Brd4 inhibition attenuates obesity-related microvascular dysfunction: role of endothelium and perivascular adipose tissue

Objective: Bromodomain and extraterminal (BET) proteins, particularly BRD4, are epigenetic readers modulating transcriptional programs implicated in inflammation, cancer and renal disease. Though several findings suggest that BET proteins’ inhibition might be particularly relevant in the cardiometabolic field, an apparent evidence gap hinders its therapeutic potential. We aimed to define the impact of BRD4-related inflammatory response in the early stages of obesity to exploit the therapeutic potential of its inhibition. Design and method: Healthy controls (n = 13) and patients with obesity without other comorbidities (n = 13) were included in a case-control study. Small arteries from visceral fat depots were mounted on a pressurised myograph to assess vasorelaxation to acetylcholine and inhibition to L-NAME at baseline and after incubation with RVX-208 (an FDA-approved BRD4 inhibitor), canakinumab (targeting IL-1beta), tocilizumab (targeting IL-6 receptor) and infliximab (targeting TNF-alpha). The experiments were conducted, in parallel, on two vessels, one mounted with perivascular adipose tissue (PVAT) and the other without PVAT. Vascular- and PVAT-specific levels of NAPDH-derived ROS, mtROS and nitric oxide availability were assessed by confocal microscopy. Gene expression was evaluated by qPCR. Results: In patients with obesity, microvascular function and nitric oxide availability were reduced, where NADPH- and mtROS were increased. BRD4, TNF-alpha, IL-1beta and IL-6 expression levels were higher in the vessel wall and the PVAT of patients with obesity. In these patients, RVX-208 substantially attenuated microvascular dysfunction. The effect was more significant in vessels with intact PVAT, implying a restoration of the PVAT anti-contractile phenotype (Figure). The exploration of the distinct inflammatory pathways showed that the amelioration observed with BRD-4 inhibition was higher than with canakinumab, tocilizumab or infliximab. Peculiarly, anti-IL-1beta restoration of microvascular function was not affected by the presence of the PVAT, while the ones observed with the targeting of IL-6 receptor and TNF-alpha were. Conclusions: The inhibition of BRD4 restores microvascular dysfunction in patients with obesity by modulating pan-inflammatory response involving distinct IL-1beta, IL-6 and TNF-alpha pathways and restoring PVAT anti-contractile properties. Epigenetic drugs might represent a promising therapeutic strategy to rescue microvascular dysfunction, a hallmark of early cardiometabolic disease.