Cellular cholesterol efflux mediated by cyclodextrins

Engineering the Hydrophilic-Hydrophobic Interface of Polymeric Micelles by Cationic Blocks for Enhanced Chemotherapy

The cationic surface charge critically influences the biological functions and therapeutic outcomes of the cancer nanomedicines. However, the basic correlation between the cationic group categories and their therapeutic efficacy has not been elucidated. In this study, cationic polymeric nanoparticles with amino groups (primary, tertiary, and quaternary amines) as the single variable were leveraged to investigate the various effects of amino species for enhanced antitumor chemotherapy. The nanoparticles were constructed from a series of triblock polymers with varying cationic repeating units at the hydrophilic-hydrophobic interface. Our results suggested that quaternary ammonium outperforms its primary and tertiary counterparts in destroying mitochondrial membranes to induce apoptosis, penetrating deep inside the tumor tissue, and damaging tumor vasculatures. As a result, we were able to effectively inhibit tumor growth in mice by a quaternary ammonium conjugate without causing significant toxicity. Our work demonstrated that the chemical structures played vital roles in regulating their biological functions and provided valuable information for designing cationic drug delivery systems.

Study of Host-Guest Interaction and In Vitro Neuroprotective Potential of Cinnamic Acid/Randomly Methylated β-Cyclodextrin Inclusion Complex

Cinnamic acid (CA) has many beneficial effects on human health. However, its poor water solubility (0.23 g/L, at 25 °C) is responsible for its poor bioavailability. This drawback prevents its clinical use. To overcome the solubility limits of this extraordinary natural compound, in this study, we developed a highly water-soluble inclusion complex of CA with randomly methylated-β-cyclodextrin (RAMEB). The host-guest interaction was explored in liquid and solid states by UV-Vis titration, phase solubility analysis, FT-IR spectroscopy, and 1H-NMR. Additionally, molecular modeling studies were carried out. Both experimental and theoretical studies revealed a 1:1 CA/RAMEB inclusion complex, with a high apparent stability constant equal to 15,169.53 M-1. The inclusion complex increases the water solubility of CA by about 250-fold and dissolves within 5 min. Molecular modeling demonstrated that CA inserts its phenyl ring into the RAMEB cavity with its propyl-2-enoic acid tail leaning from the wide rim. Finally, a biological in vitro study of the inclusion complex, compared to the free components, was performed on the neuroblastoma SH-SY5Y cell line. None of them showed cytotoxic effects at the assayed concentrations. Of note, the pretreatment of SH-SY5Y cells with CA/RAMEB at 10, 30, and 125 µM doses significantly counteracted the effect of the neurotoxin MPP+, whilst CA and RAMEB alone did not show any neuroprotection. Overall, our data demonstrated that inclusion complexes overcome CA solubility problems, supporting their use for clinical applications.

Advancements in cyclodextrin-based controlled drug delivery: Insights into pharmacokinetic and pharmacodynamic profiles

This article discusses and summarizes some fascinating outcomes and applications of cyclodextrins (CDs) and their derivatives in drug delivery. These applications include the administration of protein, peptide medications, and gene delivery. Several innovative drug delivery systems, including NPs, microspheres, microcapsules, and liposomes, are designed with the help of CD, which is highlighted in this article. The use of these compounds as excipients in medicine formulation is reviewed, in addition to their well-known effects on drug solubility and dissolution, as well as their bioavailability, safety, and stability. Furthermore, the article focuses on many factors that influence the development of inclusion complexes, as having this information is necessary to manage these diverse materials effectively. An overview of the commercial availability, regulatory status, and patent status of CDs for pharmaceutical formulation is also presented. Due to the fact that CDs can discover new uses in drug delivery consistently, it is predicted that they will solve a wide range of issues related to the distribution of a variety of unique medications through various delivery channels.

Oxysterols Suppress Release of DNA from Granulocytes into Extracellular Space After Stimulation with Phorbol Myristate Acetate

BACKGROUND

Neutrophils eject their DNA strings and cellular proteins into the extracellular space upon treatment with various stimulants. In the present study, we examined the effects of four major oxidized cholesterol metabolites on DNA release from granulocytes.

METHODS AND RESULTS

When oxysterols were added to HL-60-derived granulocytes stimulated with phorbol 12-myristate 13-acetate (PMA), they suppressed the release of DNA and myeloperoxidase from the cells. Among the four oxysterols tested, 7-ketocholesterol was the most effective. Addition of the same concentration of 7-ketocholesterol did not induce any cytotoxic effects, as evaluated based on the release of lactate dehydrogenase and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) assays. DNA release from human peripheral blood neutrophils after PMA stimulation was also suppressed by 7-ketocholesterol. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis was used to quantify sterol content in the cells. The addition of oxysterols increased the cellular content of the corresponding compounds by more than 10-fold compared to those at baseline. Treatment of HL-60-derived granulocytes with methyl-β-cyclodextrin that removes sterol compounds from the membranes increased DNA release from the cells in a dose-dependent manner.

CONCLUSIONS

These results suggest that oxysterols have suppressive effects on DNA release from granulocytes stimulated with PMA.

Self-Adaptive Activation of DNAzyme Nanoassembly for Synergistically Combined Gene Therapy

DNAzyme represents a promising gene silencing toolbox yet is obstructed by the poor substrate accessibility in specific cells. Herein, a compact DNA nanoassembly, incorporating multimeric therapeutic DNAzyme, was prepared for selective delivery of gene-silencing DNAzyme with requisite cofactors and auxiliary chemo-drugs. By virtue of the sequence-conservative duplex-specific nuclease, the endogenous miRNA catalyzes the successive and site-specific cleavage of DNA nanoassembly substrate (nominated as the localized RNA walking machine) and thus ensures the liberation/activation of therapeutic agents with high accuracy and efficacy. The miR-10b-stimulated DNAzyme was designed to downregulate the TWIST transcription factor, an upstream promotor of miR-10b, thus acquiring the self-sufficient downregulation of TWIST/miR-10b signaling nodes (self-adaptive negative feedback loop) for abrogating tumor metastasis and chemo-resistance issues.

Cyclohexanediamine Triazole (CHDT) Functionalization Enables Labeling of Target Molecules with Al18F/68Ga/111In

The Al18F-labeling approach offers a one-step access to radiofluorinated biomolecules by mimicking the labeling process for radiometals. Although these labeling conditions are considered to be mild compared to classic radiofluorinations, improvements of the chelating units have led to the discovery of (±)-H3RESCA, which allows Al18F-labeling already at ambient temperature. While the suitability of (±)-H3RESCA for functionalization and radiofluorination of proteins is well established, its use for small molecules or peptides is less explored. Herein, we advanced this acyclic pentadentate ligand by introducing an alkyne moiety for the late-stage functionalization of biomolecules via click chemistry. We show that in addition to Al18F-labeling, the cyclohexanediamine triazole (CHDT) moiety allows stable complexation of 68Ga and 111In. Three novel CHDT-functionalized PSMA inhibitors were synthesized and their Al18F-, 68Ga-, and 111In-labeled analogs were subjected to a detailed in vitro radiopharmacological characterization. Stability studies in vitro in human serum revealed among others a high kinetic inertness of all radiometal complexes. Furthermore, the Al18F-labeled PSMA ligands were characterized for their biodistribution in a LNCaP derived tumor xenograft mouse model by PET imaging. One radioligand, Al[18F]F-CHDT-PSMA-1, bearing a small azidoacetyl linker at the glutamate-urea-lysine motif, provided an in vivo performance comparable to that of [18F]PSMA-1007 but with even higher tumor-to-blood and tumor-to-muscle ratios at 120 min p.i. Overall, our results highlight the suitability of the novel CHDT moiety for functionalization and radiolabeling of small molecules or peptides with Al18F, 68Ga, and 111In and the triazole ring seems to entail favorable pharmacokinetic properties for molecular imaging purposes.

Caveolin-1 differentially regulates the transforming growth factor-β and epidermal growth factor signaling pathways in MDCK cells

Caveolin-1 is critical for interacting with the TGF-β receptor (TGFβR) and EGF receptor (EGFR) signaling, often observed in advanced cancers and tissue fibrosis. However, the mechanism underlying caveolin-1-mediated transactivation of TGFβR and EGFR signaling remains unclear. Therefore, we sought to determine whether caveolin-1 is involved in canonical and non-canonical TGFβR and EGFR signaling transactivation in this study. Methyl-β-cyclodextrin (MβCD) was used to disrupt the cholesterol-containing membranes domains, and the caveolin-1 scaffolding domain (CSD) peptide was used to mimic the CSD of caveolin-1. Additionally, we transfected the Madin-Darby canine kidney cells with wild-type or phosphorylation-defective caveolin-1. We discovered that tyrosine 14 of caveolin-1 was critical for the negative regulation of TGFβR and EGFR canonical signaling. On the contrary, caveolin-1 inhibited TGF-β1-induced ERK2 activation independent of tyrosine 14 phosphorylation. Although EGF failed to induce Smad3 phosphorylation in caveolin-1 knockdown cells, it activated Smad3 upon MβCD co-treatment, indicating that caveolin-1 indirectly regulated the non-canonical pathway of EGF. In conclusion, caveolin-1 differentially modulates TGFβR and EGFR signaling. Thus, targeting caveolin-1 is a potential strategy for treating diseases involving TGF-β1 and EGF signaling.

Cyclodextrin-Induced Suppression of the Crystallization of Low-Molar-Mass Poly(ethylene glycol)

We examine the effect of alpha-cyclodextrin (αCD) on the crystallization of poly(ethylene glycol) (PEG) [poly(ethylene oxide), PEO] in low-molar-mass polymers, with M w = 1000, 3000, or 6000 g mol-1. Differential scanning calorimetry (DSC) and simultaneous synchrotron small-/wide-angle X-ray scattering (SAXS/WAXS) show that crystallization of PEG is suppressed by αCD, provided that the cyclodextrin content is sufficient. The PEG crystal structure is replaced by a hexagonal mesophase of αCD-threaded polymer chains. The αCD threading reduces the conformational flexibility of PEG and, hence, suppresses crystallization. These findings point to the use of cyclodextrin additives as a powerful means to tune the crystallization of PEG (PEO), which, in turn, will impact bulk properties including biodegradability.

Nuclear-penetrating scleroderma autoantibody inhibits topoisomerase 1 cleavage complex formation

The contributions of anti-Topoisomerase 1 (Top1) autoantibodies to the pathophysiology of diffuse cutaneous systemic sclerosis (dcSSc), the most aggressive scleroderma subtype, are unknown. Top1 catalyzes DNA relaxation and unwinding in cell nuclei, a site previously considered inaccessible to antibodies. The discovery of autoantibodies in systemic lupus erythematosus that penetrate nuclei and inhibit DNA repair raised the possibility that nuclear-penetrating autoantibodies contribute to mechanisms of autoimmunity. Here we show that an anti-Top1 autoantibody produced by a single B cell clone from a patient with dcSSc penetrates live cells and localizes into nuclei. Functionally, the autoantibody inhibits formation of the Top1 cleavage complex necessary for DNA nicking, which distinguishes it from cytotoxic camptothecin Top1 inhibitors used in cancer therapy that trap the cleavage complex rather than preventing its formation. Discovery of a patient-derived cell-penetrating scleroderma anti-Top1 autoantibody that inhibits Top1 cleavage complex formation supports the hypothesis that anti-Top1 autoantibodies contribute to cellular dysfunction in dcSSc and offers a valuable antibody reagent resource for future studies on anti-Top1 autoantibody contributions to scleroderma pathophysiology.

Fe3O4-Incorporated Metal-Organic Framework for Chemo/Ferroptosis Synergistic Anti-Tumor via the Enhanced Chemodynamic Therapy

Metal-organic framework (MOF)-based drug delivery nanomaterials for cancer therapy have attracted increasing attention in recent years. Here, an enhanced chemodynamic anti-tumor therapy strategy by promoting the Fenton reaction by using core-shell zeolitic imidazolate framework-8 (ZIF-8)@Fe3O4 as a therapeutic platform is proposed. Carboxymethyl cellulose (CMC) is used as a stabilizer of Fe3O4, which is then decorated on the surface of ZIF-8 via the electrostatic interaction and serves as an efficient Fenton reaction trigger. Meanwhile, the pH-responsive ZIF-8 scaffold acts as a container to encapsulate the chemotherapeutic drug doxorubicin (DOX). The obtained DOX-ZIF-8@Fe3O4/CMC (DZFC) nanoparticles concomitantly accelerate DOX release and generate more hydroxyl radicals by targeting the lysosomes in cancer cells. In vitro and in vivo studies verify that the DZFC nanoparticles trigger glutathione peroxidase 4 (GPX4)-dependent ferroptosis via the activation of the c-Jun N-terminal kinases (JNK) signaling pathway, following to achieve the chemo/ferroptosis synergistic anti-tumor efficacy. No marked toxic effects are detected during DZFC treatment in a tumor-bearing mouse model. This composite nanoparticle remarkably suppresses the tumor growth with minimized systemic toxicity, opening new horizons for the next generation of theragnostic nanomedicines.

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.

Membrane lipid modulations by methyl-β-cyclodextrin uncouple the Drosophila light-activated phospholipase C from TRP and TRPL channel gating

Sterols are hydrophobic molecules, known to cluster signaling membrane-proteins in lipid rafts, while methyl-β-cyclodextrin (MβCD) has been a major tool for modulating membrane-sterol content for studying its effect on membrane proteins, including the transient receptor potential (TRP) channels. The Drosophila light-sensitive TRP channels are activated downstream of a G-protein-coupled phospholipase Cβ (PLC) cascade. In phototransduction, PLC is an enzyme that hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) generating diacylglycerol, inositol-tris-phosphate, and protons, leading to TRP and TRP-like (TRPL) channel openings. Here, we studied the effects of MβCD on Drosophila phototransduction using electrophysiology while fluorescently monitoring PIP2 hydrolysis, aiming to examine the effects of sterol modulation on PIP2 hydrolysis and the ensuing light-response in the native system. Incubation of photoreceptor cells with MβCD dramatically reduced the amplitude and kinetics of the TRP/TRPL-mediated light response. MβCD also suppressed PLC-dependent TRP/TRPL constitutive channel activity in the dark induced by mitochondrial uncouplers, but PLC-independent activation of the channels by linoleic acid was not affected. Furthermore, MβCD suppressed a constitutively active TRP mutant-channel, trpP365, suggesting that TRP channel activity is a target of MβCD action. Importantly, whole-cell voltage-clamp measurements from photoreceptors and simultaneously monitored PIP2-hydrolysis by translocation of fluorescently tagged Tubby protein domain, from the plasma membrane to the cytosol, revealed that MβCD virtually abolished the light response when having little effect on the light-activated PLC. Together, MβCD uncoupled TRP/TRPL channel gating from light-activated PLC and PIP2-hydrolysis suggesting the involvement of distinct nanoscopic lipid domains such as lipid rafts and PIP2 clusters in TRP/TRPL channel gating.

A Ru(II)-Strained Complex with 2,9-Diphenyl-1,10-phenanthroline Ligand Induces Selective Photoactivatable Chemotherapeutic Activity on Human Alveolar Carcinoma Cells via Apoptosis

[Ru(bipy)2(dpphen)]Cl2 (where bipy = 2,2'-bipyridine and dpphen = 2,9-diphenyl-1,10-phenanthroline) (complex 1) is a sterically strained compound that exhibits promising in vitro photocytotoxicity on an array of cell lines. Since lung adenocarcinoma cancer remains the most common lung cancer and the leading cause of cancer deaths, the current study aims to evaluate the plausible effect and uptake of complex 1 on human alveolar carcinoma cells (A549) and mesenchymal stem cells (MSC), and assess its cytotoxicity in vitro while considering its effect on cell morphology, membrane integrity and DNA damage. MSC and A549 cells showed similar rates of complex 1 uptake with a plateau at 12 h. Upon photoactivation, complex 1 exhibited selective, potent anticancer activity against A549 cells with phototoxicity index (PI) values of 16, 25 and 39 at 24, 48 and 72 h, respectively. This effect was accompanied by a significant increase in A549-cell rounding and detachment, loss of membrane integrity and DNA damage. Flow cytometry experiments confirmed that A549 cells undergo apoptosis when treated with complex 1 followed by photoactivation. In conclusion, this present study suggests that complex 1 might be a promising candidate for photochemotherapy with photoproducts that possess selective anticancer effects in vitro. These results are encouraging to probe the potential activity of this complex in vivo.

Proteomics reveals time-dependent protein corona changes in the intracellular pathway

The intracellular protein corona has not been fully investigated in the field of nanotechnology-biology (nano-bio) interactions. To effectively understand intracellular protein corona formation and dynamics, we established a workflow to isolate the intracellular protein corona at different uptake times of two nanoparticles - magnetic hydroxyethyl starch nanoparticles (HES-NPs) and magnetic human serum albumin nanocapsules (HSA-NCs). We performed label-free quantitative LC-MS proteomics to analyze the composition of the intracellular protein corona and correlated our findings with results from conventional methods for intracellular trafficking of nanocarriers, such as flow cytometry, transmission electron microscopy (TEM), and confocal microscopy (cLSM). We determined the evolution of the intracellular protein corona. At different time stages the protein corona of the HES-NPs with a slower uptake changed, but there were fewer changes in that of the HSA-NCs with a more rapid uptake. We identified proteins that are involved in macropinocytosis (RAC1, ASAP2) as well as caveolin. This was confirmed by blocking experiments and by TEM studies. The investigated nanocarrier predominantly trafficked from early endosomes as determined by RAB5 identification in proteomics and in cLSM to late endosomes/lysosomes (RAB7, LAMP1, cathepsin K and HSP 90-beta) We further demonstrated differences between nanoparticles with slower and faster uptake kinetics and determined the associated proteome at different time points. Analysis of the intracellular protein corona provides us with effective data to examine the intracellular trafficking of nanocarriers used in efficient drug delivery and intracellular applications. STATEMENT OF SIGNIFICANCE: Many research papers focus on the protein corona on nanoparticles formed in biological fluids, but there are hardly any articles dealing with proteins that come in contact with nanoparticles inside cells. The "intracellular protein corona" studied here is a far more complex and highly demanding field. Most nanocarriers are designed to be taken up into cells. Given this, we chose two different nanocarriers to reveal changes in the proteins in dendritic cells during contact at specific times. Further studies will allow us to examine molecular target proteins using these methods. Our research is a significant addition towards the goal of understanding and thus improving the efficacy of drug nanocarriers.

Lysosomal cholesterol overload in macrophages promotes liver fibrosis in a mouse model of NASH

Accumulation of lipotoxic lipids, such as free cholesterol, induces hepatocyte death and subsequent inflammation and fibrosis in the pathogenesis of nonalcoholic steatohepatitis (NASH). However, the underlying mechanisms remain unclear. We have previously reported that hepatocyte death locally induces phenotypic changes in the macrophages surrounding the corpse and remnant lipids, thereby promoting liver fibrosis in a murine model of NASH. Here, we demonstrated that lysosomal cholesterol overload triggers lysosomal dysfunction and profibrotic activation of macrophages during the development of NASH. β-cyclodextrin polyrotaxane (βCD-PRX), a unique supramolecule, is designed to elicit free cholesterol from lysosomes. Treatment with βCD-PRX ameliorated cholesterol accumulation and profibrotic activation of macrophages surrounding dead hepatocytes with cholesterol crystals, thereby suppressing liver fibrosis in a NASH model, without affecting the hepatic cholesterol levels. In vitro experiments revealed that cholesterol-induced lysosomal stress triggered profibrotic activation in macrophages predisposed to the steatotic microenvironment. This study provides evidence that dysregulated cholesterol metabolism in macrophages would be a novel mechanism of NASH.

Efficient clathrin-mediated entry of enteric adenoviruses in human duodenal cells

IMPORTANCE

Enteric adenoviruses have historically been difficult to grow in cell culture, which has resulted in lack of knowledge of host factors and pathways required for infection of these medically relevant viruses. Previous studies in non-intestinal cell lines showed slow infection kinetics and generated comparatively low virus yields compared to other adenovirus types. We suggest duodenum-derived HuTu80 cells as a superior cell line for studies to complement efforts using complex intestinal tissue models. We show that viral host cell factors required for virus entry differ between cell lines from distinct origins and demonstrate the importance of clathrin-mediated endocytosis.

Visualization of accessible cholesterol using a GRAM domain-based biosensor

Cholesterol is important for membrane integrity and cell signaling, and dysregulation of the distribution of cellular cholesterol is associated with numerous diseases, including neurodegenerative disorders. While regulated transport of a specific pool of cholesterol, known as "accessible cholesterol", contributes to the maintenance of cellular cholesterol distribution and homeostasis, tools to monitor accessible cholesterol in live cells remain limited. Here, we engineer a highly sensitive accessible cholesterol biosensor by taking advantage of the cholesterol-sensing element (the GRAM domain) of an evolutionarily conserved lipid transfer protein, GRAMD1b. Using this cholesterol biosensor, which we call GRAM-W, we successfully visualize in real time the distribution of accessible cholesterol in many different cell types, including human keratinocytes and iPSC-derived neurons, and show differential dependencies on cholesterol biosynthesis and uptake for maintaining levels of accessible cholesterol. Furthermore, we combine GRAM-W with a dimerization-dependent fluorescent protein (ddFP) and establish a strategy for the ultrasensitive detection of accessible plasma membrane cholesterol. These tools will allow us to obtain important insights into the molecular mechanisms by which the distribution of cellular cholesterol is regulated.

Interplay of Cholesterol and Actin in Neurotransmitter GPCR Signaling: Insights from Chronic Cholesterol Depletion Using Statin

Serotonin1A receptors are important neurotransmitter receptors in the G protein-coupled receptor (GPCR) family and modulate a variety of neurological, behavioral, and cognitive functions. We recently showed that chronic cholesterol depletion by statins, potent inhibitors of HMG-CoA reductase (the rate-limiting enzyme in cholesterol biosynthesis), leads to polymerization of the actin cytoskeleton that alters lateral diffusion of serotonin1A receptors. However, cellular signaling by the serotonin1A receptor under chronic cholesterol depletion remains unexplored. In this work, we explored signaling by the serotonin1A receptor under statin-treated condition. We show that cAMP signaling by the receptor is reduced upon lovastatin treatment due to reduction in cholesterol as well as polymerization of the actin cytoskeleton. To the best of our knowledge, these results constitute the first report describing the effect of chronic cholesterol depletion on the signaling of a G protein-coupled neuronal receptor. An important message arising from these results is that it is prudent to include the contribution of actin polymerization while analyzing changes in membrane protein function due to chronic cholesterol depletion by statins. Notably, our results show that whereas actin polymerization acts as a negative regulator of cAMP signaling, cholesterol could act as a positive modulator. These results assume significance in view of reports highlighting symptoms of anxiety and depression in humans upon statin administration and the role of serotonin1A receptors in anxiety and depression. Overall, these results reveal a novel role of actin polymerization induced by chronic cholesterol depletion in modulating GPCR signaling, which could act as a potential therapeutic target.

Cholesterol-Depletion-Induced Membrane Repair Carries a Raft Conformer of P-Glycoprotein to the Cell Surface, Indicating Enhanced Cholesterol Trafficking in MDR Cells, Which Makes Them Resistant to Cholesterol Modifications

The human P-glycoprotein (P-gp), a transporter responsible for multidrug resistance, is present in the plasma membrane's raft and non-raft domains. One specific conformation of P-gp that binds to the monoclonal antibody UIC2 is primarily associated with raft domains and displays heightened internalization in cells overexpressing P-gp, such as in NIH-3T3 MDR1 cells. Our primary objective was to investigate whether the trafficking of this particular P-gp conformer is dependent on cholesterol levels. Surprisingly, depleting cholesterol using cyclodextrin resulted in an unexpected increase in the proportion of raft-associated P-gp within the cell membrane, as determined by UIC2-reactive P-gp. This increase appears to be a compensatory response to cholesterol loss from the plasma membrane, whereby cholesterol-rich raft micro-domains are delivered to the cell surface through an augmented exocytosis process. Furthermore, this exocytotic event is found to be part of a complex trafficking mechanism involving lysosomal exocytosis, which contributes to membrane repair after cholesterol reduction induced by cyclodextrin treatment. Notably, cells overexpressing P-gp demonstrated higher total cellular cholesterol levels, an increased abundance of stable lysosomes, and more effective membrane repair following cholesterol modifications. These modifications encompassed exocytotic events that involved the transport of P-gp-carrying rafts. Importantly, the enhanced membrane repair capability resulted in a durable phenotype for MDR1 expressing cells, as evidenced by significantly improved viabilities of multidrug-resistant Pgp-overexpressing immortal NIH-3T3 MDR1 and MDCK-MDR1 cells compared to their parents when subjected to cholesterol alterations.

Endocytosis in cancer and cancer therapy

Endocytosis is a complex process whereby cell surface proteins, lipids and fluid from the extracellular environment are packaged, sorted and internalized into cells. Endocytosis is also a mechanism of drug internalization into cells. There are multiple routes of endocytosis that determine the fate of molecules, from degradation in the lysosomes to recycling back to the plasma membrane. The overall rates of endocytosis and temporal regulation of molecules transiting through endocytic pathways are also intricately linked with signalling outcomes. This process relies on an array of factors, such as intrinsic amino acid motifs and post-translational modifications. Endocytosis is frequently disrupted in cancer. These disruptions lead to inappropriate retention of receptor tyrosine kinases on the tumour cell membrane, changes in the recycling of oncogenic molecules, defective signalling feedback loops and loss of cell polarity. In the past decade, endocytosis has emerged as a pivotal regulator of nutrient scavenging, response to and regulation of immune surveillance and tumour immune evasion, tumour metastasis and therapeutic drug delivery. This Review summarizes and integrates these advances into the understanding of endocytosis in cancer. The potential to regulate these pathways in the clinic to improve cancer therapy is also discussed.

Insights into recent preclinical studies on labelled cyclodextrin-based imaging probes: towards a novel oncological era

As malignancies remain one of the major health concerns worldwide, increasing focus has been centered around the application of cyclodextrins (CDs) in cancer imaging and therapy due to their outstanding inclusion forming capability. Albeit the physicochemical properties of CDs were intensively elucidated, the spread of their clinical application is limited by the relative paucity of knowledge about their pharmacokinetic profile, especially biodistribution. Studies applying fluorescently- CDs, or CD-based MRI contrast agents revealed much about pharmacokinetics and diagnostic applications; however, derivatives labelled with positron emitters seem superior molecular probes in the investigation of the route of CDs in biological niche. In vivo imaging based on preclinical tumor-bearing model systems are well-suited to evaluate the whole-body distribution of the two most frequently assessed CDs: randomly methylated β-cyclodextrin (RAMEB), and hydroxypropyl-β-cyclodextrin (HPBCD). Exploiting the firm signaling interaction between cancer-related cyclooxygenase-2, prostaglandin E2 (PGE2) and RAS oncoprotein, radioconjugated, PGE2-affine CDs project the establishment of novel imaging probes and therapeutic agents. Currently, we provide an overview of the preclinical studies on CD pharmacokinetics highlighting the significance of the integration of translational discoveries into human patient care.

Cytotoxicity and mechanism of action of metal complexes: An overview

After the discovery of cisplatin, many metal compounds were investigated for the therapy of diseases, especially cancer. The high therapeutic potential of metal-based compounds is related to the special properties of these compounds, such as their redox activity and ability to target vital biological sites. The overproduction of ROS and the consequent destruction of the membrane potential of mitochondria and/or the DNA helix is one of the known pathways leading to the induction of apoptosis by metal complexes. The apoptosis process can occur via the death receptor pathway and/or the mitochondrial pathway. The expression of Bcl2 proteins and the caspase family play critical roles in these pathways. In addition to apoptosis, autophagy is another process that regulates the suppression or promotion of various cancers through a dual action. On the other hand, the ability to interact with DNA is an important property found in several metal complexes with potent antiproliferative effects against cancer cells. These interactions were classified into two important categories: covalent/coordinated or subtle, and non-coordinated interactions. The anticancer activity of metal complexes is sometimes achieved by the simultaneous combination of several mechanisms. In this review, the anticancer effect of metal complexes is mechanistically discussed by different pathways, and some effective agents on their antiproliferative properties are explained.

Assaying Sterol-Regulated ER-to-Golgi Transport of SREBP Cleavage-Activating Protein Using Immunofluorescence Microscopy

Sterol regulatory element-binding proteins (SREBPs) are a family of membrane-bound transcription factors that regulate the uptake and synthesis of cholesterol and fatty acids in mammalian cells. SREBP cleavage-activating protein (SCAP) is an endoplasmic reticulum (ER) protein that binds newly synthesized SREBP, retaining it in the ER where SREBP is inactive. SCAP binds cholesterol and functions as the cholesterol sensor in this regulatory system. Under low cholesterol conditions, SCAP escorts SREBP from the ER to the Golgi apparatus where two proteases sequentially cleave and activate SREBP. Given their central importance in maintaining cellular lipid homeostasis, other mechanisms exist to regulate SREBP activity, such as control of protein synthesis and degradation. Here, we describe methods to assay ER-to-Golgi transport of SCAP in vitro using immunofluorescence microscopy and two different cell systems, Chinese hamster ovary (CHO) cells stably expressing hamster GFP-SCAP and human HeLa cells transiently expressing human GFP-SCAP. These methods will permit investigators to determine if cellular perturbations act by affecting the ER-to-Golgi transport of SCAP.

Lysine 101 in the CRAC Motif in Transmembrane Helix 2 Confers Cholesterol-Induced Thermal Stability to the Serotonin1A Receptor

G protein-coupled receptors (GPCRs) constitute the largest class of membrane proteins that transduce signals across the plasma membrane and orchestrate a multitude of physiological processes within cells. The serotonin_1A receptor is a crucial neurotransmitter receptor in the GPCR family involved in a multitude of neurological, behavioral and cognitive functions. We have previously shown, using a combination of experimental and simulation approaches, that membrane cholesterol acts as a key regulator of organization, dynamics, signaling and endocytosis of the serotonin_1A receptor. In addition, we showed that membrane cholesterol stabilizes the serotonin_1A receptor against thermal deactivation. In the present work, we explored the molecular basis of cholesterol-induced thermal stability of the serotonin_1A receptor. For this, we explored the possible role of the K101 residue in a cholesterol recognition/interaction amino acid consensus (CRAC) motif in transmembrane helix 2 in conferring the thermal stability of the serotonin_1A receptor. Our results show that a mutation in the K101 residue leads to loss in thermal stability of the serotonin_1A receptor imparted by cholesterol, independent of membrane cholesterol content. We envision that our results could have potential implications in structural biological advancements of GPCRs and design of thermally stabilized receptors for drug development.

Monocytic Cell Adhesion to Oxidised Ligands: Relevance to Cardiovascular Disease

Atherosclerosis, the major cause of vascular disease, is an inflammatory process driven by entry of blood monocytes into the arterial wall. LDL normally enters the wall, and stimulates monocyte adhesion by forming oxidation products such as oxidised phospholipids (oxPLs) and malondialdehyde. Adhesion molecules that bind monocytes to the wall permit traffic of these cells. CD14 is a monocyte surface receptor, a cofactor with TLR4 forming a complex that binds oxidised phospholipids and induces inflammatory changes in the cells, but data have been limited for monocyte adhesion. Here, we show that under static conditions, CD14 and TLR4 are implicated in adhesion of monocytes to solid phase oxidised LDL (oxLDL), and also that oxPL and malondialdehyde (MDA) adducts are involved in adhesion to oxLDL. Similarly, monocytes bound to heat shock protein 60 (HSP60), but this could be through contaminating lipopolysaccharide. Immunohistochemistry on atherosclerotic human arteries demonstrated increased endothelial MDA adducts and HSP60, but endothelial oxPL was not detected. We propose that monocytes could bind to MDA in endothelial cells, inducing atherosclerosis. Monocytes and platelets synergized in binding to oxLDL, forming aggregates; if this occurs at the arterial surface, they could precipitate thrombosis. These interactions could be targeted by cyclodextrins and oxidised phospholipid analogues for therapy.

Cyclodextrins: Only Pharmaceutical Excipients or Full-Fledged Drug Candidates?

Cyclodextrins, representing a versatile family of cyclic oligosaccharides, have extensive pharmaceutical applications due to their unique truncated cone-shaped structure with a hydrophilic outer surface and a hydrophobic cavity, which enables them to form non-covalent host-guest inclusion complexes in pharmaceutical formulations to enhance the solubility, stability and bioavailability of numerous drug molecules. As a result, cyclodextrins are mostly considered as inert carriers during their medical application, while their ability to interact not only with small molecules but also with lipids and proteins is largely neglected. By forming inclusion complexes with cholesterol, cyclodextrins deplete cholesterol from cellular membranes and thereby influence protein function indirectly through alterations in biophysical properties and lateral heterogeneity of bilayers. In this review, we summarize the general chemical principles of direct cyclodextrin-protein interactions and highlight, through relevant examples, how these interactions can modify protein functions in vivo, which, despite their huge potential, have been completely unexploited in therapy so far. Finally, we give a brief overview of disorders such as Niemann-Pick type C disease, atherosclerosis, Alzheimer's and Parkinson's disease, in which cyclodextrins already have or could have the potential to be active therapeutic agents due to their cholesterol-complexing or direct protein-targeting properties.

Kiaa1024L/Minar2 is essential for hearing by regulating cholesterol distribution in hair bundles

Unbiased genetic screens implicated a number of uncharacterized genes in hearing loss, suggesting some biological processes required for auditory function remain unexplored. Loss of Kiaa1024L/Minar2, a previously understudied gene, caused deafness in mice, but how it functioned in the hearing was unclear. Here, we show that disruption of kiaa1024L/minar2 causes hearing loss in the zebrafish. Defects in mechanotransduction, longer and thinner hair bundles, and enlarged apical lysosomes in hair cells are observed in the kiaa1024L/minar2 mutant. In cultured cells, Kiaa1024L/Minar2 is mainly localized to lysosomes, and its overexpression recruits cholesterol and increases cholesterol labeling. Strikingly, cholesterol is highly enriched in the hair bundle membrane, and loss of kiaa1024L/minar2 reduces cholesterol localization to the hair bundles. Lowering cholesterol levels aggravates, while increasing cholesterol levels rescues the hair cell defects in the kiaa1024L/minar2 mutant. Therefore, cholesterol plays an essential role in hair bundles, and Kiaa1024L/Minar2 regulates cholesterol distribution and homeostasis to ensure normal hearing.

Enzyme-Free Liposome Active Motion via Asymmetrical Lipid Efflux

As a class of biocompatible, water-dispersed colloids, liposomes have found widespread applications ranging from food to drug delivery. Adding mobility to these colloids, i.e., liposome micromotors, represents an attractive approach to next-generation liposome carriers with enhanced functionality and effectiveness. Currently, it remains unclear as to the scope of material features useful for building liposome micromotors or how they may differ functionally from their inorganic/polymer counterparts. In this work, we demonstrate liposome active motion taking advantage of mainly a pair of intrinsic material properties associated with these assemblies: lipid phase separation and extraction. We show that global phase separation of ternary lipid systems (such as DPPC/DOPC/cholesterol) within individual liposomes yields stable Janus particles with two distinctive liquid domains. While these anisotropic liposomes undergo pure Brownian diffusion in water, similar to their homogeneous analogues, adding extracting agents, cyclodextrins, to the system triggers asymmetrical cholesterol efflux about the liposomes, setting the latter into active motion. We present detailed analyses of liposome movement and cholesterol extraction kinetics to establish their correlation. We explore various experimental parameters as well as mechanistic details to account for such motion. Our results highlight the rich possibility to hierarchically design lipid-based artificial motors, from individual lipids, to their organization, surface chemistry, and interfacial mechanics.

Pentacyclic triterpenoid ursolic acid interferes with mast cell activation via a lipid-centric mechanism affecting FcεRI signalosome functions

Pentacyclic triterpenoids, including ursolic acid (UA), are bioactive compounds with multiple biological activities involving anti-inflammatory effects. However, the mode of their action on mast cells, key players in the early stages of allergic inflammation, and underlying molecular mechanisms remain enigmatic. To better understand the effect of UA on mast cell signaling, here we examined the consequences of short-term treatment of mouse bone marrow-derived mast cells with UA. Using IgE-sensitized and antigen- or thapsigargin-activated cells, we found that 15 min exposure to UA inhibited high affinity IgE receptor (FcεRI)–mediated degranulation, calcium response, and extracellular calcium uptake. We also found that UA inhibited migration of mouse bone marrow-derived mast cells toward antigen but not toward prostaglandin E₂ and stem cell factor. Compared to control antigen-activated cells, UA enhanced the production of tumor necrosis factor-α at the mRNA and protein levels. However, secretion of this cytokine was inhibited. Further analysis showed that UA enhanced tyrosine phosphorylation of the SYK kinase and several other proteins involved in the early stages of FcεRI signaling, even in the absence of antigen activation, but inhibited or reduced their further phosphorylation at later stages. In addition, we show that UA induced changes in the properties of detergent-resistant plasma membrane microdomains and reduced antibody-mediated clustering of the FcεRI and glycosylphosphatidylinositol-anchored protein Thy-1. Finally, UA inhibited mobility of the FcεRI and cholesterol. These combined data suggest that UA exerts its effects, at least in part, via lipid-centric plasma membrane perturbations, hence affecting the functions of the FcεRI signalosome.

Differential Ganglioside and Cholesterol Depletion by Various Cyclodextrin Derivatives and Their Effect on Synaptosomal Glutamate Release

Gangliosides are glycosphingolipids of the plasma membrane and are highly enriched in the nervous system where they play a vital role in normal cell functions. Furthermore, several studies suggest their potential involvement in the pathogenesis of neurological conditions. Since cyclodextrins (CDs) can form inclusion complexes with various lipids, methylated beta-CDs are widely used in biomedical research to extract cholesterol from the membrane and study its cellular role. Despite CDs being known to interact with other membrane lipid components, their effect on gangliosides is poorly characterized. The aim of this research was to investigate the effect of dimethyl-beta-cyclodextrin (DIMEB), hydroxypropyl-beta-cyclodextrin (HPBCD), randomly methylated-alpha-cyclodextrin (RAMEA), and hydroxypropyl-alpha-cyclodextrin (HPACD) on ganglioside and cholesterol levels in rat brain synaptosomes. Their effect on membrane integrity and viability was also assessed. We examined the role of lipid depletion by CDs on the release of the major excitatory neurotransmitter, glutamate. Selective concentration range for cholesterol depletion was only found with HPBCD, but not with DIMEB. Selective depletion of gangliosides was achieved by both RAMEA and HPACD. The inhibition of stimulated glutamate release upon ganglioside depletion was found, suggesting their potential role in neurotransmission. Our study highlights the importance of the characterization of the lipid depleting capability of different CDs.

Killing the Culprit: Pharmacological Solutions to Get Rid of Cholesterol Crystals

Cholesterol crystals (CCs) play a key role in the pathophysiology of cardiovascular diseases (CVD) via triggering inflammation, plaque formation and subsequently plaque rupture. Although statins can stabilize plaques via calcification and alteration of the lipid composition within plaques, there is still a high residual risk of CVD events among statins users. Several studies have tried to blunt the detrimental effects of cholesterol crystals by pharmacological interventions. Cyclodexterins (CDs) and other nanoformulations, including polymers of CDs and liposomes, have the ability to dissolve CCs in vitro and in vivo. CDs were the first in their class that entered clinical trials and showed promising results, though their ototoxicity outweighed their benefits. Moreover, small molecules with structural similarity to cholesterol may also perturb cholesterol-cholesterol interactions and prevent from expansion of 2D crystalline domains to large 3D CCs. The results from ethyl eicosapentaenoic acid and ursodeoxycholic acid were encouraging and worth further consideration. In this review, the significance of CCs in pathogenesis of CVD is discussed and pharmacological agents with the ability to dissolve CCs or prevent from CCs formation are introduced.

A multiple functional supramolecular system for synergetic treatments of hepatocellular carcinoma

In the current times, achieving specific targeted and controllable drug delivery remains one of the major challenges in the treatment of hepatocellular carcinoma (HCC). The present study reported the development of a multiple functional indocyanine green (ICG)-cyclodextrin (CD) system, wherein loaded etoposide (EPS) was used as the model chemotherapeutic drug. In the developed system, ICG segment served as a photosensitizer for photothermal therapy (PTT) and the targeting moiety, which was primarily attributed to the specific retention properties in HCC tissues. The Ex vivo evaluation showed that ICG-CD@EPS exhibited a laser-triggered release profile with the photothermal efficiency and cytotoxicity towards HepG2 cells. In vivo evaluation suggested that ICG could navigate the systems to HCC tissues and retained at the site for 48 h, producing a drug accumulation in HCC. Further, laser irradiation boosted EPS release and local hyperthermia effects in HCC. Thus, the present study explored a novel and specific HCC targeting mechanism, and provided a feasible and controllable strategy for synergistic PTT and chemotherapy treatments for HCC.

Modulation of CD36-mediated lipid accumulation and senescence by vitamin E analogs in monocytes and macrophages

The CD36/FAT scavenger receptor/fatty acids transporter regulates cellular lipid accumulation important for inflammation, atherosclerosis, lipotoxicity, and initiation of cellular senescence. Here we compared the regulatory effects of the vitamin E analogs alpha-tocopherol (αT), alpha-tocopheryl phosphate (αTP), and αTP/βCD (a nanocarrier complex between αTP and β-cyclodextrin [βCD]) and investigated their regulatory effects on lipid accumulation, phagocytosis, and senescence in THP-1 monocytes and macrophages. Both, αTP and αTP/βCD inhibited CD36 surface exposition stronger than αT leading to more pronounced CD36-mediated events such as inhibition of DiI-labeled oxLDL uptake, phagocytosis of fluorescent Staphylococcus aureus bioparticles, and cell proliferation. When compared to βCD, the complex of αTP/βCD extracted cholesterol from cellular membranes with higher efficiency and was associated with the delivery of αTP to the cells. Interestingly, both, αTP and more so αTP/βCD inhibited lysosomal senescence-associated beta-galactosidase (SA-β-gal) activity and increased lysosomal pH, suggesting CD36-mediated uptake into the endo-lysosomal phagocytic compartment. Accordingly, the observed pH increase was more pronounced with αTP/βCD in macrophages whereas no significant increase occurred with αT, alpha-tocopheryl acetate (αTA) or βCD. In contrast to αT and αTA, the αTP molecule is di-anionic at neutral pH, but upon moving into the acidic endo-lysosomal compartment becomes protonated and thus is acting as a base. Moreover, it is expected to be retained in lysosomes since it still carries one negative charge, similar to lysosomotropic drugs. Thus, treatment with αTP or αTP/βCD and/or inhibition of conversion of αTP to αT as it occurs in aged cells may counteract CD36-mediated overlapping inflammatory, senescent, and atherosclerotic events.

Anchoring β-CD on simvastatin-loaded rHDL for selective cholesterol crystals dissolution and enhanced anti-inflammatory effects in macrophage/foam cells

Macrophage/foam cells and cholesterol crystals (CCs) have been regarded as the central triggers of maladaptive inflammation in atherosclerotic plaque. Despite the tremendous progress of recombinant high-density lipoprotein (rHDL) serving for targeted drug delivery to alleviate inflammation in macrophage/foam cells, the active attempt to modulate/improve its CCs dissolution capacity remains poorly explored. The untreated CCs can seriously aggravate inflammation and threaten plaque stability. Based on the superb ability of β-cyclodextrin (β-CD) to bind CCs and promote cholesterol efflux, simvastatin-loaded discoidal-rHDL (ST-d-rHDL) anchored with β-CD (βCD-ST-d-rHDL) was constructed. We verified that βCD-ST-d-rHDL specifically bound and dissolved CCs extracellularly and intracellularly. Furthermore, anchoring β-CD onto the surface of ST-d-rHDL enhanced its cholesterol removal ability in RAW 264.7 cell-derived foam cells characterized by accelerated cholesterol efflux, reduced intracellular lipid deposition, and improved cell membrane fluidity/permeability. Finally, βCD-ST-d-rHDL exerted efficient drug delivery and effective anti-inflammatory effects in macrophage/foam cells. Collectively, anchoring β-CD onto the surface of ST-d-rHDL for selective CCs dissolution, accelerated cholesterol efflux, and improved drug delivery represents an effective strategy to enhance anti-inflammatory effects for the therapy of atherosclerosis.

Formation of Neutrophil Extracellular Traps by Reduction of Cellular Cholesterol Is Independent of Oxygen and HIF-1α

Formation of neutrophil extracellular traps (NETs) is a two-faced innate host defense mechanism, which, on the one hand, can counteract microbial infections, but on the other hand, can contribute to massive detrimental effects on the host. Cholesterol depletion from the cellular membrane by Methyl-β-cyclodextrin (MβCD) is known as one of the processes initiating NET formation. Since neutrophils mainly act in an inflammatory environment with decreased, so-called hypoxic, oxygen conditions, we aimed to study the effect of oxygen and the oxygen stress regulator hypoxia-inducible factor (HIF)-1α on cholesterol-dependent NET formation. Thus, murine bone marrow-derived neutrophils from wild-type and HIF-knockout mice or human neutrophils were stimulated with MβCD under normoxic (21% O₂) compared to hypoxic (1% O₂) conditions, and the formation of NETs were studied by immunofluorescence microscopy. We found significantly induced NET formation after treatment with MβCD in murine neutrophils derived from wild-type as well as HIF-1α KO mice at both hypoxic (1% O₂) as well as normoxic (21% O₂) conditions. Similar observations were made in freshly isolated human neutrophils after stimulation with MβCD or statins, which block the HMG-CoA reductase as the key enzyme in the cholesterol metabolism. HPLC was used to confirm the reduction of cholesterol in treated neutrophils. In summary, we were able to show that NET formation via MβCD or statin-treatment is oxygen and HIF-1α independent.

Pathways and Mechanisms of Cellular Cholesterol Efflux-Insight From Imaging

Cholesterol is an essential molecule in cellular membranes, but too much cholesterol can be toxic. Therefore, mammalian cells have developed complex mechanisms to remove excess cholesterol. In this review article, we discuss what is known about such efflux pathways including a discussion of reverse cholesterol transport and formation of high-density lipoprotein, the function of ABC transporters and other sterol efflux proteins, and we highlight their role in human diseases. Attention is paid to the biophysical principles governing efflux of sterols from cells. We also discuss recent evidence for cholesterol efflux by the release of exosomes, microvesicles, and migrasomes. The role of the endo-lysosomal network, lipophagy, and selected lysosomal transporters, such as Niemann Pick type C proteins in cholesterol export from cells is elucidated. Since oxysterols are important regulators of cellular cholesterol efflux, their formation, trafficking, and secretion are described briefly. In addition to discussing results obtained with traditional biochemical methods, focus is on studies that use established and novel bioimaging approaches to obtain insight into cholesterol efflux pathways, including fluorescence and electron microscopy, atomic force microscopy, X-ray tomography as well as mass spectrometry imaging.

Partial inclusion complex assisted crosslinked β-cyclodextrin nanoparticles for improving therapeutic potential of docetaxel against breast cancer

The present investigation demonstrates the development of crosslinked β-cyclodextrin nanoparticles (β-CD NPs) for enhancing the therapeutic efficacy of docetaxel (DTX) against breast cancer. Initially, a partial inclusion complex between β-CD and polypropylene glycol (PPG) was formed to induce self-assembly. This was followed by crosslinking of β-CDs using epichlorohydrin (EPI) and removal (by solubilization) of PPG to yield uniform β-CD NPs. The formed particles were used for loading DTX to form DTX β-CD NPs. The resultant DTX β-CD NPs exhibited particle size of 223.36 ± 17.73 nm with polydispersity index (PDI) of 0.13 ± 0.09 and showed entrapment efficiency of 54.53 ± 2%. Increased cell uptake (~5-fold), cytotoxicity (~3.3-fold), and apoptosis were observed in MDA-MB-231 cells when treated with DTX β-CD NPs in comparison to free DTX. Moreover, pharmacokinetic evaluation of DTX β-CD NPs revealed ~2 and ~5-fold increase in AUC0-∞ and mean residence time (MRT) of DTX when compared to Docepar®. Further, the anti-tumor activity using DMBA-induced cancer model showed that DTX β-CD NPs were capable of reducing the tumor volume to ~40%, whereas Docepar® was able to reduce tumor volume till ~80%. Finally, the toxicity evaluation of DTX β-CD NPs revealed no short-term nephrotoxicity and was confirmed by estimating the levels of biomarkers and histopathology of the organs. Thus, the proposed formulation strategy can yield uniformly formed β-CD NPs which can be effectively utilized for improving the therapeutic efficacy of DTX.

Cellular Effects of Cyclodextrins: Studies on HeLa Cells

Cyclodextrins are high molecular weight, hydrophilic, cyclic, non-reducing oligosaccharides, applied as excipients for the improvement of the solubility and permeability of insoluble active pharmaceutical ingredients. On the other hand, beta-cyclodextrins are used as cholesterol sequestering agents in life sciences. Recently, we demonstrated the cellular internalization and intracellular effects of cyclodextrins on Caco-2 cells. In this study, we aimed to further investigate the endocytosis of (2-hydroxylpropyl)-beta-(HPBCD) and random methylated-beta-cyclodextrin (RAMEB) to test their cytotoxicity, NF-kappa B pathway induction, autophagy, and lysosome formation on HeLa cells. These derivatives were able to enter the cells; however, major differences were revealed in the inhibition of their endocytosis compared to Caco-2 cells. NF-kappa B p65 translocation was not detected in the cell nuclei after HPBCD or RAMEB pre-treatment and cyclodextrin treatment did not enhance the formation of autophagosomes. These cyclodextrin derivates were partially localized in lysosomes after internalization.

The Role of Membrane Lipids in Light-Activation of Drosophila TRP Channels

Transient Receptor Potential (TRP) channels constitute a large superfamily of polymodal channel proteins with diverse roles in many physiological and sensory systems that function both as ionotropic and metabotropic receptors. From the early days of TRP channel discovery, membrane lipids were suggested to play a fundamental role in channel activation and regulation. A prominent example is the Drosophila TRP and TRP-like (TRPL) channels, which are predominantly expressed in the visual system of Drosophila. Light activation of the TRP and TRPL channels, the founding members of the TRP channel superfamily, requires activation of phospholipase Cβ (PLC), which hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP₂) into Diacylglycerol (DAG) and Inositol 1, 4,5-trisphosphate (IP₃). However, the events required for channel gating downstream of PLC activation are still under debate and led to several hypotheses regarding the mechanisms by which lipids gate the channels. Despite many efforts, compelling evidence of the involvement of DAG accumulation, PIP₂ depletion or IP₃-mediated Ca²⁺ release in light activation of the TRP/TRPL channels are still lacking. Exogeneous application of poly unsaturated fatty acids (PUFAs), a product of DAG hydrolysis was demonstrated as an efficient way to activate the Drosophila TRP/TRPL channels. However, compelling evidence for the involvement of PUFAs in physiological light-activation of the TRP/TRPL channels is still lacking. Light-induced mechanical force generation was measured in photoreceptor cells prior to channel opening. This mechanical force depends on PLC activity, suggesting that the enzymatic activity of PLC converting PIP₂ into DAG generates membrane tension, leading to mechanical gating of the channels. In this review, we will present the roles of membrane lipids in light activation of Drosophila TRP channels and present the many advantages of this model system in the exploration of TRP channel activation under physiological conditions.

Potential-Independent Intracellular Drug Delivery and Mitochondrial Targeting

In this study, two types of the fluoroamphiphile analogs were synthesized and self-assembled into the "core-shell" micellar nanocarriers for intracellular delivery and organelle targeting. Using the fluorescent dyes or vitamin E succinate as the cargo, the drug delivery and targeting capabilities of the fluoroamphiphiles and their micelles were evaluated in the cell lines, tumor cell spheroids, and tumor-bearing mice. The "core-fluorinated" micelles exhibited favorable physicochemical properties and improved the cellular uptake of the cargo by around 20 times compared to their "shell-fluorinated" counterparts. The results also indicated that the core-fluorinated micelles underwent an efficient clathrin-mediated endocytosis and a rapid endosomal escape thereafter. Interestingly, the internalized fluoroamphiphile micelles preferentially accumulated in mitochondria, by which the efficacy of the loaded vitamin E succinate was boosted both in vitro and in vivo. Unlike the popularly used cationic mitochondrial targeting ligands, as a charge-neutral nanocarrier, the fluoroamphiphiles' mitochondrial targeting was potential independent. The mechanism study suggested that the strong binding affinity with the phospholipids, particularly the cardiolipin, played an important role in the fluoroamphiphiles' mitochondrial targeting. These charge-neutral fluoroamphiphiles might have great potential to be a simple and reliable tool for intracellular drug delivery and mitochondrial targeting.

CRMP4-mediated fornix development involves Semaphorin-3E signaling pathway

Neurodevelopmental axonal pathfinding plays a central role in correct brain wiring and subsequent cognitive abilities. Within the growth cone, various intracellular effectors transduce axonal guidance signals by remodeling the cytoskeleton. Semaphorin-3E (Sema3E) is a guidance cue implicated in development of the fornix, a neuronal tract connecting the hippocampus to the hypothalamus. Microtubule-associated protein 6 (MAP6) has been shown to be involved in the Sema3E growth-promoting signaling pathway. In this study, we identified the collapsin response mediator protein 4 (CRMP4) as a MAP6 partner and a crucial effector in Sema3E growth-promoting activity. CRMP4-KO mice displayed abnormal fornix development reminiscent of that observed in Sema3E-KO mice. CRMP4 was shown to interact with the Sema3E tripartite receptor complex within detergent-resistant membrane (DRM) domains, and DRM domain integrity was required to transduce Sema3E signaling through the Akt/GSK3 pathway. Finally, we showed that the cytoskeleton-binding domain of CRMP4 is required for Sema3E's growth-promoting activity, suggesting that CRMP4 plays a role at the interface between Sema3E receptors, located in DRM domains, and the cytoskeleton network. As the fornix is affected in many psychiatric diseases, such as schizophrenia, our results provide new insights to better understand the neurodevelopmental components of these diseases.

Patched 1 reduces the accessibility of cholesterol in the outer leaflet of membranes

A long-standing mystery in vertebrate Hedgehog signaling is how Patched 1 (PTCH1), the receptor for Hedgehog ligands, inhibits the activity of Smoothened, the protein that transmits the signal across the membrane. We previously proposed (Kinnebrew et al., 2019) that PTCH1 inhibits Smoothened by depleting accessible cholesterol from the ciliary membrane. Using a new imaging-based assay to directly measure the transport activity of PTCH1, we find that PTCH1 depletes accessible cholesterol from the outer leaflet of the plasma membrane. This transport activity is terminated by binding of Hedgehog ligands to PTCH1 or by dissipation of the transmembrane potassium gradient. These results point to the unexpected model that PTCH1 moves cholesterol from the outer to the inner leaflet of the membrane in exchange for potassium ion export in the opposite direction. Our study provides a plausible solution for how PTCH1 inhibits SMO by changing the organization of cholesterol in membranes and establishes a general framework for studying how proteins change cholesterol accessibility to regulate membrane-dependent processes in cells.

Anaplasma phagocytophilum Hijacks Flotillin and NPC1 Complex To Acquire Intracellular Cholesterol for Proliferation, Which Can Be Inhibited with Ezetimibe

The intracellular cholesterol transport protein Niemann-Pick type C1 (NPC1) and lipid-raft protein flotillin (FLOT) are required for cholesterol uptake by the obligatory intracellular bacterium Anaplasma phagocytophilum and for infection, and each protein localizes to membrane-bound inclusions containing replicating bacteria. Here, we found striking localization of FLOT2 in NPC1-lined vesicles and a physical interaction between FLOT2 and NPC1. This interaction was cholesterol dependent, as a CRAC (cholesterol recognition/interaction amino acid cholesterol-binding) domain mutant of FLOT2 did not interact with NPC1, and the cholesterol-sequestering agent methyl-β-cyclodextrin reduced the interaction. The stomatin-prohibitin-flotillin-HflC/K domain of FLOT2, FLOT2^1–183, was sufficient for the unique FLOT2 localization and interaction with NPC1. NPC1, FLOT2, and FLOT2^1–183 trafficked to the lumen of Anaplasma inclusions. A loss-of-function mutant, NPC1^P691S (mutation in the sterol-sensing domain), did not colocalize or interact with FLOT2 or with Anaplasma inclusions and inhibited infection. Ezetimibe is a drug that blocks cholesterol absorption in the small intestine by inhibiting plasma membrane Niemann-Pick C1-like 1 interaction with FLOTs. Ezetimibe blocked the interaction between NPC1 and FLOT2 and inhibited Anaplasma infection. Ezetimibe did not directly inhibit Anaplasma proliferation but inhibited host membrane lipid and cholesterol traffic to the bacteria in the inclusion. These data suggest that Anaplasma hijacks NPC1 vesicles containing cholesterol bound to FLOT2 to deliver cholesterol into Anaplasma inclusions to assimilate cholesterol for its proliferation. These results provide insights into mechanisms of intracellular cholesterol transport and a potential approach to inhibit Anaplasma infection by blocking cholesterol delivery into the lumen of bacterial inclusions.

Measurement of Single-Molecule Forces in Cholesterol and Cyclodextrin Host-Guest Complexes

Biological host molecules such as β-cyclodextrins (β-CDs) have been used to remove cholesterol guests from membranes and artery plaques. In this work, we calibrated the host-guest intermolecular mechanical forces (IMMFs) between cholesterol and cyclodextrin complexes by combining single-molecule force spectroscopy in optical tweezers and computational molecular simulations for the first time. Compared to native β-CD, methylated beta cyclodextrins complexed with cholesterols demonstrated higher mechanical stabilities due to the loss of more high-energy water molecules inside the methylated β-CD cavities. This result is consistent with the finding that methylated β-CD is more potent at solubilizing cholesterols than β-CD, suggesting that the IMMF can serve as a novel indicator to evaluate the solubility of small molecules such as cholesterols. Importantly, we found that the force spectroscopy measured in such biological host-guest complexes is direction-dependent: pulling from the alkyl end of the cholesterol molecule resulted in a larger IMMF than that from the hydroxyl end of the cholesterol molecule. Molecular dynamics coupled with umbrella sampling simulations further revealed that cholesterol molecules tend to enter or leave from the wide opening of cyclodextrins. Such an orientation rationalizes that cyclodextrins are rather efficient at extracting cholesterols from the phospholipid bilayer in which hydroxyl groups of cholesterols are readily exposed to the hydrophobic cavities of cyclodextrins. We anticipate that the IMMF measured by both experimental and computational force spectroscopy measurements help elucidate solubility mechanisms not only for cholesterols in different environments but also to host-guest systems in general, which have been widely exploited for their solubilization properties in drug delivery, for example.

High-density lipoproteins, reverse cholesterol transport and atherogenesis

Plasma HDL-cholesterol concentrations correlate negatively with the risk of atherosclerotic cardiovascular disease (ASCVD). According to a widely cited model, HDL elicits its atheroprotective effect through its role in reverse cholesterol transport, which comprises the efflux of cholesterol from macrophages to early forms of HDL, followed by the conversion of free cholesterol (FCh) contained in HDL into cholesteryl esters, which are hepatically extracted from the plasma by HDL receptors and transferred to the bile for intestinal excretion. Given that increasing plasma HDL-cholesterol levels by genetic approaches does not reduce the risk of ASCVD, the focus of research has shifted to HDL function, especially in the context of macrophage cholesterol efflux. In support of the reverse cholesterol transport model, several large studies have revealed an inverse correlation between macrophage cholesterol efflux to plasma HDL and ASCVD. However, other studies have cast doubt on the underlying reverse cholesterol transport mechanism: in mice and humans, the FCh contained in HDL is rapidly cleared from the plasma (within minutes), independently of esterification and HDL holoparticle uptake by the liver. Moreover, the reversibility of FCh transfer between macrophages and HDL has implicated the reverse process - that is, the transfer of FCh from HDL to macrophages - in the aetiology of increased ASCVD under conditions of very high plasma HDL-FCh concentrations.

Bacterial Engulfment Mechanism Is Strongly Conserved in Evolution Between Earthworm and Human Immune Cells

Invertebrates, including earthworms, are applied to study the evolutionarily conserved cellular immune processes. Earthworm immunocytes (so-called coelomocytes) are functionally similar to vertebrate myeloid cells and form the first line of defense against invading pathogens. Hereby, we compared the engulfment mechanisms of THP-1 human monocytic cells, differentiated THP-1 (macrophage-like) cells, and Eisenia andrei coelomocytes towards Escherichia coli and Staphylococcus aureus bacteria applying various endocytosis inhibitors [amantadine, 5-(N-ethyl-N-isopropyl) amiloride, colchicine, cytochalasin B, cytochalasin D, methyl-ß-cyclodextrin, and nystatin]. Subsequently, we investigated the messenger RNA (mRNA) expressions of immune receptor-related molecules (TLR, MyD88, BPI) and the colocalization of lysosomes with engulfed bacteria following uptake inhibition in every cell type. Actin depolymerization by cytochalasin B and D has strongly inhibited the endocytosis of both bacterial strains in the studied cell types, suggesting the conserved role of actin-dependent phagocytosis. Decreased numbers of colocalized lysosomes/bacteria supported these findings. In THP-1 cells TLR expression was increased upon cytochalasin D pretreatment, while this inhibitor caused a dropped LBP/BPI expression in differentiated THP-1 cells and coelomocytes. The obtained data reveal further insights into the evolution of phagocytes in eukaryotes. Earthworm and human phagocytes possess analogous mechanisms for bacterial internalization.

Supramolecular copolymer modified statin-loaded discoidal rHDLs for atherosclerotic anti-inflammatory therapy by cholesterol efflux and M2 macrophage polarization

Foam cells with the pro-inflammatory macrophage phenotype (M1) play an essential role in atherosclerosis progression. Either cellular cholesterol removal or drug intervention was reported to polarize M1 into the anti-inflammatory phenotype (M2) for atherosclerosis regression. These might be realized simultaneously by drug-loaded discoidal reconstituted high-density lipoproteins (d-rHDLs) with the functions of cellular cholesterol efflux and targeted drug delivery on macrophages. However, cholesterol reception can drive the remodelling of d-rHDLs, which serves to release drugs specifically in the atherosclerotic plaque but might incur premature drug leakage in blood circulation. Given that, the proposed strategy is to inhibit the remodelling behaviour of the carrier in blood circulation and responsively accelerate it under the atherosclerotic microenvironmental stimulus. Herein, atorvastatin calcium-loaded d-rHDL was modified by a PEGylated ferrocene/β-cyclodextrin supramolecular copolymer (PF/TC) to construct ROS-responsive PF/TC-AT-d-rHDL, which is expected to possess plasma stability and biosafety as well as triggered drug release by cholesterol efflux promotion. As a result, PF/TC-AT-d-rHDL could responsively dissemble into β-cyclodextrin modified AT-d-rHDL under the ROS-triggered dissociation of PF/TC, therefore exhibiting increased cholesterol efflux from the cholesterol donor and drug release through the remodelling behaviour of the carrier in vitro. Moreover, PF/TC-AT-d-rHDL enhanced cellular cholesterol removal in foam cells after response to ROS, inhibiting intracellular lipid deposition compared with other d-rHDL carriers. Interestingly, cellular drug uptake was significantly promoted upon cellular cholesterol removal by restoring the permeability and fluidity of foam cell membranes as indicated by flow cytometry and fluorescence polarization analysis, respectively. Importantly, compared with untreated foam cells, PF/TC-AT-d-rHDL obviously increased the ratio of M2/M1 by 6.3-fold, which was even higher than the effect of PF/TC-d-rHDL (3.4-fold) and free drugs (1.9-fold), revealing that PF/TC-AT-d-rHDL synergistically promoted the M2 polarization of macrophages. Accordingly, PF/TC-AT-d-rHDL boosted the secretion of anti-inflammatory cytokines and inhibited that of inflammatory cytokines. Collectively, PF/TC-AT-d-rHDL exerted synergistic M2 polarization effects on foam cells for atherosclerotic immunomodulatory therapy via responsively mediating cholesterol efflux and delivering drugs.

Regulation of EGFR activation and signaling by lipids on the plasma membrane

Lipids on the plasma membrane are not only components of the membrane biophysical structures but also regulators of receptor functions. Recently, the critical roles of lipid-protein interactions have been intensively highlighted. Epidermal growth factor receptor (EGFR) is one of the most extensively studied receptors exhibiting various lipid interactions, including interactions with phosphatidylcholine, phosphatidylserine, phosphatidylinositol phosphate, cholesterol, gangliosides, and palmitate. Here, we review recent findings on how direct interaction with these lipids regulates EGFR activation and signaling, providing unprecedented insight into the comprehensive roles of various lipids in the control of EGFR functions. Finally, the current limitations in investigating lipid-protein interactions and novel technologies to potentially overcome these limitations are discussed.