Exosome-transmitted circ_0004664 suppresses the migration and invasion of cadmium-transformed human bronchial epithelial cells by regulating PTEN expression via miR-942-5p

Exosomes play a crucial role in regulating extracellular communication between normal and cancer cells within the tumor microenvironment, thereby affecting tumor progression through their cargo molecules. However, the specific impact of exosomal circular RNAs (circRNAs) on the development of cadmium-induced carcinogenesis remains unclear. To address this, we investigated whether exosomes derived from normal human bronchial epithelial BEAS-2B (N-B2B) cells could transmit circRNA to cadmium-transformed BEAS-2B (Cd-B2B) cells and the potential effects on Cd-B2B cells. Our findings demonstrated a significant downregulation of circ_0004664 in Cd-B2B cells compared to N-B2B cells (P < 0.01). Overexpression of circ_0004664 in Cd-B2B cells led to a significant inhibition of cell migration and invasion (P < 0.01 or P < 0.05). Furthermore, N-B2B cells could transfer circ_0004664 into recipient Cd-B2B cells via exosomes, subsequently inhibiting cell migration and invasion (P < 0.05 or P < 0.01). Mechanistic investigations revealed that exosomal circ_0004664 functioned as a competitive endogenous RNA for miR-942-5p, resulting in an upregulation of PTEN (P < 0.05). Our study highlights the involvement of exosomal circ_0004664 in cell-cell communication during cadmium carcinogenesis, providing a novel insight into the role of exosomal circRNA in this process.

Exploring the Mechanisms of Yishen Tongluo Decoction on Repairing DNA Damage in Mouse Spermatogonia Cells Based on Whole Transcriptome Sequencing

The aim of this study was to investigate the potential mechanism through which Yishen Tongluo decoction (YSTL) repairs DNA damage caused by benzo(a)pyrene diol epoxide (BPDE) in mouse spermatocytes (GC-2). The GC-2 cells were divided randomly into the control group, BPDE group, and low-, medium-, and high-dose YSTL groups of YSTL decoction. A comet assay was used to detect the DNA fragment index (DFI) of cells in each group. Based on the DFI results, whole transcriptome sequencing was conducted, followed by trend analysis, gene ontology (GO) enrichment analysis, kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and ceRNA network analysis. Compared with the control group, the BPDE group reported a significant increase in the DNA fragmentation index (DFI) (p < .05). Compared with the BPDE group, the low-, high- and medium-dose YSTL groups had a significantly reduced DFI (p < .05). Whole-transcriptome sequencing revealed seven differentially expressed circRNAs, 203 differentially expressed miRNAs, and 3,662 differentially expressed mRNAs between the control group and the BPDE group. There was a total of 12 differentially expressed circRNAs, 204 miRNAs, and 2150 mRNAs between the BPDE group and the traditional Chinese medicine group. The pathways involved include DNA repair pathway, nucleotide excision repair pathway, base excision repair pathway, etc. The ceRNA network reported that Hmga2 was the core protein involved, novel_cir_000117 and mmu-miR-466c-3p were located upstream of Hmga2, and they were regulatory factors associated with Hmga2. Finally, we conclude that YSTL decoction may repair sperm DNA damage caused by BPDE through the novel_cir_000117-mmu-miR-466c-3p-Hmga2 pathway.

MicroRNAs as Potential Biomarkers of Environmental Exposure to Polycyclic Aromatic Hydrocarbons and Their Link with Inflammation and Lung Cancer

Exposure to atmospheric air pollution containing volatile organic compounds such as polycyclic aromatic hydrocarbons (PAHs) has been shown to be a risk factor in the induction of lung inflammation and the initiation and progression of lung cancer. MicroRNAs (miRNAs) are small single-stranded non-coding RNA molecules of ~20-22 nucleotides that regulate different physiological processes, and their altered expression is implicated in various pathophysiological conditions. Recent studies have shown that the regulation of gene expression of miRNAs can be affected in diseases associated with outdoor air pollution, meaning they could also be useful as biomarkers of exposure to environmental pollution. In this article, we review the published evidence on miRNAs in relation to exposure to PAH pollution and discuss the possible mechanisms that may link these compounds with the expression of miRNAs.

DNMT3A-mediated high expression of circ_0057504 promotes benzo[a]pyrene-induced DNA damage via the NONO-SFPQ complex in human bronchial epithelial cells

Benzo[a]pyrene (B[a]P) is a class I carcinogen and hazardous environmental pollutant with genetic toxicity. Understanding the molecular mechanisms underlying genetic deterioration and epigenetic alterations induced by environmental contaminants may contribute to the early detection and prevention of cancer. However, the role and regulatory mechanisms of circular RNAs (circRNAs) in the B[a]P-induced DNA damage response (DDR) have not been elucidated. In this study, human bronchial epithelial cell lines (16HBE and BEAS-2B) were exposed to various concentrations of B[a]P, and BALB/c mice were treated with B[a]P intranasally. B[a]P exposure was found to induce DNA damage and upregulate circular RNA hsa_circ_0057504 (circ_0057504) expression in vitro and in vivo. In addition, B[a]P upregulated TMEM194B mRNA and circ_0057504 expression through inhibition of DNA methyltransferase 3 alpha (DNMT3A) expression in vitro. Modulation (overexpression or knockdown) of circ_0057504 expression levels using a lentiviral system in human bronchial epithelial cells revealed that circ_0057504 promoted B[a]P-induced DNA damage. RNA pull-down and western blot assays showed that circ_0057504 interacted with non-POU domain-containing octamer-binding (NONO) and splicing factor proline and glutamine rich (SFPQ) proteins and regulated formation of the NONO-SFPQ protein complex. Thus, our findings indicate that circ_0057504 acts as a novel regulator of DNA damage in human bronchial epithelial cells exposed to B[a]P. The current study reveals novel insights into the role of circRNAs in the regulation of genetic damage, and describes the effect and regulatory mechanisms of circ_0057504 on B[a]P genotoxicity.

Circular RNA_0120376 regulates microRNA-148b-3 and centrosomal protein 55 to promote non-small cell lung cancer development

Circular RNAs (circRNAs) are non-coding RNAs with covalent closed-loop structures that are vital in regulating diverse pathological processes. This work is aimed to investigate the role of circ_0120376 in non-small cell lung cancer (NSCLC). Circ_0120376, microRNA (miR)-148b-3p, and centrosomal protein 55 (CEP55) mRNA expression in NSCLC tissues and cells were determined using qRT-PCR. The influences of circ_0120376 and miR-148b-3p on the proliferation of NSCLC cell lines were analyzed by CCK-8 and colony formation assays. Apoptosis was analyzed by flow cytometry. Cell migration and invasion were analyzed using the Transwell experiment. Binding relationships between circ_0120376 and miR-148b-3p and between miR-148b-3p and CEP55 3'UTR were investigated using the dual-luciferase reporter experiment and the RIP experiment. Western blot was conducted to analyze the regulatory effect of circ_0120376 and miR-148b-3p on CEP55 expression. We found that circ_0120376 was markedly overexpressed in NSCLC, and its overexpression was positively associated with increased T stage and lymph node metastasis of the patients. Functional experiments unveiled that circ_0120376 enhanced the proliferation, migration and invasion of NSCLC cells and impeded apoptosis, while knocking down circ_0120376 remarkably suppressed the malignant features of NSCLC cells mentioned above. Circ_0120376 could adsorb miR-148b-3p to reduce miR-148b-3p expression, and circ_0120376 could increase CEP55 expression via adsorbing miR-148b-3p. In summary, circ_0120376 contributes to the malignancy of NSCLC cells through a ceRNA mechanism via regulating miR-148b-3p/CEP55 axis. Circ_0120376 is likely to be a potential diagnostic biomarker and therapeutic target for NSCLC.

The Preventive Effect of Cardiac Sympathetic Denervation Induced by 6-OHDA on Myocardial Ischemia-Reperfusion Injury: The Changes of lncRNA/circRNAs-miRNA-mRNA Network of the Upper Thoracic Spinal Cord in Rats

In this study, we investigated whether chemical 6-hydroxydopamine (6-OHDA) stimuli caused cardiac sympathetic denervation (SD), and we analyzed gene expression profiles to determine the changes in the lncRNA/circRNAs-miRNA-mRNA network in the affected spinal cord segments to identify putative target genes and molecular pathways in rats with myocardial ischemia–reperfusion injury (MIRI). Our results showed that cardiac sympathetic denervation induced by 6-OHDA alleviated MIRI. Compared with the ischemia reperfusion (IR, MIRI model) group, there were 148 upregulated and 51 downregulated mRNAs, 165 upregulated and 168 downregulated lncRNAs, 70 upregulated and 52 downregulated circRNAs, and 12 upregulated and 11 downregulated miRNAs in the upper thoracic spinal cord of the SD-IR group. Furthermore, we found that the differential genes related to cellular components were mainly enriched in extracellular and cortical cytoskeleton, and molecular functions were mainly enriched in chemokine activity. Pathway analysis showed that the differentially expressed genes were mainly related to the interaction of cytokines and cytokine receptors, sodium ion reabsorption, cysteine and methionine metabolism, mucoglycan biosynthesis, cGMP-PKG signaling pathway, and MAPK signaling pathway. In conclusion, the lncRNA/circRNAs-miRNA-mRNA networks in the upper thoracic spinal cord play an important role in the preventive effect of cardiac sympathetic denervation induced by 6-OHDA on MIRI, which offers new insights into the pathogenesis of MIRI and provides new targets for MIRI.

Circ-SHPRH suppresses cadmium-induced transformation of human bronchial epithelial cells by regulating QKI expression via miR-224-5p

Circular RNAs (circRNAs) have been demonstrated to play critical roles in the pathogenesis of human cancers and carcinogenesis of several environmental pollutants. Nevertheless, the function of circRNAs in cadmium carcinogenesis is unclear. circ-SHPRH is down-regulated in many cancers including non-small cell lung cancer. In our present study, during cadmium-induced transformation of human bronchial epithelial BEAS-2B cells, epithelial-mesenchymal transition (EMT) was induced. Meanwhile, at the middle and late stages of cell transformation, cadmium down-regulated the expression of circ-SHPRH, as well as QKI, a tumor suppressor protein known to prevent the proliferation and EMT during progression of human cancers, compared with passage-matched control BEAS-2B cells. Overexpression of circ-SHPRH in cadmium-transformed BEAS-2B cells promoted the expression of QKI and significantly inhibited proliferation, EMT, invasion, migration and anchorage-independent growth in soft agar of the cells. Mechanistic studies showed that circ-SHPRH functioned as a sponge of miR-224-5p to regulate QKI expression. Interestingly, QKI and circ-SHPRH could form a positive-feedback loop that perpetuated circ-SHPRH/miR-224-5p/QKI axis. Collectively, our results demonstrated that circ-SHPRH inhibited cadmium-induced transformation of BEAS-2B cells through sponging miR-224-5p to regulate QKI expression under cadmium treatment. Our study uncovered a novel molecular mechanism involved in circRNAs in the development of lung cancer due to cadmium exposure.

Circular RNA circ_Cabin1 promotes DNA damage in multiple mouse organs via inhibition of non-homologous end-joining repair upon PM2.5 exposure

Fine particulate matter (PM_2.5) has been shown to induce DNA damage. Circular RNAs (circRNAs) have been implicated in various disease processes related to environmental chemical exposure. However, the role of circRNAs in the regulation of DNA damage response (DDR) after PM_2.5 exposure remains unclear. In this study, male ICR mice were exposed to PM_2.5 at a daily mean concentration of 382.18 μg/m³ for 3 months in an enriched-ambient PM_2.5 exposure system in Shijiazhuang, China, and PM_2.5 collected form Shijiazhuang was applied to RAW264.7 cells at 100 µg/mL for 48 h. The results indicated that exposure to PM_2.5 induced histopathological changes and DNA damage in the lung, kidney and spleen of male ICR mice, and led to decreased cell viability, increased LDH activity and DNA damage in RAW264.7 cells. Furthermore, circ_Cabin1 expression was significantly upregulated in multiple mouse organs as well as in RAW264.7 cells upon exposure to PM_2.5. PM_2.5 exposure also resulted in impairment of non-homologous end joining (NHEJ) repair via the downregulation of Lig4 or Dclre1c expression in vivo and in vitro. Importantly, circ_Cabin1 promoted PM_2.5-induced DNA damage via inhibiting of NHEJ repair. Moreover, the expression of circ_Cabin1 and Lig4 or Dclre1c was strongly correlated in multiple mouse organs, as well as in the blood. In summary, our study provides a new perspective on circRNAs in the regulation of DDR after environmental chemical exposure.

Benzo[a]pyrene diol epoxide-induced transformed cells identify the significance of hsa_circ_0051488, a ERCC1-derived circular RNA in pulmonary squamous cell carcinoma

ERCC1 is a gene for repairing DNA damage whose function is related to carcinogenic-induced tumorigenesis and the effectiveness of platinum therapies. Circular RNAs (circRNAs) are products of posttranscriptional regulation with pleiotropic effects on the pathogenesis of lung cancer. We aim to identify that specific circRNAs derived from ERCC1 can regulate key biological processes involved in the development of lung cancer. We performed bioinformatics analysis, in vitro experiments, and analyzed clinical samples, to determine the biological features of a certain ERCC1-derived circRNA termed as hsa_circ_0051488 in benzo[a]pyrene diol epoxide-induced malignant transformed cell and lung cancer cell. The well-established model of transformed cells provided an ideal platform for analyzing the molecular characteristics of this circRNA in the malignant transformation of lung epithelial cell, which supports that hsa_circ_0051488 functions in the onset and growth of lung squamous cell carcinoma (LUSC). Further analysis indicates that the absence of hsa_circ_0051488 promoted the proliferation of cells with the malignant phenotype. Extensive experiments confirm that hsa_circ_0051488 is present in the cytoplasm and functioned as a competing endogenous RNA. In particular, hsa_circ_0051488 binds to mir-6717-5p, thereby modulating the expression of SATB2 gene, a lung cancer suppressor. Furthermore, our in silico experiments indicate that SATB2 can inhibit multiple tumor pathways and its expression positively correlated with the tumor suppressor gene CRMP1. These findings suggest a possible regulatory mechanism of hsa_circ_0051488 in LUSC, and that the newly discovered hsa_circ_0051488/miR-6717-5p/SATB2 axis may be a potential route for therapeutic intervention of LUSC.

A novel circular RNA, circPUS7 promotes cadmium-induced transformation of human bronchial epithelial cells by regulating Kirsten rat sarcoma viral oncogene homolog expression via sponging miR-770

Cadmium is a human carcinogen, which induces cancers by mechanisms that are not fully understood. Induction of oxidative stress, apoptosis resistance, genotoxic effects, and epigenetic modulations have been indicated to regulate cadmium-induced carcinogenesis. Circular RNAs are epigenetic regulators that have been recognized to play essential roles in carcinogenesis. Yet, the involvement of circular RNAs in cadmium carcinogenesis remains unclear. In this study, a novel circular RNA, circPUS7, was identified and described for the first time. CircPUS7 was significantly upregulated at week 12, 16, and 20 during the cadmium-induced transformation of human bronchial epithelial BEAS-2B cells. Knockdown of circPUS7 in cadmium-transformed BEAS-2B (T-BEAS-2B) cells significantly attenuated transformation markers including cell proliferation, migration, invasion, and anchorage-independent growth. Moreover, circPUS7 promoted malignant phenotypes by competitively binding with miR-770. Overexpression of miR-770 significantly inhibited the transformation properties of T-BEAS-2B cells while inhibition of miR-770 potently reversed the inhibitory effects of circPUS7 knockdown in proliferation, migration, invasion, and anchorage-independent growth of the T-BEAS-2B cells. Kirsten rat sarcoma viral oncogene homolog (KRAS), which was increased synchronically with circPUS7 during cadmium-induced cell transformation, was regulated by circPUS7 through sponging miR-770. In summary, our findings demonstrate that circPUS7 promotes cadmium-induced cell transformation through sponging miR-770 to regulate KRAS expression, providing a new perspective with the involvement of circular RNAs to further understand the mechanisms of cadmium carcinogenesis.

Exosomes derived from circRNA Rtn4-modified BMSCs attenuate TNF-α-induced cytotoxicity and apoptosis in murine MC3T3-E1 cells by sponging miR-146a

Osteoporosis is the most common and complex skeletal disorder worldwide. Exosomes secreted by bone marrow-derived mesenchymal stromal cells (BMSCs) are considered as an ideal seed source for bone tissue regeneration. However, the role of exosomes secreted by BMSCs (BMSCs-Exos) in osteoporosis and its underlying mechanisms remain unclear. In the present study, the expression of microRNA (miRNA)-146a and circular RNA (circRNA) Rtn4 (circ-Rtn4) was evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), and their protein expression was determined by Western blotting. Enzyme-linked immunosorbent assay was performed to detect caspase-3 activity. Cell viability and apoptosis were assessed using 3-(4,5-Dimethylthiazol-2yl-)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry analysis, respectively. Luciferase reporter assay was exploited for target validation. Results showed that tumor necrosis factor-α (TNF-α) dose-dependently increased miR-146a expression, inhibited cell viability, and promoted cell apoptosis, as indicated by increased caspase-3, cleaved caspase-3, and Bcl-2-associated X protein (Bax) expression as well as caspase-3 activity. However, miR-146a silencing or co-culture with BMSCs-Exos blocked these effects. Moreover, co-culture with exosomes-derived from circ-Rtn4-modified BMSCs (Rtn4-Exos) attenuated TNF-α-induced cytotoxicity and apoptosis in MC3T3-E1 cells, as evidenced by the decrease in caspase-3, cleaved caspase-3, and Bax protein expression and caspase-3 activity. In addition, miR-146a was identified as a target of circ-Rtn4, and Rtn4-Exos exerted their function in TNF-α-treated MC3T3-E1 cells by sponging miR-146a. Hence, our findings suggested that Rtn4-Exos attenuated TNF-α-induced cytotoxicity and apoptosis in murine MC3T3-E1 cells by sponging miR-146a, suggesting that Rtn4-Exos may serve as novel candidates for treating osteoporosis.

Hsa_circ_0048179 attenuates free fatty acid-induced steatosis via hsa_circ_0048179/miR-188-3p/GPX4 signaling

Although circular RNAs (circRNAs) are known to play key roles in non-alcoholic fatty liver disease, much about their targets and mechanisms remains unknown. We therefore investigated the actions and mechanisms of hsa_circ_0048179 in an in vitro model of NAFLD. HepG2 cells were exposed to oleate/palmitate (2:1 ratio) for 24 h to induce intracellular lipid accumulation. Using CCK-8 assays, flow cytometry, fluorescence microscopy, western blotting, RT-qPCR, and Oil red O staining, we found that oleate/palmitate treatment reduced cell viability while increasing apoptosis and lipid accumulation in HepG2 cells. Levels of the antioxidant enzyme GPX4 were decreased in oleate/palmitate-treated HepG2 cells, and there were corresponding increases in reactive oxygen species and damage to mitochondrial cristae. Levels of hsa_circ_0048179 expression were also suppressed by oleate/palmitate treatment, and GPX4 levels were markedly increased in HepG2 cells following transfection with hsa_circ_0048179. Analysis of its mechanism revealed that hsa_circ_0048179 upregulated GPX4 levels by acting as a competitive “sponge” of miR-188-3p and that hsa_circ_0048179 attenuated oleate/palmitate-induced lipid accumulation in HepG2 cells by sponging miR-188-3p. Collectively, our findings suggest that hsa_circ_0048179 may play a key role in the pathogenesis of steatosis and may thus be a useful target for drug development.

CircCFL1/MiR-107 Axis Targeting HMGB1 Promotes the Malignant Progression of Diffuse Large B-Cell Lymphoma Tumors

Objective

The pathogenesis of diffuse large B-cell lymphoma (DLBCL) has not yet been fully elucidated. An increasing number of studies have shown that circular RNAs (circRNAs) play an important role in tumorigenesis and development. The aim of this study was to investigate the effect of CircCFL1 on the malignant progression of DLBCL.

Methods

RT-qPCR was used to detect the expression levels of CircCFL1 and miR-107. A dual-luciferase reporter gene experiment was conducted to verify that CircCFL1 targeted miR-107 and the miR-107 target gene HMGB1. BrdU, transwell, and MTT tests were performed to detect cell invasion and proliferation. Western blot analysis was used to detect the phosphorylation of proteins. Xenograft models were established to confirm the effect of CircCFL1 on DLBCL tumor growth in vivo.

Results

The expression of CircCFL1 in cells transfected with the CircCFL1 overexpression vector was higher than that in the control group. After overexpressing CircCFL1, the expression of miR-107 in cells decreased significantly, and the protein level of HMGB1 increased. The dual-luciferase reporter gene experiment showed that CircCFL1 directly bound to miR-107 and reduced the inhibition of the target gene HMGB1. After CircCFL1 was overexpressed, cell migration and proliferation were enhanced. The tumor volume and weight in the lentivirus CircCFL1 group were higher than those in the lentivirus NC group.

Conclusion

Results showed that the circRNA CircCFL1 could regulate the expression of HMGB1 through miR-107 to promote the proliferation and migration of DLBCL.

Circular RNA hsa_circ_0002052 promotes osteosarcoma via modulating miR-382/STX6 axis

Circular RNAs (circRNAs) exert pivotal effects on regulating the progression of osteosarcoma (OS). It was found through microarray analysis that circ-0002052 is abnormally expressed in OS, but the role of circ-0002052 in OS remains obscure. The results of this research manifested that relative to that in non-tumor controls, circ-0002052 level was raised in OS tissues. Up-regulated circ-0002052 was associated with advanced stage, tumor size, and metastasis. Additionally, circ-0002052 elevation indicated a low survival rate in OS patients and silencing of circ-0002052 suppressed proliferation, migration, and invasion of OS cells. It was proved that circ-0002052 sponged miR-382 and stimulated STX6 expression, thus activating Wnt/β-catenin. The function of circ-0002052 reduction in OS cells was effectively reversed by miR-382 suppression. To sum up, it can be concluded that circ-0002052, functioning as a sponge for miR-382, enhances the activation of Wnt/β-catenin mediated by STX6 to stimulate the progression of OS, and circ-0002052 may be an underlying treatment target and a biomarker for prognosis of osteosarcoma.

Circ-IGF1R inhibits cell invasion and migration in non-small cell lung cancer

BACKGROUND

Circular RNA (circRNA) is a novel molecular marker and target candidate that is closely associated with tumor invasion and migration. The mechanism of action of hsa_circ_0005035 (circ-IGF1R) in non-small cell lung cancer remains unclear. In this study, we aimed to study the mechanism of action of circ-IGF1R in lung cancer.

METHODS

We screened circ-IGF1R, one of the most notable differential expressions, from the Gene Expression Omnibus database, GSE104854, for further research. The expression level of circ-IGF1R was examined using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in five different lung cancer cell lines and 50 pairs of lung cancer and adjacent tissues. Wound-healing and Transwell assays were used for verifying the biological function of circ-IGF1R. The effect of overexpressing circ-IGF1R on the transcriptome of whole lung cancer cells was explored in lung cancer cell lines using RNA-seq.

RESULTS

The expression level of circ-IGF1R was notably lower in lung cancer tissues and lung cancer cell lines than in the adjacent normal tissues and cells (P < 0.0001). In addition, the expression level of circ-IGF1R was associated with larger tumors (T2/T3/T4) and lymph node metastasis (N1/ N2/N3) (P < 0.05). The overexpression of circ-IGF1R significantly inhibited the invasion and migration of the lung cancer cells. The potential network of circ-IGF1R-miR-1270-VANGL2 was preliminarily determined, and the expression patterns of miR-1270 and VANGL2 were verified in lung cancer cell lines.

CONCLUSION

Circ-IGF1R may inhibit lung cancer invasion and migration through a potential network of circ-IGF1R-miR-1270-VANGL2.

Circular RNAs as biomarkers and therapeutic targets in environmental chemical exposure-related diseases

Chemical contamination in the environment is known to cause abnormal circular RNA (circRNA) expression through multiple exposure routes; yet, the underlying molecular mechanisms remain unclear. Non-coding RNAs (ncRNAs), especially circRNAs, play important roles in epigenetic regulation and disease pathogenesis; however, few studies have examined the function of circRNAs in chemical contamination-induced diseases. CircRNAs are covalently closed continuous loops that do not possess 5' and 3' ends, increasing their structural stability and limiting degradation by exoribonucleases. In addition, environmental chemical exposure-related diseases are often accompanied by aberrant expression of specific circRNAs and those circRNAs are often detected in tissues and body fluids. Based on these characteristics, circRNAs may serve as candidate biomarkers for the diagnosis of diseases related to environmental chemical exposure. Here, we review the generation and function of circRNAs, and the possible molecular mechanisms underlying the regulation of environmental chemical exposure-related disorders by circRNAs. This is the first comprehensive review of the relationship between environmental chemical exposure and circRNAs in chemical exposure-induced diseases.

Reconstruction and analysis of competitive endogenous RNA network reveals regulatory role of long non‑coding RNAs in hepatic fibrosis

Hepatic fibrosis (HF), one of the leading global health problems, is defined as aberrant and excess production of extracellular matrix components. The pathogenesis of HF is complex and poorly understood. Long non‑coding RNAs (LncRNAs) can interact with microRNAs (miRNAs) as competing endogenous RNAs (ceRNAs) to regulate the expression of target genes, which play a significant role in the initiation and progression of HF. In the present study, the LncRNA‑associated ceRNA network was reconstructed based on LncRNA, miRNA and mRNA expression profiles that were downloaded from National Center for Biotechnology Information Gene Expression Omnibus. Bioinformatics assessments including Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes pathway analyses were performed with Database for Annotation, Visualization and Integration Discovery. The ceRNA network was composed of 220 LncRNA nodes, 24 miRNA nodes, 164 mRNA nodes and 1,149 edges. Functional assays identified that a total of 338 GO terms and 25 pathways, including regulation of cytokine and collagen, and the transforming growth factor‑β and Toll‑like receptor signaling pathways, were significantly enriched. In addition, 4 LncRNAs (NONMMUT036242, XR_877072, XR_378619 and XR_378418) were highly related to HF and thereby chosen as key LncRNAs. The present study uncovered a ceRNA network that could further the understanding of the mechanisms underlying HF development and provide potential novel markers for clinical diagnosis and targets for treatment.