Cardiolipin is a normal component of human plasma lipoproteins.
Anticardiolipin (anti-CL) antibodies, diagnostic for antiphospholipid antibody syndrome, are associated with increased risks of venous and arterial thrombosis. Because CL selectively enhances activated protein C/protein S-dependent anticoagulant activities in purified systems and because CL is not known to be a normal plasma component, we searched for CL in plasma. Plasma lipid extracts [chloroform/methanol (2:1, vol/vol)] were subjected to analyses by using TLC, analytical HPLC, and MS. A plasma lipid component was purified that was indistinguishable from reference CL (M:1448). When CL in 40 fasting plasma lipid extracts (20 males, 20 females) was quantitated by using HPLC, CL (mean +/- SD) was 14.9 +/- 3.7 microgram/ml (range 9.1 to 24.2) and CL was not correlated with phosphatidylserine (3.8 +/- 1.7 microgram/ml), phosphatidylethanolamine (64 +/- 20 microgram/ml), or choline-containing phospholipid (1,580 +/- 280 microgram/ml). Based on studies of fasting blood donors, CL (>/=94%) was recovered in very low density, low density, and high density lipoproteins (11 +/- 5.3%, 67 +/- 11.0%, and 17 +/- 10%, respectively), showing that the majority of plasma CL (67%) is in low density lipoprotein. Analysis of relative phospholipid contents of lipoproteins indicated that high density lipoprotein is selectively enriched in CL and phosphatidylethanolamine. These results shows that CL is a normal plasma component and suggest that the epitopes of antiphospholipid antibodies could include CL or oxidized CL in lipoproteins or in complexes with plasma proteins (e. g., beta(2)-glycoprotein I, prothrombin, protein C, or protein S) or with platelet or endothelial surface proteins.
Deguchi
H
H
Departments of Molecular Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Fernandez
J A
JA
Hackeng
T M
TM
Banka
C L
CL
Griffin
J H
JH
D017152:Antibodies, Antiphospholipid / Q000097:blood / Q000276:immunology; D016736:Antiphospholipid Syndrome / Q000276:immunology; D002308:Cardiolipins / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D005260:Female; D006801:Humans; D008074:Lipoproteins / Q000097:blood* / Q000737:chemistry; D008297:Male; D013058:Mass Spectrometry; D010743:Phospholipids / Q000032:analysis
D017152:Antibodies, Antiphospholipid; D002308:Cardiolipins; D008074:Lipoproteins; D010743:Phospholipids