Effect of acetylsalicylic acid on the current–voltage characteristics of planar lipid membranes

Effect of the cholesterol on electroporation of planar lipid bilayer

Electroporation threshold depends on the membrane composition, with cholesterol being one of its key components already studied in the past, but the results were inconclusive. The aim of our study was to determine behaviour of planar lipid bilayers with varying cholesterol concentrations under electric field. This would give us a better insight into cholesterol effect on membrane properties during electroporation process, since cholesterol is one of the major components of biological membranes and plays a crucial role in membrane organisation, dynamics, and function. Planar lipid bilayers were prepared from phosphatidylcholine lipids with 0, 20, 30, 50 and 80 mol% cholesterol. Capacitance was measured using the discharge method. Results show no statistical difference of cBLM between the cholesterol concentrations. Breakdown voltage Ubr of planar lipid bilayers was measured by means of linear rising voltage with seven different slopes. Obtained results were fitted to a strength-duration curve, where parameter Ubrmin represents minimal breakdown voltage, and parameter τRC represents the inclination of the strength-duration curve. Adding cholesterol to planar lipid bilayer gradually increased its Ubrmin until 50 mol% cholesterol concentration. Afterwards at 80 mol% Ubrmin does not further increase, in fact it reduces by 20% of the Ubrmin at 50 mol% cholesterol concentration.

Pore formation in lipid bilayer membranes made of phosphatidylcholine and cholesterol followed by means of constant current

This paper describes the application of chronopotentiometry to lipid bilayer research. The experiments were performed on bilayer lipid membranes composed of phosphatidylcholine and cholesterol and formed using the painting technique. Chronopotentiometric (U = f(t)) measurements were used to determine the membrane capacitance, resistance, and breakdown voltage as well as pore conductance and diameter.

The effect of a platelet cholesterol modulation on the acetylsalicylic acid-mediated blood platelet inhibition in hypercholesterolemic patients

Aspirin (acetylsalicylic acid, ASA) is widely used in the prevention of cardiovascular disease, but its beneficial effects may be restrained in some individuals, where the reduced ability of ASA to protect against arterial thrombotic events is observed. We analyzed the influence of the treatment with atorvastatin (10mg/day) on the platelet sensitivity to ASA monitored under in vitro conditions in hypercholesterolemic patients. The associations between plasma or platelet cholesterol parameters and the ASA-mediated inhibition of platelet reactivity or the extent of platelet protein acetylation by ASA were estimated in the patients treated with atorvastatin for 1, 3, or 6 months. Out of 27 patients, in 17 individuals platelets appeared significantly more sensitive to 50 μM ASA in arachidonic acid- or collagen-induced whole blood aggregation following 1 month atorvastatin therapy (inhibition by 60.9 ± 5.6% vs. 48.8 ± 5.4%, P<0.05 for 0.5mM arachidonic acid, 40.8 ± 2.9% vs. 27.0 ± 4.1%, P<0.05 for 1 μg/ml collagen), and this effect lasted for 3 and 6 months, remaining in a weak, although significant, relation to the reduction of platelet cholesterol content (R(S)=-0.277, P<0.002 for arachidonic acid, R(S)=-0.197, P<0.02 for collagen). It was, however, not dependent upon either antiplatelet action or plasma lipid-lowering activity of atorvastatin. In addition, in about 50% of patients, we noticed that ASA (50 μM) significantly and time-dependently diminished thromboxane B(2) concentration in atorvastatin-treated patients. The ASA-induced acetylation of platelet proteins significantly increased in the course of atorvastatin therapy and was associated with reduced platelet cholesterol (R(S)=-0.598, P<0.0001). In conclusion, statin therapy may improve platelet sensitivity to ASA in some hypercholesterolemic patients. This effect may extend beyond the action of atorvastatin as merely a lipid-lowering agent. The mechanisms of resistance of some patients to such a combined ASA-statin treatment remain to be elucidated.