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Hazardous effects of arsine: a short review.

This review details the known health effects of arsine as well as the existing theories on the mechanism by which arsine exerts its toxic effect and conditions of occupational exposure to this gas. Exposure to arsine in occupational settings occurs mostly in the chemical and metallurgical industries when nascent hydrogen reacts with metallic arsenic or arsenic compounds. The available data indicate that in these branches of industry arsine is often a cause of unexpected serious poisoning. The gas affects primarily blood and kidneys. Acute arsine poisoning is known to result in massive damage to red blood cells through the oxidative mechanism, probably by the formation of hydrogen peroxide and adducts with oxyhemoglobin. According to another hypothesis, arsine acts on sodium-potassium pomp mechanism, producing subsequent red blood cell swelling and hemolysis. Rapid hemolysis may lead to oliguric renal failure and death. Symptoms of chronic poisoning are similar to those observed in acute poisoning. The main difference is a longer latency period. Late effects of chronic exposure to low levels of arsine have not yet been precisely identified.

Arsenic Poisoning↗

Comparative study of atomic fluorescence spectroscopy and inductively coupled plasma mass spectrometry for mercury and arsenic multispeciation.

Mercury and arsenic are two elements of undoubted importance owing to their toxic character. Although speciation of these elements has been developed separately, in this work for the first time the speciation of As and Hg using two atomic fluorescence detectors in a sequential ensemble is presented. A coupling based on the combination of high-performance liquid chromatography (where mercury and arsenic species are separated) and two atomic fluorescence detectors in series, with several online treatments, including photooxidation (UV) and hydride generation, has allowed the determination of mercury and arsenic compounds simultaneously. The detection limits for this device were 16, 3, 17, 12 and 8 ng mL(-1) for As(III), monomethylarsinic acid, As(V), Hg2+ and methylmercury, respectively. This coupling was compared with an analogous one based on inductively coupled plasma-mass spectrometry (ICP-MS) detection, with detection limits of 0.7, 0.5, 0.8, 0.9 and 1.1 ng mL(-1), respectively. Multispeciation based on ICP-MS exhibits better sensitivity than the coupling based on tandem atomic fluorescence, but this second device is a very robust system and exhibits obvious advantages related to the low cost of acquisition and maintenance, as well as easy handling, which makes it a suitable system for routine laboratories.

Arsenic↗

Effect of phenylarsine oxide on hepatic alpha 1-adrenoreceptor responsiveness. Dissociation between ionotropic and metabolic responses.

The present studies analyze the effect of the tervalent arsenical compound phenylarsine oxide (PAO) on hepatic response to alpha 1-adrenoreceptor stimulation. PAO, while not significantly altering the rate of glycogen breakdown, was found to inhibit many characteristic alpha 1-adrenoreceptor mediated responses including H+ and Ca2+ release, increased energy production, and vascular smooth muscle contraction. PAO inhibited basal gluconeogenesis but failed to inhibit the alpha 1-agonist induced stimulation of glucose production. These data suggest that alpha 1-adrenoreceptor mediated stimulation of metabolism and rates of ion flux across the plasma membrane are separate processes and that exchange in ion homeostasis is not essential to elicit the receptor-mediated metabolic responses. The selective effect of PAO offers an interesting tool for studying the alpha 1-adrenoreceptor signaling mechanisms.

Animals↗

Toxicity and metabolism of trimethylarsine in mice and hamsters.

Trimethylarsine (TM-As) proved to be an arsenic compound of low toxicity, with a po LD50 of 7870 mg/kg in mice. A single po dose of 10 mg/kg of TM-As caused no hemolysis, but a single po dose of 750 mg/kg induced mild, transient hemolysis in hamsters. TM-As was very rapidly eliminated into the urine, with a biological half-life of 3.7 hr. TM-As was oxidized in vivo to form trimethylarsine oxide (TMAO) and excreted as such into the urine. TM-As was never demethylated in vivo. A mechanism was demonstrated by which a part of TM-As was eliminated directly into the expired air. We drew a conclusion that TM-As is far less an toxic than arsine, most probably due to its in vivo conversion to TMAO.

Animals↗

A theoretical study of properties and reactions involving arsenic and selenium compounds present in coal combustion flue gases.

Species of arsenic and selenium thought to be present in coal combustion flue gases were studied using density functional theory and a broad range of ab initio methods. At each level of theory, the calculated geometries and vibrational frequencies of each species as well as the reaction enthalpies of anticipated reactions were compared with experimental data where available. Comparisons between each calculation are given along with a discussion of the better performance of some theoretical calculations for a given species/reaction.

Air Pollutants↗

[Internal hazardous substance burden of persons from various regions of origin--studies of lead, mercury, arsenic and cadmium exposure].

AIM OF THE STUDY: The aim of this study was to investigate the concentration of metals of environmental-medical relevance in biological materials in persons seeking asylum with regard to their country of origin. COLLECTIVE AND METHOD: During medical examination after entry into Germany of persons seeking asylum, samples were taken for determination of the following biological monitoring parameters: lead in blood, and arsenic, cadmium and mercury in urine. A total of 103 males were investigated (13 from former Yugoslavia, 29 from the former USSR, 33 Africans and 28 Asians) ranging from 16 to 53 years of age (median 27 years). 34 male Germans without occupational exposure to these substances and a similar age structure (age 25-36 years; median 26 years) served as a control group. RESULTS: The countries of origin had a significant influence on all the biological monitoring parameters investigated. The mean blood lead concentration in the Asians of 75.4 micrograms/L was the highest level found, while the lowest concentration of 38.0 micrograms/L was measured in the German controls. Also the level of arsenic excreted in the urine was on average much higher in the persons seeking asylum than in the German controls. In the Africans a mean level of 9.7 micrograms/g creatinine was reached. The Germans had the lowest arsenic concentrations in urine of 5.3 micrograms/g creatinine. There were, however, considerable interindividual fluctuations, which are probably due to oral uptake of arsenic compounds as a result of eating seafoods. The highest mean concentration of mercury excreted in urine was found in the German controls. Values of 0.9 microgram/g creatinine were determined. The men seeking asylum from former Yugoslavia had significantly higher values than other groups for cadmium excreted in urine. The median of 0.6 microgram/g creatinine was nearly three times as high as found in the Germans. CONCLUSIONS: For all parameters investigated, with the exception of mercury, higher internal exposure was found in the persons seeking asylum than in the German controls. This may be due to individual life style, dietary habits or environmental conditions in the country of origin. For clinical environmental medicine, the 95th percentile, as the upper limit of the reference range, can only be regarded as an orientation aid for classifying the exposure to hazardous substances of an individual compared to other persons from the same environment.

Adolescent↗

Toxic effects of arsenic (As3+) and other metal ions on acute promyelocytic leukemia cells.

Since arsenic compounds reportedly induced complete remission in patients with acute promyelocytic leukemia (APL) in China, we studied the in vitro effect of metal ions including As3+, As5+, Cd2+, Ga3+, Ge4+, Hg2+, Se4+, and Zn2+ on myeloid cell lines. One-tenth microM As3+ caused growth suppression and morphological changes resembling differentiation in NB4 cells, but did not induce the maturation-markers, CD11b, CD14 and NBT-reductase. More than 1 microM As3+ caused the time- and dose-dependent apoptosis of NB4 cells. Other metal ions at the same concentrations induced neither morphological changes nor apoptosis in myeloid cell lines including NB4, whereas Cd2+, Ga3+, and Hg2+ induced moderate and non-specific growth suppression. All-trans retinoic acid (ATRA)-resistant NB4 cells were similarly sensitive to As3+. Among the clinical leukemia samples, As3+ was selectively toxic to APL cells regardless of ATRA-sensitivity. These findings suggest that APL cells are sensitive to As3+, and that As3+ acts on APL cells via a different pathway than ATRA.

Apoptosis↗

Induction of apoptosis and inhibition of human gastric cancer MGC-803 cell growth by arsenic trioxide.

Arsenic trioxide (As2O3), used to treat human diseases for centuries in traditional Chinese medicine, has been identified as a very effective antileukaemic agent, but its effect on solid tumours which could be more suitable for clinical treatment with arsenic compounds is still unknown. In this study, we investigated the in vitro effect of As2O3 at concentrations of 0.01-1 microM against six human malignant cell lines, MGC-803, HIC, MCF-7, HeLa, BEL-7402 and A549 cells. As2O3 inhibited growth and induced apoptosis in these malignant cells at varying degrees, in a time dose-dependent manner. The most marked effects were seen in the gastric cancer cell line, MGC-803. In contrast, minimal growth inhibition and induction of apoptosis occurred in human embryonic pulmonary cells following treatment with As2O3 found at the same concentrations. Changes in intracellular Ca2+, following As2O3 treatment were measured by Ca2+ sensitive fluorescent probe Indo-1/AM in flow cytometric assays. The increase in intracellular Ca2+ correlated with the sensitivity of these cells to As2O3, possibly indicating that a critical intracellular Ca2+ signal transduction pathway could be involved in As2O3-mediated cell-death and its selectivity. The marked sensitivity of MGC-803 cells in vitro suggests that As2O3 may be a potential antigastric cancer agent.

Antineoplastic Agents↗

Arsenic trioxide induces apoptosis of HPV16 DNA-immortalized human cervical epithelial cells and selectively inhibits viral gene expression.

Arsenic trioxide (As2O3), a major ingredient of arsenic compounds in traditional Chinese medicine, exhibits anti-acute promyelocytic leukemic activity. Considering that over 80% of human malignant tumors derive from epithelial cells, we studied the effect of As2O3 on HPV 16 DNA-immortalized human cervical epithelial cells (HCE16/3 cells) in vitro. As2O3 reduced HCE16/3 cell survival, induced apoptosis at a low concentration and selectively inhibited expression of viral early genes. This effect was evidenced by a reduction of cell viability in the MTT assay, G1 arrest and significant apoptosis upon flow-cytometric analysis, presence of apoptotic bodies, formation of DNA ladders upon gel electrophoresis and inhibition of viral early gene expression by RT-PCR and Western blot. There was a good correlation between cell apoptosis and viral early gene inhibition after As2O3 treatment, suggesting that induction of apoptosis of HCE16/3 cells by As2O3 treatment might be associated with down-regulation of viral oncogene expression. In conclusion, our findings indicate that As2O3 induces apoptosis of HCE16/3 cells, which may provide a new approach for treating HPV-associated tumors.

Antineoplastic Agents↗

Interaction of p-aminophenyldichloroarsine, an arsenical with specificity for vicinal cysteines, with [3H]cytisine binding sites in rat brain membranes.

The arsenical compound p-aminophenyldichloroarsine (APA) is selective for spatially close thiols with which it forms a stable complex. The alpha subunits of nicotinic acetylcholine receptors are defined by the presence of a pair of adjacent cysteines close to the agonist binding site. Here the interaction of APA with [3H]cytisine binding sites, which correspond to the major subtype of nicotinic receptors in rat brain has been examined. Incubation of brain membranes with 10 microM APA abolished [3H]cytisine binding. The action of APA was dependent on prior reduction of sulphydryls with dithiothreitol. APA effects could not be reversed by oxidizing agents but could be reversed by the antiarsenical reagent 2,3-dimercapto-1-propane sulphonic acid. Under the conditions used, the concentration of APA producing a half-maximal decrease in binding was 130 nM. The loss of [3H]cytisine binding was due to a decrease in the number of binding sites (Bmax) with no effect on affinity for the radioligand (Kd). Nicotinic ligands failed to protect against the reduction and arsenylation of neuronal receptor sites. These observations are consistent with the potent interaction of APA with this neuronal nicotinic receptor.

Alkaloids↗

Arsenite induces apoptosis via a direct effect on the mitochondrial permeability transition pore.

The molecular mode of action of arsenic, a therapeutic agent employed in the treatment of acute promyelocytic leukemia, has been elusive. Here we provide evidence that arsenic compounds may act on mitochondria to induce apoptosis. Arsenite induces apoptosis accompanied by a loss of the mitochondrial transmembrane potential (Delta Psim). Inhibition of caspases prevents the arsenite-induced nuclear DNA loss, but has no effect on the Delta Psim dissipation and cytolysis induced by arsenite. In contrast, Bcl-2 expression induced by gene transfer prevents all hallmarks of arsenite-induced cell death, including the Delta Psim collapse. PK11195, a ligand of the mitochondrial benzodiazepine receptor, neutralizes this Bcl-2 effect. Mitochondria are required in a cell-free system to mediate arsenite-induced nuclear apoptosis. Arsenite causes the release of an apoptosis-inducing factor (AIF) from the mitochondrial intermembrane space. This effect is prevented by the permeability transition (PT) pore inhibitor cyclosporin A, as well as by Bcl-2, which is known to function as an endogenous PT pore antagonist. Arsenite also opens the purified, reconstituted PT pore in vitro in a cyclosporin A- and Bcl-2-inhibitible fashion. Altogether these data suggest that arsenite can induce apoptosis via a direct effect on the mitochondrial PT pore.

Apoptosis↗

Inhibition of cell proliferation and the action mechanisms of arsenic trioxide (As2O3) on human breast cancer cells.

Arsenic trioxide (As(2)O(3)) is one of the arsenic compounds found in nature. As(2)O(3) has recently been used to treat patients suffering from retinoic acid receptor (AML). It is of clinical interest to investigate whether As(2)O(3) is also effective in treating solid tumors. Here, we report that As(2)O(3) exhibited inhibitory effects on the proliferation of human breast cancer MCF-7 cells in a dose- and time-dependent manner. The 50% inhibitory concentration (IC(50)) of As(2)O(3) in inhibiting proliferation of MCF-7 cells were 8, 1.8, and 1.2 microM upon 1-, 2-, and 3-day treatment, respectively. In elucidating the underlying action mechanisms, the results of experiments concerning DNA fragmentation and externalization indicated that As(2)O(3) exerted its action on MCF-7 cells via apoptosis, whereas the result of flow cytometry also indicated that As(2)O(3) could induce mitochondrial mediated cell-cycle arrest at G(1) phase. Further studies by Western blot analysis indicated that As(2)O(3) regulated apoptosis and the expression of cell-cycle-related proteins as it upregulated p53 protein level and downregulated bcl-2 protein level. Results in present study indicated that As(2)O(3) might also be a good candidate for treating breast cancer.

Antineoplastic Agents↗

Effects of Lewisite on cell membrane integrity and energy metabolism in human keratinocytes and SCL II cells.

Lewisite is a highly toxic arsenic compound which can cause skin damage. In the present study effects of Lewisite on cell membrane integrity and energy metabolism as well as antidotal effects of DL-2,3-dimercaptopropanesulfonate (DMPS), and meso-2,3-dimercaptosuccinic acid (m-DMSA) were investigated in a keratinocyte derived cell line (SCL II) and primary human keratinocytes (HK). Cells were incubated in Lewisite (60 microM) containing medium for 5 min. During the following 6 h lactate dehydrogenase (LDH) activity in the supernatant, intracellular ATP content, tetrazolium reduction, glucose consumption and lactate formation were measured. Glucose consumption and lactate production were decreased in both cell lines after Lewisite exposure. In SCL II cells an increase of LDH activity in the supernatant, a decrease of ATP content, and an impaired ability to reduce tetrazolium was found 3 h after Lewisite exposure. In HK cultures tetrazolium reduction was significantly decreased already after 2 h, whereas LDH increase in the supernatant and ATP content decrease occurred only at 6 h after Lewisite exposure. When DMPS or m-DMSA was added directly after Lewisite exposure to SCL II cells, glucose consumption and lactate formation were restored and LDH leakage was prevented. SCL II cells might be more prone to membrane damage whereas in keratinocytes mitochondrial impairment seems to be the predominant effect of Lewisite.

Adenosine Triphosphate↗

Phenylarsine oxide stimulates a cytosolic tyrosine kinase activity and glucose transport in mouse fibroblasts.

In the present report we further approach the mechanism by which insulin and phenylarsine oxide (PAO), a trivalent arsenical compound, regulate glucose transport in mouse fibroblasts (NIH3T3). First, we show that PAO is a powerful stimulatory agent on glucose transport. Second, at least three series of observations indicate that this action of PAO is not mediated through the insulin receptor: (i) the same effect of PAO is observed in NIH3T3 and in transfected cells expressing 6 x 10(6) insulin receptors, while the effect of insulin is markedly increased in the transfected cells; (ii) PAO does not affect the tyrosine phosphorylation of the insulin receptor; (iii) the tyrosine kinase activity of the insulin receptor toward exogenous substrates is not increased by PAO. Since PAO appears to act on glucose transport by a different mechanism than insulin, we have compared the effect of PAO and insulin on tyrosine phosphorylation of cellular proteins. Using Western blot analysis we did not detect common substrates in PAO- and insulin-treated cells. However, we found in cell extracts from both PAO- and insulin-treated cells a 50-kDa protein that is immunoprecipitated by antiphosphotyrosine antibody. In addition, PAO activates a cytosolic tyrosine kinase capable of poly(Glu/Tyr) phosphorylation. As a whole, our data suggest that the 50-kDa protein found in cells incubated with PAO and insulin could be the convergence point of the insulin and PAO signaling pathways.

3T3 Cells↗

Phenylarsine oxide (PAO) more intensely induces apoptosis in acute promyelocytic leukemia and As2O3-resistant APL cell lines than As2O3 by activating the mitochondrial pathway.

We studied the cytotoxic effect of an organic arsenical compound, phenylarsine oxide (PAO) on an acute promyelocytic leukemia (APL) cell line (NB4) and an As2O3-resistant NB4 subline (NB4/As). Cell growth was inhibited by 50% (IC50) upon 2-day treatment with As2O3 or PAO at 0.54 and 0.06 microM, respectively in NB4 cells (P = 0.025), and 2.80 and 0.08 microM, respectively in NB4/As (P = 0.030). 0.1 microM PAO increased the proportion of hypodiploid cells (50.3%) by a greater degree than the same dose of As2O3 (3.8%) in NB4 cells. In NB4 cells, 0.1 microM PAO reduced the mitochondrial transmembrane potential (20.5% in a PI(negative)-Rhodamine123(low) fraction) by a greater degree than 1 microM As2O3 (7.1%). Western blotting showed that 0.1 microM PAO downregulated the expression of both Bcl-2 and Bcl-X(L) proteins, whereas I microM As2O3 downregulated only Bcl-2 expression. These results suggest that the cytotoxic effect of PAO on an APL cell line and As2O3-resistant subline is significantly higher than that of As2O3. PAO-induced apoptosis seems to be related to the activation of the mitochondrial pathway and downregulation of both Bcl-2 and Bcl-X(L). PAO is a considerable agent for relapsed/refractory APL and for purging APL cells following stem cell transplantation.

Apoptosis↗

Stimulation of intracellular Ca2+ elevation in neutrophils by thiol-oxidizing phenylarsine oxide.

Phenylarsine oxide (PAO), a trivalent arsenical compound, stimulated [Ca2+]i elevation in rat neutrophils in a Ca2+-containing medium but caused no appreciable response in a Ca2+-free medium. PAO also induced external Mn2+ entry, which was inhibited by N-acetyl-L-cysteine (NAC), but failed to elicit any appreciable Ba2+ and Sr2+ entry. Pretreatment of neutrophils with thiol-reducing agents including dithiothreitol (DTT), NAC, 2,3-dimercapto-1-propanol (DMP), 2,3-dimercaptopropane-1-sulfonic acid (DMPS) and tris-(2-carboxyethyl)phosphine (TCEP), all greatly inhibited PAO-induced [Ca2+]i elevation. Addition of Ni2+ or La3+ followed by PAO stimulation also attenuated the Ca2+ signals in a concentration-dependent manner. PAO had no significant effect on the production of reactive oxygen intermediates (ROI) and nitric oxide (NO) nor did it decrease cellular low molecular weight thiols levels. PAO-induced [Ca2+]i elevation was significantly inhibited by 1-[6-[17beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122), the inhibitor of phospholipase C-coupled processes, genistein, a general tyrosine kinase inhibitor, phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, calyculin A, a cortical actin stabilizer, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY 294002), a phosphoinositide 3-kinase inhibitor, 1-[beta-[3-(4-methoxyphenyl)propoxy]-4-methoxyphenethyl]-1H-imidazole (SKF-96365), and cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine (MDL-12,330A), the blockers of receptor-gated and store-operated Ca2+ channels, whereas there was no appreciable effect exerted by aristolochic acid, a phospholipase A2 inhibitor, 7-nitroindazole and N-(3-aminomethyl)benzylacetamidine (1400W), the blockers of NO synthase, and by suspension in a Na+-deprived medium. In contrast, 2-aminoethoxydiphenyl borane (2-APB), the blocker of IP3 receptor and Ca2+ influx, enhanced the PAO-induced response. PAO had no effect on the plasma membrane Ca2+-ATPase (PMCA) activity in the pharmacological isolated neutrophil preparation and the neutrophil membrane fractions. These results indicate that PAO stimulates [Ca2+]i rise in rat neutrophils mainly through the oxidation of vicinal thiol groups on the cell surface membrane to activation of a non-store operated Ca2+ entry (non-SOCE) without affecting the activity of PMCA and the plasmalemmal Na+/Ca2+ exchanger.

Animals↗

African sleeping sickness in the United States. Successful treatment with eflornithine.

The traditional treatment of African sleeping sickness (trypanosomiasis) with central nervous system involvement is an organic arsenical compound, melarsoprol, which is associated with severe and even life-threatening side effects. A polyamine biosynthesis inhibitor, eflornithine (chemical name, DL-alpha-difluoromethylornithine, supplied as monohydrochloride monohydrate), was used to treat a 3 1/2-year-old child with newly diagnosed severe trypanosomiasis that had been acquired more than two years previously in Zaire or the Congo. Treatment consisted of 300 to 400 mg/kg/d of eflornithine by continuous intravenous infusion for 25 days followed by 300 mg/kg/d of eflornithine by mouth divided in four equal doses daily for 17 days. The child's recovery was dramatic, with eradication of blood and cerebrospinal fluid parasites in the first week. Cerebrospinal fluid pleocytosis resolved completely. Her generalized adenopathy and fever gradually resolved. Severe ataxia, inability to walk or to change posture on her own, marked language regression, and lethargy all improved during and after her therapy. The drug was well tolerated; the only noted adverse effect was transient thrombocytopenia during the fourth week of therapy. Eflornithine was a safe and effective agent for treatment of trypanosomiasis with central nervous system involvement in this child.

Animals↗

Food additives and contaminants. An update.

Food additives continue to be a source of benefits to the consuming public but there are also perceived risks. Concern for the latter in the last decade has produced a society afflicted with cancer phobia. The intentional additives including sugars, salt, corn syrup, and dextrose make up 90% of the direct additives. These, along with a limited number of familiar items make up a large proportion of the remainder of the additives. Such common ingredients as nitrates and nitrites, solanine, cyanogenetic compounds, arsenic, etc., are unavoidably consumed in the diet and with little if any evidence for public health consequences. Major concern on the part of the public in recent years has been focused on man-made chemicals which are intentionally added to foods to enhance flavors and acceptability, nutrient value, shelf life and increased availability. These include food colors, nonnutritive and low-nutrient sweeteners, (saccharin, cyclamate, aspartame); antioxidants; and nitrites. Contaminants, sometimes incorrectly included in lists of food additives, present the greatest potential threat to public health. Such contaminants as mycotoxins, nitrosamines, polychlorinated biphenyls (PCBs), pesticides, among others, provide a continuing challenge to our regulatory agencies and to public health authorities. Evidence to date indicate that these responsible for food safety are doing an admirable job, and as a society, our food supply has never been better, or safer, and, as a population, we have never been healthier. Aside from contaminants, major concerns relate to an excess of good food and to obesity. These comments should not be taken to infer that we should relax our concern and surveillance; instead more concern and surveillance should be exerted toward those uncontrolled substances such as natural plant products and alleged natural nutrients, roots, herbs, etc., which are given much credit for positive health effects, without meeting the high standards of our legitimate food industry.

Animals↗