Redox activity associated with the maturation and capacitation of mammalian spermatozoa

Insight into oxidative stress in varicocele-associated male infertility: part 1

Varicocele is recognized as the leading cause of male infertility because it can impair spermatogenesis through several distinct pathophysiological mechanisms. Current evidence supports oxidative stress as a key element in the pathophysiology of varicocele-related infertility, although these mechanisms have not yet been fully described. Measurement of the reactive oxygen species and other markers of oxidative stress, including the levels of the antioxidant enzymes catalase and superoxide dismutase, can provide valuable information on the extent of oxidative stress and might guide therapeutic management strategies. The testis can respond to varicocele-associated cell stressors, such as heat stress, ischaemia or production of vasodilators (for example, nitric oxide) at the expense of the generation of excessive reactive oxygen species. These responses have their own implications in exacerbating the underlying oxidative stress and on the subsequent infertility.

Metabolic substrates exhibit differential effects on functional parameters of mouse sperm capacitation

Although substantial evidence exists that sperm ATP production via glycolysis is required for mammalian sperm function and male fertility, conflicting reports involving multiple species have appeared regarding the ability of individual glycolytic or mitochondrial substrates to support the physiological changes that occur during capacitation. Several mouse models with defects in the signaling pathways required for capacitation exhibit reductions in sperm ATP levels, suggesting regulatory interactions between sperm metabolism and signal transduction cascades. To better understand these interactions, we conducted quantitative studies of mouse sperm throughout a 2-h in vitro capacitation period and compared the effects of single substrates assayed under identical conditions. Multiple glycolytic and nonglycolytic substrates maintained sperm ATP levels and comparable percentages of motility, but only glucose and mannose supported hyperactivation. These monosaccharides and fructose supported the full pattern of tyrosine phosphorylation, whereas nonglycolytic substrates supported at least partial tyrosine phosphorylation. Inhibition of glycolysis impaired motility in the presence of glucose, fructose, or pyruvate but not in the presence of hydroxybutyrate. Addition of an uncoupler of oxidative phosphorylation reduced motility with pyruvate or hydroxybutyrate as substrates but unexpectedly stimulated hyperactivation with fructose. Investigating differences between glucose and fructose in more detail, we demonstrated that hyperactivation results from the active metabolism of glucose. Differences between glucose and fructose appeared to be downstream of changes in intracellular pH, which rose to comparable levels during incubation with either substrate. Sperm redox pathways were differentially affected, with higher levels of associated metabolites and reactive oxygen species generated during incubations with fructose than during incubations with glucose.

Soy lecithin interferes with mitochondrial function in frozen-thawed ram spermatozoa

Egg yolk and milk are the 2 major membrane cryoprotectants commonly used in freezing media for the long-term preservation of semen (alone or in combination with others). However, in recent years, there have been increasing arguments against the use of egg yolk or milk because of the risk of introducing diseases through the use of cryopreserved semen. In this study, we analyzed the protective effect of lecithin as an alternative to egg yolk for the cryopreservation of ram semen, using a range of functional markers for sperm viability, motility, apoptosis, and mitochondrial functionality analyses (mitochondrial inner membrane surface [MIMS], mitochondrial inner membrane potential [MIMP], and cell membrane potential) as methods of assessment in samples diluted in 3 different media: Tris-citrate-glucose as control and 2 media supplemented with soy lecithin or egg yolk. The results showed that lecithin was able to effectively protect certain sperm quality characteristics against freezing-induced damage. However, lecithin induced loss of mitochondrial membrane potential or mitochondrial loss that was not reflected by modifications in sperm motility in fresh semen. MIMS and MIMP values decreased in thawed lecithin-treated samples, concomitant with a lower (P < .05) percentage of total and progressively motile cells, compared with those in egg yolk-containing samples. Further incubation of thawed samples revealed changes in motility and mitochondrial functionality that otherwise would not have been detected. These results indicated that lecithin may have affected the inner mitochondrial membrane in frozenthawed spermatozoa and confirmed that sublethal damages that seriously affect sperm functionality, not detected by classic sperm quality analyses, can be evidenced by changes in the inner mitochondrial membrane surface. These findings strengthen the relationship between mitochondrial membrane potential and motility and show that the mitochondrial alterations induced by the cryopreservation process could be specific targets for the improvement of semen cryopreservation protocols.

NOX5 in human spermatozoa: expression, function, and regulation

Physiological and pathological processes in spermatozoa involve the production of reactive oxygen species (ROS), but the identity of the ROS-producing enzyme system(s) remains a matter of speculation. We provide the first evidence that NOX5 NADPH oxidase is expressed and functions in human spermatozoa. Immunofluorescence microscopy detected NOX5 protein in both the flagella/neck region and the acrosome. Functionally, spermatozoa exposed to calcium ionophore, phorbol ester, or H(2)O(2) exhibited superoxide anion production, which was blocked by addition of superoxide dismutase, a Ca(2+) chelator, or inhibitors of either flavoprotein oxidases (diphenylene iododonium) or NOX enzymes (GKT136901). Consistent with our previous overexpression studies, we found that H(2)O(2)-induced superoxide production by primary sperm cells was mediated by the non-receptor tyrosine kinase c-Abl. Moreover, the H(V)1 proton channel, which was recently implicated in spermatozoa motility, was required for optimal superoxide production by spermatozoa. Immunoprecipitation experiments suggested an interaction among NOX5, c-Abl, and H(V)1. H(2)O(2) treatment increased the proportion of motile sperm in a NOX5-dependent manner. Statistical analyses showed a pH-dependent correlation between superoxide production and enhanced sperm motility. Collectively, our findings show that NOX5 is a major source of ROS in human spermatozoa and indicate a role for NOX5-dependent ROS generation in human spermatozoa motility.

Calcium antagonists modulate oxidative stress and acrosomal reaction in rat spermatozoa

INTRODUCTION

Calcium ions are vital in many biological processes and qualify as an almost ubiquitous intracellular second messenger. This indicates the multiplicity of the effects associated with drug actions aimed at interfering with calcium ions. To examine the cellular process involved in the induction of infertility in males by calcium antagonist (CA) even in the presence of normal semen parameters, we studied the effects of different CA namely; nifedipine, verapamil and diltiazem on oxidative balance and acrosome reaction in the sperm.

MATERIAL AND METHODS

For this purpose, lipid peroxidation, antioxidants such as superoxide dismutase, catalase and reduced glutathione, and acrosomal reaction were determined in sperm samples of rats.

RESULTS

Calcium antagonist causes significant oxidative stress in the epididymal sperm with increased malondialdehyde level and a concomitant decrease in antioxidant activities of catalase and superoxide dismutase. The percentage value of acrosomal-reacted sperm in the nifedipine, verapamil and diltiazem-treated rats were 41 ±2.45, 39 ±2.92 and 42 ±1.22 respectively, compared with the control group value of 86 ±2.92.

CONCLUSIONS

It appears CA oxidatively modify the sperm resulting in functional inhibition of acrosomal reaction. Suppression of the sperm acrosomal reaction is known to have serious adverse implications for fertilization.

Flow cytometry for the assessment of animal sperm integrity and functionality: state of the art

Flow cytometry is now a recognized methodology within animal spermatology, and has moved from being a research tool to become routine in the assessment of animal semen destined to breeding. The availability of 'bench-top' flow cytometers and of newer and versatile markers for cell structure and function had allowed the instrumentation to measure more sperm parameters, from viability to reactiveness when exposed to exogenous stimuli, and to increase our capabilities to sort spermatozoa for potential fertilizing capacity, or chromosomal sex. The present review summarizes the state of the art regarding flow cytometry applied to animal andrology, albeit keeping an open comparative intent. It critically evaluates the present and future capabilities of flow cytometry for the diagnostics of potential fertility and for the development of current reproductive technologies such as sperm freezing, sperm selection and sperm sorting. The flow cytometry methods will probably further revolutionize our understanding of the sperm physiology and their functionality, and will undoubtedly extend its application in isolating many uncharacterized features of spermatozoa. However, continuous follow-up of the methods is a necessity owing to technical developments and the complexity of mapping spermatozoa.

Redox regulation of fertilisation and the spermatogenic process

Oxidative stress is one of the major causes of male infertility; it damages spermatogenic cells, the spermatogenic process and sperm function. Recent advances in redox biology have revealed the signalling role of reactive oxygen species (ROS) that are generated by cells. While highly reactive oxidants, such as the hydroxyl radical, exert largely deleterious effects, hydrogen peroxide can feasibly serve as a signal mediator because it is moderately reactive and membrane permeable and because it can oxidize only limited numbers of functional groups of biological molecules. The amino acid side chain most sensitive to oxidation is cysteine sulphydryl, which is commonly involved in the catalysis of some enzymes. Although the reactivity of cysteine sulphhydryl is not very high in ordinary proteins, some phosphatases possess a highly reactive sulphydryl group at their catalytic centre and are thereby oxidatively inactivated by transiently elevated hydrogen peroxide levels after extracellular stimuli and under certain environmental conditions. Peroxiredoxins, in turn, show moderate hydrogen peroxide-reducing activity, and their role in the modulation of ROS-mediated signal transduction in ordinary cells, mediated by protecting phosphatases from oxidative inactivation, has attracted much attention. Although knowledge of the signalling role of ROS in the male reproductive system is limited at present, its significance is becoming a focal issue. Here, we present a review of the emerging signalling role of hydrogen peroxide in testes.

Mass spectrometric detection of cholesterol oxidation in bovine sperm

We report on the presence and formation of cholesterol oxidation products (oxysterols) in bovine sperm. Although cholesterol is the most abundant molecule in the membrane of mammalian cells and is easily oxidized, this is the first report on cholesterol oxidation in sperm membranes as investigated by state-of-the-art liquid chromatographic and mass spectrometric methods. First, oxysterols are already present in fresh semen samples, showing that lipid peroxidation is part of normal sperm physiology. After chromatographic separation (by high-performance liquid chromatography), the detected oxysterol species were identified with atmospheric pressure chemical ionization mass spectrometry in multiple-reaction-monitoring mode that enabled detection in a broad and linear concentration range (0.05-100 pmol for each oxysterol species detected). Second, exposure of living sperm cells to oxidative stress does not result in the same level and composition of oxysterol species compared with oxidative stress imposed on reconstituted vesicles from protein-free sperm lipid extracts. This suggests that living sperm cells protect themselves against elevated oxysterol formation. Third, sperm capacitation induces the formation of oxysterols, and these formed oxysterols are almost completely depleted from the sperm surface by albumin. Fourth, and most importantly, capacitation after freezing/thawing of sperm fails to induce both the formation of oxysterols and the subsequent albumin-dependent depletion of oxysterols from the sperm surface. The possible physiological relevance of capacitation-dependent oxysterol formation and depletion at the sperm surface as well as the omission of this after freezing/thawing semen is discussed.

Selenium-vitamin E supplementation in infertile men: effects on semen parameters and pregnancy rate

Objectives

Infertility is an important medical and social problem that has an impact on well-being. A significant development in the last 10 years in the study of human infertility has been the discovery that oxidative sperm DNA damage has a critical role in the etiology of poor semen quality and male infertility. Selenium (Se) is an essential element for normal testicular development, spermatogenesis, and spermatozoa motility and function. The predominant biochemical action of Se in both humans and animals is to serve as an antioxidant via the Se-dependent enzyme glutathione peroxidase and thus protect cellular membranes and organelles from peroxidative damage. We explored the efficacy of Se in combination with vitamin E for improving semen parameters and pregnancy rates in infertile men.

Materials and methods

The study included 690 infertile men with idiopathic asthenoteratospermia who received supplemental daily Se (200 μg) in combination with vitamin E (400 units) for at least 100 days. The mean age of cases was 28.5 years (range 20–45), and the median age was 30 years. These cases had presented with male factor infertility (primary or secondary) for at least 1 year. The longest and shortest duration of infertility was 10 years and 1 year, respectively. The median time of diagnosis of infertility was 1 year with a mean of 2.5 years.

Results

We observed 52.6% (362 cases) total improvement in sperm motility, morphology, or both, and 10.8% (75 cases) spontaneous pregnancy in comparison with no treatment (95% confidence interval: 3.08 to 5.52). No response to treatment occurred in 253 cases (36.6%) after 14 weeks of combination therapy. Mean difference between semen analyses of cases before and after treatment was 4.3% with a standard deviation of 4.29. On the basis of paired t-test results, combination therapy with oral Se and vitamin E was effective for treatment of asthenospermia or asthenoteratospermia or induction of spontaneous pregnancy (P ≤ 0.001).

Conclusions

Supplemental Se and vitamin E may improve semen quality and have beneficial and protective effects, especially on sperm motility. We advocate their use for the treatment of idiopathic male infertility diagnosed with asthenoteratospermia or asthenospermia in semen analysis.

Nitric oxide stimulates human sperm motility via activation of the cyclic GMP/protein kinase G signaling pathway

Nitric oxide (NO), a modulator of several physiological processes, is involved in different human sperm functions. We have investigated whether NO may stimulate the motility of human spermatozoa via activation of the soluble guanylate cyclase (sGC)/cGMP pathway. Sperm samples obtained by masturbation from 70 normozoospermic patients were processed by the swim-up technique. The kinetic parameters of the motile sperm-rich fractions were assessed by computer-assisted sperm analysis. After a 30–90 min incubation, the NO donor S-nitrosoglutathione (GSNO) exerted a significant enhancing effect on progressive motility (77, 78, and 78% vs 66, 65, and 62% of the control at the corresponding time), straight linear velocity (44, 49, and 48 μm/s vs 34, 35, and 35.5 μm/s), curvilinear velocity (81, 83, and 84 μm/s vs 68 μm/s), and average path velocity (52, 57, and 54 μm/s vs 40, 42, and 42 μm/s) at 5 μM but not at lower concentrations, and in parallel increased the synthesis of cGMP. A similar effect was obtained with the NO donor spermine NONOate after 30 and 60 min. The GSNO-induced effects on sperm motility were abolished by 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (a specific sGC inhibitor) and mimicked by 8-bromo-cGMP (8-Br-cGMP; a cell-permeating cGMP analog); the treatment with Rp-8-Br-cGMPS (an inhibitor of cGMP-dependent protein kinases) prevented both the GSNO- and the 8-Br-cGMP-induced responses. On the contrary, we did not observe any effect of the cGMP/PRKG1 (PKG) pathway modulators on the onset of hyperactivated sperm motility. Our results suggest that NO stimulates human sperm motility via the activation of sGC, the subsequent synthesis of cGMP, and the activation of cGMP-dependent protein kinases.

Glucose transporters in gametes and preimplantation embryos

The oocyte, sperm and preimplantation embryo have unique metabolic needs that must be met to ensure successful pregnancy. The family of facilitative glucose transporters (GLUTs) plays a major role in providing metabolic substrates to these tissues. The variety of GLUTs expressed in these tissues allows for flexibility to adapt to a changing environment. Alterations in glucose transport and metabolism at the earliest stages of development can impact fetal development. Research into the mechanisms of normal glucose transport into cells is critical for improving outcomes in the increasingly common diabetic maternal environment. Here, we review the current understanding in the distribution and role of glucose transporters in gametes and preimplantation embryos under normal and diabetic conditions.

Role of antioxidants in the treatment of male infertility

Male infertility continues to be a clinical challenge of increasing significance. While male factors such as decreased semen quality are responsible for 25% of all infertility issues, the etiology of suboptimal semen quality is poorly understood. Many physiological, environmental, and genetic factors have been implicated, including oxidative stress. Oxidative stress is induced by reactive oxygen species (ROS), or free radicals, and although ROS are required for critical aspects of sperm function, excessive levels of ROS can negatively impact sperm quality. The origin of ROS generation, and the etiologies of increased ROS in men with suboptimal sperm quality have only recently been elucidated, offering multiple targets for potential therapy. Here, we present a critical review of the literature describing the role of oxidative stress on decreased sperm function, as well as the role of antioxidants in the treatment of male factor infertility.

Reactive oxygen species generators affect quality parameters and apoptosis markers differently in red deer spermatozoa

Fe2+/ascorbate, hydrogen peroxide (H2O2), and hypoxanthine/xanthine oxidase (XOD) are commonly used for inducing oxidative stress on spermatozoa. A comparative study of these agents was carried out on thawed spermatozoa from red deer. First, we tested a high, medium, and low concentration of each agent: 100, 10, and 1 μM Fe2+ (hydroxyl radical generator); 1 mM, 100, and 10 μM H2O2; and 100, 10, and 1 mU/ml XOD (superoxide and H2O2 generator), incubated at 37 °C for 180 min. Intracellular reactive oxygen species (ROS; H2DCFDA) increased with dose and time similarly for the three systems at each concentration level. Motility and mitochondrial membrane potential (Δψm) were considerably decreased by H2O2 (1 mM and 100 μM) and XOD (100 and 10 mU/ml). Only 1 mM H2O2 reduced viability. The antioxidant Trolox (10 μM) reduced intracellular ROS, but could not prevent the H2O2 or XOD effects. In a second experiment, YO-PRO-1 and M540 were used as apoptotic and membrane stability markers respectively. Only H2O2 increased the proportion of apoptotic and membrane-destabilized spermatozoa. Catalase added to XOD prevented Δψm loss, confirming that H2O2 was the causative agent, not superoxide. In a third experiment, caspase activation was tested using the (FAM-VAD-FMK) probe. Viable spermatozoa with activated caspases could be detected in untreated samples, and only H2O2 increased their proportion after 60 min. There were important differences between ROS generators, H2O2 being the most cytotoxic. Although H2O2 and XOD caused Δψm dissipation, this was not reflected in increasing apoptotic markers.

Mitochondria in mammalian sperm physiology and pathology: a review

While, for a long time, the role of mitochondria in sperm physiology and pathology has been largely ignored, recent research points out the mitochondria as a major organelle with key roles in sperm function both under physiological and biotechnological conditions. This paper briefly reviews these novel findings regarding the role of mitochondria in sperm, paying special attention to the most practical, readily applicable, aspects of the topic such as their role as a major source of the sublethal damage that sperm experiments after cryopreservation.

Effect of antioxidant supplementation in semen extenders on semen quality and reactive oxygen species of chilled canine spermatozoa

The objective of this study was to evaluate quality of chilled dog semen processed with extenders containing various antioxidants. Single ejaculates from five dogs were always pooled and evaluated for concentration, sperm motility, progressive motility (RSF-movement), viability, acrosomal integrity and by the hypo-osmotic swelling (HOS)-test. Also, superoxide (O(2)(-)) production, hydroxyl radicals (OH) and total reactive oxygen species (tROS) were determined. Pooled semen was divided in seven aliquots (for control and test conditions), which were diluted to a final concentration of 67x10(6)spermatozoa/ml with TRIS-glucose-egg yolk extender with or without the following supplements: control (without antioxidants), vitamin C (0.5mM), N-acetyl-l-cysteine (NAC; 0.5mM), taurine (0.2mM), catalase (100u/ml), vitamin E (0.1mM) and 5-(4-dimethylamino-phenyl)-2-phenyl-penta-2,4-dienoic acid (B16; 0.1mM). The semen aliquots were chilled and preserved at 4 degrees C. Portions of chilled semen were removed at 24 and 72h, and semen quality was evaluated after rewarming. At 24h the mean (+/-S.E.M.) sperm motility was higher (p<0.001) when vitamin E, taurine and B16 were added in the extender, whereas more spermatozoa with RSF-movement were observed (p<0.001) in the vitamin E, catalase, B16 and taurine groups. Sperm viability was higher (p=0.040) in B16 and vitamin E groups and the percentage of swollen spermatozoa was higher (p=0.002) only in the B16 group. Acrosomal integrity and OH were not significantly influenced by any of the antioxidants tested. Superoxide production was significantly lower when vitamin C, B16 and vitamin E were added in semen extenders compared with the control (p=0.017). All antioxidant groups, except vitamin C and NAC, contained less tROS compared to the control group, but only the B16 group value differed significantly (p=0.05). At 72h sperm motility was higher (p<0.001) when vitamin E, catalase, B16, taurine and NAC were added in the extender. More spermatozoa with RSF-movement were observed (p<0.001) in the vitamin E, catalase, B16, taurine and NAC treatment groups. Sperm viability was higher (p=0.001) when vitamin E, B16, taurine and vitamin C were added in semen extenders. HOS-test percentages were higher (p=0.016) in the B16, vitamin E, catalase and NAC groups. Acrosomal integrity was not influenced in any case. Production of O(2)(-) was significantly higher using catalase compared to all the other groups (p=0.006), while OH was not significantly influenced by any of the antioxidants tested. The addition of vitamin E, catalase and B16 in semen extenders resulted in significantly lower tROS values compared with the controls (p<0.0005). The results suggest that vitamin E and B16 had the most pronounced effect in preserving semen quality of chilled dog spermatozoa.

Effect of antioxidant supplementation on semen quality and reactive oxygen species of frozen-thawed canine spermatozoa

The objective of this study was to evaluate post-thaw quality of frozen dog semen processed with diluents containing different antioxidants. Ejaculates were collected, pooled and evaluated for concentration, motility, rapid steady forward movement (RSF movement), viability, acrosomal integrity and by the hypo-osmotic swelling test. Also, superoxide production, hydroxyl radicals and total reactive oxygen species (tROS) were determined. The pool was divided in seven aliquots, for control and test conditions, which were processed for cryopreservation. The sperm pellets were diluted to a final concentration of 200x10(6)sperm/ml with TRIS-glucose-egg yolk extender containing one of the following supplements: vitamin C (1.5mM), NAC (N-acetyl-l-cysteine; 1.5mM), taurine (0.6mM), catalase (300U/ml), vitamin E (0.3mM) and B16 [5-(4-dimethylamino-phenyl)-2-phenyl-penta-2,4-dienoic acid; 0.3mM]. Post-thaw semen evaluation showed that mean (+/-S.E.M.) motility was increased (p<0.001) after addition of catalase (49.75+/-3.63 versus 39.00+/-2.90 in controls), whereas more spermatozoa with RSF movement were observed (p<0.001) after the catalase, NAC and vitamin E treatments (31.75+/-3.46, 28.00+/-3.27, 26.75+/-3.15, respectively, versus 17.00+/-2.26 in controls). Viability was increased (p<0.001) after addition of catalase, taurine, NAC and tocopherol (66.00+/-3.03, 61.90+/-2.48, 60.60+/-1.93 and 60.50+/-4.12, respectively, versus 51.70+/-2.81 in controls). The percentage of swollen spermatozoa was increased after addition of catalase and taurine (61.75+/-1.61 and 61.25+/-1.49, respectively, versus 55.65+/-1.64 in controls). Acrosomal integrity was not influenced in any case. B16 addition had adverse effects on all parameters evaluated. None of the reactive oxygen species were significantly reduced post-thaw in antioxidant treated semen. The results suggest that catalase had the most pronounced effect in improving post-thaw quality of canine spermatozoa.

Proteomic changes in mammalian spermatozoa during epididymal maturation

Epididymal maturation is associated with the activation of a cAMP-induced tyrosine phosphorylation cascade, which is ultimately associated with the expression of capacitation-dependent sperm functions, such as hyperactivated movement and acrosomal exocytosis. As spermatozoa progress through the epididymis they first acquire the capacity to phosphorylate tyrosine on targets on the principal piece, followed by the midpiece. By the time these cells have reached the cauda epididymidis they can phosphorylate the entire tail from neck to endpiece. This particular pattern of phosphorylation is associated with the ontogeny of fully functional spermatozoa that are capable of fertilizing the oocyte. Proteomic analyses indicate that this change is associated with the phosphorylation of several mitochondrial proteins, creation of a mitochondrial membrane potential and activation of mitochondrial free radical generation. At least in rodent species, activation of sperm mitochondria appears to be a particularly important part of epididymal maturation.

Vitamin E Biochemistry and Function: A Case Study in Male Rabbit

Vitamin E supplementation has become a common procedure to promote growth and health and improve the qualitative characteristics of farm animals. It has been demonstrated to be an efficient strategy for improving their reproductive function. Germ cells are particularly vulnerable to oxidative damage and may thus require additional antioxidant protection. The aim of this review is to give a comprehensive overview of the current knowledge of the biochemistry and physiology of vitamin E; successively, the effect of this compound on the reproductive activity of rabbit buck is accurately described. In particular, this review examines studies on the effects of animal age, dose and duration of vitamin E supplementation, as well as the co-supplementation with selenium, vitamin C and polyunsaturated fatty acids. Several investigations have shown beneficial effects in bucks supplemented with vitamin E levels higher than the standard dietary requirement (50 mg/kg) particularly when the semen is stored. However, the exact dietary intake of vitamin E should be decided according to specific tissue needs for the individual vitamin E forms and the specific saturation markers.

Reactive oxygen species as an independent marker of male factor infertility

OBJECTIVE

To determine the abnormal patterns of reactive oxygen species (ROS) production in male factor infertility (MFI) patients and to define the ROS reference values in such patients.

DESIGN

A retrospective study.

SETTING

Male infertility clinic at a tertiary healthcare center.

PATIENT(S)

We examined 132 MFI patients (all normal sperm parameters, n = 24, and all abnormal sperm parameters, n = 38) and 34 healthy donors.

INTERVENTION(S)

Routine semen analysis, measurement of ROS.

MAIN OUTCOME MEASURE(S)

Sperm parameters, ROS levels (10(4) cpm/20 x 10(6) sperm).

RESULT(S)

Normal, healthy donors had significantly higher (P<.0001) sperm concentration, motility, and morphology compared with all MFI patients. Univariate analysis indicated a significant association between MFI and log (ROS + 1) (odds ratio [OR] = 3.84), besides sperm parameters and age. A multivariate model using logistic regression analysis also indicated an independent association of log ROS with MFI (OR = 4.25). The ROS cutoff values of 1.2-1.4 had a sensitivity of 0.70-0.78 with a corresponding specificity of 0.82. However, at a cutoff point of 1.2, the OR was 68.6, which increased with an increase in the cutoff.

CONCLUSION(S)

High ROS is an independent marker of MFI, irrespective of whether these patients have normal or abnormal semen parameters. We suggest the inclusion of ROS measurement as part of idiopathic infertility evaluation. Treatment with antioxidants may be beneficial in such patients.

Antimicrobial drug ornidazole inhibits hamster sperm capacitation, in vitro

To be fertilization competent, spermatozoa undergo a series of changes in the female reproductive tract collectively referred to as capacitation. In an attempt to understand, if ornidazole, a known anti-fertility drug, adversely affects sperm functions by targeting capacitation, we designed experiments to study the influence of this drug on hyperactivation (HA), capacitation-associated protein tyrosine phosphorylation (pY) and the acrosome reaction (AR). Addition of ornidazole at 0 h, inhibited the onset of HA and total pY in a dose dependent manner. However, when ornidazole was added at 3.5h, severe effects were still seen on HA and pY of high molecular weight proteins but, pY of lower M(r) proteins (50-56 kDa) was affected only marginally. Further, lower doses of ornidazole (5 and 10 mM) had greater inhibitory effect when added at 0 h, while addition of ornidazole at 3.5 h required higher doses of ornidazole (25 mM) to cause significant inhibition of acrosome reaction. Collectively, through in vitro studies, we demonstrate that ornidazole affects the onset and progression of hamster sperm hyperactivation, capacitation associated protein tyrosine phosphorylation and acrosome reaction, and the severity depends on the dose (5, 10 or 25 mM) and the time of addition (0 or 3.5 h) of the drug to the spermatozoa.

Redox-sensitive target detection in gibberellic acid-induced barley aleurone layer

Reactive oxygen species (ROS) are involved in redox regulation by their capacity to reversibly oxidize cysteine residues. This regulation is used by cells to modulate and integrate different responses to extracellular stimuli. In the barley (Hordeum vulgare L.) aleurone layer, gibberellic acid (GA(3)) is perceived at the plasma membrane and induces the synthesis and secretion of alpha-amylase. All aleurone membrane systems participate in the elaboration of this response. During these events, ROS are generated as a by-product from intense lipid metabolism. Therefore, we hypothesized that redox regulation may be operating in the GA(3)-induced response. To test this hypothesis, we measured if GA(3) treatment induced changes in the redox state of aleurone membrane-associated proteins. Membrane proteins with sulfhydryl and disulfide groups were isolated from reduced and in situ NEM-alkylated microsomal fractions, respectively. Each fraction was enriched by thiol-affinity chromatography and separated by two-dimensional electrophoresis. The in vivo redox state of each membrane protein present in GA(3)-treated and -untreated tissue was determined. Results showed that GA(3) induced the reduced state in 17 constitutive proteins and the oxidized state in another 5. These data indicate that redox changes occur in membrane proteins after GA(3) signaling in the aleurone layer.

Cytosolic calcium levels in spermatozoa are modulated differently in healthy subjects and patients with varicocele

OBJECTIVE

To study parameters connected to fertility in the semen of patients with varicocele.

DESIGN

We examine the ability of spermatozoa obtained from patients with varicocele to respond with an increase of cytosolic Ca2+ ([Ca2+]i) to some stimuli that are connected with spermatozoa activation.

SETTING

An academic research environment.

PATIENT(S)

Ten healthy volunteer donors and 10 patients affected by II or III grade left varicocele.

INTERVENTION(S)

Spermatozoa and prostasomes (vesicles of prostatic origin obtained from semen) were prepared according to standard procedures. Spermatozoa were stimulated with 1 microM P. The [Ca2+]i was evaluated with the FURA II method.

MAIN OUTCOME MEASURE(S)

The level of [Ca2+]i.

RESULT(S)

In resting cells, the level of [Ca2+]i was 120 +/-15 nmol/L (10 determinations). This value increases by > or =100 nmol/L upon stimulation with P. No difference was observed between spermatozoa obtained from healthy donors or from patients with varicocele. S-nitrosocysteine, a nitric oxide donor, and the fusion between spermatozoa and prostasomes increased the effect of P on [Ca2+]i in control spermatozoa but not in spermatozoa obtained from patients with varicocele.

CONCLUSION(S)

Different responsiveness of varicocele patients' spermatozoa to S-nitrosocysteine and/or to fusion with prostasomes may be among the possible causes of reduced fertility.

Reactive oxygen species in spermatozoa: methods for monitoring and significance for the origins of genetic disease and infertility

Human spermatozoa generate low levels of reactive oxygen species in order to stimulate key events, such as tyrosine phosphorylation, associated with sperm capacitation. However, if the generation of these potentially pernicious oxygen metabolites becomes elevated for any reason, spermatozoa possess a limited capacity to protect themselves from oxidative stress. As a consequence, exposure of human spermatozoa to intrinsically- or extrinsically- generated reactive oxygen intermediates can result in a state of oxidative stress characterized by peroxidative damage to the sperm plasma membrane and DNA damage to the mitochondrial and nuclear genomes. Oxidative stress in the male germ line is associated with poor fertilization rates, impaired embryonic development, high levels of abortion and increased morbidity in the offspring, including childhood cancer. In this review, we consider the possible origins of oxidative damage to human spermatozoa and reflect on the important contribution such stress might make to the origins of genetic disease in our species.

Identification of cytochrome-b5 reductase as the enzyme responsible for NADH-dependent lucigenin chemiluminescence in human spermatozoa

Lucigenin-dependent chemiluminescence together with 2-[4-iodophenyl]-3-[4-nitrophenyl]-5-[2,4-disulfophenyl]-2H tetrazolium monosodium salt (WST-1) reduction can be detected following addition of NADH to many cell types, including human sperm suspensions. Although many reports suggest that such a phenomenon is due to reactive oxygen species production, other oxygen detecting metabolite probes, such as MCLA and luminol, do not produce a chemiluminescent signal in this model system. The enzyme responsible for NADH-dependent lucigenin chemiluminescence was purified and identified as cytochrome-b5 reductase. In support of this concept, COS-7 cells overexpressing cytochrome-b5 reductase displayed at least a 3-fold increase in the previously mentioned activity compared with mock-transfected cells. Fractions containing cytochrome-b5 reductase were capable of inducing both lucigenin-dependent chemiluminescence and WST-1 reduction. Oxygen radicals clearly did not mediate the cytochrome b5-mediated activation of these probes in vitro since neither luminol nor MCLA gave a chemiluminescence response in the presence of the enzyme and the cofactor NADH. These results emphasize the importance of the direct NADH-dependent reduction of these putative superoxide-sensitive probes by cytochrome-b5 reductase even though this enzyme does not, on its own accord, produce reactive oxygen species.

Regulation of sperm function by reactive oxygen species

Sperm capacitation can be increased by the addition of reactive oxygen species (ROS) and decreased by antioxidants. Broadly consistent results have been achieved with a wide variety of methods and across different species. Exposure to ROS increases protein tyrosine phosphorylation consequent on an increase in cAMP and activation of tyrosine kinase and inhibition of tyrosine phosphatase. The measurement of ROS production by sperm is complicated by contamination of suspensions by leukocytes, laying many studies open to doubt. In human sperm the observation that extracellular NADPH could support superoxide production detected with the chemiluminescent probe lucigenin and had physiological effects similar to hydrogen peroxide led to the suggestion that they contained NADPH oxidase activity to generate ROS to support capacitation. However, the realization that lucigenin can signal superoxide artefactually, combined with failure to detect superoxide production using spin trapping techniques or to detect NADPH oxidase components in mature sperm, and confirmation of old reports that NADPH solution contains substantial amounts of hydrogen peroxide due to autoxidation, have undermined this hypothesis. Although the presence of significant NADPH oxidase activity in mature human sperm now seems less likely, other observations continue to suggest that they can make ROS in some way. There is stronger evidence that animal sperm can make ROS although these may be mainly of mitochondrial origin.