A model membrane approach to the epidermal permeability barrier

Area of Science:

• Biophysics
• Dermatology
• Lipid Science

Background:

• Mammalian skin's permeability barrier is crucial for protection.
• This barrier is mainly composed of ceramide, cholesterol, and free fatty acids.
• The precise organization and phase behavior of these lipids remain unclear.

Purpose of the Study:

• To investigate the relationship between lipid composition and phase behavior in skin barrier lipids.
• To understand how ceramide, cholesterol, and free fatty acids interact and organize.
• To compare ceramide-based lipid systems with sphingomyelin-based systems.

Main Methods:

• 2H Nuclear Magnetic Resonance (NMR) spectroscopy was used.
• Aqueous dispersions of bovine brain ceramide, cholesterol, and palmitic acid were studied.
• These systems were compared to analogous systems where sphingomyelin replaced ceramide.

Main Results:

• Ceramide-containing dispersions exhibited complex phase behavior influenced by temperature and pH.
• Cholesterol-containing ceramide dispersions showed phase coexistence and a "solid" phase with inhibited molecular motion.
• In the presence of cholesterol, a fluid lamellar signal was observed, similar to sphingomyelin systems.

Conclusions:

• Skin barrier lipid organization is complex and highly dependent on lipid composition, temperature, and pH.
• Cholesterol plays a critical role in forming fluid lamellar structures essential for barrier function.
• Ceramide's interaction with cholesterol is key to achieving a functional permeability barrier.