Chronic Exposure to Low Doses of Mercury Impairs Sperm Quality and Induces Oxidative Stress in Rats

Mercury (Hg) is a widespread environmental pollutant that adversely affects the male reproductive system. The precise mechanisms underlying mercuric chloride (HgCl₂)-induced toxicity are not fully understood; however, evidence indicates that oxidative stress may be involved in this process. Although the adverse effects of high levels of inorganic Hg on the male reproductive system have been investigated, the effects of low levels of exposure are unknown. Therefore, the aim of this study was to investigate the effects of chronic exposure to low concentrations of HgCl₂ on sperm parameters, lipid peroxidation, and antioxidant activity of male rats. Three-month-old male Wistar rats were treated for 30 d and divided into groups: control (saline, i.m.) and HgCl₂ group (i.m., first dose 4.6 μg/kg, subsequent doses 0.07 μg/kg/d). Sperm parameters (count, motility and morphology) and biomarkers of oxidative stress in testis, epididymis, prostate, and vas deferens were analyzed. Mercury treatment produced a reduction in sperm quantity (testis and epididymis) and daily sperm production, following by decrease in sperm motility and increase on head and tail morphologic abnormalities. HgCl₂ exposure was correlated with enhanced oxidative stress in reproductive organs, represented not only by augmented lipid peroxidation but also by changes in antioxidant enzymes activity superoxide dismutase (SOD) and catalase (CAT) and nonprotein thiol levels. In conclusion, chronic exposure to low doses of Hg impaired sperm quality and adversely affected male reproductive functions, which may be due, at least in part, to enhanced oxidative stress.     

Exposure of spermatozoa to duroquinone may impair reproduction of the common carp (Cyprinus carpio) through oxidative stress

Toxicity of many waterborne organic contaminants to aquatic organisms is mediated through oxidative damages resulting from the production of reactive oxygen species (ROS). Using duroquinone as a model ROS inducer, we carried out in vitro and in vivo experiments to test the hypothesis that reproduction in common carp (Cyprinus carpio) can be impaired through oxidative damage of their spermatozoa. In vitro exposure of fish spermatozoa to 0, 12.5, 25, 50, 100 and 200 microM duroquinone for 2 h showed a significant increase in the level of ROS in a dose-dependant manner. Sperm motility was significantly reduced in all exposure groups, but lipid peroxidation (LPO) and DNA strand break (measured by comet assay) were only enhanced at 50 microM and above. A significant decrease in subsequent hatching rate was recorded in all the exposure groups, despite fertilization rate was not affected. In the in vivo experiment, spermatozoa were collected 24 and 72 h after fish received intra-peritoneal injections of 1.0 and 10 mg kg(-1) body weight duroquinone. DNA damage was clearly evident in spermatozoa of all treatment groups after 72 h exposure, and ROS was significantly enhanced in the high concentration group. LPO however, remained unchanged in both treatment groups. The overall results of both our in vitro and in vivo experiments demonstrated that duroquinone can induce ROS production in spermatozoa, which may impair sperm quality and subsequently reproductive success through oxidative stress.     

Toxic effects induced by mycotoxin fumonisin B1 on equine spermatozoa: Assessment of viability,sperm chromatin structure stability,ROS production and motility

Fumonisin B1 (FB1) is a mycotoxin produced by Fusarium species that exerts its toxic effect through interference with the sphingolipid pathway by inhibiting ceramide synthase. A FB1-dependent sperm toxicity was reported in boars. No information on FB1-related reproductive toxicity in stallions, the most sensitive animal species, has been reported. The aim of the present study was to assess the in vitro toxicity of FB1 on fresh and frozen-thawed equine spermatozoa by analyzing sperm viability, chromatin stability (SCSA) and reactive oxygen species (ROS) production by flow cytometry and sperm motility by CASA system. Fumonisin B1 did not affect viability of fresh spermatozoa after 2 h exposure up to 25 μM. Damage on sperm chromatin structure was observed only in one frozen sample after exposure up to 2.5 × 10⁻⁵ μM FB1 without associated increase of ROS. Increase of ROS, at FB1 levels up to 2.5 × 10⁻⁴ μM, was found on another frozen-thawed sperm sample, may be as a consequence of seminal plasma removal. At 7.5 and 15 μM, FB1 induced reduction of total and progressive motility.     

Detrimental effects of temephos on male fertility: An in vitro study on a mouse model

The World Health Organization recommends temephos as a nonsystemic organophosphorus pesticide due to its low mammalian toxicity compared with other chemical compounds. Although several studies have reported that temephos may be toxic under certain conditions, little research effort has been made to evaluate its effects on mammalian fertility. Therefore, the present study was designed to evaluate the effect of temephos on sperm functions and male fertility. Initially, cauda epididymis from mouse spermatozoa was incubated with temephos (0, 0.1, 1, 10, and 100 μM). Then, sperm motility and motion kinematics, capacitation status, intracellular adenosine triphosphate level, lactate dehydrogenase level, protein kinase A (PKA) activity, and degree of tyrosine phosphorylation were analyzed. Finally, the rates of fertilization and early embryonic development were evaluated. Sperm motility and motion kinematics were found to be significantly altered in temephos groups. In addition, the acrosome reaction and capacitation significantly increased and decreased in the 100 μM temephos group, respectively. Intracellular adenosine triphosphate levels significantly decreased in the 1, 10, and 100 μM temephos groups compared with that in the control group. Moreover, PKA activity and tyrosine phosphorylation significantly decreased in most temephos groups. Further, the rates of fertilization and early embryonic development significantly decreased in all temephos groups. Taken together, it was determined that temephos had harmful effects on male fertility. Therefore, the reproductive toxicity of temephos should be considered before its use.     

Inorganic mercury exposure: toxicological effects,oxidative stress biomarkers and bioaccumulation in the tropical freshwater fish matrinxã, <Emphasis Type="Italic">Brycon amazonicus</Emphasis> (Spix and Agassiz, 1829)

Alterations in the antioxidant cellular system have often been proposed as biomarkers of pollutant-mediated toxicity. This study evaluated the effects of mercury on oxidative stress biomarkers and bioaccumulation in the liver, gills, white muscle and heart of the freshwater fish matrinxã, Brycon amazonicus, exposed to a nominal and sub-lethal concentration (~20% of 96 h-LC₅₀) of 0.15 mg L^?1 of mercury chloride (HgCl₂) for 96 h in a static system. Increases in superoxide dismutase, catalase, glutathione peroxidase (GPx), glutathione S-transferase (GST) and glutathione reductase (GR) were observed in all tissues after HgCl₂ exposure, except for white muscle GR activity and hepatic GPx. In the liver and gills, the exposure to HgCl₂ also induced significant increases in reduced glutathione (GSH). Conversely, exposure to HgCl₂ caused a significant decrease in the GSH levels and an increase in the oxidized glutathione (GSSG) content in the white muscle, while both GSH and GSSG levels increased significantly in the heart muscle. Metallothionein concentrations were significantly high after HgCl₂ exposure in the liver, gills and heart, but remained at control values in the white muscle. HgCl₂ exposure induced oxidative damage, increasing the lipid peroxidation and protein carbonyl content in all tissues. Mercury accumulated significantly in all the fish tissue. The pattern of accumulation follows the order gills > liver ? heart > white muscle. In conclusion, these data suggest that oxidative stress in response to inorganic mercury exposure could be the main pathway of toxicity induced by this metal in fish.     

In vitro assessment of the adverse effects of antiretroviral drugs on the human male gamete

This study was designed to investigate the in vitro effects of didanosine, zidovudine, saquinavir and indinavir, commonly used in highly active antiretroviral therapy, on human sperm fertility parameters. Thirty semen samples from healthy men were collected and prepared by gradient density method. Aliquots of 90% fractions with >80% motile spermatozoa were incubated for 1, 3, and 6 h with different concentrations of the antiretroviral drugs (20, 40, and 80 μg/ml). Sperm motility was evaluated by computer assisted sperm analysis system. Sperm mitochondrial potential was evaluated using 3,3′-dihexyloxacarbocyanine iodide (DIOC₆) and the acrosome reaction was examined using pisum sativum agglutinin method. A dose-dependent decrease in sperm motility was observed with saquinavir. Saquinavir also induced a significant time and dose-dependent decrease in mitochondrial potential and an increase in spontaneous acrosome reaction. These findings indicate that, in vitro, higher doses of saquinavir have adverse effects on sperm motility, mitochondrial potential and acrosome reaction.     

Binding pattern and toxicological effects of lectins from genus Canavalia on bovine sperm

The aim of this study was to determine the binding patterns of Canavalia ensiformis (ConA), Canavalia boliviana (ConBol) and Canavalia brasiliensis (ConBr) lectins to bovine sperm and their effects on sperm motility, viability, lipid peroxidation, reactive oxygen species production and fertilization ability. ConA bound to whole spermatozoa, with the exception of the equatorial segment, ConBol did not interact with the acrosome region and ConBr exhibited a fragmented binding pattern. The three lectins decreased sperm motility but did not affect cell viability or lipid peroxidation. Nevertheless, ROS production was increased in comparison to controls and a reduction in the cleavage and blastocyst ratio was induced in comparison to controls. In conclusion, this study determined that structurally similar lectins interact differently with bovine sperm and affect sperm motility, viability, lipid peroxidation, ROS production and fertilization ability in various ways.     

Lead-induced changes in the stabilization of the mouse sperm chromatin

Long-term exposure of male mice to inorganic lead was previously found to reduce their fertility. In the present study chromatin stability in spermatozoa from such mice was investigated by means of quantitative cytochemical analysis. Sperm head sizes were determined and the capacity for nuclear chromatin decondensation (NCD) was evaluated after exposure to a solution of sodium dodecyl sulfate/dithiothreitol. A decreased uptake of propidium iodide (PI), a DNA intercalating dye, was found in spermatozoa from the vas deferens of the lead-exposed mice. However, after thermal denaturation of the DNA, the spermatozoa showed a higher uptake of PI in comparison to those of the controls. After reductive cleavage of S-S bonds with DTT and staining with a thiol-specific reagent (monobromobimane), significantly fewer reactive disulfide bonds were also observed in the spermatozoa. Furthermore, a significant delay in the capacity for NCD was noted. These findings indicate that exposure to lead increases the stabilization of the sperm chromatin, which in turn probably affects the decondensation of the nucleus, thereby interfering with the fertility of the mice.     

Characterisation of the prostanoid receptor mediating inhibition of smooth muscle contractility in the rat prostate gland

This study characterised the inhibitory actions of prostaglandins on smooth muscle contractility in the rat prostate gland. Immunohistochemical studies were carried out to identify and localise the two isoforms of cyclooxygenase (COX) enzyme and the subtypes of prostanoid receptors present in the rat prostate. Isolated organ bath studies were carried out to pharmacologically characterise the subtype of prostanoid receptor mediating the inhibitory effects of prostanoids on the rat prostate. Immunohistochemical studies confirmed the presence of mainly COX-2 within the prostatic stroma. Isolated organ bath studies showed that prostaglandin E₂ (PGE₂; 10 nM–10 μM) but not prostaglandin D₂ (10 nM–10 μM), $ {\hbox{PG}}{{\hbox{F}}_2}_\alpha $ (10 nM–10 μM), prostacyclin (10 nM–10 μM) or U46619 (10 nM–10 μM) inhibited nerve-mediated contractile responses to electrical field stimulation. Similarly, sulprostone (10 nM–10 μM) had no affect on the magnitude of the electrically evoked contractions. PGE₂ (0.1–10 μM) did not affect contractions elicited by noradrenaline or adenosine 5′-triphosphate. PGE₂-mediated inhibition of electrical field stimulation induced contractions was attenuated by AH 6809 (10 μM) but not SC 19220 (10 μM) or AH 23848 (10 μM). It is concluded that prostaglandins can inhibit contractions of the rat prostate gland through a prostanoid receptor of the EP₂ subtype.     

Antioxidative potential of melatonin against mercury induced intoxication in spermatozoa in vitro

Mercury is one of the most investigated natural elements and potential contaminants in the environment. Antioxidants have long been known to reduce the free radical-induced oxidative damage. Considering the antioxidant properties of melatonin, this study was aimed to evaluate the effect of melatonin on antioxidant system of rat epididymal sperm in vitro. Sperm samples were dispersed in RPS medium (pH 6.9) and incubated with mercury in the form of mercuric chloride (MC) at three different concentrations (1 μM, 10 μM, 100 μM), melatonin (MLT) at a concentration (100 μM) and mercuric chloride+melatonin (100 μM each) for 3 h at 32 °C. Sperm viability and motility were assessed every 30 min during the 3-h incubation period. An aliquot of sperm sample was homogenised, centrifuged and used for the assay of superoxide dismutase, glutathione peroxidase, glutathione reductase, TBARS assay to detect lipid peroxidation and hydrogen peroxide generation assay. Samples treated with mercury showed a dose-dependent decrease in motility while there was no significant decrease in sperm viability. In mercury-incubated sperm, the activity of superoxide dismutase, glutathione peroxidase and glutathione reductase decreased significantly while TBARS levels and H₂O₂ generation were increased in a dose-dependent manner. Co-incubation of sperm with mercury and melatonin exhibited no significant changes in the levels of motility, viability and antioxidant indices as compared to untreated controls. The results suggest that graded doses of mercury elicit depletion of antioxidant defense system in sperm without altering the viability and melatonin treatment was found to significantly inhibit oxidative damage caused by mercury.     

Antioxidants and reactive oxygen species in human fertility

The cellular components of the human reproductive system are as vulnerable as other cells to the potential detrimental effects of reactive oxygen species (ROS). Antioxidant protection is thus required, though not yet fully characterized, at sites of gametogenesis, fertilization and implantation. Spermatozoa are highly susceptible to oxidative damage due to the high content of polyunsaturated fatty acids within their plasma membrane and such damage may underlie certain aspects of male infertility. However, oral antioxidant therapy with, for example, Vitamin E or glutathione has to date only achieved limited success in treatment programmes. Infertility treatments involve in vitro manipulation of gametes and embryos, ranging from simple spermatozoa preparation techniques to several days culture, exposing cells to increased oxygen levels and potential oxidative stress compared with in vivo. A considerable body of data has demonstrated the benefits for animal embryo culture and human sperm preparation of antioxidant supplementation as well as the removal of sources of ROS such as leucocytes, although data supporting supplementation for human embryo culture are limited. However, the use of exogenous superoxide dismutase may improve embryo development to the blastocyst stage. Evidence is accumulating for a role for ROS in signalling events mediating both sperm capacitation and luteal function. Potential also exists for ROS (including nitric oxide) to fulfill as yet unidentified roles in modulation signalling, gene expression and/or apoptotic events during fertilization, embryo development and implantation. Increasing knowledge of the mechanisms whereby ROS and endogenous antioxidant systems influence reproductive processes can assist to optimise the application of exogenous antioxidants to fertility treatment.     

Copper attenuates early and late biochemical alterations induced by inorganic mercury in young rats

Mercury (Hg), a divalent metal, produces adverse effects predominantly in the renal and central nervous systems. The aim of this study was to determine the effectiveness of copper (Cu) in prevention of mercuric mercury (Hg²⁺)-mediated toxic effects as well as the role metallothioneins (MT) play in this protective mechanism in young rats. Wistar rats were treated subcutaneously with saline (Sal) or CuCl₂.2H₂O (Cu 2.6 mg/kg/day) from 3 to 7 days old and with saline or HgCl₂ (Hg 3.7 mg/kg/day) from 8 to 12 days old. The experimental groups were (1) Sal-Sal, (2) Cu-Sal, (3) Sal-Hg, and (4) Cu-Hg. MTs and metal contents were determined at 13 and 33 days of age. Porphobilinogen synthase (PBG-synthase) activity as well as renal and hepatic parameters were measured at 33 days. At 13 day, Hg²⁺ exposure increased hepatic MT, Hg, zinc (Zn) and iron (Fe) levels, in kidney elevated Cu and Hg and decreased renal Fe concentrations, accompanied by elevated blood Hg levels. At 33 days, Hg²⁺ exposure inhibited renal PBG-synthase activity, increased serum urea levels and lowered Fe and Mg levels. Copper partially prevented the rise in blood Hg and liver Fe noted at 13 days; and completely blocked urea rise and diminished renal PBG-synthase activity inhibition at 33 days. In 13-day-old rats, Cu exposure redistributed the Hg in the body, decreasing hepatic and blood levels while increasing renal levels, accompanied by elevated renal and hepatic MT levels in Hg²⁺-exposed animals. These results suggest that hepatic MT might bind to hepatic and blood Hg for transport to the kidney in order to be excreted.

Abbreviations: MT: metallothioneins; PBG-synthase: porphobilinogen synthase.     

Influence of chlorocholinechloride-treated wheat on selected in vitro fertility parameters in male mice

The aim of this study was to evaluate the influence of feeding with food and water containing chlorocholinechloride (CCC) on the fertility of male mice in a two-generation study. For this purpose the number of testicular spermatozoa and the relative proportion of primary and secondary spermatocytes involved in spermatogenesis were measured. Furthermore, the fertility of epididymal spermatozoa from tested male mice was investigated in a special in-vitro fertilization system. The experimental food was composed of CCC-treated wheat in the first experiment and CCC-free wheat and water mixed with pure CCC in the second experiment. The CCC residue content in the treated food and water was 0.21 mg/kg and 0.2 mg/L, respectively. Under the influence of feeding with CCC-treated wheat (Experiment 1) the fertilization and cleavage rates of oocytes incubated with spermatozoa from CCC-fed mice were reduced: the fertilization rate 65.1% vs. 21.1% and the cleavage rate 51.9% vs. 20.3%, p < 0.01 (control feeding vs. CCC feeding, respectively). Feeding of sperm donors with pure CCC mixed with untreated wheat pellets or water (Experiment 2) led to a reduction in the fertilization and cleavage rate (control: 60.8%, 32.4%; CCC-food: 29.8%, 12.1%; CCC-water: 30.1%, 10.2%; CCC-food/water: 36.6%, 12.5%; p < 0.01, respectively). The normal course of spermatogenesis was unchanged after the exposure to CCC. Testicular weight, the number of spermatozoa, and the proportion of haploid, diploid, and tetraploid testicular cells were not influenced. However, the functional competence of epididymal spermatozoa from CCC-fed donors was reduced, resulting in a significantly diminished fertilization and cleavage rate in vitro. The results suggest that CCC could interfere with epididymal protein secretion and the process of sperm maturation during passage through the epididymis.     

Melatonin Protects Against Mercury(II)‐Induced Oxidative Tissue Damage in Rats

Abstract: Mercury exerts a variety of toxic effects in the body. Lipid peroxidation, DNA damage and depletion of reduced glutathione by Hg(II) suggest an oxidative stress‐like mechanism for Hg(II) toxicity. Melatonin, the main secretory product of the pineal gland, was recently found to be a potent free radical scavenger and antioxidant. N‐Acetylcysteine, a precursor of reduced glutathione and an antioxidant, is used in the therapy of acute heavy metal poisoning. In this study the protective effects of melatonin in comparison to that of N‐acetylcysteine against Hg‐induced oxidative damage in the kidney, liver, lung and brain tissues were investigated. Wistar albino rats of either sex (200–250 g) were divided into six groups, each consisting of 8 animals. Rats were intraperitoneally injected with 1) 0.9% NaCl, control (C) group; 2) a single dose of 5 mg/kg mercuric chloride (HgCl₂), Hg group; 3) melatonin in a dose of 10 mg/kg, 1 hr after HgCl₂ injection, Hg‐melatonin group; 4) melatonin in a dose of 10 mg/kg one day before and 1 hr after HgCl₂ injection, melatonin‐Hg‐melatonin group; 5) N‐acetylcysteine in a dose of 150 mg/kg, 1 hr after HgCl₂ injection, Hg‐N‐acetylcysteine group, and 6) N‐acetylcysteine in a dose of 150 mg/kg one day before and 1 hr after HgCl₂ injection, N‐acetylcysteine‐Hg‐N‐acetylcysteine group. Animals were killed by decapitation 24 hr after the injection of HgCl₂. Tissue samples were taken for determination of malondialdehyde, an end‐product of lipid peroxidation; glutathione (GSH), a key antioxidant, and myeloperoxidase activity, an index of neutrophil infiltration. The results revealed that HgCl₂ induced oxidative tissue damage, as evidenced by increases in malondialdehyde levels. Myeloperoxidase activity was also increased, and GSH levels were decreased in the liver, kidney and the lungs. All of these effects were reversed by melatonin or N‐acetylcysteine treatment. Since melatonin or N‐acetylcysteine administration reversed these responses, it seems likely that melatonin or N‐acetylcysteine can protect all these tissues against HgCl₂‐induced oxidative damage.     

Reactive oxygen species induced by beauvericin,patulin and zearalenone in CHO-K1 cells

The cytotoxic effects of mycotoxins, induction of reactive oxygen species (ROS) and generation of lipid peroxidation products in CHO-K1 cells were determined as function of increasing time of exposure and concentrations of beauvericin (BEA), patulin (PAT) and zearalenone (ZEA). The end points were evaluated after 24 h of exposure, by the tetrazolium salt (MTT) and neutral red (NR) assays. The IC₅₀ values obtained on the MTT and NR assays ranged from 0.69 to 79.40 μM and 4.40 to 108.76 μM, respectively. To determine the intracellular production of ROS, the intensity of fluorescence emitted from the probe H₂-DCFDA was measured. The relative intensity of fluorescence from cells incubated with BEA, PAT and ZEA was approximately 4-, 7- and 4-fold higher in comparison with control cells at 0 min, respectively. Lipid peroxidation induced by ROS generation was assessed using the thiobarbituric acid reactive substances (TBARS) method for 2, 24 and 48 h. The malondialdehyde (MDA) production was increased with BEA and PAT exposure in a concentration- and time-dependent manner. MDA was not increased after 1 and 5 μM ZEA exposures for 2 h, but was slightly increased at 50 μM.In conclusion, PAT was the most cytotoxic mycotoxin to CHO-K1 cells, followed by BEA and ZEA. Mycotoxins reduce cell viability correlated with the increases of ROS generation and MDA formation in concentration- and time-dependent manner. These data suggested that cytotoxicity and ROS generation are mechanisms of mycotoxins mediated toxicity.     

Effect of the organophosphate insecticide chlorpyrifos exposure on oxidative stress and quality of Salmo coruhensis spermatozoa

The use of pesticides has been increasing along with increasing farming activities and has caused deleterious environmental impacts. Non-target organisms in particular, including fish, are affected by pesticides. In this work, the impacts of Chlorpyrifos (CPF) on sperm oxidative stress markers and sperm motility were investigated in vitro. CPF concentrations were 0?μg/L (control), 5?μg/L, 10?μg/L and 15?μg/L. Lipid peroxidation [malondialdehyde (MDA)], nonenzymatic antioxidants [glutathione (GSH)] and enzymatic [superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT)] activities in sperm cells were examined for the determination of oxidative stress status. Our findings showed that motility and survival of sperm cells significantly decreased with exposure to Chlorpyrifos. Biochemical assays revealed that CAT activity and levels of MDA and, GSH increased in spermatozoa based on CPF concentration while activity of GSH-Px and SOD decreased. Consequently, spermatozoa were highly sensitive to CPF exposure. It can be deduced that CPF has the potential to disrupt sperm quality and to cause to oxidative stress in sperm cells of S. coruhensis.     

精液密度梯度离心联合上游法优选的意义

目的 观察密度梯度离心法联合上游法优选精子前后各项参数的变化情况,证实优选技术对精液参数的改善作用,探讨它们之间的内在联系.方法 密度梯度离心法联合上游法精子优选前后,使用计算机辅助精子活动分析仪检测精子活动力变化;使用流式细胞仪,检测早期凋亡、MMP和细胞内ROS;使用单细胞凝胶电泳观察nDNA完整性变化.结果 优选后精子运动能力、正常形态率和nDNA完整性明显提高,差异具有统计学意义;优选前,MMP与a级精子百分比、VSL具有正相关（相关系数分别为0.641,0.708,P＜0.05）;当白细胞≤1 × 10^6/ml时,优选前和优选后正常形态率与ROS呈负相关（相关系数分别为-0.629,-0.685,P＜0.05）.结论 密度梯度离心法联合上游法优选精子是安全有效的方法;MMP能反映精子的运动能力;形态不正常的精子是ROS的重要来源.     

New insights into male (in)fertility: the importance of NO

Infertility is a global problem that is on the rise, especially during the last decade. Currently, infertility affects approximately 10–15% of the population worldwide. The frequency and origin of different forms of infertility varies. It has been shown that reactive oxygen and nitrogen species (ROS and RNS) are involved in the aetiology of infertility, especially male infertility. Various strategies have been designed to remove or decrease the production of ROS and RNS in spermatozoa, in particular during in vitro fertilization. However, in recent years it has been shown that spermatozoa naturally produce a variety of ROS/RNS, including superoxide anion radical (O₂^⋅−), hydrogen peroxide and NO. These reactive species, in particular NO, are essential in regulating sperm capacitation and the acrosome reaction, two processes that need to be acquired by sperm in order to achieve fertilization potential. In addition, it has recently been shown that mitochondrial function is positively correlated with human sperm fertilization potential and quality and that NO and NO precursors increase sperm motility by increasing energy production in mitochondria. We will review the new link between sperm NO-driven redox regulation and infertility herein. A special emphasis will be placed on the potential implementation of new redox-active substances that modulate the content of NO in spermatozoa to increase fertility and promote conception.

Linked Articles

This article is part of a themed section on Pharmacology of the Gasotransmitters. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-6     

β2-adrenoceptor agonists can both stimulate and inhibit glucose uptake in mouse soleus muscle through ligand-directed signalling

The β-adrenoceptor agonists BRL37344 and clenbuterol have opposite effects on glucose uptake in mouse soleus muscle, even though the β₂-adrenoceptor mediates both effects. Different agonists may direct the soleus muscle β₂-adrenoceptor to different signalling mechanisms. Soleus muscles were incubated with 2-deoxy[1-¹⁴C]-glucose, β-adrenoceptor agonists, other modulators of cyclic AMP, and inhibitors of intracellular signalling. The adenylyl cyclase activator forskolin (1 μM), the phosphodiesterase inhibitor rolipram (10 μM) and BRL37344 (10, but not 100 or 1,000, nM) increased, whereas clenbuterol (100 nM) decreased, glucose uptake. Forskolin increased, whereas clenbuterol decreased, muscle cyclic AMP content. BRL37344 (10 nM) did not increase cyclic AMP. Nevertheless, protein kinase A (PKA) inhibitors prevented the stimulatory effect of BRL37344. Nanomolar but not micromolar concentrations of adrenaline stimulated glucose uptake. After preincubation of muscles with pertussis toxin (100 ng/ml), 100 nM clenbuterol, 0.1-10 μM adrenaline and 100 nM BRL37344 stimulated glucose uptake. Clenbuterol increased the proportion of phosphorylated to total β₂-adrenoceptor. Inhibitors of phosphatidylinositol 3-kinase (PI3K) and the stress-activated mitogen-activated protein kinase (MAPK), but not of the classical MAPK pathway, prevented stimulation of glucose uptake by BRL37344. Elevation of the cyclic AMP content of soleus muscle stimulates glucose uptake. Clenbuterol, and high concentrations of adrenaline and BRL37344 direct the β₂-adrenoceptor partly to Gα_i, possibly mediated by β₂-adrenoceptor phosphorylation. The stimulatory effect of 10 nM BRL37344 requires the activity of PKA, PI3K and p38 MAPK, consistent with BRL37344 directing the β₂-adrenoceptor to Gα_s. Ligand-directed signalling may explain why β₂-adrenoceptor agonists have differing effects on glucose uptake in soleus muscle.     

Mangiferin,a dietary xanthone protects against mercury‐induced toxicity in HepG2 cells

Mercury is one of the noxious heavy metal environmental toxicants and is a cause of concern for human exposure. Mangiferin (MGN), a glucosylxanthone found in Mangifera indica, reported to have a wide range of pharmacological properties. The objective of this study was to evaluate the cytoprotective potential of MGN, against mercury chloride (HgCl₂) induced toxicity in HepG2 cell line. The cytoprotective effect of MGN on HgCl₂ induced toxicity was assessed by colony formation assay, while antiapoptotic effect by fluorescence microscopy, flow cytometric DNA analysis, and DNA fragmentation pattern assays. Further, the cytoprotective effect of MGN against HgCl₂ toxicity was assessed by using biochemical parameters like reduced glutathione (GSH), glutathione‐S‐transferase (GST), superoxide dismutase (SOD), catalase (CAT) by spectrophotometrically, mitochondrial membrane potential by flowcytometry and the changes in reactive oxygen species levels by DCFH‐DA spectrofluoremetric analysis. A significant increase in the surviving fraction was observed with 50 μM of MGN administered two hours prior to various concentrations of HgCl₂. Further, pretreatment of MGN significantly decreased the percentage of HgCl₂ induced apoptotic cells. Similarly, the levels of ROS generated by the HgCl₂ treatment were inhibited significantly (P < 0.01) by MGN. MGN also significantly (P < 0.01) inhibited the HgCl₂ induced decrease in GSH, GST, SOD, and CAT levels at all the post incubation intervals. Our study demonstrated the cytoprotective potential of MGN, which may be attributed to quenching of the ROS generated in the cells due to oxidative stress induced by HgCl₂, restoration of mitochondrial membrane potential and normalization of cellular antioxidant levels. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2012.