Cholesterol transfer at the plasma membrane

Liposomes modified with a multivalent glutamic hexapeptide: A novel and effective way to promote bone targeting

It is well known that bone-related diseases are difficult to treat due to the relatively low blood flow. Therefore, targeting the delivery of drugs to bone may not only improve the therapeutic effect but also reduce the dose. To prepare liposomes, a series of novel multivalent glutamic hexapeptide derivatives were designed and synthesized as liposome ligands, which can effectively deliver paclitaxel (PTX) to bone. The liposomes were prepared and their encapsulation efficiency, particle size, stability, zeta potential, hemolysis, and release behavior were characterized. The results indicated that the coated liposomes, PTX-Glu61 -Lip, PTX-Glu62 -Lip, PTX-Glu63 -Lip, and PTX-Glu65 -Lip, showed remarkable bone-targeting activity. Compared with the other coated liposomes, PTX-Glu65 -Lip showed prominent targeting ability and anti-bone metastasis activity on the basis of in vitro and in vivo evaluations. Our study may contribute to the field of design of bone-targeting drugs.

Cholesterol depletion inhibits rabies virus infection by restricting viral adsorption and fusion

Rabies is an ancient zoonotic disease caused by the rabies virus (RABV), and a sharp increase in rabies cases and deaths were observed following the COVID-19 pandemic, indicating that it still poses a severe public health threat in most countries in the world. Cholesterol is one of the major lipid components in cells, and the exact role of cholesterol in RABV infection remains unclear. In this study, we initially observed that cellular cholesterol levels were significantly elevated in RABV infected cells, while cholesterol depletion by using methyl-β-cyclodextrin (MβCD) could restrict RABV entry. We further found that decreasing the cholesterol level of the viral envelope could change the bullet-shaped morphology of RABV and dislodge the glycoproteins on its surface to affect RABV entry. Moreover, the depletion of cholesterol could decrease lysosomal cholesterol accumulation to inhibit RABV fusion. Finally, it was found that the depletion of cholesterol by MβCD was due to the increase of oxygen sterol production in RABV-infected cells and the enhancement of cholesterol efflux by activating liver X receptor alpha (LXRα). Together, our study reveals a novel role of cholesterol in RABV infection, providing new insight into explore of effective therapeutics for rabies.

Durvillaea antarctica: A Seaweed for Enhancing Immune and Cardiometabolic Health and Gut Microbiota Composition Modulation

Durvillaea antarctica is the seaweed that is the most consumed by the Chilean population. It is recognized worldwide for its high nutritional value in protein, vitamins, minerals, and dietary fiber. This is a narrative review in which an extensive search of the literature was performed to establish the immunomodulator, cardiometabolic, and gut microbiota composition modulation effect of Durvillaea antarctica. Several studies have shown the potential of Durvillaea antarctica to function as prebiotics and to positively modulate the gut microbiota, which is related to anti-obesity, anti-inflammatory, anticancer, lipid-lowering, and hypoglycemic effects. The quantity of Bacteroides was negatively correlated with that of inflammatory monocytes and positively correlated with the levels of several gut metabolites. Seaweed-derived polysaccharides modulate the quantity and diversity of beneficial intestinal microbiota, decreasing phenol and p-cresol, which are related to intestinal diseases and the loss of intestinal function. Additionally, a beneficial metabolic effect related to this seaweed was observed, mainly promoting the decrease in the glycemic levels, lower cholesterol levels and cardiovascular risk. Consuming Durvillaea antarctica has a positive impact on the immune system, and its bioactive compounds provide beneficial effects on glycemic control and other metabolic parameters.

Is reverse cholesterol transport regulated by active cholesterol?

This review considers the hypothesis that a small portion of plasma membrane cholesterol regulates reverse cholesterol transport in coordination with overall cellular homeostasis. It appears that almost all of the plasma membrane cholesterol is held in stoichiometric complexes with bilayer phospholipids. The minor fraction of cholesterol that exceeds the complexation capacity of the phospholipids is called active cholesterol. It has an elevated chemical activity and circulates among the organelles. It also moves down its chemical activity gradient to plasma HDL, facilitated by the activity of ABCA1, ABCG1, and SR-BI. ABCA1 initiates this process by perturbing the organization of the plasma membrane bilayer, thereby priming its phospholipids for translocation to apoA-I to form nascent HDL. The active excess sterol and that activated by ABCA1 itself follow the phospholipids to the nascent HDL. ABCG1 similarly rearranges the bilayer and sends additional active cholesterol to nascent HDL, while SR-BI simply facilitates the equilibration of the active sterol between plasma membranes and plasma proteins. Active cholesterol also flows downhill to cytoplasmic membranes where it serves both as a feedback signal to homeostatic ER proteins and as the substrate for the synthesis of mitochondrial 27-hydroxycholesterol (27HC). 27HC binds the LXR and promotes the expression of the aforementioned transport proteins. 27HC-LXR also activates ABCA1 by competitively displacing its inhibitor, unliganded LXR. § Considerable indirect evidence suggests that active cholesterol serves as both a substrate and a feedback signal for reverse cholesterol transport. Direct tests of this novel hypothesis are proposed.

Lipoprotein Particles as Shuttles for Hydrophilic Cargo

Lipoprotein particles (LPs) are excellent transporters and have been intensively studied in cardiovascular diseases, especially regarding parameters such as their class distribution and accumulation, site-specific delivery, cellular internalization, and escape from endo/lysosomal compartments. The aim of the present work is the hydrophilic cargo loading of LPs. As an exemplary proof-of-principle showcase, the glucose metabolism-regulating hormone, insulin, was successfully incorporated into high-density lipoprotein (HDL) particles. The incorporation was studied and verified to be successful using Atomic Force Microscopy (AFM) and Fluorescence Microscopy (FM). Single-molecule-sensitive FM together with confocal imaging visualized the membrane interaction of single, insulin-loaded HDL particles and the subsequent cellular translocation of glucose transporter type 4 (Glut4).

Atorvastatin differentially regulates the interactions of cocaine and amphetamine with dopamine transporters

The function of the dopamine transporter (DAT) is regulated by membrane cholesterol content. A direct, acute removal of membrane cholesterol by methyl-β-cyclodextrin (MβCD) has been shown to reduce dopamine (DA) uptake and release mediated by the DAT. This is of particular interest because a few widely prescribed statins that lower peripheral cholesterol levels are blood-brain barrier (BBB) penetrants, and therefore could alter DAT function through brain cholesterol modulation. The goal of this study was to investigate the effects of prolonged atorvastatin treatment (24 h) on DAT function in neuroblastoma 2A cells stably expressing DAT. We found that atorvastatin treatment effectively lowered membrane cholesterol content in a concentration-dependent manner. Moreover, atorvastatin treatment markedly reduced DA uptake and abolished cocaine inhibition of DA uptake, independent of surface DAT levels. These deficits induced by atorvastatin treatment were reversed by cholesterol replenishment. However, atorvastatin treatment did not change amphetamine (AMPH)-induced DA efflux. This is in contrast to a small but significant reduction in DA efflux induced by acute depletion of membrane cholesterol using MβCD. This discrepancy may involve differential changes in membrane lipid composition resulting from chronic and acute cholesterol depletion. Our data suggest that the outward-facing conformation of DAT, which favors the binding of DAT blockers such as cocaine, is more sensitive to atorvastatin-induced cholesterol depletion than the inward-facing conformation, which favors the binding of DAT substrates such as AMPH. Our study on statin-DAT interactions may have clinical implications in our understanding of neurological side effects associated with chronic use of BBB penetrant statins.

Review on the Antioxidant Activity of Phenolics in o/w Emulsions along with the Impact of a Few Important Factors on Their Interfacial Behaviour

This review paper focuses on the antioxidant properties of phenolic compounds in oil in water (o/w) emulsion systems. The authors first provide an overview of the most recent studies on the activity of common, naturally occurring phenolic compounds against the oxidative deterioration of o/w emulsions. A screening of the latest literature was subsequently performed with the aim to elucidate how specific parameters (polarity, pH, emulsifiers, and synergistic action) affect the phenolic interfacial distribution, which in turn determines their antioxidant potential in food emulsion systems. An understanding of the interfacial activity of phenolic antioxidants could be of interest to food scientists working on the development of novel food products enriched with functional ingredients. It would also provide further insight to health scientists exploring the potentially beneficial properties of phenolic antioxidants against the oxidative damage of amphiphilic biological membranes (which link to serious pathologic conditions).

Lipid Nanoparticles and Liposomes for Bone Diseases Treatment

Because of their outstanding biocompatibility, sufficient capacity to control drug release, and passive targeting capability, lipid nanoparticles are one of the world's most widely utilized drug delivery systems. However, numerous disadvantages limit the use of lipid nanoparticles in clinical settings, especially in bone regeneration, such as challenges in transporting, storing, and maintaining drug concentration in the local area. Scaffolds are frequently employed as implants to provide mechanical support to the damaged area or as diagnostic and imaging tools. On the other hand, unmodified scaffolds have limited powers in fostering tissue regeneration and curing illnesses. Liposomes offer a solid foundation for the long-term development of various commercial solutions for the effective drug delivery-assisted treatment of medical conditions. As drug delivery vehicles in medicine, adjuvants in vaccination, signal enhancers/carriers in medical diagnostics and analytical biochemistry, solubilizers for various ingredients as well as support matrices for various ingredients, and penetration enhancers in cosmetics are just a few of the industrial applications for liposomes. This review introduces and discusses the use of lipid nanoparticles and liposomes and the application of lipid nanoparticles and liposome systems based on different active substances in bone diseases.

Cholesterol-induced robust Ca oscillation in astrocytes required for survival and lipid droplet formation in high-cholesterol condition

Cholesterol, one of the major cell membrane components, stabilizes membrane fluidity and regulates signal transduction. Beside its canonical roles, cholesterol has been reported to directly activate signaling pathways such as hedgehog (Hh). We recently found that astrocytes, one of the glial cells, respond to Hh pathway stimulation by Ca signaling. These notions led us to test if extracellularly applied cholesterol triggers Ca signaling in astrocytes. Here, we found that cholesterol application induces robust Ca oscillation only in astrocytes with different properties from the Hh-induced Ca response. The Ca oscillation has a long delay which corresponds to the onset of cholesterol accumulation in the plasma membrane. Blockade of the Ca oscillation resulted in enhancement of astrocytic cell death and disturbance of lipid droplet formation, implying a possibility that the cholesterol-induced Ca oscillation plays important roles in astrocytic survival and cholesterol handling under pathological conditions of cholesterol load such as demyelination.

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Robust Ca oscillation by cholesterol in astrocytes but not in neurons and microglia

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Cholesterol-induced Ca oscillation relates to membrane cholesterol accumulation

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The Ca oscillation is driven via the PLC-IP₃ signaling pathway

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Ca oscillation inhibition leads to astrocytic death and lipid droplet malformation

LDL Promotes Disorders in β-Cell Cholesterol Metabolism, Implications on Insulin Cellular Communication Mediated by EVs

Dyslipidemia is described as a hallmark of metabolic syndrome, promoting a stage of metabolic inflammation (metainflammation) that could lead to misbalances in energetic metabolism, contributing to insulin resistance, and modifying intracellular cholesterol pathways and the renin-angiotensin system (RAS) in pancreatic islets. Low-density lipoprotein (LDL) hypercholesterolemia could disrupt the tissue communication between Langerhans β-cells and hepatocytes, wherein extracellular vesicles (EVs) are secreted by β-cells, and exposition to LDL can impair these phenomena. β-cells activate compensatory mechanisms to maintain insulin and metabolic homeostasis; therefore, the work aimed to characterize the impact of LDL on β-cell cholesterol metabolism and the implication on insulin secretion, connected with the regulation of cellular communication mediated by EVs on hepatocytes. Our results suggest that β-cells can endocytose LDL, promoting an increase in de novo cholesterol synthesis targets. Notably, LDL treatment increased mRNA levels and insulin secretion; this hyperinsulinism condition was associated with the transcription factor PDX-1. However, a compensatory response that maintains basal levels of intracellular calcium was described, mediated by the overexpression of calcium targets PMCA1/4, SERCA2, and NCX1, together with the upregulation of the unfolded protein response (UPR) through the activation of IRE1 and PERK arms to maintain protein homeostasis. The LDL treatment induced metainflammation by IL-6, NF-κB, and COX-2 overexpression. Furthermore, LDL endocytosis triggered an imbalance of the RAS components. LDL treatment increased the intracellular levels of cholesterol on lipid droplets; the adaptive β-cell response was portrayed by the overexpression of cholesterol transporters ABCA1 and ABCG1. Therefore, lipotoxicity and hyperinsulinism induced by LDL were regulated by the natural compound auraptene, a geranyloxyn coumarin modulator of cholesterol-esterification by ACAT1 enzyme inhibition. EVs isolated from β-cells impaired insulin signaling via mTOR/p70S6Kα in hepatocytes, a phenomenon regulated by auraptene. Our results show that LDL overload plays a novel role in hyperinsulinism, mechanisms associated with a dysregulation of intracellular cholesterol, lipotoxicity, and the adaptive UPR, which may be regulated by coumarin-auraptene; these conditions explain the affectations that occur during the initial stages of insulin resistance.

MicroRNA-379-5p regulates free cholesterol accumulation and relieves diet induced-liver damage in db/db mice via STAT1/HMGCS1 axis

Lipotoxicity induced by the overload of lipid in the liver, especially excess free cholesterol (FC), has been recognized as one of driving factors in the transition from non-alcoholic fatty liver (NAFL) to non-alcoholic steatohepatitis (NASH). MicroRNA (miR)-379-5p has been reported to play regulatory roles in hepatic triglyceride homeostasis, but the relationship of miR-379-5p and hepatic cholesterol homeostasis has never been touched. In the current study, we found that hepatic miR-379-5p levels were decreased obviously in NAFLD patients and model mice compared with their controls. Moreover, miR-379-5p was discovered to be able to inhibit intracellular FC accumulation and alleviate mitochondrial damage induced by palmitic acid (PA) in vitro. Furthermore, overexpression of miR-379-5p in HFHC-fed db/db mice could reduce the level of hepatic total cholesterol (TC) and FC, and ameliorate hepatic injury reflected by the lower serum alanine aminotransferase (ALT) and aspartate transaminase (AST). Subsequently, by combining spectrometry (MS) and luciferase assay, we identified miR-379-5p suppressed STAT1 through transcriptional and translational regulation. Finally, we confirmed that STAT1 was a transcriptional factor of HMGCS1. In conclusion, miR-379-5p inhibits STAT1 expression and regulates cholesterol metabolism through the STAT1/HMGCS1 axis, suggesting miR-379-5p might be applied to improve lipotoxicity in the future.

Loading of cell cultures with cholesterol-dextran particles as a new functional test for Niemann-Pick type C disease

Deuterium-labeled cholesterol-dextran particles (d4-CholDex), prepared by co-precipitation, were internalized by cultured human skin fibroblasts and HEK293 cells. Subcellular particles from d4-CholDex-treated HEK293 cells were fractionated on iodixanol gradients. More than 60% of d4-cholesterol (d4-UC) in the gradient co-fractionated with lysosomal markers and NPC1. This and formation of d4-cholesteryl esters (d4-CE) in the cells suggests that d4-CholDex is lysosomally processed. In accordance with these findings, we observed an increase in lysosomal cholesterol content by fluorescence microscopy in CholDex-loaded cells. Fibroblast cultures including 13 NPC1-deficient, four heterozygous and six control lines were treated with d4-CholDex at final d4-UC concentration of 0.05 mg/ml (127.98 μmol/L) for 3 h and chased for 48 h in medium without d4-CholDex. Concentrations of d4-UC and d4-CE in harvested cells were measured by tandem mass spectrometry (MS/MS). d4-UC/d4-CE ratios were elevated in NP-C lines compared to controls (n = 6, mean = 4.36, range = 1.89-8.91), with the highest ratios in severe NP-C1 phenotypes and the lowest in adolescent/adult type patients. There were overlaps between NP-C1 forms: early infantile (n = 1, mean = 48.6), late infantile (n = 4, mean = 36.3, range = 20.6-54.0), juvenile (n = 5, mean = 24.7, range = 13.4-38.3), adolescent/adult (n = 3, mean = 14.5, range = 11.7-19.8). The ratios in NP-C1 heterozygotes were mildly elevated (n = 4, mean = 16.4, range = 14.9-17.4) and comparable to patients with adolescent/adult NP-C1. The test can be useful in evaluation of suspected NP-C patients with inconclusive results of biomarker or molecular tests. Its advantages include standardized preparation of particles with longer shelf life at 4 °C, quantitative results, and no requirement for radioactive chemicals.

Plasma Membrane Lipids: An Important Binding Site for All Lipoprotein Classes

Cholesterol is one of the main constituents of plasma membranes; thus, its supply is of utmost importance. This review covers the known mechanisms of cholesterol transfer from circulating lipoprotein particles to the plasma membrane, and vice versa. To achieve homeostasis, the human body utilizes cellular de novo synthesis and extracellular transport particles for supply of cholesterol and other lipids via the blood stream. These lipoprotein particles can be classified according to their density: chylomicrons, very low, low, and high-density lipoprotein (VLDL, LDL, and HDL, respectively). They deliver and receive their lipid loads, most importantly cholesterol, to and from cells by several redundant routes. Defects in one of these pathways (e.g., due to mutations in receptors) usually are not immediately fatal. Several redundant pathways, at least temporarily, compensate for the loss of one or more of them, but the defects trigger systemic diseases, such as atherosclerosis later on. Recently, intracellular membrane–membrane contact sites were shown to be involved in intracellular cholesterol transfer and the plasma membrane itself has been proposed to act as a binding site for lipoprotein-mediated cargo unloading.

Revisiting food-sourced vitamins for consumer diet and health needs: a perspective review, from vitamin classification, metabolic functions, absorption, utilization, to balancing nutritional requirements

The significant attention gained by food-sourced vitamins has provided insights into numerous current researches; for instance, the potential reversal of epigenetic age using a diet and lifestyle intervention, the balance between food and dietary supplements in the general population, the role of diet and food intake in age-related macular degeneration, and the association of dietary supplement use, nutrient intake and mortality among adults. As relevant literature about food-sourced vitamin increases, continuous synthesis is warranted. To supplement existing information, this perspective review discussed food-sourced vitamins for consumer diet and health needs, scoping from vitamin absorption, metabolic functions, utilization, to balancing nutritional requirements. Relevant literatures were identified through a search of databases like Google Scholar, Web of Science, the Interscience Online Library, ScienceDirect, and PubMed. We demonstrated that vitamins whether from plant- and animal-based sources are prerequisites for the metabolic functions of the human body. The fat- and water-soluble classification of vitamins remains consistent with their respective absorption and dissolution potentials, underpinned by numerous physiological functions. Vitamins, largely absorbed in the small intestine, have their bioavailability dependent on the food composition, its associated interactions, as well as alignment with their metabolic functions, which involves antioxidants, coenzymes, electron acceptor/donor, and hormones. Moreover, vitamin deficiencies, in every form, pose a serious threat to human health. Vitamin toxicities remain rare, but can still occur mainly from supplementation, although it appears much less in water-soluble vitamins of which some excesses get readily removed by the human body, different from the fat-soluble ones that are stored in tissues and organs. Besides discussions of absorption, transport, and cellular uptake of vitamins, this perspective review also included approaches to meeting vitamin requirements and therapeutic strategies against micronutrient deficiency and COVID-19. We have also attempted on how to strike the balance between food-sourced vitamins and dietary supplements.

Toward the Effective Bioengineering of a Pathological Tissue for Cardiovascular Disease Modeling: Old Strategies and New Frontiers for Prevention, Diagnosis, and Therapy

Cardiovascular diseases (CVDs) still represent the primary cause of mortality worldwide. Preclinical modeling by recapitulating human pathophysiology is fundamental to advance the comprehension of these diseases and propose effective strategies for their prevention, diagnosis, and treatment. In silico, in vivo, and in vitro models have been applied to dissect many cardiovascular pathologies. Computational and bioinformatic simulations allow developing algorithmic disease models considering all known variables and severity degrees of disease. In vivo studies based on small or large animals have a long tradition and largely contribute to the current treatment and management of CVDs. In vitro investigation with two-dimensional cell culture demonstrates its suitability to analyze the behavior of single, diseased cellular types. The introduction of induced pluripotent stem cell technology and the application of bioengineering principles raised the bar toward in vitro three-dimensional modeling by enabling the development of pathological tissue equivalents. This review article intends to describe the advantages and disadvantages of past and present modeling approaches applied to provide insights on some of the most relevant congenital and acquired CVDs, such as rhythm disturbances, bicuspid aortic valve, cardiac infections and autoimmunity, cardiovascular fibrosis, atherosclerosis, and calcific aortic valve stenosis.

Brown Algae Potential as a Functional Food against Hypercholesterolemia: Review

Brown algae have been part of the human diet for hundreds of years, however, in recent years, commercial and scientific interest in brown algae has increased due to the growing demand for healthier diet by the world population. Brown algae and its metabolites, such as carotenoids, polysaccharides, phlorotannins, and proteins, have been associated with multiple beneficial health effects for different diseases, such as cardiovascular diseases, one of the main causes of death in Europe. Since high blood cholesterol levels are one of the major cardiovascular risks, this review intends to provide an overview of current knowledge about the anti-hypercholesterolemic effect of different brown algae species and/or their isolated compounds.

Phenolic Acids of Plant Origin-A Review on Their Antioxidant Activity In Vitro (O/W Emulsion Systems) Along with Their in Vivo Health Biochemical Properties

Nature has generously offered a wide range of herbs (e.g., thyme, oregano, rosemary, sage, mint, basil) rich in many polyphenols and other phenolic compounds with strong antioxidant and biochemical properties. This paper focuses on several natural occurring phenolic acids (caffeic, carnosic, ferulic, gallic, p-coumaric, rosmarinic, vanillic) and first gives an overview of their most common natural plant sources. A summary of the recently reported antioxidant activities of the phenolic acids in o/w emulsions is also provided as an in vitro lipid-based model system. Exploring the interfacial activity of phenolic acids could help to further elucidate their potential health properties against oxidative stress conditions of biological membranes (such as lipoproteins). Finally, this review reports on the latest literature evidence concerning specific biochemical properties of the examined phenolic acids.

Dual-targeting liposome modified by glutamic hexapeptide and folic acid for bone metastatic breast cancer

Bone is the most common organ affected by metastatic breast cancer. Targeting delivery of drugs to bone may not only enhance the treatment efficacy, but also reduce the quantity of drug administered. In order to increase the distribution of paclitaxel (PTX) in bone, herein, a novel bone metastasis-targeted glutamic hexapeptide-folic acid (Glu₆-FA) derivative was designed and synthesized as liposome ligand to deliver PTX to bone metastasis effectively. The liposomes were prepared by thin film hydration method and its particle size, zeta potential, encapsulation efficiency, release profile, stability, hemolysis were also characterized. What's more, the anti-tumor effects of PTX-Glu₆-FA-Lip were confirmed by the detection of cell cycle, migration, and further measurement of microtubule stabilization. In addition, the PTX-Glu₆-FA-Lip showed superior targeting ability in vitro and in vivo evaluation as compared to naked PTX, non-coated, singly-modified and co-modified by physical blending liposomes. All the results suggested that Glu₆-FA-modified liposome showed excellent targeting activity to metastatic bone cancer. These findings suggested that Glu₆-FA-Lip was a promising bone metastasis-targeting carrier for the delivery of PTX. This study may therefore be conducive to the field of bone-targeting drugs delivery.