Sperm-zona pellucida interaction involves a carbonyl reductase activity in the hamster

Influence of Two Widely Used Solvents, Ethanol and Dimethyl Sulfoxide, on Human Sperm Parameters

To study mechanisms involved in fertility, many experimental assays are conducted by incubating spermatozoa in the presence of molecules dissolved in solvents such as ethanol (EtOH) or dimethyl sulfoxide (DMSO). Although a vehicle control group is usually included in such studies, it does not allow to evaluate the intrinsic effect of the solvent on sperm parameters and its potential influence on the outcome of the experiment. In the present study, we incubated human spermatozoa for 4 h in a capacitation medium in the absence or the presence of different concentrations of EtOH and DMSO (0.1, 0.5, 1.0, and 2.0%) to assess the impact of these solvents on sperm motility, vitality, capacitation, and acrosome integrity. The presence of statistically significant relationships between increasing solvent concentrations and the investigated parameters was assessed using linear mixed models. A significant effect was observed with both solvents for total and progressive sperm motilities. We also evaluated the effect of time for these parameters and showed that the influence of the solvents was stable between 0 and 4 h, indicating an almost direct impact of the solvents. While EtOH did not influence sperm vitality and acrosome integrity, a significant effect of increasing DMSO concentrations was observed for these parameters. Finally, regarding capacitation, measured via phosphotyrosine content, although a dose-dependent effect was observed with both solvents, the statistical analysis did not allow to precisely evaluate the intensity of the effect. Based on the results obtained in the present study, and the corresponding linear mixed models, we calculated the concentration of both solvents which would result in a 5% decline in sperm parameters. For EtOH, these concentrations are 0.9, 0.7, and 0.3% for total motility, progressive motility, and capacitation, respectively, while for DMSO they are 1.5, 1.1, >2, 0.3 and >2% for total motility, progressive motility, vitality, capacitation, and acrosome integrity, respectively. We recommend using solvent concentrations below these values to dissolve molecules used to study sperm function in vitro, to limit side effects.

Effect of diclofenac on semen quality: A review

Diclofenac is an effective nonsteroidal anti-inflammatory drug and one of the most prescribed medicines worldwide. So far, there are many published articles that directly link between diclofenac and semen quality; however, hitherto, there is no collective review or comprehensive discussion that reveal such imperative link. Therefore, this work reviews and judges the association between diclofenac administration and semen quality, henceforth male infertility. As a tool to accomplish this scientific input, Scopus, Embase and PubMed databases have been searched for all original articles using the keywords "diclofenac" versus "semen" and "sperm" since August 1987 through November 2020. In summary, diclofenac appears to induce negative effects on both qualitative and quantitative measures of sperm; however, this conclusion requires confirmation by human studies. The detected negative effects of diclofenac on semen quality measures may be owed to reduced levels of gonadal hormones, decreased antioxidant defence mechanism, increased oxidative stress, altered concentrations of nitric oxide that are required to maintain normal sperm physiology and reduced synthesis of prostaglandins.

Enzymatic characterization of a recombinant carbonyl reductase from Acetobacter sp. CCTCC M209061

Background

Acetobacter sp. CCTCC M209061 could catalyze carbonyl compounds to chiral alcohols following anti-Prelog rule with excellent enantioselectivity. Therefore, the enzymatic characterization of carbonyl reductase (CR) from Acetobacter sp. CCTCC M209061 needs to be investigated.

Results

A CR from Acetobacter sp. CCTCC M209061 (AcCR) was cloned and expressed in E. coli. AcCR was purified and characterized, finding that AcCR as a dual coenzyme-dependent short-chain dehydrogenase/reductase (SDR) was more preferred to NADH for biocatalytic reactions. The AcCR was activated and stable when the temperature was under 35 °C and the pH range was from 6.0 to 8.0 for the reduction of 4′-chloroacetophenone with NADH as coenzyme, and the optimal temperature and pH were 45 °C and 8.5, respectively, for the oxidation reaction of isopropanol with NAD⁺. The enzyme showed moderate thermostability with half-lives of 25.75 h at 35 °C and 13.93 h at 45 °C, respectively. Moreover, the AcCR has broad substrate specificity to a range of ketones and ketoesters, and could catalyze to produce chiral alcohol with e.e. >99% for the majority of tested substrates following the anti-Prelog rule.

Conclusions

The recombinant AcCR exhibited excellent enantioselectivity, broad substrate spectrum, and highly stereoselective anti-Prelog reduction of prochiral ketones. These results suggest that AcCR is a powerful catalyst for the production of anti-Prelog alcohols.Graphical abstract

Sperm surface changes and physiological consequences induced by sperm handling and storage

Spermatozoa interact with their immediate environment and this contact remodels the sperm surface in preparation for fertilisation. These fundamental membrane changes will be critically covered in this review with special emphasis on the very specific surface destabilisation event, capacitation. This process involves very subtle and intricate modifications of the sperm membrane including removal of suppression (decapacitation) factors and changes in the lateral organisation of the proteins and lipids of the sperm surface. Processing of sperm for assisted reproduction (storage, sex-sorting, etc.) subjects spermatozoa to numerous stressors, and it is possible that this processing overrides such delicate processes resulting in sperm instability and cell damage. To improve sperm quality, novel mechanisms must be used to stabilise the sperm surface during handling. In this review, different types of membrane stress are considered, as well as novel surface manipulation methods to improve sperm stability.

New evidences for the involvement of 20beta-hydroxysteroid dehydrogenase in final oocyte maturation of air-breathing catfish

20beta-hydroxysteroid dehydrogenase (20beta-HSD) synthesizes 17alpha,20beta-dihdroxy-4-pregnen-3-one, the steroid required for resumption of prophase-I arrested oocytes in teleosts. Though 20beta-HSD cDNAs have been cloned from few fish species, its role in final oocyte maturation (FOM) is still questionable. To study the role of 20beta-HSD in FOM more explicitly, we cloned and characterized 20beta-HSD from ovary of air-breathing catfish, Clarias gariepinus. Interestingly, Escherichia coli expressed recombinant proteins, both full-length and an N-terminal truncated proteins catalyzed the reduction of steroids and xenobiotics, however there was significant difference between them. Semi-quantitative RT-PCR and Western blots demonstrated the presence of 20beta-HSD transcript and protein in various tissues with relatively higher level in gonads, gill, kidney and brain. A positive correlation of 20beta-HSD expression was observed in different phases of ovarian cycles. Immunocytochemical/immunofluoroscence analysis with specific antibody identified presence of 20beta-HSD in follicular layer of ovary. Real-time RT-PCR and Western blotting showed an induction of 20beta-HSD expression during human chorionic gonadotropin (hCG)-induced oocyte maturation, in vitro and in vivo. Concomitantly, a rise in 20beta-HSD enzyme activity was also noticed. Specific inhibitors of carbonyl reductase inhibited not only recombinant protein catalytic activity but also hCG-induced oocyte maturation in a dose-dependent manner as evidenced by blocking of germinal vesicle break down. These results together provide new evidences for the involvement of 20beta-HSD in the FOM/meiotic maturation.

Multiple proteins present in purified porcine sperm apical plasma membranes interact with the zona pellucida of the oocyte

An important step in fertilization is the recognition and primary binding of the sperm cell to the zona pellucida (ZP). Primary ZP binding proteins are located at the apical plasma membrane of the sperm head. In order to exclusively study primary zona binding proteins, plasma membranes of sperm heads were isolated, highly purified and subsequently solubilized with a mild or a strong solubilization procedure. Native, highly purified ZP ghosts were used as the binding substrate for solubilized sperm plasma membrane proteins, and a proteomic approach was employed to identify ZP binding proteins. Two-dimensional gel electrophoresis of ZP fragments with bound sperm proteins showed very reproducibly 24 sperm protein spots to be associated to the zona ghosts after mild plasma membrane solubilization whereas only three protein spots were detected after strong plasma membrane solubilization. This indicates the involvement of multiple sperm proteins in ZP binding. The three persistently bound proteins were identified by a tandem mass spectrometry as isoforms of AQN-3 and probably represent the main sperm protein involved in ZP binding. P47, fertilin beta and peroxiredoxin 5 were also conclusively identified. None of the identified proteins has a known acrosomal origin, which further indicated that there was no sample contamination with secondary ZP binding proteins from the acrosomal matrix. In this study, we showed and identified multiple zona binding proteins involved in primary sperm-zona binding. Although we were not able to identify all of the proteins involved, this is a first step in understanding the event of primary sperm-zona interactions and the relevance of this for fertilization is discussed.

Sperm N-acetylglucosaminidase is involved in primary binding to the zona pellucida

The glycosidase-recognizing N-acetylglucosamine terminal residue, N-acetylglucosaminidase (NAG), has been repetitively implicated in fertilization. Nevertheless, its role in the multiple steps comprising this process is a matter of debate because it has been involved in zona pellucida (ZP) binding and penetration and polyspermy block. In this study, the involvement of NAG during sperm interaction with the ZP was analysed. Soluble ZP was able to inhibit sperm NAG activity, suggesting that it can be recognized as a ligand by this enzyme. Sperm-ZP binding assays were carried out under conditions where acrosome reaction (AR) could not take place (salt-stored oocytes and a modified medium where Ca(2+) was replaced by Sr(2+)). Different NAG-specific reagents-an inhibitor (2-acetamido-2-deoxy-D-glucono-1,5-lactone), a substrate (p-nitrophenyl-N-acetylglucosaminide) and an anti-NAG antibody-were able to impair sperm binding to the ZP when present during these assays. The lactone was also able to inhibit oocyte penetration during IVF assays, although not when present after primary binding had taken place. This result was not related to the interference of lactone with AR or zona penetrability. Exogenous NAG also inhibited sperm-oocyte interaction when present during binding and IVF assays or used for oocyte pre-incubation. These results suggest the participation of NAG in sperm primary binding to the ZP.

Aldose reductase and macrophage migration inhibitory factor are associated with epididymosomes and spermatozoa in the bovine epididymis

During the epididymal transit, mammalian spermatozoa acquire new surface proteins necessary for male gamete function. We have previously shown that membranous vesicles, called epididymosomes, interact with spermatozoa allowing the transfer of some proteins to sperm surface within the epididymal lumen. The protein composition of those vesicles has been investigated to document the mechanisms of protein transfer from epididymosomes to spermatozoa. Electrophoretic analysis revealed that protein composition is different from the epididymal soluble compartment as well as from similar vesicles present in the semen. Protein association with epididymosome is very strong as revealed by resistance to extraction with detergent. Matrix-assisted laser desorption ionization time-of-flight as well as immunodetection techniques have been used to identify some proteins associated to epididymosomes and spermatozoa. An aldose reductase known for its 20alpha-hydroxysteroid dehydrogenase activity and the cytokine (macrophage migration inhibitory factor) have been identified. These two proteins have been immunolocalized in principal cells of the epididymal epithelium, a more intense signal being detected in the distal epididymal segment as well as in the vas deferens. Database search revealed that these two proteins are characterized by the lack of a signal peptide. These results are discussed with regard to a possible apocrine mode of secretion of these proteins acquired by spermatozoa during the epididymal transit.

Ovarian Carbonyl Reductase-Like 20β-Hydroxysteroid Dehydrogenase Shows Distinct Surge in Messenger RNA Expression During Natural and Gonadotropin-Induced Meiotic Maturation in Nile Tilapia1

Meiotic maturation in fish is accomplished by maturation-inducing hormones. 17alpha,20beta-Dihydroxy-4-pregnen-3-one (17alpha,20beta-DP) was identified as the maturation-inducing hormone of several teleosts, including Nile tilapia. A cDNA encoding 20beta-hydroxysteroid dehydrogenase (20beta-HSD), the enzyme that converts 17alpha-hydroxyprogesterone to 17alpha,20beta-DP, was cloned from the ovarian follicle of Nile tilapia. Genomic Southern analysis indicated that 20beta-HSD probably exists as a single copy in the genome. The Escherichia coli-expressed cDNA product oxidized both carbonyl and steroid compounds, including progestogens, in the presence of NADPH. Carbonyl reductase-like 20beta-HSD is broadly expressed in various tissues of tilapia, including ovary, testis, and gill. Northern blot and reverse transcription polymerase chain reaction analyses during the 14-day spawning cycle revealed that the expression of 20beta-HSD in ovarian follicles is low from Day 0 to Day 8 after spawning and is not detectable on Day 11. Distinct expression was evident at Day 14, the day of spawning. In males, 20beta-HSD expression was observed continually in mature testes but not in immature testes of 30-day-old fish. In vitro incubation of postvitellogenic immature follicles (corresponding to Day 11 after spawning) with hCG induced the expression of 20beta-HSD mRNA transcripts within 1-2 h, followed by the final meiotic maturation of oocytes. In tissues such as gill, muscle, brain, and pituitary, however, hCG treatment did not induce any changes in the levels of mRNA transcripts. Actinomycin D blockade of hCG-induced 20beta-HSD expression and final oocyte maturation demonstrated the involvement of transcriptional factors. The carbonyl reductase-like 20beta-HSD plays an important role in the meiotic maturation of tilapia gametes.