Protective effect of unsymmetrical dichalcogenide, a novel antioxidant agent, in vitro and an in vivo model of brain oxidative damage

Chemistry and Chemical Biology of Selenenyl Sulfides and Thioseleninic Acids

Significance: Selenenyl sulfides (RSeSRs) and thioseleninic acids (RSeSHs) are the monoselenium (Se) analogs of disulfides and persulfides that contain Se-S bonds. These bonds are found in several antioxidant-regenerating enzymes as derivatives of selenocysteine, making them an important player in redox biology as it pertains to sulfur redox regulation. Recent Advances: Mechanistic studies of redox-regulating selenoenzymes such as thioredoxin reductase and glutathione peroxidase suggest crucial Se-S bonds in the active sites. Peptide models and small-molecule mimics of these active sites have been prepared to study their fundamental chemistry. These advances help pave the road to better understand the functions of the Se-S bond in the body. Critical Issues: The Se-S bond is unstable at atmospheric temperatures and pressures. Therefore, studying their properties proposes a major challenge. Currently, there are no trapping reagents specific to RSeSRs or RSeSHs, making their presence, identity, and fates in biological environments difficult to track. Future Directions: Further understanding of the fundamental chemistry/biochemistry of RSeSRs and RSeSHs is needed to understand what their intracellular targets are and to what extent they impact signaling. Besides antioxidant regeneration and peroxide radical reduction, the roles of RSeSR and RSeSHs in other systems need to be further explored.

Organoselenium group is critical for antioxidant activity of 7-chloro-4-phenylselenyl-quinoline

The quinolone compounds have been reported for many biological properties, especially as potent antioxidants. This study investigated the antioxidant effect of 7-chloro-4-phenylselenyl-quinoline (PSQ), a quinolone derivative with organoselenium group, against oxidative stress induced by sodium nitroprusside (SNP) in brains of mice. A second objective was to verify the importance of phenylselenyl group presents at position 4 of the quinoline structure to antioxidant effect of compound. So, it was compared the antioxidant effect of PSQ with a quinoline without organoseleniun group (7-chloroquinoline [QN]). Swiss mice were used and received SNP (0.335 μmol/site, intracerebroventricular) 30 min after treatment with PSQ or QN, at the doses of 50 mg/kg (intragastrically). After 1 h, animals were sacrificed and the brains were removed to biochemistry analysis. Thiobarbituric acid reactive species (TBARS), protein carbonyl (PC) and non-protein thiol (NPSH) levels, as well as catalase (CAT), glutathione S transferase (GST) and δ -aminolevulinic acid (δ-ALA-D) activities were determined. SNP increased TBARS and PC levels, and reduced the enzymatic (CAT and GST activity) and non-enzymatic (NPSH levels) antioxidant defenses and inhibited the δ-ALA-D activity. PSQ avoided the increase in the lipid peroxidation and PC levels, as well as the decrease in the NPSH levels, CAT, GST and δ-ALA-D activities QN partially avoided the increase in lipid peroxidation, but it not protected against alterations induced by SNP. In conclusion, phenylselenyl group present in quinoline structure is critical for antioxidant activity of PSQ.

Protective effect of ((4-tert-butylcyclohexylidene) methyl) (4-methoxystyryl) sulfide, a novel unsymmetrical divinyl sulfide, on an oxidative stress model induced by sodium nitroprusside in mouse brain: involvement of glutathione peroxidase activity

OBJECTIVES

In this study, the antioxidant action of ((4-tert-butylcyclohexylidene) methyl) (4-methoxystyryl) sulfide, a novel unsymmetrical divinyl sulfide, against oxidative damage induced by sodium nitroprusside (SNP) in brains of mice was investigated.

METHODS

Mice received SNP (0.335 μmol/site, intracerebroventricular) 30 min after administration of sulfide (10 mg/kg, intragastrically). After 1 h, animals were sacrificed and the brains were removed to biochemistry analysis. Thiobarbituric acid reactive species (TBARS), protein carbonyl (PC) and non-protein thiol (NPSH) levels, as well as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) activities were determined.

KEY FINDINGS

SNP increased TBARS and PC levels, CAT, GPx, GR and GST activities and reduced NPSH levels. Administration of the sulfide attenuated the changes produced by SNP and increased per se GPx activity in brains of mice. Toxicological parameters revealed that this compound did not cause acute renal or hepatic damage.

CONCLUSIONS

In conclusion, ((4-tert-butylcyclohexylidene) methyl) (4-methoxystyryl) sulfide protected against oxidative damage caused by SNP in mouse brain. GPx activity is involved, at least in part, in the cerebral antioxidant action of this compound.

Seleno- and telluro-xylofuranosides attenuate Mn-induced toxicity in C. elegans via the DAF-16/FOXO pathway

Organochalcogens are promising pharmacological agents that possess significant biological activities. Nevertheless, because of the complexity of mammalian models, it has been difficult to determine the molecular pathways and specific proteins that are modulated in response to treatments with these compounds. The nematode worm Caenorhabditis elegans is an alternative experimental model that affords easy genetic manipulations, green fluorescent protein tagging and in vivo live analysis of toxicity. Abundant evidence points to oxidative stress in mediating manganese (Mn)-induced toxicity. In this study we challenged worms with Mn, and investigated the efficacy of inedited selenium- and tellurium-xylofuranosides in reversing and/or protecting the worms from Mn-induced toxicity. In addition, we investigated their putative mechanism of action. First, we determined the lethal dose 50% (LD50) and the effects of the xylofuranosides on various toxic parameters. This was followed by studies on the ability of xylofuranosides to afford protection against Mn-induced toxicity. Both Se- and Te-xylofuranosides increased the expression of superoxide dismutase (SOD-3). Furthermore, we observed that the xylofuranosides induced nuclear translocation of the transcription factor DAF-16/FOXO, which in the worm is known to regulate stress responsiveness, aging and metabolism. These findings suggest that xylofuranosides attenuate toxicity Mn-induced, by regulating the DAF-16/FOXO signaling pathway.

D-512 and D-440 as novel multifunctional dopamine agonists: characterization of neuroprotection properties and evaluation of in vivo efficacy in a Parkinson's disease animal model

In this article, we have demonstrated the in vivo efficacy of D-512 and D-440 in a 6-OHDA-induced unilaterally lesioned rat model experiment, a Parkinson's disease animal model. D-512 is a novel highly potent D2/D3 agonist, and D-440 is a novel highly selective D3 agonist. We evaluated the neuroprotective properties of D-512 and D-440 in the dopaminergic MN9D cells. Cotreatment of these two drugs with 6-OHDA and MPP+ significantly attenuated and reversed 6-OHDA- and MPP+-induced toxicity in a dose-dependent manner in the dopaminergic MN9D cells. The inhibition of caspase 3/7 and lipid peroxidation activities along with the restoration of tyrosine hydroxylase levels by D-512 in 6-OHDA-treated cells may partially explain the mechanism of its neuroprotective property. Furthermore, studies were carried out to elucidate the time-dependent changes in the pERK1/2 and pAkt, two kinases implicated in cell survival and apoptosis, levels upon treatment with 6-OHDA in presence of D-512. The neuroprotective property exhibited by these drugs was independent of their dopamine-agonist activity, which is consistent with our multifunctional drug-development approach that is focused on the generation of disease-modifying symptomatic-treatment agents for Parkinson's disease.

Organochalcogens inhibit mitochondrial complexes I and II in rat brain: possible implications for neurotoxicity

Organochalcogens, such as organoselenium and organotellurium compounds, can be neurotoxic to rodents. Since mitochondrial dysfunction plays a pivotal role in neurological disorders, the present study was designed to test the hypothesis that rat brain mitochondrial complexes (I, II, I-III, II-III and IV) could be molecular targets of organochalcogens. The results show that organochalcogens caused statistically significant inhibition of mitochondrial complex I activity, which was prevented by preincubation with NADH and fully blunted by reduced glutathione (GSH). Mitochondrial complex II activity remained unchanged in response to (PhSe)₂ treatment. Ebs and (PhTe)₂ caused a significant concentration-dependent inhibition of complex II that was also blunted by GSH. Mitochondrial complex IV activity was not modified by organochalcogens. Collectively, Ebs, (PhSe)₂ and (PhTe)₂ were more effective inhibitors of brain mitochondrial complex I than of complex II, whereas they did not affect complex IV. These observations are consistent with organochalcogens inducing mitochondrial complex I and II inhibition via their thiol-oxidase-like activity, with Ebs, (PhSe)₂ and (PhTe)₂ effectively oxidising critical thiol groups of these complexes.

Methane biogenesis during sodium azide-induced chemical hypoxia in rats

Previous studies demonstrated methane generation in aerobic cells. Our aims were to investigate the methanogenic features of sodium azide (NaN(3))-induced chemical hypoxia in the whole animal and to study the effects of l-α-glycerylphosphorylcholine (GPC) on endogenous methane production and inflammatory events as indicators of a NaN(3)-elicited mitochondrial dysfunction. Group 1 of Sprague-Dawley rats served as the sham-operated control; in group 2, the animals were treated with NaN(3) (14 mg·kg(-1)·day(-1) sc) for 8 days. In group 3, the chronic NaN(3) administration was supplemented with daily oral GPC treatment. Group 4 served as an oral antibiotic-treated control (rifaximin, 10 mg·kg(-1)·day(-1)) targeting the intestinal bacterial flora, while group 5 received this antibiotic in parallel with NaN(3) treatment. The whole body methane production of the rats was measured by means of a newly developed method based on photoacoustic spectroscopy, the microcirculation of the liver was observed by intravital videomicroscopy, and structural changes were assessed via in vivo fluorescent confocal laser-scanning microscopy. NaN(3) administration induced a significant inflammatory reaction and methane generation independently of the methanogenic flora. After 8 days, the hepatic microcirculation was disturbed and the ATP content was decreased, without major structural damage. Methane generation, the hepatic microcirculatory changes, and the increased tissue myeloperoxidase and xanthine oxidoreductase activities were reduced by GPC treatment. In conclusion, the results suggest that methane production in mammals is connected with hypoxic events associated with a mitochondrial dysfunction. GPC is protective against the inflammatory consequences of a hypoxic reaction that might involve cellular or mitochondrial methane generation.

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.

Selenol protecting groups in organic chemistry: special emphasis on selenocysteine Se-protection in solid phase peptide synthesis

The appearance of selenium in organic synthesis is relatively rare, and thus examples in the literature pertaining to the masking of its considerable reactivity are similarly uncommon. Greene's Protecting Groups in Organic Synthesis, the standard reference for the state of the art in this arena, offers no entries for selenium protective methodology, in stark comparison to its mention of the great variety of protecting groups germane to its chalcogen cousin sulfur. This scarcity of Se-protection methods makes it no less interesting and pertinent toward the construction of selenium-containing organic systems which do indeed require the iterative blocking and de-blocking of selenol functionalities. A selenium-containing system which is especially relevant is selenocysteine, as its use in Solid Phase Peptide Synthesis requires extensive protection of its selenol side chain. This review will attempt to summarize the current state of understanding with regard to selenium protection protocol in organic synthesis. Moreover, it will provide a special emphasis on selenocysteine side chain protection, comprising both the breadth of functionality used for this purpose as well as methods of deprotection.

The potential antioxidant activity of 2,3-dihydroselenophene, a prototype drug of 4-aryl-2,3-dihydroselenophenes

Here we present our results in palladium cross-coupling reaction of aryl boronic acids with 4-iodo-2,3-dihydroselenophene derivatives. The cross-coupled products were obtained in satisfactory yields. A dehydrogenation of 4,5-diphenyl-2,3-dihydroselenophene was activated by DDQ and the 2,3-diarylselenophene was obtained in good yield. Regarding the antioxidant activity, the selenophene derivative 3a was effective in counteracting lipid and protein oxidation as well as scavenging ABTS radical. The findings of the present study indicate that 3a is a prototype for future drug development programs to treat disorders mediated by reactive oxygen species.

Antioxidant effect of alkynylselenoalcohol compounds on liver and brain of rats in vitro

Alkynylselenoalcohol compounds were screened for in vitro antioxidant activity. Alkynylselenoalcohols (2a-2d) were tested against lipid and protein oxidation induced by sodium nitroprusside (SNP) in rat brain and liver. The influence of molecular structural modifications of alkynylselenoalcohols in their antioxidant activity was investigated. The 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity and the interaction of alkynylselenoalcohols with iron were carried out. The results revealed that the antioxidant activity depends on their chemical structures. Compounds 2e (without hydroxyl group) and 3a (with a tellurium atom) presented better antioxidant profiles than 2b (with a hydroxyl group and selenium atom) against lipid and protein oxidation. Compound 1a (with a butyl group) did not modify the effect of compound 2a (with a phenyl group) on lipid oxidation. Compounds 2e and 3a showed DPPH radical-scavenging activity. Compounds 2b, 2c and 3a inhibited isocitrate-mediated oxidation of Fe(2+). Alkynylselenoalcohols demonstrated antioxidant effects and the modifications in the molecular structure of compound 2b improved its antioxidant potency.

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.