PCSK9 inhibition in myeloid cells enhances cardioprotection beyond its LDL cholesterol-lowering effects

Abstract

BACKGROUND: Circulating levels of proprotein convertase subtilisin/kexin type 9 (PCSK9), which regulates plasma cholesterol content by degrading LDL receptor, are correlated with the risk of acute myocardial infarction (AMI). Recent studies suggested that PCSK9 improves cardiac function beyond its effects on LDL cholesterol levels after cardiac ischemic injury, but its precise mechanism remains unclear. METHODS: We examined the interrelationship and functional significance of PCSK9 and cardiac myeloid cells in ischemic hearts from AMI-induced Pcsk9-/- and Lyz2crePcsk9fl/fl mice, as well as in serum samples from coronary artery disease (CAD) patients treated with PCSK9 antibodies (Ab). Single-cell RNA sequencing (scRNA-seq) was conducted to identify heterogenous cardiac macrophage clusters and to investigate the impact of adaptive remodeling due to PCSK9 deficiency during AMI. Additionally, the regulatory effect of the myeloid-PCSK9/VEGF-C pathway was assessed in vitro as a potential therapeutic strategy. RESULTS: Our study demonstrated that PCSK9 deficiency induces diverse changes in myeloid cells and macrophages, potentially offering cardiac protection following AMI, irrespective of LDL cholesterol homeostasis. The scRNA-seq identified a subset of PCSK9-dependent cardiac macrophages (PDCMs) enriched in activator protein-1 (AP-1)?related pathways, functioning as reparative macrophages. These PDCMs were shown to enhance vascular endothelial growth factor C (VEGF-C) secretion and activate Akt signaling in cardiac endothelial cells, leading to improved cardiac remodeling. Notably, CAD patients treated with PCSK9 inhibitors exhibited increased numbers of myeloid cells with PDCM-like features, including elevated VEGF-C levels, consistent with our findings in mice. COUNCLUSIONS: Targeting PCSK9 in myeloid cells could offer cardioprotective effects by increasing AP-1 activity and VEGF-C expression of PDCMs, presenting a novel approach to preventing cardiac dysfunction in AMI. This strategy could expand the clinical use of existing PCSK9 inhibitors beyond just lowering LDL cholesterol. Key Words: coronary artery disease, lipid homeostasis, PCSK9 inhibitors, cardiac macrophages, activator protein-1, vascular endothelial growth factor C