Abstract 12203: Fxr1 Regulates Inflammatory mRA Stability and Vascular Disease

Abstract

Introduction: Vascular smooth muscle cells (VSMC) play a critical role in the etiology and progression of many vascular diseases, and reduction of inflammatory gene expression in VSMC is a rational approach to limit the severity of these diseases. HuR is an mRNA stability protein that recognizes AU-rich elements (ARE) present almost exclusively in the 3’UTR of pro-inflammatory gene mRNA. Proteins and pathways which limit HuR activity in vascular cells may reduce inflammatory mRNA stability, but are currently uncharacterized. Using un-biased LC-MS/MS to identify HuR-interacting proteins under different inflammatory conditions, we identified one protein termed Fragile X-related protein (FXR1), which interacts with HuR in inflammatory, but not basal conditions. Results and Conclusions: Using immunohistochemical and molecular biological approaches, preliminary data shows that FXR1 expression is increased in VSMC in plaque from atherosclerotic mouse and human arteries. FXR1 translocates from the nucleus into the cytoplasm and co-localizes with HuR in cytoplasm. FXR1 expression is also increased by TNFα and oxLDL stimulation of cultured human VSMC. Importantly, siRNA knock down of FXR1 in VSMC increases inflammatory mRNA stability, increases abundance of ARE-containing inflammatory proteins, and increases cholesterol uptake. Surprisingly, FXR1 expression is also increased by anti-inflammatory interleukins. Since FXR1 is induced by both pro-inflammatory stimuli as well as IL-19, and yet deletion of FXR1 leads to enhanced expression of pro-inflammatory proteins, our overall hypothesis is that FXR1 expression is a negative, compensatory, counter-regulatory mechanism used by VSMC to respond to and dampen inflammation. Our specific hypothesis is that FXR1 antagonizes HuR function by numerous mechanisms leading to a reduction in stability of pro-inflammatory, ARE-containing mRNA. Currently, very little is understood concerning negative regulation of inflammatory mRNA stability, particularly so in vascular disease. Nothing at all is known about FXR1 expression and function in VSMC and vascular disease. This work may identify FXR1 as part of an anti-inflammatory gene expression program and uncover a novel role for FXR1 in vascular disease.