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

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. RNA isolation for microarray analysis was prepared 6 h after treating human smooth muscle cells with growth medium or (+)-JQ1. SMCs in basal medium served as control. We analysed four control replicates and three replicates of each growth medium and (+)-JQ treated SMC.