The structure of lipopeptides impacts their antiviral activity and mode of action against SARS-CoV-2 in vitro.

Microbial lipopeptides are synthesized by nonribosomal peptide synthetases and are composed of a hydrophobic fatty acid chain and a hydrophilic peptide moiety. These structurally diverse amphiphilic molecules can interact with biological membranes and possess various biological activities, including antiviral properties. This study aimed to evaluate the cytotoxicity and antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) of 15 diverse lipopeptides to understand their structure-activity relationships. Non-ionic lipopeptides were generally more cytotoxic than charged ones, with cationic lipopeptides being less cytotoxic than anionic and non-ionic variants. At 100 µg/mL, six lipopeptides reduced SARS-CoV-2 RNA to undetectable levels in infected Vero E6 cells, while six others achieved a 2.5- to 4.1-log reduction, and three had no significant effect. Surfactin, white line-inducing principle (WLIP), fengycin, and caspofungin emerged as the most promising anti-SARS-CoV-2 agents. Detailed analysis revealed that these four lipopeptides affected various stages of the viral life cycle involving the viral envelope. Surfactin and WLIP significantly reduced viral RNA levels in replication assays, comparable to neutralizing serum. Surfactin uniquely inhibited viral budding, while fengycin impacted viral binding after pre-infection treatment of the cells. Caspofungin demonstrated a lower antiviral effect compared to the others. Key structural traits of lipopeptides influencing their cytotoxic and antiviral activities were identified. Lipopeptides with a high number of amino acids, especially charged (preferentially anionic) amino acids, showed potent anti-SARS-CoV-2 activity. This research paves the way for designing new lipopeptides with low cytotoxicity and high antiviral efficacy, potentially leading to effective treatments. IMPORTANCE: This study advances our understanding of how lipopeptides, which are molecules mostly produced by bacteria, with both fat and protein components, can be used to fight viruses like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). By analyzing 15 different lipopeptides, researchers identified key structural features that make some of these molecules particularly effective at reducing viral levels while being less harmful to cells. Specifically, lipopeptides with certain charged amino acids were found to have the strongest antiviral effects. This research lays the groundwork for developing new antiviral treatments that are both potent against viruses and safe for human cells, offering hope for better therapeutic options in the future.

A Biomimetic Multiparametric Assay to Characterise Anti-Amyloid Drugs.

Alzheimer's disease (AD) is the most widespread form of senile dementia worldwide and represents a leading socioeconomic problem in healthcare. Although it is widely debated, the aggregation of the amyloid ß peptide (Aß) is linked to the onset and progression of this neurodegenerative disease. Molecules capable of interfering with specific steps in the fibrillation process remain of pharmacological interest. To identify such compounds, we have set up a small molecule screening process combining multiple experimental methods (UV and florescence spectrometry, ITC, and ATR-FTIR) to identify and characterise potential modulators of Aß1-42 fibrillation through the description of the biochemical interactions (molecule-membrane Aß peptide). Three known modulators, namely bexarotene, Chicago sky blue and indomethacin, have been evaluated through this process, and their modulation mechanism in the presence of a biomembrane has been described. Such a well-adapted physico-chemical approach to drug discovery proves to be an undeniable asset for the rapid characterisation of compounds of therapeutic interest for Alzheimer's disease. This strategy could be adapted and transposed to search for modulators of other amyloids such as tau protein.

Added Value of Biophysics to Study Lipid-Driven Biological Processes: The Case of Surfactins, a Class of Natural Amphiphile Molecules.

The role of membrane lipids is increasingly claimed to explain biological activities of natural amphiphile molecules. To decipher this role, biophysical studies with biomimetic membrane models are often helpful to obtain insights at the molecular and atomic levels. In this review, the added value of biophysics to study lipid-driven biological processes is illustrated using the case of surfactins, a class of natural lipopeptides produced by Bacillus sp. showing a broad range of biological activities. The mechanism of interaction of surfactins with biomimetic models showed to be dependent on the surfactins-to-lipid ratio with action as membrane disturber without membrane lysis at low and intermediate ratios and a membrane permeabilizing effect at higher ratios. These two mechanisms are relevant to explain surfactins' biological activities occurring without membrane lysis, such as their antiviral and plant immunity-eliciting activities, and the one involving cell lysis, such as their antibacterial and hemolytic activities. In both biological and biophysical studies, influence of surfactin structure and membrane lipids on the mechanisms was observed with a similar trend. Hence, biomimetic models represent interesting tools to elucidate the biological mechanisms targeting membrane lipids and can contribute to the development of new molecules for pharmaceutical or agronomic applications.

Encapsulation of Vitamin C by Glycerol-Derived Dendrimers, Their Interaction with Biomimetic Models of Stratum corneum and Their Cytotoxicity.

Vitamin C is one of the most sensitive cosmetic active ingredients. To avoid its degradation, its encapsulation into biobased carriers such as dendrimers is one alternative of interest. In this work, we wanted to evaluate the potential of two biobased glycerodendrimer families (GlyceroDendrimers-Poly(AmidoAmine) (GD-PAMAMs) or GlyceroDendrimers-Poly(Propylene Imine) (GD-PPIs)) as a vitamin C carrier for topical application. The higher encapsulation capacity of GD-PAMAM-3 compared to commercial PAMAM-3 and different GD-PPIs, and its absence of cytotoxicity towards dermal cells, make it a good candidate. Investigation of its mechanism of action was done by using two kinds of biomimetic models of stratum corneum (SC), lipid monolayers and liposomes. GD-PAMAM-3 and VitC@GD-PAMAM-3 (GD-PAMAM-3 with encapsulated vitamin C) can both interact with the lipid representatives of the SC lipid matrix, whichever pH is considered. However, only pH 5.0 is suggested to be favorable to release vitamin C into the SC matrix. Their binding to SC-biomimetic liposomes revealed only a slight effect on membrane permeability in accordance with the absence of cytotoxicity but an increase in membrane rigidity, suggesting a reinforcement of the SC barrier property. Globally, our results suggest that the dendrimer GD-PAMAM-3 could be an efficient carrier for cosmetic applications.

PIP2 Phospholipid-Induced Aggregation of Tau Filaments Probed by Tip-Enhanced Raman Spectroscopy.

The morphology and secondary structure of peptide fibers formed by aggregation of tubulin-associated unit (Tau) fragments (K18), in the presence of the inner cytoplasmic membrane phosphatidylinositol component (PIP2 ) or heparin sodium (HS) as cofactors, are determined with nanoscale (<10 nm) spatial resolution. By means of tip-enhanced Raman spectroscopy (TERS), the inclusion of PIP2 lipids in fibers is determined based on the observation of specific C=O ester vibration modes. Moreover, analysis of amide I and amide III bands suggests that the parallel ß-sheet secondary structure content is lower and the random coil content is higher for fibers grown from the PIP2 cofactor instead of HS. These observations highlight the occurrence of some local structural differences between these fibers. This study constitutes the first nanoscale structural characterization of Tau/phospholipid aggregates, which are implicated in deleterious mechanisms on neural membranes in Alzheimer's disease.

Tau protein aggregation: Key features to improve drug discovery screening.

Tauopathies are neurodegenerative disorders associated with the accumulation of abnormal tubulin associated unit (tau) protein in the brain. Tau pathologies include a broad spectrum of diseases, with Alzheimer's disease (AD) being the most common tauopathy. The pathophysiological mechanisms of AD are still only partially understood. As a consequence, attempts to establish therapeutic approaches have led to numerous clinical trial failures and, to date, no curative treatment is available for AD despite the considerable number of research programs. Therefore, over the past decade, the aggregation of the tau protein in AD has become a therapeutic target of interest. In this review, we gather in silico, in vitro, and in vivo methodologies that are relevant to assess compounds targeting tau aggregation, from early drug design to clinical trials.

ß-Amyloid peptide interactions with biomimetic membranes: A multiparametric characterization.

Alzheimer's disease is the most common form of senile dementia in the world, and amyloid ß peptide1-42 (Aß1-42) is one of its two principal biological hallmarks. While interactome concept was getting forward the scientific community, we proposed that the study of the molecular interactions of amyloid ß peptide with the biological membranes will allow to highlight underlying mechanisms responsive of AD. We have developed two simple liposomal formulations (phosphatidylcholine, cholesterol, phosphatidylglycerol) mimicking neuronal cell membrane (composition, charge, curvature radius). Interactions with Aß1-42 and mutant oG37C, a stable oligomeric form of the peptide, were characterized according to a simple multiparametric procedure based on ThT fluorescence, liposome leakage assay, ATR-FTIR spectroscopy. Kinetic aggregation, membrane damage and peptide conformation provided our first methodologic bases to develop an original model to describe interactions of Aß peptide and lipids.

Microplate assay for lipophilicity determination using intrinsic fluorescence of drugs: Application to a promising anticancer lead, pyridoclax.

Lipophilicity must be necessarily determined in drug discovery since this physicochemical property will directly influence the pharmacokinetics of a drug as its pharmacodynamics profile. Pyridoclax is an original lead, recently identified as very promising in treatment of chemoresistant cancers. The partition coefficient (Kp) of this anticancer drug was determined by microplate assays, well adapted in drug discovery, since being rapid, and requiring only poor drug amounts. The analytical approach was performed either by UV derivative spectrophotometry after validation thanks to a set of basic, neutral and acid reference substances, or originally, by raw fluorescence spectrophotometry by taking advantage of the pyridoclax intrinsic fluorescence. Large unilamellar vesicles (LUVs) were formulated from soybean-, egg-, or dipalmitoyl-phosphatidylcholine, characterized in terms of granulometric properties, ζ potential (determined by DLS), and of phospholipid content (quantified by 1H NMR, also in presence of cholesterol). Whatever the detection method used, log Kp of pyridoclax were in the same magnitude order, and pyridoclax appeared as a lipophilic compound. It was also established that interactions between this lead and biomimetic membranes were influenced by the relative fluidity of the membranes, as confirmed by results of a liposome leakage assay.