Abstract 16902: Molecular Basis of the Vascular Cell Phenotypic Switch and Wall Remodeling in Abdominal Aortic Aneurysm: NOX4 NADPH Oxidase-Derived Mitochondrial Oxidative Stress and DNA Damage

Abstract

Vascular cells phenotypic changes and wall remodeling are the hallmarks of abdominal aortic aneurysm (AAA) pathology. Mitochondrial oxidative stress (mtOS) is associated with the vascular smooth muscle cells (SMC) and macrophage phenotypic switch. We previously reported that NOX4 NADPH oxidase expression is increased in cardiovascular cells in response to pathological insult inducing mtOS and dysfunction and vascular disease progression. We tested the hypothesis that NOX4-dependent mtOS and DNA damage induce vascular phenotypic changes and remodeling resulting in AAA progression. In angiotensin II (Ang II)-induced AAA model Apoe -/- / Nox4 Tg mice with mitochondria-targeted overexpression of NOX4 had the highest, whereas Apoe -/- / Nox4 -/- displayed the lowest incidence of AAA, abdominal aorta area and diameter as compared with Apoe -/- mice. The aortic wall ROS levels, oxidative DNA damage and DNA damage response markers, elastin degradation index, MMP2 expression, and macrophage infiltration were significantly higher in AngII-treated Apoe -/- / Nox4 TG mice compared with Apoe -/- or Apoe -/- / Nox4 -/- mice. Spectral flow cytometry analysis of AAA cell suspension from Ang II-infused mice revealed a decrease in contractile SMCs but an increase in macrophage-like SMC populations, as well as increased number of infiltrating pro-inflammatory macrophages in Apoe -/- / Nox4 TG mice. As compared with wild-type or Nox4 -/- mice, Ang II-treated SMC from Nox4 TG mice showed significantly elevated mtOS, DNA damage, dysfunction, as well as activation of cGAS-STING pathway and NLRP3/AIM2 inflammasome expression. Flow cytometry analysis of Ang II-treated Nox4 TG mice SMC contained a lower proportion of cells with contractile markers (ACTA2 + , MYH11 + , TAGLN + ) and a higher proportion of cells with macrophage-like markers (CD68 + , CD11b + , LGALS3 + ). These data suggest that NOX4-dependent mitochondrial DNA damage and activation of DNA-sensing pathways have a causal role in AAA development, leading to macrophage-like SMCs, increased inflammation, and vessel wall remodeling. NOX4 inhibition and mitochondrial function augmentation may be beneficial in preserving aortic wall integrity in AAA-susceptible patients.