Evaluation of new apolipoprotein C-II and apolipoprotein C-III automatized immunoturbidimetric kits.

BACKGROUND: Apolipoprotein C-II and apolipoprotein C-III play an important and complex role in plasma triglycerides metabolism, respectively, as inhibitor and activator of lipoprotein lipase. Thus, they appear to be suitable markers for clinical studies of triglyceride-rich lipoproteins and related cardiovascular risk. Our aim was to evaluate, for routine analysis, the accuracy to quantify these apolipoprotein in human sera. METHODS: Precision (intra- and inter-run), limit of detection and quantification, linearity, common interferents (lipids, haemoglobin, bilirubin) and reference intervals were determined according to guidelines of the French Society of Clinical Biology and ISO Norm 5725 specifications. RESULTS: Intra- and inter-run CVs were respectively less than 5.0% and 7.5%. Linearities extended from 10.8 mg/L to 112.9 mg/L for apolipoprotein C-II and from 31.8 mg/L to 375.5 mg/L for apolipoprotein C-III. Haemolysis (up to 227.6 micromol/L haemoglobin) and lipemia (up to 19.3 mmol/L triglycerides) do not interfere, contrary to bilirubin, which has a positive effect above 350 micromol/L. Comparison of methods shows good agreement between immunoturbidimetric and electro-immunodiffusion methods for measuring apolipoprotein C-III in 62 samples within a wide range (n = 62, r = 0.954, y = 3.81 x -14.4). CONCLUSION: This study shows the reliability of these kits for measuring apolipoprotein C-II and apolipoprotein C-III in human sera, and their suitability for routine analysis.

Anionic peptide factor/phosphatidylcholine particles promote the inhibition of vascular cell adhesion molecule-1 in human umbilical vein endothelial cells.

OBJECTIVE: High-density lipoproteins (HDLs) have significant cardiovascular benefits by retarding the progression of atherosclerosis. One of the mechanisms is the inhibition by HDLs of the vascular cell adhesion molecule-1 (VCAM-1) expression in endothelial cells. Our objective was to test the effect on VCAM-1 expression by the human umbilical vein endothelial cells (HUVEC) of a minor HDL2 and HDL3 apolipoprotein, the anionic peptide factor (APF). The peptide has previously been found to develop some beneficial effects against atherosclerosis, i.e. by promoting the cholesterol efflux from endothelial cells. METHODS: We examined the effects of two HDL apolipoproteins A-I and APF, either in presence or absence of phosphatidylcholines (PCs), or free PCs, on the expression of VCAM-1 by HUVEC. The cells were stimulated with either the tumor necrosis factor-alpha (TNFalpha, 500 pg/ml) or the calcium bound to heparin (10 microg Ca2+/ml, 50 microg heparin/ml). RESULTS: In the presence of TNFalpha, only the free PCs (0.25 and 1 mM) developed an inhibitory effect (up to 50%). In the absence of TNFalpha and in the presence of calcium bound to heparin, either the lipid-free APF (3.5 microM) or the APF/PC complexes (1:57 molar ratio) or the free PCs (0.25 mM) exhibited a substantial inhibitory effect (72, 71 and 42%, respectively). CONCLUSION: Our present findings suggest for the first time that one of the mechanisms of the antiatherogenic action of APF involves the inhibition of VCAM-1 expression by HUVEC. The peptide, through its phospholipid-binding and its calcium antagonist abilities, appears to confer on the HDLs a protective effect against the early cellular event of the inflammatory process.