Changes of RNA m6A/m5C Modification Regulatory Molecules in Ferroptosis of T2DM Rat Pancreas.

N6-methyladenine (m6A) and 5-methylcytosine (m5C) are two common forms of RNA methylation that play an important role in the epigenetics of type 2 diabetes mellitus (T2DM). One type of cell death, ferroptosis, has been implicated in islet ß-cell damage in T2DM. Notably, RNA methylation, an upstream regulatory mechanism of mRNAs, can regulate the expression of ferroptosis signaling molecules, thereby affecting cell proliferation and death. Here, we found that the ferroptosis signaling pathway was activated in pancreas of T2DM rats, followed by significant changes in m6A/m5C modification regulatory molecules. These detection data together with the prediction results that m6A and m5C exist in the mRNAs of ferroptosis molecules, we speculate that m6A and m5C are probably involved in pancreatic cell damage by modifying of ferroptosis signaling molecules. In short, our findings provide a new research idea for future studies on the molecular mechanisms of pancreatic cell damage and point to a new direction for exploring the mechanisms of ferroptosis from the perspective of RNA methylation modification.

Changes of m6A Regulatory Proteins and Nrf2 Signaling Molecules in Liver Tissue of Type 2 Diabetes Mellitus Rats.

Both dysregulation of N6-methyladenosine (m6A) regulatory proteins and Nrf2 signaling molecules are involved in the process of injury to multiple tissues. However, changes of m6A regulatory proteins and Nrf2 signaling molecules in liver tissue of T2DM remain unclear. In present study, changes of m6A regulatory proteins (Mettl3, Mettl16, Fto, Alkbh5 and Ythdc2) and Nrf2 signaling molecules (Nrf2, Sod1, Ho-1, Gclc) were detected in the liver tissues of T2DM rats, which constructed by high fat-diet feeding and intraperitoneal injection of streptozotocin. Our results indicated that the morphology of liver tissues from T2DM rats showed obvious abnormalities, as well as levels of liver function indicators and expressions of Nrf2 signaling molecules Nrf2, Sod1, Ho-1 were significantly increased in T2DM rats when compared with those in corresponding control rats. More importantly, m6A regulatory proteins such as Mettl3, Mettl16, Fto, Alkbh5 and Ythdc2 were dramatically higher than those in control rat. In a word, m6A regulatory proteins and Nrf2 signaling molecules may significantly change in liver tissue of T2DM rats. And This provides clues and ideas for the study of liver injury in T2DM from the perspective of RNA epigenetics in the future.

Effects of food wastes based on different components on digestibility and energy recovery in hydrogen and methane co-production.

This study was conducted for four organic fractions (carbohydrates, proteins, cellulose, lipids) at an inoculum concentration of 30 % and a total solid (TS) of 8 % to investigate the effect of the main components of food waste on the performance of the two-stage anaerobic digestion. The results showed that the gas phase products were closely related to the composition of the substrate, with the carbohydrate and lipid groups showing the best hydrogen (154.91 ± 2.39mL/gVS) and methane (381.83 ± 12.691mL/gVS) production performance, respectively. However, the increased protein content predisposes the system to inhibition of gas production, which is mutually supported by changes in the activity of dehydrogenase and coenzyme F420. Butyric acid (53.19 %) dominated the liquid phase products in both stages, indicating that all four organic fractions were butyric acid-based fermentation and that the final soluble chemical oxygen demand degradation reached 72.97 %-82.86 %. The carbohydrate and cellulose groups achieved the best energy recovery performance, with conversion rates exceeding 65 %. The above results can provide a useful reference for the resource utilization of food waste.

Changes of LncRNAs during the Process of Antioxidants Antagonize Cadmium-Induced Oxidative Damage in Islet ß Cells.

Long non-coding RNAs (LncRNAs) play important regulatory roles in oxidative damage. Resveratrol, curcumin, and cyanidin are phytogenic antioxidants widely existing in nature and they have been proved to antagonize certain heavy metal-induced oxidative damage in cells. However, can they antagonize oxidative damage induced by cadmium in islet ß cells? Are their mechanisms of antagonizing oxidative damage related to LncRNAs? In this study, we first detected the cell viability of each group by CCK8 assay. Next, reactive oxygen species (ROS) were detected by the fluorescent probe. The contents of malondialdehyde (MDA) and the activities of superoxide dismutase (SOD) were detected according to the instructions of corresponding kits. At last, the levels of LncRNAs were detected by fluorescence quantitative real-time polymerase chain reaction (qPCR). The results showed that resveratrol, curcumin and cyanidin were able to reverse the reduction of cell viability induced by cadmium (CdSO4). Further determination revealed that SOD activities of the resveratrol+CdSO4, curcumin+CdSO4, and cyanidin+CdSO4 treatment groups increased significantly, and ROS levels and MDA contents dramatically decreased when compared with single CdSO4-treated group. More importantly, the levels of three CdSO4-elevated LncRNAs (NONMMUT029382, ENSMUST00000162103, ENSMUST00000117235) were all decreased and levels of three CdSO4-inhibited LncRNAs (NONMMUT036805, NONMMUT014565, NONMMUT065427) were increased after the pretreatment of resveratrol, curcumin and cyanidin. In summary, resveratrol, curcumin and cyanidin may effectly reverse the cadmium-induced oxidative damage and suggest that phytogenic antioxidants may prevent cells from cadmium-induced oxidative damage through changing the levels of LncRNAs.

Emerging roles of epigenetics in lead-induced neurotoxicity.

Lead is a common environmental heavy metal contaminant. Humans are highly susceptible to lead accumulation in the body, which causes nervous system damage and leads to a variety of nervous system diseases, such as Alzheimer's disease, Parkinson's disease, and autism spectrum disorder. Recent research has focused on the mechanisms of lead-induced neurotoxicity at multiple levels, including DNA methylation, histone modifications, and non-coding RNAs, which are involved in various lead-induced nervous system diseases. We reviewed the latest articles and summarised the emerging roles of DNA methylation, histone modification, and non-coding RNAs in lead-induced neurotoxicity. Our summary provides a theoretical basis and directions for future research on the prevention, diagnosis, and treatment of lead-induced neurological diseases.

Novel insights into mutual regulation between N6-methyladenosine modification and LncRNAs in tumors.

N6-methyladenosine (m6A), one of the most common RNA methylation modifications, has emerged in recent years as a new layer of the regulatory mechanism controlling gene expression in eukaryotes. As a reversible epigenetic modification, m6A not only occurs on mRNAs but also on Long non-coding RNAs (LncRNAs). As we all known, despite LncRNAs cannot encode proteins, they affect the expression of proteins by interacting with mRNAs or miRNAs, thus playing important roles in the occurrence and development of a variety of tumors. Up to now, it has been widely accepted that m6A modification on LncRNAs affects the fate of the corresponding LncRNAs. Interestingly, levels and functions of m6A modifications are also mediated by LncRNAs through affecting the m6A methyltransferases (METTL3, METTL14, WTAP, METTL16, etc.), demethylases (FTO, ALKBH5) and methyl-binding proteins (YTHDFs, YTHDCs, IGF2BPs, HNRNPs, etc.), which are collectively referred to as "m6A regulators". In this review, we summarized the mutual regulation mechanisms between N6-methyladenosine modification and LncRNAs in cancer progression, metastasis, invasion and drug resistance. In detail, we focus on the specific mechanisms of m6A modification, which is mediated by methyltransferases and demethylases, involves in the regulation of LncRNA levels and functions in the first part. And section two intensively displays the mediation roles of LncRNAs in m6A modification via changing the regulatory proteins. At last part, we described the interaction effects between LncRNAs and methyl-binding proteins of m6A modification during various tumor occurrence and development.

Emerging Mutual Regulatory Roles between m6A Modification and microRNAs.

N6-metyladenosine (m6A), one of the most common RNA methylation modifications in mammals, has attracted extensive attentions owing to its regulatory roles in a variety of physiological and pathological processes. As a reversible epigenetic modification on RNAs, m6A is dynamically mediated by the functional interplay among the regulatory proteins of methyltransferases, demethylases and methyl-binding proteins. In recent years, it has become increasingly clear that m6A modification is associated with the production and function of microRNAs (miRNAs). In this review, we summarize the specific kinds of m6A modification methyltransferases, demethylases and methyl-binding proteins. In particular, we focus on describing the roles of m6A modification and its regulatory proteins in the production and function of miRNAs in a variety of pathological and physiological processes. More importantly, we further discuss the mediating mechanisms of miRNAs in m6A modification and its regulatory proteins during the occurrence and development of various diseases.

Study on the Correlation Between Regulatory Proteins of N6-methyladenosine and Oxidative Damage in Cadmium-induced Renal Injury.

As a common environmental heavy metal pollutant, cadmium has been well evidenced to cause kidney damage; yet, the underlying mechanisms are still not fully clarified. In this study, cell viability of human renal tubular epithelial cell (HK-2) was determined by CCK-8 assay after treatment with CdSO4. Then, apoptotic morphology of cells was observed by Hoechst staining and level of reactive oxygen species (ROS) was detected by fluorescent probes. Subsequently, mRNA levels of Nrf2, HO-1, m6A methyltransferases (METTL3, METTL14, METTL16, WATP), m6A demethylases (FTO, ALKBH5), m6A methyl-binding proteins (YTHDF1, YTHDF2, YTHDF3, YTHDC1, YTHDC2) were detected by real-time polymerase chain reaction (RT-PCR), closely followed by correlation analysis between Nrf2 mRNA levels and m6A methyltransferases and demethylases. Lastly, protein expressions of Nrf2, METTL3, and FTO were tested by western blotting assay. The detection results demonstrated that the treatment of CdSO4 decreased viability while increased apoptosis rate. The Nrf2 mRNA level in CdSO4-treated cells was significantly increased when compared with that in the control cells, and the HO-1 mRNA level elevated with the increasing of CdSO4 concentrations. In addition, mRNA levels of METTL3, METTL14, METTL16, WTAP, FTO, and methyl-binding proteins in CdSO4-treated cells were all higher than those in corresponding control cells. Further determination showed that protein expressions of Nrf2, METTL3, and FTO were also upregulation under the treatment of CdSO4. Lastly, correlation analysis indicated that mRNA level of Nrf2 was positively correlated with mRNA levels of m6A methyltransferases and demethylases. In a word, our results demonstrated that the molecular changes of Nrf2 signaling pathway are correlated with the levels of m6A regulatory proteins, suggesting that there may be a regulatory relationship between Nrf2 signaling pathway and m6A regulatory proteins in the process of cadmium-induced renal cell cytotoxicity.

The association of high-fluoride and high-iodine combined exposure with dental fluorosis and goiter: a meta-analysis.

It is controversial that high-fluoride and high-iodine combined exposure affects the prevalence of dental fluorosis and goiter. The aim of this study was to explore the potential association between high-fluoride and high-iodine combined exposure with dental fluorosis and goiter. We retrieved relevant articles from PubMed, Cochrane Library, China National Knowledge Infrastructure, Wanfang Database and China Science and Technology Journal Database (VIP). The query format was 1 # "Fluorosis" OR "Fluoride," 2 # "Iodine" OR "Iodide," and 3 # 1 AND 2. A total of 20 papers were included in this study after independent review by two investigators. Our analysis showed that high-fluoride and high-iodine biphasic exposure was significantly associated with the prevalence of goiter (OR = 4.69, 95% CI 2.82-7.80, P < 0.001). The prevalence of dental fluorosis was also significantly raised (OR = 11.71, 95% CI 7.57-18.14, P < 0.001). Sensitivity analysis suggested that combined statistics of multiple studies were reliable. For goiter, subgroup analysis revealed study province, sample size and published year as sources of heterogeneity (P < 0.001). For dental fluorosis, only sample size was the impact factor of heterogeneity. As well, funnel plot, Begg's test and Egger's test suggested there was no publication bias (P > 0.05). Overall, our study demonstrates that high-fluoride and high-iodine combined exposure is a risk factor for occurrence of dental fluorosis and goiter. The chronic of high-fluoride and high-iodine combined exposure is a significant higher risk of disease than normal.

Effects of different low temperature conditions on anaerobic digestion efficiency of pig manure and composition of archaea community.

To explore the effect of low temperature on the anaerobic digestion of pig manure, the anaerobic digestion experiment was carried out under the conditions of inoculum concentration of 30% and TS of 8%. Five low-temperature gradients of 4, 8, 12, 16 and 20 °C were set to study the activities of gas production, pH, solluted chemical oxygen demand (SCOD), volatile fatty acids (VFAs), coenzymes F420 and archaea community composition in the digestion process. The results were demonstrated: as the temperature decreased, the more unstable the gas production became, the less gas production produced, and the later the gas peak occurred. There were no significant peaks at either 4 °C or 8 °C, and the SCOD was unstable over time. From 12 °C, the SCOD increased over time, and the higher the temperature, the faster the growth trend. The pH was always greater than 7.6. 8, 12, 16, 20 °C had different degrees of VFAs accumulation at the late digestion stage. The higher the temperature, the greater the amount of volatile acid accumulation. When the VFAs of each reactor reached the maximum, the proportion of acetic acid also reached the highest. The digestion system of the five treatment groups was dominated by hydrogen-nutrient methanogenic pathway. The results could provide a further reference for the mechanism of anaerobic digestion of pig manure at low temperatures.

Controlled Release of Insulin Based on Temperature and Glucose Dual Responsive Biomicrocapsules.

The treatment of diabetes lies in developing novel functional carriers, which are expected to have the unique capability of monitoring blood glucose levels continuously and dispensing insulin correctly and timely. Hence, this study is proposing to create a smart self-regulated insulin delivery system according to changes in glucose concentration. Temperature and glucose dual responsive copolymer microcapsules bearing N-isopropylacrylamide and 3-acrylamidophenylboronic acid as main components were developed by bottom-spray coating technology and template method. The insulinoma ß-TC6 cells were trapped in the copolymer microcapsules by use of temperature sensitivity, and then growth, proliferation, and glucose-responsive insulin secretion of microencapsulated cells were successively monitored. The copolymer microcapsules showed favorable structural stability and good biocompatibility against ß-TC6 cells. Compared with free cells, the biomicrocapsules presented a more effective and safer glucose-dependent insulin release behavior. The bioactivity of secreted and released insulin did not differ between free and encapsulated ß-TC6 cells. The results demonstrated that the copolymer microcapsules had a positive effect on real-time sensing of glucose and precise controlled release of insulin. The intelligent drug delivery system is supposed to mimic insulin secretion in a physiological manner, and further provide new perspectives and technical support for the development of artificial pancreas.

Changes and relationship of N6-methyladenosine modification and long non-coding RNAs in oxidative damage induced by cadmium in pancreatic ß-cells.

N6-methyladenosine (m6A) modification and m6A-modified Long non-coding RNAs (LncRNAs) play crucial roles in various pathological processes, yet their changes and relationship in cadmium-induced oxidative damage are largely unknown. Here, five m6A-modified LncRNAs (LncRNA-TUG1, LncRNA-PVT1, LncRNA-MALAT1, LncRNA-XIST, LncRNA-NEAT1), which have been evidenced to involve in oxidative damage, were selected and their binding proteins were submitted to bioinformatics analysis. Our analysis results showed that these five m6A-modified LncRNAs bound to different regulatory proteins of m6A modification, implicating that m6A modification on LncRNAs may synergistically control by multiple regulatory proteins. Furthermore, the detection data revealed that levels of m6A modification, methyltransferase-like 3 (METTL3) and fat mass and obesity-associated protein (FTO) were all significantly decreased in CdSO4-induced oxidative damage, which was demonstrated by increasing ROS accumulation and MDA contents as well as decreasing SOD activities. More importantly, LncRNA-MALAT1 and LncRNA-PVT1 indicated downward trend and showed positive relationship with m6A modification. Collectively, our results showed that m6A modification and m6A-modified LncRNAs may involve in oxidative damage induced by cadmium.

Emerging Roles of MicroRNAs and Long Noncoding RNAs in Cadmium Toxicity.

Metal cadmium (Cd) and its compounds are ubiquitous industrial and environmental pollutants and they have been believed to exert severe damage to multiple organs and tissues. MicroRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are the two most common noncoding RNAs and have pivotal roles in various cellular and physiological processes. Since the importance of miRNAs and lncRNAs in Cd toxicity has been widely recognized, we focus our interests on the current researches of miRNAs and lncRNAs as well as their regulation roles in Cd toxicity. In this paper, the keywords "cadmium" in combination with "miRNA" or "LncRNA" or "noncoding RNA" was used to retrieve relevant articles in PubMed, EMbase, CNKI, Wan Fang, and CBM databases. The literatures which contained the above keywords and carried out in animals (in vivo and in vitro) have been collected, collated, analyzed, and summarized. Our summary results showed that hundreds of miRNAs and lncRNAs are involved in the Cd toxicity, which have been demonstrated as multiple organ injury, reproductive toxicity, malignant transformation, and abnormal repair of DNA damage. In this paper, we also discussed the blank in present research field of Cd toxicity as well as suggested some ideas for future study in Cd toxicity.

N6-methyladenosine mediates the cellular proliferation and apoptosis via microRNAs in arsenite-transformed cells.

N6-methyladenosine (m6A) modification is implicated to play an important role in cellular biological processes, but its regulatory mechanisms in arsenite-induced carcinogenesis are largely unknown. Here, human bronchial epithelial (HBE) cells were chronically treated with 2.5 µM arsenite sodium (NaAsO2) for about 13 weeks and these cells were identified with malignant phenotype which was demonstrated by increased levels of cellular proliferation, percentages of plate colony formation and soft agar clone formation, and high potential of resistance to apoptotic induction. Our results firstly demonstrated that m6A modification on RNA was significantly increased in arsenite-transformed cells and this modification may be synergistically regulated by methyltransferase-like 3 (METTL3), methyltransferase-like 14 (METTL14), Wilms tumor 1-associated protein (WTAP) and Fat mass and obesity-associated protein (FTO). In addition, knocking down of METTL3 in arsenite-transformed cells can dramatically reverse the malignant phenotype, which was manifested by lower percentages of clone and colony formation as well as higher rates of apoptotic induction. Given the critical roles of miRNAs in cellular proliferation and apoptosis, miRNAs regulated by m6A in arsenite-transformed cells were analyzed by Venn diagram and KEGG pathway in this study. The results showed that these m6A-mediated miRNAs can regulate pathways which are closely associated with cellular proliferation and apoptosis, implicating that these miRNAs may be the critical bridge by which m6A mediates dysregulation of cell survival and apoptosis in arsenite-transformed cells. Taken together, our results firstly demonstrated the significant role of m6A in the prevention of tumor occurrence and progression induced by arsenite.

The selectivity of artemisinin-based drugs on human lung normal and cancer cells.

Artemisinin-based drugs are documented to possess anticancer potential that is selectively effective to cancer cells. However, this selectivity is disputable in different studies and the mechanism is still unclear. To clarify this discrepancy, this study employed five assays to evaluate the cytotoxic effects of artemisinin and artesunate on normal human bronchial epithelial (HBE) cells and lung adenocarcinoma A549 cells. The results of five cytotoxic assays coherently showed that artemisinin and artesunate caused dose-dependent cytotoxicity in both HBE and A549 cells with a slight selectivity to A549 cells. Further, both HBE cells and A549 cells demonstrated elevated levels of intracellular reactive oxygen species (ROS) and increased DNA damage. Since artemisinin and artesunate exerted significant cytotoxic effect on both normal cells and cancer cells via the same pathway of ROS-mediated DNA damage, the side effects of artemisinin and artesunate on normal cell cannot be ignored when developing their antitumor effects.

Regulation of ABCG2 by nuclear factor kappa B affects the sensitivity of human lung adenocarcinoma A549 cells to arsenic trioxide.

Arsenic trioxide (As2O3) is successfully used as an anticancer agent against acute promyelocytic leukemia and some solid tumors. However, the application of As2O3 is largely limited by its drug resistance in the treatment of non-small cell lung carcinoma (NSCLC). Therefore, it is an urgent task to enhance the sensitivity of lung cancer cells to As2O3. In this study, using human lung adenocarcinoma A549 cells as a cell culture model, we demonstrated that an adenosine triphosphate binding cassette (ABC) transporter, ABCG2, was significantly increased by As2O3 treatment, while other ABC transporters, ABCB1 and ABCC1 showed no remarkable change in the response to As2O3. After inhibition of ABCG2 by its specific inhibitor, the drug sensitivity of As2O3 to A549 cells was significantly enhanced, manifested by decreased cell viability and colony formation as well as the increased ROS production and cell apoptosis. To further understand the molecular mechanism underlying the elevation of ABCG2 expression in As2O3-treated cells, we detected the activation state of nuclear factor kappa B (NF-κB) pathway and its relationship with ABCG2 expression. Our results revealed that the increased expression of ABCG2 was regulated by NF-κB, and thus affecting the cell death of As2O3-treated A549 cells. These findings indicate that inhibition of NF-κB/ABCG2 pathway by specific inhibitors may be a new strategy for the improvement of As2O3 sensitivity in NSCLC treatment.

[miR-155/BACH1 Signaling Pathway in Human Lung Adenocarcinoma Cell Death Induced by Arsenic Trioxide].

OBJECTIVE: To explore the changes of micro RNA 155 (miR-155),BTB and CNC homologous protein 1 (BACH1),quinone oxidoreductase 1 (NQO1) and heme-oxygenase-1 (HO-1) in the process of arsenic trioxide-induced cell death,and to clarify the relationship between miR-155 and BACH1,providing experimental basis for the sensitivity of arsenic trioxide (ATO) treatment. METHODS: Human lung adenocarcinoma cell line A549 cells were treated with different concentrations of ATO. MTT assay and total antioxidant capacity detection kit were used to determine cell viability and total antioxidant capacity,respectively. BACH1,NQO1 and HO-1 protein expression were probed by Western blot and real-time fluorescence quantitative (qRT-PCR) was utilized to test the miR-155 level. A549 cells were transfected with miR-155 mimic and its negative control,then the expression level of miR-155 was detected by qRT-PCR,and these cells were treated with 20 µmol/L for 24 h followed by MTT and Western blot detection. RESULTS: 10 µmol/L ATO significantly reduced the cell viability in A549 cells. 10 µmol/L and 20 µmol/L ATO treatment activated BACH1 expression and inhibited miR-155,NQO1 and HO-1 expression,leading to decreased total antioxidant capacity. Importantly,the cell death induced by 20 µmol/L ATO was significantly decreased in miR-155 mimic transfection cells in comparison with non-transfected cells and miR-155 mimic negative control transfected cells. Moreover,high expression of miR-155 reduced BACH1 activation and increased NQO1 and HO-1 expression in cells treated with 20 µmol/L ATO ( P<0.05). CONCLUSION: Restraining total antioxidant capacity contributes to ATO induced cell death,the underlying mechanisms may be that ATO can activate BACH1 expression through inhibition of the miR-155 level,leading to subsequent inhibition of NQO1 and HO-1 expression. Taken together,these data suggest that miR-155 and BACH1 could be used as sensitivity targets for ATO treatment in lung cancer.

Alterations of miRNAs and Their Potential Roles in Arsenite-Induced Transformation of Human Bronchial Epithelial Cells.

The alterations of micro RNAs (miRNAs) and their potential roles in arsenite-induced tumorigenesis are still poorly understood. In this study, miRNA Array was used to detect the expression level of miRNAs in human bronchial epithelial (HBE) cells that were transformed by 2.5 µM arsenite for 13 weeks. These cells exhibited a neoplastic phenotype manifested by increased levels of cellular proliferation and migration and clone formation. Subsequently, 191 dysregulated miRNAs were identified to be associated with arsenite-induced transformation by miRNA Array. Among them, six miRNAs were validated by their expression levels with quantitative real-time polymerase chain reaction (qPCR), and 17 miRNAs were further explored via their target genes as well as regulatory network. Three databases, TargetMiner, miRDB, and TarBase, were used to predict the target genes of the 17 miRNAs, and a total of 954 common genes were sorted. Results of Gene Ontology (GO) analyses showed that the 954 genes were involved in diverse terms of GO categories, such as positive regulation of macroautophagy, epithelial cell maturation, and synaptic vesicle clustering. Moreover, results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses demonstrated that most of these target genes were enriched in various cancer-related pathways, including non-small cell lung cancer, Wnt signaling pathway, cell cycle, and p53 signaling pathway. The miRNA-gene regulatory network, which was constructed by cytoscape software with miRNAs and their target genes, showed that miR-15b-5p, miR-106b-5p, and miR-320d were the core hubs. Collectively, our results provide new insights into miRNA-mediated mechanisms underlying arsenite-induced transformation, although more experimental verification is still needed to prove these predictions.

miR-155 mediates arsenic trioxide resistance by activating Nrf2 and suppressing apoptosis in lung cancer cells.

Arsenic trioxide (ATO) resistance is a challenging problem in chemotherapy. However, the underlying mechanisms remain to be elucidated. In this study, we identified a high level of expression of miR-155 in a human lung adenocarcinoma A549R cell line that is highly resistant to ATO. We showed that the high level of miR-155 was associated with increased levels of cell survival, colony formation, cell migration and decreased cellular apoptosis, and this was mediated by high levels of Nrf2, NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1) and a high ratio of Bcl-2/Bax. Overexpression of the miR-155 mimic in A549R cells resulted in increased levels of colony formation and cell migration as well as reduced apoptosis along with increased Nrf2, NQO1 and HO-1. In contrast, silencing of miR-155 expression with its inhibitor in the cells, significantly decreased the cellular levels of Nrf2, NQO1 and HO-1 as well as the ratio of Bcl-2/Bax. This subsequently reduced the level of colony formation and cell migration facilitating ATO-induced apoptosis. Our results indicate that miR-155 mediated ATO resistance by upregulating the Nrf2 signaling pathway, but downregulating cellular apoptosis in lung cancer cells. Our study provides new insights into miR-155-mediated ATO resistance in lung cancer cells.

MicroRNA-155 regulates arsenite-induced malignant transformation by targeting Nrf2-mediated oxidative damage in human bronchial epithelial cells.

Arsenite is a well-documented human lung carcinogen but the detailed mechanisms of carcinogenesis remain unclear. In this study, human bronchial epithelial (16-HBE) cells were continuously exposed to 2.5µM arsenite for about 13 weeks to induce the phenotypes of malignant transformation. Our results showed that Nrf2 expression was gradually decreased whereas no significant change was observed on NF-κB activation with increased time of arsenite exposure. To test the roles of Nrf2-meidtaed oxidative damage in the arsenite-induced malignant transformation, we compared the levels of cGMP, PKG and oxidative damage-related indicators between arsenic-transformed cells and control cells. Our data demonstrated there were no significantly differences on the contents of cGMP, PKG, MDA and the production of ROS, but the levels of GSH and NO, the activities of SOD, tNOS and iNOS were significantly enhanced in the arsenic-transformed cells. Importantly, Nrf2 inactivation could be modulated by miR-155, and inhibition of miR-155 remarkably attenuated the malignant phenotypes and promoted apoptotic cell death in the arsenic-transformed cells. Together, our findings provide the novel mechanism that miR-155 may regulate arsenite-induced cell malignant transformation by targeting Nrf2-mediated oxidative damage, indicating that inhibition of miR-155 may be a potential strategy against lung carcinogenesis of arsenite.