Reactive oxygen species and boar sperm function

The effects of sericin in recovering spermatogenesis and sexual hormone levels in diabetic rats

Sericin-S (a hydrolysate from the silk protein sericin) is a natural antioxidant, which may improve spermatogenesis while having high biological safety, thus potentially useful for the treatment of male infertility. Our objective was to determine the effects of sericin-S on the sperm parameters and sexual hormone levels in a diabetic rat model. Thirty-six adult male rats were randomly divided in two groups, inducing diabetes in one of them by intraperitoneal administration of streptozotocin (STZ; 65 mg/kg). Both groups were randomly assigned to three subgroups, receiving oral gavage of saline, 1% or 2% sericin extract for 60 days. Therefore, the experimental design was a 2 × 3 factorial design of STZ and sericin treatments. One day after the last treatment, the rats were euthanized, weighed, the testes were processed (weigh, volume, and histology), and serum samples were processed for measuring sex hormone levels [testosterone, follicle-stimulating hormone, and luteinizing hormone (LH)]. STZ treatment decreased LH concentration and counts of spermatogonia, spermatocytes, and spermatids. Body and testis weights were significantly (p < 0.05) lower in the control group (non-diabetic saline) compared to the treated groups. In non-diabetic rats, sericin treatments increased (p < 0.05) the number of testicular cells (spermatogonia, spermatocytes, spermatids, Sertoli, and Leydig cells) and sex hormone concentrations. In diabetic rats, administration of sericin significantly (p < 0.05) improved sperm cell number and sex hormones levels. In nutshell, sericin can clearly modify sperm parameters and overall sex hormone function, and could improve spermatogenesis in normal and diabetic rats.

Effects of Isatis root polysaccharide on boar sperm quality during liquid storage and in vitro fertilization

Liquid preservation of boar semen is a preferred method in pig husbandry, and antioxidants to protect against sperm oxidative stress during periods of storage have become the focus of recent research. Through its antioxidant activity, Isatis root polysaccharide (IRPS), a plant extract, can effectively reduce the cellular lipid peroxidation caused by the accumulation of reactive oxygen species inside mitochondria. In the present study, there was examination of the effects of no supplementation (Control) of a semen extender with or supplementation in different concentrations of IRPS (0.2, 0.4, 0.6, 0.8, and 1.2 mg/mL) on sperm quality variables and antioxidant capacity during liquid storage. The results indicate that after prolonged storage (≥ 3 days), the sperm motility was greater in the group supplemented with 0.6 mg/mL IRPS than in the other groups (P <  0.05). The use of this IRPS concentration also resulted in maintanence of acrosome integrity, plasma membrane integrity, mitochondrial membrane potential, and antioxidant capacity of the sperm (P <  0.05). Furthermore, the results of an in vitro fertilization study indicate IRPS at 0.6 mg/mL markedly increased the sperm fertilization capacity (P <  0.01) and embryonic development to the blastocyst stage (P <  0.05). The addition of 0.6 mg/mL IRPS enhanced the antioxidant capacity of boar sperm, resulting in greater preservation of sperm motility and fertilization capacity during liquid storage. These findings indicate that IRPS has the potential to be used as a component of a semen-preserving diluent to maintain sperm quality during storage.

An update on boar semen assessments by flow cytometry and CASA

In the quest for predicting fertility of an individual, enhancing semen handling, dilution and storage protocols, and understanding the impact of environment and, andrologists have changed their approaches to semen analysis. The technologies used today are fast developing and readily implemented in research. Semen is one of a few naturally occurring monocellular suspensions, so sperm function analysis by flow cytometry (FC) and utilization of fluorochromes is an ideal technique for high throughput, objective and accurate analysis. The complementary use of microscopical assessments by Computer-Assisted Semen Analysis (CASA), where sperm cell parameters can be objectively assessed is equally important. The objectivity and repeatability of these techniques have driven research on the function, identification of heterogeneity and fertility of the ejaculate. The wealth of knowledge obtained from the application of these powerful methods has changed our view of the spermatozoon. Although there is some application of these methods in the industry producing boar semen for artificial insemination (AI) and to eliminate sires of sub-standard semen quality, uptake of advanced methods is still slow. Instruments are becoming cheaper and technically more user friendly. Standardization of methodology and optimization of instrument settings is important for full implementation of these systems, including comparison between labs. This review provides an update on two technologies: flow cytometry and CASA for objective analysis of boar semen quality.

The in vitro effects of gibberellin on human sperm motility

Gibberellin, a plant growth regulator, is widely used to increase the shelf life and quality of fruits and vegetables. In this study, human semen samples were exposed to different concentrations of gibberellin, which reduced spermatozoa motility in vitro. Gibberellin exposure also increased levels of reactive oxygen species and the protein levels of apoptosis markers in human sperm. Gibberellin inhibited the activity of Na+/K+-adenosine triphosphatase (ATPase) and Ca2+-ATPase, which maintain the stability of ions inside and outside the membranes of spermatozoa. Moreover, gibberellin exposure suppressed adenosine triphosphate production and reduced the protein levels of adenosine triphosphate synthases, which may have induced the protein expression of adenosine 5'-monophosphate-activated protein kinase (AMPK) and its phosphorylated form. These results suggest that gibberellin reduces human sperm motility in vitro by increasing reactive oxygen species levels and reducing ATPase activity, which may upregulate AMPK and consequently reduce the fertilization potential of spermatozoa.

Aminoguanidine Protects Boar Spermatozoa against the Deleterious Effects of Oxidative Stress

Aminoguanidine is a selective inhibitor of the inducible nitric oxide synthase (iNOS) and a scavenger of reactive oxygen species (ROS). Numerous studies have shown the antioxidant properties of aminoguanidine in several cell lines, but the in vitro effects of this compound on spermatozoa under oxidative stress are unknown. In this study, we tested the hypothesis that aminoguanidine may protect against the detrimental effects of oxidative stress in boar spermatozoa. For this purpose, sperm samples were incubated with a ROS generating system (Fe²⁺/ascorbate) with or without aminoguanidine supplementation (10, 1, and 0.1 mM). Our results show that aminoguanidine has powerful antioxidant capacity and protects boar spermatozoa against the deleterious effects of oxidative stress. After 2 h and 3.5 h of sperm incubation, the samples treated with aminoguanidine showed a significant increase in sperm velocity, plasma membrane and acrosome integrity together with a reduced lipid peroxidation in comparison with control samples (p < 0.001). Interestingly, except for the levels of malondialdehyde, the samples treated with 1 mM aminoguanidine did not differ or showed better performance than control samples without Fe²⁺/ascorbate. The results from this study provide new insights into the application of aminoguanidine as an in vitro therapeutic agent against the detrimental effects of oxidative stress in semen samples.

Determination of the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues: A comparison between two breeding seasons

The key prerequisite for successful insemination is sperm characterized to have positive values for morphological and biological variables which are determined by, among others, effective antioxidant protection during the lifespan of sperm cells. This study evaluated the activity and relative abundance of mRNA for antioxidant enzymes in stallion testicular and epididymal tissues during breeding (n = 5) and non-breeding (n = 5) seasons. The activity of superoxide dismutase (SOD) was greater (P < 0.05) during the breeding season, in particular in the testes and the caput epididymis, and SOD1 was the predominant isoform of the enzyme. The expression of the SOD3 gene was markedly less in the analyzed tissues, which indicates that this enzyme contributes to the antioxidant protection of the stallion reproductive tract. The activity of catalase (CAT) was less (P < 0.05) in the testes during both seasons while its relative abundances only during the breeding season. The greatest CAT activity was noted in the cauda epididymis during the breeding season. The activity of glutathione peroxidases (GPx) was greater (P < 0.05) in the testes than in other tissues and 10-fold greater during the breeding season. Similarly, relative abundance of GPx5 mRNA was greater (P < 0.05) in the caput epididymis than in the remaining tissues during both seasons. This study demonstrated that season has an ambiguous influence on the antioxidant defense system in stallion reproductive tissues. Seasonal differences in the present study, however, indicate that the reproductive system of stallions adapts well to environmental seasonal changes.

Melatonin affects the motility and adhesiveness of in vitro capacitated boar spermatozoa via a mechanism that does not depend on intracellular ROS levels

This work sought to address the effects of melatonin during in vitro capacitation (IVC) and progesterone-induced acrosome exocytosis (IVAE) in boar spermatozoa. With this purpose, two different experiments were set. In the first one, IVC and IVAE were induced in the absence or presence of melatonin, which was added either at the start of IVC or upon triggering the IVAE with progesterone. Different parameters were evaluated, including intracellular levels of peroxides and superoxides, free cysteine radicals and distribution of specific lectins. While melatonin neither affected most capacitation-associated parameters nor IVAE, it dramatically decreased sperm motility, with a maximal effect at 5 μm. This effect was accompanied by a significant increase in the percentage of agglutinated spermatozoa, which was independent from noticeable changes in the distribution of lectins. Levels of free cysteine radicals were significantly lower in melatonin treatments than in the control after 4 h of incubation in capacitating medium. The second experiment evaluated the effects of melatonin on in vitro fertilising ability of boar spermatozoa. Spermatozoa previously subjected to IVC in the presence of 1 μm melatonin and used for in vitro fertilisation exhibited less ability to bind the zona pellucida (ZP) and higher percentages of monospermy. In conclusion, melatonin affects sperm motility and the stability of nucleoprotein structure and also modulates the ability of in vitro capacitated boar spermatozoa to bind the oocyte ZP. However, such effects do not seem to be related to either its antioxidant properties or changes in the sperm glycocalix.

Factors and pathways involved in capacitation: how are they regulated?

In mammals, fertilization occurs via a comprehensive progression of events. Freshly ejaculated sperm have yet to acquire progressive motility or fertilization ability. They must first undergo a series of biochemical and physiological changes, collectively known as capacitation. Capacitation is a significant prerequisite to fertilization. During the process of capacitation, changes in membrane properties, intracellular ion concentration and the activities of enzymes, together with other protein modifications, induce multiple signaling events and pathways in defined media in vitro or in the female reproductive tract in vivo. These, in turn, stimulate the acrosome reaction and prepare spermatozoa for penetration of the egg zona pellucida prior to fertilization. In the present review, we conclude all mainstream factors and pathways regulate capacitation and highlight their crosstalk. We also summarize the relationship between capacitation and assisted reproductive technology or human disease. In the end, we sum up the open questions and future avenues in this field.

Decrease in the cytosolic NADP+-dependent isocitrate dehydrogenase activity through porcine sperm capacitation

In order to understand the molecular mechanisms involved in the sperm capacitation, we have identified the proteins tyrosine-phosphorylated during the capacitation especially in conjunction with the regulation of the levels of reactive oxygen species (ROS) in sperm. In the present study, the effects of the tyrosine phosphorylation of cytosolic NADP⁺-dependent isocitrate dehydrogenase (IDPc) on its catalytic activity and on the levels of ROS in sperm have been studied. The tyrosine phosphorylated IDPc showed a significantly lowered enzymatic activity. The immunocytochemical analyses using the highly specific antisera against IDPc revealed that IDPc was mainly localized to the principal piece of the porcine sperm flagellum. As IDPc is one of the major NADPH regenerating enzymes in porcine sperm, it is strongly suggested that the decrease in IDPc activity is involved in the increased levels of ROS, which results in the induction of hyperactivated flagellar movement and capacitation.

Effects of season on boar semen parameters and antioxidant enzymes in the south subtropical region in Brazil

Although boar semen productivity is affected by seasonality, its effects are not equal among different regions which raise concerns regarding the profitability of boar stud farms. Therefore, the goals of this study were (i) to evaluate the seasonal effect on semen production in a commercial boar stud farm located in a subtropical climate region and (ii) to verify whether the activities of superoxide dismutase and glutathione peroxidase in spermatozoa and seminal plasma were associated with seminal traits of fresh and cooled semen. Nine boars were collected twice per season, and routine seminal parameter analyses were performed together with superoxide dismutase and glutathione peroxidase activities in seminal plasma and spermatozoa. Despite a reduction in sperm concentration in spring and summer, most seminal parameters were constant year-round. Temperature-humidity index was higher in the summer compared to spring, autumn and winter (p < .05). Superoxide dismutase activity in spermatozoa was increased in summer compared to autumn and winter (p < .05). The activities of both enzymes in seminal plasma and spermatozoa glutathione peroxidase remained unaltered throughout the seasons. In conclusion, seasonality showed little influence in overall boar seminal parameters despite microclimatic differences among seasons, and spermatozoa collected during summer increased superoxide dismutase activity.

Seminal plasma antioxidants are directly involved in boar sperm cryotolerance

Boar ejaculates are ejected in fractions with a specific composition in terms of sperm numbers and seminal plasma (SP), which is reflected in the varying sperm cryotolerance observed among different fractions. As boar sperm are particularly sensitive to oxidative stress, this study evaluated the role of SP antioxidants in the observed differences in sperm cryotolerance among ejaculate fractions. Ten ejaculates from five boars were manually collected in fractions: the first 10 mL of the sperm-rich fraction (SRF), the rest of the SRF and the post-SRF. Semen samples comprising the entire ejaculate (EE) were created by proportionally mixing the three fractions described above. Each of the 40 resulting semen samples was split into two aliquots: one was used for sperm cryopreservation following a standard protocol utilizing 0.5-mL straws, and the other was used to collect SP for antioxidant assessment. Frozen-thawed (FT) sperm from the SRF (the first 10 mL of the SRF and the rest of the SRF) and those from post-SRF were of the highest and worst quality, respectively, which was measured in terms of total and objective progressive motility and viability (P < 0.01). Viable FT sperm from the post-SRF generated more reactive oxygen species and experienced more lipid peroxidation than those from the SRF (both the first 10 mL and the rest of the SRF) (P < 0.01). The percentage of FT sperm exhibiting fragmented nuclear DNA did not differ among ejaculate fractions and the EE. Catalase, glutathione peroxidase and glutathione peroxidase 5 (GPx-5) were lowest in SP from the first 10 mL of the SRF (P < 0.001), whereas superoxide dismutase (SOD) and paraoxonase 1 (PON-1) were highest in SP of the SRF (both the first 10 mL and the rest of the SRF) (P < 0.01). Trolox-equivalent antioxidant capacity (TEAC) and the ferric-reducing ability of plasma (FRAP) were highest in SP from the first 10 mL of the SRF and lowest in the post-SRF (P < 0.001), whereas cupric-reducing antioxidant capacity was lowest (P < 0.05) in SP from the first 10 mL of the SRF. Regression analyses indicated that certain SP antioxidants had good predictive value for post-thaw recovery rates of total motility (R² = 54.8%, P < 0.001; including SOD, TEAC and FRAP) and viability (R² = 56.1%, P < 0.001; including SOD, PON-1, GPx-5 and TEAC). These results demonstrated that certain SP antioxidants are positively involved in boar sperm cryotolerance, minimizing the oxidative stress imposed by cryogenic handling.

Enhancement of sperm motility and viability by turmeric by-product dietary supplementation in roosters

Improving sperm motility and viability are major goals to improve efficiency in the poultry industry. In this study, the effects of supplemental dietary turmeric by-product (TBP) from commercial turmeric production on sperm motility, viability, and antioxidative status were examined in domestic fowl. Mature Rhode Island Red roosters were divided into two groups - controls (groupC) without TBP administration and test subjects (groupT) fed a basal diet supplemented with 0.8g of TBP/day in a temperature-controlled rearing facility (Experiment 1) and 1.6g/day under heat stress (Experiment 2) for 4 weeks. In Experiment 1, TBP dietary supplementation increased the sperm motility variables straight-line velocity, curvilinear velocity, and linearity based on a computer-assisted semen analysis, 2 weeks following TBP supplementation. In Experiment 2, using flow cytometry, sperm viability at 3 and 4 weeks following TBP supplementation was greater in Group T than C, and this increase was consistent with a reduction in reactive oxygen species (ROS) production at 2 and 4 weeks. The results of both experiments clearly demonstrate that dietary supplementation with TBP enhanced sperm motility in the controlled-temperature conditions as well as sperm viability, and reduced ROS generation when heat stress prevailed. Considering its potential application in a range of environments, TBP may serve as an economical and potent antioxidant to improve rooster fertility.

Rooibos (Aspalathus linearis) extract enhances boar sperm velocity up to 96 hours of semen storage

Rooibos (Aspalathus linearis) is a native shrub from South African fynbos and has become very popular in the last decades for its antioxidant and medicinal attributes. Several studies have shown its beneficial properties in numerous cell lines, but to date, the in vitro effects of rooibos extract on sperm cells are still unknown. In this study, boar semen was supplemented with four concentrations both of fermented and unfermented rooibos extracts during 96 h of liquid storage at 17°C. The effects of rooibos extracts on sperm velocity, membrane integrity, and acrosomal status were evaluated at 2 h, 48 h, and 96 h of semen storage. Overall our results indicate that rooibos extract enhances sperm velocity, protects the acrosome structure, and tends to preserve the membrane integrity during semen storage. Although the unfermented rooibos showed higher total polyphenol content and total antioxidant capacity than the fermented one, the latter had better effects on sperm velocity leading to, for instance, an increase of 30% in the rectilinear velocity (VSL) at 48 h compared to the control group. Taking into account the different storage times, we established a suitable range of extracts concentrations to be used in boar semen. The rooibos extract ought to be considered as a powerful and natural source of antioxidants for the preservation of boar semen.

Bovine serum albumin and skim-milk improve boar sperm motility by enhancing energy metabolism and protein modifications during liquid storage at 17 °C

Both bovine serum albumin (BSA) and skim-milk have been reported to improve sperm quality, primarily by enhancing sperm motility, but the underlying molecular mechanism remains unknown. In this study, boar semen samples were collected and diluted with Androstar^® Plus extender containing different concentrations (0, 2, 4 g/l) of BSA and skim-milk. On days 0, 3, 5 and 7, the sperm motility parameters were determined using computer-assisted sperm analysis (CASA), and the ATP concentrations, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity and mitochondrial membrane potential were evaluated using commercial kits. The levels of protein phosphorylation, acylation and ubiquitination were analyzed by western blot. The results showed that supplementation with BSA and skim-milk provided higher sperm motility parameters, ATP levels, GAPDH activity and mitochondrial membrane potential than the control group (P < 0.05). Interestingly, we found that the levels of protein phosphorylation, acetylation and succinylation of the spermatozoa in the treated groups were dramatically higher than those in the control group (P < 0.05). Though the protein ubiquitination level had a decreasing trend, the change in ubiquitination modification was not significantly different between the control group and treated groups. Moreover, the changes in protein modifications between the BSA treated group and skim-milk treated group were not distinctly dissimilar. Taken together, these results suggest that BSA and skim-milk had a positive role in the regulation of boar sperm motility by influencing sperm protein modifications changes as well as increasing the GAPDH activity, mitochondrial membrane potential, and intracellular ATP content. This research provides novel insights into the molecular mechanisms underlying BSA and skim-milk protective effects on boar sperm in the male reproductive system and suggests the feasibility of using skim-milk instead of BSA as a boar semen extender supplement.

Influence of iodine in excess on seminiferous tubular structure and epididymal sperm character in male rats

Excess iodine induced public health problems are now emerging in many iodine sufficient regions for indiscriminate intake of iodine through various iodized products. It has been reported that excess iodine can disrupt overall male reproductive physiology by generating oxidative stress in the testis. However, information on the possible effect of iodine in excess on spermatozoa found less. In the present investigation flow cytometric techniques and scanning electron microscopy (SEM) have been used to study the spermatozoal functional as well as structural status under the influence of excess iodine; generation of ROS in the spermatozoa as evident by DCFDA, altered acrosomal integrity as observed by fluorescence lectin staining method and depolarized mitochondrial membrane potential (ΔΨ_m ) noticed by JC-1 staining. Ultrastructure of seminiferous tubule after excess iodine exposure indicated severe deterioration of seminiferous tubular surface architecture. Significant increase in spermatozoal DNA fragmentation and apoptotic sperms were found by acridine orange and Annexin V, respectively, however the plasma membrane integrity/viability was decreased as evident by propidium iodide staining in various incremental doses and durations under iodine excess. The study reveals that excess iodine could cause apoptosis of spermatozoal cells by inducing ROS that ultimately affects male fertility potential.

Seminal plasma affects sperm sex sorting in boars

Two experiments were conducted in boar semen samples to evaluate how both holding time (24h) and the presence of seminal plasma (SP) before sorting affect sperm sortability and the ability of sex-sorted spermatozoa to tolerate liquid storage. Whole ejaculate samples were divided into three aliquots immediately after collection: one was diluted (1:1, v/v) in Beltsville thawing solution (BTS; 50% SP); the SP of the other two aliquots was removed and the sperm pellets were diluted with BTS + 10% of their own SP (10% SP) or BTS alone (0% SP). The three aliquots of each ejaculate were divided into two portions, one that was processed immediately for sorting and a second that was sorted after 24h storage at 15-17°C. In the first experiment, the ability to exhibit well-defined X- and Y-chromosome-bearing sperm peaks (split) in the cytometry histogram and the subsequent sorting efficiency were assessed (20 ejaculates). In contrast with holding time, the SP proportion influenced the parameters examined, as evidenced by the higher number of ejaculates exhibiting split and better sorting efficiency (P<0.05) in semen samples with 0-10% SP compared with those with 50% SP. In a second experiment, the quality (viability, total and progressive motility) and functionality (plasma membrane fluidity and intracellular generation of reactive oxygen species) of sex-sorted spermatozoa were evaluated after 0, 72 and 120h storage at 15-17°C (10 ejaculates). Holding time and SP proportion did not influence the quality or functionality of stored sex-sorted spermatozoa. In conclusion, a holding time as long as 24h before sorting did not negatively affect sex sorting efficiency or the ability of sorted boar spermatozoa to tolerate long-term liquid storage. A high proportion of SP (50%) in the semen samples before sorting reduced the number of ejaculates to be sorted and negatively influenced the sorting efficiency, but did not affect the ability of sex-sorted spermatozoa to tolerate liquid storage.

Effects of difructose dianhydride (DFA)-IV on in vitro fertilization in pigs

Difructose dianhydride IV (DFA-IV) is produced from levan, which is a natural polysaccharide that belongs to the fructan family, through the activity of levan fructotransferase (LF) derived from microorganisms. Recently, DFA-IV has been expected to have diverse applications in the food and medical industry. Here, we examined the potential application of DFA-IV forin vitro fertilization (IVF) in pigs. In the assessment of acrosomal integrity during incubation, intact acrosomal or viable spermatozoa were highly sustained in 0.1% or 0.25% DFA-IV (69.8%-70.8%,P<0.05). Reactive oxygen species (ROS) levels during sperm incubation decreased following the addition of DFA-IV, and 0.1%-0.5% DFA-IV in particular significantly decreased ROS production relative to that seen with no addition or 0.75% DFA-IV. Total fertilization (mono+ polyspermic oocyte) rate was significantly higher in the addition of 0.1% DFA-IV (94.2%) than with other concentrations (71.8%-86.7%,P<0.05). When using reduced IVF times and lower sperm numbers, we found that addition of 0.1%–0.5% DFA-IV significantly increased the fertilization rate (P<0.05). Fertilized oocytes treated with 0.1% DFA-IV exhibited higher embryonic development and blastocyst formation than those treated with other concentrations (P<0.05). Consequently, the addition of DFA-IV during IVF improved fertilization and embryonic development, suggesting the possible use of novel sugars for enhancement of assisted reproductive technology (ART) in mammals.

Hydrogen Sulfide and/or Ammonia Reduces Spermatozoa Motility through AMPK/AKT Related Pathways

A number of emerging studies suggest that air pollutants such as hydrogen sulfide (H₂S) and ammonia (NH₃) may cause a decline in spermatozoa motility. The impact and underlying mechanisms are currently unknown. Boar spermatozoa (in vitro) and peripubertal male mice (in vivo) were exposed to H₂S and/or NH₃ to evaluate the impact on spermatozoa motility. Na₂S and/or NH₄Cl reduced the motility of boar spermatozoa in vitro. Na₂S and/or NH₄Cl disrupted multiple signaling pathways including decreasing Na⁺/K⁺ ATPase activity and protein kinase B (AKT) levels, activating Adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) and phosphatase and tensin homolog deleted on chromosome ten (PTEN), and increasing reactive oxygen species (ROS) to diminish boar spermatozoa motility. The increase in ROS might have activated PTEN, which in turn diminished AKT activation. The ATP deficiency (indicated by reduction in Na⁺/K⁺ ATPase activity), transforming growth factor (TGF_β) activated kinase-1 (TAK1) activation, and AKT deactivation stimulated AMPK, which caused a decline in boar spermatozoa motility. Simultaneously, the deactivation of AKT might play some role in the reduction of boar spermatozoa motility. Furthermore, Na₂S and/or NH₄Cl declined the motility of mouse spermatozoa without affecting mouse body weight gain in vivo. Findings of the present study suggest that H₂S and/or NH₃ are adversely associated with spermatozoa motility.

Glutathione Peroxidase 5 Is Expressed by the Entire Pig Male Genital Tract and Once in the Seminal Plasma Contributes to Sperm Survival and In Vivo Fertility

Glutathione peroxidase-5 (GPX5) is an H₂O₂-scavenging enzyme identified in boar seminal plasma (SP). This study attempted to clarify its origin and role on sperm survival and fertility after artificial insemination (AI). GPX5 was expressed (Western blot and immunocytochemistry using a rabbit primary polyclonal antibody) in testes, epididymis and accessory sex glands (6 boars). SP-GPX5 concentration differed among boars (11 boars, P < 0.001), among ejaculates within boar (44 ejaculates, P < 0.001) and among portions within ejaculate (15 ejaculates). The first 10 mL of the sperm rich fraction (SRF, sperm-peak portion) had a significantly lower concentration (8.87 ± 0.78 ng/mL) than the rest of the SRF and the post-SRF (11.66 ± 0.79 and 12.37 ± 0.79 ng/mL, respectively, P < 0.005). Sperm motility of liquid-stored semen AI-doses (n = 44, at 15–17°C during 72h) declined faster in AI-doses with low concentrations of SP-GPX5 compared to those with high-levels. Boars (n = 11) with high SP-GPX5 showed higher farrowing rates and litter sizes than those with low SP-GPX5 (a total of 5,275 inseminated sows). In sum, GPX5 is widely expressed in the boar genital tract and its variable presence in SP shows a positive relationship with sperm quality and fertility outcomes of liquid-stored semen AI-doses.

High total antioxidant capacity of the porcine seminal plasma (SP-TAC) relates to sperm survival and fertility

The study attempted to clarify the role of total antioxidant capacity of seminal plasma (SP-TAC) on boar sperm survival and fertility after artificial insemination (AI). SP-TAC differed (P < 0.001) among boars (n° = 15) and, to a lesser degree, among ejaculates within male (4 ejaculates/boar). SP-TAC also differed (P < 0.001) among ejaculate fractions (43 ejaculates and 3 fractions per ejaculate), of which the sperm-peak portion of the sperm rich ejaculate fraction (SRF) had the highest SP-TAC. SP-TAC was not correlated with sperm quality (motility and viability) or functionality (intracellular ROS generation and lipid peroxidation) of liquid AI-semen samples stored at 17 °C for 72 h (90 AI-samples), but the decline in sperm quality was larger (P < 0.05) in ejaculates with low, compared with high SP-TAC (hierarchically grouped). The SP-TAC differences among ejaculate portions agree with sperm cryosurvival rates (14 ejaculates from 7 boars), showing sperm from sperm-peak portion better (P < 0.01) post-thaw quality and functionality than those from the entire ejaculate (mainly post-SRF). Boars (n° = 18) with high SP-TAC (hierarchically grouped) had higher (P < 0.05) fertility outcomes (5,546 AI-sows) than those with low SP-TAC. Measurement of SP-TAC ought to be a discriminative tool to prognosis fertility in breeding boars.

Exposure to Endosulfan can result in male infertility due to testicular atrophy and reduced sperm count

Endosulfan (ES) is a widely used organochlorine pesticide and is speculated to be detrimental to human health. However, very little is known about mechanism of its genotoxicity. Using mouse model system, we show that exposure to ES affected physiology and cellular architecture of organs and tissues. Among all organs, damage to testes was extensive and it resulted in death of different testicular-cell populations. We find that the damage in testes resulted in qualitative and quantitative defects during spermatogenesis in a time-dependent manner, increasing epididymal reactive oxygen species levels, affecting sperm chromatin integrity. This further culminated in reduced number of epididymal sperms and actively motile sperms. Finally, we show that ES exposure affected fertility in male but not in female mice. Therefore, we demonstrate that ES exerts pathophysiological changes in mice, induces testicular atrophy, affects spermatogenesis, reduces quantity and vigour of epididymal sperm and leads to infertility in males.

Sperm cryopreservation update: Cryodamage, markers, and factors affecting the sperm freezability in pigs

Cryopreservation is the most efficient method for long-term preservation of mammalian sperm. However, freeze-thawing procedures may strongly impair the sperm function and survival and thus decrease the reproductive performance. In addition, the sperm resilience to withstand cryopreservation, also known as freezability, presents a high individual variability. The present work summarizes the principles of cryoinjury and the relevance of permeating and nonpermeating cryoprotective agents. Descriptions about sperm cryodamage are mainly focused on boar sperm, but reference to other mammalian species is also made when relevant. Main cryoinjuries not only regard to sperm motility and membrane integrity, but also to the degradation effect exerted by freeze-thawing on other important components for sperm fertilizing ability, such as mRNAs. After delving into the main differences between good and poor freezability boar ejaculates, those protein markers predicting the sperm ability to sustain cryopreservation are also mentioned. Moreover, factors that may influence sperm freezability, such as season, diet, breed, or ejaculate fractions are discussed, together with the effects of different additives, like seminal plasma and antioxidants. After briefly referring to the effects of long-term sperm preservation in frozen state and the reproductive performance of frozen-thawed boar sperm, this work speculates with new research horizons on the preservation of boar sperm, such as vitrification and freeze-drying.

Effect of Conjugated Linoleic Acid on Boar Semen Quality After Long-term Refrigeration at 17°C

In this study, the effect of conjugated linoleic acid (10 trans, 12 cis) (CLA) on refrigerated boar sperm quality parameters up to 14 days at 17°C was assessed. Semen was extended in Androhep and divided into four treatments supplemented with CLA (25, 50, 100 and 200 μm) and control group, then kept for 2 h at 22°C. Afterwards an aliquot of each treatment was removed, and mitochondrial activity, viability, lipid membrane peroxidation (LPO) and stability of the sperm plasma membrane were assessed by flow cytometry. The remaining extended semen was maintained at 17°C until 336 h, repeating the same analysis every 48 h. Regarding percentage of live spermatozoa, no statistical differences were observed among treatments up to 96 h. After this time, viability decreased significantly (p < 0.05) for CLA concentrations of 100 and 200 μm. Despite these results, there was an individual response to CLA. Although in the control group, the boar A presented better results when compared with the other boars, especially at concentrations of 50 and 100 μm boar B showed significantly higher results (p < 0.05). Supplementation with CLA improved (p < 0.05) LPO, but not the mitochondrial membrane potential of sperm. The highest two CLA concentrations showed to be toxic for sperm as all results were lower than the observed for the control. In conclusion, CLA at 50 μm seems to be an efficient concentration for reducing the oxidative stress, decreasing LPO, maintaining viability, membrane stability and mitochondrial potential on refrigerated boar spermatozoa.

Selenium in pig nutrition and reproduction: boars and semen quality-a review

Selenium plays an important role in boar nutrition via participating in selenoprotein synthesis. It seems likely that selenoproteins are central for antioxidant system regulation in the body. Se-dependent enzyme glutathione peroxidase (GSH-Px) is the most studied selenoprotein in swine production. However, roles of other selenoproteins in boar semen production and maintenance of semen quality also need to be studied. Boar semen is characterised by a high proportion of easily oxidized long chain polyunsaturated fatty acids and requires an effective antioxidant defense. The requirement of swine for selenium varies depending on many environmental and other conditions and, in general, is considered to be 0.15 to 0.30 mg/kg feed. It seems likely that reproducing sows and boars are especially sensitive to Se deficiency, and meeting their requirements is an important challenge for pig nutritionists. In fact, in many countries there are legal limits as to how much Se may be included into the diet and this restricts flexibility in terms of addressing the Se needs of the developing and reproducing swine. The analysis of data of various boar trials with different Se sources indicates that in some cases when background Se levels were low, there were advantages of Se dietary supplementation. It is necessary to take into account that only an optimal Se status of animals is associated with the best antioxidant protection and could have positive effects on boar semen production and its quality. However, in many cases, background Se levels were not determined and therefore, it is difficult to judge if the basic diets were deficient in Se. It can also be suggested that, because of higher efficacy of assimilation from the diet, and possibilities of building Se reserves in the body, organic selenium in the form of selenomethionine (SeMet) provided by a range of products, including Se-Yeast and SeMet preparations is an important source of Se to better meet the needs of modern pig genotypes in commercial conditions of intensive pig production.

The effect of low-level laser irradiation on sperm motility, and integrity of the plasma membrane and acrosome in cryopreserved bovine sperm

BACKGROUND AND OBJECTIVE

Freezing changes sperm integrity remarkably. Cryopreservation involves cooling, freezing, and thawing and all these contribute to structural damage in sperm, resulting in reduced fertility potential. Low-level laser irradiation (LLLI) could increase energy supply to the cell and cause reactive oxygen species reduction (ROS), contributing to the restoration of oxygen consumption and adenosine triphosphate synthesis (ATP) in the mitochondria. Our goal was to analyze the effects of low-level laser irradiation on sperm motility and integrity of the plasma membrane and acrosome in cryopreserved bovine sperm.

STUDY DESIGN/MATERIALS AND METHODS

We analyzed 09 samples of bull semen (Bos taurus indicus), divided into three groups: a control group without laser irradiation, a 4J group subjected to a laser irradiation dose of 4 joules, and a 6J group subjected to dose of 6 joules. Samples were divided for the analysis of cell viability and acrosomal membrane integrity using flow cytometry; another portion was used for motion analysis. Irradiation was performed in petri dishes of 30 mm containing 3 ml of semen by an aluminum gallium indium phosphide laser diode with a wavelength of 660 nm, 30 mW power, and energy of 4 and 6 joules for 80 and 120 seconds respectively. Subsequently, the irradiated and control semen samples were subjected to cryopreservation and analyzed by flow cytometry (7AAD and FITC-PSA) using the ISAS--Integrated Semen Analysis System.

RESULTS

Flow cytometry showed an increase in the percentage of live sperm cells and acrosome integrity in relation to control cells when subjected to irradiation of low-power laser in two different doses of 4 and 6 joules (p < 0.05). In the analysis of straightness, percentage of cell movement, and motility, a dose of 4 joules was more effective (p < 0.05).

CONCLUSION

We conclude that LLLI may exert beneficial effects in the preservation of live sperm. A dose of 4 joules prior to cryopreservation was more effective than a dose of 6 joules in preserving sperm motility.

Abnormalities in the male reproductive system after exposure to diesel and biodiesel blend

Altering the fuel source from petroleum-based ultralow sulfur diesel to biodiesel and its blends is considered by many to be a sustainable choice for controlling exposures to particulate material. As the exhaust of biodiesel/diesel blends is composed of a combination of combustion products of polycyclic aromatic hydrocarbons and fatty acid methyl esters, we hypothesize that 50% biodiesel/diesel blend (BD50) exposure could induce harmful outcomes because of its ability to trigger oxidative damage. Here, adverse effects were compared in murine male reproductive organs after pharyngeal aspiration with particles generated by engine fueled with BD50 or neat petroleum diesel (D100). When compared with D100, exposure to BD50 significantly altered sperm integrity, including concentration, motility, and morphological abnormalities, as well as increasing testosterone levels in testes during the time course postexposure. Serum level of luteinizing hormone was significantly depleted only after BD50 exposure. Moreover, we observed that exposure to BD50 significantly increased sperm DNA fragmentation and the upregulation of inflammatory cytokines in the serum and testes on Day 7 postexposure when compared with D100. Histological evaluation of testes sections from BD50 exposure indicated more noticeable interstitial edema, degenerating spermatocytes, and dystrophic seminiferous tubules with arrested spermatogenesis. Significant differences in the level of oxidative stress assessed by accumulation of lipid peroxidation products and depletion of glutathione were detected on exposure to respirable BD50 and D100. Taken together, these results indicate that exposure of mice to inhalable BD50 caused more pronounced adverse effects on male reproductive function than diesel.

Effects of bovine serum albumin on boar sperm quality during liquid storage at 17°C

This study aimed to investigate the effects of bovine serum albumin (BSA) on boar sperm quality during liquid storage at 17°C. Boar semen samples were collected and diluted with Modena containing different concentrations (0, 1, 2, 3, 4, 5 and 6 g/l) of BSA, and sperm motility, plasma membrane integrity, acrosome integrity, total antioxidative capacity (T-AOC) activity and malondialdehyde (MDA) content were measured and analysed. The results showed that Modena supplemented with 3, 4 and 5 g/l BSA could improve boar sperm motility, effective survival time and plasma membrane integrity (p < 0.05), decrease MDA content (p < 0.05), while no statistical difference was observed for sperm acrosome integrity and T-AOC activity among these three groups (p > 0.05). The semen sample diluted with Modena containing 4 g/l BSA could achieve optimum effect, and sperm survival time was 7.5 days. After 7 days preservation, sperm motility, plasma membrane integrity and acrosome integrity were 54%, 49% and 78%, respectively. T-AOC activity and MDA content were 1.03 U/ml and 17.5 nmol/ml, respectively. In conclusion, Modena supplemented with BSA reduced the oxidative stress and improved the sperm quality of boar semen during liquid storage at 17°C, and 4 g/l BSA was the optimum concentration. Further studies are required to obtain more concrete results on the determination of antioxidant capacities of BSA in liquid preserved boar semen.

The activity of paraoxonase type 1 (PON-1) in boar seminal plasma and its relationship with sperm quality, functionality, and in vivo fertility

Paraoxonase 1 (PON-1) is a hydrolytic enzyme present in body fluids, capable of protecting cells against oxidative stress. The hypothesis was hereby to test that PON-1, present in seminal plasma (SP), acts protecting boar spermatozoa when showing a reasonable high activity in the ejaculate. SP-PON-1 activity differed (p < 0.001) among boars (from 0.10 to 0.29 IU/mL). Intra-boar variability was also observed (p < 0.05), but only in two of the 15 boars. SP-PON-1 activity differed among ejaculate portions, showing the spermatozoa-peak portion of spermatozoa-rich ejaculate fraction the highest levels (0.35 ± 0.03 IU/mL, ranging from 0.12 to 0.69) and the post-sperm ejaculate fraction the lowest levels (0.12 ± 0.01 IU/mL, ranging from 0.03 to 0.21). SP-PON-1 activity was positively correlated with the percentage of spermatozoa with rapid and progressive movement (p < 0.01) and negatively correlated with the generation of intracellular reactive oxygen species (p < 0.01) in semen samples after 72 h of liquid storage. SP-PON-1 activity was highest (p < 0.01) in boars with highest farrowing rates. In conclusion, SP-PON-1 activity differed among boars and ejaculate fractions/portions. SP-PON-1 activity was positively correlated with sperm quality and functionality of liquid-stored semen samples and it evidenced a positive association with in vivo fertility.

Measurement of activity and concentration of paraoxonase 1 (PON-1) in seminal plasma and identification of PON-2 in the sperm of boar ejaculates

This study revealed and characterised the presence of the antioxidant enzymes paraoxonase (PON) type 1 (PON-1, extracellular) and type 2 (PON-2, intracellular) in boar semen. To evaluate PON-1, an entire ejaculate from each of ten boars was collected and the seminal plasma was harvested after double centrifugation (1,500g for 10 min). Seminal plasma was analysed for concentration as well as enzymatic activity of PON-1 and total cholesterol levels. Seminal-plasma PON-1 concentration ranged from 0.961 to 1.670 ng/ml while its enzymatic activity ranged from 0.056 to 0.400 IU/ml, which represent individual variance. Seminal-plasma PON-1 concentration and enzymatic activity were negatively correlated (r = -0.763; P < 0.01). The activity of seminal-plasma PON-1 negatively correlated with ejaculate volume (r = -0.726, P < 0.05), but positively correlated with sperm concentration (r = 0.654, P < 0.05). Total seminal-plasma cholesterol concentration positively correlated with PON-1 activity (r = 0.773; P < 0.01), but negatively correlated with PON-1 concentration (r = -0.709; P < 0.05). The presence of intracellular PON-2 was determined via immunocytochemistry in spermatozoa derived from artificial insemination. PON-2 localised to the post-acrosomal area of the sperm head and principal piece of the tail in membrane-intact spermatozoa. In summary, PON is present in boar semen, with PON-1 at low levels in seminal plasma and PON-2 within the spermatozoa. Further studies are needed to characterise the relationship between antioxidant PONs with sperm and other seminal-plasma parameters.

Oxidative stress and male reproductive health

One of the major causes of defective sperm function is oxidative stress, which not only disrupts the integrity of sperm DNA but also limits the fertilizing potential of these cells as a result of collateral damage to proteins and lipids in the sperm plasma membrane. The origins of such oxidative stress appear to involve the sperm mitochondria, which have a tendency to generate high levels of superoxide anion as a prelude to entering the intrinsic apoptotic cascade. Unfortunately, these cells have very little capacity to respond to such an attack because they only possess the first enzyme in the base excision repair (BER) pathway, 8-oxoguanine glycosylase 1 (OGG1). The latter successfully creates an abasic site, but the spermatozoa cannot process the oxidative lesion further because they lack the downstream proteins (APE1, XRCC1) needed to complete the repair process. It is the responsibility of the oocyte to continue the BER pathway prior to initiation of S-phase of the first mitotic division. If a mistake is made by the oocyte at this stage of development, a mutation will be created that will be represented in every cell in the body. Such mechanisms may explain the increase in childhood cancers and other diseases observed in the offspring of males who have suffered oxidative stress in their germ line as a consequence of age, environmental or lifestyle factors. The high prevalence of oxidative DNA damage in the spermatozoa of male infertility patients may have implications for the health of children conceived in vitro and serves as a driver for current research into the origins of free radical generation in the germ line.