• Frank M Davis, William J Melvin, Kevin Mangum, Lam C Tsoi, Amrita D Joshi, Qing Cai, Peter K Henke, Johann E Gudjonsson, and Katherine A Gallagher.
• Department of Surgery, Section of Vascular Surgery, University of Michigan, Ann Arbor, MI.
• Ann. Surg. 2023 Sep 1; 278 (3): 426440426-440.

ObjectiveTo determine macrophage-specific alterations in epigenetic enzyme function contributing to the development of abdominal aortic aneurysms (AAAs).BackgroundAAA is a life-threatening disease, characterized by pathologic vascular remodeling driven by an imbalance of matrix metalloproteinases and tissue inhibitors of metalloproteinases (TIMPs). Identifying mechanisms regulating macrophage-mediated extracellular matrix degradation is of critical importance to developing novel therapies.MethodsThe role of SET Domain Bifurcated Histone Lysine Methyltransferase 2 (SETDB2) in AAA formation was examined in human aortic tissue samples by single-cell RNA sequencing and in a myeloid-specific SETDB2 deficient murine model induced by challenging mice with a combination of a high-fat diet and angiotensin II.ResultsSingle-cell RNA sequencing of human AAA tissues identified SETDB2 was upregulated in aortic monocyte/macrophages and murine AAA models compared with controls. Mechanistically, interferon-β regulates SETDB2 expression through Janus kinase/signal transducer and activator of transcription signaling, which trimethylates histone 3 lysine 9 on the TIMP1-3 gene promoters thereby suppressing TIMP1-3 transcription and leading to unregulated matrix metalloproteinase activity. Macrophage-specific knockout of SETDB2 ( Setdb2f/fLyz2Cre+ ) protected mice from AAA formation with suppression of vascular inflammation, macrophage infiltration, and elastin fragmentation. Genetic depletion of SETDB2 prevented AAA development due to the removal of the repressive histone 3 lysine 9 trimethylation mark on the TIMP1-3 gene promoter resulting in increased TIMP expression, decreased protease activity, and preserved aortic architecture. Lastly, inhibition of the Janus kinase/signal transducer and activator of the transcription pathway with an FDA-approved inhibitor, Tofacitinib, limited SETDB2 expression in aortic macrophages.ConclusionsThese findings identify SETDB2 as a critical regulator of macrophage-mediated protease activity in AAAs and identify SETDB2 as a mechanistic target for the management of AAAs.Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.

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