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Lipid composition of human serum lipoproteins.

ABSTRACT: 1. The lipid compositions of the low-density lipoproteins, the high-density lipoproteins and the ultracentrifugal residue of human serum are presented, with emphasis on certain lipoprotein classes and lipid components not previously described. 2. Except for the lipoproteins with the lowest and highest densities, there is a trend for stepwise successive increase or, respectively, decrease in the relative amounts of the main constituents of lipoproteins. 3. High-density lipoprotein-2 and high-density lipoprotein-3 have different amounts of certain lipids; high-density lipoprotein-2 has relatively more free cholesterol and sphingomyelin; high-density lipoprotein-3 has more free fatty acids, diglycerides and ceramide monohexosides. 4. All the lipoproteins contain hydrocarbons of the alkane series. The greatest amount, which averages 4.4% of total lipid extracted, is in the ultracentrifugal residue; n-alkanes comprise 18-50% of the hydrocarbons. 5. All the lipoproteins contain ceramide monohexosides. The highest relative contents of these glycolipids are in high-density lipoprotein-3 and in the ultracentrifugal residue. 6. The ultracentrifugal residue contains 55% of the total quantity of free fatty acids present in serum. The remaining free fatty acids are distributed among the other lipoprotein classes. 7. The choline-containing phospholipids (phosphatidylcholine, lysophosphatidylcholine and sphingomyelin) comprise about 90% of the phospholipids in all the lipoprotein classes except the low-density lipoprotein-2, which contains about 80% of these phospholipids. 8. The presence of a large amount of lysophosphatidylcholine in the ultracentrifugal residue and the successive decrease of sphingomyelin from the low-density lipoprotein-1 to the ultracentrifugal residue was confirmed. 9. The low-density lipoprotein-2 and the ultracentrifugal residue are characterized by relatively high contents of the lower glycerides.

SUBMITTER: Skipski VP

PROVIDER: S-EPMC1270593 | biostudies-other | 1967 Aug

REPOSITORIES: biostudies-other

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Project description:BACKGROUND: Chlamydia trachomatis was previously shown to express a lipoprotein, the macrophage infectivity potentiator (Mip), exposed at the bacterial surface, and able to stimulate human primary monocytes/macrophages through Toll Like Receptor (TLR)2/TLR1/TLR6, and CD14. In PMA-differentiated THP-1 cells the proinflammatory activity of Mip was significantly higher in the absence than in the presence of serum. The present study aims to investigate the ability of different serum factors to attenuate Mip proinflammatory activity in PMA-differentiated THP-1 cells and in primary human differentiated macrophages. The study was also extend to another lipoprotein, the Borrelia burgdorferi outer surface protein (Osp)A. The proinflammatory activity was studied through Tumor Necrosis Factor alpha (TNF-?) and Interleukin (IL)-8 release. Finally, TLR1/2 human embryonic kidney-293 (HEK-293) transfected cells were used to test the ability of the serum factors to inhibit Mip and OspA proinflammatory activity. RESULTS: In the absence of any serum and in the presence of 10% delipidated FBS, production of Mip-induced TNF-? and IL-8 in PMA-differentiated THP-1 cells were similar whereas they were significantly decreased in the presence of 10% FBS suggesting an inhibiting role of lipids present in FBS. In the presence of 10% human serum, the concentrations of TNF-? and IL-8 were 2 to 5 times lower than in the presence of 10% FBS suggesting the presence of more potent inhibitor(s) in human serum than in FBS. Similar results were obtained in primary human differentiated macrophages. Different lipid components of human serum were then tested (total lipoproteins, HDL, LDL, VLDL, triglyceride emulsion, apolipoprotein (apo)A-I, B, E2, and E3). The most efficient inhibitors were LDL, VLDL, and apoB that reduced the mean concentration of TNF-? release in Mip-induced macrophages to 24, 20, and 2%, respectively (p < 0.0001). These lipid components were also able to prevent TLR1/2 induced activation by Mip, in HEK-293 transfected cells. Similar results were obtained with OspA. CONCLUSIONS: These results demonstrated the ability of serum lipids to attenuate proinflammatory activity of bacterial lipoproteins and suggested that serum lipoproteins interact with acyl chains of the lipid part of bacterial lipoproteins to render it biologically inactive.

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Lipid composition of human serum lipoproteins.

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