The Mechanism Of Inflammasome AIM2 In Mediating Thoracic Aortic Aneurysm And Dissection Through Recruitment Of USP21

Objective:Thoracic aortic aneurysm and dissection(TAAD)is a multifactorial vascular disease associated with life-threatening complications.Identifying the underlying mechanism is a key step in developing effective therapies to prevent disease progression.There is evidence that abnormal activation of the intracellular DNA pattern recognition receptor absent in melanoma 2(AIM2)plays a key role in vascular inflammation and destruction.When activated as an inflammasome,AIM2 induces pyroptosis,tissue inflammation,and extracellular matrix destruction.However,the specific mechanism of AIM2 activation in TAAD has not been elucidated.Therefore,this study aims to uncover the mechanism of action of AIM2 in the development of TAAD and to explore new therapeutic treatments.Methods:The TAAD model was constructed by feeding 3-week-old male C57BL/6J mice with β-amino propionitrile(BAPN).In vivo,the accumulation of double-stranded DNA(dsDNA)break in the thoracic aorta of TAAD mice and the expressions of Caspase-1 and GSDMD in the pyroptosis signaling pathway were examined.In vitro,we used Poly(dA:dT)stimulation to induce the specific activation of AIM2 inflammasome in mouse vascular smooth muscle cells(VSMC).The expressions of Caspase-1 and GSDMD were examined after AIM2 silencing with siRNA.The positive rate of pyroptosis was determined by propidium iodide(PI)staining.The interaction between AIM2 and USP21 was verified by bioinformatics and co-immunoprecipitation.Finally,the relationship between miR-485-5p and AIM2 was verified by dual-luciferase assay.PBS,control exosome,and miR-485-5p inhibitor exosome were injected into mice through the caudal vein to determine whether exosomes can play a palliative and therapeutic role in TAAD mice by delivering miR-4855p.Results:We successfully constructed a mouse TAAD model by BAPN administration.We found that intracellular dsDNA breaks and the expression of AIM2 in the thoracic aorta of TAAD mice were significantly higher than that of the control group.Western Blot analysis showed that the degree of ubiquitination of the activated AIM2 inflammasomes was significantly reduced.The co-immunoprecipitation results confirmed the binding between AIM2 and the deubiquitination enzyme USP21.This binding increased significantly after the activation of AIM2.AIM2 activation in VSMC was induced by Poly(dA:dT)in vitro.Western Blot and real-time quantitative PCR showed increased expressions of AIM2,Caspase-1,and GSDMD.ELISA showed increased release of the proinflammatory factors interleukin-(IL-)1β and IL-18 in Poly(dA:dT)-treated VSMC.After AIM2 silencing,PI staining showed that the incidence of pyroptosis in VSMC was significantly reduced.Dualluciferase assay demonstrated that miR-485-5p enriched in UMSC-Exo could bind to AIM2 and inhibit its expression.The expansion of the thoracic aortic arch of TAAD mice was reduced by injecting exosomes enriched in miR-485-5p into the tail vein of TAAD mice.We further showed that exosome treatment also inhibited pyroptosis of the thoracic aorta cells and reduced serum Matrix metalloproteinases 9(MMP9)content.However,these beneficial effects of UMSC-Exos were suppressed by silencing miR-485-5p.Conclusion:Increased expression and activation of AIM2 contribute to the development of TAAD by inducing vascular inflammation and aortic arch dilation.Activated AIM2 contributes to pyroptosis by recruiting USP21,which reduces AIM2 ubiquitination and stabilizes its protein levels.The high expression of miR-485-5p in exosomes can play an anti-inflammatory and protective role in the thoracic aorta by inhibiting the expression of AIM2.These findings provide new ideas for developing novel treatments for TAAD.