The influence of plant stanol (β-sitostanol) on inner leaflet of human erythrocytes membrane modeled with the Langmuir monolayer technique

The presence of dietary phytocompounds – plant sterols and stanols – in human plasma and membranes raises the question on their influence on membrane properties. A good way to get an insight into interactions of these biomolecules with membranes at molecular level is to perform experiments on artificial systems, e.g. Langmuir monolayers, composed of membrane lipids. In this paper the influence of plant stanol – β-sitostanol – on monolayers imitating the inner leaflet of human membrane, composed of phosphatidylethanolamine (POPE)/phosphatidylserine (POPS)/cholesterol (Chol) was studied. Two effects have been investigated and compared, namely the systematic increase of plant stanol (β-sitostanol) content in the mixed film as well as the replacement of cholesterol by β-sitostanol in POPE/POPS/Chol monolayer. The analysis of the collected data evidenced that the plant stanol strongly influences the condensation and interactions in POPE/POPS/Chol film. BAM images taken for the studied monolayers demonstrated that the presence of β-sitostanol in the mixture leads to the formation of 3D crystallites within the film, which seems to result from a limited solubility of plant stanol in phospholipids environment. All these effects have got intensified upon systematic elimination of cholesterol and its replacement by plant stanol in the mixed monolayer. The obtained results evidence that the presence of plant stanol may significantly alter organization of the inner leaflet of human membrane.