition of DL-PCA (DL-pipecolinic acid) rescued the reduction of progressive motility and total motility caused by H₂O₂, and THFA (tetrahydro-2-furoic acid) failed to provide protection. Furthermore, addition of proline at 75 mM increased the activity of proline dehydrogenase (PRODH) and attenuated the H₂O₂-induced reduction in progressive motility. These data demonstrate that proline protects sperm against oxidative stress through the secondary amine structure and proline dehydrogenase-mediated metabolism.

Improving the Rabbit Semen Cryopreservation Protocol: Comparison Between Two Extenders and Inseminating Doses

This study has been designed to optimize the semen freezing protocol in rabbits, in this regard we compared a Tris-citrate-glucose (TCG) extender with a commercial one (Cortalap®), that to the best of our knowledge has never been used up to now on the in vitro freezability and fertilizing ability of cryopreserved rabbit semen. Two different inseminating semen doses were considered. Five pooled semen samples were divided into two subsamples and each of them were diluted to a ratio 1:1 (v:v) with a freezing extender composed of TCG or Cortalap® containing 16% of dimethylsulfoxide and 0.1 mol/L of sucrose. The extended semen was filled into 0.25 mL plastic straws and frozen above a liquid nitrogen surface. After thawing (50°C/10 seconds) we determined sperm motility, viability, membrane functionality, acrosome and DNA integrity. Our results showed that the Cortalap® extender significantly improved the in vitro post-thaw sperm quality, in comparison to TCG. When we compared the extenders in vivo, no significant differences in the reproductive performances were observed independently by inseminating doses used. In this study we demonstrated that Cortalap® extender can be used as an alternative to TCG. Thus, the Cortalap® being a ready to use extender, implies a reduction of time, mistakes and microbial contaminations during its preparation. This discovery results as significant because it provides beyond an important contribution to the creation of the first Italian semen cryobank of rabbit breeds and also for livestock rabbit farms based on artificial insemination (AI) program.

Notoginsenoside R1 protects boar sperm during liquid storage at 17°C

Reactive oxygen species (ROS) damage mammalian sperm during liquid storage. Notoginsenoside R1 (NR1) is a compound isolated from the roots of Panax notoginseng; it has powerful ROS-scavenging activities. This work hypothesized that the antioxidant capacity of NR1 could improve boar sperm quality and fertility during liquid storage. During liquid storage at 17°C, the supplementation of semen extender with NR1 (50 μM) significantly improved sperm motility, membrane integrity and acrosome integrity after 5 days of preservation. NR1 treatment also reduced ROS and lipid peroxidation (LPO) levels at day 5 (p <0.05). Higher glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) levels and sperm-zona pellucida binding capacity were observed in the 50 μM NR1 group than those in the control group at day 7 (p <0.05). Importantly, statistical analysis of the fertility of 200 sows indicated that addition of NR1 to the extender improved the fertility parameters of boar spermatozoa during liquid storage at 17°C (p <0.05). These results demonstrate the practical feasibility of using 50 μM NR1 as an antioxidant in boar extender during liquid storage at 17°C, which is beneficial to both spermatozoa quality and fertility.

Sperm Antioxidant Biomarkers and Their Correlation with Clinical Condition and Lifestyle with Regard to Male Reproductive Potential

Measurement of sperm oxidative-antioxidant indicators is widely used in the assessment and detection of biochemical causes of male infertility The main purpose of this study was to identify biomarkers that assist in diagnostics and monitoring of male reproductive potential. We performed the assessment of oxidative-antioxidant malondialdehyde (MDA), glutathione (GSH), and total redox antioxidant potential (TRAP) indicators in seminal plasma, seminogram, clinical condition, and lifestyle of people with reproductive problems. The combined assessment of GSH and TRAP as potential biomarkers of male infertility in semen plasma was characterized by the highest total sensitivity and specificity. Furthermore, we provide evidence that male reproductive potential is significantly correlated with basic sperm parameters, sperm cell membrane integrity, their morphology, lifestyle, eating habits, occupation, and mental health. Our results provide evidence on the importance of oxidative stress and defense against free radicals in diagnosing and monitoring men with infertility that are consistent with previously conducted research. We provide an alternative approach on the possibility of interpreting the combination of the biomarkers that can bring benefits to a multi-threaded approach to the diagnosis and treatment of male infertility.

Resveratrol protects boar sperm in vitro via its antioxidant capacity

The objective of the present study was to elucidate whether resveratrol could facilitate the survival of boar sperm during liquid preservation and fast cooling processes. Boar semen were diluted with Modena extender containing different concentrations of resveratrol. Sperm motility was evaluated by visual estimation. Membrane integrity, acrosome integrity and mitochondrial membrane potentials were measured by SYBR-14/PI, FITC-PNA and JC-1 staining, respectively. Moreover, the levels of reactive oxygen species (ROS), malonaldehyde (MDA) and total antioxidant capacity (T-AOC) were measured using commercial assay kits. B-cell lymphoma protein-2 (BCL2) content was determined by western blotting. During liquid preservation at 17oC, the addition of 50 μM resveratrol to the Modena extender significantly improved sperm motility, membrane integrity, acrosome integrity, and sperm mitochondrial membrane potentials. Similar results were also observed in the 150 μM resveratrol group during the fast cooling process. Furthermore, addition of resveratrol led to a decrease of ROS and MDA, and an increase in the content of T-AOC and BCL2. These observations suggest that addition of resveratrol to Modena extender protects boar sperm against oxidative stress. The optimal concentrations of resveratrol are 50 μM and 150 μM during liquid preservation and fast cooling process, respectively.

Cryopreservation of Sperm: Effects on Chromatin and Strategies to Prevent Them

Cryopreservation is a technique that can keep sperm alive indefinitely, enabling the conservation of male fertility. It involves the cooling of semen samples and their storage at -196 °C in liquid nitrogen. At this temperature all metabolic processes are arrested. Sperm cryopreservation is of fundamental importance for patients undergoing medical or surgical treatments that could induce sterility, such as cancer patients about to undergo genotoxic chemotherapy or radiotherapy, as it offers these patients not only the hope of future fertility but also psychological support in dealing with the various stages of the treatment protocols.Despite its importance for assisted reproduction technology (ART) and its success in terms of babies born, this procedure can cause cell damage and impaired sperm function. Various studies have evaluated the impact of cryopreservation on chromatin structure, albeit with contradictory results. Some, but not all, authors found significant sperm DNA damage after cryopreservation. However, studies attempting to explain the mechanisms involved in the aetiology of cryopreservation-induced DNA damage are still limited. Some reported an increase in sperm with activated caspases after cryopreservation, while others found an increase in the percentage of oxidative DNA damage. There is still little and contradictory information on the mechanism of the generation of DNA fragmentation after cryopreservation. A number of defensive strategies against cryoinjuries have been proposed in the last decade. Most studies focused on supplementing cryoprotectant medium with various antioxidant molecules, all aimed at minimising oxidative damage and thus improving sperm recovery. Despite the promising results, identification of the ideal antioxidant treatment method is still hampered by the heterogeneity of the studies, which describe the use of different antioxidant regimens at different concentrations or in different combinations. For this reason, additional studies are needed to further investigate the use of antioxidants, individually and in combination, in the cryopreservation of human sperm, to determine the most beneficial conditions for optimal sperm recovery and preservation of fertility.

Resveratrol Improves Boar Sperm Quality via 5'AMP-Activated Protein Kinase Activation during Cryopreservation

Mammalian sperm is highly susceptible to the reactive oxygen species (ROS) stress caused by biochemical and physical modifications during the cryopreservation process. 5'AMP-activated protein kinase (AMPK) is involved in regulating both cell metabolism and cellular redox status. The aim of the present study was to investigate whether the resveratrol protects boar sperm against ROS stress via activation of AMPK during cryopreservation. Boar sperm was diluted with the freezing medium supplemented with resveratrol at different concentrations (0, 25, 50, 75, 100, and 125 μM). It was observed that the addition of 50 μM resveratrol significantly improved the postthaw sperm progressive motility, membrane integrity, acrosome integrity, mitochondrial activity, glutathione (GSH) level, activities of enzymatic antioxidants (glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase), and the phosphorylation of AMPK. Meanwhile, the lipid peroxidation, ROS levels, and apoptosis of postthaw sperm were reduced in the presence of 50 μM resveratrol. Furthermore, when fresh boar sperm was incubated with the medium in the presence of 50 μM resveratrol and 30 μM Compound C (an AMPK inhibitor), the effects of the resveratrol were partly counteracted by the Compound C. These observations suggest that the resveratrol protects boar sperm via promoting AMPK phosphorylation. In conclusion, the addition of resveratrol to the freezing extenders protects boar sperm against ROS damage via promoting AMPK phosphorylation for decreasing the ROS production and improving the antioxidative defense system of postthaw sperm. These findings provide novel insights into understanding the mechanisms of resveratrol on how to protect boar sperm quality contrary to the ROS production during cryopreservation.

Negative effects of ROS generated during linear sperm motility on gene expression and ATP generation in boar sperm mitochondria

Mitochondrial oxidative phosphorylation (OXPHOS) is essential for ATP production to maintain sperm linear motility during migration from the uterus to the oviduct. However, ROS are generated as by-products of OXPHOS, causing stress and damaging the sperm quality. This study aimed to clarify the ROS targets in sperm mitochondria that decrease linear motility and to investigate whether mitochondria-target antioxidants (PQQ and CoQ10) affect mitochondrial activity and sperm motility. Sperm linear motility pattern, ATP production, and mitochondrial activity were decreased with increasing ROS levels during incubation in the low-glucose medium. However, sperm motility patterns and ROS levels were not significantly changed in the high-glucose medium. Moreover, the gene expression system (mt-DNA, mitochondrial transcription factor-A (TFAM) and RNA polymerase (POLRMT)) in sperm mitochondria was damaged during incubation in the low-glucose medium. Interestingly, PQQ treatment increased the mt-DNA stability and decreased the damage to TFAM and POLRMT, which resulted in high expression of mitochondrial genes. Furthermore, the antioxidants increased mitochondrial activity and maintained sperm linear motility under the low glucose condition. These results revealed that both ATP production and the mitochondrial transcription system are damaged with increasing ROS levels in sperm that show a linear motility pattern. Treatment with antioxidants, such as PQQ and CoQ10, is beneficial tool to maintain sperm linear motility.

Glycogen Synthase Kinase-3 Regulates Sperm Motility and Acrosome Reaction via Affecting Energy Metabolism in Goats

Hyperactivation and acrosome reaction of sperm are pre-requisite steps for fertilization. However, the hyperactivation and acrosome reaction are critically controlled through the phosphorylation of specific proteins. Glycogen synthase kinase-3 (GSK3), a serine/threonine kinase with two different isoforms (α and β), is involved in biochemical signaling pathways. This study was aimed to investigate whether the GSK3α/β is present in goat sperm and its regulatory role in sperm motility and acrosome reaction. GSK3α/β was detected with immunofluorescence and Western blotting. Sperm motility, membrane integrity, acrosome reaction, mitochondrial membrane potential, phospho-Ser21-GSK3α and phospho-Ser9-GSK3β were analyzed. The ATP production and activities of lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and succinate dehydrogenase (SDH) were measured. It was observed that the GSK3α/β was expressed in goat sperm, especially in the peri-acrosomal, mid-piece and principal piece of the tail. The abundance of GSK3α/β in sperm was increased during transit along the epididymis. Addition of either 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or CHIR99021 significantly increased the sperm motility patterns and GSK3α/β phosphorylation. Interestingly, the adenosine triphosphate (ATP) production, activities of LDH, MDH and SDH were observed to be increased in the CHIR99021 treatment. The results suggested that GSK3α/β regulates sperm motility and acrosome reaction via phospho-ser21-GSK3α and phospho-ser9-GSK3β that involved in the regulation of sperm energy metabolism.

Apolipoprotein-J blocks increased cell injury elicited by ox-LDL via inhibiting ROS-CaMKII pathway

Background

Oxidized low-density lipoprotein (ox-LDL) is crucial in cardiac injury. Apolipoprotein-J (ApoJ) contributes to antiapoptotic effects in the heart. We aimed to evaluate the protective effects of ApoJ against ox-LDL cytotoxicity in Neonatal rat ventricular cells (NRVCs).

Methods and results

NRVCs were damaged by exposure to ox-LDL, as shown by increased caspase-3/7 activity, enhanced caspase-3 expression, and decreased cell viability. ApoJ overexpression, using an adenovirus vector, significantly reduced ox-LDL-induced cell injury. ApoJ also prevented ox-LDL from augmenting reactive oxygen species (ROS) production, as demonstrated by elevated Nox2/gp91^phox and P47 expression. Furthermore, ApoJ overexpression reduced CaMKIIδ expression elicited by ox-LDL in cultured NRVCs. Upregulating CaMKIIδ activity, mediated by ox-LDL, was significantly inhibited by ApoJ overexpression. A CaMKIIδ inhibitor, KN93, prevented ApoJ’s protective effect against ox-LDL cytotoxicity. A ROS scavenger, Mn (III)meso-tetrakis (4-benzoic acid) porphyrin (Mn (III)TBAP), also attenuated CaMKIIδ’s increased expression and activity, induced by ox-LDL, and showed similar results to ApoJ by attenuating ox-LDL-induced cell damage, as ApoJ did.

Conclusions

ApoJ confers cytoprotection to NRVCs against ox-LDL cytotoxicity through the ROS-CaMKII pathways.

Distribution of Polysulfide in Human Biological Fluids and Their Association with Amylase and Sperm Activities

Intracellular polysulfide could regulate the redox balance via its anti-oxidant activity. However, the existence of polysulfide in biological fluids still remains unknown. Recently, we developed a quantitative analytical method for polysulfide and discovered that polysulfide exists in plasma and responds to oxidative stress. In this study, we confirmed the presence of polysulfide in other biological fluids, such as semen and nasal discharge. The levels of polysulfide in these biological fluids from healthy volunteers (n = 9) with identical characteristics were compared. Additionally, the circadian rhythm of plasma polysulfide was also investigated. The polysulfide levels detected from nasal discharge and seminal fluid were approximately 400 and 600 μM, respectively. No correlation could be found between plasma polysulfide and the polysulfide levels of tear, saliva, and nasal discharge. On the other hand, seminal polysulfide was positively correlated with plasma polysulfide, and almost all polysulfide contained in semen was found in seminal fluid. Intriguingly, saliva and seminal polysulfide strongly correlated with salivary amylase and sperm activities, respectively. These results provide a foundation for scientific breakthroughs in various research areas like infertility and the digestive system process.

Chlorpyrifos Induction of Testicular-Cell Apoptosis through Generation of Reactive Oxygen Species and Phosphorylation of AMPK

Chlorpyrifos (CPF) is the most frequently applied insecticide. Aside from effects on the neuronal cholinergic system, previous studies suggested a potential relationship between CPF exposure and male infertility; however, the molecular mechanism remains elusive. The aim of this study was to investigate the toxic effect of CPF on testicular cells and the potential mechanism via in vitro and in vivo experiments. The cytotoxic effects of CPF on mouse-derived spermatogonial cell lines (GC-1), Sertoli cell lines (TM4) and Leydig cell lines (TM3) were assessed by a CCK-8 assay, flow cytometry, a TUNEL assay, quantitative RT-PCR, and Western blotting. Exposure to CPF (10-50 μM) for 12 or 24 h resulted in significant death in all three testicular cell lines. The number of TUNEL-positive apoptotic cells were dose-dependent and increased with raised CPF concentrations. Further investigation indicated that CPF induced cell-cycle arrest and then promoted cell apoptosis. Additionally, CPF increased reactive-oxygen-species (ROS) production and lipid peroxidation (MDA) and reduced mitochondrial-membrane potential. The mechanism of cell apoptosis induced by CPF involved an increase in phosphorylated-AMP-activated-protein-kinase (p-AMPK) levels in the tested cells. In vivo, the expression of steroid-hormone-biosynthesis-related genes in testis, spleen, and lung in F0 and F1 mice were downregulated when there was intraperitoneal injection or dietary supplementation of CPF. This study provides a potential molecular mechanism of CPF-induced toxicity in testicular cells and a theoretical basis for future treatment of male infertility.