Document Detail


Aggregation of dimyristoylphosphatidylglycerol liposomes by human plasma low density lipoprotein.
MedLine Citation:
PMID:  9733956     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Turbidity (absorbance at 470 nm) measurements revealed human serum low density lipoprotein (LDL) to cause, within a few minutes and at physiological pH and [NaCl], the aggregation of liquid crystalline large unilamellar liposomes (LUVs) of dimyristoylphosphatidylglycerol (DMPG). No evidence for concomitant lipid or aqueous contents mixing was obtained with fluorescent assays for these processes, in keeping with the lack of fusion of LUVs. Involvement of apoB is implicated by the finding that tryptic digestion of LDL abrogates its ability to cause aggregation. Aggregation is not caused by VLDL, HDL2, or HDL3. Interestingly, also oxidised LDL failed to aggregate DMPG vesicles. Aggregation of DMPG LUVs by LDL did depend on the ionic strength of the medium as well as on the phase state of the lipid. More specifically, below the main transition temperature Tm maximal aggregation was seen in the presence of 25-100 mM NaCl, whereas slightly higher (up to 150 mM) [NaCl] were required when T>Tm. Aggregation due to LDL was also observed for dimyristoylphosphatidylserine as well as for dipalmitoylphosphatidylglycerol LUVs, whereas liposomes composed of either unsaturated acidic phospholipids or different phosphatidylcholines were not aggregated. Involvement of electrostatic attraction between the acidic phosphate of DMPG and cationic residues in apoB is suggested by the finding that increasing the content of dimyristoylphosphatidylcholine (DMPC) in DMPG liposomes reduced their aggregation and at XDMPC=0.50 no response was evident. Notably, increasing the mole fraction of 1-palmitoyl-2-oleyl-PG (POPG) in DMPG LUVs progressively reduced their aggregation by LDL and at XPOPG=0.50 there was complete inhibition. The latter effect of POPG is likely to be due to augmented hydration of the unsaturated lipid constituting a barrier for the contact between apoB and the vesicle surface. In keeping with this view, the presence of the strongly hygroscopic polymer, poly(ethylene glycol) at 1% (by weight) enhanced the aggregation and could partly reverse the inhibition by POPG.
Authors:
S Lauraeus; J M Holopainen; M R Taskinen; P K Kinnunen
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  1373     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1998 Aug 
Date Detail:
Created Date:  1998-10-07     Completed Date:  1998-10-07     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  147-62     Citation Subset:  IM    
Affiliation:
Biomembrane Research Group, Department of Medical Chemistry, Institute of Biomedicine, P.O. Box 8, University of Helsinki, Siltavuorenpenger 10A, Helsinki, FIN-00014, Finland.
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MeSH Terms
Descriptor/Qualifier:
Apolipoproteins B / metabolism
Humans
Hydrogen-Ion Concentration
Lipoproteins, LDL / blood*
Liposomes*
Osmolar Concentration
Phosphatidylglycerols / metabolism*
Static Electricity
Chemical
Reg. No./Substance:
0/Apolipoproteins B; 0/Lipoproteins, LDL; 0/Liposomes; 0/Phosphatidylglycerols; 61361-72-6/dimyristoylphosphatidylglycerol

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