Histone deacetylase 9 represses cholesterol efflux and alternatively activated macrophages in atherosclerosis development

OBJECTIVE - Recent genome-wide association studies revealed that a genetic variant in the loci corresponding to histone deacetylase 9 (HDAC9) is associated with large vessel stroke. HDAC9 expression was upregulated in human atherosclerotic plaques in different arteries. The molecular mechanisms how HDAC9 might increase atherosclerosis is not clear. APPROACH AND RESULTS - In this study, we show that systemic and bone marrow cell deletion of HDAC9 decreased atherosclerosis in LDLr (low density lipoprotein receptor) mice with minimal effect on plasma lipid concentrations. HDAC9 deletion resulted upregulation of lipid homeostatic genes, downregulation of inflammatory genes, and polarization toward an M2 phenotype via increased accumulation of total acetylated H3 and H3K9 at the promoters of ABCA1 (ATP-binding cassette transporter), ABCG1, and PPAR-γ (peroxisome proliferator-activated receptor) in macrophages. CONCLUSIONS - We conclude that macrophage HDAC9 upregulation is atherogenic via suppression of cholesterol efflux and generation of alternatively activated macrophages in atherosclerosis.