Sublethal Xanthine Oxidase Stress Prefreezing of Bull Sperm Improves the Post-Thaw Functionality and Fertility Potential Parameters

Oxidative stress during cryopreservation causes mechanical, biochemical, and structural damage to the sperm, leading to lower viability and fertility potential. In recent years, a novel method based on the use of mild stress for preconditioning of sperm before cryopreservation has been applied to improve the quality of thawed sperm, although its molecular mechanism remains unknown. In this study, we investigated the protective effects of sublethal oxidative stress by xanthine oxidase (XO) on thawed bull sperm performance through modulations of mitochondrial uncoupling protein 2 (UCP2) expression. Semen samples were collected from six bulls, then mixed and divided into four aliquots: frozen control (XO-0) and frozen groups treated with different concentrations of XO, 0.01 μM (XO-0.01), 0.1 μM (XO-0.1), and 1 μM (XO-1). Thawed sperm were evaluated for motion parameters, viability, acrosome integrity, mitochondria activity, membrane integrity, and UCP2 expression. A significant increase of total motility and viability rate was observed in XO-0.1 compared with other frozen groups (p < 0.05). The highest percentage of progressive motility was in XO-0.01 and XO-0.1 compared with other groups (p < 0.05). Moreover, a significantly higher level of sperm mitochondrial membrane potential and membrane integrity was observed in XO-0.1 (p < 0.05). We also found the lowest percentage of sperm mitochondria activity in XO-1 (p < 0.05). In addition, the highest expression of UCP2 was observed in XO-1 (p < 0.05). Our findings suggest that stress preconditioning of bull sperm before cryopreservation can improve thawed sperm functions, which might be mediated through an increase of UCP2 expression.

Rooster frozen-thawed semen quality following sublethal xanthine oxidase treatments

Reactive oxygen species are associated with cryodamage and may be a factor causing or exacerbating cellular cryodamage during freezing and thawing processes. Induction of sublethal oxidative stress as a new approach for preconditioning of sperm improves the cryo-resistance of sperm. The aim of this study was to investigate effects of sublethal concentrations of xanthine oxidase (XO), which induces oxidative stress before cryopreservation on values for semen quality variables of rooster sperm post-thawing. Semen samples were collected from 15 roosters and treated with different concentrations of XO [XO-0, XO-0.005, XO-0.05, XO-0.5, XO-5, and XO-50 U/ml]; then, the effects of treatments with XO as sublethal stressors, were examined. Results indicated the XO-0.5 and XO-5 treatments resulted in a greater percentage of sperm total motility, progressive motility, viability, and membrane functionality compared to other groups. There was no difference after treatments with XO-0, XO-0.005, and XO-0.05 on sperm total motility, membrane functionality, apoptosis, mitochondria activity, and viability. There was a greater percentage of mitochondria activity in sperm of the XO-0.05, XO-0.5, and XO-5 groups. Furthermore, there was the greatest concentration of malondialdehyde (MDA) in samples of the XO-50 group. Values for sperm abnormal morphology, acrosome integrity, and DNA fragmentation were not different among samples post-thawing. Sperm treated with XO-0.5 and XO-5 had a greater fertilization capacity than those of the control group. In conclusion, treatment of sperm with 0.5 and 5 U/ml XO as inducers of mild oxidative stress before cryopreservation, improved several function quality indices of sperm post-thawing.

Proteomics study reveals the molecular mechanisms underlying cryotolerance induced by mild sublethal stress in human sperm

The preconditioning of human sperm with sublethal nitrosative stress before cryopreservation can potentially improve the thawed sperm quality. However, the underlying mechanisms behind this protective strategy are not entirely understood. We compared the cryosurvival of human sperm exposed to 0.01 μM nitric oxide (NO) throughout the cryopreservation and used multiplexed quantitative proteomics approach to identify changes in the proteome profile of preconditioned sperm cells. Semen samples were obtained from 30 normospermia donors and then each sample was divided into three equal parts: fresh (F), frozen-control (C), and frozen exposed to nitric oxide (NO). The sperm undergoing mild sublethal stress showed higher values for motility and viability compared to the frozen control sperm. Moreover, out of 2912 identified proteins, 248 proteins were detected as differentially abundant proteins (DAPs) between cryopreserved groups and fresh group (F) (p < 0.05). Gene ontology (GO) analysis of differentially abundant proteins indicated that the abundance of proteins associated with glycolysis, gluconeogenesis, and fertilization processes was reduced while oxidative phosphorylation pathway was increased in abundance in cryopreserved sperm compared to the fresh sperm. Moreover, redox protein such as thioredoxin 17 was increased in abundance in the NO group compared to the control freezing group. Therefore, the pre-conditioning of sperm prior to cryopreservation may play an important role in maintaining the redox balance in mitochondria of sperm after freezing. Overall, our results indicate that arylsulfatase A (ARSA), serine protease 37 (PRSS37), and sperm surface protein (SP17) may potentially serve as protein biomarkers associated with screening the fertilization potential of the thawed sperm.

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.

Sperm cryopreservation: A review on current molecular cryobiology and advanced approaches

The cryopreservation of spermatozoa was introduced in the 1960s as a route to fertility preservation. Despite the extensive progress that has been made in this field, the biological and biochemical mechanisms involved in cryopreservation have not been thoroughly elucidated to date. Various factors during the freezing process, including sudden temperature changes, ice formation and osmotic stress, have been proposed as reasons for poor sperm quality post-thaw. Little is known regarding the new aspects of sperm cryobiology, such as epigenetic and proteomic modulation of sperm and trans-generational effects of sperm freezing. This article reviews recent reports on molecular and cellular modifications of spermatozoa during cryopreservation in order to collate the existing understanding in this field. The aim is to discuss current freezing techniques and novel strategies that have been developed for sperm protection against cryo-damage, as well as evaluating the probable effects of sperm freezing on offspring health.

Induction of Sublethal Oxidative Stress on Human Sperm before Cryopreservation: A Time-Dependent Response in Post-Thawed Sperm Parameters

Objective

A recent innovative approach, based on induction of sublethal oxidative stress to enhance sperm cryosurvival, has been applied before sperm cryopreservation. The purpose of this study was to investigate the effects of different induction times of sublethal oxidative stress before cryopreservation on human post-thawed sperm quality.

Materials and Methods

In this experimental study, we selected semen samples (n=20) from normozoospermic men according to 2010 World Health Organization (WHO) guidelines. After processing the samples by the density gradient method, we divided each sample into 5 experimental groups: fresh, control freezing, and 3 groups exposed to 0.01 μM sodium nitroprusside (SNP) [nitric oxide (NO) donor] for 30 (T30), 60 (T60), or 90 minutes (T90) at 37˚C and 5% CO₂ before cryopreservation. Motion characteristics [computer-assisted sperm analyser], viability, apoptosis [annexin V/propidium iodide (PI) assay], DNA fragmentation [sperm chromatin structure assay (SCSA)], and caspase 3 activity (FLICA Caspase Detection Kit) were assessed after thawing. The results were analysed by using one-way ANOVA and Tukey's test. The means were significantly different at P<0.05.

Results

Cryopreservation significantly decreased sperm viability and motility parameters, and increased the percentage of apoptosis, caspase 3 activity, and DNA fragmentation (P<0.01) compared to the fresh group. The T60 group had a higher significant percentage of total motility (TM) and progressive motility compared with other cryopreserved groups (P<0.05). We observed a significantly lower percentage of apoptotic rate and caspase 3 activity in the T60 group compared to the other cryopreserved groups (P<0.05). DNA integrity was not significantly affected by this time of sublethal stress induction (P>0.05).

Conclusion

Our results have demonstrated that the application of sublethal oxidative stress by using 0.01 μM NO for 60 minutes before the freezing process can be a beneficial approach to improve post-thawed human sperm quality.

Geranylgeranylacetone induction of HSP90α exerts cryoprotective effect on Acipenser sinensis sperm

Heat Shock Protein 90 (HSP90) is a fertility-associated protein, the expression of which positively correlates with sperm quality in many species. Geranylgeranylacetone (GGA) is reported to induce expression of HSP90. The present study aimed to investigate whether GGA induced expression of HSP90 in Acipenser sinensis sperm to exert a cryoprotective effect. Sperm from five male A. sinensis was combined with extender containing 20 mmol/L tris pH = 8.1, 10% v/v methanol, 2-5 mmol/L KCl, 15 mmol/L lactose, and 15 mmol/L trehalose, with GGA at 0, 14, 67, 135, 673, 1346, or 6731 μmol/L. After cryopreservation and thawing, the percentage of motile spermatozoa, spermatozoon curvilinear velocity (VCL), straight-line velocity (VSL), average path velocity (VAP), acrosome integrity, and membrane integrity, as well as fertility were evaluated. Sperm quality increased with the increase of GGA to 673 μmol/L, but decreased at higher concentrations. Expression levels of HSP90α were detected by Western blot in sperm frozen with GGA at 673 μmol/L (highest obtained sperm quality), 6731 μmol/L (highest GGA concentration), and a control without GGA. The expression of HSP90α increased with the increase in GGA, with lowest expression observed in the control. GGA was found to induce increase of HSP90α, and this increase was associated with higher quality cryopreserved sperm at concentrations ≤673 μmol/L. This research suggests a viable technique to increase the quality of cryopreserved A. sinensis sperm by adding GGA to induce expression of HSP90α.

Protein phosphorylation in spermatozoa motility of Acipenser ruthenus and Cyprinus carpio

Spermatozoa of externally fertilizing freshwater fish possess several different modes of motility activation. Spermatozoa of common carp (Cyprinus carpio L.) are activated by hypoosmolality, whereas spermatozoa of sterlet (Acipenser ruthenus) require Ca2+ and low concentration of K+ for motility activation. Intracellular signaling differs between these two species as well, particularly in terms of utilization of secondary messengers (cAMP and Ca2+), and kinase activities. The current study was performed in order to determine the importance of protein phosphorylation and protein kinases for activation of sperm motility in carp and sterlet. Treatment with kinase inhibitors indicates that protein kinases A and C (PKA and PKC) participate in spermatozoa motility of both species. Immunodetection of phospho-(Ser/Thr) PKA substrates shows that phosphorylated proteins are localized differently in spermatozoa of carp and sterlet. Strong phosphorylation of PKC substrate was observed in flagella of sterlet spermatozoa, whereas in carp sperm, PKC substrates were lightly phosphorylated in the midpiece and flagella. Motility activation induced either phosphorylation or dephosphorylation on serine, threonine and tyrosine residues of numerous proteins in carp and sterlet spermatozoa. Proteomic methods were used to identify proteins whose phosphorylation state changes upon the initiation of sperm motility. Numerous mitochondrial and glycolytic enzymes were identified in spermatozoa of both species, as well as axonemal proteins, heat shock proteins, septins and calcium-binding proteins. Our results contribute to an understanding of the roles of signaling molecules, protein kinases and protein phosphorylation in motility activation and regulation of two valuable fish species, C. carpio and A. ruthenus.

Progesterone Accelerates the Completion of Sperm Capacitation and Activates CatSper Channel in Spermatozoa from the Rhesus Macaque

During transit through the female reproductive tract, mammalian spermatozoa are exposed to increasing concentrations of progesterone (P4) released by the cumulus oophorus. P4 triggers massive calcium influx into human sperm through activation of the sperm-specific calcium channel CatSper. These properties of human spermatozoa are thought to be unique since CatSper is not progesterone sensitive in rodent sperm. Here, by performing patch clamp recording from spermatozoa from rhesus macaque for the first time, we report that they express P4-sensitive CatSper channel identically to human sperm and react to P4 by inducing responsiveness to zona pellucida, unlike human sperm, which respond directly to P4. We have also determined the physiologic levels of P4 capable of inducing capacitation-associated changes in macaque sperm. Progesterone (1 μM) induced up to a 3-fold increase in the percentage of sperm undergoing the zona pellucida-induced acrosome reaction with the lowest threshold as low as 10 nM of P4. Submicromolar levels of P4 induced a dose-dependent increase in curvilinear velocity and lateral head displacement, while sperm protein tyrosine phosphorylation was not altered. Macaque spermatozoa exposed to 10 μM of P4 developed fully hyperactivated motility. Similar to human sperm, on approaching cumulus mass and binding to zona pellucida, macaque spermatozoa display hyperactivation and undergo an acrosome reaction that coincides with the rise in the sperm intracellular calcium. Taken together, these data indicate that P4 accelerates the completion of capacitation and provides evidence of spermatozoa "priming" as they move into a gradient of progesterone in search for the oocyte.

Beneficial Effects of Nitric Oxide Induced Mild Oxidative Stress on Post-Thawed Bull Semen Quality

Background

Cryopreservation of semen requires optimized conditions to minimize the harmful effects of various stresses. The main approach for protection of sperm against stress is based on the use of antioxidants and cryoprotectants, which are described as defensive methods. Recently, the application of controlled mild stressors has been de- scribed for activation of a temporary response in oocyte, embryo and somatic cells. In this study a sub-lethal oxidative stress induced by precise concentrations of nitric oxide (NO) has been evaluated for sperm during cryopreservation.

Materials and Methods

In this experimental study, we used different concentrations of NO [0 µM (NO-0), 0.01 µM (NO-0.01), 0.1 µM (NO-0.1), 1 µM (NO-1), 10 µM (NO-10) and 100 µM (NO-100)] during cryopreservation of bull semen. Their effects on post-thawed sperm quality that included motility and velocity parameters, plasma mem- brane functionality, acrosome integrity, apoptosis status, mitochondrial activity and lipid peroxidation after freezing-thawing were investigated.

Results

Exposure of sperm before freezing to NO-1 significantly increased total motility (88.4 ± 2.8%), progressive motility (50.4 ± 3.2%) and average path velocity (VAP, 53.8 ± 3.1 µm/s) compared to other extenders. In addition, NO-1 significantly increased plasma mem- brane functionality (89.3 ± 2.9%) compared to NO-0 (75.3 ± 2.9%), NO-0.01 (78.3 ± 2.9%), NO-0.1 (76.4 ± 2.9%), NO-10 (64 ± 2.9%) and NO-100 (42 ± 2.9%). Sperm exposed to NO-1 produced the highest percentage of viable (85.6 ± 2.3%) and the lowest percentage of apoptotic (10.8 ± 2.4%) spermatozoa compared to the other extenders. Also, NO-100 resulted in a higher percentage of dead spermatozoa (27.1 ± 2.7%) compared to the other extenders. In terms of mitochondrial activity, there was no significant difference among NO-0 (53.4 ± 3.2), NO-0.01 (52.1 ± 3.2), NO-0.1 (50.8 ± 3.2) and NO-1 (53.1 ± 3.2). For acrosome integrity, no significant different was observed in sperm exposed to different concentrations of NO.

Conclusion

Induction of sub-lethal oxidative stress with 1 µM NO would be beneficial for cryopreservation of bull semen.

Effect of ethanol induced mild stress on post-thawed bull sperm quality

This study was performed to investigate the effect of sub-lethal exposure of bull semen to ethanol on the post-thaw spermatozoa quality. Semen samples (n=24, 6 ejaculates/bull) from 4 Holstein bulls were collected and pooled. Pooled samples were divided into 4 equal parts and each part was frozen after being diluted with Optidyl® extender containing 0 (O-E0), 0.03 (O-E3), 0.09 (O-E9) and 0.15 (O-E15) % (v/v) absolute ethanol. Sperm motility and velocity, plasma membrane integrity and functionality, mitochondrial activity, malondialdehyde concentration, and apoptosis status were evaluated after thawing. A higher percentage of total motility was observed in the O-E9 group as compared to the O-E0, O-E3 and O-E15 groups (p<0.05). Also, plasma membrane integrity was higher (p<0.05) in the O-E9 group compared to the O-E3, and O-E15 groups. However, the difference between the O-E9 and O-E0 groups was not significant (p>0.05). In terms of the proportion of sperm abnormality and plasma membrane functionality no differences (p>0.05) were observed between the groups. Our results revealed that malondialdehyde level was lower in ethanol treated (O-E3, O-E9 and O-E15) groups compared to the O-E0 group (p<0.05). Furthermore, the percentage of live spermatozoa with active mitochondria was higher in the O-E9 and O-E15 groups compared to the O-E0 and O-E3 groups (p<0.05). The O-E3 and O-E9 groups resulted in the highest and lowest percentage of apoptotic spermatozoa, respectively (p<0.05). The results of this study demonstrate that supplementation of semen extender with sub-lethal concentration of ethanol influences post-thawed bull sperm quality in a dose dependent manner.

The protein tyrosine phosphorylation during in vitro capacitation and cryopreservation of mammalian spermatozoa

Before the process of fertilization, spermatozoa necessitate a period of residence in the female reproductive environment, and undergo a sequence of physiological and biochemical changes collectively referred to as capacitation. Accumulated evidences from several laboratories indicated that the protein tyrosine phosphorylation (PTP) is one of the most important intracellular signaling events regulating sperm function, and is a meaningful indicator of capacitation. Different factors that affect PTP are cholesterol efflux, influx of HCO3(-), increased intracellular Ca(2+), cAMP and reactive oxygen species (ROS). cAMP/PKA and extracellular signal regulated kinases (ERKs) are the known important signaling pathways primarily involved in PTP. Advanced proteomics approaches have revealed several proteins that undergo tyrosine phosphorylation during capacitation. Semen cryopreservation subjects spermatozoa to frequent stressors, which result in capacitation like changes (cryo-capacitation). The cryo-capacitated spermatozoa usually show different patterns of PTP than the normal in vitro capacitated spermatozoa. In the current manuscript, we have summarized some information about the proteins undergoing tyrosine phosphorylation during capacitation and the effect of cryopreservation on PTP as well as the possibilities to reduce the changes associated with cryopreservation process.

Heat shock protein 90 has roles in intracellular calcium homeostasis, protein tyrosine phosphorylation regulation, and progesterone-responsive sperm function in human sperm

Heat shock protein 90 plays critical roles in client protein maturation, signal transduction, protein folding and degradation, and morphological evolution; however, its function in human sperm is not fully understood. Therefore, our objective in this study was to elucidate the mechanism by which heat shock protein 90 exerts its effects on human sperm function. By performing indirect immunofluorescence staining, we found that heat shock protein 90 was localized primarily in the neck, midpiece, and tail regions of human sperm, and that its expression increased with increasing incubation time under capacitation conditions. Geldanamycin, a specific inhibitor of heat shock protein 90, was shown to inhibit this increase in heat shock protein 90 expression in western blotting analyses. Using a multifunctional microplate reader to examine Fluo-3 AM-loaded sperm, we observed for the first time that inhibition of heat shock protein 90 by using geldanamycin significantly decreased intracellular calcium concentrations during capacitation. Moreover, western blot analysis showed that geldanamycin enhanced tyrosine phosphorylation of several proteins, including heat shock protein 90, in a dose-dependent manner. The effects of geldanamycin on human sperm function in the absence or presence of progesterone was evaluated by performing chlortetracycline staining and by using a computer-assisted sperm analyzer. We found that geldanamycin alone did not affect sperm capacitation, hyperactivation, and motility, but did so in the presence of progesterone. Taken together, these data suggest that heat shock protein 90, which increases in expression in human sperm during capacitation, has roles in intracellular calcium homeostasis, protein tyrosine phosphorylation regulation, and progesterone-stimulated sperm function. In this study, we provide new insights into the roles of heat shock protein 90 in sperm function.

The increase in phosphorylation levels of serine residues of protein HSP70 during holding time at 17°C is concomitant with a higher cryotolerance of boar spermatozoa

Boar-sperm cryopreservation is not usually performed immediately after semen collection, but rather a holding time (HT) of 4 h–30 h at 17°C is spent before starting this procedure. Taking this into account, the aim of this study was to go further in-depth into the mechanisms underlying the improving effects of HT at 17°C on boar-sperm cryotolerance by evaluating the effects of two different HTs (3 h and 24 h) on overall boar-sperm function and survival before and after cryopreservation. Given that phospho/dephosphorylation mechanisms are of utmost importance in the overall regulation of sperm function, the phosphorylation levels of serine residues (pSer) in 30 different sperm proteins after a 3 h- or 24 h-HT period were also assessed. We found that a HT of 24 h contributed to a higher sperm resistance to freeze-thawing procedures, whereas mini-array protein analyses showed that a HT of 24 h induced a significant (P<0.05) increase in pSer (from 100.0±1.8 arbitrary units in HT 3 h to 150.2±5.1 arbitrary units in HT 24 h) of HSP70 and, to a lesser extent, in protein kinases GSK3 and total TRK and in the cell-cycle regulatory protein CDC2/CDK1. In the case of HSP70, this increase was confirmed through immunoprecipation analyses. Principal component and multiple regression analyses indicated that a component explaining a percentage of variance higher than 50% in sperm cryotolerance was significantly correlated with pSer levels in HSP70. In addition, from all the parameters evaluated before freeze-thawing, only pSer levels in HSP70 resulted to be able to predict sperm cryotolerance. In conclusion, our results suggest that boar spermatozoa modulate its function during HT, at least partially, by changes in pSer levels of proteins like HSP70, and this is related to a higher cryotolerance.

Proteome and phosphoproteome characterization reveals new response and defense mechanisms of Brachypodium distachyon leaves under salt stress

Salinity is a major abiotic stress affecting plant growth and development. Understanding the molecular mechanisms of salt response and defense in plants will help in efforts to improve the salt tolerance of crops. Brachypodium distachyon is a new model plant for wheat, barley, and several potential biofuel grasses. In the current study, proteome and phosphoproteome changes induced by salt stress were the focus. The Bd21 leaves were initially treated with salt in concentrations ranging from 80 to 320 mm and then underwent a recovery process prior to proteome analysis. A total of 80 differentially expressed protein spots corresponding to 60 unique proteins were identified. The sample treated with a median salt level of 240 mm and the control were selected for phosphopeptide purification using TiO2 microcolumns and LC-MS/MS for phosphoproteome analysis to identify the phosphorylation sites and phosphoproteins. A total of 1509 phosphoproteins and 2839 phosphorylation sites were identified. Among them, 468 phosphoproteins containing 496 phosphorylation sites demonstrated significant changes at the phosphorylation level. Nine phosphorylation motifs were extracted from the 496 phosphorylation sites. Of the 60 unique differentially expressed proteins, 14 were also identified as phosphoproteins. Many proteins and phosphoproteins, as well as potential signal pathways associated with salt response and defense, were found, including three 14-3-3s (GF14A, GF14B, and 14-3-3A) for signal transduction and several ABA signal-associated proteins such as ABF2, TRAB1, and SAPK8. Finally, a schematic salt response and defense mechanism in B. distachyon was proposed.

The role of hyperosmotic stress in inflammation and disease

Hyperosmotic stress is an often overlooked process that potentially contributes to a number of human diseases. Whereas renal hyperosmolarity is a well-studied phenomenon, recent research provides evidence that many non-renal tissues routinely experience hyperosmotic stress that may contribute significantly to disease initiation and progression. Moreover, a growing body of evidence implicates hyperosmotic stress as a potent inflammatory stimulus by triggering proinflammatory cytokine release and inflammation. Under physiological conditions, the urine concentrating mechanism within the inner medullary region of the mammalian kidney exposes cells to high extracellular osmolarity. As such, renal cells have developed many adaptive strategies to compensate for increased osmolarity. Hyperosmotic stress is linked to many maladies, including acute and chronic, as well as local and systemic, inflammatory disorders. Hyperosmolarity triggers cell shrinkage, oxidative stress, protein carbonylation, mitochondrial depolarization, DNA damage, and cell cycle arrest, thus rendering cells susceptible to apoptosis. However, many adaptive mechanisms exist to counter the deleterious effects of hyperosmotic stress, including cytoskeletal rearrangement and up-regulation of antioxidant enzymes, transporters, and heat shock proteins. Osmolyte synthesis is also up-regulated and many of these compounds have been shown to reduce inflammation. The cytoprotective mechanisms and associated regulatory pathways that accompany the renal response to hyperosmolarity are found in many non-renal tissues, suggesting cells are commonly confronted with hyperosmotic conditions. Osmoadaptation allows cells to survive and function under potentially cytotoxic conditions. This review covers the pathological consequences of hyperosmotic stress in relation to disease and emphasizes the importance of considering hyperosmolarity in inflammation and disease progression.

Dissecting the molecular damage to stallion spermatozoa: the way to improve current cryopreservation protocols?

We review recent developments in the technology of freezing stallion sperm, paying special attention to the molecular lesions that spermatozoa suffer during freezing and thawing, such as osmotic stress, oxidative damage, and apoptotic changes. We also discuss the applicability of colloidal centrifugation in stallion sperm cryobiology. Increased knowledge about the molecular injuries that occur during cryopreservation may lead to improved protective techniques and thus to further improvements in fertility in the current decade.