An investigation by electron microscopy of chylomicron remnant uptake by human monocyte-derived macrophages

• Published in: Atherosclerosis Vol. 188; no. 2; pp. 251 - 259
• Main Authors: Elsegood, Caryn L., Mamo, John C.L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ireland Ltd 01.10.2006; Elsevier
• Subjects: Atherosclerosis (general aspects, experimental research); Biological and medical sciences; Biological Transport - physiology; Blood and lymphatic vessels; Blood vessels and receptors; Cardiology. Vascular system; Cardiovascular system; Cell Membrane Structures - metabolism; Cell Membrane Structures - ultrastructure; Chylomicron remnant; Chylomicron Remnants - ultrastructure; Endocytosis; Fundamental and applied biological sciences. Psychology; Gold Colloid; Human monocyte-macrophage; Humans; Macrophages - metabolism; Medical sciences; Microscopy, Electron, Transmission; Non-clathrin coated; Pharmacology. Drug treatments; Surface-connected compartment; Transport Vesicles - metabolism; Transport Vesicles - ultrastructure; Vasodilator agents. Cerebral vasodilators; Vertebrates: cardiovascular system; Surface-connected compartment; HMM; Endocytosis; Chylomicron remnant; Human monocyte-macrophage; Non-clathrin coated; Human; Monocyte; Cardiovascular disease; Lipoprotein; Electron microscopy; Uptake; Vascular disease; Chylomicron; Transmission electron microscopy; Ultrastructure; Atherosclerosis; Affinity; Phagocytosis; Macrophage
• ISSN: 0021-9150; 1879-1484
• DOI: 10.1016/j.atherosclerosis.2005.10.043

Human monocyte-derived macrophages (HMM) internalise proatherogenic chylomicron remnants via several high affinity receptor pathways. However, the endocytic ultrastructures responsible for the uptake of chylomicron remnants by macrophages have not previously been described. In this study, we have utilised transmission electron microscopy together with colloidal gold-labelling of chylomicron remnants to investigate the pathways involved in macrophage uptake of chylomicron remnants. We found that macrophages internalise chylomicron remnants via surface-connected compartments of up to 600 nm as well as non-clathrin coated pits. Chylomicron remnants were found to be distributed internally in a number of endocytic vesicles including early cysternal endosomes, spherical late endosomes and tubular vesicular compartments. Uptake of chylomicron remnants by HMM via phagocytosis or macropinocytosis was excluded based on the observations that lipoproteins were not found in phagolysosomes nor modified by inhibitors of these two processes, respectively. The latter observation contrasts with previous reports of chylomicron remnant internalisation by macrophages of other species.