Red Blood Cells Play a Role in Reverse Cholesterol Transport

Abstract Lecithin:cholesterol acyl transferase (LCAT)-dependent conversion of cholesterol (CH) to cholesteryl ester (CE), a key component of the reverse cholesterol transport (RCT) pathway, is essential for cholesterol processing. We hypothesized that red blood cells (RBCs) function in this pathway by facilitating phosphatidylcholine (PC) re-generation from LCAT-derived lysophosphatidylcholine (LPC). Addition of 14C-oleate to fresh RBCs resulted in an ATP-dependent incorporation of radiolabel into PC via the Lands pathway. Prior depletion of red cell LPC content reduced the incorporation of 14C-oleate into PC, which was restored by the addition of LPC. Reconstituted PC/cholesterol/apolipoprotein A-I (apoA-I) high-density lipoprotein (rHDL) was used as substrate for LCAT dependent conversion of CH to CE. Addition of LPC to this reaction mix inhibited CE production. The inhibition was overcome, however, by inclusion of RBCs, suggesting rHDL-generated LPC migration to RBCs. RBCs depleted of LPC increased their ability to generate 14C-PC from 14C-oleate in the presence of rHDL with LCAT, indicating that LCAT-derived LPC can be utilized as a substrate for PC production in RBCs. Radio-labeled CH associated with RBCs was recovered as CE only when rHDL substrate and LCAT were present, indicating RBC-associated CH migration to rHDL. When RBCs containing 14C-PC were incubated with rHDL and LCAT, PC transferred from RBCs to the rHDL particles. The interaction of apoA-I with the membrane lipid transporter ATP-Binding Cassette A1 protein (ABCA1) in cell membranes has been shown to play an essential role in the formation of HDL and facilitates RCT. Using monoclonal antibodies, we were able to show that RBCs contain ABCA7, closely related to ABCA1. Our data show that fluorescently labeled apoA-I binds to RBCs, suggesting that the interaction between ABCA7 and apoA-I may be important for HDL/RBC interaction. Together, our data supports an active role for RBCs, the major cell type in blood, in LCAT-mediated lipoprotein remodeling. Thus, RBCs represent a hitherto underappreciated component of the RCT pathway.

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Red blood cells participate in reverse cholesterol transport by mediating cholesterol efflux of high-density lipoprotein and apolipoprotein A-I from THP-1 macrophages

Biological Chemistry ◽

10.1515/hsz-2019-0244 ◽

2019 ◽

Vol 400 (12) ◽

pp. 1593-1602 ◽

Cited By ~ 1

Author(s):

Shao-Jui Lai ◽

Ryunosuke Ohkawa ◽

Yuna Horiuchi ◽

Tetsuo Kubota ◽

Minoru Tozuka

Keyword(s):

High Density Lipoprotein ◽

Red Blood Cells ◽

Blood Cells ◽

Reverse Cholesterol Transport ◽

Cholesterol Efflux ◽

Density Lipoprotein ◽

High Density ◽

Cholesterol Transport ◽

Main Role ◽

Apolipoprotein A

Abstract High-density lipoprotein (HDL) plays a main role in reverse cholesterol transport (RCT), one of the most important functions for preventing atherosclerosis. Recent reports have shown that red blood cells (RBCs) can be associated with RCT, an interaction facilitated by albumin. However, the RCT function of RBCs has not been thoroughly elucidated. In this study, the RCT function of RBCs was assessed using cholesterol efflux capacity (CEC) assays, in which [3H]-labeled cholesterol-loaded human acute monocytic leukemia (THP-1) macrophages were incubated with RBCs as a cholesterol acceptor in the presence or absence of HDL or its main component protein apolipoprotein A-I (apoA-I). The CEC of RBCs was found to be dose dependent, enabling uptake of cholesterol from THP-1 macrophages through apoA-I and HDL, and directly from apoA-I and HDL in medium without the presence THP-1 macrophages. Moreover, RBCs could exchange cholesterol with HDL in a bidirectional manner but could only exchange cholesterol with apoA-I in a single direction. Although albumin promoted the movement of cholesterol, synergistic effects were not observed for both apoA-I and HDL, in contrast to previous findings. These results strongly suggested that RBCs may play important roles in RCT by mediating cholesterol efflux as temporary cholesterol storage.

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Cholesterol transport between red blood cells and lipoproteins contributes to cholesterol metabolism in blood

The Journal of Lipid Research ◽

10.1194/jlr.ra120000635 ◽

2020 ◽

Vol 61 (12) ◽

pp. 1577-1588

Author(s):

Ryunosuke Ohkawa ◽

Hann Low ◽

Nigora Mukhamedova ◽

Ying Fu ◽

Shao-Jui Lai ◽

...

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Cholesterol Efflux ◽

Cholesterol Metabolism ◽

Plasma Cholesterol ◽

Translocator Protein ◽

Plasma Lipoproteins ◽

Cholesterol Transport ◽

Autologous Plasma

Lipoproteins play a key role in transport of cholesterol to and from tissues. Recent studies have also demonstrated that red blood cells (RBCs), which carry large quantities of free cholesterol in their membrane, play an important role in reverse cholesterol transport. However, the exact role of RBCs in systemic cholesterol metabolism is poorly understood. RBCs were incubated with autologous plasma or isolated lipoproteins resulting in a significant net amount of cholesterol moved from RBCs to HDL, while cholesterol from LDL moved in the opposite direction. Furthermore, the bi-directional cholesterol transport between RBCs and plasma lipoproteins was saturable and temperature-, energy-, and time-dependent, consistent with an active process. We did not find LDLR, ABCG1, or scavenger receptor class B type 1 in RBCs but found a substantial amount of ABCA1 mRNA and protein. However, specific cholesterol efflux from RBCs to isolated apoA-I was negligible, and ABCA1 silencing with siRNA or inhibition with vanadate and Probucol did not inhibit the efflux to apoA-I, HDL, or plasma. Cholesterol efflux from and cholesterol uptake by RBCs from Abca1+/+ and Abca1−/− mice were similar, arguing against the role of ABCA1 in cholesterol flux between RBCs and lipoproteins. Bioinformatics analysis identified ABCA7, ABCG5, lipoprotein lipase, and mitochondrial translocator protein as possible candidates that may mediate the cholesterol flux. Together, these results suggest that RBCs actively participate in cholesterol transport in the blood, but the role of cholesterol transporters in RBCs remains uncertain.

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Hemoglobin crystals of the red blood cells in the human renal cortex: electron microscopic observations of the renal lithiasis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100083266 ◽

1978 ◽

Vol 36 (2) ◽

pp. 480-481

Author(s):

Kosuke Ueda ◽

Hiroto Washida ◽

Nakazo Watari

Keyword(s):

Red Blood Cells ◽

Blood Cells ◽

Renal Cortex ◽

Uranyl Acetate ◽

Osmic Acid ◽

Renal Lithiasis ◽

Electron Microscopic ◽

Hemoglobin C ◽

First Case ◽

Ultrathin Sections

IntroductionHemoglobin crystals in the red blood cells were electronmicroscopically reported by Fawcett in the cat myocardium. In the human, Lessin revealed crystal-containing cells in the periphral blood of hemoglobin C disease patients. We found the hemoglobin crystals and its agglutination in the erythrocytes in the renal cortex of the human renal lithiasis, and these patients had no hematological abnormalities or other diseases out of the renal lithiasis. Hemoglobin crystals in the human erythrocytes were confirmed to be the first case in the kidney.Material and MethodsTen cases of the human renal biopsies were performed on the operations of the seven pyelolithotomies and three ureterolithotomies. The each specimens were primarily fixed in cacodylate buffered 3. 0% glutaraldehyde and post fixed in osmic acid, dehydrated in graded concentrations of ethanol, and then embedded in Epon 812. Ultrathin sections, cut on LKB microtome, were doubly stained with uranyl acetate and lead citrate.

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Densitometric Identification of Primitive Erythroblasts After Reaction With Diaminobenzidine

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100072083 ◽

1973 ◽

Vol 31 ◽

pp. 328-329

Author(s):

John A. Trotter

Keyword(s):

Red Blood Cells ◽

Analytical Method ◽

Blood Cells ◽

Guinea Pigs ◽

Specific Protein ◽

Visual Examination ◽

Hemoglobin Synthesis ◽

Peroxidatic Activity ◽

Small Density

Hemoglobin is the specific protein of red blood cells. Those cells in which hemoglobin synthesis is initiated are the earliest cells that can presently be considered to be committed to erythropoiesis. In order to identify such early cells electron microscopically, we have made use of the peroxidatic activity of hemoglobin by reacting the marrow of erythropoietically stimulated guinea pigs with diaminobenzidine (DAB). The reaction product appeared as a diffuse and amorphous electron opacity throughout the cytoplasm of reactive cells. The detection of small density increases of such a diffuse nature required an analytical method more sensitive and reliable than the visual examination of micrographs. A procedure was therefore devised for the evaluation of micrographs (negatives) with a densitometer (Weston Photographic Analyzer).

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Scanning electron microscopy of erythrophagocytosis by Entamoeba histolytica trophozoites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012480x ◽

1992 ◽

Vol 50 (1) ◽

pp. 880-881

Author(s):

Victor Tsutsumi ◽

Adolfo Martinez-Palomo ◽

Kyuichi Tanikawa

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Red Blood Cells ◽

Entamoeba Histolytica ◽

Causative Agent ◽

Blood Cells ◽

Protozoan Parasite ◽

Complex Phenomenon ◽

Great Capacity ◽

Scanning Electron

The protozoan parasite Entamoeba histolytica is the causative agent of amebiasis in man. The trophozoite or motile form is a highly dynamic and pleomorphic cell with a great capacity to destroy tissues. Moreover, the parasite has the singular ability to phagocytize a variety of different live or death cells. Phagocytosis of red blood cells by E. histolytica trophozoites is a complex phenomenon related with amebic pathogenicity and nutrition.

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Ultrastructural observations on the in vitro cytoadherence of Plasmodium falciparum infected red blood cells

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100162132 ◽

1990 ◽

Vol 48 (3) ◽

pp. 914-915

Author(s):

D.J.P. Ferguson ◽

A.R. Berendt ◽

J. Tansey ◽

K. Marsh ◽

C.I. Newbold

Keyword(s):

Plasmodium Falciparum ◽

Red Blood Cells ◽

Blood Cells ◽

Umbilical Vein ◽

Cell Types ◽

Amelanotic Melanoma ◽

Cytoplasmic Process ◽

Umbilical Vein Endothelial Cells

In human malaria, the most serious clinical manifestation is cerebral malaria (CM) due to infection with Plasmodium falciparum. The pathology of CM is thought to relate to the fact that red blood cells containing mature forms of the parasite (PRBC) cytoadhere or sequester to post capillary venules of various tissues including the brain. This in vivo phenomenon has been studied in vitro by examining the cytoadherence of PRBCs to various cell types and purified proteins. To date, three Ijiost receptor molecules have been identified; CD36, ICAM-1 and thrombospondin. The specific changes in the PRBC membrane which mediate cytoadherence are less well understood, but they include the sub-membranous deposition of electron-dense material resulting in surface deformations called knobs. Knobs were thought to be essential for cytoadherence, lput recent work has shown that certain knob-negative (K-) lines can cytoadhere. In the present study, we have used electron microscopy to re-examine the interactions between K+ PRBCs and both C32 amelanotic melanoma cells and human umbilical vein endothelial cells (HUVEC).We confirm previous data demonstrating that C32 cells possess numerous microvilli which adhere to the PRBC, mainly via the knobs (Fig. 1). In contrast, the HUVEC were relatively smooth and the PRBCs appeared partially flattened onto the cell surface (Fig. 2). Furthermore, many of the PRBCs exhibited an invagination of the limiting membrane in the attachment zone, often containing a cytoplasmic process from the endothelial cell (Fig. 2).

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