The Roles And Mechanisms Of Macrophage-Derived Interferon Regulatory Factor 5 And Exosomes In Pathogenesis Of Abdominal Aortic Aneurysm

Part ? The role and mechanisms of macrophage-derived interferon regulatory factor 5 in pathogenesis of abdominal aortic aneurysmBackground:Abdominal aortic aneurysm(AAA)is a chronic inflammatory disease characterized by the expansion of the aortic wall.Macrophages are important inflammatory cells during AAA development.Interferon regulatory factor 5(IRF5)is a potent regulator of macrophage function.The role of macrophage-derived IRF5 in macrophage infiltration and AAA formation remains unknown.Methods and results:RNA sequencing of AAA adventitia identified IRF5 was significantly increased in elastase-induced AAA.Immunofluorescence staining and western blot confirmed that IRF5 was significantly increased in human and elastase-induced AAA tissues,and mainly localized in macrophages.Global and myeloid specific deficiency of IRF5 reduced AAA progression,with preserved elastin integrity and marked reduction of macrophage infiltration.Further cellular investigations indicated that IRF5 promoted macrophage migration,and RNA sequencing indicated that this effect was mediated by phosphoinositide 3-kinase gamma(PI3K?).Mechanistic studies by chromatin immunoprecipitation(Ch IP)and luciferase reporter assay demonstrated that IRF5 can directly bind promoter region of PI3K? to regulate PI3K? expression in macrophages.PI3K? ablation hindered elastase-induced AAA progression,accompanied by decreased macrophage infiltration.However,myeloid-specific salvage of PI3K? in myeloid specific IRF5 deficiency mice restored AAA progression and promoted macrophage infiltration.Conclusions:These findings first uncovered that the IRF5-dependent regulation of PI3K? is essential for macrophage migration and subsequent AAA formation.IRF5-PI3K? pathway in macrophages was a potential target for AAA treatment in the future.Part ? Involvement of macrophage-derived exosomes in abdominal aortic aneurysm developmentBackground:Exosomes mediate intercellular communication and are involved in different diseases.Whether exosomes play a role in AAA is poorly understood.Methods and results:Immunofluorescence staining of exosomal markers,CD63 and Alix,in human and calcium phosphate(Ca PO4)-induced AAA tissues revealed that exosomes were detected in the adventitia of aneurysmal tissues,and mainly expressed in clusters of macrophages.GW4869,an inhibitor of exosome biogenesis,was intraperitoneally injected into Ca PO4-induced AAA for two weeks.GW4869 significantly attenuated the AAA progression,preserved elastin integrity and decreased MMP-2 expression.Similarly,administration of GW4869 suppressed the systemic and aneurysmal exosome generation.The human monocytic cell line THP-1 was differentiated into macrophages,and exosomes were collected from macrophages.Treatment with macrophage-derived exosomes elevated MMP-2 expression in human aortic smooth muscle cells(Ao SMCs)?In inflammatory environments,THP-1-derived macrophages cocultured with human Ao SMCs facilitated MMP-2 levels in Ao SMCs.However,macrophages with GW4869 pretreatment abolished the effects.The activation of mitogen-activated protein kinases(MAPKs)pathways was observed in Ao SMCs treated with macrophage-derived exosomes.It was also found that JNK and p38 pathways were responsible for production of MMP-2.Conclusions:This study suggests that exosomes derived from macrophages are involved in the pathogenesis of AAA.Macrophage-derived exosomes trigger MMP-2 expression in VSMC via JNK and p38 pathways.