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Adsorption kinetics of low-density lipoproteins with Langmuir monolayer.

ABSTRACT: The present work utilizes the Langmuir monolayer technique to detect the adsorption kinetics of native low-density lipoproteins and their oxidized form with the lipid monolayer. We found that low-density lipoproteins and oxidized low-density lipoproteins are able to penetrate the LM up to pressure ??=?9.9 and 11.6 mN/m. Also, the adsorption constants of both particles were found to depend strongly on the monolayer initial pressure. It is found that less compressed lipid monolayers could accommodate more native low-density lipoproteins than the oxidized ones due their higher binding affinity toward monolayers. The probable ?-helical regions along the apoproteinB-100 secondary structure and average hydrophobicity could explain partially their adsorption kinetics into lipid monolayers. This simplified 'in vitro' study of low-density lipoprotein-monolayer interaction may serve as a step further to understand the mechanism and bioactivity of the atherosclerotic process. Also, it may shed light on the oxidized low-density lipoprotein's role in plaque formation in the innermost arterial wall in blood vessels.

SUBMITTER: Khattari Z

PROVIDER: S-EPMC5059594 | biostudies-literature | 2016 Oct

REPOSITORIES: biostudies-literature

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Adsorption kinetics of low-density lipoproteins with Langmuir monolayer.

Khattari Ziad Z

Journal of biological physics 20160719 4

The present work utilizes the Langmuir monolayer technique to detect the adsorption kinetics of native low-density lipoproteins and their oxidized form with the lipid monolayer. We found that low-density lipoproteins and oxidized low-density lipoproteins are able to penetrate the LM up to pressure π = 9.9 and 11.6 mN/m. Also, the adsorption constants of both particles were found to depend strongly on the monolayer initial pressure. It is found that less compressed lipid monolayers could accommod ...[more]

PMID: 27435195

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Project description:BACKGROUND:Oxidized low-density lipoprotein (oxLDL) uptake by macrophages plays an important role in foam cell formation. It has been suggested the presence of heterogeneous subsets of macrophage, such as M1 and M2, in human atherosclerotic lesions. To evaluate which types of macrophages contribute to atherogenesis, we performed cDNA microarray analysis to determine oxLDL-induced transcriptional alterations of each subset of macrophages. RESULTS:Human monocyte-derived macrophages were polarized toward the M1 or M2 subset, followed by treatment with oxLDL. Then gene expression levels during oxLDL treatment in each subset of macrophages were evaluated by cDNA microarray analysis and quantitative real-time RT-PCR. In terms of high-ranking upregulated genes and functional ontologies, the alterations during oxLDL treatment in M2 macrophages were similar to those in nonpolarized macrophages (M0). Molecular network analysis showed that most of the molecules in the oxLDL-induced highest scoring molecular network of M1 macrophages were directly or indirectly related to transforming growth factor (TGF)-?1. Hierarchical cluster analysis revealed commonly upregulated genes in all subset of macrophages, some of which contained antioxidant response elements (ARE) in their promoter regions. A cluster of genes that were specifically upregulated in M1 macrophages included those encoding molecules related to nuclear factor of kappa light polypeptide gene enhancer in B-cells (NF-?B) signaling pathway. Quantitative real-time RT-PCR showed that the gene expression of interleukin (IL)-8 after oxLDL treatment in M2 macrophages was markedly lower than those in M0 and M1 cells. HMOX1 gene expression levels were almost the same in all 3 subsets of macrophages even after oxLDL treatment. CONCLUSIONS:The present study demonstrated transcriptional alterations in polarized macrophages during oxLDL treatment. The data suggested that oxLDL uptake may affect TGF-?1- and NF-?B-mediated functions of M1 macrophages, but not those of M0 or M2 macrophages. It is likely that M1 macrophages characteristically respond to oxLDL.

Project description:In previous studies we have shown that in HepG2 cells, as compared with fibroblasts, the low-density lipoprotein (LDL) receptor is only weakly down-regulated upon incubation of the cells with LDL. To explain this difference in down-regulation of the LDL-receptor activity, we studied simultaneously the intracellular processing of 125I-labelled LDL in both cell lines. Upon incubation of HepG2 cells with 125I-LDL, the appearance of degradation products started at 90 min, whereas in fibroblasts this lag time was only 30 min. The degradation efficiency (representing the ratio degradation/cell association of LDL) in HepG2 was less than 50% of that in fibroblasts up to 5h of incubation at 37 degrees C. The longer lag time and low efficiency of the degradation of LDL in HepG2 cells were independent of the cell density. Pulse-chase experiments indicated that the internalization rate of surface-bound LDL in HepG2 cells is similar to that of fibroblasts. Endosomal loading of 125I-LDL by incubation at 18 degrees C for 4.5 h, followed by a shift to 37 degrees C, resulted in degradation of LDL within 30 min in fibroblasts, whereas in HepG2 cells the lag time of the degradation was 90 min. In parallel experiments using subcellular fractionation by Percoll-gradient centrifugation of homogenized cells and 125I-tyramine-cellobiose-labelled LDL, we observed that in both cell types LDL is equally rapidly shifted from a low- to a high-density compartment (within 15 min), representing the endosomal and the late-endosomal plus lysosomal compartment respectively. We conclude that in HepG2 cells the cell-bound LDL, upon internalization, goes through the intracellular itinerary at the same rate as in fibroblasts, but that either the fusion between late endosomes and lysosomes or the lysosomal degradation itself is proceeding at a lower efficiency. A low degradation rate of LDL may contribute to explain the relatively weak down-regulation of the LDL-receptor activity in HepG2 cells by LDL.

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Adsorption kinetics of low-density lipoproteins with Langmuir monolayer.

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Adsorption kinetics of low-density lipoproteins with Langmuir monolayer.

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