Abstract 669: Apabetalone (rvx-208) Decreases Risk of Major Adverse Cardiovascular Events in Diabetes Mellitus Patients With Cvd by Attenuating Monocyte Adhesion to Endothelial Cells

Abstract

Apabetalone (RVX-208, 200 mg/d) given orally to patients with diabetes mellitus (DM) and CVD leads to a 57% relative risk reduction in major adverse cardiovascular events (MACE). Potential actions of RVX-208, an inhibitor (BETi) of bromodomain extra-terminal (BET) proteins that are epigenetic readers of acetylated lysine residues within histones, in lowering MACE is explored by testing its effect on genes mediating monocyte adhesion to endothelial cells in response to high glucose (HG) and the dietary metabolite trimethyl-amine oxide (TMAO). Cultured THP-1 monocytes, HUVEC endothelial cells and primary human hepatocytes (PHH) were exposed to varying concentrations of glucose and TMAO. Results showed that HG (25.6 mM) induced Very Late Antigen-4 (VLA-4) mRNA, a gene mediating THP-1 adhesion by 1.3-fold and RVX-208 suppressed it >50%. Similarly, BETi blocked TMAO induction of VLA-4 mRNA by >50% in THP-1. In HUVECs RVX-208 abrogated HG induction of E-selectin and MYD88 mRNA by 2- and 1.3-fold, respectively and lowered TMAO induction of these mRNAs by >50%. Microbiome processing of dietary phospholipids followed by hepatic flavin mono-oxygenase-3 (FMO3) metabolism yields TMAO. In PHH exposed for 24 hrs to RVX-208, FMO3 mRNA was lower by 40% but it also suppressed a transcriptional regulator of FMO3, farnesoid X receptor (FXR). BETi suppressed both FXR mRNA and protein within 6 hrs by >80% suggesting a direct effect of BETi on the gene encoding FXR. Furthermore, ChiP data showed that BRD4, a BET protein, dissociated immediately from FXR gene upon exposure to RVX-208. Since BRD4 guides a complex containing RNA pol II along actively transcribed genes containing histones that are highly acetylated, the dissociation of BRD4 from FXR DNA would halt transcription of this gene. In summary, Apabetalone inhibits HG and TMAO enhanced adhesion of THP-1 to HUVECs a process that mimics a step in the pathogenesis of CVD. RVX-208 suppresses genes underlying cellular adhesion; VLA-4 in THP-1 and both E-selectin plus MYD88 in HUVECs. BETi blocks not only activity of TMAO but also its production by inhibiting FXR expression, a regulator of FMO3 gene transcription. The rapid actions of BETi in dissociating BRD4 from FXR DNA suggests a direct effect of RVX-208 on transcription of this gene.