Abstract 159: Palmitic Acid Alters Enhancers And Super Enhancers Near Inflammatory And Efferocytosis-associated Genes In Human Monocytes

Abstract

Background: Elevated free fatty acids (FFA) like palmitic acid (PA) are associated with inflammatory cardiometabolic disorders like diabetes and atherosclerosis. FFA induced dysregulated gene expression in monocytes plays important roles in inflammation, but the epigenetic mechanisms involved are unclear. Here we examined PA induced alterations in enhancer and super-enhancer (E/SE) repertoires to elucidate epigenetic mechanisms of inflammatory gene regulation in monocyte dysfunction. Methods: Human CD14 + monocytes from healthy volunteers were treated with PA (200 μM, 24 h) or vehicle (0.2% BSA). ChIP-seq with histone-H3K27ac was performed to identify Es/SEs and RNA-seq to analyze gene expression genome-wide. Publicly available Genomic Regions Enrichment of Annotations Tool, and datasets from promoter capture Hi-C (PCHiC) and GWAS on diabetes, obesity and BMI were used to analyze functions/disease relevance of Es/SEs. ChIP/RT-qPCRs were used to validate ChIP-/RNA-seq results. Functions of SEs were determined using JQ1 (SE/BET bromodomain inhibitor). Results: ChIP-seq results showed PA extensively dysregulated Es/SEs in CD14 + monocytes vs. vehicle control. PA-regulated Es/SEs showed enrichment of immune system related processes, differentiation, and cytokine production. RNA-seq showed significant correlations between dysregulated enhancers and differential expression of nearby genes. These genes were also altered in adipose tissue macrophages from high fat fed mice, and bone marrow derived macrophages from type2 diabetic db/db mice and Apoe -/- mice with accelerated atherosclerosis. Differentially regulated Es/SEs harbored SNPs associated with diabetes, obesity, and BMI. PCHiC revealed interactions between Es/SEs and promoters of key genes associated with efferocytosis ( MERTK ), metabolism ( OSBPL8 ) and inflammation ( IRAK2, CSF2 and RIPK2 ). Changes in gene expression and H3K27ac at Es/SEs were validated. Treatment with JQ1 reversed PA-induced inflammatory genes in monocytes. Conclusions: PA treatment dysregulated Es/SEs involved in key monocyte functions including efferocytosis, inflammation and metabolism. Targeting such epigenetic mechanisms could be beneficial in the treatment of cardiometabolic diseases.