2023 AIChE Annual Meeting

Behavior of Myelin Lipid Compositions at the Air-Solution Interface

The myelin sheath is a multilamellar lipid membrane wrapped around axons of neurons in the central nervous system (CNS) that facilitates rapid nerve impulse transmission, which is essential for the proper functioning of the CNS. Myelin destruction, called demyelination, causes Multiple Sclerosis (MS), a neurodegenerative disorder that results in the loss of sensory and motor functions due to nerve impulse leakage. In healthy subjects, the amphipathic lipids that compose myelin form a remarkably stable membrane. Changes in lipid composition have just recently been identified as a signature of demyelination; however, the details of these changes and the role they play in MS is not currently understood. We hypothesize that changes in lipid composition impact the packing of the film, which in turn impacts its stability. This work addresses the relationship between the structure and function of myelin to develop a biophysical model of the myelin sheath. Using a Langmuir-Pockels trough, we measured the interfacial properties (surface pressure (SP) and compressibility modulus) exhibited by monomolecular films of different lipid compositions when subjected to dilatational interfacial stresses. Major lipid components of myelin were used in this work: L-α-phosphatidylcholine (Brain PC), L-α-phosphatidylethanolamine (Brain PE), L-α-phosphatidylserine (Brain PS), and cholesterol. “Healthy” and “sick” brains were experimentally modeled by varying lipid ratios based on the lipid profile found in “healthy” and “sick” mice brain extracts. While little difference was observed between models in the absence of cholesterol, the addition of cholesterol promoted major differences in the mechanical properties of the interfacial film. Changes in SP with surface area and compressibility modulus suggested differences in packing due to differences in the amount of cholesterol in the model mixtures mimicking “healthy” brain compared to the “sick” brain.