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Effects of Different Concentrations of AmB on the Unsaturated Phospholipid-Cholesterol Membrane Using the Langmuir
Juan Wang1, Jia Wang2, Mingyue Zheng1
1Xi'an Key Laboratory of Advanced Photo-Electronics Materials and Energy Conversion Device, School of Electronic Information, Xijing University, Xi'an 710123, China.
Abstract:
Amphotericin B (AmB) causes toxicity to the erythrocyte membrane, leading to hemolysis, which limits the clinically effective dose for AmB intravenous therapy in invasive fungal infections. The molecular mechanism by which AmB adheres to the membrane of erythrocytes is the key factor in causing AmB to be toxic to the membrane of erythrocytes, but it is not yet fully understood; the mechanism by which AmB adheres to the liquid microdomains with higher fluidity formed by cholesterol and unsaturated phospholipids remains especially unclear. This study examined the adsorption of AmB at different concentrations, 5, 45, 85, and 125 μg/mL, on unsaturated phospholipid membranes containing 50 mol% cholesterol. The thermodynamic properties and structure of DOPC monolayers and DOPC/cholesterol mixed monolayers at different concentrations of AmB have been investigated using the Langmuir monolayer model and the BAM method. The impact of varying concentrations of AmB on the hydrophilic and hydrophobic domains of the DOPC bilayers and the DOPC/cholesterol mixed bilayers have also been discussed using large unilamellar vesicle liposomes and fluorescence techniques. It is shown that for AmB concentrations greater than 5 μg/mL, with an increase in AmB's concentration, the reorganization time for the DOPC/cholesterol monolayer increases, and the elastic modulus of the DOPC/cholesterol mixed monolayer decreases. In particular, when AmB's concentration is higher than 85 μg/mL, the liquid-condensed phase domains on the DOPC/cholesterol monolayer reduce significantly and the liquid-expanded phase domain enlarges from the BAM images. When the AmB concentration reaches 5 μg/mL, the disorder of the hydrophobic and hydrophilic domains of the DOPC/cholesterol bilayer increases as the AmB concentration increases. The way in which AmB interacts with the DOPC/cholesterol mixed membrane is related to the concentration of AmB. The higher the concentration of AmB, the more likely it is to remove cholesterol from the unsaturated phospholipid membrane. The results are helpful to understand the mechanism of AmB's toxicity to the erythrocyte's membrane, which has a guiding value for seeking ways to reduce the AmB's toxicity.
Insights
Amphotericin B (AmB) toxicity to red blood cell membranes is linked to its concentration. Higher AmB levels disrupt cholesterol-rich domains, potentially reducing its harmful effects.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Pharmacology
Background:
- Amphotericin B (AmB) is crucial for treating invasive fungal infections.
- AmB's erythrocyte membrane toxicity, causing hemolysis, limits its clinical dose.
- The precise molecular mechanism of AmB-erythrocyte interaction, especially within cholesterol-rich domains, remains unclear.
Purpose of the Study:
- To investigate the adsorption and interaction mechanism of Amphotericin B (AmB) with unsaturated phospholipid membranes containing cholesterol.
- To elucidate how varying AmB concentrations affect the structural and thermodynamic properties of these membranes.
- To understand the molecular basis of AmB-induced erythrocyte membrane toxicity.
Main Methods:
- Langmuir monolayer model and Brewster Angle Microscopy (BAM) to study DOPC/cholesterol monolayers.
- Large unilamellar vesicle liposomes and fluorescence techniques to analyze DOPC bilayers.
- Investigated AmB adsorption at concentrations of 5, 45, 85, and 125 μg/mL.
Main Results:
- AmB concentrations above 5 μg/mL increased reorganization time and decreased elastic modulus in DOPC/cholesterol monolayers.
- High AmB concentrations (>85 μg/mL) led to reduced liquid-condensed domains and enlarged liquid-expanded domains in BAM images.
- Increased AmB concentration elevated disorder in both hydrophobic and hydrophilic domains of DOPC/cholesterol bilayers.
- Higher AmB concentrations promoted cholesterol removal from the phospholipid membrane.
Conclusions:
- AmB's interaction with cholesterol-containing phospholipid membranes is concentration-dependent.
- Increased AmB concentration disrupts membrane structure, particularly by removing cholesterol.
- Findings offer insights into AmB's erythrocyte toxicity and guide strategies for reducing its adverse effects.
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