Phagocytosis of apoptotic bodies by liver endothelial cells

Abstract

Using electron microscopy and cytofluorimetry we studied the role of carbohydrate-specific recognition systems in the interaction of apoptotic bodies with normal and interleukin 1-activated sinusoidal endothelial cells. Microfluorimetric observation of liver tissue sections revealed octadecylrhodamine B-labelled apoptotic body binding to the sinusoidal wall of mouse liver, when they were injected intraportally. Plate-scanning cytofluorimetry demonstrated that about 20–25% of Acridine Orange-labelled apoptotic bodies could adhere specifically to cultured endothelial cells after 15 minutes of incubation. Adhesion increased to 30% when the cells were incubated for 60 minutes. Using a mixture of galactose/N-acetylglucosamine/mannose as competition solution apoptotic body adhesion was significantly reduced especially after longer times of incubation, when the percentage of inhibition reached 50%. Following 4 hours exposure of liver endothelial cells to 1 ng/ml human recombinant interleukin-1 beta adhesion markedly increased after 60 minutes of incubation, whereas the co-incubation of interleukin-1 beta with the inhibitors brings down the adhesion to basal values obtained in controls. Electron microscopic observation of the adhesion process showed that the number of endothelial cells binding apoptotic bodies gradually increased from low to high values with time. After 60 minutes of incubation, the majority of apoptotic bodies were seen inside phagosomes and only a few remained at the cell surface. Liver endothelial cells bound and endocytosed apoptotic bodies through carbohydrate-specific receptors. Moreover, this scavenger action was interleukin-1 enhanced, thus suggesting its possible activation during inflammatory and immune processes.

Immunomodulation by endothelial cells — partnering up with the immune system?

“…In addition, a combined single-cell RNA sequencing (scRNA-seq) and single-cell assay for transposase-accessible chromatin sequencing study identified an "immune cells (for example, they have been shown to kill ovarian tumour-homing cytotoxic T cells via FAS ligand (FASL) in human co-cultures and mice 12 ), secretion of cytokines and their acting as (semi-professional) antigen-presenting cells (APCs). They can also act as phagocytes and scavengers of circulating waste macromolecules and participate in efferocytosis 4,[11][12][13][14] . Notably, immunomodulation by ECs can be influenced by cytokines, such as interleukin-35 (IL-35) 15 and IL-17A 16 .…”

Leishmania Promastigotes Enhance Neutrophil Recruitment through the Production of CXCL8 by Endothelial Cells

“…To investigate the mechanisms by which Leishmania promastigotes induce the production of CXCL8 by HMEC-1, the role of phagocytosis and of TLR4 receptor was investigated. Although endothelial cells are non-professional phagocytes, they can internalize apoptotic neutrophils, apoptotic bodies, platelets and pathogens such as Listeria monocytogenes [30][31][32][33].…”

Opinion: Endothelial Cells - Macrophage-Like Gatekeepers?

“…Dini et al. reported that 60 minutes after co-incubating liver ECs with apoptotic cells, the majority of apoptotic bodies were seen inside EC phagosomes and only a few remained at the cell surface ( 3 ). Another study by Xie et al.…”

“…More interestingly, ECs and macrophages share evolutionarily conserved defense mechanisms such as phagocytosis and autophagy ( 8 , 9 ). Macrophages are considered professional phagocytes and are highly specialized in the detection and removal of pathogens, apoptotic cells, and cell debris ( 3 , 10 ). Additionally, macrophages are classical immune cells and play important roles in the innate immune system ( 11 ).…”