Abstract 10474: The Bet Protein Inhibitor Apabetalone Rescues Diabetes Induced Impairment of Angiogenic Response

Abstract

Introduction: Therapeutic modulation of blood vessel growth is a promising therapeutic strategy for the prevention of limb ischemia in diabetic (DM) patients with peripheral artery disease (PAD). Epigenetic changes, namely posttranslational histone modifications, participate in angiogenic response suggesting that chromatin-modifying drugs could be beneficial in this setting. Apabetalone (APA), a selective inhibitor of bromodomain (BRD) and extra-terminal (BET) proteins, prevents BRD4 interactions with chromatin thus modulating transcriptional programs in different organs. Hypothesis: We sought to investigate whether APA affects angiogenic response in diabetes. Methods: Primary human aortic endothelial cells (HAECs) were exposed to normal glucose (NG, 5 mM) or high glucose (HG, 20 mM) for 48 hours in presence of RVX-208 (20μM) or vehicle (DMSO). Streptozotocin-induced diabetic mice were orally treated with APA or vehicle for 5 days. Hindlimb ischemia was induced in diabetic mice and blood flow recovery analyzed at 30 minutes, 7, & 14 days by laser Doppler imaging. Gastrocnemius muscle samples from patients with and without diabetes were employed to translate our experimental findings. Results: APA restored tube formation and migration in human endothelial aortic cells (HAECs) exposed to HG levels. Expression profiling of angiogenesis genes showed that APA prevents HG-induced upregulation of the anti-angiogenic molecule thrombospondin (THBS1). ChIP-seq and chromatin immunoprecipitation (ChIP) assays in HG-treated HAECs showed the enrichment of both BRD4 and active regulatory marks (H3K27ac) on THBS1 promoter, whereas BRD4 inhibition by APA prevented chromatin accessibility and THBS1 transcription. Mechanistically, we show that THBS1 inhibits angiogenesis by suppressing VEGFA signaling, while APA prevents these detrimental changes. In diabetic mice with hindlimb ischemia, epigenetic editing by APA restored THSB1/VEGFA axis thus improving limb vascularization and perfusion. Finally, epigenetic regulation of THSB1 by BRD4/H3K27ac was also reported in DM patients with PAD as compared to non-diabetic controls. Conclusion: Our findings set the stage for clinical trials testing APA in DM patients with PAD.