RESUMEN
BACKGROUND AND PURPOSE: Arsenic exposure frequently leads to reproductive failures by disrupting the rat uterine histology, hormonal integrity and estrogen signaling components of the rat uterus, possibly by generating reactive oxygen species. All-trans retinoic acid (ATRA) was assessed as a prospective therapeutic agent for reversing reproductive disorders. EXPERIMENTAL APPROACH: Rats exposed to arsenic for 28 days were allowed to either recover naturally or were treated simultaneously with ATRA for 28 days or treatment continued up to 56 days. Hematoxylin-eosin double staining was used to evaluate changes in the uterine histology. Serum gonadotropins and estradiol were assayed by ELISA. Expression of the estrogen receptor (ERα), an estrogen responsive gene vascular endothelial growth factor (VEGF), and cell cycle regulatory proteins, cyclin D1 and CDK4, was assessed by RT-PCR, immunohistochemistry and western blot analysis. KEY RESULTS: ATRA ameliorated sodium arsenite-induced decrease in circulating estradiol and gonadotropin levels in a dose- and time-dependent manner, along with recovery of luminal epithelial cells and endometrial glands. Concomitant up regulation of ERα, VEGF, cyclin D1, CDK4 and Ki-67 was also observed to be more prominent for ATRA-treated rats as compared to the rats that were allowed to recover naturally for 56 days. CONCLUSIONS AND IMPLICATIONS: Collectively, the results reveal that ATRA reverses arsenic-induced disruption of the circulating levels of gonadotropins and estradiol, and degeneration of luminal epithelial cells and endometrial glands of the rat uterus, indicating resumption of their functional status. Since structural and functional maintenance of the pubertal uterus is under the influence of estradiol, ATRA consequently up regulated the estrogen receptor and resumed cellular proliferation, possibly by an antioxidant therapeutic approach against arsenic toxicity.
Asunto(s)
Arsenitos/toxicidad , Sustancias para el Control de la Reproducción/toxicidad , Compuestos de Sodio/toxicidad , Tretinoina/uso terapéutico , Útero/efectos de los fármacos , Útero/metabolismo , Animales , Arsénico/antagonistas & inhibidores , Arsénico/toxicidad , Arsenitos/antagonistas & inhibidores , Femenino , Distribución Aleatoria , Ratas , Ratas Sprague-Dawley , Sustancias para el Control de la Reproducción/antagonistas & inhibidores , Compuestos de Sodio/antagonistas & inhibidores , Tretinoina/administración & dosificaciónRESUMEN
The present study was aimed to test the hypothesis that inorganic phosphate may reduce arsenic toxicity by decreasing its intestinal transference. Co-administration of inorganic phosphate (6.56 M) and arsenic (6.07 mM) in the intestinal loops of rats, in situ, caused significant reduction of arsenic transference. Short-term arsenic exposure (3mg/kg body weight/day for 30 days) caused liver damage evidenced by activities of liver enzymes and necroinflammatory changes. These effects of arsenic were coupled with enhanced mitochondrial swelling, inhibition of cytochrome c oxidase, Ca(2+)-ATPase, a decrease in mitochondrial calcium content, changes in indices of hepatic mitochondrial oxidative stress and iNOS expression. Arsenic also increased hepatic caspase 3 activity and DNA fragmentation. All these apoptosis-related molecular changes caused by arsenic could be alleviated by supplementation with inorganic phosphate, which likely suggests a protective role of phosphate against arsenic-induced hepatotoxic changes.
Asunto(s)
Arsénico/antagonistas & inhibidores , Arsénico/toxicidad , Enfermedad Hepática Inducida por Sustancias y Drogas/patología , Enfermedad Hepática Inducida por Sustancias y Drogas/prevención & control , Mitocondrias Hepáticas/efectos de los fármacos , Mitocondrias Hepáticas/patología , Fosfatos/uso terapéutico , Fósforo Dietético/farmacología , Venenos/toxicidad , Animales , Intoxicación por Arsénico/metabolismo , Caspasa 3/metabolismo , Catalasa/metabolismo , Fragmentación del ADN/efectos de los fármacos , Suplementos Dietéticos , Radical Hidroxilo/metabolismo , Mucosa Intestinal/metabolismo , Peroxidación de Lípido/efectos de los fármacos , Hígado/patología , Masculino , Membranas Mitocondriales/efectos de los fármacos , Óxido Nítrico/metabolismo , Óxido Nítrico Sintasa de Tipo II/metabolismo , Ratas , Ratas Wistar , Superóxido Dismutasa/metabolismoRESUMEN
Chronic arsenic exposure induces oxidative damage to liver leading to liver fibrosis. We aimed to define the effect of grape seed extract (GSE), an antioxidant dietary supplement, on arsenic-induced liver injury. First, Male Sprague-Dawley rats were exposed to a low level of arsenic in drinking water (30ppm) with or without GSE (100mg/kg, every other day by oral gavage) for 12months and the effect of GSE on arsenic-induced hepatotoxicity was examined. The results from this study revealed that GSE co-treatment significantly attenuated arsenic-induced low antioxidant defense, oxidative damage, proinflammatory cytokines and fibrogenic genes. Moreover, GSE reduced arsenic-stimulated Smad2/3 phosphorylation and protein levels of NADPH oxidase subunits (Nox2, Nox4 and p47phox). Next, we explored the molecular mechanisms underlying GSE inhibition of arsenic toxicity using cultured rat hepatic stellate cells (HSCs). From the in vitro study, we found that GSE dose-dependently reduced arsenic-stimulated ROS production and NADPH oxidase activities. Both NADPH oxidases flavoprotein inhibitor DPI and Nox4 siRNA blocked arsenic-induced ROS production, whereas Nox4 overexpression suppressed the inhibitory effects of GSE on arsenic-induced ROS production and NADPH oxidase activities, as well as expression of TGF-ß1, type I procollagen (Coll-I) and α-smooth muscle actin (α-SMA) mRNA. We also observed that GSE dose-dependently inhibited TGF-ß1-induced transactivation of the TGF-ß-induced smad response element p3TP-Lux, and that forced expression of Smad3 attenuated the inhibitory effects of GSE on TGF-ß1-induced mRNA expression of Coll-I and α-SMA. Collectively, GSE could be a potential dietary therapeutic agent for arsenic-induced liver injury through suppression of NADPH oxidase and TGF-ß/Smad activation.
Asunto(s)
Arsénico/toxicidad , Enfermedad Hepática Inducida por Sustancias y Drogas/prevención & control , Extracto de Semillas de Uva/farmacología , NADPH Oxidasas/antagonistas & inhibidores , Proteína Smad2/antagonistas & inhibidores , Proteína smad3/antagonistas & inhibidores , Factor de Crecimiento Transformador beta/antagonistas & inhibidores , Animales , Arsénico/antagonistas & inhibidores , Células Cultivadas , Enfermedad Hepática Inducida por Sustancias y Drogas/metabolismo , Extracto de Semillas de Uva/uso terapéutico , Humanos , Cirrosis Hepática/inducido químicamente , Cirrosis Hepática/enzimología , Cirrosis Hepática/prevención & control , Masculino , NADPH Oxidasas/metabolismo , Ratas , Ratas Sprague-Dawley , Proteína Smad2/metabolismo , Proteína smad3/metabolismo , Factor de Crecimiento Transformador beta/metabolismoRESUMEN
Cysteine (Cys) residues are often crucial to the function and structure of proteins. Cys157 and Cys207 in recombinant mouse arsenic (+3 oxidation state) methyltransferase (AS3MT) are shown to be related to enzyme activity and considered to be the catalytic sites. The roles of some conserved Cys residues in the N-terminal region of the rat AS3MT also have been examined. However, little is known about the roles of the Cys residues in the middle region. The metabolism of inorganic arsenic in human is different from rat and mouse in some aspects though the AS3MT has a high degree of similarity in these species. In order to determine whether the Cys156 and Cys206 (corresponding to the catalytic sites, Cys157 and Cys207 in the mouse AS3MT) in the hAS3MT act as the catalytic sites and to study the roles of the Cys residues (Cys226 and Cys250) near the catalytic center in the middle region, we designed and prepared four mutants (C156S, C206S, C226S, and C250S) in which one Cys residue replaced by serine by PCR-based site-directed mutagenesis. The native form and cysteine/serine mutants were assayed for enzyme activity, free thiols, and the secondary structures by circular dichroism and Fourier transform infrared. Our data show that, besides C156S and C206S, C250S is another potential important site. C226S seems to have the same action as the wild-type hAS3MT with the consistent K(M) and V(max) values. Meanwhile, selenium can also inhibit the methylation of inorganic arsenic by C226S. All the mutants except C226S are calculated to have dramatic changes in the secondary structures. Cys250 might form an intramolecular disulfide bond with another Cys residue. These findings demonstrate that Cys residues at positions 156, 206, and 250 play important roles in the enzymatic function and structure of the hAS3MT.
Asunto(s)
Cisteína/genética , Cisteína/metabolismo , Metiltransferasas/genética , Metiltransferasas/metabolismo , Mutagénesis Sitio-Dirigida , Arsénico/antagonistas & inhibidores , Arsénico/metabolismo , Arsénico/toxicidad , Dicroismo Circular , Relación Dosis-Respuesta a Droga , Humanos , Cinética , Metilación , Metiltransferasas/química , Estructura Secundaria de Proteína , Selenio/farmacología , Serina/genética , Serina/metabolismo , Espectroscopía Infrarroja por Transformada de Fourier , Relación Estructura-ActividadRESUMEN
A review of published information on the arsenic contamination of groundwater in the Terai regions of Nepal showed that the source was mainly geogenic due to the dissolution of the arsenic-bearing minerals. Clinical observations of patients in the arsenic affected districts revealed chronic arsenic poisoning from drinking water. Half a million people inhabiting the region are believed to have been exposed to arsenic levels greater than 50 microg/L in their drinking water. Thirty-one percent of the population (3.5 million) in the region are estimated to have been exposed to arsenic levels between 10 and 50 microg/L. Iron assisted biosand filters currently distributed and in operation are a suitable alternative to mitigate the interim arsenic standard of 50 microg/L, as set by the Nepal Government. Arsenic biosand filters were also effective in removing bacteria and viruses from drinking water in laboratory and field tests. However, groundwater treatment targeting cluster communities in the Terai region is the sustainable way of mitigating the arsenic problem.
Asunto(s)
Intoxicación por Arsénico/epidemiología , Arsénico/antagonistas & inhibidores , Restauración y Remediación Ambiental/métodos , Contaminación Química del Agua , Purificación del Agua/métodos , Arsénico/toxicidad , Bacterias/aislamiento & purificación , Filtración/métodos , Humanos , Nepal/epidemiología , Virus/aislamiento & purificaciónRESUMEN
Arsenic is a potent environmental toxin. Present study has been designed to evaluate the protective role of taurine (2-aminoethanesulfonic acid) against arsenic induced cytotoxicity in murine hepatocytes. Sodium arsenite (NaAsO(2)) was chosen as the source of arsenic. Incubation of hepatocytes with the toxin (1 mM) for 2 h reduced the cell viability as well as intra-cellular antioxidant power. Increased activities of alanine transaminase (ALT) and alkaline phosphatase (ALP) due to toxin exposure confirmed membrane damage. Toxin treatment caused reduction in the activities of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR) and glutathione peroxidase (GPx). In addition, the same treatment reduced the level of glutathione (GSH), elevated the level of oxidized glutathione (GSSG) and increased the extent of lipid peroxidation. Incubation of hepatocytes with taurine, both prior to and in combination with NaAsO(2), attenuated the extent of lipid peroxidation and enhanced the activities of enzymatic as well as non enzymatic antioxidants. Besides, taurine administration normalized the arsenic-induced enhanced levels of the marker enzymes ALT and ALP in hepatocytes. The cytoprotective activity of taurine against arsenic poisoning was found to be comparable to that of a known antioxidant, vitamin C. Combining all, the results suggest that taurine protects mouse hepatocytes against arsenic induced cytotoxicity.
Asunto(s)
Arsénico/toxicidad , Citotoxinas/toxicidad , Hepatocitos/efectos de los fármacos , Taurina/farmacología , Alanina Transaminasa , Fosfatasa Alcalina , Aminoácidos Esenciales/farmacología , Animales , Antioxidantes , Arsénico/antagonistas & inhibidores , Biomarcadores , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Citotoxinas/antagonistas & inhibidores , Glutatión , Disulfuro de Glutatión , Hepatocitos/enzimología , Peroxidación de Lípido , Masculino , RatonesRESUMEN
Ascorbic acid treatment in arsenic trioxide treated rats increased arsenic excretion, inhibited lipid peroxidation, improved GSH status, regulated GSSG turnover and also restored glutathione-S-transferases activity in liver and kidney. Suitable mechanisms leading to ascorbic acid protection have been discussed. Upregulation of GSH dependent enzymes was found to be necessary for a protective effect. Protection is finally attributed to higher GSH levels observed in the liver and kidney of ascorbic acid and inorganic arsenic treated rats. It is also concluded that ascorbic acid protection is influenced by gender dependent factors. Arsenic poisoning is a global problem now. Gender differences need to be considered while applying therapeutic measures.
Asunto(s)
Antioxidantes/farmacología , Arsénico/antagonistas & inhibidores , Ácido Ascórbico/farmacología , Riñón/efectos de los fármacos , Hígado/efectos de los fármacos , Estrés Oxidativo/efectos de los fármacos , Animales , Arsénico/toxicidad , Femenino , Masculino , Ratas , Ratas WistarRESUMEN
Oxidative stress has been suggested to be a major cause of male reproductive failure. Here, we investigated whether arsenic, which impairs male reproductive functions in rodent models, acts by inducing oxidative stress. Male 8-week-old ICR mice were given drinking water containing 20 or 40 mg/l sodium arsenite with or without 0.75 or 1.5 g/l of the antioxidant ascorbic acid for 5 weeks. The arsenic-treated mice showed decreased epididymidal sperm counts and testicular weights compared to untreated mice. These effects were reversed in mice that were co-treated with ascorbic acid. Similarly, arsenic treatment lowered the activities of testicular 3beta-hydroxysteroid dehydrogenase (HSD) and 17beta-HSD, which play important roles in steroidogenesis, and this was reversed by co-treatment with ascorbic acid. The testicles of arsenic-treated mice had decreased glutathione (GSH) levels (which correlate inversely with the degree of cellular oxidative stress) and elevated levels of protein carbonyl (a marker of oxidative damage to tissue proteins). Ascorbic acid co-treatment reversed both of these effects. Thus, ascorbic acid blocks both the adverse effects of arsenic on male reproductive functions and the arsenic-induced testicular oxidative changes. These observations support the notion that arsenic impairs male reproductive function by inducing oxidative stress.
Asunto(s)
Antioxidantes/farmacología , Arsénico/antagonistas & inhibidores , Arsénico/toxicidad , Ácido Ascórbico/farmacología , Enfermedades Testiculares/inducido químicamente , Enfermedades Testiculares/prevención & control , Animales , Biomarcadores , Glutatión/metabolismo , Masculino , Malondialdehído/metabolismo , Ratones , Ratones Endogámicos ICR , Tamaño de los Órganos/efectos de los fármacos , Reproducción/efectos de los fármacos , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Recuento de Espermatozoides , Motilidad Espermática/efectos de los fármacos , Enfermedades Testiculares/patología , Testículo/enzimología , Testículo/patología , Testosterona/sangreRESUMEN
Arsenic is a widespread environmental toxicant that may cause neuropathy, skin lesions, vascular lesions and cancer upon prolonged exposure. Improving nourishment like supplementation of micronutrients, antioxidants, vitamins and amino acids could be able to halve the risk in those who were previously the poor nourished. The present study was planned to investigate the preventive effects of zinc and n-acetylcysteine (NAC) supplementation either alone or in combination with arsenic on selected biochemical variables indicative of oxidative stress and liver injury in male rats. For 3 weeks 25 male wistar rats were exposed to arsenic as sodium arsenite (2 mg/kg, orally through gastric intubation) either alone or in combination with NAC (10 mg/kg, intraperitoneally), zinc (5 mg/kg, orally) or zinc plus NAC. Animals were sacrificed 24h after the last dosing for various biochemical parameters. Concomitant administration of zinc with arsenic showed remarkable protection against blood delta-aminolevulinic acid dehydratase (ALAD) activity as well as providing protection to hepatic biochemical variables indicative of oxidative stress (like thiobarbituric acid reactive substances (TBARS) level, catalase) and tissue injury. NAC supplementation on the other hand, was moderately effective in protecting animals from the toxic effects of arsenic. Interestingly, concomitant administration of zinc and NAC was most effective compared to zinc or NAC in eliciting above-mentioned protective effects. The above results suggest significant protective value of combined zinc and NAC administration in acute arsenic exposure.
Asunto(s)
Acetilcisteína/administración & dosificación , Arsénico/toxicidad , Estrés Oxidativo/efectos de los fármacos , Zinc/administración & dosificación , Administración Oral , Alanina Transaminasa/sangre , Animales , Arsénico/antagonistas & inhibidores , Arsénico/farmacocinética , Arsenitos/toxicidad , Aspartato Aminotransferasas/sangre , Sinergismo Farmacológico , Riñón/efectos de los fármacos , Riñón/metabolismo , Hígado/efectos de los fármacos , Hígado/metabolismo , Masculino , Porfobilinógeno Sintasa/sangre , Ratas , Ratas Wistar , Compuestos de Sodio/toxicidad , Distribución Tisular , Zinc/sangreRESUMEN
In the last decade arsenic metabolism has become an important matter of discussion. Methylation of inorganic arsenic (iAs) to monomethylarsonic acid (MMA(V)) and dimethylarsinic acid (DMA(V)) is considered to decrease arsenic toxicity. However, in addition to these pentavalent metabolites, the trivalent metabolites monomethylarsonous (MMA(III)) and dimethylarsinous acid (DMA(III)) have been identified recently as intermediates in the metabolic pathway of arsenic in cultured human cells. To examine the role of oxidative damage in the generation of DNA strand breaks by methylated trivalent arsenic metabolites, we treated human lymphocytes with both metabolites at non-cytotoxic concentrations. We further tested whether these effects are sensitive to modulation by the antioxidants ascorbate (Vitamin C) and selenomethionine (Se-Met). Both trivalent metabolites produced oxidative stress related DNA damage, consisting of single strand breaks and alkali-labile sites, with MMA(III) being more potent at low concentrations than DMA(III). Neither MMA(III) nor DMA(III) induced DNA-double strand breaks. The oxidative stress response profiles of the metabolites were parallel as determined by lipid peroxidation induction. MMA(III) induced peroxidation from the lowest concentration tested, while effects of DMA(III) were apparent only at concentrations above 10 muM. The antioxidant Se-Met exhibited a more pronounced inhibition of trivalent arsenic metabolite-induced oxidative-DNA damage than did vitamin C. The present findings suggest that DNA damage by methylated trivalent metabolites at non-cytotoxic concentrations may be mediated by a mix of reactive oxygen and nitrogen oxidized species.
Asunto(s)
Álcalis/química , Antioxidantes/farmacología , Arsénico/metabolismo , Arsénico/farmacología , Daño del ADN , Especies Reactivas de Oxígeno/metabolismo , Adulto , Arsénico/antagonistas & inhibidores , Arsenicales/antagonistas & inhibidores , Arsenicales/metabolismo , Arsenicales/farmacología , Ácido Ascórbico/farmacología , Ácido Cacodílico/antagonistas & inhibidores , Ácido Cacodílico/metabolismo , Ácido Cacodílico/farmacología , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , ADN/efectos de los fármacos , ADN/metabolismo , Relación Dosis-Respuesta a Droga , Humanos , Linfocitos/efectos de los fármacos , Metilación , Oxidación-Reducción , Valores de Referencia , Selenometionina/farmacologíaRESUMEN
The innate immune response, the first line of defense against invading pathogens, can be perturbed by environmental toxicants such as arsenic. This study reports the effects of arsenic on innate immunity of zebrafish. Respiratory burst activity, messenger RNA expression of tumor necrosis factor alpha (TNF-alpha), a primer of the respiratory burst response, and mRNA expression of the antiviral cytokines interferon (IFN) and MX, : before and after viral infection, were examined in arsenic-exposed zebrafish larvae. Respiratory burst activity and TNF-alpha expression were decreased upon arsenic exposure, indicating inhibition of TNF-alpha priming of the respiratory burst response. Arsenic enhanced IFN expression slightly over time, but reduced MX : expression. In zebrafish infected with snakehead rhabdovirus, arsenic decreased induction and altered the kinetics of IFN and MX : upon infection. Differences in IFN and MX : expression in arsenic-exposed larvae point toward an interruption of the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway.
Asunto(s)
Arsénico/toxicidad , Inmunidad Innata/efectos de los fármacos , Estallido Respiratorio/efectos de los fármacos , Pez Cebra/inmunología , Pez Cebra/metabolismo , Animales , Arsénico/antagonistas & inhibidores , Cartilla de ADN , Infecciones por Virus ADN/metabolismo , Enfermedades de los Peces/inmunología , Expresión Génica/efectos de los fármacos , Inmunocompetencia/efectos de los fármacos , Interferones/biosíntesis , Interferones/genética , Larva/metabolismo , Novirhabdovirus/inmunología , Reacción en Cadena de la Polimerasa/métodos , ARN Mensajero/biosíntesis , ARN Mensajero/efectos de los fármacos , Infecciones por Rhabdoviridae/inmunología , Infecciones por Rhabdoviridae/veterinaria , Factor de Necrosis Tumoral alfa/biosíntesis , Factor de Necrosis Tumoral alfa/genética , Pez Cebra/virologíaRESUMEN
Oxidative stress due to enhanced production of free radicals has been incriminated as one of the several mechanisms involved in arsenic-induced toxic effects in different organs. In the present study, ameliorative potential of certain amino acids like cysteine, methionine and vitamins like ascorbic acid and thiamine on some of the parameters indicative of oxidative stress in liver, kidney and blood and of hepatic and renal infliction was investigated in arsenic exposed rats. Rats were given 0 ppm (group I healthy controls) or 10 ppm arsenic in drinking water ad lib for a period of 12 weeks. During oral exposure to arsenic rats of different groups received daily oral dose of placebo, cysteine, methionine, ascorbic acid or thiamine at 25mg/kg body weight. After the end of the experimental period, animals were sacrificed under light anesthesia and blood, liver and kidney were collected. Samples were processed for estimation of arsenic, biochemical parameters indicative of oxidative stress and hepatic and renal function. Arsenic exposure resulted in significantly (P<0.05) higher accumulation of arsenic in blood, liver and kidney. It was associated with significant (P<0.05) rise in lipid peroxide level and decrease in superoxide dismutase and catalase activities in liver and kidneys. However, alterations in biochemical parameters did not reach statistical (P>0.05) significance. Treatment with vitamins and amino acids resulted in reversal of oxidative stress with significant (P<0.05) decline in tissue arsenic burden. All the treatment produced tissue specific changes in lipid peroxide level, antioxidant enzyme activities and tissue arsenic burden.
Asunto(s)
Antioxidantes/farmacología , Arsénico/antagonistas & inhibidores , Arsénico/toxicidad , Ácido Ascórbico/farmacología , Cisteína/farmacología , Metionina/farmacología , Estrés Oxidativo/efectos de los fármacos , Tiamina/farmacología , Alanina Transaminasa/sangre , Animales , Antioxidantes/metabolismo , Arsénico/farmacocinética , Aspartato Aminotransferasas/sangre , Proteínas Sanguíneas/metabolismo , Peso Corporal/efectos de los fármacos , Creatinina/metabolismo , Eritrocitos/efectos de los fármacos , Eritrocitos/metabolismo , Riñón/efectos de los fármacos , Riñón/enzimología , Peróxidos Lipídicos/sangre , Hígado/efectos de los fármacos , Hígado/enzimología , Masculino , Malondialdehído/metabolismo , Ratas , Ratas Wistar , Urea/metabolismoRESUMEN
Arsenic, a naturally ocurring chemical element, is considered hazardous to human health. Inorganic arsenic compounds were found to induce cytotoxicity in Chinese hamster V-79 cells in culture. The arsenite form was more toxic than arsenate. Extracts of green and two varieties of black tea, as well as their principal polyphenols, (-)-epigallocatechingallate and theaflavin, efficiently counteracted the cytotoxic effects of arsenic compounds. On the basis of the amount of tea extract that afforded 50% protection to the cells from arsenic induced cytotoxicity, black tea was found to be as effective as green tea. The protective effect was attributable to the contents of not only (-)-epigallocatechingallate but also of theaflavin, the latter being a predominant polyphenol present in black tea.
Asunto(s)
Arsénico/antagonistas & inhibidores , Citotoxinas/antagonistas & inhibidores , Té , Animales , Arsénico/toxicidad , Línea Celular Tumoral , Quimioprevención , Cricetinae , Cricetulus , MasculinoRESUMEN
Epidemiological studies on arsenic contamination in drinking water indicated presence of arsenic in fetal tissues. Experiments on human fetal brain explants on exposure to arsenic in culture showed disturbance in lipid peroxidation, generation of nitric oxide (NO), reactive oxygen species (ROS) and apoptosis. The oxidative stress challenged by antioxidant vitamins C, E or chelator dimercaptosuccinic acid (DMSA) may reverse arsenic toxicity on neuronal development. The concept was tested with the models: (A) human fetal brain explants exposed to arsenic, 0.3 mg/l in culture for 24 h; (B) rat neonatal brain explants from 1-day-old litters exposed to 0.3 mg/l arsenic in drinking water during gestation. Rats (n=10) were given oral administration of vitamin C, 2.5 mg/kg/day, vitamin E, 148 microg/kg/day during gestation and DMSA, 50 mg/kg for 2 days at the end of gestation. (A) The arsenic induced in human fetal brain explants increase in production of NO, 20% and ROS, 25%, and decrease in DNA, 62% and protein, 54% synthesis. The morphological analyses showed growth of viable cells, neural networking vis-à-vis apoptosis on exposure to arsenic for 24 h and necrosis and loss of ground matrix on arsenic exposure for 18 days. The occurrence of two processes of apoptosis and necrosis in different neurons of same culture indicated existence of a selective cellular defense against arsenic toxicity. (B) The rats exposed to arsenic showed increased generation of NO, 25% and ROS, 22%, loss of glutathione content from 42 to 35 microg/mg protein, 40% increase in lipid peroxidation and decreased superoxide dismutase at 32%. The administration of vitamins C, E and DMSA showed partial reversal of the effects indicating possible protection from arsenic toxicity.
Asunto(s)
Antioxidantes/toxicidad , Apoptosis/efectos de los fármacos , Arsénico/toxicidad , Encéfalo/patología , Animales , Arsénico/administración & dosificación , Arsénico/antagonistas & inhibidores , Encéfalo/efectos de los fármacos , Encéfalo/crecimiento & desarrollo , División Celular/efectos de los fármacos , Membrana Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Quelantes/farmacología , Técnicas de Cultivo , Femenino , Glutatión/metabolismo , Humanos , Leucina/metabolismo , Masculino , Necrosis , Neuronas/patología , Neuronas/ultraestructura , Óxido Nítrico/metabolismo , Embarazo , Ratas , Ratas Endogámicas , Especies Reactivas de Oxígeno/metabolismo , Timidina/metabolismo , Abastecimiento de AguaRESUMEN
AIM: To investigate regulative effects of thiol reagents, N-acetyl-l-cysteine (NAC) and natrii dimercaptosussinas (NDMS), catalase (CAT), and calcium chelator 2-[(2-bis-[carboxymethyl]-amino-5-methyl-phenoxy)-met]-6-methoxy-8-bis-[carboxy-methyl]-aminoquinoline (Quin 2) on apoptosis and telomerase activity induced by arsenic trioxide (As2O3) in three myelocytic leukemia cell lines. METHODS: Flow cytometry was used to examine apoptosis and a PCR ELISA kit was used to detect telomerase activity. RESULTS: As2O3 induced about 40 % - 60 % of apoptosis in NB4, K562, and HL-60 cells at the concentration of 0.6, 2.7, and 8.1 micromol/L respectively, as well as down-regulated telomerase activities in three cell lines. NAC 4 mmol/L, NDMS 200 micromol/L, CAT 80 kU/L, and Quin 2 20 micromol/L could down-regulate apoptosis variously induced by As2O3. NAC and CAT alone could decline telomerase activity in three cell lines and further decline telomerase activities that had been decreased by As2O3, whereas Quin 2 antagonized the decline in K562 and HL-60 cells. CONCLUSION: Thiol activity loss, free radical alteration, intracellular calcium changes, and decline of telomerase activity might be involved in As2O3-induced apoptosis. NAC, NDMS, CAT, and Quin 2 antagonized in some extent the effect of As2O3 on the three tested cell lines.
Asunto(s)
Antineoplásicos/farmacología , Apoptosis/efectos de los fármacos , Arsénico/antagonistas & inhibidores , Arsenicales/farmacología , Leucemia Mieloide/patología , Óxidos/farmacología , Telomerasa/metabolismo , Acetilcisteína/farmacología , Aminoquinolinas/farmacología , Trióxido de Arsénico , Catalasa/farmacología , Regulación hacia Abajo , Células HL-60/patología , Humanos , Células K562/patología , Leucemia Mieloide/enzimologíaRESUMEN
Culture models of target cells are anticipated to help elucidate the mechanism by which inorganic arsenic acts as a carcinogen in humans. Present work characterizes the response of human keratinocytes, a target cell type, to arsenic suppression of their differentiation program. Four representative differentiation marker mRNAs (involucrin, keratinocyte transglutaminase, small proline-rich protein 1, and filaggrin) were suppressed by both arsenate and arsenite in normal, spontaneously immortalized (premalignant), and malignant keratinocytes with EC50 values in the low micromolar range. The suppression was almost completely reversed 9 days after removal of arsenate from the culture medium. In the case of the involucrin gene, suppression was mediated primarily by two functional AP1 response elements in the gene promoter. Both glucocorticoid and serum stimulation of differentiation occurred to a similar extent in the presence and absence of arsenic, indicating neither stimulation was a specific target of arsenic action and neither agent could overcome arsenic suppression. In contrast, 12-O-tetradecanoylphorbol-13-acetate prevented the suppression of keratinocyte transglutaminase, suggesting that arsenic acts upstream of protein kinase C.
Asunto(s)
Arsénico/farmacología , Queratinocitos/efectos de los fármacos , Fosfoproteínas/metabolismo , Acetato de Tetradecanoilforbol/farmacología , Factor de Transcripción AP-1/metabolismo , Arseniatos/farmacología , Arsénico/antagonistas & inhibidores , Arsenitos/farmacología , Línea Celular , Regulación hacia Abajo , Proteínas Filagrina , Humanos , Queratinocitos/metabolismo , Modelos Logísticos , Precursores de Proteínas/biosíntesis , ARN Mensajero/biosíntesis , Elementos de Respuesta , Factor de Transcripción AP-1/genética , Transglutaminasas/biosíntesisRESUMEN
It has been proposed that arsenic exerts its toxic effects, in part, by perturbing cellular methyl metabolism. Based on the hypothesis that folic acid treatment will attenuate the cytotoxic and growth inhibitory effects of arsenic, SWV/Fnn embryo fibroblasts were cultured in media supplemented with various concentrations of folic acid during treatment with sodium arsenite or dimethylarsinic acid (DMA). It was found that folic acid protects SWV/Fnn embryo fibroblasts from sodium arsenite and DMA cytotoxicity in a dose-dependent manner. In contrast, folic acid supplementation has no effect on toxicity resulting from treatment with ethanol or staurosporine, suggesting that folic acid is not generally protective against necrosis and apoptosis. Although folic acid protects against acute arsenic toxicity, this agent shows a modest and delayed ability to attenuate the growth inhibitory effect of arsenic on these cells. These results support a model in which perturbations of methyl metabolism contribute to the acute cytotoxicity of arsenic.
Asunto(s)
Arsénico/antagonistas & inhibidores , Arsénico/toxicidad , Ácido Fólico/uso terapéutico , Animales , Arsenitos/antagonistas & inhibidores , Arsenitos/toxicidad , Ácido Cacodílico/antagonistas & inhibidores , Ácido Cacodílico/toxicidad , Carcinógenos/toxicidad , División Celular/efectos de los fármacos , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Depresores del Sistema Nervioso Central/toxicidad , Etanol/toxicidad , Femenino , Fibroblastos/efectos de los fármacos , Ratones , Ratones Endogámicos , Compuestos de Sodio/antagonistas & inhibidores , Compuestos de Sodio/toxicidad , Estaurosporina/toxicidadRESUMEN
Inhibition bioassay of sister chromatid exchanges (SCE) and DNA synthesis was carried out to study the mechanism that selenium, as a chemical agent for intervention, could antagonize the effects of arsenic on body damage and lower incidence of tumor. Results demonstrated that SCE frequency in peripheral lymphocytes induced by As2O3 could be significantly reduced by preincubation with 5 x 10(-7), 1 x 10(-6) mol/L Na2SeO3 and co-exposure of 1 x 10(-6) mol/L selenomethionine. Inhibition of DNA synthesis could be antagonized by preincubation in with 5 x 10(-6) mol/L Na2SeO3 and co-exposure of 1 x 10(-6), 5 x 10(-6) mol/L selenomethionine. But, the mechanism that protective effects of selenium on the damage to cell genetic material induced by arsenic should be studied further.
Asunto(s)
Antimutagênicos/farmacología , Arsénico/antagonistas & inhibidores , ADN/biosíntesis , Linfocitos/metabolismo , Selenometionina/farmacología , Intercambio de Cromátides Hermanas/efectos de los fármacos , Selenito de Sodio/farmacología , Arsénico/toxicidad , Humanos , Pruebas de MutagenicidadRESUMEN
The cytotoxic effect of arsenite seems to be inversely related to the intracellular glutathione (GSH) content, and GSH seems to facilitate the metabolism of arsenic in cell. Arsenite is also known to induce chromosome aberration, to enhance the cytotoxicity and clastogenicity of ultraviolet (UV) light, and to inhibit UV-induced DNA repair. We have investigated whether these toxic effects of arsenite and the cellular arsenic content are also modulated by the intracellular GSH. A 2-h pretreatment of the cultured ovary (CHO) cells with GSH reduced the clastogenicity and cytotoxicity of arsenite. The enhancing effects of arsenite on chromosome aberrations and cell destruction induced by UV were also reduced by a 2-h pretreatment with GSH. The inhibitory effect of arsenite on the strand-break rejoining during UV-induced DNA repair was reduced by GSH pretreatment and was enhanced by pretreatment with buthionine sulfoximine, which is known to deplete the cellular GSH. The cellular arsenic content was reduced by GSH pretreatment and increased by buthionine sulfoximine pretreatment. GSH given before or simultaneously with arsenite, effectively reduced the clastogenicity and coclastogenicity of arsenite. GSH given after treatment with arsenite decreased the cellular arsenic content, and increased the cell survival, but did not reduce the clastogenicity or the coclastogenicity of arsenite.
Asunto(s)
Arsénico/toxicidad , Arsenitos , Glutatión/farmacología , Animales , Antimetabolitos/farmacología , Arsénico/antagonistas & inhibidores , Butionina Sulfoximina , Células CHO , Supervivencia Celular/efectos de los fármacos , Aberraciones Cromosómicas , Cricetinae , Cricetulus , Metionina Sulfoximina/análogos & derivados , Metionina Sulfoximina/farmacología , Rayos UltravioletaRESUMEN
Exposure of splenocytes in vivo or in vitro to gallium arsenide (GaAs) dose-dependently suppresses the ability of these cells to produce antibody after in vitro immunization with sheep red blood cells. In addition, it has been demonstrated that GaAs exerts immunosuppressive effects early (36 hr) in the generation of a primary antibody-forming cell (AFC) response. The objective of this study was to determine if the GaAs-induced suppression was produced as a result of a GaAs-induced alteration in the secretion of soluble mediators. Supernatants from in vivo and in vitro vehicle (VH)-exposed splenocyte cultures time-dependently reversed GaAs-induced suppression of the in vitro-generated primary AFC response produced by both in vitro (50 microM) and in vivo (200 mg/kg) exposure to GaAs. Supernatants from in vitro GaAs-exposed cells suppressed the VH response 40, 89 and 93% at 24, 36 and 48 hr, respectively. Using the arsenic-binding compound meso-2,3-dimercaptosuccinic acid (100 microM), it was determined that the suppression of the VH response by supernatants from in vitro GaAs-exposed cultures was confounded by the presence of free arsenic in the in vitro GaAs-exposed culture supernatant. In contrast, suppression of in vivo VH-exposed AFC responses by supernatants from in vivo GaAs-exposed cells was not seen. The time-dependent reversal of immunosuppression produced by in vivo or in vitro exposure to GaAs, by supernatants from in vivo and in vitro VH-exposed cells mimics the reported kinetics of suppression by addition of GaAs to antibody cultures.(ABSTRACT TRUNCATED AT 250 WORDS)