The Antifungal Mechanism of Amphotericin B Elucidated in Ergosterol and Cholesterol-Containing Membranes Using Neutron Reflectometry

Abstract

We have characterized and compared the structures of ergosterol- and cholesterol-containing 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membranes before and after interaction with the amphiphilic antifungal drug amphotericin B (AmB) using neutron reflection. AmB inserts into both pure POPC and sterol-containing membranes in the lipid chain region and does not significantly perturb the structure of pure POPC membranes. By selective per-deuteration of the lipids/sterols, we show that AmB extracts ergosterol but not cholesterol from the bilayers and inserts to a much higher degree in the cholesterol-containing membranes. Ergosterol extraction by AmB is accompanied by membrane thinning. Our results provide new insights into the mechanism and antifungal effect of AmB in these simple models of fungal and mammalian membranes and help understand the molecular origin of its selectivity and toxic side effects.

Hijacking the intrinsic vitamin B12 pathway for the oral delivery of nanoparticles, resulting in enhanced in vivo anti-leishmanial activity

“…39 However, its water-soluble oligomers are highly toxic due to their relatively high affinity to the cholesterol in the host cell, while the monomeric form binds explicitly to ergosterol, reducing the host cell toxicity. 40 Achieving the monomerization of AmB generally relies on employing biocompatible lipid carriers, which induce disaggregation with longer chain surfactants. Additionally, previous reports revealed the more effective monomerization of AmB by micellar stearates, as present in the VBS coated on SLNs, for improving the lipid compatibility of the hydrophilic VB 12 .…”

Deuterated squalene and sterols from modifiedSaccharomyces cerevisiae

“…For ergosterol, the principal native fungal sterol, production of a deuterated material in Pichia and its use in neutron studies have been reported, including a methodology for the isolation of the material in high purity by precipitation. 25,26…”

Polyene Antibiotics Physical Chemistry and Their Effect on Lipid Membranes; Impacting Biological Processes and Medical Applications

“…Finally, Kaminski made an argument that the fungal cell wall is made up of hydrophilic chitin, which poses a serious obstacle in transporting ergosterol from the cell membrane and into the polyene aggregates. Additionally, there is evidence that not only is the affinity lower for cholesterol, but that AmB does not extract it from POPC membranes [ 163 ]. The authors used neutron reflectometry and found that AmB is not capable of extracting cholesterol from a POPC-cholesterol lipid bilayer, but it does extract ergosterol from a POPC-ergosterol lipid bilayer.…”