Abstract 4363113: A Systems Biology–Driven Strategy to ‘Defat’ Lipid-Associated Macrophages and Reverse Atherosclerosis

Abstract

Introduction: Current atherosclerosis therapies like statins lower LDL cholesterol, but they do not reverse established plaques. Even with aggressive LDL-lowering, residual risk persists, driven in part by immunologic factors. A key player in these processes is lipid-associated macrophages (LAM), which accumulate lipids and drive inflammation and plaque instability. Despite their central role, LAM remain un-targetable and here we tackle their untapped therapeutic potential. Methods: We used a systems biology–driven network transcriptomics approach to identify key myeloid modulators of atherosclerosis. Computational analyses identified CCDC88A , which encodes the cAMP-inhibitor GIV, as a proatherogenic factor. This finding was validated by in vivo and in vitro studies. Our study includes two mouse models: myeloid-specific GIV knockout ( Mac GIV-KO) and ApoE-deficient Mac GIV-KO (n = 8–15, both sexes). Mice were on a Western diet for 12 wks; aortic plaque burden was assessed using Oil Red O staining. For in vitro study, murine peritoneal and THP1-derived macrophages were treated with oxLDL to assess LAM formation, cholesterol uptake/efflux and lipolysis. RNA-seq was used to identify genes in cholesterol metabolism and efflux. Translational relevance was assessed using human PBMCs and a small-molecule inhibitor targeting the GIV/cAMP pathway. Results: Compared to WT and ApoE-KO controls, GIV-KO reduces aortic plaque burden by 70% and 40%, respectively. Macrophage GIV deficiency inhibits LAM formation, increases cholesterol efflux and basal lipolysis, and is associated with increased mRNA expression of the ‘gatekeeper’ of reverse cholesterol transport (RCT) from peripheral tissues ( Abca1 ) and its transcriptional regulators (LXRα/β). Mechanistically, GIV activates Gαi/βγ proteins and inhibits a well-established anti-atherogenic cyclic AMP (cAMP). GIV binds and sequesters ABCA1 on the endomembrane, suppressing cholesterol efflux. GIV-KO raises cAMP levels, positions ABCA1 at the cell surface and unleashes its activity via a 2-pronged mechanism—both converging on the GIV/cAMP axis: (1) transcriptional activation (CREB), and (2) post-translational modulation via PKA. Small-molecule inhibitors of the GIV/cAMP axis reverse LAMs in both murine and human macrophages, where statins and β-blockers fail. Conclusion: This study reveals a therapeutic strategy to augment RCT via ABCA1, ‘defat’ LAM and regress plaques, offering a novel approach to treat advanced atherosclerosis.