5-Azacytidine suppresses the incidence of abdominal aortic aneurysm through the epigenetic regulation of macrophage polarization.

Objective: Abdominal aortic aneurysm (AAA) is a life-threatening disease characterized by chronic vascular inflammation and extracellular matrix degradation. Macrophage polarization and epigenetic regulation via DNA methylation contribute to AAA pathogenesis. This study aimed to investigate the effects of DNA methyltransferase 1 (DNMT1) inhibitor 5-azacytidine (5-aza) on AAA development and its underlying mechanisms. Methods: Apolipoprotein E knockout mice were infused with angiotensin II (Ang II) to induce AAA formation and treated with 5-aza or left untreated. Histological and immunohistochemical analyses were performed to evaluate DNA methylation status and macrophage phenotype. In vitro, RAW 264.7 macrophages were stimulated with Ang II with or without 5-aza, followed by immunostaining, reverse transcription quantitative polymerase chain reaction, and Western blotting. DNMT1 was silenced using small-interfering RNA. Promoter methylation status was evaluated by methylation-specific polymerase chain reaction. Publicly available bulk microarray datasets were analyzed to support the experimental findings. Results: 5-Aza considerably reduced AAA incidence and elastin degradation in Ang II-infused apolipoprotein E knockout mice. It suppressed DNMT1 expression and global DNA methylation in the abdominal aorta and reduced M1/M2 macrophage ratio, as evidenced by decreased proinflammatory M1 macrophages. In vitro, 5-aza inhibited macrophage proliferation, migration, and matrix metalloproteinase expression. Bulk microarray analysis data supported these findings, demonstrating DNMT1 upregulation and peroxisome proliferator-activated receptor gamma (PPARγ) downregulation in Ang II treated aortas. 5-Aza reduced methylation of the Conclusions: 5-Aza suppresses AAA formation by epigenetically regulating macrophage polarization through modulation of Clinical relevance: There is currently no established pharmacological therapy for abdominal aortic aneurysm (AAA). We demonstrate that DNA methyltransferase 1 inhibition by 5-azacytidine suppresses AAA formation by reducing DNA methylation and the M1/M2 macrophage ratio via upregulation of peroxisome proliferator-activated receptor γ expression. These findings identify epigenetic regulation as a key mechanism in AAA pathogenesis. Given that 5-azacytidine is already clinically available, targeting DNA methylation may represent a potential translational strategy to inhibit AAA formation, although optimization of dosing and safety will be required.