Abstract 5558: MicroRNA Regulation of Endothelial Cell Growth

Abstract

MicroRNAs (miRNAs) are short non-coding RNAs which inhibit gene expression at the post-transcriptional level. MiRNAs affect a wide variety of cellular functions such as proliferation, differentiation, and apoptosis, but the role of miRNA in endothelial cells is not well understood. The silent information regulator 1 (SIRT1) is an NAD-dependent deacetylase that regulates not only life-span but also cell growth arrest or apoptosis in response to oxidative and genotoxic stress. SIRT1 suppresses apoptosis thresholds by deacetylating molecular targets such as p53, FOXO transcription factors, and Ku70. We hypothesized that miRNA-34a regulates endothelial cell growth and senescence. We discovered that human endothelial cells (HUVEC and HAEC) express miRNA-34a by microarray analysis. When we over-expressed miR-34a in HUVEC, we found that SIRT1 protein was decreased. In contrast, transfection of HUVEC with antagomirs to miR-34a decreased endogenous miR-34a and increased SIRT1 protein. We identified a miR-34a binding site in the 3′ untranslated region (3′UTR) of SIRT1 and showed miR-34a directly inhibits SIRT1 translation using a luciferase assay. Next we examined the effect of miR-34a upon cell growth and senescence. Over-expression of miR-34a decreased SIRT1 protein, increased acetylated p53, and increased expression of p21, a transcriptional target of p53. When we co-transfected HUVEC with miR-34a precursor and SIRT1 expression vector to rescue SIRT1 expression, acetylated p53 and p21 expression were decreased. Finally over-expression of miR-34a induced cell cycle arrest and senescence in HUVEC using FACS and SA-gal assay. Our data suggest that miR-34a regulates cell growth and senescence through a SIRT1 - p53 pathway.