通过靶向PI3Kγ特异抑制巨噬细胞趋化及极化而阻止腹主动脉瘤形成及进展的机制研究

Abdominal aortic aneurysm (AAA) is a common degenerative disease of the abdominal aorta that leads to its dilatation and to rupture. To date, no pharmacology strategy has been proven effective in limiting aneurysm progression or reducing risk of rupture. Accumulating evidence suggests that vascular inflammation is characterized by the increased infiltration of inflammatory cells into the vascular wall. Increasing evidence accumulated over recent years suggests an important regulatory role for Hypoxia-inducible factors (HIFs) in inflammation. Our previous experiments demonstrate the ability of the HIF1α inhibitor to both suppress experimental AAA initiation and stabilize existing aneurysms, through mechanisms likely related to impair mural macrophage infiltration and polariztion. These findings suggest that HIF1α inhibitor may hold substantial translational value for AAA diseases. However, the important physical function of HIF1α limits the use of HIF-1α inhibitor systemically in clinical. Our further investigation revealed that HIF1α located in macrophage and regulated by PI3K potentially during AAA progression. It is well document that PI3Kγ expressed mainly in myeloid cells. Importantly, there is a small molecule compound which inhibits PI3Kγspecially, named IPI-549, has been approved by PDA in clinical. ..Based on these observations, it is our FUNDAMENTAL HYPOTHESIS that PI3Kγ/HIF1α signal pathway takes as a pivotal role of modulating macrophage migration in progression of abdominal aortic aneurysm. To pursue this hypothesis, we proposed the following Specific Aims: ① Explore the possibility of inhibition AAA progression through targeting PI3Kγ, and evaluate the translational value of PI3Kγ in AAA treatment; ② Clarify the critical regulation of PI3Kγ to HIF1α in macrophages during AAA disease progression..In the present project, we will employ human AAA tissues, experimental AAA mice, and primary culture cells. Firstly, to quantify and locate PI3Kγ during human and experimental AAA disease progression; Then we will explore the possibility of inhibition AAA progression through targeting PI3Kγ; Furthermore, the critical regulation of PI3Kγ to HIF1α in macrophages mobilization and polarization during AAA disease will be investigated; Finally, IPI-549, a FDA-approved PI3Kγ inhibitor will be employed to limit the progression of aneurysm in experimental AAA mice to evaluate the translational value of PI3Kγ in AAA treatment. The result of our project is anticipated and will have translational potential for clinical AAA disease management.

巨噬细胞趋化和极化是腹主动脉瘤（AAA）形成及进展的关键因素。我们前期研究表明：巨噬细胞中HIF1α是治疗AAA的靶点；进一步发现HIF1α上游受PI3K调控。鉴于系统性抑制HIF1α或PI3K毒副作用大，为实现特异性抑制巨噬细胞中HIF1α而治疗AAA，我们巧妙地利用PI3K在巨噬细胞中主要为其γ亚型这一特征，原创性地假设：通过靶向PI3Kγ而特异抑制巨噬细胞中HIF1α来治疗AAA（详见第12页假说示意图）。在已获先期预实验证据支持的基础上，为进一步证实该假说并探讨其机制，本项目拟利用已有的材料和方法，从人体组织、动物模型、原代细胞三个不同层面，首先研究PI3Kγ在AAA的表达及分布；其次明确靶向PI3Kγ是否可抑制AAA；然后阐明特异靶向PI3Kγ抑制HIF1α调控巨噬细胞趋化及极化的具体机制；最后评价PI3Kγ治疗AAA的转化医学价值。本项目将为研发AAA的干预药物提供新的思路。

阐明腹主动脉瘤(AAA)的发病机制和干预靶点是AAA防治的关键和基础。本项目采用骨髓移植技术、体内荧光示踪、细胞和分子生物学技术以及免疫学等研究手段在多种AAA模型中系统阐述了PI3Kγ通过AKT/mTOR通路调控细胞自噬促进髓系炎症细胞浸润，最终介导AAA发生发展。研究发现，PI3Kγ在AAA外膜组织表达增加且和炎症浸润有关；经骨髓移植和谱系示踪手段确认，PI3Kγ增加主要来源于髓系炎症细胞；进一步在PPE灌注和AngII诱导的小鼠AAA模型中证实了PI3Kγ 参与小鼠AAA的发生发展，PI3Kγ敲除和药物抑制均有效抑制AAA及相关组织病理改变；骨髓移植实验表明AAA发生发展依赖于髓系细胞 PI3Kγ；机制上，体内外实验表明PI3Kγ的敲除通过AKT/mTOR通路增强细胞自噬，抑制小鼠髓系炎症细胞浸润、巨噬细胞趋化和极化；进一步利用自噬抑制剂氯喹在体内验证了PI3Kγ 通过自噬调控小鼠AAA发生发展；我们进一步探索发现，首款批准应用于临床的PI3Kγ 特异性抑制剂 IPI-549，可以有效延缓小鼠AAA进展和炎症浸润，为未来预防及治疗AAA提供了良好的临床应用前景。本研究首次揭示了PI3Kγ在AAA发病中的关键作用，为开发防治AAA的药物提供了新靶点和实验基础。