Oral arsenite exposure induces inflammation and apoptosis in pulmonary tissue: acute and chronic evaluation in young and adult mice

Inorganic arsenic is a well-known environmental toxicant, and exposure to this metalloid is strongly linked with severe and extensive toxic effects in various organs including the lungs. In the present study, we aimed to investigate the acute and chronic effects of arsenite exposure on pulmonary tissue in young and adult mice. In brief, young and adult female Balb/C mice were exposed to 3 and 30 ppm arsenite daily via drinking water for 30 and 90 days. Subsequently, the animals were sacrificed and various histological and immunohistochemistry (IHC) analyses were performed using lung tissues. Our findings showed arsenite was found to cause dose-dependent pathological changes such as thickening of the alveolar septum, inflammatory cell infiltrations and lung fibrosis in young and adult mice. In addition, arsenite exposure significantly increased the expression of inflammatory markers NF-κB and TNF-α, indicating that arsenite-exposed mice suffered from severe lung inflammation. Moreover, the IHC analysis of fibrotic proteins demonstrated an increased expression of TGF-β1, α-SMA, vimentin and collagen-I in the arsenite-exposed mice compared to the control mice. This was accompanied by apoptosis, which was indicated by the upregulated expression of caspase-3 in arsenite-exposed mice compared to the control. Adult mice were generally found to be more prone to arsenite toxicity during chronic exposure relative to their younger counterparts. Overall, our findings suggest that arsenite in drinking water may induce dose-dependent and age-dependent structural and functional impairment in the lungs through elevating inflammation and fibrotic proteins.

Targeted arsenite-loaded magnetic multifunctional nanoparticles for treatment of hepatocellular carcinoma

Arsenic trioxide (ATO), an FDA-approved drug for acute promyelocytic leukemia, also has great potential for treatment of solid tumors. Drug delivery powered by recent advances in nanotechnology has boosted the efficacy of many drugs, which is enlightening for applications of ATO in treating solid tumors. Herein, we reported arsenite-loaded multifunctional nanoparticles that are capable of pH-responsive ATO release for treating hepatocellular carcinoma (HCC) and real-time monitoring via magnetic resonance imaging. We fabricated these nanoparticles (designated as magnetic large-pore mesoporous silica nanoparticle (M-LPMSN)-NiAsO _x ) by loading nanoparticulate ATO prodrugs (NiAsO _x ) into the pores of large-pore mesoporous silica nanoparticles (LPMSNs) that contain magnetic iron oxide nanoparticles in the center. The surface of these nanodrugs was modified with a targeting ligand folic acid (FA) to further enhance the drug efficacy. Releasing profiles manifest the responsive discharging of arsenite in acidic environment. In vitro experiments with SMMC-7721 cells reveal that M-LPMSN-NiAsO _x -FA nanodrugs have significantly higher cytotoxicity than traditional free ATO and induce more cell apoptosis. In vivo experiments with mice bearing H22 tumors further confirm the superior antitumor efficacy of M-LPMSN-NiAsO _x -FA over traditional free ATO and demonstrate the outstanding imaging ability of M-LPMSN-NiAsO _x -FA for real-time tumor monitoring. These targeted arsenite-loaded magnetic mesoporous silica nanoparticles integrating imaging and therapy hold great promise for treatment of HCC, indicating the auspicious potential of LPMSN-based nanoplatforms.

Evaluation of metabolic reactivity in macrophages from mice with chronic sodium arsenite intake and experimental carcinogenesis

 Arsenic is carcinogenic to human beings, and environmental exposure to arsenic is a public health issue that affects large populations around the world. Thus, studies are needed to determine the mode of action of arsenic and to prevent harmful effects that arise from arsenic intake. In particular, knowledge of the effects of arsenic exposure in individuals who are undergoing a carcinogenesis process is lacking. The present study was performed in mice to evaluate the effect of chronic As3+ administration on peritoneal and alveolar macrophages; the As3+ was administered in drinking water over 9 months and there was a two-stage carcinogenesis process. At the end of the experiment, the number of tumors stabilized to below the control values, but the tumors showed increased malignancy. Our objective was to evaluate the systemic effects of chronic As3+ingestion in a population of macrophages that was derived from the peritoneal cavity and the broncho-alveolar trunk of cancerized mice since they are the first line of defense in the immune system. The results showed that the macrophages under all conditions retained their ability to self-regulate their metabolic reactivity. This feature was more evident in peritoneal macrophages than in alveolar macrophages. Furthermore, an increase in the number of macrophages from animals receiving higher doses of As3+ compared to untreated animals was observed. These findings indicate that certain parameters associated with two-stage skin carcinogenesis are modified by the presence of As3+ in drinking water.

Arsenic Induces Thioredoxin 1 and Apoptosis in Human Liver HHL-5 Cells

To further characterize the mechanisms underlying liver toxicity induced by arsenic, we examined in this study the effect of arsenic on thioredoxin (Trx) and the apoptotic signaling pathways in human liver HHL-5 cells. The cells were treated with 0, 2, 5, and 10 μM of sodium arsenite for 24 h, and the changes of Trx1 and thioredoxin reductase (TrxR1) as well as intracellular ROS and apoptosis were examined. A concentration-dependent increase in mRNA and protein levels of Trx1 and TrxR1 was observed in arsenic-treated cells. Intracellular ROS levels and apoptosis were also significantly increased in a concentration-dependent manner. In line with this, protein levels of Bax and cytochrome C were increased and Bcl-2 was decreased by arsenic treatments. Increases in caspase 3 activity were observed. These results indicate that Trx is involved in arsenic-induced liver cell injury, probably through the apoptotic signaling pathway. However, further studies are needed to elucidate on these findings.

Changes in Serum Adiponectin in Mice Chronically Exposed to Inorganic Arsenic in Drinking Water

Cardiovascular disease and diabetes mellitus are prominent features of glucose and lipid metabolism disorders. Adiponectin is a key adipokine that is largely involved in glucose and lipid metabolism processes. A growing body of evidence suggests that chronic exposure to inorganic arsenic is associated with cardiovascular disease and diabetes mellitus. We hypothesized that arsenic exposure may increase the risk of cardiovascular disease and diabetes mellitus by affecting the level of adiponectin. In this study, we examined serum adiponectin levels, as well as serum levels of metabolic measures (including fasting blood glucose, insulin, total cholesterol, triglyceride, and high-density lipoprotein (HDL)-cholesterol) in C57BL/6 mice exposed to inorganic arsenic in drinking water (5 and 50 ppm NaAsO₂) for 18 weeks. Body mass and adiposity were monitored throughout the study. We found no significant changes in serum insulin and glucose levels in mice treated with arsenic for 18 weeks. However, arsenic exposure decreased serum levels of adiponectin, triglyceride, and HDL-cholesterol. Further, an inverse relationship was observed between urinary concentrations of total arsenic and serum levels of adiponectin. This study suggests that arsenic exposure could disturb the metabolism of lipids and increase the risk of cardiovascular disease by reducing the level of adiponectin.

Tissue-specific distributions of inorganic arsenic and its methylated metabolites, especially in cerebral cortex, cerebellum and hippocampus of mice after a single oral administration of arsenite

Groundwater contaminated with inorganic arsenic (iAs) is the main source of human exposure to arsenic and generates a global health issue. In this study, the urinary excretion, as well as the time-course distributions of various arsenic species in murine tissues, especially in different brain regions were determined after a single oral administration of 2.5, 5, 10 and 20mg/kg sodium arsenite (NaAsO₂). Our data showed that the peak times of urinary, hepatic and nephritic total arsenic (TAs) were happened at about 1h, then TAs levels decreased gradually and almost could not be observed after 72h. On contrast, the time course of TAs in lung, urinary bladder and different brain regions exhibited an obvious process of accumulation and elimination,and the peak times were nearly at 6h to 9h. TAs levels of 10 and 20mg/kg NaAsO₂ groups were significantly higher than 2.5 and 5mg/kg groups, and the amounts of TAs in 5mg/kg groups were in the order of liver>lung>kidney>urinary bladder>hippocampus>cerebral cortex>cerebellum. In addition, iAs was the most abundant species in liver and kidney, while lung and urinary bladder accumulated the highest concentrations of dimethylated arsenicals (DMA). What's more, the distributions of arsenic species were not homogeneous among different brain regions, as DMA was the sole species in cerebral cortex and cerebellum, while extremely high concentrations and percentages of monomethylated arsenicals (MMA) were found in hippocampus. These results demonstrated that distributions of iAs and its methylated metabolites were tissue-specific and even not homogeneous among different brain regions, which must be considered as to the tissue- and region-specific toxicity of iAs exposure. Our results thus provide useful information for clarifying and reducing the uncertainty in the risk assessment for this metalloid.

Individual and Combined Effects of Arsenic and Lead on Behavioral and Biochemical Changes in Mice

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.

Subchronic Arsenic Exposure Through Drinking Water Alters Lipid Profile and Electrolyte Status in Rats

Arsenic is a groundwater pollutant and can cause various cardiovascular disorders in the exposed population. The aim of the present study was to assess whether subchronic arsenic exposure through drinking water can induce vascular dysfunction associated with alteration in plasma electrolytes and lipid profile. Rats were exposed to arsenic as 25, 50, and 100 ppm of sodium arsenite through drinking water for 90 consecutive days. On the 91st day, rats were sacrificed and blood was collected. Lipid profile and the levels of electrolytes (sodium, potassium, and chloride) were assessed in plasma. Arsenic reduced high-density lipoprotein cholesterol (HDL-C) and HDL-C/LDL-C ratio, but increased the levels of triglycerides, total cholesterol, low-density lipoprotein cholesterol (LDL-C), and electrolytes. The results suggest that the arsenic-mediated dyslipidemia and electrolyte retention could be important mechanisms in the arsenic-induced vascular disorder.

Ameliorative effect of two Ayurvedic herbs on experimentally induced arsenic toxicity in calves

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic arsenic poisoning due to contaminated subsoil water is a threat to society in West Bengal, India and in Bangladesh. The human being may also be affected by the exposed cattle from the affected area by consuming milk, egg, meat and others. In Ayurveda, several herbs like Haridra (turmeric), Shunthi (dried ginger root) and others are used for the management of arsenic poisoning.

AIM OF THE STUDY

The study was conducted to find out the ameliorative effect of turmeric and ginger powder against experimentally induced arsenic toxicity in calves.

MATERIALS AND METHODS

Twenty four calves were divided into four groups (group I, II, III and IV) having six animals in each group. Animals of group I, II and III were orally administered with sodium arsenite at 1mg/kg body weight for 90 days and in addition group II and group III animals were treated orally with turmeric and ginger powder respectively at 10mg/kg body weight from 46th day onwards. Group IV animals were given food and water without drug and served as control. Arsenic content was estimated in faeces, hair, urine and plasma in every 15 days. Bio-chemical, haematological and anti-oxidant parameters were also assessed.

RESULTS

Turmeric and ginger powder significantly (P<0.05) reduced the plasma and hair arsenic levels through increased excretion via faeces and urine. Haemoglobin level, TEC and TLC were decreased in groups I, II and III, however these were improved significantly (P<0.05) from 75th day onwards in turmeric and ginger treated groups. Increased activity of AST and ALT were significantly decreased (P<0.05) from 75th day onwards in group II and III. Blood urea nitrogen and plasma creatinine were also significantly decreased (P<0.05) in group II and III than group I from 60th day onwards. The SOD and catalase activity were significantly (P<0.05) reduced in groups I, II and III, but these were restored at the end of the experiment in turmeric and ginger treated groups.

CONCLUSION

The test drugs are found significantly effective not only to eliminate arsenic from the body but also give protection from possible damage caused by arsenic exposure, it may be concluded from the present study that turmeric and ginger can be helpful in the therapy of chronic arsenic toxicity in calves.

Co-delivery of doxorubicin and arsenite with reduction and pH dual-sensitive vesicle for synergistic cancer therapy

Drug resistance is the underlying cause for therapeutic failure in clinical cancer chemotherapy. A prodrug copolymer mPEG-PAsp(DIP-co-BZA-co-DOX) (PDBD) was synthesized and assembled into a nanoscale vesicle comprising a PEG corona, a reduction and pH dual-sensitive hydrophobic membrane and an aqueous lumen encapsulating doxorubicin hydrochloride (DOX·HCl) and arsenite (As). The dual stimulation-sensitive design of the vesicle gave rise to rapid release of the physically entrapped DOX·HCl and arsenite inside acidic lysosomes, and chemically conjugated DOX inside the cytosol with high glutathione (GSH) concentration. In the optimized concentration range, arsenite previously recognized as a promising anticancer agent from traditional Chinese medicine can down-regulate the expressions of anti-apoptotic and multidrug resistance proteins to sensitize cancer cells to chemotherapy. Consequently, the DOX-As-co-loaded vesicle demonstrated potent anticancer activity. Compared to the only DOX-loaded vesicle, the DOX-As-co-loaded one induced more than twice the apoptotic ratio of MCF-7/ADR breast cancer cells at a low As concentration (0.5 μM), due to the synergistic effects of DOX and As. The drug loading strategy integrating chemical conjugation and physical encapsulation in stimulation-sensitive carriers enabled efficient drug loading in the formulation.

Oleuropein ameliorates arsenic induced oxidative stress in mice

The objective of this study is to investigate the potential preventive effect of oleuropein in an experimental arsenic toxicity in mice. For this purpose, mice were exposed to 5mg/kg/day sodium arsenite (NaAsO2) in drinking water and treated with 30mg/kg/day oleuropein for 15 days. At the end of the experiment, animals were sacrificed and selected organs were processed for biochemical and histopahtological investigations. Blood, liver, kidney and brain malondialdehyde (MDA) and nitric oxide (NO) levels were determined by colorimetric methods. Protein carbonyl content is measured by a commercial kit. Liver morphology and immunoreactivity for inducible NOS (iNOS) and endothelial NOS (eNOS) was evaluated microscopically. Level of NO was determined to decrease in blood and tissues whereas MDA increased in arsenic given mice. Tissue protein carbonyl content also increased in this group. Immunoreactivity for iNOS and eNOS was noted to increase with arsenic treatment. Oleuropein treatment had significant effects in normalizing the MDA and NO levels as well as protein carbonyl content. Immunohistochemical staining also showed reduction of the expression of iNOS and eNOS in liver. The results indicate that oleuropein ameliorates oxidative tissue damage by scavenging free radicals.

Effects of Sodium Arsenite and Arsenate in Testicular Histomorphometry and Antioxidants Enzymes Activities in Rats

The main source of environmental arsenic exposure in most countries of the world is drinking water in which inorganic forms of arsenic predominate. The present study was aimed to test the impact of two different compounds of inorganic arsenic in histomorphometric and enzymatic parameters in the testes by oral exposition. Adult Wistar male rats were exposed to sodium arsenite and arsenate in drinking water, testing for each chemical form the concentrations of 0.01 and 10 mg/L per 56 days. The animals intoxicated with arsenic, mainly sodium arsenite, showed reduction in the percentage of seminiferous epithelium and in proportion and volume of Leydig cells. Moreover, there was an increase in the percentage of tunica propria, lumen, lymphatic space, blood vessels, and macrophages. The activity of superoxide dismutase (SOD) did not change among the groups. However, the activity of catalase (CAT) decreased in animals exposed to both arsenic compounds. In addition, the higher concentration of arsenic, mainly as sodium arsenite, caused vacuolization in the seminiferous epithelium. The body and testes weight as well as testosterone concentration remained unchanged among the groups. In conclusion, exposition to arsenic, mainly as sodium arsenite, caused alteration in histomorphometric parameters and antioxidant defense system in the testes.

Effect of Acetyl-L-Carnitine on Antioxidant Status, Lipid Peroxidation, and Oxidative Damage of Arsenic in Rat

Arsenic (As) is a widespread environmental contaminant present around the world in both organic and inorganic forms. Oxidative stress is postulated as the main mechanism for As-induced toxicity. This study was planned to examine the protective effect of acetyl-L-carnitine (ALC) on As-induced oxidative damage in male rats. Animals were randomly divided into four groups of control (saline), sodium arsenite (NaAsO2, 20 mg/kg), ALC (300 mg/kg), and NaAsO2 plus ALC. Animals were dosed orally for 28 successive days. Blood and tissue samples including kidney, brain, liver, heart, and lung were collected on the 28th day and evaluated for oxidative damage and histological changes. NaAsO2 exposure caused a significant lipid peroxidation as evidenced by elevation in thiobarbituric acid-reactive substances (TBARS). The activity of antioxidant enzymes such as glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), as well as sulfhydryl group content (SH group) was significantly suppressed in various organs following NaAsO2 treatment (P < 0.05). Furthermore, NaAsO2 administration increased serum values of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and bilirubin. Our findings revealed that co-administration of ALC and NaAsO2 significantly suppressed the oxidative damage induced by NaAsO2. Tissue histological studies have confirmed the biochemical findings and provided evidence for the beneficial role of ALC. The results concluded that ALC attenuated NaAsO2-induced toxicity, and this protective effect may result from the ability of ALC in maintaining oxidant-antioxidant balance.

[Study on congenital cardiac anomalies induced by arsenic exposure before and during maternal pregnancy in fetal rats]

OBJECTIVE

To investigate the effects of arsenic exposure before and during maternal pregnancy on heart development of fetal rats.

METHODS

According to body weight, thirty-two female SD rats (30 to 40 days of age) were randomly divided into control group, low dose group, middle dose group and high dose group with 8 rats per group. They were allowed free access to drinking water with 0, 37.5, 75 and 150 mg/L of sodium arsenite (NaAsO2) for 6 weeks, respectively. Then all the female rats and adult male SD rats were caged together for mating. Once female rats were determined to be pregnant, they would continue to drink deionized distilled water containing different concentrations of sodium arsenite for another 2 weeks. On embryonic day 16, rats were sacrificed to harvest fetuses. Female rats' weight changes, abortions, absorbed fetus number, growth and development of fetal rats were observed. Hematoxylin-eosin staining of serial cardiac slices was performed in embryos to observe cardiac morphology and structure. Fur arsenic contents of female rats were determined with the method of atomic fluorescence spectrometry.

RESULTS

Subchronic arsenic exposure caused slow weight growth in female rats. There were two cases of abortion in middle dose group and high dose group, respectively. Compared with these of control group, fetal and placental weight decreased (P < 0.05), and the incidence of fetal absorption increased (P < 0.05) in all arsenic-treated groups. Cardiac malformations in fetal rats including ventricular septal defect, atrial septal defect and tetralogy of Fallot were observed in low, middle and high dose group. The incidence of cardiac malformations increased with the increase of arsenic concentrations in drinking water. Compared with that of control group, the incidence of cardiac malformations remarkably increased in both middle and high dose groups (P < 0.05). Fur arsenic contents increased with the increase of arsenic concentrations in drinking water (P < 0.01).

CONCLUSION

Arsenic exposure before and during maternal pregnancy could cause abnormal cardiac development in fetal rats, and increased the risk of congenital heart disease.

High accumulation of arsenic in the esophagus of mice after exposure to arsenite

Arsenic-induced toxicity appears to be dependent on the tissue- or cell-specific accumulation of this metalloid. An early study showed that arsenic was retained in the esophagus as well as the liver, kidney cortex and skin of marmosets after intraperitoneal administration of (74)As-arsenite. However, there is little available information regarding the distribution of arsenic in the esophagus. Here, we compared the retention of arsenic in the esophagus, liver, lung, kidney and heart in mice intraperitoneally administered 1 or 5 mg/kg sodium arsenite (As(III)) daily for 3 or 7 days. The results showed that the arsenic concentration was highest in the esophagus. We compared the mRNA levels of aquaglyceroporin (AQP) 3, AQP7 and AQP9, which are responsible for arsenic influx, and those of multidrug-resistance protein (MRP) 1 and MRP2, which are responsible for arsenic efflux. The levels of AQP3 mRNA in the esophagus were much higher than those in liver, lung and heart, while the mRNA levels of MRP2 were very low in the esophagus. In addition, we found extremely low expression of Nrf2 in the esophagus at the basal and under the activated conditions, which might have resulted in low levels of glutamyl-cysteine ligase catalytic and modulatory subunits, and subsequently in the low levels of glutathione. Thus, the highest retention of arsenic was detected in the esophagus after intraperitoneal administration of As(III) to mice, and this appeared to result from multiple factors, including high expression of AQP3, low expression of MRP2, low capacity of glutathione synthesis and low activation of Nrf2.

KML001 displays vascular disrupting properties and irinotecan combined antitumor activities in a murine tumor model

KML001 is sodium metaarsenite, and has shown cytotoxic activity in human tumor cell lines. The anti-cancer mechanism of KML001 involves cancer cell destruction due to DNA damage at the telomeres of cancer cell chromosomes. In this study, we assessed the vascular disrupting properties of KML001 and investigated whether KML001 as VDA is able to increase anti-tumor activity in irinotecan combined treatment. We used a murine model of the CT26 colon carcinoma cell line. CT26 isograft mice treated intraperitoneally with 10 mg/kg KML001 displayed extensive central necrosis of tumor by 24 h. The vascular disrupting effects of KML001 were assessed by dynamic contrast enhanced magnetic resonance imaging. Gadopentetic acid-diethylene triaminepentaacetic acid contrast enhancement was markedly decreased in KML001-treated mice one day after treatment, whereas persistently high signal enhancement was observed in mice injected with saline. Rate constant K(ep) value representing capillary permeability was significantly decreased (p<0.05) in mice treated with KML001. Cytoskeletal changes of human umbilical vein endothelial cells (HUVECs) treated with 10 uM KML001 were assessed by immune blotting and confocal imaging. KML001 degraded tubulin protein in HUVECs, which may be related to vascular disrupting properties of KML001. Finally, in the mouse CT26 isograft model, KML001 combined with irinotecan significantly delayed tumor growth as compared to control and irinotecan alone. These results suggest that KML001 is a novel vascular disrupting agent, which exhibits significant vascular shut-down activity and enhances anti-tumor activity in combination with chemotherapy. These data further suggest an avenue for effective combination therapy in treating solid tumors.

[Purification of arsenic-binding proteins in hamster plasma after oral administration of arsenite]

OBJECTIVE

To purify the arsenic-binding proteins (As-BP) in hamster plasma after a single oral administration of arsenite (iAs(III)).

METHODS

Arsenite was given to hamsters in a single dose. Three types of HPLC columns, size exclusion, gel filtration and anion exchange columns, combined with an inductively coupled argon plasma mass spectrometer (ICP MS) were used to purify the As-BP in hamster plasma. SDS-PAGE was used to confirm the arsenic-binding proteins at each purification step.

RESULTS

The three-step purification process successfully separated As-BP from other proteins (ie, arsenic unbound proteins) in hamster plasma. The molecular mass of purified As-BP in plasma was approximately 40-50 kD on SDS-PAGE.

CONCLUSION

The three-step purification method is a simple and fast approach to purify the As-BP in plasma samples.

[Comparison of the total arsenic concentration between saliva and blood after oral administration of sodium arsenite to rats]

OBJECTIVE

To compare the total arsenic concentration between blood and saliva after oral administration of sodium arsenite to SD rats.

METHODS

A single oral gavage dose of sodium arsenite (20mg/kg) was administrated to 21 adult male Sprague-Dawley rats. Then collected blood and saliva samples at 0, 1-2, 4-5, 7-8, 11-12, 17-18, 23-24 hour for total arsenic detection. The blood samples were detected for total arsenic concentration by Atomic Fluorescence Spectrometry (AFS-230) and the salivary arsenic were detected by inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

After intake of 20 mg/kg BW sodium arsenite, the total arsenic concentration in blood of SD rats was increased rapidly, and reached the peak value at the 1-2 hour, then descended gradually. However, there was a second peak value at the 7-8 hour. The upward trend of salivary arsenic was more slowly than blood arsenic, and reached the peak value at the 7-8 hour, then descended gradually. The variation tendency of salivary arsenic and blood arsenic with time were basically the same. Besides, there was an obvious positive association between them, the correlation coefficient was 0.678, P < 0.01.

CONCLUSION

The excretion of arsenic in saliva was slower than that of blood samples after administrated a single oral gavage dose of sodium arsenite (20 mg/kg) to SD rate, but the metabolism mode of arsenic in saliva was similar with that in blood, suggested that salivary arsenic can also well reflect the exposure level of arsenic in the body.

Subacute arsenic exposure through drinking water reduces the pharmacodynamic effects of ketoprofen in male rats

We evaluated the modulatory role of the groundwater contaminant arsenic on the pharmacodynamic responses of the nonsteroidal analgesic-antipyretic drug ketoprofen and the major pro-inflammatory mediators linked to the mechanism of ketoprofen's therapeutic effects. Rats were pre-exposed to sodium arsenite (0.4, 4 and 40 ppm) through drinking water for 28 days. The pharmacological effects of orally administered ketoprofen (5 mg/kg) were evaluated the following day. Pain, inflammation and pyretic responses were, respectively, assessed through formalin-induced nociception, carrageenan-induced inflammation and lipopolysaccharide-induced pyrexia. Arsenic inhibited ketoprofen's analgesic, anti-inflammatory and antipyretic effects. Further, arsenic enhanced cyclooxygenase-1 and cyclooxygenase-2 activities and tumor necrosis factor-α, interleukin-1β and prostaglandin-E(2) production in hind paw muscle. These results suggest a functional antagonism of ketoprofen by arsenic. This may relate to arsenic-mediated local release of tumor necrosis factor-α and interleukin-1β, which causes cyclooxygenase induction and consequent prostaglandin-E(2) release. In conclusion, subacute exposure to environmentally relevant concentrations of arsenic through drinking water may aggravate pain, inflammation and pyrexia and thereby, may reduce the therapeutic efficacy of ketoprofen.

Using iron precipitants to remove arsenic from water: is it safe?

Arsenic-associated health complications are reported worldwide. Arsenic is a documented toxic element in drinking water. Removing arsenic from drinking water is widely dependent on iron-based techniques. Although inorganic arsenic has long been known to be toxic to humans, little is known about the toxic effect of the interaction between arsenic and iron. We investigated the effect of arsenic plus iron on the liver of rats. We gave rats sodium arsenite, iron, or sodium arsenite plus iron. Neither the arsenic-alone nor the iron-alone treatments altered their serum aspartate or alanine transaminase levels. However, a combination of non-toxic doses of arsenite and iron synergistically increased serum aspartate and alanine transaminase levels and lipid peroxidation in liver tissue. Therefore, we hypothesize that arsenic plus iron synergistically induces hepatic damage mediated through oxidative stress in rats. Our study indicates an important public health issue: using iron precipitants to remove arsenic from water may cause oxidative hepatic damage in humans.

Arsenite induces aquaglyceroporin 9 expression in murine livers

Mice exposed to sodium arsenite show a dose-related accumulation of inorganic arsenic (iAs) and its methylated metabolites in the liver. While the accumulation of iAs forms increased linearly with dose in liver cells, a different pattern was observed in other tissues such as the brain and lung, as well as in the peripheral nerves of the rat. As such, trivalent iAs enters the cells, using aquaglyceroporin transporters to modulate cell arsenic accumulation and cytotoxicity. We investigated here if the dose-related accumulation of arsenic in the liver was related to the expression of aquaglyceroporin 9 (AQP9) in the same organ. CD1 male mice were treated with different concentrations (0, 2.5, 5 or 10mg/kg/day) of sodium arsenite during 1, 3 or 9 days. A significant dose-related, up-regulation of AQP9 mRNA and protein was observed and which was verified by immunohistochemistry in liver sections using specific antibodies. The increased transcription of AQP9 has been observed in fasting and diabetic rats, suggesting that this channel could play a role in the diabetogenic effect of arsenic.

Biological responses of duckweed (Lemna minor L.) exposed to the inorganic arsenic species As(III) and As(V): effects of concentration and duration of exposure

The accumulation of arsenic (As) and physiological responses of Lemna minor L. under different concentration (0, 1, 4, 16 and 64 microM) and duration (1, 2, 4 and 6 days) of two species As, NaAsO(2) and Na(2)HAsO(4).7H(2)O, were studied in hydroponics. The accumulation of both As species depended on As concentration and exposure duration. The highest accumulation of As was found as 17408 and 8674 microg g(-1), for plants exposed to 64 microM of As(III) and As(V), respectively, after 6 days. Two-way ANOVA analyses indicated that, for plants exposed to arsenite (As(III)), exposure duration had a greater effect than concentration on As accumulation. Conversely, exposure concentration had a greater effect on As accumulation in plants exposed to arsenate (As(V)). Arsenic exposure levels, approaching 16 microM for As(III) and 64 microM for As(V), did not significantly affect EC values. Beyond these exposure concentrations, EC values increased in a manner that depended on duration. Significant effect of As(III) on lipid peroxidation was observed at 1 microM application whereas, this effect started to be significant after an exposure to 16 microM As(V). For both As(III) and As(V), photosynthetic pigment levels slightly increased for the first day with respect to the control, followed by a gradual decline at higher concentrations and durations. An increase in protein content and enzyme activity was observed at moderate exposure conditions, followed by a decrease. Significant positive correlations were determined between accumulated As and ion leakage and lipid peroxidation. Negative correlations were found between accumulated As and total chlorophyll and protein content. Our results suggested that exposure duration and concentration had a strong synergetic effect on antioxidant enzyme activity. The findings of the present study may be useful when this plant is used as a phytoremediator in arsenic-polluted water.

Arsenic exposure in utero and nonepidermal proliferative response in adulthood in Tg.AC mice

To expand our knowledge on the transplacental carcinogenic potential of inorganic arsenic, pregnant Tg.AC mice received drinking water with 0, 42.5, or 85 ppm arsenite from gestation day 8 to 18. After birth, groups (n = 25) of offspring received topical 12-O-tetradecanoyl phorbol-13-acetate (TPA) (2 microg twice a week) for 36 weeks and were killed; nonskin tumors were assessed. Arsenic increased adrenal cortical adenomas (ACAs; 25%-29%) compared with control (0%) independent of TPA in all male groups. Arsenic increased urinary bladder (UB) hyperplasia in males, but only with TPA. Arsenic induced ACAs in all female groups (control 0%; arsenic 17%-26%). Arsenic-treated females had UB hyperplasia in most groups (control 0%; arsenic 26%-32%), with 2 UB papillomas. All arsenic-treated females had uterine hyperplasia (26%-40%; control 4%) independent of TPA, and 3 had uterine tumors. Thus, arsenic in utero rapidly induces ACAs and uterine and UB preneoplasias in Tg.AC mice, showing transplacental carcinogenic potential in yet another strain of mice.

Transcriptional changes associated with reduced spontaneous liver tumor incidence in mice chronically exposed to high dose arsenic

Exposure of male C3H mice in utero (from gestational days 8-18) to 85ppm sodium arsenite via the dams' drinking water has previously been shown to increase liver tumor incidence by 2 years of age. However, in our companion study (Ahlborn et al., 2009), continuous exposure to 85ppm sodium arsenic (from gestational day 8 to postnatal day 365) did not result in increased tumor incidence, but rather in a significant reduction (0% tumor incidence). The purpose of the present study was to examine the gene expression responses that may lead to the apparent protective effect of continuous arsenic exposure. Genes in many functional categories including cellular growth and proliferation, gene expression, cell death, oxidative stress, protein ubiquitination, and mitochondrial dysfunction were altered by continuous arsenic treatment. Many of these genes are known to be involved in liver cancer. One such gene associated with rodent hepatocarcinogenesis, Scd1, encodes stearoyl-CoA desaturase and was down-regulated by continuous arsenic treatment. An overlap between the genes in our study affected by continuous arsenic exposure and those from the literature affected by long-term caloric restriction suggests that reduction in the spontaneous tumor incidence under both conditions may involve similar gene pathways such as fatty acid metabolism, apoptosis, and stress response.

Acute and subchronic toxicity of arsenite and zinc to tadpoles of Rhinella arenarum both alone and in combination

The current study evaluated acute and subchronic toxicity of arsenite (As(3+)) and zinc (Zn(2+)) to stage 25 tadpoles of Rhinella arenarum in both single and joint laboratory exposures. LC50 values obtained for As(3+) were elevated and remained within the range of 46 to 50 mg/L of As(3+) between 4 and 17 d of exposure. Growth of tadpoles was completely inhibited with 30 mg/L of As(3+), demonstrating the presence of ecologically relevant sublethal effects at concentrations lower than those resulting in lethality. With respect to Zn(2+), a 96-h LC50 value of 2.49 mg/L was calculated in soft water. Contrary to results obtained for As(3+), LC50 values of Zn(2+) gradually decreased with increasing exposure duration, from 2.49 mg/L at 96 h to 1.30 mg/L after 21 d. In joint exposures to both metals, the type of interaction observed between As(3+) and Zn(2+) was concentration dependent. Lethal effects of As(3+) were mitigated, unaffected, or potentiated by 0.01, 0.1, and 1-2 mg/L of Zn(2+), respectively. However, although 0.01 mg/L of Zn(2+) significantly reduced lethality of As(3+)-exposed tadpoles, the same concentration of Zn(2+) did not help to reverse the stunt growth of these animals. Further studies need to examine which are the lowest concentrations As(3+) required to reduce growth and whether Zn(2+) serves to antagonize growth effects in this range of concentrations.

A trial of the efficacy, safety and impact on drug resistance of four drug regimens for seasonal intermittent preventive treatment for malaria in Senegalese children

In the Sahel, most malaria deaths occur among children 1-4 years old during a short transmission season. A trial of seasonal intermittent preventive treatment (IPT) with sulfadoxine-pyrimethamine (SP) and a single dose of artesunate (AS) showed an 86% reduction in the incidence of malaria in Senegal but this may not be the optimum regimen. We compared this regimen with three alternatives.

METHODS

2102 children aged 6-59 months received either one dose of SP plus one dose of AS (SP+1AS) (the previous regimen), one dose of SP plus 3 daily doses of AS (SP+3AS), one dose of SP plus three daily doses of amodiaquine (AQ) (SP+3AQ) or 3 daily doses of AQ and AS (3AQ+3AS). Treatments were given once a month on three occasions during the malaria transmission season. The primary end point was incidence of clinical malaria. Secondary end-points were incidence of adverse events, mean haemoglobin concentration and prevalence of parasites carrying markers of resistance to SP.

FINDINGS

The incidence of malaria, and the prevalence of parasitaemia at the end of the transmission season, were lowest in the group that received SP+3AQ: 10% of children in the group that received SP+1AS had malaria, compared to 9% in the SP+3AS group (hazard ratio HR 0.90, 95%CI 0.60, 1.36); 11% in the 3AQ+3AS group, HR 1.1 (0.76-1.7); and 5% in the SP+3AQ group, HR 0.50 (0.30-0.81). Mutations associated with resistance to SP were present in almost all parasites detected at the end of the transmission season, but the prevalence of Plasmodium falciparum was very low in the SP+3AQ group.

CONCLUSIONS

Monthly treatment with SP+3AQ is a highly effective regimen for seasonal IPT. Choice of this regimen would minimise the spread of drug resistance and allow artemisinins to be reserved for the treatment of acute clinical malaria.

In vivo distribution of arsonoliposomes: Effect of vesicle lipid composition

Sonicated arsonoliposomes were prepared using arsonolipid with palmitic acid acyl chain (C16), mixed with 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC-based), and cholesterol (Chol) with a molar ratio C16/DSPC/Chol 8:12:10. PEG-lipid (1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated to polyethylenoglycol 2000) containing vesicles (Pegylated-arsonoliposomes) were also prepared. DSPC-based and Pegylated-arsonoliposomes, were administered by intraperitoneal injection in balb/c mice (15 mg arsenic/kg) and the distribution of As in the organs was measured by atomic absorption spectroscopy. Results demonstrate that a high portion of the dose administered is rapidly excreted since 1 h post-injection only about 30-40% of the dose was detected cumulatively in animal tissues. After this, the whole body elimination of arsenic was a slow process with a half-life of 27.6 h for Pegylated-arsonoliposomes, and 83 h, for the DSPC-based ones. For both arsonoliposomes, arsenic distribution was greater in intestines, followed by liver, carcass+skin stomach, spleen, kidney, lung and heart. Different arsenic kinetics in blood between the two liposome types were observed. Compared to the results obtained previously with PC-based arsonoliposomes, both the DSPC-based and Pegylated-arsonoliposomes have better bioavailability. This proves that arsonoliposome lipid composition (and consequently their integrity) influences their pharmacokinetic profile. Thus, the proper arsonoliposome composition should be used according to the intended application.

Quantitative GFP fluorescence as an indicator of arsenite developmental toxicity in mosaic heat shock protein 70 transgenic zebrafish

In transgenic zebrafish (Danio rerio), green fluorescent protein (GFP) is a promising marker for environmental pollutants. In using GFP, one of the obstacles which we faced was how to compare toxicity among different toxicants or among a specific toxicant in different model species with the intensity of GFP expression. Using a fluorescence detection method, we first validated our method for estimating the amount of GFP fluorescence present in transgenic fish, which we used as an indicator of developmental toxicity caused by the well-known toxicant, arsenite. To this end, we developed mosaic transgenic zebrafish with the human heat shock response element (HSE) fused to the enhanced GFP (EGFP) reporter gene to indicate exposure to arsenite. We confirmed that EGFP expression sites correlate with gross morphological disruption caused by arsenite exposure. Arsenite (300.0 microM) caused stronger EGFP fluorescence intensity and quantity than 50.0 microM and 10.0 microM arsenite in our transgenic zebrafish. Furthermore, arsenite-induced apoptosis was demonstrated by TUNEL assay. Apoptosis was inhibited by the antioxidant, N-acetyl-cystein (NAC) in this transgenic zebrafish. The distribution of TUNEL-positive cells in embryonic tissues was correlated with the sites of arsenite toxicity and EGFP expression. The EGFP values quantified using the standard curve equation from the known GFP quantity were consistent with the arsenite-induced EGFP expression pattern and arsenite concentration, indicating that this technique can be a reliable and applicable measurement. In conclusion, we propose that fluorescence-based EGFP quantification in transgenic fish containing the hsp70 promoter-EGFP reporter-gene construct is a useful indicator of development toxicity caused by arsenite.

Endoplasmic reticulum stress is involved in arsenite-induced oxidative injury in rat brain

The mechanism underlying sodium arsenite (arsenite)-induced neurotoxicity was investigated in rat brain. Arsenite was locally infused in the substantia nigra (SN) of anesthetized rat. Seven days after infusion, lipid peroxidation in the infused SN was elevated and dopamine level in the ipsilateral striatum was reduced in a concentration-dependent manner (0.3-5 nmol). Furthermore, local infusion of arsenite (5 nmol) decreased GSH content and increased expression of heat shock protein 70 and heme oxygenase-1 in the infused SN. Aggregation of alpha-synuclein, a putative pathological protein involved in several CNS neurodegenerative diseases, was elevated in the arsenite-infused SN. From the breakdown pattern of alpha-spectrin, both necrosis and apoptosis were involved in the arsenite-induced neurotoxicity. Pyknotic nuclei, cellular shrinkage and cytoplasmic disintegration, indicating necrosis, and TUNEL-positive cells and DNA ladder, indicating apoptosis was observed in the arsenite-infused SN. Arsenite-induced apoptosis was mediated via two different organelle pathways, mitochondria and endoplasmic reticulum (ER). For mitochondrial activation, cytosolic cytochrome c and caspase-3 levels were elevated in the arsenite-infused SN. In ER pathway, arsenite increased activating transcription factor-4, X-box binding protein 1, C/EBP homologues protein (CHOP) and cytosolic immunoglobulin binding protein levels. Moreover, arsenite reduced procaspase 12 levels, an ER-specific enzyme in the infused SN. Taken together, our study suggests that arsenite is capable of inducing oxidative injury in CNS. In addition to mitochondria, ER stress was involved in the arsenite-induced apoptosis. Arsenite-induced neurotoxicity clinically implies a pathophysiological role of arsenite in CNS neurodegeneration.

Acute toxicity of sodium arsenite in a complex food matrix

Acute toxicity of a single oral dose of sodium arsenite (As), administered in half and half cream (HH), was assessed in male and non-pregnant female rats (0.41, 4.1, 41.0 and 410.0mg/kg body weight) and pregnant rats (0.41, 4.1 and 41.0mg/kg body weight). Control rats received deionized water alone, HH alone or 41.0mg/kg As in deionized water (41 mg/kg As-water). Male and non-pregnant rats were monitored for 14 consecutive days post-dosing. Pregnant rats, dosed on gestation day 10 (GD-10), were monitored until fetuses were collected on GD 20. High mortality (100%) was observed in male and non-pregnant female rats exposed to 410.0mg/kg As-HH. Low mortality (25%) was observed in non-pregnant female rats exposed to 41 mg/kg As-water. No mortality was observed in other control or treated groups. Reduced female fetal numbers were observed in the 41 mg/kg As-water group but not in the other control groups. Developmental effects were not observed in the controls or the As-HH treatment groups. In conclusion, As toxicity was not reduced when a high dose (410 mg/kg) was administered in HH however, at lower doses (41 mg/kg), HH reduced acute As oral toxicity in the female and developing fetus.

Trypanocidal activity of arsonoliposomes: Effect of vesicle lipid composition

Sonicated arsonoliposomes were prepared using an arsonolipid with palmitic acid acyl chain (C16), mixed with phosphatidylcholine (PC-based) or 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC-based), and cholesterol (Chol) with a molar ratio C16 /PC or DSPC/ Chol 8:12:10. PEG-lipid (1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated to polyethylenoglycol 2000) containing vesicles (pegylated-arsonoliposomes) were also prepared. The in vitro and in vivo trypanocidal activity of the various types of arsonoliposomes was evaluated. Although PC-based arsonoliposomes exhibited in vivo activity on an acute trypanosomiasis animal model, no evidence of activity was demonstrated for DSPC-based or pegylated-arsonoliposomes on a chronic model. Despite the fact that DSPC-based and pegylated-arsonoliposomes have better bioavailability compared to PC-based ones, their in vitro activity is lower than that of PC-based arsonoliposomes, indicating the importance of arsonoliposome lipid composition on their trypanocidal activity and suggesting that further arsonoliposome structure design is required to overcome these disadvantages.

Sequential treatment by ionizing radiation and sodium arsenite dramatically accelerates TRAIL-mediated apoptosis of human melanoma cells

Melanoma is the most lethal form of skin cancer. There is a lack of effective treatments for individuals with advanced disease. Many melanomas exhibit high levels of radioresistance. The direct consequence of gamma-irradiation for most melanoma cells is growth arrest at the G2-M phase of cell cycle. However, radiation-induced signaling pathways may affect numerous additional targets in cancer cells. We show in the present study that gamma-irradiation, as well as alpha-particle exposure, dramatically increases the susceptibility of melanoma cells to recombinant tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-mediated apoptosis via up-regulation of surface TRAIL-receptor 1/receptor 2 (DR4/DR5) levels and to Fas ligand-mediated apoptosis via up-regulation of surface Fas levels. Additionally, increased dynamin-2 expression after irradiation is critically important in the translocation of death receptor to the cell surface. Moreover, sodium arsenite treatment may up-regulate expression of endogenous TRAIL and induces its translocation to cell surface and further down-regulates cFLIP levels in melanoma cells. We have evaluated the effects of sequential gamma-irradiation and arsenite treatment of melanoma cells for the induction of death signaling. Such treatment results in an efficient TRAIL-mediated apoptosis via a paracrine mechanism. These data highlight the efficacy of combined modality treatment involving radiation and arsenite in clinical management of this often fatal form of skin cancer.

Preliminary morphological and morphometric study of rat cerebellum following sodium arsenite exposure during rapid brain growth (RBG) period

The effects of arsenic exposure during rapid brain growth (RBG) period were studied in rat brains with emphasis on the Purkinje cells of the cerebellum. The RBG period in rats extends from postnatal day 4 (PND 4) to postnatal day 10 (PND 10) and is reported to be highly vulnerable to environmental insults. Mother reared Wistar rat pups were administered intraperitoneal injections (i.p.) of sodium arsenite (aqueous solution) in doses of 1.0, 1.5 and 2.0mg/kg body weight (bw) to groups II, III and IV (n=6 animals/group) from PND 4 to 10 (sub acute). Control animals (group I) received distilled water by the same route. On PND 11, the animals were perfusion fixed with 4% paraformaldehyde in 0.1M phosphate buffer (PB) with pH 7.4. The cerebellum obtained from these animals was post-fixed and processed for paraffin embedding. Besides studying the morphological characteristics of Purkinje cells in cresyl violet (CV) stained paraffin sections (10 microm), morphometric analysis of Purkinje cells was carried out using Image Analysis System (Image Proplus software version 4.5) attached to Nikon Microphot-FX microscope. The results showed that on PND 11, the Purkinje cells were arranged in multiple layers extending from Purkinje cell layer (PL) to outer part of granule cell layer (GL) in experimental animals (contrary to monolayer arrangement within PL in control animals). Also, delayed maturation (well defined apical cytoplasmic cones and intense basal basophilia) was evident in Purkinje cells of experimental animals on PND 11. The mean Purkinje cell nuclear area was significantly increased in the arsenic treated animals compared to the control animals. The observations of the present study (faulty migration, delayed maturation and alteration in nuclear area measurements of Purkinje cells subsequent to arsenic exposure) thus provided the morphological evidence of structural alterations subsequent to arsenite induced developmental neurotoxicity which could be presumed to be the underlying basis for some of the functional deficits encountered in the later period of life.

In utero arsenic exposure induces early onset of atherosclerosis in ApoE-/- mice

Consumption of arsenic contaminated drinking water has been linked to higher rates of coronary disease, stroke, and peripheral arterial disease. Recent evidence suggests that early life exposures may play a significant role in the onset of chronic adult diseases. To investigate the potential for in utero arsenic exposure to accelerate the onset of cardiovascular disease we exposed pregnant ApoE-knockout (ApoE(-/-)) mice to arsenic in their drinking water and examined the aortic trees of their male offspring for evidence of early disease 10 and 16 weeks after birth. Mice were maintained on normal chow after weaning. ApoE(-/-) mice are a commonly used model for atherogenesis and spontaneously develop atherosclerotic disease. Mice exposed to arsenic in utero showed a >2-fold increase in lesion formation in the aortic roots as well as the aortic arch compared to control mice at both 10 and 16 weeks of age. The mice exposed to arsenic also had a 20-40% decrease in total triglycerides, but no change in total cholesterol, phospholipids and total abundance of VLDL or HDL particles. Subfractionation of VLDL particles showed a decrease in large VLDL particles. In addition, the arsenic-exposed mice showed a vasorelaxation defect in response to acetylcholine suggesting disturbance of endothelial cell signalling. These results indicate that in utero arsenic exposure induces an early onset of atherosclerosis in ApoE(-/-) mice without a hyperlipidemic diet and support the hypothesis that in utero arsenic exposure may be atherogenic in humans.

Investigation on the Genotoxic Effects of Long-Term Administration of Sodium Arsenite in Bone Marrow and Testicular Cells In Vivo Using the Comet Assay

The main source of environmental arsenic exposure in most populations is drinking water in which inorganic forms of arsenic predominate. The single-cell gel electrophoresis technique (the comet assay) measures DNA damage, including double-strand and single-strand breaks, in somatic cells after a variety of genotoxic insults. We have used this method to measure damage to cellular DNA in the bone marrow and testicular cells of mice using the alkaline comet assay for the former and neutral comet assay for the latter. Swiss albino male mice were exposed to sodium arsenite in drinking water at concentrations of 10, 50,100, and 200 mg/l for a period of three months. Concurrently, negative and positive control sets were maintained. The negative control animals were given distilled water as drinking water for the same period of treatment while the animals in positive control sets were either given single or multiple injections of EMS (100 mg/kg body weight) according to the tissue sampled. Following long-term exposure, there was a significant dose-dependent reduction in the size and weight of testes. The comet parameters of DNA, such as tail length (microm), % of DNA in tail, and Olive tail moment (arbitrary units) were increased in both bone marrow and testicular cells due to arsenic-induced DNA strand breaks. A positive dose response relationship was noted. The magnitude of DNA strand break was more pronounced in the bone marrow cells than in the testicular cells. The minimum effective concentrations for inducing DNA damage in bone marrow cells and testicular cells were 10 mg/l and 50 mg/l, respectively. The results of the study indicate that arsenic in drinking water is genotoxic in mice and the comet assay can be used for examining DNA damage in testicular cells as a parameter for evaluating male reproductive toxicity.

Effects of low-level arsenic exposure on the developmental toxicity of anilofos in rats

In view of the increased use of anilofos for crop protection and ever increasing arsenic levels in drinking water in many countries, the coexistence of arsenic and anilofos in the environment is a reality and simultaneous exposure of humans and animals to these contaminants could be potentially hazardous. The aim of the present study was to examine whether coexposure to arsenic at the groundwater contamination level could alter the embryofetal toxicity of anilofos in rat model. Anilofos (100 mg kg(-1) day(-1)) and sodium arsenite (1 mg arsenic kg(-1) day(-1)) were administered by gavage either individually or in combination to the pregnant rats from day 6 to day 15 of gestation. Arsenic did not produce any significant effects either on maternal or fetal parameters at the given dose. Anilofos alone significantly decreased maternal weight gain, feed and water intakes, gravid uterine weights, number of live fetuses and fetal body weights and increased resorptions. There were increased incidences of gross, skeletal and visceral anomalies in the fetuses of anilofos-treated group. The main skeletal abnormality was increased intercostal space, while the visceral anomaly was an interventricular septal defect. Treatment with the combination of arsenic and anilofos significantly enhanced the fetal changes with much greater magnitude compared with the effects produced by anilofos alone. Anomalies such as midfacial cleft, exencephaly and anophthalmia were seen only in the fetuses of the combination group. The results show that anilofos interferes with embryofetal development and coexposure with arsenic at environmentally realistic concentrations produces additive or synergistic effects on the developmental toxicity of anilofos in rats.

Possible beneficial effects of melatonin supplementation on arsenic-induced oxidative stress in Wistar rats

The effects of melatonin on arsenic-induced changes on cellular antioxidant system were studied in male rats of the Wistar strain. Arsenic treatment (i.p. as sodium arsenite) was done at a dose of 5.55 mg/kg body weight (equivalent to 35% of LD50) per day for a period of 30 days, while melatonin supplementation (i.p.) was performed at a dose of 10 mg/kg body weight per day for the last 5 days prior to sacrifice. Melatonin supplementation reversed the arsenic-mediated changes in reduced glutathione (GSH) level and lipid peroxidation in liver and kidney. Arsenic-induced decreased glutathione reductase activity in liver and increased activity in kidney was appreciably counteracted by melatonin. Melatonin also inhibited arsenic-induced free hydroxyl radical production in the tissues. The decreased superoxide dismutase (SOD) activity in liver and kidney and that of catalase in liver due to arsenic treatment were also counteracted by melatonin. It is suggested that melatonin acts as a protective agent against arsenic-induced cellular oxidative stress.

Decreased Nitric Oxide Production in the Rat Brain after Chronic Arsenic Exposure

Chronic arsenic exposure is associated with nervous system damage, vascular disease, hepatic and renal damage as well as different types of cancer. Alterations of nitric oxide (NO) in the periphery have been detected after arsenic exposure, and we explored here NO production in the brain. Female Wistar rats were exposed to arsenite in drinking water (4-5 mg/kg/day) from gestation, lactation and until 4 months of age. NOS activity, NO metabolites content, reactive oxygen species production (ROS) and lipid peroxidation (LPx) were determined in vitro in the striatum, and NO production was estimated in vivo measuring citrulline by microdialysis. Exposed animals showed a significantly lower response to NMDA receptor stimulation, reduction of NOS activity and decreased levels of nitrites and nitrates in striatum. These markers of NO function were accompanied by significantly higher levels of LPx and ROS production. These results provide evidence of NO dysfunction in the rat brain associated with arsenic exposure.

Effects of individual and combined exposure to sodium arsenite and sodium fluoride on tissue oxidative stress, arsenic and fluoride levels in male mice

Arsenic and fluoride are potent toxicants, widely distributed through drinking water and food and often result in adverse health effects. The present study examined the effects of sodium meta-arsenite (100 mg/l in drinking water) and sodium fluoride (5 mg/kg, oral, once daily), administered either alone or in combination for 8 weeks, on various biochemical variables indicative of tissue oxidative stress and cell injury in Swiss albino male mice. A separate group was first exposed to arsenic for 4 weeks followed by 4 weeks of fluoride exposure. Exposure to arsenic or fluoride led to a significant depletion of blood delta-aminolevulinic acid dehydratase (ALAD) activity and glutathione (GSH) level. These changes were accompanied by increased level of blood and tissues reactive oxygen species (ROS) level. An increase in the level of liver and kidney thiobarbituric acid reactive substance (TBARS) along with a concomitant decrease in the activities of superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) and reduced GSH content were observed in both arsenic and fluoride administered mice. The changes were significantly more pronounced in arsenic exposed animals than in fluoride. It was interesting to observe that during combined exposure the toxic effects were less pronounced compared to the effects of arsenic or fluoride alone. In some cases antagonistic effects were noted following co-exposure to arsenic and fluoride. Arsenic and fluoride concentration increased significantly on exposure. Interestingly, their concentration decreased significantly on concomitant exposure for 8 weeks. However, the group which was administered arsenic for 4 weeks followed by 4 weeks of fluoride administration showed no such protection suggesting that the antagonistic effect of fluoride on arsenic or vice versa is possible only during interaction at the gastro intestinal sites. These results are new and interesting and require further exploration.

Arsenic induced apoptosis in rat liver following repeated 60 days exposure

BACKGROUND

Accumulation of the wide spread environmental toxin arsenic in liver results in hepatotoxcity. Exposure to arsenite and other arsenicals has been previously shown to induce apoptosis in certain tumor cell lines at low (1-3 microM) concentration.

AIM

The present study was focused to elucidate the role of free radicals in arsenic toxicity and to investigate the nature of in vivo sodium arsenite induced cell death in liver.

METHODS

Male wistar rats were exposed to arsenite at three different doses of 0.05, 2.5 and 5mg/l for 60 days. Oxidative stress in liver was measured by estimating pro-oxidant and antioxidant activity in liver. Histopathological examination of liver was carried out by light and transmission electron microscopy. Analysis of DNA fragmentation by gel electrophoresis was used to identify apoptosis after the exposure. Terminal deoxy-nucleotidyl transferase mediated dUTP Nick end-labeling (TUNEL) assay was used to qualify and quantify apoptosis.

RESULTS

A significant increase in cytochrome-P450 and lipid peroxidation accompanied with a significant alteration in the activity of many of the antioxidants was observed, all suggestive of arsenic induced oxidative stress. Histopathological examination under light and transmission electron microscope suggested a combination of ongoing necrosis and apoptosis. DNA-TUNEL showed an increase in apoptotic cells in liver. Agarose gel electrophoresis of DNA of hepatocytes resulted in a characteristic ladder pattern.

CONCLUSION

Chronic arsenic administration induces a specific pattern of apoptosis called post-mitotic apoptosis.

Arsenite Regulates Cystic Fibrosis Transmem­brane Conductance Regulator and P-glycoprotein: Evidence of Pathway Independence

In the past, people have argued for and against the theory of reciprocal regulation of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) and P-glycoprotein (Pgp). Data have indicated that this may occur in vitro during drug-induced selection of cells, and in vivo during development. Much of this debate has been caused by a severe lack of mechanistic details involved in such regulation. Our past data indicate that certain Pgp modulators can affect CFTR expression and function. The goal of this study was to investigate the effects of trivalent arsenic (arsenite), a known transcriptional activator of Pgp, on CFTR expression. In vitro analyses in T-84 cells that express basal levels of Pgp and CFTR were conducted using a variety of molecular techniques. Expressions of both genes were altered following treatment with arsenite in a dose- and time-dependent fashion. CFTR expression was suppressed almost three-fold by arsenite, along with a concomitant increase in P-glycoprotein expression. We also report that a member of the MAPK-family, the ERK-mediated signaling cascade is implicated in suppression of CFTR expression following treatment with arsenite. However, this particular pathway is not involved in regulation of P-glycoprotein expression in T-84 cells following treatment with arsenite. Thus, the regulatory pathways that control functional expression of CFTR and P-glycoprotein following arsenite treatment in T-84 cells are distinct and independent.

Mechanism of arsenite-mediated decreases in CYP3A23 in rat hepatocytes

In primary cultures of rat hepatocytes, exposure to arsenite causes a major decrease in dexamethasone (DEX)-mediated induction of CYP3A23 hemoprotein, with a minor decrease in CYP3A23 mRNA. Here we show that addition of heme did not prevent the arsenite-mediated decreases in CYP3A23 protein, and arsenite did not decrease intracellular glutathione levels, indicating that heme and glutathione were not limiting for formation of holoCYP3A23. We also investigated whether arsenite decreases CYP3A23 protein by increasing CYP3A23 degradation by the calpain pathway. The calpain inhibitor, calpeptin, caused greater than a 90% inhibition of calpain-mediated proteolysis, but had no effect on DEX-mediated induction of CYP3A23 protein following 24h treatments. However, calpeptin enhanced the effect of arsenite to decrease induction of CYP3A23 protein. In addition, in short-term studies, calpeptin appeared to be a suicidal inhibitor of CYP3A-catalyzed enzyme activity. Our findings suggest that CYP3A23 protein is not degraded by calpain-mediated proteolysis, even in the presence of arsenite.

Vitamin E and organoselenium prevent the cocarcinogenic activity of arsenite with solar UVR in mouse skin

Arsenic-induced carcinogenesis is a worldwide problem for which there is currently limited means for control. Recently, we showed that arsenite in drinking water greatly potentiates solar ultraviolet radiation (UVR) induced skin cancer in mice, at concentrations as low as 1.25 mg/l. In this study, we examined the protective efficacy of vitamin E and 1,4-phenylenebis(methylene)selenocyanate (p-XSC) against tumors induced by UVR and UVR + arsenite. Hairless mice were exposed to UVR alone (1.0 kJ/m(2) x 3 times weekly) or UVR + sodium arsenite (5 mg/l in drinking water) and fed lab chow supplemented or not with vitamin E (RRR-alpha-tocopheryl acetate, 62.5 IU/kg diet) or p-XSC (10 mg/kg) for 26 weeks. The tumor yield for mice receiving UVR alone was 3.6 tumors/mouse and the addition of arsenite to the drinking water increased the yield to 7.0 tumors/mouse (P < 0.005). Vitamin E and p-XSC reduced the tumor yield in mice given UVR + arsenite by 2.1-fold (P < 0.001) and 2-fold (P < 0.002), respectively. Vitamin E, but not p-XSC, reduced the tumor yield induced by UVR alone by 30% (P < 0.05). No significant difference in tumor types or grade of malignancy was observed in mice treated with or without chemopreventives. Immunostaining of mouse skin for 8-oxo-2'-deoxyguanosine (8-oxo-dG) revealed a significant reduction of 8-oxo-dG formation in mice treated with vitamin E or p-XSC compared with those treated with UVR + arsenite. These results show that vitamin E and p-XSC protect strongly against arsenite-induced enhancement of UVR carcinogenesis.

Low level, long-term inorganic arsenite exposure causes generalized resistance to apoptosis in cultured human keratinocytes: potential role in skin co-carcinogenesis

Inorganic arsenic is a human carcinogen that targets the skin. Carcinogenesis is a multistep process in which acquired apoptotic resistance is a common event and prior work in non-skin cells shows acquired resistance to apoptosis occurs with chronic arsenite exposure. In the present study, when HaCaT cells, an immortalized, non-tumorigenic human keratinocyte cell line, were continuously exposed to low-level inorganic arsenite (as sodium arsenite; 100 nM) for 28 weeks, the cells acquired a generalized resistance to apoptosis. This included resistance to apoptosis induced by acute high concentrations of arsenite, ultraviolet A (UVA) irradiation, and several chemotherapeutic compounds (cisplatin, etoposide and doxorubicin). These arsenite-tolerant (As-TL) cells showed similar levels of UVA-induced reactive oxygen species (ROS) and oxidative DNA damage when compared to passage match control cells. Because cellular apoptosis is dependent on the balance between proapoptotic and survival pathways, the roles of protein kinase B (PKB), a key antiapoptotic molecule, in this acquired apoptotic resistance were investigated. Stimulation of apoptosis markedly decreased nuclear phosphorylated PKB (P-PKB) levels in control cells, but As-TL cells showed greatly increased stability of nuclear P-PKB. Pretreatment of the As-TL cells with LY294002 or Wortmannin, which specifically inhibit PKB phosphorylation, completely blocked apoptotic resistance in As-TL cells, indicating acquired apoptotic resistance is associated with increased stability of nuclear P-PKB. Because arsenic and UV irradiation are co-carcinogenic in mouse skin, resistance to UV-induced apoptosis in As-TL cells may allow UV-damaged cells to escape normal cell population controls and initiate the carcinogenic cascade. The observation that As-TL cells show no lessening of UV-induced genotoxicity supports this possibility.

Male reproductive toxicity of sodium arsenite in mice

The effect of chronic oral exposure to arsenic on male mouse testicular and accessory sex organ weights, sperm parameters and testicular marker enzymes was studied. In addition, the distribution of arsenic in reproductive organs was measured using atomic absorption spectrophotometry. Sodium arsenite administered to mice (Mus musculus) via drinking water at a dose of 53.39 micromol/L (4 ppm As) for 365 days caused a decrease in the absolute and relative testicular weight. However, epididymal and accessory sex organ weight was similar to control. The activities of marker testicular enzymes such as sorbitol dehydrogenase, acid phosphatase and 17beta-hydroxy-steroid dehydrogenase (17beta-HSD) were significantly decreased, but those of lactate dehydrogenase and gamma-glutamyl transpeptidase (gamma-GT) were significantly increased. A decrease in sperm count and sperm motility, along with an increase in abnormal sperm, was observed in arsenite-exposed mice. A significant accumulation of arsenic in testes, epididymis, seminal vesicle and prostate gland was observed in treated animals. Thus long term exposure (365 days) at the dose level of 53.39 micromol/L sodium arsenite (4 ppm As), to which human beings are likely to be exposed via drinking water, may cause testicular and spermatotoxic effect.

Biokinetics and subchronic toxic effects of oral arsenite, arsenate, monomethylarsonic acid, and dimethylarsinic acid in v-Ha-ras transgenic (Tg.AC) mice

Previous research demonstrated that 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment increased the number of skin papillomas in v-Ha-ras transgenic (Tg.AC) mice that had received sodium arsenite [(As(III)] in drinking water, indicating that this model is useful for studying the toxic effects of arsenic in vivo. Because the liver is a known target of arsenic, we examined the pathophysiologic and molecular effects of inorganic and organic arsenical exposure on Tg.AC mouse liver in this study. Tg.AC mice were provided drinking water containing As(III), sodium arsenate [As(V)], monomethylarsonic acid [(MMA(V)], and 1,000 ppm dimethylarsinic acid [DMA(V)] at dosages of 150, 200, 1,500, or 1,000 ppm as arsenic, respectively, for 17 weeks. Control mice received unaltered water. Four weeks after initiation of arsenic treatment, TPA at a dose of 1.25 microg/200 microL acetone was applied twice a week for 2 weeks to the shaved dorsal skin of all mice, including the controls not receiving arsenic. In some cases arsenic exposure reduced body weight gain and caused mortality (including moribundity). Arsenical exposure resulted in a dose-dependent accumulation of arsenic in the liver that was unexpectedly independent of chemical species and produced hepatic global DNA hypomethylation. cDNA microarray and reverse transcriptase-polymerase chain reaction analysis revealed that all arsenicals altered the expression of numerous genes associated with toxicity and cancer. However, organic arsenicals [MMA(V) and DMA(V)] induced a pattern of gene expression dissimilar to that of inorganic arsenicals. In summary, subchronic exposure of Tg.AC mice to inorganic or organic arsenicals resulted in toxic manifestations, hepatic arsenic accumulation, global DNA hypomethylation, and numerous gene expression changes. These effects may play a role in arsenic-induced hepatotoxicity and carcinogenesis and may be of particular toxicologic relevance.

Mechanisms underlying arsenic carcinogenesis: hypersensitivity of mice exposed to inorganic arsenic during gestation

Inorganic arsenic is an important human carcinogen of unknown etiology. Defining carcinogenic mechanisms is critical to assessing the human health hazard of arsenic exposure but requires appropriate model systems. It has proven difficult to induced tumors in animals with inorganic arsenic alone. Several groups have studied the carcinogenic potential of inorganic arsenic in rodents, finding it to act as co-promoter or co-carcinogen, but not as a complete carcinogen. As gestation is a time of high sensitivity to chemical carcinogenesis, we performed two in utero exposure studies with inorganic arsenic. In the first study, pregnant mice received drinking water containing sodium arsenite at 0 (control), 42.5 and 85 ppm arsenic from gestation day 8 to 18, and the offspring were observed for up to 90 weeks. As adults, male offspring developed hepatocellular carcinoma (HCC) and adrenal tumors after in utero arsenite exposure. Although liver tumors were not induced by arsenic in female offspring, they did develop lung carcinoma, ovarian tumors, and uterine and oviduct preneoplasia. In a second study, the same doses of arsenic were used and the skin tumor promoting phorbol ester, TPA, was applied to the skin after birth in an effort to promote skin tumors potentially initiated by arsenic in utero. TPA did not promote dermal tumors after in utero arsenite exposure. Otherwise, results from the second chronic study largely duplicated the first and, irrespective of additional TPA exposure, arsenic exposure in utero induced HCC and adrenal tumors in males and ovarian tumors in females. In addition, combined arsenic and TPA induced a significant increase in hepatocellular tumors in female offspring, although arsenic alone was not effective. Thus, in utero inorganic arsenic exposure can act as a complete carcinogen in mice, with brief exposures consistently inducing tumors at several sites. In addition, it appears gestational arsenic can act as a tumor initiator in the female mouse liver, inducing liver lesions that can be promoted by TPA.

Vascular permeability alterations induced by arsenic

The impact of arsenic on the integrity of blood vessels in vivo via in situ exposure (local injection) of arsenic was investigated. Vascular permeability changes were evaluated by means of the Evans blue assay and the India ink tracer techniques. Rats were intravenously injected with Evans blue followed by intradermal injections of various doses of sodium arsenite on the back skins of the animals. Evans blue at different time points was extracted and assayed as indices of vascular leakage. Skin at various time point injection sites was sampled for arsenic measurement via graphite furnace atomic absorption spectroscopy. Our time course study with Evans blue technique demonstrated a biphasic pattern of vascular permeability change: an early phase of permeability reduction and a later phase of permeability promotion at all dose levels tested. The India ink tracer technique also demonstrated a time-correlated increase in vascular labelling in the tissues examined, signifying an increase in vascular leakage with time. Moreover, we found that despite an early increase in tissue arsenic content at time of injection, tissue arsenic declined rapidly and returned to near control levels after 30-60 min. Thus, an inverse correlation between tissue arsenic content and the extent of vascular permeability was apparent. This study provides the first demonstration that in situ exposure to arsenic will produce vascular dysfunction (vascular leakage) in vivo.

Effect of dietary co-administration of sodium selenite on sodium arsenite-induced ovarian and uterine disorders in mature albino rats

The subchronic treatment of mature female Wistar-strain albino rats in diestrous phase with sodium arsenite at a dose of 0.4 ppm/100 g body weight/rat/day via drinking water for period of 28 days (seven estrous cycles) caused a significant reduction in the plasma levels of leutinizing hormone (LH), follicle-stimulating hormone (FSH), and estradiol along with a significant decrease in ovarian activities of delta five, 3 beta-hydroxysteroid dehydrogenase (Delta5,3beta-HSD), and 17 beta-hydroxysteroid dehydrogenase (17beta-HSD) followed by a reduction in ovarian and uterine peroxidase activities. A significant weight loss of the ovary and uterus was also observed after this treatment, along with a prolonged diestrous phase and a high accumulation of arsenic in the plasma and these organs. Moreover, sodium arsenite was also responsible for ovarian follicular and uterine cell degeneration characterized by a high number of regressing follicles and a reduction in the uterine luminal diameter, respectively, in comparison with the controls. A dietary supplementation of sodium selenite at the dose of 0.6 mg/100 g body weight/rat/day for a period of 28 days along with arsenic treatment minimized the gonadal weight loss significantly and increased the activities of the ovarian steroidogenic enzymes as well as the ovarian and uterine peroxidase at the control level. Selenium was also able to increase the plasma levels of LH, FSH, and estradiol toward the control level. Vaginal smears showed normal estrous cyclicity in sodium selenite-supplemented arsenic-treated rats along with lower arsenic levels in the plasma and gonadal tissue in comparison with arsenic-only-treated rats. Histological sections of ovary and uterine tissues in the control and experimental groups confirmed that sodium selenite supplementation was able to prevent arsenic-induced histopathological changes in the ovary and uterus. Plasma levels of norepinephrine and dopamine in the midbrain and diencephalon decreased significantly, whereas the serotonin level was increased significantly after 28 days of sodium arsenite treatment. All of these parameters were, in most cases, unchanged from the control level when sodium selenite was co-administered with sodium arsenite. Arsenic intoxication was also associated with increased liver weight and elevation in the activities of hepatic and renal acid phosphatase, alkaline phosphatase, and transaminases, but selenium co-administration was not able to change these toxic effects of arsenic. The results of our experiments indicate the significant protective action of sodium selenite on arsenic-induced toxicity in the female reproductive system, while there was no significant protective effect of selenium on arsenic-induced toxicity in other organs.