Decreased Glutathione Peroxidase Activity Research Articles

Diphenyl ditelluride targets brain selenoproteins in vivo: inhibition of cerebral thioredoxin reductase and glutathione peroxidase in mice after acute exposure

In this study, we investigated the effect of diphenyl ditelluride (PhTe)(2) administration (10 and 50 μmol/kg) on adult mouse behavioral performance as well as several parameters of oxidative stress in the brain and liver. Adult mice were injected with (PhTe)(2) or canola oil subcutaneously (s.c.) daily for 7 days. Results demonstrated that (PhTe)(2) induced prominent signs of toxicity (body weight loss), behavioral alterations and increased in lipid peroxidation in brain. 50 μmol/kg (PhTe)(2) inhibited blood δ-aminolevulinic acid dehydratase (δ-ALA-D), a redox sensitive enzyme. (PhTe)(2) caused an increase in cerebral non-protein thiol (NPSH) and protein thiol (PSH) groups. In the liver, 50 μmol/kg (PhTe)(2) decreased NPSH, but did not alter the content of protein thiol groups. (PhTe)(2) decreased cerebral antioxidant enzymes (catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GPx), and thioredoxin reductase (TrxR). In liver, (PhTe)(2) increase SOD and GR and decreased GPx activity. Results obtained herein suggest that the brain was more susceptible to oxidative stress induced by (PhTe)(2) than the liver. Furthermore, we have demonstrated for the first time that TrxR is an in vivo target for (PhTe)(2.) Combined, these results highlight a novel molecular mechanism involved in the toxicity of (PhTe)(2). In particular the inhibition of important selenoenzymes (TrxR and GPx) seems to be involved in the neurotoxicity associated with (PhTe)(2) exposure in adult mice.

Environmental Tobacco Smoke Induces Oxidative Stress in Distinct Brain Regions of Infant Mice

Environmental tobacco smoke (ETS) leads to the death of 600,000 nonsmokers annually and is associated with disturbances in antioxidant enzyme capacity in the adult rodent brain. However, little is known regarding the influence of ETS on brain development. The aim of this study was to determine levels of malonaldehyde (MDA) and 3-nitrotyrosine (3-NT), as well as enzymatic antioxidant activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD), in distinct brain structures. BALB/c mice were exposed to ETS twice daily for 1 h from postnatal day 5 through postnatal day 18. Acute exposure was performed for 1 h on postnatal day 18. Mice were euthanized either immediately (0) or 3 h after the last exposure. Immediately after an acute exposure there were higher GR and GST activities and MDA levels in the hippocampus, higher GPx and SOD activities in the prefrontal cortex, and higher GST activity and MDA levels in the striatum and cerebellum. Three hours later there was an increase in SOD activity and MDA levels in the hippocampus and a decrease in the activity of all enzymes in the prefrontal cortex. Immediately after final repeated exposure there were elevated levels of GST and GR activity and decreased GPx activity in the hippocampus. Moreover, a rise was found in GPx and GST activities in the prefrontal cortex and increased GST and GPx activity in the striatum and cerebellum, respectively. After 3 h the prefrontal cortex showed elevated GR and GST activities, and the striatum displayed enhanced GST activity. Data showed that enzymatic antioxidant system in the central nervous system responds to ETS differently in different regions of the brain and that a form of adaptation occurs after several days of exposure.

Caloric restriction improves basal redox parameters in hippocampus and cerebral cortex of Wistar rats

Caloric restriction (CR) has been shown to either decrease or prevent the progression of several age-related pathologies. In previous work, we demonstrated that CR modulates astrocyte functions, suggesting that CR may exert neuroglial modulation. Here, we investigated the effects of CR on hippocampal (Hc) and cortical (Cx) oxidative stress parameters of male Wistar rats. Our results showed that CR-fed rats had 17% less body weight gain after 12 weeks of treatment. CR improved locomotion performance, increased glutathione levels and decreased glutathione peroxidase activity and the production of reactive oxygen species. However, no changes were observed in lipid peroxidation, nitric oxide content and catalase activity. Single cell gel electrophoresis assay (comet assay) revealed a reduction in the extent of basal DNA damage upon CR. Our data suggest that dietary CR could induce both hippocampal and cortical modulation resulting in metabolic changes and as a consequence, significant improvement of cellular defense-associated parameters.

Age-related changes in the rat brain mitochondrial antioxidative enzyme ratios: Modulation by melatonin

Oxidative stress is an important factor for aging. The antioxidative enzymes glutathione peroxidase (GPx), glutathione reductase (GRd) and superoxide dismutase (SOD) play a crucial role protecting the organism against the age-dependent oxidative stress. Glutathione (GSH) is present in nearly all living cells. GSH is one of the main antioxidants in the cell and it serves several physiological functions. Our purpose was to evaluate the age-related changes in mitochondrial GPx, GRd and SOD activities, and mitochondrial GSH pool in the brains of young (3months) and aged rats (24months). We also investigated whether melatonin administration influences these brain mitochondrial enzyme activities and GSH levels in young and aged rats. The results showed that GPx activity increased with age, whereas melatonin treatment decreased GPx activity in the aged rats at levels similar to those in young and young+melatonin groups. The activities of GRd and SOD, however, did not change with age. But, melatonin treatment increased SOD activity in the aged rats. GSH levels, which also increased with age, were not modified by melatonin treatment. The reduction in the SOD/GPx and GR/GPx ratios with age was prevented by melatonin administration. Together, our results suggest that the age-related oxidative stress in rat brain mitochondria is more apparent when the antioxidant enzyme ratios are analyzed instead of their absolute values. The antioxidative effects of melatonin were also supported by the recovery of the enzyme ratios during aging.

Erythrocyte antioxidants in aging and dementia

Age of patients and oxidative stress in brain cells may contribute to pathogenesis of Alzheimer’s disease (AD). Erythrocytes (red blood cells, RBC) are considered as passive “reporter cells” for the oxidative status of the whole body and remain poorly investigated in AD. The aim of this study was to assess whether the antioxidant status of RBC changes in aging and AD. Blood was taken from AD and non-Alzheimer’s dementia patients, aged-matched and younger controls. The antioxidant status of RBC was evaluated in each person participated in the study by measuring levels of H2O2, organic hydroperoxides, glutathione (GSH) and glutathione disulfide (GSSG), activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase, and glucose-6-phosphate dehydrogenase. In both aging and dementia, oxidative stress in RBC was shown to increase as evidenced by elevated concentrations of H2O2, organic hydroperoxides, decreased GSH/GSSG ratio, and decreased glutathione S-transferase activity. Decreased glutathione peroxidase activity in RBC may be considered as a new peripheral marker for Alzheimer’s disease while changes of other parameters of oxidative stress reflect age-related events.

Plasma oxidative stress parameters in men and women with early stage Alzheimer type dementia

It is well known that oxidative stress is one of the earliest events in Alzheimer's disease pathogenesis, indicating that may play a key role in this disease. In our study, we measured the levels of oxidative stress indicators (TBARS and protein carbonyls content) and the non-enzymatic (glutathione (GSH) and oxidized glutathione (GSSG)) and enzymatic (glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD)) defense systems in the plasma of 46 patients diagnosed of ATD and 46 age-matched controls. We found decreased levels in total GSH in ATD patients, although healthy control women showed lower levels of total GSH than healthy control men. On the contrary, we found increased levels of TBARS and carbonyl groups content in ATD patients in both genders. The activity of the plasma antioxidant enzymes showed no changes for SOD activity in ATD patients, independently of the gender, although western blot analysis showed an increase in SOD-1 protein. CAT activity was also decreased in ATD patients, although this decrease is mainly due to the decrease found in men but not in women. However, western blot analysis did not show differences in CAT protein between controls and ATD patients. Finally, a decrease of GPx activity was found in ATD patients in both genders. However, as with CAT protein, western blot analysis did not show differences in GPx protein between controls and ATD patients. Our results suggest that there is a defect in the antioxidant defense system that is incapable of responding to increased free radical production, which may lead to oxidative damage and the development of the pathological alterations that characterize the neurodegenerative disorder of patients with ATD. Thus, oxidative damage could be one important aspect for the onset of ATD and oxidative stress markers could be useful to diagnose the illness in their earliest stages through both non-invasive, reliable and cost-affordable methods.

Malabaricone-A induces a redox imbalance that mediates apoptosis in U937 cell line.

BackgroundThe ‘two-faced’ character of reactive oxygen species (ROS) plays an important role in cancer biology by acting both as secondary messengers in intracellular signaling cascades and sustaining the oncogenic phenotype of cancer cells, while on the other hand, it triggers an oxidative assault that causes a redox imbalance translating into an apoptotic cell death.Principal FindingsUsing a tetrazolium [{3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl}-2H-tetrazolium] based cell viability assay, we evaluated the cytotoxicity of a plant derived diarylnonanoid, malabaricone-A on leukemic cell lines U937 and MOLT-3. This cytotoxicity hinged on its ability to cause a redox imbalance via its ability to increase ROS, measured by flow cytometry using 5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate and by decreasing glutathione peroxidase activity. This redox imbalance mediated apoptosis was evident by an increase in cytosolic [Ca2+], externalization of phosphatidyl serine as also depolarization of the mitochondrial membrane potential as measured by flow cytometry. There was concomitant peroxidation of cardiolipin, release of free cytochrome c to cytosol along with activation of caspases 9, 8 and 3. This led to cleavage of the DNA repair enzyme, poly (ADP-ribose) polymerase that caused DNA damage as proved by labeling with 4′,6-diamidino-2-phenylindole (DAPI); furthermore, terminal deoxy ribonucleotide transferase catalysed incorporation of deoxy uridine triphosphate confirmed DNA nicking and was accompanied by arrest of cell cycle progression.ConclusionsTaken together, compounds like MAL-A having pro-oxidant activity mediate their cytotoxicity in leukemic cells via induction of oxidative stress triggering a caspase dependent apoptosis.

4‐Hydroxynonenal Induces Mitochondrial‐Mediated Apoptosis and Oxidative Stress in SH‐SY5Y Human Neuronal Cells

Excessive and sustained increases in oxidative stress and apoptosis have been implicated in the pathogenesis of many diseases. In this study, we demonstrated that 4-hydroxynonenal (4-HNE), a product of lipid peroxidation in a range of concentration (0.1-50 μM) showed cytotoxic effects on SH-SY5Y cell culture at a concentration >5 μM at 4 hr of exposure. 4-HNE dose dependently decreased cell viability and significantly promoted reactive oxygen species formation and enhanced oxidative stress as reflected in the increased level of lipid peroxidation and catalase activity and decreased glutathione peroxidase activity as well as glutathione levels. 4-HNE-induced oxidative stress was associated with increased transcriptional and translational expressions of Bax and p53 in SH-SY5Y cells. Mitochondrial-mediated apoptosis was confirmed by increased expression and activity of caspase-3. Our data demonstrate that 4-HNE induces neuronal cell death through abnormal expression of apoptotic markers (p53, Bax and caspase-3). Oxidative stress may be involved in the initial priming of SH-SY5Y cells to 4-HNE-induced cytotoxicity in vitro.

Oxidative Stress Indices in Rats Under Immunosuppression

Immunosuppressants lead to generation of reactive oxygen species (ROS). Oxidative stress (OxS) can initiate chronic allograft nephropathy (CAN). The most active antioxidant enzymes, superoxide dysmutase (SOD) and catalase (CAT), are present in erythrocytes. Glutathione peroxidase (GPx) is produced in the proximal tubules of nephrons. Malonyldialdehyde (MDA) concentrations are a marker of OxS intensity in plasma. In vitro and animal model studies have shown increased or decreased OxS during treatment with tacrolimus (Tac) or cyclosporine (CyA). Results obtained in humans after solid organ transplantation have been contradictory, because of confounding factors such as ischemia-reperfusion injury, donor and recipient ages, endothelial injury, and comorbidity. The aim of this study was to assess the intensity of OxS among rats under chronic immunosuppression (IS) without a transplantation. We examined 49 male Wistar rats. IS started at 12 weeks of age was continued for 6 months: group I were controls (n = 7); group II, Tac + sirolimus (Rapamycin [Rapa]) + corticosteroids (CS; n = 6); group III, CyA + Rapa + CS (n = 4 of which 2 died); group IV, Rapa + mycophenolate mofetil (MMF) + CS (n = 6); group V, CyA + MMF + CS (n = 6); group VI, CsA + MMF + CS for 3 months followed by conversion to Rapa (n = 6); group VII, Tac + MMF + CS (n = 6 rats); and group VIII, Tac + MMF + CS for 3 months followed by conversion to Rapa (n = 6). The drug doses were as follows: Tac 4 mg/kg/d; MMF 20 mg/kg/d; CyA 5mg/kg/d; Rapa 0.5mg/kg/d; and CS 4 mg/kg/d. Multiple regression analysis revealed that all IS drugs decreased GPx activity ( P < .001) except CS, which increased it ( P < .0001). Multiple regression analysis showed that CsA and Tac decreased plasma MDA concentrations ( P < .01), whereas CS increased them ( P < .05). In conclusion, all IS drugs except CS damage proximal tubules of nephrons.

Effect of zinc supplementation on glutathione peroxidase activity and selenium concentration in the serum, liver and kidney of rats chronically exposed to cadmium

It was investigated whether the ability of zinc (Zn) to prevent cadmium (Cd)-induced lipid peroxidation may be connected with its impact on glutathione peroxidase (GPx) activity and selenium (Se) concentration. GPx and Se were determined in the serum, liver and kidney of the rats that received Cd (5 or 50mg/L) or/and Zn (30mg/L) in drinking water for 6 months in whose the protective Zn impact was noted (Rogalska J, Brzóska MM, Roszczenko A, Moniuszko-Jakoniuk J. Enhanced zinc consumption prevents cadmium-induced alterations in lipid metabolism in male rats. Chem Biol Interact 2009;177:142–52). Moreover, dependences between these parameters, and indices of lipid peroxidation (F2-isoprostane, lipid peroxides, oxidized low density lipoprotein cholesterol) as well as concentrations of Cd and Zn were estimated. The supplementation with Zn during the exposure to 5mg Cd/L entirely antagonized the Cd-induced increase in GPx activity and Se concentration in the liver and kidney, but not in the serum. Zn administration during the treatment with 50mg Cd/L totally or partially prevented from the Cd-caused decrease in GPx activity and Se concentration in the serum, liver and kidney. At the higher level of Cd exposure, GPx activity in the serum and tissues positively correlated with Se concentration. Moreover, numerous correlations were noted between GPx and/or Se and the indices of lipid peroxidation. The results indicate that the protective impact of Zn against the Cd-induced lipid peroxidation during the relatively high exposure might be connected with its beneficial influence on Se concentration and GPx activity in the serum and tissues, whereas this bioelement influence at the moderate exposure seems to be independent of GPx and Se.

Addition of IGF-I to storage-cooled boar semen and its effect on sperm quality

Objective To evaluate in vitro IGF-I treatment during warming of storage-cooled boar semen and its effect on seminal quality parameters and metabolism in spermatic cells. Design Semen samples (n = 7) warmed after stored at 15 °C for 24 or 72 h were divided into four equal parts. Different IGF-I concentrations (0, 50, 100 and 150 ng/mL) were added to the semen samples. The samples were incubated at 37 °C, and assessments were made after 0 and 120 min of incubation. Results For semen samples that were stored for 24 h, the addition of IGF-I had no effect (p > 0.05) on the total motility and intensity of movements by spermatic cells, osmotic resistance, live:dead cell ratio or total spermatic abnormalities. However, incubation with 150 ng/mL IGF-I did decrease glutathione peroxidase activity (p < 0.05) and reduce lipid peroxidation after 120 min of incubation. For semen samples stored for 72 h and incubated with IGF-I for 120 min, there was a linear relationship between the IGF-I concentration and the live:dead ratio (p < 0.05). There was a quadratic relationship between the IGF-I concentration and both the osmotic resistance (peak results at IGF-I = 62.4 ng/mL) and glutathione peroxidase activity (peak results at IGF-I = 77.8 ng/mL). There was no effect on lipid peroxidation (p > 0.05) after 120 min of incubation. Addition of IGF-I also decreased fructose utilization by spermatic cells regardless of semen storage time (p < 0.05). Conclusion This study suggests that IGF-I may be beneficial to semen stored for longer periods of time. Adding 150 ng/mL IGF-I improved the quality of semen stored for 24 h, and adding 78 ng/mL IGF-I improved the quality of semen stored for 72 h.

Oxidative markers in spontaneous intracerebral hemorrhage: leukocyte 8-hydroxy-2'-deoxyguanosine as an independent predictor of the 30-day outcome.

Oxidative stress may play a role in spontaneous intracerebral hemorrhage (ICH), but data on oxidative burden in cerebral hemorrhage are limited, and it is not clear whether oxidative markers add predictive power regarding ICH outcome beyond that of traditional factors. The authors therefore examined redox status and traditional factors in ICH patients within 3 days of hemorrhage onset to delineate redox status in ICH and investigate the predictive value with respect to 30-day functional outcome. Sixty-four patients with ICH and 114 controls were prospectively enrolled in this study. Blood samples were collected within 3 days of ICH onset and processed for isolation of plasma, erythrocytes, and leukocytes. The authors evaluated levels or activities of leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG), erythrocyte glucose-6-phosphate dehydrogenase (G6PD), erythrocyte glutathione peroxidase (GPx), plasma malondialdehyde (MDA), vitamin E, and vitamin A, as well as traditional factors including the presence of hypertension or diabetes mellitus, total cholesterol level, and measures of liver function. A general linear model and multivariable logistic regression were used for analyses where appropriate. After adjustment for age and sex and traditional risk factors, ICH was significantly associated with an increased level of 8-OHdG (p < 0.0001), decreased GPx activity (p = 0.0002), and a decreased level of vitamin E (p = 0.003). There was no association of ICH risk with G6PD activity or MDA or vitamin A level. Considering all the oxidative markers and traditional risk factors together, logistic regression showed an independent association of ICH with 8-OHdG (OR 2.7, 95% CI 1.7-4.2, p < 0.0001). The association between increased 8-OHdG level and lower 30-day Barthel Index was also independent of the effects of age, sex, hemorrhage location and size, and traditional factors (p = 0.026). Unfavorable outcome (modified Rankin Scale score ≥ 3) at 30 days after ICH onset was not significantly associated with any of the examined oxidative markers. Increased leukocyte 8-OHdG levels, as well as decreased GPx activity and vitamin E levels, were found during acute ICH. Only 8-OHdG was associated with ICH and the 30-day outcome independently from the other oxidative markers and traditional factors. Leukocyte 8-OHdG may add power beyond the traditional factors in predicting ICH outcome and thus may be used as an independent surrogate for clinical ICH study.

The Antioxidative Effect of Electro-Acupuncture in a Mouse Model of Parkinson's Disease

Accumulating evidence indicates that oxidative stress plays a critical role in Parkinson's disease (PD). Our previous work has shown that 100 Hz electro-acupuncture (EA) stimulation at ZUSANLI (ST36) and SANYINJIAO (SP6) protects neurons in the substantia nigra pars compacta from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) toxicity in male C57BL/6 mice, a model of PD. In the present study we administered 100 Hz EA stimulation at the two acupoints to MPTP-lesioned mice for 12 sessions starting from the day prior to the first MPTP injection. We found that in the striatum of MPTP treated mice 100 Hz EA stimulation effectively inhibited the production of hydrogen peroxide and malonaldehyde, and increased glutathione concentration and total superoxide dismutase activity through biochemical methods. However, it decreased glutathione peroxidase activity via biochemical analysis and did not affect the level of 1-methyl-4-phenylpyridinium in the striatum revealed by high performance liquid chromatography with ultraviolet detection. These data suggest that 100 Hz EA stimulation at ST36 and SP6 has antioxidative effects in the MPTP model of PD. This data, along with our previous work, indicates that 100 Hz EA stimulation at ST36 and SP6 protects the nigrostriatal system by multiple mechanisms including antioxidation and antiapoptosis, and suggests that EA stimulation is a promising therapy for treating PD.

The Effect Of The Oral Iron Chelator Deferiprone On The Liver Damage Induced By Tamoxifen In Female Rats

Tamoxifen (TAM) is a non-steroidal antiestrogen used in the treatment and prevention of hormone-dependent breast cancer. Tamoxifen therapy may be accompanied with hepatic injury and iron accumulation in this organ. The present study investigates the influence of the effective oral iron chelator, deferiprone (L1), in TAM-induced acute liver injury. Four groups of female Wistar rats were used: I, control; II, TAM; III, TAM+L1; IV, L1. Tamoxifen (75 mg/kg) was administered orally on the first and second day; L1 (50 mg/kg) was administered orally on the first, second and third day of the experiment. On the fourth day, parameters of oxidative state: lipid peroxidation (LP), glutathione (GSH) and catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities were estimated in liver homogenates. Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamate dehydrogenase (GLDH) levels and iron hepatic content were also evaluated. The TAM-induced oxidative damage was demonstrated by increased LP (52% above controls) and decreased GPx activity (to 92% of controls). The protective effect of L1 was manifested by attenuation of LP (p <0.05) and preserving of GPx activity. The TAM-induced increase of serum ALT and AST activity remained unchanged by L1 treatment. Significant increase of hepatic iron (Fe) level (41% above controls) was found in TAM-treated rats. Hepatic Fe accumulation was completely prevented by L1 treatment.

Effect of Selenium Depletion on Oxidative Stress in Mature Horses

s / Journal of Equine Veterinary Science 31 (2011) 230-356 257 [5] Bryden WL. Amino acid requirements of horses estimated from tissue composition. Proc Nutr Soc 1991;16:53. [6] Wilson JA, Graham-Thiers PM. Muscle and plasma amino acids in pregnant/lactating mares and their weanling foals. J Equine Vet Sci 2009;29:370. [7] Nutrient Requirements of Horses. 6th ed. Washington, DC: The National Academies Press; 2007. [8] Waggoner JW, LOxest CA, Mathis CP, Hallford DM, Petersen MK. Effects of rumen-protected methionine supplementation and bacterial lipopolysaccharide infusion on nitrogen metabolism and hormonal responses of growing beef steers. J Anim Sci 2009;87:681. Effect of Selenium Depletion on Oxidative Stress in Mature Horses M. Brummer, S. Hayes, J.E. Earing, S.M. McCown, and L.M. Lawrence University of Kentucky, Lexington, KY, USA Introduction: Glutathione peroxidase (GPx) plays an important role in the neutralization of hydroperoxides andhydrogenperoxide. Hydrogen peroxide can generate hydroxyl radicals which are regarded as a very harmful reactive oxygen species [1]. Selenium (Se) deficiency can result in decreased GPx activity; therefore our aim was to investigate the effect of low Se status on oxidative stress in mature idle horses. We hypothesized that Se depletion would result in a decrease in GPx activity, serum total antioxidant capacity (TAC) and an increase in oxidative stress, measured as serum malondialdehyde concentration (MDA). Type I deiodinase, is a selenoenzyme responsible for the conversion of inactive T4 to active T3. Therefore as additional indicators of Se status we measured triiodothyronine (T3), thyroxine (T4), and the T3:T4 ratio as changes in these hormones or in their ratio has been evaluated in horses fed varying levels of Se before [2]. Materials and Methods: Twenty eight mature horses (6 24 yr) were used in this study. The 28 horses included 8 geldings and 20 mares that had resided on the farm for at least 60 days prior to the study. The study period was 28 wks. Horses were kept on pasture ( .05). MDA concentrationwas not different between AS and LS at the initial or final time point, howeverMDAdid increaseover time (P< .05) in LS (from3.40 .86 nmol/mL to 4.04 .89 nmol/mL) while it remained similar in AS (4.68 1.78 nmol/mL to 5.09 1.09 nmol/mL). Two traditional indicators of Se status were measured: whole blood Se concentration and GPx activity. In addition the serum T3/ T4 ratio was determined. Type I deiodinase, the enzyme responsible for converting T4 to T3, has a greater ranking in terms of priority of Se supply than cytosolic GPx [2]. A change in this ratio is generally not observed during a marginal Se deficiency [2], so the increased ratio of T3/T4 in the LS horses along with the changes in whole blood Se and GPx suggests that the LS horses were at, or approaching, deficient Se status. TAC was expected to decrease in LS horses, but it was unaffected. The lack of change in TAC may point towards a compensatory mechanism within the antioxidant system, or lack of sensitivity of the assay as a measure of the GPx-associated antioxidant capacity in serum. GPx is only one of several compounds that contribute to total antioxidant capacity. MDA is a byproduct of lipid peroxidation [4]. We hypothesized that MDA concentrations would increase with decreasing Se status. Although MDA concentrations increased over time in the LS horses, the magnitude of the changes were relatively small. Much larger changes in MDA have been reported in response to exercise or disease in other studies [4] and some type of oxidative challenge might be necessary to produce more marked differences in MDA in the horses studied here. Conclusion: In this study feeding a low Se diet for 28 wks altered indicators of Se status, but appears to have hadminimal effects on the indicator of oxidative damage. However, more marked effects might have been observed if the horses had been challenged with an oxidative stressor such as exercise or disease. Further research in this area may provide better insight into the importance of Se in oxidative stress.

Testicular toxicity of cyanobacterial biomass in Japanese quails

Previous studies demonstrated the toxic effects of cyanobacteria in Japanese quails ( Coturnix coturnix japonica) in various experimental set-ups including acute, sub-chronic and reproduction toxicity, co-exposures with toxic metals and the Newcastle vaccination. This study aimed to assess the testicular toxicity of a complex cyanobacterial biomass administered to Japanese quails in the feed for eight weeks (daily dose of 61.62 μg microcystins pro toto including 26.54 μg MC-RR, 7.62 μg MC-YR and 27.39 μg MC-LR). There was no mortality in the controls or the biomass-exposed birds. However, males exposed to cyanobacteria in the feed showed moderate to marked atrophy of the seminiferous tubular epithelium with only sparse numbers of the developmental stages of spermatozoa and Sertoli cells. Biomass-exposed birds had elevated catalase activities but decreased glutathione peroxidase activities and surprisingly lower levels of lipid peroxides in the testes. The other biochemical parameters studied (i.e., glutathione level and glutathione reductase, glutathione-S-transferase and superoxide dismutase activities) showed no differences. The cell defensive system protecting testicular tissue from the damage associated with toxic effects of the complex cyanobacterial biomass seemed to be insufficient and partly depleted after the chronic exposure of male birds to this biomass.

The Cryoprotective Effects of Vitamin B12 Supplementation on Bovine Semen Quality

The present study aimed to investigate the effects of vitamin B(12) supplementation on standard bovine semen quality parameters and anti-oxidative enzyme activities. Vitamin B(12) was supplemented at concentrations of 1.25, 2.5, 3.75 and 5.0 mg/ml to bovine semen cryoprotective medium. The results indicated that the motility and straight line velocity, curvilinear velocity, mean coefficient, velocity of the average path values of sperm supplemented with 2.50 mg/ml vitamin B(12) were significantly higher than that of other groups (p<0.05). No significant difference was observed for linearity index, lateral head displacement values and the percentage of grade A spermatozoa between the extenders containing 2.50 and 3.75 mg/ml vitamin B(12) (p>0.05). The percentages of acrosome-intact and plasma membrane-intact spermatozoa were significantly improved (p<0.05) by supplementing with 2.50 mg/ml vitamin B(12) . The results of biochemical assay revealed that vitamin B(12) supplementation did not cause significant changes in superoxide dismutase levels compared with control (p>0.05). However, the catalase levels were higher in the treatment supplemented with vitamin B(12) at 2.50 mg/ml, when compared with other groups (p<0.05). The extender supplemented with vitamin B(12) significantly decreased glutathione peroxidase activity compared with the control (p<0.05). The supplementation of 3.75 mg/ml vitamin B(12) caused the highest value of glutathione reductase activity, compared with other groups (p<0.05). In conclusion, the extender supplemented with vitamin B(12) could reduce the oxidative stress provoked by freezing-thawing and improve bovine semen quality. Further studies are required to obtain more concrete results on the determination of lipid peroxidation and antioxidant capacities of vitamin B(12) in cryopreserved bovine semen.

The effect of alkali burn on corneal glutathione peroxidase activities in rabbits

Glutathione peroxidase (GPx) is an important corneal defense enzyme for protecting against hydrogen peroxides and lipid peroxides. In the present study, corneal GPx activities after alkali burn of the cornea were evaluated in rabbits. Materials and methods: Corneal alkali burn was created in the right eye of 10 rabbits by applying a 6 mm round filter paper soaked in 1 N NaOH onto the central cornea for 60 s. The right eyes of 10 healthy rabbits served as controls. The corneal GPx activities were determined by the method of Paglia and Valentina, 10 days after the burn. Results: GPx activities were reduced significantly in alkali burned corneas compared to the normal controls (P < 0.05). Conclusion: The data suggest that decreased GPx activities predispose the cornea to injury from reactive oxygen radicals, besides the initial chemical damage of alkali burn.

P43 KCNQ/KCNE isoform expression in placentae from pre-eclamptic women delivering at term or preterm vs. controls

Selenium deficiency causes a fall in the concentrations of selenoproteins but selenoprotein P and type I iodothyronine 5′-deiodinase (5′-deiodinase) are more resistant to this effect than is glutathione peroxidase. To investigate the differential regulation of these selenoproteins, a selenium-deficient diet was fed to weanling rats for 14.5 weeks and their hepatic mRNAs were measured by Northern analysis. Levels of all 3 mRNAs fell progressively with time. Selenoprotein P and 5′-deiodinase mRNAs remained higher at all time points relative to control than glutathione peroxidase mRNA. mRNA decreases were mirrored by decreases in glutathione peroxidase activity and selenoprotein P concentration. However, the decreases in the protein levels were greater than the decreases in their mRNAs, suggesting that synthesis of both proteins was limited to a similar extent at the translational level by the availability of selenium. In addition to this apparently unregulated translational effect, these results point to a pretranslational regulation, affecting mRNA levels, which could account for the differential effect of selenium deficiency on glutathione peroxidase and the other selenoproteins. This regulation might serve to direct selenium to selenoprotein P and 5′-deiodinase when limited amounts of the element are available.

Hyperhomocysteinemia’s effect on antioxidant capacity in rats

Abstract Hyperhomocysteinemia represents elevated homocysteine (Hcys) concentrations in blood above the normal range. In humans, the normal range of homocysteine is 5.0–15.9 mM/ml. High levels of homocysteine disturb the normal epithelial functions and correlate with cardiovascular diseases even at slightly increased concentrations. In homocysteine metabolism, vitamins play an important role. The mechanism through which homocysteine triggers these effects is not yet elucidated, but the involvement of reactive species may be the answer. It is not known whether the intra- or extracellular antioxidant system is more affected by elevated homocysteine levels. We studied the effects of hyperhomocysteinemia on the intra- and extracellular antioxidant defense systems in two different types of diet in rats. Type I was food with low folic acid and vitamin B12 content and type II was food with normal amounts of these two vitamins. Hyperhomocysteinemia was experimentally induced by oral administration of methionine 2 mg/kg body weight, single daily dose, for a 15-day period. Plasma concentrations of homocysteine were measured using an HPLC method. In the response of the intracellular antioxidant defense system against hyperhomocysteinemia, we determined the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in red blood cells, using RANDOX kits for manual use. For the extracellular response we determined the plasma total antioxidant status (TAS) also using a RANDOX kit for manual use. Our data show that methionine load induces hyperhomocysteinemia despite normal vitamin supply in rats. SOD activity rose with simultaneous decrease in GPx activity independently of diet; this might suggest that the intracellular defense system was disturbed by the rise in homocysteine level. TAS decrease suggests that the extracellular antioxidant defense was also affected. We assume that hyperhomocysteinemia is directly linked to reactive species generation and the intracellular space seems to be more affected than the extracellular one.