Crossregulation between the insertion of Hexadecylphosphocholine (miltefosine) into lipid membranes and their rheology and lateral structure

Investigation of miltefosine-model membranes interactions at the molecular level for two different PS levels modeling cancer cells

Miltefosine (MLT) is a broad-spectrum drug included in the alkylphospholipids (APL) used against leishmania and various types of cancer. The most crucial feature of APLs is that they are thought to only kill cancerous cells without harming normal cells. However, the molecular mechanism of action of APLs is not completely understood. The increase in the phosphatidylserine (PS) ratio is a marker showing the stage of cancer and even metastasis. The goal of this research was to investigate the molecular effects of miltefosine at the molecular level in different PS ratios. The effects of MLT on membrane phase transition, membrane orders, and dynamics were studied using DPPC/DPPS (3:1) and DPPC/DPPS (1:1) multilayer (MLV) vesicles mimicking DPPS ratio variation, Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared spectroscopy (FTIR). Our findings indicate that miltefosine is evidence at the molecular level that it is directed towards the tumor cell and that the drug's effect increases with the increase of anionic lipids in the membrane depending on the stage of cancer.

Differential scanning calorimetry in drug-membrane interactions

Differential Scanning Calorimetry (DSC) is a central technique in investigating drug - membrane interactions, a critical component of pharmaceutical research. DSC measures the heat difference between a sample of interest and a reference as a function of temperature or time, contributing essential knowledge on the thermally induced phase changes in lipid membranes and how these changes are affected by incorporating pharmacological substances. The manuscript discusses the use of phospholipid bilayers, which can form structures like unilamellar and multilamellar vesicles, providing a simplified yet representative membrane model to investigate the complex dynamics of how drugs interact with and penetrate cellular barriers. The manuscript consolidates data from various studies, providing a comprehensive understanding of the mechanisms underlying drug - membrane interactions, the determinants that influence these interactions, and the crucial role of DSC in elucidating these components. It further explores the interactions of specific classes of drugs with phospholipid membranes, including non-steroidal anti-inflammatory drugs, anticancer agents, natural products with antioxidant properties, and Alzheimer's disease therapeutics. The manuscript underscores the critical importance of DSC in this field and the need for continued research to improve our understanding of these interactions, acting as a valuable resource for researchers.

3'Nucleotidase/nuclease is required for Leishmania infantum clinical isolate susceptibility to miltefosine

BACKGROUND

Miltefosine treatment failure in visceral leishmaniasis in Brazil has been associated with deletion of the miltefosine susceptibility locus (MSL) in Leishmania infantum. The MSL comprises four genes, 3'-nucleotidase/nucleases (NUC1 and NUC2); helicase-like protein (HLP); and 3,2-trans-enoyl-CoA isomerase (TEI).

METHODS

In this study CRISPR-Cas9 was used to either epitope tag or delete NUC1, NUC2, HLP and TEI, to investigate their role in miltefosine resistance mechanisms. Additionally, miltefosine transporter genes and miltefosine-mediated reactive oxygen species homeostasis were assessed in 26 L. infantum clinical isolates. A comparative lipidomic analysis was also performed to investigate the molecular basis of miltefosine resistance.

FINDINGS

Deletion of both NUC1, NUC2 from the MSL was associated with a significant decrease in miltefosine susceptibility, which was restored after re-expression. Metabolomic analysis of parasites lacking the MSL or NUC1 and NUC2 identified an increase in the parasite lipid content, including ergosterol; these lipids may contribute to miltefosine resistance by binding the drug in the membrane. Parasites lacking the MSL are more resistant to lipid metabolism perturbation caused by miltefosine and NUC1 and NUC2 are involved in this pathway. Additionally, L. infantum parasites lacking the MSL isolated from patients who relapsed after miltefosine treatment were found to modulate nitric oxide accumulation in host macrophages.

INTERPRETATION

Altogether, these data indicate that multifactorial mechanisms are involved in natural resistance to miltefosine in L. infantum and that the absence of the 3'nucleotidase/nuclease genes NUC1 and NUC2 contributes to the phenotype.

FUNDING

MRC GCRF and FAPES.

What can we learn about amphiphile-membrane interaction from model lipid membranes?

Surface-active amphiphiles find applications in a wide range of areas of industry such as agrochemicals, personal care, and pharmaceuticals. In many of these applications, interaction with cell membranes is a key factor for achieving their purpose. How do amphiphiles interact with lipid membranes? What are their bases for membrane specificity? Which biophysical properties of membranes are susceptible to modulation by amphiphilic membrane-effectors? What aspects of this interaction are important for performing their function? In our work on membrane biophysics over the years, questions like these have arisen and we now share some of our findings and discuss them in this review. This topic was approached focusing on the membrane properties and their alterations rather than on the amphiphile structure requirements for their interaction. Here, we do not aim to provide a comprehensive list of the modes of action of amphiphiles of biological interest but to help in understanding them.

Exploring the Toxicity, Lung Distribution, and Cellular Uptake of Rifampicin and Ascorbic Acid-Loaded Alginate Nanoparticles as Therapeutic Treatment of Lung Intracellular Infections

Nanotechnology is a very promising technological tool to combat health problems associated with the loss of effectiveness of currently used antibiotics. Previously, we developed a formulation consisting of a chitosan and tween 80-decorated alginate nanocarrier that encapsulates rifampicin and the antioxidant ascorbic acid (RIF/ASC), intended for the treatment of respiratory intracellular infections. Here, we investigated the effects of RIF/ASC-loaded NPs on the respiratory mucus and the pulmonary surfactant. In addition, we evaluated their cytotoxicity for lung cells in vitro, and their biodistribution on rat lungs in vivo after their intratracheal administration. Findings herein demonstrated that RIF/ASC-loaded NPs display a favorable lung biocompatibility profile and a uniform distribution throughout lung lobules. RIF/ASC-loaded NPs were mainly uptaken by lung macrophages, their primary target. In summary, findings show that our novel designed RIF/ASC NPs could be a suitable system for antibiotic lung administration with promising perspectives for the treatment of pulmonary intracellular infections.

Self-assembled nanostructures of L-ascorbic acid alkyl esters support monomeric amphotericin B

Hypothesis

Amphotericin B (AmB) is a highly effective antimicrobial, with broad antimycotic and antiparasitic effect. However, AmB poor water-solubilisation and aggregation tendency limits its use for topical applications. We studied the capacity of nanostructures formed by alkyl esters of L-ascorbic acid (ASCn) to solubilise AmB and tested the relationship between the prevalence of the monomeric form of AmB and its effectiveness as antimicrobial agent.

Experiments

We developed self-assembled nanostructures formed by the commercial compound, palmitoyl ascorbic acid, as well as the shorter chained myristoyl and lauroyl ascorbic acid. AmB loaded ASCn nanostructures were studied by a combination of spectroscopic techniques, together with particle analysis, differential scanning calorimetry, microbiological tests, and Langmuir monolayer visualisation.

Findings

We found no direct relation between the antimicrobial capacity and the prevalence of the monomeric form of the drug. However, the later was related to chemical stability and colloidal robustness. Nanostructures formed by ASC16 in its anionic state provide an appropriate environment for AmB in its monomeric form, maintaining its antimicrobial capacity. Langmuir film visualisation supports spectrophotometric evidence, indicating that ASC16 allows the in-plane solubilisation of AmB. Coagels formed by ASC16 appear as promising for carrying AmB for dermal delivery.

l-Ascorbic acid alkyl esters action on stratum corneum model membranes: An insight into the mechanism for enhanced skin permeation

L-ascorbic acid alkyl esters (ASCn) are lipophilic forms of vitamin C, which act as skin permeation enhancers. We investigated the physical changes induced by incorporating ASCn into stratum corneum (SC) lipid membranes and correlated this with the mechanism proposed in the literature for skin permeation enhancement phenomena. We used lipid monolayers to explore the 2D structure and elasticity of the lipid-enhancer systems. As a comparison, the classic permeation enhancer, oleic acid (OA) and the non-enhancer analogue stearic acid (SA) were analysed. The incorporation of ASCn or OA into SC membranes resulted in more liquid-like films, with a dose-dependent lowering of the compressibility modulus. Brewster angle microscopy (BAM) evidenced partial miscibility of the enhancer with SC lipid components, stabilising the liquid-expanded phase. At the nanoscale, AFM showed that SC lipids form heterogeneous membranes, which underwent structural alterations after incorporating ASCn and fatty acids, such as SA and OA. The lower, cholesterol-enriched phase appears to concentrate the enhancers, whilst the higher ceramide-enriched phase concentrated the non-enhancer SA. Our results and previously reported pieces of evidence indicate a strong pattern in which the rheological properties of SC lipid films are determinant for skin permeation phenomena.

Psychosine remodels model lipid membranes at neutral pH

β-Galactosylsphingosine or psychosine (PSY) is a single chain sphingolipid with a cationic group, which is degraded in the lysosome lumen by β-galactosylceramidase during sphingolipid biosynthesis. A deficiency of this enzyme activity results in Krabbe's disease and PSY accumulation. This favors its escape to extralysosomal spaces, with its pH changing from acidic to neutral. We studied the interaction of PSY with model lipid membranes in neutral conditions, using phospholipid vesicles and monolayers as classical model systems, as well as a complex lipid mixture that mimics the lipid composition of myelin. At pH 7.4, when PSY is mainly neutral, it showed high surface activity, self-organizing into large structures, probably lamellar in nature, with a CMC of 38 ± 3 μM. When integrated into phospholipid membranes, PSY showed preferential partition into disordered phases, shifting phase equilibrium. The presence of PSY reduces the compactness of the membrane, making it more easily compressible. It also induces lipid domain disruption in vesicles composed of the main myelin lipids. The surface electrostatics of lipid membranes was altered by PSY in a complex manner. A shift to positive zeta potential values evidenced its presence in the vesicles. Furthermore, the increase of surface potential and surface water structuring observed may be a consequence of its location at the interface of the positively charged layer. As Krabbe's disease is a demyelinating process, PSY alteration of the membrane phase state, lateral lipid distribution and surface electrostatics appears important to the understanding of myelin destabilization at the supramolecular level.

Regulation of phase boundaries and phase-segregated patterns in model membranes

Demixing of components has long been described in model membranes. It is a consequence of non-ideal lateral interactions between membrane components, and it causes the presence of segregated phases, forming patches (domains) of different properties, thus introducing heterogeneity into the membrane. In the present review we first describe the processes through which domains are generated, how they grow, and why they are rounded, striped or fractal-like, as well as why they get distributed forming defined patterns. Next, we focus on the effect of an additive on a lipid mixture, which usually induces shifts in demixing points, thus stabilizing or destabilizing the phase-segregated state. Results found for different model membranes are summarized, detailing the ways in which phase segregation and the generated patterns may be modulated. We focus on which are, from our viewpoint, the most relevant regulating factors affecting the surface texture observed in model membranes. This article is part of a Special Issue entitled: Emergence of Complex Behavior in Biomembranes edited by Marjorie Longo.

The insertion of Polybia-MP1 peptide into phospholipid monolayers is regulated by its anionic nature and phase state

Polybia-MP1 or simply MP1 (IDWKKLLDAAKQIL-NH₂) is a peptide with broad-spectrum bactericidal activity and a strong inhibitory effect against cancer cells. The aim of this work was to evaluate the effect of biophysical properties such as membrane texture and film thickness on MP1 interaction with neutral and anionic lipid membranes. For this purpose, we first explored the peptide's surface behavior. MP1 showed high surface activity, adsorbing onto bare air/aqueous interfaces up to higher surface pressures than the collapse pressure of MP1 Langmuir films. The MP1-lipid membrane interaction was studied using Langmuir phosphatidylcholine and phosphatidylserine (PS) monolayers as model membrane systems. PS was chosen since this negatively charged lipid was found predominantly on the outer leaflet of tumor cells, and it enhances MP1 activity for PS-containing membranes to a greater extent than for other negatively charged lipids. MP1 incorporated into anionic PS monolayers, which show a liquid-expanded (LE) phase or LE-liquid-condensed (LC) phase coexistence, up to lipid-packing densities higher than those of cell membranes. The mixed lipid/MP1 films were explored by Brewster angle microscopy and atomic force microscopy. MP1 partitioned preferentially into the LE phase state of PS films, and were thus excluded from the coexisting LC phase. This interaction had strong electrostatic bases: in pure water, the lipid-peptide interaction was strong enough to induce formation of reversible lipid-peptide 3D structures associated with the interface. MP1 incorporation into the LE phase was accompanied by a shift of the phase transition pressure to higher values and a thinning of the lipid film. These results showed a clear correlation between peptide penetration capacity and the presence or induction of the thin LE phase. This capacity to regulate membrane physical properties may be of relevance in the binding, incorporation and membrane selectivity of this promising antitumor peptide.