Abstract TP132: Vascular HDAC9 Modulates Atherogenic Processes and Enhances NF-kB Activation

Abstract

Background: Genome-wide association studies (GWAS) identified the histone deacytelase 9 (HDAC9) gene region as the leading risk locus for large artery atherosclerotic stroke. Hdac9 deficiency was shown to attenuate atheroprogression in Apoe -/- and Ldlr -/- mice, however the mechanisms linking HDAC9 to atherosclerosis remain elusive. Objective: We aimed to determine HDAC9-related pro-inflammatory and pro-atherogenic responses in vitro and employed an early-stage atherosclerosis model to study these effects in vivo. Methods and Results: Human endothelial (ECs) and smooth muscle cells (SMCs) were cultured and transfected with HDAC9 siRNA or scrambled RNA (control) and stimulated with 20 ng/ml human TNF-α. HDAC9 depletion resulted in reduced adhesion molecule (VCAM-1, ICAM-1) and cytokine (CCL2, IL-8) expression as determined by RT-PCR, ELISA and Western Blot. Hdac9 +/+ Apoe -/- and Hdac9 -/- Apoe -/- mice were fed a western-type diet for 2 weeks. Hdac9 -deficient mice showed reduced circulating levels of Ccl2 and reduced levels of Vcam-1 and Icam-1 in whole aorta. Two-photon imaging of whole-mount carotid arteries further revealed a significant reduction of Vcam-1 expression. Motivated by the pattern of pro-inflammatory and pro-atherogenic responses, we investigated the effects of HDAC9 on NF-κB signaling. HDAC9 promoted NF-κB luciferase activity, facilitated p65 nuclear translocation, and enhanced p65 phosphorylation as determined by luciferase gene reporter assay, Western Blot and confocal microscopy. Conclusion: We demonstrate that HDAC9 promotes pro-inflammatory and pro-atherogenic responses in vascular cells and identify an activating effect of HDAC9 on NF-kB signalling. Our findings identify HDAC9 as a promising target for therapeutic interventions.