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Molecular effects of arsenic and smokeless tobacco aqueous extract in cultured cells

ABSTRACT: Chronic arsenic exposure can lead to various health issues including cancer. There has been a growing concern about co-exposure to various prevalent lifestyle habits and their role in the enhancement of arsenic toxicity. Smokeless tobacco (SLT) products are extensively consumed in many South Asian countries, where their use frequently co-occurs with exposure to arsenic from contaminated groundwater. To decipher the oral epithelial cell responses to arsenic and SLT alone and in co-exposure, we performed multi-omics analyses of DNA methylome, transcriptomic reprogramming and genotoxic effects in controlled experimental settings. Chronic exposure studies revealed hypomethylation of genes involved in inflammation response and apoptosis, further corroborated by the upregulation of genes involved in these processes due to arsenic and the combined treatment in acute exposure setting. Next, to validate the omics results at the phenotypic level, we observed a dose dependent decrease in cell viability, induction of DNA damage, cell cycle changes, and an increase in apoptotic cells, with the most pronounced effects observed under arsenic and SLT co-exposure conditions. The observed DNA damage was likely the result of apoptosis induction, as chronic exposure experiments based on whole-exome sequencing did not reveal increased mutagenicity following the arsenic and/or SLT exposure. Our integrative omics study provides insights into both chronic and acute responses to arsenic and SLT co-exposure, with both types of responses converging on some of the same mechanisms. We identified large-scale epigenomic and transcriptomic reprograming associated with arsenic and SLT co-exposure, alongside genotoxic effects presumably manifesting as consequences of apoptosis induction. The findings point to a role of arsenic and SLT in altering key molecular responses, especially in the context of the co-exposure, and call for further studies in humans in the areas of exposure, to validate the observed mechanisms.

ORGANISM(S): Homo sapiens

PROVIDER: GSE269103 | GEO | 2024/12/04

REPOSITORIES: GEO

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Project description:Chronic arsenic exposure can lead to various health issues including cancer. There has been a growing concern about co-exposure to various prevalent lifestyle habits and their role in the enhancement of arsenic toxicity. Smokeless tobacco (SLT) products are extensively consumed in many South Asian countries, where their use frequently co-occurs with exposure to arsenic from contaminated groundwater. To decipher the oral epithelial cell responses to arsenic and SLT alone and in co-exposure, we performed multi-omics analyses of DNA methylome, transcriptomic reprogramming and genotoxic effects in controlled experimental settings. Chronic exposure studies revealed hypomethylation of genes involved in inflammation response and apoptosis, further corroborated by the upregulation of genes involved in these processes due to arsenic and the combined treatment in acute exposure setting. Next, to validate the omics results at the phenotypic level, we observed a dose dependent decrease in cell viability, induction of DNA damage, cell cycle changes, and an increase in apoptotic cells, with the most pronounced effects observed under arsenic and SLT co-exposure conditions. The observed DNA damage was likely the result of apoptosis induction, as chronic exposure experiments based on whole-exome sequencing did not reveal increased mutagenicity following the arsenic and/or SLT exposure. Our integrative omics study provides insights into both chronic and acute responses to arsenic and SLT co-exposure, with both types of responses converging on some of the same mechanisms. We identified large-scale epigenomic and transcriptomic reprograming associated with arsenic and SLT co-exposure, alongside genotoxic effects presumably manifesting as consequences of apoptosis induction. The findings point to a role of arsenic and SLT in altering key molecular responses, especially in the context of the co-exposure, and call for further studies in humans in the areas of exposure, to validate the observed mechanisms.

Project description:Arsenic (As) exposure is a significant worldwide environmental health concern. Low dose, chronic arsenic exposure has been associated with higher risk of skin, lung, and bladder cancer, as well as cardiovascular disease and diabetes. While arsenic-induced biological changes play a role in disease pathology, little is known about the dynamic cellular changes due to arsenic exposure and withdrawal. In these studies, we seek to understand the molecular mechanisms behind the biological changes induced by chronic low doses of arsenic exposure. We used a comprehensive approach involving chromatin structural studies and mRNA microarray analyses to determine how chromatin structure and gene expression patterns change in response to chronic low dose arsenic exposure and its subsequent withdrawal. Our results show that cells exposed to low doses of sodium arsenite have distinct temporal and coordinated chromatin, gene expression and miRNA changes that are consistent with differentiation and activation of multiple biochemical pathways. Most of these temporal patterns in gene expression are reversed when arsenic was withdrawn. However, some of the gene expression patterns remained altered, plausibly as a result of an adaptive response by these cells. Additionally, these gene expression patterns correlated with changes in chromatin structure, further solidifying the role of chromatin structure in gene regulatory changes due to arsenite exposure. Lastly, we show that arsenite exposure influences gene regulation both at the transcription initiation as well as at the splicing level. Thus our results suggest that general patterns of alternative splicing, as well as expression of particular gene regulators, can be indicative of arsenite-induced cell transformation. A total of eight (8) samples with two biological replicates under four separate conditions: wild-type treated with deionized H2O for 36 days (NT); chronic low-dose arsenic exposure of 1 uM of sodium arsenite (iAs-T) for 36 days; chronic arsenic exposure of 1 uM of sodium arsenite for 26 days followed by removal of sodium arsenite for 10 days, measured at day 36 (iAs-Rev); and chronic arsenic exposure of 1 uM of sodium arsenite for 26 days, followed by removal of sodium arsenite exposure for 10 days, followed by 1 uM of chronic sodium arsenite exposure for 10 days (measured at day 46) (iAs-Rev-T).

Project description:Talemi2014 - Arsenic toxicity and detoxification mechanisms in yeast The model implements arsenite (AsIII) transport regulation, its distribution within main cellular AsIII pools and detoxification. The intracellular As pools considered are free AsIII (AsIIIin), protein-bound AsIII (AsIIIprot), glutathione conjugated AsIII (AsGS3) and vacuolar sequestered AsIII (vAsGS3). This model is described in the article: Mathematical modelling of arsenic transport, distribution and detoxification processes in yeast. Talemi SR, Jacobson T, Garla V, Navarrete C, Wagner A, Tamás MJ, Schaber J. Mol. Microbiol. 2014 Jun; 92(6): 1343-1356 Abstract: Arsenic has a dual role as causative and curative agent of human disease. Therefore, there is considerable interest in elucidating arsenic toxicity and detoxification mechanisms. By an ensemble modelling approach, we identified a best parsimonious mathematical model which recapitulates and predicts intracellular arsenic dynamics for different conditions and mutants, thereby providing novel insights into arsenic toxicity and detoxification mechanisms in yeast, which could partly be confirmed experimentally by dedicated experiments. Specifically, our analyses suggest that: (i) arsenic is mainly protein-bound during short-term (acute) exposure, whereas glutathione-conjugated arsenic dominates during long-term (chronic) exposure, (ii) arsenic is not stably retained, but can leave the vacuole via an export mechanism, and (iii) Fps1 is controlled by Hog1-dependent and Hog1-independent mechanisms during arsenite stress. Our results challenge glutathione depletion as a key mechanism for arsenic toxicity and instead suggest that (iv) increased glutathione biosynthesis protects the proteome against the damaging effects of arsenic and that (v) widespread protein inactivation contributes to the toxicity of this metalloid. Our work in yeast may prove useful to elucidate similar mechanisms in higher eukaryotes and have implications for the use of arsenic in medical therapy. This model is hosted on BioModels Database and identified by: BIOMD0000000547. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Project description:In the current study a systematic investigation of life stage, tissue and cell dependent sensitivity to ionizing radiation in the nematode Caenorhabditis elegans was conducted. This revealed that individuals that have reached the post-mitotic L4 stage showed no significant effects with respect to mortality, morbidity or reproduction when subjected to either acute dose ≤6 Gy(1500 mGy/h) or chronic exposure ≤4 Gy( ≤ 100 mGy/h). In contrast, chronic exposure from embryo to young adult stage caused a dose and dose rate dependent reprotoxicitiy with 43% reduction in total brood size at 6.7Gy (107 mGy/h). Systematic targeted irradiation of developmental stages showed that exposure during L1 to young L4 was sufficient to induce reprotoxic effects. Exposure during these stages was associated with a dose rate dependent genotoxic effects on gonads with 1.7 to 3.2 fold increase in germ cell apoptosis in larvae subjected to 40-100 mGy/h, respectively. Importantly, exposure to gamma radiation significantly impaired spermatogenesis in a dose rate dependent manner. The observed reduction in the number of spermatids accounted for xx% of the reprotoxic effects, thus signifying spermatids as the most radiosensitive cell type in C. elegans. Molecular responses analyzed by RNAseq of nematodes irradiated from L1 to L4 stage revealed a significant enrichment of genes related to both male and hermaphrodite reproductive processes. Gene network analysis identified adverse genotoxic effects related to down-regulation of genes required for spindle formation and sperm meiosis/maturation, including smz-1, smz-2 and htas-1. The expression of a subset of 28 set-17 regulated Major Sperm Proteins (MSP) required for spermatids production was correlated to the reduction in reproduction and the number of spermatids, thus corroborating the impairment of spermatogenesis as the major cause of gamma radiation induced life-stage dependent reprotoxic effect. Furthermore, the progeny of irradiated nematodes showed significant embryonal DNA damage that was associated with persistent effect on somatic growth. Unexpectedly, these nematodes did however maintain much of their reproductive capacity in spite of the reduced growth.

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Molecular effects of arsenic and smokeless tobacco aqueous extract in cultured cells

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