Gestational α-ketoglutarate supplementation ameliorates arsenic-induced hepatic lipid deposition via epigenetic reprogramming of ß-oxidation process in female offspring.

Inorganic trivalent arsenic (iAsⅢ) at environmentally relevant levels has been found to cause developmental toxicity. Maternal exposure to iAsⅢ leads to enduring hepatic lipid deposition in later adult life. However, the exact mechanism in iAsⅢ induced hepatic developmental hazards is still unclear. In this study, we initially found that gestational exposure to iAsⅢ at an environmentally relevant concentration disturbs lipid metabolism and reduces levels of alpha-ketoglutaric acid (α-KG), an important mitochondrial metabolite during the citric acid cycle, in fetal livers. Further, gestational supplementation of α-KG alleviated hepatic lipid deposition caused by early-life exposure to iAsⅢ. This beneficial effect was particularly pronounced in female offspring. α-KG partially restored the ß-oxidation process in hepatic tissues by hydroxymethylation modifications of carnitine palmitoyltransferase 1a (Cpt1a) gene during fetal development. Insufficient ß-oxidation capacities probably play a crucial role in hepatic lipid deposition in adulthood following in utero arsenite exposure, which can be efficiently counterbalanced by replenishing α-KG. These results suggest that gestational administration of α-KG can ameliorate hepatic lipid deposition caused by iAsⅢ in female adult offspring partially through epigenetic reprogramming of the ß-oxidation pathway. Furthermore, α-KG shows potential as an interventive target to mitigate the harmful effects of arsenic-induced hepatic developmental toxicity.

Arsenic intoxication: general aspects and chelating agents.

Arsenic (As) is widely used in the modern industry, especially in the production of pesticides, herbicides, wood preservatives, and semiconductors. The sources of As such as contaminated water, air, soil, but also food, can cause serious human diseases. The complex mechanism of As toxicity in the human body is associated with the generation of free radicals and the induction of oxidative damage in the cell. One effective strategy in reducing the toxic effects of As is the usage of chelating agents, which provide the formation of inert chelator-metal complexes with their further excretion from the body. This review discusses different aspects of the use of metal chelators, alone or in combination, in the treatment of As poisoning. Consideration is given to the therapeutic effect of thiol chelators such as meso-2,3-dimercaptosuccinic acid, sodium 2,3-dimercapto-1-propanesulfonate, 2,3-dimercaptopropanol, penicillamine, ethylenediaminetetraacetic acid, and other recent agents against As toxicity. The review also considers the possible role of flavonoids, trace elements, and herbal drugs as promising natural chelating and detoxifying agents.

NH4H2PO4-extractable arsenic provides a reliable predictor for arsenic accumulation and speciation in pepper fruits (Capsicum annum L.).

Dietary arsenic (As) intake from food is of great concern, and developing a reliable model capable of predicting As concentrations in plant edible parts is desirable. In this study, pot experiments were performed with 16 Chinese upland soils spiked with arsenate [As(V)] to develop a predictive model for As concentrations in pepper fruits (Capsicum annum L.). Our results showed that after three months' aging, concentrations of bioavailable As (extracted by 0.05 M NH4H2PO4) in various soils varied widely, depending on soil total As concentrations and soil properties such as soil pH and amorphous iron (Fe) contents. Furthermore, both the bioconcentration factor (BCF, denoted as the ratio of fruit As to soil As) and total As concentrations in pepper fruits were largely determined by concentrations of bioavailable As, which explained 27% and 69% variations in the BCF and fruit As concentrations, respectively. Apart from bioavailable As, soil pH and Fe contents were another two important factors influencing As accumulation in pepper fruits. Taking the three factors into account, concentrations of fruit As can be well predicted using a stepwise multiple linear regression (SMLR) analysis (R2 = 0.80, RMSE = 0.17). Arsenic species in soils and edible parts were also analyzed. Although As(V) predominated in soils (>96%), As in pepper fruits presented as As(V) (46%) and arsenite [As(III)] (39%) with small amount of methylated As (<15%). Aggregated boosted tree (ABT) analysis revealed that inorganic As concentrations in pepper fruits were determined by concentrations of bioavailable As, phosphorus (P) and Fe in soils. In contrast to inorganic As, methylated As concentrations were not correlated with those factors in soils. Taken together, this study established an empirical model for predicting As concentrations in pepper fruits. The predictive model can be used for establishing the As threshold in fruit vegetable farming soils.

Folic acid supplementation enhances arsenic methylation: results from a folic acid and creatine supplementation randomized controlled trial in Bangladesh.

Background: Arsenic exposure through drinking water persists in many regions. Inorganic As (InAs) is methylated to monomethyl-arsenical species (MMAs) and dimethyl-arsenical species (DMAs), facilitating urinary excretion. Arsenic methylation is dependent on one-carbon metabolism, which is influenced by nutritional factors such as folate and creatine. Objective: This study investigated the effects of folic acid (FA) and/or creatine supplementation on the proportion of As metabolites in urine. Design: In a 24-wk randomized, double-blinded, placebo-controlled trial, 622 participants were assigned to receive FA (400 or 800 µg per day), 3 g creatine per day, 400 µg FA + 3 g creatine per day, or placebo. The majority of participants were folate sufficient; all received As-removal water filters. From wk 12-24, half of the participants receiving FA received placebo. Results: Among groups receiving FA, the mean decrease in ln(%InAs) and %MMAs and increase in %DMAs exceeded those of the placebo group at wk 6 and 12 (P < 0.05). In the creatine group, the mean decrease in %MMAs exceeded that of the placebo group at wk 6 and 12 (P < 0.05); creatine supplementation did not affect change in %InAs or %DMAs. The decrease in %MMAs at wk 6 and 12 was larger in the 800 µg FA than in the 400 µg FA group (P = 0.034). There were no differences in treatment effects between the 400 µg FA and creatine + FA groups. Data suggest a rebound in As metabolite proportions after FA cessation; at wk 24, log(%InAs) and %DMAs were not significantly different than baseline levels among participants who discontinued FA supplementation. Conclusions: The results of this study confirm that FA supplementation rapidly and significantly increases methylation of InAs to DMAs. Further research is needed to understand the strong cross-sectional associations between urinary creatinine and As methylation in previous studies. This trial was registered at https://clinicaltrials.gov as NCT01050556.

Clinical outcomes, histopathological patterns, and chemical analysis of Ayurveda and herbal medicine associated with severe liver injury-A single-center experience from southern India.

INTRODUCTION: Ayurvedic and herbal medicines (AHM) are known to cause varying degrees of drug-induced liver injury (DILI). Clinical, biochemical, histological spectrum and outcomes of AHM linked to severe DILI are not well studied. METHODS: Out of 1440 liver disease patients, 94 were found to have a severe liver injury and associated AHM intake. Thirty-three patients were suspected to have AHM-DILI on Roussel Uclaf Causality Assessment Scoring Method. Forty-seven and 30 of retrieved AHM samples were analyzed for heavy metals and hepatotoxic volatile organic compounds (hVOCs), respectively. Eleven patients ingested AHM from unregistered traditional healers (UTH). Clinicopathological outcomes were analyzed in 27 patients (who underwent liver biopsy) and outcomes with respect to chemical analyses were studied in 33 patients. RESULTS: Males predominated (70.4%) with mean age 46.9±15.8 years. Mean follow up was 119.2±81.4 days. The median duration of drug intake was 28 days (10 - 84). Five patients died (18.5%). Hepatic encephalopathy, hypoalbuminemia, and hepatic necrosis were significantly associated with mortality (p < 0.005). Arsenic and mercury ingestion was significantly associated with death (p < 0.005). hVOCs were detected in more than 70% of samples. AHM intake from UTH was associated with higher mortality. CONCLUSION: Adequate regulation and scrutiny regarding AHM use among the general population is an unmet need. Early liver biopsy after clinical identification of at-risk patients can expedite definitive treatment with a liver transplant.

A novel biodegradable arsenic adsorbent by immobilization of iron oxyhydroxide (FeOOH) on the root powder of long-root Eichhornia crassipes.

In this study, FeOOH was immobilized on the biodegradable root powder, abbreviated as RP, of long-root Eichhornia crassipes, a kind of waste biomass, to improve the adsorption performances for aqueous arsenic contaminants. The adsorption kinetics and thermodynamics experiments showed that the adsorption rates and capacities of the root powder for arsenate (As(V)) and arsenite (As(III)) were both enhanced markedly after modification with FeOOH. The adsorption of As(V) and As(III) by the modified root powder, abbreviated as MRP, could arrive at equilibrium in 50 min and the saturated adsorption capacities reached up to 8.67-9.43 mg/g for As(V) and 5.21-5.65 mg/g for As(V) at temperature of 10-50 °C, respectively. Besides, the effect of pH and ionic strength on adsorption was investigated and the results showed that the optimum pH for the arsenic adsorption using the MRP was 9.0 and the As(V) adsorption was more sensitive to ionic strength. Furthermore, the complexation of hydratable hydroxyls on FeOOH with arsenic contaminants was concluded as the adsorption force according FTIR and XPS analyses. The MRP used could be regenerated via 0.4 mol/L NaOH solution and no apparent adsorption capacity losses appeared after 6 cyclic utilizations.

Ochrobactrum sp. MPV1 from a dump of roasted pyrites can be exploited as bacterial catalyst for the biogenesis of selenium and tellurium nanoparticles.

BACKGROUND: Bacteria have developed different mechanisms for the transformation of metalloid oxyanions to non-toxic chemical forms. A number of bacterial isolates so far obtained in axenic culture has shown the ability to bioreduce selenite and tellurite to the elemental state in different conditions along with the formation of nanoparticles-both inside and outside the cells-characterized by a variety of morphological features. This reductive process can be considered of major importance for two reasons: firstly, toxic and soluble (i.e. bioavailable) compounds such as selenite and tellurite are converted to a less toxic chemical forms (i.e. zero valent state); secondly, chalcogen nanoparticles have attracted great interest due to their photoelectric and semiconducting properties. In addition, their exploitation as antimicrobial agents is currently becoming an area of intensive research in medical sciences. RESULTS: In the present study, the bacterial strain Ochrobactrum sp. MPV1, isolated from a dump of roasted arsenopyrites as residues of a formerly sulfuric acid production near Scarlino (Tuscany, Italy) was analyzed for its capability of efficaciously bioreducing the chalcogen oxyanions selenite (SeO32-) and tellurite (TeO32-) to their respective elemental forms (Se0 and Te0) in aerobic conditions, with generation of Se- and Te-nanoparticles (Se- and TeNPs). The isolate could bioconvert 2 mM SeO32- and 0.5 mM TeO32- to the corresponding Se0 and Te0 in 48 and 120 h, respectively. The intracellular accumulation of nanomaterials was demonstrated through electron microscopy. Moreover, several analyses were performed to shed light on the mechanisms involved in SeO32- and TeO32- bioreduction to their elemental states. Results obtained suggested that these oxyanions are bioconverted through two different mechanisms in Ochrobactrum sp. MPV1. Glutathione (GSH) seemed to play a key role in SeO32- bioreduction, while TeO32- bioconversion could be ascribed to the catalytic activity of intracellular NADH-dependent oxidoreductases. The organic coating surrounding biogenic Se- and TeNPs was also characterized through Fourier-transform infrared spectroscopy. This analysis revealed interesting differences among the NPs produced by Ochrobactrum sp. MPV1 and suggested a possible different role of phospholipids and proteins in both biosynthesis and stabilization of such chalcogen-NPs. CONCLUSIONS: In conclusion, Ochrobactrum sp. MPV1 has demonstrated to be an ideal candidate for the bioconversion of toxic oxyanions such as selenite and tellurite to their respective elemental forms, producing intracellular Se- and TeNPs possibly exploitable in biomedical and industrial applications.

Detection of Chemical Warfare Agent-Related Phenylarsenic Compounds in Marine Biota Samples by LC-HESI/MS/MS.

A new method has been developed to determine oxidation products of three chemical warfare agent (CWA) related phenylarsenic compounds from marine biota samples by a liquid chromatography-heated electrospray ionization/tandem mass spectrometry (LC-HESI/MS/MS). The target chemicals were oxidation products of Adamsite (DM[ox]), Clark I (DPA[ox]), and triphenylarsine (TPA[ox]). Method was validated within the concentration range of 1-5, 0.2-5, and 0.2-5 ng/g for DM[ox], DPA[ox], and TPA[ox], respectively. The method was linear, precise and accurate. Limits of quantification (LOQ) were 2.0, 1.3, and 2.1 ng/g for DM[ox], DPA[ox], and TPA[ox], respectively. A total of ten fish samples and one lobster sample collected from near Swedish coast, Måseskär dumpsite were analyzed. Trace concentrations below LOQ values were detected in three samples and the elemental composition of oxidized form of Clark I and/or II was confirmed by LC-HESI/HRMS. To our knowledge, this is the first study that provides the presence of CWA related chemicals in marine biota samples.

Determination of arsenic speciation and the possible source of methylated arsenic in Panax Notoginseng.

Arsenic species and a possible source of methylated arsenic in a Panax Notoginseng (PN) medicinal plant were explored to further understand the change of inorganic arsenic to the less toxic methylated form to minimize the health risks associated with its medicinal use. Arsenic speciation in PN from major planting areas was determined using high-performance liquid chromatography coupled with hydride generator-atomic fluorescence (HPLC-HG-AFS). Pot experiments were performed to explore the source of methylated arsenic in PN, and the arsenite methyltransferase (arsM) gene abundance was determined using quantitative reverse transcription PCR (q-RTPCR). Methylated arsenic (monomethylarsonic acid (MMA) + dimethylarsinic acid (DMA)) accounted for 43% ± 30% of the total arsenic in PN from planting areas, while the primary species in soil was As(V) (94% ± 0.12%). In the pot experiments, methylated arsenic accounted for 37%-49% of the total arsenic in PN, and As (V) was the primary species in soil (>98%). The four detected arsenic species in PN increased as the amount of As added to soil increased. The methylated arsenic contents in the PN root were significantly positively correlated with the ArsM gene abundance in soil, suggesting that methylated arsenic in PN is likely from the planting soil.

Chemical and surface analysis during evolution of arsenopyrite oxidation by Acidithiobacillus thiooxidans in the presence and absence of supplementary arsenic.

Bioleaching of arsenopyrite presents a great interest due to recovery of valuable metals and environmental issues. The current study aims to evaluate the arsenopyrite oxidation by Acidithiobacillus thiooxidans during 240h at different time intervals, in the presence and absence of supplementary arsenic. Chemical and electrochemical characterizations are carried out using Raman, AFM, SEM-EDS, Cyclic Voltammetry, EIS, electrophoretic and adhesion forces to comprehensively assess the surface behavior and biooxidation mechanism of this mineral. These analyses evidence the formation of pyrite-like secondary phase on abiotic control surfaces, which contrast with the formation of pyrite (FeS2)-like, orpiment (As2S3)-like and elementary sulfur and polysulfide (Sn(2-)/S(0)) phases found on biooxidized surfaces. Voltammetric results indicate a significant alteration of arsenopyrite due to (bio)oxidation. Resistive processes determined with EIS are associated with chemical and electrochemical reactions mediated by (bio)oxidation, resulting in the transformation of arsenopyrite surface and biofilm direct attachment. Charge transfer resistance is increased when (bio)oxidation is performed in the presence of supplementary arsenic, in comparison with lowered abiotic control resistances obtained in its absence; reinforcing the idea that more stable surface products are generated when As(V) is in the system. Biofilm structure is mainly comprised of micro-colonies, progressively enclosed in secondary compounds. A more compact biofilm structure with enhanced formation of secondary compounds is identified in the presence of supplementary arsenic, whereby variable arsenopyrite reactivity is linked and attributed to these secondary compounds, including Sn(2-)/S(0), pyrite-like and orpiment-like phases.

Enzyme-assisted extraction and liquid chromatography mass spectrometry for the determination of arsenic species in chicken meat.

Chicken is the most consumed meat in North America. Concentrations of arsenic in chicken range from µg kg(-1) to mg kg(-1). However, little is known about the speciation of arsenic in chicken meat. The objective of this research was to develop a method enabling determination of arsenic species in chicken breast muscle. We report here enzyme-enhanced extraction of arsenic species from chicken meat, separation using anion exchange chromatography (HPLC), and simultaneous detection with both inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization tandem mass spectrometry (ESIMS). We compared the extraction of arsenic species using several proteolytic enzymes: bromelain, papain, pepsin, proteinase K, and trypsin. With the use of papain-assisted extraction, 10 arsenic species were extracted and detected, as compared to 8 detectable arsenic species in the water/methanol extract. The overall extraction efficiency was also improved using a combination of ultrasonication and papain digestion, as compared to the conventional water/methanol extraction. Detection limits were in the range of 1.0-1.8 µg arsenic per kg chicken breast meat (dry weight) for seven arsenic species: arsenobetaine (AsB), inorganic arsenite (As(III)), dimethylarsinic acid (DMA), monomethylarsonic acid (MMA), inorganic arsenate (As(V)), 3-nitro-4-hydroxyphenylarsonic acid (Roxarsone), and N-acetyl-4-hydroxy-m-arsanilic acid (NAHAA). Analysis of breast meat samples from six chickens receiving feed containing Roxarsone showed the presence of (mean±standard deviation µg kg(-1)) AsB (107±4), As(III) (113±7), As(V) (7±2), MMA (51±5), DMA (64±6), Roxarsone (18±1), and four unidentified arsenic species (approximate concentration 1-10 µg kg(-1)).

Transformation of arsenic species during in vitro gastrointestinal digestion of vegetables.

Arsenic is an element widely distributed in the environment, and the diet is the main source of arsenic exposure for most people. However, many of the processes related to steps before intestinal absorption are unknown. This study evaluates the effect of in vitro gastrointestinal digestion on pentavalent arsenic forms [As(V), MMA(V), DMA(V)] present in various vegetables (garlic, broccoli, asparagus, spinach) after soaking or boiling in aqueous solutions of these species. The results showed that the gastrointestinal digest contained trivalent or thiolated arsenic forms different from the pentavalent species added initially. Transformation percentages varied, depending on sample, treatment, and arsenic species. Results showed transformation of up to 22% to As(III), 35% to MMA(III)/MMAS, and 26% to DMA(III)/DMAS. These data indicate that more toxic arsenic species are present in the gastrointestinal digest, and they highlight the need to consider this process when evaluating the toxicological risk associated with ingestion of this metalloid.

Precipitation of alacranite (As8S9) by a novel As(V)-respiring anaerobe strain MPA-C3.

Strain MPA-C3 was isolated by incubating arsenic-bearing sediments under anaerobic, mesophilic conditions in minimal media with acetate as the sole source of energy and carbon, and As(V) as the sole electron acceptor. Following growth and the respiratory reduction of As(V) to As(III), a yellow precipitate formed in active cultures, while no precipitate was observed in autoclaved controls, or in uninoculated media supplemented with As(III). The precipitate was identified by X-ray diffraction as alacranite, As8 S9 , a mineral previously only identified in hydrothermal environments. Sequencing of the 16S rRNA gene indicated that strain MPA-C3 is a member of the Deferribacteres family, with relatively low (90%) identity to Denitrovibrio acetiphilus DSM 12809. The arsenate respiratory reductase gene, arrA, was sequenced, showing high homology to the arrA gene of Desulfitobacterium halfniense. In addition to As(V), strain MPA-C3 utilizes NO3(-), Se(VI), Se(IV), fumarate and Fe(III) as electron acceptors, and acetate, pyruvate, fructose and benzoate as sources of carbon and energy. Analysis of a draft genome sequence revealed multiple pathways for respiration and carbon utilization. The results of this work demonstrate that alacranite, a mineral previously thought to be formed only chemically under hydrothermal conditions, is precipitated under mesophilic conditions by the metabolically versatile strain MPA-C3.

Treating chronic arsenic toxicity with high selenium lentil diets.

Arsenic (As) toxicity causes serious health problems in humans, especially in the Indo-Gangetic plains and mountainous areas of China. Selenium (Se), an essential micronutrient is a potential mitigator of As toxicity due to its antioxidant and antagonistic properties. Selenium is seriously deficient in soils world-wide but is present at high, yet non-toxic levels in the great plains of North America. We evaluate the potential of dietary Se in counteracting chronic As toxicity in rats through serum biochemistry, blood glutathione levels, immunotoxicity (antibody response), liver peroxidative stress, thyroid response and As levels in tissues and excreta. To achieve this, we compare diets based on high-Se Saskatchewan (SK) lentils versus low-Se lentils from United States. Rats drank control (0ppm As) or As (40ppm As) water while consuming SK lentils (0.3ppm Se) or northwestern USA lentils (<0.01ppm Se) diets for 14weeks. Rats on high Se diets had higher glutathione levels regardless of As exposure, recovered antibody responses in As-exposed group, higher fecal and urinary As excretion and lower renal As residues. Selenium deficiency caused greater hepatic peroxidative damage in the As exposed animals. Thyroid hormones, triiodothyronine (T3) and thyroxine (T4), were not different. After 14weeks of As exposure, health indicators in rats improved in response to the high Se lentil diets. Our results indicate that high Se lentils have a potential to mitigate As toxicity in laboratory mammals, which we hope will translate into benefits for As exposed humans.

Reversal effect of arsenic sensitivity in human leukemia cell line K562 and K562/ADM using realgar transforming solution.

The success of arsenic trioxide (ATO) in treatment of acute promyelocytic leukemia (APL) attracts a great deal of attention to researchers to explore its activity of anti-leukemia. However, ATO has unavailable effect on chronic myeloid leukemia (CML), especially multidrug resistant (MDR)-CML, unless using high concentration. Realgar (As(4)S(4)) has been employed in Chinese traditional medicine for 1500 years. Research evidences confirmed realgar has similar effect on treating with APL as ATO, but the problem of large dose and long period in the CML/MDR-CML treatment still exist. By using a microbial leaching process with Acidithiobacillus ferrooxidans, we obtained realgar transforming solution (RTS) which showed significantly higher extent in inhibiting CML cell line K562 and MDR-CML cell line K562/ADM, and then trigger apoptosis. Both K562 and K562/ADM showed arsenic-dose-dependent effect on RTS. Interestingly, the overexpression of MDR1 mRNA and P-glucoprotein (P-gp) in K562/ADM cells were down-regulated by RTS, where there are no obvious effects on ATO and realgar and arsenic can be subsequently accumulated in K562/ADM cells efficiently. The intracellular accumulation of arsenic in K562/ADM cells treated with RTS for 4 h was 2-fold and 16-folds higher than those treated with realgar or ATO. Meanwhile, Western blot analysis of AQP9, the main transporter of arsenic, was increased by RTS treatment particularly in K562/ADM. Thus, these results suggested that the effect from a certain arsenical or a variety of arsenicals in RTS might be a promising candidate both for treating CML/MDR-CML alone and as combinations with currently used anti-CML/MDR-CML drug, although arsenical forms in RTS are undefined.

In vitro study of intestinal transport of inorganic and methylated arsenic species by Caco-2/HT29-MTX cocultures.

This study characterizes intestinal absorption of arsenic species using in vitro system Caco-2/HT29-MTX cocultures in various proportions (100/0 to 30/70). The species assayed were As(V), As(III), monomethylarsonic acid [MMA(V)], monomethylarsonous acid [MMA(III)], dimethylarsinic acid [DMA(V)], and dimethylarsinous acid [DMA(III)]. The results show that the apparent permeability (P(app)) values of pentavalent species increase significantly in the Caco-2/HT29-MTX cocultures in comparison with the Caco-2 monoculture, probably because of enhancement of paracellular transport. For MMA(III) and DMA(III), P(app) decreases in the Caco-2/HT29-MTX cell model, and for As(III), there is no change in P(app) between the two culture models. Transport studies of arsenic solubilized from cooked foods (rice, garlic, and seaweed) after applying an in vitro gastrointestinal digestion showed that arsenic absorption also varies with the model used, increasing with the incorporation of HT29-MTX in the culture. These results show the importance of choosing a suitable in vitro model when evaluating intestinal arsenic absorption processes.

Qualitative and quantitative characterization of the arsenic-binding behaviour of sulfur-containing peptides and proteins by the coupling of reversed phase liquid chromatography to electrospray ionization mass spectrometry.

Phenylarsenic-substituted cysteine-containing peptides and proteins were completely differentiated from their unbound original forms by the coupling of reversed phase liquid chromatography with electrospray ionization mass spectrometry. The analysis of biomolecules possessing structure-stabilizing disulfide bridges after reduction provides new insights into requirements concerning the accessibility of cysteine residues for reducing agents as well as for arsenic compounds in a spatial protein structure. Complementary binding studies performed using direct ESI-MS without chromatographic coupling in different solvent systems demonstrated that more than one binding site were activated for aprotinin and lysozyme in denaturing solvents because of a stronger defolding. From the intensities of the different charge states occurring in the mass spectra as well as from the LC elution behaviour, it can be deduced that the folding state of the arsenic-bound protein species resembles the native, oxidized conformation. In contrast, although the milk protein α-lactalbumin has several disulfide bridges, only one phenylarsenic moiety was bound under strongly denaturing conditions. Because of the charge state distribution in the ESI mass spectra, a conformational change to a molten globule structure is assumed. For the second considered milk protein ß-lactoglobulin, a noncovalent interaction with phenylarsine oxide was detected. In general, smaller apparent binding constants for the condensation reactions of the biomolecules with phenylarsine oxide leading to covalent arsenic-sulfur bindings were determined from direct injection ESI-MS measurements than from LC-ESI-MS coupling. The following order of binding affinities for one phenylarsenic group can be assumed from both ESI-MS and LC-ESI-MS: nonapeptide vasopressin > nonapeptide vasotocin > lysozyme > aprotinin > α-lactalbumin > thioredoxin. Kinetic investigations by LC-ESI-MS yielded a partial reaction order of 2 for vasopressin, Lys and α-lactalbumin and corresponding half-lives of 0.93, 2.56 and 123.5 min, respectively.

[Effect of subchronic realgar exposure on Glu and Gln in infant rat brain].

OBJECTIVE: To study the effect of realgar on Glu and Gln on rat brain tissues. METHODS: Forty-eight Wistar rats were divided into 4 groups randomly:control group,low dosage group, moderate dosage group and high dosage group. The treatment groups were treated with realgar by gastric perfusion at a dosage of 0.3 g/kg, 0.9 g/kg, 2.7 g/kg and the control group ones were orally given the same volume of 0.5% sodium carboxymethylcellulose (CMC-Na) for 6 weeks. The contents of inorganic arsenic, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) in brain tissues were measured by hydride generation-atomic absorption (HG-AAS) method. The contents of amino acid neurotransmitters in brain tissues of rats were determined by means of high performance liquid chromatography with precolumn derivatization. RESULTS: The levels of MMA and DMA in brain increased as the dosage of realgar increased, while the second methylation index declined. Compared with control group,the levels of Glu was significantly decreased in realgar treated group (P < 0.05); Gln also tended to decrease and that of low dosage group was obviously decreased compared with controls. CONCLUSION: Realgar exposure can cause accumulation of MMA and DMA,declination of second methylation index and the reduction of Glu and Gln in brain tissue.

Bioaccessibility of lead and arsenic in traditional Indian medicines.

Arsenic and lead have been found in a number of traditional Ayurvedic medicines, and the practice of Rasa Shastra (combining herbs with metals, minerals and gems), or plant ingredients that contain these elements, may be possible sources. To obtain an estimate of arsenic and lead solubility in the human gastrointestinal tract, bioaccessibility of the two elements was measured in 42 medicines, using a physiologically-based extraction test. The test consisted of a gastric phase at pH 1.8 containing organic acids, pepsin and salt, followed by an intestinal phase, at pH 7 and containing bile and pancreatin. Arsenic speciation was measured in a subset of samples that had sufficiently high arsenic concentrations for the X-ray absorption near edge structure analysis used. Bioaccessible lead was found in 76% of samples, with a large range of bioaccessibility results, but only 29% of samples had bioaccessible arsenic. Lead bioaccessibility was high (close to 100%) in a medicine (Mahayograj Guggulu) that had been compounded with bhasmas (calcined minerals), including naga (lead) bhasma. For the samples in which arsenic speciation was measured, bioaccessible arsenic was correlated with the sum of As(V)-O and As(III)-O and negatively correlated with As-S. These results suggest that the bioaccessible species in the samples had been oxidized from assumed As-S raw medicinal ingredients (realgar, As(4)S(4), added to naga (lead) bhasma and As(III)-S species in plants). Consumption at recommended doses of all medicines with bioaccessibile lead or arsenic would lead to the exceedance of at least one standard for acceptable daily intake of toxic elements.

Arsenic trioxide controls the fate of the PML-RARalpha oncoprotein by directly binding PML.

Arsenic, an ancient drug used in traditional Chinese medicine, has attracted worldwide interest because it shows substantial anticancer activity in patients with acute promyelocytic leukemia (APL). Arsenic trioxide (As2O3) exerts its therapeutic effect by promoting degradation of an oncogenic protein that drives the growth of APL cells, PML-RARalpha (a fusion protein containing sequences from the PML zinc finger protein and retinoic acid receptor alpha). PML and PML-RARalpha degradation is triggered by their SUMOylation, but the mechanism by which As2O3 induces this posttranslational modification is unclear. Here we show that arsenic binds directly to cysteine residues in zinc fingers located within the RBCC domain of PML-RARalpha and PML. Arsenic binding induces PML oligomerization, which increases its interaction with the small ubiquitin-like protein modifier (SUMO)-conjugating enzyme UBC9, resulting in enhanced SUMOylation and degradation. The identification of PML as a direct target of As2O3 provides new insights into the drug's mechanism of action and its specificity for APL.