Joviliano, Edwaldo Édner

Introduction: Renin-Angiotensin System (RAS) regulates the cardiovascular system and has been implicated in the development of abdominal aortic aneurysm (AAA). RAS modulates function via balancing the ACE/Chymase/AngII-AT1 receptor and ACE-2/Ang(1-7)-Mas receptor axis. Preferential activation of the ACE/Chymase/AngII-AT1 receptor pathway of the RAS contributes to dysregulation of cardiovascular system and disease while the Ang(1-7)-MasR axis contributes to anti-inflammatory pathways. Therefore, identifying the RAS axis mechanism involved in growth, progression, or the risk of rupture in AAA humans could bring a novel treatment perspective. Hypothesis: We hypothesize that in the AAA, the local RAS is altered such as it favours the ACE/AngII/AT1R axis while decreasing the ACE-2/Ang(1-7)/MasR pathway, with consequent AAA development. Objective: We sought to investigate the expression of RAS components in the AAA human aorta. Methods: Aorta tissue from AAA patients (n=21) was collected during the AAA conventional repair surgery, and aorta control aortas were obtained from organ donors (Control, n=11). Protein expression of renin, chymase, ACE, ACE-2 AT1, AT2, and MAS receptors was analyzed by Western Blotting. Results: Our AAA cohort consisted mostly males (76.6% AAA vs. 63.6% Control, p=0.68), smokers or ex-smokers (90.4% AAA vs. 36.3% Control, p=0.002) and most of them had hypertension(71.4% AAA vs. 36.3% Control, p=0.07). Analysis of protein expression in the AAA group showed that ACE and AT1 receptors were upregulated compared with Control (p=0.05; p=0.02, respectively,), while chymase expression was decreased in AAA compared to the control (p=0.03). Additionally, the AAA group showed downregulation in ACE-2 and AT2 compared with Control (respectively, p=0.01, p=0.03). There was no significant difference in the expression of renin and MAS receptors between groups (p=0.52, p=0.41, respectively,). Conclusions: Our data show that the ACE/AT1R axis was upregulated while ACE-2 and AT2 receptors were downregulated in the AAA aorta. Our results implicate local RAS in AAA development and warrant further studies.

Objective: Elastase-2 (ELA-2), a chymotrypsyn-serine protease elastase family member 2A, is expressed in several tissues such as the lungs, heart, liver, kidneys, brain, and vessels. ELA-2 was found to generate angiotensin II (AngII) in arteries and contribute to resistance arteries and vascular remodeling in animal models. It has also been shown that continuous infusion of AngII induces abdominal aortic aneurysm (AAA) in mice. Therefore, we sought to investigate the role of ELA-2 in an aortic dilation, which is a risk factor to AAA development, in a mouse model. Design and method: Male wild type (C57bl/6, WT) and ELA-2 knockout (CELA-2aTm1Bdr; ELA-2 KO) mice were treated with saline or angiotensin II (AngII, 2.28 g/g/min) for twenty-eight days by subcutaneously mini-pumps infusion. To evaluate the role of elastase-2 in a AAA development, mice were divided into four groups: WT treated with saline (WT+SAL), ELA-2KO treated with saline (ELA-2KO+SAL), WT treated with AngII (WT+AngII), and ELA-2KO treated with Ang II (ELA-2KO+AngII). The vascular ultrasound (US) was done before treatment and once a week during 28 days of treatment. The abdominal aorta measurements such as maximum aortic diameter, aortic para-renal diameter, aortic infra-renal diameter, and aortic supra-renal diameter were collected. A dilated aorta is a risk factor aortic rupture/aneurysm. Statistical analyses were performed by the Shapiro Wilk Normality test, two-way ANOVA with Sidak's multiple comparisons test. This study is approved by the Ethics Committee (CEUA-131/2019). Results: The most dilated aorta as measured by the maximum aorta diameter was detected in WT+AngII group and was 60% higher than in the WT+Saline (p = 0.01). There was no significant difference in the maximum aorta diameter between ELA-KO+SAL vs. ELA-2KO+AngII (p = 0.8). The measurement of dilation in aortic para-renal and aortic infra-renal showed that AngII induced a dilation in WT+AngII (p < 0.05), while not modified these parameters in ELA-2KO+AngII group. The aortic supra-renal diameter parameters and weight showed no differences between groups. Conclusions: These results suggest that ELA-2KO mice might be less susceptible to develop an aorta dilation. Therefore, Elastase-2 is a candidate factor that contributes to the formation and/or development of abdominal aortic aneurysm.