Low density lipoprotein-apheresis decreases oxidized low density lipoproteins and monocyte adhesion to endothelial cells.

The mutual interaction between monocytes and low density lipoprotein (LDL) in atherogenesis prompted a test of the hypothesis that LDL-apheresis could reduce the adhesive properties of monocytes to endothelium; and therefore interfere with a key mechanism in atheroma formation. Five patients affected by heterozygous familial hypercholesterolemia were studied. All patients received LDL-apheresis treatment with selective adsorption of LDL-cholesterol on dextran-sulphate columns. Low density lipoprotein particles were isolated by sequential preparative ultracentrifugation and subfractionated by ion exchange high performance liquid chromatography. Thiobarbituric acid reacting products of lipid peroxidation were measured fluorometrically. Vitamin E was estimated by high performance liquid chromatographic technique. Monocytes were isolated from patients blood before and 1 day after LDL-apheresis by Percoll gradient. The blood samples for monocyte adhesion were drawn from control subjects for 2 consecutive days. The adhesion of monocytes to an endothelial monolayer was evaluated by assaying the peroxidase content of the adherent monocytes. Low density lipoprotein-apheresis reduced total cholesterol (-65%; p < 0.01), LDL-cholesterol (-75%; p < 0.01), triglycerides (-51%; p < 0.05), and fibrinogen (-28%; p < 0.01). With LDL-apheresis treatment, a reduction of 54% in oxidized LDLs was observed; vitamin E concentration significantly increased in LDLs (+ 14.2%; p < 0.05). The monocyte adhesion decreased by approximately 61% after apheresis; the variation became statistically significant (-65%; p < 0.01) when endothelial cells were stimulated by lipopolysaccaride.

Activation of coagulation by a LDL-apheresis device.

LDL-apheresis often induces an almost constant and progressive increase of the differential pressure of plasma flowing through the dextran sulphate cellulose column, reducing the efficacy of the treatment. On two occasions we were able to identify a fibrin plug by immunofluorescence. Our aim was to verify the modification of some coagulation indicators in patients undergoing LDL-apheresis and whether an activation of coagulation occurs in the LDL-apheresis device. Blood samples were obtained from six patients with familial hypercholesterolaemia who were undergoing LDL-apheresis. During the same session further blood/ plasma samples were taken from the LDL-apheresis device at different sites and at different volumes of filtered blood. In patients after LDL-apheresis the following modifications were found: a 25% decrease of fibrinogen and a slight increase in F1 + 2 plasma levels. No relevant changes in thrombin-antithrombin complexes and fibrinopeptide A plasma levels were noted. In the LDL-apheresis device the main results were: (a) fibrinogen was trapped in the dextran sulphate cellulose column in the early phases; (b) activation of coagulation was recognisable in the plasma separator during the procedure and progressively increased with duration of LDL-apheresis; (c) thrombin-antithrombin complexes, formed in the plasma separator, were retained by the dextran sulphate cellulose column. In conclusion, LDL-apheresis activates coagulation in the device. Shortening cycle time or using nafamostat mesilate as an anticoagulant, could be interesting alternatives for improving the procedure.