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PubMed2004

Role of glutathione in dimethylarsinic acid-induced apoptosis.

Inorganic arsenicals are clearly toxicants and carcinogens in humans. In mammals, including humans, inorganic arsenicals often undergo methylation, forming compounds such as dimethylarsinic acid (DMAs(V)). Recent evidence indicates that DMAs(V) is a complete carcinogen in rodents although evidence for inorganic arsenicals as carcinogens in rodents remains equivocal. Thus, we studied the molecular mechanisms of in vitro cytolethality of DMAs(V) using a rat liver epithelial cell line (TRL 1215). DMAs(V) selectively induced apoptosis in TRL 1215 cells; its LC(50) value after 48 h exposure was 4.5 mM. The addition of a glutathione synthase inhibitor, L-buthionine-[S,R]-sulfoximine (BSO), actually decreased DMAs(V)-induced apoptosis. DMAs(V) exposure temporarily decreased cellular reduced glutathione (GSH) levels and enhanced cellular glutathione S-transferase (GST) activity from 6 h after the exposure when the cells were still alive. Also, DMAs(V) exposure activated cellular caspase 3 activity with a peak at 18 h after the exposure when apoptosis began, and BSO treatment completely inhibited this enzyme activity. The additions of inhibitors of caspase 3, caspase 8, and caspase 9 significantly reduced DMAs(V)-induced apoptosis. Taken together, these data indicate that cellular GSH was required for DMAs(V)-induced apoptosis to occur, and activation of cellular caspases after conjugation of DMAs(V) with cellular GSH appears to be of mechanistic significance. Further research will be required to determine the role of intracellular GSH and methylation in the toxicity of arsenicals in chronic arsenic poisoning or in cases where arsenicals are used as chemotherapeutics.

Animals↗
PubMed2002

Presence of organoarsenicals used in cotton production in agricultural water and soil of the southern United States.

Arsenicals have been used extensively in agriculture in the United States as insecticides and herbicides. Mono- and disodium methylarsonate and dimethylarsinic acid are organoarsenicals used to control weeds in cotton fields and as defoliation agents applied prior to cotton harvesting. Because the toxicity of most organoarsenicals is less than that of inorganic arsenic species, the introduction of these compounds into the environment might seem benign. However, biotic and abiotic degradation reactions can produce more problematic inorganic forms of arsenic, such as arsenite [As(III)] and arsenate [As(V)]. This study investigates the occurrences of these compounds in samples of soil and associated surface and groundwaters. Preliminary results show that surface water samples from cotton-producing areas have elevated concentrations of methylarsenic species (>10 microg of As/L) compared to background areas (<1 microg of As/L). Species transformations also occur between surface waters and adjacent soils and groundwaters, which also contain elevated arsenic. The data indicate that point sources of arsenic related to agriculture might be responsible for increased arsenic concentrations in local irrigation wells, although the elevated concentrations did not exceed the new (2002) arsenic maximum contaminant level of 10 microg/L in any of the wells sampled thus far.

Agriculture↗
PubMed2005

Relative leaching and aquatic toxicity of pressure-treated wood products using batch leaching tests.

Size-reduced samples of southern yellow pine dimensional lumber, each treated with one of five different waterborne chemical preservatives, were leached using 18-h batch leaching tests. The wood preservatives included chromated copper arsenate (CCA), alkaline copper quaternary, copper boron azole, copper citrate, and copper dimethyldithiocarbamate. An unpreserved wood sample was tested as well. The batch leaching tests followed methodology prescribed in the U.S. Environmental Protection Agency toxicity characteristic leaching procedure (TCLP). The wood samples were first size-reduced and then leached using four different leaching solutions (synthetic landfill leachate, synthetic rainwater, deionized water, and synthetic seawater). CCA-treated wood leached greater concentrations of arsenic and copper relative to chromium, with copper leaching more with the TCLP and synthetic seawater. Copper leached at greater concentrations from the arsenic-free preservatives relative to CCA. Arsenic leached from CCA-treated wood at concentrations above the U.S. federal toxicity characteristic limit (5 mg/L). All of the arsenic-free alternatives displayed a greater degree of aquatic toxicity compared to CCA. Invertebrate and algal assays were more sensitive than Microtox. Examination of the relative leaching of the preservative compounds indicated that the arsenic-free preservatives were advantageous over CCA with respect to waste disposal and soil contamination issues but potentially posed a greater risk to aquatic ecosystems.

Animals↗
PubMed1987

Metabolism and excretion of gallium arsenide and arsenic oxides by hamsters following intratracheal instillation.

The increasing use of gallium arsenide (GaAs) in the electronics industry has produced the need for pharmacokinetic and toxicologic data on GaAs. The disposition in male Syrian golden hamsters (n = 4) following intratracheal instillation of GaAs (mean volume diameter 5.8 micron), arsenic (III) oxide (arsenite), and arsenic (V) oxide (arsenate) at a dose of 5 mg/kg body weight was examined. Blood, kidney, liver, and lung samples were collected at 1, 2, and 4 days after administration. Excreta were collected daily. Urinary metabolite profiles were determined after separation on a mixed anion-cation-exchange column. Total As content was analyzed by direct hydride flame atomic absorption spectrophotometry after digestion. Arsenic blood levels after GaAs, arsenite, and arsenate administration were 0.185 +/- 0.041, 0.596 +/- 0.117, and 0.310 +/- 0.045 ppm, respectively, after Day 1. Arsenic blood levels after GaAs administration increased to 0.279 +/- 0.021 ppm on Day 2 indicating continued absorption while levels decreased for the arsenite and arsenate groups. At Day 1 the liver contained 0.565 +/- 0.036, 2.62 +/- 0.26, and 0.579 +/- 0.144% of the arsenic dose of GaAs, arsenite, and arsenate, respectively. The arsenite and arsenate were rapidly excreted in the urine with almost half the dose appearing after 4 days; in contrast, only about 5% of the GaAs was found at the corresponding time. Total recoveries, as arsenic equivalents, for the three compounds were between 75 and 80%. Ratios of the two major urinary metabolites (dimethylarsinic acid/total inorganic As species) were 1.41, 1.71, and 0.983 for GaAs, arsenite, and arsenate, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed2005

Arsenic release provided by MTA and Portland cement.

OBJECTIVE: The aim of the present study was to determine the release of arsenic from 2 gray Portland cements, a white Portland cement, and 2 MTAs (ProRoot and MTA-Angelus). STUDY DESIGN: The materials were manipulated and placed in plastic tubes, and the tubes were immersed in glass flasks containing water with grade reagent, pH 5.0. After 3 and 168 h, the water in which the material had been immersed was analyzed regarding the presence of arsenic by atomic absorption spectrophotometry with hydride generation. RESULTS: The levels of arsenic released were similar for Portland cements and MTAs, and were well below those considered to be harmful. CONCLUSIONS: MTA and Portland cements showed very low arsenic presence. The results suggest that MTAs and Portland cements are safe for use in clinical practice in terms of the presence of arsenic.

Aluminum Compounds↗
PubMed1995

Carbon-arsenic bond cleavage by a newly isolated gram-negative bacterium, strain ASV2.

Strain ASV2, an unidentified Gram-negative bacterium newly isolated from activated sludge, was found to utilize arsonoacetate at concentrations up to at least 30 mM as sole carbon and energy source, with essentially quantitative extracellular release of arsenate. Cell-free conversion of arsonoacetate could not be obtained, but resting-cell studies indicated that the carbon-arsenic bond cleavage activity was inducible in the presence of arsonoacetate and was of limited substrate specificity, also breaking down arsonochloroacetate. The inorganic product of the reaction may be arsenite since an inducible arsenite-oxidizing activity was also found in arsonoacetate-metabolizing cells. This is the first report of a micro-organism capable of utilizing a compound containing the carbon-arsenic bond. The results indicate that the ability of bacteria to degrade arsonoacetate is not fortuitous and may be found in environments not previously exposed to organoarsenicals.

Arsenic↗
PubMed2005

Benzodithiophenes potentiate differentiation of acute promyelocytic leukemia cells by lowering the threshold for ligand-mediated corepressor/coactivator exchange with retinoic acid receptor alpha and enhancing changes in all-trans-retinoic acid-regulated gene expression.

Differentiation induction is an effective therapy for acute promyelocytic leukemia (APL), which dramatically responds to all-trans-retinoic acid (ATRA). Recent studies have indicated that combinatorial use of retinoid and nonretinoid compounds, such as histone deacetylase inhibitors, arsenics, and PKA agonists, has higher therapeutic value in this disease and potentially in other malignancies. In a screen of 370 compounds, we identified benzodithiophene analogues as potent enhancers of ATRA-induced APL cell differentiation. These effects were not associated with changes in global histone acetylation and, for the most potent compounds, were exerted at very low nanomolar concentrations, and were paralleled by enhancement of some, but not all, ATRA-modulated gene expressions. Investigating the mechanism underlying the effects of these drugs on ATRA-induced APL cell differentiation, we have shown that benzodithiophenes enhance ATRA-mediated dissociation and association of corepressor N-CoR and coactivator p300 acetyltransferase, respectively, with retinoic acid receptor (RAR) alpha proteins. These data suggest that benzodithiophenes act at the level of receptor activation, possibly by affecting posttranslational modification of the receptor (and/or coregulators), thus leading to an enhancement in ATRA-mediated effects on gene expression and APL cell differentiation. Given the specificities of these low benzodithiophene concentrations for PML-RARalpha and RARalpha, these drugs may be useful for combinatorial differentiation therapy of APL and possibly other acute myelogenous leukemia subtypes in which the overall ATRA signaling is suppressed.

Cell Differentiation↗
PubMedDate not supplied

Total content and chemical speciation of arsenic in the polychaete Sabella spallanzanii.

An unusual feature has been observed in polychaetes regarding their capacity to accumulate high levels of relatively toxic forms of arsenic in specific tissues. Basal levels of arsenic and distribution of its compounds were investigated in tissues of the Mediterranean polychaete Sabella spallanzanii. Particularly high concentrations were measured in the branchial crown (1036+/-136 microg/g d.w.) and chemical speciation revealed that the predominant form was the relatively toxic dimethylarsinate (DMA). These data suggest a potential role of As as anti-predatory strategy in polychaetes.

Animals↗
PubMed2005

Oxidation mechanism of As(III) in the UV/TiO2 system: evidence for a direct hole oxidation mechanism.

Although it is well-known that As(III) is oxidized to As(V) in the UV/TiO2 system, the main oxidant for that reaction is still not clear. Accordingly, the present study aims at reinvestigating the TiO2-photocatalyzed oxidation mechanism of As(III). We performed a series of As(II) oxidation experiments by using UV-C/H2O2 and UV-A/TiO2, focusing on the effects of competing compounds. The experiment with UV-C/H2O2 indicated that HO2*/O2-* is not an effective oxidant of As(III) in the homogeneous phase. The effects of oxalate, formate, and Cu(II) on the photocatalytic oxidation of As(III) contradicted the controversial hypothesis that HO2*/ O2-* is the main oxidant of As(III) in the UV/TiO2 system. The effect of As(III) on the TiO2-photocatalyzed oxidations of benzoate, terephthalate, and formate was also incompatible with the superoxide-based As(II) oxidation mechanism. Instead, the experimental observations implied that OH* and/or the positive hole are largely responsible forthe oxidation of As(III) in the UV/TiO2 system. To determine which species plays a more significant role, the effects of methanol and iodide were tested. Since excess methanol did not retard the oxidation rate of As(III), OH* seems not to be the main oxidant. Therefore, the best rationale regarding the oxidation mechanism of As(III) in the UV/TiO2 system seems to be the direct electron transfer between As(III) and positive holes. Only with this mechanism, it was possible to explain the data of this study. Besides the mechanistic aspect, an application method for this technology was sought. The usage of UV/TiO2 for oxidizing As(II) requires a posttreatment in which both As(V) and TiO2 should be removed from water. For this objective, we applied FeCl3 and AIK(SO4)2 as coagulants, and the result implied that the combined usage of TiO2 and coagulation might be a feasible solution to treat arsenic contamination around the world.

Adsorption↗
PubMed1987

Histologic changes in nude mouse skin and human skin xenografts following exposure to sulfhydryl reagents: arsenicals.

This report documents the histological changes in nude mouse skin and in human skin xenografts on nude mice following exposure to phenyldichloroarsine (PDA), a vesicant arsenical. Under light microscopy, we observed in PDA-treated human skin grafts: 1) degeneration of epidermal cell nuclei (apparent by 2 hr after exposure with increasing severity through 48 hr); 2) loss of epidermal cytoplasmic basophilia (apparent by 4 hr, maximal within 12 hr); 3) epidermal cytoplasmic vacuolization (vacuoles appeared within 4 hr and increased in size through 24 hr); 4) cleft formation within the basement membrane zone (apparent by 12 hr, increasing in severity through 24 hr); 5) inflammation evidenced by polymorphonuclear leukocyte (PMN) infiltration (apparent by 4 hr and increasing through 48 hr). The PMNs frequently formed a wall around the lesion, but did not infiltrate the treated area. Nude mouse skin reacted faster to PDA than did the grafts, but the histological changes were similar. Nude mouse hair follicles and sebaceous glands showed similar cellular changes at approximately the same time as did epidermal cells. Transmission electron microscopy of mouse skin exposed to PDA revealed a widening of intercellular spaces with attenuation of desmosomes. The subepidermal clefts resulted from separation within the lamina lucida with the lamina densa forming the base of the cleft. Diphenylchloroarsine caused lesions histologically indistinguishable from those of PDA. Lesions resulting from exposure to other sulfhydryl-binding compounds were very different from arsenical lesions. The arsenical-sensitive cellular constituents were not identified.

Animals↗
PubMed2004

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements.

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure.

Arsenic↗
PubMed1996

Testicular toxicity of gallium arsenide, indium arsenide, and arsenic oxide in rats by repetitive intratracheal instillation.

The testicular toxicities of two compound semiconductor materials, gallium arsenide (GaAs) and indium arsenide (InAs), and arsenic oxide (As2O3) were examined in rats by repetitive intratracheal instillation of these substances in suspension twice a week, a total of 16 times. A single instillation dose was 7.7 mg/kg in the GaAs and the InAs groups and 1.3 mg/kg in the As2O3 group. A significant decrease in sperm count and significant increase in the proportion of morphologically abnormal sperm were found in the epididymis in the GaAs group. Especially, abnormal sperm with a straight head increased markedly in this group. In the GaAs-treated rats, there was 40-fold increase in the degenerating late elongated spermatids at the postspermiation stages, stages IX, XI, and XI. From these results, it is indicated that GaAs disturbed the spermatid head transformation at the late spermiogenic phases and caused spermiation failure. InAs caused a sperm count decrease in the epididymis, though its testicular toxicity was relatively weak compared with that of GaAs. As2O3, a probable dissolution arsenic product of GaAs and InAs in vivo, did not show any testicular toxicities in this study. It seems likely that, along with arsenics, gallium and indium play a role in the testicular toxicities of GaAs and InAs.

Animals↗
PubMedDate not supplied

Environmental distribution, analysis, and toxicity of organometal(loid) compounds.

The biochemical modification of the metals and metalloids mercury, tin, arsenic, antimony, bismuth, selenium, and tellurium via formation of volatile metal hydrides and alkylated species (volatile and involatile) performs a fundamental role in determining the environmental processing of these elements. In most instances, the formation of such species increases the environmental mobility of the element, and can result in bioaccumulation in lipophilic environments. While inorganic forms of most of these compounds are well characterized (e.g., arsenic, mercury) and some of them exhibit low toxicity (e.g., tin, bismuth), the more lipid-soluble organometals can be highly toxic. Methylmercury poisoning (e.g., Minamata disease) and tumor development in rats after exposure to dimethylarsinic acid or tributyltin oxide are just some examples. Data on the genotoxicity (and the neurotoxicity) as well as the mechanisms of cellular action of organometal(loid) compounds are, however, scarce. Many studies have shown that the production of such organometal(loid) species is possible and likely whenever anaerobic conditions (at least on a microscale) are combined with available metal(loid)s and methyl donors in the presence of suitable organisms. Such anaerobic conditions can exist within natural environments (e.g., wetlands, pond sediments) as well as within anthropogenic environmental systems (e.g., waste disposal sites and sewage treatments plants). Some methylation can also take place under aerobic conditions. This article gives an overview about the environmental distribution of organometal(loid) compounds and the potential hazardous effects on animal and human health. Genotoxic effects in vivo and in vitro in particular are discussed.

Animals↗
PubMed2002

Reclamation of pesticides in New York State.

BACKGROUND: Unwanted agrichemicals pose a unique threat that many states now address this with statewide collection programs. In New York, this is done at the discretion of individual counties. METHODS: We compiled and analyzed registration inventories from five separate county-based pesticide collections located in three different agricultural regions. Telephone surveys of thirty-one of New York's leading agricultural counties gathered information on their strategies for disposal of unwanted pesticides. RESULTS: The combined collections yielded 54,214 pounds of pesticides from 123 farms (441 lbs/farm). The most common active ingredients collected included older (and often discontinued) agents such as organochlorine (5,355 lbs, 9.8%) and arsenic (3,832 lbs, 7.1%) compounds, as well as more modern and commonly used active ingredients such as organophosphate pesticides (3,200 lbs, 5.9%). Disposal costs ranged from $2.03 to $2.86 per pound. Data from three collections indicated that 27% of the recovered pesticide (13,123 lbs) was stored in "unacceptable", "leaky", or "poor" containers. Of 31 agricultural counties, only 17 (55%) have hosted at least one farm pesticide collection event in the past. Planning for future collections is quite limited. CONCLUSIONS: There is a potentially large amount of toxic chemicals, some in decaying containers, that poses a risk to soil and groundwater in the state. The planning of future collections in New York State is haphazard. Carefully designed pesticide collection projects can be effective and should be a priority for local and state health officials.

Hazardous Waste↗