Aging-Associated Nox4-Mediated Mitochondrial Reactive Oxygen Species and DNA Damage Promote Vascular Cell...

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 has been implicated in these changes. We previously demonstrated that NOX4 (NADPH oxidase 4) expression and activity increase with age in cardiovascular cells, promoting mitochondrial oxidative stress and vascular dysfunction. This study investigates whether NOX4-driven mitochondrial oxidative stress and DNA damage promote AAA development through vascular cell reprogramming.

We used mitochondria-targeted Nox4-overexpressing (Nox4TG) mice with an Apoe^-/- background to model angiotensin II (Ang II)-induced AAA. AAA incidence, aortic morphology, reactive oxygen species levels, DNA damage markers, and wall remodeling parameters were assessed in Apoe^-/-, Apoe^-/-/Nox4TG, and Apoe^-/-/Nox4^-/- mice. Vascular cell populations were analyzed by spectral flow cytometry and gene expression profiling. In vitro, Ang II-treated smooth muscle cells (SMCs) from wild-type, Nox4TG, and Nox4^-/- mice were evaluated for mitochondrial reactive oxygen species, DNA damage, and activation of inflammatory pathways.

Apoe^-/-/Nox4TG mice exhibited the highest AAA incidence, aortic dilation, reactive oxygen species levels, DNA damage, and inflammation, whereas Apoe^-/-/Nox4^-/- mice were most protected. Macrophage-like SMCs increased, and contractile SMCs decreased in Nox4TG aortas. Ang II-treated Nox4TG SMCs showed elevated mitochondrial reactive oxygen species, DNA damage, and cyclic GMP-AMP synthase-STING (stimulator of interferon genes) activation. Flow cytometry analysis confirmed the presence of aneurysmal SMC with reduced ACTA2 (actin alpha 2, smooth muscle), MYH11 (myosin heavy chain 11), TAGLN (transgelin), and increased CD68, CD11b, and LGALS3 expression.

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.