Role of arsenic (+3 oxidation state) methyltransferase in arsenic mediated APL treatment: an in vitro investigation

Inorganic arsenic modulates cell apoptosis by regulating Argonaute 2 expression via the p53 pathway

This study explores the role of Argonaute 2 (AGO2) in the induction of apoptosis by arsenic in 16HBE cells and investigates the association between AGO2 expression and arsenic exposure in a human population. By silencing AGO2 with siRNA, we examined its impact on cell viability and apoptosis using CCK-8, HO-PI, and JC-1 assays, complemented by qRT-PCR and Western blot analyses for gene and protein expressions. Our findings revealed a significant correlation between AGO2 expression and levels of exposure to inorganic arsenic (iAs), which was more pronounced than with other arsenic forms such as monomethylarsonic (MMA) and dimethylarsinic acids (DMA). The results showed that silencing AGO2 not only reduced cell viability but also intensified apoptosis, highlighting its role in activating the p53 pathway. This was further supported by increased phosphorylation of p53 at Ser392 and Thr55, reinforcing AGO2's involvement in apoptotic processes. The study underscores the potential of AGO2 as a therapeutic target in arsenic-related pathologies and highlights the critical need for managing occupational exposure to arsenic.

Molecular Cloning of Alternative Splicing Variants of the Porcine PML Gene and Its Expression Patterns During Japanese Encephalitis Virus Infection

Promyelocytic leukemia (PML) protein is a crucial component of PML-nuclear bodies (PML-NBs). PML and PML-NBs are involved in the regulation of various cellular functions, including the antiviral immune response. The human PML gene can generate several different isoforms through alternative splicing. However, little is known about the porcine PML alternative splicing isoforms and their expression profiles during Japanese encephalitis virus (JEV) infection. In the present study, we cloned seven mature transcripts of porcine PML, all of which contained the same N-terminal sequence but differed in the C-terminal sequences due to alternative splicing. These seven transcripts encoded five proteins all of which had the RBCC motif and sumoylation sites. Amino acid sequence homology analysis showed that porcine PML-1 had relatively high levels of identity with human, cattle, and goat homologs (76.21, 77.17, and 77.05%, respectively), and low identity with the mouse homolog (61.78%). Immunofluorescence analysis showed that the typical PML-NBs could be observed after overexpression of the five PML isoforms in PK15 cells. Quantitative reverse transcription PCR (RT-qPCR) analysis showed significant upregulation of PML isoforms and PML-NB-associated genes (Daxx and SP100) at 36 and 48 h post-infection (hpi). Western blotting analysis indicated that the PML isoforms were upregulated during the late stage of infection. Moreover, the number of PML-NBs was increased after JEV infection. These results suggest that porcine PML isoforms may play essential roles in JEV infection.

Monomethylated arsenic was the Major methylated arsenic in Red blood cells of acute promyelocytic leukemia patients treated with arsenic trioxide

BACKGROUND

Arsenic trioxide (ATO) has been successfully applied in the treatment of acute promyelocytic leukemia (APL). Arsenic metabolites including inorganic arsenic and methylated arsenic could lead to different toxicity and curative effect. This study aims to establish a method to determine arsenic species in red blood cells (RBCs), clarify the distribution characteristics of arsenic species in RBCs.

METHODS

Steady state blood samples were collected from 97 APL patients. H₂O₂ and HClO₄ were used to release the hemoglobin bounding arsenic and precipitate protein. Arsenite (iAs^III), arsenate (iAs^V), monomethylarsonic acid (MMA^V) and dimethylarsinic acid (DMA^V) in plasma and RBCs were detected by HPLC-HG-AFS. Free and bound arsenic species in RBCs were separated by 30 kDa molecular mass cutoff filters and determined to evaluate hemoglobin binding capacity of different arsenic species.

RESULTS

The method was validated with accuracy ranged from 84.75% to 104.13%. Arsenic species in RBCs followed the trend iAs > MMA > DMA (p < 0.01), while the concentration of DMA was significantly higher than iAs and MMA in plasma (p < 0.01). The correlation between iAs concentration in plasma and corresponding RBCs arsenic level was weak. And the concentrations of DMA and MMA in plasma were moderately positive correlated with those in RBCs. Hemoglobin-binding ratios of iAs, MMA and DMA were all over 70 %.

CONCLUSIONS

In this study, we provided a reliable method to determine arsenic species in RBCs of APL patients treated with ATO by HPLC-HG-AFS. It was confirmed that the concentration of DMA is the highest in plasma, while MMA is the most predominant methylated arsenic in RBCs. High affinity of MMA with human Hb was responsible for the accumulation of arsenic in RBCs of APL patients.

Arsenic induced epigenetic changes and relevance to treatment of acute promyelocytic leukemia and beyond

Epigenetic alterations regulate gene expression without changes in the DNA sequence. It is well-demonstrated that aberrant epigenetic changes contribute to the leukemogenesis of acute promyelocytic leukemia (APL). Arsenic trioxide (ATO) is one of the most common drugs used in the frontline treatment of APL that act through targeting and destabilizing the PML/RARα oncofusion protein. ATO together with all-trans retinoic acid (ATRA) lead to durable remission of more than 90% non-high-risk APL patients, turning APL treatment into a paradigm of oncoprotein targeted cure. Although relapse and drug resistance in APL are yet to be resolved in the clinic, epigenetic machineries might hold the key to address this issue. Further, ATO also showed promising anticancer activities against a variety of malignancies, but its application is particularly restricted due to limited understanding of the mechanism. Thus, a thorough understanding of epigenetic mechanism behind anti-leukemic effects of ATO would benefit the development of ATO-based anticancer strategy. Role of ATRA on APL associated epigenetic alterations has been extensively studied and reviewed. Recently, accumulating evidence suggest that ATO also induces some epigenetic changes that might favor APL eradication. In this article, we comprehensively discuss arsenic induced epigenetic changes and its relevance in APL treatment and beyond, so as to provide novel insights into overcoming arsenic resistance in APL and promote application of this drug to other malignancies.

Biotransformation of arsenic trioxide by AS3MT favors eradication of acute promyelocytic leukemia: revealing the hidden facts

Arsenic trioxide (ATO) is one of the most effective drugs for treatment of acute promyelocytic leukemia (APL). It could specifically target the PML/RARα fusion oncoprotein stability and induces APL cell differentiation as well as apoptosis. Although many studies have been conducted to document the anticancer effects and mechanism of ATO, there is little information about the association between biotransformation of ATO to active arsenic metabolites and APL therapy. Generally, ATO can be rapidly converted into trivalent methylated metabolites by arsenic (+3 oxidation state) methyltransferase (AS3MT) mostly in liver and redistributed to bloodstream of APL patients who receiving ATO treatment, thereby leading to a balance between cytotoxicity and differentiation, which is proposed to be the key event in successful treatment of APL. In this review, we comprehensively discussed possible roles of AS3MT and methylated arsenic metabolites in APL therapy, so as to reveal the association between individual differences of AS3MT expression and activity with the therapeutic efficacy of ATO in APL patients.

Polymorphisms in arsenic (+ 3 oxidation state) methyltransferase (AS3MT) predict the occurrence of hyperleukocytosis and arsenic metabolism in APL patients treated with As2O3

Polymorphisms in arsenic (+ 3 oxidation state) methyltransferase (AS3MT) have been shown to be related to interindividual variations in arsenic metabolism and to influence adverse health effects in acute promyelocytic leukemia (APL) patients treated with arsenic trioxide (As₂O₃). The occurrence of hyperleukocytosis with As₂O₃ treatment seriously affects the early survival rate of APL patients, but no definite explanation for such a complication has been clearly established. To clarify the causes of this situation, AS3MT polymorphisms 14215 (rs3740390), 14458 (rs11191439), 27215 (rs11191446), and 35991 (rs10748835) and profiles of plasma arsenic metabolites were evaluated in a group of 54 newly diagnosed APL patients treated with single-agent As₂O₃. High-performance liquid chromatography-hydride generation-atomic fluorescence spectrometry (HPLC-HG-AFS) was used to determine the concentrations of plasma arsenic metabolites. Plasma arsenic methylation metabolism capacity was evaluated by the percentage of inorganic arsenic (iAs), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), primary methylation index (PMI, MMA/iAs), and secondary methylation index (SMI, DMA/MMA). The results showed that APL patients who developed hyperleukocytosis had a higher plasma iAs%, but a lower MMA% and PMI than those who did not develop hyperleukocytosis during As₂O₃ treatment. In addition, patients with the AS3MT 14215 (rs3740390) CC genotype had significantly higher plasma iAs% and incidence of hyperleukocytosis, but lower PMI than patients with the CT + TT genotype. Conversely, we did not observe statistically significant associations between the occurrence of hyperleukocytosis and AS3MT 14458 (rs11191439), 27215 (rs11191446), and 35991 (rs10748835) polymorphisms in our study subjects. These results indicated that AS3MT 14215 (rs3740390) might be used as an indicator for predicting the occurrence of hyperleukocytosis in APL patients treated with As₂O₃.

The Human Gut Microbiome's Influence on Arsenic Toxicity

PURPOSE OF REVIEW

Arsenic exposure is a public health concern of global proportions with a high degree of interindividual variability in pathologic outcomes. Arsenic metabolism is a key factor underlying toxicity, and the primary purpose of this review is to summarize recent discoveries concerning the influence of the human gut microbiome on the metabolism, bioavailability, and toxicity of ingested arsenic. We review and discuss the current state of knowledge along with relevant methodologies for studying these phenomena.

RECENT FINDINGS

Bacteria in the human gut can biochemically transform arsenic-containing compounds (arsenicals). Recent publications utilizing culture-based approaches combined with analytical biochemistry and molecular genetics have helped identify several arsenical transformations by bacteria that are at least possible in the human gut and are likely to mediate arsenic toxicity to the host. Other studies that directly incubate stool samples in vitro also demonstrate the gut microbiome's potential to alter arsenic speciation and bioavailability. In vivo disruption or elimination of the microbiome has been shown to influence toxicity and body burden of arsenic through altered excretion and biotransformation of arsenicals. Currently, few clinical or epidemiological studies have investigated relationships between the gut microbiome and arsenic-related health outcomes in humans, although current evidence provides strong rationale for this research in the future.

SUMMARY

The human gut microbiome can metabolize arsenic and influence arsenical oxidation state, methylation status, thiolation status, bioavailability, and excretion. We discuss the strength of current evidence and propose that the microbiome be considered in future epidemiologic and toxicologic studies of human arsenic exposure.

Influence of AS3MT polymorphisms on arsenic metabolism and liver injury in APL patients treated with arsenic trioxide

Arsenic-induced side effects limit its application in the treatment of acute promyelocytic leukemia (APL). We recently demonstrated that AS3MT 14215 (rs3740390) genotypes were associated with urinary arsenic metabolites and hematological and biochemical values. To further decipher the role of AS3MT genotypes on arsenic metabolism and toxicity, AS3MT 27215 (rs11191446), 35587 (rs11191453), 35991 (rs10748835), and their interactive effects were examined in fifty APL patients treated with arsenic trioxide (As₂O₃) for the first time. Urinary arsenic metabolites and methylation capacity indexes were evaluated by the percentage of inorganic arsenic (iAs), monomethylarsonate (MMA), dimethylarsinate (DMA), primary methylation index (PMI, MMA/iAs), secondary methylation index (SMI, DMA/MMA), and total methylation index (TMI, [MMA+DMA]/iAs). Results showed 27215 (rs11191446) genotypes had no statistical significance in arsenic metabolism, as only 5 (10%) patients were the non-wild-type genotypes. 35587 (rs11191453) genotypes were significantly associated with MMA%, DMA%, and SMI. 35991 (rs10748835) genotypes were significantly associated with iAs%, DMA%, PMI, TMI, and the level of ALT and AST. Patients with both 35587 (rs11191453) TT and 35991 (rs10748835) AG+GG genotypes were significantly associated with DMA% and SMI. In addition, patients with both 35991 (rs10748835) AA and 35587 (rs11191453) TC+CC genotypes had the highest DMA%, SMI, and TMI, but the lowest iAs%, ALT and AST level, indicating that additive effects exist on arsenic metabolism and liver function. Our data promotes the realization that AS3MT 35587 (rs11191453), 35991 (rs10748835), especially their joint genotypes 35991 (rs10748835) AA / 35587 (rs11191453) TC+CC, is a novel predictive biomarker for the therapeutic efficacy of As₂O₃ in the treatment of APL.

Irreversibility of arsenic trioxide induced PML/RARα fusion protein solubility changes

Arsenic trioxide induced PML/RARα fusion protein solubility change is an irreversible process, and the insoluble protein can be further degraded by the proteasomal pathway even without continuous exposure to arsenic.

Integrity of zinc finger motifs in PML protein is necessary for inducing its degradation by antimony

The presence of zinc ions in a zinc finger motif of a PML protein is a fundamental requirement for the protein's degradation by antimony.

Distribution of Arsenic Resistance Genes in Prokaryotes

Arsenic is a metalloid that occurs naturally in aquatic and terrestrial environments. The high toxicity of arsenic derivatives converts this element in a serious problem of public health worldwide. There is a global arsenic geocycle in which microbes play a relevant role. Ancient exposure to arsenic derivatives, both inorganic and organic, has represented a selective pressure for microbes to evolve or acquire diverse arsenic resistance genetic systems. In addition, arsenic compounds appear to have been used as a toxin in chemical warfare for a long time selecting for an extended range of arsenic resistance determinants. Arsenic resistance strategies rely mainly on membrane transport pathways that extrude the toxic compounds from the cell cytoplasm. The ars operons, first discovered in bacterial R-factors almost 50 years ago, are the most common microbial arsenic resistance systems. Numerous ars operons, with a variety of genes and different combinations of them, populate the prokaryotic genomes, including their accessory plasmids, transposons, and genomic islands. Besides these canonical, widespread ars gene clusters, which confer resistance to the inorganic forms of arsenic, additional genes have been discovered recently, which broadens the spectrum of arsenic tolerance by detoxifying organic arsenic derivatives often used as toxins. This review summarizes the presence, distribution, organization, and redundance of arsenic resistance genes in prokaryotes.