Hematopoietic PI3Kγ promotes abdominal aortic aneurysm by orchestrating macrophage trafficking.

Abstract

BACKGROUND AND PURPOSE: Abdominal aortic aneurysm (AAA) is characterized by progressive aortic dilation, often driven by chronic inflammation. PI3Kγ, predominantly expressed in myeloid cells, plays a pivotal role in mediating inflammatory responses in various cardiovascular conditions. This study aimed to investigate whether, and through which mechanisms, PI3Kγ promotes AAA progression. METHODS: Wild type, PI3Kγ-knockout and reciprocal bone marrow-transferred mice were used in elastase- or angiotensin II -induced AAA. Macrophage migration and recruitment were assessed by in vivo migration, peritoneal recruitment, and transwell assays. Additionally, in vitro studies using bone marrow-derived macrophages (BMDMs) were conducted to investigate the impact of PI3Kγ on autophagic flux and macrophage migration. Immunoprecipitation followed by ubiquitination immunoblotting was used to explore the association of MLC-containing complexes with ubiquitin signaling and p62-mediated selective autophagy recognition. RESULTS: PI3Kγ was upregulated in macrophage-rich regions of the aneurysmal aorta at early stages of AAA. PI3Kγ deficiency suppressed experimental AAA, reduced elastin destruction and alleviated hematopoietic cell infiltration by attenuating monocytes migration. Bone marrow transplantation experiments confirmed that hematopoietic PI3Kγ is essential for AAA formation and progression. Mechanistically, PI3Kγ inhibition suppressed short-term macrophage migration by enhancing MLCK ubiquitination and reduced MLC phosphorylation. PI3Kγ inhibition also promoted autophagic degradation of MLC, resulting in impaired long-term macrophage migratory persistence. Furthermore, autophagy inhibition abolished the protective effects of PI3Kγ deficiency, supporting a critical role for PI3Kγ in the dynamic regulation of MLC through ubiquitin-regulated MLCK turnover and p62-dependent selective autophagy. CONCLUSION AND IMPLICATIONS: Hematopoietic PI3Kγ mediates experimental AAA pathogenesis by modulating macrophage migration through ubiquitin-regulated MLCK turnover and autophagic degradation of MLC. Thus, pharmacological PI3Kγ inhibition may represent a potential therapeutic strategy for treating clinical AAA disease.