The mRNA-capping enzyme localizes to stress granules in the cytoplasm and maintains cap homeostasis of target mRNAs.

The model of RNA stability has undergone a transformative shift with the revelation of a cytoplasmic capping activity that means a subset of transcripts are recapped autonomously of their nuclear counterparts. The present study demonstrates nucleo-cytoplasmic shuttling of the mRNA-capping enzyme (CE, also known as RNA guanylyltransferase and 5'-phosphatase; RNGTT), traditionally acknowledged for its nuclear localization and functions, elucidating its contribution to cytoplasmic capping activities. A unique nuclear export sequence in CE mediates XPO1-dependent nuclear export of CE. Notably, during sodium arsenite-induced oxidative stress, cytoplasmic CE (cCE) congregates within stress granules (SGs). Through an integrated approach involving molecular docking and subsequent co-immunoprecipitation, we identify eIF3b, a constituent of SGs, as an interactive associate of CE, implying that it has a potential role in guiding cCE to SGs. We measured the cap status of specific mRNA transcripts from U2OS cells that were non-stressed, stressed and recovered from stress, which indicated that cCE-target transcripts lost their caps during stress but remarkably regained cap stability during the recovery phase. This comprehensive study thus uncovers a novel facet of cytoplasmic CE, which facilitates cellular recovery from stress by maintaining cap homeostasis of target mRNAs.

Sodium arsenite and arsenic trioxide differently affect the oxidative stress of lymphoblastoid cells: An intricate crosstalk between mitochondria, autophagy and cell death.

Although the toxicity of arsenic depends on its chemical forms, few studies have taken into account the ambiguous phenomenon that sodium arsenite (NaAsO2) acts as a potent carcinogen while arsenic trioxide (ATO, As2O3) serves as an effective therapeutic agent in lymphoma, suggesting that NaAsO2 and As2O3 may act via paradoxical ways to either promote or inhibit cancer pathogenesis. Here, we compared the cellular response of the two arsenical compounds, NaAsO2 and As2O3, on the Burkitt lymphoma cell model, the Epstein Barr Virus (EBV)-positive P3HR1 cells. Using flow cytometry and biochemistry analyses, we showed that a NaAsO2 treatment induces P3HR1 cell death, combined with drastic drops in ΔΨm, NAD(P)H and ATP levels. In contrast, As2O3-treated cells resist to cell death, with a moderate reduction of ΔΨm, NAD(P)H and ATP. While both compounds block cells in G2/M and affect their protein carbonylation and lipid peroxidation, As2O3 induces a milder increase in superoxide anions and H2O2 than NaAsO2, associated to a milder inhibition of antioxidant defenses. By electron microscopy, RT-qPCR and image cytometry analyses, we showed that As2O3-treated cells display an overall autophagic response, combined with mitophagy and an unfolded protein response, characteristics that were not observed following a NaAsO2 treatment. As previous works showed that As2O3 reactivates EBV in P3HR1 cells, we treated the EBV- Ramos-1 cells and showed that autophagy was not induced in these EBV- cells upon As2O3 treatment suggesting that the boost of autophagy observed in As2O3-treated P3HR1 cells could be due to the presence of EBV in these cells. Overall, our results suggest that As2O3 is an autophagic inducer which action is enhanced when EBV is present in the cells, in contrast to NaAsO2, which induces cell death. That's why As2O3 is combined with other chemicals, as all-trans retinoic acid, to better target cancer cells in therapeutic treatments.

Betaine Protects Mice from Cardiotoxicity Triggered by Sodium Arsenite Through Antioxidative and Anti-inflammatory Pathways.

NaAsO2 is known as a harmful pollutant all over the world, and many chronic heart diseases can be attributed to its prolonged exposure in NaAsO2-contaminated water. Therefore, considering the anti-inflammatory and antioxidant effects of betaine (BET), in this study, our team investigated the cardioprotective effects of this phytochemical agent on sodium arsenite (NaAsO2)-induced cardiotoxicity. Forty male mice were randomly divided into 4 groups: (I) Control; (II) BET (500 mg/kg); (III) NaAsO2 (50 ppm); and (IV) NaAsO2 + BET. NaAsO2 was given to the animals for 8 weeks, but BET was given in the last two weeks. After decapitation, inflammatory factors and biochemical parameters were measured, and Western blot analyses were performed. BET decrease the activity level of alanine aspartate aminotransferase, creatine kinase MB, thiobarbituric acid reactive substances level, inflammatory factors (tumor necrosis factor-α) content, and nuclear factor kappa B expression. Furthermore, BET increased cardiac total thiol and activity levels of catalase, superoxide dismutase, and glutathione peroxidase and nuclear factor erythroid-2 expression. Hence, the administration of BET ameliorated the deleterious effects stemming from the imbalance of oxidative and antioxidant pathways and histopathological alterations observed in NaAsO2-intoxicated mice, thereby attenuating oxidative stress-induced damage and inflammation.

Sodium arsenite induces hepatic stellate cells activation by m6A modification of TGF-ß1 during liver fibrosis.

The compound known as Sodium arsenite (NaAsO2), which is a prevalent type of inorganic arsenic found in the environment, has been strongly associated with liver fibrosis (LF), a key characteristic of nonalcoholic fatty liver disease (NAFLD), which has been demonstrated in our previous study. Our previous research has shown that exposure to NaAsO2 triggers the activation of hepatic stellate cells (HSCs), a crucial event in the development of LF. However, the molecular mechanism is still unknown. N6-methyladenosine (m6A) modification is the most crucial post-transcriptional modification in liver disease. Nevertheless, the precise function of m6A alteration in triggering HSCs and initiating LF caused by NaAsO2 remains unknown. Here, we found that NaAsO2 induced LF and HSCs activation through TGF-ß/Smad signaling, which could be reversed by TGF-ß1 knockdown. Furthermore, NaAsO2 treatment enhanced the m6A modification level both in vivo and in vitro. Significantly, NaAsO2 promoted the specific interaction of METTL14 and IGF2BP2 with TGF-ß1 and enhanced the TGF-ß1 mRNA stability. Notably, NaAsO2-induced TGF-ß/Smad pathway and HSC-t6 cells activation might be avoided by limiting METTL14/IGF2BP2-mediated m6A modification. Our findings showed that the NaAsO2-induced activation of HSCs and LF is made possible by the METTL14/IGF2BP2-mediated m6A methylation of TGF-ß1, which may open up new therapeutic options for LF brought on by environmental hazards.

Transformation of dissolved organic matter during groundwater arsenite removal using air cathode iron electrocoagulation.

Dissolve organic matters (DOM) usually showed negative effect on the removal of inorganic arsenic (As) in groundwater by electrochemical approaches, yet which parts of sub-component within DOM played the role was lack of evidence. Herein, we investigated the effects of land-source humic-like acid (HA) on groundwater As(III) removal using air cathode iron electrocoagulation, based on the parallel factor analysis of three-dimensional excitation-emission matrix and statistical methods. Our results showed that the land-source HA contained five kinds of components and all components presented significantly negative correlations with the removal of both As(III) and As(V). However, the high aromatic fulvic-like acid and low aromatic humic-like acid components of land-source HA presented the opposite correlations with the concentration of As(III) during the reaction. The high aromaticity fulvic-like components of land-source HA (Sigma-Aldrich HA, SAHA) produced during the reaction facilitated the oxidation of As(III) due to its high electron transfer capacities and good solubility in wide pH range, but the low aromaticity humic-like ones worked against the oxidation of As(III). Our findings offered the novel insights for the flexible activities of DOM in electron Fenton system.

Urea cycle promotion via ammonia-upregulated CPS1 is involved in arsenite-induced pulmonary fibrosis through enhancing collagen synthesis.

Arsenic exposure is connected with lung toxicity and is related to lung fibrotic changes. Idiopathic pulmonary fibrosis (IPF) is characterized by extracellular matrix (ECM) deposition. Various genetic mechanisms and environmental factors induce or exacerbate pulmonary fibrosis. Collagen synthesis induced by sodium arsenite (NaAsO2) is closely associated with IPF. Fibroblasts tend to fine-tune their metabolic networks to support their synthetic requirements in response to environmental stimuli. Alterations in metabolism have an influential role in the pathogenesis of IPF. However, it is unclear how arsenic affects the metabolism in IPF. The urea cycle (UC) is needed for collagen formation, which provides adequate levels of proline (Pro) for biosynthesis of collagen. Carbamoyl phosphate synthetase 1 (CPS1) converts the ammonia to carbamoyl phosphate, which controls the first reaction of the UC. We show that, in arsenite-exposed mice, high amounts of ammonia in the lung microenvironment promotes the expression levels of CPS1 and the Pro metabolism. Reduction of ammonia and CPS1 ablation inhibit collagen synthesis and ameliorate IPF phenotypes induced by arsenite. This work takes advantage of multi-omics data to enhance understanding of the underlying pathogenic mechanisms, the key molecules and the complicated cellular responses to this pollutant, which provide a target for the prevention of pulmonary fibrosis caused by arsenic.

In vitro study on the competitive reactions between arsenite and selenite with glutathione.

Exposure to arsenic can cause various biological effects by increasing the production of reactive oxygen species (ROS). Selenium acts as a beneficial element by regulating ROS and limiting heavy metal uptake and translocation. There are studies on the interactive effects of As and Se in plants, but the antagonistic and synergistic effects of these elements based on their binding to glutathione (GSH) molecules have not been studied yet. In this study, we aimed to investigate the antagonistic or synergistic effects of As and Se on the binding mechanism of Se and As with GSH at pH 3.0, 5.0, or 6.5. The interaction of As and Se in Se(SG)2 + As(III) or As(SG)3 + Se(IV) binary systems and As(III) + Se(IV) + GSH ternary system were examined depending on their ratios via liquid chromatography diode array detector/electrospray mass spectrometry (LC-DAD/MS) and liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The results showed that the formation of As(GS)3 was not detected in the As(III) + Se(SG)2 binary system, indicating that As(III) did not affect the stability of Se(SG)2 complex antagonistically. However, in the Se(IV) + As(SG)3 binary system, the addition of Se(IV) to As(SG)3 affected the stability of As(SG)3 antagonistically. Se(IV) reacted with GSH, disrupting the As(SG)3 complex, and consequently, Se(SG)2 formation was measured using LC-MS/DAD. In the Se(IV) + GSH + As(III) ternary system, Se(SG)2 formation was detected upon mixing As(III), Se(IV), and GSH. The increase in the concentration of As(III) did not influence the stability of the Se(SG)2 complex. Additionally, Se(IV) has a higher affinity than As(III) to the GSH, regardless of the pH of the solution. In both binary and ternary systems, the formation of the by-product glutathione trisulfide (GSSSG) was detected using LC-ESI-MS/MS.

NBR1-mediated autophagic degradation of caspase 8 protects vascular endothelial cells against arsenite-induced apoptotic cell death.

Vascular endothelial cells play a critical role in maintaining the health of blood vessels, but dysfunction can lead to cardiovascular diseases. The impact of arsenite exposure on cardiovascular health is a significant concern due to its potential adverse effects. This study aims to explore how NBR1-mediated autophagy in vascular endothelial cells can protect against oxidative stress and apoptosis induced by arsenite. Initially, our observations revealed that arsenite exposure increased oxidative stress and triggered apoptotic cell death in human umbilical vein endothelial cells (HUVECs). However, treatment with the apoptosis inhibitor Z-VAD-FMK notably reduced arsenite-induced apoptosis. Additionally, arsenite activated the autophagy pathway and enhanced autophagic flux in HUVECs. Interestingly, inhibition of autophagy exacerbated arsenite-induced apoptotic cell death. Our findings also demonstrated the importance of autophagy receptor NBR1 in arsenite-induced cytotoxicity, as it facilitated the recruitment of caspase 8 to autophagosomes for degradation. The protective effect of NBR1 against arsenite-induced apoptosis was compromised when autophagy was inhibited using pharmacological inhibitors or through genetic knockdown of essential autophagy genes. Conversely, overexpression of NBR1 facilitated caspase 8 degradation and reduced apoptotic cell death in arsenite-treated HUVECs. In conclusion, our study highlights the vital role of NBR1-mediated autophagic degradation of caspase 8 in safeguarding vascular endothelial cells from arsenite-induced oxidative stress and apoptotic cell death. Targeting this pathway could offer a promising therapeutic approach to mitigate cardiovascular diseases associated with arsenite exposure.

mTORC1 - TFEB pathway was involved in sodium arsenite induced lysosomal alteration, oxidative stress and genetic damage in BEAS-2B cells.

The mechanistic target of rapamycin (RAPA) complex 1 (mTORC1) - transcription factor EB (TFEB) pathway plays a crucial role in response to nutritional status, energy and environmental stress for maintaining cellular homeostasis. But there is few reports on its role in the toxic effects of arsenic exposure and the related mechanisms. Here, we show that the exposure of bronchial epithelial cells (BEAS-2B) to sodium arsenite promoted the activation of mTORC1 (p-mTORC1) and the inactivation of TFEB (p-TFEB), the number and activity of lysosomes decreased, the content of reduced glutathione (GSH) and superoxide dismutase (SOD) decreased, the content of malondialdehyde (MDA) increased, the DNA and chromosome damage elevated. Further, when mTORC1 was inhibited with RAPA, p-mTORC1 and p-TFEB down-regulated, GSH and SOD increased, MDA decreased, the DNA and chromosome damage reduced significantly, as compared with the control group. Our data revealed for the first time that mTORC1 - TFEB pathway was involved in sodium arsenite induced lysosomal alteration, oxidative stress and genetic damage in BEAS-2B cells, and it may be a potential intervention target for the toxic effects of arsenic.

Bacteria associated with Comamonadaceae are key arsenite oxidizer associated with Pteris vittata root.

Pteris vittata (P. vittata), an arsenic (As) hyperaccumulator commonly used in the phytoremediation of As-contaminated soils, contains root-associated bacteria (RAB) including those that colonize the root rhizosphere and endosphere, which can adapt to As contamination and improve plant health. As(III)-oxidizing RAB can convert the more toxic arsenite (As(III)) to less toxic arsenate (As(V)) under As-rich conditions, which may promote plant survial. Previous studies have shown that microbial As(III) oxidation occurs in the rhizospheres and endospheres of P. vittata. However, knowledge of RAB of P. vittata responsible for As(III) oxidation remained limited. In this study, members of the Comamonadaceae family were identified as putative As(III) oxidizers, and the core microbiome associated with P. vittata roots using DNA-stable isotope probing (SIP), amplicon sequencing and metagenomic analysis. Metagenomic binning revealed that metagenome assembled genomes (MAGs) associated with Comamonadaceae contained several functional genes related to carbon fixation, arsenic resistance, plant growth promotion and bacterial colonization. As(III) oxidation and plant growth promotion may be key features of RAB in promoting P. vittata growth. These results extend the current knowledge of the diversity of As(III)-oxidizing RAB and provide new insights into improving the efficiency of arsenic phytoremediation.

Identification of a novel RNA transcript TISPL upregulated by stressors that stimulate ATF4.

Cells sense, respond, and adapt to environmental conditions that cause stress. In a previous study using HeLa cells, we isolated reporter cells responding to the endoplasmic reticulum (ER) stress inducers, thapsigargin and tunicamycin, using a highly sensitive promoter trap vector system. Splinkerette PCR and 5' rapid amplification of cDNA ends (5' RACE) identified a novel transcript that is upregulated by ER stress. Its endogenous expression increased approximately 10-fold in response to thapsigargin and tunicamycin within 1 h, but was down-regulated after 4 h. Because the transcript starts from an intron of a long noncoding RNA known as LINC-PINT, we designated the newly identified transcript TISPL (transcript induced by stressors from LINC-PINTlocus). TISPL was also expressed under several other stress conditions. It was particularly increased > 10-fold upon glucose starvation and 7-fold by arsenite exposure. Furthermore, in silico analyses, including a ChIP-atlas search, revealed that there is an ATF4-binding region with a c/ebp-Atf response element (CARE) downstream of the transcription start site of TISPL. Based on these results, we hypothesized that TISPL may be induced by the phospho-eIF2α and ATF4- axis of the integrated stress response pathway, which is known to be activated by the stress conditions listed above. As expected, knockout of ATF4 abolished the stress-induced upregulation of TISPL. Our results indicate that TISPL may be a useful biomarker for detecting stress conditions that activate ATF4. Our highly sensitive trap vector system proved beneficial in discovering new biomarkers.

Overexpression of OsTIP1;2 confers arsenite tolerance in rice and reduces root-to-shoot translocation of arsenic.

Tonoplast Intrinsic Proteins (TIPs) are vital in transporting water and solutes across vacuolar membrane. The role of TIPs in the arsenic stress response is largely undefined. Rice shows sensitivity to the arsenite [As[III]] stress and its accumulation at high concentrations in grains poses severe health hazards. In this study, functional characterization of OsTIP1;2 from Oryza sativa indica cultivar Pusa Basmati-1 (PB-1) was done under the As[III] stress. Overexpression of OsTIP1;2 in PB-1 rice conferred tolerance to As[III] treatment measured in terms of enhanced shoot growth, biomass, and shoot/root ratio of overexpression (OE) lines compared to the wild-type (WT) plants. Moreover, seed priming with the IRW100 yeast cells (deficient in vacuolar membrane As[III] transporter YCF1) expressing OsTIP1;2 further increased As[III] stress tolerance of both WT and OE plants. The dithizone assay showed that WT plants accumulated high arsenic in shoots, while OE lines accumulated more arsenic in roots than shoots thereby limiting the translocation of arsenic to shoot. The activity of enzymatic and non-enzymatic antioxidants also increased in the OE lines on exposure to As[III]. The tissue-specific localization showed OsTIP1;2 promoter activity in root and root hairs, indicating its possible root-specific function. After As[III] treatment in hydroponic medium, the arsenic translocation factor (TF) for WT was around 0.8, while that of OE lines was around 0.2. Moreover, the arsenic content in the grains of OE lines reduced significantly compared to WT plants.

Effect of inorganic arsenic in paddy soil on the migration and transformation of selenium species in rice plants.

Selenium (Se) in paddy rice is one of the significant sources of human Se nutrition. However, the effect of arsenic (As) pollution in soil on the translocation of Se species in rice plants is unclear. In this research, a pot experiment was designed to examine the effect of the addition of 50 mg As/kg soil as arsenite or arsenate on the migration of Se species from soil to indica Minghui 63 and Luyoumingzhan. The results showed that the antagonism between inorganic As and Se was closely related to the rice cultivar and Se oxidation state in soil. Relative to the standalone selenate treatment, arsenite significantly (p < 0.05) decreased the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, sheaths, leaves, brans and kernels of both cultivars by 21.4%-100.0%, 40.0%-100.0%, 41.0%-100%, 5.4%-96.3%, 11.3%-100.0% and 26.2%-39.7% respectively, except for selenocystine in the kernels of indica Minghui 63 and selenomethionine in the leaves of indica Minghui 63 and the stems of indica Luyoumingzhan. Arsenate also decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenate in the roots, stems, brans and kernels of both cultivars by 34.9%-100.0%, 30.2%-100.0%, 11.3%-100.0% and 5.6%-39.6% respectively, except for selenate in the stems of indica Minghui 63. However, relative to the standalone selenite treatment, arsenite and arsenate decreased (p < 0.05) the accumulation of selenocystine, selenomethionine and selenite only in the roots of indica Minghui 63 by 45.5%-100.0%. Our results suggested that arsenite and arsenate had better antagonism toward Se species in selenate-added soil than that in selenite-added soil; moreover, arsenite had a higher inhibiting effect on the accumulation of Se species than arsenate.

The plastid-localized lipoamide dehydrogenase 1 is crucial for redox homeostasis, tolerance to arsenic stress and fatty acid biosynthesis in rice.

Soil contamination with arsenic (As) can cause phytotoxicity and reduce crop yield. The mechanisms of As toxicity and tolerance are not fully understood. In this study, we used a forward genetics approach to isolate a rice mutant, ahs1, that exhibits hypersensitivity to both arsenate and arsenite. Through genomic resequencing and complementation tests, we identified OsLPD1 as the causal gene, which encodes a putative lipoamide dehydrogenase. OsLPD1 was expressed in the outer cell layer of roots, root meristem cells, and in the mesophyll and vascular tissues of leaves. Subcellular localization and immunoblot analysis demonstrated that OsLPD1 is localized in the stroma of plastids. In vitro assays showed that OsLPD1 exhibited lipoamide dehydrogenase (LPD) activity, which was strongly inhibited by arsenite, but not by arsenate. The ahs1 and OsLPD1 knockout mutants exhibited significantly reduced NADH/NAD+ and GSH/GSSG ratios, along with increased levels of reactive oxygen species and greater oxidative stress in the roots compared with wild-type (WT) plants under As treatment. Additionally, loss-of-function of OsLPD1 also resulted in decreased fatty acid concentrations in rice grain. Taken together, our finding reveals that OsLPD1 plays an important role for maintaining redox homeostasis, conferring tolerance to arsenic stress, and regulating fatty acid biosynthesis in rice.

Metal-Binding Protein TaGlo1 Improves Fungal Resistance to Arsenite (AsIII) and Methylarsenite (MAsIII) in Paddy Soil.

Trivalent arsenicals such as arsenite (AsIII) and methylarsenite (MAsIII) are thought to be ubiquitous in flooded paddy soils and have higher toxicity than pentavalent forms. Fungi are widely prevalent in the rice rhizosphere, and the latter is considered a hotspot for As uptake. However, few studies have focused on alleviating As toxicity in paddy soils using fungi. In this study, we investigated the mechanism by which the protein TaGlo1, derived from the As-resistant fungal strain Trichoderma asperellum SM-12F1, mitigates AsIII and MAsIII toxicity in paddy soils. Taglo1 gene expression in Escherichia coli BL21 conferred strong resistance to AsIII and MAsIII, while purified TaGlo1 showed a high affinity for AsIII and MAsIII. Three cysteine residues (Cys13, Cys18, and Cys71) play crucial roles in binding with AsIII, while only two (Cys13 and Cys18) play crucial roles for MAsIII binding. TaGlo1 had a stronger binding strength for MAsIII than AsIII. Importantly, up to 90.2% of the homologous TaGlo1 proteins originate from fungi by GenBank searching. In the rhizospheres of 14 Chinese paddy soils, Taglo1 was widely distributed and its gene abundance increased with porewater As. This study highlights the potential of fungi to mitigate As toxicity and availability in the soil-rice continuum and suggests future microbial strategies for bioremediation.

Novel insights into the co-selection of metal-driven antibiotic resistance in bacteria: a study of arsenic and antibiotic co-exposure.

The simultaneous development of antibiotic resistance in bacteria due to metal exposure poses a significant threat to the environment and human health. This study explored how exposure to both arsenic and antibiotics affects the ability of an arsenite oxidizer, Achromobacter xylosoxidans CAW4, to transform arsenite and its antibiotic resistance patterns. The bacterium was isolated from arsenic-contaminated groundwater in the Chandpur district of Bangladesh. We determined the minimum inhibitory concentration (MIC) of arsenite, cefotaxime, and tetracycline for A. xylosoxidans CAW4, demonstrating a multidrug resistance (MDR) trait. Following this determination, we aimed to mimic an environment where A. xylosoxidans CAW4 was exposed to both arsenite and antibiotics. We enabled the strain to grow in sub-MIC concentrations of 1 mM arsenite, 40 µg/mL cefotaxime, and 20 µg/mL tetracycline. The expression dynamics of the arsenite oxidase (aioA) gene in the presence or absence of antibiotics were analyzed. The findings indicated that simultaneous exposure to arsenite and antibiotics adversely affected the bacteria's capacity to metabolize arsenic. However, when arsenite was present in antibiotics-containing media, it promoted bacterial growth. The study observed a global downregulation of the aioA gene in arsenic-antibiotic conditions, indicating the possibility of increased susceptibility through co-resistance across the entire bacterial population of the environment. This study interprets that bacterial arsenic-metabolizing ability can rescue the bacteria from antibiotic stress, further disseminating environmental cross-resistance. Therefore, the co-selection of metal-driven antibiotic resistance in bacteria highlights the need for effective measures to address this emerging threat to human health and the environment.

Elevated aerobic glycolysis driven by p62-mTOR axis promotes arsenic-induced oncogenic phenotypes in human mammary epithelial cells.

Chronic arsenic exposure is considered to increase the risk of breast cancer. p62 is a multifunctional adaptor protein that controls myriad cellular processes and is overexpressed in breast cancer tissues. Although previous studies have indicated the involvement of p62 accumulation in arsenic tumorigenesis, the underlying mechanism remains obscure. Here, we found that 0.1 µM or 0.5 µM arsenite exposure for 24 weeks induced oncogenic phenotypes in human mammary epithelial cells. Elevated aerobic glycolysis, cell proliferation capacity, and activation of p62-mTOR pathway, as indicated by increased protein levels of p62, phosphorylated-mTOR (p-mTOR) and hypoxia-inducible factor 1α (HIF1α), were observed in chronically arsenite-exposed cells, and of note in advance of the onset of oncogenic phenotypes. Moreover, p62 silencing inhibited acquisition of oncogenic phenotypes in arsenite-exposed cells. The protein levels of p-mTOR and HIF1α, as well as aerobic glycolysis and cell proliferation, were suppressed by p62 knockdown. In addition, re-activation of p­mTOR reversed the inhibitory effects of p62 knockdown. Collectively, our data suggest that p62 exerts an oncogenic role via mTORC1 activation and acts as a key player in glucose metabolism during arsenite-induced malignant transformation, which provides a new mechanistic clue for the arsenite carcinogenesis.

Transcriptomic profile of human iPSC-derived podocyte-like cells exposed to a panel of xenobiotics.

Podocytes play a critical role in the formation and maintenance of the glomerular filtration barrier and injury to these cells can lead to a breakdown of the glomerular barrier causing permanent damage leading to progressive chronic kidney disease. Matured podocytes have little proliferative potential, which makes them critical cells from a health perspective, but also challenging cells to maintain in vitro. Differentiating podocyte-like cells from induced pluripotent stem cells (iPSC) provides a novel and continuous source of cells. Here, we investigated the effect of a 24-h exposure to eight compounds, including the known glomerular toxins doxorubicin and pamidronate, on transcriptomic alterations in iPSC derived podocytes. Doxorubicin (50 nM), pamidronate (50 µM), sodium arsenite (10 µM), and cyclosporine A (15 µM) had a strong impact on the transcriptome, gentamicin (450 µg/ml), lead chloride (15 µM) and valproic acid (500 µM) had a mild impact and busulfan (50 µM) exhibited no impact. Gene alterations and pathways analysis provided mechanistic insight for example, doxorubicin exposure affected the p53 pathway and dedifferentiation, pamidronate activated several pathways including HIF1alpha and sodium arsenite up-regulated oxidative stress and metal responses. The results demonstrate the applicability of iPSC derived podocytes for toxicological and mechanistic investigations.

Investigation of the protective effect of chitosan against arsenic-induced nephrotoxicity and oxidative damage in rat kidney tissue.

Arsenic is an important metalloid that can cause poisoning in humans and domestic animals. Exposure to arsenic causes cell damage, increasing the production of reactive oxygen species. Chitosan is a biopolymer obtained by deacetylation of chitin with antioxidant and metal ion chelating properties. In this study, the protective effect of chitosan on arsenic-induced nephrotoxicity and oxidative damage was investigated. 32 male Wistar-albino rats were divided into 4 groups of 8 rats each as control group (C), chitosan group (CS group), arsenic group (AS group), and arsenic+chitosan group (AS+CS group). The C group was given distilled water by oral gavage, the AS group was given 100 ppm/day Na-arsenite ad libitum with drinking water, the CS group was given 200 mg/kg/day chitosan dissolved in saline by oral gavage, the AS+CS group was given 100 ppm/day Na-arsenite ad libitum with drinking water and 200 mg/kg/day chitosan dissolved in saline by oral gavage for 30 days. At the end of the 30-day experimental period, 90 mg/kg ketamine was administered intraperitoneally to all rats, and blood samples and kidney tissues were collected. Urea, uric acid, creatinine, P, Mg, K, Ca, Na, Cystatin C (CYS-C), Neutrophil Gelatinase Associated Lipocalin (NGAL) and Kidney Injury Molecule 1 (KIM-1) levels were measured in serum samples. Malondialdehyde (MDA), Glutathione (GSH), Catalase (CAT) and Superoxide dismutase (SOD) levels in the supernatant obtained from kidney tissue were analyzed by ELISA method. Compared with AS group, uric acid and creatinine levels of the AS+CS group were significantly decreased (p<0.001), urea, KIM-1, CYS-C, NGAL, and MDA levels were numerically decreased and CAT, GSH, and SOD levels were numerically increased (p>0.05). In conclusion, based on both biochemical and histopathological-immunohistochemical- immunofluorescence findings, it can be concluded that chitosan attenuates kidney injury and protects the kidney.