Interaction between artificial membranes and enflurane, a general volatile anesthetic: DPPC-enflurane interaction

Area of Science:

• Biophysics
• Lipidomics
• Anesthesiology

Background:

• Dipalmitoylphosphatidylcholine (DPPC) is a key component of biological membranes.
• Volatile anesthetics like enflurane interact with cell membranes, affecting their function.
• Understanding these interactions is crucial for elucidating anesthetic mechanisms.

Purpose of the Study:

• To investigate the structural modifications of DPPC organization induced by enflurane.
• To characterize the new lipid phases formed upon enflurane interaction.
• To determine the phase diagram of enflurane-DPPC mixtures in excess water.

Main Methods:

• Differential scanning calorimetry (DSC)
• Small-angle and wide-angle X-ray scattering (SAXS/WAXS)
• Fluorescent lipid probe Laurdan for titration curves

Main Results:

• Enflurane induces distinct mixed lipid phases (L(beta')(2NNN), L(beta)(i), L(alpha)(2)) in DPPC at different concentrations and temperatures.
• The L(beta)(i) phase shows interdigitated lipids with a reduced smectic distance and a fusion temperature of 33°C.
• The L(alpha)(2) fluid phase exhibits decreased smectic distance compared to pure DPPC.
• Maximal enflurane effect occurs at specific lipid ratios (1:1 for L(alpha)(2), 2:1 for L(beta)(i)).

Conclusions:

• Enflurane significantly alters DPPC lipid organization, creating novel lamellar phases.
• The observed structural changes are dependent on enflurane-to-lipid ratio and temperature.
• A pseudo-binary phase diagram for enflurane-DPPC mixtures in water was established.