Antioxidant effect of diphenyl diselenide against sodium nitroprusside (SNP) induced lipid peroxidation in human platelets and erythrocyte membranes: An in vitro evaluation

Fluoxetine scaffold to design tandem molecular antioxidants and green catalysts

Fluoxetine finds application in the treatment of depression and mood disorders. This selective serotonin-reuptake inhibitor (SSRI) also contrasts oxidative stress by direct ROS scavenging, modulation of the endogenous antioxidant defense system, and/or enhancement of the serotonin antioxidant capacity. We synthesised some fluoxetine analogues incorporating a selenium nucleus, thus expanding its antioxidant potential by enabling a hydroperoxides-inactivating, glutathione peroxidase (GPx)-like activity. Radical scavenging and peroxidatic activity were combined in a water-soluble, drug-like, tandem antioxidant molecule. Selenofluoxetine derivatives were reacted with H₂O₂ in water, and the mechanistic details of the reaction were unravelled combining nuclear magnetic resonance (NMR), electrospray ionisation-mass spectrometry (ESI-MS) and quantum chemistry calculations. The observed oxidation–elimination process led to the formation of seleninic acid and cinnamylamine in a trans-selective manner. This mechanism is likely to be extended to other substrates for the preparation of unsaturated cinnamylamines.

We modified fluoxetine by incorporating a selenium nucleus enabling a hydroperoxide-inactivating, glutathione peroxidase (GPx)-like activity and paving the way for its use as green catalyst.

Effects of sodium nitroprusside on mouse erythrocyte catalase activity and malondialdehyde status

There is controversy about the anti- or pro-oxidative effects of the nitric oxide (NO)-donor sodium nitroprusside (SNP). Hence, the activity of the antioxidant enzyme catalase (CAT) and the status of malondialdehyde (MDA) were investigated after a 2.5 mg/kg dose of SNP had been i.p. administered to different and comparable groups of mice (n = 48). The drug was administered at two different circadian times (1 and 13 h after light onset [HALO]). There were, irrespectively of sampling time, no significant differences in the means of CAT activity and MDA status between control and SNP-treated groups, no matter the treatment time. However, CAT activity was significantly (Student's t-test, p < 0.001) increased 1 h following SNP administration at 1 HALO, whereas the significant (p < 0.001) increase in the enzyme activity was found only 3 h after injection at 13 HALO. The drug dosing either at 1 or 13 HALO resulted in no significant differences of MDA status between control and treated groups regardless to the sampling time. Two-way analysis of variance (ANOVA) detected a significant (F0.05(7,88)= 5.3; p < 0.0006) interaction between sampling time and treatment in mice injected at 1 HALO, suggesting the influence of treatment on sampling-time-related changes in CAT activity. However, ANOVA validated no interaction between the two factors in mice treated at 13 HALO, illustrating that the sampling-time differences in enzyme activity were greater. Furthermore, two-way ANOVA revealed no interaction in the variation of MDA status in animals treated either at 1 or 13 HALO. This study indicates that SNP significantly affected the anti-oxidant system.

Free radical scavenging in vitro and biological activity of diphenyl diselenide-loaded nanocapsules: DPDS-NCS antioxidant and toxicological effects

Selenium compounds, such as diphenyl diselenide (DPDS), have been shown to exhibit biological activity, including antioxidant effects. However, the use of DPDS in pharmacology is limited due to in vivo pro-oxidative effects. In addition, studies have shown that DPDS-loaded nanocapsules (DPDS-NCS) have greater bioavailability than free DPDS in mice. Accordingly, the aim of this study was to investigate the antioxidant properties of DPDS-NCS in vitro and biological activity in mice. Our in vitro results suggested that DPDS-NCS significantly reduced the production of reactive oxygen species and Fe(II)-induced lipid peroxidation (LPO) in brain. The administration of DPDS-NCS did not result in death or change the levels of endogenous reduced or oxidized glutathione after 72 hours of exposure. Moreover, ex vivo assays demonstrated that DPDS-NCS significantly decreased the LPO and reactive oxygen species levels in the brain. In addition, the highest dose of DPDS-NCS significantly reduced Fe(II)- and sodium nitroprusside-induced LPO in the brain and Fe(II)-induced LPO in the liver. Also, δ-aminolevulinate acid dehydratase within the brain was inhibited only in the highest dose of DPDS-NCS. In conclusion, our data demonstrated that DPDS-NCS exhibited low toxicity in mice and have significant antioxidant characteristics, indicating that nanoencapsulation is a safer method of DPDS administration.

Dosing-time dependent effects of sodium nitroprusside on cerebral, renal, and hepatic catalase activity in mice

To investigate the time dependence of sodium nitroprusside- (NPS-) induced oxidative effects, the authors study the variation of the antioxidant enzyme CAT activity in various tissues after the administration of a single 2.5 mg/kg dose of SNP or sodium chloride (NaCl 0.9%). For each of the two dosing times (1 and 13 hours after light onset, HALO, which correspond to the beginning of diurnal rest span and of nocturnal activity span of mice, resp.), brain, kidney, and liver tissues were excised from animals at 0, 1, 3, 6, 9, 12, 24, and 36 h following the drug administration and CAT activity was assayed. The results suggest that SNP-induced stimulation of CAT activity is greater in all three tissues when the drug is administered at 1 HALO than at 13 HALO. Two-way ANOVA revealed that CAT activity significantly (P < 0.004) varied as a function of the sampling time but not of the treatment in all three tissues. Moreover, a statistically significant (P < 0.004) interaction between the organ sampling-time and the SNP treatment was revealed in kidney regardless of the dosing time, whereas a highly significant (P < 0.0002) interaction was validated in liver only in animals injected at 13 HALO.

Diphenyl diselenide (PhSe)2 inhibits biofilm formation by Candida albicans, increasing both ROS production and membrane permeability

PROJECT

The opportunistic fungal Candida albicans can produce superficial and systemic infections in immunocompromised patients. An essential stage to both colonization and virulence by C. albicans is the transition from budding yeast form to filamentous form, producing biofilms.

PROCEDURE

In this work, we studied the effect of the organochalcogenide compound (PhSe)2 on both cell growth and biofilm formation by C. albicans.

RESULTS

(PhSe)2 inhibited both growth and biofilm formation by C. albicans. The inhibitory effects of (PhSe)2 depended on the cell density and (PhSe)2 concentration. We have also observed that (PhSe)2 stimulated ROS production (67%) and increased cell membrane permeability (2.94-fold) in C. albicans. In addition, (PhSe)2 caused a marked decrease in proteinase activity (6.8-fold) in relation to non-treated group.

CONCLUSIONS

(PhSe)2 decreased both cell growth and biofilm development, decreasing the release of extracellular proteinases, which is an important facet of C. albicans pathogenicity. The toxicity of (PhSe)2 towards C. albicans can be associated with an increase in ROS production, which can increase cell permeability. The permanent damage to the cell membranes can culminate in cell death.

Syzygium jambos and Solanum guaraniticum show similar antioxidant properties but induce different enzymatic activities in the brain of rats

Syzygium jambos and Solanum guaraniticum are both employed in Brazil as medicinal plants, even though their potential toxicity is not well established and they are frequently misused. The aim of this study was investigate the effect of the aqueous leaf extracts of both plants on δ-aminolevulinate dehydratase (δ-ALA-D) and acetylcholinesterase (AChE) activities and the antioxidant action against oxidative damage induced by sodium nitroprusside in rats, using in vitro assays. In addition, the presence of gallic, caffeic and chlorogenic acids, as well as rutin, quercetin and kaempferol as bioactive compounds in the extracts was identified by HPLC and their levels quantified. The antioxidant activities of both extracts were assessed by their capabilities to scavenge nitric oxide and to inhibit lipid peroxidation. Only Syzygium jambos presented thiol-peroxidase-like activity. Although neither extract affected the AChE activity, the aqueous extract of Solanum guaraniticum inhibited brain δ-ALA-D activity, suggesting a possible impairment effect on the central nervous system. Our results showed that both extracts exhibited efficient free radical scavenger activity and are an interesting source of bioactive compounds, justifying their use in folk medicine, although Solanum guaraniticum extract could have neurotoxicity properties and we therefore suggest that its use should be restricted to ensure the health of the population.

Differential effects of organic and inorganic selenium compounds on adenosine deaminase activity and scavenger capacity in cerebral cortex slices of young rats

Selenium (Se) has anti-inflammatory and antioxidant properties and is necessary for the development and normal function of the central nervous system. This study was aimed to compare the in vitro effects of 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one (C21H2HOSe; organoselenium) and sodium selenate (inorganic Se) on adenosine deaminase (ADA) activity, cell viability, lipid peroxidation, scavenger of nitric oxide (NO) and nonprotein thiols (NP-SH) content in the cerebral cortex slices of the young rats. A decrease in ADA activity was observed when the slices were exposed to organoselenium at the concentrations of 1, 10 and 30 µM. The same compound showed higher scavenger capacity of NO than the inorganic compound. Inorganic Se was able to protect against sodium nitroprusside-induced oxidative damage and increased the NP-SH content. Both the compounds displayed distinctive antioxidant capacities and were not cytotoxic for the cerebral cortex slices in the conditions tested. These findings are likely to be related to immunomodulatory and antioxidant properties of this compound.

[Identification of genomic structure and resistance trait associated SNP loci in glutathione peroxidase gene of Hyriopsis cumingii]

Based on the cDNA sequence of GPX in Hyriopsis cumingii, the complete genomic DNA of GPX gene and it's 5'-flanking region were identified from H. cumingii using PCR and genome walking technique. The length of the complete genomic sequence was 6 708 bp including the 5'-flanking region, two exons, and one intron. Sequence analysis of the 992 bp 5'-flanking region revealed that it contained a core promoter element (TATA-box) and other transcription regulation elements such as AP1, C/EBP, and CdxA. The sequence lengths of the two exons were 273 bp and 991 bp, respectively, and the intron was 4 491 bp in length. Sixteen single nucleotide polymorphisms (SNPs) were detected in the GPX gene from resistant stock (RS) and susceptible stock (SS) of H. cumingii. These polymorphisms were analyzed with regard to resistance to Aeromonas hydrophila. Among them, three SNPs including A-99G, A-86C, and A-49C in GPX promoter and five SNPs including A2841T, C2847T, G3146C, A3150G, and G4645T in GPX introns were associated with resistance/susceptibility of H. cumingii to A. hydrophila, both in genotype and allele frequency. Linkage disequilibrium analysis revealed that A-86C, A-49C, C2847T, A3150G, G4645T, A2841T, and G3146C were in high linkage disequilibrium, and haplotype analysis revealed that the frequency of two major predominant haplotypes (ACTGT and TG) in the resistant group was significantly higher than that in the susceptible group. The results suggest that the polymorphic loci in the GPX gene could be potential genetic markers for future molecular selection of strains resistant to diseases.

Effects of diphenyl diselenide on oxidative stress induced by sepsis in rats

Sepsis is a potentially deadly complication that can be caused by different factors. Actually, it is known that oxidative stress is involved in the pathogenesis of sepsis. Thus, the aim of this study was to evaluate the effect of diphenyl diselenide (PhSe)(2), an emergent compound, on oxidative stress parameters induced by sepsis in rats. Animals were pre-injected with (PhSe)(2) or vehicle. Twenty-four hours later, sepsis was induced by cecal ligation puncture (CLP). After 12 h, liver was taken for thiobarbituric acid reactive species (TBARS) measurement, δ-aminolevunic acid dehydratase (δ-ALA-D), Cu/Zn superoxide dismutase (Cu/Zn SOD) and catalase (CAT) activities assay. The sepsis increased TBARS, inhibited δ-ALA-D, activated Cu/Zn SOD and had a tendency to decrease CAT activity. However, (PhSe)(2) prevented the TBARS formation, but did not prevent the inhibition of δ-ALA-D activity in the animals with damage. Thus, this study showed that (PhSe)(2) partially prevents the oxidative stress induced by sepsis, indicating the potential of this compound as a treatment for this pathology. Nevertheless, more tests should be performed to confirm the hypothesis suggested here.

Evaluation of the neurotoxic/neuroprotective role of organoselenides using differentiated human neuroblastoma SH-SY5Y cell line challenged with 6-hydroxydopamine

It is well established that oxidative stress plays a major role in several neurodegenerative conditions, like Parkinson disease (PD). Hence, there is an enormous effort for the development of new antioxidants compounds with therapeutic potential for the management of PD, such as synthetic organoselenides molecules. In this study, we selected between nine different synthetic organoselenides the most eligible ones for further neuroprotection assays, using the differentiated human neuroblastoma SH-SY5Y cell line as in vitro model. Neuronal differentiation of exponentially growing human neuroblastoma SH-SY5Y cells was triggered by cultivating cells with DMEM/F12 medium with 1% of fetal bovine serum (FBS) with the combination of 10 μM retinoic acid for 7 days. Differentiated cells were further incubated with different concentrations of nine organoselenides (0.1, 0.3, 3, 10, and 30 μM) for 24 h and cell viability, neurites densities and the immunocontent of neuronal markers were evaluated. Peroxyl radical scavenging potential of each compound was determined with TRAP assay. Three organoselenides tested presented low cytotoxicity and high antioxidant properties. Pre-treatment of cells with those compounds for 24 h lead to a significantly neuroprotection against 6-hydroxydopamine (6-OHDA) toxicity, which were directly related to their antioxidant properties. Neuroprotective activity of all three organoselenides was compared to diphenyl diselenide (PhSe)₂, the simplest of the diaryl diselenides tested. Our results demonstrate that differentiated human SH-SY5Y cells are suitable cellular model to evaluate neuroprotective/neurotoxic role of compounds, and support further evaluation of selected organoselenium molecules as potential pharmacological and therapeutic drugs in the treatment of PD.

Diphenyl diselenide induces apoptotic cell death and modulates ERK1/2 phosphorylation in human neuroblastoma SH-SY5Y cells

Diphenyl diselenide (PhSe)(2) is a synthetic organoselenium compound displaying glutathione peroxidase-like activity. Protective and antioxidant potential of (PhSe)(2) have been extensively investigated in in vivo and in vitro studies. In spite of this, there is a lack of studies addressed to the investigation of potential cytotoxic effect and signaling pathways modulated by this compound. Herein, we aimed to analyze the effects of 24-h treatment with (PhSe)(2) on cell viability and a possible modulation of signaling pathways in human neuroblastoma cell line SH-SY5Y. For this purpose, cells were incubated with (PhSe)(2) (0.3-30 μM) for 24 h and cell viability, apoptotic cell death and modulation of MAPKs (ERK1/2 and p38(MAPK)), and PKC substrates phosphorylation was determined. (PhSe)(2) treatment significantly decreased cell viability and increased the number of apoptotic cells with induction of PARP cleavage. An increase in ERK1/2 phosphorylation was observed at (PhSe)(2) 3 μM. In contrast, higher concentrations of the chalcogenide inhibited ERK1/2, p38(MAPK) and PKC substrate phosphorylation. Pre-treatment with ERK1/2 inhibitor, U0126, increased cell susceptibility to (PhSe)(2). Together, these data indicate a cytotoxic potential of (PhSe)(2) in a neuronal cell line, which appears to be mediated by the ERK1/2 pathway.

Acute exposure of rabbits to diphenyl diselenide: a toxicological evaluation

The simple organoselenium compound diphenyl diselenide (PhSe)(2) is a promising new pharmacological agent. However, few toxicological evaluations of this molecule have been reported. We evaluated the effects of acute administration of (PhSe)(2) on toxicological parameters in rabbits. Adult New Zealand rabbits were exposed to (PhSe)(2) (5-500 micromol kg(-1) , intraperitoneally) once a day for 5 days. Exposure to 500 micromol kg(-1) caused 85% mortality. Exposure to 50 micromol kg(-1) of (PhSe)(2) increased the glutathione levels in the hippocampus, kidney, heart, muscle and blood, whereas lipoperoxidation (TBARS) decreased in the cerebellum and kidney after exposure to 5 micromol kg(-1) . The activity of glutathione peroxidase increased in the heart and muscle of rabbits treated with 50 micromol kg(-1) of (PhSe)(2) and glutathione reductase activity was reduced in the cerebellum, cerebral cortex and kidney. Treatment with (PhSe)(2) reduced the activity of δ-aminolevulinate dehydratase in the hippocampus and increased this activity in the heart, but did not alter the activity of complexes I and II of the respiratory chain in the liver and brain. Hepatic and renal biochemical and histological parameters were not modified by (PhSe)(2) and apoptosis was not detected in these tissues; however, the hepatic cells tended to accumulate fat vacuoles. These results indicated that acute toxicology to (PhSe)(2) in rabbit is dependent on the dose, which should motivate further experiments on the therapeutic properties of this compound.

Effects of acidosis and Fe (II) on lipid peroxidation in phospholipid extract: Comparative effect of diphenyl diselenide and ebselen

The influence of acidosis on lipid peroxidation in phospholipids extract from egg yolk was studied. In addition, we have also tested the effect of pH on the anti-oxidant properties of diphenyl diselenide and ebselen. Acidosis increased rate of lipid peroxidation both in the absence and presence of Fe (II). Diphenyl diselenide significantly protected TBARS production at all studied pH values while ebselen offered only a small statistically non-significant protection. However, changing the pH of the reaction medium did not alter the anti-oxidant activity of the tested compounds. This study provides in vitro evidence for acidosis-induced oxidative stress in phospholipids extract and anti-oxidant action of diphenyl diselenide.

Antioxidant effect of a novel class of telluroacetilene compounds: studies in vitro and in vivo

AIMS

The effect of telluroacetylenes a-d on pharmacological assays was investigated in vitro. A second objective of this study was to investigate the antioxidant action of compound b against the oxidative damage induced by sodium nitroprusside (SNP) in mouse brain.

MAIN METHODS

In in vitro experiments, lipid peroxidation (LP) and protein carbonyl (PC) levels and delta-aminolevulinate dehydratase (delta-ALA-D) activity were carried out in rat brain homogenate. The thiol peroxidase-like activity and DPPH radical scavenging of telluroacetylenes a-d were investigated. In in vivo experiments, mice received SNP (0.335 micromol per site) intra cerebroventricular (i.c.v.) thirty minutes after oral administration of telluroacetylene b (10 mg/kg). After 1 h, animals were euthanized. The levels of LP and delta-ALA-D, catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST) activities were carried out in mouse brain homogenate.

KEY FINDINGS

Telluroacetylenes a-d, at low muM range, reduced LP and PC levels in rat brain homogenate. Telluroacetylenes a-d showed effect of scavenging DPPH radicals. delta-ALA-D activity was inhibited by telloruacetylenes a-d, at high muM range, in rat brain homogenate. Brains of mice treated with SNP showed an increase in LP and the reduction in delta-ALA-D, GR and GST activities. Telluroacetylene b protected against the oxidative stress caused by SNP in brain of rats.

SIGNIFICANCE

The results support an antioxidant effect of telluroacetylenes a-d in vitro. Telluroacetylene b protected against oxidative damage caused by SNP in mouse brain, suggesting an antioxidant effect of this compound.

Enhancement of iron-catalyzed lipid peroxidation by acidosis in brain homogenate: comparative effect of diphenyl diselenide and ebselen

Iron is more soluble at lower pH values; therefore we hypothesized that decreasing the environmental pH would lead to increased iron-mediated lipid peroxidation. Diphenyl diselenide and ebselen are potential candidates as neuroprotective agent, particularly in situations involving overproduction of free radicals and involving cellular pH fall. The aim of the present study was (a) to investigate the relationship between lipid peroxidation and acidosis in brain homogenate and (b) to test the influence of pH on the antioxidant properties of diphenyl diselenide and ebselen. For the purpose rat brain homogenate was incubated at different pH ranging from physiological to acidic values and extent of lipid peroxidation was measured. Thiobarbituric acid-reactive species (TBARS) production significantly increased when homogenate was incubated in the pH (5.4-6.8) medium both in the absence and presence of Fe (II) as compared with physiological pH (7.4). These data indicate that lipid peroxidation processes, mediated by iron, are enhanced with decreasing extracellular pH. The iron mobilized may come from reserves where it is weakly bound. Diphenyl diselenide significantly protected TBARS production at all studied pH values while ebselen offered only a small statistically non-significant protection. However, calculated IC(50) for TBARS inhibition indicated that pH did not change anti-oxidant activities of the tested compounds. This study provides in-vitro evidence for acidosis induced oxidative stress in brain homogenate and anti-oxidant action of diphenyl diselenide.

Diphenyl diselenide exerts anxiolytic-like effect in Wistar rats: putative roles of GABAA and 5HT receptors

Diphenyl diselenide [(PhSe)2] is an organoselenium compound which presents pharmacological antioxidant, anti-inflammatory, antinociceptive and antidepressant properties. The present study was designed to investigate the anxiolytic effect of (PhSe)2 in rats, employing the elevated plus maze task. The involvement of 5HT and GABA receptors in the anxiolytic-like effect was also evaluated. (PhSe)2 (5, 25 and 50 micromol/kg, i.p.) did not affect locomotor activity as evaluated in the open open-field test, and learning and memory when assessed in the inhibitory foot-shock avoidance task. However, (PhSe)2 at the 50 micromol/kg dose produced signs of an anxiolytic action, namely a decreased number of fecal boli in the open-field arena and an increased time spent in as well as an increased number of entries to the open arms of the elevated plus maze test. To evaluate the role of GABA and 5HT receptors in the anxiolytic-like effect of (PhSe)2, a selective GABAA receptor antagonist bicuculline, (0.75 mg/kg, i.p.), a non-selective 5HT2A/2C receptor antagonist, ritanserin (2 mg/kg, i.p.), a selective 5HT2A receptor antagonist, ketanserin (1 mg/kg, i.p.), and a selective 5HT1A receptor antagonist, WAY100635 (0.1 mg/kg, i.p.) were used. All the antagonists used were able to abolish the anxiolytic effect of (PhSe)2 suggesting that GABAA and 5HT receptors may play a role in the pharmacological property of this selenocompound in the central nervous system.

Diphenyl diselenide, a simple glutathione peroxidase mimetic, inhibits human LDL oxidation in vitro

Oxidative modification of low-density lipoprotein (LDL) represents an important factor in atherogenesis. In the present study, we have investigated the antioxidant capability of diphenyl diselenide (PhSe)(2), a simple organoseleno compound, against copper (Cu2+) and peroxyl radical-induced human LDL oxidation in vitro. In initial studies using human serum, (PhSe)(2) caused a dose-dependent inhibition of Cu(2+)-induced lipid peroxidation, which was correlated to thiol consumption. (PhSe)(2) increased lipid peroxidation lag phase and decreased lipid peroxidation rate in isolated human LDL, evaluated by measuring both conjugated diene (CD) and thiobarbituric acid reactive substances (TBARS) levels. Consistent with these observations, (PhSe)(2) showed a marked inhibitory effect on 2,2-azobis(2-amidinopropane dihydrochloride) (AAPH)-induced oxidation of LDL or parinaric acid (PnA) incorporated into LDL. (PhSe)(2) also displayed a dose-dependent protective effect against Cu(2+)-induced lipid peroxidation in rat aortic slices. Interestingly, besides the antioxidant effects of (PhSe)(2) toward the lipid moieties of LDL, which was related to its thiol-peroxidase activity, protein moieties from human isolated LDL were also protected against Cu(2+)-induced oxidation. The results presented herein are the first to show that (i) (PhSe)(2) inhibits lipid peroxidation in human isolated LDL in vitro, (ii) this phenomenon is related to its thiol-peroxidase activity, and (iii) this chalcogen also prevents the oxidation of protein moieties of human LDL. Taken together, such data render (PhSe)(2) a promising molecule for pharmacological studies with respect to the atherogenic process.

Role of nitric oxide/cyclic GMP/K(+) channel pathways in the antinociceptive effect caused by 2,3-bis(mesitylseleno)propenol

The present study examined the antinociceptive effects induced by 2,3-bis(mesitylseleno)propenol, a bis-selenide alkene derivate, given orally, in chemical models of pain in rats and mice. Selenide administered orally (p.o.) into the rats caused antinociception against the first and second phases of the formalin test, with mean ID(50) values of 28.17 and 39.68 mg/kg, respectively. The antinociceptive effect caused by selenide (50 mg/kg, p.o.) on the formalin test was reversed by pretreatment with N(G)-L-nitro-arginine methyl ester (L-NAME, a nitric oxide (NO) synthase inhibitor), methylene blue (a non-specific NO/guanylyl cyclase inhibitor) and glibenclamide (an ATP-sensitive K(+) channel inhibitor), but not by atropine (a muscarinic antagonist). Given orally selenide in mice produced an inhibition of glutamate-, histamine- and compound 48/80-induced nociception with mean ID(50) values of 27.58, 36.18 and 44.53 mg/kg, respectively. Moreover, oral treatment with selenide in mice decreased licking -- induced by serotonin (mean ID(50) value of >50 mg/kg). The data show that selenide exerts pronounced systemic antinociception in chemical (formalin, glutamate, histamine, compound 48/80 and serotonin-induced pain) models of nociception. Taken together, these results suggest that the antinociceptive effect of selenide on the formalin test involves the participation of nitric oxide/cyclic GMP/K(+) channel pathways in rats.

DNA damage in tissues and organs of mice treated with diphenyl diselenide

Diphenyl diselenide (DPDS) is an organoselenium compound with interesting pharmacological activities and various toxic effects. In previous reports, we demonstrated the pro-oxidant action and the mutagenic properties of this molecule in bacteria, yeast and cultured mammalian cells. This study investigated the genotoxic effects of DPDS in multiple organs (brain, kidney, liver, spleen, testes and urinary bladder) and tissues (bone marrow, lymphocytes) of mice using in vivo comet assay, in order to determine the threshold of dose at which it has beneficial or toxic effects. We assessed the mechanism underlying the genotoxicity through the measurement of GSH content and thiobarbituric acid reactive species, two oxidative stress biomarkers. Male CF-1 mice were given 0.2-200 micromol/kg BW DPDS intraperitonially. DPDS induced DNA damage in brain, liver, kidney and testes in a dose response manner, in a broad dose range at 75-200 micromol/kg with the brain showing the highest level of damage. Overall, our analysis demonstrated a high correlation among decreased levels of GSH content and an increase in lipid peroxidation and DNA damage. This finding establishes an interrelationship between pro-oxidant and genotoxic effects. In addition, DPDS was not genotoxic and did not increase lipid peroxidation levels in any organs at doses < 50 micromol/kg. Finally, pre-treatment with N-acetyl-cysteine completely prevented DPDS-induced oxidative damage by the maintenance of cellular GSH levels, reinforcing the positive relationship of DPDS-induced GSH depletion and DNA damage. In summary, DPDS induces systemic genotoxicity in mammals as it causes DNA damage in vital organs like brain, liver, kidney and testes.

Low Toxicity of Diphenyl Diselenide in Rabbits: A Long-Term Study

Selenium compounds, like diphenyl diselenide (Ph(2)Se(2)), possess glutathione peroxidase (GSHPx)-like activities and other antioxidant properties. The aim of this study was to evaluate the effects of a long-term oral supplementation with Ph(2)Se(2) on various toxicological parameters in rabbits. Adult New Zealand male rabbits were divided into four groups: Group I served as control; Groups II, III and IV received 0.3, 3.0 and 30 p.p.m. of Ph(2)Se(2) pulverized in the chow for 8 months. A number of toxicological parameters were examined in liver, kidney, cerebral cortex and hippocampus, such as delta-aminolaevulinic acid dehydratase (delta-ALA-D), catalase (CAT), GSHPx activities, non-protein thiol (-SH), lipid peroxidation and ascorbic acid levels. The results indicated that supplementation 30 p.p.m. Ph(2)Se(2 )significantly increased delta-ALA-D activity in liver and in cerebral cortex. Non-protein -SH levels were significantly increased in liver but not in kidney, cerebral cortex and hippocampus of rabbits. Ascorbic acid content was significantly lower in the liver and cerebral cortex after supplementation with 30 p.p.m. Ph(2)Se(2). Conversely, no alterations in GSHPx and CAT activities, nor in thiobarbituric acid reactive substances levels were observed in rabbit tissues. These results indicate that oral supplementation with Ph(2)Se(2) is relatively secure in rabbits after 8 months of exposure. The findings encourage further experiments on the potential therapeutic effects of such compound.

Antioxidant activity of diphenyl diselenide prevents the genotoxicity of several mutagens in Chinese hamster V79 cells

Diphenyl diselenide (DPDS) is an electrophilic reagent used in the synthesis of a variety of pharmacologically active organic selenium compounds. Studies have shown its antioxidant, hepatoprotective, neuroprotective, anti-inflammatory, and antinociceptive effects. We recently showed the antioxidant effect of DPDS in V79 cells, and established the beneficial and toxic doses of this compound in this cell line. Here, we report the antigenotoxic and antimutagenic properties of DPDS, investigated by using a permanent lung fibroblast cell line derived from Chinese hamsters. We determined the cytotoxicity by clonal survival assay, and evaluated DNA damage in response to several mutagens by comet assay and micronucleus test in binucleated cells. In the clonal survival assay, at concentrations ranging from 1.62 to 12.5microM, DPDS was not cytotoxic, while at concentrations up to 25microM, it significantly decreased survival. The treatment with this organoselenium compound at non-cytotoxic dose range increased cell survival after challenge with hydrogen peroxide, methyl-methanesulphonate, and UVC radiation, but did not protect against 8-methoxypsoralen plus UVA-induced cytotoxicity. In addition, the treatment prevented induced DNA damage, as verified in the comet assay. The mutagenic effect of these genotoxins, as measured by the micronucleus test, similarly attenuated or prevented cytotoxicity and DNA damage. Treatment with DPDS also decreased lipid peroxidation levels after exposure to hydrogen peroxide MMS, and UVC radiation, and increased glutathione peroxidase activity in the extracts. Our results clearly demonstrate that DPDS at low concentrations presents antimutagenic properties, which are most probably due to its antioxidant properties.

Antioxidant properties of Krebs cycle intermediates against malonate pro-oxidant activity in vitro: A comparative study using the colorimetric method and HPLC analysis to determine malondialdehyde in rat brain homogenates

A variety of Krebs cycle intermediaries has been shown to possess antioxidant properties in different in vivo and in vitro systems. Here we examined whether citrate, succinate, malate, oxaloacetate, fumarate and alpha-ketoglutarate could modulate malonate-induced thiobarbituric acid-reactive species (TBARS) production in rat brain homogenate. The mechanisms involved in their antioxidant activity were also determined using two analytical methods: 1) a popular spectrophotometric method (Ohkawa, H., Ohishi, N., Yagi, K., 1979. Assay for lipid peroxides in animal tissues by thiobarbituric acid reaction. Analytical Biochemistry 95, 351-358.) and a high performance liquid chromatographic (HPLC) procedure (Grotto, D., Santa Maria, L. D., Boeira, S., Valentini, J., Charão, M. F., Moro, A. M., Nascimento, P. C., Pomblum, V. J., Garcia, S. C., 2006. Rapid quantification of malondialdehyde in plasma by high performance liquid chromatography-visible detection. Journal of Pharmaceutical and Biomedical Analysis 43, 619-624.). Citrate, malate, and oxaloacetate reduced both basal and malonate-induced TBARS production. Their effects were not changed by pre-treatment of rat brain homogenates at 100 degrees C for 10 min. alpha-Ketoglutarate increased basal TBARS without changing malonate-induced TBARS production in fresh and heat-treated homogenates. Succinate reduced basal--without altering malonate-induced TBARS production. Its antioxidant activity was abolished by KCN or heat treatment. Fumarate reduced malonate-induced TBARS production in fresh homogenates; however, its effect was completely abolished by heat treatment. There were minimal differences among the studied methods. Citrate, oxaloacetate, malate, alpha-ketoglutarate and malonate showed iron-chelating activity. We suggest that antioxidant properties of citrate, malate and oxaloacetate were due to their ability to cancel iron redox activity by forming inactive complexes, whereas alpha-ketoglutarate and malonate pro-oxidant activity can be due to formation of active complexes with iron. In contrast, succinate and fumarate antioxidant activity was probably due to some enzymatic system.

Oxalate modulates thiobarbituric acid reactive species (TBARS) production in supernatants of homogenates from rat brain, liver and kidney: effect of diphenyl diselenide and diphenyl ditelluride

The aim of this paper was to investigate the mechanism(s) involved in the sodium oxalate pro-oxidative activity in vitro and the potential protection by diphenyl diselenide ((PhSe)(2)) and diphenyl ditelluride ((PhTe)(2)) using supernatants of homogenates from brain, liver and kidney. Oxalate causes a significant increase in the TBARS (thiobarbituric acid reactive species) production up to 4mmol/l and it had antioxidant activity from 8 to 16mmol/l in the brain and liver. Oxalate had no effect in kidney homogenates. The difference among tissues may be related to the formation of insoluble crystal of oxalate in kidney, but not in liver and brain homogenates. (PhSe)(2) and (PhTe)(2) reduced both basal and oxalate-induced TBARS in rat brain homogenates, whereas in liver homogenates they were antioxidant only on oxalate-induced TBARS production. (PhSe)(2) showed a modest effect on renal TBARS production, whereas (PhTe)(2) did not modulate TBARS in kidney preparations. Oxalate at 2mmol/l did not change deoxyribose degradation induced by Fe(2+) plus H(2)O(2), whereas at 20mmol/l it significantly prevents its degradation. Oxalate (up to 4mmol/l) did not alter iron (10micromol/l)-induced TBARS production in the brain preparations, whereas at 8mmol/l onwards it prevents iron effect. In liver preparations, oxalate amplifies iron pro-oxidant activity up to 4mmol/l, preventing iron-induced TBARS production at 16mmol/l onwards. These results support the antioxidant effect of organochalcogens against oxalate-induced TBARS production. In addition, our results suggest that oxalate pro- and antioxidant activity in vitro could be related to its interactions with iron ions.