Effect of three diaryl tellurides, and an organoselenium compound in trout erythrocytes exposed to oxidative stress in vitro

Synthesis of functionalised organochalcogenides and in vitro evaluation of their antioxidant activity

Differently substituted β-hydroxy- and β-amino dialkyl and alkyl-aryl tellurides and selenides have been prepared through ring-opening reactions of epoxides and aziridines with selenium- or tellurium-centered nucleophiles. The antioxidant properties and the cytotoxicity of such compounds have been investigated on normal human dermal fibroblasts. Most of the studied compounds exhibited a low cytotoxicity and a number of them proved to be non-toxic, not showing any effect on cell viability even at the highest concentration used (100 μM). The obtained results showed a significant antioxidant potential of the selected organotellurium compounds, particularly evident under conditions of exogenously induced oxidative stress. The antioxidant activity of selenium-containing analogues of active tellurides has also been evaluated on cells, highlighting that the replacement of Se with Te brought about a significant increase in the peroxidase activity.

Unexpected Ethyltellurenylation of Epoxides with Elemental Tellurium under Lithium Triethylborohydride Conditions

The one-pot multistep ethyltellurenylation reaction of epoxides with elemental tellurium and lithium triethylborohydride is described. The reaction mechanism was experimentally investigated. Dilithium ditelluride and triethyl borane, formed from elemental tellurium and lithium triethylborohydride, were shown to be the key species involved in the reaction mechanism. Epoxides undergo ring-opening reaction with dilithium ditelluride to afford β-hydroxy ditellurides, which are sequentially converted into the corresponding β-hydroxy-alkyl ethyl tellurides by transmetalation with triethyl borane, reasonably proceeding through the SH2 mechanism.

Sequential oxidations of phenylchalcogenides by H2O2: insights into the redox behavior of selenium via DFT analysis

The biological activity of sulfur and selenium, despite their similarity, shows some remarkable differences that have been recognized in many different scenarios.

Novel functionalized organotellurides with enhanced thiol peroxidase catalytic activity

Novel tellurium-containing small molecules exhibited remarkable GPx-like activity. Their catalytic properties are strongly influenced by the nature of the β-substituent.

Flunisolide attenuates nitric oxide-induced DNA damage in rat trachea epithelial cells

In asthma the bronchial epithelium is highly abnormal, with various structural changes. As a consequence, the epithelium becomes an important source of inflammatory mediators that contribute to the ongoing inflammation and remodeling responses occurring in asthma. Compared with normal individuals, the fraction of exhaled nitric oxide (NO) is elevated in patients with asthma, and these levels have been shown to vary with disease activity. Thus, in asthma, epithelial cells may be exposed to large amounts of NO. Increased NO production is associated with the formation of various nitrosating species capable of promoting DNA damage. In this study we investigated the effect of NO on DNA of rat trachea epithelial cells in the presence or absence of flunisolide. Rat airway epithelial cells were prepared and incubated with the NO donor S-nitroso-L-glutathione monoethyl ester (GSNO-MEE). DNA damage was evaluated using single cell gel electrophoresis 'comet assay.' The parameters used as an index of DNA damage were tail length, tail intensity, and tail moment. Results of our study demonstrated that NO induced significant DNA damage in rat airway epithelial cells. Flunisolide in amounts of 11-110 mumol/L significantly reduced all the considered parameters indicating DNA damage. These data indicate that flunisolide may protect epithelial cells from the NO-mediated DNA damage. NO overproduction could contribute to epithelial injury in asthma, and flunisolide seems to attenuate this damage.

Enzyme Mimics: Advances and Applications

Enzyme mimics or artificial enzymes are a class of catalysts that have been actively pursued for decades and have heralded much interest as potentially viable alternatives to natural enzymes. Aside from having catalytic activities similar to their natural counterparts, enzyme mimics have the desired advantages of tunable structures and catalytic efficiencies, excellent tolerance to experimental conditions, lower cost, and purely synthetic routes to their preparation. Although still in the midst of development, impressive advances have already been made. Enzyme mimics have shown immense potential in the catalysis of a wide range of chemical and biological reactions, the development of chemical and biological sensing and anti-biofouling systems, and the production of pharmaceuticals and clean fuels. This Review concerns the development of various types of enzyme mimics, namely polymeric and dendrimeric, supramolecular, nanoparticulate and proteinic enzyme mimics, with an emphasis on their synthesis, catalytic properties and technical applications. It provides an introduction to enzyme mimics and a comprehensive summary of the advances and current standings of their applications, and seeks to inspire researchers to perfect the design and synthesis of enzyme mimics and to tailor their functionality for a much wider range of applications.

Ebselen exhibits glycation-inhibiting properties and protects against osmotic fragility of human erythrocytes in vitro

Diabetic status is associated with an increase on oxidative stress markers in humans and animal models. We have investigated the in vitro effects of high concentrations of glucose on the profile of oxidative stress and osmotic fragility of blood from control and diabetic patients; we considered whether its antioxidant properties could afford some protection against glucose-induced osmotic fragility, and whether ebselen could act as an inhibitor of hemoglobin glycation. Raising blood glucose to 5-100 mmol/L resulted in a concentration-dependent increase of glycated hemoglobin (HbA1c; P < 0.001) and thiobarbituric acid reactive species (TBA-RS) content (P < 0.004). Non-protein SH groups (NPSH) also increased significantly as the concentration of glucose increased up to 30 mmol/L (P < 0.001). The osmotic fragility was more pronounced in blood of uncontrolled diabetic patients than in these non-diabetic subjects. Ebselen significantly reduced the glucose-induced increase in osmotic fragility and inhibited HbA1c formation (P < 0.0001). These results indicate that blood from patients with uncontrolled diabetes are more sensitive to osmotic shock than from patients with controlled diabetes and control subjects in relation to increased production of free radicals in vivo.

DNA damage and oxidative stress modulatory effects of glyphosate-based herbicide in freshwater fish, Channa punctatus

The present study was undertaken to evaluate the genotoxic and oxidative stress modulatory effects of commercial formulation of glyphosate-based herbicide (Roundup(®)) in freshwater fish Channa punctatus. Three sublethal test concentrations of the herbicide viz., SL-I (1/10th of LC50=∼3.25mgL(-1)), SL-II (1/8th of LC50=∼4.07mgL(-1)) and SL-III (1/5th of LC50=∼6.51mgL(-1)) were calculated using 96-LC50 value and the test specimens were exposed to these concentrations. Blood and gill cells of the exposed specimens were sampled on day 1, 7, 14, 21, 28 and 35 to examine the DNA damage using comet assay and to assess the alteration in lipid peroxidation and antioxidant enzymes activities. The highest DNA damage was observed on day 14 at all test concentrations followed by gradual non-linear decline. Induction of oxidative stress in the blood and gill cells were evidenced by increased lipid peroxidation level, while antioxidants namely superoxide dismutase, catalase and glutathione reductase responded in a concentration-dependent manner. The results supported the integrated use of comet and antioxidant assays in determining the toxicity of water pollutants which could be used as part of monitoring programs.

Evaluating the antioxidative activity of diselenide containing compounds in human blood

This study was designed to determine and compare the antioxidant effects of synthetic organoselenium compounds. In experimental trials three different diselenides were used: bis(2-hydroxyphenyl) diselenide, bis{[2-(4-hydroxybenzyl)imino]phenyl} diselenide and bis[2-(4-methylphenylsulfonylamino)phenyl] diselenide. The compounds were screened for antioxidant activities in human blood under oxidation stress conditions. Oxidative stress was induced in vitro in human blood platelet samples and in plasma by 0.1 mM peroxynitrite (ONOO(-)) or by Fe(2+). In experimental trials the levels of chosen oxidative stress markers (TBARS, O2(-), and protein carbonyl groups) were significantly decreased by the action of the tested compounds. The antioxidative properties and the changes in proteins and lipids in the presence of new synthesized selenoorganic compounds were studied in vitro and compared with activity of ebselen (2-phenyl-1,2-benzisoselenazol-3(2H)-one)--a classical antioxidant, well known as the most important glutathione peroxidase mimetic agent. Our results indicate that the tested diselenides have distinctly protective effects against oxidative alterations of biomolecules caused by ONOO(-) and Fe(2+) in blood platelets and in plasma. Therefore it seems that not only ebselen with a wide spectrum of therapeutic actions but also other organoselenium compounds can be considered in the future as active pharmacological agents.

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.

A superoxide anion-scavenger, 1,3-selenazolidin-4-one suppresses serum deprivation-induced apoptosis in PC12 cells by activating MAP kinase

Synthetic organic selenium compounds, such as ebselen, may show glutathione peroxidase-like antioxidant activity and have a neurotrophic effect. We synthesized 1,3-selenazolidin-4-ones, new types of synthetic organic selenium compounds (five-member ring compounds), to study their possible applications as antioxidants or neurotrophic-like molecules. Their superoxide radical scavenging effects were assessed using the quantitative, highly sensitive method of real-time kinetic chemiluminescence. At 166μM, the O(2)(-) scavenging activity of 1,3-selenazolidin-4-ones ranged from 0 to 66.2%. 2-[3-(4-Methoxyphenyl)-4-oxo-1,3-selenazolidin-2-ylidene]malononitrile (compound b) showed the strongest superoxide anion-scavenging activity among the 6 kinds of 2-methylene-1,3-selenazolidin-4-ones examined. Compound b had a 50% inhibitory concentration (IC(50)) at 92.4μM and acted as an effective and potentially useful O(2)(-) scavenger in vitro. The effect of compound b on rat pheochromocytome cell line PC12 cells was compared with that of ebselen or nerve growth factor (NGF) by use of the MTT [3-(4, 5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide] assay. When ebselen was added at 100μM or more, toxicity toward PC12 cells was evident. On the contrary, compound b suppressed serum deprivation-induced apoptosis in PC12 cells more effectively at a concentration of 100μM. The activity of compound b to phosphorylate mitogen-activated protein kinase/extracellular signal-regulated protein kinase (ERK) 1/2 (MAP kinase) in PC12 cells was higher than that of ebselen, and the former at 100μM induced the phosphorylation of MAP kinase to a degree similar to that induced by NGF. From these results, we conclude that this superoxide anion-scavenger, compound b, suppressed serum deprivation-induced apoptosis by promoting the phosphorylation of MAP kinase.

3-(2,6-Dimethylphenyl)-2-Selenoxo-1,3-Thiazolidin-4-One Suppresses Hydrogen Peroxide–Induced Cytotoxicity on PC12 Cells Via Activation of MAPK

We newly synthesized organic selenium compounds (5-membered ring compounds) including 2-selenoxo-1,3-thiazolidin-4-ones (compounds A) and 3-alkoxy-4,5-dihydro-5-selenoxo- 1H-1,2,4-triazole-1-carboxylates (compounds B). To address whether these compounds show antioxidative effects, we also examined their superoxide radical (O2−)-scavenging effects. Moreover, we examined the effects of compound Aa on the activation of mitogen-activated protein kinase/extracellular signal-regulated protein kinases (MAPK/ERK1/2) and suppression of hydrogen peroxide-induced cytotoxicity in rat pheochromocytoma cells (PC12 cells). We evaluated the O2−-scavenging activities of the compounds by a chemiluminescence method, and activation of ERK1/2 in PC12 cells was evaluated by Western blot analysis. At 166 μmol/L, the O2−-scavenging activities were markedly different among compounds A and B. 3-(2,6-Dimethylphenyl)-2-selenoxo-1,3-thiazolidin-4-one (compound Aa) exhibited the strongest superoxide anion-scavenging activity among compounds A and B. The concentration necessary for 50% inhibition of the activity (IC50) of compound Aa was 25.9 μmol/L. Compound Aa activated ERK1/2 of the PC12 cell, as did ebselen, and suppressed hydrogen peroxide-induced cytotoxicity more potently than ebselen. In addition, the toxicity of compound Aa was less than that of ebselen. From these results, it is assumed that compound Aa is a candidate drug to prevent oxidative stress-induced cell death.

Hepatoprotective activity of a vinylic telluride against acute exposure to acetaminophen

Acetaminophen (APAP) hepatotoxicity has been related with several cases of cirrhosis, hepatitis and suicides attempts. Notably, oxidative stress plays a central role in the hepatic damage caused by APAP and antioxidants have been tested as alternative treatment against APAP toxicity. In the present study, we observed the hepatoprotector activity of the diethyl-2-phenyl-2-tellurophenyl vinylphosphonate (DPTVP), an organotellurium compound with low toxicity and high antioxidant potential. When the dose of 200 mg/kg of APAP was used, we observed that all used doses of DPTVP were able to restore the -SH levels that were depleted by APAP. Furthermore, the increase in thiobarbituric acid reactive substances levels and in the seric alanine aminotransferase (ALT) activity and the histopathological alterations caused by APAP were restored to control levels by DPTVP (30, 50 and 100 μmol/kg). On the other hand, when the 300 mg/kg dose of APAP was used, DPTVP restored the non-proteic -SH levels and repaired the normal liver morphology of the intoxicated mice only at 50 μmol/kg. Our in vitro results point out to a scavenging activity of DPTVP against several reactive species, action that is attributed to its chemical structure. Taken together, our results demonstrate that the pharmacological action of DPTVP as a hepatoprotector is probably due to its scavenging activity related to its chemical structure.

Estimation of DNA integrity in blood cells of eastern mosquitofish (Gambusia holbrooki) inhabiting an aluminium-polluted water environment: an alkaline comet assay study

To estimate the impacts of an Al-contaminated aquatic environment on DNA integrity in the blood cells of eastern mosquitofish Gambusia holbrooki Girard 1859 inhabiting Lake Njivice (Island of Krk, Croatia), an evaluation using the alkaline comet assay was carried out. Genome integrity was studied in parallel with the same fish species inhabiting the nearby, unpolluted Lake Ponikve. The amount of DNA damage in cells was estimated from three different parameters: comet tail length as the extent of genetic material migration, tail intensity (% DNA in the comet tail) and tail moment. The results indicate the loss of genome integrity in blood cells of mosquitofish inhabiting Lake Njivice and the genotoxicity of this aquatic environment. Using the same assay, acute genotoxicity of contaminated water and sediment was evaluated and confirmed on fish, mouse and human blood cells treated ex vivo. Results of the present study indicate that the alkaline comet assay applied to fish blood cells is a valuable tool for determining the potential genotoxicity of water pollutants and confirm its usefulness in the evaluation of DNA damage in fish living in Al-polluted waters.

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.

DNA-damage induction by eight metal compounds in TK6 human lymphoblastoid cells: results obtained with the alkaline Comet assay

Metal compounds are long-lived and can react with different macromolecules, producing a wide range of biological effects, including DNA damage. Since their reactivity is associated with their chemical structure, it is important to obtain information on more than one compound from the same metal. In this study, the DNA-damaging potential of two mercury compounds (mercury chloride and methyl mercury chloride), two nickel compounds (nickel chloride and potassium hexafluoronickelate), two palladium compounds (ammonium tetrachloropalladate and ammonium hexachloropalladate), and two tellurium compounds (sodium tellurite and sodium tellurate) was evaluated in human lymphoblastoid TK6 cells by use of the alkaline version of the Comet assay. As the use of computerized image-analysis systems to collect comet data has increased, the metric used for quantifying DNA damage was the Olive tail moment. Treatments lasted for 3h and the range of concentrations tested was different for each metal compound, depending on its toxicity. Both mercury agents produced DNA damage in TK6 cells, with mercury chloride producing considerably more DNA damage than methyl mercury chloride. Of the two nickel compounds, only nickel chloride (a Ni(II) compound) induced DNA breaks. Similarly, of the two palladium compounds, only the Pd(II) compound (ammonium tetrachloropalladate) was positive in the assay. Sodium tellurite was clearly positive, producing concentration-related increases in DNA damage, while sodium tellurate gave a negative response. In conclusion, the ability of inducing DNA damage by the selected metal compounds in human TK6 cells, when measured with the Comet assay, was dependent on the chemical form and, in general, compounds containing the metal in the lower valence state displayed the greater DNA-damaging ability.

Comet assay: a reliable tool for the assessment of DNA damage in different models

New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.

Screening of potentially toxic chalcogens in erythrocytes

Previous literature reports have demonstrated that a number of human diseases, including inflammation and cancer, can be caused by environmental and occupational exposure to toxic compounds, via DNA damage, protein modifications, or lipid peroxidation. The present study was undertaken to screen the toxicity of a variety of chalcogens using erythrocytes as a model of cell injury. The toxicity of these compounds was evaluated via quantification of hemolysis and lipid peroxidation. The present investigation shows that diphenyl ditelluride and phenyl tellurides are toxic to erythrocytes. The organoselenium compounds were not toxic to erythrocytes even when tested at high concentrations and with a hematocrit of 45%. The hemolytic effect of tellurides was not positively correlated with thiobarbituric acid-reactive substance (TBARS) production suggesting that lipid peroxidation is not involved in the hemolysis provoked by organotellurium compounds. The results suggest that chalcogen compounds may be toxic to human erythrocytes, depending on their structure.

Bis selenide alkene derivatives: A class of potential antioxidant and antinociceptive agents

Bis and tris-selenide alkene derivatives, a class of organoselenium compounds, were screened for antinociceptive and antioxidant activities. In vitro, bis-selenide alkene 1c (R=2,4,6-Me(3)C(6)H(2)), 1d (R=4-ClC(6)H(4)) and 1e (R=4-MeOC(6)H(4)) protected against lipid peroxidation about 50%, whereas 1b (R=C(6)H(5)) and 1a (R=C(4)H(9)) protected only 23%. Compound 1d presented lesser IC(50) against lipid peroxidation than other bis-selenide alkene compounds (1d>1e> or =1c>1a=1b). The maximal inhibitory effect of tris-selenide alkenes on lipid peroxidation was in the following order 2c>2a=2b. Compound 1e increased the rate of GSH, but not DTT, oxidation. Tris-selenide alkene 2c (R=4-MeOC(6)H(4)) demonstrated the higher rate of thiol oxidation, while 2a (R=C(6)H(5)) did not change DTT oxidation but oxidized GSH. Conversely, compound 2b (R=4-ClC(6)H(4)) did not change the rate of GSH oxidation, but oxidized DDT. Bis-selenide alkene derivatives 1c, 1d and 1e were the most promising compounds tested in vitro. In vivo, compounds 1c and 1d (5-50mg/kg, subcutaneously) produced significant inhibition of acetic acid- and capsaicin-induced pain. Compounds 1c and 1d increased the tail-flick response latency time. The antinociception effect of 1c and 1d was not abolished by naloxone (an antagonist of opioid receptor, 1mg/kg, subcutaneously), suggesting that the antinociceptive effect is not influenced by the opioidergic mechanism.

Bis-(2-amino-5-selenazoyl) Ketone as a Superoxide Anion-Scavenger

We investigated the superoxide anion scavenging effects of 2-amino-1,3- selenazoles and bis-(2-amino-5-selenazoyl) ketones using a highly sensitive quantitative chemiluminescence method. At 166 microM, the 2-amino-1,3-selenazoles and bis-(2-amino-5-selenazoyl) ketones scavenged in the range of 10.0 to 80.0% of O(2)(-). Bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone exhibited the strongest superoxide anion-scavenging activity among the six kinds of 2-amino-1,3-selenazoles and three kinds of bis-(2-amino-5-selenazoyl) ketones. The 50% inhibitory concentration (IC(50)) of bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone was determined to be 37.1 microM. Thus, bis[2-dimethylamino-5-(1,3-selenazolyl)] ketone acted in vitro as effective and potentially useful O(2)(-) scavenger.

Detection of DNA damage by alkaline single cell gel electrophoresis in 2,4-dichlorophenoxyacetic-acid- and butachlor-exposed erythrocytes of Clarias batrachus

The alkaline single cell gel electrophoresis, also known as comet assay, is a rapid, simple and sensitive technique for measuring DNA strand breaks in individual cells. The present study was undertaken to evaluate the genotoxic potential of two widely used herbicides; 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-chloro-2,6-diethyl-N-(butoxymethyl) acetanilide (butachlor) in erythrocytes of freshwater catfish, Clarias batrachus. Fish were exposed by medium treatment with three sub-lethal concentrations of 2,4-D (25, 50, and 75ppm) and butachlor (1, 2, and 2.5ppm) and alkaline comet assay was performed on nucleated erythrocytes after 48, 72, and 96h. The amount of DNA damage in cells was estimated from comet tail length as the extent of migration of the genetic material. A significant increase in comet tail length indicating DNA damage was observed at all concentrations of both the herbicides compared with control (P<0.05). The mean comet tail length showed a concentration-related and time-dependent increase as the maximum tail length recorded at highest concentration and longer duration of 2,4-D (9.59microm) and butachlor (9.28microm). This study confirmed that the comet assay applied on the fish erythrocyte is a useful tool in determining potential genotoxicity of water pollutants and might be appropriate as a part of a monitoring program.

Selenoureas and thioureas are effective superoxide radical scavengers in vitro

Oxygen radicals, such as superoxide radicals, embellishing DNA, protein, lipids, etc., and carrying out the obstacle of the function of a cell is known. It depends for the oxidant level in the living body on the balance of a generation system and an elimination system of oxygen radicals, and research which controls an oxidant level in the living body is briskly done by taking in the substance which eliminates an oxygen radical. We investigated scavenging effects of superoxide radicals by selenoureas and thioureas using a highly sensitive and quantitative chemiluminescence method. At 330 nM, five selenoureas and five thioureas scavenged fractions of superoxide radicals (O2-) ranging from 8.4% to 87.6%. Among five N,N-unsubstituted selenoureas and N,N-unsubstituted thioureas 1-selenocarbamoylpiperidine and 1-thiocarbamoylpyrrolidine were the most effective scavengers. A possibility that selenoureas could use it as a new superoxide anion-scavenging substance from the result of this research became clear.

Selenocarbamates are effective superoxide anion scavengers in vitro

We investigated the superoxide anion-scavenging effects of six selenocarbamates and four thiocarbamates, using a highly sensitive quantitative chemiluminescence method. At 333 nM, six selenocarbamates and four thiocarbamates scavenged in the range of 2.9-68.7% of O(2)*-. Se-methyl N-phenylselenocarbamate and Se-methyl N-(4-methylphenyl)selenocarbamate exhibited the strongest superoxide anion-scavenging activity among the Se-selenocarbamates. In contrast, the corresponding S-thiocarbamates had moderate inhibitory effect. The 50% inhibitory concentrations (IC(50)) of Se-methyl-N-phenylselenocarbamate and Se-methyl-N-(4-methylphenyl)selenocarbamate were determined to be 140 nM and 162 nM, respectively. Thus, these compounds acted in vitro as effective and potentially useful O(2)*- scavengers.

Superoxide Anion-Scavenging Effect of 2-Amino-1,3-selenazoles

We investigated the superoxide anion scavenging effects of thirteen 2-amino-1,3-selenazoles using a highly sensitive quantitative chemiluminescence method. At 166 microM, the 2-amino-1,3-selenazoles scavenged in the range of 14.3 to 96.7% of O2-. 2-Piperidino-1,3-selenazole and 4-phenyl-2-piperidino-1,3-selenazole exhibited the strongest superoxide anion-scavenging activity among the 2-amino-1,3-selenazoles. The 50% inhibitory concentrations (IC50) of 2-piperidino-1,3-selenazole and 4-phenyl-2-piperidino-1,3-selenazole were determined to be 4.03 microM and 92.6 microM, respectively. Thus, these compounds acted in vitro as effective O2- scavengers.

Tertiary selenoamide compounds are useful superoxide radical scavengers in vitro

We investigated the scavenging effects of tertiary selenoamide compounds for super oxide radicals using a highly sensitive and quantitative chemiluminescence method. At 333 nM, tertiary selenoamide compounds scavenged 25.8-81.6% of O(2)(-). N-(Phenylselenocarbonyl) piperidine was the most effective scavenger of superoxide radicals. While N,N-diethyl-2-selenonaphthylamide and N,N-diethyl-4-chloroselenobenzamide was a moderately effective scavenger of superoxide radicals. The IC(50) of N-(phenylselenocarbonyl) piperidine and N,N-diethyl-2-selenonaphthylamide were determined to be 110 and 182 nM, respectively. The results suggest that tertiary selenoamide compounds are useful scavengers of superoxide radicals.

Generation of three selenium-containing catalytic antibodies with high catalytic efficiency using a novel hapten design method

A novel strategy for design of haptens that were used to produce catalytic antibodies was developed and three monoclonal antibodies, 3G5, 2F3, and 5C9, were generated using this strategy. These monoclonal antibodies were converted into selenium-containing abzymes by chemically modifying the hydroxyl group of serines followed by sodium hydrogen selenide displacement. These selenium-containing abzymes exhibited remarkable glutathione peroxidase activity, which surpasses the activity of some native glutathione peroxidases. The activities of the selenium-containing abzymes Se-3G5, Se-2F3, and Se-5C9 which catalyzed reduction of hydroperoxides by glutathione were 2.23, 4.20, and 3.79 times that of rabbit liver glutathione peroxidase, respectively. Detailed steady-state kinetics study on Se-2F3 was carried out and the value of k(cat)/K(m) (H(2)O(2)) was found to be 2.11 x 10(7) M(-1) min(-1) which was supposed to be one of the highest among the known catalytic antibodies. The data of association constants and glutathione peroxidase activities of these catalytic antibodies and the steady-state kinetics of Se-2F3 showed that the method might be a remarkably efficient one for generating catalytic antibodies with glutathione peroxidase activity.

Antioxidant activity of the organotellurium compound 3-[4-(N,N-dimethylamino)benzenetellurenyl]propanesulfonic acid against oxidative stress in synaptosomal membrane systems and neuronal cultures

Antioxidant activities of 3-[4-(N,N-dimethylamino) benzenetellurenyl]propanesulfonic acid sodium salt (NDBT) were evaluated in solution, red blood cells, synaptosomal membranes, and cultured hippocampal neuronal cells after exposure to peroxynitrite (ONOO(-)) and hydroxyl radicals. The organotellurium compound NDBT possesses significant activity towards hydrogen peroxide and/or the hydroxyl radical in solution, demonstrated by inhibition of hydroxylation of terephthalic acid. In addition, the compound displayed great antioxidant abilities as shown by: reduction of ONOO(-)-induced 2,7-dichlorofluorescein (DCF) fluorescence in synaptosomes; complete prevention of lipid peroxidation in synaptosomes caused by OH radicals (TBARS), and significant prevention of protein oxidation caused by ONOO(-) and OH, indexed by the levels of protein carbonyls in synaptosomes and neuronal cells. The presence of the compound abolished neuronal cell death caused by ONOO(-). Further, the compound was effective in preventing the oxidative changes in synaptosomal membrane protein conformation and crosslinking (EPR spin labeling). Finally, the organotellurium molecule attenuated peroxynitrite-induced, luminol-dependent chemiluminescence in red blood cells--an index of cellular oxidation. These findings demonstrate the great potential of the antioxidant and are consistent with the notion that NDBT may have a role to play in modulating oxidative stress in neurodegenerative disorders, including Alzheimer's disease.

Mitochondrial membrane potential in density-separated trout erythrocytes exposed to oxidative stress in vitro

Previous literature reports have demonstrated that nucleated trout erythrocytes in condition of oxidative stress are subjected to DNA and membrane damage, and inactivation of glutathione peroxidase. The present study was undertaken to investigate if mitochondrial membrane potential in stressed conditions was also influenced. Density-separated trout erythrocyte fractions, obtained using a discontinuous Percoll gradient, were submitted to stress conditions and the mitochondrial membrane potential was determined by means of cytofluorimetric analysis after incubation of each subfraction with JC-1, a mitochondrial specific fluorescent probe. The results clearly show that the mitochondrial membrane potential decreased significantly in all erythrocyte fractions, also if the oxidative effect on mitochondria is more severe with increased density (age) of the cell. Ebselen was very effective in preventing mitochondrial depolarization in young as well as in old erythrocytes.

A Novel Glutathione Peroxidase Mimic with Antioxidant Activity

Many diseases are associated with the overproduction of hydroperoxides that inflict cell damage. A novel cyclodextrin derivative, 6A,6B-diseleninic acid-6A',6B'-selenium bridged beta-cyclodextrin (6-diSeCD), was synthesized to be a functional mimic of glutathione peroxidase (GPX) that normally removes these hydroperoxides. The mimic had high catalytic GPX activity of 13.5 U/micromol, which is 13.6-fold higher than ebselen (PZ51), and was chemically and biologically stable in vitro. Antioxidant activity was studied by ferrous sulfate/ascorbate-induced mitochondria damage model system. These data show that the mimic has great antioxidant activity. Such mimics may result in better clinical therapies for diseases mediated by hydroperoxides.