Therapeutic modulation of epigenetic readers rescues obesity-induced vascular dysfunction: role of endothelium and perivascular adipose tissue

Abstract Background/Introduction Bromodomain and extraterminal proteins (BET), particularly BRD4, are epigenetic readers modulating transcriptional programs implicated in inflammation, cancer and renal disease. Therapeutic potential of BRD4 modulation in cardiometabolic disorders remains elusive. Purpose We investigate BRD4-related transcriptional programs and therapeutic modulation in mouse and human models of cardiometabolic disease. Methods Small arteries (100-300 μM) from healthy subjects (n=13) and patients with obesity (n=13) were dissected from visceral fat biopsies collected during elective laparoscopy and mounted on a pressurised myograph to assess the ex-vivo effects of BRD4 inhibition on vascular function. Vasorelaxation to acetylcholine and acetylcholine+L-NAME were evaluated at baseline and after incubation with the BRD4 inhibitor RVX-208. Anti-IL-1β, anti-IL-6 receptor and anti-TNF-α were also employed to assess the relative contribution of distinct BRD4-related pathways. Vasorelaxation was performed in the presence or in the absence of perivascular adipose tissue (PVAT). An experimental mouse model of cardiometabolic disease (high-fat diet+L-NAME supplementation) was orally administered RVX-208 (150 mg/kg) or vehicle for 10 days (n=6 each group) to test in vivo effect of chronic BRD4 inhibition on endothelial and PVAT functions. Vascular and PVAT levels of cytosolic and mitochondrial ROS and nitric oxide were assessed by confocal microscopy; protein and gene expression was measured by Western blot and qPCR. Transcriptional changes upon BRD4 inhibition were investigated by a custom PCR array. Results In patients with obesity, endothelial-dependent vasorelaxation and vascular nitric oxide availability were impaired. ROS levels, as well as TNF-α, IL-1β and IL-6, were increased in the vessel wall and PVAT. In these subjects, RVX-208 substantially attenuated ex-vivo vascular dysfunction. The effect was more pronounced in vessels with intact PVAT, suggesting a restoration of the PVAT anti-contractile phenotype (Figure 1). Distinct ex-vivo modulation of well-established inflammatory pathways showed that the effect observed with BRD4 inhibition was stronger than with anti-IL-1β, anti-IL-6 receptor and anti-TNF-α. In vivo, chronic treatment with RVX-208 restored endothelial vasorelaxation by rescuing PVAT dysfunction. Gene expression profiling in PVAT from cardiometabolic mice unveiled hexokinase-2 (HK2) - a glycolytic enzyme implicated in mitochondrial dysfunction and inflammation - as the top downregulated gene by RVX-208 treatment (Figure 2). Conclusions Therapeutic modulation of BRD4 restores cardiometabolic-related vascular dysfunction and PVAT anti-contractile properties. These effects are explained by a suppression of PVAT inflammation (IL-1β, IL-6 and TNF-α), likely driven by HK2 activation. BET inhibitors might represent promising epi-drugs for the prevention and treatment of vascular dysfunction, a hallmark of cardiometabolic disease.