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.     

Preventive and protective effects of Turkish propolis on H₂O₂-induced DNA damage in foreskin fibroblast cell lines

The aim of the present study was to evaluate the potential of Turkish propolis extracts if they prevent or protect foreskin fibroblast cells against hydrogen peroxide (H?O?)-induced oxidative DNA damage. Hydrogen peroxide (40 μM) was used as an inducer of oxidative DNA damage. The damage of DNA was evaluated by using the alkaline single cell gel electrophoresis (comet) assay. Turkish propolis extracts at concentrations of 25, 50, 75 and 100 μg/ml were prepared by ethanol. Anti-genotoxicity was assessed before, simultaneously, and after treatment of propolis extract (50 μg/ml) with H?O?. The results showed a significant decrease in H?O?-induced DNA damage in cultures treated with propolis extract. The antioxidant activity of phenolic components found in propolis may contribute to reduce the DNA damage induced by H?O?. Our findings confirmed the chemopreventive activity of propolis and showed that this effect may occur under different mechanisms.     

Protective effect of Ligusticum chuanxiong and Angelica sinensis on endothelial cell damage induced by hydrogen peroxide

Ligusticum chuanxiong and Angelica sinensis have been widely used in traditional Chinese medicine to treat some pathological settings such as atherosclerosis and hypertension. We determined the protective effect of the extract of Ligusticum chuanxiong and Angelica sinensis (ELCAS) on human umbilical vein endothelial cells (ECV304) damage induced by hydrogen peroxide. ECV304 cells were pre-treated with ELCAS and exposed to 5 mM hydrogen peroxide. The results show that ELCAS dose- and time-dependently protected ECV304 cells against hydrogen peroxide damage and suppressed the production of reactive oxygen species (ROS). The decrement of ROS may be associated with increased activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX). Western blot analysis revealed that ELCAS significantly increased the phosphorylation of ERK and promoted eNOS expression. These observations indicate that ELCAS protected ECV304 cells against hydrogen peroxide damage by enhancing the antioxidative ability, activating ERK and eNOS signaling pathway. Our data also provide new evidence of Ligusticum chuanxiong and Angelica sinensis in preventing both cardiovascular and cerebrovascular diseases.     

Benzo[a]yrenedione/benzo[a]pyrenediol oxidation-reduction couples and the generation of reactive reduced molecular oxygen.

The ability of the isomeric quinone metabolites of benzo[a]pyrene, benzo[a]pyrene-6,12-dione, benzo[a]pyrene-1,6-dione, and benzo[a]pyrene-3,6-dione to undergo reversible, univalent oxidation-reduction cycles involving the corresponding benzo[a]pyrenediols and intermediate semiquinone radicals has been characterized. Under anaerobic conditions, all three benzo[a]pyrenediones are easily reduced to benzo[a]pyrenediols, even by mild biological agents such as NAD(P)H, cysteamine, and glutathione. The benzo[a]pyrenediols, in turn, are very rapidly autoxidized to the benzo[a]pyrenediones when exposed to air. Substantial amounts of hydrogen peroxide are produced during these autoxidations, and other reactive reduced oxygen species, such as the superoxide and hydroxyl radicals, are probably formed transiently as well. The benzo[a]pyrenediol-benzo[a]pyrenedione interconversions proceed by one-electron steps; the corresponsing semiquinone radicals can be monitored by electron spin resonance spectroscopy as inter mediates during these reactions carried out at high pH. Benzo[a]pyrenediones induce DNA strand scission when incubated with bacteriophage T7 DNA. This damage is modified by conditions which indicate that reduced oxygen species propagate the free-radical reactions responsible for the strand scission. Benzo[a]pyrenediones are electron-acceptor substrates for NADH dehydrogenase from Clostridium kluyveri. Catalytic amounds of these benzo[a]pyrene metabolites, together with this respiratory enzyme function as cyclic oxidation-reduction couples which link NADH and molecular oxygen in the continuous production of hydrogen peroxide. These data, together with preliminary results with cells in culture, indicate that benzo[a]pyrenediones are potentially harmful metabolites of benzo[a]pyrene, acting by processes which lead to their regeneration rather than depletion; nucleic acid and call damage is probably produced by the reactive reduced oxygen species resulting from such regenerative oxidation-reduction cycles.     

Antioxidant effects of fructosyl arginine, a Maillard reaction product in aged garlic extract

The amino-carbonyl (Maillard) reaction of amino acids with sugars is a nonenzymatic browning reaction that takes place during the processing, cooking, and storage of foods. Maillard reaction products (MRPs) have been shown to possess interesting chemical and biological properties including antimutagenic and antioxidant activity. In this study, we determined the antioxidant effects of fructosyl arginine (Fru-Arg), a MRP in aged garlic extract. Low density lipoprotein (LDL) was incubated with Cu(2+) at 37 degrees C and 5% CO(2) for 24 hours, which resulted in an increase of thiobarbituric acid reactive substances (TBARS) indicating lipid peroxidation. Coincubation of Cu(2+) with Fru-Arg and LDL resulted in a significant inhibition of TBARS formation. Pulmonary artery endothelial cells (PAEC) were exposed to 0.1 mg/mL oxidized LDL (Ox-LDL) at 37 degrees C and 5% CO(2) for 24 hours. Lactate dehydrogenase (LDH) release, as an index of cell membrane damage, and TBARS were measured. Ox-LDL caused an increase of LDH release and TBARS formation. Pretreatment of PAEC with Fru-Arg inhibited these changes. Murine macrophages were incubated with Ox-LDL, and the release of peroxides was measured using a fluorometric assay. Ox-LDL caused an increased release of peroxides. Coincubation of macrophages with Fru-Arg and Ox-LDL inhibited the release of peroxides dose-dependently. In a cell free system, Fru-Arg was shown to scavenge hydrogen peroxide. These data suggest that Fru-Arg is a potent antioxidant, and thus may be useful for the prevention of atherosclerosis and other disorders associated with oxidative stress.     

Effect of heterologous and homologous seminal plasma on stallion sperm quality

Removing most of the seminal plasma (SP) from stallion semen has been shown to improve survival during cooled storage, yet adding small quantities of SP may improve pregnancy rates or cryosurvival. Furthermore, there is considerable controversy about whether the stallion's own SP or heterologous SP produces the best effect, possibly because of the variation between stallions in SP proteins or because some homologous SP remained in the sperm preparation. The SP is removed completely from stallion spermatozoa prepared by colloid centrifugation. Thus, the aim of the present study was (1) to investigate the effect of adding back SP to colloid centrifuged spermatozoa to determine its effect on spermatozoa; and (2) to investigate whether the stallion's own SP had a greater or lesser effect than heterologous SP. Conventional semen doses were sent from a stud overnight to the laboratory using standard transport conditions. Once at the laboratory, the semen samples were used for single layer centrifugation with Androcoll-E, and the resulting sperm preparations were treated with heterologous SP. Adding SP had a small but significant effect on sperm motility but no effect on the proportion of spermatozoa that had acrosome reacted. There were significant increases in hydrogen peroxide production and chromatin damage (P < 0.001). When homologous and heterologous SP were compared, considerable variation was observed between stallions, so that it was not possible to predict whether homologous or heterologous SP, or no SP, will produce the best motility for spermatozoa from any given stallion. Therefore, it is necessary to test different combinations of spermatozoa and SP to find the optimal effect on motility. The SP from most stallions increased reactive oxygen species and chromatin damage. In conclusion, the interaction between SP and spermatozoa depends on the origin of both SP and spermatozoa. If it is desirable to add SP to stallion sperm samples, it should be done directly before insemination rather than before storage, because of increased hydrogen peroxide production and sperm chromatin damage.     

Protective effects of propolis on cryopreservation of common carp (Cyprinus carpio) sperm

Cryopreservation of sperm is common procedures in aquaculture, particularly used for routine in artificial insemination. However, these application cause damages and adversely affected sperm motility, viability and consequently lower hatching rates. The objective of this study is to determine whether propolis has an effect on cryopreservation and fertilization ability and to investigate the potential protective effect of propolis on spermatozoa of Cyprinus carpio. Many studies have been done in cryopreservation offish spermatozoa, but none of them contain propolis in extender composition. The extenders were prepared by using modified Kurokura Solution to which 10% Me₂SO added with different levels of propolis (0.2, 0.4, 0.6, 0.8 and 1 mg ml⁻¹) and 10% egg yolk (as a control without propolis). The pooled semen samples diluted at the ratio of 1:9 by the extenders were subjected to cryopreservation. The percentage and duration of motility and fertilization tests of cryopreserved sperm samples have been done immediately after thawing and compared with control and fresh semen. The extenders containing propolis exhibited higher percentage motility and motility duration than control group (P < 0.05). Especially the group IV (0.8 mg ml⁻¹ propolis) and the group V (1 mg ml⁻¹ propolis) showed significant positive effects on both post thaw motility and hatching ability. The propolis maintained the integrity of the spermatozoa during the cryopreservation process. Evaluating with its contents, it has been shown that propolis is an appropriate cryoprotective agent in fish semen.     

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

Although the generation of reactive oxygen species is an activity normally associated with phagocytic leucocytes, mammalian spermatozoa were, in fact, the first cell type in which this activity was described. In recent years it has become apparent that spermatozoa are not the only nonphagocytic cells to exhibit a capacity for reactive oxygen species production, because this activity has been detected in a wide variety of different cells including fibroblasts, mesangial cells, oocytes, Leyding cells endothelial cells, thryroid cells, adipocytes, tumour cell and platelets. Since the capacity to generate reactive oxygen species is apparently so widespread, the risk-benefit equation for these potentially pernicious molecules becomes a matter of intese interest. In the case of human spermatozoa, the risk of manufacturing reactive oxygen metabolites is considerable because these cells are particularly vulnerable to lipid peroxidation. Indeed, there is now good evidence to indicate that oxygen radicals are involved in the initiation of peroxidative damage to the sperm plasma membrane, seen in many cases of male infertility. This risk is off-set by recent data suggesting that superoxide anions and hydrogen peroxide also participate in the induction of key biological events such as hyperactiavated motility and the acrosome reaction. Thus, human spermatozoa appear to use reactive oxygen species for a physiological purpose and have the difficult task of ensuring the balanced generation of these potentially harmful, but biologically important, modulators of cellular function.     

Alpha-tocopherol improves biochemical and dynamic parameters in cryopreserved boar semen

Cryopreservation is associated with the production of reactive oxygen species which lead to lipid peroxidation of sperm membranes. The objective was to determine an alpha-tocopherol concentration capable of improving the quality of cryopreserved porcine semen. Boar spermatozoa frozen with 200, 500 or 1000 microg/mL alpha-tocopherol were thawed and incubated at 37 degrees C for 4 h. Routine parameters of semen quality, susceptibility to lipid peroxidation 2-thiobarbituric acid (TBARS) and oxygen uptake were evaluated. Motility was higher (P<0.05) in samples treated with different concentrations of alpha-tocopherol up to 2 h of incubation. Viability and acrosome integrity significantly decreased during incubation (no significant differences between treatments). Two hundred micrograms per milliliter alpha-tocopherol protected spermatozoa against lipid peroxidation during incubation, but 1000 microg/mL failed to protect after 2 h of incubation. There was a negative association between TBARS and motility, suggesting that lipid peroxidation affected sperm motility. Both control and 200 microg/mL alpha-tocopherol samples preserved the capacity to generate oxidative energy up to 1 h of incubation. The addition of 200 microg/mL alpha-tocopherol in the semen extender could be useful to preserve boar spermatozoa against the oxidative stress generated by cryopreservation.     

Boronate probes for the detection of hydrogen peroxide release from human spermatozoa

Human spermatozoa are compromised by production of reactive oxygen species (ROS), and detection of ROS in spermatozoa is important for the diagnosis of male infertility. The probes 2′,7′-dichlorohydrofluorescein diacetate (DCFH), dihydroethidium (DHE), and MitoSOX red (MSR) are commonly used for detecting ROS by flow cytometry; however, these probes lack sensitivity to hydrogen peroxide (H₂O₂), which is particularly damaging to mammalian sperm cells. This study reports the synthesis and use of three aryl boronate probes, peroxyfluor-1 (PF1), carboxyperoxyfluor-1, and a novel probe, 2-(2-ethoxyethoxy)ethoxyperoxyfluor-1 (EEPF1), in human spermatozoa. PF1 and EEPF1 were effective at detecting H₂O₂ and peroxynitrite (ONOO⁻) produced by spermatozoa when stimulated with menadione or 4-hydroxynonenal. EEPF1 was more effective at detection of ROS in spermatozoa than DCFH, DHE, or MSR; furthermore it distinguished poorly motile sperm as shown by greater ROS production. EEPF1 should therefore have a significant role in the diagnosis of oxidative stress in male infertility, cryopreservation, age, lifestyle, and exposure to environmental toxicants.     

Effect of age and environmental factors on semen quality, glutathione peroxidase activity and oxidative parameters in simmental bulls

Taking into account that semen quality depends on animal age and climate conditions and that oxidative stress has been reported to be a common cause of infertility, the objective of this study was to monitor indicators of oxidative stress and antioxidant protection during four seasonal periods in service bulls of various age to get better insight into the significance of these factors upon evaluating service bull semen. The research was conducted over a year on 19 Simmental service bulls. Animals were divided into two groups according to age; Group I consisted of younger bulls aged two to four yrs (n = 9), and Group II was comprised of older bulls aged five to ten yrs (n = 10). Semen samples were obtained once in the middle of every seasonal period and blood samples for biochemical analysis were collected by jugular venipuncture immediately after ejaculate collection. The activity of total glutathione peroxidase (T-GSH-Px), selenium-dependent glutathione peroxidase (Se-GSH-Px) and selenium-independent glutathione peroxidase (non-Se-GSH-Px), together with the intensity of lipid peroxidation (thiobarbituric acid reactive substances; TBARS) and oxidative protein damage (protein carbonyl content (PCC)) were measured in seminal plasma. In samples of spermatozoa and blood serum, the activity of Se-GSH-Px and TBARS and PCC concentrations were determined. Older service bulls had significantly higher ejaculate volume in summer in comparison with younger bulls, whereas the number of spermatozoa and progressive motility percentage did not significantly vary with age. Younger animals had lower progressive motility percentage during summer than in spring, with more intensive oxidative processes observed in seminal plasma (TBARS) and spermatozoa (TBARS and PCC). Based on the results presented here, it can be concluded that younger bulls are more sensitive to elevated ambient temperatures during the summer, when intensified prooxidative processes in semen plasma and spermatozoa eventually led to decreased sperm progressive motility with consequential semen quality deterioration.     

Detection of oxidative DNA damage in human sperm and its association with sperm function and male infertility

The expanding research interest in the last two decades on reactive oxygen species (ROS), oxidative stress, and male infertility has led to the development of various techniques for evaluating oxidative DNA damage in human spermatozoa. Measurement of 8-hydroxydeoxyguanosine (8-OHdG) offers a specific and quantitative biomarker on the extent of oxidative DNA damage caused by ROS in human sperm. The close correlations of 8-OHdG level with male fertility, sperm function and routine seminal parameters indicate the potential diagnostic value of this technique in clinical applications. On the other hand, single cell gel electrophoresis (SCGE or comet assay) and terminal deoxynucleotidyl transferase (TdT) mediated dUTP nick end labeling (TUNEL) assay have also been demonstrated to be sensitive, and reliable methods for measuring DNA strand breaks in human spermatozoa. As certain technical limitations were inherent in each of these tests, it is believed that a combination of these assays will offer more comprehensive information for a better understanding of oxidative DNA damage and its biological significance in sperm function and male infertility.     

化学发光法研究莲房原花青素的体外抗氧化活性和对DNA损伤的保护作用

采用多个化学发光体系,研究了测定莲房原花青素(LSPC)的体外抗氧化活性及其对DNA损伤的保护作用。运用邻苯三酚-鲁米诺化学发光体系测定了LSPC对超氧阴离子的清除作用,硫酸铜-邻菲啰啉-抗坏血酸-双氧水、硫酸亚铁-鲁米诺-双氧水和硫酸亚铁-鲁米诺三个体系测定了LSPC对羟基自由基的清除作用,双氧水-鲁米诺体系测定了LSPC对体外双氧水的清除作用,采用硫酸铜-邻菲啰啉-抗坏血酸-双氧水-脱氧核糖核酸测定了LSPC对体外DNA损伤的保护作用。实验结果表明LSPC具有较好的体外清除活性氧和保护DNA损伤的活性,但是在不同体系中LSPC的抗氧化能力存在差异。     

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.     

Extender Supplementation with Antioxidants Selected after the Evaluation of Sperm Susceptibility to Oxidative Challenges in Goats

This study aimed to detect the most deleterious ROS for goat sperm and then supplemented the extender with a proper antioxidant. For this, 12 adult goats (aged 1–7) were used. Fresh samples were submitted to challenge with different ROS (superoxide anion, hydrogen peroxide, and hydroxyl radical) and malondialdehyde (MDA—toxic product of lipid peroxidation). After experiment 1, sperms were cryopreserved in extenders supplemented to glutathione peroxidase (Control: 0?UI/mL; GPx1: 1?UI/mL; GPx5: 5?UI/mL, and GPx10: 10?UI/mL) and catalase (Control: 0?UI/mL; CAT60: 60?UI/mL; CAT120: 120?UI/mL, and CAT240: 240?UI/mL). Each sample was evaluated by motility, plasma membrane integrity (eosin/nigrosin), acrosome integrity (fast green/rose bengal), sperm morphology, assay of the sperm chromatin structure, mitochondrial activity (3,3-diaminobenzidine), and measurement of lipid peroxidation (thiobarbituric acid reactive substances [TBARS]). It was possible to observe a mitochondrial dysfunction (DAB—Class IV) and low membrane integrity after hydrogen peroxide action. However, the high rates of TBARS were observed on hydroxyl radical. CAT240 presents the lower percentage of plasma membrane integrity. It was possible to attest that hydrogen peroxide and hydroxyl radical are the more harmful for goat sperm. Antioxidant therapy must be improving perhaps using combination between antioxidants.     

Protection by quercetin and quercetin-rich fruit juice against induction of oxidative DNA damage and formation of BPDE-DNA adducts in human lymphocytes

Flavonoids are claimed to protect against cardiovascular disease, certain forms of cancer and ageing, possibly by preventing initial DNA damage. Therefore, we investigated the protective effects of the flavonoid quercetin against the formation of oxidative DNA damage and bulky DNA adducts in human lymphocytes, both in vitro and ex vivo. First, human lymphocytes were pre-incubated with various concentrations of quercetin, followed by incubation with hydrogen peroxide; protection against oxidative DNA damage was evaluated by use of the single-cell gel electrophoresis (Comet) assay. Second, quercetin-treated human lymphocytes were challenged by treatment with benzo(a)pyrene (B(a)P), and BPDE-DNA adduct formation was measured by (32)P-postlabelling. Third, in a pilot study, lymphocytes from female volunteers who consumed a quercetin-rich blueberry/apple juice mixture for four weeks, were treated ex vivo with an effective dose of H(2)O(2) and benzo(a)pyrene, respectively, at three different time points, i.e. before (t=0 weeks), during (t=2 weeks) and after (t=4 weeks) the intervention. Results in vitro: a significant dose-dependent protection by quercetin against both the formation of oxidative DNA damage (p<0.01) and of BPDE-DNA adducts (p<0.05) was observed. Results in vivo: four weeks of juice intervention led to a significant increase in the total antioxidant capacity of plasma, as reflected by the increase of the TEAC value from 773 microM trolox equivalent at t=0 to 855 microM at t=4 weeks (p=0.04) and an increase in plasma quercetin content from 5.0 to 10.6 nM (p=0.03). After intervention, the level of oxidative damage upon ex vivo exposure to H(2)O(2) was non-significantly (p=0.07) decreased by 41%, and the BPDE-DNA adduct level induced ex vivo was non-significantly decreased by 11%. The combination of our findings in vitro and ex vivo provides evidence that quercetin is able to protect against chemically induced DNA damage in human lymphocytes, which may underlie its suggested anticarcinogenic properties.     

Hydrogen peroxide increases the activities of soxRS regulon enzymes and the levels of oxidized proteins and lipids in Escherichia coli

The effects of hydrogen peroxide treatments on Escherichia coli KS400 and AB1157 cells were assessed by monitoring the accumulation of oxidative damage products, carbonyl proteins and thiobarbituric acid-reactive substances (TBARS), as well as the activities of selected antioxidant enzymes. H(2)O(2) treatment stimulated increases in both TBARS and carbonyl protein levels in dose- and time-dependent manners in KS400 cells. The accumulation of TBARS was much more variable with H(2)O(2) treatment; TBARS content was significantly increased in response to 5 microM H(2)O(2), whereas a significant increase in carbonyl protein content occurred at 100 microM H(2)O(2). Similarly, treatment with 20 microM hydrogen peroxide for different lengths of time resulted in peak TBARS accumulation by 20 min, whereas carbonyl protein levels were significantly elevated only after 60 min. In AB1157 cells, treatment with 20 microM hydrogen peroxide for 20 min led to strong increases in both carbonyl protein and TBARS levels. This treatment also triggered increased activities of enzymes of the oxyR regulon (catalase, peroxidase, and glutathione reductase) in both strains. In the AB1157 strain, H(2)O(2) exposure also increased the activities of two enzymes of the soxRS regulon (superoxide dismutase and glucose-6-phosphate dehydrogenase) by 50-60%. The data show differential variability of lipids versus proteins to oxidative damage induced by H(2)O(2,) as well as strain-specific differences in the accumulation of damage products and the responses by antioxidant enzymes to H(2)O(2) stress.     

Comet-assay parameters as rapid biomarkers of exposure to dietary/environmental compounds -- an in vitro feasibility study on spermatozoa and lymphocytes

Twelve chemical compounds have been selected for the European NewGeneris study on the basis of their potential to damage DNA, in order to establish adequate and reliable biomarkers of exposure. These genotoxic chemicals include heterocyclic amines, organochlorines, polycyclic aromatic hydrocarbons, mycotoxins, lipid peroxidation products and alcohol. Damage in somatic cells such as lymphocytes could give rise to cancer, while damage in germ cells could not only give rise to cancer but also to heritable defects. The alkaline Comet assay, with and without metabolic activation, as well as the neutral Comet assay were used to assess DNA integrity in spermatozoa and lymphocytes after in vitro treatment with low, middle and high doses of each chemical. DNA-reactive aldehydes generated by lipid peroxidation, food mutagens such as heterocyclic amines, nitrosamine and benzo[a]pyrene produced the highest amounts of DNA damage, even without metabolic activation. Damage seen with the neutral Comet assay - detecting primarily double-strand breaks - was lower than with the alkaline assay. In general, there was increased damage in the spermatozoa by comparison with the lymphocytes, with altered slopes in the dose-response curves. The Comet assay with sperm was generally very sensitive in assessing genotoxic damage, with the Comet parameters being good biomarkers of induced DNA damage. Establishing reliable biomarkers of exposure for the evaluation of dietary/environmental carcinogens is of utmost importance to protect our health and the health of our offspring.     

Potent humanin analogue (HNG) protects human sperm from freeze-thaw-induced damage

This study was aimed to investigate the protective effect of potent humanin analogue (HNG) supplementation to freezing media on freezing-thawing induced human sperm damage. We collected semen samples with normal sperm parameters from 15 healthy men. After the swim-up processing, the motile spermatozoa from each of the men were allocated to four equal groups: In the control group, the spermatozoa were frozen in media without HNG supplementation. In the other three groups, the spermatozoa were frozen in media supplemented with different concentrations of HNG (2 μM, 10 μM and 20 μM, respectively). We analyzed the sperm motility, viability, sperm mitochondrial membrane potential, apoptosis, sperm DNA fragmentation index (DFI), reactive oxygen species (ROS) and malondialdehyde (MDA) levels, and caspase-3 activity for the sperm in each group. As a result, supplementation of HNG with 2 μM, 10 μM and 20 μM to the freezing media all significantly improved sperm motility and viability (all p < 0.05) when compared with the control group. Similarly, we found that supplementation of HNG reduced the damage to the mitochondrial membrane and DNA integrity, and inhibited the reaction of oxidative stress and the activity of caspase-3 in sperm. Although these protective effects increased with the elevated concentration of HNG in the freezing media, a final HNG concentration of 20 μM failed to exert significant improvements when compared with the concentration of 10 μM (all p > 0.05). In conclusion, our results suggested that HNG supplementation to the freezing media could protect sperm cells from freezing-thawing induced sperm damage.     

Estradiol protects cultured articular chondrocytes from oxygen-radical-induced damage

Osteoarthritis (OA) is aggravated in menopausal women possibly because of changed serum estrogen levels. Estradiol has been postulated to affect oxidative stress induced by reactive oxygen species (ROS) in articular chondrocytes. We generated ROS in cultured bovine articular chondrocytes by incubating them with combined Fe₂SO₄, vitamin C, and hydrogen peroxide. The release of thiobarbituric-acid-reactive substances (TBARS, lipid peroxidation) and lactate dehydrogenase (LDH, membrane damage) was measured photometrically. Various estradiol doses and vitamin E, serving as control with an established anti-oxidative capacity, were applied either upon each exchange of medium and during radical production (strategy 1) or only during radical production (strategy 2). In chondrocytes incubated according to strategy 1, the production of TBARS and LDH release were significantly suppressed by 10^–10–10^–4 M estradiol or by vitamin E. Under strategy 2, the production of TBARS was significantly suppressed at estradiol concentrations higher than 10^–6 M, whereas LDH release was inhibited at concentrations of 10^–6–10^–4 M. Vitamin E showed no significant effects. As repeated application of estradiol and vitamin E produced the best results, estradiol, like vitamin E, was speculated to accumulate in the plasma membrane and to decrease membrane fluidity resulting in protection against lipid peroxidation (non-genomic effect). Thus, in contrast to the neuroprotective effect of 17-estradiol in supraphysiological doses reported recently, the anti-oxidative potential of estradiol appears to protect articular chondrocytes from ROS-induced damage when the hormone is given repeatedly in a physiological range. Decreased estradiol levels may therefore contribute to menopausal OA in the long term.