Revisiting lipid – general anesthetic interactions (II): Halothane location and changes in lipid bilayer microenvironment monitored by fluorescence

Abstract

A universal mechanism for the action of general anesthetics (GA) is not yet available. In this study, we investigated the interaction between halothane and 1,2-dipalmitoyl-sn-3-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-3-glycero-3-phosphocholine (DOPC) bilayers labeled with Laurdan, Prodan, and NBD-C6-PC as the reporter probes using steady-state fluorescence spectroscopy. We have evidence that halothane is located on the acyl chain side, near the headgroup region of the bilayer. Additionally, we find that halothane may be inhomogeneously distributed within DOPC and DPPC bilayers. We also show data that indicate halothane increases the free volume available to fluorescent probes. Differential scanning calorimetry and UV scanning calorimetry experiments were implemented to further observe the effects of halothane addition to the DPPC lipid bilayer. A significant shift of the phase-transition temperature of the DPPC system was observed. Our findings suggest that general anesthetic – lipid bilayer interactions may play a significant role in the overall mechanism of anesthetic action, and these effects should not be ignored when interactions between membrane proteins and anesthetics are considered.Key words: liposomes, anesthesia, fluorescence, phase transition, phospholipid bilayers.

Effect of tetracaine on DMPC and DMPC+cholesterol biomembrane models: Liposomes and monolayers

“…Although the molecular mechanisms of local anaesthetics action are still not completely understood, three main hypotheses are generally considered to explain them: direct interaction with voltage-gated sodium channels, induction of structural alterations in the lipid matrix of the biomembranes and action on the lipid-protein interfaces [1,2]. In the latter two cases, the mechanisms involve nonspecific interactions of the anaesthetics with the lipid bilayers.…”

Fluorescence quenching of gramicidin D in model membranes by halothane

“…In previous work, we examined the location of inhaled anesthetic in a fluorescently labeled DOPC lipid bilayer (25). We found that halothane locates on the acyl chain side, near the headgroup region of the bilayer (25). Therefore, we might anticipate a heterogeneous distribution of halothane around gramicidin in bilayer environments.…”

“…This was done to ascertain the effect of the local environment on halothane-gramicidin interactions. In previous work, we examined the location of inhaled anesthetic in a fluorescently labeled DOPC lipid bilayer (25). We found that halothane locates on the acyl chain side, near the headgroup region of the bilayer (25).…”

Atomic Force Microscopy: Interaction Forces Measured in Phospholipid Monolayers, Bilayers and Cell Membranes

“…The second, short-range regime, between 0.3 and 4 nm, is attributed to the deformation of the bilayer. Most studies on the bilayer report a jump corresponding to the piercing of the bilayer for forces ranging from approximately 3 to 25 nN [71][72][73]. This jump into contact is observed when the force gradient exceeds the spring constant of the cantilever k, which is the case when k < 1 N/m.…”