Epigenetic Regulation of Protease Activity in Human Abdominal Aortic Aneurysm Development
Frank Davis*1, William Melvin1, Kevin Mangum1, Amrita Joshi1, Rachael Wasikowski1, Xianying Xing2, Johann Gudjonsson2, Katherine Gallagher1
1Surgery, University of Michigan, Ann Arbor, MI; 2Dermatology, University of Michigan, Ann Arbor, MI
Objective(s): Abdominal aortic aneurysms (AAA) are a life-threatening cardiovascular disease characterized by an inflammatory macrophage phenotype and protease production that contributes to pathological vascular remodeling predisposing patients to the potentially fatal consequence of aortic rupture. Identifying the mechanisms regulating macrophage-mediated inflammation and extracellular matrix degradation during AAA development are of critical importance to developing novel pharmacological therapies to prevent AAA progression. Recent evidence indicates that epigenetic enzymes, specifically the histone methyltransferase SETDB2, play a critical role in establishing tissue macrophage phenotype and inflammation. Here we examine the role of SETDB2 in the development of AAAs and establish SETDB2 as a novel target in the treatment AAA disease.
Methods: Human AAA and control tissue samples (n=25) were collected at the time of operative intervention and analyzed by single cell RNA-sequencing. Differential gene expression and pathway analysis was performed across cellular populations. Separately, male C57BL/6J mice with a macrophage-specific deletion of SETDB2 (Setdb2f/fLyzCre+) and littermate (Setdb2f/fLyzCre-) controls (n=50) were subjected to either the angiotensin-II induced or elastase induce murine AAA model. AAA progression and macrophage function were determined by in vivo and in vitro analysis.
Results: SETDB2 was profoundly upregulated in human and experimental murine AAA lesions (p<0.01). This pathological SETDB2 expression was driven by aberrant JAK/STAT3 signaling in AAA macrophages. In vivo studies revealed that macrophage-specific knockout of SETDB2 protected mice from both angiotensin II-induced and elastase-induced AAA formation with significant suppression of vascular inflammation, macrophage infiltration, and elastin fragmentation. Gene expression analysis and chromatin immunoprecipitation demonstrated that genetic depletion of SETDB2 prevented AAA development due to a removal of the repressive H3K9 trimethylation epigenetic mark on the gene promoter of tissue inhibitors of matrix metalloproteinases (TIMPs1-3). This thereby resulted in increased TIMP expression and preserved aortic architecture. Lastly, pharmacological inhibition of the JAK/STAT pathway with an FDA approved inhibitor, Tofacitinib, was also found to limit SETDB2 expression and inhibit AAA development.
Conclusions: These findings using human aortic tissue and multiple murine models identify the epigenetic enzyme SETDB2 as a critical regulator of macrophage-mediated inflammation and protease production in AAAs and identify SETDB2 as a mechanistic target for the management of AAA development.
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