Bisphenol A induced oxidative stress and apoptosis in mice testes: Modulation by selenium.

Spermatogenesis, a highly coordinated process, is prone to environmental insults which may lead to impaired spermatogenesis or, at worst, infertility. Bisphenol A (BPA) is a well-known global environmental toxicant and a ubiquitous oestrogenic chemical. This study evaluated the role of selenium (0.5 ppm sodium selenite/kg diet) on spermatogenesis after BPA treatment in different groups of male BALB/c mice: control, selenium, BPA and selenium+BPA. Markers of oxidative stress and apoptosis were evaluated in testis after BPA treatment. Significant decrease in sperm concentration and motility and increased reactive oxygen species(ROS) and LPO levels were seen in BPA group. Histopathological changes revealed extensive vacuolisation, lumen devoid of spermatozoa and decreased germ cell count, confirmed by testicular germ cell count studies. TUNEL assay for apoptosis showed increased number of TUNEL-positive germ cells in BPA group with increased percentage apoptotic index. However, in Se+BPA group, histopathological studies revealed systematic array of all germ cells, preserved basement membrane with relatively less vacuolisation, improved sperm parameters and ROS and LPO levels and decreased number of TUNEL-positive germ cells. These results clearly demonstrate the role of selenium in ameliorating oxidative stress and apoptosis induced upon BPA treatment in mice and can be further used as therapeutic target in male infertility.

Protective role of dietary-supplemented selenium and vitamin E in heat-induced apoptosis and oxidative stress in mice testes.

This study evaluated the role of selenium (0.5 ppm selenium/kg diet) and vitamin E (200 mg alpha-tocopherol/kg diet) on spermatogenesis after scrotal hyperthermia (42 °C, 30 min) in six different groups of male Balb/c mice; Control, Heat shock, Selenium, Selenium+heat shock, Vitamin E and Vitamin E+heat shock. Markers of the stress responses, hypoxia and oxidative stress, were evaluated in testis after the hyperthermic shock. Hyperthermia caused an elevated mRNA expression of hypoxia-inducible factor-1 alpha, haem oxygenase-1 (HMOX-1) and also glutathione peroxidase activity and reactive oxygen species (ROS). Apoptosis was evaluated by TUNEL assay and further by mRNA expression of Bcl-2, caspase 3, 8, 9, bid and AKT. TUNEL assay showed significant increase in apoptotic index of spermatogenic cells, whereas decrease in mRNA expression of Bcl-2, AKT and increase in caspase 3, 8, 9 and Bid in heat-shock group were observed. A significant decrease in sperm motility was also seen in heat-shock group in comparison with control group. These observations clearly indicate the development of oxidative stress and apoptosis after hyperthermia. Further analysis in Selenium+heat shock and Vitamin E+heat shock groups showed protective behaviour as compared to effects in heat-shock group which could be of therapeutic interest in future studies.

Modulatory effects of Azadirachta indica leaf extract on cutaneous and hepatic biochemical status during promotion phase of DMBA/TPA-induced skin tumorigenesis in mice.

The modulation in biochemical status of skin and hepatic tissue at the time point of commencement of promotion stage of skin carcinogenesis in mice and its intervention with aqueous Azadirachta indica leaf extract (AAILE) were investigated. 7,12-Dimethylbenz(a)anthracene (DMBA, 500 nmol/100 ul of acetone) was applied topically for 2 weeks (twice weekly), followed by phorbol-12-myristate-13-acetate (TPA, 1.7 nmol/100 ul) twice weekly for 6 weeks on the depilated skin of mice and AAILE was administered orally at a dose level of 300 mg/kg body wt thrice a week for 10 weeks. DMBA/TPA treatment upregulated the phase I enzymes in skin and hepatic tissue, as revealed by the increased cytochrome P450 (CYP) and cytochrome b5 (cyt b5) levels and aryl hydrocarbon hydroxylase (AHH) activity when compared to the control group and differentially modulated the activities of phase II enzymes like glutathione-s-transferase (GST), DT-diaphorase (DTD) and uridine diphosphate glucuronosyltransferase (UDP-GT). AAILE treatment decreased the DMBA/TPA-induced increase in cutaneous CYP level and enhanced the DTD and UDP-GT activities when compared with DMBA/TPA group. In the hepatic tissue of AAILE + DMBA/TPA group, an increase in UDP-GT activity was observed when compared to DMBA/TPA group. DMBA/TPA treatment did not alter the skin lipid peroxidation (LPO) level when compared to control group, however, in the animals that received AAILE treatment along with DMBA/TPA, a significant increase in LPO was observed when compared to control group. This was associated with a decrease, in cutaneous reduced glutathione (GSH) level of AAILE + DMBA/TPA group. Enhanced LPO level was observed in the hepatic tissue of DMBA/TPA and AAILE + DMBA/TPA groups when compared to control group. However, no alteration was observed in their hepatic GSH levels. The micronuclei score in hepatic tissue did not exhibit significant inter-group differences. The results of the present study suggest that apart from skin, liver may be affected during DMBA/TPA-induced skin tumorigenesis. AAILE treatment has the ability to modulate these changes potentially influencing the process of tumor formation. These findings seem to be important to carcinogenesis and its intervention with anti-cancer agents.

Azadirachta indica acts as a pro-oxidant and modulates cell cycle associated proteins during DMBA/TPA induced skin carcinogenesis in mice.

The present study was designed to determine the modulatory effect of aqueous Azadirachta indica leaf extract (AAILE) on cell cycle-associated proteins during two-stage skin carcinogenesis in mice. Considering the dual role of reactive oxygen species in cancer and its chemoprevention, the levels of lipid peroxidation (index of peroxidative damage) were also determined. Skin tumours were induced by topical application of 7,12-dimethylbenz(a)anthracene (DMBA) as a carcinogen followed by the repetitive application of 12-O-tetradecanoylphorbol-13-acetate (TPA) as a promoter. Skin tumours obtained in the DMBA/TPA group exhibited enhanced expression of proliferating cell nuclear antigen (PCNA, index of proliferation), p21 and cyclin D1, with no alterations in p53 expression in comparison to the control group. Tumours in AAILE + DMBA/TPA group exhibited low PCNA and cyclin D1 expression and enhanced expression of p53 and p21 in comparison to the DMBA/TPA group. The skin tumours obtained in the AAILE + DMBA/TPA group exhibited high lipid peroxidation levels in comparison to the tumours obtained in the DMBA/TPA group. The observations of the present study suggest that AAILE behaves as a pro-oxidant in the tumours, thereby rendering them susceptible to damage, which eventually culminates into its anti-neoplastic action. Also, cell cycle regulatory proteins may be modulated by AAILE and could affect the progression of cells through the cell cycle.

Azadirachta indica exerts chemopreventive action against murine skin cancer: studies on histopathological, ultrastructural changes and modulation of NF-kappaB, AP-1, and STAT1.

The present study reports the histopathological, ultrastructural changes and modulation of NF-kappaB, AP-1, and STAT 1 during skin carcinogenesis in LACA mice and its intervention with Azadirachta indica. Skin tumors were induced by topical application of 7,12-dimethylbenz(a)anthracene (DMBA) (500 nmol/100 microl for 2 weeks) followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) (1.7 nmol/100 microl of acetone, twice weekly) as a promoter. Male LACA mice were divided into four groups: Control, DMBA/TPA, aqueous Azadirachta indica leaf extract (AAILE), and AAILE + DMBA/TPA. AAILE was administered orally at a dose level of 300 mg/kg body weight three times a week for 20 weeks. Topical application of DMBA/ TPA to the skin resulted in well-developed squamous cell carcinomas characterized by hyperproliferation, hyperkeratosis, and corrugation of the epidermis. Degenerative changes were observed in the tumors of AAILE + DMBA/TPA-treated animals. Scanning electron microscopy revealed surface disruptions and certain rounded structures on the skin tumors of DMBA/TPA-treated animals. Topographical changes were also observed in the tumors of AAILE + DMBA/TPA-treated animals, which resembled regions of degeneration. Tumors obtained in DMBA/TPA group were associated with enhanced expression of NF-kappaB and AP-1 when compared to the control counterparts. Inhibition in tumorigenesis in response to A. indica treatment was accompanied by an overexpression of STAT 1 and AP-1 and decrease in NF-kappaB expression. The results of the present study provide a basis for the chemopreventive potential of A. indica against murine skin carcinogenesis.

Chemopreventive activity of Azadirachta indica on two-stage skin carcinogenesis in murine model.

The present study reports the chemopreventive activity of aqueous Azadirachta indica leaf extract (AAILE) in a murine two-stage skin carcinogenesis model. Skin tumors were induced by topical application of 7,12-dimethylbenz(a)anthracene (DMBA) (500 nmol/100 µL for 2 weeks) followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) (1.7 nmol/100 µL of acetone, twice weekly) as a promoter. Male LACA mice were divided into four groups: control, DMBA/TPA, AAILE and AAILE + DMBA/TPA. AAILE was administered orally at a dose level of 300 mg/kg body weight thrice a week for 20 weeks. 100% tumor incidence was observed in the DMBA/TPA treated animals, whereas the AAILE + DMBA treated animals exhibited a tumor incidence of 58.3% only. A significant reduction in the mean tumor burden (54.5%) and mean tumor volume (45.6%) was observed in the mice that received AAILE along with DMBA/TPA. Topical application of DMBA/TPA to the skin resulted in well-developed carcinomas associated with decreased expression of pro-apoptotic protein such as caspase 3 and enhanced expression of antiapoptotic protein such as bcl-2 when compared with the control counterparts. However, adminstration of AAILE inhibited skin carcinogenesis with induction of pro-apoptotic proteins such as bax, caspase 3, caspase 9 and inhibition of antiapoptotic proteins such as bcl-2. These results suggest that the induction of apoptosis may be one of the mechanisms underlying the chemopreventive effects of A. indica.

Influence of vitamin E on alcohol-induced changes in antioxidant defenses in mice liver.

It is widely accepted that oxidative stress plays a central role in alcohol-induced pathogenesis. Redox-sensitive transcription factors nuclear factor-kappaB (NFkappaB) and activator protein-1 (AP1) are involved in development of alcohol-related diseases. Because of its antioxidative properties, vitamin E is believed to prevent diseases associated with oxidative stress. The aim of the present study was to evaluate the molecular mechanism associated with alcohol-induced oxidative stress and its prevention with vitamin E supplementation. Male Balb/c mice were divided into three groups viz. group I (control), group II (alcohol-treated) and group III (alcohol-treated + Vitamin E supplemented). Group II received 8% alcohol as sole source of drinking fluid while group III was given Vitamin E orally as 5 IU/kg body weight along with 8% alcohol. After 15 days, increases in lipid peroxidation, catalase and GST activity and decreases in SOD activity as well as redox ratio were observed in group II. This was associated with increased apoptosis in this group. Vitamin E supplementation restored the redox status, reduced apoptosis and prevented oxidative stress. Further mRNA expression of cjun, cfos, p65 (NFkappaB) showed increased expression during oxidative stress in group II. Although inhibition in NFkappaB activation was observed with Vitamin E, on the contrary it stimulated AP1 expression. This study supports the fact that alcohol promoted oxidative stress and is the major cause of alcohol toxicity in liver. Vitamin E can mitigate the toxic effects of alcohol and can be suitably used as a potential therapeutic agent for alcohol-induced oxidative damage in liver.

Apoptosis induced by modulation in selenium status involves p38 MAPK and ROS: implications in spermatogenesis.

Selenium has been linked to cell survival and apoptosis. Apoptosis plays an important role in spermatogenesis. Evidence suggests that reactive oxygen species induce apoptotic pathways. Although the mechanism by which oxidants mediate apoptosis is not well defined, the mitogen-activated protein kinase (MAPK) and caspase pathways have been implicated in apoptosis. Thus, this study was designed, keeping in view the critical balance between cell proliferation and apoptosis for normal spermatogenesis, and the requirement of selenium for the maintenance of male fertility. The intracellular selenium status was modulated by feeding selenium-deficient and -excess diet for 8 weeks. Involvement of p38 MAPK and ROS was monitored. Apoptotic factors like caspases and Bcl-2 were also analyzed. It was observed that the selenium levels were altered along with an increase in ROS generation and lipid peroxidation. mRNA expression of p38, caspases 3, and 8 increased, whereas that for Bcl-2 decreased. Western immunoblot analysis and immunohistochemical localization studies for p38 showed a similar increase. Integrity of DNA was altered in the form of apoptotic cells. Thus, the results presented in this study suggest that sodium selenite causes apoptosis and the toxicity of selenite is mediated by increase in ROS. Morevoer, ROS generation is associated with increased expression of p38, caspases 3 and 8, and decreased Bcl-2 expression. Our data indicate that p38 participates in testicular apoptosis and that selenium is required for maintenance of the critical balance between cell death and proliferation.

Diminished reproductive potential of male mice in response to selenium-induced oxidative stress: involvement of HSP70, HSP70-2, and MSJ-1.

The oxidative stress imposed by nutritional variations in selenium (Se) has plausible role in reproductive toxicology and affects the reproductive potential. Also, the expression of heat shock proteins (HSPs) is a highly regulated event throughout the process of spermatogenesis and is modulated by stressful stimuli. This prompted us to investigate the possibility that Se-induced oxidative stress may affect the fertility status by altering the expressions of the constitutive and inducible HSP70 proteins, having crucial role in spermatogenesis. Different Se status-deficient, adequate, and excess, male Balb/c mice were created by feeding yeast-based Se-deficient diet (group I) and deficient diet supplemented with Se as sodium selenite at 0.2 and 1 ppm Se (group II and III) for a period of 8 weeks. After completion of the diet-feeding schedule, a significant decrease in the Se and glutathione peroxidase (GSH-Px) levels was observed in the Se-deficient group (I), whereas Se-excess group (III) demonstrated an increase. Increased levels of reactive oxygen species, malondialdehyde, and alterations in the redox status in both groups I and III indicated oxidative-stressed conditions. There was an overall reduced fertility status in mice supplemented with Se-deficient and Se-excess diet. The mRNA and protein expression of HSP70 was found to be elevated in these two groups, whereas the expression patterns of HSP70-2 and MSJ-1 demonstrated a reverse trend. In vitro CDC2 kinase assay showed reduced kinase activity in group I and group III. These findings suggest that Se-induced oxidative stress by differentially regulating various HSP70s can affect its downstream factors having crucially important role in differentiation of germ cells and completion of spermatogenesis. Therefore, it can provide an insight into the mechanism(s) by which the oxidative stress-induced reproductive toxicity can lead to increased apoptosis/growth arrest and infertility. This will thus add new dimensions to the molecular mechanism underlying the human male infertility and open new vistas in the development of various chemo-preventive methods.

Selenium variation induced oxidative stress regulates p53 dependent germ cell apoptosis: plausible involvement of HSP70-2.

BACKGROUND: Selenium at altered concentration causes abnormal spermatogenesis and male infertility. However, the exact mechanism behind this is still unexplored. AIMS: It was aimed to investigate if Se induced oxidative stress alters the expressions of testis specific HSP70-2 protein, that is crucial in normal spermatogenesis. The study was extended to delineate the apoptotic process after this change if any. METHODS: To create different Se status-deficient, adequate and excess, male Balb/c mice were fed yeast based Se deficient diet (group I) and this diet supplemented with Se as sodium selenite at 0.2 and 1 ppm Se (group II and III, respectively) for 8 weeks. RESULTS: After the feeding schedule, a dose dependent change in the Se levels and GSH-Px activity was observed in samples of different Se diet fed group animals as reported in earlier studies. Changes in the redox status in both groups I and III indicated oxidative stress conditions. The mRNA and protein expression of HSP70-2 was found to be reduced in group I and III, whereas, the expressions of p53 demonstrated a reverse trend. Increased apoptosis was observed in the group I and III animals as indicated by increased apoptotic index (AI) on the TUNEL stained sections and by DNA fragmentation indicating DNA damage in these groups. CONCLUSION: These findings suggest that Se variations induced oxidative stress leads to germ cell apoptosis and downregulation of HSP70-2. This study suggests that there can be a possible link between these two events and the fate of HSP70-2 in case of oxidative damage can provide an insight into the mechanism(s) by which the nutritional variation induced oxidative stress can affect reproductive potential and thus demonstrates the importance of nutrition at molecular level as well.

Effect of vitamin E on alcohol-induced changes in oxidative stress and expression of transcription factors NFkappaB and AP-1 in mice brain cerebral hemispheres.

Redox sensitive transcription factors nuclear factor kappaB (NF-kappaB) and activator protein-1 are involved in the pathogenesis of alcohol-induced disorders. Because of its antioxidative properties, vitamin E may help prevent oxidative stress-induced disorders. The aim of the present study was to delineate the molecular mechanisms associated with alcohol-induced oxidative stress and to see whether vitamin E supplementation counters the alcohol-induced adverse effects. The results showed that vitamin E supplementation restored the redox status and thus prevented the alcohol-induced oxidative stress. Further measurements of the mRNA expressions of cjun, cfos, p65 (NFkappaB) indicated an increase in their expression during oxidative stress. Although Vit E inhibited NFkappaB activation, it stimulated AP1 expression. The results support the findings that alcohol induces oxidative stress in nervous tissue. The data further show that vitamin E can mitigate the toxic effects of alcohol and thus can be suitable as a potential therapeutic agent for alcohol-induced oxidative damage in brain.

Lantadenes and their esters as potential antitumor agents.

Lantadenes are pentacyclic triterpenoids of the weed Lantana camara. Five new lantadenes (14-18) and their methyl esters (20-24) were synthesized, characterized, and screened for cytotoxicity against four human cancer cell lines. The parent compound (1) and the four most active compounds (15, 16, 21, and 22) were further studied for their in vivo tumor inhibitory potential on squamous cell carcinogenesis in Swiss albino mice induced by 7,12-dimethylbenz[a]anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA). These results were supported by histopathological studies and discussed in terms of structure-activity relationships. The results inferred the importance of the groups attached to C-22 and C-17 in relation to the antitumor activity of these compounds.

Decreased glutathione levels potentiate the apoptotic efficacy of selenium: possible involvement of p38 and JNK MAPKs--in vitro studies.

The present study was designed to evaluate the apoptotic efficacy of selenium (Se) under glutathione-deprived conditions. Testicular cells were used as a model to assess the above. For the study, cells were maintained for 4 h under various treatments; control (media only), selenium (0.5 microM and 1.5 microM), BSO (20 nM), selenium + BSO (0.5 microM Se + 20 nM BSO and 1.5 microM Se + 20 nM BSO). The treated cells were harvested for various estimations viz. viability, GSH, GSSG, redox ratio, ROS generation and integrity of DNA. mRNA was extracted for RT-PCR analysis of JNK, p38, caspase 3 and Bcl-2. It was observed that the cell viability decreased concomitant with the decrease in GSH levels, increase in GSSG levels and increase in the generation of ROS in the combined treatment group in comparison to control and individual treatments. Also, there was an increase in the mRNA expression of JNK and p38 MAPK along with an increase in caspase 3 expression and decrease in Bcl-2 expression. The integrity of DNA was also found to be altered in the combined treatment. Thus, the results presented in this work agree with those earlier reports in a notion that sodium selenite causes apoptosis and the toxicity of selenite is mediated by increase of intracellular ROS. Also, reduction in endogenous GSH along with selenite treatment is associated with increased apoptosis, increased expression of p38 and JNK MAPK, decreased Bcl-2 expression, and increase in caspase-3 expression. Our data indicates that GSH participates in apoptosis in testicular cells and that depletion of this molecule may be critical in predisposing these cells to apoptotic cell death.

Dietary selenium deficiency as well as excess supplementation induces multiple defects in mouse epididymal spermatozoa: understanding the role of selenium in male fertility.

Selenium (Se) is essential for male fertility. The present study was carried out to observe the defects associated with Se deficiency as well as excess Se supplementation by analyzing the sperm ultrastructure and chromatin organization. Different Se status mice were generated viz. Se deficient (group I), Se adequate (group II) and Se excess (group III) by feeding the respective diets for a period of 4 (group Ia, IIa and IIIa) and 8 weeks (group Ib, IIb and IIIb). Reduction in sperm concentration, motility and percentage fertility was observed in Se deficient and Se excess groups. Electron microscopy revealed mitochondrial swelling and gaps between adjacent mitochondria in mice fed Se-deficient diet for 4 weeks. At 8 weeks, several abnormalities such as loose contact of the mitochondrial helix with the plasma membrane, loss of mitochondria, retention of cytoplasmic droplet, fracturing of outer dense fibres and presence of both the midpiece and the principal piece cross-sections in a common plasma membrane were observed. In Se excess group, the predominant defect was the frequent presence of equidistant, cross-sectioned midpieces of the tail embedded in a common cytoplasm. These defects are indicative of loss of sperm motility. Spermatozoa from Se-deficient mice had incompletely condensed chromatin and indicated an increase in occurrence of DNA strand breaks. The animals fed Se excess diet also indicated increase in DNA breaks but this was significantly less than the deficient diet fed groups. Our study reveals the defects associated with Se deficiency that result in loss of reproductive ability and also reflects its possible harmful effects on spermatozoa after prolonged consumption at supranutritional level.

Alterations in selenium status influences reproductive potential of male mice by modulation of transcription factor NFkappaB.

Selenium (Se), an essential dietary trace element, is required for the maintenance of male fertility. In order to study its role in spermatogenesis, Balb/c mice with different Se status (Se deficient, group I; adequate, group II and excess, group III) were generated by feeding yeast based Se deficient diet for group I and deficient diet supplemented with Se as sodium selenite at adequate (0.2 ppm) and excess (1 ppm) for group II and III, respectively, for a period of 4 and 8 weeks. Percentage fertility was reduced in group I and III as compared to group II. A significant decrease in Se levels and glutathione peroxidase (GSH-Px) activity were observed in group I animals, whereas increase in GSH-Px activity was seen in group III. Further, significant increase in lipid peroxidation was observed in both Se deficient and excess groups. This indicated that dietary manipulation of Se levels either deficiency or excess leads to increased oxidative stress. Nuclear factor kappa B (NFkappaB), a well-known redox regulated transcription factor has also been suggested to play a crucial role in spermatogenesis. The expression of both p65 and p50 genes (components of NFkappaB) increased in Se deficient group I mice while the expression of the inhibitory IkappaBalpha declined significantly. This indicated activation of NFkappaB in Se deficiency. We also studied iNOS expression, which is a known target gene of NFkappaB, by RT-PCR. Significant elevation in the iNOS levels as well as NO levels was recorded. Both enhanced NO levels and NFkappaB are harmful in the progression of normal spermatogenic cycle. Therefore, present result clearly demonstrates the effect of reduced supply of Se on up-regulation and activation of NFkappaB in testis and its influence on spermatogenesis.

Inhibition of CDC2/Cyclin B1 in response to selenium-induced oxidative stress during spermatogenesis: potential role of Cdc25c and p21.

Various cell cycle regulators control and coordinate the process of cell cycle. Because of the crucial involvement of CDC2, Cyclin B1, Cdc25c, and p21 in cell cycle regulation, the present study was aimed to investigate the possibility that selenium (Se)-induced oxidative stress mediated alterations in Cdc25c and p21 may cause modulations in the CDC2/Cyclin B1 complex responsible for G2/M phase checkpoint during meiosis I of spermatogenesis. To create different Se status-deficient, adequate and excess Se, male Balb/c mice were fed yeast based Se deficient diet (group I) and deficient diet supplemented with Se as sodium selenite at 0.2 and 1 ppm Se (group II and III) for a period of 8 weeks. After completion of the diet feeding schedule, a significant decrease in the Se and glutathione peroxidase levels were observed in the Se deficient group (I), whereas Se excess group (III) demonstrated an increase in Se levels. Increased levels of lipid peroxidation (LPO) were seen in both group I and group III when compared to group II, thus indicating oxidative stressed conditions. The mRNA and protein expression of CDC2, Cyclin B1, and Cdc25c were found to be significantly decreased in groups I and III. However, the expression of p21, a kinase inhibitor, was found to be elevated in Se deficient and Se excess fed groups. A statistically significant decrease in the CDC2 kinase activity was also seen in the Se deficient and excess groups. These findings suggest that under the influence of Se-induced oxidative stress, the down regulation of CDC2/Cyclin B1 complex is mediated through changes in Cdc25c and p21 leading to the cell cycle arrest and thus providing new dimensions to the molecular mechanisms underlying male infertility.

Selenium enrichment and anti-oxidant status in baker's yeast, saccharomyces cerevisiae at different sodium selenite concentrations.

The use of selenized yeast as enriched selenium supplements in human nutrition has become a topic of increasing interest over the last decade. The present study was designed with the aim to achieve a balance between selenium (Se) incorporation and optimal growth of yeast cells along with effect of Se enrichment on antioxidant defense status of yeast cells. Since oxidative stress has been known to play a role in the life span of all types of cells, so in the present studies anti-oxidant defense status was evaluated in the Se- enriched baker's yeast cell culture model. Upon Se supplementation as sodium selenite at various concentrations in the growth medium, a continuous increase in glutathione peroxidase (GSH-Px) activity and Se content was observed. In case of reduced glutathione (GSH) decreasing trend were observed with increasing Se concentrations. An increasing trend in total glutathione as well as glutathione-s-transferase activity was observed at increasing Se concentrations. Thus, Se supplementation significantly enhanced GSH-Px levels along with alterations in other anti-oxidant enzymes, suggesting the role of Se in the enzyme defense system of yeast against oxidative damage. Further, as Se exerts growth inhibitory effect on cells, the growth inhibition study was carried out and decrease in biomass was observed with increasing concentrations of Se. Due to nutritional benefits, Se-enriched yeast may be considered a safe source of Se supplementation.

Selenium, a versatile trace element: current research implications.

Selenium (Se), a trace element, has evolved from its toxic properties to an essential element. Se was known a potent antioxidant through glutathione peroxidase (selenium being part of this molecule). Later, many other selenium-binding proteins were discovered and their functions were tried to be known with unsuccessful results in many cases. Se is known to be involved in carcinogenesis, immune function, male reproduction, cardiovascular diseases etc. The specific mechanism of the involvement of the element is still not known. Recent research with application of modern research tools viz. bioinformatics, cDNA microarray and transgenesis have revealed the mechanism of selenium involvement in various processes. This review highlights mysterious and useful roles of selenium in biological processes.

Role of selenium in regulation of spermatogenesis: involvement of activator protein 1.

Selenium (Se) is involved in the process of male reproduction. Several studies have been carried out to find the mechanism of Se action through identified selenoproteins. Especially selenoenzyme phospholipid glutathione peroxidase (PHGPx, GPx-4) plays a pivotal role in regulating spermatogenesis. However, the action of selenium is best known as an antioxidant which acts through various selenoproteins viz. glutathione peroxidase, thioredoxin reductase and selenoprotein P. Oxidative stress is currently being considered a leading cause of male infertility. Presently, the involvement of redox active transcription factor, AP1 (Activator protein1) in testicular function was studied. AP1 is redox sensitive and also controls cell proliferation. The effects of Se might be mediated through it. Different Se status - deficient, adequate and excess Se - were generated in male Balb/c mice by feeding yeast based selenium deficient diet and deficient diet supplemented with Se as sodium selenite (0.2 and 1 ppm Se), respectively, for a period of 4 and 8 weeks. Se status was checked by measuring the Se levels and glutathione peroxidase (GSH-Px) activity in testis and liver. The reproductive potential of mice was affected at these changed Se levels. Changes in the activity of superoxide dismutase (SOD), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) were observed indicating increased oxidative stress at both the levels. Further, changes in the mRNA expression of GSH-Px, gamma-glutamylcysteine synthetase gammaGCS) and Mn superoxide dismutase (MnSOD) were observed. Decrease in cjun and cfos mRNA levels were observed at both the Se status (deficient and excess) which might be responsible for decreased germ cell number, differentiation and reduced fertility observed at the altered Se levels.

Influence of selenium induced oxidative stress on spermatogenesis and lactate dehydrogenase-X in mice testis.

AIM: To evaluate the effect of oxidative stress on the spermatogenesis and lactate dehydrogenase-X (LDH-X) activity in mouse testis. METHODS: For creating different levels of oxidative stress in mice, three selenium (Se) level diets were fed in separate groups for 8 weeks. Group 1 animals were fed yeast-based Se-deficient (0.02 ppm) diet. Group 2 and Group 3 animals were fed with the same diet supplemented with 0.2 ppm and 1 ppm Se as sodium selenite, respectively. After 8 weeks, biochemical and histopathological observations of the testis were carried out. LDH-X levels in the testis were analyzed by western immunoblot and ELISA. RESULTS: A significant decrease in testis Se level was observed in Group 1 animals, whereas it was enhanced in Group 3 as compared to Group 2. The glutathione peroxidase (GSH-Px) activity was significantly reduced in both the liver and testis in Group 1, but not in Group 2 and 3. A significant increase in the testis glutathione-S-transferase (GST) activity was observed in Group 1, whereas no significant change was seen in Groups 2 and 3. Histological analysis of testis revealed a normal structure in Group 2. A significant decrease in the germ cell population in Group 1 was observed as compared to Group 2 with the spermatids and mature sperm affected the most. Decrease in the lumen size was also observed. In the Se-excess group (Group 3), displacement of germ cell population was observed. Further, a decrease in the LDH-X level in testis was observed in Group 1. CONCLUSION: Excessive oxidative stress in the Se deficient group, as indicated by changes in the GSH-Px/GST activity, affects the spermatogenic process with a reduction in mature sperm and in turn the LDH-X level.