Abstract:
:Previous studies have established that incubation of low density lipoprotein (LDL) with cultured endothelial cells (EC) converts it to a new form (EC-modified LDL) that is now recognized by a specific receptor on macrophages (the acetyl LDL receptor) and is taken up and degraded 3-10 times more rapidly than native LDL (biological modification). The formation of EC-modified LDL depended on generation of free radicals with consequent peroxidation of LDL lipids and was accompanied by extensive hydrolysis of LDL phosphatidylcholine at the 2-position. The present studies show that p-bromophenacyl bromide, a site-specific irreversible inhibitor of phospholipase A2 activity, blocks this hydrolysis and, at the same time, the enhanced macrophage degradation. We show further that during EC modification the apoprotein B of LDL undergoes considerable modification and that this also is prevented by the phospholipase inhibitor. Finally, as reported previously, changes similar to those observed on incubation of LDL with EC can be induced by incubation in the absence of cells but in the presence of a sufficiently high concentration of Cu2+. This also is accompanied by hydrolysis of phosphatidylcholine at the 2-position and breakdown of apoprotein B. These changes are also inhibited by p-bromophenacyl bromide, suggesting the presence of a phospholipase A2 activity associated with LDL as it is isolated. A hypothesis is presented linking lipid peroxidation, phosphatidylcholine hydrolysis, and changes in the LDL apoprotein during EC modification.
journal_name
Proc Natl Acad Sci U S Aauthors
Parthasarathy S,Steinbrecher UP,Barnett J,Witztum JL,Steinberg Ddoi
10.1073/pnas.82.9.3000subject
Has Abstractpub_date
1985-05-01 00:00:00pages
3000-4issue
9eissn
0027-8424issn
1091-6490journal_volume
82pub_type
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