6-Gingerol-rich fraction from Zingiber officinale ameliorates carbendazim-induced endocrine disruption and toxicity in testes and epididymis of rats

This study evaluated the protective effects of 6-gingerol-rich fraction (6-GRF) from Zingiber officinale on carbendazim (CBZ)-induced reproductive toxicity in rats. Adult male rats were treated with either CBZ (50 mg/kg) alone or in combination with 6-GRF (50, 100 and 200 mg/kg) for 14 consecutive days. Gas chromatography-mass spectrometry (GCMS) analysis revealed that 6-GRF consists of ten bioactive chemical components with 6-gingerol being the most abundant (30.76%). Administration of 6-GRF significantly (p < .05) prevented CBZ-mediated increase in absolute and relative testes weights as well as restored the sperm quantity and quality in the treated rats to near control. In testes and epididymis, 6-GRF significantly abolished CBZ-mediated increase in oxidative damage as well as augmented antioxidant enzymes activities and glutathione level in the treated rats. Moreover, CBZ administration alone significantly decreased plasma levels of testosterone, thyrotropin, triiodothyronine and tetraiodothyronine, whereas follicle-stimulating hormone was significantly elevated without affecting luteinising hormone and prolactin levels when compared with the control. Conversely, 6-GRF ameliorated the disruption in the hormonal levels and restored their levels to near normalcy in CBZ-treated rats. Collectively, 6-GRF inhibited the adverse effects of CBZ on the antioxidant defence systems, hormonal balance and histology of the testes and epididymis in rats.

Dexmedetomidine decreases the inflammatory response to myocardial surgery under mini-cardiopulmonary bypass

Cardiopulmonary bypass (CPB) with extracorporeal circulation produces changes in the immune system accompanied by an increase in proinflammatory cytokines and a decrease in anti-inflammatory cytokines. We hypothesize that dexmedetomidine (DEX) as an anesthetic adjuvant modulates the inflammatory response after coronary artery bypass graft surgery with mini-CPB. In a prospective, randomized, blind study, 12 patients (4 females and 8 males, age range 42-72) were assigned to DEX group and compared with a conventional total intravenous anesthesia (TIVA) group of 11 patients (4 females and 7 males). The endpoints used to assess inflammatory and biochemical responses to mini-CPB were plasma interleukin (IL)-1, IL-6, IL-10, interferon (INF)-γ, tumor necrosis factor (TNF)-α, C-reactive protein, creatine phosphokinase, creatine phosphokinase-MB, cardiac troponin I, cortisol, and glucose levels. These variables were determined before anesthesia, 90 min after beginning CPB, 5 h after beginning CPB, and 24 h after the end of surgery. Endpoints of oxidative stress, including thiobarbituric acid reactive species and delta-aminolevulinate dehydratase activity in erythrocytes were also determined. DEX+TIVA use was associated with a significant reduction in IL-1, IL-6, TNF-α, and INF-γ (P<0.0001) levels compared with TIVA (two-way ANOVA). In contrast, the surgery-induced increase in thiobarbituric acid reactive species was higher in the DEX+TIVA group than in the TIVA group (P<0.01; two-way ANOVA). Delta-aminolevulinate dehydratase activity was decreased after CPB (P<0.001), but there was no difference between the two groups. DEX as an adjuvant in anesthesia reduced circulating IL-1, IL-6, TNF-α, and INF-γ levels after mini-CPB. These findings indicate an interesting anti-inflammatory effect of DEX, which should be studied in different types of surgical interventions.

Possible involvement of membrane lipids peroxidation and oxidation of catalytically essential thiols of the cerebral transmembrane sodium pump as component mechanisms of iron-mediated oxidative stress-linked dysfunction of the pump's activity

The precise molecular events defining the complex role of oxidative stress in the inactivation of the cerebral sodium pump in radical-induced neurodegenerative diseases is yet to be fully clarified and thus still open. Herein we investigated the modulation of the activity of the cerebral transmembrane electrogenic enzyme in Fe²⁺-mediated in vitro oxidative stress model. The results show that Fe²⁺ inhibited the transmembrane enzyme in a concentration dependent manner and this effect was accompanied by a biphasic generation of aldehydic product of lipid peroxidation. While dithiothreitol prevented both Fe²⁺ inhibitory effect on the pump and lipid peroxidation, vitamin E prevented only lipid peroxidation but not inhibition of the pump. Besides, malondialdehyde (MDA) inhibited the pump by a mechanism not related to oxidation of its critical thiols. Apparently, the low activity of the pump in degenerative diseases mediated by Fe²⁺ may involve complex multi-component mechanisms which may partly involve an initial oxidation of the critical thiols of the enzyme directly mediated by Fe²⁺ and during severe progression of such diseases; aldehydic products of lipid peroxidation such as MDA may further exacerbate this inhibitory effect by a mechanism that is likely not related to the oxidation of the catalytically essential thiols of the ouabain-sensitive cerebral electrogenic pump.

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Fe²⁺ evoked lipid peroxidation (LPO) and inhibition of sodium pump (SP) in rat brain.

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However, dithiothreitol prevented both Fe²⁺-mediated LPO and inhibition of SP.

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Conversely, vitamin E prevented only Fe²⁺-mediated LPO but not inhibition of SP.

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Thus Fe²⁺ mediated inactivation of SP likely by oxidizing the essential thiol on SP.

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However, malondialdehyde inhibited SP by a mechanism not related to thiol oxidation.

Impact of SIN-1-derived peroxynitrite flux on endothelial cell redox homeostasis and bioenergetics: protective role of diphenyl diselenide via induction of peroxiredoxins

Increased production of reactive nitrogen (RNS) and oxygen (ROS) species and its detrimental effect to mitochondria are associated with endothelial dysfunction. This study was designed to determine the effect of a peroxynitrite flux, promoted by 1,3-morpholinosydnonimine (SIN-1), in mitochondrial function and some redox homeostasis parameters in bovine aortic endothelial cells (BAEC). Moreover, the effect of diphenyl diselenide (PhSe)2, a simple organic selenium compound, in preventing peroxynitrite-mediated cytotoxicity was also investigated. Our results showed that overnight exposure to SIN-1 (250 μM) caused a profound impairment of oxygen consumption, energy generation and reserve capacity in mitochondria of BAEC. Mitochondrial dysfunction resulted in an additional intracellular production of peroxynitrite, amplifying the phenomenon and leading to changes in redox homeostasis. Moreover, we observed an extensive decline in mitochondrial membrane potential (ΔΨm) induced by peroxynitrite and this event was associated with apoptotic-type cell death. Alternatively, the pretreatment of BAEC with (PhSe)2, hindered peroxynitrite-mediated cell damage by preserving mitochondrial and endothelial function and consequently preventing apoptosis. The protective effect of (PhSe)2 was related to its ability to improve the intracellular redox state by increasing the expression of different isoforms of peroxiredoxins (Prx-1-3), efficient enzymes in peroxynitrite detoxification.

Effects of Hg(II) exposure on MAPK phosphorylation and antioxidant system in D. melanogaster

The heavy metal mercury is a known toxin, but while the mechanisms involved in mercury toxicity have been well demonstrated in vertebrates, little is known about toxicological effects of this metal in invertebrates. Here, we present the results of our study investigating the effects associated with exposure of fruit fly Drosophila melanogaster to inorganic mercury (HgCl2 ). We quantify survival and locomotor performance as well as a variety of biochemical parameters including antioxidant status, MAPK phosphorylation and gene expression following mercury treatment. Our results demonstrate that exposure to Hg(II) through diet induced mortality and affected locomotor performance as evaluated by negative geotaxis, in D. melanogaster. We also saw a significant impact on the antioxidant system including an inhibition of acetylcholinesterase (Ache), glutathione S-transferase (GST) and superoxide dismutase (SOD) activities. We found no significant alteration in the levels of mRNA of antioxidant enzymes or NRF-2 transcriptional factor, but did detect a significant up regulation of the HSP83 gene. Mercury exposure also induced the phosphorylation of JNK and ERK, without altering p38(MAPK) and the concentration of these kinases. In parallel, Hg(II) induced PARP cleavage in a 89 kDa fragment, suggesting the triggering of apoptotic cell death in response to the treatment. Taken together, this data clarifies and extends our understanding of the molecular mechanisms mediating Hg(II) toxicity in an invertebrate model.

In vitro glutathione peroxidase mimicry of ebselen is linked to its oxidation of critical thiols on key cerebral suphydryl proteins - A novel component of its GPx-mimic antioxidant mechanism emerging from its thiol-modulated toxicology and pharmacology

The antioxidant mechanism of ebselen in rats brain is largely linked with its glutathione peroxidase (GPx) rather than its peroxiredoxin mimicry ability. However, the precise molecular dynamics between the GPx-mimicry of ebselen and thiol utilization is yet to be fully clarified and thus still open. Herein, we investigated the influence of dithiothreitol (DTT) on the antioxidant action of ebselen against oxidant-induced cerebral lipid peroxidation and deoxyribose degradation. Furthermore, the critical inhibitory concentrations of ebselen on the activities of sulphydryl enzymes such as cerebral sodium pump, δ-aminolevulinic acid dehydratase (δ-ALAD) and lactate dehydrogenase (LDH) were also investigated. We observe that ebselen (at ≥42 μM) markedly inhibited lipid peroxidation in the presence and absence of DTT, whereas it inhibited deoxyribose degradation only in the presence of DTT. Furthermore, under in vitro conditions, ebselen inhibited the thiol containing enzymes; cerebral sodium pump (at ≥40 μM), δ-ALAD (≥10 μM) and LDH (≥1 μM) which were either prevented or reversed by DTT. However, the inhibition of the activities of these sulphydryl proteins in diabetic animals was prevented by ebselen. Summarily, it is apparent that the effective in vitro inhibitory doses of ebselen on the activity of the sulphydryl proteins are far less than its antioxidant doses. In addition, the presence of DTT is evidently a critical requirement for ebselen to effect its antioxidant action against deoxyribose degeradation and not lipid peroxidation. Consequently, we conclude that ebselen possibly utilizes available thiols on sulphydryl proteins to effect its GPx mimicry antioxidant action against lipid peroxidation in rat brain homogenate.

Is the lobster cockroach Nauphoeta cinerea a valuable model for evaluating mercury induced oxidative stress?

Organic and inorganic forms of mercury are highly neurotoxic environmental contaminants. The exact mechanisms involved in mercury neurotoxicity are still unclear. Oxidative stress appears to play central role in this process. In this study, we aimed to validate an insect-based model for the investigation of oxidative stress during mercury poisoning of lobster cockroach Nauphoeta cinerea. The advantages of using insects in basic toxicological studies include the easier handling, rapid proliferation/growing and absence of ethical issues, comparing to rodent-based models. Insects received solutions of HgCl2 (10, 20 and 40mgL(-1) in drinking water) for 7d. 24h after mercury exposure, animals were euthanized and head tissue samples were prepared for oxidative stress related biochemical determinations. Mercury exposure caused a concentration dependent decrease in survival rate. Cholinesterase activity was unchanged. Catalase activity was substantially impaired after mercury treatment 40mgL(-1). Likewise, GST had a significant decrease, comparing to control. Peroxidase and thioredoxin reductase activity was inhibited at concentrations of 20mgL(-1) and 40mgL(-1) comparing to control. These results were accompanied by decreased GSH levels and increased hydroperoxide and TBARS formation. In conclusion, our results show that mercuric compounds are able to induce oxidative stress signs in insect by modulating survival rate as well as inducing impairments on important antioxidant systems. In addition, our data demonstrates for the first time that Nauphoeta cinerea represents an interesting animal model to investigate mercury toxicity and indicates that the GSH and thioredoxin antioxidant systems plays central role in Hg induced toxicity in insects.

Irrigation of Solanum lycopersicum L. with magnetically treated water increases antioxidant properties of its tomato fruits

Antioxidant effects of tomatoes (Solanum lycopersicum L.) have been studied and an association between dietary intake of tomatoes and lowered risk of cancer, neurodegenerative, and cardiovascular diseases has been suggested. Here we used magnetically treated water (MTW; 0.03-0.15 T), which promotes better germination and productivity in tomatoes, and we investigated the effects of aqueous and ethanolic (10-400 μg/ml) extracts of S. lycopersicum as potential antioxidant against 10 μM Fe(II)-induced thiobarbituric acid reactive species (TBARS) in liver and brain homogenates from rats. The ethanolic extracts from magnetically treated plants were more effective than aqueous extracts in preventing TBARS formation in brain and liver. The protective effects of ethanolic extract can be associated with antioxidants (polyphenols and flavonoids), lycopene and other lipophilic components found in the extract. In effect, magnetically treated plants had higher content of polyphenolic and flavonoid compounds than nontreated plants and they can be a better source of antioxidants than nontreated plants. Consequently, MTW can be used to produce functional foods with high contents of antioxidant components and may have better beneficial health effects than traditionally produced foods.

Antioxidant properties of β-seleno amines against lipid peroxidation in rat brain and liver

β-Seleno amines were screened for in vitro antioxidant activity. The compounds (C1-C4) were tested against lipid peroxidation induced by iron and sodium nitroprusside in rat brain and liver homogenates. The compounds showed inhibition against thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants (10μM FeSO(4) and 5μM sodium nitroprusside (SNP) in rat brain and liver homogenates. The compounds exhibited strong antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and phosphomolybdenum assays. The IC(50) values revealed that the β-seleno amines in which the amino group was protected with protecting groups tert-butyloxycarbonyl (Boc) and Tosyl (Ts) groups showed better antioxidant profiles compared to the free monoselenides. The total antioxidant activity of C1, C2, C3 and C4 were found to be 85.2±11.5, 114±7.9, 138±8.5, 125.81±5.2μM/ml of ascorbic acid respectively. Therefore, these compounds may be used as synthetic antioxidants.

Molecular docking studies of disubstituted diaryl diselenides as mammalian δ-aminolevulinic acid dehydratase enzyme inhibitors

δ-Aminolevulinic acid dehydratase (δ-ALAD) is a metalloprotein that catalyzes porphobilinogen formation. This enzyme is sensitive to pro-oxidants and classically used as a biomarker of lead (Pb) intoxication. Diphenyl diselenide [(PhSe)₂] and analogs bis(4-chlorophenyl) diselenide [(pCl₃PhSe)₂], bis(4-methoxyphenyl)diselenide [(pCH₃OPhSe)₂], and bis[3-(trifluoromethy)phenyl] diselenide [(mCF₃PhSe)₂] inhibit mammalian δ-ALAD by oxidizing enzyme cysteinyl residues, which are involved in diselenide-induced toxicity. 2-Cysteinyl residues from δ-ALAD are believed to sequentially interact with (PhSe)₂. Thus this study utilized protein-ligand docking analyses to determine which cysteinyl residues might be involved in the inhibitory effect of (PhSe)₂ and analogs toward δ-ALAD. All diselenides that interact in a similar manner with the active site of δ-ALAD were examined. Docking simulations indicated an important role for π-π interactions involving Phe208 and cation-π interactions involving Lys199 and Arg209 residues with the aromatic ring of (PhSe)₂ and analogs. Based upon these interactions an approximation between Se atoms and -SH of Cys124, with distances ranging between 3.3 Å and 3.5 Å, was obtained. These data support our previous postulations regarding the mechanism underlying δ-ALAD oxidation mediated by (PhSe)₂ and analogs. Based on protein-ligand docking analyses, data indicated that -SH of Cys124 attacks one of the Se atoms of -SH of (PhSe)₂ releasing one PhSeH (selenophenol). Subsequently, the -SH of Cys132 attacks the sulfur atom of Cys124 (from the bond of E-S-Se-Ph indermediate), generating the second PhSe⁻, and the oxidized and inhibited δ-ALAD. In conclusion, AutoDock Vina 1.1.1 was a useful tool to search for diselenides inhibitors of δ-ALAD, and, most importantly, it provided insight into molecular mechanisms involved in enzyme inhibition.

Could dietary trans fatty acids induce movement disorders? Effects of exercise and its influence on Na⁺K⁺-ATPase and catalase activity in rat striatum

The influence of trans fatty acids (FA) on development of orofacial dyskinesia (OD) and locomotor activity was evaluated. Rats were fed with diets enriched with 20% soybean oil (SO; n-6 FA), lard (L; saturated FA) or hydrogenated vegetable fat (HVF; trans FA) for 60 weeks. In the last 12 weeks each group was subdivided into sedentary and exercised (swimming). Brains of HVF and L-fed rats incorporated 0.33% and 0.20% of trans FA, respectively, while SO-fed group showed no incorporation of trans FA. HVF increased OD, while exercise exacerbated this in L and HVF-fed rats. HVF and L reduced locomotor activity, and exercise did not modify. Striatal catalase activity was reduced by L and HVF, but exercise increased its activity in the HVF-fed group. Na(+)K(+)-ATPase activity was not modified by dietary FA, however it was increased by exercise in striatum of SO and L-fed rats. We hypothesized that movement disorders elicited by HVF and less by L could be related to increased dopamine levels in striatum, which have been related to chronic trans FA intake. Exercise increased OD possibly by increase of brain dopamine levels, which generates pro-oxidant metabolites. Thus, a long-term intake of trans FA caused a small but significant brain incorporation of trans FA, which favored development of movement disorders. Exercise worsened behavioral outcomes of HVF and L-fed rats and increased Na(+)K(+)-ATPase activity of L and SO-fed rats, indicating its benefits. HVF blunted beneficial effects of exercise, indicating a critical role of trans FA in brain neurochemistry.

Inorganic mercury interacts with thiols at the nucleotide and cationic binding sites of the ouabain-sensitive cerebral electrogenic sodium pump

The molecular events leading to neuronal dysfunction often associated with mercury toxicity can be complex and is yet to be fully elucidated. Hence, the present study sought to evaluate the interaction of inorganic mercury (Hg(2+)) with the ouabain-sensitive electrogenic pump in partially purified mammalian brain membrane preparations. The results show that Hg(2+) significantly inhibited the transmembrane enzyme in a concentration dependent manner. In addition, Hg(2+) exerts its inhibitory effect on the activity of the enzyme by interacting with groups at the adenosine triphosphate (ATP), Na(+) and K(+) binding sites. However, preincubation of the enzyme with exogenous monothiols, cysteine, prevented the inhibition of Hg(2+) on the pump's activity suggesting that Hg(2+) may be interacting with the thiols at the nucleotide (ATP) and cationic (Na(+) and K(+)) binding sites. In fact, our data show that Hg(2+) oxidizes sulphydryl groups in cysteine in a time dependent fashion in vitro. Finally, we speculate that the small molecular volume of Hg(2+) in comparison with the substrates (ATP, Na(+) and K(+)) of sodium pump, its possibly high reactivity and strong affinity for thiols may account for its high toxicity towards the membrane bound ouabain-sensitive electrogenic pump.

Comparative study on the influence of subcutaneous administration of diphenyl and dicholesteroyl diselenides on sulphydryl proteins and antioxidant parameters in mice

Although in vitro data from our previous studies show that the antioxidant effect and reactions of both diphenyl diselenide (DPDS) and dicholesteroyl diselenide (DCDS) towards thiol-containing proteins differ considerably, the present study sought to evaluate the interaction of both organodiselenides with thiol-containing proteins in vivo. Mice were injected subcutaneously with DPDS or DCDS previously dissolved in soya bean oil at doses of 0.5 mmol kg⁻¹ body weight for four consecutive days. The activities of delta aminolevulinic acid dehydratase (ALA-D), Na+/K+-ATPase, and isoforms of lactate dehydrogenase (LDH) and catalase were investigated. In addition, the antioxidant status of the mice was determined by measuring the levels of glutathione (GSH), vitamin C (Vit C) and thiobarbituric acid reactive substances. The results show that both diselenides significantly increased the levels of GSH and Vit C but did not markedly alter other antioxidant indices. With respect to the thiol-containing enzymes that were evaluated, DPDS and not DCDS caused a marked reduction in the activities of hepatic ALA-D; however, both diselenides inhibited all isoforms of LDH evaluated. In addition, the activities of cerebral Na+/K+-ATPase were not markedly inhibited by both diselenides, suggesting that this cerebral enzyme may not be a molecular target of organodiselenides toxicity. Taken together, the pharmacological and toxicological chemistry of organoselenium compounds is complex and multifactorial and is dependent on delicate equations which include vehicle solution, animal species and mode of delivery.

Attachment of rhamnosyl glucoside on quercetin confers potent iron-chelating ability on its antioxidant properties

The pharmacological essence of the natural addition of rhamnosyl glucoside on quercetin that is commonly found in nature in medicinal plants is rather obscure. The present study therefore sought to compare the antioxidant activities of both compounds by comparing their ability to decolourise DPPH radicals, reduce Fe(3+), chelate Fe(2+), prevent deoxyribose degradation and inhibit hepatic thiobarbituric acid reactive substances induced by both Fe(2+) and sodium nitroprusside. The results show that quercetin is generally a more potent antioxidant than its rhamnosyl glucoside derivative (rutin). However, rutin exerted a more potent iron-chelating ability than quercetin which diminishes in a time dependent fashion suggesting why it exhibited a reduced inhibitory effect on lipid peroxidation and deoxyribose degradation under harsh prooxidant assault than quercetin. Taken together, we speculate that rutin may have been produced initially in plants as a possible defense mechanism for protection and survival under oxidative assaults and where both flavonoids are found to co-exist in nature, there is a possible synergy in their antioxidant actions.

Antioxidant and hepatoprotective activity of aqueous extract of Solanum fastigiatum (false "Jurubeba") against paracetamol-induced liver damage in mice

AIM OF THE STUDY

Solanum fastigiatum is a medicinal plant widely distributed in the south of Brazil and has been used mainly to treat hepatitis, spleen disorders, uterine tumors, irritable bowel syndrome and chronic gastritis. The present research was aimed to evaluate the potential antioxidant and hepatoprotective activity of aqueous extracts of leaves using in vitro and in vivo models to validate the folkloric use of the plant.

MATERIALS AND METHODS

Antioxidant activity was evaluated by different assays, including thiobarbituric acid reactive species (TBARS), total antioxidant, 2,2-diphenlyl-1-picrylhydrazyl (DPPH) radical and metal ion-chelating activities. The hepatoprotective activity of the aqueous extracts was studied on mice liver damage induced by paracetamol (250mg/kg) by monitoring biochemical parameters.

RESULTS

The extract showed inhibition against TBARS, induced by 10microM FeSO(4) and 5microM sodium nitroprusside in rat liver, brain and phospholipid homogenates from egg yolk. The plant exhibited strong antioxidant activity in the DPPH (IC(50), 68.96+/-1.25microg/ml) assay. The aqueous extract also showed significant hepatoprotective activity that was evident by enzymatic examination and brought back the altered levels of TBARS, non-protein thiol and ascorbic acid to near the normal levels in a dose dependent manner. Acute toxicity studies revealed that the LD(50) value of the extract is more than the dose 4g/kg body weight of mice.

CONCLUSIONS

The results indicate that this plant possesses potential antioxidant and hepatoprotective properties and has therapeutic potential for the treatment of liver diseases.

Hot Pepper (Capsicum spp.) protects brain from sodium nitroprusside- and quinolinic acid-induced oxidative stress in vitro

One practical way through which free radical-mediated neurodegenerative diseases could be prevented is through the consumption of food rich in antioxidants. The ability of aqueous extracts of ripe and unripe Capsicum annum, Tepin (CAT) and Capsicum chinese, Habanero (CCH) to prevent lipid peroxidation induced by sodium nitroprusside and quinolinic acid in rat brain in vitro is assessed in this study. The aqueous extract of the peppers were prepared (1 g/20 mL). Incubating rat brain homogenates with pro-oxidant (7 microM sodium nitroprusside [222.5%] and 1 mM quinolinic acid [217.4%]) caused a significant increase (P < .05) in lipid peroxidation in rat brain homogenates. However, the aqueous extract of the peppers (4.2-16.8 mg/mL) caused a significant decrease (P < .05) in the lipid peroxidation in a dose-dependent manner. However, unripe CAT (92.5-55.2%) caused the highest inhibition of sodium nitroprusside-induced lipid peroxidation, while unripe CCH caused the least inhibition (161.0-102.1%). Furthermore, unripe CAT and CCH peppers had a significantly higher (P < .05) inhibitory effect on quinolinic acid-induced lipid peroxidation in rat brain than the ripe pepper (CAT and CCH). Therefore, the protection of the brain tissues by hot pepper depends on the total phenol content in sodium nitroprusside-induced lipid peroxidation, while ripening would reduce the protective properties of hot pepper against quinolinic acid-induced lipid peroxidation. However, unripe CAT has the highest protective properties against sodium nitroprusside- and quinolinic acid-induced lipid peroxidation in rat brain.

Importance of schedule of administration in the therapeutic efficacy of guanosine: early intervention after injury enhances glutamate uptake in model of hypoxia-ischemia

Perinatal cerebral hypoxia-ischemia (HI) is an important cause of mortality and neurological disabilities such as cerebral palsy, epilepsy, and mental retardation. The potential for neuroprotection in HI can be achieved mainly during the recovery period. In previous work, we demonstrated that guanosine (Guo) prevented the decrease of glutamate uptake by hippocampal slices of neonatal rats exposed to a hypoxic-ischemic (HI) insult in vivo when administrated before and after insult. In the present study, we compared the effect of Guo administration only after HI using various protocols. When compared with the control, a decrease of [(3)H] glutamate uptake was avoided only when three doses of Guo were administered immediately, 24 h and 48 h after insult, or at 3 h, 24 h, and 48 h after injury or at 6 h, 24 h, and 48 h after HI. These findings indicate that early Guo administration (until 6 h) after HI, in three doses may enhance glutamate uptake into brain slices after hypoxia/ischemia, probably resulting in decreased excitotoxicity.

Diphenyl diselenide [(PhSe)2] inhibits Drosophila melanogaster delta-aminolevulinate dehydratase (delta-ALA-D) gene transcription and enzyme activity

The main objective of the present study was to compare the inhibitory effect of diphenyl diselenide (PhSe)(2) and Pb(2+) on mice and fruit fly delta-Aminolevulinate dehydratase (delta-ALA-D). Optimum pH was quite different for mice (pH 6.5) and flies (pH 8.5). At pH 8.5, the inhibitory potency of (PhSe)(2) was higher for the fruit flies (IC(50) 8.2 micromol/l) than for mice (IC(50) 19.5 micromol/l). Pb(2+) inhibited mice delta-ALA-D at pH 6.5 (IC(50) 6.2 micromol/l) and 8.5 (IC(50) 5.6 micromol/l) with higher potency than the fly enzyme (IC(50) 43.7 micromol/l). delta-ALA-D transcription was reduced by 15% in flies exposed to 0.3 mmol/kg (PhSe)(2), which is similar to the reduction observed in activity measured in the presence of dithiothreitol. The three-dimensional prediction by SWISS-PROT mouse and fly delta-ALA-D revealed differences in the number of hydrogen bonds and turns for the 2 enzymes. Sulfhydryl groups (-SH) that could be oxidized by (PhSe)(2) are conserved in the two sources of enzyme. Distinct responsiveness to pH, (PhSe)(2) and Pb(2+) of these enzymes may be related to subtle differences in tertiary or quaternary structure of mouse and fly delta-ALA-D. Furthermore, mechanism underlying enzyme inhibition after in vivo exposure seems to be different for Drosophila melanogaster and rodent enzymes.

Dietary diphenyl diselenide reduces the STZ-induced toxicity

Oxidative stress is implicated in the pathogenesis of diabetes mellitus. Selenium supplementation has some benefits in experimental models of diabetes mellitus. This study evaluated whether dietary diphenyl diselenide, a simple synthetic organoselenium compound with antioxidant properties, reduces the streptozotocin (STZ)-induced toxicity. STZ-induced diabetic rats were fed with either standard and diphenyl diselenide (10 ppm) supplemented diets. In experimental trials, dietary diphenyl diselenide significantly decreased mortality rate (p<0.05) induced by STZ treatment. No correlation between this effect and glycemic levels were found. Diphenyl diselenide intake also promoted an increase in vitamin C, -SH levels (liver, kidney and blood) and in catalase (liver and kidney) activity, which were decreased in STZ-treated rats. In enzyme assays, diphenyl diselenide supplementation caused a significant improvement in platelets NTPDase and 5'-nucleotidase activities in STZ-induced diabetic rats when compared to the control and diabetic groups (p<0.05). Nevertheless, this supplementation did not modify the inhibition induced by STZ in delta-ALA-D activity. Our findings suggest that diphenyl diselenide compound showed beneficial effects against the development of diabetes by exhibiting antioxidant properties.

Repeated administration of diphenyl ditelluride induces hematological disorders in rats

In the present study, we investigated potential toxic effects of diphenyl ditelluride, as measured by biochemical and hematological parameters. Rats were given a daily dose of 0.3 micromol/kg diphenyl ditelluride by subcutaneous route and sacrificed at different times (24 and 48 h). Hepatic and renal TBARS levels were changed by diphenyl ditelluride exposure at the dose 0.9 micromol/Kg in rats. Diphenyl ditelluride exposure demonstrated an increase in AST (aspartate aminotransferase), ALT (alanine aminotransferase) and LDH (lactate dehydrogenase) activities. Plasma creatinine and urea levels increase after diphenyl ditelluride exposure. Diphenyl ditelluride also produced a significant decrease in plasma triglyceride and cholesterol levels. In contrast, this compound, at all doses tested, induced a marked increase in total leukocyte counts. The present study suggests that diphenyl ditelluride induces hematological disorders and provides evidence for renal and hepatic toxicity in rats.

Ebselen and diorganylchalcogenides decrease in vitro glutamate uptake by RAT brain slices: Prevention by DTT and GSH

The purpose of this study was to investigate the possible involvement of the glutamatergic system in the neurotoxicity of diorganylchalcogenides or organochalcogenides from slices of cerebral cortex in different ages of development: 12- and 60-day-old rats. Glutamate uptake was evaluated in cortical slices of 12 and 60 days old rats. Cortex slices were incubated with three different organochalcogenides with or without reduced glutathione or dithiothreitol. At 100 microM, ebselen, diphenyl diselenide (PhSe)2 and diphenyl ditelluride (PhTe)2 in vitro inhibited the [3H]glutamate uptake in both age. Both 60-day-old rats and for 12-day-old rats, GSH and DTT prevented the (PhTe)2-induced inhibition of glutamate uptake but did not protect the inhibition caused by ebselen and (PhSe)2. These findings suggest that the neurotoxicity of organochalcogenides could be related to their effects on brain glutamate uptake, conceivably involving a redox modulation of reactive amino acids from the glutamate transporter proteins.

Heavy metals modulate glutamatergic system in human platelets

Research strategies have been developed to characterize parameters in peripheral tissues that might easily be measured in humans as surrogate markers of damage, dysfunction or interactions involving neural targets of toxicants. The similarities between platelet and neuron may even be clinically important, as a number of biochemical markers show parallel changes in the central nervous system (CNS) and platelets. The purpose of our research was to investigate the effect of Hg(2+), Pb(2+) and Cd(2+) on the [(3)H]-glutamate binding and [(3)H]-glutamate uptake in human platelets. The involvement of oxidative stress in the modulation of glutamatergic system induced by heavy metals was also investigated. The present study clearly demonstrates that Hg(2+), Cd(2+), and Pb(2+) inhibited [(3)H]-glutamate uptake in human platelets. Hg(2+) inhibited [(3)H]-glutamate binding, while Cd(2+) and Pb(2+) stimulated [(3)H]-glutamate binding in human platelets. Hg(2+), Cd(2+) and Pb(2+) increased lipid peroxidation levels and reactive oxygen species (ROS) measurement in platelets. The present limited results could suggest that glutamatergic system may be used as a potential biomarker for neurotoxic action of heavy metals in humans.

Involvement of glutamate and reactive oxygen species in methylmercury neurotoxicity

This review addresses the mechanisms of methylmercury (MeHg)-induced neurotoxicity, specifically examining the role of oxidative stress in mediating neuronal damage. A number of critical findings point to a central role for astrocytes in mediating MeHg-induced neurotoxicity as evidenced by the following observations: a) MeHg preferentially accumulates in astrocytes; b) MeHg specifically inhibits glutamate uptake in astrocytes; c) neuronal dysfunction is secondary to disturbances in astrocytes. The generation of reactive oxygen species (ROS) by MeHg has been observed in various experimental paradigms. For example, MeHg enhances ROS formation both in vivo (rodent cerebellum) and in vitro (isolated rat brain synaptosomes), as well as in neuronal and mixed reaggregating cell cultures. Antioxidants, including selenocompounds, can rescue astrocytes from MeHg-induced cytotoxicity by reducing ROS formation. We emphasize that oxidative stress plays a significant role in mediating MeHg-induced neurotoxic damage with active involvement of the mitochondria in this process. Furthermore, we provide a mechanistic overview on oxidative stress induced by MeHg that is triggered by a series of molecular events such as activation of various kinases, stress proteins and other immediate early genes culminating in cell damage.

Diphenyl diselenide reduces temporarily hyperglycemia: Possible relationship with oxidative stress

This study was designed to determine the effect of diphenyl diselenide and ebselen, synthetic organoselenium compounds with antioxidant properties, in diabetic rats. Diabetes was induced by the administration of streptozotocin (STZ) (45mg/kg, intravenous). In experimental trials, diphenyl diselenide, but not ebselen, caused a significant reduction in blood glucose levels of STZ-treated rats. This effect of diphenyl diselenide was accompanied by a reduction in the levels of glycated proteins. Diphenyl diselenide ameliorate superoxide dismutase activity (liver and erythrocytes) and Vitamin C levels (liver, kidney and blood), which were decreased in STZ-treated rats. In normal rats, diphenyl diselenide caused per se an increase in hepatic, renal and blood GSH levels. Similarly, treatment with diphenyl diselenide restored hepatic and renal GSH levels in STZ-treated rats. TBARS and protein carbonyl levels were not modified by STZ and/or diphenyl diselenide and ebselen treatments. Our findings suggest that diphenyl diselenide can be considered an anti-diabetogenic agent by exhibiting anti-hyperglycemic and antioxidant properties.

Antioxidants and metallothionein levels in mercury-treated mice

Acute effects of mercury on mouse blood, kidneys, and liver were evaluated. Mice received a single dose of mercuric chloride (HgCl2, 4.6 mg/kg, subcutaneously) for three consecutive days. We investigated the possible beneficial effects of antioxidant therapy (N-acetylcysteine (NAC) and diphenyl diselenide (PhSe)2) compared with the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS), an effective chelating agent in HgCl2 exposure in mice. We also verified whether metallothionein (MT) induction might be involved in a possible mechanism of protection against HgCl2 poisoning and whether different treatments would modify MT levels and other toxicological parameters. The results demonstrated that HgCl2 exposure significantly inhibited delta-aminolevulinate dehydratase (delta-ALA-D) activity in liver and only DMPS treatment prevented the inhibitory effect. Mercuric chloride caused an increase in renal non-protein thiol groups (NPSH) and none of the treatments modified renal NPSH levels. Urea concentration was increased after HgCl2 exposure. NAC plus (PhSe)2 was partially effective in protecting against the effects of mercury. DMPS and (PhSe)2 were effective in restoring the increment in urea concentration caused by mercury. Thiobarbituric acid-reactive substances (TBARS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities and ascorbic acid levels were not modified after mercury exposure. Mercuric chloride poisoning caused an increase in hepatic and renal MT levels and antioxidant treatments did not modify this parameter. Our data indicated a lack of therapeutic effect of the antioxidants tested.

Diphenyl ditelluride- and methylmercury-induced hyperphosphorilation of the high molecular weight neurofilament subunit is prevented by organoselenium compounds in cerebral cortex of young rats

Organotellurides are important intermediates in organic synthesis and, consequently, the occupational exposure to them is a constant risk for laboratory workers. These compounds can elicit many neurotoxic events in the central nervous system (CNS) that are associated with several neurological symptoms. In contrast, organoselenium compounds are considered to exert neuroprotective actions on such effects. Neurofilaments (NF) are important cytoskeletal proteins and phosphorylation/dephosphorylation of NF is important to stabilize the cytoskeleton. In this work we investigated the potential protective ability of the selenium compounds ebselen and diphenyl diselenide (PhSe)(2) against the effect of diphenyl ditelluride (PhTe)(2) and methylmercury (MeHg) on the total (phosphorylated plus nonphosphorylated) and phosphorylated immunocontent of the high molecular weight neurofilament subunit (NF-H) from slices of cerebral cortex of 17-day-old rats. We observed that 1muM MeHg induced hyperphosphorylation, increasing the total immunocontent of this subunit of the high-salt Triton insoluble NF-H. Otherwise, 15muM (PhTe)(2) induced hyperphosphorylation of the high-salt Triton insoluble NF-H without altering the total immunocontent of this protein into the cytoskeletal fraction. Concerning the selenium compounds, 15muM (PhSe)(2) and 5muM ebselen did not induce alteration per se on the in vitro phosphorylation of NF-H. In addition, (PhSe)(2) and ebselen at these concentrations, presented a protective effect against the action of (PhTe)(2) and MeHg, on the immunoreactivity of NF-H. Considering that hyperphosphorylation of NF-H is associated with neuronal dysfunction it is probable that the effects of (PhTe)(2) and MeHg could be related to the remarkable neurotoxicity of these organocalcogenides. Furthermore the neuroprotective action of selenium compounds against (PhTe)(2) and MeHg effects could be a promising route to be exploited for a possible treatment of calcogenides poisoning.

2,3-Dimercaptopropanol, 2,3-dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase lead-induced inhibition of δ-aminolevulinate dehydratase in vitro and ex vivo

We investigated the effects of dimercaprol (BAL), meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercapto-1-propanesulphonic acid (DMPS) on human blood delta-aminolevulinate dehydratase (delta-ALA-D) activity, the most reliable indicator of lead intoxication in humans, in the presence of lead in vitro. Furthermore, we studied the effects of the chelating agents, administered subcutaneously, on delta-ALA-D activity in blood and tissues of mice submitted to sub-acute lead exposure (50 mg/kg for 15 consecutive days, subcutaneously). In vitro results demonstrated that human blood delta-ALA-D activity was significantly inhibited (62%) by lead acetate. Lead acetate (1-1000 microM) pre-incubated with human blood increased the inhibitory potency of this compound on delta-ALA-D when compared to the assay without pre-incubation (89%). Chelating agents caused a marked potentiation of delta-ALA-D inhibition induced by lead, in vitro. One of the most notable observations in the present study was the correspondence between in vitro and ex vivo effects. In fact, BAL and DMPS increase the inhibitory effect of lead on delta-ALA-D activity from mice blood. The complexes formed (lead and chelators) were more inhibitory than lead alone in kidney and liver enzyme activity, ex vivo.

Ebselen protects glutamate uptake inhibition caused by methyl mercury but does not by Hg2+

Alterations of the neurotransmitter release systems in CNS have been reported in a variety of neuropathological processes associated with heavy metal toxicity. Neurotoxic effects of mercurials were investigated in vitro in cerebral cortex slices from young rats. The present study indicates that: (i) the environmental contaminants methylmercury (MeHg) and mercuric chloride (Hg2+) (50 microM) inhibited the glutamate net uptake from the cerebral cortex of 17-day-old rats; (ii) ebselen (10 microM) reverted the MeHg-induced inhibition of glutamate net uptake but did not protect the inhibition caused by Hg2+. At same time, we investigated another diorganochalcogenide, diphenyl diselenide (PhSe)2 and it was observed that this compound did not revert the action of MeHg or Hg2+; (iii) in addition, we observed that exposure of slices to 50 microM MeHg and Hg2+ for 30 min followed by Trypan blue exclusion assay resulted in 58.5 and 67.5% of staining cells, respectively, indicating a decrease in cell viability. Ebselen protected slices from the deleterious effects of MeHg, but not of Hg2+ on cell viability. Conversely, ebselen did not modify the reduction of MTT caused by MeHg and Hg2+; (iv) the protective effect of ebselen on MeHg-induced inhibition of glutamate net uptake seems to be related to its ability in maintaining cell viability.

Hypoxic-ischemic insult decreases glutamate uptake by hippocampal slices from neonatal rats: prevention by guanosine

Brain injury secondary to hypoxic-ischemic disease is the predominant form of damage encountered in the perinatal period. The impact of neonatal hypoxia-ischemia (HI) in 7-day-old pups on the high-affinity [3H] glutamate uptake into hippocampal slices at different times after insult was examined. Immediately following, and 1 day after the insult there was no effect. But at 3 to 5 days after the HI insult, glutamate uptake into the hippocampus was markedly reduced; however, after 30 or 60 days the glutamate uptake into hippocampal slices returned to control levels. Also, this study demonstrated the effect of the nucleoside guanosine (Guo) on the [3H] glutamate uptake in neonatal HI injury, maintaining the [3H] glutamate uptake at control levels when injected before and after insult HI. We conclude that neonatal HI influences glutamate uptake a few days following insult, and that guanosine prevents this action.

Effect of diphenyl diselenide, diphenyl ditelluride and ebselen on cerebral Na+, K+-ATPase activity in rats

In the present study, we investigated the in vitro effect of diphenyl ditelluride, diphenyl diselenide and ebselen on Na(+), K(+)-ATPase activity of rat brain. The results demonstrated that all compounds significantly inhibited (in the muM range) Na(+), K(+)-ATPase activity. Diphenyl ditelluride, at low concentrations, provoked an increase in Na(+), K(+)-ATPase activity. Dithiothreitol (DTT), at 3mM, protected the inhibition caused by diphenyl ditelluride, diphenyl diselenide and ebselen in Na(+), K(+)-ATPase activity. Post-incubation of diphenyl diselenide-treated homogenate with DTT completely recovered enzyme activity. DTT was able to recover the enzyme inhibition induced by 20muM of diphenyl ditelluride, but was partially able to recover inhibition induced by high concentrations of organotellurium compound. Conversely, DTT did not recover ebselen-induced Na(+), K(+)-ATPase inhibition. The mechanism of inhibition by diphenyl diselenide, diphenyl ditelluride and ebselen in Na(+), K(+)-ATPase activity revealed: decreased maximal velocity and K(m). Cerebral Na(+), K(+)-ATPase is a potential molecular target for the toxic effect of organochalcogens and the inhibition may occur through a change in the crucial thiol groups of this enzyme.

Human erythrocyte δ-aminolevulinate dehydratase inhibition by monosaccharides is not mediated by oxidation of enzyme sulfhydryl groups

The heme pathway enzyme delta-aminolevulinate dehydratase is a good marker for oxidative stress and metal intoxication. This sulfhydryl enzyme is inhibited in such oxidative pathologies as lead, mercury and aluminum intoxication, exposure to selenium organic species and diabetes. Oxidative stress is a complicating factor in diabetes, inducing non-enzymatic glucose-mediated reactions that change protein structures and impair enzyme functions. We have studied the effects of high glucose, fructose and ribose concentrations on delta-ALA-D activity in vitro. These reducing sugars inhibited delta-ALA-D with efficacies in the order fructose=ribose>glucose. The possible mechanism of glucose inhibition was investigated using lysine, DTT, and t-butylamine. Oxidation of the enzyme's critical sulfhydryl groups was not involved because DTT had no effect. We concluded that high concentrations of reducing sugars or their autoxidation products inhibit delta-ALA-D by a mechanism not related to thiol oxidation. Also, we are not able to demonstrate that the formation of a Schiff base with the critical lysine residue of the enzyme is involved in the inhibition of delta-ALA-D by hexoses.

Organoselenium compounds prevent hyperphosphorylation of cytoskeletal proteins induced by the neurotoxic agent diphenyl ditelluride in cerebral cortex of young rats

In this work we investigated the protective ability of the selenium compounds ebselen and diphenyl diselenide against the effect of diphenyl ditelluride on the in vitro incorporation of 32P into intermediate filament (IF) proteins from slices of cerebral cortex of 17-day-old rats. We observed that ditelluride in the concentrations of 1, 15 and 50 microM induced hyperphosphorylation of the high-salt Triton insoluble neurofilament subunits (NF-M and NF-L), glial fibrillary acidic protein (GFAP) and vimentin, without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1,15 and 50 microM) did not induce alteration of the in vitro phosphorylation of the IF proteins. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. At intermediate concentrations (15 and 30 microM) it increased the in vitro phosphorylation even though, at low (5 microM) or high (50 and 100 microM) concentrations this compound was ineffective in altering the activity of the cytoskeletal-associated phosphorylating system. In addition, 15 microM diselenide and 5 microM ebselen, presented a protective effect against the action of ditelluride, on the phosphorylation of the proteins studied. Considering that hyperphosphorylation of cytoskeletal proteins is associated with neuronal dysfunction and neurodegeneration, it is probable that the effects of ditelluride could be related to the remarkable neurotoxicity of this organic form of tellurium. Furthermore the neuroprotective action of selenium compounds against tellurium effects could be a promising route to be exploited for a possible treatment of organic tellurium poisoning.

Hematological changes in rats chronically exposed to oral aluminum

This study was aimed to investigate the effects of the long-term oral exposure to aluminum sulfate on hematological parameters in rats. For this purpose, 24 adult female Wistar rats were divided in three groups with 8 animals each (control, citrate, and citrate plus aluminum groups). Rats from control and citrate groups had free access to tap water and to a sodium citrate solution (35 mM), respectively. Rats from citrate plus aluminum group received, as unique source of liquid, an aluminum sulfate solution (30 mM) diluted in the above-mentioned sodium citrate solution, ad libitum. After the treatment period (18 months), aluminum-exposed rats showed a significant decrease in the number of red blood cells, blood hemoglobin concentration and hematocrit when compared to rats from the control group. Serum iron levels were also significantly lower in citrate plus aluminum group, whereas total iron binding capacity did not change after citrate plus aluminum exposure. Erythrocyte thiobarbituric acid-reactive substances (TBARS) and nonprotein thiols (NPSH) levels, erythrocyte osmotic fragility and hepatic delta-aminolevulinic acid dehydratase (delta-ALA-D) activity did not change after treatment with citrate plus aluminum. Conversely, aluminum exposure increased delta-ALA-D activity in bone marrow. The present results indicate that long-term oral exposure to low doses of aluminum sulfate promotes alterations on erythrocyte parameters in rats, probably as a consequence of alterations in the iron status. In addition, although the details of the underlying mechanism remain unclear, our study reports, for the first time, a stimulatory effect of chronic aluminum exposure on bone marrow delta-ALA-D activity.

Antinociceptive properties of acetylenic thiophene and furan derivatives: Evidence for the mechanism of action

The aim of the present study was to evaluate the antinociceptive potential of the acetylenic thiophene and furan derivatives: 3-(furan-2-il) prop-2-yn-1-ol 1, 1-(thiofen-2-il) pent-1yn-3-ol 2 and 4-(thiofen-2-il)-2-metilbut-3-yn-2-ol 3 on three different pain models in mice. The pain models evaluated were the acetic acid-induced writhing, capsaicin-induced pain and the tail immersion test. The possible mechanisms involved in the antinociceptive effect of these compounds were also investigated. Thus, the acetylenic thiophene and furan derivatives presented antinociceptive effect in the pain tests caused by chemical agents. Statistical analysis showed that compounds 1 and 3 increased the latency for tail withdrawal in the tail immersion test (phasic pain). Besides, the role of the opioidergic, muscarinic cholinergic and dopaminergic systems in the acetic acid-induced writhing was examined. The antinociceptive effect of compounds 2 and 3 was prevented by pretreatment with naloxone (1 mg/kg, s.c), but not by atropine (5 mg/kg, s.c) or metoclopramide (1 mg/kg, s.c). Neither naloxone nor metoclopramide prevented the antinociceptive effect caused by compound 1, while the pretreatment with atropine antagonized the antinociceptive action of this compound. The compounds 1-3 used in this study did not reveal any motor impairment to mice in the open field. The results suggest that compounds 2 and 3 induced antinociception in the abdominal writhing test and that their effects are mediated by opiodergic receptors, while the antinociceptive effect of compound 1 may involve muscarinic cholinergic receptors.

Selenium Compounds Prevent the Effects of Methylmercury on the in Vitro Phosphorylation of Cytoskeletal Proteins in Cerebral Cortex of Young Rats

In this study we investigated the protective ability of the selenium compounds ebselen and diphenyldiselenide against the effect of methylmercury on the in vitro incorporation of 32P into intermediate filament (IF) proteins from the cerebral cortex of 17-day-old rats. We observed that methylmercury in the concentrations of 1 and 5 microM was able to inhibit the phosphorylating system associated with IF proteins without altering the immunocontent of these proteins. Concerning the selenium compounds, diselenide (1, 15, and 50 microM) did not induce alteration of the in vitro phosphorylation of IF proteins. Conversely, 15 microM diselenide was effective in preventing the toxic effects induced by methylmercury. Otherwise, ebselen induced an altered in vitro phosphorylation of the cytoskeletal proteins in a dose-dependent manner. Ebselen at intermediate concentrations (15 and 30 microM) increased the in vitro phosphorylation. However, at low (5 microM) or high (50 and 100 microM) concentrations it was ineffective in altering the cytoskeletal-associated phosphorylating system. Furthermore, 5 microM ebselen presented a protective effect against the action of methylmercury on the phosphorylating system. In conclusion, our results indicate that the selenium compounds ebselen and diselenide present protective actions toward the alterations of the phosphorylating system associated with the IF proteins induced by methylmercury in slices of the cerebral cortex of rats.

Methylmercury increases S100B content in rat cerebrospinal fluid

S100B, a calcium binding protein physiologically produced and released by astrocytes, has been used as a peripheral marker of brain damage. Here, we investigated the effects of subcutaneous injections of methylmercury chloride (MeHg-5mg/kg), an environmental neurotoxicant, on S100B protein content in cerebrospinal fluid (CSF) of adult rats. In addition, the performance of animals in an open field (number of squares crossing and rearings) was also analyzed in order to obtain a possible link between alteration in S100B protein content in CSF and parameters related to neurological injury. MeHg treatment increased serum mercury and S100B protein levels in the CSF. A decrease in the numbers of crossings and rearings was observed in MeHg-treated animals when compared to control group, which suggests a possible neurological injury. The present data show, for the first time, increased S100B levels in CSF after exposure to a neurotoxic metal. Authors discuss the possibility of astrocytic involvement in MeHg-induced neurotoxicity.

Ebselen and diphenyl diselenide change biochemical hepatic responses to overdosage with paracetamol

The toxicity of paracetamol is largely related to its conversion to the reactive intermediate alkylating metabolite N-acetyl-para-benzo-quinoneimine (NAPQI). δ-Aminolevulinate dehydratase (δ-ALA-D) is a sulfhydril containing enzyme which is extremely sensitive to oxidizing and alkylating agents. In the present study, we examined whether acute treatment with paracetamol changes δ-ALA-D activity. The influence of two organochalcogenides with glutathione peroxidase-like activity, diphenyl diselenide [(PhSe)(2)] and ebselen was also assessed as potential protecting agents against paracetamol toxicity. Paracetamol (1200mg/kg for three days 4h after the injection of DMSO, diphenyl diselenide (100μmol/kg) or ebselen (100μmol/kg) caused an inhibition of about 40% (P < 0.01) in hepatic δ-ALA-D. Ebselen restored enzyme activity to control values. Non-protein-SH and ascorbic acid were diminished to 50% of control value by paracetamol, independent of chalcogenides treatment (all P values <0.05). In view of the fact that paracetamol caused a massive reduction in non-protein-SH and ascorbic acid, we realize that the protective effect of ebselen on δ-ALA-D activity is mediated by its thiol peroxidase-like activity or by a direct interaction with NAPQI and other reactive species formed during paracetamol metabolism.

Teratogenic vulnerability of Wistar rats to diphenyl ditelluride

The effect of single maternal subcutaneous (s.c.) injection of 0.12 mg/kg diphenyl ditelluride, (PhTe)2, diluted in canola oil at days 6, 10 or 17 of gestation were evaluated in Wistar rats. The reduction of body weight gain was statistically significant at GD9, for the dams that received (PhTe)2, at GD6; at GD13, for the dams that received (PhTe)2, at GD10, and at GD20, for the dams that received (PhTe)2, at GD17, when compared to respective control groups. External and internal fetal soft tissues examination was performed on day 20 of gestation. Single maternal injection at day 10 of gestation resulted in appearance of malformation in fore- and hind-limbs, absent or short tail, subcutaneous blood clots, exophthalmia, hydrocephalus and absence of the cranial bone and cutaneous tissue in fetuses on day 20 of gestation. Besides, (PhTe)2 reduced fetal body and cerebral weight, kidney length, measurements of body dimension and provoked 73% of fetal mortality. Subcutaneous administration of (PhTe)2 on day 17 of gestation was associated with 94% mortality, hydrocephalus and edema. Histological evaluations of fetal brain demonstrated displaced brain tissue with absence of the cranial bone and cutaneous tissue when diphenyl ditelluride was administered in GD10. Histological evaluation of fetal head exposed at GD17 revealed a decrease of the brain volume with consequent dilation of the lateral ventricles and the adjacent tissues were thinner than that of control group tissues. No fetal changes were observed after administration of (PhTe)2 at day 6 of gestation. Thus, (PhTe)2 can be teratogenic to rat fetuses and toxic for dams. The late fetal stages of rat prenatal development appeared uniquely sensitive to organic tellurium exposure.

Ebselen Protects Ca2+Influx Blockage But Does Not Protect Glutamate Uptake Inhibition Caused By Hg2+

The goal of this study was to investigate the isolated and combined effect of ebselen and Hg2+ on calcium influx and on glutamatergic system. We examined the in vitro effects of 2 phenyl-1,2-benzisoselenazol-3(2H)-ona), (Ebselen) on 45Ca2+ influx in synaptosomes of rat at rest and during depolarization and glutamate uptake into synaptosomes. Entry of 45Ca was measured during exposure to mercury in non-depolarizing and depolarizing solutions. Ebselen abolished the inhibition of 45Ca2+ influx on non-depolarizing conditions; however, ebselen did no modify inhibition uptake of 45Ca2+ caused by Hg2+ in high K+ depolarizing medium. Ebselen did not modify glutamate uptake inhibition caused by Hg2+ in synaptosomes. These results indicate that ebselen has an in vitro protective effect against Hg2+ induced inhibition of Ca2+ influx into synaptosomes, depending on the depolarizing conditions of the assay. The effects of Hg2+ on glutamate uptake were not modified by ebselen, suggesting that its protection is dependent on the target protein considered.

Organochalcogens Affect the Glutamatergic Neurotransmission in Human Platelets

Blood platelets have repeatedly been suggested as an excellent model for various aspects of the synaptic apparatus. Considering that organochalcogens affect some parameters of glutamatergic neurotransmission in rats, in the current study we evaluated the effect of diphenyl diselenide (PhSe)2, diphenyl ditelluride (PhTe)2, and Ebselen on glutamatergic neurotransmission in human platelets. (PhTe)2 and (PhSe)2 caused a significant inhibition, but Ebselen did not interfere in Na-independent glutamate binding. Dithiothreitol (DTT) did not completely prevent the [3H]glutamate binding inhibition caused by 100 microM (PhTe)2. (PhSe)2, (PhTe)2, and Ebselen (100 microM) significantly inhibited [3H]glutamate uptake, whereas organochalcogens at 1 and 10 microM had no significant effect on the [3H]glutamate uptake in human platelets. In this study, platelets were demonstrated to be a suitable model for neurotoxicological research, and, to the best of our knowledge, this is the first report documenting the toxic effects of organochalcogens in human platelets.

Maternal Milk as Methylmercury Source for Suckling Mice: Neurotoxic Effects Involved with the Cerebellar Glutamatergic System

Methylmercury (MeHg) is a highly neurotoxic compound and several studies have reported intoxication signs in children whose mothers were exposed to this environmental toxicant. Although it is well established that the in utero exposure to MeHg causes neurological deficits in animals and humans, there is no evidence of the exclusive contribution of lactational exposure to MeHg as a possible cause of neurotoxicity in the offspring. In this study, we investigated the exclusive contribution of MeHg exposure through maternal milk on biochemical parameters related to the glutamatergic homeostasis (glutamate uptake by slices) and to the oxidative stress (total and nonprotein sulfhydryl groups, nonprotein hydroperoxides, glutathione peroxidase and catalase activities) in the cerebellum of suckling mice (Swiss albino). The same parameters were also evaluated in the cerebellum of mothers. Our results showed, for the first time, that lactational exposure to MeHg caused a high percent of inhibition (50%) on glutamate uptake by cerebellar slices in pups. Contrarily, this effect was not observed in mothers, which were submitted to a direct oral exposure to MeHg (15 mg/l in drinking water). In addition, behavioral/functional changes were observed in the weaning mice exposed to MeHg. It was observed an increase in the levels of nonprotein hydroperoxides in cerebellum, and this increase was negatively correlated to the glutamate uptake by cerebellar slices. This study indicates that (1) the exposure of lactating mice to MeHg causes inhibition of the glutamate uptake by cerebellar slices in the offspring; (2) this inhibitory effect seems to be related to increased levels of hydroperoxide.

Voltage-dependent ebselen and diorganochalcogenides inhibition of 45Ca2+ influx into brain synaptosomes

By mediating the Ca(2+) influx, Ca(2+) channels play a central role in neurotransmission. Chemical agents that potentially interfere with Ca(2+) homeostasis are potential toxic agents. In the present investigation, changes in Ca(2+) influx into synaptosomes by organic forms of selenium and tellurium were examined under nondepolarizing and depolarizing conditions induced by high KCl concentration (135 mM) or by 4-aminopyridine (4-AP). Under nondepolarizing conditions, ebselen (400 micro M) increased Ca(2+) influx; diphenyl ditelluride (40-400 micro M) decreased Ca(2+) in all concentrations tested; and diphenyl diselenide decreased Ca(2+) influx at 40 and 100 micro M, but had no effect at 400 micro M. In the presence of KCl as depolarizing agent, ebselen and diphenyl ditelluride decreased Ca(2+) influx in a linear fashion. In contrast, diphenyl diselenide did not modify Ca(2+) influx into isolated nerve terminals. In the presence of 4-AP (3 mM) as depolarizing agent, ebselen (400 micro M) caused a significant increase, whereas diphenyl diselenide and diphenyl ditelluride inhibited Ca(2+) influx into synaptosomes. The results can be explained by the fact that the mechanism through which 4-AP and high K(+) induced elevation of intracellular Ca(2+) is not exactly coincident. The mechanism by which diphenyl ditelluride and ebselen interact with Ca(2+) channel is unknown, but may be related to reactivity with critical sulfhydryl groups in the protein complex. The results of the present study indicate that the effects of organochalcogenides were rather complex depending on the condition and the depolarizing agent used.

2,3-Dimercaptopropanol, 2,3-dimercaptopropane-1-sulfonic acid, and meso-2,3-dimercaptosuccinic acid inhibit delta-aminolevulinate dehydratase from human erythrocytes in vitro

The effects of dithiol chelating agents meso-2,3-dimercaptosuccinic acid (DMSA), 2,3-dimercaptopropane-1-sulfonic acid (DMPS), and 2,3-dimercaptopropanol (BAL) on delta-aminolevulinate dehydratase (delta-ALA-D) from human erythrocytes were evaluated. Furthermore, possible protective effects of zinc chloride (ZnCl(2)), dithiothreitol (DTT), and cysteine were studied. delta-ALA-D activity from human erythrocytes was inhibited by dithiol chelating agents in a concentration-dependent manner. Cysteine, at all concentrations tested, did not protect the inhibitory effect of 1 and 4 mM DMPS and DMSA, but protected 1 mM BAL inhibition. Dithiotreitol was able to protect the inhibition caused by 1 mM BAL (28%), DMPS (56%), and DMSA (40%) in a concentration-dependent manner. Zinc chloride protected and restored 1 mM BAL inhibitory effect on delta-ALA-D. Zinc chloride at 500 microM and 1 mM, respectively, protected inhibitory effects of DMPS and DMSA (1 and 4 mM), but did not reverse its effects. The preincubation of dithiol chelating agents with enzyme demonstrated that DMSA was the most potent delta-ALA-D inhibitor of human erythrocytes. These data are in agreement with delta-ALA-D activity from purified enzyme. ZnCl(2) (1 microM) added, in the reaction mixture, increased enzyme activity and DTT (100 microM) totally restored the enzyme activity for all chelating agents tested.

Protective role of aryl and alkyl diselenides on lipid peroxidation

The concept that selenium-containing molecules may be better nucleophiles (and therefore antioxidants) than classical antioxidants has led to the design of synthetic organoselenium compounds. In the present study we appraised the antioxidant potential, thiol peroxidase activity, and rate of dithiotreitol and reduced glutathione oxidation of simple organodiselenide compounds in rats and mice. The present results demonstrate that alkyl and aryl diselenides are antioxidant compounds. We verified that the substitution on the aromatic moiety of diphenyl diselenide or the replacement of on aryl group by an alkyl substitute on diselenides changes their antioxidant and thiol peroxidase-like properties. The diaryl diselenides (PhSe)(2) and (p-ClPhSe)(2) presented higher thiol peroxidase activity and demonstrated better antioxidant potential than the other diselenides tested. In fact, the results revealed that alkyl diselenides, at low concentrations, were prooxidants and that aryl diselenides did not present this effect. Alkyl diselenides [(C(2)H(5)Se)(2) and (C(3)H(7)Se)(2)] demonstrated a higher potential for -SH group oxidation than aryl diselenides. In addition, this study demonstrated that diselenide protection against lipid peroxidation was different in mice and rats. The compounds tested acted more as antioxidants in the brains of mice than in the brains of rats.