Effect of miR-497 on myocardial cell apoptosis in rats with myocardial ischemia/reperfusion through the MAPK/ERK signaling pathway.

OBJECTIVE: The aim of this study was to investigate the effect of micro ribonucleic acid (miR)-497 on myocardial cell apoptosis in rats with myocardial ischemia/reperfusion (I/R) through the mitogen-activated protein kinase (MAPK)/extracellular regulated protein kinase (ERK) signaling pathway. MATERIALS AND METHODS: A rat model of myocardial I/R was established, myocardial cells were extracted, and miR-497 was inhibited by inhibitors and overexpressed using miRNA mimics. The cell apoptosis rate was detected by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. The interaction between miR-497 and ERK was determined by dual-luciferase reporter gene assay. The change in the protein level was measured via Western blotting (WB). RESULTS: Up-regulation of miR-497 promoted myocardial cell apoptosis, and the 3'-untranslated region (3'-UTR) of ERK was highly conserved to combine with miR-497. The luciferase reporter gene assay showed that the transfection of miR-497 could significantly inhibit the relative luciferase activity in cells. CONCLUSIONS: MiR-497 overexpression significantly down-regulated the ERK expression at messenger RNA (mRNA) and protein levels in cells. MiR-497 plays an important role in regulating I/R injury-induced myocardial cell apoptosis by targeting the ERK-induced apoptosis pathway.

Nicotinamide protects chronic hypoxic myocardial cells through regulating mTOR pathway and inducing autophagy.

OBJECTIVE: To determine the protective effect of nicotinamide on chronic hypoxic myocardial cells and its underlying mechanism. MATERIALS AND METHODS: The H9C2 cell lines were taken as objects of study, and were divided into blank group, hypoxia group and nicotinamide treatment group. The cell viability, apoptosis level, autophagy level and mammalian target of rapamycin (mTOR) pathway activity in each group were detected via Cell Counting Kit-8 (CCK8) assay, Hoechst staining, immunofluorescence staining, Polymerase Chain Reaction (PCR) and Western blotting, respectively. RESULTS: Nicotinamide could protect the viability of normoxic and chronic hypoxic myocardial cells. Besides, it could also inhibit the expression of caspase3 messenger ribonucleic acid (mRNA) in chronic hypoxic myocardial cells, and reduce the expression of apoptosis-related proteins. Furthermore, it could induce the mRNA expression of autophagy-associated gene 5 (ATG5) and increase the expression of autophagy-related proteins. Further study on the mechanism of nicotinamide showed that nicotinamide could inhibit the activity of the mTOR pathway, thus regulating the autophagy. CONCLUSIONS: Nicotinamide induces the autophagy of chronic hypoxic myocardial cells by regulating the mTOR pathway, thereby protecting cells from apoptosis.

HOTAIR promotes inflammatory response after acute myocardium infarction by upregulating RAGE.

OBJECTIVE: The aim of this study was to explore the role of HOTAIR in inflammatory response after acute myocardium infarction (AMI) and to investigate its underlying mechanism. MATERIALS AND METHODS: The AMI model was first constructed in rats, and heart tissues were harvested. Expression levels of HOTAIR and receptor of advanced glycation end-products (RAGE) in rat heart were detected by quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). The protein expression level of pEKR in rat heart was detected by Western blot. The levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in rats were determined by enzyme-linked immunosorbent assay (ELISA). The hypoxia-induced H9C2 cells were used to construct the MI model in vitro. Meanwhile, the expression levels of HOTAIR and RAGE in H9C2 cells were detected. The levels of TNF-α and IL-6 in the culture medium were determined by ELISA. Rescue experiments were conducted by co-transfecting pcDNA-HOTAIR and si-RAGE in H9C2 cells. Subsequently, the levels of pERK, TNF-α, and IL-6 were detected. RESULTS: The mRNA expression levels of HOTAIR and RAGE in the AMI group were significantly higher than those of the control group. Western blot showed remarkably higher protein levels of RAGE and pERK in AMI rats when compared with those of controls. Similarly, results of ELISA indicated that the levels of TNF-α and IL-6 in AMI rats were significantly higher than those of controls. Meanwhile, overexpression of HOTAIR in H9C2 cells remarkably elevated the expression levels of HOTAIR and RAGE. In addition, upregulated pERK, TNF-α, and IL-6 were observed in H9C2 cells overexpressing HOTAIR, which could be reversed by RAGE knockdown. CONCLUSIONS: HOTAIR promotes inflammatory response after AMI by upregulating RAGE expression.

[Effect of Notch1, 2, 3 genes silencing on Notch and nuclear factor-κB signaling pathway of macrophages derived from patients with coronary artery disease].

Objective: To investigate the effects of Notch1, 2, 3 genes silencing by siRNA on Notch signaling pathway (Delta-like 4(DLL4), Jagged 1(JAG1)) and nuclear factor-κB (NF-κB) signaling pathway (IκBα, P52) of macrophages derived from patients with coronary artery disease (CAD), thus to explore the potential genetic treatment perspectives for CAD. Methods: Peripheral blood mononuclear cells of CAD patients were isolated by density gradient centrifugation and transformed by phorbol-12-myristate-13-acetate (PMA) to macrophages. Macrophages were then transfected with Notch1-small interference RNA (siRNA, Notch1-siRNA group), Notch2-siRNA (Notch2-siRNA group), Notch3-siRNA (Notch3-siRNA group), negative control siRNA (NC group) and none siRNA (control group) respectively. Reverse transcription-polymerase chain reaction (RT-PCR) and Western blot analysis were applied to assess the mRNA and protein expression levels of DLL4, JAG1, IκBα and p52, respectively. Electrophoretic mobility shift assay (EMSA) was used to observe the NF-κB DNA binding activity. Subcellular distributions of NF-κB/p52 were detected through immunofluorescence. Results: (1) The mRNA and protein expressions of DLL4, JAG1 and p52 in Notch1-siRNA group, Notch2-siRNA group and Notch3-siRNA group were significantly downregulated, while the mRNA and protein expression of IκBα was significantly upregulated compared with NC group and control group(P<0.05 or 0.01). The mRNA and protein expressions of DLL4, JAG1 and p52 in Notch1-siRNA group were significantly downregulated, while the mRNA and protein expression of IκBα was significantly upregulated compared with Notch2-siRNA group and Notch3-siRNA group(P<0.05 or 0.01). The mRNA and protein expressions of DLL4, JAG1, IκBα and p52 were similar between NC group and control group (all P>0.05). (2) The binding activity of NF-κB DNA was significantly lower in Notch1-siRNA group (613±57), Notch2-siRNA group (1 169±85) and Notch3-siRNA group (1 454±90) compared with control group (2 643±115) and NC group (2 407±100) (all P<0.01), which was also significantly lower in Notch1-siRNA group compared to Notch2-siRNA group and Notch3-siRNA group (P<0.01); was significantly lower in Notch2-siRNA group compared with Notch3-siRNA group (P<0.01) and was similar between control group and NC group (P>0.05). (3) The fluorescence intensity of NF-κB/p52 was significantly lower both in the nucleus and cytoplasm in Notch1-siRNA group, Notch2-siRNA group and Notch3-siRNA group compared with NC group and control group (all P<0.01), and the decrease was more obviously in the nucleus than in cytoplasm in Notch1-siRNA group, Notch2-siRNA group and Notch3-siRNA group (P<0.05 or 0.01). The fluorescence intensity of NF-κB/p52 was similar between control group and NC group (P>0.05). Conclusion: There is a positive regulation between Notch and NF-κB pathway in macrophages derived from CAD patients, the regulation power on NF-κB signaling pathway of Notch1 is stronger than that of Notch2 and Notch 3.