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Effects of amphotericin B on membrane permeability--kinetics of spin probe reduction
Abstract:
The effect of the polyene antibiotic amphotericin B on the permeability of both unilamellar and multilamellar model membranes is investigated. The method measures the loss of the electron paramagnetic resonance signal of a spin probe, trapped in the aqueous compartment of a lipid dispersion, upon addition of ascorbate ions to the bulk aqueous phase. Amphotericin B causes large increases in the permeability of cholesterol-containing egg phosphatidylcholine membranes, whereas the effects are small in the absence of sterol and do not depend on surface charge. The effect of amphotericin depends upon the antibiotic:sterol mole ratio. The antibiotic appears to be unable to cross the membrane, acting only on the outermost bilayer of a multibilayer dispersion. When a phospholipid in the gel phase is used, amphotericin B causes large increases in permeability, independently of the presence or absence of sterol. It is suggested that the mechanism of action of amphotericin B is different for lipids in the liquid crystalline or gel states.
Insights
The polyene antibiotic amphotericin B significantly increases model membrane permeability, especially with cholesterol. Its mechanism differs between lipid gel and liquid crystalline states, impacting drug delivery research.
Area of Science:
- Biochemistry
- Membrane Biophysics
- Pharmacology
Background:
- Model membranes are crucial for understanding drug interactions.
- Polyene antibiotics like amphotericin B are used to treat fungal infections.
- Membrane permeability is vital for drug efficacy and cellular function.
Purpose of the Study:
- To investigate the effect of amphotericin B on model membrane permeability.
- To explore the role of cholesterol and lipid phase state in amphotericin B's action.
- To elucidate the mechanism of amphotericin B interaction with lipid bilayers.
Main Methods:
- Utilized unilamellar and multilamellar lipid model membranes.
- Employed electron paramagnetic resonance (EPR) spectroscopy with a spin probe.
- Measured the loss of EPR signal upon ascorbate ion addition to assess permeability.
Main Results:
- Amphotericin B greatly increased permeability in cholesterol-containing phosphatidylcholine membranes.
- Effects were minimal in membranes lacking sterols and independent of surface charge.
- Permeability increases were observed in gel-phase lipids, irrespective of sterol presence.
- Amphotericin B's action appeared localized to the outer membrane layer.
Conclusions:
- Amphotericin B's membrane-disrupting activity is highly dependent on cholesterol content.
- The antibiotic's mechanism of action varies between gel and liquid crystalline lipid phases.
- Findings suggest potential for targeted drug delivery strategies based on lipid composition.