Phospholipid Monolayers Research Articles

Targeted modulation of pennycress lipid droplet proteins impacts droplet morphology and seed oil content.

Lipid droplets (LDs) are unusual organelles that have a phospholipid monolayer surface and a hydrophobic matrix. In oilseeds, this matrix is nearly always composed of triacylglycerols (TGs) for efficient storage of carbon and energy. Various proteins play a role in their assembly, stability and turnover, and even though the major structural oleosin proteins in seed LDs have been known for decades, the factors influencing LD formation and dynamics are still being uncovered mostly in the "model oilseed" Arabidopsis. Here we identified several key LD biogenesis proteins in the seeds of pennycress, a potential biofuel crop, that were correlated previously with seed oil content and characterized here for their participation in LD formation in transient expression assays and stable transgenics. One pennycress protein, the lipid droplet associated protein-interacting protein (LDIP), was able to functionally complement the Arabidopsis ldip mutant, emphasizing the close conservation of lipid storage among these two Brassicas. Moreover, loss-of-function ldip mutants in pennycress exhibited increased seed oil content without compromising plant growth, raising the possibility that LDIP or other LD biogenesis factors may be suitable targets for improving yields in oilseed crops more broadly.

Behavior of Microbubbles on Air-Aqueous Interfaces.

Animal-derived lung surfactants have saved millions of lives of preterm neonates with neonatal Respiratory Distress Syndrome (nRDS). However, a replacement for animal-derived lung surfactants has been sought for decades due to its high manufacturing cost, inaccessibility in low-income countries, and failure to show efficacy when nebulized. This study investigated the use of lipid-coated microbubbles as potential replacements for exogenous lung surfactants. Three different formulations of microbubbles (DPPC with/out PEG40-stearate and poractant alfa) were prepared, and their equilibrium and dynamic surface tensions were tested on a clean air-saline interface or a simulated air-lung fluid interface using a Langmuir-Blodgett trough. In dynamic surface measurements, microbubbles reduced the minimum surface tension compared with the equivalent composition lipid suspension: e.g., PEG-free microbubbles had a minimum surface tension of 4.3 mN/m while the corresponding lipid suspension and poractant alfa had 20.4 (p ≤ 0.0001) and 21.8 mN/m (p ≤ 0.0001), respectively. Two potential mechanisms for the reduction of surface tension were found: Fragmentation of the foams created by microbubble coalescence; and clustering of microbubbles in the aqueous subphase disrupting the interfacial phospholipid monolayer. The predominant mechanism appears to depend on the formulation and/or the environment. The use of microbubbles as a replacement for exogenous lung surfactant products thus shows promise and further work is needed to evaluate efficacy in vivo.

Effects of Spontaneous Curvature on Interfacial Adsorption and Collapse of Phospholipid Monolayers.

To function effectively, pulmonary surfactant must adsorb rapidly to the alveolar air/water interface, but avoid collapse from the interface when compressed to low surface tensions. Prior studies show that phospholipids in the cylindrical monolayers of the inverse hexagonal (HII) phase adsorb quickly. The monolayers have negative curvature, defined by the concave shape of the hydrophilic face. Formation of the HII structures, however, involves significant disruption of optimal chain-packing. Samples with significant spontaneous curvature, formed in the absence of applied force, may nonetheless have lamellar structures. The experiments here tested whether planar lamellar bilayers formed by phospholipids with negative spontaneous curvature might adsorb rapidly but collapse slowly. Prior studies have shown that binary mixtures of dioleoyl phosphatidylcholine-dioleoyl phosphatidylethanolamine (DOPC-DOPE) with higher mol fractions of DOPE (XPE) have more negative spontaneous curvature. Samples with higher XPE adsorbed more rapidly but also collapsed more quickly. Over that range of XPE, small angle X-ray scattering showed only lamellar structures. The HII phase was undetectable. The results suggest that the innate tendency of the phospholipids to form curved structures has primary importance for adsorption rather than the presence of HII structures. Planar structures are insufficient to minimize the tendency of spontaneous curvature to promote collapse. These findings are consistent with adsorption and collapse that occur via rate-limiting structures with significant negative curvature.

Hydrolysis of phospholipid monolayers by phospholipase A2 revealed by heterodyne-detected sum frequency generation (HD-SFG) spectroscopy.

Phospholipase A2 (PLA2) catalyzes the hydrolysis of the sn-2 acyl ester linkage in phospholipid, producing lysophospholipid and fatty acid in the presence of Ca2+. The hydrolysis mediated by PLA2 has attracted much interest in various fields, such as pharmacy and biotechnology. It is recognized that PLA2 cannot hydrolyze phospholipid monolayers at high surface coverage. However, the origin of different PLA2 activities is not fully understood yet. The present study investigated the interaction between DPPC (16:0 PC) monolayer and PLA2 using heterodyne-detected sum frequency generation spectroscopy, which is interface-specific spectroscopy and highly sensitive to molecular symmetry based on a second-order nonlinear optical process. It was revealed that PLA2 adsorbs to the DPPC monolayer on the aqueous solution surface only when the surface coverage is low. The adsorption at the low surface coverage significantly changes the interfacial structures of PLA2 and the hydration, which are stabilized by the presence of Ca2+. Therefore, the restriction of the hydrolysis of phospholipid monolayers at high surface coverage can be rationalized by the inhabitation of the PLA2 adsorption. The present study deepens our molecular-level understanding of the hydrolysis of phospholipids by PLA2.

Physicochemical Properties of Seed Oil Blends and Their Potential for the Creation of Synthetic Oleosomes with Modulated Polarities.

There is an increasing demand within the pharmaceutical and cosmetic industries for biofriendly lipid-based active ingredient delivery systems. Micelles, liposomes, and lipid nanoparticles are currently the most used systems despite their limitations. Oleosomes, also known as lipid droplets, are promising alternatives to the existing strategies. Oleosomes are typically found in plant cells and are characterized by a nonpolar triacylglycerol core surrounded by a phospholipid monolayer punctuated with the protein oleosin. Producing oleosomes synthetically allows the customization of their lipid content, size, protein content, and oil core characteristics, expanding their versatility. Herein we demonstrate a proof of concept for the use of synthetic oleosomes to sequester polar molecules by modulating their core polarity with blends of sunflower and castor oils. The physical properties (density, refractive index, and permittivity) of the oil blends are characterized and demonstrate ideal mixing of the oils, which is supported by molecular dynamics simulations. Spectroscopic examination of the oil blends using fluorescent probes shows that the polarity of oil blends increases as the fraction of castor oil increases. Finally, we show that the uptake of a polar fluorescent probe (NBD-glucose) into synthetic oleosomes is enhanced by increasing the polarity of the oil core, but large charged molecules are excluded from the core regardless of polarity. These experiments show that synthetic oleosomes with tunable oil cores can expand the range of molecules that can be loaded into a biofriendly package as desired for biotechnology applications.

Lipid Droplets Big and Small: Basic Mechanisms That Make Them All.

Lipid droplets (LDs) are dynamic storage organelles with central roles in lipid and energy metabolism. They consist of a core of neutral lipids, such as triacylglycerol, which is surrounded by a monolayer of phospholipids and specialized surface proteins. The surface composition determines many of the LD properties, such as size, subcellular distribution, and interaction with partner organelles. Considering the diverse energetic and metabolic demands of various cell types, it is not surprising that LDs are highly heterogeneous within and between cell types. Despite their diversity, all LDs share a common biogenesis mechanism. However, adipocytes have evolved specific adaptations of these basic mechanisms, enabling the regulation of lipid and energy metabolism at both the cellular and organismal levels. Here, we discuss recent advances in the understanding of both the general mechanisms of LD biogenesis and the adipocyte-specific adaptations controlling these fascinating organelles.

The role of oleosins and phosphatidylcholines on the membrane mechanics of oleosomes

HypothesisOilseeds use triacylglycerides as main energy source, and pack them into highly stable droplets (oleosomes) to facilitate the triacylglycerides’ long-term storage in the aqueous cytosol. To prevent the coalescence of oleosomes, they are stabilized by a phospholipid monolayer and unique surfactant-shaped proteins, called oleosins. In this study, we use state-of-the-art interfacial techniques to reveal the function of each component at the oleosome interface. ExperimentsWe created model oil–water interfaces with pure oleosins, phosphatidylcholines, or mixtures of both components (ratios of 3:1, 1:1, 1:3), and applied large oscillatory dilatational deformations (LAOD). The obtained rheological response was analyzed with general stress decomposition (GSD) to get insights into the role of phospholipids and oleosins on the mechanics of the interface. FindingsOleosins formed viscoelastic solid interfacial films due to network formation via in-plane interactions. Between adsorbed phosphatidylcholines, weak interactions were observed, suggesting the surface stress response upon dilatational deformations was dominated by density changes. In mixtures with 3:1 and 1:1 oleosin-to-phosphatidylcholine ratios, oleosins dominated the interfacial mechanics and formed a network, while phosphatidylcholines contributed to interfacial tension reduction. At higher phosphatidylcholine concentrations (1:3 oleosin-to-phosphatidylcholine), phosphatidylcholine dominated the interface, and no network formation occurred. Our findings improve the understanding of both components’ role for oleosomes.

Thermodynamic Study on Biomimetic Legionella gormanii Bacterial Membranes.

The presented studies were aimed at determining the interactions in model membranes (Langmuir monolayers) created of phospholipids (PL) isolated from Legionella gormanii bacteria cultured with (PL + choline) or without (PL - choline) choline and to describe the impact of an antimicrobial peptide, human cathelicidin LL-37, on PL's monolayer behavior. The addition of choline to the growth medium influenced the mutual proportions of phospholipids extracted from L. gormanii. Four classes of phospholipids-phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), cardiolipin (CL), and their mixtures-were used to register compression isotherms with or without the LL-37 peptide in the subphase. Based on them the excess area (Ae), excess (ΔGe), and total (ΔGm) Gibbs energy of mixing were determined. The thermodynamic analyses revealed that the PL - choline monolayer showed greater repulsive forces between molecules in comparison to the ideal system, while the PL + choline monolayer was characterized by greater attraction. The LL-37 peptide affected the strength of interactions between phospholipids' molecules and reduced the monolayers stability. Accordingly, the changes in interactions in the model membranes allowed us to determine the difference in their susceptibility to the LL-37 peptide depending on the choline supplementation of bacterial culture.

Encapsulation of cannabidiol in hemp seed oleosomes

Oleosomes are natural lipid droplets that can be extracted intact from oil seeds, forming oil/water emulsions. Their lipid cores, surrounded by a monolayer of phospholipids and proteins, make oleosomes suitable as carriers of hydrophobic bioactive compounds like cannabidiol (CBD). As CBD is crystalline at room temperature, it first has to be liquified to allow better encapsulation. This was done by heating (80 °C for 4 h) or by pre-solubilizing CBD in ethanol and then the liquified CBD was mixed with oleosome dispersions for the encapsulation. Both methods exhibit good encapsulation efficiency, but the results were significantly influenced by the ratio of CBD to lipid contents, regardless of the encapsulation method applied. At higher concentrations of CBD relative to that of the lipid in the oleosomes, the encapsulation efficiency decreased as saturation was attained. Moreover, the in vitro digestion analysis was conducted to investigate the potential of oleosomes as carriers to transport CBD. The relatively slow and steady release of CBD from oleosomes indicates that oleosomes are a slow-release carrier for hydrophobic functional ingredients. An important finding is that the encapsulation and in vitro digestive properties of the oleosomes remain unaffected by the presence of CBD, heating treatment or ethanol, which could bring more opportunities for the applications of oleosomes as carriers in various fields.

Interactions of Alkali Ions and Phospholipid Monolayers at Organic-Water Interfaces

The self-assembled phospholipids monolayers at interfaces between two immiscible electrolyte solutions (ITIES) are commonly used to study the interactions between cell membranes and species passing in and out through membrains such as ions, drugs, and other nutrients. In this study, we utilized electrochemical techniques such as open circuit potential (OCP), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) to study the pure phospholipd monolayer formed by 1,2-Dioleoyl-sn-glycero-3-phosphocholine (DOPC) and its mixture with 1,2-dioleoyl-sn-glycero-3-phospho-(1'-racglycerol) (sodium salt) (DOPG) at 1,2-dichloroethane-water interfaces. Our study has shown that at higher applied electric potentials, there seems to be no change in the facilitation of cation transfers by DOPC/DOPG monolayer compared to DOPC monolayer. However, at lower applied potentials, the DOPGs in the mixed monolayer seemed to leave the interface under the influence of the applied electric field, indicated by both the higher capacitance obtained throught the EIS measurements and the higher currents from the CV measurements compared to results obtained from the sample consisted of the pure DOPC monolayer. Furthermore, our study also showed a general rise in capacitance when incorporating heavier alkali ions in the aqueous phase for the sample with the mixture of DOPC/DOPG at higher applied electric potentials.

Unlocking Secrets: Lipid Metabolism and Lipid Droplet Crucial Roles in SARS-CoV-2 Infection and the Immune Response.

Lipid droplets (LD) are crucial for maintaining lipid and energy homeostasis within cells. LDs are highly dynamic organelles that present a phospholipid monolayer rich in neutral lipids. Additionally, LDs are associated with structural and non-structural proteins, rapidly mobilizing lipids for various biological processes. Lipids play a pivotal role during viral infection, participating during viral membrane fusion, viral replication, and assembly, endocytosis, and exocytosis. Severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection often induces LD accumulation, which is used as a source of energy for the replicative process. These findings suggest that LDs are a hallmark of viral infection, including SARS-CoV-2 infection. Moreover, LD participates in the inflammatory process and cell signaling, activating pathways related to innate immunity and cell death. Accumulating evidence demonstrates that LD induction by SARS-CoV-2 is a highly coordinated process, aiding replication and evading the immune system, and may contribute to the different cell death process observed in various studies. Nevertheless, recent research in the field of LDs suggests these organelles according to the pathogen and infection conditions may also play roles in immune and inflammatory responses, protecting the host against viral infection. Understanding how SARS-CoV-2 influences LD biogenesis is crucial for developing novel drugs or repurposing existing ones. By targeting host lipid metabolic pathways exploited by the virus, it is possible to impact viral replication and inflammatory responses. This review seeks to discuss and analyze the role of LDs during SARS-CoV-2 infection, specifically emphasizing their involvement in viral replication and the inflammatory response.

Cationic Biocides Tend to Embed into the Inner Layer of the Model Outer Membrane Vesicles of Gram-negative Bacteria: Computational Insights

The outer membrane vesicles (OMVs), produced by many pathogenic bacteria, play a significant role in bacterial pathogenesis. They promote bacterial resistance to antibiotics and act as natural protective barriers. The study of OMVs is essential both for understanding the general mechanisms of bacterial pathogenicity and for the development of the antibacterial drugs. In this paper, we created model vesicle that imitate the OMVs of Gram-negative bacteria using molecular modeling techniques. To investigate the interaction of the cationic antimicrobial compounds with the outer lipopolysaccharide (LPS) monolayer and the inner phospholipid monolayer of the OMV membrane, we performed molecular dynamics simulations by placing molecules of the cationic antiseptic octenidine on the outside or inside of model vesicles. The interaction of octenidine with the outer and inner monolayer was significantly different: octenidine interacted weakly with the outer LPS surface of the model OMV, but exhibited high affinity for the phospholipids of the inner monolayer. To study the translocation of cationic antimicrobial molecules within model OMV, we performed steered molecular dynamics simulations. For all three cationic biocide molecules, antiseptic octenidine, photosensitizer octakis(cholinyl)zinc phthalocyanine, and dye methylene blue, it turned out that, along with the LPS of the outer membrane of the OMV, the phosphates of lipid A molecules represent the final barrier to their penetration into the model OMV.

Foliar spraying with amino acids and their chitosan nanocomposites as promising way to alleviate abiotic stress in iceberg lettuce grown at different temperatures

We analyzed the effects of foliar spraying with amino acids, chitosan (CHS) and nanocomposites (NCs) of chitosan with the amino acids proline, l-cysteine and glycine betaine (CHS-Pro NCs; CHS-Cys NCs, CHS-GB NCs, respectively) on the changes in the physiological and biochemical parameters of iceberg lettuce grown at the control temperature (20 °C) and under chilling conditions (4 °C). The physicochemical parameters of the phospholipid monolayers (PLs) extracted from plants showed the effects of the treatments on the properties of the monolayers, namely, the packing density and flexibility. We observed increased accumulation of proline at 4 °C, and differences in the concentrations of sugars in most of the analyzed variants were a consequence of the lowered temperature and/or the use of organic compounds. A temperature of 4 °C caused a significant increase in the l-ascorbic acid level compared with that at 20 °C. Differences were also found in glutathione (GSH) content depending on the temperature and treatment with the tested organic compounds. CHS NCs loaded with Pro and GB were effective at increasing the amount of phenols under stress temperature conditions. We noted that a significant increase in the antioxidant activity of plants at 4 °C occurred after priming with Cys, CHS-Cys NCs, Pro and CHS-Pro NCs, and the CHS nanocomposites were more effective in this respect. Both low-temperature stress and foliar spraying of lettuce with various organic compounds caused changes in the activity of antioxidant enzymes. Two forms of dismutase (SOD), iron superoxide dismutase (FeSOD) and copper/zinc superoxide dismutase (Cu/ZnSOD), were identified in extracts from the leaves of iceberg lettuce seedlings. The application of the tested organic compounds, alone or in combination with CHS, increased the amount of malondialdehyde (MDA) in plants grown under controlled temperature conditions. Chilling caused an increase in the content of MDA, but some organic compounds mitigated the impact of low temperature. Compared with that of plants subjected to 20 °C, the fresh weight of plants exposed to chilling decreased. However, the tested compounds caused a decrease in fresh weight at 4 °C compared with the corresponding control samples. An interesting exception was the use of Cys, for which the difference in the fresh weight of plants grown at 20 °C and 4 °C was not statistically significant. After Cys application, the dry weight of the chilled plants was greater than that of the chilled control plants but was also greater than that of the other treated plants in this group. To our knowledge, this is the first report demonstrating that engineered chitosan–amino acid nanocomposites could be applied as innovative protective agents to mitigate the effects of chilling stress in crop plants.

Size-switchable and dual-targeting nanomedicine for cancer chemoimmunotherapy by potentiating deep tumor penetration and antitumor immunity

The effectiveness of commonly adopted therapeutic regimen is low for treating triple-negative breast cancer (TNBC), especially for inoperable patients at advanced stage. Herein, we reported a nano-based recipe for orthotopic and metastatic TNBC management by potentiating the deep penetration of antitumor agents in solid tumors and remodeling the tumor immune microenvironment through combinational chemoimmunotherapy. Specifically, doxorubicin (DOX) was loaded in DSPE-PEG2000-modified poly(amidoamine) (PAMAM) dendrimer to obtain small-sized DOX@P nanoparticles, which were further inserted into the phospholipid monolayer of imiquimod (R837)-encapsulated reconstituted high-density lipoprotein (rHDL) to acquire R@rHDP. Finally, M2 macrophage-targeting peptide (M2pep) was modified on the surface of R@rHDP to obtain R@rHDP-M2pep nanoparticles with special targeting ability towards M2-like tumor-associated macrophages (TAMs). Upon intravenous injection, R@rHDP-M2pep actively anchored TNBC sites owing to the natural tumor targeting potential of rHDL. Once reaching tumor sites, small-sized DOX@P was released from large-sized R@rHDP-M2pep due to the breakdown of imine bond in acidic tumor microenvironment (TME), further carrying DOX into the deep tumor core to exert chemotherapeutic effect. On the other hand, the remaining R@rH-M2pep continued to target M2-like TAMs to deliver R837 for effective polarization of TAM phenotype from protumoral M2-like into antitumoral M1-like type. Consequently, the immunosuppressive TME was remodeled to facilitate improved immunotherapeutic performance. Hence, the designed R@rHDP-M2pep nanoparticles displayed potent antitumor efficacy against TNBC, which not only remarkably suppressed orthotopic tumor growth, but also prevented the lethal lung metastasis of TNBC, largely prolonging the survival time of mice suffered from TNBC. Altogether, the proposed strategy exhibited promising research value in advancing the therapeutic protocols for TNBC.

The Role of Lipid Intrinsic Curvature in the Droplet Interface Bilayer.

Model bilayers are constructed from lipids having different intrinsic curvatures using the droplet interface bilayer (DIB) method, and their static physicochemical properties are determined. Geometrical and tensiometric measurements are used to derive the free energy of formation (ΔF) of a two-droplet DIB relative to a pair of isolated aqueous droplets, each decorated with a phospholipid monolayer. The lipid molecules employed have different headgroup sizes but identical hydrophobic tail structure, and each is characterized by an intrinsic curvature value (c0) that increases in absolute value with decreasing size of headgroup. Mixtures of lipids at different ratios were also investigated. The role of curvature stress on the values of ΔF of the respective lipid bilayers in these model membranes is discussed and is illuminated by the observation of a decrement in ΔF that scales as a near linear function of c02. Overall, the results reveal an association that should prove useful in studies of ion channels and other membrane proteins embedded in model droplet bilayer systems that will impact the understanding of protein function in cellular membranes composed of lipids of high and low curvature.

Perilipins: A family of five fat-droplet storing proteins that play a significant role in fat homeostasis.

Lipid droplets are organelles with unique spherical structures. They consist of a hydrophobic neutral lipid core that varies depending on the cell type and tissue. These droplets are surrounded by phospholipid monolayers, along with heterogeneous proteins responsible for neutral lipid synthesis and metabolism. Additionally, there are specialized lipid droplet-associated surface proteins. Recent evidence suggests that proteins from the perilipin family (PLIN) are associated with the surface of lipid droplets and are involved in their formation. These proteins have specific roles in hepatic lipid droplet metabolism, such as protecting the lipid droplets from lipase action and maintaining a balance between lipid storage and utilization in specific cells. Metabolic dysfunction-associated steatotic liver disease (MASLD) is characterized by the accumulation of lipid droplets in more than 5% of the hepatocytes. This accumulation can progress into metabolic dysfunction-associated steatohepatitis, fibrosis, cirrhosis, and hepatocellular carcinoma. The accumulation of hepatic lipid droplets in the liver is associated with the progression of MASLD and other diseases such as sarcopenic obesity. Therefore, it is crucial to understand the role of perilipins in this accumulation, as these proteins are key targets for developing novel therapeutic strategies. This comprehensive review aims to summarize the structure and characteristics of PLIN proteins, as well as their pathogenic role in the development of hepatic steatosis and fatty liver diseases.

CHARMM-GUI Membrane Builder for Lipid Droplet Modeling and Simulation.

Lipid droplets (LDs) are organelles that are necessary for eukaryotic and prokaryotic metabolism and energy storage. They have a unique structure consisting of a spherical phospholipid monolayer encasing neutral lipids such as triacylglycerol (TAG). LDs have garnered increased interest for their implications in disease and for drug delivery applications. Consequently, there is an increased need for tools to study their structure, composition, and dynamics in biological contexts. In this work, we utilize CHARMM-GUI Membrane Builder to simulate and analyze LDs with and without a plant LD protein, oleosin. The results show that Membrane Builder can generate biologically relevant all-atom LD systems with relatively short equilibration times using a new TAG library having optimized headgroup parameters. TAG molecules originally inserted into a lipid bilayer aggregate in the membrane center, forming a TAG-only core flanked by two monolayers. The TAG-only core thickness stably grows with increasing TAG mole fraction. A 70 % TAG system has a core that is thick enough to house oleosin without its interactions with the distal leaflet or disruption of its secondary structure. We hope that Membrane Builder can aid in the future study of LD systems, including their structure and dynamics with and without proteins.

Effect of high sodium ion level on the interaction of AmB with a cholesterol-rich phospholipid monolayer.

Invasive fungal infections are a primary reason for high mortality in immunocompromised people, especially in critically ill patients, such as intensive care unit (ICU) patients, advanced cancer patients, or severe burn patients. Hypernatremia also can increase mortality in severely ill patients. Amphotericin B (AmB) is the gold standard for treating infections, but in severely ill patients, AmB can cause hematotoxicity when administered intravenously due to its interaction with cholesterol on red blood cell membranes. This results in limited doses of AmB and affects the treatment of infections. The proportion of cholesterol molecules in membrane lipids in red blood cells is as high as 50mol%, and the sodium ions can influence the interaction between AmB and lipids on the membrane. Therefore, in the complex clinical situation of a severely ill patient with a fungal infection and hypernatremia, the interaction between amphotericin B and the red blood cell membranes is worth studying in depth. In this work, the interaction between AmB and the dipalmitoyl phosphatidylcholine (DPPC)/cholesterol mixed monolayer in the presence of high sodium ion levels was studied when the proportion of cholesterol was 50%. The results show that the effect of AmB on reducing the monolayer's area at a high level of sodium ions is slightly stronger at 30mN/m. The effect of AmB on reducing the elastic modulus of the DPPC/Chol monolayer is significantly weakened by a high sodium ion level, compared with the level of sodium ions at normal physiological concentration. The higher the sodium ion concentration, the weaker the intermolecular force of the DPPC/Chol/AmB mixed monolayers. The scanning electron microscope (SEM) and atomic force microscopy (AFM) observations suggest that at a high sodium ion level, the presence of AmB significantly reduces the surface roughness of the DPPC/Chol monolayer. AmB may bind to cholesterol molecules, and it isolates cholesterol from the monolayer, resulting in a reduced height of the cholesterol-rich monolayer and an increasingly dispersed monolayer region. The results are beneficial to understanding the mechanism of impact of a high sodium ion level on the relationship between AmB and red blood cell membranes rich in cholesterol and are valuable for understanding the hemolytic toxicity of AmB to red blood cells at a high sodium ion level.

Acoustic Delivery of Plasma Low-Density Lipoprotein into Liver via ApoB100-Targeted Microbubbles Inhibits Atherosclerotic Plaque Growth.

Atherosclerosis is the main risk factor for cardiovascular disease, which accounts for the majority of mortality worldwide. A significantly increased plasma level of low-density lipoprotein cholesterol (LDL-C), surrounded by a monolayer of phospholipids, free cholesterol, and one apolipoprotein B-100 (ApoB-100) in the blood, plays the most significant role in driving the development of atherosclerosis. Commercially available cholesterol-lowering drugs are not sufficient for preventing recurrent cardiovascular events. Developing alternative strategies to decrease the plasma cholesterol levels is desirable. Herein, we develop an approach for reducing LDL-C levels using gas-filled microbubbles (MBs) that were coated with anti-ApoB100 antibodies. These targeted MBApoB100 could selectively capture LDL particles in the bloodstream through forming LDL-MBApoB100 complexes and transport them to the liver for degradation. Further immunofluorescence staining and lipidomic analyses showed that these LDL-MBApoB100 complexes may be taken up by Kupffer cells and delivered to liver cells and bile acids, greatly inhibiting atherosclerotic plaque growth. More importantly, ultrasound irradiation of these LDL-MBApoB100 complexes that accumulated in the liver may induce acoustic cavitation effects, significantly enhancing the delivery of LDL into liver cells and accelerating their degradation. Our study provides a strategy for decreasing LDL-C levels and inhibiting the progression of atherosclerosis.

A Membrane-Targeting Aggregation-Induced Emission Probe for Monitoring Lipid Droplet Dynamics in Ischemia/Reperfusion-Induced Cardiomyocyte Ferroptosis.

Myocardial ischemia/reperfusion injury (MIRI) is the leading cause of irreversible myocardial damage. A pivotal pathogenic factor is ischemia/reperfusion (I/R)-induced cardiomyocyte ferroptosis, marked by iron overload and lipid peroxidation. However, the impact of lipid droplet (LD) changes on I/R-induced cardiomyocyte ferroptosis is unclear. In this study, an aggregation-induced emission probe, TPABTBP is developed that is used for imaging dynamic changes in LD during myocardial I/R-induced ferroptosis. TPABTBP exhibits excellent LD-specificity, superior capability for monitoring lipophagy, and remarkable photostability. Molecular dynamics (MD) simulation and super-resolution fluorescence imaging demonstrate that the TPABTBP is specifically localized to the phospholipid monolayer membrane of LDs. Imaging LDs in cardiomyocytes and myocardial tissue in model mice with MIRI reveals that the LD accumulation level increase in the early reperfusion stage (0-9h) but decrease in the late reperfusion stage (>24h) via lipophagy. The inhibition of LD breakdown significantly reduces the lipid peroxidation level in cardiomyocytes. Furthermore, it is demonstrated that chloroquine (CQ), an FDA-approved autophagy modulator, can inhibit ferroptosis, thereby attenuating MIRI in mice. This study describes the dynamic changes in LD during myocardial ischemia injury and suggests a potential therapeutic target for early MIRI intervention.