scholarly journals Quantitative role of parenchymal and non-parenchymal liver cells in the uptake of [14C]sucrose-labelled low-density lipoprotein in vivo

1984 ◽  
Vol 224 (1) ◽  
pp. 21-27 ◽  
Author(s):  
L Harkes ◽  
J C Van Berkel
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cell Types ◽  
Liver Cells ◽  
Low Density ◽  
Apo B ◽  
Parenchymal Liver ◽  
Ldl Uptake ◽  
Parenchymal Cells

In order to assess the relative importance of the receptor for low-density lipoprotein (LDL) (apo-B,E receptor) in the various liver cell types for the catabolism of lipoproteins in vivo, human LDL was labelled with [14C]sucrose. Up to 4.5h after intravenous injection, [14C]sucrose becomes associated with liver almost linearly with time. During this time the liver is responsible for 70-80% of the removal of LDL from blood. A comparison of the uptake of [14C]sucrose-labelled LDL and reductive-methylated [14C]sucrose-labelled LDL ([14C]sucrose-labelled Me-LDL) by the liver shows that methylation leads to a 65% decrease of the LDL uptake. This indicated that 65% of the LDL uptake by liver is mediated by a specific apo-B,E receptor. Parenchymal and non-parenchymal liver cells were isolated at various times after intravenous injection of [14C]sucrose-labelled LDL and [14C]sucrose-labelled Me-LDL. Non-parenchymal liver cells accumulate at least 60 times as much [14C]sucrose-labelled LDL than do parenchymal cells accumulate at least 60 times as much [14C]sucrose-labelled LDL than do parenchymal cells when expressed per mg of cell protein. This factor is independent of the time after injection of LDL. Taking into account the relative protein contribution of the various liver cell types to the total liver, it can be calculated that non-parenchymal cells are responsible for 71% of the total liver uptake of [14C]sucrose-labelled LDL. A comparison of the cellular uptake of [14C]sucrose-labelled LDL and [14C]sucrose-labelled Me-LDL after 4.5h circulation indicates that 79% of the uptake of LDL by non-parenchymal cells is receptor-dependent. With parenchymal cells no significant difference in uptake between [14C]sucrose-labelled LDL and [14C]sucrose-labelled Me-LDL was found. A further separation of the nonparenchymal cells into Kupffer and endothelial cells by centrifugal elutriation shows that within the non-parenchymal-cell preparation solely the Kupffer cells are responsible for the receptor-dependent uptake of LDL. It is concluded that in rats the Kupffer cell is the main cell type responsible for the receptor-dependent catabolism of lipoproteins containing only apolipoprotein B.

scholarly journals Processing of acetylated human low-density lipoprotein by parenchymal and non-parenchymal liver cells. Involvement of calmodulin?

1982 ◽  
Vol 208 (2) ◽  
pp. 493-503 ◽  
Author(s):  
Theo J. C. Van Berkel ◽  
Jan F. Nagelkerke ◽  
Leen Harkes ◽  
Johan K. Kruijt
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Liver Cells ◽  
Cell Protein ◽  
Low Density ◽  
Calmodulin Inhibitors ◽  
Parenchymal Liver ◽  
Modified Lipoproteins ◽  
Parenchymal Cells

1. Modified lipoproteins have been implicated to play a significant role in the pathogenesis of atherosclerosis. In view of this we studied the fate and mechanism of uptake in vivo of acetylated human low-density lipoprotein (acetyl-LDL). Injected intravenously into rats, acetyl-LDL is rapidly cleared from the blood. At 10min after intravenous injection, 83% of the injected dose is recovered in liver. Separation of the liver into a parenchymal and non-parenchymal cell fraction indicates that the non-parenchymal cells contain a 30–50-fold higher amount of radioactivity per mg of cell protein than the parenchymal cells. 2. When incubated in vitro, freshly isolated non-parenchymal cells show a cell-association of acetyl-LDL that is 13-fold higher per mg of cell protein than with parenchymal cells, and the degradation of acetyl-LDL is 50-fold higher. The degradation of acetyl-LDL by both cell types is blocked by chloroquine (10–50μm) and NH4Cl (10mm), indicating that it occurs in the lysosomes. Competition experiments indicate the presence of a specific acetyl-LDL receptor and degradation pathway, which is different from that for native LDL. 3. Degradation of acetyl-LDL by non-parenchymal cells is completely blocked by trifluoperazine, penfluridol and chlorpromazine with a relative effectivity that corresponds to their effectivity as calmodulin inhibitors. The high-affinity degradation of human LDL is also blocked by trifluoperazine (100μm). The inhibition of the processing of acetyl-LDL occurs at a site after the binding-internalization process and before intralysosomal degradation. It is suggested that calmodulin, or a target with a similar sensitivity to calmodulin inhibitors, is involved in the transport of the endocytosed acetyl-LDL to or into the lysosomes. 4. It is concluded that the liver, and in particular non-parenchymal liver cells, are in vivo the major site for acetyl-LDL uptake. This efficient uptake and degradation mechanism for acetyl-LDL in the liver might form in vivo the major protection system against the potential pathogenic action of modified lipoproteins.

scholarly journals Characterization of the low-density-lipoprotein-receptor-independent interaction of β-very-low-density lipoprotein with rat and human parenchymal liver cells in vitro

1992 ◽  
Vol 282 (1) ◽  
pp. 41-48 ◽  
Author(s):  
R De Water ◽  
J A A M Kamps ◽  
M C M Van Dijk ◽  
E A M J Hessels ◽  
J Kuiper ◽  
...  
Keyword(s):  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Liver Cells ◽  
Recognition Site ◽  
Low Density ◽  
Hep G2 ◽  
Hep G2 Cells ◽  
Parenchymal Liver ◽  
Parenchymal Cells

beta-Migrating very-low-density lipoprotein (beta-VLDL) is a cholesteryl-ester-enriched lipoprotein which under normal conditions is rapidly cleared by parenchymal liver cells. In this study the characteristics of the interaction of beta-VLDL with rat parenchymal cells, Hep G2 cells and human parenchymal cells are evaluated. The binding of beta-VLDL to these cells follows saturation kinetics (Bmax. respectively 117, 106 and 103 ng of beta-VLDL apoliprotein/mg of cell protein), with a relatively high affinity (Kd respectively for beta-VLDL of 10.7, 5.1 and 8.4 micrograms/ml). Competition studies of unlabelled beta-VLDL, low-density lipoprotein (LDL) or acetylated LDL with the binding of radiolabelled beta-VLDL indicate that a LDL-receptor-independent, Ca(2+)-independent, specific recognition site for beta-VLDL is present on rat and human parenchymal cells, whereas with Hep G2 cells or mouse macrophages beta-VLDL recognition is performed by the LDL receptor. The binding of beta-VLDL to Hep G2 cells was down-regulated by 89% by prolonged exposure to beta-VLDL, whereas for human parenchymal and rat parenchymal cells down-regulation of 44% and 20% respectively was observed. Studies with antibodies against the LDL receptor support the presence of a LDL-receptor-independent specific beta-VLDL recognition site on rat and human parenchymal cells. It is concluded that a LDL-receptor-independent recognition site for beta-VLDL is present on rat and human parenchymal liver cells. The presence of a LDL-receptor-independent recognition site on human parenchymal cells may mediate in vivo the uptake of beta-VLDL during consumption of a cholesterol-rich diet, when LDL receptors are down-regulated, thus protecting against the extrahepatic accumulation of the atherogenic beta-VLDL constituents.

scholarly journals Recognition of lactoferrin and aminopeptidase M-modified lactoferrin by the liver: involvement of proteoglycans and the remnant receptor

1996 ◽  
Vol 313 (1) ◽  
pp. 289-295 ◽  
Author(s):  
Gijsbertus J. ZIERE ◽  
J. Kar KRUIJT ◽  
Martin K. BIJSTERBOSCH ◽  
Theo J. C. van BERKEL
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Liver Cells ◽  
Recognition Site ◽  
Low Density ◽  
Liver Uptake ◽  
Aminopeptidase M ◽  
Parenchymal Liver ◽  
Parenchymal Cells ◽  
Initial Binding

1. Lactoferrin and aminopeptidase M-modified lactoferrin (APM-lactoferrin; which lacks its 14 N-terminal amino acids) inhibit the liver uptake of lipoprotein remnants. In the present study, the role of proteoglycans in the initial interaction of β-migrating very-low-density lipoprotein (β-VLDL), native and APM-lactoferrin with isolated rat parenchymal liver cells was investigated. Treatment of the cells with chondroitinase lowered the Kd of lactoferrin binding (from 10 to 2.4 μM), and the number of sites/cell (from 20×106 to 7×106), while heparinase treatment did not affect the binding. The binding characteristics of APM-lactoferrin and β-VLDL were not altered by treatment of the cells with chondroitinase or heparinase. It is concluded that proteoglycans are not involved in the initial binding of APM-lactoferrin and β-VLDL to parenchymal cells, while chondroitin sulphate proteoglycans are mainly responsible for the massive, low-affinity binding of native lactoferrin. 2. The binding of lactoferrin, APM-lactoferrin and β-VLDL to parenchymal liver cells was not influenced by the glutathione S-transferase-receptor-associated protein (GST-RAP) (97.2±4.0%, 95.5±3.7% and 98.5% of the control binding), while the binding of α2-macroglobulin was fully blocked at 10 μg/ml GST-RAP (1.8±0.5% of the control binding). Since GST-RAP blocks the binding of all the known ligands to the low-density lipoprotein (LDL)-receptor-related protein (LRP), it is concluded that LRP is not the initial primary recognition site for lactoferrin, APM-lactoferrin and β-VLDL on parenchymal liver cells. 3. We showed earlier that APM-lactoferrin, as compared with lactoferrin, is a more effective inhibitor of the liver uptake of lipoprotein remnants (49.4±4.0% versus 80.8±4.8% of the control at 500 μg/ml respectively). We found in the present study that β-VLDL is able to inhibit the binding of APM-lactoferrin to parenchymal liver cells significantly (74.9±3.3% of the control; P < 0.002), while the lactoferrin binding was unaffected. It is concluded that a still unidentified specific recognition site (the putative remnant receptor) is responsible for the initial binding of remnants to parenchymal cells and it is suggested that the partial cross-competition between APM-lactoferrin and β-VLDL may be of further help in the elucidation of the molecular nature of this recognition site.

scholarly journals Uptake and degradation of human low-density lipoprotein by human liver parenchymal and Kupffer cells in culture

1991 ◽  
Vol 276 (1) ◽  
pp. 135-140 ◽  
Author(s):  
J A A M Kamps ◽  
J K Kruijt ◽  
J Kuiper ◽  
T J C Van Berkel
Keyword(s):  
Kupffer Cells ◽  
Human Liver ◽  
Low Density Lipoprotein ◽  
Ldl Receptor ◽  
Density Lipoprotein ◽  
Cell Types ◽  
Liver Cells ◽  
Cell Protein ◽  
Parenchymal Liver ◽  
Parenchymal Cells

The association with and degradation by cultured human parenchymal liver cells and human Kupffer cells of human low-density lipoprotein (LDL) was investigated in order to define, for the human situation, the relative abilities of the various liver cell types to interact with LDL. With both human parenchymal liver cells and Kupffer cells the association of LDL with the cells followed saturation kinetics which were coupled to LDL degradation. The association of LDL (per mg of cell protein) to both cell types was comparable, but the association with human Kupffer cells was much more efficiently coupled to degradation than was the case in parenchymal cells. The capacity of human Kupffer cells to degrade LDL was consequently 18-fold higher (per mg of cell protein) than that of the human parenchymal liver cells. Competition studies showed that unlabelled LDL competed efficiently with the cell association and degradation of 125I-labelled LDL with both parenchymal and Kupffer cells, while unlabelled acetyl-LDL was ineffective. The degradation of LDL by parenchymal and Kupffer cells was blocked by chloroquine and NH4Cl, indicating that it occurs in the lysosomes. Binding and degradation of LDL by human liver parenchymal cells and human Kupffer cells appeared to be completely calcium-dependent. It is concluded that the association and degradation of LDL by human Kupffer and parenchymal liver cells proceeds through the specific LDL receptor, whereas the association of LDL to Kupffer cells is more efficiently coupled to degradation. The presence of the highly active LDL receptor on human Kupffer cells might contribute significantly to LDL catabolism by human liver, especially under conditions whereby the LDL receptor on parenchymal cells is down-regulated.

High Levels of Acetylated Low Density Lipoprotein Uptake and Low Tie2 Promoter Activity Distinguishes Sinusoids from Other Vessel Types in the Murine Bone Marrow

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 5465-5465
Author(s):  
Xiaomiao Li ◽  
Zhongbo Hu ◽  
Marda Jorgenson ◽  
William Slayton
Keyword(s):  
Bone Marrow ◽  
Blood Vessels ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cell Types ◽  
Blood Stream ◽  
Low Density ◽  
Murine Bone Marrow ◽  
Different Types

Abstract Background: The bone marrow contains a variety of blood vessels that have different functions in maintaining the bone marrow as the major blood producing organ in adulthood. For instance, arterioles function to control the flow of blood into bone marrow compartments, and the sinusoids serve as a conduit to the blood stream and niches for megakaryocyte development. Most current studies of the bone marrow vasculature, including studies quantifying changes in the marrow vascular by microvascular density, do not differentiate between different types of marrow vessels. Recognizing the changes in different types of blood vessels has important physiologic implications. Here we report a new method to distinguish sinusoids from arterioles in the murine bone marrow. Methods and Results: We used transgenic mice with GFP expressed downstream of the Tie-2 promoter, combined with in vivo acetylated low-density lipoprotein (Ac-LDL) uptake method to differentiate sinusoids from arterioles. We found that Ac-LDL was specifically endocytosed by sinusoids, and Tie-2 expression was more pronounced in the arteries, arterioles, and transitional capillaries. Combining these two functional endothelial markers and using confocal microscopy to obtain three dimensional images, we identified transitional zones where arterioles emptied into the sinusoids. Conclusions: These results demonstrate that the marrow vasculature and specific endothelial cell types are functionally heterogeneous. Methods to study changes in the marrow vasculature and particularly the vascular niche, a function of sinusoids, need to take into account this heterogeneity.

scholarly journals Low-density-lipoprotein receptors in different rabbit liver cells

1989 ◽  
Vol 261 (2) ◽  
pp. 587-593 ◽  
Author(s):  
M S Nenseter ◽  
O Myklebost ◽  
R Blomhoff ◽  
C A Drevon ◽  
A Nilsson ◽  
...  
Keyword(s):  
Kupffer Cells ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Binding Activity ◽  
Rabbit Liver ◽  
Low Density ◽  
Apo B ◽  
Liver Parenchymal ◽  
Ldl Binding ◽  
Parenchymal Cells

Receptor-dependent uptake mechanisms for low-density lipoprotein (LDL) were studied in rabbit liver parenchymal and non-parenchymal cells. Hybridization studies with a cDNA probe revealed that mRNA for the apo (apolipoprotein) B,E receptor was present in endothelial and Kupffer cells as well as in parenchymal cells. By ligand-blotting experiments we showed that apo B,E-receptor protein was present in both parenchymal and non-parenchymal cells. Studies of binding of homologous LDL in cultured rabbit parenchymal cells suggested that about 63% of the specific LDL binding was mediated via the apo B,E receptor. Approx. 47% of the specific LDL binding was dependent on Ca2+, suggesting that specific Ca2+-dependent as well as Ca2+-independent LDL-binding sites exist in liver parenchymal cells. Methylated LDL bound to the parenchymal cells in a saturable manner. Taken together, our results showed that apo B,E receptors are present in rabbit liver endothelial and Kupffer cells as well as in the parenchymal cells, and that an additional saturable binding activity for LDL may exist on rabbit liver parenchymal cells. This binding activity was not inhibited by EGTA or reductive methylation of lysine residues in apo B. LDL degradation in parenchymal cells was mainly mediated via the apo B,E receptor.

scholarly journals Lipoprotein lipase stimulates the binding and uptake of moderately oxidized low-density lipoprotein by J774 macrophages

1996 ◽  
Vol 314 (2) ◽  
pp. 563-568 ◽  
Author(s):  
Wendy L. HENDRIKS ◽  
Hans van der BOOM ◽  
Leonie C. van VARK ◽  
Louis M. HAVEKES
Keyword(s):  
Lipoprotein Lipase ◽  
Oxidized Ldl ◽  
Low Density Lipoprotein ◽  
Heparan Sulphate ◽  
Density Lipoprotein ◽  
Cell Types ◽  
Low Density ◽  
Dependent Manner ◽  
Dose Dependent

Lipoprotein lipase (LPL) stimulates the uptake of low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) in different cell types, including macrophages, through bridging of LPL between lipoproteins and extracellular heparan sulphate proteoglycans (HSPG). Because macrophages produce LPL and because modified lipoproteins are present in the arterial wall in vivo, we wondered whether LPL also enhances the uptake of oxidized LDL by J774 macrophages. LDL samples with different degrees of oxidation, as evaluated by relative electrophoretic mobility (REM) as compared with native LDL are used, as well as native and acetylated LDL. Addition of 5 μg/ml LPL to the J774 cell culture medium stimulated the binding of both native LDL and moderately oxidized LDL (REM < 3.5) 50–100-fold, and their uptake was stimulated approx. 20-fold. The LPL-mediated binding of native LDL and moderately oxidized LDL was dose-dependent. Preincubation of the cells with heparinase (2.4 units/ml) inhibited the stimulatory effect of LPL, indicating that this LPL-mediated stimulation was due to bridging between the lipoproteins and HSPG. The binding to J774 macrophages of severely oxidized LDL (REM = 4.3) was stimulated less than 3-fold by LPL, whereas its uptake was not stimulated significantly. The binding and uptake of acetylated LDL (AcLDL) were not stimulated by LPL, although the LPL-molecule itself does bind to AcLDL. Measurements of the cellular lipid content showed that addition of LPL also stimulated the accumulation in the cells of cholesteryl ester derived from both native LDL and moderately oxidized LDL in a dose-dependent manner. We conclude that our results present experimental evidence for the hypothesis that LPL serves as an atherogenic component in the vessel wall.

Sign in / Sign up

Export Citation Format

Share Document