CircRNA-PTPRA promoted the progression of atherosclerosis through sponging with miR-636 and upregulating the transcription factor SP1

OBJECTIVE: Atherosclerosis (AS) is the leading cause of death for humans worldwide, and some circular RNAs (circRNAs) have been demonstrated to play important roles in its progression. In this study, we mainly investigated the functions and molecular mechanisms of circRNA-PTPRA (circPTPRA) in AS. PATIENTS AND METHODS: The expressions of circPTPRA and miR-636 were detected in serum samples of AS patients (n=30) and healthy controls (n=30) by RT-PCR. Then levels of circPTPRA were detected after ox-LDL treatment into vascular smooth muscle cell (VSMCs), macrophage and endothelial cells. LV-sh circPTPRAs were constructed and infected into VSMCs. CCK-8 assay was performed to measure cell proliferation abilities, flow cytometry (FACS) was performed to measure cell-cycle distribution and TUNEL staining was performed to detect cell apoptosis. Western blot (WB) was performed to detect protein levels of SP1, Cyclin D1, Cyclin E, Bax, Bad. Cleaved Caspase3. Luciferase reporter assay was performed to verify the potential binding sites of circPTPRA and miR-636, miR-636 and SP1. RESULTS: RT-PCR showed that circPTPRA was upregulated in serum samples of AS patients, which was increased by ox-LDL in VSMCs. CircPTPRA inhibition repressed cell proliferation, improved cell-cycle distribution in G0/G1 phase and promoted cell apoptosis. MiR-636, a potential target for circPTPRA, was reduced in serum samples of AS patients and Luciferase reporter assay confirmed that circPTPRA could directly sponge with miR-636 in VSMCs. Furthermore, miR-636 inhibition promoted proliferation and repressed apoptosis of VSMCs, while miR-636 overexpression reversed these results. SP1, a transcription factor that played some roles in the progression of AS, was predicted to be a target of miR-636. MiR-636 inhibition increased SP1 while miR-636 overexpression repressed SP1 expression, Luciferase reporter assay proved that miR-636 could target at SP1 in VSMCs. Moreover, the repressed cell proliferation and promoted cell apoptosis abilities in LV-sh SP1 were reversed following with miR-636 inhibitor transfection. In addition, the repressed cell proliferation and promoted cell apoptosis abilities in VSMCs with LV-sh circPTPRAs were reversed following with miR-636 inhibitor transfection, which suggested that circPTPRA regulated cell proliferation and apoptosis through miR-636/SP1 axis in AS. CONCLUSIONS: According to the results, we found that circPTPRA was upregulated in serum samples of AS patients, which promoted cell proliferation and inhibited cell apoptosis through repressing miR-636 and upregulating SP1 signaling axis. Our results uncovered a potential role of circPTPRA. which might be a marker and therapeutic target for AS patients.