Importance of monitoring arsenic methylation metabolism in acute promyelocytic leukemia patients receiving the treatment of arsenic trioxide

Chronic arsenic exposure affects stromal cells and signaling in the small intestine in a sex-specific manner

Arsenic is a toxicant that is ingested through drinking water and food, exposing nearly 140 million people to levels above the 10 ppb guideline concentration. Studies have shown that arsenic affects intestinal stem cells (ISCs), but the mechanisms by which arsenic alters the formation of adult cells in the small intestine are not well understood. Signals derived from intestinal stromal cells initiate and maintain differentiation. The goal of this study is to evaluate arsenic's effect on intestinal stromal cells, including PdgfrαLo trophocytes, located proximal to the ISCs, and PdgfrαHi telocytes, located proximal to the transit-amplifying region and up the villi. Adult Sox9tm2Crm-EGFP mice were exposed to 0, 33, and 100 ppb sodium arsenite in their drinking water for 13 weeks, and sections of duodenum were examined. Flow cytometry indicated that arsenic exposure dose-responsively reduced Sox9+ epithelial cells and trended toward increased Pdgfrα+ cells. The trophocyte marker, CD81, was reduced by 10-fold and 9.0-fold in the 100 ppb exposure group in male and female mice, respectively. Additionally, a significant 2.2- to 3.1-fold increase in PdgfrαLo expression was found in male mice in trophocytes and Igfbp5+ cells. PdgfrαHi protein expression, a telocyte marker, was more prevalent along the villus/crypt structure in females, whereas Gli1 expression (telocytes) was reduced in male mice exposed to arsenic. Principle coordinate analysis confirmed the sex-dependent response to arsenic exposure, with an increase in trophocyte and decrease in telocyte marker expression observed in male mice. These results imply that arsenic alters intestinal mesenchymal cells in a sex-dependent manner.

Urine Self-Sampling Kit Combined with an Automated Preparation-Sampler Device for Convenient and Reliable Analysis of Arsenic Metabolites by HPLC-ICPMS

Speciation analysis of arsenic in urine is essential for the studies of arsenic metabolism and biological effects, but the unstable arsenic species represented by MMAIII and DMAIII pose a huge challenge to analytical accuracy. Herein, a novel urine self-sampling (USS) kit combined with an automated preparation-sampler (APS) device is rationally designed and used for convenient analysis of arsenic metabolites by high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICPMS). The subject can collect urine into a sampling vial at home and use a homemade syringe to pump argon to displace oxygen in the vial, thereby inhibiting the oxidation of MMAIII and DMAIII. After USS and transportation, the sampling vial is loaded directly onto the APS device, where the urine sample can be automatically mixed with diluent, filtered, and loaded into HPLC-ICPMS for arsenic speciation analysis under anaerobic conditions. For a single sample, the sampling time and the analysis time are <8 and <18 min, respectively. The recoveries of MMAIII and DMAIII in urine over 24 h at 4 °C are 86 and 67%, surpassing the conventional sampling method by 28 and 67%, respectively. When the APS is coupled to HPLC-ICPMS, the detection limits of AsC, iAsIII, MMAIII, DMAV, MMAV, DMAIII, and iAsV are 0.03-0.10 μg L-1 with precisions of <10%. The present method provides a convenient and reliable tool for the storage and analysis of unstable arsenic species in urine and lays the foundation for studying the metabolic and biological effects of methylated trivalent arsenicals.

Torsemide increases arsenic concentrations by inhibition of multidrug resistance protein 4 in arsenic trioxide treated acute promyelocytic leukemia patients

Torsemide is commonly used to relieve edema during the treatment of acute promyelocytic leukemia (APL) with arsenic trioxide (ATO). We explored the effect of torsemide on the plasma concentrations of inorganic arsenic (iAs), monomethylarsonic acid (MMA^V) and dimethyarsinic acid (DMA^V) in APL patients treated with ATO and clarified its molecular mechanism in rats and cells. The study included 146 APL patients treated with ATO. 60（41.1 %) of these 146 patients were co-administered with torsemide. The treatment of torsemide increased plasma concentrations of iAs (P < 0.05) and DMA^V (P < 0.05) in APL patients. The single co-administration of ATO and torsemide in rats significantly increased the plasma concentrations and AUC_(0-t) of iAs (P < 0.05) and MMA^V (P < 0.05), decreased the urinary excretion rates and the urine concentrations of iAs (P < 0.05) and DMA^V (P < 0.05), and enhanced iAs (P < 0.05) and MMA^V (P < 0.05) concentrations in the kidneys of rats. In addition, torsemide decreased the expression of multidrug resistance protein 4 (MRP4) in rat kidneys after 7 days of continuous co-administration (P < 0.05). We also treated MRP4-overexpressing HEK293T cells with ATO and different concentrations of torsemide. Torsemide markedly increased the concentrations of iAs, MMA^V and DMA^V by inhibiting MRP4 compared with ATO alone (P < 0.05). In conclusion, torsemide increased the plasma concentrations of arsenic metabolites in APL patients treated with ATO by inhibiting the transporter MRP4 in a dose-dependent manner.

The relevance of arsenic speciation analysis in health & medicine

Long term exposure to arsenic through consumption of contaminated groundwater has been a global issue since the last five decades; while from an alternate standpoint, arsenic compounds have emerged as unparallel chemotherapeutic drugs. This review highlights the contribution from arsenic speciation studies that have played a pivotal role in the progression of our understanding of the biological behaviour of arsenic in humans. We also discuss the limitations of the speciation studies and their association with the interpretation of arsenic metabolism. Chromatographic separation followed by spectroscopic detection as well as the utilization of biotinylated pull-down assays, protein microarray and radiolabelled arsenic have been instrumental in identifying hundreds of metabolic arsenic conjugates, while, computational modelling has predicted thousands of them. However, these species exhibit a variegated pattern, which supports more than one hypothesis for the metabolic pathway of arsenic. Thus, the arsenic species are yet to be integrated into a coherent mechanistic pathway depicting its chemicobiological fate. Novel biorelevant arsenic species have been identified due to significant evolution in experimental methodologies. However, these methods are specific for the identification of only a group of arsenicals sharing similar physiochemical properties; and may not be applicable to other constituents of the vast spectrum of arsenic species. Consequently, the identity of arsenic binding partners in vivo and the sequence of events in arsenic metabolism are still elusive. This resonates the need for additional focus on the extraction and characterization of both low and high molecular weight arsenicals in a combinative manner.