Infection and reactive oxygen species

Summary. In previous years the physiologic and pathophysiologic significance of reactive oxygen species (ROS) on sperm function has been recognized. The impact of ROS during the invasion, adhesion and multiplication of microorganisms in the male genital tract are largely unknown. However, it is known that the resulting activation of leukocytes leads to an increased generation of ROS. There is growing evidence that spermatozoa are protected from detrimental ROS effects by the powerful antioxidants in seminal plasma since disturbances of sperm function by ROS were demonstrated in the absence of seminal plasma, i.e., during epididymitis or after semen preparation. If seminal plasma is present, ROS generated by physiologic numbers of granulocytes (< 1 times 10⁶ ml⁻¹) apparently do not damage spermatozoa. Interestingly, ROS generated by leukocytes during male genital tract infections are critical for the techniques of semen preparation for assisted reproduction. These ROS impair sperm function if the protective effects of seminal plasma are not present. The relevance of ROS production by higher leukocyte numbers in human semen is presently unknown as is the relevance of ROS generated in the female reproductive tract.
In previous years the ambiguous role of reactive oxygen species (ROS) generation in human semen has been recognized. On one hand, ROS appear to be involved in physiologic reactions such as capacitation (De Lamirande & Gagnon, 1995; Griveau et al. , 1995a), while on the other hand, there is ample evidence that an increased ROS production impairs sperm functions and the fertilizing capacity of spermatozoa (Ochsendorf & Fuchs, 1993; Aitken, 1994; Griveau et al. , 1995b). The objective of this review is to summarize the relevance of reactive oxygen species during infections of the male genital tract.     

Progesterone-induced reorganisation of NOX-2 components in membrane rafts is critical for sperm functioning in Capra hircus

Spermatozoa produce increasing levels of reactive oxygen species (ROS) during development. We examined the functional organisation of NOX-2 subunits in developing spermatozoa and its involvement in ROS generation. We found NOX-2 components associated predominantly with caveolin-rich microdomains of sperm head and mid piece membranes. Capacitation in vitro enriched NOX-2 components within the caveolin-positive sperm membrane rafts. Progesterone, but not 17β-oestradiol, brought about loss of caveolin and extensive reorganisations in NOX-2 distribution on sperm head microdomains and accompanying activation in the levels of superoxide. The sensitivity of superoxide production by spermatozoa to methyl-β-cyclodextrin confirms that NOX-2 function in spermatozoa is tightly dependent on raft organisation. We conclude that progesterone-induced reorganisation of NOX-2 components in sperm membrane rafts is critical for sperm functioning.     

Reactive oxygen species and human spermatozoa. I. Effects on the motility of intact spermatozoa and on sperm axonemes.

Mammalian spermatozoa are sensitive to oxygen-induced damages mediated by lipid peroxidation of the cell membrane. The aim of this study was to evaluate whether reactive oxygen species (ROS) could also induce axonemal damage. When Percoll-separated spermatozoa were treated with hydrogen peroxide, or the combination xanthine and xanthine oxidase (X + XO), there was a progressive decrease, leading to a complete arrest, in sperm flagellar beat frequency. Once demembranated in a medium containing magnesium adenosine triphosphate (Mg.ATP), ROS-immobilized spermatozoa still reactivated motility; however, the percentage and duration of motility obtained in these tests gradually decreased to zero in the next hour. In 50% of the cases, motility of intact spermatozoa spontaneously reinitiated after 6 to 24 hours of immobilization due to ROS treatment, although with percentages and beat frequencies lower than those of untreated spermatozoa. Studies using ROS scavengers (such as catalase, superoxide dismutase, and dimethylsulfoxide) indicated that hydrogen peroxide was the most toxic of the ROS involved, but that .O2- and .OH probably also played a role in immobilization of spermatozoa by ROS. The data suggest that ROS induce a chain of events leading to sperm immobilization, that axonemes are affected, and that limited endogenous repair mechanisms exist to reverse these damages.     

Antioxidant effects of penicillamine against in vitro-induced oxidative stress in human spermatozoa

Oxidative stress contributes importantly to the aetiology of male infertility, impairing sperm function. The protective effect of antioxidants on seminal parameters has been established, and the antioxidant penicillamine has shown beneficial effects; however, its protective effect on human spermatozoa exposed to oxidative stress has not been reported. The objective of this work was to evaluate the effect of penicillamine on human spermatozoa exposed in vitro to oxidative stress. First, the effect of penicillamine on spermatozoa from normozoospermic donors was evaluated. Then, the effect of penicillamine on spermatozoa exposed to oxidative stress induced separately by ionomycin and hydrogen peroxide (H₂O₂) was analysed. An untreated control and a control treated only with the oxidative stress inducer were included. Reactive oxygen species (ROS) levels, viability, mitochondrial membrane potential (MMP) and motility were analysed. The results showed that penicillamine, added to the incubation medium, decreased the ROS levels induced by ionomycin and H₂O₂, and this effect was associated with better preservation of MMP, motility, and ATP levels. These results highlight the potential advantages of penicillamine supplementation of sperm culture medium, especially for semen samples with high ROS levels and also in circumstances where laboratory handling can cause an increase in ROS production.     

Effects of reactive oxygen species from activated leucocytes on human sperm motility, viability and morphology

The accumulated data suggest that inflammation can increase the level of reactive oxygen species (ROS), which contribute to impaired sperm function and male infertility. Therefore, we propose that inflammation-mediated production of ROS in male and female reproductive tracts hinder sperm fertilisation. To test this hypothesis, phorbol myristate acetate (PMA) with polymorphonuclear leucocytes (PMNs) was applied to generate endogenous ROS. We evaluated the time-dependent effects of ROS on human sperm motility, viability and mitochondrial membrane potential (MMP). The results showed that after treatment with PMA and PMNs, the motility of human spermatozoa significantly decreased to 50% on Day 1 and 15% on Day 4 compared with that of the, respectively, negative controls (P = 0.012). The viability of human spermatozoa decreased on Day 4 of PMA + PMNs treatment (P = 0.028). The MMP of human spermatozoa significantly decreased from Day 2 to Day 4 in the PMA + PMN group compared with that of the controls (P = 0.019). Taken together, the 4-day cultivation approach provided an accurate evaluation of sperm quality, especially sperm motility and MMP. Our findings indicated that endogenous inflammation increased ROS levels, which might induce sperm oxidative damage. Additionally, sperm motility might be one of the earliest and most sensitive indicators of this damage.     

氧化胁迫与精子功能损伤

人类精子对氧化胁迫特别敏感 ,损伤精子功能的氧化胁迫有两个细胞来源 :精子自身和白细胞。由于精子膜含有高浓度的不饱和脂肪酸 ,而且精子自身的抗氧化能力很弱 ,在过量活性氧的攻击下 ,易发生脂类过氧化反应 ,使精子膜的流动性和完整性受到损伤 ,进而破坏精子功能 ,并最终引起男性不育。此外 ,过量的活性氧还可造成精子核DNA的损伤 ,而父代精子DNA的损伤又与子代儿童癌症的发生有密切的关联。     

Significance of reactive oxygen species and antioxidants in defining the efficacy of sperm preparation techniques

The mechanisms responsible for mediating the influence of sperm preparation protocols on human sperm function have been investigated. Techniques that involved the separation of motile spermatozoa prior to centrifugation were found to yield sperm suspensions of highest quality. If the spermatozoa were centrifuged prior to isolation of the motile cells, sperm function was impaired. The detrimental effects of centrifugation were associated with a sudden burst of reactive oxygen species production by a discrete subpopulation of cells (characterized by significantly diminished motility and fertilizing capacity) that could be separated from normal functional spermatozoa on Percoll gradients. If unfractionated sperm suspensions were subjected to centrifugation, the reactive oxygen species generated by this subpopulation impaired the functional competence of normal spermatozoa in the same suspension. Assessment of the ability of the antioxidants, butylated hydroxytoluene, and vitamin E, to curtail the peroxidative damage inflicted by such cells in response to centrifugation revealed a significant improvement of sperm function in the presence of vitamin E.     

Effect of mitochondrial calcium uniporter blocking on human spermatozoa

Calcium (Ca²⁺) regulates a number of essential processes in spermatozoa. Ca²⁺ is taken up by mitochondria via the mitochondrial calcium uniporter (mCU). Oxygen‐bridged dinuclear ruthenium amine complex (Ru360) has been used to study mCU because it is a potent and specific inhibitor of this channel. In bovine spermatozoa, it has been demonstrated that mitochondrial calcium uptake inhibition adversely affects the capacitation process. It has been demonstrated in human spermatozoa that mCU blocking, through Ru360, prevents apoptosis; however, the contribution of the mCU to normal human sperm function has not been studied. Therefore, the aim of this study was to evaluate the effect of mCU blocking on human sperm function. Spermatozoa obtained from apparently healthy donors were incubated with 5 and 10 μm Ru360 for 4 h at 37 °C. Viability was assessed using propidium iodide staining; motility was determined by computer‐aided sperm analysis, adenosine triphosphate (ATP) levels using a luminescence‐based method, mitochondrial membrane potential (ΔΨm) using JC‐1 staining and reactive oxygen species (ROS) production using dihydroethidium dye. Our results show that mCU blocking significantly reduced total sperm motility and ATP levels without affecting sperm viability, ΔΨm and ROS production. In conclusion, mCU contributes to the maintenance of sperm motility and ATP levels in human spermatozoa.     

Reactive oxygen species and cryopreservation promote DNA fragmentation in equine spermatozoa

The objective of this study was to examine the effect of reactive oxygen species (ROS) and cryopreservation on DNA fragmentation of equine spermatozoa. In experiment 1, equine spermatozoa were incubated (1 hour, 38 degrees C) according to the following treatments: 1) sperm alone; 2) sperm + xanthine (X, 0.3 mM)-xanthine oxidase (XO, 0.025 U/mL); 3) sperm + X (0.6 mM)-XO (0.05 U/mL); and 4) sperm + X (1 mM)-XO (0.1 U/mL). In experiment 2, spermatozoa were incubated (1 hour, 38 degrees C) with X (1 mM)-XO (0.1 U/mL) and either catalase (200 U/mL), superoxide dismutase (SOD, 200 U/mL), or reduced glutathione (GSH, 10 mM). Following incubation, DNA fragmentation was determined by the single cell gel electrophoresis (comet) assay. In experiment 3, equine spermatozoa were cryopreserved, and DNA fragmentation was determined in fresh, processed, and postthaw sperm samples. In experiment 1, incubation of equine spermatozoa in the presence of ROS, generated by the X-XO system, increased DNA fragmentation (P <.005). In Experiment 2, the increase in DNA fragmentation associated with X-XO treatment was counteracted by the addition of catalase and GSH but not by SOD, suggesting that hydrogen peroxide and not superoxide appears to be the ROS responsible for such damage. In experiment 3, cryopreservation of equine spermatozoa was associated with an increase (P <.01) in DNA fragmentation when compared with fresh or processed samples. This study indicates that ROS and cryopreservation promote DNA fragmentation in equine spermatozoa; the involvement of ROS in cryopreservation-induced DNA damage remains to be determined.     

Reactive oxygen species and human spermatozoa. II. Depletion of adenosine triphosphate plays an important role in the inhibition of sperm motility.

Under moderate conditions, reactive oxygen species (ROS) have been shown to inhibit sperm motility after several hours of incubation. The rapid decrease in flagellar beat frequency observed within the first hour of contact between ROS and spermatozoa was associated with a rapid loss of intracellular adenosine triphosphate (ATP). Motility of intact spermatozoa ceased when their ATP concentration was reduced by 85 +/- 5%. Axonemal damage was confirmed when ROS-treated spermatozoa could not reactivate motility after demembranation in a medium containing magnesium adenosine triphosphate (Mg.ATP). However, in conditions allowing rephosphorylation of the axonemes (addition of cyclic adenosine monophosphate, or cAMP, and protein kinase or sperm extracts to the demembranation medium), the motility could reactivate. Three lines of evidence suggested that ATP depletion induced by ROS treatment was responsible for the effects observed in spermatozoa. First, the rapid decrease in intracellular ATP observed after ROS treatment was closely followed by a decrease in beat frequency, loss of intact sperm motility, and axonemal damage due to insufficient phosphorylation. Second, incubation of spermatozoa with the combination pyruvate-lactate allowed maintenance of sperm ATP at a normal level and prevented the effects of ROS; furthermore, spermatozoa immobilized after ROS treatment, then supplemented with pyruvate-lactate, were able to reinitiate motility in parallel with an increase in their ATP level. Third, treatment of spermatozoa with rotenone, an ATP depleting agent, produced effects similar to ROS treatment and could also be reversed by the addition of pyruvate-lactate. These data are consistent with the conclusion that ROS treatment produced axonemal damage mostly as a result of ATP depletion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spermatozoa have decreased antioxidant enzymatic capacity and increased reactive oxygen species production during aging in the Brown Norway rat

As the proportion of aged males attempting to reproduce continues to rise, so does the concern regarding the quality of spermatozoa from aged men. An imbalance between the generation of reactive oxygen species (ROS) and cellular antioxidant defenses, as occurs in aging, ultimately leads to decreased protein, lipid, and DNA quality. Spermatozoa are highly susceptible to oxidative damage, and thus an age-related shift in redox status may have serious implications for fertility. Therefore, we examined the effect of age on antioxidant enzymatic activity, ROS production, and extent of lipid peroxidation in both caput and cauda epididymal spermatozoa from young (4-month-old) and old (21-month-old) Brown Norway rats. Glutathione peroxidase (Gpx1, Gpx4) and superoxide dismutase (SOD) enzymes had decreased activity in aging spermatozoa. Immunofluorescence studies indicated that Gpx4 expression was decreased in both the head and midpiece regions of spermatozoa in aged animals. The decrease in nuclear Gpx4 points to a novel potential mechanism that may explain the previously noted decreased levels of protamine disulfide bonds in aged sperm nuclei. Further, hydrogen peroxide (H2O2) and superoxide (O2(.-)) production were increased significantly in aging spermatozoa. Finally, lipid peroxidation was found to be drastically increased in aged spermatozoa. Taken together, these results suggest a decreased capacity for aged spermatozoa to handle oxidative stress and provide a potential basis for understanding the underlying cause of decreased quality of spermatozoa during aging.     

Protective effects of exogenous gangliosides on ROS-induced changes in human spermatozoa

This article summarizes the available evidence on the efficacy of gangliosides to reduce the degree of reactive oxygen species (ROS)-mediated damage. The antioxidative efficacy of exogenous gangliosides in protecting different cells encouraged us to examine their ability to protect human spermatozoa. Gangliosides are sialic acid-containing glycosphingolipids with strong amphiphilic character due to the bulky headgroup made of several sugar rings with sialic acid residues and the double-tailed hydrophobic lipid moiety. The amphiphilicity of gangliosides allows them to exist as micelles in aqueous media when they are present at a concentration above their critical micellar concentration. The protective effect of ganglioside micelles on spermatozoa is believed to stem from their ability to scavenge free radicals and prevent their damaging effects. In our study, we particularly focused our attention on the protective effect of ganglioside micelles on DNA in human spermatozoa exposed to cryopreservation. The results indicate that ganglioside micelles can modulate the hydrophobic properties of the sperm membrane to increase tolerance to DNA fragmentation, thus protecting the DNA from cryopreservation-induced damage. Further actions of ganglioside micelles, which were documented by biochemical and biophysical studies, included (i) the modulation of superoxide anion generation by increasing the diffusion barrier for membrane events responsible for signal translocation to the interior of the cell; (ii) the inhibition of iron-catalysed hydroxyl radical formation due to the iron chelation potential of gangliosides; and (iii) inhibition of hydrogen peroxide diffusion across the sperm membrane.     

Participation of superoxide anion in the capacitation of cryopreserved bovine sperm

Mammalian spermatozoa must undergo a preparation period known as capacitation to become capable of fertilizing oocytes. Controlled amounts of reactive oxygen species (ROS), such as superoxide anion (O2.-) and hydrogen peroxide (H2O2) have been shown essential for capacitation and acrosome reaction. The presence of an oxidase in the sperm plasma membrane has been suggested. The objective of the present study was to provide evidence for the production of O2.- by capacitating cryopreserved bovine spermatozoa. Percentages of capacitation and acrosome reaction were determined by the chlortetracycline assay. The effect of several nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors on capacitation was also studied. H2O2 production was determined by the fluorometric assay using the p-hydroxyphenylacetic acid-horseradish peroxidase system. Superoxide dismutase (SOD) activity was determined spectrophotometrically at 480 nm. Heparin-dependent capacitation was inhibited by all NADPH oxidase inhibitors tested (p < 0.05). Significant levels of H2O2 were produced during capacitation with heparin; such production was inhibited by diphenyleneiodonium, one of the NADPH oxidase inhibitors. The addition of catalase to the incubation medium failed to modify the capacitation rate; inhibition was only observed when SOD was present (p < 0.05). Endogenous SOD activity was diminished during heparin-dependent capacitation (p < 0.05). Similar levels of acrosome reaction induced by lysophosphatidylcholine were obtained in both heparin and O2.--dependent capacitation. Overall results suggest the participation of a sperm oxidase in bovine sperm capacitation. H2O2, generated by O2.- dismutation, failed to participate in capacitation, although this ROS may have been able to decrease endogenous SOD activity. Exogenous O2.- promotes physiological capacitation in cryopreserved bovine sperm, thus allowing the acquisition of fertilizing capacity.     

The effect of reactive oxygen species on equine sperm motility, viability, acrosomal integrity, mitochondrial membrane potential, and membrane lipid peroxidation

The objective of this study was to examine the influence of reactive oxygen species (ROS), generated through the use of the xanthine (X)-xanthine oxidase (XO) system, on equine sperm motility, viability, acrosomal integrity, mitochondrial membrane potential, and membrane lipid peroxidation. Equine spermatozoa were separated from seminal plasma on a discontinuous Percoll gradient, and spermatozoa were incubated with 0.6 mM X and 0.05 U/mL XO for 30 minutes. Catalase (150 U/mL), superoxide dismutase (SOD, 150 U/mL), or glutathione (GSH, 1.5 mM) were evaluated for their ability to preserve sperm function in the presence of the induced oxidative stress. At the end of the 30-minute incubation, sperm motility was determined by computer-assisted semen analysis. Viability and acrosomal integrity were determined by Hoechst-Pisum sativum staining, and mitochondrial membrane potential was determined by staining with JC-1. Incubation with the X-XO system led to a significant (P < .01) increase in hydrogen peroxide production and an associated decrease (P < .01) in motility parameters. Total motility was significantly (P < .01) lower in the presence of X-XO compared with the case of the control (29%+/-9% vs 73%+/-1%, respectively). Catalase, but not SOD, prevented a decline in motility secondary to oxidative stress (71%+/-4% vs 30%+/-3%, respectively). The addition of glutathione had an intermediate effect in preserving sperm motility at the end of the 30-minute incubation (53%+/-3%). No influence of X-XO could be determined on viability, acrosomal integrity, or mitochondrial membrane potential. In order to promote lipid peroxidation, samples were incubated with ferrous sulfate (0.64 mM) and sodium ascorbate (20 mM) for 2 hours after the X-XO incubation. No increase in membrane lipid peroxidation was detected. This study indicates that hydrogen peroxide is the major ROS responsible for damage to equine spermatozoa. The decrease in sperm motility associated with ROS occurs in the absence of any detectable decrease in viability, acrosomal integrity, or mitochondrial membrane potential or of any detectable increase in lipid peroxidation.     

Redox regulation of mammalian sperm capacitation

Capacitation is a series of morphological and metabolic changes necessary for the spermatozoon to achieve fertilizing ability. One of the earlier happenings during mammalian sperm capacitation is the production of reactive oxygen species (ROS) that will trigger and regulate a series of events including protein phosphorylation, in a time-dependent fashion. The identity of the sperm oxidase responsible for the production of ROS involved in capacitation is still elusive, and several candidates are discussed in this review. Interestingly, ROS-induced ROS formation has been described during human sperm capacitation. Redox signaling during capacitation is associated with changes in thiol groups of proteins located on the plasma membrane and subcellular compartments of the spermatozoon. Both, oxidation of thiols forming disulfide bridges and the increase on thiol content are necessary to regulate different sperm proteins associated with capacitation. Reducing equivalents such as NADH and NADPH are necessary to support capacitation in many species including humans. Lactate dehydrogenase, glucose-6-phospohate dehydrogenase, and isocitrate dehydrogenase are responsible in supplying NAD (P) H for sperm capacitation. Peroxiredoxins (PRDXs) are newly described enzymes with antioxidant properties that can protect mammalian spermatozoa; however, they are also candidates for assuring the regulation of redox signaling required for sperm capacitation. The dysregulation of PRDXs and of enzymes needed for their reactivation such as thioredoxin/thioredoxin reductase system and glutathione-S-transferases impairs sperm motility, capacitation, and promotes DNA damage in spermatozoa leading to male infertility.     

活性氧致人精子运动功能和存活力变化的分析

目的 :对活性氧 (ROS)作用后精子的运动参数和存活率的变化进行分析 ,以证实ROS是否为引起精子运动功能障碍的病因之一。　方法 :采用Percoll梯度离心法选择具有正常生理功能的人精子作为正常精子模型 ,应用次黄嘌呤 黄嘌呤氧化酶体系产生ROS ,在有氧环境下与精子模型孵育后 ,运用计算机辅助精液分析 (CASA)系统 ,分析ROS攻击后精子运动参数的改变。　结果 :与对照组相比 ,正常精子模型与ROS孵育 30min后 ,精子活动率、曲线速度 (VCL)、直线速度 (VSL)、平均路径速度 (VAP)均明显下降 (P <0 .0 0 1) ,头侧摆幅度 (ALH)尚无明显改变 (P >0 .0 5 ) ,而与ROS孵育 6 0min后 ,精子运动功能近乎丧失 ,精子主要运动参数趋向于零。　结论 :ROS与正常精子作用后 ,可导致精子运动功能下降 ,从而证实ROS为精子运动功能障碍的病因之一。     

Relative contribution of leukocytes and of spermatozoa to reactive oxygen species production in human sperm suspensions

The contribution of leukocytes and of spermatozoa to reactive oxygen species (ROS) production in prepared sperm suspensions from donors and subfertility patients was compared. In both groups, more leukocytes/10(6) spermatozoa were counted in samples which produced detectable ROS than in those that did not: Donors-645 vs. 170 (medians, n = 7; p < 0.01, Kruskal-Wallis), Subfertile group-1785 (n = 18) vs. 11 (n = 8) (p < 0.005, Kruskal-Wallis), respectively. Leukocyte concentrations were correlated with basal (r = 0.826, p < 0.001) and with ROS production stimulated with 50 mumol N-formyl, met, leu, phe l-1 (N-FMLP) (r = 0.835, p < 0.001) and 100 nmol phorbol 12-myristate 13-acetate l-1 (PMA) (r = 0.835, p < 0.001) measured using a chemiluminescence assay. Leukocytes were removed from the sperm suspensions of 6 donors and from 96 ejaculates from 21 subfertility patients and ROS production was determined. Subsequently, in all 6 donors, N-FMLP did not stimulate ROS production indicating that leukocyte removal was complete, though in one case PMA stimulated low levels of ROS production. In 65 ejaculates from subfertile men the N-FMLP response was completely eliminated but in 7 of these samples PMA continued to stimulate ROS production. We conclude that infiltrating leukocytes are the predominant source of ROS production in unpurified sperm preparations. Some purified sperm suspensions could be stimulated to produce ROS by the addition of PMA indicating that spermatozoa themselves may produce ROS, albeit in much smaller amounts.     

Spontaneous lipid peroxidation and production of hydrogen peroxide and superoxide in human spermatozoa. Superoxide dismutase as major enzyme protectant against oxygen toxicity

Spontaneous lipid peroxidation in washed human spermatozoa was induced by aerobic incubation at 32 C and measured by malonaldehyde production; loss of motility during the incubation was determined simultaneously. Malonaldehyde production at the point of complete loss of motility, defined as the lipoperoxidative lethal endpoint (LLE), was 0.10 +/- 0.03 nmol/10(8) cells (mean +/- SD, n = 40), and was independent of the time to complete loss of motility. Human spermatozoa produced both H2O2 and O2-. during aerobic incubation. Inhibition of superoxide dismutase in these cells with KCN showed that all the H2O2 production is due to action of the dismutase. The superoxide dismutase activity of individual human sperm samples varied between 1 and 10 U/10(8) cells, variations between samples from a single donor being nearly as great as those between different donors. The time to complete motility loss (tL) showed equal variation of 1 to 10 hours among samples. The rate of spontaneous lipid peroxidation, calculated as LLE/tL, for a given sperm sample and the superoxide dismutase activity of the same sample, determined prior to aerobic incubation, gave a good linear correlation (r = 0.97). Glutathione reductase, glutathione peroxidase, and glutathione were found to be present in human spermatozoa, but showed little variation among samples. These results suggest that superoxide dismutase plays the major role in protecting human spermatozoa against lipid peroxidation. In addition, the superoxide dismutase activity of a fresh sperm sample appears to be a good predictor of the lifetime (up to the complete loss of motility) of that particular sample, and so may prove useful in semen analysis.     

褪黑素在活性氧致精子线粒体功能损伤中的保护作用

目的 :探讨活性氧 (ROS)对精子线粒体功能的损伤以及褪黑素 (MLT)的保护作用。　方法 :采用Percoll梯度离心法选择具有正常生理功能的精子 ,作为本实验的正常精子模型。应用次黄嘌呤—黄嘌呤氧化酶体系产生ROS ,在MLT存在与不存在情况下 ,与精子模型分别孵育 30和 6 0min后 ,采用酶组织化学方法分析精子线粒体部位的琥珀酸脱氢酶 (SDH)活性 ,采用Rhodamine 1 2 3(Rh1 2 3)荧光探针标记精子 ,通过流式细胞仪检测线粒体膜电位。　结果 :正常精子与ROS孵育后 ,精子线粒体膜电位明显降低 ,线粒体SDH活力降低极为显著 ;而MLT则减轻了ROS对精子线粒体功能的损伤。　结论 :ROS可通过对精子线粒体膜电位和SDH活力的影响 ,而导致精子线粒体功能损伤 ;MLT可通过其有效的抗氧化能力 ,保护精子对抗ROS对其线粒体功能的损伤     

抗氧化剂可以治疗男性不育吗？

不育男性精液中活性氧（ROS）的浓度高于正常男性。精液中ROS水平的升高会导致精于功能障碍,精子DNA损伤,降低男性的生殖能力。这一现象启发临床医生通过补充抗氧化剂来治疗男性不育。本综述旨在探讨抗氧化剂治疗男性不育的基本原理,并通过数据分析评价饮食及体外抗氧化剂的补充对精子功能和DNA损伤的修复效果。迄今为止,多数临床研究表明饮食中补充抗氧化剂有益于精子功能及DNA完整性方面的改善。但是,膳食抗氧化剂的作用机制以及最佳膳食补充方案尚未建立。此外,多数临床研究的样本较少,而且很少有人评价怀孕率。多数研究表明体外抗氧化补充剂在保护精予免受外源氧化剂的损伤方面是有效的,然而,这些抗氧化剂在保护精子免受内源性活性氧、轻微的精子处理及冷冻保存的损伤方面尚无定论。