Dibucaine interaction with phospholipid vesicles. A resonance energy-transfer study (original) (raw)
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Interaction of general anesthetics with phospholipid vesicles and biological membranes
Biochimica Et Biophysica Acta - Biomembranes, 1977
Low concentrations of general anesthetics, including halothane, ethrane, trilene, diethyl ether and chloroform are observed to shift the phase transitions of phospholipid vesicles to lower temperatures, and from these data partition coefficients for the anesthetic between lipid and water can be calculated. In contrast to the anesthetics, high concentrations of ethanol are required to shift the phase transition of lipids and glycerol causes no effect. Above the phase transition general anesthetics alter nuclear magnetic resonance spectra of phospholipid dispersions and increase the rotational and lateral diffusion rates of fluorescent probes located in the hydrocarbon core of the bilayer, indicating that they induce disorder in the structure. In red blood cell membranes and sarcoplasmic reticulum fragments, the rotational diffusion rate of 1-phenyl-6phenylhexatriene is increased in the presence of general anesthetics. The 220 MHz nuclear magnetic resonance spectra of sarcoplasmic reticulum reveal some resolved lines from the lecithin fatty acid protons; addition of general anesthetic increases the contribution of these peaks. The data from the NMR and fluorescence techniques lead to the conclusion that general anesthetics increase the pool size of melted lipids in the bimolecular phospholipid layers of biological membranes; this would account for the ability of general anesthetics to increase passive diffusion rates of various substances in membranes.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1988
The binding of the charged form of two local anesthetics, dibucaine and etidocaine, to bilayers composed of l-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) was measured simultaneously with ultraviolet spectroscopy and deuterium magnetic resonance. Because of their amphiphilic molecular structure, both drugs intercalate between the lipid molecules, increasing the surface area and imparting a positive electric charge onto the membrane. The ultraviolet (U-V) binding isotherms were therefore analyzed in terms of a model which specifically took into account the bilayer expansion as well as the charge-induced concentration variations near the membrane surface. By formulating a quantitative expression for the change in surface area upon drug intercalation and combining it with the Gouy-Chapman theory, the binding of charged dibucaine and etidocaine to the lipid membrane was best described by a partition equilibrium, with surface partition coefficients of 660 + 80 M-t and 11 + 2 M-l for dibucaine and etidocaine, respectively (pH 5.5, 0.1 M NaCI/50 mM buffer). Deuterium magnetic resonance demonstrated further that the binding of drug changed the head-group conformation of the lipid molecules. Invoking the intercalation model, a linear variation of the deuterium quadrupole splittings of the choline segments with the surface charge density was observed, suggesting that the phosphocholine bead-group may act as a 'molecular electrometer' with respect to sudace charges.
The interaction of local anaesthetics with synthetic phospholipid bilayers
Biochemical Pharmacology, 1982
The preferred position and orientation of two local anaesthetics in lipid bilayers has been determined using fluorescence quenching techniques. The aromatic amine of tetracaine and butesin quenches the fluorescence of a series of n-(9-anthroyloxy) fatty acids (n = 2,6,9,12,16) which place a fluorophore at a graded series of depths from the surface to the centre of a bilayer. A fluorescence method is used to resolve partition coefficients in the transverse plane of the membrane. The results show that the anaesthetics take up a distribution of positions about one or more preferred maxima. The aromatic amine group of tetracaine appears to be buried deep in the bilayer whereas the same group in butesin assumes positions at the surface as well as in the interior of the membrane.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1991
A general microscopic interaction model is proposed to describe the changes in the physical properties of phnspholipid bUayer membranes due t¢ ~oreiga molecules which, to different degrees, partition between the membrane phases and the aqueous environment. The modO is a multi-state lattice model for the main phase transition of lipid bilayers and the foreign molecules are assumed to intercalate as interstitials in the lattice. By varying the model parameters, the diversity in the thermodynamic properties oi the model is explored using computer-simulatlon techniques which faithfully take account of the thermal fluctuations. The calculations are performed in both the canonical and the grand canonical ensembles corresponding to the cases where the concentration of foreign molecules in the membrane is either fixed or varies as the external conditions are changed. A classification of the diverse thermal behaviour, specifically with regard to the phase diagram, the specific heat, the density fluctuations, and the partition coefficient, is suggested with a view to rationalizing a large body of experimental measurements of the effects of different foreign molecules on membrane properties. The range of foreign molecules considered includes compounds as diverse as volatile general anaesthetics like halothane, cocaine-derived local anaesthetics like procaine, calcium-channel blocking drugs like verapamil, antidepressants like cblorpromazine, and anti-cancer agents like adriamycin.
Interaction of local and general anaesthetics with liposomal membrane models: A QCM-D and DSC study
Colloids and Surfaces B: Biointerfaces, 2012
The behaviour of four local anaesthetics (lidocaine, levobupivacaine, ropivacaine and tetracaine) and one general anaesthetic (propofol) is compared when interacting with two types of model membranes: supported layers of liposomes and liposomes in solution. Several liposomal compositions were tested: dimyristoylphosphatidylcholine (DMPC), binary mixtures of DMPC with cholesterol (CHOL), and ternary mixtures of dipalmitoylphosphatidylcholine (DPPC), DMPC, and CHOL. A quartz crystal microbalance with dissipation, QCM-D, was used to assess changes in the properties of supported layers of liposomes. The effect of the anaesthetics on the phase behaviour of the liposomes in suspension was determined by differential scanning calorimetry. Both techniques show that all anaesthetics have a fluidizing effect on the model membranes but, apparently, the solid supported liposomes are less affected by the anaesthetics than the liposomes in solution. Although the different anaesthetics were compared at different concentrations, tetracaine and propofol seem to induce the strongest perturbation on the liposome membrane. The resistance of the liposomes to the anaesthetic action was found to increase with the presence of cholesterol, while adding DPPC to the binary mixture DMPC + CHOL does not change its behaviour. The novelty of the present work resides upon three points: (1) the use of supported layers of liposomes as model membranes to study interactions with anaesthetics; (2) application of QCM-D to assess changes of the adsorbed liposomes; (3) a comparison of the effect of local and general anaesthetics interacting with various model membranes in similar experimental conditions.
Membrane-Mediated Activity of Local Anesthetics
Molecular Pharmacology
The activity of local anesthetics (LAs) has been attributed to the inhibition of ion channels, causing anesthesia. However, there is a growing body of research showing that LAs act on a wide range of receptors and channel proteins, far beyond simple analgesia. The current concept of ligand recognition may no longer explain the multitude of protein targets influenced by LAs. We hypothesize that LAs can cause anesthesia without directly binding to the receptor proteins, just by changing the physical properties of the lipid bilayer surrounding these proteins and ion channels, based on LAs' amphiphilicity. It is possible that LAs act in one of the following ways: they (a) dissolve raft-like membrane micro-domains, (b) impede nerve impulse propagation by lowering the lipid phase transition temperature, or (c) modulate the lateral pressure profile of the lipid bilayer. This could also explain the numerous additional effects of LA besides anesthesia. Furthermore, the concepts of membrane-mediated activity and binding to ion channels do not have to exclude each other. If we were to consider LA as the middle part of a continuum, between unspecific membrane mediated activity on one end, and highly specific ligand binding on the other end, we could describe LA as the link between the unspecific action of general anesthetics, and toxins with their highly specific receptor binding. This comprehensive membrane-mediated model offers a fresh perspective to clinical and pharmaceutical research and therapeutic applications of local anesthetics.
Do General Anaesthetics Perturb Lipid Membranes?
BJA: British Journal of Anaesthesia, 1984
The effect of enflurane and methoxyflurane on the permeability of liposomes to H + was rested. Liposomes were prepared with phospholipids alone or as mixtures of cholesterol and phospholipids having the ratios of 1:2 or 1:1. Both anaesthetic drugs facilitated the release of H + from pure phoipholipid liposomes and from those with a 1:2 ratio. The facilitated release of H + was prevented by the presence of high concentrations of cholesterol. As the cholesterol: phospholipid ratio in synaptic vesicles is of the order 1:2, it is expected that their permeability might be affected by volatile anaesthetics, l«*°Hing to a modification of synaptic transmission.
The Journal of Membrane Biology, 2018
Local anesthetics (LAs) are known to act on membrane level; however, the molecular mechanism of their activity is still not fully understood. One hypothesis holds that these drugs can incorporate into lipid membrane of nerve cells and in this way change conformation of channel proteins responsible for transport of sodium ions. However, the action of anesthetics is not limited to nerve cells. These drugs also affect other types of cells and organelles, causing severe side effects. In this paper, we applied Langmuir monolayers-as model of cellular membranes-and investigated interactions between selected amide-type local anesthetics (lidocaine prilocaine, mepivacaine and ropivacaine, in the form of hydrochlorides) and lipid components of natural membranes: cholesterol, POPC and cardiolipin (CL) and their mixtures (POPC/cholesterol and POPC/CL/cholesterol), which can serve as simplified models of nerve cell membranes, erythrocytes, and mitochondria. The influence of the drug was monitored by registering the surface pressure (π) as a function of surface area per molecule (A) in a monolayer in the presence of the drug in the subphase. The structure of lipid monolayers on subphases containing and devoid of the studied drugs were visualized with Brewster angle microscopy (BAM). Langmuir monolayer studies complemented with surface visualization technique reveal the expansion and fluidization of lipid monolayers, with the most pronounced effect observed for cardiolipin. In mixed systems, the effect of LAs was found to depend on cholesterol proportion. The observed fluidization of membranes by local anesthetics may negatively affect cells functioning and therefore can explain side effects of these drugs both on the cardiovascular and nervous systems.
Local anesthetics and pressure: a comparison of dibucaine binding to lipid monolayers and bilayers
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1987
The bindln~ of the local anesthetic dilmcaine to myers composed of 1-paimitoyl-2-uleoyl-sn-giyeero-3plmsplmclmline was studied with a Langmuir trough at pH 5.5 (22°C, 0.1 M NaO). At this pH value only the charged form of the local anesthetic exists in solution. Charged dibucaine was found to be surface active and to penetrate into the lipid monolayer, with the hydrophobic part of the molecule being accommodated between the fatty acyl chains of the Hpid. The dibucaine intercalation could be quantitated by meastwing the expansion of the film area, AA, at constant surface pressme, yr. At a given surface pressure, AA increased with increasing dilmcaine in the buffer phase. On the other hand, keeping the dibucaine concentration constant, the area increase, AA, was strongly dependent on the surface pressure. The area increase, AA, was large at low surface pressure and decreased with increasing sm~ace pressure. A plot of the relative change in surface area, /tA/A, versus the surface pressure yielded straight lines in the pressure range of 25-36 mN/m for five different concentrations. The AA/A vs. vr isotherms intersected at vr-39.5 + 1 mN/m with AA =0, indicating that charged dilmcaine apparentiy can no longer penetrate into the monolayer film. By making judicial assumptions about the area requirement of dilmcaine the monolayer expansion curves could be transformed into true binding isotherms. Dibucaine binding isotherms were constructed for different monolayer pressures and were compared to a bilayer binding isotherm measured under similar conditions with ultraviolet spectroscopy. The best agreement between monolayer and bilayer binding data was obtained for a monolayer held at a pressure of 30.7 to 32.5 raN/m, which can thus be considered as the bilayer-monolayer equivalence lW&,sure. It is further suggested from this analogy that the binding of dibueaine does not change the internal pressure in the bilayer phase, at least not in the concentration range of physiological interest (0-2 mM dilmcaiue) but induces a lateral expansion. At higher molar ratios of cationic dilmeaine to lipid, Xb, in the monolayer (x b >0.20) the area increase is larger than would be expected from the molecular dimensions of dibueaine. This is probably due to charge repulsion effects, which at still higher molar ratios (x b > 0.6) lead to a micemsation. The pressure dependence of the intercalation of cationic dibueaine into lipid membranes may also be of relevance for the phenomenon of pressure reversal in anesthesia.