| BackgroundAbdominal aortic aneurysm(AAA)is a common arterial degenerative disease,which is characterized by permanent local ectasia of abdominal aorta.With the enlargement of the aneurysm,the rupture risk of abdominal aortic aneurysm increases gradually.Once rupture occurs,the mortality can be as high as 90%.Currently,surgical treatment is commonly used for abdominal aortic aneurysm with the largest diameter≥5.5cm.For the small abdominal aortic aneurysm with diameter<5.5cm,the longterm survival rate has not been significantly improved by surgical treatment,the followup observation is mainly adopted at present.However,the abdominal aortic aneurysm has a natural course of progressive dilatation.During the follow-up observation,some patients died of rupture,so this strategy is obviously imperfect.Renin-angiotensin system(RAS)is an important regulatory system for maintaining blood pressure,water and electrolyte balance and cardiovascular homeostasis in vivo,which is widely expressed in heart,blood vessel,kidney and other organs.In recent years,many studies have found that some new members of RAS family also play an important role in the occurrence and development of cardiovascular diseases.Alamandine is an important member of RAS family.Alamandine can be generated by the degradation and transformation of Angiotensin A(Ang A)in the classical RAS pathway,or by the degradation and transformation of Angiotensin(1-7)[Ang-(1-7)],and its receptor is MrgD;Alamandine and its specific receptor(MrgD)constitute the Alamandine/MrgD axis.At present,metabolic axes such as Ang-(1-7)/Mas and Alamandine/MrgD axis are called the second metabolic axis of RAS.Many studies have found that the Alamandine/MrgD axis plays an anti-inflammatory role in the pathophysiological process of many diseases.In arteriosclerosis model,alamandine can significantly inhibit the aggregation of inflammatory cells.Alamandine can antagonize the cardiac hypertrophy caused by Ang Ⅱ through MrgD pathway,and can also reduce the damage of sepsis to the heart by inhibiting the inflammation.However,it is not clear whether Alamandine has therapeutic effect on AAA as an anti-inflammatory factor.Current studies have confirmed that chronic inflammation is an important pathological feature in the formation,progression and rupture of abdominal aortic aneurysm.Currently,scholars at home and abroad have focused on the impact of classical RAS pathway on abdominal aortic aneurysm,and few people pay attention to the role of the second metabolic axis of RAS system in abdominal aortic aneurysm.In this paper,the mouse abdominal aortic aneurysm model was established to study whether the Alamandine/MrgD axis can play a therapeutic role in AAA by inhibiting the inflammatory response of the aortic wall,providing a new idea for clinical treatment of abdominal aortic aneurysm.Research contents1.B-mode ultrasound was used to evaluate the model of abdominal aortic aneurysm and establish the growth curve.2.The therapeutic effect of Alamandine on abdominal aortic aneurysm was clarified in mice3.The role of Alamandine/MrgD in the pathogenesis and development of abdominal aortic aneurysm was explored in mice.Methods:1.AAA mouse model was established by perfusion of porcine trypsin into abdominal aorta:C57BL/6 male mice were divided into sham operation group and abdominal aortic aneurysm model group.A segment of the abdominal aorta from horizontal left renal vein to the bifurcation was separated.The proximal end of the abdominal aorta was made into slipknot to block the blood flow.The anterior wall of the distal end of the abdominal aorta was punctured with a 21G needle.The PPE-10 tube was inserted into the abdominal aorta cavity along the puncture hole and sent to the proximal segment.The distal end of the abdominal aorta was fixed with slipknot and injected with elastase solution.After the modeling operation,B-mode ultrasound examination,HE staining and EVG staining were used to determine whether the modeling was successful.2.The effect of alamandine and MrgD antagonist D-Pro7-Ang-(1-7)on abdominal aortic aneurysm was explored in mice:in this study,D-Pro7-Ang-(1-7)was selected as the antagonist of alamandine.Mice were randomly divided into three groups(control group,alamandine group,Ala+D-Pro7-Ang-(1-7)group).Control group was infused with PBS,Alamandine group was injected with alamandine(90 μ g/kg/h),Ala+D-Pro7-Ang-(1-7)group was injected with alamandine(90 μg/kg/h),D-Pro7-Ang-(1-7)(90μg/kg/h).Abdominal aorta in each group was measured at 3rd,7th and 14th day after the operation,and diameter changes were observed by B-mode ultrasound.3.HE staining,EVG staining and immunohistochemistry were used to detect the pathological changes of aneurysms and the inflammatory reaction.Results:1.Modeling:B-scan ultrasonography was performed 3,7 and 14 days after modeling.It was shown that the diameter of the animal model of abdominal aortic aneurysm gradually increased over time.14 days after surgery,the maximum diameter of AAA was 50%more than the preoperative diameter.As evidenced by the diameter,the mouse model of abdominal aortic aneurysm was successfully established.HE and EVG staining showed that the tissue structure of the aortic wall was disordered,elastic fibers were degraded and destroyed on a large scale,smooth muscle cells in the middle layer of the aortic wall were disordered and the number was significantly reduced.The infiltration of inflammatory cells can be seen in all layers,which further suggested that the AAA model was successfully established.2.Compared with the control group,the maximum diameter of the mouse aneurysm in the alamandine treatment group was significantly reduced.EVG staining showed that the degradation of elastic fibers on the aortic wall was significantly reduced than that of the control group.Immunohistochemistry showed that the infiltration degrees of CD68+ macrophages,CD80+ M1 macrophages,CD8+ T cell on the aortic wall and CD31+ angiogenesis in the Alamandine group were significantly lower than those of the control group.Meanwhile,the expression of MMP-9 and the degradation of smooth muscle cells on the aortic wall of the alamandine group were significantly decreased than those of the control group,while the infiltration of CD206+M2 macrophages in the Alamandine group was increased than that of the control group.3.After D-Pro7-Ang-(1-7),the MrgD antagonist was applied,EVG staining showed that the degradation of elastic fibers on the aortic wall of the Almandine+D-Pro7-Ang(1-7)group was significantly higher than that of the Almandine group.Immunohistochemistry showed that:The infiltration degrees of CD68+ macrophages,CD80+M1 macrophages and CD8+T cells and CD31+ angiogenesis in the almandine+D-Pro7-Ang-(1-7)group were significantly higher than those of the alamandine group.The expression of MMP-9 and the degradation of smooth muscle cells on the aortic wall of the Almandine+D-Pro7-Ang-(1-7)group were significantly lower than those of the Alamandine group,while the infiltration of CD206+M2 macrophages was decreased than that of the Alamandine group.Conclusion1.A mouse model of abdominal aortic aneurysm was successfully established by applying an intracavitary perfusion model of elastase.Alamandine restricted the growth of experimental abdominal aortic aneurysm.2.Alamandine can inhibit the occurrence and development of abdominal aortic aneurysm in mice by inhibiting the inflammatory reaction on the aortic wall of abdominal aortic aneurysm,the degradation of elastin and vascular smooth muscle cells,as well as neovascularization.3.MrgD receptor antagonist D-Pro7-Ang-(1-7)can block the therapeutic effect of alamandine.4.Alamandine/MrgD axis is a possible pathway by which Alamandine inhibits the development of experimental abdominal aortic aneurysm. |
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