Drunken Membranes: Short-Chain Alcohols Alter Fusion of Liposomes to Planar Lipid Bilayers

Abstract

Although the effects of ethanol on protein receptors and lipid membranes have been studied extensively, ethanol's effect on vesicles fusing to lipid bilayers is not known. To determine the effect of alcohols on fusion rates, we utilized the nystatin/ergosterol fusion assay to measure fusion of liposomes to a planar lipid bilayer (BLM). The addition of ethanol excited fusion when applied on the cis (vesicle) side, and inhibited fusion on the trans side. Other short-chain alcohols followed a similar pattern. In general, the inhibitory effect of alcohols (trans) occurs at lower doses than the excitatory (cis) effect, with a decrease of 29% in fusion rates at the legal driving limit of 0.08% (w/v) ethanol (IC 50 ¼ 0.2% v/v, 34 mM). Similar inhibitory effects were observed with methanol, propanol, and butanol, with ethanol being the most potent. Significant variability was observed with different alcohols when applied to the cis side. Ethanol and propanol enhanced fusion, butanol also enhanced fusion but was less potent, and low doses of methanol mildly inhibited fusion. The inhibition by trans addition of alcohols implies that they alter the planar membrane structure and thereby increase the activation energy required for fusion, likely through an increase in membrane fluidity. The cis data are likely a combination of the above effect and a proportionally greater lowering of the vesicle lysis tension and hydration repulsive pressure that combine to enhance fusion. Alternate hypotheses are also discussed. The inhibitory effect of ethanol on liposome-membrane fusion is large enough to provide a possible biophysical explanation of compromised neuronal behavior.

The Impact of Solvent Selection: Strategies to Guide the Manufacturing of Liposomes Using Microfluidics

“…Ethanol is also reported to reduce the transition temperature of lipid bilayers (through promoting bilayer disorder) and at high concentrations can cause lipid interdigitation [39,40]. This disordering effect is not restricted to ethanol, and all three of the alcohols used within our studies had a bilayer disordering effect [41]. Thus, during the production of liposomes, the miscible alcohols present during the mixing process may reduce the transition temperature of the bilayer discs, hence increasing their elasticity and promoting vesicle formation.…”

The SNAP-25 linker supports fusion intermediates by local lipid interactions

“…Application of short-chain alcohols was reported to facilitate hemifusion/fusion of liposomes in reduced protein-free systems by altering membrane properties ( Chanturiya et al, 1999 ; Paxman et al, 2017 ). Here, we introduced low concentrations (2%) of methanol (MeOH) into cells via the patch pipette and characterized potential changes of secretion properties in Ca 2+ -uncaging experiments.…”

Real-Time Monitoring of Interactions between Solid-Supported Lipid Vesicle Layers and Short- and Medium-Chain Length Alcohols: Ethanol and 1-Pentanol

“…Some examples of small foreign molecules include cholesterol, fatty acids, and alcohols, systems that partition differently between the membrane phases and the aqueous environment. The latter have attracted a great deal of attention since they display a wide spectrum of physiological and pharmacological actions such as metabolism, membrane fusion, alcohol toxicity, and general anesthesia [1,2,3,4,5]. In particular, much research has been devoted to the study of lipids–alcohols interactions to elucidate the mechanisms of anesthesia.…”

“…Compared to GUVs formed in the presence of ethanol, GUVs preformed in water with subsequent ethanol addition exhibit different shape and phase transition temperatures. Furthermore, a recent capacitance study showed that alcohols alter fusion of small liposomes to planar lipid bilayers by enhancing the energy barrier for vesicle fusion, likely through an increase in membrane fluidity due to the presence of alcohol [2].…”