Circ-JA760602 promotes the apoptosis of hypoxia-induced cardiomyocytes by transcriptionally suppressing BCL2.

Acute myocardial infarction (AMI) is myocardial necrosis caused by the complete or partial obstruction of a coronary artery. Circular RNAs (circRNAs) have been proven as regulators in the progression of various human diseases, including AMI. However, the role of novel circ-JA760602 in AMI remains unknown. Here, we investigated the role of circ-JA760602 in modulating the apoptosis of hypoxia-induced AMI cells using the AC16 cardiomyocyte in vitro cell model. The expression of circ-JA760602 in AC16 cardiomyocytes subjected to hypoxia was measured by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability was measured by cell counting kit-8 (CCK-8) assay. Apoptosis of cardiomyocytes was evaluated by TUNEL assay and flow cytometry analysis. The cellular location of circ-JA760602 was identified through fluorescence in situ hybridization (FISH) assay and subcellular fractionation assay. The downstream molecular mechanisms of circ-JA760602 were demonstrated by luciferase reporter assay, RNA binding protein immunoprecipitation (RIP) assay and chromatin immunoprecipitation (ChIP) assay. Rescue assays were performed to demonstrate the effects of BCL2 knockdown on circ-JA760602 silencing-mediated cardiomyocyte apoptosis. Circ-JA760602 expression was elevated after hypoxia treatment. Knockdown of circ-JA760602 enhanced viability and curbed apoptosis of hypoxia-treated cardiomyocytes. EGR1 and E2F1 could activate BCL2 transcription. Cytoplasmic circ-JA760602 bound with EGR1 and E2F1 to thus inhibit their nuclear translocation. BCL2 knockdown reversed the effects of circ-JA760602 silencing on the apoptosis of hypoxia-treated AC16 cells. Circ-JA760602 promotes hypoxia-induced apoptosis of cardiomyocytes by binding with EGR1 and E2F1 to inhibit the transcriptional activation of BCL2.

Circular RNA hsa_circ_0000848 Regulates Cardiomyocyte Proliferation and Apoptosis Under Hypoxia via Recruiting ELAVL1 and Stabilizing SMAD7 mRNA.

BACKGROUND: Myocardial infarction has been recognized globally as a serious problem featured with high mortality and morbidity. In addition, hypoxia represents the central feature of myocardial infarction. Recently, it has been reported that circular RNAs can exert critical functions in the biological processes of diseases. However, the functions of most circular RNAs remain unclear in cells cultured under hypoxic conditions. In this study, we focused on exploring the role of circ_SMAD7 (namely hsa_circ_0000848 in this study) in cardiomyocyte cells cultured under hypoxic conditions to provide a novel insight for future myocardial infarction studies. METHODS: Firstly, a real-time quantitative polymerase chain reaction assay was adopted to analyze hsa_circ_0000848 expression. Functional assays were performed to detect the functions of hsa_circ_0000848 in cardiomyocyte cells cultured under hypoxic conditions. Furthermore, mechanism assays were implemented to explore the regulatory mechanism of hsa_circ_0000848. RESULTS: Hsa_circ_0000848 was notably downregulated in hypoxia-induced cardiomyocytes. The silencing of hsa_circ_0000848 hindered the proliferation while accelerating the apoptosis of hypoxia-induced cardiomyocytes cells. Moreover, hsa_circ_0000848 interacted with ELAV-like RNA-binding protein 1 protein to stabilize SMAD family member 7 mRNA. Moreover, SMAD family member 7 overexpression could reverse the suppressive effect of hsa_circ_0000848 knockdown on myocardial infarction progression. CONCLUSIONS: Our research was the first in the field to confirm that the hsa_circ_0000848/ ELAV-like RNA-binding protein 1/SMAD family member 7 axis could affect the development of cardiomyocyte cells cultured under hypoxia, indicating that hsa_circ_0000848 might function as a novel biomarker in cells under hypoxia thus laying the groundwork for future study on myocardial infarction.