Dysregulation of the Urothelial Cancer Associated 1 Long Noncoding RNA Promotes Proliferation of Vascular Smooth Muscle Cells by Modulating Expression of P27KIP1/CDK2

Abstract

Background: Atherosclerosis is one of the leading causes of morbidity and mortality worldwide. A variety of long noncoding RNAs (lncRNAs) have been reported to be significantly involved in vascular smooth muscle cell (VSMC) proliferation, which is an essential process for atherosclerotic plaque formation. The aim of this study was to investigate the mechanism of lncRNA urothelial cancer associated 1 (UCA1) involvement in atherosclerosis. Method: The effects of oxidized low-density lipoprotein (oxLDL) and UCA1 on VSMC proliferation and colony-forming ability was measured by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyl-2H-tetrazolium bromide (MTT) assays, real-time polymerase chain reaction (PCR), and western blots, as well as to determine the effect that oxLDL has on UCA1 expression, and the effect of oxLDL and UCA1 on the expression of cyclin-dependent kinase 2 (CDK2). Results: oxLDL treatment increased the proliferation rate of VSMCs in a concentration-dependent manner. Importantly, UCA1 apparently increased the viability of VSMCs as the VSMCs exhibited a significantly reduced growth rate when UCA1 expression was knocked down by specific small interfering RNAs (siRNAs). In conjunction with increasing cell viability, oxLDL also enhanced the colony-forming ability of VSMCs while UCA1 siRNA decreased the colony-forming ability of VSMCs. Furthermore, UCA1 significantly decreased the percentage of VSMCs in G1 phase, while increasing their percentage in S phase. In contract siRNA knockdown of UCA1 caused an increased percentage of cell in G1 phase, and a reduction in the percentage of cells in S phase. Using real-time PCR and western blot assays, we showed that oxLDL significantly increased the expression levels of UCA1 and CDK2. Furthermore, UCA1 siRNA and CDK2 siRNA almost abolished the positive effect of oxLDL on CDK2 expression. Finally, overexpression of UCA1 induced an increase in CDK2 levels, and knockdown of UCA1 caused inhibition of CDK2 expression. Conclusion: Upregulation of UCA1 enhances abnormal proliferation of VSMC by promoting G1/S transition through modulating the expression of CDK2.