Organochalcogens effects on delta-aminolevulinate dehydratase activity from human erythrocytic cells in vitro

Hepatotoxicity and ALAD Activity Profile for Prediction of NOAEL of Metal Welding Fumes in Albino Rats

Metal fume pollutants of urban Kano, a city of over 10 million people, and widespread metal works have increased exposure with related health effects. Few data on metal fume toxicity and atmospheric levels have been documented in Nigeria and Kano in particular. Hence, the work was aimed at evaluating the metal fume toxicity to laboratory rat species for setting the permissible limit of exposure in urban Kano. The investigation involved the collection of metal welding fumes and subsequent laboratory analysis. Experimental animals were then exposed intratracheally to varying doses of the fumes which were equivalent to normal metal workers' daily routine of 2, 4, and 8 h for 3, 5, 10, and 20 years. Following euthanization, whole blood samples were collected and functions of liver and delta-aminolevunilic acid dehydratase were evaluated in the serum. Exposure to the fumes has caused significant mortality that was observed to be dose-dependent and statistically different (p < 0.05); moreover, the fumes had synergistically affected the functions of liver. In addition, the fumes had increased (statistically) the activity delta-aminolevinilic acid dehydratase. This has indicated that exposure to metal welding fumes being multi-elemental is toxic and had produced mortality at exposure to higher doses of metal welding fumes. It was therefore established from the study that no-observed-adverse-effect level (NOAEL) for metal welding fumes is 25.73 mg with LD₅₀ of 270 mg which corresponds to the metal worker's 4-h shifts daily for 5 years under existing working conditions. It was recommended that regular monitoring should be put in place to limit exposure and extent of engagement in metal works beyond NOAEL levels.

Evaluation of antioxidant activity and toxicity of sulfur- or selenium-containing 4-(arylchalcogenyl)-1H-pyrazoles

Pyrazoles represent a significant class of heterocyclic compounds that exhibit pharmacological properties. The present study aimed to investigate the antioxidant potential of pyrazol derivative compounds in brain of mice in vitro and the effect of pyrazol derivative compounds in the oxidative damage and toxicity parameters in mouse brain and plasma of mice. The compounds tested were 3,5-dimethyl-1-phenyl-4-(phenylselanyl)-1H-pyrazol (1a), 3,5-dimethyl-4-(phenylselanyl)-1H-pyrazole (2a), 4-((4-methoxyphenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (3a), 4-((4-chlorophenyl)selanyl)-3,5-dimethyl-1-phenyl-1H-pyrazole (4a), 3,5-dimethyl-1-phenyl-4-(phenylthio)-1H-pyrazole (1b), 3,5-dimethyl-4-(phenylthio)-1H-pyrazole (2b), 4-((4-methoxyphenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (3b), 4-((4-chlorophenyl)thio)-3,5-dimethyl-1-phenyl-1H-pyrazole (4b), and 3,5-dimethyl-1-phenyl-1H-pyrazole (1c). In vitro, 4-(arylcalcogenyl)-1H-pyrazoles, at low molecular range, reduced lipid peroxidation and reactive species in mouse brain homogenates. The compounds also presented ferric-reducing ability as well nitric oxide-scavenging activity. Especially compounds 1a, 1b, and 1c presented efficiency to 1,1-diphenyl-2-picryl-hydrazyl-scavenging activity. Compounds 1b and 1c presented 2,20 -azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)-scavenging activity. In vivo assays demonstrated that compounds 1a, 1b, and 1c (300 mg/kg, intragastric, a single administration) did not cause alteration in the of δ-aminolevulinic acid dehydratase activity, an enzyme that exhibits high sensibility to prooxidants situations, in the brain, liver, and kidney of mice. Compound 1c reduced per se the lipid peroxidation in liver and brain of mice. Toxicological assays demonstrate that compounds 1a, 1b, and 1c did not present toxicity in the aspartate aminotransferase, alanine aminotransferase, urea, and creatinine levels in the plasma. In conclusion, the results demonstrated the antioxidant action of pyrazol derivative compounds in in vitro assays. Furthermore, the results showed low toxicity of compounds in in vivo assays.

The Se…S/N interactions as a possible mechanism of δ-aminolevulinic acid dehydratase enzyme inhibition by organoselenium compounds: A computational study

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DPDS and PSA interacts with cysteine residues from AlaD active site.

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The Se…S interactions could be involved in the δ-AlaD inhibition.

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δ-AlaD from Cucumis sativus does not present cysteine residues in the active site.

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Se…N interactions could be involved in the organoselenium action.

Organoselenium compounds present many pharmacological properties and are promising drugs. However, toxicological effects associated with inhibition of thiol-containing enzymes, such as the δ-aminolevulinic acid dehydratase (δ-AlaD), have been described. The molecular mechanism(s) by which they inhibit thiol-containing enzymes at the atomic level, is still not well known. The use of computational methods to understand the physical–chemical properties and biological activity of chemicals is essential to the rational design of new drugs. In this work, we propose an in silico study to understand the δ-AlaD inhibition mechanism by diphenyl diselenide (DPDS) and its putative metabolite, phenylseleninic acid (PSA), using δ-AlaD enzymes from Homo sapiens (Hsδ-AlaD), Drosophila melanogaster (Dmδ-AlaD) and Cucumis sativus (Csδ-AlaD). Protein modeling homology, molecular docking, and DFT calculations are combined in this study. According to the molecular docking, DPDS and PSA might bind in the Hsδ-AlaD and Dmδ-AlaD active sites interacting with the cysteine residues by Se^…S interactions. On the other hand, the DPDS does not access the active site of the Csδ-AlaD (a non-thiol protein), while the PSA interacts with the amino acids residues from the active site, such as the Lys291. These interactions might lead to the formation of a covalent bond, and consequently, to the enzyme inhibition. In fact, DFT calculations (mPW1PW91/def2TZVP) demonstrated that the selenylamide bond formation is energetically favored. The in silico data showed here are in accordance with previous experimental studies, and help us to understand the reactivity and biological activity of organoselenium compounds.

Stability of di-butyl-dichalcogenide-capped gold nanoparticles: experimental data and theoretical insights

Metals capped with organochalcogenides have attracted considerable interest due to their practical applications, which include catalysis, sensing, and biosensing, due to their optical, magnetic, electrochemical, adhesive, lubrication, and antibacterial properties. There are numerous reports of metals capped with organothiol molecules; however, there are few studies on metals capped with organoselenium or organotellurium. Thus, there is a gap to be filled regarding the properties of organochalcogenide systems which can be improved by replacing sulfur with selenium or tellurium. In the last decade, there has been significant development in the synthesis of selenium and tellurium compounds; however, it is difficult to find commercial applications of these compounds because there are few studies showing the feasibility of their synthesis and their advantages compared to organothiol compounds. Stability against oxidation by molecular oxygen under ambient conditions is one of the properties which can be improved by choosing the correct organochalcogenide; this can confer important advantages for many more suitable applications. This paper reports the successful synthesis and characterization of gold nanoparticles functionalized with organochalcogenide molecules (dibutyl-disulfide, dibutyl-diselenide and dibutyl-ditelluride) and evaluates the oxidation stability of the organochalcogenides. Spherical gold nanoparticles with diameters of 24 nm were capped with organochalcogenides and were investigated using X-ray photoelectron spectroscopy (XPS) to show the improved stability of organoselenium compared with organothiol and organotellurium. The results suggest that the organoselenium is a promising candidate to replace organothiol because of its enhanced stability towards oxidation by molecular oxygen under ambient conditions and its slow oxidation rate. The observed difference in the oxidation processes, as discussed, is also in agreement with theoretical calculations.

This study presents the improved stability against oxidation by molecular oxygen under ambient conditions of organoselenium compared with organothiol, and organotellurium.

Experimental Hypothyroidism Inhibits δ-Aminolevulinate Dehydratase Activity in Neonatal Rat Blood and Liver

The aim of this study was to investigate the potential relationship between hypothyroidism and δ-aminolevulinate dehydratase (δ-ALA-D) activity in rat blood and liver. Experimental hypothyroidism was induced in weanling rats by exposing their mothers to propylthiouracil (PTU) diluted in tap water (0.05% w/ v), ad libitum, during the lactational period (PTU group). Control (euthyroid) group included weanling rats whose mothers received just tap water, ad libitum, during the lactational period. Reverted-hypothyroid group (PTU + 3,3′,5-triiodo-L-thyronine [T3]) included weanling rats whose mothers were exposed to PTU similarly to those in the hypothyroid group, but pups received daily subcutaneous injections of T3(20 μg/kg, from Postnatal Days 2–20). After the treatment, serum T3levels were drastically decreased (around 70%) in the PTU group, and this phenomenon was almost reverted by exogenous T3. PTU decreased blood δ-ALA-D activity by 75%, and T3treatment prevented such phenomena. Erythrocytes and hemoglobin levels were increased by 10% in PTU-treated animals and higher increments (around 25%) were observed in these parameters when exogenous T3was coadministered. Dithiothreitol did not change blood δ-ALA-D activity of PTU-exposed animals when present in the reaction medium, suggesting no involvement of the enzyme’s essential thiol groups in PTU-induced δ-ALA-D inhibition. PTU did not affect blood δ-ALA-D activity in vitro. These results are the first to show a correlation between hypothyroidism and decreased δ-ALA-D activity and point to this enzyme as a potential molecule involved with hypothyroidism-related hematological changes.

Safety assessment and behavioral effects of Solanum guaraniticum leaf extract in rats

ABSTRACT Solanum guaraniticum is a medicinal plant traditionally used to treat gastric and liver diseases. However, there is no documented evidence corroborating its safety. The present study evaluated the potential toxicity of S. guaraniticum leaf extract after acute administration in rats. Single doses of the extract (1.250, 2.500, and 5.000 mg/kg) were administered by gavage, and the rats were then monitored for 48 h and/or 14 days. Mortality, acute signs of toxicity, and general activity in the open field test were assessed as well as hematological and biochemical parameters, enzymatic activity (δ-aminolevulinate dehydratase and acetylcholinesterase), and oxidative stress parameters (lipid peroxidation level, non-protein thiol content, tissue catalase activity, and serum ferrous reducing power). Phytochemical analysis was also performed by HPLC. The results showed that extract administration produced no deaths (LD50 > 5,000 mg/kg), and no significant adverse effects regarding food consumption, body weight gain, gross pathology, or other parameters. However, the open field tests showed a decrease in spontaneous activity (crossing and rearing) mainly at 48 h after treatment. The results suggest that S. guaraniticum extract is not acutely toxic, but causes alterations in central nervous system activity.

Phenylselanyl-1H-1,2,3-triazole-4-carbonitriles: synthesis, antioxidant properties and use as precursors to highly functionalized tetrazoles

We describe herein our results on the synthesis, antioxidant properties and chemical diversification of phenylselanyl-1H-1,2,3-triazole-4-carbonitriles.

Quercetin protects the impairment of memory and anxiogenic-like behavior in rats exposed to cadmium: Possible involvement of the acetylcholinesterase and Na(+),K(+)-ATPase activities

The present study investigated the effects of quercetin in the impairment of memory and anxiogenic-like behavior induced by cadmium (Cd) exposure. We also investigated possible alterations in acetylcholinesterase (AChE), Na(+),K(+)-ATPase and δ-aminolevulinate dehydratase (δ-ALA-D) activities as well as in oxidative stress parameters in the CNS. Rats were exposed to Cd (2.5mg/kg) and quercetin (5, 25 or 50mg/kg) by gavage for 45days. Animals were divided into eight groups (n=10-14): saline/control, saline/Querc 5mg/kg, saline/Querc 25mg/kg, saline/Querc 50mg/kg, Cd/ethanol, Cd/Querc 5mg/kg, Cd/Querc 25mg/kg and Cd/Querc 50mg/kg. Results demonstrated that Cd impaired memory has an anxiogenic effect. Quercetin prevented these harmful effects induced by Cd. AChE activity decreased in the cerebral cortex and hippocampus and increased in the hypothalamus of Cd-exposed rats. The Na(+),K(+)-ATPase activity decreased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin prevented these effects in AChE and Na(+),K(+)-ATPase activities. Reactive oxygen species production, thiobarbituric acid reactive substance levels, protein carbonyl content and double-stranded DNA fractions increased in the cerebral cortex, hippocampus and hypothalamus of Cd-exposed rats. Quercetin totally or partially prevents these effects caused by Cd. Total thiols (T-SHs), reduced glutathione (GSH), and reductase glutathione (GR) activities decreased and glutathione S-transferase (GST) activity increased in Cd exposed rats. Co-treatment with quercetin prevented reduction in T-SH, GSH, and GR activities and the rise of GST activity. The present findings show that quercetin prevents alterations in oxidative stress parameters as well as AChE and Na(+),K(+)-ATPase activities, consequently preventing memory impairment and anxiogenic-like behavior displayed by Cd exposure. These results may contribute to a better understanding of the neuroprotective role of quercetin, emphasizing the influence of this flavonoid in the diet for human health, possibly preventing brain injury associated with Cd intoxication.

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.

Sub-acute administration of (S)-dimethyl 2-(3-(phenyltellanyl) propanamido) succinate induces toxicity and oxidative stress in mice: unexpected effects of N-acetylcysteine

The organic tellurium compound (S)-dimethyl 2-(3-(phenyltellanyl) propanamide) succinate (TeAsp) exhibits thiol-peroxidase activity that could potentially offer protection against oxidative stress. However, data from the literature show that tellurium is a toxic agent to rodents. In order to mitigate such toxicity, N-acetylcysteine (NAC) was administered in parallel with TeAsp during 10 days. Mice were separated into four groups receiving daily injections of (A) vehicle (PBS 2.5 ml/kg, i.p. and DMSO 1 ml/kg, s.c.), (B) NAC (100 mg/kg, i.p. and DMSO s.c.), (C) PBS i.p. and TeAsp (92.5 μmol/kg, s.c), or (D) NAC plus TeAsp. TeAsp treatment started on the fourth day. Vehicle or NAC-treated animals showed an increase in body weight whereas TeAsp caused a significant reduction. Contrary to expected, NAC co-administration potentiated the toxic effect of TeAsp, causing a decrease in body weight. Vehicle, NAC or TeAsp did not affect the exploratory and motor activity in the open-field test at the end of the treatment, while the combination of NAC and TeAsp produced a significant decrease in these parameters. No DNA damage or alterations in cell viability were observed in leukocytes of treated animals. Treatments produced no or minor effects on the activities of antioxidant enzymes catalase, glutathione peroxidase and glutathione reductase, whereas the activity of the thioredoxin reductase was decreased in the brain and increased the liver of the animals in the groups receiving TeAsp or TeAsp plus NAC. In conclusion, the toxicity of TeAsp was potentiated by NAC and oxidative stress appears to play a central role in this process.

Evaluation of in vitro antioxidant effect of new mono and diselenides

This study was designed to examine the antioxidant activity in vitro of novel mono- and diselenide compounds. We compared whether the formation of p-methyl-selenol from compounds 1-phenyl-3-(p-tolylselanyl)propan-2-amine (C1) and 1,2-dip-tolyldiselenide (C4) and o-methoxy-selenol from compounds 1-(2-methoxyphenylselanyl)-3-phenylpropan-2-amine (C2) and 1,2-bis(2-methoxyphenyl)diselenide (C3) may be involved in their antioxidant effects. The compounds were tested against Fe(II) and sodium nitroprusside (SNP)-induced lipid peroxidation in rat brain and liver homogenates. Likewise, the antioxidant capacity of the compounds was assessed by their ability to decolorize the DPPH radical as well as the Fe(II) chelating assay through the reduction of molybdenum(VI) (Mo6+) to molybdenum(V) (Mo5+). This colorimetric assay was also used to quantify thiol peroxidase (GPx) and oxidase activity and thioredoxin reductase (TrxR) activity. The results showed that the novel selenide compounds inhibit the thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants, but the monoselenides effects were significant only at concentrations higher than the concentrations of the diselenides. Similarly, the total antioxidant activity was higher in the diselenides. Moreover, GPx and TrxR activity was only observed for the diselenides, which indicates that these compounds are more stable selenol molecules than monoselenides.

Effects of 4,4'-dichloro-diphenyl diselenide (ClPhSe)2 on toxicity induced by mercuric chloride in mice: a comparative study with diphenyl diselenide (PhSe)2

The effects of 4,4'-dichloro-diphenyl diselenide (ClPhSe)(2) on the toxicity induced by mercuric chloride (HgCl(2)) were investigated and compared with diphenyl diselenide (PhSe)(2). Mice received HgCl(2) for three days and, on the third day, received (PhSe)(2) or (ClPhSe)(2). The results verified that the administration of (ClPhSe)(2) in mice exposed to HgCl(2) increased renal δ-aminolevulinate dehydratase (δ-ALA-D), Na(+), K(+)-ATPase activities and non-protein thiol (NPSH) levels and also decreased thiobarbituric acid-reactive substances (TBARS) and ascorbic acid levels, when compared to mice exposed to HgCl(2)+(PhSe)(2). Plasma and urinary protein, hemoglobin and hematocrit levels and histological parameters were also ameliorated in mice exposed to HgCl(2)+(ClPhSe)(2). In addition, the hepatic damage in mice exposed to HgCl(2)+(PhSe)(2) was reduced in animals exposed to (ClPhSe)(2). To sum up, the introduction of a functional group (chloro) in the aromatic ring of diaryl diselenide reduced the toxicity of this compound in liver and kidney of mice exposed to HgCl(2).

Kinetic studies on the inhibition of creatine kinase activity by 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one in the cerebral cortex of rats

Tellurium has been used as an industrial component of many alloys and in the electronic industry. Organotellurium compounds can cause poisoning which leads to neurotoxic symptoms such as significant impairment of learning, spatial memory and are potentially neurotoxic to human beings. However, the molecular mechanisms of neurotoxicity of organotellurium compounds are not well understood. Considering that creatine kinase plays a key role in energy metabolism of tissues with intermittently high and fluctuating energy requirements, such as nervous tissue, the main objective of this study was to investigate the mechanisms by which 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one inhibit creatine kinase activity, a key enzyme of energy homeostasis, in the cerebral cortex of 30-day-old Wistar rats. For the kinetic studies, the Lineweaver-Burk plot was used to characterize the mechanisms of enzyme inhibition by 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one. The results suggested that this compound inhibits creatine kinase activity by two different mechanisms: competition with ADP and oxidation of critical sulfhydryl groups for the functioning of the enzyme. The potential for inhibition of creatine kinase to occur in vivo may contribute to the neurotoxicity observed by this organochaocogen.

Reduction of acute hepatic damage induced by acetaminophen after treatment with diphenyl diselenide in mice

In this study, the authors evaluated the ability of diphenyl diselenide (PhSe)(2) to reverse acute hepatic failure induced by acetaminophen (APAP) in mice. The animals received an APAP dose of 600 mg/kg intraperitoneally (i.p.), and then 1 hour later, they received 15.6 mg/kg i.p. of (PhSe)(2). Three hours after (PhSe)(2) administration, the animals were sacrificed and blood and liver samples were collected for analysis. The serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were measured. The levels of reduced glutathione (GSH) and oxidized glutathione (GSSG), thiobarbituric acid-reactive substances (TBARS), 2',7'-dichlorofluorescein (DFC), catalase activity (CAT), and myeloperoxidase (MPO) activity were determined in the liver. A methyl-tetrazolium reduction (MTT) assay was also performed on the liver. Histopathological studies were conducted in all groups. Exposure of animals to APAP induced oxidative stress, increased lipid peroxidation (LPO), and the generation of reactive species, reduced the levels of GSH, and caused an increase in the MPO activity. Treatment with (PhSe)(2) reduced LPO and the formation of reactive species and inhibited the processes of inflammation, reducing the hepatic damage induced by APAP. The results of this study show that (PhSe)(2) is a promising therapeutic option for the treatment of acute hepatic failure.

Effect of chronic administration of the vinyl chalcogenide 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one on oxidative stress in different brain areas of rats

Selenium (Se) is an essential mineral for mammals. It is a nutrient related to the complex metabolic and enzymatic functions. Although Se has important physiological functions in the cells, organic compounds of Se can be extremely toxic, and may affect the central nervous system. This study aims to investigate the effect of the chronic treatment with the vinyl chalcogenide 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one on some parameters of oxidative stress in the brain of rats. Animals received the vinyl chalcogenide (125, 250 or 500 μg/kg body weight) intraperitoneally once a day during 30 days. The cerebral cortex, the hippocampus, and the cerebellum were dissected and homogenized in KCl. Afterward, thiobarbituric acid reactive substances (TBARS), carbonyl, sulfhydryl, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were measured in the brain. Results showed that the organoselenium enhanced TBARS in the cerebral cortex of rats but the compound was not able to change carbonyl levels. Furthermore, the organoselenium reduced thiol groups measured by the sulfhydryl assay in all tissues studied. The activity of the antioxidant enzyme CAT was increased by the organochalcogen in the cerebral cortex and in the cerebellum, and the activity of SOD was increased in the hippocampus. On the other hand, the activity of the antioxidant enzyme GPx was reduced in all brain structures. Our findings indicate that this organoselenium compound induces oxidative stress in different brain regions of rats, corroborating to the fact that this tissue is a potential target for organochalcogen action.

High doses of 2,2'-dithienyl diselenide cause systemic toxicity in rats: an in vitro and in vivo study

Organoselenium compounds have important pharmacological properties. However, these compounds can cause toxicity, typically related to oxidation of endogenous thiols. The aim of this study was to investigate whether 2,2'-dithienyl diselenide (DTDS) has potential toxicity in vitro and in vivo. Therefore, sulfhydryl-containing enzyme activities, δ-aminolevulinic acid dehydratase (δ-ALA-D) and Na(+) -K(+) -ATPase were used to predict DTDS toxicity in rat brain homogenate in vitro. In in vivo experiments, a DTDS administration (50 or 100 mg kg(-1) , p.o.) to rats was performed and toxicological parameters were determined. DTDS inhibited δ-ALA-D (IC50 2 µm) and Na(+) -K(+) -ATPase (IC50 17 µm) activities in vitro. The inhibitory effect of DTDS on δ-ALA-D and Na(+) -K(+) -ATPase activities was restored by dithiothreitol. DTDS (5-25 µm) elicited a thiol oxidase-like activity. In vivo, DTDS (50 and 100 mg kg(-1) ) caused systemic toxicity, evidenced by a decrease in water and food intakes and body weight gain, as well as the death of rats. DTDS at the dose of 100 mg kg(-1) increased plasma alanine and aspartate aminotransferase activities and decreased urea levels. At 50 and 100 mg kg(-1) , it increased lipid peroxidation levels. At the highest dose, DTDS inhibited δ-ALA-D activity. By contrast, Na(+) -K(+) -ATPase activity and antioxidant defense were not altered in the brains of rats exposed to DTDS. In conclusion, interaction with the cisteinyl residues seems to mediate the inhibitory effect of DTDS on sulfhydryl-containing enzymes in vitro. In addition, high oral doses of DTDS induce toxicity in rats.

An in vitro comparison of a new vinyl chalcogenide and sodium selenate on adenosine deaminase activity of human leukocytes

Selenium (Se) is a dietary essential trace element with important biological roles. Sodium selenate (Na(2)SeO(4)) is an inorganic Se compound used in human and animal nutrition that acts as precursor for selenoprotein synthesis. The organoselenium 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one (C(21)H(2)HOSe) is an α,β-unsaturated ketone functionalized vinyl chalcogenide that has been found as a potential tool in organic synthesis. Adenosine deaminase (ADA) is an important enzyme in the degradation of adenine nucleotides. In this study, we investigated the in vitro effects of both Se compounds on ADA activity and cell viability in leukocyte suspension (LS) of healthy donors (n=12). We first observed an inhibition of ADA activity using 0.1 μM of 3-methyl-1-phenyl-2-(phenylseleno)oct-2-en-1-one, and an increase in cellular viability when 30 μM were used. However, we did not observe alterations in the presence of sodium selenate. Moreover, both Se compounds did not alter lactate dehydrogenase activity and thiobarbituric acid reactive substance levels. These results suggest that the inhibition of ADA activity caused by α,β-unsaturated ketone may affect the adenosine levels in LS and modulate cell viability, attenuating conditions that involve the activation of the immune system.

Effect of in vitro exposure of human serum to 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one on oxidative stress

The objective of this study was to verify the effect of the organochalcogen 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one on some parameters of oxidative stress in human serum. Serum of volunteers were incubated for 30 min in the presence or absence of 1, 10, or 30 microM of 3-butyl-1-phenyl-2-(phenyltelluro)oct-en-1-one and oxidative stress was measured. First, we tested the influence of the compound on 1,1-diphenyl-2-picrylhydrazyl (DPPH(*)) radical-scavenging and verified that the organotellurium did not have any antioxidant properties. The organochalcogen was capable to enhance TBARS but the compound was not able to alter carbonyl assay. Furthermore, the organochalcogen provoked a reduction of protein thiol groups measured by the sulfhydryl assay. Moreover, the organotellurium enhanced the activity of catalase and superoxide dismutase, inhibited the activity of glutathione peroxidase and did not modify the glutathione S-transferase activity. Furthermore, nitric oxide production and hydroxyl radical activity were not affected by the compound. Our findings showed that this organochalcogen induces oxidative stress in human serum, indicating that this compound is potentially toxic to human beings.

Hepatoprotective effect of 3-alkynyl selenophene on acute liver injury induced by D-galactosamine and lipopolysaccharide

The aim of this study was to investigate the hepatoprotective effect of 3-alkynyl selenophene (compound a), a selenophene compound, on acute liver injury induced by D-galactosamine (D-GalN) and lipopolysaccharide (LPS) in rats. The animals received compound a (25 and 50 mg/kg; per oral, p.o.) in the first day of treatment. In the second day, the rats received D-GalN (500 mg/kg; intraperitoneal, i.p.) and LPS (50 microg/kg; intraperitoneal, i.p.). Twenty-four hours after D-GalN/LPS administration animals were euthanized to the biochemical and histological analysis. Compound a (25 and 50 mg/kg; p.o.) protected against the increase in aspartate aminotransferase (AST) activity induced by D-GalN/LPS. Compound a at 50 mg/kg protected against the increase in alanine aminotransferase (ALT) activity induced by D-GalN/LPS. The inhibition of delta-aminolevulinic dehydratase (delta-ALA-D) activity and the decrease of ascorbic acid levels caused by D-GalN/LPS were protected by compound a (25 and 50 mg/kg). Glutathione S-transferase (GST) and catalase activities were not altered in all groups. The histological data showed that sections of liver from D-GalN/LPS-treated rats presented massive hemorrhage, the presence of inflammatory cells and necrosis. Compound a attenuated D-GalN/LPS-induced hepatic histopathological alterations. Based on the results, we demonstrated the hepatoprotective effect of compound a on acute liver injury induced by D-GalN/LPS.

Acute diphenyl diselenide treatment reduces hyperglycemia but does not change delta-aminolevulinate dehydratase activity in alloxan-induced diabetes in rats

This study was designed to evaluate the effect of diphenyl diselenide in a classical model of alloxan-induced diabetes in rats. Oxidative stress is involved in alloxan toxic effects and we have hypothesized that diphenyl diselenide via its antioxidant properties could confer protection against alloxan pancreatic toxicity. Diabetes was induced by administration of alloxan (150 mg/kg, intravenously). Diphenyl diselenide (10 mg/kg, subcutaneously) was administered for 6 d before (prevention group) or for 6 d after (remediation group) diabetes induction. Diphenyl diselenide treatment reduced the blood glucose and fructosamine levels, which were increased in alloxan-treated rats. However, the delta-aminolevulinate dehydratase (delta-ALA-D) activity inhibited by alloxan was not restored by diphenyl diselenide. Moreover, diphenyl diselenide caused by itself an inhibition in hepatic and renal delta-ALA-D activity. Our findings suggest that the acute treatment with diphenyl diselenide reduces the hyperglycemia but does not improve delta-ALA-D activity decreased by alloxan. Although the dose of diphenyl diselenide used here for treating diabetic animals has been relatively high and produced toxic effects, the compound or analogous molecules might not be rejected as a promising anti-hyperglycemic agent.

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.

Involvement of non-enzymatic antioxidant defenses in the protective effect of diphenyl diselenide on testicular damage induced by cadmium in mice

The involvement of non-enzymatic antioxidant defenses in the protective effect of diphenyl diselenide (PhSe)(2) on testicular damage caused by cadmium in mice was investigated. Mice received a single dose of CdCl(2) (5mg/kg, intraperitoneally). Thirty minutes after the CdCl(2) injection, they received a single oral dose of (PhSe)(2) (400micromol/kg). Twenty-four hours after CdCl(2) administration, blood samples were collected and mice were killed and had their testes dissected. Parameters in plasma (aspartate (AST) and alanine (ALT) aminotransferases and lactato dehydrogenase (LDH) activities as well as creatinine levels) were determined. The activity of delta-aminolevulinate dehydratase (delta-ALA-D), the levels of thiobarbituric acid-reactive substances (TBARS), ascorbic acid and nonprotein thiols (NPSH) and histological analysis were determined in collected samples. Results demonstrated that (PhSe)(2) protected against toxicity induced by CdCl(2) on delta-ALA-D activity, ascorbic acid and NPSH levels. (PhSe)(2) protected against the increase in plasma AST, ALT and LDH activities caused by CdCl(2). Testes of mice exposed to CdCl(2) showed marked histopathological alterations that were ameliorated by administration of (PhSe)(2). (PhSe)(2) protected against toxicity induced by CdCl(2) in testes of mice. Ascorbic acid and NPSH, non-enzymatic antioxidant defenses, are involved in the protective effect of (PhSe)(2) against testicular damage caused by CdCl(2) in mice.

Probing the active site of rat porphobilinogen synthase using newly developed inhibitors

The structurally related tetrapyrrolic pigments are a group of natural products that participate in many of the fundamental biosynthetic and catabolic processes of living organisms. Porphobilinogen synthase catalyzes a rate-limiting step for the biosyntheses of tetrapyrrolic natural products. In the present study, a variety of new substrate analogs and reaction intermediate analogs were synthesized, which were used as probes for studying the active site of rat porphobilinogen synthase. The compounds 1, 3, 6, 9, 14, 16, and 28 were found to be competitive inhibitors of rat porphobilinogen synthase with inhibition constants ranging from 0.96 to 73.04mM. Compounds 7, 10, 12, 13, 15, 17, 18, and 26 were found to be irreversible enzyme inhibitors. For irreversible inhibitors, loose-binding inhibitors were found to give stronger inactivation. The amino group and carboxyl group of the analogs were found to be important for their binding to the enzyme. This study increased our understanding of the active site of porphobilinogen synthase.

Redox modulation at the peripheral site alters nociceptive transmission in vivo

1. The aim of the present study was to investigate the role of redox modulation during the peripheral nociceptive transmission in vivo. The nociceptive response was evaluated by the amount of time that mice spent licking the footpad injected with glutamate (20 micromol/paw). Thiol groups in footpad tissue were quantified using a colourimetric reaction with 5,5'-dithio-bis-2-nitrobenzoic acid (DTNB). 2. When coadministered with glutamate, the thiol alkylating agent iodoacetate (200 nmol/paw) caused significant antinociception in footpad tissue, in parallel with a decrease in free thiol groups. Treatment with the reducing agent dithiothreitol (200 nmol/paw) 5 min before glutamate and iodoacetate prevented the antinociception and thiol loss caused by iodoacetate. Injection of 100 nmol/paw ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one), an in vitro redox modulator of the N-methyl-d-aspartate (NMDA) receptor, also prevented iodoacetate-induced antinociception. However, ebselen did not prevent thiol loss in the footpad. Dithiothreitol and ebselen had a synergic nociceptive effect with glutamate. 3. Alone, ebselen (100 nmol/paw) exhibited a pronociceptive effect. The nociception induced by ebselen was blocked by glutathione depletion induced by buthionine-sulphoximine (BSO; 2.5 micromol/paw). In addition, ebselen-induced nociception was prevented by 75 +/- 2% following injection of 5 nmol/paw MK-801 (an NMDA receptor antagonist). The nitric oxide synthase inhibitor N(G)-nitro-l-arginine (250 nmol/paw) had no effect on the nociception produced by ebselen. 4. In conclusion, the present paper reports on the effect of redox modulation on the glutamatergic system during peripheral nociceptive transmission in vivo. Antinociception was directly correlated with the availability of thiol groups, whereas the pronociceptive response of the reducing agents likely occurs via positive modulation of the NMDA receptor.