The future of equine semen analysis

We are currently experiencing a period of rapid advancement in various areas of science and technology. The integration of high throughput 'omics' techniques with advanced biostatistics, and the help of artificial intelligence, is significantly impacting our understanding of sperm biology. These advances will have an appreciable impact on the practice of reproductive medicine in horses. This article provides a brief overview of recent advances in the field of spermatology and how they are changing assessment of sperm quality. This article is written from the authors' perspective, using the stallion as a model. We aim to portray a brief overview of the changes occurring in the assessment of sperm motility and kinematics, advances in flow cytometry, implementation of 'omics' technologies, and the use of artificial intelligence/self-learning in data analysis. We also briefly discuss how some of the advances can be readily available to the practitioner, through the implementation of 'on-farm' devices and telemedicine.

Pyruvate enhances stallion sperm function in high glucose media improving overall metabolic efficiency

If a mechanism of more efficient glycolysis depending on pyruvate is present in stallion spermatozoa, detrimental effects of higher glucose concentrations that are common in current commercial extenders could be counteracted. To test this hypothesis, spermatozoa were incubated in a 67 mM Glucose modified Tyrode's media in the presence of 1- or 10-mM pyruvate and in the Tyrode's basal media which contains 5 mM glucose. Spermatozoa incubated for 3 h at 37 °C in 67 mM Tyrode's media with 10 mM pyruvate showed increased motility in comparison with aliquots incubated in Tyrode's 5 mM glucose and Tyrode's 67 mM glucose (57.1 ± 3.5 and 58.1 ± 1.9 to 73.0 ± 1.1 %; P < 0.01). Spermatozoa incubated in Tyrode's with 67 mM glucose 10 mM pyruvate maintained the viability along the incubation (64.03 ± 15.4 vs 61.3 ± 10.2), while spermatozoa incubated in 67 mM Glucose-Tyrode's showed a decrease in viability (38.01 ± 11.2, P < 0.01). 40 mM oxamate, an inhibitor of the lactate dehydrogenase LDH, reduced sperm viability (P < 0.05, from 76 ± 5 in 67 mM Glucose/10 mM pyruvate to 68.0 ± 4.3 %, P < 0.05). Apoptotic markers increased in the presence of oxamate. (P < 0.01). UHPLC/MS/MS showed that 10 mM pyruvate increased pyruvate, lactate, ATP and NAD+ while phosphoenolpyruvate decreased. The mechanisms that explain the improvement of in presence of 10 mM pyruvate involve the conversion of lactate to pyruvate and increased NAD+ enhancing the efficiency of the glycolysis.

Spermatozoa cooled to 5°C one day after collection from porcine commercial semen doses retain sperm functionality with reduced bacterial load

BACKGROUND

Commercial porcine semen is stored at 17°C, leading to a reduction of sperm quality and increase of bacterial growth.

OBJECTIVES

To evaluate the effect of 5°C storage on porcine sperm functionality cooled one day after collection.

MATERIALS AND METHODS

Semen doses (n = 40) were transported at 17°C and cooled at 5°C one day after collection. Spermatozoa were evaluated at Days 1, 4, and 7 for motility, viability, acrosome integrity, membrane stability, intracellular zinc, oxidative stress, and bacterial growth.

RESULTS

Contaminated semen doses predominantly exhibited Serratia marcescens, with increasing bacterial load during 17°C storage. Under hypothermal storage, negative doses for bacteria growth at Day 1 remained negative, and bacterial load did not increase in bacterial contaminated samples. Motility was significantly reduced through 17°C storage, but at 5°C, motility was only reduced at Day 4. Samples with bacterial growth (35.0%, 14/40) had significantly reduced motility at 17°C, but motility was unaltered at 5°C. Plasma membrane and acrosome integrity without bacterial contamination were unaffected at 17°C, but were significantly reduced at 5°C on Day 7. Plasma membrane and acrosome integrity significantly decreased with bacterial contamination regardless of temperature. High mitochondrial activity in viable spermatozoa without bacteria was not altered by temperature, but was significantly reduced by bacterial contamination at 17°C. Membrane stability was significantly reduced at Day 4, but tended (p = 0.07) to be higher in samples without bacterial growth. Viable spermatozoa exhibiting high zinc were significantly reduced throughout storage regardless of temperature. Oxidative stress levels were not altered, but significantly increased with bacterial contamination at 17°C.

DISCUSSION AND CONCLUSION

Porcine spermatozoa cooled to 5°C one day after collection retain functional attributes similar to spermatozoa stored at 17°C, but have a reduced bacterial load. Cooling extended boar semen to 5°C is feasible after transport to avoid modifying semen production.

The concentration of glucose in the media influences the susceptibility of stallion spermatozoa to ferroptosis

In brief

Although common in many commercial extenders, supraphysiological concentrations of glucose in the media may be detrimental to stallion spermatozoa. In this study, we present evidence that these elevated glucose levels may predispose spermatozoa to ferroptosis.

Abstract

Stallion spermatozoa depend on oxidative phosphorylation as their major source of ATP; however, the metabolism of these cells is complex and a great degree of metabolic plasticity exists. The composition of the media in which the spermatozoa are extended, or exposed to in the mare's reproductive tract, exerts a profound effect on sperm function and may even accelerate cell demise. Recent research indicates that high concentrations of glucose in the media, although common in commercial extenders, may be detrimental. To determine if supraphysiological glucose concentration may induce or predispose to ferroptosis (a caspase-independent form of programmed cell death, triggered by oxidative stress), stallion spermatozoa were incubated under different concentrations of glucose, 67 mM (HG) or 1 mM plus 10 mM pyruvate (LG-HP), in the presence or absence of known inductors of ferroptosis. Furthermore, we developed a single-cell flow metabolic assay to identify different metabolic phenotypes in spermatozoa. Storage and incubation of spermatozoa under high glucose concentrations led to an increase in the percentage of necrotic spermatozoa (P < 0.0001). Moreover, ferroptosis was induced more intensely in sperm in media with high glucose concentrations (P < 0.0001). Finally, we observed that induction of ferroptosis modified two proteins (oxoglutarate dehydrogenase and superoxide dismutase 2) in spermatozoa incubated in media containing 67 mM glucose but not in media containing 1 mM glucose and 10 mM pyruvate. The composition of the media, especially the concentration of glucose, exerts a major impact on the functionality and life span of the spermatozoa. The results reported here may pave the way for improvements in existing semen extenders.

Aging of stallion spermatozoa stored in vitro is delayed at 22°C using a 67 mm glucose-10 mm pyruvate-based media

BACKGROUND

Most commerce of equine seminal doses is carried out using commercial extenders under refrigeration at 5°C.

OBJECTIVES

To determine if 10 mm pyruvate in a 67 mm glucose extender and storage at 22°C could be the basis of an alternative storage method to cooling to 5°C.

MATERIAL AND METHODS

Stallion ejaculates were extendedin: INRA96 (67 mm glucose, non-pyruvate control), modified Tyrode's (67 mm glucose-10 mm pyruvate), supplemented with 0, 10, 50, and 100 μM itaconate. As itaconate was vehiculated in DMSO, a control vehicle was also included. Sperm motility, viability, mitochondrial membrane potential, and production of reactive oxygen species were measured after collection and again after 48 and 96 h of storage at 22°C. To disclose molecular metabolic changes, spermatozoa were incubated up to 3 h in modified Tyrode's 67 mm glucose-10 mm pyruvate and modified Tyrode's 67 mm glucose, and metabolic analysis conducted.

RESULTS

After 96 h of storage aliquots stored in the control, INRA96 had a very poor total motility of 5.6% ± 2.3%, while in the 67 mm glucose-10 mm pyruvate/10 μm itaconate extender, total motility was 34.7% ± 3.8% (p = 0.0066). After 96 h, viability was better in most pyruvate-based media, and the mitochondrial membrane potential in spermatozoa extended in INRA96 was relatively lower (p < 0.0001). Metabolomics revealed that in the spermatozoa incubated in the high pyruvate media, there was an increase in the relative amounts of NAD+ , pyruvate, lactate, and ATP.

DISCUSSION AND CONCLUSIONS

Aliquots stored in a 67 mm glucose-10 mm pyruvate-based medium supplemented with 10 μM itaconate, maintained a 35% total motility after 96 h of storage at 22°C, which is considered the minimum acceptable motility for commercialization. Improvements may be related to the conversion of pyruvate to lactate and regeneration of NAD+ .

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

Proteomic research on new urinary biomarkers of renal disease in canine leishmaniosis: Survival and monitoring response to treatment

The objective of our study was to search for survival biomarkers (SB) and treatment response monitoring biomarkers (TRMB) in the urinary proteome of dogs with renal disease secondary to canine leishmaniosis (CanL), using UHPLC-MS/MS. The proteomic data are available via ProteomeXchange with identifier PXD042578. Initially, a group of 12 dogs was evaluated and divided into survivors (SG; n = 6) and nonsurvivors (NSG; n = 6). A total of 972 proteins were obtained from the evaluated samples. Then, bioinformatic analysis reduced them to 6 proteins like potential SB increased in the NSG, specifically, Haemoglobin subunit Alpha 1, Complement Factor I, Complement C5, Fibrinogen beta chain (fragment), Peptidase S1 domain-containing protein, and Fibrinogen gamma chain. Afterwards, SG was used to search for TRMB, studying their urine at 0, 30, and 90 days, and 9 proteins that decreased after treatment were obtained: Apolipoprotein E, Cathepsin B, Cystatin B, Cystatin-C-like, Lysozyme, Monocyte differentiation CD14, Pancreatitis-associated precursor protein, Profilin, and Protein FAM3C. Finally, enrichment analysis provided information about the biological mechanisms in which these proteins are involved. In conclusion, this study provides 15 new candidate urinary biomarkers and an improved understanding of the pathogenesis of kidney disease in CanL.

Phosphoproteomics for the identification of new mechanisms of cryodamage: the role of SPATA18 in the control of stallion sperm function†

Although recent research has addressed the impact of cryopreservation on the stallion sperm proteome, studies addressing the stallion sperm phosphoproteome are lacking. In the present study, the data set of proteomes of fresh and cryopreserved spermatozoa were reanalyzed, showing that cryopreservation caused significant changes in the phosphoproteome. The phosphoproteins reduced most significantly by cryopreservation were Ca2+binding tyrosine phosphorylation regulated, protein kinase cAMP-activated catalytic subunit beta (CABYR), mitochondria eating protein (SPATA18), A kinase anchoring protein 4 (AKAP4), A-kinase anchoring protein 3 (AKAP3) and the Family with sequence similarity 71 member B (FAM71B). These proteins belong to the gene ontology (GO) terms sperm fibrous sheath (GO: 0035686), and sperm principal piece (GO: 0097228). The regulatory interactions between kinases and phosphorylation sites on the proteins that were affected most were also investigated, and the potential kinases (based on human orthologs) involved in the regulation of these phosphoproteins identified were: PKCß for SPATA18 and GSK3ß for CABYR. Kinase inhibition assays were also conducted showing that kinases phosphorylating the above-mentioned proteins play an important role in their activity and thus, phosphorylation controls the activity of these proteins and their role in the regulation of the functionality and viability of stallion spermatozoa. In conclusion, the data reported here contribute to the understanding of the fact that the dephosphorylation of certain proteins is a molecular lesion induced by cryopreservation in the stallion spermatozoa.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

Ellagic Acid Triggers the Necrosis of Differentiated Human Enterocytes Exposed to 3-Nitro-Tyrosine: An MS-Based Proteomic Study

To study the molecular basis of the toxicological effect of a dietary nitrosated amino acid, namely, 3-nitrotyrosine (3-NT), differentiated human enterocytes were exposed to dietary concentrations of this species (200 μM) and analyzed for flow cytometry, protein oxidation markers and MS-based proteomics. The possible protective role of a dietary phytochemical, ellagic acid (EA) (200 μM), was also tested. The results revealed that cell viability was significantly affected by exposure to 3-NT, with a concomitant significant increase in necrosis (p < 0.05). 3-NT affected several biological processes, such as histocompatibility complex class II (MHC class II), and pathways related to type 3 metabotropic glutamate receptors binding. Addition of EA to 3-NT-treated cells stimulated the toxicological effects of the latter by reducing the abundance of proteins involved in mitochondrial conformation. These results emphasize the impact of dietary nitrosated amino acids in intestinal cell physiology and warn about the potential negative effects of ellagic acid when combined with noxious metabolites.

Dataset of the sperm proteome of stallions with different motility

This paper provides a detailed set of data on how the stallion sperm proteome differs among stallions with different sperm motilities, although within normal ranges. Findings distinguish proteins that may help to identify stallions of superior sperm motility. Sperm proteins were analyzed using a UHPLC/MS/MS system comprising of an Agilent 1290 infinity series UHPLC coupled to an Agilent 6550 Q-TOF mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). These data can be used to disclose potential targets to identify good sperm samples and to study specific pathways involved in the regulation of sperm motility. This data article is linked to the paper “Proteins involved in mitochondrial metabolic functions and fertilization predominate in stallions with better motility Journal of Proteomics 247:104335 doi: 10.1016/j.jprot.2021.104335”.

OXIDATIVE STRESS AND REPRODUCTIVE FUNCTION: Oxidative stress and the long-term storage of horse spermatozoa

In brief

The growing understanding of the mechanisms regulating redox homeostasis in the stallion spermatozoa, together with its interactions with energetic metabolism, is providing new clues applicable to the improvement of sperm conservation in horses. Based on this knowledge, new extenders, adapted to the biology of the stallion spermatozoa, are expected to be developed in the near future.

Abstract

The preservation of semen either by refrigeration or cryopreservation is a principal component of most animal breeding industries. Although this procedure has been successful in many species, in others, substantial limitations persist. In the last decade, mechanistic studies have shed light on the molecular changes behind the damage that spermatozoa experience during preservation. Most of this damage is oxidative, and thus in this review, we aim to provide an updated overview of recent discoveries about how stallion spermatozoa maintain redox homeostasis, and how the current procedures of sperm preservation disrupt redox regulation and cause sperm damage which affects viability, functionality, fertility and potentially the health of the offspring. We are optimistic that this review will promote new ideas for further research to improve sperm preservation technologies, promoting translational research with a wide scope for applicability not only in horses but also in other animal species and humans.

An integrated overview on the regulation of sperm metabolism (glycolysis-Krebs cycle-oxidative phosphorylation)

An overview of the sperm metabolism is presented; using the stallion as a model we review glycolysis, Krebs Cycle and oxidative phosphorylation, paying special attention to the interactions among them. In addition, metabolism implies a series of coordinated oxidation-reduction reactions and in the course of these reactions reactive oxygen species (ROS) and reactive oxoaldehydes are produced ; the electron transport chain (ETC) in the mitochondria is the main source of the anion superoxide and hydrogen peroxide, while glycolysis produces 2-oxoaldehydes such as methylglyoxal as byproducts; due to the adjacent carbonyl groups are strong electrophiles (steal electrons oxidizing other compounds). Sophisticated mechanisms exist to maintain redox homeostasis, because ROS under controlled production also have important regulatory functions in the spermatozoa. The interactions between metabolism and production of reactive oxygen species are essential for proper sperm function, and deregulation of these processes rapidly leads to sperm malfunction and finally death. Lastly, we briefly describe two techniques that will expand our knowledge on sperm metabolism in the coming decades, metabolic flow cytometry and the use of the "omics" technologies, proteomics and metabolomics, specifically the micro and nano proteomics/metabolomics. A better understanding of the metabolism of the spermatozoa will lead to big improvements in sperm technologies and the diagnosis and treatment of male factor infertility.

Advances in the ultrasound diagnosis in equine reproductive medicine: New approaches

Ultrasound technology has led to new lines of research in equine reproduction, and it has helped to greatly improve clinical diagnosis and reproductive outcomes in equine practice. This review aims to discuss the potential clinical uses and new approaches of ultrasonography in equine reproduction. Doppler modalities are usually used to evaluate the vascularization of the follicles, corpus luteum (CL), and the uterus in the mare for diagnostic purposes. Inclusion of Doppler ultrasound in artificial insemination and embryo transfer programs could improve the reproductive outcome of these techniques. Better selection of recipients based on CL functionality, early pregnancy diagnosis 7-8 days postovulation of the donor before flushing or diagnosis of mares with endometritis with pathological increases of blood flow are examples of clinical applications in the mare. In the stallion, colour Doppler ultrasound has improved the diagnostic potential of B-mode ultrasound, improving the differential diagnosis of pathologies such as testicular torsion (decrease or absence of blood flow in the cord) and orchitis (increased blood flow in the cord). The incorporation of pulsed Doppler ultrasound into the reproductive evaluation of the stallion has enabled early identification of stallions with testicular dysfunction, thus allowing administration of timely treatment and subsequent improvements of the fertility prognosis for these animals. In addition, this technique has been used in the monitoring of patients undergoing medical and surgical treatments, thus verifying their efficacy. Recently, computer-assisted pixel analysis using specific software has been performed in research work in order to semi-quantitatively evaluate the vascularization (colour and power Doppler) and echotexture of different organs. These softwares are now being developed for clinical purposes, as is the case with Ecotext, a computer program developed for the evaluation of testicular echotexture, providing information on testicular functionality.

Validation of a new multiparametric protocol to assess viability, acrosome integrity and mitochondrial activity in cooled and frozen thawed boar spermatozoa

BACKGROUND

Motility, morphology, membrane integrity and DNA fragmentation are sperm characteristics routinely used to assess quality of boar spermatozoa. However, the evaluation of individual parameters has intrinsic restrictions in the estimation of potential fertility. Therefore, we aimed to validate a new multiparametric protocol to assess fertility potential through the evaluation of viability, acrosome integrity and mitochondrial activity within the same sperm population for cooled and frozen-thawed boar spermatozoa.

METHOD

Three multicolor protocols to assess viability, acrosome integrity and/or mitochondrial activity were compared for agreement containing two dyes (HM-panel; Hoechst 33342, MitoTracker™ Deep Red), three dyes (3-panel; SYBR®14, propidium iodide and lectin PNA-Alexa™ 647) or four dyes (4-panel; Hoechst 33342, lectin PNA-Alexa™ 488, propidium iodide and MitoTracker™ Deep Red). Cooled (n = 132) and frozen-thawed (n = 254) samples of boar spermatozoa were assessed by flow cytometry.

RESULTS

4-Panel enabled the detection of several sperm subpopulations based on plasma membrane integrity, acrosome status and mitochondrial activity in cooled and frozen-thawed spermatozoa. No significant differences were observed between 3-panel and 4-panel for the percentage of live, live-acrosome intact, and dead-acrosome reacted spermatozoa. However, the percentage of acrosome-intact spermatozoa was significantly higher in cooled samples when stained by 3-panel than 4-panel. Percentages of sperm parameters between protocols were strongly correlated, and agreement analysis demonstrated that both assays resulted in similar values for both sperm sample type.

CONCLUSION

Our results indicate that a four-color protocol is a practical, simple and reliable procedure to simultaneously evaluate boar sperm viability, acrosome integrity and mitochondrial activity under clinical conditions.

The Stallion Spermatozoa: A Valuable Model to Help Understand the Interplay Between Metabolism and Redox (De)regulation in Sperm Cells

Significance: Proper functionality of the spermatozoa depends on the tight regulation of their redox status; at the same time these cells are highly energy demanding and in the energetic metabolism, principally in the electron transport chain in the mitochondria, reactive oxygen species are continuously produced, in addition to that observed in the Krebs cycle and during the β-oxidation of fatty acids. Recent Advances: In addition, in glycolysis, elimination of phosphate groups from glyceraldehyde 3-phosphate and dihydroxyacetone phosphate results in the byproducts glyoxal (G) and methylglyoxal (MG); these products are 2-oxoaldehydes. The presence of adjacent carbonyl groups makes them strong electrophiles that react with nucleophiles in proteins, lipids, and DNA, forming advanced glycation end products. Critical Issues: This mechanism is behind subfertility in diabetic patients; in the animal breeding industry, commercial extenders for stallion semen contain a supraphysiological concentration of glucose that promotes MG production, constituting a potential model of interest. Future Directions: Increasing our knowledge of sperm metabolism and its interactions with redox regulation may improve current sperm technologies in use, and shall provide new clues to understanding infertility in males. Moreover, stallion spermatozoa due to its accessibility, intense metabolism, and suitability for proteomics/metabolomic studies may constitute a suitable model for studying regulation of metabolism and interactions between metabolism and redox homeostasis. Antioxid. Redox Signal. 37, 521-537.

Proteomics reveal the protective effects of chlorogenic acid on Enterococcus faecium Q233 in a simulated pro-oxidant colonic environment

Certain phytochemicals have been found to promote the beneficial effects of probiotic bacteria although the molecular mechanisms of such interactions are poorly understood. The objective of the present study was to evaluate the impact of the exposure to 0.5 mM chlorogenic acid (CA) on the redox status and proteome of Enterococcus faecium isolated from cheese and challenged with 2.5 mM hydrogen peroxide (H₂O₂). The bacterium was incubated in anaerobic conditions for 48 h at 37 °C. CA exposure led to a more intense oxidative stress and accretion of bacterial protein carbonyls than those induced by H₂O₂. The oxidative damage to bacterial proteins was even more severe in the bacterium treated with both CA and H₂O₂, yet, such combination led to a strengthening of the antioxidant defenses, namely, a catalase-like activity. The proteomic study indicated that H₂O₂ caused a decrease in energy supply and the bacterium responded by reinforcing the membrane and wall structures and counteracting the redox and pH imbalance. CA stimulated the accretion of proteins related to translation and transcription regulators, and hydrolases. This phytochemical was able to counteract certain proteomic changes induced by H₂O₂ (i.e. increase of ATP binding cassete (ABC) transporter complex) and cause the increase of Rex, a redox-sensitive protein implicated in controlling metabolism and responses to oxidative stress. Although this protection should be confirmed under in vivo conditions, such effects point to benefits in animals or humans affected by disorders in which oxidative stress plays a major role.

Protein oxidation marker, α-amino adipic acid, impairs proteome of differentiated human enterocytes: Underlying toxicological mechanisms

Protein oxidation and oxidative stress are involved in a variety of health disorders such as colorectal adenomas, inflammatory bowel's disease, neurological disorders and aging, among others. In particular, the specific final oxidation product from lysine, the α-amino adipic acid (α-AA), has been found in processed meat products and emphasized as a reliable marker of type II diabetes and obesity. Currently, the underlying mechanisms of the biological impairments caused by α-AA are unknown. To elucidate the molecular basis of the toxicological effect of α-AA, differentiated human enterocytes were exposed to dietary concentrations of α-AA (200 μM) and analyzed by flow cytometry, protein oxidation and proteomics using a Nanoliquid Chromatography-Orbitrap MS/MS. Cell viability was significantly affected by α-AA (p < 0.05). The proteomic study revealed that α-AA was able to alter cell homeostasis through impairment of the Na⁺/K⁺-ATPase pump, energetic metabolism, and antioxidant response, among other biological processes. These results show the importance of dietary oxidized amino acids in intestinal cell physiology and open the door to further studies to reveal the impact of protein oxidation products in pathological conditions.

Urinary proteome of dogs with renal disease secondary to leishmaniosis

Canine leishmaniosis is frequently associated with the development of renal disease. Its pathogenesis is complex and not fully understood. For this reason, this study aimed to describe the urinary proteome, and identify possible new biomarkers in dogs with kidney disease secondary to leishmaniosis. Urine samples were collected from 20 dogs, 5 from healthy dogs, and 15 from stages Leishvet III and IV. Urine samples were analyzed by UHPLC-MS/MS. The data are available via ProteomeXchange with identifier PXD029165. A total of 951 proteins were obtained. After bioinformatic analysis, 93 urinary proteins were altered in the study group. Enrichment analysis performed on these proteins showed an overrepresentation of the complement activation pathway, among others. Finally, 12 discriminant variables were found in dogs with renal disease secondary to leishmaniosis, highlighting C4a anaphylatoxin, apolipoprotein A-I, haptoglobin, leucine-rich alpha-2-glycoprotein 1, and beta-2-microglobulin. This study is the first to describe the urinary proteomics of dogs with renal disease caused by leishmaniosis, and it provides new possible biomarkers for the diagnosis and monitoring of this disease.

Seminal plasma proteins as potential biomarkers for sperm motility and velocities

Seminal plasma proteins have important roles in sperm functionality, and different mechanisms including micro-vesicle transport of proteins are involved in the regulation of sperm biology. Due to the role of seminal plasma, we hypothesized that specific proteins present in seminal plasma may be used as discriminant variables with potential to identify stallions producing different quality ejaculates; 10 fertile stallions, with different motility and velocity values (although within normal ranges) were used in this study. Motilities and velocities were studied using computer assisted sperm analysis (CASA), while protein composition of the seminal plasma was studied using UHPLC-MS/MS. Specific proteins were more abundant in samples with poorer percentages of total motility, average path velocity and circular velocity, and were: Secreted phosphoprotein 1, Fructose-bisphosphate aldolase (p = 1,95E-09; q = 0.0005) and Malate dehydrogenase 1 (p = 1,41E-11; q = 0.002), to the contrary samples with better straight-line velocity values were enriched in Glutathione peroxidase (p=0.00013; q=0.04) and Triosephosphate isomerase (p=0.00015; q=0.04).

The seminal plasma proteins Peptidyl arginine deaminase 2, rRNA adenine N (6)-methyltransferase and KIAA0825 are linked to better motility post thaw in stallions

Seminal plasma plays an important role in sperm physiology. Seminal plasma proteins vehiculated in microvesicles, carry RNAs and proteins with a potential role in early embryo development. Additionally, proteins present in seminal plasma participate in redox regulation and energy metabolism. In view of these facts, we hypothesized that differences in protein composition of the seminal plasma among stallions may help to explain differences in freeze-ability seen among them. Three independent ejaculates from 10 different stallions of varying breeds were frozen using standard protocols in our laboratory. Aliquots of the ejaculate were separated and stored at -80 °C until further proteomic analysis. Semen analysis was performed using computer assisted sperm analysis and flow cytometry. Significant differences in proteome composition of seminal plasma were observed in the group of stallions showing better motility post thaw. 3116 proteins were identified, and of these, 34 were differentially expressed in stallions with better motility post thaw, 4 of them were also differentially expressed in stallions with different percentages of linearly motile sperm post thaw and 1 protein, Midasin, was expressed in stallions showing high circular velocity post thaw. Seminal plasma proteins may play a major role in sperm functionality; being vehiculated through extracellular vesicles and participating in sperm physiology. Bioinformatic analysis identifies discriminant proteins able to predict the outcome of cryopreservation, identifying potential new biomarkers to assess ejaculate quality.

An in vitro assay of the effect of lysine oxidation end-product, α-aminoadipic acid, on the redox status and gene expression in probiotic Lactobacillus reuteri PL503

This study was designed to gain information about the underlying mechanisms of the effects of a food-occurring free oxidized amino acid, α-aminoadipic acid (AAA), on the probiotic Lactobacillus reuteri PL503. This bacterium was incubated in colonic-simulated conditions (37 °C for 24 h in microaerophilic conditions) and exposed to three food-compatible AAA concentrations, namely, 1 mM, 5 mM, and 10 mM. A control group with no AAA exposure was also considered. Each of the four experimental conditions was replicated three times and samplings were collected at 12, 16, 20, and 24 h. The downregulation of the uspA gene by AAA (0.5-fold decrease as compared to control) suggests that AAA is identified as a potential chemical threat. The dhaT gene, implicated in the antioxidant defense, was found to be upregulated in bacteria treated with 1 and 5 mM AAA (up to twofold increase, as compared to control), which suggest the ability of the oxidized amino acid to impair the redox status of the bacterium. In fact, AAA caused an increased production of reactive oxygen species (ROS) and the accretion of post-translational changes (protein carbonylation) in L. reuteri (up to 13 nmol allysine/mg protein vs 1.8 nmol allysine/mg protein in control). These results suggest that probiotic bacteria identify oxidized amino acids as harmful species and activate mechanisms that may protect themselves and the host against their noxious effects.

Mass spectrometry reveals distinct proteomic profiles in high- and low-quality stallion spermatozoa

The horse breeding industry relies upon optimal stallion fertility. Conventional sperm assessments provide limited information regarding ejaculate quality and are not individually predictive of fertilizing potential. The aim of this study was to harness mass spectrometry to compare the proteomic profiles of high- and low-quality stallion spermatozoa, with the ultimate goal of identifying fertility biomarker candidates. Extended stallion semen (n = 12) was fractionated using Percoll density gradients to isolate low-quality and high-quality sperm populations. Motility and morphological assessments were carried out, and proteomic analyses was conducted using UHPLC-MS/MS. High-quality spermatozoa recorded higher total (95.2 ± 0.52% vs 70.6 ± 4.20%; P ≤ 0.001) and progressive motilities (43.4 ± 3.42% vs 27.3 ± 4.32%; P ≤ 0.05), and a higher proportion of morphologically normal cells (50.2 ± 4.34% vs 38.8 ± 2.72%; P ≤ 0.05). In total, 1069 proteins were quantified by UHPLC-MS/MS, of which 22 proteins were significantly more abundant in the high-quality sperm population (P ≤ 0.05). A-kinase anchor protein 4 (AKAP4) and Hexokinase 1 (HK1) were considered possible biomarker candidates and their differential expression was confirmed by immunoblot. Protein expression was significantly correlated with total (AKAP4 R2 = 0.38, P ≤ 0.01; HK1 R2 = 0.46, P ≤ 0.001) and progressive motilities (AKAP4 R 2 = 0.51, P ≤ 0.001; HK1 R2 = 0.55, P ≤ 0.01), percentage rapid (AKAP4 R2 = 0.29, P ≤ 0.05; HK1 R2 = 0.58, P ≤ 0.001), straight-line velocity (HK1 R2 = 0.50, P ≤ 0.01) and straightness (HK1 R2 = 0.40, P ≤ 0.01). Furthermore, AKAP4 was highly susceptible to adduction by 4-hydroxynonenal (4HNE), which resulted in a global reduction in the phosphorylation profiles following capacitation. In conclusion, the proteomic profiles of high- and low-quality stallion spermatozoa differ substantially, and proteins such as AKAP4 and HK1 could serve as biomarkers of ejaculate quality.

The SLC7A11: sperm mitochondrial function and non-canonical glutamate metabolism

Spermatozoa are redox-regulated cells, and stallion spermatozoa, in particular, present an intense mitochondrial activity in which large amounts of reactive oxygen species (ROS) are produced. To maintain the redox potential under physiological conditions, sophisticated mechanisms ought to be present, particularly in the mitochondria. In the present study, we investigated the role of the SLC7A11 antiporter. This antiporter exchanges intracellular glutamate for extracellular cystine. In the spermatozoa, cystine is reduced to cysteine and used for GSH synthesis. The importance of the antiporter for mitochondrial functionality was studied using flow cytometry and UHPLC/MS/MS approaches. Intracellular GSH increased in the presence of cystine, but was reduced in the presence of Buthionine sulphoximine (BSO), a γ-glutamylcysteine synthetase inhibitor (P < 0.001). Inhibition of the SLC7A11 antiporter with sulfasalazine caused a dramatic drop in intracellular GSH (P < 0.001) and in the percentage of spermatozoa showing active mitochondria (P < 0.001). These findings suggest that proper functionality of this antiporter is required for the mitochondrial function of spermatozoa. We also describe that under some conditions, glutamate may be metabolized following non-conventional pathways, also contributing to sperm functionality. We provide evidences, that the stallion spermatozoa have important metabolic plasticity, and also of the relation between redox regulation and metabolic regulation. These findings may have important implications for the understanding of sperm biology and the development of new strategies for sperm conservation and treatment of male factor infertility.

Proteins involved in mitochondrial metabolic functions and fertilization predominate in stallions with better motility

Even in stallions with sperm quality within normal reference ranges at ejaculation, subtle differences in sperm quality exist that in many cases lead to reduced time frames for conservation of the ejaculate and/or reduced fertility. The spermatozoon is a cell highly suitable for proteomics studies, and the use of this technique is allowing rapid advances in the understanding of sperm biology. The aim of the present study was to investigate differences among stallions of variable sperm quality (based on motility and sperm velocities), although all horses had sperm characteristics within normal ranges. The proteome was studied using UHPLC/MS/MS and posterior bioinformatic and enrichment analysis; data are available via ProteomeXchange with identifier PXD025807. Sperm motility, linear motility and circular, straight line and average velocities (VCL, VSL, VAP) were measured using computer assisted sperm analysis (CASA). In stallions showing better percentages of motility, circular and average velocity predominated mitochondrial proteins with roles in the Citric acid cycle, pyruvate metabolism and oxidative phosphorylation. Interestingly, in stallions with better percentages of total motility, sperm proteins were also enriched in proteins within the gene ontology (G0) terms, single fertilization (G0: 0007338), fertilization (G0: 0009566), and zona pellucida receptor complex (GO:0002199). The enrichment of this proteins in samples with better percentages of total motility may offer a molecular explanation for the link between this parameter and fertility. SIGNIFICANCE: Proteomic analysis identified a high degree of specificity of stallion sperm proteins with discriminant power for motility, linear motility, and sperm velocities (VCL, VAP and VSL). These findings may represent an interesting outcome in relation to the molecular biology regulating the movement of the spermatozoa, and the biological meaning of the measurements that computer assisted sperm analysis (CASA) provide. Of a total of 903 proteins identified in stallion spermatozoa, 24 were related to the percentage of total motility in the sample; interestingly, gene ontology (G0) analysis revealed that these proteins were enriched in terms like single fertilization and fertilization, providing a molecular link between motility and fertility. Field studies indicate that the percentage of total motility is the CASA derived parameter with the best correlation with fertility in stallions.

In Stallion Spermatozoa, Superoxide Dismutase (Cu-Zn) (SOD1) and the Aldo-Keto-Reductase Family 1 Member b (AKR1B1) Are the Proteins Most Significantly Reduced by Cryopreservation

Although cryopreservation is widely used in animal breeding, the technique is still suboptimal. The population of spermatozoa surviving the procedure experiences changes attributed to alteration in their redox regulation. In order to expand our knowledge regarding this particular aspect, the proteome in fresh and frozen thawed aliquots of equine spermatozoa was studied to identify the proteins most severely affected by the procedure. If alteration of redox regulation is a major factor explaining cryodamage, proteins participating in redox regulation should be principally affected. Using a split sample design, 30 ejaculates from 10 different stallions were analyzed as fresh spermatozoa, and another aliquot from the same ejaculate was analyzed as a frozen thawed sample. The proteome was studied under both conditions using UHPLC-MS/MS and bioinformatic analysis conducted to identify discriminant variables between both conditions. Data are available through the ProteomeXchange Consortium with identifier PXD022236. The proteins most significantly reduced were Aldo-keto reductase family 1 member B (p = 2.2 × 10-17) and Superoxide dismutase (Cu-Zn) (p = 4.7 × 10-14). This is the first time that SOD1 has been identified as a discriminating variable using bioinformatic analysis, where it was one of the most highly significantly different proteins seen between fresh and frozen thawed semen. This finding strongly supports the theory that alteration in redox regulation and oxidative stress is a major factor involved in cryodamage and suggests that control of redox regulation should be a major target to improve current cryopreservation procedures.

Low glucose and high pyruvate reduce the production of 2-oxoaldehydes, improving mitochondrial efficiency, redox regulation, and stallion sperm function†

Energy metabolism in spermatozoa is complex and involves the metabolism of carbohydrate fatty acids and amino acids. The ATP produced in the electron transport chain in the mitochondria appears to be crucial for both sperm motility and maintaining viability, whereas glycolytic enzymes in the flagella may contribute to ATP production to sustain motility and velocity. Stallion spermatozoa seemingly use diverse metabolic strategies, and in this regard, a study of the metabolic proteome showed that Gene Ontology terms and Reactome pathways related to pyruvate metabolism and the Krebs cycle were predominant. Following this, the hypothesis that low glucose concentrations can provide sufficient support for motility and velocity, and thus glucose concentration can be significantly reduced in the medium, was tested. Aliquots of stallion semen in four different media were stored for 48 h at 18°C; a commercial extender containing 67 mM glucose was used as a control. Stallion spermatozoa stored in media with low glucose (1 mM) and high pyruvate (10 mM) (LG-HP) sustained better motility and velocities than those stored in the commercial extender formulated with very high glucose (61.7 ± 1.2% in INRA 96 vs 76.2 ± 1.0% in LG-HP media after 48 h of incubation at 18°C; P < 0.0001). Moreover, mitochondrial activity was superior in LG-HP extenders (24.1 ± 1.8% in INRA 96 vs 51.1 ± 0.7% in LG-HP of spermatozoa with active mitochondria after 48 h of storage at 18°C; P < 0.0001). Low glucose concentrations may permit more efficient sperm metabolism and redox regulation when substrates for an efficient tricarboxylic acid cycle are provided. The improvement seen using low glucose extenders is due to reductions in the levels of glyoxal and methylglyoxal, 2-oxoaldehydes formed during glycolysis; these compounds are potent electrophiles able to react with proteins, lipids, and DNA, causing sperm damage.

The inhibition of spermatic cystine/glutamate antiporter xCT (SLC7A11) influences the ability of cryopreserved stallion sperm to bind to heterologous zonae pellucidae

Sperm are redox-regulated cells, and deregulation of their redox status is considered to affect male fertility and to reduce their fertilizing ability following biotechnological procedures, such as cryopreservation. Cystine (CysS), after incorporation in sperm via SLC7A11 antiporter, has been demonstrated to increase intracellular GSH content, the most important non enzymatic antioxidant. This study was aimed at investigating the role of SLC7A11 antiporter on frozen-thawed stallion sperm ability to respond to in vitro capacitating environment after post-thaw incubation with CysS and/or Sulfasalazine (SS), a specific inhibitor of SLC7A11 antiporter. Viability, motility, immunolocalization of tyrosine phosphorylated proteins and the ability to bind to heterologous zonae pellucidae were evaluated. Thawed sperm from seven stallions (2 ejaculates/stallion) was washed and resuspended in Tyrodes media; each thawed ejaculate was divided in Control (CTR) and 3 samples supplemented with: 0.5 mM Cystine (CysS), 500 μM Sulfasalazine (SS) and 0.5 mM CysS + 500 μM SS (CysS + SS). After 1 h of incubation at 37 °C, samples were washed twice, resuspended in capacitating BWW medium and incubated at 38 °C under 5% CO₂. After 30 and 60 min, sperm motility, viability and tyrosine phosphorylated protein immunolocalization, used as capacitation status index, were evaluated. After 30 min of capacitation, 4 × 10⁵ sperm were co-incubated with denuded pig oocytes in capacitation medium for 30 min for the heterologous binding assay. None of the sperm parameters studied (motility, viability and tyrosine phosphorylation) showed any difference respective to control. The number of sperm bound per oocyte (mean ± SEM) tended to increase in CysS group (44.0 ± 12.3) respect CTR (40.8 ± 10.8) while decreased in SS group (32.4 ± 7.8) (p < 0.01). Moreover, CysS + SS group showed a lower binding rate (32.0 ± 10.0) compared to CysS (p < 0.001). Our results suggest that CysS supplementation of thawed stallion sperm can influence their ability to bind to heterologous zona pellucidae as the inhibition of CysS incorporation by SLC7A11 reduced the number of sperm bound per oocyte. This effect does not seem to be ascribed to a modification of sperm motility, membrane integrity and tyrosine phosphorylation.

Differences in the proteome of stallion spermatozoa explain stallion-to-stallion variability in sperm quality post-thaw†

The identification of stallions and or ejaculates that will provide commercially acceptable quality post-thaw before cryopreservation is of great interest, avoiding wasting time and resources freezing ejaculates that will not achieve sufficient quality to be marketed. Our hypothesis was that after bioinformatic analysis, the study of the stallion sperm proteome can provide discriminant variables able to predict the post-thaw quality of the ejaculate. At least three ejaculates from 10 different stallions were frozen following a split sample design. Half of the ejaculate was analyzed as a fresh aliquot and the other half was frozen and then analyzed as a frozen-thawed aliquot. Computer-assisted sperm analysis and flow cytometry were used to analyze sperm quality. Detailed proteomic analysis was performed on fresh and frozen and thawed aliquots, and bioinformatic analysis was used to identify discriminant variables in fresh samples able to predict the outcome of cryopreservation. Those with a fold change > 3, a P = 8.2e-04, and a q = 0.074 (equivalent to False discovery rate (FDR)) were selected, and the following proteins were identified in fresh samples as discriminant variables of good motility post-thaw: F6YTG8, K9K273, A0A3Q2I7V9, F7CE45, F6YU15, and F6SKR3. Other discriminant variables were also identified as predictors of good mitochondrial membrane potential and viability post-thaw. We concluded that proteomic approaches are a powerful tool to improve current sperm biotechnologies.

Molecular mechanisms of the disturbance caused by malondialdehyde on probiotic Lactobacillus reuteri PL503

This study aimed to provide insight into the molecular and genetic mechanisms implicated in the responses of Lactobacillus reuteri against the oxidative stress induced by malondialdehyde (MDA) by analysing protein oxidation and assessing the uspA and the dhaT genes. Four experimental groups were evaluated depending on the concentration of MDA added in Man, Rogosa and Sharpe (MRS) broth: Control (L. reuteri), 5 µM (L. reuteri + 5 µM MDA), 25 µM (L. reuteri + 25 µM MDA) and 100 µM (L. reuteri + 100 µM MDA). Three replicates were incubated at 37 °C for 24 h in microaerophilic conditions and sampled at 12, 16, 20 and 24 h. The upregulation of the uspA gene by L. reuteri indicates the recognition of MDA as a potential DNA‐damaging agent. The dhaT gene, encoding a NADH‐dependent‐oxidoreductase, was also upregulated at the highest MDA concentrations. This gene was proposed to play a role in the antioxidant response of L. reuteri. The incubation of L. reuteri with MDA increased the production of ROS and caused thiol depletion and protein carbonylation. L. reuteri is proposed to detoxify pro‐oxidative species while the underlying mechanism requires further elucidation.

Prenatal histomorphological development of the reticulum in fallow deer (Dama dama)

The histomorphological changes occurring in the Dama dama reticulum during prenatal development have been investigated. Twenty-five Dama dama embryos were used, from the first stages of prenatal life until birth. Differentiation of the reticulum was observed at 23% gestation. By 25% gestation the reticular wall comprised three layers: an internal epithelial layer, a middle layer of pluripotential blastemic tissue and an external layer or serosa. Primary reticular crests were visible at 38% gestation. Secondary reticular crests were observed at 61% gestation. Neuroendocrine cells were detected by synaptophysin (SYP) at 35% gestation, in the lamina propria-submucosa, tunica muscularis, and serosa. Epithelial Cytokeratin-18 (CK-18) cells were observed at 35% gestation extended throughout the epithelial layers. The glial cells (vimentin -VIM- and glial fibrillary acidic protein-GFAP-markers) were discerned at 25% and 43% gestation, respectively, in myenteric and submucosal plexuses, lamina propria, muscularis mucosae, tunica muscularis, and perivascular connective tissue. The neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP) markers were immunodetected at 75% and 80 gestation, respectively, in the lamina propria-submucosa, muscularis mucosae, tunica muscularis, serosa, and myenteric plexuses. The prenatal development of the fallow deer reticular mucosa evidenced a considerable precocity similar to that previously reported in goat and red deer.

The incorporation of cystine by the soluble carrier family 7 member 11 (SLC7A11) is a component of the redox regulatory mechanism in stallion spermatozoa†

Oxidative stress is considered a major mechanism causing sperm damage during cryopreservation and storage, and underlies male factor infertility. Currently, oxidative stress is no longer believed to be caused only by the overproduction of reactive oxygen species, but rather by the deregulation of redox signaling and control mechanisms. With this concept in mind, here, we describe for the first time the presence of the soluble carrier family 7 member 11 (SLC7A11) antiporter, which exchanges extracellular cystine (Cyss) for intracellular glutamate, in stallion spermatozoa, as well as its impact on sperm function using the specific inhibitor sulfasalazine. Spermatozoa incubated with Cyss exhibited an increased intracellular GSH content compared with controls (P < 0.01): 50% in fresh extended stallion spermatozoa and 30% in frozen-thawed spermatozoa. This effect was prevented by the addition of sulfasalazine to the media. Cystine supplementation also reduced the oxidation-reduction potential of spermatozoa, with sulfasalazine only preventing this effect on fresh spermatozoa that were incubated for 3 h at 37°C, but not in frozen-thawed spermatozoa. While sulfasalazine reduced the motility of frozen-thawed spermatozoa, it increased motility in fresh samples. The present findings provide new and relevant data on the mechanism regulating the redox status of spermatozoa and suggest that a different redox regulatory mechanism exists in cryopreserved spermatozoa, thus providing new clues to improve current cryopreservation technologies and treat male factor infertility.

Seminal plasma AnnexinA2 protein is a relevant biomarker for stallions which require removal of seminal plasma for sperm survival upon refrigeration†

Some stallions yield ejaculates that do not tolerate conservation by refrigeration prior to artificial insemination (AI), showing improvement after removal of most of the seminal plasma (SP) by centrifugation. In this study, the SP-proteome of 10 different stallions was defined through high-performance liquid chromatography with tandem mass spectrometry and bioinformatic analysis in relation to the ability of the ejaculates to maintain semen quality when cooled and stored at 5°C. Stallions were classified into three groups, depending on this ability: those maintaining good quality after direct extension in a commercial extender (good), stallions requiring removal of seminal plasma (RSP) to maintain seminal quality (good-RSP), and stallions, unable to maintain good semen quality even after RSP (poor). Pathway enrichment analysis of the proteins identified in whole equine SP using human orthologs was performed using g: profiler showing enriched Reactome and the Kyoto Encyclopedia of Genes and Genomes pathways related to hexose metabolism, vesicle mediated transport, post translational modification of proteins and immune response. Specific proteins overrepresented in stallions tolerating conservation by refrigeration included a peroxiredoxin-6 like protein, and transcobalamin-2, a primary vitamin B12-binding, and transport protein. Also, the protein involved in protein glycosylation, ST3 beta-galactoside alpha-2,3-sialyltransferase 1 was present in good stallions. These proteins were nearly absent in poor stallions. Particularly, annexinA2 appeared as to be the most powerful discriminant variable for identification of stallions needing RSP prior to refrigeration, with a P = 0.002 and a q value = 0.005. Overall this is the first detailed study of the equine SP-proteome, showing the potential value of specific proteins as discriminant bio-markers for clinical classification of stallions for AI.

Noxious effects of selected food-occurring oxidized amino acids on differentiated CACO-2 intestinal human cells

The harmful effects of food-occurring oxidized amino acids, namely, aminoadipic acid (AAA), dityrosine (DTYR), L-kynurenine (KN), kynurenic acid (KA) and 3-nitrotyrosine (3NT), were studied on differentiated CACO-2 cells by flow cytometry and quantification of glutathione (GSH), and allysine. Cells were exposed to food-relevant doses (200 μM) of each compound for 4 or 72h and compared to a control (no stimulated cells). All oxidized amino acids induced apoptosis and results indicated that underlying mechanisms depended on the chemical nature of the species. AAA, KN and KA caused ROS generation and severe oxidative stress in 96%, 98% and 89% of exposed cells (77% in control cells), leading to significant GSH depletion and allysine accretion (1.5, 1.5 and 1.6 nmol allysine/mg protein, respectively at 4h; control: 0.22 nmol/mg protein; p < 0.05). DTYR and 3NT induced significant apoptosis to 29% and 25% of cells (control: 16%; p < 0.05) and necrosis to 28% and 26% of cells (control: 23%) at 72h by ROS-independent mechanisms. KN and KA were found to induce a cycle arrest effect on CACO-2 cells. These findings emphasize the potential harmful effects of the intake of oxidized proteins and amino acids and urge the necessity of carrying out further molecular studies.

Data set of the proteome of fresh and frozen thawed stallion spermatozoa

This paper provides the dataset of proteins of stallion ejaculates before and after cryopreservation. The data report the analysis and identification of stallion sperm proteins obtained from the same ejaculates and split in two subsamples. The first aliquot consisted on fresh spermatozoa and the second aliquot was frozen and thawed spermatozoa. Samples were analyzed using a UHPLC/MS/MS system consisting of an Agilent 1290 infinity series UHPLC coupled to an Agilent 6550 Q-TOF mass spectrometer (Agilent Technologies, Santa Clara, CA, USA). We provide a data set of 2226 different proteins, with 2180 aligned to the equine proteome database. The data can be used to identify potential targets to be explored to improve techniques for cryopreservation of spermatozoa. This data article refers to the article "Proteomic profiling of stallion spermatozoa suggests changes in sperm metabolism and compromised redox regulation after cryopreservation" (Martín Cano et al.; 2020) [1].

Melatonin modulates proliferation of pancreatic stellate cells through caspase-3 activation and changes in cyclin A and D expression

In this study, the effects of melatonin (1 μM-1 mM) on pancreatic stellate cells (PSC) have been examined. Cell viability and proliferation, caspase-3 activation, and the expression of cyclin A and cyclin D were analyzed. Our results show that melatonin decreased PSC viability in a time- and concentration-dependent manner. This effect was not inhibited by treatment of cells with MT1, MT2, calmodulin, or ROR-alpha inhibitors prior to melatonin addition. Activation of caspase-3 in response to melatonin was detected. The expression of cyclin A and cyclin D was decreased in cells treated with melatonin. Finally, changes in BrdU incorporation into the newly synthesized DNA of proliferating cells were also observed in the presence of melatonin. We conclude that melatonin, at pharmacological concentrations, modulates proliferation of PSC through activation of apoptosis and involving crucial regulators of the cell cycle. These actions might not require specific melatonin receptors. Our observations suggest that melatonin, at high doses, could potentially exert anti-fibrotic effects and, thus, could be taken into consideration as supportive treatment in the therapy of pancreatic diseases.

Dataset of endometrial blood flow from pregnant and non-pregnant mares on day 7 and 8 post-ovulation

This article provides the dataset for the use of power Doppler ultrasound to assess the equine uterus from the recent research article titled “Power Doppler can detect the presence of 7-8 days conceptuses prior to flushing in an equine embryo transfer program”(1). The vascularization of the endometrium was objectively assessed in mares by quantification of pixels in bitmap format (BMP) using computer assisted analysis of images. Fifty-two mares were examined on days 7 (26 mares) and 8 (26 mares) post-ovulation prior to performing flushing procedures for embryo recovery. Receiver operating characteristic (ROC) curves and Youden's J statistics were used to evaluate the value of the suggested variable in terms of its diagnostic value for identification of early pregnancy and to establish cut-off values allowing differentiation between pregnant and non-pregnant mares on days 7 and 8 post-ovulation.

Proteomic profiling of stallion spermatozoa suggests changes in sperm metabolism and compromised redox regulation after cryopreservation

Proteomic technologies allow the detection of thousands of proteins at the same time, being a powerful technique to reveal molecular regulatory mechanisms in spermatozoa and also sperm damage linked to low fertility or specific biotechnologies. Modifications induced by the cryopreservation in the stallion sperm proteome were studied using UHPLC/MS/MS. Ejaculates from fertile stallions were collected and split in two subsamples, one was investigated as fresh (control) samples, and the other aliquot frozen and thawed using standard procedures and investigated as frozen thawed subsamples. UHPLC/MS/MS was used to study the sperm proteome under these two distinct conditions and bioinformatic enrichment analysis conducted. Gene Ontology (GO) and pathway enrichment analysis were performed revealing dramatic changes as consequence of cryopreservation. The terms oxidative phosphorylation, mitochondrial ATP synthesis coupled electron transport and electron transport chain were significantly enriched in fresh samples (P = 5.50 × 10^-12, 4.26 × 10^-8 and 7.26 × 10^-8, respectively), while were not significantly enriched in frozen thawed samples (P = 1). The GO terms oxidation reduction process and oxidoreductase activity were enriched in fresh samples and the enrichment was reduced in frozen thawed samples (1.40 × 10^-8, 1.69 × 10^-6 versus 1.13 × 10^-2 and 2-86 × 10^-2 respectively). Reactome pathways (using human orthologs) significantly enriched in fresh sperm were TCA cycle and respiratory electron transport (P = 1.867 × 10^-8), Respiratory electron transport ATP synthesis by chemiosmosis coupling (P = 2.124 × 10^-5), Citric acid cycle (TCA cycle)(P = 8.395 × 10^-4) Pyruvate metabolism and TCA cycle (P = 3.380 × 10^-3), Respiratory electron transport (P = 2.764 × 10^-2) and Beta oxidation of laurolyl-CoA to decanoyl CoA-CoA (P = 1.854 × 10^-2) none of these pathways were enriched in thawed samples (P = 1). We have provided the first detailed study on how the cryopreservation process impacts the stallion sperm proteome. Our findings identify the metabolic proteome and redoxome as the two key groups of proteins affected by the procedure. SIGNIFICANCE: In the present manuscript we investigated how the cryopreservation of stallion spermatozoa impacts the proteome of these cells. This procedure is routinely used in horse breeding and has a major impact in the industry, facilitating the trade of genetic material. This is still a suboptimal biotechnology, with numerous unresolved problems. The limited knowledge of the molecular insults occurring during cryopreservation is behind these problems. The application and development of proteomics to the spermatozoa, allow to obtain valuable information of the specific mechanisms affected by the procedure. In this paper, we report that cryopreservation impacts numerous proteins involved in metabolism regulation (mainly mitochondrial proteins involved in the TCA cycle, and oxidative phosphorylation) and also affects proteins with oxidoreductase activity. Moreover, specific proteins involved in the sperm-oocyte interaction are also affected by the procedure. The information gathered in this study, opens interesting questions and offer new lines of research for the improvement of the technology focusing the targets here identified, and the specific steps in the procedure (cooling, toxicity of antioxidants etc.) to be modified to reduce the damage.

Power Doppler can detect the presence of 7-8 day conceptuses prior to flushing in an equine embryo transfer program

In order to determine whether differences in uterine blood flow between pregnant and non-pregnant mares can be used to predict the presence of the equine embryo prior to flushing in an embryo transfer program, power Doppler ultrasonography was used on a total of 52 mares on days 7 or 8 post-ovulation. Computer analysis of Doppler images was subsequently performed using ImageJ v1.48 software. Vascular perfusion of the endometrium was analyzed using spot meter techniques, measuring mean pixel intensity and area of blood flow. Mares with positive flushings presented a higher uterine blood flow area (one embryo: 54.01 ± 2.27 mm² or two embryos: 61.01 ± 6.73 mm²) prior to embryo recovery compared to barren mares (21.77 ± 2.22 mm²) (p≤0.05). However, significant differences in vascular perfusion were not detected between single or twin pregnancies. Blood flow area appears to be a good predictor for differentiation between pregnant and non-pregnant mares with an AUC: 0.869; p≤0.001 and an optimal cut-off value of 37.21 mm². Both the mare's age and day of embryo recovery caused effects on uterine vascular perfusion. According to Youden's J statistics the uterine blood flow area of young pregnant mares was greater than 25.4 mm² on day 7 (with a sensitivity of 75% and a specificity of 87.5%) and greater than 21.02 mm² on day 8 post-ovulation (with a sensitivity of 93.8% and a specificity of 100%). The uterine blood flow area in adult pregnant mares was greater than 41.4 mm² on day 7 (with a sensitivity of 80% and a specificity of 85.5%) and greater than 35.55 mm² on day 8 after ovulation (with a sensitivity of 97.2% and a specificity of 85.7%). Evaluation on day 8 is therefore considered to be more reliable. Older and middle aged pregnant mares (5-18 years old) had increased uterine vascularization compared to young pregnant mares (2-5 years old) (p≤0.001). Conversely, older barren mares showed higher endometrial vascularity (35.06 ± 2.56 mm²) than young (17.21 ± 1.26 mm²) and middle aged non-pregnant mares (23.84 ± 1.50 mm²) (p≤0.05). We hypothesized that the higher blood flow area seen in older barren mares may be a consequence of a subclinical endometritis due to repeated flushing for embryo recovery. The results of the present study indicate that power Doppler ultrasound combined with computer assisted analysis of images are reliable techniques to detect early pregnancy prior to embryo recovery.

Redox Regulation and Oxidative Stress: The Particular Case of the Stallion Spermatozoa

Redox regulation and oxidative stress have become areas of major interest in spermatology. Alteration of redox homeostasis is recognized as a significant cause of male factor infertility and is behind the damage that spermatozoa experience after freezing and thawing or conservation in a liquid state. While for a long time, oxidative stress was just considered an overproduction of reactive oxygen species, nowadays it is considered as a consequence of redox deregulation. Many essential aspects of spermatozoa functionality are redox regulated, with reversible oxidation of thiols in cysteine residues of key proteins acting as an “on–off” switch controlling sperm function. However, if deregulation occurs, these residues may experience irreversible oxidation and oxidative stress, leading to malfunction and ultimately death of the spermatozoa. Stallion spermatozoa are “professional producers” of reactive oxygen species due to their intense mitochondrial activity, and thus sophisticated systems to control redox homeostasis are also characteristic of the spermatozoa in the horse. As a result, and combined with the fact that embryos can easily be collected in this species, horses are a good model for the study of redox biology in the spermatozoa and its impact on the embryo.

Extracellular vesicles isolated from porcine seminal plasma exhibit different tetraspanin expression profiles

Seminal extracellular vesicles (EVs) include exosomes (ø 40–120 nm) and microvesicles (MVs, ø 120–1000 nm), which would be involved in multiple functional reproductive roles. The study aimed to establish which EV subtypes are present in pig semen, using a high-resolution flow cytometer to explore differences in their tetraspanin expression profile. The EVs were isolated from 12 pig ejaculates using serial ultracentrifugation and characterized by dynamic light scattering and electron microscopy for size and morphology as well as for tetraspanin expression using flow cytometry with Carboxyfluorescein succinimidyl ester (CFSE) and antibodies against CD9, CD63 and CD81. Pig semen contained a heterogeneous EV-population regarding size and morphology. Flow cytometric analysis demonstrated that the proportion of EVs expressing CD63 and CD9 was higher in MVs (P < 0.001 and P < 0.05, respectively) than in exosomes, while the opposite was true for CD81; higher (P < 0.001) in exosomes than in MVs. In conclusion, (1) the new generation of flow cytometers are able to accurately identify EVs and to gate them in two size-different populations named exosomes and MVs. (2) Tetraspanins CD9, CD63 and CD81 are present in both seminal EVs, albeit with exosomes and MVs differing in expression profiles, suggesting dissimilar cargo and binding affinity.

Transcriptome analysis reveals that fertilization with cryopreserved sperm downregulates genes relevant for early embryo development in the horse

Artificial insemination with cryopreserved spermatozoa is a major assisted reproductive technology in many species. In horses, as in humans, insemination with cryopreserved sperm is associated with lower pregnancy rates than those for fresh sperm, however, direct effects of sperm cryopreservation on the development of resulting embryos are largely unexplored. The aim of this study was to investigate differences in gene expression between embryos resulting from fertilization with fresh or cryopreserved sperm. Embryos were obtained at 8, 10 or 12 days after ovulation from mares inseminated post-ovulation on successive cycles with either fresh sperm or frozen-thawed sperm from the same stallion, providing matched embryo pairs at each day. RNA was isolated from two matched pairs (4 embryos) for each day, and cDNA libraries were built and sequenced. Significant differences in transcripts per kilobase million (TPM) were determined using (i) genes for which the expression difference between treatments was higher than 99% of that in the random case (P < 0.01), and (ii) genes for which the fold change was ≥ 2, to avoid expression bias in selection of the candidate genes. Molecular pathways were explored using the DAVID webserver, followed by network analyses using STRING, with a threshold of 0.700 for positive interactions. The transcriptional profile of embryos obtained with frozen-thawed sperm differed significantly from that for embryos derived from fresh sperm on all days, showing significant down-regulation of genes involved in biological pathways related to oxidative phosphorylation, DNA binding, DNA replication, and immune response. Many genes with reduced expression were orthologs of genes known to be embryonic lethal in mice. This study, for the first time, provides evidence of altered transcription in embryos resulting from fertilization with cryopreserved spermatozoa in any species. As sperm cryopreservation is commonly used in many species, including human, the effect of this intervention on expression of developmentally important genes in resulting embryos warrants attention.

Progesterone stimulates the long-distance migration of capacitated ram spermatozoa through viscous media under geotactic condition

Forward progressive motility of spermatozoa is an essential prerequisite for reproductive success, and sperm navigation is assisted by guidance mechanisms that may depend on micro-environmental factors. In the present study, we performed an integrated analysis of long-distance ram sperm migration in vitro that combined two environmental factors (10 μM progesterone and a geotactic effect) and the physiological status of the cells (capacitation treatment). A penetration assay was used in which spermatozoa had to travel 20 mm in a viscous medium (two media of differing viscosity: acrylamide and hyaluronic acid) through a tube device. The number of migrating spermatozoa, the physiology of the cells (motility analyzed using a CASA system; acrosomal status, viability and active mitochondria evaluated by flow cytometry; DNA fragmentation index calculated by quantitative PCR) and the morphometry of sperm heads (performed using an image analysis system) were evaluated after long-distance sperm migration. Ram sperm capacitation significantly stimulates cell migration through viscous media under geotactic conditions, and this effect is enhanced by progesterone induction. The rheological characteristics of viscous media have a marked impact on ram sperm migration, and acrylamide more favorably facilitates navigation over a large distance. The migrating spermatozoa are morphologically better adapted (high ellipticity) for displacement in viscous media and exhibit remarkably depleted mitochondrial membrane potential.

Prenatal histomorphological development of the rumen in Dama dama

This work studies the morphological changes taking place in the Dama dama rumen during prenatal development using histomorphometrics, surface microstructure and immunohistochemistry analysis as well as carrying out a comparative analysis of this species with other wild (red deer) and domestic-type ruminants. A total of 25 fallow deer embryos and fetuses were used, from the first stage of prenatal life until birth. The appearance of the rumen from the primitive gastric tube was observed at 51 days of prenatal life (CRL 3 cm, 21% gestation). By 57 days (CRL 4.3 cm, 24% gestation) the ruminal wall comprised three layers: an internal epithelial layer, a middle layer of pluripotential blastemic tissue and an external layer or serosa. Ruminal pillars were visible at 72 days (CRL 6 cm, 30% gestation), and by 85 days (CRL 7.2 cm, 35% gestation) ruminal papillae were starting to appear. Under scanning electron microscopy, by 80 days (CRL 7 cm, 33% gestation) small ruminal papillae were observed protruding from the surface. Morphometric results showed accelerated growth of the epithelial layer and the tunica muscularis at 180 days (75% gestation). By contrast, the growth-rate of the lamina propria and submucosa declined from the early embryonic stages until birth. The serosa maintained a steady rate of growth until birth. Neuroendocrine cells (synaptophysin) were detected at 85 days (CRL 7.2 cm CRL, 35% gestation), while glial cell markers (glial fibrillary acidic protein and vimentin) were found at 108 days (CRL 31 cm, 45% gestation) and 63 days (CRL 4.4 cm, 26% gestation) respectively. Neuropeptide Y and vasoactive intestinal polypeptide were detected immunohistochemically at 180 days (CRL 33 cm, 75% gestation) and 192 days (CRL 35 cm, 80% gestation) respectively. In comparison to other wild and domestic-type ruminants, histomorphogenesis of the rumen in Dama dama was similar to that reported in red deer and goats, but rather slower than that observed for sheep or cattle.

piRNA-associated proteins and retrotransposons are differentially expressed in murine testis and ovary of aryl hydrocarbon receptor deficient mice

Previous studies suggested that the aryl hydrocarbon receptor (AhR) contributes to mice reproduction and fertility. However, the mechanisms involved remain mostly unknown. Retrotransposon silencing by Piwi-interacting RNAs (piRNAs) is essential for germ cell maturation and, remarkably, AhR has been identified as a regulator of murine B1-SINE retrotransposons. Here, using littermate AhR^+/+ and AhR^−/− mice, we report that AhR regulates the general course of spermatogenesis and oogenesis by a mechanism likely to be associated with piRNA-associated proteins, piRNAs and retrotransposons. piRNA-associated proteins MVH and Miwi are upregulated in leptotene to pachytene spermatocytes with a more precocious timing in AhR^−/− than in AhR^+/+ testes. piRNAs and transcripts from B1-SINE, LINE-1 and IAP retrotransposons increased at these meiotic stages in AhR-null testes. Moreover, B1-SINE transcripts colocalize with MVH and Miwi in leptonema and pachynema spermatocytes. Unexpectedly, AhR^−/− males have increased sperm counts, higher sperm functionality and enhanced fertility than AhR^+/+ mice. In contrast, piRNA-associated proteins and B1-SINE and IAP-derived transcripts are reduced in adult AhR^−/− ovaries. Accordingly, AhR-null female mice have lower numbers of follicles when compared with AhR^+/+ mice. Thus, AhR deficiency differentially affects testis and ovary development possibly by a process involving piRNA-associated proteins, piRNAs and transposable elements.

Mitochondrial ATP is required for the maintenance of membrane integrity in stallion spermatozoa, whereas motility requires both glycolysis and oxidative phosphorylation

To investigate the hypothesis that oxidative phosphorylation is a major source of ATP to fuel stallion sperm motility, oxidative phosphorylation was suppressed using the mitochondrial uncouplers CCCP and 2,4,-dinitrophenol (DNP) and by inhibiting mitochondrial respiration at complex IV using sodium cyanide or at the level of ATP synthase using oligomycin-A. As mitochondrial dysfunction may also lead to oxidative stress, production of reactive oxygen species was monitored simultaneously. All inhibitors reduced ATP content, but oligomycin-A did so most profoundly. Oligomycin-A and CCCP also significantly reduced mitochondrial membrane potential. Sperm motility almost completely ceased after the inhibition of mitochondrial respiration and both percentage of motile sperm and sperm velocity were reduced in the presence of mitochondrial uncouplers. Inhibition of ATP synthesis resulted in the loss of sperm membrane integrity and increased the production of reactive oxygen species by degenerating sperm. Inhibition of glycolysis by deoxyglucose led to reduced sperm velocities and reduced ATP content, but not to loss of membrane integrity. These results suggest that, in contrast to many other mammalian species, stallion spermatozoa rely primarily on oxidative phosphorylation to generate the energy required for instance to maintain a functional Na⁺/K⁺ gradient, which is dependent on an Na⁺-K⁺ antiporter ATPase, which relates directly to the noted membrane integrity loss. Under aerobic conditions, however, glycolysis also provides the energy required for sperm motility.

Stallion spermatozoa surviving freezing and thawing experience membrane depolarization and increased intracellular Na. Andrology 2017;5:1174-1182. [PMID: 28973824 DOI: 10.1111/andr.12419]

In order to gain insight of the modifications that freezing and thawing cause to the surviving population of spermatozoa, changes in the potential of the plasma membrane (Em) and intracellular Na⁺ content of stallion spermatozoa were investigated using flow cytometry. Moreover, caspase 3 activity was also investigated and the functionality of the Na⁺ -K⁺ ATPase pump was investigated before and after freezing and thawing. Cryopreservation caused a significant (p < 0.001) increase in the subpopulation of spermatozoa with depolarized sperm membranes, concomitantly with an increase (p < 0.05) in intracellular Na⁺ . These changes occurred in relation to activation of caspase 3 (p < 0.001). Cryopreservation reduced the activity of the Na-K⁺ pump and inhibition of the Na⁺ -K⁺ ATPase pump with ouabain-induced caspase 3 activation. It is concluded that inactivation of Na⁺ -K⁺ ATPase occurs during cryopreservation, an inhibition that could play a role explaining the accelerated senescence of the surviving population of spermatozoa.