Abstract
BACKGROUND: Macrophages are key players in the pathogenesis of atherosclerosis. They trigger immune responses through their cell-surface receptors. However, how macrophages regulate those receptors in response to pro-inflammatory stimuli is not completely understood. Endocytic membrane trafficking involving receptor internalization, followed by endosomal transport and recycling of the internalized receptors, plays essential roles in balancing cell-surface receptors to meet cellular needs. Here, we explored the role of the endocytic regulator EHD1 in immune responses in macrophages and determined its contribution to atherosclerosis progression. METHODS: EHD1 expression profiles in mouse and human plaques were determined by single-cell RNA sequencing (scRNA-seq) and immunofluorescence staining. Bone marrow transplantation (BMT) by transplanting bone marrow cells from Ehd1 (-/-) or littermate wild-type mice to irradiated Ldlr (-/-) mice was performed to determine the effect of EHD1 deletion on atherosclerosis progression. In vitro mechanistic studies including inflammation signaling and endocytosis assays were performed in bone marrow-derived macrophages. RESULTS: EHD1 expression in macrophages is enhanced as atherosclerosis progresses in both mice and humans. Histological analysis of aortic root sections from BMT mice showed that EHD1 deletion reduces lesion size. ScRNA-seq of aortic CD45 (+) cells demonstrated that EHD1 deletion attenuates pro-inflammatory responses and cell-cell interactions. Mechanistic studies revealed that EHD1 accelerates the endocytic recycling of TNFR2 and activates NF-kB, leading to increased expression of inflammatory cytokines. Moreover, EHD1 interacts with retromer and stabilizes sortilin, a retrograde cargo of retromer and a risk factor for atherosclerosis. CONCLUSIONS: EHD1 promotes inflammation by enhancing TNFR2-NF-kB signaling and stabilizing sortilin, leading to accelerated atherosclerosis. Our study reveals novel roles for EHD1-mediated membrane trafficking in macrophage function and paves the way to innovative therapeutic strategies that aim to address dysregulated membrane trafficking in atherosclerosis.