Histone deacetylase 9 promotes endothelial-mesenchymal transition and an unfavorable atherosclerotic plaque phenotype.

Laura Lecce,Manfred Boehm,Venu Pothula,Bhargavi V’Gangula,Yang Xu,Neal L Weintraub,Ha Won Kim,Przemek A Gorski,Lijiang Ma,Simon Koplev,Nirupama Chandel,Andrew H Baker,Jason C Kovacic,Maria Paola Santini,Axelle Caudrillier,Emily Bernstein,Valentina D’Escamard,Delaine K Ceholski,Valentín Fuster ,Johan Björkegren ,Jacob F Bentzon ,Martin Björklund

doi:10.1172/jci131178

Abstract

Endothelial-mesenchymal transition (EndMT) is associated with various cardiovascular diseases and in particular with atherosclerosis and plaque instability. However, the molecular pathways that govern EndMT are poorly defined. Specifically, the role of epigenetic factors and histone deacetylases (HDACs) in controlling EndMT and the atherosclerotic plaque phenotype remains unclear. Here, we identified histone deacetylation, specifically that mediated by HDAC9 (a class IIa HDAC), as playing an important role in both EndMT and atherosclerosis. Using in vitro models, we found class IIa HDAC inhibition sustained the expression of endothelial proteins and mitigated the increase in mesenchymal proteins, effectively blocking EndMT. Similarly, ex vivo genetic knockout of Hdac9 in endothelial cells prevented EndMT and preserved a more endothelial-like phenotype. In vivo, atherosclerosis-prone mice with endothelial-specific Hdac9 knockout showed reduced EndMT and significantly reduced plaque area. Furthermore, these mice displayed a more favorable plaque phenotype, with reduced plaque lipid content and increased fibrous cap thickness. Together, these findings indicate that HDAC9 contributes to vascular pathology by promoting EndMT. Our study provides evidence for a pathological link among EndMT, HDAC9, and atherosclerosis and suggests that targeting of HDAC9 may be beneficial for plaque stabilization or slowing the progression of atherosclerotic disease.

Highlights

Endothelial-mesenchymal transition (EndMT) is an essential process during cardiac development, contributing to cardiac valve formation and the stabilization of new vasculature in the developing embryo [1, 2]
A combination of TGF-β2 plus H2O2 was more potent in inducing EndMT in human coronary artery endothelial cells (HCAECs) than either agent alone and resulted in significant downregulation of endothelial genes, including zona occludens 2 (ZO2), intercellular adhesion molecule 2 (ICAM2), occludin, and endothelial nitric oxide synthase (Supplemental Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/ JCI131178DS1), with upregulation of mesenchymal genes transgelin (SM22α), fibroblast activation protein (FAP), versican, and calponin (Supplemental Figure 1B)
In view of the above data indicating that knockout of HDAC9 inhibits EndMT as well as prior knowledge that EndMT is associated with atherosclerotic plaque burden [11] and an unstable plaque phenotype [12, 13], we investigated to determine whether HDAC9 modulates EndMT in vivo and thereby affects atherosclerosis

Summary

Introduction

Endothelial-mesenchymal transition (EndMT) is an essential process during cardiac development, contributing to cardiac valve formation and the stabilization of new vasculature in the developing embryo [1, 2]. EndMT participates in vascular remodeling and neointima formation, for example, as a response to vein graft transplantation into the arterial circulation [10]. Several signaling pathways have been associated with EndMT, most notably the TGF-β pathway [2, 14]. A recent study showed that the long noncoding antisense transcript of GATA6 regulates EndMT via downstream changes in histone methylation [18]. Little is known about the biologic pathways and signaling mechanisms governing EndMT and the higher-order regulators at the apex of these EndMT pathways [1]

Methods

Results

Conclusion