Abstract 693: RNA Stability Protein ILF3 Mediates IL-19 Induced Angiogenesis

Abstract

Angiogenesis is a physiological process vital for growth, development and wound healing but is also a promising therapeutic target for the treatment of ischemic cardiovascular disease. Presently, there is nothing known regarding the role of, the RNA binding protein, Interleukin Enhancer-binding Factor 3 (ILF3) in angiogenesis. RNA binding proteins play crucial roles in cellular processes, specifically, post-transcriptional control of RNAs through mRNA stabilization. We hypothesized that ILF3 plays an essential role in angiogenesis through the stabilization of pro-angiogenic mRNA transcripts. Using immunohistochemistry we identified abundant ILF3 expression in CD31 + vessels of hypoxic porcine cardiac tissue exposed to ischemic myocardial infarction. Using both western blotting and qRT-PCR, we found that pro-angiogenic stimuli, IL-19 and VEGF, induce ILF3 expression in cultured human coronary artery endothelial cells (hEC). Angiogenic proliferation, migration and tube formation are all significantly reduced in hEC when ILF3 is knocked down using siRNA. Importantly, these angiogenic assays are significantly increased when ILF3 is overexpressed in hEC using adenovirus. Using ILF3 siRNA in addition to VEGF stimulation in hEC, several angiogenic factors including CXCL1, IL-8, and HGF are decreased at the transcript and protein level. However, these angiogenic factors are increased when hEC are infected with AdILF3 and stimulated with VEGF. Through immunohistochemistry we found that ILF3 translocates from the nucleus to the cytoplasm of hEC stimulated with VEGF or IL-19 at various time points, suggesting a role in mRNA stability. Using the transcription inhibitor actinomycin D, we found that ILF3 stabilizes pro-angiogenic transcripts including VEGF, CXCL1, and IL-8 in hEC. Together these data suggest that in endothelial cells, the RNA stability protein, ILF3, plays a novel and central role in angiogenesis. We believe that ILF3 is impacting functional angiogenesis through cytokine-inducible mRNA stabilization of pro-angiogenic transcripts.