Oxidative stress induced by realgar in neurons: p38 MAPK and ERK1/2 perturb autophagy and induce the p62-Keap1-Nrf2 feedback loop to activate the Nrf2 signalling pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Due to the modernization of traditional Chinese medicine (TCM) and the influence of traditional medication habits (TCM has no toxicity or side effects), arsenic poisoning incidents caused by the abuse of realgar and realgar-containing Chinese patent medicines have occurred occasionally. However, the potential mechanism of central nervous system toxicity of realgar remains unclear. AIM OF THE STUDY: This study aimed to clarify the specific mechanism of realgar-induced neurotoxicity. MATERIALS AND METHODS: In this study, the roles of ERK1/2 and p38 MAPK in realgar-induced neuronal autophagy and overactivation of the nuclear factor erythroid-derived factor 2-related factor (Nrf2) signalling pathways was investigated in vivo and in vitro. RESULTS: The arsenic in realgar passed through the blood-brain barrier and accumulated in the brain, resulting in damage to neurons, synapses and myelin sheaths in the cerebral cortex and a decrease in the total antioxidant capacity. The specific mechanism is that the excessive activation of Nrf2 is regulated by the upstream signalling molecules ERK1/2 and p38MAPK. At the same time, p38 MAPK and ERK1/2 interfere with autophagy, thereby promoting autophagy initiation but causing subsequent dysfunctional autophagic degradation and inducing the p62-Keap1-Nrf2 feedback loop to promote Nrf2 signalling pathway activation and nerve cell apoptosis. CONCLUSIONS: This study confirmed the role of the signalling molecules p38 MAPK and ERK1/2 in perturbing autophagy and inducing the p62-Keap1-Nrf2 feedback loop to activate the Nrf2 signalling pathway in realgar-induced neurotoxicity.

Toxicokinetic characteristics and effects of diphenylarsinic acid on dopamine in the striatum of free-moving mice.

Diphenylarsinic acid (DPAA), an artificial phenyl arsenic compound, is considered a groundwater pollutant in Japan. Previous human and animal studies suggested that DPAA affects the central nervous system; however, these effects are poorly understood. The present study investigated the toxicokinetic characteristics and effects of DPAA on dopamine (DA) in the striatum of free-moving mice after a single oral administration. In a simultaneous blood and brain microdialysis study, only DPAA was detectable in both blood and striatum dialysate samples immediately after DPAA administration. DPAA concentrations in the striatum and blood dialysate rapidly reached a maximum, then decreased over time in an essentially parallel manner. A more detailed brain microdialysis examination of intracerebral kinetics revealed that the concentration of DPAA in the striatum dialysate began to increase within 15 min, reaching a maximum approximately 1 h after administration, and then decreased with a biological half-life of approximately 2 h. Moreover, a single oral administration of DPAA at 0.5-32 mg/kg affected the extracellular DA level in the striatum. The effect on DA level changed slowly after DPAA administration, with a bell-shaped dose-response relationship. The present study suggests that DPAA is rapidly absorbed into the blood circulating in the gastrointestinal tract and passes through the blood-brain barrier to subsequently affect DA levels in the striatum in mice after a single oral administration.

Toxicokinetics of the tumour cell mitochondrial toxin, PENAO, in rodents.

PENAO (4-(N-(S-penicillaminylacetyl)amino)phenylarsonous acid) is a second-generation peptide arsenical that inactivates mitochondria in proliferating tumour cells by covalently reacting with mitochondrial inner-membrane adenine nucleotide transferase. The toxicokinetics of PENAO has been investigated in Sprague-Dawley rats to inform route of administration and dosing for human clinical trials. PENAO was well tolerated at 3.3 mg/kg daily intravenous injections but associated with significant toxicity at 10 mg/kg, primarily in the males. The major target organ for toxic effects was the kidney, with changes observed in tubular dilation, presence of casts, basophilic tubules, lymphoid aggregates and interstitial fibrosis. Kidney function was impaired in males with dose-dependent increase in serum creatinine concentration. The severity of the microscopic lesions was reduced in the females, but not the males, at the completion of the four-week recovery period. The elimination phase half-life of PENAO varied between 0.4 and 1.7 h and volume of distribution ranged from 0.25 to 0.88 L/kg for the different dose groups and treatment days, suggesting that PENAO distributes in the extracellular fluids at the doses tested. The area under the curve and clearance values indicate that male rats had reduced elimination of PENAO compared to females, which may account for the increased toxicity in males. PENAO is significantly better tolerated in rodents than its predecessor, GSAO. As GSAO was generally well tolerated with few side effects in a phase I trial in patients with solid tumours, these findings bode well for the tolerability of intravenous dosing of PENAO in patients.

Phase I studies of darinaparsin in patients with relapsed or refractory peripheral T-cell lymphoma: a pooled analysis of two phase I studies conducted in Japan and Korea.

OBJECTIVE: Two phase I studies of darinaparsin including Japanese and Korean patients with relapsed/refractory peripheral T-cell lymphoma were performed to evaluate its safety (primary purpose), efficacy and pharmacokinetic profile (ClinicalTrials.gov: NCT01435863 and NCT01689220). METHODS: Patients received intravenous darinaparsin for 5 consecutive days at 200 mg/m2/day in 4-week cycles, 300 mg/m2/day in 4-week cycles or 300 mg/m2/day in 3-week cycles. RESULTS: Seventeen Japanese and 6 Korean patients were enrolled and treated. Drug-related adverse events developed in 18 patients (78%). Dose-limiting toxicity, grade 3 hepatic dysfunction, was reported on Day 15 of cycle 1 in 1 Japanese patient who received 300 mg/m2/day. The most common drug-related, grade ≥ 3 adverse events were lymphopenia (9%), neutropenia (9%) and thrombocytopenia (9%). No deaths occurred. In 14 evaluable patients, 1 and 3 patients had complete response and partial response, respectively. The plasma concentration-time profiles of arsenic, a surrogate marker for darinaparsin, were similar between Japanese and Korean patients. No significant difference was found in its pharmacokinetic profile. CONCLUSIONS: These data indicate the good tolerability and potential efficacy of darinaparsin in patients with relapsed/refractory peripheral T-cell lymphoma. Darinaparsin 300 mg/m2/day for 5 consecutive days in 3-week cycles is the recommended regimen for phase II study.

Determination of arsenicals in mouse tissues after simulated exposure to arsenic from rice for sixteen weeks and the effects on histopathological features.

The accumulation of arsenic in rice has become a worldwide concern. In this study, dose-dependency in tissues (intestine, liver and kidney) and blood distribution of inorganic arsenicals and their methylated metabolites were investigated in male C57BL/6 mice exposed to four arsenic species (arsenite [iAs]III, arsenate [iAs]V, monomethylarsonate [MMA]V, and dimethylarsinate [DMA]V) at four doses (control [C]: 0 µg/g, simulation [S]: 0.91 µg/g, medium [M]: 9.1 µg/g and high [H]: 30 µg/g) according to the arsenical composition in rice for 8 and 16 weeks. No adverse effects were observed, while body weight gain decreased in group H. Increases in total arsenic concentrations (CtAs) and histopathological changes in the tissues occurred in all of the test groups. CtAs presented a tendency of kidney > intestine > liver > blood and were time-/dose-dependent in the liver and kidney in groups M and H. In the intestine and blood, abundant iAs (23%-28% in blood and 36%-49% in intestine) was detected in groups M and H, and CtAs decreased in group H from the 8th week to the 16th week. PMI decreased in the liver and SMI decreased in the kidney. These results indicate that the three tissues are injured through food arsenic. The intestine can also accumulate food arsenic, and the high arsenic dose will cause a deficiency in the absorbing function of the intestine. Thus, long-term exposure to arsenic-contaminated rice should be taken seriously attention.

Study of the accumulation and distribution of arsenic species and association with arsenic toxicity in rats after 30 days of oral realgar administration.

AIM OF THE STUDY: Because the toxicity and efficacy of arsenic is closely related to its chemical species, we conducted examinations of arsenic species accumulation and distribution in the rat body after one-time and 30-day realgar administration and then elucidated the probable roles of different arsenic species in the short-term toxicity of realgar. MATERIALS AND METHODS: According to ICH M3 guidelines for non-clinical repeated dose toxicity studies and OECD Test guideline TG407 "Repeated Dose 28-Day oral Toxicity Study in Rodents, the doses of realgar set were 10.6 mg/kg, 40.5 mg/kg and 170 mg/kg. Rats were orally administered with realgar for one-tme and 30 days, respectively. Thereafter, biological samples (plasma, urine, liver, kidney, and brain) were obtained from rats and analyzed using high-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) to determine realgar metabolism, arsenic species accumulation and distribution. Additionally, the toxicity of realgar in rats was evaluated. RESULTS: The absorption, distribution and elimination half-life of total arsenic species in realgar were 3.33 hs, 16.08 hs and 24.65 hs, respectively. After 30 days of oral administration of realgar in rats, no significant drug-related toxicity occurred in the rats. Dimethylarsenic acid (DMA) is the most abundant arsenic species. The DMA contents of the liver and kidney of the high-dose realgar group were approximately 40-fold and 50-fold higher than those in the corresponding tissues of the control group, respectively. The arsenic species (III) was mainly detected in the liver and its content was about 40-fold higher than that of the control group. MMA was mainly detected in rat kidney, and the MMA content of the realgar treatment group was more than 2000 times higher than that of the control group. CONCLUSIONS: Arsenic is rapidly absorbed and distributed over the liver, kidneys and brain, and the distribution and elimination of arsenic in the blood is slow. The realgar doses corresponded to human equivalent doses (HED) of 1.7, 6.4 and 27.2 mg/kg, respectively. Considering that humans are 10 times more sensitive than animals, the realgar dose is equivalent to 0.17, 0.64 and 2.7 mg/kg HED. It can be considered that if patients take no more than 2.7 mg/kg realgar for 2 weeks, there will be no adverse reactions.

Effect of selenium in soil on the toxicity and uptake of arsenic in rice plant.

Selenium can regulate arsenic toxicity by strengthening antioxidant potential, but the antagonism between selenite or selenate nutrient and the translocation of arsenic species from paddy soil to different rice organs are poorly understood. In this study, a pot experiment was designed to investigate the effect of selenite or selenate on arsenite or arsenate toxicity to two indica rice cultivars (namely Ming Hui 63 and Lu You Ming Zhan), and the uptake and transportation of arsenic species from paddy soil to different rice organs. The results showed that selenite or selenate could significantly decrease the arsenate concentration in pore water of soils, and thus inhibited arsenate uptake by rice roots. However, the existence of selenite or selenate didn't decrease arsenate concentration in rhizosphere pore water of two indica rice cultivars. There existed good antagonistic effect between selenite or selenate and the uptake of arsenite and arsenate in rice plant in the case of low arsenic paddy soil. However, this antagonism depended on rice cultivars, arsenic species and arsenic level in soil. There existed both synergistic and inhibiting effects between the addition of selenite or selenate and the uptake of trimethylarsinoxide and dimethylarsinic acid by two indica rice cultivars, but the mechanism was unclear. Both selenite and selenate are all effective to decrease the translocation of inorganic arsenic from the roots to their above-ground rice organs in arsenite/arsenate-spiked paddy soil, but selenate had stronger inhibiting effect on their transfer factors than selenite.

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

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

Interspecific differences in the bioaccumulation of arsenic of three Patagonian top predator fish: Organ distribution and arsenic speciation.

Interspecific differences in arsenic bioaccumulation and organ distribution (muscle, liver, kidney and gills) in three predator fish (creole perch, rainbow trout and brown trout) from a Patagonian lake impacted by volcanic eruptions were studied. Arsenic in fish organs were compared analyzing: 1) temporal (before and after volcanic eruption) and spatial (near and far from the volcano) influence of Puyehue-Cordón Caulle volcanic complex activity on arsenic concentrations; 2) the influence of growth (as total length), organ type and their interactions over arsenic accumulation; and 3) arsenic speciation and total arsenic relationship with carbon to nitrogen ratios (C:N), as a proxy of lipid presence, in fish muscle. In general, total arsenic concentrations in creole perch organs were 2-7 times higher than those recorded in the corresponding organs of salmonids. Arsenic was preferentially accumulated in liver and kidney in the three fish species. The influence of the volcanic activity over arsenic concentrations was more evident in creole perch: organs from creole perch captured closest to the volcano exhibited higher arsenic concentrations. Temporal variations were not so consistent. No clear relationship between arsenic and fish length was observed. Positive and linear relationship between arsenic in all pair of organs was found in creole perch, while rainbow trout showed a quadratic relationship between muscle and the remaining organs, indicating different arsenic assimilation-elimination relationships between organs and fish. The arsenic liver:muscle ratio in the three fish species was greater than 1, suggesting some level of arsenic stress. Arsenobetaine (AB) and dimethylarsinic acid (DMA) were the dominant arsenic species in muscle of these fish, having creole perch 3-4 times higher AB than rainbow trout. A positive relationship between C:N ratio and total arsenic concentrations was found, with higher C:N in creole perchs near the volcano. In terms of food safety, no inorganic arsenic compound were detected, therefore arsenic levels in fish from Lake Nahuel Huapi does not represent any health risk to consumers.

Using mathematical modeling to infer the valence state of arsenicals in tissues: A PBPK model for dimethylarsinic acid (DMAV) and dimethylarsinous acid (DMAIII) in mice.

Chronic exposure to inorganic arsenic (iAs), a contaminant of water and food supplies, is associated with many adverse health effects. A notable feature of iAs metabolism is sequential methylation reactions which produce mono- and di-methylated arsenicals that can contain arsenic in either the trivalent (III) or pentavalent (V) valence states. Because methylated arsenicals containing trivalent arsenic are more potent toxicants than their pentavalent counterparts, the ability to distinguish between the +3 and +5 valence states is a crucial property for physiologically based pharmacokinetic (PBPK) models of arsenicals to possess if they are to be of use in risk assessment. Unfortunately, current analytic techniques for quantifying arsenicals in tissues disrupt the valence state; hence, pharmacokinetic studies in animals, used for model calibration, only reliably provide data on the sum of the +3 and +5 valence forms of a given metabolite. In this paper we show how mathematical modeling can be used to overcome this obstacle and present a PBPK model for the dimethylated metabolite of iAs, which exists as either dimethylarsinous acid, (CH3)2AsIIIOH (abbreviated DMAIII) or dimethylarsinic acid, (CH3)2AsV(O)OH (abbreviated DMAV). The model distinguishes these two forms and sets a lower bound on how much of an organ's DMA burden is present in the more reactive and toxic trivalent valence state. We conjoin the PBPK model to a simple model for DMAIII-induced oxidative stress in liver and use this extended model to predict cytotoxicity in liver in response to the high oral dose of DMAV. The model incorporates mechanistic details derived from in vitro studies and is iteratively calibrated with lumped-valence-state PK data for intravenous or oral dosing with DMAV. Model formulation leads us to predict that orally administered DMAV undergoes extensive reduction in the gastrointestinal (GI) tract to the more toxic trivalent DMAIII.

A novel RGDyC/PEG co-modified PAMAM dendrimer-loaded arsenic trioxide of glioma targeting delivery system.

BACKGROUND: The Traditional Chinese Medicine, arsenic trioxide (ATO, As2O3) could inhibit growth and induce apoptosis in a variety of solid tumor cells, but it is severely limited in the treatment of glioma due to its poor BBB penetration and nonspecifcity distribution in vivo. PURPOSE: The objective of this study was encapsulating ATO in the modified PAMAM den-drimers to solve the problem that the poor antitumor effect of ATO to glioma, which provide a novel angle for the study of glioma treatment. METHODS: The targeting drug carrier (RGDyC-mPEG-PAMAM) was synthesized based on Arg-Gly-Asp (RGDyC) and αvß3 integrin targeting ligand, and conjugated to PEGylated fifth generation polyamidoamine dendrimer (mPEG-PAMAM). It was characterized by nuclear magnetic resonance, fourier transform infrared spectra, Nano-particle size-zeta potential analyzer,etc. The in vitro release characteristics were studied by dialysis bag method. MTT assay was used to investigate the cytotoxicity of carriers and the antitumor effect of ATO formulation. In vitro blood-brain barrier (BBB) and C6 cell co-culture models were established to investigate the inhibitory effect of different ATO formulation after transporting across BBB. Pharmacokinetic and antitumor efficacy studies were investigated in an orthotopic murine model of C6 glioma. RESULTS: The prepared RGDyC-mPEG-PAMAM was characterized for spherical dendrites, comparable size (21.60±6.81 nm), and zeta potential (5.36±0.22 mV). In vitro release showed that more ATO was released from RGDyC-mPEG-PAMAM/ATO (79.5%) at pH 5.5 than that of pH 7.4, during 48 hours. The cytotoxicity of PEG-modified carriers was lower than that of the naked PAMAM on both human brain microvascular endothelial cells and C6 cells. In in vitro BBB model, modification of RGDyC heightened the cytotoxicity of ATO loaded on PAMAM, due to an increased uptake by C6 cells. The results of cell cycle and apoptosis analysis revealed that RGDyC-mPEG-PAMAM/ATO arrested the cell cycle in G2-M and exhibited threefold increase in percentage of apoptosis to that in the PEG-PAMAM/ATO group. Compared with ATO-sol group, both RGDyC-mPEG-PAMAM/ATO and mPEG-PAMAM/ATO groups prolonged the half-life time, increased area under the curve, and improved antitumor effect, significantly. While the tumor volume inhibitory of RGDyC-mPEG-PAMAM/ATO was 61.46±12.26%, it was approximately fourfold higher than the ATO-sol group, and twofold to the mPEG-PAMAM/ATO group. CONCLUSION: In this report, RGDyC-mPEG-PAMAM could enhance the antitumor of ATO to glioma, it provides a desirable strategy for targeted therapy of glioma.

Evaluation of a Physiologically Based Pharmacokinetic (PBPK) Model for Inorganic Arsenic Exposure Using Data from Two Diverse Human Populations.

BACKGROUND: Multiple epidemiological studies exist for some of the well-studied health endpoints associated with inorganic arsenic (iAs) exposure; however, results are usually expressed in terms of different exposure/dose metrics. Physiologically based pharmacokinetic (PBPK) models may be used to obtain a common exposure metric for application in dose-response meta-analysis. OBJECTIVE: A previously published PBPK model for inorganic arsenic (iAs) was evaluated using data sets for arsenic-exposed populations from Bangladesh and the United States. METHODS: The first data set was provided by the Health Effects of Arsenic Longitudinal Study cohort in Bangladesh. The second data set was provided by a study conducted in Churchill County, Nevada, USA. The PBPK model consisted of submodels describing the absorption, distribution, metabolism and excretion (ADME) of iAs and its metabolites monomethylarsenic (MMA) and dimethylarsenic (DMA) acids. The model was used to estimate total arsenic levels in urine in response to oral ingestion of iAs. To compare predictions of the PBPK model against observations, urinary arsenic concentration and creatinine-adjusted urinary arsenic concentration were simulated. As part of the evaluation, both water and dietary intakes of arsenic were estimated and used to generate the associated urine concentrations of the chemical in exposed populations. RESULTS: When arsenic intake from water alone was considered, the results of the PBPK model underpredicted urinary arsenic concentrations for individuals with low levels of arsenic in drinking water and slightly overpredicted urinary arsenic concentrations in individuals with higher levels of arsenic in drinking water. When population-specific estimates of dietary intakes of iAs were included in exposures, the predictive value of the PBPK model was markedly improved, particularly at lower levels of arsenic intake. CONCLUSIONS: Evaluations of this PBPK model illustrate its adequacy and usefulness for oral exposure reconstructions in human health risk assessment, particularly in individuals who are exposed to relatively low levels of arsenic in water or food. https://doi.org/10.1289/EHP3096.

Hepatic histopathological changes and dysfunction in primates following exposure to organic arsenic diphenylarsinic acid.

Organic arsenic diphenylarsinic acid (DPAA[V]) accumulates at high concentrations in the liver of primates after its subchronic administration. However, no studies on the hepatic effects of organic arsenic compounds, including DPAA(V), on primates have been reported to date. To clarify the toxicokinetics of DPAA(V) in the liver of primates, hepatic tissue specimens were collected from cynomolgus monkeys (n = 32) at 5, 29, 170, and 339 days after repeated administration of DPAA(V) for 28 days. Four histopathological changes in the specimens were observed and pathologically evaluated. Atypical ductular proliferation was found in the DPAA(V)-exposed liver throughout the period. Inflammatory cell infiltration in Glisson's capsules and lipid droplets were seen at earlier periods after administration. Conversely, inflammatory cell infiltration in liver lobules was seen later after administration. In this experiment, we did not confirm the hepatic dysfunction of DPAA(V)-exposed monkeys by blood chemistry tests. To compensate for this, we further investigated the blood from a patient who exhibited several neurological symptoms after DPAA(V) exposure. Her blood chemistry test values for aspartate transaminase, alanine transaminase, and lactate dehydrogenase were elevated, suggesting that her liver may have been damaged by DPAA(V) exposure. Together, these findings suggest that the accumulation of DPAA(V) may induce differential histopathological changes in primate hepatocytes, resulting in decreased liver function. This is the first report to investigate the liver of primates pathologically after exposure to organic arsenic DPAA(V). Our findings will help expand our knowledge regarding the effect of DPAA(V) on the liver of primates.

High-sensitivity quantitative analysis reveals the non-linear relationship between the dose and deposition of diphenylarsinic acid in the rat central nervous system following its subchronic exposure.

In the year 2003, the residents of Kamisu, Japan, were exposed to pentavalent organic arsenic diphenylarsinic acid (DPAA[V]) via their normal drinking water. Following the exposure, they developed cerebellar and brainstem symptoms. Although the relatively high dose of DPAA(V) is assumed to have caused their symptoms, the relationship between the exposed dose of DPAA(V) and the level of their deposition in the central nervous system (CNS) remains unclear. Using liquid chromatography-tandem mass spectrometry, we examined the deposition of DPAA(V) and its pentavalent metabolites in the CNS tissues of Crl:CD(SD) rats following the administration of DPAA(V) for 28days. We found that the concentrations of DPAA(V) in the CNS were very high, given a dose of 5.0mg/kg/day. However, very low concentrations of DPAA(V) were detected at a dose of 0.3 or 1.2mg/kg/day, suggesting the absence of a linear dose-response relationship between the dose and deposition of DPAA(V). We also found that this non-linear relationship was commonly observed in various non-CNS tissues, including the excretory system. Our study showed for the first time the exact relationship between the dose and tissue deposition of the organic arsenic following its subchronic administration.

Effects of arsenolipids on in vitro blood-brain barrier model.

Arsenic-containing hydrocarbons (AsHCs), a subgroup of arsenolipids (AsLs) occurring in fish and edible algae, possess a substantial neurotoxic potential in fully differentiated human brain cells. Previous in vivo studies indicating that AsHCs cross the blood-brain barrier of the fruit fly Drosophila melanogaster raised the question whether AsLs could also cross the vertebrate blood-brain barrier (BBB). In the present study, we investigated the impact of several representatives of AsLs (AsHC 332, AsHC 360, AsHC 444, and two arsenic-containing fatty acids, AsFA 362 and AsFA 388) as well as of their metabolites (thio/oxo-dimethylpropionic acid, dimethylarsinic acid) on porcine brain capillary endothelial cells (PBCECs, in vitro model for the blood-brain barrier). AsHCs exerted the strongest cytotoxic effects of all investigated arsenicals as they were up to fivefold more potent than the toxic reference species arsenite (iAsIII). In our in vitro BBB-model, we observed a slight transfer of AsHC 332 across the BBB after 6 h at concentrations that do not affect the barrier integrity. Furthermore, incubation with AsHCs for 72 h led to a disruption of the barrier at sub-cytotoxic concentrations. The subsequent immunocytochemical staining of three tight junction proteins revealed a significant impact on the cell membrane. Because AsHCs enhance the permeability of the in vitro blood-brain barrier, a similar behavior in an in vivo system cannot be excluded. Consequently, AsHCs might facilitate the transfer of accompanying foodborne toxicants into the brain.

Arsenic trioxide at conventional dosage does not aggravate hemorrhage in the first-line treatment of adult acute promyelocytic leukemia.

OBJECTIVES: The arsenic trioxide (ATO) plus all-trans retinoic acid (ATRA) therapy has demonstrated a tremendous success in the first-line treatment of acute promyelocytic leukemia (APL). Actually, early death (ED) is currently thought as a major challenge in APL. ATO has been reported to inhibit platelet function in vitro, and whether it increases the ED rate by exacerbating the hemorrhagic symptoms remains to be investigated. METHODS: Effects of ATO on platelet aggregation and adhesion were evaluated in vitro and in thirty-two complete remission (CR) and four newly diagnosed APL patients. Furthermore, concentrations of plasma total arsenic were monitored in APL patients via ICP-MS. RESULTS: The inhibition of platelet function, either aggregation or adhesion, did occur in vitro when the concentration of ATO reached 2 µmol/L. However, in CR APL patients receiving ATO with normal platelet count, the platelets responded normally when being activated and so did those in the newly diagnosed patients with thrombocytopenia. Our data further showed that the conventional dosage of ATO reached a plasma concentration substantially below the required concentration to inhibit platelets. CONCLUSIONS: In the first-line treatment of APL, the use of ATO is safe and effective and does not compromise the hemostatic potential that may eventually increase ED rate.

Bone-targeting nanoparticle to co-deliver decitabine and arsenic trioxide for effective therapy of myelodysplastic syndrome with low systemic toxicity.

Myelodysplastic syndromes (MDS) are a diverse group of bone marrow disorders and clonal hematopoietic stem cell disorders characterized by abnormal blood cells, or reduced peripheral blood cell count. Recent clinical studies on combination therapy of decitabine (DAC) and arsenic trioxide (ATO) have demonstrated synergy on MDS treatment, but the treatment can cause significant side effects to patients. In addition, both drugs have to be administered on a daily basis due to their short half-lives. In addressing key issues of reducing toxic side effects and improving pharmacokinetic profiles of the therapeutic agents, we have developed a new formulation by co-packaging DAC and ATO into alendronate-conjugated bone-targeting nanoparticles (BTNPs). Our pharmacokinetic studies revealed that intravenously administered BTNPs increased circulation time up to 3days. Biodistribution analysis showed that the BTNP facilitated DAC and ATO accumulation in the bone, which is 6.7 and 7.9 times more than untargeted NP. Finally, MDS mouse model treated with BTNPs showed better restoration of complete blood count to normal level, and significantly longer median survival as compared to free drugs or untargeted NPs treatment. Our results support bone-targeted co-delivery of DAC and ATO for effective treatment of MDS.

Long-term accumulation of diphenylarsinic acid in the central nervous system of cynomolgus monkeys.

Diphenylarsinic acid (DPAA) is an organic arsenic compound used for the synthesis of chemical weapons. We previously found that the residents of Kamisu city in Ibaraki Prefecture, Japan, were exposed to DPAA through contaminated well water in 2003. Although mounting evidence strongly suggests that their neurological symptoms were caused by DPAA, the dynamics of DPAA distribution and metabolism after ingestion by humans remain to be elucidated. To accurately predict the distribution of DPAA in the human body, we administrated DPAA (1.0 mg/kg/day) to cynomolgus monkeys (n = 28) for 28 days. The whole tissues from these monkeys were collected at 5, 29, 170, and 339 days after the last administration. The concentration of DPAA in these tissues was measured by liquid chromatography-mass spectrometry. We found that DPAA accumulated in the central nervous system tissues for a longer period than in other tissues. This finding would extend our knowledge on the distribution dynamics and metabolism of DPAA in primates, including humans. Furthermore, it may be useful for developing a treatment strategy for patients who are exposed to DPAA.

Preparation, properties and anticancer effects of mixed As4S4/ZnS nanoparticles capped by Poloxamer 407.

Arsenic sulfide compounds have a long history of application in a traditional medicine. In recent years, realgar has been studied as a promising drug in cancer treatment. In this study, the arsenic sulfide (As4S4) nanoparticles combined with zinc sulfide (ZnS) ones in different molar ratio have been prepared by a simple mechanochemical route in a planetary mill. The successful synthesis and structural properties were confirmed and followed via X-ray diffraction and high-resolution transmission electron microscopy measurements. The morphology of the particles was studied via scanning electron microscopy and transmission electron microscopy methods and the presence of nanocrystallites was verified. For biological tests, the prepared As4S4/ZnS nanoparticles were further milled in a circulation mill in a water solution of Poloxamer 407 (0.5wt%), in order to cover the particles with this biocompatible copolymer and to obtain stable nanosuspensions with unimodal distribution. The average size of the particles in the nanosuspensions (~120nm) was determined by photon cross-correlation spectroscopy method. Stability of the nanosuspensions was determined via particle size distribution and zeta potential measurements, confirming no physico-chemical changes for several months. Interestingly, with the increasing amount of ZnS in the sample, the stability was improved. The anti-cancer effects were tested on two melanoma cell lines, A375 and Bowes, with promising results, confirming increased efficiency of the samples containing both As4S4 and ZnS nanocrystals.

Pharmacodynamics of S-dimethylarsino-glutathione, a putative metabolic intermediate of inorganic arsenic, in mice.

Inorganic arsenicals are well-known carcinogens, whereas arsenite (iAsIII) compounds are now recognized as potent therapeutic agents for several leukemias, and arsenic trioxide has been used for the treatment of recurrent acute promyelocytic leukemia (APL). However, recent clinical trials revealed that arsenite is not always effective for non-APL malignancies. Another arsenical, S-dimethylarsino-glutathione ([DMAIII(GS)]), which is a putative metabolic intermediate in the hepatic metabolism of iAsIII, shows promise for treating several types of lymphoma. However, the metabolism of [DMAIII(GS)] has not been well investigated, probably because [DMAIII(GS)] is not stable in biological fluids where the concentration of glutathione is low. In the present study, we injected [DMAIII(GS)] intravenously into mice and compared the tissue distribution and metabolic dynamics of [DMAIII(GS)] with those of sodium arsenite (NaAsO2). We found a unique organ preference for the distribution of [DMAIII(GS)] to the lung and brain in comparison to NaAsO2. Furthermore, [DMAIII(GS)] appeared to bind to serum albumin by exchanging its glutathione moiety quickly after administration, providing novel insights into the longer retention of [DMAIII(GS)] in plasma.