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BET bromodomain containing epigenetic reader proteins regulate vascular smooth muscle cell proliferation and neointima formation

ABSTRACT: Recent studies revealed that the bromodomain and extraterminal (BET) epigenetic reader proteins resemble key regulators in the underlying pathophysiology of cancer, diabetes or cardiovascular disease. However, whether they also regulate vascular remodeling processes by direct effects on vascular cells is unknown. In this study we investigated the effects of the BET proteins on neointima formation in response to vascular injury in vivo and on human smooth muscle cell function in vitro. In this study we showed that the selective inhibition of BETs by the small molecule (+)-JQ1 dose dependently reduced proliferation and migration of SMCs without apoptotic or toxic effects caused by cell cycle arrest in the G0/G1 phase. Whole genome microarray expression profiling analysis revealed a substantial transcriptional regulation of gene sets controlled by the FOXO1-transcription factor. Additional data confirmed that the BET protein BRD4 directly binds to FOXO1 and regulates FOXO1 transactivational capacity. Inhibition of BET epigenetic reader proteins might represent a promising therapeutic strategy to prevent adverse vascular remodeling.

ORGANISM(S): Homo sapiens

PROVIDER: GSE138323 | GEO | 2020/03/27

REPOSITORIES: GEO

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Project description:Rationale: Neointima formation is a common pathological feature of atherosclerosis and restenosis after angioplasty and involves the proliferation and migration of vascular smooth muscle cells (VSMCs). N6-methyladenosine (m6A), the most prevalent mRNA internal modification and being proposed to be primarily produced by RNA methyltransferase METTL3, plays a vital role in post-transcriptional regulations. Nevertheless, the role of RNA m6A modification in VSMCs and neointima formation remains disputable and undetermined. Objective: To determine the role of METTL3 and its produced RNA modification m6A in VSMCs and neointima formation after vascular injury. Methods and Results: We examined the expression of m6A writers and erasers in the carotid artery collected from human carotid endarterectomy (CEA) as well as in that of mice and unanimously found that METTL3 expression is increased significantly after vascular injury. Then, VSMC-confined METLL3 knockout mice (Myh11CreERT2 METTL3flox/flox) were generated, and carotid artery injury was induced. METTL3 knockout markedly attenuated artery neointima formation induced by wire injury. Moreover, we discovered that METTL3 deficiency repressed both ex vivo and in vivo proliferation of VSMCs. Through a joint analysis of the data from bulk RNA and m6A sequencing, serum- and glucocorticoid-inducible kinase 1 (SGK1) was identified due to its well-documented role in promoting VSMC proliferation and migration. Mechanistically, METTL3-mediated SGK1 mRNA methylation (A146 and A210) was proposed to facilitate SGK1 transcription by recruiting the m6A reader YTHDC1, as shown by well-designed experiments involving methylation site mapping, m6A RNA immunoprecipitation (m6A-RIP), chromatin immunoprecipitation quantitative PCR (ChIP-qPCR) and reporter gene analysis. As anticipated, VSMC proliferation and intimal hyperplasia that had already been mitigated by METTL3 ablation were both restored by SGK1 overexpression. Conclusions: Our findings suggest that METTL3 promotes SGK1 expression via mRNA methylation-mediated facilitation of its own transcription, thus predisposing VSMCs to a proliferative state and contributing to neointima formation after vascular injury, underscoring the essential role METTL3 plays in vascular remodeling.