Aging-Associated Nox4 -Mediated Mitochondrial ROS and DNA Damage Promote Vascular Cell Reprogramming and Aortic Remodeling in Abdominal Aneurysms

Abstract Background Aging and male sex are major risk factors for abdominal aortic aneurysm (AAA), a disease characterized by vascular cell phenotypic switching and aortic wall remodeling. Mitochondrial oxidative stress (mtOS) has been implicated in these changes. We previously demonstrated that NOX4 expression and activity increase with age in cardiovascular cells, promoting mtOS and vascular dysfunction. This study investigates whether NOX4-driven mtOS and DNA damage promote AAA development through vascular cell reprogramming. Methods We used mitochondria-targeted Nox4 -overexpressing ( Nox4 TG) mice with an Apoe -/- background to model Angiotensin II (Ang II)-induced AAA. AAA incidence, aortic morphology, reactive oxygen species (ROS) levels, DNA damage markers, and wall remodeling parameters were assessed in Apoe -/- , Apoe -/- / Nox4 TG, and Apoe -/- /Nox4 -/- mice. Vascular cell populations were analyzed by spectral flow cytometry and gene expression profiling. In vitro, Ang II-treated SMCs from wild-type, Nox4 TG, and Nox4 -/- mice were evaluated for mtROS, DNA damage, and activation of inflammatory pathways. Results Apoe -/- /Nox4TG mice exhibited the highest AAA incidence, aortic dilation, ROS levels, DNA damage, and inflammation, while Apoe -/- /Nox4 -/- mice were most protected. Macrophage-like SMCs increased, while contractile SMCs decreased in Nox4TG aortas. Ang II-treated Nox4 TG SMCs showed elevated mtROS, DNA damage, and cGAS-STING activation. Flow cytometry analysis confirmed the presence of aneurysmal SMC with reduced ACTA2, MYH11, TAGLN and increased CD68, CD11b, LGALS3 expression. Conclusions NOX4-dependent mitochondrial DNA damage and activation of DNA- sensing pathways promote SMC phenotypic switching, inflammation, and aortic wall remodeling in AAA. Targeting NOX4 and enhancing mitochondrial function may offer therapeutic strategies for AAA prevention. CLINICAL PERSPECTIVE What Is New? This study identifies mitochondrial NOX4-derived ROS and oxidative mitochondrial DNA damage as early and causal events in AAA pathogenesis, promoting pro-inflammatory reprogramming of vascular smooth muscle cells toward a macrophage-like phenotype. Activation of cytosolic DNA sensing (cGAS-STING) and DNase II pathways in response to mitochondrial damage links redox imbalance to innate immune activation and progressive aortic wall remodeling in AAA. What Are the Clinical Implications? Targeting mitochondrial-specific oxidative stress or downstream DNA-sensing pathways offers a novel therapeutic strategy to halt AAA progression in patients with small, asymptomatic aneurysms. These findings provide a mechanistic basis for developing mitochondria-targeted antioxidants or NOX4 inhibitors as potential pharmacologic interventions to delay or prevent AAA rupture, which could reduce the need for surgical repairs.