Search

Nephrotoxicity is within the recognized toxic effects of arsenic. In this study we assessed the effect of arsenite on the renal capacity to metabolize and handle arsenicals in rats exposed to drinking water with 0, 1, 5, or 10 ppm sodium arsenite for ten days. Arsenite treatment did not affect the gene expression of the main enzyme catalyzing methylation of arsenite, As3mt, while it reduced the expression of GSTO1 mRNA and protein. Arsenite decreased the expression of Aqp3, Mrp1, Mrp4, and Mdr1b (i.e., transporters and channels used by arsenic), but not that of Aqp7, Glut1, Mrp2, and Mdr1a. The protein abundance of AQP3 was also reduced by arsenite. Arsenite increased urinary NGAL and FABP3 and decreased Klotho plasma levels, without alteration of creatinine, which evidenced early tubular damage. Renal Klotho mRNA and protein expressions were also downregulated, which may exacerbate renal damage. No effect was observed in selected miRNAs putatively associated with renal injury. Plasma PTH and FGF23 were similar between groups, but arsenite decreased the renal expression of Fgfr1 mRNA. In conclusion, exposure to arsenite alters the gene expression of proteins involved in the cellular handling of arsenical species and elicits tubular damage., Competing Interests: Declaration of Competing Interest The authors declare that they have no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Over 200 million people worldwide are exposed to the human carcinogen, arsenic, in contaminated drinking water. In laboratory animals, arsenic and the essential trace element, selenium, can undergo mutual detoxification through the formation of the seleno-bis(S-glutathionyl) arsinium ion [(GS) 2 AsSe] - , which undergoes biliary and fecal elimination. [(GS) 2 AsSe] - , formed in animal red blood cells (RBCs), sequesters arsenic and selenium, and slows the distribution of both compounds to peripheral tissues susceptible to toxic effects. In human RBCs, the influence of arsenic on selenium accumulation, and vice versa, is largely unknown. The study aims were to characterize arsenite (As III ) and selenite (Se IV ) uptake by human RBCs, to determine if Se IV and As III increase the respective accumulation of the other in human RBCs, and ultimately to determine if this occurs through the formation and sequestration of [(GS) 2 AsSe] - . 75 Se IV accumulation was temperature and Cl - -dependent, inhibited by 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulfonic acid (H 2 DIDS) (IC 50 1 ± 0.2 µM), and approached saturation at 30 µM, suggesting uptake is mediated by the erythrocyte anion-exchanger 1 (AE1 or Band 3, gene SLC4A1). HEK293 cells overexpressing AE1 showed concentration-dependent 75 Se IV uptake. 73 As III uptake by human RBCs was temperature-dependent, partly reduced by aquaglyceroporin 3 inhibitors, and not saturated. As III increased 75 Se IV accumulation (in the presence of albumin) and Se IV increased 73 As III accumulation in human RBCs. Near-edge X-ray absorption spectroscopy revealed the formation of [(GS) 2 AsSe] - in human RBCs exposed to both As III and Se IV . The sequestration of [(GS) 2 AsSe] - in human RBCs potentially slows arsenic distribution to susceptible tissues and could reduce arsenic-induced disease., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Arsenic exposure has been linked to an impaired immune response and inflammation. Our study investigated the effects of sodium arsenite on host immune response and vascular inflammation during malarial infection. Mice were divided into three groups: control (C), Plasmodium berghei infection (I) and sodium arsenite exposure with Plasmodium berghei infection (As-I). The results showed that splenocyte proliferation stimulated by lipopolysaccharide (LPS) and pokeweed mitogen (PWM) was suppressed in the I group, and the suppression was more pronounced in the As-I group, suggesting that acquired immunity in infected mice was worsening following arsenic exposure. ICAM-1, an adhesion protein involved in parasite-infected red blood cell (iRBC) binding to endothelium, and HIF-1α, a hypoxia marker protein in the descending aorta, were increased in the As-I group compared to the I group. Collectively, our results suggest that arsenic may increase host susceptibility to malaria through suppression of B cell proliferation and enhancement of adhesion between iRBC and endothelium by increasing ICAM-1., (Copyright © 2018 Elsevier B.V. All rights reserved.)

A rapid and sensitive method was established for arsenic (As) speciation based on high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). This method was validated for the quantification of four arsenic species, including arsenite (As III ), arsenate (As V ), monomethylarsonic acid (MMA V ) and dimethylarsinic acid (DMA V ) in cynomolgus macaque plasma. Separation was achieved in just 3.7 min with an alkyl reverse phase column and highly aqueous mobile phase containing 20 mM citric acid and 5 mM sodium hexanesulfonate (pH = 4.3). The calibration curves were linear over the range of 5⁻500 ng·mL -1 (measured as As), with r > 0.99. The above method was validated for selectivity, precision, accuracy, matrix effect, recovery, carryover effect and stability, and applied in a comparative pharmacokinetic study of arsenic species in cynomolgus macaque samples following intravenous and intragastrical administration of arsenic trioxide solution (0.80 mg·kg -1 ; 0.61 mg·kg -1 of arsenic); in addition, the absolute oral bioavailability of the active ingredient As III of arsenic trioxide in cynomolgus macaque samples was derived as 60.9 ± 16.1%.

Arsenic (As) toxicity has caused an environmental tragedy affecting millions of people in the world. Little is known about the toxic effects of As on neurobehavioral and biochemical changes in vivo. Along this line of metal toxicity, co-exposure of lead (Pb) could aggravate the situation in the host. The present study was designed to explore the combined effects of As and Pb on behavioral changes like anxiety, spatial memory and learning impairment, and blood indices related to organ dysfunction. Exposure of mice to As (10 mg/kg body weight), Pb (10 mg/kg body weight), and As + Pb via drinking water significantly decreased the time spent exploring the open arms while it increased the time spent in the closed arms compared to control mice in the elevated plus maze. The mean latency time of the control group to find the platform decreased significantly during the learning for 7 days compared to all three treated groups in the Morris water maze test, and the As-exposed group spent significantly less time in the desired quadrant as compared to the control group in the probe trial. Both metals posed an anxiety-like behavior and deficits in spatial memory and learning, and also altered blood indices related to liver and kidney dysfunction, and a combined exposure of these metals inhibited the individual accumulation of As and Pb. Taken together, these data suggest that As has more toxic effects on neurobehavioral and biochemical changes than Pb, and there may be antagonism in the effects and accumulation between these two toxicants.

Arsenic (As) is a metalloid usually found in organic and inorganic forms with different oxidation states, while inorganic form (arsenite As-III and arsenate As-v) is considered to be more hazardous as compared to organic form (methylarsonate and dimethylarsinate), with mild or no toxicity in mammals. Due to an increasing trend to using arsenicals as growth promoters or for treatment purposes, the understanding of metabolism and toxicity of As gets vital importance. Its toxicity is mainly depends on oxi-reduction states (As-III or As-v) and the level of methylation during the metabolism process. Currently, the exact metabolic pathways of As have yet to be confirmed in humans and food producing animals. Oxidative methylation and glutathione conjugation is believed to be major pathways of As metabolism. Oxidative methylation is based on conversion of Arsenite in to mono-methylarsonic acid and di-methylarsenic acid in mammals. It has been confirmed that As is only methylated in the presence of glutathione or thiol compounds, suggesting that As is being methylated in trivalent states. Subsequently, non-conjugated trivalent arsenicals are highly reactive with thiol which converts the trivalent arsenicals in to less toxic pentavalent forms. The glutathione conjugate stability of As is the most important factor for determining the toxicity. It can lead to DNA damage by alerting enzyme profile and production of reactive oxygen and nitrogen species which causes the oxidative stress. Moreover, As causes immune-dysfunction by hindering cellular and humeral immune response. The present review discussed different metabolic pathways and toxic outcomes of arsenicals in mammals which will be helpful in health risk assessment and its impact on biological world., (Copyright © 2016. Published by Elsevier B.V.)

The arsenic species in rat plasma were studied after oral administration of realgar and Niu Huang Jie Du Pian (NHJDP) and the possible compatible effects of realgar was evaluated by comparing the pharmacokinetics of arsenic species after administration of realgar and NHJDP. The separation of the arsenicals was performed by a high performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) technique. Dimethylarsinic acid (DMA) was found to be the main species in rats’ plasma after dosing. No traces of arsenite [As(Ⅲ)], monomethylarsonic acid (MMA) or arsenate [As(Ⅴ)] were detected at any sampling time points. Compared with realgar administration alone, dose-normalized peak concentration(C(max)) and AUC(0-t) of DMA were significantly decreased by NHJDP administration, while the t(max) was significantly delayed with the clearance and apparent volume of distribution significantly increased, indicating that the pharmacokinetics of As from realgar was affected by other ingredients in the compound prescription of NHJDP.

Fluoride and arsenic are two common inorganic contaminants in drinking water that are associated with impairment in child development and retarded intelligence. The present study was conducted to explore the effects on spatial learning, memory, glutamate levels, and group I metabotropic glutamate receptors (mGluRs) expression in the hippocampus and cortex after subchronic exposure to fluoride, arsenic, and a fluoride and arsenic combination in rats. Weaned male Sprague-Dawley rats were assigned to four groups. The control rats drank tap water. Rats in the three exposure groups drank water with sodium fluoride (120 mg/L), sodium arsenite (70 mg/L), and a sodium fluoride (120 mg/L) and sodium arsenite (70 mg/L) combination for 3 months. Spatial learning and memory was measured in Morris water maze. mGluR1 and mGluR5 mRNA and protein expression in the hippocampus and cortex was detected using RT-PCR and Western blot, respectively. Compared with controls, learning and memory ability declined in rats that were exposed to fluoride and arsenic both alone and combined. Combined fluoride and arsenic exposure did not have a more pronounced effect on spatial learning and memory compared with arsenic and fluoride exposure alone. Compared with controls, glutamate levels decreased in the hippocampus and cortex of rats exposed to fluoride and combined fluoride and arsenic, and in cortex of arsenic-exposed rats. mGluR5 mRNA and protein expressions in the hippocampus and mGluR5 protein expression in the cortex decreased in rats exposed to arsenic alone. Interestingly, compared with fluoride and arsenic exposure alone, fluoride and arsenic combination decreased mGluR5 mRNA expression in the cortex and protein expression in the hippocampus, suggesting a synergistic effect of fluoride and arsenic. These data indicate that fluoride and arsenic, either alone or combined, can decrease learning and memory ability in rats. The mechanism may be associated with changes of glutamate level and mGluR5 expression in cortex and hippocampus.

We investigated protective efficacy of α-lipoic acid (LA), an antioxidant against arsenic and DDVP co-exposed rats. Biochemical variables suggestive of oxidative stress, neurological dysfunction, and tissue histopathological alterations were determined. Male rats were exposed either to 50 ppm sodium arsenite in drinking water or in combination with DDVP (4 mg/kg, subcutaneously) for 10 weeks. α-Lipoic acid (50mg/kg, pos) was also co-administered in above groups. Arsenic exposure led to significant oxidative stress along, hepatotoxicity, hematotoxicity and altered brain biogenic amines levels accompanied by increased arsenic accumulation in blood and tissues. These altered biochemical variables were supported by histopathological examinations leading to oxidative stress and cell death. These biochemical alterations were significantly restored by co-administration of α-lipoic acid with arsenic and DDVP alone and concomitantly. The results indicate that arsenic and DDVP induced oxidative stress and cholinergic dysfunction can be significantly protected by the supplementation of α-lipoic acid., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Arsenic speciation in blood can improve understanding of the metabolism and toxicity of arsenic. In this study, arsenic species in the plasma and red blood cells (RBCs) of arsenite-treated female F344 rats were characterized using anion exchange and size exclusion chromatography separation with inductively coupled plasma mass spectrometry (ICPMS) and electrospray ionization tandem mass spectrometry (ESI MS/MS) detection. Arsenite (iAs(III)), arsenate (iAs(V)), monomethylarsonic acid (MMA(V)), dimethylarsinic acid (DMA(V)), trimethylarsine oxide (TMAO(V)), monomethylmonothioarsonic acid (MMMTA(V)), and dimethylmonothioarsinic acid (DMMTA(V)) were detected in the plasma, with DMA(V) being the predominant metabolite. Upon oxidative pretreatment with 5% hydrogen peroxide (H2O2), plasma proteins released bound arsenic in the form of DMA(V) as the major species and MMA(V) as the minor species. The ratio of protein-bound arsenic to total arsenic decreased with increasing dosage of iAs(III) administered to the rats, suggesting a possible saturation of the binding capacity of the plasma proteins. The proportion of the protein-bound arsenic in the plasma varied among rats. In the H2O2-treated lysates of red blood cells of rats, DMA(V) was consistently found as the predominant arsenic species, probably reflecting the preferential binding of dimethylarsinous acid (DMA(III)) to rat hemoglobin. iAs(V), MMA(V), and trimethylarsine oxide (TMAO(V)) were also detected in the hydrogen peroxide-treated lysates of red blood cells. Importantly, DMMTA(V) and MMMTA(V) have not been reported in rat blood, and the present finding of DMMTA(V) and MMMTA(V) in the rat plasma is toxicologically relevant because these pentavalent thioarsenicals are more toxic than their counterparts DMA(V) and MMA(V). Identifying novel thiolated arsenicals and determining protein-bound arsenicals in the blood provide useful insights into the metabolism and toxicity of arsenic in animals.

Although studies have shown that arsenic exposure can induce apoptosis in a variety of cells, the exact molecular mechanism of chronic arsenicosis remains unclear. Based on our previous study on human serum, the present study was to determine whether pigment epithelium-derived factor (PEDF) plays a role in the damage induced by chronic arsenic exposure in a rat model and to explore the possible signaling pathway involved. Thirty male Wistar rats were randomly divided into three groups and the arsenite doses administered were 0, 10, and 50 mg/L, respectively. The experiment lasted for 6 months. Our results showed that level of arsenic increased significantly in serum, liver, brain, and kidney in arsenic-exposed groups. It was indicated that PEDF protein was widely distributed in the cytoplasm of various types of cells in liver, brain, and kidney. PEDF protein level was only changed when the arsenite dose reached 50 mg/L in liver and brain, whereas it was not changed in the kidney. In order to investigate the possible mechanism of PEDF-exerted damages upon arsenite exposure, apoptosis in liver and brain was assessed. The proportion of apoptotic cells gradually increased with increasing arsenic administration. The ratio of Bax/Bcl-2 in the high arsenic group (50 mg/L) was significantly higher than that in the control group. Therefore, we thought PEDF played a role in cell apoptosis of liver and brain which induced by sodium arsenite exposure, and the results also demonstrated that Bax and Bcl-2 might be two key targets in the action of PEDF.

The etiology of numerous grievous human diseases, including Alzheimer's and Parkinson's Disease is not well understood. Conversely, the concentration toxic metals and metalloids, such as As, Cd, Hg and Pb in human blood of the average population is well established, yet we know strikingly little about the role that they might play in the etiology of disease processes. Establishing functional connections between the chronic exposure of humans to these and other inorganic pollutants and the etiology of certain human diseases is therefore viewed by many as one of the greatest challenges in the post-genomic era. Conceptually, this task requires us to uncover hitherto unknown biomolecular mechanisms which must explain how small doses of a toxic metal/metalloid compound (low μg per day) - or mixtures thereof - may eventually result in a particular human disease. The biological complexity that is inherently associated with mammals, however, makes the discovery of these mechanisms a truly monumental task. Recent findings suggest that a better understanding of the bioinorganic chemistry of inorganic pollutants in the mammalian bloodstream represents a fruitful strategy to unravel relevant biomolecular mechanisms. The adverse effect(s) that toxic metals/metalloid compounds exert on the transport of essential ultratrace elements to internal organs appear particularly pertinent. A brief overview of the effect that arsenite and Hg(2+) exert on the mammalian metabolism of selenium is presented., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Arsenic (+3 oxidation state) methyltransferase (As3mt) catalyzes methylation of inorganic arsenic (iAs) producing a number of methylated arsenic metabolites. Although methylation has been commonly considered a pathway for detoxification of arsenic, some highly reactive methylated arsenicals may contribute to toxicity associated with exposure to inorganic arsenic. Here, adult female wild-type (WT) C57BL/6 mice and female As3mt knockout (KO) mice received drinking water that contained 1, 10, or 25 ppm (mg/l) of arsenite for 33 days and blood, liver, kidney, and lung were taken for arsenic speciation. Genotype markedly affected concentrations of arsenicals in tissues. Summed concentrations of arsenicals in plasma were higher in WT than in KO mice; in red blood cells, summed concentrations of arsenicals were higher in KO than in WT mice. In liver, kidney, and lung, summed concentrations of arsenicals were greater in KO than in WT mice. Although capacity for arsenic methylation is much reduced in KO mice, some mono-, di-, and tri-methylated arsenicals were found in tissues of KO mice, likely reflecting the activity of other tissue methyltransferases or preabsorptive metabolism by the microbiota of the gastrointestinal tract. These results show that the genotype for arsenic methylation determines the phenotypes of arsenic retention and distribution and affects the dose- and organ-dependent toxicity associated with exposure to inorganic arsenic.

Arsenic (As) contamination in groundwater is of increasing health concern in West Bengal, India. Arsenic has been associated with various human cancers, but the precise mechanism of its co-carcinogenic action is not clearly elucidated. Oxidative stress and defective repair mechanisms may promote accumulation of mutations and may be a stepping stone for carcinogenesis. Prevention of arsenic-induced oxidative stress and repair inhibition may reduce the chances of initiation of cancer. Tea polyphenols are reported to have excellent chemopreventive properties against cancer. This study aimed to elucidate the role of tea against arsenic-induced formation of 8-hydroxy-2'-deoxyguanosine (8OHdG) and arsenic-suppressed DNA repair in Swiss albino mice. Both green and black tea gave fruitful results in the reduction of 8OHdG and 8-oxoguanine DNA glycosylase (OGG1) in Swiss albino mice administered sodium arsenite (As III). DNA repair enzymes--such as PARP1, DNA β-polymerase, XRCC1, DNA ligase III, DNA protein kinase (catalytic subunit), XRCC 4, DNA ligase IV, and DNA topoisomerase IIβ--were induced by the phytochemicals at both the protein and genetic levels. Thus, tea polyphenols may prove effective in treating arsenic-induced carcinogenesis.

We studied the effects of combined exposure to arsenic and fluoride on (i) brain biogenic amines, oxidative stress and its correlation with glutathione and linked enzymes; (ii) alterations in the structural integrity of DNA; and (iii) brain and blood arsenic and fluoride levels. Efficacy of alpha-tocopherol in reducing these changes was also determined. Male mice were exposed to sodium meta arsenite (50 ppm) and sodium fluoride (50 ppm) individually and in combination for ten weeks. Animals were given vitamin E supplementation (5 mg/kg, i.m., alternate days) throughout the experiment. Exposure to arsenic and fluoride significantly decreased the levels of brain biogenic amines. However; acetyl cholinesterase (AChE) and monoamine oxidase (MAO) activities showed an increase on fluoride exposure. There was also an increase in reactive oxygen species, thiobarbituric acid reactive species level, glutathione S-transferase and glutathione peroxidase activities and decreased superoxide dismutase activity, GSH:GSSG ratio, glucose 6-phosphate dehydrogenase activity. Combined exposure to these toxicants produced more pronounced effects on AChE, MAO, SOD and catalase activities. Infrared spectra showed less toxicity during combined exposure as the characteristic peaks of cytosine and alpha-helical structure of DNA were observed in normal and arsenic plus fluoride-exposed animals. Vitamin E reduced brain fluoride level and tissue oxidative stress but had no effect on arsenic. Combined exposure to arsenic and fluoride does not necessarily lead to more pronounced toxicity and interestingly exhibit some antagonistic effects. Vitamin E supplementation may be of added value in reverting some of the toxic effects.

Present study examined the genotoxic effects of arsenite in ovarian tissue of rat at 56 days of age. Immature (28 days old) female rats were exposed to different doses (50, 100, and 200 ppm) of sodium arsenite in drinking water for 28 days. DNA damage in ovarian tissue was measured by comet assay. All doses induced significant decrease in ovarian weight in a dose-dependent manner compared to control, more prominently at (P<0.001) 100 and 200 ppm. All the comet assay parameters showed significant difference with arsenite treatment compared to control group. In treatment groups, mean number of cells with intact DNA decreased while, mean comet number increased (P<0.001) in a dose-dependent manner compared to control. Significant decrease (P<0.05) was observed in mean comet length, height, comet head diameter and %DNA in comet head of high dose groups compared to control group. Dose dependent increase was found in mean comet tail length, %DNA in tail, tail moment and olive tail moment in high dose groups compared to control group. The study indicates that arsenic caused DNA damage to ovarian cells particularly at high doses and ensure comet assay as an effective method to detect DNA damage in tissue caused by metals.

Millions of people are currently exposed to a multitude of environmentally persistent toxic metals and metalloid compounds mainly through the ingestion of drinking water and food. Despite the fact that biomonitoring studies have revealed several toxic metals to be present in the bloodstream of the general population, the interpretation of the established blood concentrations with regard to their health relevance continues to be an active research area. To this end, a better understanding of the bioinorganic chemistry of individual metals and metalloid compounds in the mammalian bloodstream could greatly advance the interpretation of the available biomonitoring data. Arsenite represents a case in point, since >100 million people are currently exposed to unsafe levels of inorganic arsenic via drinking water. The elucidation of the underlying biomolecular mechanism(s) of toxicity is therefore of the utmost importance and could involve the antagonistic toxic effect between arsenite and selenite, which was discovered in mammals approximately 70 years ago. After a concise overview of animal studies that aimed to understand this trace element antagonism at the molecular level, the in vivo formation and biliary excretion of the seleno-bis(S-glutathionyl) arsinium ion, (GS)(2)AsSe(-), is introduced as a likely biomolecular basis. Arguments in favor of a critical involvement of (GS)(2)AsSe(-) in the chronic toxicity and carcinogenicity of arsenite are presented. The in vivo formation of this toxicologically relevant metabolite in the mammalian bloodstream (mediated by erythrocytes) indicates that the elucidation of bioinorganic chemistry-related mechanisms that take place in the bloodstream represents a promising research strategy to better understand the etiology of numerous human diseases some of which may be ultimately caused by the low level exposure to certain inorganic pollutants.

A method combining gel filtration chromatography (GFC), protease digestion, and ion pair chromatography with inductively coupled plasma mass spectrometry detection was developed for the determination of arsenic species bound to proteins. The method was first established by examining the interactions of two model proteins, metallothionein (MT) and hemoglobin, with three reactive trivalent arsenic species. It was then successfully applied to the speciation of arsenic in red blood cells of rats. Inorganic arsenite (iAs(III)), monomethylarsonous acid (MMA(III)), and dimethylarsinous acid (DMA(III)) were efficiently released from the proteins by protease digestion at pH 8.0, with the recovery ranging from 93% to 106%. There was no oxidation of iAs(III) or MMA(III) during the protease digestion process. Up to 61% DMA(III) (the least stable arsenic species) was unchanged, and the rest was oxidized to the pentavalent dimethylarsinic acid (DMA(V)). The arsenic species in the red blood cells of control rats was present as DMA(III) complex with hemoglobin. The method enabling the determination of the specific arsenic species that bind to cellular proteins is potentially useful for studying arsenic distribution, metabolism, and toxicity.

Epidemiological investigations indicate that chronic arsenic exposure can damage neurobehavioral function in children. The present study was aimed to study the effects of arsenic exposure from drinking water on the spatial memory, and hippocampal ultra-structures and N-methyl-d-aspartate receptor (NMDAR) gene expression in rats. Sprague-Dawley rats were assigned to four groups: rats in control group drank regular water, rats in other groups drank water with final arsenic concentration of 2.72 mg/L (group A), 13.6 mg/L (group B) and 68 mg/L (group C), respectively, for 3 months. The levels of arsenic in blood serum and hippocampus were monitored. Rats were tested in Morris water maze (MWM) for memory status. Samples of hippocampus were collected from two rats in each group for transmission electron microscopic study and the detection of NMDAR expression by RT-PCR. The rats in group C showed a significant delay in hidden platform acquisition. Neurons and endothelial cells presented pathological changes and the expression of NR2A was down-regulated in hippocampus in arsenic exposed rats. Our data indicated that arsenic exposure of 68 mg/L caused spatial memory damage, of which the morphological and biochemical bases could be the ultra-structure changes and reduced NR2A expression in hippocampus.

Although the accumulation of arsenic (As) in human blood is linked with some diseases and with occupational exposure, there are few reports on speciation of As in blood. On the basis of our earlier article, elevated level of arsenicals in human urine and blood were found in the ex-exposed population via As-containing drinking water. The aim of the present study was to get an insight on impact of As in foodstuffs on the people living in the As-affected areas. Moreover, speciation of arsenicals in urine, and water-samples found in arsenobetaine (AsB). Since sampling population (n=25) was not taking any seafood, As in foodstuffs was thought to be the prime source for this discrepancy. So, speciation of methanol extract of freeze-dried red blood cells (RBCs) and foodstuffs, and trichloro acetic acid (TCA) treated plasma by high performance liquid chromatography-inductively coupled argon plasma mass spectrometer (HPLC-ICP MS) collected from the study population (n=33) was carried out to support our hypothesis. Results showed that urine contained AsB (1.7%), arsenite (iAs(III)) (14.3), arsenate (iAs(V)) (4.9), monomethylarsonous acid (MMA(III)) (0.64), monomethylarsonic acid (MMA(V)) (13.6), dimethylarsinous acid (DMA(III)) (7.7), and dimethylarsinic acid (DMA(V)) (65.4). Blood contained 21.3 microg L(- 1) (mean) As and of which 27.3% was in plasma and 72.7% in RBCs. RBCs contained AsB (21.6%) and DMA(V) (78.4) and blood plasma contained AsB (12.4%), iAs(III) (25.9), MMA(V) (30.3), and DMA(V) (31.4). Furthermore, speciation of As in foodstuffs showed that most of them contained AsB (3.54-25.81 microg kg(- 1)) (25.81-312.44 microg kg(- 1)) along with iAs(III) (9.62-194.93), iAs(V) (17.63-78.33), MMA(V) (9.47-73.22) and DMA(V) (13.43-101.15) that supported the presence of AsB and elevated As in urine and blood samples of the present study group. Inorganic As (iAs) predominates in rice (67.17-86.62%) and in spices (40-90.35%), respectively over organic As. So, As in the food chain is a real threat to human health.

Adult female Fisher 344 rats received drinking water containing 0, 4, 40, 100, or 200 parts per million of dimethylarsinic acid or 100 parts per million of arsenate for 14 days. Urine was collected during the last 24 h of exposure. Tissues were then taken for analysis of dimethylated and trimethylated arsenicals; urines were analyzed for these arsenicals and their thiolated derivatives. In dimethylarsinic acid-treated rats, highest concentrations of dimethylated arsenic were found in blood. In lung, liver, and kidney, concentrations of dimethylated arsenic exceeded those of trimethylated species; in urinary bladder and urine, trimethylated arsenic predominated. Dimethylthioarsinic acid and trimethylarsine sulfide were present in urine of dimethylarsinic acid-treated rats. Concentrations of dimethylated arsenicals were similar in most tissues of dimethylarsinic acid- and arsenate-treated rats, including urinary bladder which is the target for dimethylarsinic acid-induced carcinogenesis in the rat. Mean concentration of dimethylated arsenic was significantly higher (P<0.05) in urine of dimethylarsinic acid-treated rats than in arsenate-treated rats, suggesting a difference between treatment groups in the flux of dimethylated arsenic through urinary bladder. Concentrations of trimethylated arsenic concentrations were consistently higher in dimethylarsinic acid-treated rats than in arsenate-treated rats; these differences were significant (P<0.05) in liver, urinary bladder, and urine. Concentrations of dimethylthioarsinic acid and trimethylarsine sulfide were higher in urine from dimethylarsinic acid-treated rats than from arsenate-treated rats. Dimethylarsinic acid is extensively metabolized in the rat, yielding significant concentrations of trimethylated species and of thiolated derivatives. One or more of these metabolites could be the species causing alterations of cellular function that lead to tumors in the urinary bladder.

Arsenic and fluoride are common environmental contaminants. Coexposure to these elements can occur through groundwater. We investigated the effects of sodium meta arsenite (50 mg/L in drinking water) and sodium fluoride (50 mg/L in drinking water) individually and in combination. Biochemical parameters suggestive of alterations in heme synthesis pathway, oxidative stress in liver and kidneys, and concentration of essential metals in blood and soft tissues were studied in Swiss albino male mice given the chemicals for 3 weeks. The possible beneficial effect of vitamin E administration (25 mg/kg, oral, alternate days after arsenic/fluoride exposure) on the above variables was investigated. Exposure to arsenic or fluoride caused a significant depletion in blood delta-aminolevulinic acid dehydratase (ALAD) activity, platelet counts (PLT), and glutathione (GSH) level. Blood white blood cell (WBC) counts also decreased. These changes were accompanied by increased reactive oxygen species (ROS) levels. Arsenic and fluoride exposure led to a significant depletion of super oxide dismutase (SOD) activity with no effect on catalase and glutathione peroxidase (GPx) activities. Combined exposure to these toxicants had no synergistic effect on blood ALAD activity and WBC counts, and the effects seen appeared to result predominantly from arsenic. Hepatic catalase activity, on the other hand, increased significantly on exposure to arsenic and fluoride. There was only moderate antagonistic effect on arsenic and fluoride concentration in blood and liver, and kidney arsenic concentration was less pronounced during coexposure compared with arsenic alone. Interestingly, fluoride concentration showed less pronounced uptake during concomitant exposure compared with fluoride exposure alone. Vitamin E supplementation during coexposure to arsenic and fluoride provided only moderate recovery in the altered antioxidant enzymes and in depleting ROS level, but the altered essential metal concentration, particularly calcium level, responded more favorably to vitamin E administration. It can be concluded from the current study that (i) coadministration of arsenic and fluoride was less toxic to the animals compared with individual toxic effects of these toxicants, and (ii) vitamin E supplementation during coexposure had only limited additional beneficial effects in restoring altered biochemical variables, maintaining pro-oxidant/antioxidant balance, and reducing body arsenic store but plays a significant role in maintaining essential metal balance.

Arsenate (AsV), the environmentally prevalent form of arsenic, is converted sequentially in the body to arsenite (AsIII), monomethylarsonic acid (MMAsV), monomethylarsonous acid (MMAsIII), and dimethylarsinic acid (DMAsV) and some trimethylated metabolites. Although the biliary excretion of arsenic in rats is known to be glutathione (GSH)-dependent, involving transport of arsenic-GSH conjugates, the role of GSH in the reduction of AsV to the more toxic AsIII in vivo has not been defined. Therefore, we studied how the fate of AsV is influenced by buthionine sulfoximine (BSO), which depletes GSH in tissues. Control and BSO-treated rats were given AsV (50 micromol/kg, i.v.) and arsenic metabolites in bile, urine, blood and tissues were analysed by HPLC-HG-AFS. BSO increased retention of AsV in blood and tissues and decreased appearance of AsIII in blood, bile (by 96%) and urine (by 63%). The biliary excretion of MMAsIII was also nearly abolished, the appearance of MMAsIII and MMAsV in the blood was delayed and the renal concentrations of these monomethylated arsenicals were decreased by BSO. Interestingly, appearance of DMAsV in blood and urine remained unchanged and the concentrations of this metabolite in the kidneys and muscle were even increased in response to BSO. To test the role of gamma-glutamyltranspeptidase (GGT) in arsenic disposition, the effect of the of the GGT inhibitor acivicin was investigated in rats injected with AsIII (50 micromol/kg, i.v.). Acivicin lowered the hepatic and renal GGT activities and increased the biliary as well as urinary excretion of GSH, but failed to alter the disposition (i.e. blood and tissue concentrations, biliary and urinary excretion) of AsIII and its metabolites. In conclusion, shortage of GSH decreases not only the hepatobiliary transport of arsenic, but also reduction of AsV and the formation of monomethylated arsenic, while not hindering the production of dimethylated arsenic. While GSH plays an important role in the disposition and toxicity of arsenic, GGT, which hydrolyses GSH and GSH conjugates, apparently does not influence the fate of the GSH-reactive trivalent arsenicals in rats.

Heme oxygenase (HO) is the rate-limiting enzyme in heme degradation and its activity has a significant impact on intracellular heme pools. Rat studies indicate that HO induction is a sensitive, dose-dependent response to arsenite (As(III)) exposure in both liver and kidney. The objective of this study was to evaluate the relationship of HO induction to administered As(III) dose, and concentrations of inorganic arsenic (iAs) in tissues and urine. Levels of iAs, mono- (MMA) and dimethylated arsenic (DMA) as well as HO activity were determined in liver, lung and kidney over time in female B6C3F1 mice given a single oral dose of 0, 1, 10, 30 or 100 micromol/kg As(III). Increased HO activity was a time and dose-dependent response in liver and kidney, but not in lung. Activity peaked in the 4-6 h time range in liver and kidney with the responsiveness in liver being approximately 2- to 3-fold greater than kidney. The lowest observed effect levels (LOELs) in this study for HO induction are 30 and 100 micromol/kg, respectively, in liver and kidney. The predominant form of arsenic (As) was iAs in liver at all doses, whereas DMA was the predominant form of As in kidney at all doses. Three- to four-fold higher levels of iAs were achieved in liver compared to kidney. MMA was the least abundant form of As in liver and kidney, never exceeding more than 20% of the total As present. The concentration of iAs in tissue or urine demonstrated the strongest correlation with HO activity in both liver and kidney. Results of this study suggest that HO induction is a biomarker of effect that is specific for tissue iAs because a high, but nontoxic, acute dose of DMA (5220 micromol/kg) did not induce HO in mice. Thus, HO induction has potential for use as a biomarker of effect for inorganic arsenic exposure and may be used as an indicator response to further the development of a biologically-based dose response model for As.

Selenite (SeIV) and inorganic arsenicals counter the toxicity of each other. SeIV inhibits arsenic methylation in hepatocytes, however, it is unknown whether it decreases the formation of the highly toxic monomethylarsonous acid (MMAsIII). Therefore, we examined, in comparison with the methylation inhibitor periodate-oxidised adenosine (PAD), the effect of SeIV (10 micromol/kg, i.v.) on the appearance of arsenic metabolites in blood, bile and urine as well as the distribution of arsenic metabolites in the liver and kidneys in rats injected i.v. with 50 micromol/kg arsenite (AsIII) or arsenate (AsV). Arsenic metabolites were analysed by HPLC-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS). In rats given either arsenical, PAD decreased the excretion and tissue concentrations of methylated arsenic metabolites (MMAsIII, monomethylarsonic acid [MMAsV], and dimethylarsinic acid [DMAsV]), while increasing the tissue retention of AsV and AsIII. The effect of SeIV on arsenic disposition differed significantly from that of PAD. For example, both in AsIII- and AsV-injected animals, SeIV lowered the tissue levels of MMAsIII and MMAsV, but increased the levels of DMAsV. SeIV almost abolished the biliary excretion of MMAsIII in AsV-exposed rats, but barely influenced it in AsIII-dosed rats. The SeIV-induced changes in arsenic disposition may largely be ascribable to formation of the known complex containing trivalent arsenic and selenide (SeII), which not only depends on but also influences the availability and effects of these metalloid species in tissues. By such complexation SeII compromises monomethylation of arsenic when trivalent arsenic availability is limited (e.g. in AsV-exposed rats), but affects it less when the presence of AsIII is overwhelming (e.g. in AsIII-dosed rats). As an auxiliary finding, it is shown that DMAsV occurs in the blood of rats not injected with arsenic and that DMAsV formation in rats can be followed by measuring the build-up of blood-borne DMAsV.

Arsenite (AsIII) is eliminated via excretion and methylation. Monomethylarsonous acid (MMAsIII) is a super toxic metabolite of AsIII, while dimethylarsinic acid produced in the next metabolic step is relatively atoxic. Since the role of methylation in the acute toxicity and elimination of AsIII in vivo is unclear, we have examined the excretion and tissue retention of AsIII and its metabolites in rats exposed to increasing AsIII doses. Rats were injected i.v. with 20, 50 and 125 micromol/kg AsIII and arsenic metabolites in bile, urine and tissues were analysed. The excretion of AsIII increased almost proportionately to the dose, while its concentration in tissues rose more than proportionately. In contrast, the excretion and tissue concentrations of methylated metabolites increased less than the dosage, or they even decreased after injection of the largest dose of AsIII. To elucidate the mechanism of the dose-dependent decrease of methylation, we quantified S-adenosylmethionine (SAME), glutathione (GSH), and adenine nucleotides in the liver of AsIII-injected rats. AsIII decreased the hepatic concentrations of GSH and adenosine 5'-triphosphate (ATP) and the energy charge in a dose-dependent manner, but increased the level of SAME. Thus, impaired methylation after AsIII overdose is not due to SAME shortage, but probably to methyltransferase inhibition. It appears that exhausted elimination capacity of AsIII, rather than MMAsIII produced from AsIII, contributes significantly to the acute toxicity of AsIII. After GSH depletion the retained AsIII can increasingly inhibit SH-enzymes, thus causing ATP depletion and energetic disorder.

The uptake by rabbit erythrocytes of 0.4 mM arsenate, As(V), monomethylarsinate, MMA(V) and dimethylarsonate, DMA(V) were compared over 24 h. In membrane-free hemolysate, the distribution of As between proteins (10 kDa) and ultrafiltrate was determined by ultrafiltration and arsenic species in the ultrafiltrate were identified by thin layer chromatography methods. 1H spin-echo Fourier transform NMR was used to follow the binding of these arsenic species to glutathione (GSH). 31P-NMR was used to observe their effects on high-energy adenine nucleotide levels (ATP, ADP). These results demonstrate that As(III) readily accumulates in cells, reaches a quasi-plateau at 78% of the total As in the incubation after 1 h and 88% of the total As after 24 h. On average, 20% of the total erythrocyte As(III) burden is associated with the protein fraction, particularly with hemoglobin (Hb). About 68% of the erythrocyte As(III) burden is bound to GSH. As(III) has no effect on ATP levels during a 5-h incubation. By comparison, As(V) enters erythrocytes more slowly (53% of the total As after 5 h). Erythrocytes take up 81% of the As(V) in the reaction system after a 24 h incubation. Of the total As burden in As(V)-exposed erythrocytes, 22% was associated with the proteins (10 kDa) and possibly reduced to As(III) and 59% was in the ultrafiltrate (8% as As(III) and 51% as As(V)). This finding indicates that, over a 24 h incubation period, the reduction of As(V) to As(III) may account for 30% of the total As in rabbit erythrocytes. As(V) present in the erythrocytes enters the phosphate pool and depletes ATP. In comparison, about 65% of the total MMA(V) or about 44% of the total DMA(V) in the incubation system is taken up by rabbit erythrocytes during a 24 h incubation. Neither organoAs species perturbed the Hb signals observed by spin-echo Fourier transform NMR and the binding to GSH was minimal. Unlike As(V), MMA(V) and DMA(V) do not perturb phosphate metabolism, showing that, despite their pentavalent oxidation state, these arsenic species are not analogs for phosphate.

Effects of inorganic arsenicals on DNA synthesis in unsensitized human blood lymphocytes were biphasic: The chemicals at very low concentrations enhanced DNA synthesis, whereas higher concentrations inhibited DNA synthesis. The concentrations of arsenicals at which the maximum stimulating effect was found were 1 x 10(-5) M, 1 x 10(-6) or 2 x 10(-6) M, and 0.8 x 10(-6) or 1 x 10(-6) M for sodium arsenite exposure of 1 h, 3 d, and 6 d, respectively; for sodium arsenate, 1 x 10(-5) M, 1 x 10(-5) M, and 2 x 10(-6) or 5 x 10(-6) M, respectively. Arsenicals must be present for the entire 6-d culture period to produce maximum stimulation of DNA synthesis in human lymphocytes. The longer exposure of the lymphocytes to arsenicals, the lower the concentrations of arsenicals at which the maximum stimulating effect on DNA synthesis was found. Stimulating effect of trivalent arsenic (sodium arsenite) on DNA synthesis was stronger than pentavalent arsenic (sodium arsenate), and the stronger the effect of trivalent arsenic than pentavalent, the longer exposure of the cells to the chemicals. Both sodium arsenite and sodium arsenate stimulated DNA synthesis in human lymphocytes to a lower degree than phytohemagglutinin (PHA).