Benzene and its metabolite decreases cell proliferation via LncRNA-OBFC2A-mediated anti-proliferation effect involving NOTCH1 and KLF15

Extracellular vesicles-derived long noncoding RNAs participated in benzene hematotoxicity by mediating apoptosis and autophagy

Benzene is a common contaminant in the workplace and wider environment, which induces hematotoxicity. Our previous study has implicated that lncRNAs mediated apoptosis and autophagy induced by benzene. Nevertheless, the roles of extracellular vesicle(EVs)-derived lncRNAs in benzene toxicity are unknown. However, the role of EVs and EVs-derived lncRNAs in benzene-induced toxicity remains unclear. In this research, we explored the function of EVs and EVs-derived lncRNAs in cell-cell communication through benzene-induced apoptosis and autophagy. Our findings demonstrated that EVs derived from 1,4-BQ-treated cells treated cells and coculture with 1,4-BQ-treated cells enhanced apoptosis and autophagy via regulating the pathways of PI3K-AKT-mTOR and chaperone-mediated autophagy. Treating with GW4869 in 1,4-BQ-treated cells significantly inhibited EV secretion, which reduced apoptosis and autophagy. Furthermore, we identified a set of differentially expressed autophagy- and apoptosis-related lncRNAs using EVs-derived lncRNA sequencing. Among them, 8 candidate lncRNAs were upregulated in EVs derived from 1,4-BQ-treated cells, as determined by lncRNA sequencing and qRT-PCR. Importantly, these lncRNAs were also increased in the serum EVs of benzene-exposed workers. 1,4-BQ-treated cells released EVs that transfer differentially expressed lncRNAs, thereby inducing apoptosis and autophagy in the recipient cells. The above results support the hypothesis that EVs-derived lncRNAs participate in intercellular communication during benzene-induced hematotoxicity and function as potential biomarkers for risk assessment of benzene-exposed workers.

Non-coding RNAs: A new frontier in benzene-mediated toxicity

One of the most frequent environmental contaminants, benzene is still widely used as an industrial solvent around the world, especially in developing nations, posing a serious occupational risk. While the processes behind the toxicity of benzene grounds are not fully understood, it is generally accepted that its metabolism, which involves one or more reactive metabolites, is crucial to its toxicity. In order to evaluate the many ways that benzene could influence gene regulation and thus have an impact on human health, new methodologies have been created. The pathophysiology of the disorder may result from epigenetic reprogramming caused by exposure to benzene, including changes in non-coding RNA (ncRNA) markers, according to recent studies. We are interested in the identification of hazardous regulatory ncRNAs, the identification of these ncRNAs' targets, and the comprehension of the significance of these interactions in the mechanisms behind benzene toxicity. Hence, the focus of recent research is on long non-coding RNAs (lncRNAs), circular RNAs (circRNAs) and microRNAs (miRNAs), and some of the more pertinent articles are also discussed.

LncRNA OBFC2A modulated benzene metabolites-induced autophagy and apoptosis by interacting with LAMP2

Exposure to benzene results in peripheral blood cell reduction, aplastic anemia, and leukemia. We previously observed that the lncRNA OBFC2A was upregulated significantly in benzene-exposed workers and correlated with reduced blood cell counts. However, the role of lncRNA OBFC2A in benzene hematotoxicity remains unclear. In this study, we discovered that lncRNA OBFC2A was regulated by oxidative stress and played roles in cell autophagy and apoptosis caused by the benzene metabolite 1,4-Benzoquinone (1,4-BQ) in vitro. Mechanistically, protein chip, RNA pull-down and FISH colocalization uncovered that lncRNA OBFC2A directly bound to LAMP2, a regulator of chaperone-mediated autophagy (CMA), and upregulated its expression in 1,4-BQ-treated cells. LncRNA OBFC2A knockdown alleviated LAMP2 overexpression caused by 1,4-BQ, which confirmed their regulatory relationship. In conclusion, we demonstrate that lncRNA OBFC2A mediates 1,4-BQ-induced apoptosis and autophagy by interacting with LAMP2. LncRNA OBFC2A could serve as a biomarker for hematotoxicity caused by benzene.

Epigenetic alterations induced by genotoxic occupational and environmental human chemical carcinogens: An update of a systematic literature review

Epigenetic alterations, such as changes in DNA methylation, histones/chromatin structure, nucleosome positioning, and expression of non-coding RNAs, are recognized among key characteristics of carcinogens; they may occur independently or concomitantly with genotoxic effects. While data on genotoxicity are collected through standardized guideline tests, data collected on epigenetic effects is far less uniform. In 2016, we conducted a systematic review of published studies of genotoxic carcinogens that reported epigenetic endpoints to better understand the evidence for epigenetic alterations of human carcinogens, and the potential association with genotoxic endpoints. Since then, the number of studies of epigenetic effects of chemicals has nearly doubled. This review stands as an update on epigenetic alterations induced by occupational and environmental human carcinogens that were previously and recently classified as Group 1 by the International Agency for Research on Cancer. We found that the evidence of epigenetic effects remains uneven across agents. Studies of DNA methylation are most abundant, while reports concerning effects on non-coding RNA have increased over the past 5 years. By contrast, mechanistic toxicology studies of histone modifications and chromatin state alterations remain few. We found that most publications of epigenetic effects of carcinogens were studies in exposed humans or human cells. Studies in rodents represent the second most common species used for epigenetic studies in toxicology, in vivo exposures being the most predominant. Future studies should incorporate dose- and time-dependent study designs and also investigate the persistence of effects following cessation of exposure, considering the dynamic nature of most epigenetic alterations.

LncRNA-ENST00000556926 regulates the proliferation, apoptosis and mRNA transcriptome of malignant-transformed BEAS-2B cells induced by coal tar pitch

As a byproduct of coal tar distillation, coal tar pitch (CTP) has been proven to be carcinogenic to human. However, the mechanisms of lung cancer induced by CTP are still unclear. It has been shown that long non-coding RNAs (LncRNAs) play an important role in the development of human cancers. This study aims to investigate the effect of LncRNA-ENST00000556926 on malignant-transformed human bronchial epithelial (BAES-2B) cells induced by coal tar pitch extracts (CTPE). In this study, BEAS-2B cells were treated with 2.4 μg/ml of CTPE for 72 h and then passaged; and the cells were treated 4 times in the same procedure, then passaged until passage 30 (CTPE30). Cell counting kit-8 (CCK-8) assay was used to detect cell viability, then cell cycle and apoptosis were analyzed by flow cytometry, and transcriptome sequencing analysis was used to detect differentially expressed mRNAs after interference of ENST00000556926. The results indicated that the expression of ENST00000556926 in CTPE30 group was significantly higher compared with control group. Furthermore, after interfering the expression of ENST00000556926, cell viability was inhibited, and cell cycle was arrested while apoptosis of malignant-transformed BEAS-2B cells was promoted. Moreover, a total of 159 differentially expressed mRNAs were screened out after interference of ENST00000556926, including 62 up-regulated mRNAs and 97 down-regulated mRNAs. In addition, knockdown of ENST00000556926 decreased the expression of thioredoxin domain containing 5 (TXNDC5) and FOXD1. In conclusion, LncRNA-ENST00000556926 could regulate the proliferation, apoptosis and mRNA transcriptome of malignant-transformed BEAS-2B cells induced by CTP, which may provide a novel treatment strategy for lung cancer.

Long Non-coding RNAs: Potential Players in Cardiotoxicity Induced by Chemotherapy Drugs

One of the most important side effects of chemotherapy is cardiovascular complications, such as cardiotoxicity. Many factors are involved in the pathogenesis of cardiotoxicity; one of the most important of which is long non-coding RNAs (lncRNAs). lncRNA has 200-1000 nucleotides. It is involved in important processes such as cell proliferation, regeneration and apoptosis; today it is used as a prognostic and diagnostic factor. A, various drugs by acting on lncRNAs can affect cells. Therefore, by accurately identifying IncRNAs function, we can play an effective role in preventing the development of cardiotoxicity-induced chemotherapy drugs, and use them as a therapeutic strategy to improve clinical symptoms and increase patient survival.

Comparative toxicity reduction potential of UV/sodium percarbonate and UV/hydrogen peroxide treatments for bisphenol A in water: An integrated analysis using chemical, computational, biological, and metabolomic approaches

Bisphenol A (BPA) is a common industrial chemical with significant adverse impacts on biological systems as an environmental contaminant. UV/hydrogen peroxide (UV/H₂O₂) is a well-established technology for BPA treatment in water while UV/sodium percarbonate (UV/SPC) is an emerging technology with unclear biological impacts of treated effluent. Therefore, in this study, the toxicity evaluation of BPA solution treated with UV/H₂O₂ and UV/SPC was preformed and compared based on transformation products (TPs) profile, quantitative structure-activity relationship (QSAR), Escherichia coli (E. coli) toxicity assays, and metabolomic analysis. TPs with hydroxylation, double-ring split, and single-ring cleavage were generated from BPA during the treatments with both technologies, but TPs with quinonation were specifically detected in UV/H₂O₂ treated solution at the UV dose of 1470 mJ cm^-2. QSAR prediction based on TPs profile (excluding benzoquinone TPs) suggested that UV/H₂O₂ and UV/SPC treatments of BPA may increase matrix toxicity due to the formation of multi-hydroxylated TPs; however decreased bioaccumulation potential of all TPs may mitigate the increase of toxicity by reducing the chance of TPs to reach the concentration of toxicity threshold. In vivo assays with E. coli showed inhibited cell growth, arrested cell cycle, and increased cell death in BPA solution treated with UV/H₂O₂ at the UV dose of 1470 mJ cm^-2. Metabolomic analysis indicated that BPA solution treated with UV/H₂O₂ at UV dose of 1470 mJ cm^-2 impacted E. coli metabolism differently than other solutions with unique inhibition on glycerolipid metabolism. Moreover, BPA interfered in various metabolic pathways including alanine, aspartate and glutamate metabolism, starch and sucrose metabolism, pentose phosphate pathway, and lysine degradation, which were mitigated after the treatments. UV/SPC showed advantage over UV/H₂O₂ of attenuated impact on butanoate metabolism with UV irradiation. This study has generated valuable data for better understanding of biological impacts of BPA and its solutions treated with UV/H₂O₂ or UV/SPC, thus providing insights for their application prospect for water and wastewater treatment.

Regulatory loop between lncRNA FAS-AS1 and DNMT3b controls FAS expression in hydroquinone-treated TK6 cells and benzene-exposed workers

Hydroquinone (HQ), one of the main metabolites of benzene, is a well-known human leukemogen. However, the specific mechanism of how benzene or HQ contributes to the development of leukemia is unknown. In a previous study, we demonstrated the upregulation of DNA methyltransferase (DNMT) expression in HQ-induced malignant transformed TK6 (HQ-TK6) cells. Here, we investigated whether a regulatory loop between the long noncoding RNA FAS-AS1 and DNMT3b exists in HQ-TK6 cells and benzene-exposed workers. We found that the expression of FAS-AS1 was downregulated in HQ-TK6 cells and workers exposed to benzene longer than 1.5 years via histone acetylation, and FAS-AS1 expression was negatively correlated with the time of benzene exposure. Restoration of FAS-AS1 in HQ-TK6 cells promoted apoptosis and inhibited tumorigenicity in female nude mice. Interestingly, treatment with a DNMT inhibitor (5-aza-2-deoxycytidine), histone deacetylase inhibitor (trichostatin A), or DNMT3b knockout led to increased FAS-AS1 through increased H3K27ac protein expression in HQ-TK6 cells, and DNMT3b knockout decreased H3K27ac and DNMT3b enrichment to the FAS-AS1 promoter region, which suggested that DNMT3b and/or histone acetylation involve FAS-AS1 expression. Importantly, restoration of FAS-AS1 resulted in reduced expression of DNMT3b and SIRT1 and increased expression of FAS in both HQ-TK6 cells and xenograft tissues. Moreover, the average DNMT3b expression in 17 paired workers exposed to benzene within 1.5 years was decreased, but that of the remaining 103 paired workers with longer exposure times was increased. Conversely, DNMT3b was negatively correlated with FAS-AS1 expression. Both FAS-AS1 and DNMT3b influenced the enrichment of H3K27ac in the FAS promoter region by regulating the expression of SIRT1, consequently upregulating FAS expression. Taken together, these observations demonstrate crosstalk between FAS-AS1 and DNMT3b via a mutual inhibition loop and indicate a new mechanism by which FAS-AS1 regulates the expression of FAS in benzene-related carcinogenesis.

PTP4A3, A Novel Target Gene of HIF-1alpha, Participates in Benzene-Induced Cell Proliferation Inhibition and Apoptosis through PI3K/AKT Pathway

Benzene, a commonly used chemical, has been confirmed to specifically affect the hematopoietic system as well as overall human health. PTP4A3 is overexpressed in leukemia cells and is related to cell proliferation. We previously found that HIF-1alpha was involved in benzene toxicity and PTP4A3 may be the target gene of HIF-1alpha via ChIP-seq. The aim of this study is to confirm the relationship between HIF-1alpha and PTP4A3 in benzene toxicity, as well as the function of PTP4A3 on cell toxicity induced by 1,4-benzoquinone (1,4-BQ). Our results indicate that HIF-1alpha could regulate PTP4A3 with in vivo and in vitro experiments. A cell line with suppressed PTP4A3 was established to investigate the function of PTP4A3 in 1,4-BQ toxicity in vitro. The results revealed that cell proliferation inhibition was more aggravated in PTP4A3 low-expression cells than in the control cells after 1,4-BQ treatment. The relative oxygen species (ROS) significantly increased in cells with inhibited PTP4A3, while the rise was inferior to the control cells at the 20 μM 1,4-BQ group. An increase in DNA damage was seen in PTP4A3 down-regulated cells at the 10 μM 1,4-BQ group, whereas the results reversed at the concentration of 20 μM. Moreover, the apoptosis rate increased higher in down-regulated PTP4A3 cells after 1,4-BQ exposure. In addition, PI3K/AKT pathway was significantly restrained in cells with inhibited PTP4A3 after 1,4-BQ treatment. Our results indicate that HIF-1alpha may regulate PTP4A3 to be involved in benzene toxicity. Inhibition of PTP4A3 could aggravate cell proliferation suppression and apoptosis by regulating PI3K/AKT pathway after 1,4-BQ treatment.

lncRNAVNN3 mediated benzene-induced hematotoxicity through promoting autophagy and apoptosis

The potential toxicity of low-dose benzene exposure to human health has received attention, but the mechanisms of low-dose benzene-induced hematotoxicity remain largely unknown. The purpose of our study was to investigate the relationships between lncRNAVNN3 expression with benzene-induced autophagy and apoptosis in control and benzene-exposed workers. Seventy benzene-exposed workers and seventy non-benzene-exposed healthy workers were recruited. The expression of lncRNAVNN3, serum autophagy-associated and apoptosis-associated proteins were evaluated, and the relationship among them were also analysed. Furthermore, the mechanism of lncRNAVNN3 on autophagy and apoptosis induced by benzene metabolite (1, 4-benzoquinone, 1, 4-BQ) was investigated in vitro. The results showed that the expression of lncRNAVNN3 increased in benzene-exposed workers (p < 0.05). A positive correlation was found between lncRNAVNN3, serum autophagy-associated and apoptosis-associated proteins. In addition, we found that the knockdown of lncRNAVNN3 reduced phosphorylation of beclin1 and Bcl-2, which mediated 1, 4-benzoquinone-induced autophagy and apoptosis. Overall, lncRNAVNN3 mediated 1, 4-benzoquinone-induced autophagy and apoptosis though regulating phosphorylation of beclin1 and Bcl-2, suggesting that lncRNAVNN3 might be a novel early sensitive biomarker of benzene-induced hematotoxicity.

Identification of Long Non-Coding RNA-Associated Competing Endogenous RNA Network in the Differentiation of Chicken Preadipocytes

Emerging evidence indicates that long noncoding RNAs (lncRNAs) play important roles in the regulation of cell differentiation by acting as competing endogenous RNA (ceRNA). However, the regulatory mechanisms of lncRNA and the lncRNA-associated ceRNA network involved in adipogenic differentiation of chicken preadipocytes remain elusive. Here, we first constructed the chicken preadipocyte in vitro induction model. Then, we identified differentially expressed lncRNAs (DELs), miRNAs (DEMis), and mRNAs (DEMs) between differentiated and undifferentiated preadipocytes. Furthermore, we constructed the lncRNA associated ceRNA network by gene expression correlation analysis and target prediction of DELs, DEMis, and DEMs. Finally, we determined twelve candidate lncRNA-miRNA-mRNA interactions from the lncRNA associated ceRNA network. Eight out of the twelve interactions were validated by RT-qPCR, indicating their potential role in the regulation of chicken preadipocytes differentiation. Among the eight interactions, TCONS_00026544-gga-miR-128-1-5p-RASD1, TCONS_00055280-gga-miR-135a-5p-JAM3, TCONS_00055280-gga-miR-135a-5p-GPR133, TCONS_00055280-gga-miR-135a-5p-CLDN1, and TCONS_00055280-gga-miR-135a-5p-TMEM123 may promote adipogenic differentiation of chicken preadipocytes while TCONS_00057272-gga-miR-146a-3p-FOXO6, TCONS_00057242-gga-miR-6615-3p-FOXO6, and TCONS_00057242-gga-miR-6615-3p-ENSGALT00000043224 have the opposite effects. Our results not only provide novel insights into ceRNA roles of lncRNAs in chicken preadipocytes differentiation and but also contribute to a better understanding of chicken fat deposition.

Expression profiles of long non-coding RNA in mouse lung tissue exposed to radon

Long non-coding RNAs (lncRNA) exert biological functions by interacting with RNAs, proteins, and DNA. Although lung damage associated with radon exposure was attributed to disturbances in microRNA and protein expression, the influence of radon on lncRNA is at present not known. The aim of this study was to (1) examine the effect of radon on lncRNA-mediated expression of transcription factors in mRNA in mouse lung tissue and (2) determine potential function and targets. Female BALB/c mice were divided into two groups: control and radon exposure to approximately 100,000 Bq/m³ (equivalent up to 60 working level month, WLM).RNA was extracted from lung tissue and used for high through-put lncRNA microarray analysis. A total of 1256 lncRNA transcripts were differentially expressed between the two groups of mice. Among these, the top 200 lncRNA-mRNA sets, with fold change of >2 and p-value <.05, were selected for KEGG analysis. Functional analysis via bioinformatics prediction in this study also suggested involvement of ErbB and Notch pathways in radon-induced mouse pulmonary injury. The results from immunohistochemical and Western blot analysis indicated that EbB2 and k-Ras protein expressions were significantly increased. In conclusion, approximately 1,000 dysregulated lncRNA transcripts were found in radon-exposed mice and these lncRNA may play an important role in lung damage following radon exposure. The observations in this study also suggested that ErbB2 and Notch pathways are activated and may be involved in radon-induced pulmonary toxicity.

Long non-coding RNA H19 is responsible for the progression of lung adenocarcinoma by mediating methylation-dependent repression of CDH1 promoter

Lung adenocarcinoma is a common histologic type of lung cancer with a high death rate globally. Increasing evidence shows that long non-coding RNA H19 (lncRNA H19) and CDH1 methylation are involved in multiple tumours. Here, we tried to investigate whether lncRNA H19 or CDH1 methylation could affect the development of lung adenocarcinoma. First, lung adenocarcinoma tissues were collected to detect CDH1 methylation. Then, the regulatory mechanisms of lncRNA H19 were detected mainly in concert with the treatment of overexpression of lncRNA H19, siRNA against lncRNA H19, overexpression of CDH1 and demethylating agent A-5az in lung adenocarcinoma A549 cell. The expression of lncRNA H19 and epithelial-mesenchymal transition (EMT)-related factors as well as cell proliferation, sphere-forming ability, apoptosis, migration and invasion were detected. Finally, we observed xenograft tumour in nude mice so as to ascertain tumorigenicity of lung adenocarcinoma cells. LncRNA H19 and methylation of CDH1 were highly expressed in lung adenocarcinoma tissues. A549 cells with silencing of lncRNA H19, overexpression of CDH1 or reduced CDH1 methylation by demethylating agent 5-Az had suppressed cell proliferation, sphere-forming ability, apoptosis, migration and invasion, in addition to inhibited EMT process. Silencing lncRNA H19 could reduce methylation level of CDH1. In vivo, A549 cells with silencing lncRNA H19, overexpression of CDH1 or reduced CDH1 methylation exhibited low tumorigenicity, reflected by the smaller tumour size and lighter tumour weight. Taken together, this study demonstrates that silencing of lncRNA H19 inhibits EMT and proliferation while promoting apoptosis of lung adenocarcinoma cells by inhibiting methylation of CDH1 promoter.

TCDD Toxicity Mediated by Epigenetic Mechanisms

Dioxins are highly toxic and persistent halogenated organic pollutants belonging to two families i.e., Polychlorinated Dibenzo-p-Dioxins (PCDDs) and Polychlorinated Dibenzo Furans (PCDFs). They can cause cancer, reproductive and developmental issues, damage to the immune system, and can deeply interfere with the endocrine system. Dioxins toxicity is mediated by the Aryl-hydrocarbon Receptor (AhR) which mediates the cellular metabolic adaptation to these planar aromatic xenobiotics through the classical transcriptional regulation pathway, including AhR binding of ligand in the cytosol, translocation of the receptor to the nucleus, dimerization with the AhR nuclear translocator, and the binding of this heterodimeric transcription factor to dioxin-responsive elements which regulate the expression of genes involved in xenobiotic metabolism. 2,3,7,8-TCDD is the most toxic among dioxins showing the highest affinity toward the AhR receptor. Beside this classical and well-studied pathway, a number of papers are dealing with the role of epigenetic mechanisms in the response to environmental xenobiotics. In this review, we report on the potential role of epigenetic mechanisms in dioxins-induced cellular response by inspecting recent literature and focusing our attention on epigenetic mechanisms induced by the most toxic 2,3,7,8-TCDD.

Analysis of long non-coding RNA profiled following MC-LR-induced hepatotoxicity using high-throughput sequencing

The occurrence of microcystin-LR(MC-LR) variant a known hepatotoxin constitutes a global public health concern. However, the molecular mechanisms underlying MC-LR-induced hepatotoxicity remain to be determined. The aim of this study was to investigate whether long noncoding RNAs (lncRNA) were involved in MC-LR-mediated hepatotoxicity using human normal liver cell line HL7702 to profile lncRNAs after 24 hr treatment with MC-LR. With the use of high-throughput sequencing techniques, data showed that the expression levels of 37, 33, 34, 35 lncRNA were significantly altered following exposure to 1, 2.5, 5, or 10 μM MC-LR, respectively. In particular, the expression levels of LINC00847, MIR22HG and LNC_00027 were markedly increased in all treatment groups. It is of interest that LNC_00027 was identified as a novel lncRNA. Quantitative real-time PCR (qPCR) was employed to determine the differentially expressed lncRNA levels. Analysis using Gene Ontology (GO) enrichment identified the functions of target genes involved in systems development, metabolism, and protein binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that MC-LR exposure upregulated some important signaling pathways including pathway in cancer, PI3K-AKT signaling and MAPK pathway. In summary, data indicate that the MC-LR-induced alterations in lncRNA may be associated with hepatotoxicity and that upregulation of LINC00847, MIR22HG and LNC_00027 may play important roles in the observed MC-mediated liver damage.

Emerging roles of long non-coding RNAs in the toxicology of environmental chemicals

Environmental chemicals (ECs) are drawing great attention to their effects on health and their toxicological mechanisms are being investigated. Long non-coding RNA (lncRNA) is a class of RNA with more than 200 nucleotides and does not have protein coding potential. Recently, it is emerging as a star molecule that participates in a wide range of physiological and pathological processes. It has been reported to be abnormally expressed in diseases. As an epigenetic factor, lncRNAs play an important role in the response of organisms to environmental stress. Their roles in the toxicity of ECs are being identified. Altered expression profiles of lncRNAs have been explored after exposure to ECs. Various kinds of ECs are reported to disturb the expression of lncRNAs in vitro and in vivo. Then, dysregulated lncRNAs can affect the expression of target genes directly or indirectly via regulating the level of microRNAs. The network among lncRNAs, microRNAs and mRNAs can initiate or impede specific signaling pathway and lead to adverse outcome upon exposure to ECs. Recovery of the lncRNAs level by overexpression or knockdown technology diminished the effect induced by ECs. In the review, biological roles of lncRNAs are depicted. The lncRNAs involved in the toxicology are summarized. Types of ECs that have been reported to affect the expression of lncRNAs are categorized. The interaction between various types of ECs and lncRNAs is discussed.