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

Hao Chai,Wen Chen,Hongwei Chen,Zhonghao Tao,Haoyu Qi,Yueyue Xu,Leiyang Zhang,Yongchao Qi,Xin Chen

doi:10.1155/2020/3602824

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.

Highlights

Abdominal aortic aneurysm (AAA) is a chronic inflammatory vascular disease in the elderly population
We found that angiotensin II (Ang II) infusion for 7 days leads to a significant increase in the expression of IKKε in aorta tissue in this model (Figure 1(c)), and the uptrends remain to the end of infusion
These results suggest that IKKε is significantly increased during AAA formation and may play an important role in this process

Summary

Introduction

Abdominal aortic aneurysm (AAA) is a chronic inflammatory vascular disease in the elderly population. Using mouse deficiency in IKKε and apolipoprotein E (Apoe), we recently showed that IKKε is a key player in the pathogenesis of the cardiovascular disease [6, 7]; deficiency of IKKε has been suggested to have an anti-inflammatory effect and to inhibit malignant transformation [8, 9]. The current study is aimed at investigating the role of IKKε in response to angiotensin II (Ang II) and at elucidating its role in AAA formation. We used a mouse model of inflammatory AAA [10], in which chronic subcutaneous infusion of Ang II occurred in Apoe−/− and IKKε−/−Apoe−/− mice over a 28-day time course. This study was conducted to investigate whether IKKε serves as a detrimental adaptive mechanism in response to Ang II infusion

Methods

Results

Discussion

Conclusion