| Objective: Abdominal aortic aneurysm(AAA)is a high-risk vascular disease with rupture risk.It is usually clinically defined as irreversible local expansion of the abdominal aorta,and its maximum diameter is greater than 3 cm or 50 % larger than that of the normal aorta.AAA mainly involves the abdominal aorta below the renal artery branch,most patients usually have no obvious symptoms.Patients with AAA are often screened by physical examination or occasionally found in abdominal ultrasound and abdominal CT examination due to other diseases,so it is very difficult to find and diagnose AAA early.When AAA ruptures unfortunately,the mortality rate can reach85 %-90 %.AAA with diameter greater than 5 cm is mainly treated by surgery,including open surgery and endovascular repair,but no drug can effectively control and treat AAA.The main reason is that there is no clear research on the pathogenesis of AAA.Therefore,it is very important and urgent to study the causes of AAA.In recent years,many scholars have proposed the main pathological features related to AAA,namely the formation of inflammatory microenvironment,the phenotypic switch of vascular smooth muscle cell(VSMC)from contraction to synthesis,and extracellular matrix degradation(ECM).The inflammatory microenvironment is mainly composed of inflammatory cells and some inflammatory factors.Macrophage is an important component of the inflammatory microenvironment in AAA.Macrophages can be divided into pro-inflammatory M1 macrophages and anti-inflammatory M2 macrophages according to their different functions.M1 macrophages recruit and activate inflammatory cells by secreting pro-inflammatory factors such as IL-1β,TNF-α and MCP-1 to aggravate the inflammatory response in the aortic wall,or degrade elastic fibers and collagen by releasing MMP-9 and MMP-2 to destroy the aortic structure and lead to AAA formation.M2 macrophages mainly showed inhibitory effects on AAA development in animal experiments.Therefore,it is necessary to clarify the pathogenic role of M1 macrophages in exploring the pathogenesis of AAA.But what factors induce and aggravate the activation of M1 macrophages in AAA and whether M1 macrophages can promote VSMC phenotype conversion through paracrine effect are rarely studied.Some studies have reported that some intestinal flora metabolites can cause aortic macrophage infiltration and increase the expression of inflammatory factors TNF-α and IL-6.Many studies have shown that intestinal flora disorders can cause imbalance of human inflammation and immune balance.Intestinal flora imbalance can cause intestinal mucosal damage,leading to endotoxin and other macromolecular compounds into the blood caused by inflammatory damage to the blood vessels.Therefore,in previous studies,the research group studied whether there was intestinal flora disorder in patients with AAA,and the results showed that the proportion of intestinal thick-walled bacteria in patients with AAA was increased.It has been reported that the increased proportion of parietal bacteria can increase the level of trimethylamine N-oxide(TMAO)in peripheral blood.TMAO is a widely concerned intestinal flora metabolite,which may promote atherosclerosis,cardiovascular disease and kidney disease.But whether TMAO promotes AAA formation has not been reported.Methods: 1.Obtain blood samples from AAA patients and the control group,detect the changes in serum TMAO levels in the two groups,and detect the presence of VSMC phenotypic conversion and M1 macrophage infiltration in the tumor wall tissue of patients with abdominal aortic aneurysm.2.The abdominal aortic aneurysm model was established by calcium chloride infiltration method to study the effect of TMAO on experimental abdominal aortic aneurysm.Firstly,the change of the maximum diameter of abdominal aorta was detected.Then,by immunohistochemical staining,the damage degree of TMAO on the elastic fiber integrity of the vascular wall,the infiltration degree of M1 macrophages,and the phenotypic transformation of vascular smooth muscle were explored.Finally,the expression changes of α-SMA,SM22α,OPN and other proteins were verified by Western blotting.3.Firstly,bioinformatics methods were used to mine the sequencing data of single cell of aortic aneurysm,and the relationship between NLRP3 / IL-1β pathway and the interaction between M1 macrophages and VSMC was explored.Then,the effects of TMAO on macrophage M1 polarization and NLRP3 / IL-1β pathway activation were explored in cell experiments.In addition,VSMCs were treated with M1 macrophage conditioned medium(CM)to explore the effect of M1 macrophages on VSMC phenotype conversion.Finally,the expression of NLRP3 / IL-1β pathway was verified in human and rat aneurysm specimens.Results: 1.ELISA results showed that serum TMAO levels in patients with AAA were significantly higher than those in controls(P < 0.01);compared with the control group,the tumor wall tissue of abdominal aortic aneurysm patients had VSMC phenotypic transition and M1 Macrophage infiltration.2.In AAA model rats,compared with the control group,TMAO can accelerate the expansion of aneurysm diameter,and the AAA model group injected with TMAO has an aggravation of M1 cell infiltration and VSMC phenotypic conversion.3.Firstly,bioinformatics methods were used to mine the sequencing data of single cell of aortic aneurysm,and the relationship between NLRP3 / IL-1β pathway and the interaction between M1 macrophages and VSMC was explored.Then,the effects of TMAO on macrophage M1 polarization and NLRP3 / IL-1β pathway activation were explored in cell experiments.In addition,VSMCs were treated with M1 macrophage conditioned medium(CM)to explore the effect of M1 macrophages on VSMC phenotype conversion.Finally,the expression of NLRP3 / IL-1β pathway was verified in human and rat aneurysm specimens.Conclusion: This study showed that the level of TMAO in patients with AAA was increased,and TMAO aggravated the expansion of experimental abdominal aortic aneurysm with calcium chloride infiltration,the infiltration of M1 macrophages and the phenotype conversion of VSMC.The possible mechanism of TMAO promoting AAA formation is to induce macrophage M1 polarization,thereby inducing VSMC phenotype conversion.TMAO-induced M1 macrophages promote VSMC phenotype conversion by secreting IL-1β. |
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