474-P: Novel Changes in Chromatin 3D Architecture under Diabetic Conditions in Human Macrophages

Aberrant activation of monocytes and macrophages in diabetes increases chemokines and cytokines associated with chronic inflammation and diabetic vascular complications like atherosclerosis and nephropathy. Epigenetic mechanisms are implicated; however, the chromatin 3D reorganization during macrophage activation in diabetes is unclear. We examined chromatin architecture in human CD14⁺ monocytes (from healthy volunteers) differentiated into macrophages and treated with High glucose +TNF-α (HT, 72 h) versus normal glucose using HiChIP and ChIP-seq with H3K27ac antibody (enhancer mark) and integrated these datasets with gene expression (RNA-seq) and chromatin-accessibility (ATAC-seq) data. We found HT induced dramatic changes in transcriptional programs that regulate inflammatory pathways similar to CD14⁺ monocytes from diabetic volunteers. HT promoted extensive changes in open chromatin (OC) and chromatin loops between enhancers and other regulatory elements and disrupted transcriptionally active/inactive (A/B) genomic compartments and topologically associating domains. Upregulated inflammatory genes were associated with increased OC and promoter-enhancer loops, which were reduced at downregulated cell cycle genes. We identified key pro-inflammatory transcription factor motifs enriched in OC/chromatin loops, and interactions between distal enhancers and promoters of chemokine, cytokine, and upstream signaling genes. ChIP and 3C assays confirmed HT-induced H3K27ac at distal enhancers and enhancer interactions with the CCL2 and IRAK2 promoters. Moreover, HT-induced enhancers harbored SNPs linked with type 2 diabetes. These results reveal unique rewiring of the epigenome and chromatin 3D architecture by HT, which likely promotes macrophage activation in diabetes. They can reveal potential targets for epigenetic therapies to mitigate chronic inflammatory diabetes complications.