Abstract 10591: Epigenetic BET Reader Inhibitor Apabetalone (RVX-208) Counters Proinflammatory Aortic Gene Expression in a Diet Induced Obesity Mouse Model

Abstract

Introduction: Obesity increases the risk of type 2 diabetes (DM2) and cardiovascular disease (CVD), due to associated insulin resistance, dyslipidemia, high blood pressure and chronic inflammation. Bromodomain and extraterminal (BET) proteins such as BRD4 enhance the expression of proinflammatory genes by recruiting transcription factors to promoters and enhancers. Inhibition of BET binding to chromatin leads to anti-inflammatory and anti-atherogenic effects in models of DM2 and CVD. Hypothesis: BET inhibition with apabetalone, a clinical-stage small molecule, reduces vascular inflammation in a mouse model of diet-induced obesity. Methods: From 8 to 30 weeks of age, C57 BL/6J mice were fed a high-fat (HFD) or low-fat diet (LFD). Mice received apabetalone at 150 mg/kg b.i.d between 14 and 30 weeks. Gene expression was analyzed post necropsy in the aorta by PCR, nCounter® Inflammation Panel and Ingenuity® Pathway Analysis. Human aortic endothelial cells (HAECs) treated with TNFα and apabetalone were analyzed by BRD4 ChIP-seq and RNA-seq to assess BRD4 chromatin occupancy and transcriptional changes. Results: Profiling of 254 genes in the aorta showed an upregulation of 27 inflammatory genes in HFD-fed mice as compared to LFD (p<0.05), including transcription factors Rela (22%), Hif1a (25%) and Tcf4 (44%), involved in inflammation, hypoxia and cell growth, respectively. Other upregulated genes mapped to cytokine, cytoskeleton, coagulation and complement pathways. Apabetalone reduced aortic mRNA expression of transcription factors Rela (12%), Nfkb1 (22%) and Tcf4 (15%), chemokines Ccl2 (47%), Ccl7 (49%) and Ccl8 (69%), leukocyte receptors Ccr2 (64%) and Itgam (29%) and endothelial receptors Sele (64%) and Icam1 (36%). Bioinformatics predicted enhanced signaling by TNFα in the HFD vs. LFD aorta, which was countered by apabetalone. In HAECs, apabetalone lowered gene expression and BRD4 binding to Rela , Hif1a and Tcf4 genes and prevented TNFα-mediated BRD4 accumulation in proximity of Ccl2 , Sele and Icam1 genes. Conclusions: HFD induces vascular inflammation in mice. Apabetalone treatment diminishes this proinflammatory phenotype, providing mechanistic insight into how BET inhibitors may reduce CVD risk in DM2 patients.