GADD45α mediates arsenite‐induced cell apoptotic effect in human hepatoma cells via JNKs/AP‐1‐dependent pathway

Arsenite (As(III)), an effective chemotherapeutic agent for the acute promyelocytic leukemia (APL) and multiple myeloma (MM), might be also a promise for the therapy of other cancers, including the solid tumors. However, the molecular bases of arsenite‐induced cytotoxicity in the tumor cells have not been fully defined. In this study, we have disclosed that arsenite effectively induces the apoptotic response in the HepG2 human hepatoma cells by triggering GADD45α induction and the subsequent activation of JNKs/AP‐1 cell death pathway. However, signaling events relating to GADD45α/JNKs/AP‐1 pathway activation have not been observed in HL7702 human diploid hepatic cells under the same arsenite exposure condition. Our results thus have illustrated the selective pro‐apoptotic role of arsenite in the hepatoma cells by activating GADD45α‐dependent cell death pathway whereas with little effect on the normal hepatic cells. The approaches to up‐regulate GADD45α levels might be helpful in improving the chemotherapeutic action of arsenite on certain solid tumors including hepatoma. J. Cell. Biochem. 109: 1264–1273, 2010. © 2010 Wiley‐Liss, Inc.     

miR‐29a modulates tumor necrosis factor‐α‐induced osteogenic inhibition by targeting Wnt antagonists

We previously found that miR‐29a was significantly downregulated in Ankylosing spondylitis (AS) patients, a chronic inflammatory disease associated with bone metabolic disorder, however, the underlying mechanism remains unclear. In this study, we demonstrated that miR‐29a regulates tumor necrosis factor‐α (TNF‐α) mediated bone loss mainly by targeting DKK1 and GSK3β, thus activating the Wnt/β‐catenin pathway. Our findings may provide new insight into the pathogenesis of the bone metabolism disorder in inflammation environment and provide promising therapeutic target.     

Host relieves lnc‐IRAK3‐3‐sequestered miR‐891b to attenuate apoptosis in Enterovirus 71 infection

Enterovirus 71 (EV71) is an emerging life‐threatening pathogen particularly in the Asia‐Pacific region. Apoptosis is a major pathogenic feature in EV71 infection. However, which molecular mechanism participating in EV71‐induced apoptosis is not completely understood. Long noncoding RNAs (lncRNAs), a newly discovered class of regulatory RNA molecules, govern a wide range of biological functions through multiple regulatory mechanisms. Whether lncRNAs involved in EV71‐induced apoptosis was investigated in this study. We conducted an apoptosis‐oriented approach by integrating lncRNA and mRNA profilings. lnc‐IRAK3‐3 is down‐regulated in EV71 infection and plays an important role in EV71 infection‐induced apoptosis. Compensation of lnc‐IRAK3‐3 in EV71 infection promoted cell apoptosis wherein GADD45β expression was increased and further triggered caspase3 and PARP cleavage. Using bioinformatics analysis and functional assays, lnc‐IRAK3‐3 could functionally sequester miR‐891b and GADD45β 3′UTR whereas miR‐891b showed the inhibitory activity on GADD45β expression. Taken together, lnc‐IRAK3‐3 has the ability capturing miR‐891b to enforce GADD45β expression and eventually promotes apoptosis. On the contrary, host cells suppress lnc‐IRAK3‐3 to relieve lnc‐IRAK3‐3‐sequestered miR‐891b, restrain GADD45β, and attenuate apoptosis in EV71 infection that prevent host cells from severe damages. We discover a new molecular mechanism by which host cells counteract EV71‐induced apoptosis through the lnc‐IRAK3‐3/miR‐891b/GADD45β axis partially.     

LncRNA NR2F2‐AS1 promotes tumourigenesis through modulating BMI1 expression by targeting miR‐320b in non‐small cell lung cancer

Recently, long noncoding RNAs (lncRNAs) are attracting wide attention in the field of cancer research because of its important role in cancer diagnosis and prognosis. But studies on the biological effects and relevant mechanisms of lncRNAs in non‐small cell lung cancer (NSCLC) remain few and need to be enriched. Our study discussed the expression and biological effects of LncRNA NR2F2‐AS1, and further explored its possible molecular mechanisms. As a result, elevated expression of NR2F2‐AS1 was detected in NSCLC tissues and cells and was remarkably associated with the tumor, node, metastasis (TNM) stage and the status of lymphatic metastasis of patients. Down‐regulated NR2F2‐AS1 contributed to the promotion of cell apoptosis and the inhibition of cell proliferation and invasion in A549 and SPC‐A‐1 cells in vivo and vitro. Through bioinformatics analysis, NR2F2‐AS1 functions as a ceRNA directly binding to miR‐320b, BMI1 was a direct target of miR‐320b. Combined with the following cellular experiments, the data showed that NR2F2‐AS1 may influence the NSCLC cell proliferation, invasion and apoptosis through regulating miR‐320b targeting BMI1.     

MiR‐155 promotes interleukin‐1β‐induced chondrocyte apoptosis and catabolic activity by targeting PIK3R1‐mediated PI3K/Akt pathway

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation, in which elevated chondrocyte apoptosis and catabolic activity play an important role. MicroRNA‐155 (miR‐155) has recently been shown to regulate apoptosis and catabolic activity in some pathological circumstances, yet, whether and how miR‐155 is associated with OA pathology remain unexplored. We report here that miR‐155 level is significantly up‐regulated in human OA cartilage biopsies and also in primary chondrocytes stimulated by interleukin‐1β (IL‐1β), a pivotal pro‐catabolic factor promoting cartilage degradation. Moreover, miR‐155 inhibition attenuates and its overexpression promotes IL‐1β‐induced apoptosis and catabolic activity in chondrocytes in vitro. We also demonstrate that the PIK3R1 (p85α regulatory subunit of phosphoinositide 3‐kinase (PI3K)) is a target of miR‐155 in chondrocytes, and more importantly, PIK3R1 restoration abrogates miR‐155 effects on chondrocyte apoptosis and catabolic activity. Mechanistically, PIK3R1 positively regulates the transduction of PI3K/Akt pathway, and a specific Akt inhibitor reverses miR‐155 effects on promoting chondrocyte apoptosis and catabolic activity, phenocopying the results obtained via PIK3R1 knockdown, hence establishing that miR‐155 promotes chondrocyte apoptosis and catabolic activity through targeting PIK3R1‐mediated PI3K/Akt pathway activation. Altogether, our study discovers novel roles and mechanisms of miR‐155 in regulating chondrocyte apoptosis and catabolic activity, providing an implication for therapeutically intervening cartilage degradation and OA progression.     

β‐arrestin2/miR‐155/GSK3β regulates transition of 5′‐azacytizine‐induced Sca‐1‐positive cells to cardiomyocytes

Stem‐cell antigen 1–positive (Sca‐1+) cardiac stem cells (CSCs), a vital kind of CSCs in humans, promote cardiac repair in vivo and can differentiate to cardiomyocytes with 5′‐azacytizine treatment in vitro. However, the underlying molecular mechanisms are unknown. β‐arrestin2 is an important scaffold protein and highly expressed in the heart. To explore the function of β‐arrestin2 in Sca‐1+ CSC differentiation, we used β‐arrestin2–knockout mice and overexpression strategies. Real‐time PCR revealed that β‐arrestin2 promoted 5′‐azacytizine‐induced Sca‐1+ CSC differentiation in vitro. Because the microRNA 155 (miR‐155) may regulate β‐arrestin2 expression, we detected its role and relationship with β‐arrestin2 and glycogen synthase kinase 3 (GSK3β), another probable target of miR‐155. Real‐time PCR revealed that miR‐155, inhibited by β‐arrestin2, impaired 5′‐azacytizine‐induced Sca‐1+ CSC differentiation. On luciferase report assay, miR‐155 could inhibit the activity of β‐arrestin2 and GSK3β, which suggests a loop pathway between miR‐155 and β‐arrestin2. Furthermore, β‐arrestin2‐knockout inhibited the activity of GSK3β. Akt, the upstream inhibitor of GSK3β, was inhibited in β‐arrestin2‐Knockout mice, so the activity of GSK3β was regulated by β‐arrestin2 not Akt. We transplanted Sca‐1+ CSCs from β‐arrestin2‐knockout mice to mice with myocardial infarction and found similar protective functions as in wild‐type mice but impaired arterial elastance. Furthermore, low level of β‐arrestin2 agreed with decreased phosphorylation of AKT and increased phophorylation of GSK3β, similar to in vitro findings. The β‐arrestin2/miR‐155/GSK3β pathway may be a new mechanism with implications for treatment of heart disease.     

miR‐542‐3p prevents ovariectomy‐induced osteoporosis in rats via targeting SFRP1

Secreted frizzled‐related protein‐1 (SFRP1) is a negative regulatory molecule of the WNT signaling pathway and serves as a therapeutic target for bone formation in osteoporosis. In this study, we first established an ovariectomized (OVX) rat model to simulate postmenopausal osteoporosis and found significant changes in miR‐542‐3p and sFRP1 expression by RNA sequencing and qRT‐PCR. In addition, there was a significant negative correlation between miR‐542‐3p and sFRP1 mRNA levels in postmenopausal women with osteoporosis. We found that miR‐542‐3p inhibited the expression of sFRP1 mRNA by luciferase reporter assay. When the miR‐542‐3p binding site in sFRP1 3'UTR was deleted, it did not affect its expression. Western blot results showed that miR‐542‐3p inhibited the expression of SFRP1 protein. The expression of SFRP1 was significantly increased in osteoblast‐induced mesenchymal stem cells (MSC), whereas the expression of miR‐542‐3p was significantly decreased. And miR‐542‐3p transfected MSCs showed a significant increase in osteoblast‐specific marker expression, indicating that miR‐542‐3p is necessary for MSC differentiation. Inhibition of miR‐542‐3p reduced bone formation, confirmed miR‐542‐3p play a role in bone formation in vivo. In general, these data suggest that miR‐542‐3p play an important role in bone formation via inhibiting SFRP1 expression and inducing osteoblast differentiation.     

miR‐181a and miR‐150 regulate dendritic cell immune inflammatory responses and cardiomyocyte apoptosis via targeting JAK1–STAT1/c‐Fos pathway

The immune inflammatory response plays a crucial role in many cardiac pathophysiological processes, including ischaemic cardiac injury and the post‐infarction repair process. MicroRNAs (miRNAs) regulate the development and function of dendritic cells (DCs), which are key players in the initiation and regulation of immune responses; however, the underlying regulatory mechanisms remain unclear. Here, we used the supernatants of necrotic primary cardiomyocytes (Necrotic‐S) to mimic the myocardial infarction (MI) microenvironment to investigate the role of miRNAs in the regulation of DC‐mediated inflammatory responses. Our results showed that Necrotic‐S up‐regulated the DC maturation markers CD40, CD83 and CD86 and increased the production of inflammatory cytokines, concomitant with the up‐regulation of miR‐181a and down‐regulation of miR‐150. Necrotic‐S stimulation activated the JAK/STAT pathway and promoted the nuclear translocation of c‐Fos and NF‐κB p65, and silencing of STAT1 or c‐Fos suppressed Necrotic‐S‐induced DC maturation and inflammatory cytokine production. The effects of Necrotic‐S on DC maturation and inflammatory responses, its activation of the JAK/STAT pathway and the induction of cardiomyocyte apoptosis under conditions of hypoxia were suppressed by miR‐181a or miR‐150 overexpression. Taken together, these data indicate that miR‐181a and miR‐150 attenuate DC immune inflammatory responses via JAK1–STAT1/c‐Fos signalling and protect cardiomyocytes from cell death under conditions of hypoxia.     

miR‐499 released during myocardial infarction causes endothelial injury by targeting α7‐nAchR

The surged systemic vascular inflammation after acute myocardial infarction (AMI) aggravates the atherosclerotic endothelial injury. To explore roles of miR‐499 released from cardiomyocytes during AMI in endothelial injury. Using qPCR and ELISA, we discovered that patients with AMI had significantly increased plasma miR‐499, which was directly correlated with serum thrombomodulin, a marker for endothelial injury. Plasma of AMI patients, when incubated with human umbilical vein endothelial cells (HUVECs), significantly increased the expression of endothelial injury markers, which could be abrogated by antagomiR‐499. In vitro, neonatal rat cardiomyocytes subjected to hypoxia/reoxygenation (HX/R) released miR‐499 that could be internalized into rat pulmonary microvascular endothelial cells (RPMECs), worsening the high glucose‐induced injury. In silico analysis demonstrated that CHRNA7 encoding α7‐nAchR is a target of miR‐499, which was validated in cell lines expressing endogenous α7‐nAchR. In high glucose‐induced RPMECs injury model, miR‐499 aggravated, whereas forced CHRNA7 expression ameliorated the injury. Moreover, the perfusate from Langendorff perfused rat heart subjected to HX/R contained higher level of miR‐499 that significantly impaired the Bradykinin‐mediated endothelium‐dependent relaxation in both conduit and resistance arteries, which could be partially abrogated by antagomiR‐499. Finally, the correlation between plasma miR‐499 and endothelial injury was further confirmed in another cohort of AMI patients. We conclude that miR‐499 released from injured cardiomyocytes contributes to the endothelial injury by targeting α7‐nAchR. This study implies that miR‐499 may serve as a potential target for the treatment of the surged vascular inflammation post‐AMI.