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Background Neutrophils play an integral role in atherogenesis yet are rarely detected within human plaques. Neutrophils release large-extracellular vesicles (NL-EVs), which adhere to atheroprone regions of endothelium and increase macrophage content and lipid staining within plaques. We hypothesise that NL-EVs induce lipid accumulation in macrophages, promoting foam cell formation.Methods NL-EVs were isolated from human neutrophils. To assess NL-EV transmigration, human coronary artery endothelial cells were cultured on transwell inserts with fluorescent NL-EVs layered above. After 24hr, permeating NL-EV were imaged and quantified. Internalisation was assessed by incubation of human monocyte-derived macrophages (HMDM) with fluorescent NL-EV (1-24hr) prior to quantification by flow cytometry. To determine the mechanism of NL-EV uptake, HMDM were pretreated with inhibitors of macropinocytosis (EIPA), actin polymerisation (Cytochalasin D), and protein interaction (Proteinase K) before addition of NL-EVs. The effect of NL-EVs on lipid handling was determined by staining with oil red O. HMDM were treated with NL-EV 24hr ahead of incubation with oxLDL for a further 24hr.Results NL-EVs crossed the endothelium in a dose-dependent manner. HMDM internalised NL-EVs, with percentage internalisation increasing over time. Inhibition of macropinocytosis, actin polymerisation, and protein interaction all reduced NL-EV internalisation by HMDM. NL-EV treatment increased HMDM lipid content.Conclusions NL-EVs can cross endothelial monolayers and are internalised by macrophages via multiple internalisation pathways. NL-EVs may impact macrophage lipid metabolism and promote foam cell formation. Further work is required to elucidate the mechanism by which NL-EVs may induce changes in macrophage lipid handling.