Bing-Yang Zhu

CHANGES IN microRNA (miR) profile and effects of miR-320 in insulin-resistant 3T3-L1 adipocytes.

1 MicroRNAs (miRNAs) play essential roles in many biological processes. It is known that aberrant miRNA expression contributes to some pathological conditions. However, it is not known whether miRNAs play any role in the development of insulin resistance in adipocytes, a key pathophysiological link between obesity and diabetes. 2 To investigate the function of miRNAs in the development of insulin resistance, using miRNA microarray analysis we compared miRNA expression profiles between normal insulin‐sensitive 3T3‐L1 adipocytes and 3T3‐L1 adipocytes rendered insulin resistant following treatment with high glucose (25 mmol/L) and high insulin (1 µmol/L). Furthermore, adipocytes were transfected with specific antisense oligonucleotides against miRNA‐320 (anti‐miR‐320 oligo) and the effects on the development of insulin resistance were evaluated. 3 We identified 50 upregulated and 29 downregulated miRNAs in insulin‐resistant (IR) adipocytes, including a 50‐fold increase in miRNA‐320 (miR‐320) expression. Using bioinformatic techniques, the p85 subunit of phosphatidylinositol 3‐kinase (PI3‐K) was found to be a potential target of miR‐320. In experiments with anti‐miR‐320 oligo, insulin sensitivity was increased in IR adipocytes, as evidenced by increases in p85 expression, phosphorylation of Akt and the protein expression of the glucose transporter GLUT‐4, as well as insulin‐stimulated glucose uptake. These beneficial effects of anti‐miR‐320 oligo were observed only in IR adipocytes and not in normal adipocytes. 4 In conclusion, the miRNA profile changes in IR adipocytes compared with normal 3T3‐L1 adipocytes. Anti‐miR‐320 oligo was found to regulate insulin resistance in adipocytes by improving insulin–PI3‐K signalling pathways. The findings provide information regarding a potentially new therapeutic strategy to control insulin resistance.

MicroRNA-375 promotes 3T3-L1 adipocyte differentiation through modulation of extracellular signal-regulated kinase signalling

1. Adipocyte hypertrophy and hyperplasia are important processes in the development of obesity. To understand obesity and its associated diseases, it is important to elucidate the molecular mechanisms governing adipogenesis. MicroRNA‐375 has been shown to inhibit differentiation of neurites, and participate in the regulation of insulin secretion and blood homeostasis. However, it is unknown whether miR‐375 plays a role in adipocyte differentiation.

siRNA‐MEDIATED BCL‐2 AND BCL‐XL GENE SILENCING SENSITIZES HUMAN HEPATOBLASTOMA CELLS TO CHEMOTHERAPEUTIC DRUGS

1 The aim of the present study was to investigate the changes in chemotherapeutic drug sensitivity of HepG2 cells transfected with Bcl‐2 and Bcl‐xl siRNA expression vectors. 2 Bcl‐2 and Bcl‐xl siRNA and negative siRNA expression vectors were constructed and stably transfected into HepG2 cells. Reverse transcriptase–polymerase chain reaction was used to detect the target gene expression, and the Bcl‐2, Bcl‐xl, Bax and caspase‐3 protein levels were measured using western blots and immunofluorescence. The sensitivity of the cells to the chemotherapeutic drugs 5‐fluorouracil (5‐FU) and 10‐hydroxycamptothecin (HCPT) was analysed by 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazoliumbromide (MTT) and flow cytometry. 3 The Bcl‐2 and Bcl‐xl gene expression and corresponding protein levels in Bcl‐2 siRNA, Bcl‐xl siRNA and Bcl‐2/Bcl‐xl siRNA transfected cells were reduced compared with negative siRNA transfected or untreated cells. The Bax protein level remained unaltered but the caspase‐3 level was enhanced when Bcl‐2 and Bcl‐xl protein levels were reduced. The MTT results demonstrated that Bcl‐2 and Bcl‐xl transfected cells exhibited increased sensitivity to 5‐FU or HCPT. Flow cytometry demonstrated that the sub G1 cell population increased in Bcl‐2/Bcl‐xl siRNA co‐transfected and Bcl‐xl siRNA and Bcl‐2 siRNA transfected cells when compared with negative siRNA or untreated cells. The latter trend was strengthened further in the presence of 5‐FU or HCPT. 4 Thus, Bcl‐2 and Bcl‐xl siRNA‐mediated gene silencing, in combination with chemotherapy, may be a potential therapeutic strategy against human hepatoblastoma.

Effects and underlying mechanisms of curcumin on the proliferation of vascular smooth muscle cells induced by Chol:MβCD.

Proliferation of vascular smooth muscle cells (VSMCs) contributes to the development of various cardiovascular diseases. Curcumin, extracted from Curcumae longae, has been shown a variety of beneficial effects on human health, including anti-atherosclerosis by mechanisms poorly understood. In the present study, we attempted to investigate whether curcumin has any effect on VSMCs proliferation and the potential mechanisms involved. Our data showed curcumin concentration-dependently abrogated the proliferation of primary rat VSMCs induced by Chol:MbetaCD. To explore the underlying cellular and molecular mechanisms, we found that curcumin was capable of restoring caveolin-1 expression which was reduced by Chol:MbetaCD treatment. Moreover, curcumin abrogated the increment of phospho-ERK1/2 and nuclear accumulation of ERK1/2 in primary rat VSMCs induced by Chol:MbetaCD, which led to a suppression of AP-1 promoter activity stimulated by Chol:MbetaCD. In addition, curcumin was able to reverse cell cycle progression induced by Chol:MbetaCD, which was further supported by its down-regulation of cyclinD1 and E2F promoter activities in the presence of Chol:MbetaCD. Taking together, our data suggest curcumin inhibits Chol:MbetaCD-induced VSMCs proliferation via restoring caveolin-1 expression that leads to the suppression of over-activated ERK signaling and causes cell cycle arrest at G1/S phase. These novel findings support the beneficial potential of curcumin in cardiovascular disease.

Static pressure drives proliferation of vascular smooth muscle cells via caveolin-1/ERK1/2 pathway

Intimal hyperplasia plays an important role in various types of vascular remodeling. Mechanical forces derived from blood flow are associated with the proliferation of vascular smooth muscle cells (VSMC). This contributes to many vascular disorders such as hypertension, atherosclerosis and restenosis after percutaneous transluminal angioplasty (PTA). In this study, we show that static pressure induces the proliferation of VSMC and activates its related signal pathway. VSMC from a rat aorta were treated with different pressures (0, 60, 90, 120, 150 and 180 mm Hg) in a custom-made pressure incubator for 24h. The most active proliferation of VSMC was detected at a pressure of 120 mm Hg. VSMC was also incubated under a static pressure of 120 mm Hg for different time intervals (0, 2, 4, 8, 12 and 24h). We found that static pressure significantly stimulates VSMC proliferation. Extracellular signal-regulated kinases 1/2 (ERK1/2) activation showed a peak at the pressure of 120 mm Hg at 4-h time point. Moreover, caveolin-1 expression was significantly inhibited by rising static pressure. Downregulation of VSMC proliferation could be found after PD98059 (ERK1/2 phosphorylation inhibitor) treatment. Our data also showed that a siRNA-mediated caveolin-1 knock down increased ERK1/2 phosphorylation and VSMC proliferation. These results demonstrate that static pressure promotes VSMC proliferation via the Caveolin-1/ERK1/2 pathway.

High density lipoprotein 3 inhibits oxidized low density lipoprotein-induced apoptosis via promoting cholesterol efflux in RAW264.7 cells

AbstractAim:To investigate the protective effect of high density lipoprotein 3 (HDL3) on oxidized low density lipoprotein (ox-LDL)-induced apoptosis in RAW264.7 cells.Methods:RAW264.7 cells were exposed to 50 mg/L ox-LDL for various durations up to 48 h, and apoptosis was detected using Hoechst 33258 staining and flow cytometric analysis. Total cholesterol levels were detected by high performance liquid chromatography, cholesterol efflux was determined by Tritium labeling, and the cellular lipid droplets were assayed by oil red O staining.Results:Treatment with 50 mg/L ox-LDL for 12, 24, and 48 h increased the apoptotic rate of RAW264. 7 cells in a time-dependent manner. The peak apoptotic rate (47.7%) was observed after 48 h incubation. HDL3 at various concentrations (50 mg/L, 100 mg/L, and 200 mg/L) inhibited the ox-LDL (50 mg/L for 48 h)-mediated apoptosis that was accompanied by an increased rate of intracellular cholesterol efflux, and decreased total cholesterol levels in cells in a concentration-dependent manner. Blockage of cholesterol efflux by brefeldin decreased the protective effect of HDL3 on ox-LDL induced apoptosis. Increase of the cholesterol efflux effected by another cholesterol acceptor, β-cyclodextrin, led to a dramatic decrease in the apoptotic rate of cells.Conclusion:HDL3 antagonizes ox-LDL-induced apoptosis in RAW264.7 cells, through reducing the accumulation of toxic cholesterol.

Onychin inhibits proliferation of vascular smooth muscle cells by regulating cell cycle.

AbstractAim:To investigate the effects of onychin on the proliferation of cultured rat artery vascular smooth muscle cells (VSMCs) in the presence of 10% new-born calf serum (NCS).Methods:Rat VSMCs were incubated with onychin 1–50 μmol/L or genistein 10 μmol/L in the presence of 10% NCS for 24 h. The proliferation of VSMCs was measured by cell counting and MTS/PMS colorimetric assays. Cell cycle progression was evaluated by flow cytometry. Retinoblastoma (Rb) phosphorylation, and expression of cyclin D1 and cyclin E were measured by Western blot assays. The tyrosine phosphorylation of ERK1/2 was examined by immunoprecipitation techniques using anti-phospho-tyrosine antibodies.Results:The proliferation of VSMCs was accelerated significantly in the presence of 10% NCS. Onychin reduced the metabolic rate of MTS and the cell number of VSMCs in the presence of 10% NCS in a dose-dependent manner. Flow cytometry analysis revealed that the G1-phase fraction ratio in the onychin group was higher than that in the 10% NCS group (85.2% vs 70.0%, P < 0.01), while the S-phase fraction ratio in the onychin group was lower than that in 10% NCS group (4.3% vs 16.4%, P < 0.01). Western blot analysis showed that onychin inhibited Rb phosphorylation and reduced the expression of cyclin D1 and cyclin E. The effects of onychin on proliferation, the cell cycle and the expression of cyclins in VSMCs were similar to those of genistein, an inhibitor of tyrosine kinase. Furthermore immunoprecipitation studies showed that both onychin and genistein markedly inhibited the tyrosine phosphorylation of ERK1/2 induced by 10% NCS.Conclusion:Onychin inhibits the proliferation of VSMCs through G1 phase cell cycle arrest by decreasing the tyrosine phosphorylation of ERK1/2, and the expression of cyclin D1 and cyclin E, and sequentially inhibiting Rb phosphorylation.

Bcl-2 siRNA induced apoptosis and increased sensitivity to 5-fluorouracil and HCPT in HepG2 cells

To investigate the changes in drug sensitivity of Bcl-2 siRNA transfected HepG2 cells. Bcl-2 siRNA and negative siRNA expression vector were constructed and stably transfected into HepG2 cells. RT-PCR and Immunofluorescence were used to detect the target gene expression. Western Blotting was used to detect Bcl-2, Bax and caspase-3 protein expressiom. Drug sensitivity of the cells to 5-fluorouracil (5-FU) and 10-hydroxycamptothecin (HCPT) were analyzed with MTT and flow cytometry. Results were following: (1) the mRNA and protein expression level of Bcl-2 in Bcl-2 siRNA stable transfectants were reduced compared with negative siRNA transfected or untreated cells. Accordingly, Bax protein expression had no change and caspase-3 protein expression showed significantly be up regulated; (2) MTT results showed that Bcl-2 siRNA transfectants had higher cell inhibitory rates after treated with 5-FU or HCPT; (3) flow cytometry results demonstrated that sub G1 population increased in Bcl-2 siRNA transfected cells compared with negative siRNA or untreated cells. After addition 5-FU (1300 mg/l) and HCPT (0.72 mg/l), Bcl-2 siRNA cells showed higher sub G1 population than negative siRNA or untreated cells. siRNA targeting Bcl-2 gene can specifically down-regulate Bcl-2 expression, increased Bax/Bcl-2 ratio expression and caspase-3 activity in HepG2 cells, which lead to increase cells spontaneous apoptosis and sensitize cells to 5-FU or HCPT. Bcl-2 siRNA may be a potential therapy agent against human hepatoblastoma.

Heat shock protein 90 acts as a molecular chaperone in late-phase activation of extracellular signal-regulated kinase 1/2 stimulated by oxidative stress in vascular smooth muscle cells

AbstractAim:To investigate whether cytosolic heat shock protein 90 (HSP90) acts as a molecular chaperone on the activated extracellular signal-regulated kinase 1/2 (ERK1/2) and cell proliferation stimulated by reactive oxygen species (ROS) in rat vascular smooth muscle cells (VSMC).Methods:VSMC were exposed to 1 μmol/L LY83583 (6-anilinoquinoline-5,8-quinolinedione, producer of ROS) for 120 min in the presence or absence of 5 μmol/L geldanamycin, a specific inhibitor of HSP90. Then the total, soluble, and insoluble proteins of the cells were collected. HSP90, ERK1/2, and phosphor-ERK1/2 in the cell lysate were measured by Western blotting. The interaction of HSP90 and phosphor-ERK1/2 was analyzed by immunoprecipi-tation assay, and the nuclear phosphor-ERK1/2 was measured by Western blotting and immunofluorescence. Cell proliferation was tested by cell counting and 3-(4,5-dimethylthiazol-2-y1)-3,5-di-phenyltetrazolium bromide (MTT).Results:The cytosolic HSP90 of VSMC was upregulated by LY83583 in a time-dependent manner with the peak at 120 min, which is consistent with the late peak of phosphor-ERK1/2. Immunoprecipitation and Western blotting analyses showed that LY83583 increased the interaction of HSP90 with phosphor-ERK1/2, the phosphor-ERK1/2 level, and the soluble phosphor-ERK1/2 level by 1.8-, 2.5-, and 2.9-fold, respectively. In contrast, the insoluble phosphor-ERK1/2 of VSMC was decreased. Interestingly, LY83583 treatment promoted the nuclear phosphor-ERK1/2 by 7.6-fold as confirmed by Western blotting and immunofluorescence assays. Furthermore, cell counting and the MTT assay showed that LY83583 stimulated VSMC proliferation with the increased expression of HSP90 and levels of soluble and nuclear phosphor-ERK1/2. Pretreatment of geldanamycin antagonized the effect of LY83583.Conclusion:HSP90 could mediate the oxidative stress-stimulated, late-phase activation of ERK1/2 and VSMC proliferation by promoting the ERK1/2 phosphorylation, the association of itself with phosphor-ERK1/2, and the solubility and nuclear translocation of phosphor-ERK1/2.

Angiopoietin-1 protects myocardial endothelial cell function blunted by angiopoietin-2 and high glucose condition

Aim:To evaluate the effects of angiopoietin-1 (Ang-1) on myocardial endothelial cell function under high glucose (HG) condition.Methods:Mouse heart myocardial endothelial cells (MHMECs) were cultured and incubated under HG (25 mmol/L) or normal glucose (NG, 5 mmol/L) conditions for 72 h. MTT was used to determine cellular viability, and TUNEL assay and caspase-3 enzyme linked immunosorbent assays were used to assay endothelial apoptosis induced by serum starvation. Immunoprecipitation and Western blot analysis were used to analyze protein phosphorylation and expression. Endothelial tube formation was used as an in vitro assay for angiogenesis.Results:Exposure of MHMECs to HG resulted in dramatic decreases in phosphorylation of the Tie-2 receptor and its downstream signaling partners, Akt/eNOS, compared to that under NG conditions. Ang-1 (250 ng/mL) increased Tie-2 activation, inhibited cell apoptosis, and promoted angiogenesis. Ang-1-mediated protection of endothelial function was blunted by Ang-2 (25 ng/mL).Conclusion:Ang-1 activates the Tie-2 pathway and restores hyperglycemia-induced myocardial microvascular endothelial dysfunction. This suggests a protective role of Ang-1 in the ischemic myocardium, particularly in hearts affected by hyperglycemia or diabetes.