Study On The Function And Mechanism Of Long - Chain Non - Coding RNA TUG1 In Vascular Endothelial Cells

Background and objective:Coronary artery disease (CAD) is the leading cause of morbidity and mortality worldwide, which causes serious health problem and financial burden. Atherosclerosis (AS) has critical role in the development of CAD. However, the pathogenesis of atherosclerosis is due to complex inflammation and metabolic effects, and it has not been fully understood. Long noncoding RNAs (lncRNAs) gain increasing attention in recent years as new regulators in biological and pathological pathways. LncRNAs are involved in various steps of transcription and post-transcription to regulate genes expression. Thus lncRNAs could be potential biomarkers of diseases diagnosis and treatment. LncRNA taurine up-regulated gene 1 (TUG1) participated in the progression of tumors and highly expressed in endothelial cells. However, to our best knowledge, there is no report on potential biological function of TUG1 in cardiovascular diseases. Our study investigated the expression of TUG1 in CAD patients and its function in human umbilical vein endothelial cells (HUVECs), which will contribute to further explore the role of TUG1 in atherosclerosis and CAD.Methods:1. We performed a case-control study, which enrolled 54 diagnosed cases of CAD and 75 health controls, to investigate the linkage between TUG1 and CAD. The total RNA from human peripheral blood mononuclear cells (PBMCs) was extracted by standard method. The level of TUG1 was detected in PBMCs of CAD patients and health controls using real-time PCR.2. Knockdown strategy was performed to reduce expression of TUG 1 in HUVECs by specific siRNA. The siRNAs were transfected into HUVECs using RNAimax according to the manufacturer’s protocol. Endothelial proliferation and apoptosis, expression of intercellular adhesive molecular-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and phosphorylation of p38 was analyzed. Apoptosis and proliferation of HUVECs was detected by Annexin V-FITC Apoptosis Detection Kit and MTT assay, respectively. The endothelial cell injury mode in vitro was induced by hypoxia and tumor necrosis factor-a (TNF-a). The mRNA and protein expression was assessed by real-time PCR and Western blot.Results:1. The TUG1 expression was significantly up-regulated to 1.4 times in PBMCs of CAD patients compared with normal controls (P<0.001).2. TUG1 was highly expressed in HUVECs. TUG1 knockdown decreased the number of apoptotic cells and promoted cell proliferation (P<0.05). And TUG1 knockdown inhibited cell apoptosis in both hypoxia and TNF-α induced endothelial injury model (P<0.05).3. The mRNA and protein expression levels of ICAM-1 and VCAM-1 were decreased with knockdown of TUG1 (P<0.05). TUG1 knockdown also inhibited ICAM-1 and VCAM-1 expression under TNF-α treatment (P<0.05).4. TUG1 knockdown inhibited p38 phosphorylation under normal physiological conditions and TNF-α treatment (P<0.05).Conclusion:In present study, we first profiled the expression level of TUG1 in CAD patients and potential function in HUVECs. The TUG1 expression was significantly up-regulated in CAD patients. Knockdown of TUG1 in vascular endothelial cells could inhibit endothelial cell apoptosis and reduce the damage of endothelial cells induced by hypoxia and TNF-α. TUG1 knockdown also decreased ICAM-1 and VCAM-1 expression and inhibited p38 phosphorylation, suggesting that TUG1 knockdown might alleviate inflammatory reaction and protect endothelial cells. Here, the present study demonstrates that TUG1 may involve in endothelial dysfunction and pathogenesis of atherosclerosis. The results will provide experimental foundation to further study of TUG1 in CAD.