Myocardin-Related Transcription Factor A Mediates OxLDL-Induced Endothelial Injury

• DOI: 10.1161/circresaha.111.240655
• Publication Date: 2011-02-18T04:19:01Z
• Authors: Fei Fang; Yuyu Yang; Zhibin Yuan; Yuqi Gao; Jiliang Zhou; Qi Chen; Yong Xu
• Keywords: 0301 basic medicine; Serum Response Factor; Nitric Oxide Synthase Type III; Oncogene Proteins, Fusion; NF-kappa B; Atherosclerosis; Intercellular Adhesion Molecule-1; Epigenesis, Genetic; DNA-Binding Proteins; Lipoproteins, LDL; 03 medical and health sciences; Trans-Activators; Humans; Endothelium, Vascular; Cells, Cultured

Rationale:

Atherosclerosis proceeds through a multistep reaction that begins with endothelial injury caused by a host of stress signals, among which oxidized low-density lipoprotein (oxLDL) plays a critical role. OxLDL disrupts normal functionality of the endothelium by upregulating adhesion molecules (eg, ICAM-1) and concomitantly downregulating endothelial nitric oxide synthase (eNOS) expression. The transcriptional modulator that mediates the cellular response to oxLDL remains largely obscure.

Objective:

Our goal was to determine whether myocardin-related transcription factor (MRTF)-A, a key protein involved in the transcriptional regulation of smooth muscle cell phenotype, is responsible for the endothelial injury by oxLDL, and, if so, how MRTF-A promotes the proatherogenic agenda initiated by oxLDL.

Methods and Results:

OxLDL stimulated the expression of MRTF-A in endothelial cells as evidenced by Western blotting and immunofluorescence. Overexpression of MRTF-A synergistically enhanced the induction of ICAM-1 and suppression of eNOS by oxLDL. In contrast, disruption of MRTF-A, either by small interfering RNA or dominant negative mutation, abrogated the pathogenic program triggered by oxLDL. Finally, chromatin immunoprecipitation assays indicate that oxLDL preferentially augmented MRTF-A binding to ICAM-1 and eNOS promoters and that MRTF-A drove differential epigenetic alterations taking place on these promoters in response to oxLDL.

Conclusions:

Therefore, our data provide the first demonstration that MRTF-A is critically linked to pivotal pathophysiological events in the vascular endothelium.