Abstract 329: Systems-based Target Discovery Reveals PPARa as a Key Metabolic Regulator for Macrophage Activation in Vein Graft Disease

Abstract

Objectives: Vein graft (VG) failure rates after surgical bypass for PAD remain high, which can cause limb loss. Yet, the underlying mechanisms for VG lesion development remain obscure. We took a systems approach to explore key pathways in a mouse model. Approach and Results: We implanted the inferior vena cava into the left carotid artery of fat-fed Ldlr-/- mice and monitored lesion development up to 4 weeks post-surgery. Unbiased proteomic profiling followed by hierarchical clustering showed distinct clusters. One protein cluster is decreased in vein grafts with overt lesions (poor outcome) relative to the group of non-diseased veins devoid of lesions and vein grafts with minimal lesion (favorable outcome). Conversely, this can be viewed as increased in the “favorable” outcome group. Using the “favorable outcome” predominant protein cluster, network analysis and pathway enrichment identified PPARα pathway as a top-ranked key hub node with high betweeness centrality measure. This implies that PPARα may play a key regulatory role in limiting lesion severity. We examined whether network-based prediction of PPARα can also serve as a therapeutic target to attenuate the development of experimental VG lesions. A blinded in vivo loss-of-function study using PPARα siRNA encapsulated in macrophage-targeted lipid nanoparticles (LNP) demonstrated higher plaque volume as seen by 3D ultrasound and histologic morphometry in the test group (n=7) versus the control group (n=8). In contrast, a randomized drug study on another set of VG mice using the new PPARα-selective agonist pemafibrate demonstrated less plaque lesions and macrophage accumulation in the drug group (n=11) compared to the control group (n=11). In vitro validation studies (alongside loss-of-function) including high-throughput qPCR, single cell qPCR, CyTOF, ELISA, FACS, and metabolic assays all suggested that pemafibrate-induced PPARα activation promotes a phenotype shift of activated macrophages into a less inflammatory state through metabolic reprogramming. Conclusion: Systems-based target discovery on VG demonstrates that PPARα agonism reduces lesion development and inflammatory burden. Targeting this pathway might furnish a novel therapeutic option to prevent VG lesion development.