IKK Epsilon Deficiency Attenuates Angiotensin II-Induced Abdominal Aortic Aneurysm Formation in Mice by Inhibiting Inflammation, Oxidative Stress, and Apoptosis

Abstract

Abdominal aortic aneurysm (AAA) is a vascular disorder that is considered a chronic inflammatory disease. However, the precise molecular mechanisms involved in AAA have not been fully elucidated. Recently, significant progress has been made in understanding the function and mechanism of action of inhibitor of kappa B kinase epsilon (IKKϵ) in inflammatory and metabolic diseases. The angiotensin II-(Ang II-) induced or pharmacological inhibitors were established to test the effects of IKKϵ on AAA in vivo. After mice were continuously stimulated with Ang II for 28 days, morphologically, we found that knockout of IKKϵ reduced AAA formation and drastically reduced maximal diameter and severity. We also observed a decrease in elastin degradation and medial destruction, which were independent of systolic blood pressure or plasma cholesterol concentrations. Western blot analyses and immunohistochemical staining were carried out to measure IKKϵ expression in AAA tissues and cell lines. AAA phenotype of mice was measured by ultrasound and biochemical indexes. In zymography, immunohistology staining, immunofluorescence staining, and reactive oxygen species (ROS) analysis, TUNEL assay was used to examine the effects of IKKϵ on AAA progression in AAA mice. IKKϵ deficiency significantly inhibited inflammatory macrophage infiltration, matrix metalloproteinase (MMP) activity, ROS production, and vascular smooth muscle cell (VSMC) apoptosis. We used primary mouse aortic VSMC isolated from apolipoprotein E (Apoe) -/- and Apoe-/-IKKϵ-/- mice. Mechanistically, IKKϵ deficiency blunted the activation of the ERK1/2 pathway. The IKKϵ inhibitor, amlexanox, has the same impact in AAA. Our results demonstrate a critical role of IKKϵ in AAA formation induced by Ang II in Apoe-/- mice. Targeting IKKϵ may constitute a novel therapeutic strategy to prevent AAA progression.