Influence of the lipid composition on the membrane affinity, and the membrane-perturbing ability of cetylpyridinium chloride

Phosphatidylinositol 4,5-Bisphosphate Mediates the Co-Distribution of Influenza A Hemagglutinin and Matrix Protein M1 at the Plasma Membrane

The fully assembled influenza A virus (IAV) has on its surface the highest density of a single membrane protein found in nature-the glycoprotein hemagglutinin (HA) that mediates viral binding, entry, and assembly. HA clusters at the plasma membrane of infected cells, and the HA density (number of molecules per unit area) of these clusters correlates with the infectivity of the virus. Dense HA clusters are considered to mark the assembly site and ultimately lead to the budding of infectious IAV. The mechanism of spontaneous HA clustering, which occurs with or without other viral components, has not been elucidated. Using super-resolution fluorescence photoactivation localization microscopy (FPALM), we have previously shown that these HA clusters are interdependent on phosphatidylinositol 4,5-biphosphate (PIP2). Here, we show that the IAV matrix protein M1 co-clusters with PIP2, visualized using the pleckstrin homology domain. We find that cetylpyridinium chloride (CPC), which is a positively charged quaternary ammonium compound known for its antibacterial and antiviral properties at millimolar concentrations, disrupts M1 clustering and M1-PIP2 co-clustering at micromolar concentrations well below the critical micelle concentration (CMC). CPC also disrupts the co-clustering of M1 with HA at the plasma membrane, suggesting the role of host cell PIP2 clusters as scaffolds for gathering and concentrating M1 and HA to achieve their unusually high cluster densities in the IAV envelope.

Cetylpyridinium chloride (CPC) reduces zebrafish mortality from influenza infection: Super-resolution microscopy reveals CPC interference with multiple protein interactions with phosphatidylinositol 4,5-bisphosphate in immune function

The COVID-19 pandemic raises significance for a potential influenza therapeutic compound, cetylpyridinium chloride (CPC), which has been extensively used in personal care products as a positively-charged quaternary ammonium antibacterial agent. CPC is currently in clinical trials to assess its effects on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) morbidity. Two published studies have provided mouse and human data indicating that CPC may alleviate influenza infection, and here we show that CPC (0.1 μM, 1 h) reduces zebrafish mortality and viral load following influenza infection. However, CPC mechanisms of action upon viral-host cell interaction are currently unknown. We have utilized super-resolution fluorescence photoactivation localization microscopy to probe the mode of CPC action. Reduction in density of influenza viral protein hemagglutinin (HA) clusters is known to reduce influenza infectivity: here, we show that CPC (at non-cytotoxic doses, 5-10 μM) reduces HA density and number of HA molecules per cluster within the plasma membrane of NIH-3T3 mouse fibroblasts. HA is known to colocalize with the negatively-charged mammalian lipid phosphatidylinositol 4,5-bisphosphate (PIP2); here, we show that nanoscale co-localization of HA with the PIP2-binding Pleckstrin homology (PH) reporter in the plasma membrane is diminished by CPC. CPC also dramatically displaces the PIP2-binding protein myristoylated alanine-rich C-kinase substrate (MARCKS) from the plasma membrane of rat RBL-2H3 mast cells; this disruption of PIP2 is correlated with inhibition of mast cell degranulation. Together, these findings offer a PIP2-focused mechanism underlying CPC disruption of influenza and suggest potential pharmacological use of this drug as an influenza therapeutic to reduce global deaths from viral disease.

Thiazolium-derivative functionalized silver nanocomposites for suppressing bacterial resistance and eradicating biofilms

Commercial antibiotic therapies are becoming less efficient due to the emergence of bacterial resistance and the formation of bacterial biofilms.

Selective Bactericidal Activity of Divalent Metal Salts of Lauric Acid

Bacteria play a crucial role in skin health. For example, Staphylococcus aureus and Propionibacterium acnes cause skin roughness and acne, whereas Staphylococcus epidermidis enhances innate barrier immunity. Therefore, controlling the bacterial flora is important in dermatology and cosmetic chemistry. In this study, the bactericidal activities of different metal salts of lauric acid were evaluated. The bactericidal behavior of the salts changed according to the type of metal ion. Specifically, the Mg-, Ca-, and Mn-containing salts effectively sterilized only S. aureus and P. acnes. Their Co, Ni, and Cu salts sterilized all bacteria, including S. epidermidis, whereas the Zn salt proved ineffective. The Cu salt displayed the strongest bactericidal activity. Spin-trapping, detected using electron spin resonance, showed that this salt catalyzed the generation of hydroxyl radicals, which can destroy bacterial cell membranes. These findings demonstrate that metal-ion selection is an important factor in the design of bactericidal agents for healthcare products.

Quatsomes for the treatment of Staphylococcus aureus biofilm

The anti-biofilm effect of drug delivery systems composed of the antiseptic quaternary ammonium compound cetylpyridinium chloride (CPC) and cholesterol was evaluated in Staphylococcus aureus biofilm. Self-assembly of CPC/cholesterol to approximately 100 nm CPC-quatsomes was successfully accomplished by a simple sonication/dispersion method over a broad concentration range from 0.5 to 10 mg ml^-1 CPC. CPC-quatsomes showed a dose-dependent anti-biofilm effect, killing >99% of biofilm-associated S. aureus from 5% mg ml^-1 after 10 minutes exposure. Cell toxicity studies with CPC-quatsomes in Nuli-1 cells revealed no adverse effects at all tested CPC concentrations. CPC-quatsomes, therefore, have a promising potential as novel drug delivery systems with "built-in" anti-biofilm activity.

Interaction of hexadecylbetainate chloride with biological relevant lipids

The present work investigates the interaction of hexadecylbetainate chloride (C(16)BC), a glycine betaine-based ester with palmitoyl-oleoyl-phosphatidylcholine (POPC), sphingomyelin (SM), and cholesterol (CHOL), three biological relevant lipids present in the outer leaflet of the mammalian plasma membrane. The binding affinity and the mixing behavior between the lipids and C(16)BC are discussed based on experimental (isothermal titration calorimetry (ITC) and Langmuir film balance) and molecular modeling studies. The results show that the interaction between C(16)BC and each lipid is thermodynamically favorable and does not affect the integrity of the lipid vesicles. The primary adsorption of C(16)BC into the lipid film is mainly governed by a hydrophobic effect. Once C(16)BC is inserted in the lipid film, the polar component of the interaction energy between C(16)BC and the lipid becomes predominant. Presence of CHOL increases the affinity of C(16)BC for membrane. This result can be explained by the optimal matching between C(16)BC and CHOL within the film rather by a change of membrane fluidity due to the presence of CHOL. The interaction between C(16)BC and SM is also favorable and gives rise to highly stable monolayers probably due to hydrogen bonds between their hydrophilic groups. The interaction of C(16)BC with POPC is less favorable but does not destabilize the mixed monolayer from a thermodynamic point of view. Interestingly, for all the monolayers investigated, the exclusion surface pressures are above the presumed lateral pressure of the plasma membranes suggesting that C(16)BC would be able to penetrate into mammalian plasma membranes in vivo. These results may serve as a useful basis in understanding the interaction of C(16)BC with real membranes.

Interactions of surfactants with lipid membranes

Surfactants are surface-active, amphiphilic compounds that are water-soluble in the micro- to millimolar range, and self-assemble to form micelles or other aggregates above a critical concentration. This definition comprises synthetic detergents as well as amphiphilic peptides and lipopeptides, bile salts and many other compounds. This paper reviews the biophysics of the interactions of surfactants with membranes of insoluble, naturally occurring lipids. It discusses structural, thermodynamic and kinetic aspects of membrane-water partitioning, changes in membrane properties induced by surfactants, membrane solubilisation to micelles and other phases formed by lipid-surfactant systems. Each section defines and derives key parameters, mentions experimental methods for their measurement and compiles and discusses published data. Additionally, a brief overview is given of surfactant-like effects in biological systems, technical applications of surfactants that involve membrane interactions, and surfactant-based protocols to study biological membranes.

Passive diffusion of polymeric surfactants across lipid bilayers

Self-assembling polymeric surfactant, mmePEG(750)P(CL-co-TMC) [monomethylether poly(ethylene glycol)(750)-poly(caprolactone-co-trimethylene carbonate)], increases drug solubility and crosses an enterocyte monolayer both in vitro and in vivo. The aims of the present work were to investigate whether mmePEG(750)P(CL-co-TMC) polymers can diffuse passively through lipid bilayer using parallel artificial membrane permeability assay (PAMPA) and affect membrane properties using liposomes as model. The mmePEG(750)P(CL-co-TMC) polymer was able to cross by passive diffusion an enterocyte-mimicking membrane in PAMPA at concentration which did not perturb membrane integrity. A weak rigidification associated with a low increase in permeability of liposomal lipid bilayers was observed. These data suggest that polymeric surfactants can cross the lipid membrane by passive diffusion and interact with lipid bilayers.

Isothermal titration calorimetric study of calcium association to lipid bilayers: influence of the vesicle preparation and composition

The association of Ca2+ ions with phospholipid bilayers was investigated using isothermal titration calorimetry. The study reveals that the binding enthalpy of these cations to bilayers formed with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) depends strongly on the method of preparation of the unilamellar vesicles. Extruded vesicles lead to an exothermic association, whereas sonicated ones lead to an endothermic association. In the later case, the calorimetric signal is sensitive to the length of the sonication period. It is proposed that a reorganization of the lipid bilayers under stress, obtained with sonicated small unilamellar vesicles, contributes to the calorimetric signal upon the titration with Ca2+. The analysis of the titrations indicates that, as expected, the nature of the association of Ca2+ with negatively charged phospholipid bilayers is essentially of electrostatic nature. Using a Scatchard approach, it is found that bilayers become saturated in Ca2+ approximately when the electroneutrality of the bilayer interface is reached. Moreover, the affinity constant was reduced by the increase of the ionic strength of the aqueous buffer. It was found that the intrinsic binding constant of Ca2+ to membranes containing 30 and 50 mol% of POPG was about 11 mM-1, in a MES buffer containing 10 mM NaCl, at pH 5.6.