Abstract 332: Inhibition of the Enhancer of Zeste Homolog Family Mitigates Intimal Hyperplasia in Rat Carotid Arteries

Abstract

Rationale: The enhancer of zeste homologs 1 and 2 (EZH1 and EZH2) are histone-lysine N-methyltransferases that modify histones by methylation which leads to transcriptional repression. It has recently been shown that EZH1 and EZH2 play an important role in various cancers. Whether they play a role in recurrent vascular diseases is not known. Objective: We assessed whether EZH1 and EZH2 are important contributors to the development of intimal hyperplasia (IH) and restenosis. Methods and Results: Following rat carotid balloon angioplasty, EZH2 showed highest expression at day 3 post procedure and then decreased at day 7 in injured arteries, as determined by Western blotting. Change of EZH1 is less prominent. Dual inhibition of EZH1 and EZH2 through peri-adventitial administration of a selective inhibitor, UNC-1999, effectively inhibited intimal hyperplasia, with ~40% reduction in the ratio of intima to media (I/M). Moreover, in cultured primary rat smooth muscle cells (SMCs) as well as MOVAS cells, pretreatment with 5μM UNC-1999 resulted in a 60% decrease in cell proliferation and ~80% reduction of migration that were stimulated by PDGF-BB. Simultaneous knockdown of EZH1 and EZH2, as well as knockdown of their shared scaffold protein(EED), led to effective inhibition of proliferation and migration of SMCs. However, knockdown of EZH2 alone did not recapitulate the effects of dual inhibition of EZH1 and EZH2. Conclusions: This study demonstrates that dual inhibition of EZH1 and EZH2, both histone modifiers, mitigates intimal hyperplasia in vivo and attenuates PDGF-BB stimulated SMC proliferation and migration in vitro.