Metabolism of a Phenylarsenical in Human Hepatic Cells and Identification of a New Arsenic Metabolite

Synergistic Mitochondrial Genotoxicity of Carbon Dots and Arsenate in Earthworms Eisenia fetida across Generations: The Critical Role of Binding

The escalating utilization of carbon dots (CDs) in agriculture raises ecological concerns. However, their combined toxicity with arsenic remains poorly understood. Herein, we investigated the combined mitochondrial genotoxicity of CDs and arsenate at environmentally relevant concentrations across successive earthworm generations. Iron-doped CDs (CDs-Fe) strongly bound to arsenate and arsenite, while nitrogen-doped CDs (CDs-N) exhibited weaker binding. Both CDs enhanced arsenate bioaccumulation without affecting its biotransformation, with most arsenate being reduced to arsenite. CDs-Fe generated significantly more reactive oxygen species than did CDs-N, causing stronger mitochondrial DNA (mtDNA) damage. Arsenate further exacerbated the oxidative mtDNA damage induced by CDs-N, as evidenced by increased reactive oxygen species, elevated 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-OHdG) levels, and a higher correlation between 8-OHdG and mtDNA damage. This was due to arsenic inhibiting the antioxidant enzyme catalase. This exacerbation was negligible with CDs-Fe because their strong binding with arsenic prevented catalase inhibition. Maternal mitochondrial DNA damage was inherited by filial earthworms, which experienced significant weight loss in coexposure groups coupled with mtDNA toxicity. This study reveals the synergistic genotoxicity of CDs and arsenate, suggesting that CDs could disrupt the arsenic biogeochemical cycle, increase arsenate risk to terrestrial animals, and influence ecosystem stability and health through multigenerational impacts.

Facile preparation of maghemite based on iron sludge for arsenic removal from water

In this study, we demonstrated the effective acquisition of magnetic iron oxide (MIO) for As(V) adsorption by high-temperature pyrolysis of waste iron sludge from the water treatment plant under a confined environment without adding extra chemical reagents. The operating temperature and time in the pyrolysis process were optimized to improve the yield of MIO and its As(V) adsorption capacity. MIO500-2(500 °C, 2 h) had both relatively high yield and arsenic adsorption efficiency, which was characterized by XRD and XPS as mainly γ-Fe2O3 with small particle size (100-900 nm), significant mesopore (12.43 nm), high specific surface area (65.25 m2/g), and effective saturation magnetization intensity (14.45 emu/g). The maximum adsorption capacity was 14.2 ± 0.4 mg/g, and the removal rate could still reach about 80 % after five times of adsorbent regeneration. Considering this facile preparation route and its high yield, large-scale production of MIO from waste iron sludge is feasible, which is expected to provide a low-cost and efficient adsorbent for the treatment of arsenic-containing water in less economically developed areas.

Enhanced adsorption of roxarsone on iron-nitrogen co-doped biochar from peanut shell: Synthesis, performance and mechanism

Efficient removal of organic arsenic (roxarsone, ROX) from wastewater is highly demanded on the purpose of human health and environmental protection. This work aims to prepare Fe-N co-doped biochar (Fe-N-BC) via one-pot hydrothermal method using waste peanut shell, FeCl3·6H2O and urea, followed by pyrolysis. The effect of Fe-N co-doping on biochar's physicochemical properties, and adsorption performance for ROX were systematically investigated. At the pyrolysis temperature of 650 °C, Fe-N-BC-650 shows a significantly increased specific surface area of 358.53 m2/g with well-developed micro-mesoporous structure. Its adsorption capacity for ROX reaches as high as 197.32 mg/g at 25 °C, with > 90 % regeneration efficiency after multiple adsorption-desorption cycles. Correlation and spectral analysis revealed that the pore filling, π-π interactions, as well as hydrogen bonding play the dominant role in ROX adsorption. These results suggest that the Fe-N co-doped biochar shows great potential in the ROX removal from wastewater with high efficiency.

Interaction between roxarsone, an organic arsenic compound, with humic substances in the soil simulating environmental conditions

In environmental systems, the soil is a principal route of contamination by various potentially toxic species. Roxarsone (RX) is an arsenic (V) organic compound used to treat parasitic diseases and as an additive for animal fattening. When the animal excretes RX, the residues may lead to environmental contamination. Due to their physicochemical properties, the soil's humic substances (HS) are important in species distribution in the environment and are involved in various specific interaction/adsorption processes. Since RX, an arsenic (V) compound, is considered an emerging contaminant, its interaction with HS was evaluated in simulated environmental conditions. The HS-RX interaction was analyzed by monitoring intrinsic HS fluorescence intensity variations caused by complexation with RX, forming non-fluorescent supramolecular complexes that yielded a binding constant Kb (on the order of 103). The HS-RX interaction occurred through static quenching due to complex formation in the ground state, which was confirmed by spectrophotometry. The process was spontaneous (ΔG < 0), and the predominant interaction forces were van der Waals and hydrogen bonding (ΔH < 0 and ΔS < 0), with an electrostatic component evidenced by the influence of ionic strength in the interaction process. Structural changes in the HS were verified by synchronized and 3D fluorescence, with higher variation in the region referring to the protein-like fraction. In addition, metal ions (except ions Cu(II)) favored HS-RX interaction. When interacting with HS, the RX epitope was suggested by 1H NMR, which indicated that the entire molecule interacts with the superstructure. An enzyme inhibition assay verified the ability to reduce the alkaline phosphatase activity of free and complexed RX (RX-HS). Finally, this work revealed the main parameters associated with HS and RX interaction in simulated environmental conditions, thus, providing data that may help our understanding of the dynamics of organic arsenic-influenced soils.

The VEGFR2/mTOR/S6K1 pathway involved in the angiogenic effects of roxarsone in vitro and in vivo

Roxarsone, an organoarsenic compound used in poultry industry to increase weight gain, is widely used as a feed additive in some developing countries. Roxarsone has a low absorption rate and is mostly excreted with feces, which could pose a risk to human health through environmental and animal food routes. Roxarsone has been demonstrated to have tumor-promoting and proangiogenic effects. Herein, we report the role of VEGFR2/mTOR/S6K1 signaling in roxarsone-promoted vessel endothelial cell growth and angiogenesis in the Matrigel plug model and the mouse B16 cell tumor transplantation model. In angiogenesis-related experiments in vitro, 1.0 μM roxarsone significantly increased the activity, proliferation, migration, and tube formation of rat vascular endothelial cells. In addition, 1.0 μM roxarsone upregulated the protein levels of mTOR, phosphorylated mTOR, S6K1, and phosphorylated S6K1 and significantly increase the expression of Mtor and S6k1 mRNA. Rapamycin and SU5416 significantly inhibited the effects of 1.0 μM roxarsone on cell growth. Furthermore, the weight, volume, and CD31 expression of B16-F10 xenografts and Matrigel plugs in mice were upregulated by 25 mg/kg roxarsone. The protein and mRNA levels of mTOR, S6K1 and its phosphorylated protein were significantly increased in the roxarsone treatment group in xenografts. SU5416 and a short hairpin RNA targeting Vegfr2 significantly reduced roxarsone-promoted xenograft and Matrigel plug growth. In summary, this study indicated that the VEGFR2/mTOR/S6K1 signaling plays a regulatory role in roxarsone-mediated promotion angiogenesis and enhanced tumor growth.

Phenylarsonics in concentrated animal feeding operations: Fate, associated risk, and treatment approaches

Phenylarsonics are present as additives in animal feed in some countries. As only a small fraction of these additives is metabolized in animals, they mostly end up in the environment. A comprehensive investigation of the fate of these additives is crucial for evaluating their risks. This review aims to provide a clear understanding of the transformation mechanism of phenylarsonics in vivo and in vitro and to evaluate their fate and associated risks. Degradation of phenylarsonics releases toxic As species (mainly as inorganic arsenic (iAs)). Trivalent phenylarsonics are the metabolites or biotic degradation intermediates of phenylarsonics. The cleavage of As groups from trivalent phenylarsonics catalyzed by C-As lyase or other unknown pathways generates arsenite (As(III)). As(III) can be further oxidized to arsenate (As(V)) and methylated to methyl-arsenic species. The half-lives associated with abiotic degradation of phenylarsonics ranged from a few minutes to tens of hours, while those associated with biotic degradation ranged from several days to hundreds of days. Abiotic degradation resulted in a higher yield of iAs than biotic degradation. The use of phenylarsonics led to elevated total As and iAs levels in animal products and environmental matrices, resulting in As exposure risk to humans. The oxidation of phenylarsonics to As(V) facilitated the sorptive removal of As, which provides a general approach for treating these compounds. This review provides solid evidence that the use of phenylarsonics has adverse effects on both human health and environmental safety, and therefore, supports their withdrawal from the global market.

2,6-Di-tert-butylphenol and its quinone metabolite trigger aberrant transcriptional responses in C57BL/6 mice liver

2,6-Di-tert-butylphenol (2,6-DTBP) is used as an antioxidant with wide commercial applications and its residues have been detected in various environmental matrices. 2,6-DTBP may enter human body via ingestion, inhalation or other exposure pathways. However, its susceptibility to biotransformation and potential of the metabolic products to trigger aberrant transcriptional responses remain unclear. Here, we investigated in vitro and in vivo biotransformation of 2,6-DTBP and characterized the RNA-Seq based transcriptional profiling of C57BL/6 mice liver after the exposure to 2,6-DTBP and its metabolites. 2,6-DTBP was metabolized into hydroxylated (2,6-DTBH) and para-quinone (2,6-DTBQ) products with residues detected in serum and liver of C57BL/6 mice. 2,6-DTBP and 2,6-DTBQ induced the aberrant transcription in C57BL/6 mice liver featured with 373-2861 differentially expressed genes (DEGs). They also up-regulated 1.09-2.92 fold mRNA expression of carcinogenesis-related genes such as Ccnd1, TGFβ1 and FOS in C57BL/6 mice liver. Our study indicated potential carcinogenic risk of 2,6-DTBP and its metabolites, beneficial to further evaluation of health risk of TBPs-related contaminants.

Degradation of roxarsone in UV-based advanced oxidation processes: A comparative study

Organoarsenicals such as roxarsone (ROX) pose a great threat to the eco-environment and human health. Herein, the degradation of ROX via UV-based advanced oxidation processes (AOPs) including UV/hydrogen peroxide (UV/H₂O₂), UV/peroxydisulfate (UV/PDS), and UV/peroxymonosulfate (PMS) processes are comparatively investigated. The removal efficiency of ROX in the UV-based AOPs follows the order of UV/H₂O₂ >UV/PDS>UV/PMS at pH 7.0, while UV/PDS is the most effective process in reducing the total organic carbon (TOC). The second-order rate constants of ROX with hydroxyl radicals (^•OH) and sulfate radicals (SO₄^•-) are determined to be (2.71 ± 0.27)× 10⁹ and (7.68 ± 0.37)× 10⁸ M^-1s^-1, respectively. The degradation of ROX obeys the pseudo-first-order kinetics model, and the apparent rate constants (k) linearly increase with increasing the oxidants dosage from 0.10 to 1.0 mM. The solution pH (5.0-11.0) exhibits a limited effect on the oxidation of ROX in UV/H₂O₂ and UV/PDS processes, but a great enhancement is observed at pH 11.0 in UV/PMS process. Humic acid and bicarbonate obviously suppress the photodegradation of ROX. In addition, arsenic in ROX is mainly converted to As(V) in the three UV-based AOPs. Overall, this study provides essential information for the degradation of ROX via the traditional UV-based AOPs.

Screening of hub genes and prediction of putative drugs in arsenic-related bladder carcinoma: An in silico study

BACKGROUND

Evidence showed that inorganic arsenic (iAs) can trigger malignant transformation in cells with complex mechanisms. Thus, we aimed to investigate the possible molecules, pathways and therapeutic drugs for iAs-induced bladder cancer (BC) by using bioinformatics approaches.

METHODS

Microarray-based data were analyzed to screen the differentially expressed genes (DEGs) between iAs-related BC cells and controls. Then, the roles of DEGs were annotated and the hub genes were screened out by protein-protein interaction network. The key genes were further selected from the hub genes through an assessment of the prognostic values. Afterward, potential drugs were predicted by using CMAP analysis.

RESULTS

Analysis of a dataset (GSE90023) generated 21 upregulated and 47 downregulated DEGs, which were enriched in various signaling pathways. Among the DEGs, four hub genes including WNT7B, SFRP1, DNAJB2, and ATF3, were identified as the key genes because they might predict poor prognosis in BC patients. Lastly, Cantharidin was predicted to be a potential drug reversing iAs-induced malignant transformation in urinary epithelium cells.

CONCLUSION

The present study found several hub genes involved in iAs-induced malignant transformation in urinary epithelium cells, and predicted several small agents for iAs toxicity prevention or therapy.

Arsenic species in electronic cigarettes: Determination and potential health risk

Human exposure to contaminants from electronic cigarettes (e-cigarettes) and the associated health effects are poorly understood. There has been no report on the speciation of arsenic in e-liquid (solution used for e-cigarettes) and aerosols. We report here determination of arsenic species in e-liquids and aerosols generated from vaping the e-liquid. Seventeen e-liquid samples of major brands, purchased from local and online stores in Canada and China, were analyzed for arsenic species using high-performance liquid chromatography and inductively coupled plasma mass spectrometry. Aerosols condensed from vaping the e-liquids were also analyzed and compared for arsenic species. Six arsenic species were detected, including inorganic arsenate (iAs^V), arsenite (iAs^III), monomethylarsonic acid (MMA), and three new arsenic species not reported previously. In e-liquids, iAs^III was detected in 59%, iAs^V in 94%, and MMA in 47% of the samples. In the condensate of aerosols from vaping the e-liquids, iAs^III was detected in 100%, iAs^V in 88%, and MMA in 13% of the samples. Inorganic arsenic species were predominant in e-liquids and aerosols of e-cigarettes. The concentration of iAs^III in the condensate of aerosols (median 3.27 μg/kg) was significantly higher than that in the e-liquid (median 1.08 μg/kg) samples. The concentration of inorganic arsenic in the vaping air was approximately 3.4 μg/m³, which approaches to the permissible exposure limit (10 μg/m³) set by the United States Occupational Safety and Health Administration (OSHA). According to the Environmental Protection Agency's unit risk factor (4.3 × 10^-3 per μg/m³) for inhalation exposure to inorganic arsenic in the air, the estimated excess lung cancer risk from lifetime exposure to inorganic arsenic in the e-cigarette vaping air (3.4 μg/m³), assuming e-cigarette vaping at 1% of the time, is as high as 1.5 × 10^-4. These results raise health concerns over the exposure to arsenic from electronic cigarettes.

Biotransformation of arsenic-containing roxarsone by an aerobic soil bacterium Enterobacter sp. CZ-1

Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, ROX) is an arsenic-containing compound widely used as a feed additive in poultry industries. ROX excreted in chicken manure can be transformed by microbes to different arsenic species in the environment. To date, most of the studies on microbial transformation of ROX have focused on anaerobic microorganisms. Here, we isolated a pure cultured aerobic ROX-transforming bacterial strain, CZ-1, from an arsenic-contaminated paddy soil. On the basis of 16S rRNA gene sequence, strain CZ-1 was classified as a member of the genus Enterobacter. During ROX biotransformation by strain CZ-1, five metabolites including arsenate (As[V]), arsenite (As[III]), N-acetyl-4-hydroxy-m-arsanilic acid (N-AHPAA), 3-amino-4-hydroxyphenylarsonic acid (3-AHPAA) and a novel sulfur-containing arsenic species (AsC₉H₁₃N₂O₆S) were detected and identified based on high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS), HPLC-ICP-MS/electrospray ionization mass spectrometry (ESI-MS) and HPLC-electrospray ionization hybrid quadrupole time-of-flight mass spectrometry (ESI-qTOF-MS) analyses. N-AHPAA and 3-AHPAA were the main products, and 3-AHPAA could also be transformed to N-AHPAA. Based on the results, we propose a novel ROX biotransformation pathway by Enterobacter. sp CZ-1, in which the nitro group of ROX is first reduced to amino group (3-AHPAA) and then acetylated to N-AHPAA.