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 (ApoE–/–) 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 (RT-qPCR), and western blotting. DNMT1 was silenced using small interfering RNA (siRNA). Promoter methylation status was evaluated by methylation-specific PCR. 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 ApoE–/– mice. It suppressed DNMT1 expression and global DNA methylation in the abdominal aorta and reduced M1/M2 macrophage ratio, as evidenced by decreased pro-inflammatory 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 PPARγ promoter in vivo and in vitro , which was associated with increased PPARγ expression and a reduced M1/M2 macrophage ratio. Conclusions 5-aza suppresses AAA formation by epigenetically regulating macrophage polarization through modulation of PPARγ promoter methylation. Targeting DNA methylation represents a potential therapeutic strategy for AAA.