MEG3 Expression Research Articles

Altered Long Non-coding RNAs Expression and Cytotoxic and Anti-proliferative Activity of Dendrosomal Nano-curcumin in Ovarian Cancer Cells

Curcumin is a polyphenol derived from the rhizome of turmeric, which has significant chemoprevention and chemotherapeutic effects. Long non-coding RNAs (lncRNAs) are longer than 200 nucleotides and play a crucial role in various biological processes. Since aberrant lncRNAs expression affects the development and progression of tumors, the present study was conducted to determine the cytotoxic potential of dendrosomal nano-curcumin (DNC) against ovarian cancer cell proliferation and apoptosis and altered expression of some lncRNAs involved in ovarian cancer. In vitro cytotoxic activity of DNC against OVCAR3 and SKOV3 human ovarian cancer cells and HFSF-PI3 human fibroblasts cells as a control was evaluated by MTT assay. Real-time PCR and western blot methods were used to determine the apoptosis-inducing effect of DNC through analyzing apoptosis marker genes and protein expression, respectively. We also checked the ovarian cancer cells apoptosis induced with change in expression levels of some lncRNAs. Our results revealed that DNC significantly decreased viability of ovarian cancer cells as compared to Cur. Moreover, DNC reduced the relative expression levels of HOTAIR and H19 and increased the expression of MEG3. Bcl2 expression was down-regulated in mRNA and protein level after DNC treatment, whereas knockdown of MEG3 reduced it. Our findings discovered the effect of DNC on growth inhibition as well as modulation of some lncRNAs in ovarian cancer cells. We also observed that MEG3 down-regulation can suppress the effect of DNC on down-regulation of Bcl-2 as an anti-apoptotic protein. This may suggest the role of MEG3 in DNC-induced apoptosis.

Ox-low density lipoprotein (ox-LDL) increased the susceptibility of primary nephrotic syndrome (PNS) by regulating the Treg/Th17 ratio via the MEG3 signaling

IntroductionPatients with primary nephrotic syndrome (PNS) were reported to exhibit the evident imbalance between the number of Th17 and Treg cells in their peripheral blood monocytes (PBMCs), which might be the immunological basis of the disease.Material and methods40 PNS patients and 42 healthy individuals were recruited in this study. FCM assay was used to observe the levels of Treg and Th17 cells.ResultsThe Treg/Th17 ratio was evidently decreased in PNS patients. The levels of MEG3 and RORγt were increased in the PNS group, while the levels of miR-17, miR-125a and FOXP3 mRNA were reduced in the PNS group. Moreover, the levels of IL-6 and IL-1β were highly increased in PNS patients. Ox-low density lipoprotein (ox-LDL) treatment significantly increased the levels of MEG3 and RORγt mRNA/protein while decreasing the levels of miR-17, miR-125a, and FOXP3 mRNA/protein in THP-1 cells, and the transfection of MEG3 siRNA partly alleviated the dysregulation in the expression of MEG3, relevant miRNAs and relevant mRNAs induced by ox-LDL. Also, the expression of miR-17 and miR-125a was evidently decreased upon the successful transfection of MEG3, but the RORγt mRNA/protein levels were promoted while the FOXP3 mRNA/protein levels were inhibited.ConclusionsOur results demonstrated that ox-LDL could promote the inflammatory response of PNS by decreasing the Treg/Th17 ratio via activating the MEG3 signaling. The activation of MEG3/miR-125a/FOXP3 axis and MEG3/miR-17/RORγt axis respectively lead to the Treg/Th17 imbalance, which resulted in up-regulated IL-6 and IL-1β levels, thus increasing the susceptibility of PNS.

Aberrant expression of BAX, MEG3, and miR-214-3P genes in recurrent pregnancy loss

Aims Recurrent pregnancy loss (RPL), with unknown causes, is one of the most common challenges facing pregnancy. Apoptotic signaling pathways are involved in the normal and abnormal pregnancy process. Despite the evidence pointing toward the aberrant expression of apoptotic and apoptotic-related genes in pregnancy complications, the involvement of these genes in RPL remains to be elucidated. This study aimed to investigate the expression levels of BAX, MEG3, and miR-214-3p (as a microRNA), and their associations in an Iranian population. Materials and methods Following the extraction of RNA from blood samples of RPL patients and controls, quantitative expression levels of BAX, MEG3, and miR-214-3p genes were analyzed by real-time RT-PCR. Results The findings showed that the expression levels of BAX and miRNA-214-3p were significantly higher in the blood samples of RPL patients than in control samples. In contrast, the expression of MEG3 was significantly down-regulated in women RPL. Furthermore, altered expressions of MEG3 and miRNA-214-3p are associated with their target gene BAX, where the BAX expression is positively and negatively correlated with the expressions of has-miR-214-3P and MEG3, respectively. ROC curve evaluation demonstrated the highest specificity and diagnostic value for miR-214-3p expression in distinguishing RPL samples from the healthy controls. Conclusions These data indicated that the aberrant expression of BAX, MEG3, miRNA-214-3p genes in RPL patients could provide new insights into the biological characteristics and related pathways of differentially expressed genes, which could help as potential diagnostic biomarkers and a better understanding of the molecular mechanisms of RPL.

The gene expression of long non-coding RNAs (lncRNAs): MEG3 and H19 in adipose tissues from obese women and its association with insulin resistance and obesity indices.

BackgroundThere is evidence regarding the role of two lncRNAs: MEG3 and H19 the pathomechanism of obesity and related disorders. Here, we aimed to evaluate the expression of MEG3 and H19 in visceral adipose tissues (VAT) and subcutaneous adipose tissues (SAT) of obese women (n = 18), as compared to normal‐weight women (n = 17). Moreover, we sought to identify the association of expression of MEG3 and H19 in SAT and VAT with obesity parameters, insulin resistance, and the mRNA expression of possible target genes involved in adipogenesis and lipogenesis including peroxisome proliferator‐activated receptor gamma (PPARγ), fatty acid synthase (FAS), and acetyl‐CoA carboxylase (ACC).MethodsReal‐time PCR was performed to investigate the mRNA expression of the above‐mentioned genes in VAT and SAT from all participants.ResultsThe results showed lower mRNA levels of H19 in SAT of obese women, compared to normal‐weight women, while MEG3 expression was significantly higher in the SAT of the obese group rather than controls. Correlation analysis indicated that the transcript level of H19 had an inverse correlation with obesity indices and HOMA‐IR values. However, MEG3 expression displayed a positive correlation with all the indicated parameters in all participants. Interestingly, a positive correlation was found between transcript level of MEG3 in SAT with FAS and PPARγ. However, there was an inverse correlation between SAT expression of H19 and FAS.ConclusionsIt appears that lncRNAs, MEG3 and H19, are involved in obesity‐related conditions. However, more clinical studies are still required to clarify the relationships between lncRNAs with obesity and related abnormalities.

C-MYC-induced long noncoding RNA MEG3 aggravates kidney ischemia\u2013reperfusion injury through activating mitophagy by upregulation of RTKN to trigger the Wnt/\u03b2-catenin pathway

Ischemia–reperfusion injury (IRI)-induced acute kidney injury (AKI) is a life-threatening disease. The activation of mitophagy was previously identified to play an important role in IRI. Maternally expressed 3 (MEG3) can promote cerebral IRI and hepatic IRI. The present study was designed to study the role of MEG3 in renal IRI. Renal IRI mice models were established, and HK-2 cells were used to construct the in vitro models of IRI. Hematoxylin–eosin staining assay was applied to reveal IRI-triggered tubular injury. MitoTracker Green FM staining and an ALP kit were employed for detection of mitophagy. TdT-mediated dUTP-biotin nick-end labeling assay was used to reveal cell apoptosis. The results showed that renal cortex of IRI mice contained higher expression of MEG3 than that of sham mice. MEG3 expression was also elevated in HK-2 cells following IRI, suggesting that MEG3 might participate in the development of IRI. Moreover, downregulation of MEG3 inhibited the apoptosis of HK-2 cells after IRI. Mitophagy was activated by IRI, and the inhibition of MEG3 can restore mitophagy activity in IRI-treated HK-2 cells. Mechanistically, we found that MEG3 can bind with miR-145-5p in IRI-treated cells. In addition, rhotekin (RTKN) was verified to serve as a target of miR-145-5p. MEG3 upregulated RTKN expression by binding with miR-145-5p. Further, MEG3 activated the Wnt/β-catenin pathway by upregulation of RTKN. The downstream effector of Wnt/β-catenin pathway, c-MYC, served as the transcription factor to activate MEG3. In conclusion, the positive feedback loop of MEG3/miR-145-5p/RTKN/Wnt/β-catenin/c-MYC promotes renal IRI by activating mitophagy and inducing apoptosis, which might offer a new insight into the therapeutic methods for renal IRI in the future.

Overexpression of lncRNA MEG3 inhibits proliferation and invasion of glioblastoma U251 cells in vitro by suppressing HIF1α expression

To investigate the effects of overexpression of long noncoding RNA (lncRNA) MEG3 on the proliferation and invasion of glioblastoma U251 cells by suppressing the expression of hypoxia inducible factor 1α(HIF1α). The expression of lncRNA MEG3 and HIF1α mRNA were examined in human fetal glial cells (HFGCs) and U251 cells using realtime quantitative PCR (qRT-PCR), and the expression of HIF1α protein was detected with Western blotting.U251 cells in normal culture or transfected with pcDNA3.1 vector (NC group) or pcDNA3.1-MEG3 vector via lipofectamine2000 were exposed to hypoxia for 12h, and the expressions of HIF1α mRNA and protein were detected with qRT-PCR and Western blotting, respectively.MTT assay and Transwell assay were employed to examine the influence of MEG3 overexpression on the proliferation and invasion of U251 cells. The expression of MEG3 was significantly lower and HIF1α mRNA and protein expressions were significantly higher in U251 cells than in HFGCs (P < 0.05).In U251 cells, overexpression of MEG3 significantly decreased the mRNA and protein expressions of HIF1α(P < 0.05).Hypoxic exposure for 12h also resulted in significantly lowered expression of HIF1α protein in U251 cells (P < 0.05).Overexpression of MEG3 obviously suppressed the proliferation and invasiveness of U251 cells (P < 0.05). MEG3 overexpression inhibits the proliferation and invasion of U251 cells through suppressing the expression of HIF1α mRNA and protein, suggesting that MEG3 may serve as a potential therapeutic target for glioblastomas.

Hypermethylation-mediated downregulation of long non-coding RNA MEG3 inhibits osteogenic differentiation of bone marrow mesenchymal stem cells and promotes pediatric aplastic anemia

BackgroundThe reduced osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is the typical characteristics of pediatric aplastic anemia (AA) pathogenesis. Long non-coding RNA MEG3 is reported to promote osteogenic differentiation of BMSCs via inducing BMP4 expression. ObjectiveThis study aims to investigate the mechanism of DNMT1/MEG3/BMP4 pathway in osteogenic differentiation of BMSCs in pediatric AA. MethodsBMSCs were isolated and purified from bone marrows of pediatric AA patients (n = 5) and non-AA patients (n = 5). The expression of DNMT1, MEG3, and BMP4 in isolated BMSCs was detected using quantitative real-time PCR and western blot analysis. Osteogenic differentiation was determined using Alizarin red staining. The methylation of MEG3 promoter and the interaction between DNMT1 and MEG3 promoter were detected using methylation-specific PCR and chromatin immunoprecipitation assay, respectively. ResultsLowly expressed MEG3 and BMP4 and highly expressed DNMT1 were observed in BMSCs of pediatric AA patients. The overexpression of MEG3 promoted osteogenic differentiation of BMSCs. Luciferase reporter assay showed that MEG3 overexpression increased transcriptional activity of BMP4. The inhibitor of methylation, 5-azacytidine, suppressed DNMT1 expression and reduced methylation of MEG3 promoter. Overexpression of DNMT1 increased the binding between DNMT1 and MEG3 promoter. The simultaneous overexpression of DNMT1 and MEG3 restored the inhibition of osteogenic differentiation caused by DNMT1 overexpression alone. ConclusionsOur findings indicated that DNMT1 mediated the hypermethylation of MEG3 promoter in BMSCs, and DNMT1/MEG3/BMP4 pathway modulated osteogenic differentiation of BMSCs in pediatric AA.

Long noncoding RNA MEG3 expressed in human dental pulp regulates LPS-Induced inflammation and odontogenic differentiation in pulpitis

Pulpitis refers to inflammation of the inner pulp by invading microbes, and tissue repair occurs due to odontogenic differentiation of human dental pulp cells (hDPCs) with multidifferentiation potential. Long noncoding RNAs (lncRNAs) can modulate numerous pathological and biological processes; however, the role of lncRNAs in the inflammation and regeneration of the dentin-pulp complex in pulpitis is unclear. Here, we performed high-throughput sequencing to identify differentially expressed lncRNAs between human normal and inflamed pulp and concluded that lncMEG3 (lncRNA maternally expressed gene 3, MEG3) was significantly upregulated in both inflamed pulp and LPS-treated hDPCs. MEG3 expression in the pulp tissue was detected using the RNAscope® technique. RNA pulldown assays identified the MEG3-interacting proteins and the potential mechanisms. With MEG3 knockdown, we investigated the role of MEG3 in the secretion of inflammatory cytokines in LPS-treated hDPCs and odontogenic differentiation of hDPCs. MEG3 downregulation inhibited the secretion of TNF-α, IL-1β and IL-6 in LPS-treated hDPCs, and the p38/MAPK signaling pathway may be related to this effect. MEG3 knockdown promoted odontogenic differentiation of hDPCs by regulating the Wnt/β-catenin signaling pathway. Our study suggested that MEG3 has a negative effect on inflammation and regeneration of the dentin-pulp complex in pulpitis.

Long non-coding RNA Meg3 deficiency impairs glucose homeostasis and insulin signaling by inducing cellular senescence of hepatic endothelium in obesity

Obesity-induced insulin resistance is a risk factor for diabetes and cardiovascular disease. However, the mechanisms underlying endothelial senescence in obesity, and how it impacts obesity-induced insulin resistance remain incompletely understood. In this study, transcriptome analysis revealed that the long non-coding RNA (lncRNA) Maternally expressed gene 3 (Meg3) is one of the top differentially expressed lncRNAs in the vascular endothelium in diet-induced obese mice. Meg3 knockdown induces cellular senescence of endothelial cells characterized by increased senescence-associated β–galactosidase activity, increased levels of endogenous superoxide, impaired mitochondrial structure and function, and impaired autophagy. Moreover, Meg3 knockdown causes cellular senescence of hepatic endothelium in diet-induced obese mice. Furthermore, Meg3 expression is elevated in human nonalcoholic fatty livers and nonalcoholic steatohepatitis livers, which positively correlates with the expression of CDKN2A encoding p16, an important hallmark of cellular senescence. Meg3 knockdown potentiates obesity-induced insulin resistance and impairs glucose homeostasis. Insulin signaling is reduced by Meg3 knockdown in the liver and, to a lesser extent, in the skeletal muscle, but not in the visceral fat of obese mice. We found that the attenuation of cellular senescence of hepatic endothelium by ablating p53 expression in vascular endothelium can restore impaired glucose homeostasis and insulin signaling in obesity. In conclusion, our data demonstrate that cellular senescence of hepatic endothelium promotes obesity-induced insulin resistance, which is tightly regulated by the expression of Meg3. Our results suggest that manipulation of Meg3 expression may represent a novel approach to managing obesity-associated hepatic endothelial senescence and insulin resistance.

Long non-coding RNA MEG3 silencing and microRNA-214 restoration elevate osteoprotegerin expression to ameliorate osteoporosis by limiting TXNIP.

Studies have shown that long non‐coding RNA (lncRNA) MEG3 plays a key role in osteoporosis (OP), but its regulatory mechanism is somewhat incompletely clear. Here, we intend to probe into the mechanism of MEG3 on OP development by modulating microRNA‐214 (miR‐214) and thioredoxin‐interacting protein (TXNIP). Rat models of OP were established. MEG3, miR‐214 and TXNIP mRNA expression in rat femoral tissues were detected, along with TXNIP, OPG and RANKL protein expression. BMD, BV/TV, Tb.N and Tb.Th in tissue samples were measured. Ca, P and ALP contents in rat serum were also determined. Primary osteoblasts were isolated and cultured. Viability, COL‐I, COL‐II and COL‐Χ mRNA expression, PCNA, cyclin D1, OCN, RUNX2 and osteolix protein expresion, ALP content and activity, and mineralized nodule area of rat osteoblasts were further detected. Dual‐luciferase reporter gene and RNA‐pull down assays verified the targeting relationship between MEG3, miR‐214 and TXNIP. MEG3 and TXNIP were up‐regulated while miR‐214 was down‐regulated in femoral tissues of OP rats. MEG3 silencing and miR‐214 overexpression increased BMD, BV/TV, Tb.N, Tb.Th, trabecular bone area, collagen area and OPG expression, and down‐regulated RANKL of femoral tissues in OP rats. MEG3 silencing and miR‐214 overexpression elevated Ca and P and reduced ALP in OP rat serum, elevated osteoblast viability, differentiation ability, COL‐I and COL‐Χ expression and ALP activity, and reduced COL‐II expression of osteoblasts. MEG3 specifically bound to miR‐214 to regulate TXNIP. MEG3 silencing and miR‐214 overexpression promote proliferation and differentiation of osteoblasts in OP by down‐regulating TXNIP, which further improves OP.

Over-expression of MEG3 promotes differentiation of bone marrow mesenchymal stem cells into chondrocytes by regulating miR-129-5p/RUNX1 axis

ABSTRACT This study explored the role of MEG3 in the cartilage differentiation of bone marrow mesenchymal stem cells (BMSCs). We investigated the effects of over-expression and knockdown of MEG3 on cell viability, cell differentiation, and the expressions of MEG3, miR-129-5p, COL2, chondrocyte differentiation-related genes (sry-type high-mobility-group box 9 (SOX9), SOX5, Aggrecan, silent information regulator 1 (SIRT1), and Cartilage oligomeric matrix protein (COMP)). The targeting relationship between MEG3 and miR-129-5p and the target gene of miR-129-5p was confirmed through Starbase, TargetScan and luciferase experiments. Finally, a series of rescue experiments were conducted to study the regulatory effects of MEG3 and miR-129-5p. BMSCs were identified as CD29+ and CD44+ positive, and their differentiation was time-dependent. As BMSCs differentiated, MEG3 expression was up-regulated, but miR-129-5p was down-regulated. Over-expressed MEG3 promoted the viability and differentiation of BMSCs, up-regulated the expressions of COL2 and chondrocyte differentiation-related genes, and inhibited miR-129-5p. Runt-related transcription factor 1 (RUNX1) was negatively regulated as a target gene of miR-129-5p. Results of rescue experiments showed that the inhibitory effect of miR-129-5p mimic on BMSCs could be partially reversed by MEG3. Over-expression of MEG3 regulated the miR-129-5p/RUNX1 axis to promote the differentiation of BMSCs into chondrocytes. This study provides a reliable basis for the application of lncRNA in articular cartilage injury.

Upregulated expression of long non-coding RNA MEG3 serves as a prognostic biomarker in severe pneumonia children and its regulatory mechanism

ABSTRACT Severe pneumonia is a high-mortality disorder in children. The expression and underlying effects of lncRNA maternally expressed 3 (MEG3) were detected. The relationships between MEG3 and other parameters were reported by Pearson correlation. The prognostic importance of MEG3 was assessed by Kaplan-Meier (K-M) curve and COX analysis and its diagnostic potential was uncovered by the receiver operating characteristic (ROC) curve. Luciferase activity assay was performed to demonstrate the target gene of MEG3. Elevated expression of MEG3 and reduced microRNA-29 c (miR-29 c) were evaluated in severe pneumonia children, and a negative relationship between MEG3 and miR-29 c was propounded. MEG3 might function as an independent prognostic indicator. The diagnostic efficiency of MEG3 was also indicated for severe pneumonia children. In MRC-5 cell models and MH-S cell models, lipopolysaccharide (LPS) contributed to the increased expression of MEG3. Interference of MEG3 restricted the upregulation of MEG3 triggered by LPS. Silenced MEG3 protected MRC-5 and MH-S cells against damages managed by LPS on cell apoptosis, viability, and inflammation. MiR-29 c was a ceRNA of MEG3 and the absence of MEG3 abrogated the decreased expression of miR-29 c caused by LPS. Overall, the increased expression of MEG3 and the reduced levels of miR-29 c were identified in severe pneumonia. Prognostic and diagnostic significances of MEG3 provided a novel perspective for severe pneumonia. Disruption of MEG3 alleviated cell injury and inflammation as characterized by high LPS by binding miR-29 c.

LncRNA MCM3AP-AS1 Downregulates LncRNA MEG3 in Triple Negative Breast Cancer to Inhibit the Proliferation of Cancer Cells.

The oncogenic role of lncRNA MCM3AP-AS1 has been reported in several types of cancer, while its role in triple negative breast cancer (TNBC) is unknown. The expression levels of MCM3AP-AS1 and MEG3 in TNBC and paired nontumor tissues from 60 TNBC patients were measured by RT-qPCR. The effects of overexpression of MCM3AP-AS1 and MEG3 on the proliferation of BT-20 and BT-549 cells were evaluated by cell proliferation assay. We found that MCM3AP-AS1 was upregulated in TNBC, while lncRNA MEG3 was downregulated in TNBC, and they were inversely correlated with each other. In addition, the expression levels of MCM3AP-AS1 increased with the increase in tumor size, while the expression levels of MEG3 decreased with the increase in tumor size. In TNBC cells, overexpression of MCM3AP-AS1 led to downregulated expression of MEG3, while overexpression of MEG3 did not affect the expression of MCM3AP-AS1. Cell proliferation analysis showed that overexpression of MCM3AP-AS1 led to increased cell proliferation rate and reduced the inhibitory effects of overexpression of MEG3 on cancer cell proliferation. Therefore, MCM3AP-AS1 downregulates MEG3 in TNBC to inhibit the proliferation of cancer cells.

Abstract 13836: Long Noncoding Rna Meg3 Protects Against Hepatic Endothelial Senescence in Obesity by Regulating Mitochondrial Function

Introduction: Long noncoding RNAs (lncRNAs) contribute to the pathogenesis of obesity, a risk factor for cardiovascular disease. The underlying mechanisms are not completely understood, in part, due to that the functions of the majority of them remain unknown in many processes such as mitochondrial homeostasis and cellular senescence. Here, we set out to test the hypothesis that lncRNAs play key roles in obesity by regulating mitochondrial function and cellular senescence in the endothelium. Methods and Results: In this study, transcriptome analysis revealed that lncRNA maternally expressed gene 3 (Meg3) is one of the top induced lncRNAs in the endothelium from adipose tissue in diet-induced obese mice. Meg3 knockdown potentiated obesity-induced insulin resistance revealed by intraperitoneal glucose and insulin tolerance tests and an increase in fasting plasma insulin levels (1.67-fold increase; p&lt;0.05); diminished insulin signaling revealed by 43% reduction (p=0.038) in Akt phosphorylation on serine 473 in liver and, to a lesser extent, in skeletal muscle (32%; p&lt;0.05), but not in visceral fat; and increased hepatic endothelial senescence in obese mice (e.g., 2.74- and 3.40-fold increase in p21 and p16 expression, respectively; p&lt;0.001). Endothelial cell-specific p53 knockout partially attenuated Meg3 knockdown-induced cellular senescence and completely restored hepatic insulin signaling in obese mice. Meg3 knockdown inhibited mitochondrial bioenergetics, increased mitochondrial superoxide production, and caused fragmentation of mitochondrial network; also impaired autophagy, induced a type 1 interferon response, and triggered cellular senescence in HUVECs. Finally, the expression of Meg3 is induced in fatty livers of obese patients and strongly correlates with the cellular senescence marker p16 (r=0.50; p=0.0007). Conclusions: Deficiency of lncRNA Meg3 contributes to mitochondrial dysfunction, hepatic endothelial senescence, and accelerated obesity-induced insulin resistance. Meg3 induction is important in limiting obesity-induced endothelial senescence and insulin resistance, suggesting that manipulation of Meg3 expression may represent a novel approach to manage obesity-associated cardiometabolic disease.

LncRNA-Meg3 promotes Nlrp3-mediated microglial inflammation by targeting miR-7a-5p

Recent studies have identified neuroinflammation as a significant contributor to the pathological process of traumatic brain injury (TBI) and as a potentially effective target for treatment. LncRNA maternally expressed gene 3 (Meg3) has further been observed to play a critical role in diverse biological processes, including microglial activation and the inflammatory response. However, its target gene and associated signaling pathway require further elucidation. This study found that lipopolysaccharide + ATP upregulated Meg3, promoted microglia activation, Nlrp3/caspase1 activation and inflammation, and markedly reduced miR-7a-5p. Overexpression of miR-7a-5p attenuated Meg3-induced microglial activation, but not Meg3 expression. Bioinformatic analysis and dual-luciferase assays indicated that Meg3 was a direct target of miR-7a-5p that negatively regulates miR-7a-5p expression. Further, we showed that Meg3 acted as a competing endogenous RNA for miR-7a-5p and induced microglial inflammation by regulating nod-like receptor protein 3 (Nlrp3) expression. Our study thus demonstrates Meg3 regulates microglia inflammation by targeting the miR-7a-5p /Nlrp3 pathway.

MEG3 aggravates hypoxia/reoxygenation inducedapoptosis of renal tubular epithelial cells via the miR-129-5p/HMGB1 axis.

The apoptosis of renal tubular epithelial cells (TECs) during ischemia/reperfusion (I/R) facilitates the progression of acute kidney injury (AKI). This study aimed to probe the role of long noncoding RNA maternally expressed 3 (MEG3) in I/R-induced apoptosis of TECs. In this study, with CoCl2 and hypoxia/reoxygenation treatments, cell models were established to mimic I/R using the human kidney tubular cell line HK-2. In HK-2 cells, expression of MEG3 detected using quantitative real-time polymerase chain reaction (qRT-PCR), was significantly upregulated after CoCl2 treatment and hypoxia/reoxygenation treatment. The results of cell counting kit-8 assay and flow cytometry suggested that knockdown of MEG3 significantly increased the viability of HK-2 cells but inhibited its apoptosis, while overexpression of MEG3 exerted the reverse effects. Additionally, expression levels of interleukin 6 and tumor necrosis factor-α in the medium were elevated after MEG3 was overexpressed in HK-2 cells. Together with qRT-PCR and Western blot analysis, a dual-luciferase reporter gene assay was used to verify the interactions among MEG3, miR-129-5p, and HMGB1. The results demonstrated that in HK-2 cells, miR-129-5p was a target of MEG3, and HMGB1 served as a target gene of miR-129-5p. Besides this, compared with the control group, the expression levels of MEG3 and HMGB1 in samples derived from AKI patients were remarkably upregulated, and the expression of miR-129-5p was downregulated. Therefore, taken together, we conclude that the overexpression of MEG3 induced by I/R promotes apoptosis of TECs via regulating the miR-129-5p/HMGB1 axis.

Long non-coding RNA MEG3 inhibits M2 macrophage polarization by activating TRAF6 via microRNA-223 down-regulation in viral myocarditis.

Viral myocarditis (VMC) commonly triggers heart failure, for which no specific treatments are available. This study aims to explore the specific role of long non‐coding RNA (lncRNA) maternally expressed 3 (MEG3) in VMC. A VMC mouse model was induced by Coxsackievirus B3 (CVB3). Then, MEG3 and TNF receptor‐associated factor 6 (TRAF6) were silenced and microRNA‐223 (miR‐223) was over‐expressed in the VMC mice, followed by determination of ventricular ejection fraction (LVEF) and left ventricular fractional shortening (LVFS). Dual‐luciferase reporter assay was introduced to test the interaction among MEG3, TRAF6 and miR‐223. Macrophages were isolated from cardiac tissues and bone marrow, and polarization of M1 or M2 macrophages was induced. Then, the expressions of components of NLRP3 inflammatory body (NLRP3, ASC, Caspase‐1), M1 markers (CD86, iNOS and TNF‐α) and M2 markers (CD206, Arginase‐1 and Fizz‐1) were measured following MEG3 silencing. In the VMC mouse model, MEG3 and TRAF6 levels were obviously increased, while miR‐223 expression was significantly reduced. Down‐regulation of MEG3 resulted in the inhibition of TRAF6 by promoting miR‐223. TRAF6 was negatively correlated with miR‐223, but positively correlated with MEG3 expression. Down‐regulations of MEG3 or TRAF6 or up‐regulation of miR‐223 was observed to increase mouse weight, survival rate, LVEF and LVFS, while inhibiting myocarditis and inflammation via the NF‐κB pathway inactivation in VMC mice. Down‐regulation of MEG3 decreased M1 macrophage polarization and elevated M2 macrophage polarization by up‐regulating miR‐223. Collectively, down‐regulation of MEG3 leads to the inhibition of inflammation and induces M2 macrophage polarization via miR‐223/TRAF6/NF‐κB axis, thus alleviating VMC.

Inorganic arsenic influences cell apoptosis by regulating the expression of MEG3 gene.

Arsenic is a wildly distributed carcinogen in the environment. Arsenic-induced apoptosis has been extensively studied in therapeutics and toxicology. LncRNA MEG3 has been extensively studied as apoptosis regulatory gene in recent years. However, it stays unclear regarding how the mechanism of MEG3 regulates arsenic-induced apoptosis. Our focus was to explore the effects of MEG3 on arsenic-induced apoptosis. MTS assay was used to test cell viability, and qRT-PCR was for the examination of gene expressions. The effect of the apoptosis and necrosis after knockdown MEG3 was detected with double staining. Our results demonstrated that MEG3 expression was positively correlated with the concentration of three arsenic species (inorganic arsenic (iAs), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA)) (p < 0.05). The ability of iAs to induce MEG3 expression was much higher compared with that induced by MMA and DMA. In addition, our experiments confirmed that MEG3 knockdown increased cell viability and arsenic-induced apoptosis, but cell viability decreased after iAs treatment. Moreover, LncRNA MEG3 regulated apoptosis via down-regulate API5 while up-regulate CASP7, CCND3 and APAF1. It is further proved that arsenic-induced apoptosis increased after the knockdown of MEG3, which regulates these genes. These findings provide experimental evidence and possible mechanisms for subsequent research on the effects of arsenic on health.

LncRNA MEG3 inhibits self-renewal and invasion abilities of oral cancer stem cells by sponging miR-421

Oral cancer stem cells (CSCs) have been considered as the key cells that are implicated in tumor recurrence and metastasis. In recent years, great attention has been paid to the significance of various non-coding RNAs due to their regulatory roles in oral CSCs. Although the function of long non-coding RNA MEG3 in various cancers has been investigated, its effects on the features of oral CSCs remained to be determined. The expression levels of MEG3 in tongue squamous cell carcinomas and prognostic effect have been evaluated. We assessed the expression of MEG3 in sphere cells (oral CSCs) using qRT-PCR. Secondary sphere formation and invasion assays were conducted to evaluate the self-renewal and metastatic abilities, respectively. Bioinformatics software and luciferase reporter assay were used to predict and verify the relationship between MEG3 and miR-421. MEG3 was downregulated in the tissues of oral cancer and associated with a poor prognosis. In oral CSCs, the expression of MEG3 was repressed and overexpression of MEG3 resulted in suppression of self-renewal and invasion abilities. Luciferase reporter assay showed that miR-421 directly interacted with MEG3, and our subsequent experiment demonstrated that elevation of miR-421 reversed the MEG3-inhibited characteristics of oral CSCs. Our findings suggest that MEG3 can serve as a tumor suppressor in oral CSCs by impeding the action of miR-421. Moreover, targeting MEG3-miR-421 axis has the potential to mitigate the tumor recurrence and metastasis.

LncRNA MEG3 Reduces Hippocampal Neuron Apoptosis via the PI3K/AKT/mTOR Pathway in a Rat Model of Temporal Lobe Epilepsy.

PurposeTemporal lobe epilepsy (TLE) is a common neurological disorder, which is characterized by recurrent spontaneous seizures. Exploring the mechanisms of epileptogenesis has been considered as a priority. The aim of this study is to investigate the effects of LncRNA MEG3 in spontaneous recurrent epileptiform discharges (SREDs) and rats with TLE.MethodsRat model of TLE was produced by intraperitoneal injection of lithium chloride and pilocarpine. Rat hippocampal neuronal model of SREDs was established by Mg2+-free treatment. MEG3 was overexpressed by transfection of AAV-MEG3 in TLE and SREDs model. The expression of MEG3, interleukin-1β (IL-1β), interleukin-6 (IL-6) and recombinant human tumor necrosis factor-alpha (TNF-α) was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Malondialdehyde (MDA) content and superoxide dismutase (SOD) activity were detected by corresponding kit. The apoptosis of hippocampal neurons was detected by terminal deoxynucleotidyl transferase transfer‑mediated dUTP nick end‑labeling (TUNEL) assay and flow cytometry. The expression of proteins related to apoptosis (Caspase-3, Bax, and Bcl-2) and the PI3K/AKT/mTOR pathway was detected by Western blot.ResultsMEG3 expression was downregulated in SREDs and rats with TLE. Overexpression of MEG3 reduced the expression of IL-1β, IL-6, and TNF-α, MDA content, apoptosis rate of hippocampal neuron, increased SOD activity, and inhibited the PI3K/AKT/mTOR pathway in rats with TLE. In addition, overexpression of MEG3 enhanced cell viability and inhibited apoptosis through the activation of the PI3K/AKT/mTOR pathway in SREDs.ConclusionMEG3 reduced proinflammatory cytokines, oxidative stress, and apoptosis rate of hippocampal neuron and enhanced cell viability through the activation of the PI3K/AKT/mTOR pathway in SREDs and rats with TLE. Our findings may contribute to find a new therapeutic target for the treatment of epilepsy.