Showing papers on "Sodium arsenite published in 2001"
TL;DR: Methylated trivalent arsenicals were the only arsenic compounds that were observed to damage naked DNA and required no exogenously added enzymatic or chemical activation systems, and are considered here to be direct-acting forms of arsenic that are genotoxic, though they are not, necessarily, the onlygenotoxic species of arsenic That could exist.
Abstract: The reactivities of methyloxoarsine (MAs(III)) and iododimethylarsine (DMAs(III)), two methylated trivalent arsenicals, toward supercoiled phiX174 RFI DNA were assessed using a DNA nicking assay. The induction of DNA damage by these compounds in vitro in human peripheral lymphocytes was assessed using a single-cell gel (SCG, "comet") assay. Both methylated trivalent arsenicals were able to nick and/or completely degrade phiX174 DNA in vitro in 2 h incubations at 37 degrees C (pH 7.4) depending on concentration. MAs(III) was effective at nicking phiX174 DNA at 30 mM; however, at 150 microM DMAs(III), nicking could be observed. Exposure of phiX174 DNA to sodium arsenite (iAs(III); from 1 nM up to 300 mM), sodium arsenate (from 1 microM to 1 M), and the pentavalent arsenicals, monomethylarsonic acid (from 1 microM to 3 M) and dimethylarsinic acid (from 0.1 to 300 mM), did not nick or degrade phiX174 DNA under these conditions. In the SCG assay in human lymphocytes, methylated trivalent arsenicals were much more potent than any other arsenicals that were tested. On the basis of the slopes of the concentration-response curve for the tail moment in the SCG assay, MAs(III) and DMAs(III) were 77 and 386 times more potent than iAs(III), respectively. Because methylated trivalent arsenicals were the only arsenic compounds that were observed to damage naked DNA and required no exogenously added enzymatic or chemical activation systems, they are considered here to be direct-acting forms of arsenic that are genotoxic, though they are not, necessarily, the only genotoxic species of arsenic that could exist.
495 citations
TL;DR: It is demonstrated that MMA(III) is more toxic than inorganic arsenite, both in vivo and in vitro, and the hypothesis that methylation of inorganic arsenic is a detoxication process is called into question.
Abstract: Monomethylarsonous acid (MMAIII), a metabolite of inorganic arsenic, has received very little attention from investigators of arsenic metabolism in humans MMAIII, like sodium arsenite, contains arsenic in the +3 oxidation state Although we have previously demonstrated that it is more toxic than arsenite in cultured Chang human hepatocytes, there are no data showing in vivo toxicity of MMAIII When MMAIII or sodium arsenite was administered intraperitoneally to hamsters, the LD50s were 293 and 1120 μmol/kg of body wt, respectively In addition, inhibition of hamster kidney or purified porcine heart pyruvate dehydrogenase (PDH) activity by MMAIII or arsenite was determined To inhibit hamster kidney PDH activity by 50%, the concentrations (mean ± SE) of MMAIII as methylarsine oxide, MMAIII as diiodomethylarsine, and arsenite were 599 ± 65, 620 ± 18, and 1157 ± 23 μM, respectively To inhibit activity of purified porcine heart PDH activity by 50%, the concentrations (mean ± SE) of MMAIII as methyla
335 citations
TL;DR: The results suggest that the failure to find an animal model for arsenic carcinogenesis is because arsenite is not a carcinogen per se, but rather acts as an enhancing agent (cocarcinogen) with a genotoxic partner.
219 citations
TL;DR: The gene expression pattern in mice treated with inorganic arsenicals is profiled, which adds to the understanding of acute arsenic poisoning and toxicity.
199 citations
TL;DR: It is indicated that short-term arsenic exposure induces neural and behavioral changes that may reflect a neurotoxic effect, and that these alterations are correlated to dose, time of exposure, and experimental conditions.
170 citations
TL;DR: Primary cultures of rat cerebellar neurons were used to study mechanisms of arsenic neurotoxicity and data suggest that arsenite neurotoxicity may be due to apoptosis caused by activation of p38 and JNK3 MAP kinases.
160 citations
TL;DR: In this study, male rats of Wistar strain, maintained on either 18% or 6% protein (casein) diet, received an acute i.p. exposure to sodium arsenite at its LD50 dose, which significantly increased the glutathione peroxidase activity in liver of both dietary groups and in kidney of only the 18% protein-fed group of animals.
Abstract: Arsenic is a potent toxin, carcinogen and modulator of antioxidant defense system In this study, male rats of Wistar strain, maintained on either 18% or 6% protein (casein) diet, received an acute ip exposure to sodium arsenite (As3+) at its LD50 dose (1586 mg/kg body weight) One hour after the arsenic exposure, glutathione (GSH) concentration was significantly depleted and lipid peroxidation was increased A relationship between any two of tissue arsenic concentrations, GSH levels and lipid peroxidation values was observed only for liver when the proportional changes of respective parameters in either of the dietary groups of animals were compared This suggests that, in liver, arsenic metabolism appears dependant upon the GSH concentration Acute arsenic exposure significantly increased the glutathione peroxidase (GPx) activity in liver of both dietary groups and in kidney of only the 18% protein-fed group of animals The glutathione-S-transferase (GST) activity significantly decreased in liver of the 18% protein-fed animals while GST increased in kidney of both the 18% and the 6% protein-fed groups No significant change in glutathione reductase (GR) or glucose-6-phosphate dehydrogenase (G6PDH) activity was observed In the present investigation, liver as a whole seems to be more affected in terms of GSH level and GST activity The mode of responses of GPx and GR activities as well as the unaltered G6PDH activity might result in arsenic-induced GSH depletion and increase in lipid peroxidation The animals of the 6% protein-fed group, appeared to be affected less in terms of tissue arsenic concentration, GSH level and GST activity lipid peroxidation,
123 citations
TL;DR: The findings are consistent with a potential role for both hypermethylation and hypomethylation of DNA that coexist after exposure to arsenite, and could support the existence of a state of DNA methylation imbalance that could conceivably disrupt appropriate gene expression in arsenite exposed cells.
122 citations
TL;DR: The results do not implicate a direct interaction of As with the glutathione-related enzymes, GR, GPx, and GST, in the mechanism of arsenic toxicity, but it is unclear whether this product of arsenic metabolism is produced at a sufficiently high concentration in critical target tissues to play a major role in either arsenic toxicity or carcinogenesis.
Abstract: The mechanism of arsenic toxicity is believed to be due to the ability of arsenite (As(III)) to bind protein thiols Glutathione (GSH) is the most abundant cellular thiol, and both GSH and GSH-related enzymes are important antioxidants that play an important role in the detoxification of arsenic and other carcinogens The effect of arsenic on the activity of a variety of enzymes that use GSH has been determined using purified preparations of glutathione reductase (GR) from yeast and bovine glutathione peroxidase (GPx) and equine glutathione S-transferase (GST) The effect on enzyme activity of increasing concentrations (from 1 microM to 100 mM) of commercial sodium arsenite (As(III)) and sodium arsenate (As(V)) and a prepared arsenic(III)-glutathione complex [As(III)(GS)(3)] and methylarsenous diiodide (CH(3)As(III)) has been examined GR, GPx, and GST are not sensitive to As(V) (IC(50) > 50 mM), and none of the enzymes are inhibited or activated by physiologically relevant concentrations of As(III), As(III)(GS)(3), or CH(3)As(III), although CH(3)As(III) is the most potent inhibitor (03 mM < IC(50) < 15 mM) GPx is the most sensitive to arsenic treatment and GST the least Our results do not implicate a direct interaction of As with the glutathione-related enzymes, GR, GPx, and GST, in the mechanism of arsenic toxicity CH(3)As(III) is the most effective inhibitor, but it is unclear whether this product of arsenic metabolism is produced at a sufficiently high concentration in critical target tissues to play a major role in either arsenic toxicity or carcinogenesis
119 citations
TL;DR: It is concluded that L-ascorbate plays a pivotal role in maintaining normal ovarian activities and brain monoamines in arsenic-treated rats and restored the estrous cycle in a regular manner.
Abstract: Arsenic, a major water pollutant in India, produces toxic effects on female reproductive system in rodent models at the dose available in drinking water in arsenic-intoxicated zones. This study examines the coadministration of L-ascorbate (vitamin C) on ovarian steroidogenesis, plasma levels of gonadotrophins, brain monoamines, and ovarian as well as uterine peroxidase activities in sodium arsenite–treated rats. After sodium arsenite treatment, relative ovarian and uterine weights, ovarian Δ5-3β-HSD and 17β-HSD activities, plasma levels of gonadotrophins, norepinephrine levels in midbrain and diencephalon, and the activities of peroxidase in ovary and uterus were decreased significantly. On the other hand, serotonin levels in midbrain and diencephalon were increased significantly 28 days after sodium arsenite treatment at the dose of 0.4 ppm/100 g body weight/rat/day. All these parameters were protected significantly and in most cases were unchanged from control level when L-ascorbate at 25 mg/100 g body weight/rat/day was coadministered orally with sodium arsenite. This cotreatment of L-ascorbate with sodium arsenite also restored the estrous cycle in a regular manner. We concluded that L-ascorbate plays a pivotal role in maintaining normal ovarian activities and brain monoamines in arsenic-treated rats.
101 citations
TL;DR: It is indicated that noncytotoxic concentrations of arsenite are capable of affecting signal transduction pathways and gene expression in the lung.
TL;DR: A significant decrease in sperm count and motility along with increase in abnormal sperm were noticed and significant accumulation of arsenic in testes and accessory sex organs may be attributed to the arsenic binding to the tissues or greater cellular uptake.
Abstract: Arsenic, a known human carcinogen, was given to mice via drinking water as sodium arsenite at a dose 53.39, 133.47, 266.95 and 533.90 micromol 1 for 35 days. A decrease in the activity of 17 beta HSD along with increase in LDH, gammaGT activity were observed at 533.90 micromol l. The observed sperm count, motility and morphological abnormalities in sperm were similar to control at lower dose levels. However at 533.90 micromol l a significant decrease in sperm count and motility along with increase in abnormal sperm were noticed. Significant accumulation of arsenic in testes and accessory sex organs may be attributed to the arsenic binding to the tissues or greater cellular uptake. No effects were observed on indices studied for reproductive effects at 53.39 micromol l arsenic close to which human being are exposed through drinking water under the present set of experimental conditions.
TL;DR: Evaluating the degree of damage induced by Cd and As salts in a human lung fibroblasts cell line using the single cell gel electrophoresis assay revealed that the majority of exposed cells showed more DNA damage than cells obtained from control cultures.
Abstract: Human exposure to metals is frequent due to their ubiquity, wide use in industry, and environmental persistence. Direct and indirect genotoxic effects of cadmium (Cd) and arsenic (As) were reported. However, the mechanisms of induction of genetic damage are not well known. The aim of the present work was to evaluate the degree of damage induced by Cd and As salts in a human lung fibroblasts cell line using the single cell gel electrophoresis assay (SCGE). MRC-5 cells were treated with cadmium chloride (CdCl(2)), cadmium sulfate (CdSO(4)), sodium arsenite (NaAsO(2)) and cacodylic acid (C(2)H(7)AsO(2)). A significant dose-dependent increment in the extent of DNA migration as well as in the percentage of cells with tails was observed (P<0.001) after treatment with CdSO(4) and NaAsO(2). Treatment with CdCl(2) induced a relatively low level of DNA strand breaks in comparison with that induced by CdSO(4). The increase migration observed with the three compounds could be originated either by the direct induction of DNA lesions or by the inhibition of excision repair mechanisms. On the other hand, cells treated with C(2)H(7)AsO(2) showed a decrease in the migration length with the three doses employed (P<0.001). The decrease in the rate of DNA migration could be a consequence of the induction of DNA cross-links by organic arsenicals.Cd and As salts induced DNA damage in fibroblast cells, detected as DNA migration in the single cell gel (SCG) assay. The distribution of DNA migration among cells as a function of dose revealed that the majority of exposed cells showed more DNA damage than cells obtained from control cultures. The potential for human exposure to both metals has been increased over the years due to the increment in their use. For this reason, elucidation of carcinogenic mechanisms is very important.
TL;DR: Results indicate that the inhibitory action of SA on NO production in LPS-stimulated macrophages might be due to abrogation of inducible NO synthase induction, and it might be closely related to inactivation of the NF-κB and Erk1/2 MAP kinase pathways through loss of Raf-1.
Abstract: The effect of sodium arsenite (SA) on LPS-induced NO production in RAW 2674 murine macrophage cells was studied SA pretreatment of LPS-stimulated RAW cells resulted in a striking reduction in NO production No significant difference in LPS binding was observed between RAW cells pretreated with SA and control untreated RAW cells, suggesting that SA might impair the intracellular signal pathway for NO production SA inhibited LPS-induced NF-kappaB activation by preventing loss of IkappaB-alpha and -beta Furthermore, SA blocked phosphorylation of extracellular signal-regulated kinase 1/2 (Erk1/2), but not phosphorylation of p38 and c-Jun N-terminal kinase SA treatment resulted in the disappearance of Raf-1, suggesting that it might cause the inhibition of the Erk1/2 mitogen-activated protein (MAP) kinase pathway The SA-mediated loss of Raf-1 also abolished LPS-induced NF-kappaB activation as well as the Erk1/2 pathway The dominant negative mutant of MAP kinase kinase 1 inhibited both NO production and NF-kappaB activation in LPS-stimulated RAW cells Taken together, these results indicate that the inhibitory action of SA on NO production in LPS-stimulated macrophages might be due to abrogation of inducible NO synthase induction, and it might be closely related to inactivation of the NF-kappaB and Erk1/2 MAP kinase pathways through loss of Raf-1
Journal Article•
TL;DR: The results of this study confirm that some metals strongly regulate expression of detoxifying proteins, including biliary drug transporters.
Abstract: Metals, such as arsenic or cadmium, have recently been demonstrated to interact with metabolic pathways, including phase I and phase II enzymes and the phase III efflux pump P-glycoprotein. In the present study, we investigated the effects of heavy metals and metalloids on the expression of the multidrug resistance-associated protein 2 (MRP2), a major hepatic transporter. Treatment of primary rat hepatocytes by sodium arsenite [As(III)], sodium arsenate and potassium antimony tartrate, but not cadmium chloride, was shown to markedly increase MRP2 mRNA and protein levels; As(III)-mediated induction was dose- and time-dependent and paralleled a strong increase in MRP2 amounts as assessed by Western blotting. As(III) was also demonstrated to markedly up-regulate MRP2 gene expression in primary human hepatocytes. MRP2 mRNA induction occurring in As(III)-treated rat hepatocytes was fully blocked by actinomycin D, indicating that it required active gene transcription. It was associated with an activation of the c-Jun N-terminal kinase pathway and with a reduction of cellular glutathione levels. Quercetin, a flavonoid compound known to block As(III)-related induction of P-glycoprotein, was also found to prevent up-regulation of MRP2 gene expression in rat hepatocytes exposed to As(III). Such an effect was unlikely to be due to alteration of JNK pathway since quercetin failed to abolish As(III)-induced JNK phosphorylation. It may rather be linked to the increase of cellular glutathione levels by quercetin, thus limiting the depleting effects of As(III) on glutathione amounts. Finally, these results confirm that some metals strongly regulate expression of detoxifying proteins, including biliary drug transporters.
TL;DR: The enhanced expression of HSPs may play a role in regulating PMNL function in patients with sepsis, and oxidative activity is increased and apoptosis is inhibited in PMNLs with enhanced expressionof HSP70.
Abstract: Background: Heat shock proteins (HSPs) in cells, as molecular chaperons, have been reported to regulate cell functions. The objective of this study was to investigate the HSP expression in polymorphonuclear leukocytes (PMNLs) from severe septic patients and the relation between the expression of HSPs and PMNL function. Methods: In blood samples from 21 patients with sepsis and serum C-reactive protein levels more than 10 mg/dL, we used flow cytometry to measure expressions of HSP27, HSP60, HSP70, and HSP90; oxidative activity; and levels of apoptosis in PMNLs during sepsis. In in vitro studies, we used cells from 14 healthy volunteers to examine the relation between the expression of HSP70 and PMNL function. Quercetin (30 μM), a suppressor of HSP, and sodium arsenite (100 μM), an inducer of HSP, were used to regulate the expression of HSP70 in PMNLs, and oxidative activity and apoptosis in these cells were measured. Results: In patients with sepsis, the expressions of HSP27, HSP60, HSP70, and HSP90 and oxidative activity in PMNLs were significantly increased. Apoptosis of these PMNLs was markedly inhibited. In the in vitro studies, administration of sodium arsenite enhanced the expression of HSP70, significantly increased oxidative activity, and inhibited apoptosis. Administration of quercetin before sodium arsenite prevented the expression of HSP70, the increase in oxidative activity, and the inhibition of apoptosis. Conclusion: Sepsis causes the enhanced expression of HSPs in activated PMNLs. In PMNLs with enhanced expression of HSP70, oxidative activity is increased and apoptosis is inhibited. The enhanced expression of HSPs may play a role in regulating PMNL function in patients with sepsis.
TL;DR: Only sodium arsenite had the capacity to alter mitotic and replication indices, while Sodium arsenite and its metabolites were capable of inducing single strand DNA breaks on stimulated human lymphocytes treated in vitro for 24 h; however, the differences observed were between individual responses, one donor being more susceptible even at the lower doses.
Abstract: Inorganic arsenic is a human carcinogen associated with different types of cancer. Arsenic metabolism produces two methylated species: monomethylarsonic and dimethylarsinic acids. Although this metabolic route has been involved in arsenic detoxification, it is still not clear whether these methylated metabolites participate in the carcinogenic process. In this work, we studied the cytotoxic and genotoxic effects of arsenic and its metabolites. Cytotoxicity was evaluated in cultured lymphocytes from three donors. Mitotic and replication indices were the parameters analyzed. The results indicate a clear cytotoxic effect by sodium arsenite but not by its metabolites. Genotoxicity was assessed by the single cell gel electrophoresis assay. Sodium arsenite increased DNA migration in stimulated lymphocytes only at doses greater than 5 × 10–6 M; meanwhile in leukocytes a weak response was observed. Monomethylarsonic acid produced in leukocytes a weak induction of DNA damage, while in stimulated lymphocytes, a dose-increase in DNA migration was observed. The injury caused by dimethylarsinic acid was more evident than that observed in cultures treated with sodium arsenite and monomethylarsonic acid in stimulated lymphocytes, although in leukocytes no effect on DNA migration was found. In conclusion, only sodium arsenite had the capacity to alter mitotic and replication indices, while sodium arsenite and its metabolites were capable of inducing single strand DNA breaks on stimulated human lymphocytes treated in vitro for 24 h; however, the differences observed were between individual responses, one donor being more susceptible even at the lower doses. This individual susceptibility to arsenic compounds has been repeatedly observed for different end-points and should be studied further. Teratogenesis Carcinog. Mutagen. 21:249–260, 2001. © 2001 Wiley-Liss, Inc.
TL;DR: The results indicated that the ERK signaling pathway can participate in HSP70 gene expression induced by the prooxidant sodium arsenite, but not by the antioxidant curcumin.
TL;DR: Although the experimental design did not allow statistical modeling of the entire dose-response curve, the general shape of the dose- response curve is not inconsistent with the previously proposed hypothesis that arsenic-induced cancer follows a non-linear dose- Response model.
TL;DR: The results suggest, for the first time, that the toxic necrotic effect of selenite can be neutralized by arsenite/arsenate at the cellular level, and indicates different mechanisms through which apoptosis is induced by these two elements.
Abstract: Selenium, an essential trace element for humans, has been shown to have anticancer effects. Arsenic, a possibly essential ultratrace element for humans, has been used in the treatment of leukemia. Anticancer effects of selenium and arsenic have been related to their ability to induce apoptosis. Because humans are exposed to diverse trace elements simultaneously, it is important to learn their interrelationship. In this study, we demonstrate that sodium selenite (Na2SeO3) causes apoptosis at 3 microM and necrosis at high concentrations (> 3 microM) in HL-60 cells. Similarly, both sodium arsenite (NaAsO2) at 50 microM and sodium arsenate (Na2HAsO4) induce apoptosis at 500 microM and necrosis at higher concentrations (> 50 microM and > 500 microM, respectively) in HL-60 cells. Arsenite/arsenate, but not selenite, enhances AP-1 DNA-binding activity. This finding indicates different mechanisms through which apoptosis is induced by these two elements. Interestingly, we observed that HL-60 cell necrosis induced by a high concentration (> 3 microM) of selenite was essentially inhibited by arsenic (50 microM of NaAsO2 or 500 microM of Na2HAsO4), which resulted in a net effect of apoptosis. Because AP-1 DNA-binding activity was not induced in the presence of a combination of necrotic amount of selenite and apoptotic amount of arsenite/arsenate, the observed apoptosis apparently was through the mechanism used by selenite. Our results suggest, for the first time, that the toxic necrotic effect of selenite can be neutralized by arsenite/arsenate at the cellular level.
Journal Article•
TL;DR: It is suggested that the fish is able to respond to the stressful situations by gearing up the metabolic activity as revealed by the elevated protein, amino acid content and the activities of AAT and ALAT.
Abstract: The sublethal toxicity of sodium arsenite on protein metabolism was investigated in teleost fish, Tilalpia mossambica at the end of 24, 48, 72 and 96 h of exposure Total protein content, free amino acid content and activities of the enzymes aspartate amino transferase (AAT) and alanine amino transferase (ALAT) in liver, gill, brain and muscle exhibited significant (P<005) alterations throughout the investigation in relation to that of control It is suggested that the fish is able to respond to the stressful situations by gearing up the metabolic activity as revealed by the elevated protein, amino acid content and the activities of AAT and ALAT
TL;DR: The results suggest that although there are differences in the regulation of the stress response between the immortal HK-2 and mortal HPT cell lines, as long as these differences are recognized, theHK-2 cell line should be a valuable adjunct to study the stressresponse of the proximal tubule in general and when exposed to environmental pollutants such as cadmium.
Abstract: The expression of hsp 27, hsp 60, hsc 70, and hsp 70 mRNA and protein was determined in immortalized human proximal tubule cells (HK-2) exposed to heat shock, sodium arsenite, or cadmium chloride (CdCl2) under both acute and extended conditions of exposure. It was demonstrated that the HK-2 cells did not exhibit the classic heat-shock response when subjected to an acute physical (heat) or chemical stress (sodium arsenite or CdCl2). Heat stress, elevated temperature at 42.5 degrees C for 1 h, caused a marked increase only in hsp 70 mRNA and protein, but not hsp 27 or hsp 60 mRNA and protein. Similar results were obtained when the cells were subjected to a classic chemical stress of exposure to 100 microM sodium arsenite for 4 h or CdCl2 for 4 h. These findings were in contrast to those found previously with mortal human proximal tubule (HPT) cells, where acute stress by all three stimuli elicited marked increases in hsp 27, hsp 60, and hsp 70 mRNA and protein. It was shown that the basal levels of expression of hsp 27 and hsp 60 in the HK-2 cells were elevated when compared to those found in unstressed HPT cells and that the basal levels were similar to those found in HPT cells under stress conditions. These results suggest that the failure of the HK-2 cells to increase hsp 27 and hsp 60 levels in response to physical and chemical stress is because they already possess elevated basal levels of these proteins. This would indicate that one or more of the genetic events that resulted in the immortalization of the HK-2 cells also elicited a stress response for hsp 27 and hsp 60, but not for hsp 70, stress response family members. Overall, the results suggest that although there are differences in the regulation of the stress response between the immortal HK-2 and mortal HPT cell lines, as long as these differences are recognized, the HK-2 cell line should be a valuable adjunct to study the stress response of the proximal tubule in general and when exposed to environmental pollutants such as cadmium.
TL;DR: Southern hybridization and mating experiments confirmed the functioning of the ars genes in the operon, thereby conferring increased resistance to sodium arsenate and sodium arsenite.
TL;DR: Results show that there are changes in gene expression in blastocyst-stage bovine embryos in response to genotoxic stress, suggesting that an increase in gadd153 mRNA is a useful marker of DNA damage and metabolic stress in preimplantation embryos.
Abstract: DNA damage and other forms of stress are believed to be important factors in reducing the efficiency of in vitro embryo transfer techniques in farm animals. The expression of mRNAs from stress-responsive genes such as gadd153 (CHOP-10, ddit3) may provide a means of assessing the quality of embryos produced in vitro. Treatment of bovine granulosa cell cultures with the DNA-damaging agents, methyl methane-sulphonate (MMS) or sodium arsenite, induced the expression of an mRNA, which hybridized with the hamster gadd153 cDNA. Part of the corresponding bovine cDNA was amplified by nested polymerase chain reaction (PCR), cloned, and sequenced. Using a sensitive reverse transcriptase-PCR assay we have investigated the expression of gadd153 and beta-actin in blastocyst-stage bovine embryos treated with MMS or sodium arsenite. Both agents produced an increase in the ratio of gadd153 mRNA relative to beta-actin. These results show that there are changes in gene expression in blastocyst-stage bovine embryos in response to genotoxic stress, suggesting that an increase in gadd153 mRNA is a useful marker of DNA damage and metabolic stress in preimplantation embryos.
TL;DR: In this article, the cytotoxic effects of three arsenic compounds were assessed: sodium arsenite, sodium arsenate and sodium cacodylate, representing the trivalent and pentavalent species of arsenic.
Abstract: Numerous epidemiological studies suggest that arsenic (As) compounds are carcinogens, however, recent data have renewed the interest in their anticarcinogenic properties. The cytotoxic effects of three arsenic compounds were assessed: sodium arsenite, sodium arsenate and sodium cacodylate, representing the trivalent and pentavalent species of arsenic, along with a dimethylated pentavalent arsenic specie. HeLa cells and Salmonella typhimurium (strains TA98 and TA100) were exposed to As compounds and the cytotoxic effects were evaluated. Alterations on RNA and DNA synthesis in HeLa cells were also examined. All arsenic compounds produced a dose-dependent inhibition on colony formation and DNA synthesis in HeLa cells, yet any of them significantly influenced RNA synthesis in these cells. No evidence of arsenic-induced mutagenicity or antimutagenicity was observed using the Ames assay. In bacterial cells, only sodium arsenite caused a dose-dependent inhibition of colony formation. Collectively, these results indicate that in both, HeLa and S. typhimurium cell systems, only trivalent sodium arsenite can act as an effective inhibitor of cell growth. The possible mechanism(s) of the cytotoxic effect of arsenite in these two different cell systems might be due to its reactivity with intracellular sulfhydryl groups.
TL;DR: It is demonstrated that SAAD potentiated cytotoxicity induced by arsenic or mercury and that activation of ERK1/2, p38 kinase and JNK1 was responsible for the potentiated arsenic toxicity, whereas the mercury toxicity enhanced by SAAD was mediated with the activity of J NK1.
TL;DR: The findings demonstrate the unique and potent biological effects in mammalian cells of AsBe, a major organic arsenic compound in various marine animals which are ingested daily as seafood in many countries.
Abstract: 1. In this study, we investigated the biological effects of trimethyl (carboxymethyl) arsonium zwitterion, namely arsenobetaine (AsBe), which is a major organic arsenic compound in marine animals using murine bone marrow (BM) cells and compared them with those of an inorganic arsenical, sodium arsenite, in vitro. 2. Sodium arsenite showed strong cytotoxicity in BM cells, and its IC(50) was 6 microM. In contrast, AsBe significantly enhanced the viability of BM cells in a dose-dependent manner during a 72-h incubation; about a twofold increase in the viability of cells compared with that of control cells cultured with the medium alone was observed with a microM level of AsBe. 3. In morphological investigations, AsBe enhanced the numbers of large mature adherent cells, especially granulocytes, during a 72-h BM culture. When BM cells were cultured together with AsBe and a low dose (1 u ml(-1)) of recombinant murine granulocyte/macrophage colony-stimulating factor (rMu GM-CSF), significant additive-like increasing effects were observed on the numbers of both granulocytes and macrophages originated from BM cells. However, AsBe did not cause proliferation of BM cells at all as determined by colony-forming assay using a gelatinous medium. 4. These findings demonstrate the unique and potent biological effects in mammalian cells of AsBe, a major organic arsenic compound in various marine animals which are ingested daily as seafood in many countries.
TL;DR: The genes for arsenic resistance were cloned into the HindIII site of pBluescript vector producing three clones MSA1, MSA2 and MSI3 conferring resistance to sodium arsenate and arsenite salts, and three open reading frames homologous to the arsR, arsB and arsC genes of arsenic resistance.
Abstract: We reported earlier about the detection of a chromosomally located arsenic operon (arsRBC) in a gram-negative bacterium Pseudomonas fluorescens strain MSP3, which showed resistance to elevated levels of sodium arsenate and sodium arsenite The genes for arsenic resistance were cloned into the HindIII site of pBluescript vector producing three clones MSA1, MSA2 and MSI3 conferring resistance to sodium arsenate and arsenite salts They were further sub-cloned to delineate the insert size and the sub-clones were designated as MSA11, MSA12 and MSI13 The sub-clone pMSA12 (26 kb) fragment was further packaged into EcoRI-PstI site of M13mp19 and sequenced Nucleotide sequencing revealed the presence of three open reading frames homologous to the arsR, arsB and arsC genes of arsenic resistance Three cistrons of the ars operon encoded polypeptides ArsR, ArsB and ArsC with molecular weights ranging approximately 12, 37and 24 kDa, respectively These polypeptides were visualized on SDS-PAGE stained with Coomassie blue and measured in a densitometer The arsenic resistance operon (arsRBC) of strain MSP3 plasmid pMSA12 consists of 3 genes namely, arsR – encoding a repressor regulatory protein, arsB – the determinant of the membrane efflux protein that confers resistance by pumping arsenic from the cells and arsC – a small cytoplasmic polypeptide required for arsenate resistance only, not for arsenite resistance ArsB protein is believed to use the cell membrane potential to drive the efflux of intracellular arsenite ions ArsC encodes for the enzyme arsenate reductase which reduces intracellular As(V) (arsenate) to more toxic As(III) (arsenite) and is subsequently extruded from the cell The arsenate reductase activity was present in the soluble cytoplasmic fraction in E coli clones In the context of specified function of the arsenic operon encoded proteins, uptake and efflux mechanisms were studied in the wild strain and the arsenate/arsenite clones The cell free filtrates of the arsenate clones (MSA11 and MSA12) obtained from P fluorescens containing the arsC gene showed that arsenate reduction requires glutathione reductase, glutathione (GSH), glutaredoxin and ArsC protein The protein was purified in an active form and a spectrophotometric assay was developed in which the oxidation of NADPH was coupled to reduction of arsenate The molecular weights and the location of the polypeptides were obtained from Coomassie stained SDS-PAGE of extracellular and intracellular fractions of the cells
TL;DR: It is demonstrated that acute exposure to As3+ increases the levels of metallothionein protein and that this elevation most likely arises from increased expression of the MT-1X isoform.
Abstract: The expression of metallothionein (MT) mRNA and protein was determined in human proximal tubule cells (HPT) following acute exposure to the classic stimulators of the stress response, heat and sodium arsenite (As3+). Treatment of the cells with 100 µ M As3+ for 4 h resulted in a significant increase in the MT-1 and MT-2 proteins immediately preceding and following removal of the stress. The level of the MT-3 isoform protein was unchanged as a result of As3+ treatment. An analysis of the MT isoform-specific mRNA demonstrated that control cells express the MT-1E, MT-1F, MT-1X, MT-2A, and MT-3 genes, but not the MT-1A, MT-1B, MT-1G, MT-1H, and MT-4 genes. Treatment with As3+ resulted in a significant increase in the expression of the MT-1X gene and appearance of mRNA for the MT-1A gene. Expression of the other MT genes was unaffected by As3+ exposure, except one isolate expressed a low level of MT-1G mRNA at several time points. It is likely that the increase in MT protein seen in As3+-treated cells is due t...
Journal Article•
TL;DR: Inorganic arsenicals alter the methylation patterns and the expression of p 16 gene in BEP2D cells, which suggests that the hypermethylation of p16 gene CpG islands may be one of the mechanisms of carcinogenesis of inorganic arsenicals.
Abstract: Objective To study the effects of inorganic arsenicals on the methylation of p16 gene CpG islands and the expression of p16 gene in BEP2D cells. Methods The methylation of p16 gene CpG islands and the expression of p16 gene in BEP2D cells were measured by methylation-specific PCR (MSP) and RT-PCR methods. Results (1) The exposure of the BEP2D cells to sodium arsenite (0.016 approximately 2 micromol/L) or high-density sodium arsenate (80 approximately 160 micromol/L), but not low-density sodium arsenate (20 approximately 40 micromol/L), produced significant hypermethylation of p16 gene CpG islands in BEP2D cells. (2) The expressions of p16 gene in the groups of sodium arsenite and sodium arsenate at the test were lower than that of the control group, especially in the groups of sodium arsenite. Conclusions Inorganic arsenicals alter the methylation patterns and the expression of p16 gene in BEP2D cells, which suggests that the hypermethylation of p16 gene CpG islands may be one of the mechanisms of carcinogenesis of inorganic arsenicals.