JMJD3 Influences Macrophage-Mediated Inflammation in Abdominal Aortic Aneurysms

Abstract

Abdominal aortic aneurysms (AAAs) are characterized by inflammatory macrophage (Mφ) infiltration and pathologic vascular remodeling. The mechanisms regulating Mφ polarization during AAA development remain unknown. There is increasing evidence that epigenetic enzymes, specifically the histone demethylase JMJD3, direct Mφ polarization. The purpose of this study was to investigate whether JMJD3-mediated epigenetic modifications regulate Mφ inflammation and drive AAA formation. Single-cell RNA sequencing was conducted on human AAA and age-matched atherosclerotic control tissue samples. In addition, the angiotensin (Ang) II-induced AAA model was used to gain mechanistic insight. Briefly, after 4 weeks of high-fat diet, mice were infused with AngII or saline to induce AAAs. AAA maximum diameters were quantified and Mφs were sorted. Messenger RNA abundance of inflammatory cytokines and Jmjd3 were determined by quantitative polymerase chain reaction; levels of histone 3 lysine 27 trimethylation (H3K27me3) on gene promoters were determined by chromatin immunoprecipitation. Statistical significance was determined using Student t-test or analysis of variance. Single-cell RNA sequencing analysis of human AAAs and age-matched atherosclerotic controls demonstrated a significant upregulation of Jmjd3 and inflammatory cytokine expression in monocyte and Mφ subsets within AAA tissue. Congruently, AAA tissue- and bone marrow-derived Mφs from AngII-induced AAAs displayed marked upregulation of Jmjd3 and increased messenger RNA abundance of inflammatory genes (interleukins 1β, 12, and 23) during AAA development (P < .05). To determine the mechanistic impact of JMJD3 on Mφ polarization, histone methylation was evaluated on monocyte-macrophages and demonstrated decreased levels of the repressive histone methylation mark H3K27me3 on inflammatory gene promoters in AngII-induced AAAs compared with controls. In vitro inhibition of JMJD3 using short interfering RNA significantly reduced Mφ inflammatory cytokine expression (P < .05). These Results suggest an important role for JMJD3 in regulating macrophage-mediated inflammation and identify a potential target for the treatment of chronic inflammation in human AAAs.