Inhibition of polycomb repressor complex 2 ameliorates neointimal hyperplasia by suppressing trimethylation of H3K27 in vascular smooth muscle cells

Abstract

Background and Purpose The increased proliferation and migration of vascular smooth muscle cells (VSMCs) after arterial injury contributes greatly to the pathogenesis of neointimal hyperplasia. As a major component of epigenetics, histone methylation plays an important role in several cardiovascular diseases. However, its role in restenosis is still unclear. Experimental Approach Human aortic VSMCs were challenged with PDGF‐BB, and total histones were extracted and analysed by HPLC/MS. For the in vivo study, rats were subjected to wire‐guided common carotid injury. Key Results PDGF‐BB markedly increased the H3K27me3 level, as demonstrated by use of HPLC/MS and confirmed by western blot analysis. Enhancer of zeste homologue 2 (EZH2), the histone H3K27 methyltransferase component of polycomb repressive complex 2, was also up‐regulated by PDGF‐BB in VSMCs, and in the neointimal hyperplasia induced by wire injury of the rat carotid artery. Furthermore, inhibiting H3K27me3 by treatment with 3‐μM UNC1999, an EZH2/1 inhibitor, significantly suppressed PDGF‐BB‐induced VSMC proliferation compared with the PDGF‐BB‐treated group. Consistently, neointimal formation was significantly attenuated by oral or perivascular administration of UNC1999 compared with the sham group. Mechanistically, the increase in H3K27me3 inhibited the transcription of the cyclin‐dependent kinase inhibitor p16INK4A and thus promoted VSMC proliferation. Conclusions and Implications Vascular injury elevated the expression of EZH2 and the downstream target H3K27me3, which suppressed p16INK4A expression in VSMCs and promoted VSMC proliferation and neointimal hyperplasia. EZH2 inhibition might be a potential therapeutic target for restenosis.

Angioplasty-induced epigenomic remodeling entails BRD4 and EZH2 hierarchical regulations

“…Since EZH2 is the primary methyltransferase that deposits H3K27me3 27 , the striking H3K27me3 upsurge due to angioplasty led us to investigate the underlying epigenetic regulations. As observed in our data 16 and recently reproduced by others 17,18 , pharmacological evidence implicated EZH2 as potentially important in neointima formation. Interestingly, both BRD4-and H3K27ac-associated ChIPseq peaks enriched at Ezh2, more in injured vs uninjured arteries ( Figure 2A).…”

“…EZH2 recently emerged as a driver of cell state transitions such as cancer cell proliferation and migration, yet reports on EZH1 are limited and discrepant regarding its redundancy with EZH2 13,15 . Pharmacological evidence from our 16 and other groups 17,18 supports an IH-mitigating effect of pan-EZH1/2 inhibition, underscoring the importance of dissecting their functional roles and the mechanisms governing their expression levels. Moreover, BRD4 as an acetylation reader and EZH2 as a methylation writer are seemingly unrelated; their relationship has been overlooked 19 , especially in vascular pathogenesis.…”

“…Consistently, perivascular local treatment of injured arteries with the pan-EZH1/2 inhibitor UNC1999 ( Figure 4F) diminished IH and enlarged the lumen ( Figure 4, G and H). While clarifying the preconceived role of EZH2 17,18 , our results indicate that EZH1 also plays a positive role in neointima development, as demonstrated in the rat angioplasty model.…”

“…However, EZH1 is much less studied. Its specific role in IH was not known, since previous pharmacological studies using a pan inhibitor of EZH1/2 failed to distinguish their individual contributions to IH 17,18 . To address this knowledge gap, we first observed that pre-treatment of SMCs with JQ1, a bromodomain blocker binding BRD4 (and other BETs) 11 abrogated PDGF-stimulated mRNA expression of not only EZH2 but also EZH1 ( Figure 4A).…”

Histone methylation and vascular biology

“…Angioplasty and coronary artery bypass grafting are highly effective treatment for narrowed coronary arteries due to atherosclerosis. However, restenosis resulting from neointima hyperplasia after angioplasty greatly dampens the satisfactory prognosis of the atherosclerosis for patients [59]. Recent research advances have indicated that histone methylation is critical for regulating neointima hyperplasia ( Fig.…”