2024 AIChE Annual Meeting
Investigating Interfacial Properties of Major Lipid Components Using a Brain Myelin Model for Multiple Sclerosis
The myelin sheath is a vital multilayer lipid membrane wrapped around the axons of neurons in the central nervous system (CNS) that protects nerves and facilitates rapid impulse transmission, essential for a proper functioning CNS. Myelin destruction, referred to as demyelination, is the cause of Multiple Sclerosis (MS), a neurodegenerative autoimmune disorder resulting in the interruption of nerve signals and consequent loss of motor and sensory functions. Healthy myelin is composed of an incredibly robust amphipathic lipid membrane, a quality that has been used to relate the properties of the membrane to disease development. Additionally, changes in lipid composition have recently been identified as a signature of demyelination; however, the specifics of these changes and their importance to MS are not yet understood. We hypothesize that changes in lipid composition impact the packing and rigidity of the film thus impacting its stability. To detail the relationship between the structure and function of myelin, this work attempts to develop a realistic biophysical model of the myelin sheath in the brain. Using a Langmuir-Pockels trough, we measured the interfacial properties (surface pressure (SP) and compressibility modulus) presented by monomolecular films of varying lipid compositions, subjected to dilatational interfacial stresses. We also conducted rheological studies by measuring elasticity and viscosity moduli of the films. Lipid mixtures used in these works were composed of major brain myelin lipid components L-a-phosphatidylcholine (Brain PC), L-a-phosphatidylethanolamine (Brain PE), and L-a-phosphatidylserine (Brain PS). While in both studies the differences in lipid concentrations had small effects on the mechanical and viscoelastic properties of the interfacial film, the small increase in SP and elasticity modulus observed corresponded with decreased Brain PC and PE components. This suggests slight changes in surface conformation due to differences in the types of head groups and lengths of alkyl chains present in the lipid mixtures.