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Arsenic trioxide (ATO) is used as a chemotherapeutic agent for the treatment of acute promyelocytic leukemia. However, increasing drug resistance is reducing its efficacy. Therefore, a better understanding of ATO resistance mechanism is required. In this study, we established an ATO-resistant human epidermoid carcinoma cell line, KB/ATO, from its parental KB-3-1 cells. In addition to ATO, KB/ATO cells also exhibited cross-resistance to other anticancer drugs such as cisplatin, antimony potassium tartrate, and 6-mercaptopurine. The arsenic accumulation in KB/ATO cells was significantly lower than that in KB-3-1 cells. Further analysis indicated that neither application of P-glycoprotein inhibitor, breast cancer resistant protein (BCRP) inhibitor, or multidrug resistance protein 1 (MRP1) inhibitor could eliminate ATO resistance. We found that the expression level of ABCB6 was increased in KB/ATO cells. In conclusion, ABCB6 could be an important factor for ATO resistance in KB/ATO cells. The ABCB6 level may serve as a predictive biomarker for the effectiveness of ATO therapy., Graphical abstract An ATO-resistant human epidermoid carcinoma cell line, KB/ATO, was established from its parental KB-3-1 cells. The arsenic accumulation in KB/ATO cells was significantly lower than that in KB-3-1 cells and the expression level of ABCB6 was increased. The upregulated ABCB6 may be important for ATO resistance in KB/ATO cells.fx1

2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47), a predominant polybrominated diphenyl ether (PBDE), has received extensive attention for its potential environmental impact. An integrated study of metabolomics and transcriptomics was conducted on two rice (Oryza sativa) cultivars, Lianjing-7 (LJ-7) and Yongyou-9 (YY-9), which have been identified as tolerant and sensitive cultivars to BDE-47, respectively. The objective was to investigate the molecular mechanisms of their different ability to tolerate BDE-47. Both rice plants were cultivated to maturity in soils containing three concentrations of BDE-47 (10, 20, and 50 mg/kg). Metabolomic analyses of rice grains identified 65 metabolites in LJ-7 and 45 metabolites in YY-9, including amino acids, saccharides, organic acids, fatty acids, and secondary metabolites. In the tolerant cultivar LJ-7 exposed to 50 mg/kg BDE-47, concentrations of most of the metabolites increased significantly, with α-ketoglutaric acid increased by 20-fold and stigmastanol increased by 12-fold. In the sensitive cultivar YY-9, the concentrations of most metabolites increased after the plant was exposed to 1 and 10 mg/kg BDE-47 but decreased after the plant was exposed to 50 mg/kg BDE-47. Transcriptomic data demonstrated that regulation of gene expressions was affected most in LJ-7 exposed to 50 mg/kg BDE-47 (966 genes up-regulated and 620 genes down-regulated) and in YY-9 exposed to 10 mg/kg BDE-47 (85 genes up-regulated and 291 genes down-regulated), in good accordance with the observed metabolic alternation in the two cultivars. Analyses of metabolic pathways and KEGG enrichment revealed that many biological processes, including energy consumption and biosynthesis, were perturbed in the two rice cultivars by BDE-47. A majority of metabolites and genes involved in dominating pathways of energy consumption (e.g., tricarboxylic acid cycle) and the biosynthesis (e.g., metabolism of saccharides and amino acids) were enhanced in LJ-7 by BDE-47. In contrast, energy consumption was increased while biosynthetic processes were inhibited in YY-9 by BDE-47, which could lead to the sensitivity of YY-9 to BDE-47. The combined results suggest that the different defensive abilities of these two rice cultivars in response to BDE-47 could be attributed to their differences in energy-consumption strategy and biosynthesis of nutritional components in grains. This study provides a useful reference for rice cultivation in PBDE-polluted areas. Keywords: Polybrominated diphenyl ethers, Rice, Metabolomics, Transcriptomics, Plant resistance, Defense mechanism

Understanding how cells interact and communicate with each other in multicellular organisms is essential to understanding diverse life and biological processes. However, the complicated nature of cells, their various in vivo microenvironments, and the multitude of changing environmental and biological signals that confront cells make it challenging to probe and control cell–cell interaction and communication using conventional macro-scale and population-averaged tools. With the rapid advances in bioengineering, we now have ever finer tools to peek increasingly closely at cellular processes, including the interaction and communication of cells with each other. In this chapter, we discuss established as well as emerging micro-, nano-, and molecular-scale genetic, chemical, and engineering tools designed to address remaining challenges in cell–cell interactions and communication. Microengineering tools, such as microfluidic chips, microwells, and microdroplets, make possible the manipulation of the spatial and temporal distribution of individual cells or defined homotypic and heterotypic cell clusters, thus simplifying the complicated in vivo microenvironments into well-controlled in vitro platforms. Molecular tools based on genetic or chemical approaches, frequently utilizing fluorescent or luminescent reporter signals, are being used at increased resolution to interrogate target cells. Moreover, with advances in complementary imaging systems, such as two-photon imaging, it is now possible to probe cell–cell interactions in their in vivo microenvironments. The knowledge derived from these studies is expected to not only increase the information content on various biological processes but also reveal novel paradigms of cellular and physiological processes, thereby also helping in the design of novel strategies to diagnose and treat diseases.

Arsenic speciation in biological specimens can provide quantitative data for the evaluation of arsenic toxicity since the toxicity of arsenic can vary significantly depending on the chemical form and oxidation state. Extraction of arsenic from biological specimens is a critical step, prior to arsenic speciation analysis, which often involves high-performance liquid chromatography separation followed by inductively coupled plasma mass spectrometry detection. Mild conditions during extractions are necessary to maintain the integrity of arsenic species originally present in samples, although extraction efficiencies may be compromised under these mild conditions. Enzymatic digestion of biological specimens can be utilized to help improve extraction efficiency. Individual groups of enzymes, such as proteases, lipases, and carbohydrases, as well as various combinations of these enzymes, have been applied for the digestion of proteins, cell lysates, hair, fish tissues, and plant materials. This enzymatic treatment step has been conducted with or without the use of microwave digestion or sonication. The enzyme digestion method not only provides efficient digestion capability to cut matrix macromolecules into small fragments and release arsenic into the extraction solution, but also provides a mild environment in which the chemical integrity of the less stable arsenic species is maintained.

Urine, as a normal biologically excreted body fluid, is very useful specimen for disease diagnosis and biomarker analysis. Urine sample collection is generally noninvasive. Many procedures have been developed and validated for the collection of urine samples from healthy people, patients, and animal species. Methods for handling, storage, and treatment of urine samples depend on the purpose of the analysis, the nature of the analysis, and the target analytes. This chapter describes the types of urine samples, protocols of urine collection, procedures for sample handling, and methods of sample treatment, with examples of target analyte and analytical purposes. Various sample pretreatment methods, including centrifugation, extraction, protein depletion, and nucleic acid purification, are discussed for different analytical objectives. Commonly used sampling protocols in clinical laboratories for routine urine analysis are summarized. More sophisticated analysis and research involving genomics, proteomics, and metabolomics demand further development of appropriate sample handling and treatment procedures.

Publisher Summary Metabolism of arsenate (As[V]) in most mammalian species proceeds via reduction to arsenite (As[III]) and biomethylation to monomethylarsonic acid (MMA[V]). MMA[V] is subsequently reduced to monomethylarsonous acid (MMA[III]) and then biomethylated to dimethylarsinic acid (DMA[V]), which is the major arsenic (As) metabolite excreted in the urine of most mammalian species. Both methylation reactions are catalyzed by methyltransferases that require S-adenosylmethionine (SAM) as the methyl donor. SAM is eventually regenerated by remethylation through the homocysteine remethylation cycle, a process that requires (6S)-5-methyl tetrahydrofolate as a co-factor, and thus it seems as if arsenic biomethylation is dependent on an adequate folate supply.

Publisher Summary Biomethylation is the major metabolic process for inorganic arsenic (As). The methylation process involves stepwise two-electron reduction of As, followed by oxidative addition of a methyl group. Methyltransferases are responsible for methyl transfer, and S-adenosyl-methionine (SAM) is the methyl donor. Trimethylarsine oxide (TMAOV) and trimethylarsine (TMAIII) are the end products formed by some microorganisms. Dimethylarsinic acid (DMAV) is the usual end product detected in humans, although dimethylarsinous acid (DMAIII) has recently been detected in human urine. An important issue regarding the speciation of monomethylarsonous acid (MMAIII) and dimethylarsinous acid (DMAIII) is the stability and preservation of these species. It has been reported that MMAIII and DMAIII are less stable than the other As species, suggesting that new strategies for sample handling are needed for the analysis of these trivalent As species.