Reactive oxygen species generation and human spermatozoa: the balance of benefit and risk

HIV: reactive oxygen species, enveloped viruses and hyperbaric oxygen

This paper demonstrates that there are many examples in the literature of contradictory data concerning reactive oxygen intermediates (ROIs), responsible for producing cellular oxidative stress (OS), and their enhancement or diminution of viral replication. Nevertheless, ROIs repeatedly have been shown to be virucidal against enveloped-viruses, like the human immunodeficiency virus (HIV). Hyperbaric oxygen therapy (HBOT) increases the production of ROIs throughout the body, leaving no safe harbor for the virus to hide outside the genome. This technique already has been tried on acquired immune deficiency syndrome (AIDS) patients, with exciting results. Historically, the biggest setback to demonstrating HBO's antiviral effects has been the investigator's folly of studying non-enveloped viruses or failing to initiate ROI production. ROIs specifically attack areas of unsaturation occurring in the polyunsaturated fatty acids of cell membranes and viral envelopes. Moreover, it consistently has been shown that a peroxidized viral envelope breaches, and a breached viral envelope causes viral disintegration.

Smoking is associated with the retention of cytoplasm by human spermatozoa

OBJECTIVES

To determine whether cigarette smoking is associated with the abnormal retention of residual sperm cytoplasm in infertile men.

METHODS

Semen samples were obtained from 87 consecutive non-azoospermic men with idiopathic infertility (18 smokers and 69 nonsmokers) and from 20 men presenting for vasectomy (fertile controls). Standard semen parameters and the percentage of spermatozoa with residual cytoplasm (on Papanicolaou smears) were recorded.

RESULTS

Subject age, semen volume, and sperm density, motility, and morphology were not significantly different between the two groups of infertile men. However, a significant difference was found in the mean +/- SEM percentages of sperm with cytoplasm droplets between smokers and nonsmokers (12.9% +/- 1.7% and 8.1% +/- 0.9%, respectively; P < 0.001).

CONCLUSIONS

Our data suggest that cigarette smoking is associated with retention of sperm cytoplasmic droplets in infertile men, a morphologic characteristic associated with impaired sperm function.

Varicocele is associated with abnormal retention of cytoplasmic droplets by human spermatozoa

OBJECTIVE

To determine whether varicocele is associated with retention of sperm cytoplasmic droplets in infertile men.

DESIGN

Retrospective study.

SETTING

University infertility clinic.

PATIENT(S)

Nonazoospermic men with idiopathic (n = 69) and varicocele-associated infertility (n = 73), and 20 fertile controls presenting for vasectomy.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURES(S)

Standard semen parameters and percentage of spermatozoa with cytoplasmic droplets on Papanicolaou smears.

RESULT(S)

No statistically significant differences were found between the fertile and infertile groups with respect to semen volume. Fertile controls had significantly greater mean percent sperm motility and normal morphology than infertile men. The mean percentage of sperm with residual cytoplasm was statistically significantly different in all three groups. Infertile men with varicocele had the highest percentage of sperm with cytoplasmic droplets, the next highest level being in men with idiopathic infertility and the lowest level in fertile controls (11.7 +/- 1.0, 8.1 +/- 0.9 and 3.2 +/- 0.4%, respectively, P<.0001).

CONCLUSION(S)

Our data show that idiopathic and even moreso, varicocele-related male infertility are conditions associated with impaired disposal of residual sperm cytoplasm by the testis and/or epididymis. These data provide a possible mechanism for the observed semen abnormalities and reduced fertility potential associated with varicocele and idiopathic male infertility.

Tyrosine as important contributor to the antioxidant capacity of seminal plasma

A novel post-addition method, based on the trapping of ABTS-radicals, is applied for studying the total antioxidant capacity of seminal plasma. A remarkable profile is observed, in which seminal plasma quenches radicals in a continuous, relatively slow fashion. Five putative antioxidants present in seminal plasma were studied using the same assay. Some of the compounds such as ascorbic acid, alpha-tocopherol and uric acid exert immediate, fast radical trapping, whereas hypotaurine and tyrosine give rise to the same slow radical trapping curve as seminal plasma. Due to this slow, continuous radical trapping, quantification of the total antioxidant capacity (expressed as trolox equivalent antioxidant capacity, TEAC) strongly depends on the chosen time point after onset of radical trapping. When determined during the slow antioxidant trapping phase, tyrosine has a powerful antioxidant capacity, which in combination with its relatively high plasma concentration makes it an important contributor to the total antioxidant capacity of seminal plasma.

Antioxidant activity in the semen of fertile and infertile men

OBJECTIVES

To evaluate catalase- and superoxide dismutase (SOD)-like activities in the seminal plasma of fertile and infertile men.

METHODS

Semen samples were obtained from consecutive men presenting for vasectomy (n = 12) and infertility evaluation (n = 105) at our institution. Catalase-like activity was measured by the decrease in hydrogen peroxide after incubation with seminal plasma. SOD-like activity was measured as the inhibition of nitroblue tetrazolium reduction due to superoxide anion generation by xanthine plus xanthine oxidase.

RESULTS

Mean seminal catalase-like activity (+/-SEM) in fertile men was not significantly different from that of infertile men (369 +/- 49 versus 326 +/- 17 U/mL, respectively). Mean SOD-like activity in the semen of infertile men was significantly greater than in the semen of fertile controls (46.7 +/- 1.5 versus 37.0 +/- 2.8 U/mL, respectively, P <0.05).

CONCLUSIONS

Our data show that infertile men do not have deficient seminal plasma SOD- and/or catalase-like activity (two key antioxidants). These findings suggest that the high semen ROS levels in some infertile men are likely due to excessive generation of ROS rather than deficient ROS scavenging activity in semen.

Seminal plasma reduces exogenous oxidative damage to human sperm, determined by the measurement of DNA strand breaks and lipid peroxidation

Exposure of spermatozoa to reactive oxygen species (ROS) has been associated with cellular injury, that includes DNA damage and lipid peroxidation. In addition, sperm preparation techniques such as centrifugation, commonly used prior to in vitro fertilization and scientific studies, are associated with the generation of ROS and an increase in the level of DNA damage. The preservation, therefore, of sperm in vitro that might decrease the potential for oxidative DNA damage to arise and allow for an improvement in semen quality used for artificial insemination, is of importance. Seminal plasma is a rich source of antioxidants, which, potentially, safeguards sperm from oxidative attack during storage and once ejaculated. We have investigated the protection of human spermatozoa from ROS afforded by seminal plasma. Sperm were exposed to exogenous ROS by incubating the cells with hydrogen peroxide in the presence of ferrous sulfate and ADP. Aliquots of seminal plasma were added to the incubation mixture in differing amounts, and the generation of DNA strand breaks and thiobarbituric acid reactive species (TBARS), indicative of lipid peroxidation, determined. Incubation of sperm with exogenous ROS resulted in a significant generation of DNA strand breaks and lipid peroxidation compared to basal levels of damage (P<0.05). Addition of seminal plasma to the incubation media produced a significant decrease in DNA strand breaks and TBARS (P<0. 05), when the amount of plasma added exceeded 60% v/v. The results indicate that spermatozoal oxidative damage induced by exogenous ROS, specifically DNA damage and lipid peroxidation, is reduced by the presence of seminal plasma.

The reactive oxygen species-total antioxidant capacity score is a new measure of oxidative stress to predict male infertility

The imbalance between reactive oxygen species (ROS) production and total antioxidant capacity (TAC) in seminal fluid indicates oxidative stress and is correlated with male infertility. A composite ROS-TAC score may be more strongly correlated with infertility than ROS or TAC alone. We measured ROS, TAC, and ROS-TAC scores in semen from 127 patients and 24 healthy controls. Of the patients, 56 had varicocele, eight had varicocele with prostatitis, 35 had vasectomy reversals, and 28 had idiopathic infertility. ROS levels were higher among infertile men, especially those with varicocele with prostatitis (mean +/- SE, 3.25 +/- 0.89) and vasectomy reversals (2.65 +/- 1.01). All infertile groups had significantly lower ROS-TAC scores than control. ROS-TAC score identified 80% of patients and was significantly better than ROS at identifying varicocele and idiopathic infertility. The 13 patients whose partners later achieved pregnancies had a mean ROS-TAC score of 47.7 +/- 13.2, similar to controls but significantly higher than the 39 patients who remained infertile (35.8 +/- 15.0; P < 0.01). ROS-TAC score is a novel measure of oxidative stress and is superior to ROS or TAC alone in discriminating between fertile and infertile men. Infertile men with male factor or idiopathic diagnoses had significantly lower ROS-TAC scores than controls, and men with male factor diagnoses that eventually were able to initiate a successful pregnancy had significantly higher ROS-TAC scores than those who failed.

Fertilizing ability of DNA-damaged spermatozoa

In order to investigate the fertilizing ability of DNA-damaged sperm, they were exposed to gamma radiation prior to insemination. The presence of DNA-strand breaks were detected by the TUNEL test. Fertilization rates of 64.3, 59.9, 58.5, and 61.1% were achieved when sperm were subjected to 5, 10, 50, and 100 GY, respectively. This rate was 53.2% in the control group with no significant difference (P > 0.01). The blastocyst development was decreased from 49.8% in the control group to 20.3, 7.8, 3.4, and 2.3% with sperm exposed to doses of 5, 10, 50, and 100 GY, respectively. Of the transferred blastocyst in the control group, 69.8% were implanted and 33.9% developed into live fetuses. These rates were 57.1 and 21. 4%, 20 and 0% when sperm were exposed to doses of 5 and 10 GY with a significant difference (P < 0.01). The present study clearly shows that DNA-damaged sperm (regardless of degree of damage) have the ability to fertilize the oocyte, but that embryonic development is very much related to the degree of DNA damage. However, the oocyte has the capacity to repair DNA damage of sperm when it is damaged less than 8%. Damage beyond this level will result in low rate of embryonic development and high early pregnancy loss. J. Exp. Zool. 284:696-704, 1999.

Antioxidant capacity of the epididymis

The human epididymis provides an optimal environment for the storage and maturation of spermatozoa. However, the ability of the epididymis to protect spermatozoa from oxidative attack whilst stored at this site, through the local actions of antioxidants, has not thus far been well studied. This study assessed the contribution of the epididymis to seminal plasma antioxidant activity, by comparing the semen of normozoospermic and vasectomized men. Total seminal plasma antioxidant activity was measured, as were concentrations of urate, ascorbate and thiols, antioxidants that are abundant in human semen. Thiobarbituric acid reactive species (TBARS) were measured to indicate lipid peroxidation. Total antioxidant activity and thiol content were significantly lower (P < 0.05) in the plasma from vasectomized men compared with that of normozoospermic donors. Ascorbate and urate were found at similar concentrations in the plasma of both groups. The concentration of TBARS was significantly higher (P < 0.001) in the semen from vasectomized individuals compared with the normozoospermic group. The results indicate that the epididymis contributes to the antioxidant capacity of seminal plasma and possesses region-specific antioxidant activity, which may potentially protect spermatozoa from oxidative attack during storage at this site.

Potential adverse effect of semen processing on human sperm deoxyribonucleic acid integrity

OBJECTIVE

To examine the effect of standard Percoll density-gradient centrifugation on human sperm DNA denaturation.

DESIGN

Prospective, observational study.

SETTING

University-based infertility clinic.

PATIENT(S)

Twenty-five nonazoospermic men.

INTERVENTION(S)

Semen samples (n = 25) were obtained from consecutively seen nonazoospermic men presenting for infertility evaluation. Samples were processed by two-layer and four-layer Percoll density gradients. Sperm motility and sperm chromatin structure (evaluated by flow cytometry analysis of acridine orange-treated spermatozoa) were monitored before and after semen processing. Sperm chromatin integrity was expressed as the percentage of spermatozoa that demonstrated denatured DNA.

MAIN OUTCOME MEASURE(S)

Sperm motility and DNA integrity.

RESULT(S)

Mean sperm motility improved significantly after processing with two-layer and four-layer Percoll gradients compared with whole semen (54% and 57% motility versus 44% motility, respectively). In contrast, the percentage of sperm with denatured DNA increased after processing with two-layer and four-layer Percoll gradients compared with whole semen (34% and 32% versus 18%, respectively).

CONCLUSION(S)

Our data demonstrate that the improvement seen in sperm motility after Percoll processing is not associated with a similar improvement in sperm DNA integrity. These data suggest that we reexamine current sperm processing techniques to minimize sperm DNA damage and the potential transmission of genetic mutations in assisted reproductive cycles.

Effect of varicocelectomy on the abnormal retention of residual cytoplasm by human spermatozoa

Abnormal retention of cytoplasmic residues by human spermatozoa is associated with the generation of reactive oxygen species (ROS) in semen and defective sperm function. We have examined the effect of varicocelectomy on the retention of residual cytoplasm by human spermatozoa. Clinical reports of 43 men who underwent microsurgical varicocelectomy at our institution during a 1 year period beginning July 1996 were reviewed. Standard semen parameters (concentration, motility and morphology) and residual cytoplasm retention (monitored by Papanicolaou stain) were assessed before and 6 months after varicocelectomy. The percentage of spermatozoa with residual cytoplasm decreased significantly following varicocelectomy compared to pre-operatively (25.8 versus 18.1% respectively). The percentages of motile spermatozoa and normal forms increased significantly (P = 0.0003, P = 0.005 respectively) following varicocelectomy (22.6 versus 32.9% and 46.4 versus 54.4% respectively). Our data suggest that varicocelectomy can improve the disposal of residual sperm cytoplasm by the testis and/or epididymis in infertile men with varicocele. These data also suggest that varicocelectomy reduces the potential for ROS generation by human spermatozoa in these men.

Structural and functional characterization of seven spermicidal vanadium(IV) complexes: potentiation of activity by methyl substitution on the cyclopentadienyl rings

In a systematic effort to identify and develop effective vanadocene(IV) complexes as a new class of contraceptive agents, the effect of methyl substitution in the cyclopentadienyl rings of Cpx2VCl2 on their spermicidal activity has been examined. The spermicidal activities of compounds Cpx2VCl2 [Cpx = Me5Cp (Cp*) (1), Cp (3), MeCp (Cp') (5)], as well as two of their corresponding vanadium(V) oxidation products Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), were examined by computer-assisted sperm analysis (CASA). These analyses have established that penta-substitution of the Cp ring by electron-donating methyl groups augments the spermicidal activity 10-fold. The corresponding V(V) oxo compounds, Cp*V(O)Cl2 (2) and CpV(O)Cl2 (4), tested under identical conditions did not show as effective spermicidal activity even though these complexes have a pseudo-tetrahedral geometry similar to the active vanadocene(IV) dichlorides. Two pseudo-octahedral V(IV) complexes with tris-pyrazolyl borate as ligand, (HBpz3)V(O)Cl.DMF (6) and (HB(3,5-Me2pz)3)V(O)Cl.DMF (7), were also found to exhibit potent spermicidal activity. Although some vanadium(IV) complexes may immobilize sperm due to the generation of .OH radicals, the lack of spermicidal activity of VOSO4 which generates .OH radicals, and the potent spermicidal activity of [Cp2V(acac)][O3SCF3] (8), and [Cp2V(DeDtc)][O3SCF3] (9) which do not generate .OH radicals, indicate that .OH radical mediated reactions may not be essential for the spermicidal activity of vanadium(IV) complexes.

Relationship between human sperm lipid peroxidation, comprehensive quality parameters and IVF outcome

The membranes of human spermatozoa contain an extremely high concentration of polyunsaturated fatty acids and are therefore susceptible to lipid peroxidation damage. The aim of this study was to retrospectively determine the association between the lipid peroxidation levels of washed spermatozoa, as indicated by thiobarbituric-acid-reactive substance concentration, and: (a) semen quality evaluated by basic routine, biochemical, cytological and quantitative ultramorphological analyses; (b) IVF fertilization rate. Semen samples from 45 male partners of couples who had been referred for IVF treatment due to a female infertility factor were evaluated for quality as well as for thiobarbituric-acid-reactive substance concentrations. The latter were found to have a negative correlation with total sperm count, semen volume, zinc/fructose ratio, and the integrity of sperm acrosome and axonema. It was suggested that lipid peroxidation has a deleterious effect on the ultramorphological status of the sperm cells and, thereby, on the male fertilization potential. The content of the seminal fluid, about 30% of which is produced by the prostate, may protect spermatozoa from this destructive process. A negative correlation was also found between thiobarbituric-acid-reactive substance concentrations and IVF fertilization rate. When the patients were subdivided into fertilizing (fertilization rate > 0%) and nonfertilizing (fertilization rate = 0%) subgroups (n = 33 and n = 12, respectively), the former exhibited significantly lower thiobarbituric-acid-reactive substance concentrations than the latter. A new IVF fertilization index based on the lipid peroxidation level was established. This index had a predictive power of 93% (94% sensitivity and 92% specificity). The clinical value of this index should be further verified.

Spermicidal activity of oxovanadium(IV) complexes of 1, 10-phenanthroline, 2,2'-bipyridyl, 5'-bromo-2'-hydroxyacetophenone and derivatives in humans

We have recently reported that tetrahedral metallocene complexes containing vanadium(IV) (vanadocene) have potent spermicidal activity against human sperm. The spermicidal activity was dependent on vanadium(IV) as the central metal ion within the bis-cyclopentadienyl (Cp2)-metal complex, but the variation of diacido groups and/or replacement with bidentate ligands coordinated to the Cp2-vanadium(IV) moiety also significantly modulated the spermicidal potency. To assess the structure-activity relationship between vanadocenes and other coordination complexes of vanadium(IV), a set of 11 oxovanadium(IV) complexes with different geometrical configurations were synthesized and evaluated for spermicidal activity by computer-assisted sperm analysis. These complexes included mono and bis ancillary ligands, 1,10-phenanthroline (phen): [VO(phen), VO(phen)2, VO(Me2-phen), VO(Me2-phen)2, VO(Cl-phen), and VO(Cl-phen)2]; 2,2'-bipyridyl (bipy): [VO(bipy), VO(bipy)2, VO(Me2-bipy), and VO(Me2-bipy)2], linked via nitrogen atoms; and 5'-bromo-2'-hydroxyacetophenone (acph): [VO(Br,OH-acph)2], linked via oxygen donor atoms. All 11 oxovanadium(IV) complexes elicited concentration-dependent spermicidal activity at micromolar concentrations (EC50 values: 5.5-118 microM). The bis-phenanthroline complex of oxovanadium(IV), VO(Cl-phen)2, was the most active, and the mono bipyridyl complex, VO(bipy), was the least active; the order of efficacy was VO(Cl-phen)2 > VO(phen)2 > VO(Br,OH-acph)2 > VO(Me2-phen) > VO(bipy)2 > VO(phen) > VO(Cl-phen) > VO(Me2-phen)2 > VO(Me2-bipy)2 > VO(Me2-bipy) > VO(bipy). The neutral complex, VO(Br, OH-acph)2, induced rapid sperm immobilization (T1/2 = 38 sec). The sperm-immobilizing activity of mono- and bis-ligated oxovanadium(IV) complexes was irreversible, since the treated sperm underwent apoptosis, as determined by the flow cytometric quantitation of mitochondrial membrane potential, surface Annexin V binding assay, and in situ DNA nick-end labeling of sperm nuclei. The percentages of apoptotic sperm quantitated by the flow cytometric assay correlated well with the spermicidal potency of oxovanadium(IV) complexes. These results provide unprecedented evidence that the spermicidal and apoptosis-inducing activities of vanadium(IV) complexes are determined by the oxidation state of vanadium as well as their geometry. Because of its rapid and potent sperm-immobilizing activity, the bromo-hydroxyacetophenone complex, [VO(Br,OH-acph)2], may be useful as a contraceptive agent.

Relative impact of oxidative stress on the functional competence and genomic integrity of human spermatozoa

Reactive oxygen metabolites are known to disrupt sperm-oocyte fusion, sperm movement, and DNA integrity; however, the relative sensitivities of these elements to oxidative stress are unknown. In this study these factors were assessed in human spermatozoa exposed to increasing levels of oxidative stress achieved through the stimulation of endogenous oxidant generation with NADPH or direct exposure to hydrogen peroxide. At low levels of oxidative stress, DNA fragmentation was significantly reduced while the rates of sperm-oocyte fusion were significantly enhanced. As the level of oxidative stress increased, the spermatozoa exhibited significantly elevated levels of DNA damage (p < 0.001) and yet continued to express an enhanced capacity for sperm-oocyte fusion. At the highest levels of oxidative stress, extremely high rates of DNA fragmentation were observed but the spermatozoa exhibited a parallel loss in their capacities for movement and oocyte fusion. These studies emphasize how redox mechanisms can either enhance or disrupt the functional and genomic integrity of human spermatozoa depending on the intensity of the oxidative stimulus. Because these qualities are affected at different rates, spermatozoa exhibiting significant DNA damage are still capable of fertilizing the oocyte. These results may have long-term implications for the safety of assisted conception procedures in cases associated with oxidative stress.

Structural and biological characterization of a novel spermicidal vanadium(IV) complex: bis(pi-cyclopentadienyl)-N,N-diethyl dithiocarbamato vanadium(IV) tetrafluoro borate, [VCp2(DeDtc)](BF4)

In a systematic search for vanadocene complexes with sperm immobilizing activity as a new class of contraceptive agents, we identified V(eta 5-C5H5)2((C2H5)2 NCS2)(BF4) (=[VCp2(DeDtc)](BF4)) as the most potent and stable spermicidal compound. Here we report the detailed biologic and physicochemical characterization of this lead spermicidal compound by computer-assisted sperm analysis, electron paramagnetic resonance spectroscopy, electrochemistry, and X-ray crystallography. [VCp2(DeDtc)](BF4) crystallized in the monoclinic space group P2(1)/c, with unit cell dimensions a = 7.0877(4) A, b = 22.2881(14) A, c = 11.8021(7) A, beta = 94.107(1) degree, V = 1859.6(2) A3. The final structure of [VCp2(DeDtc)](BF4) had an R factor of 0.0581 for 3191 independent reflections. The two sulfur atoms of the dithiocarbamate and centroids of the cyclopentadienyl rings in this vanadocene complex with unique contraceptive potential occupy four tetrahedral--like coordination sites about the central metal atom.

Effects of vitamin E and/or C on reactive oxygen species-related lead toxicity in the rat sperm

This study was undertaken to investigate whether treatment with vitamin E (VE) and/or vitamin C (VC) protects rat sperm by inhibiting reactive oxygen species generation induced by lead (Pb) exposure. Male Sprague-Dawley rats were assigned to the following five groups: vitamin-unsupplemented; 150 mg VE/kg chow supplemented; 300 mg VE/kg chow supplemented; 500 mg VC/l drinking water supplemented and 150 mg VE/kg chow + 500 mg VC/l drinking water supplemented group. Rats in each group were divided into Pb-unexposed and Pb-exposed subgroups, received weekly intraperitoneal injection of 10 mg sodium acetate or 10 mg Pb acetate/kg for 6 weeks, respectively. The blood and sperm Pb levels were analyzed by graphite furnace atomic absorption spectrophotometer. Chemiluminescence was measured to evaluate the generation of sperm reactive oxygen species (ROS). Motility and sperm-oocyte penetration rate (SOPR) were measured. In Pb-unexposed rats, epididymal sperm counts, motility, ROS, and SOPR were not different in the five supplemented groups. Lead exposure might decrease the defense capacity of sperm to the oxidative stress and therefore elevate the ROS generation, reduce sperm motility, and reduce SOPR. Supplementation with VE and/or VC reduced ROS generation, prevented loss of motility and capacity of oocyte penetration in Pb-exposed rats. This study suggests that supplementation with VE and/or VC inhibits Pb-related ROS generation, protects spermatozoa from loss of motility and oocyte penetration capability.

Fatty acid composition, glutathione peroxidase and superoxide dismutase activity and total antioxidant activity of avian semen

This work demonstrates that spermatozoa from five avian species (chicken, turkey, guinea fowl, duck and goose) are all characterised by high proportions of polyunsaturated fatty acids, from 46 (turkey) to 55% (duck) of total. For each of the species, the most abundant fatty acids were arachidonic (20:4n-6) and docosatetraenoic (22:4n-6) acids, representing between 22 (turkey) and 40% (chicken) of total. Significant activities of the major isozymes of superoxide dismutase and glutathione peroxidase, which protect against the peroxidation associated with high degree of fatty acid unsaturation, were found in spermatozoa from all species. The seminal plasma also had these activities and showed additional mechanisms for protecting spermatozoa from peroxidation. In general terms, these lipid and enzyme proteins were similar between the five avian species and different from those reported for mammalian sperm.

Flavonoids modulate comet assay responses to food mutagens in human lymphocytes and sperm

The flavonoids, silymarin, myricetin, quercitin, kaempferol, rutin and kaempferol-3-rutinoside have been examined in combination with the food mutagens, 3-amino-1-methyl-5H-pyrido (4,3-b)indole (Trp-P-2) and 2-amino-3-methylimidazo-(4,5-f) quinoline (IQ), in the Comet assay in human lymphocytes from donor A and human sperm from donor B. These compounds alone have been shown to produce positive responses in the Comet assay, as have the food mutagens. However, in combination with the food mutagens, the flavonoids produced antigenotoxic effects since DNA damage was reduced in the Comet assay in lymphocytes and sperm. The assays were performed in the absence of metabolic activation, since when quercetin and kaempferol were examined in blood with metabolic activation, there was little or no difference in response to that obtained in its absence. In the blood, there was an exacerbation or synergy of response at the lowest doses of the flavonoids. In the sperm, with silymarin, myricetin and quercitin, antigenotoxic effects only were observed, but with kaempferol, in general, there were no protective effects. The food mutagen, 2-amino-1-methyl-6-phenylimadazo (4,5-b)pyridine (PhIP), was also examined in addition to Trp-P-2 and IQ in combination with silymarin and myricetin in donors A and C in human lymphocytes only. Similar exacerbation of effects were found at low doses of these flavonoids with antigenotoxic effects at high doses. This was confirmed in the Ames test. There were slightly different profiles in lymphocytes and sperm, but antigenotoxic effects were observed over a similar dose range. This would suggest that effects occur in somatic and germ cells on a one-to-one ratio. These results have implications for man in terms of risk assessment and in the modulation of isolated food constituents.

Evaluation of a spectrophotometric assay for the measurement of malondialdehyde and 4-hydroxyalkenals in human spermatozoa: relationships with semen quality and sperm function

A spectrophotometric assay for the measurement of malondialdehyde and 4 hydroxyalkenals (MA + 4HA) has been evaluated for the detection of sperm pathologies involving oxidative stress. In order to make sensitive measurements of MA + 4HA on human spermatozoa, the stimulation of a lipid peroxidation cascade with a ferrous ion promoter was found to be necessary. The optimal configuration for the promoter was defined (0.64 mM FeSO4 + 20 mM ascorbate for 2 h in Ca2+ and Mg2 free Hanks' balanced salt solution) and the assay used in a series of studies to elucidate the functional significance of MA + 4HA determinations. Such measurements were found to give highly significant correlations (p < 0.001) with the loss of motility induced by oxidative stress created either with a xanthine oxidase, free radical generating system or by prolonged incubation under aerobic conditions. Experiments involving the stimulation and suppression of lipid peroxide release from human sperm suspensions, in concert with a bioassay for cytotoxicity, confirmed the strength and causative nature of these associations. Measurements of lipid peroxidation potential in highly purified, leucocyte-free sperm suspensions revealed the presence of inverse correlations with the motility of the spermatozoa, their viability, their competence for sperm-oocyte fusion and, most significantly, the quality of sperm movement in the original semen samples. Similar negative correlations were observed between sperm function and phorbol ester-stimulated reactive oxygen species generation but, unlike the MA + 4HA determinations, these relationships were obfuscated by the presence of leucocytes. We conclude that the measurement of MA + 4HA in human spermatozoa provides important information on the underlying quality of spermatogenesis and should be of value in the clinical diagnosis of infertility involving oxidative stress and the selection of patients for antioxidant therapy.

Human sperm NADH and NADPH diaphorase cytochemistry: correlation with sperm motility

OBJECTIVES

We have examined the correlation between the retention of residual sperm cytoplasm and sperm motility in semen from men presenting for infertility evaluation.

METHODS

Semen samples (n = 12) were obtained from nonazoospermic men presenting for infertility evaluation at our institution. Samples were fractionated into high-, intermediate-, and low-density subpopulations by Percoll gradients in order to examine the correlation between the retention of residual sperm cytoplasm and sperm motility. Residual sperm cytoplasm retention was detected by cytochemical staining of sperm for nicotinamide adenine dinucleotide (NADH)- or nicotinamide adenine dinucleotide phosphate (NADPH)-dependent diaphorase activity.

RESULTS

The different sperm subpopulations (low, intermediate, and high density) had significantly different percentages of sperm with droplet retention (analysis of variance, P < 0.05). Using either NADH or NADPH diaphorase staining as a marker of the cytoplasmic space, a significant negative correlation was observed between the percentage of sperm with residual cytoplasmic droplets and the percentage of motile sperm (r = -0.58 and -0.61, respectively, P < 0.05).

CONCLUSIONS

Assessment of residual sperm cytoplasm retention is a simple diagnostic test. Although this test is of unproven value in the management of infertile men, this and other studies suggest that it may provide useful data on sperm function.

Sperm deoxyribonucleic acid fragmentation is increased in poor-quality semen samples and correlates with failed fertilization in intracytoplasmic sperm injection

OBJECTIVE

To determine the incidence of DNA fragmentation in human sperm used for intracytoplasmic sperm injection (ICSI) and to correlate any detected DNA damage with semen analysis parameters and fertilization rates in ICSI.

DESIGN

Descriptive and correlational clinical study.

SETTING

Tertiary care fertility clinic.

PATIENT(S)

A total of 150 semen samples was collected from men in the ICSI program.

INTERVENTION(S)

For each sample, sperm wash and swim-up were performed, and the percentage of recovered sperm with DNA fragmentation was determined with the use of terminal transferase-mediated deoxyuridine triphosphate-biotin end labeling.

MAIN OUTCOME MEASURE(S)

The percentage of sperm with DNA fragmentation was correlated with semen analysis parameters and ICSI fertilization rates.

RESULTS(S)

The mean (+/- SD) percentage of sperm with fragmented DNA was 14.5% +/- 1.5% and ranged from 0.5% to 75%. A significant negative association was found between the percentage of sperm with DNA fragmentation and the ICSI fertilization rate. We also observed that the motility and morphology of the ejaculated sperm were correlated negatively with the percentage of DNA fragmentation in the washed sperm recovered by the swim-up technique.

CONCLUSION(S)

Our results suggest that when poor-quality semen samples are used for ICSI, there is a greater likelihood that some sperm selected for injection, despite appearing normal, contain fragmented DNA. Whether sperm DNA damage may contribute to failure of pronuclear formation and embryo development in some apparently unfertilized ICSI oocytes is unclear.

Inhibition of sperm glutathione S-transferase leads to functional impairment due to membrane damage

The role of glutathione S-transferase (GST) in the defense mechanisms of sperm is not known. We report here interference with normal motility, acrosome reaction and fertilizing ability of the goat sperm as a consequence of inhibition of GST activity. That these functional impairments were due to membrane changes was evident from the alteration in the lipid peroxidation status of these cells after GST inhibitor treatment. Increased reactive oxygen species production by the cell which occurred when GST activity was suppressed may be the mediator for membrane damage. The data argue for a role of GST in maintaining sperm membrane status.

Relationship between sperm cell ubiquinone and seminal parameters in subjects with and without varicocele

In a previous paper it was demonstrated that Coenzyme Q10, a lipidic molecule with important antioxidant properties, is present at remarkable levels in human seminal fluid, and shows a direct correlation with seminal parameters (sperm count and motility). In patients with varicocele, on the contrary, correlation with sperm motility was lacking and a higher proportion of Coenzyme Q10 was found in seminal plasma. In the present study, the levels of Coenzyme Q10 in the cell pellet of spermatozoa, obtained after centrifugation of semen, were evaluated. In nonvaricocele subjects it was observed that a higher concentration of Coenzyme Q10 (expressed as ng of the molecule per million of cells) was present in the spermatozoa of oligospermic and asthenospermic patients (sperm count < 20 x 10(6) spermatozoa ml-1, sperm motility < 40%). This relationship was not observed in varicocele subjects, who also showed slightly lower intracellular absolute values of the conenzyme. Since Coenzyme Q10 is an antioxidant molecule involved in the defence of the cell from free radical damage, higher intracellular concentrations may represent a mechanism of protection of the spermatozoa. In varicocele patients, this mechanism could be deficient, leading to higher sensitivity to oxidative damage.

Advances in the evaluation and treatment of the infertile man

Numerous advances in technology have been made in the last several years in the diagnosis and treatment of the infertile man. Using case presentations, this article highlights these important new developments and reviews the basics of a comprehensive male infertility evaluation. The use of ultrasound as a critical, indispensable, yet noninvasive tool in the evaluation of possible male reproductive tract obstruction is discussed. Since assisted reproductive techniques (ARTs) have become increasingly important in the management of the otherwise untreatable infertile man, specialized testing of sperm function, e.g., the sperm penetration assay (SPA), and strict morphology assessment are often useful prior to the initiation of some of these assisted reproductive procedures such as intrauterine insemination (IUI) or in vitro fertilization (IVF). Testicular touch preparation cytology and image analysis are also important additions to routine testicular biopsy for quantifying the extent of spermatogenesis. Finally, the revolutionary micromanipulation procedure of intracytoplasmic sperm injection (ICSI) has forever changed the practice of andrology by enabling men previously thought to be irreversibly infertile the chance to initiate their own biologic pregnancy.

Testis-specific expression of a functional retroposon encoding glucose-6-phosphate dehydrogenase in the mouse

The X-chromosomal gene glucose-6-phosphate dehydrogenase (G6pd) is known to be expressed in most cell types of mammalian species. In the mouse, we have detected a novel gene, designated G6pd-2, encoding a G6PD isoenzyme. G6pd-2 does not contain introns and appears to represent a retroposed gene. This gene is uniquely transcribed in postmeiotic spermatogenic cells in which the X-encoded G6pd gene is not transcribed. Expression of the G6pd-2 sequence in a bacterial system showed that the encoded product is an active enzyme. Zymogramic analysis demonstrated that recombinant G6PD-2, but not recombinant G6PD-1 (the X-chromosome-encoded G6PD), formed tetramers under reducing conditions. Under the same conditions, G6PD tetramers were also found in extracts of spermatids and spermatozoa, indicating the presence of G6pd-2-encoded isoenzyme in these cell types. G6pd-2 is one of the very few known expressed retroposons encoding a functional protein, and the presence of this gene is probably related to X chromosome inactivation during spermatogenesis.

Two potential clinical applications of the alkaline single-cell gel electrophoresis assay: (1). Human bladder washings and transitional cell carcinoma of the bladder; and (2). Human sperm and male infertility

Part 1: The alkaline single-cell gel electrophoresis (comet) assay was used to analyse the integrity and DNA content of exfoliated cells extracted from bladder washing specimens from 9 transitional cell carcinoma patients and 15 control patients. DNA damage, as expressed by % tail DNA and tail moment values, was observed to occur in cells from both control and bladder cancer samples. The extent of the damage was, however, found to be significantly greater in the cancer group than in the control group. Comet optical density values were also recorded for each cell analysed in the comet assay and although differences observed between tumour grades were not found to be statistically significant, the mean comet optical density value was observed to be greater in the cancer group than in the control population studied. These preliminary results suggest that the comet assay may have potential as a diagnostic tool and as a prognostic indicator in transitional cell carcinoma. Part 2: Baseline DNA damage in sperm cells from 13 normozoospermic fertile males, 17 normozoospermic infertile males and 11 asthenozoospermic infertile males were compared using a modified alkaline comet assay technique. No significant difference in the level of baseline DNA damage was observed between the 3 categories of sperm studied; however the untreated sperm cells were observed to display approximately 20% tail DNA. This is notably higher than the background DNA damage observed in somatic cells where the % tail DNA is normally less than 5%. Sperm from the 3 groups of men studied were also compared for sensitivity to DNA breakage, using the modified alkaline comet assay, following X-ray irradiations (5, 10 and 30 Gy) and hydrogen peroxide treatments (40, 100 and 200 microM). Significant levels of X-ray-induced damage were found relative to untreated control sperm in the two infertile groups following 30 Gy irradiation. Significant damage in hydrogen peroxide-treated sperm was observed in sperm from fertile samples, at 200 microM and in infertile samples at 100- and 200-microM doses relative to controls. These results therefore indicate that fertile sperm samples are more resistant to X-ray- and hydrogen peroxide-induced DNA breakage than infertile samples. Further studies involving greater numbers of individuals are currently in progress to confirm these findings.

Comparative analysis of the ability of precursor germ cells and epididymal spermatozoa to generate reactive oxygen metabolites

Male germ cells at various stages of differentiation from pachytene spermatocytes to mature caudal epididymal spermatozoa were examined for their ability to generate reactive oxygen species (ROS) using sensitive chemiluminescence techniques. In general, spermatozoa were found to spontaneously generate hydrogen peroxide as they progressed through the epididymis, maximal activity being observed on the release of mature cells from the caudal region into a modified Krebs-Ringer's solution. The spontaneous production of hydrogen peroxide rose rapidly during the first 10 min after the spermatozoa had been diluted into culture medium and thereafter stabilized, neither phorbol esters nor A23187 subsequently influencing this activity. Low levels of superoxide generation were also detected in suspensions of epididymal spermatozoa, but did not correlate with maturation status. However, superoxide production could be dramatically enhanced by the addition of exogenous NADPH, in a manner that was closely correlated with the stage of epididymal development being maximal for immature cells recovered from the caput epididymis in all species. Precursor germ cells (pachytene spermatocytes, round and elongate spermatids) similarly generated chemiluminescent signals compatible with the low level generation of ROS. Superoxide generation in these cells could again be stimulated by NADPH, via mechanisms that were inversely related to the stage of germ cell differentiation, the greatest activity being observed in pachytene spermatocytes. These results demonstrate that differentiating male germ cells have the potential to generate ROS, and have implications for the redox regulation of gonadal function and the development of reproductive pathologies involving oxidative stress.

Comparison of individual antioxidants of sperm and seminal plasma in fertile and infertile men

OBJECTIVE

To measure individual antioxidants in sperm and seminal plasma from fertile and infertile men to determine if any particular antioxidant is reduced in infertile men.

DESIGN

Semen samples were prepared by a discontinuous Percoll gradient to separate sperm and seminal plasma, and the antioxidant concentrations of each were assessed. Samples also were screened for phorbol ester-induced reactive oxygen species (ROS) activity.

SETTING

Departments of Obstetrics and Gynaecology, and Clinical Biochemistry, The Queen's University of Belfast, Northern Ireland.

PATIENT(S)

Fifty-nine male patients attending our infertility center: 18 men whose wives had ongoing pregnancies from IVF with normozoospermic semen profiles, 20 infertile men with normozoospermic and 21 men with asthenozoospermic semen profiles.

MAIN OUTCOME MEASURE(S)

Ascorbate, urate, sulphydryl groups, tocopherol and carotenoid concentrations were measured in sperm and seminal plasma from fertile and infertile men.

RESULT(S)

In seminal plasma, ascorbate contributes almost twice as much as urate and thiol levels are about one third of ascorbate. Ascorbate levels in seminal plasma of asthenozoospermic individuals (+ROS) are significantly reduced. In sperm, thiols contributed most and ascorbate only a fraction of the total.

CONCLUSION(S)

In seminal plasma, ascorbate, urates, and thiols are the major antioxidants present. In contrast, within sperm, this group is the major contributor. In samples exhibiting ROS activity, ascorbate concentrations in the seminal plasma are significantly reduced.

Role of reactive oxygen species in male infertility

Human spermatozoa exhibit a capacity to generate ROS and initiate peroxidation of the unsaturated fatty acids in the sperm plasma membrane, which plays a key role in the etiology of male infertility. The short half-life and limited diffusion of these molecules is consistent with their physiologic role in key biological events such as acrosome reaction and hyperactivation. The intrinsic reactivity of these metabolites in peroxidative damage induced by ROS, particularly H2O2 and the superoxide anion, has been proposed as a major cause of defective sperm function in cases of male infertility. The number of antioxidants known to attack different stages of peroxidative damage is growing, and it will be of interest to compare alpha-tocopherol and ascorbic acid with these for their therapeutic potential in vitro and in vivo. Both spermatozoa and leukocytes generate ROS, although leukocytes produce much higher levels. The clinical significance of leukocyte presence in semen is controversial. Seminal plasma confers some protection against ROS damage because it contains enzymes that scavenge ROS, such as catalase and superoxide dismutase. A variety of defense mechanisms comprising a number of anti-oxidants can be employed to reduce or overcome oxidative stress caused by excessive ROS. Determination of male infertility etiology is important, as it will help us develop effective therapies to overcome excessive ROS generation. ROS can have both beneficial and detrimental effects on the spermatozoa and the balancing between the amounts of ROS produced and the amounts scavenged at any moment will determine whether a given sperm function will be promoted or jeopardized. Accurate assessment of ROS levels and, subsequently, OS is vital, as this will help clinicians both elucidate the fertility status and identify the subgroups of patients that respond or do not respond to these therapeutic strategies. The overt commercial claims of antioxidant benefits and supplements for fertility purposes must be cautiously looked into, until proper multicentered clinical trials are studied. From the current data it appears that no single adjuvant will be able to enhance the fertilizing capacity of sperm in infertile men, and a combination of the possible strategies that are not toxic at the dosage used would be a feasible approach.

Effect of rotation on the generation of reactive oxygen species in human semen

Rotation of semen after liquefaction is a standard procedure in an Andrology laboratory. During rotation under aerobic conditions the semen is exposed to oxygen. Oxygen toxicity induces lipid peroxidation which is responsible for the loss of sperm function. The generation of reactive oxygen species was significantly increased after rotation. This may have a detrimental effect on sperm function during assisted reproduction.

Production of reactive oxygen species by and hydrogen peroxide scavenging activity of spermatozoa in an IVF program

PURPOSE

Reactive oxygen species (ROS) including H2O2 produced by spermatozoa have been suggested, on one hand, to be associated with idiopathic male infertility and, on the other hand, to stimulate certain sperm function leading to fertilization. The influence of ROS on fertilization was investigated in 75 IVF patients by correlating fertilization rates with the production of ROS and the H2O2-scavenging activity of swim-up spermatozoa prepared in parallel with the IVF samples.

RESULTS

Low rates of ROS production by the swim-up sperm was detected by the luminol-dependent chemiluminescence assay. They were not correlated with fertilization rates. The hydrogen peroxide scavenging capacity of these spermatozoa, measured as the removal of exogenous H2O2 assayed spectrophotometrically, decreased stepwise in groups of patients achieving higher fertilization rates, suggesting a positive effect of this ROS on fertilization. An alternative explanation of this correlation is plausible in view of the association of both high scavenging activities and poor fertilization rates with poor sperm morphology.

CONCLUSIONS

ROS produced by spermatozoa selected by swim-up plays no negative, if not a positive, role in fertilization.

Impact of in vitro fertilization culture media on peroxidative damage to human spermatozoa

OBJECTIVE

To compare different culture media for their effects on sperm motility and lipid peroxidation.

DESIGN

The ability of four different culture media to sustain the motility of human spermatozoa during an overnight incubation was examined in relation to the induction of lipid peroxidation. The role of transition metals in the genesis of peroxidative damage was investigated in experiments involving the addition of iron or the chelating reagent ethylenediamine tetra acetic acid (EDTA).

SETTING

Academic research institute.

MAIN OUTCOME MEASURES

The generation of malondialdehyde and 4-hydroxyalkenals after the addition of a ferrous ion promoter and the measurement of sperm motility.

RESULTS

Spermatozoa incubated in Ham's F-10 medium (GIBCO, Paisley, Scotland) exhibited a marked loss of motility in association with a significant increase in peroxidative damage. Addition of EDTA to Ham's F-10 medium significantly reduced the degree of lipid peroxidation and induced a simultaneous increase in sperm motility.

CONCLUSIONS

Ham's F-10 medium is a suboptimal medium for the long-term culture of human spermatozoa because it induces peroxidative damage and a concomitant decline of sperm motility.

Superoxide dismutase in human sperm suspensions: relationship with cellular composition, oxidative stress, and sperm function

Sensitive techniques have been developed for monitoring superoxide dismutase (SOD) activities in human sperm preparations. In contradiction to the protective role normally assigned to SOD, populations of defective spermatozoa recovered from the low density region of Percoll gradients were found to have three times more SOD than functionally competent preparations pelleting in high density Percoll. SOD activity was negatively correlated with the movement characteristics of human spermatozoa and their capacity for oocyte fusion, and positively associated with the induction of peroxidative damage. SOD activity was also highly correlated with other markers of the cytoplasmic space, creatine kinase (CK), and glucose-6-phosphate dehydrogenase (G-6-PDH). We conclude that while SOD may play a physiological role in maintaining a balance between O2.- and H2O2, high levels of this enzyme are associated with impaired sperm function because (a) the human spermatozoon is highly susceptible to the cytotoxic effects of H2O2, (b) O2.- is an important mediator of normal sperm function, and (c) high SOD activities reflect errors in spermatogenesis associated with germ cell exfoliation and the retention of excess residual cytoplasm by the spermatozoa.

Hypotaurine and taurine in gamete and embryo environments: de novo synthesis via the cysteine sulfinic acid pathway in oviduct cells

Taurine and hypotaurine seem to be important compounds for sperm survival and capacitation, the fertilisation process and embryo development, and are present in both sperm and genital secretions. Hypotaurine has protective effects against peroxidative damage. We have established a simple method for hypotaurine quantification in sperm and genital secretions. The mean concentration of hypotaurine is significantly higher in bovine than in human spermatozoa and in seminal plasma. We observed that both molecules are secreted by cow, sow, goat and rabbit oviduct epithelial cell monolayers. In rabbit the release is ascorbic acid dependent. Goat oviduct epithelial cells are able to use the transsulfuration pathway to form hypotaurine and taurine from methionine. We were able to identify cysteine sulfinate decarboxylase (EC 4.1.1.29) activity in cow and goat tubal monolayers. Our results demonstrate that hypotaurine and taurine are secreted by oviduct epithelium, and synthesised by tubal cells via the cysteine sulfinic acid pathway. The data obtained emphasise the importance of hypotaurine and taurine for gamete maturation, fertilisation and early embryonic development.

Predicting the fertilizing potential of human sperm suspensions in vitro: importance of sperm morphology and leukocyte contamination

OBJECTIVE

To determine the relationships between sperm function tests and fertilization of human oocytes in vitro.

DESIGN

Analysis of infertile patients undergoing IVF therapy.

SETTING

Diagnostic Andrology Laboratory and Assisted Conception Service.

PATIENTS

Forty-one couples who underwent IVF-ET therapy were studied.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

The ability of human spermatozoa to achieve fertilization in vitro was examined in relation to numerous criteria of semen quality, including the conventional semen profile, the computer-aided assessment of sperm movement, ionophore-induced acrosome reaction, acridine orange staining, sperm morphology, and chemiluminescent signals induced by phorbol ester and N-formyl-methionyl-leucyl-phenylalanine (FMLP).

RESULTS

Significant correlations were observed between fertilization rates and several attributes of the sperm preparations, including elements of sperm function (acrosome reaction), movement (percentage motile, hyperactivation, the amplitude of lateral sperm head displacement), morphology (normal morphology, midpiece defects, multiple anomalies index), nuclear normality (acridine orange staining), and reactive oxygen species generation (chemiluminescence induced by phorbol ester and FMLP). In a stepwise multiple regression analysis, an accurate prediction of fertilization rates was obtained using a multiple regression equation incorporating six variables of which sperm morphology and FMLP-induced chemiluminescence were the most informative.

CONCLUSIONS

A set of criteria have been identified that accurately predict the fertilizing potential of human sperm suspensions in vitro and that place particular emphasis on sperm morphology and the degree of leukocyte contamination.