Kardiyovasküler Sistem Patofizyolojisinde Rol Alan Mikrornaların İncelenmesi

Abstract

The diseases and attendant complications of cardiovascular system consist of acute coronary syndrome, peripheral vascular disease and stroke that are distinct clinical manifestations yet stem from metabolically-originated processes. Diabetes mellitus, chronic inflammatory state and the lack of proper response to angiogenic stimuli account for predisposing risk factors to cardiovascular diseases. Endothelium constitutes crucial inner lining of the vasculature. It regulates blood flow to the organs as well as responds to a variety of stimuli, which are important in re-modeling of vascular structure in the long-term. Major groups of stimuli consist of VEGF and bFGF that govern angiogenesis, TNFα that drives inflammation, and D-glucose that is a diabetogenic stimulant. MicroRNAs are non-coding 20-22 nt RNA sequences that regulate gene expression at the post-transcriptional level. Recent studies have shown that microRNAs (miRs) function broadly from early stage of development to several disease processes. This study aims to address two major questions. First, to explore the expression levels of a cohort of miRs that might take functional roles in vascular endothelium. Second, to identify the pathways by which miRs can exert their effects and localize the specificity via examining closely-related signaling mechanisms. To this end, two independent microarray profiling are performed in patients with ACS compared to controls. A panel of concordant miRs in both cohorts are elicited for further analysis. This panel is subjected to qPCR analysis in endothelial cells in the presence of respective stimuli such as TNFα, VEGF, bFGF and D-glucose for aforementioned processes. MicroRNA-615-5p is significantly regulated in response to different stimuli, and can reciprocally regulate vessel network formation through gain- and loss-of-function studies in the presence of basal membrane. In addition, miR-615-5p specifically acts on Akt/eNOS pathway without altering p38, ERK1/2 pathways that are closely-associated with angiogenic effects. MiR-615-5p overexpression can suppress Akt/eNOS pathways whereas inhibition of miR-615-5p leads to dynamic amplification of Akt/eNOS signaling. This dissertation contributes to an understanding of mechanism of miR-615-5p that is regulated in patients with ACS, and hence can distinctly modulate Akt/eNOS pathway in the presence of VEGF.