Search for inhibitors of endocytosis: Intended specificity and unintended consequences

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.

Efficient intracellular drug delivery by co-administration of two antibodies against cell adhesion molecule 1

Cell adhesion molecule 1 (CADM1), a single-pass transmembrane protein, is involved in oncogenesis. We previously demonstrated the therapeutic efficacy of anti-CADM1 ectodomain monoclonal antibodies against mesothelioma; however, the underlying mechanism is unclear. In the present study, we explored the molecular behavior of anti-CADM1 antibodies in CADM1-expressing tumor cells. Sequencing analyses revealed that the anti-CADM1 chicken monoclonal antibodies 3E1 and 9D2 are IgY and IgM isotype antibodies, respectively. Co-administration of 3E1 and 9D2 altered the subcellular distribution of CADM1 from the detergent-soluble fraction to the detergent-resistant fraction in tumor cells. Using recombinant chicken-mouse chimeric antibodies that had been isotype-switched from IgG to IgM, we demonstrated that the combination of the variable region of 3E1 and the constant region of IgM was required for CADM1 relocation. Cytochemical studies showed that 3E1 colocalized with late endosomes/lysosomes after co-administration with 9D2, suggesting that the CADM1-antibody complex is internalized from the cell surface to intracellular compartments by lipid-raft mediated endocytosis. Finally, 3E1 was conjugated with the antimitotic agent monomethyl auristatin E (MMAE) via a cathepsin-cleavable linker. Co-administration of 3E1-monomethyl auristatin E and 9D2 suppressed the growth of multiple types of tumor cells, and this anti-tumor activity was confirmed in a syngeneic mouse model of melanoma. 3E1 and 9D2 are promising drug delivery vehicles for CADM1-expressing tumor cells.

Comparing Cell Penetration of Biotherapeutics across Human Cell Lines

A major obstacle in biotherapeutics development is maximizing cell penetration. Ideally, assays would allow for optimization of cell penetration in the cell type of interest early in the drug development process. However, few assays exist to compare cell penetration across different cell types independent of drug function. In this work, we applied the chloroalkane penetration assay (CAPA) in seven mammalian cell lines as well as primary cells. Careful controls were used to ensure that data could be compared across cell lines. We compared the nuclear penetration of several peptides and drug-like oligonucleotides and saw significant differences among the cell lines. To help explain these differences, we quantified the relative activities of endocytosis pathways in these cell lines and correlated them with the penetration data. Based on these results, we knocked down clathrin in a cell line with an efficient permeability profile and observed reduced penetration of peptides but not oligonucleotides. Finally, we used small-molecule endosomal escape enhancers and observed enhancement of cell penetration of some oligonucleotides, but only in some of the cell lines tested. CAPA data provide valuable points of comparison among different cell lines, including primary cells, for evaluating the cell penetration of various classes of peptides and oligonucleotides.

Peptide nanocarriers co-delivering an antisense oligonucleotide and photosensitizer elicit synergistic cytotoxicity

Combination therapies demand co-delivery platforms with efficient entrapment of distinct payloads and specific delivery to cells and possibly organelles. Herein, we introduce the combination of two therapeutic modalities, gene and photodynamic therapy, in a purely peptidic platform. The simultaneous formation and cargo loading of the multi-micellar platform is governed by self-assembly at the nanoscale. The multi-micellar architecture of the nanocarrier and the positive charge of its constituent micelles offer controlled dual loading capacity with distinct locations for a hydrophobic photosensitizer (PS) and negatively charged antisense oligonucleotides (ASOs). Moreover, the nuclear localization signal (NLS) sequence built-in the peptide targets PS + ASO-loaded nanocarriers to the nucleus. Breast cancer cells treated with nanocarriers demonstrated photo-triggered enhancement of radical oxygen species (ROS) associated with increased cell death. Besides, delivery of ASO payloads resulted in up to 90 % knockdown of Bcl-2, an inhibitor of apoptosis that is overexpressed in more than half of all human cancers. Simultaneous delivery of PS and ASO elicited synergistic apoptosis to an extent that could not be reached by singly loaded nanocarriers or the free form of the drugs. Both, the distinct location of loaded compounds that prevents them from interfering with each other, and the highly efficient cellular delivery support the great potential of this versatile peptide platform in combination therapy.

Synthesis of ionizable lipopolymers using split-Ugi reaction for pulmonary delivery of various size RNAs and gene editing

We present an efficient approach for synthesizing cationic poly(ethylene imine) derivatives using the multicomponent split-Ugi reaction to rapidly create a library of complex functional ionizable lipopolymers. We synthesized a diverse library of 155 polymers, formulated them into polyplexes to establish structure-activity relationships crucial for endosomal escape and efficient transfection. After discovering a lead structure, lipopolymer-lipid hybrid nanoparticles are introduced to preferentially deliver to and elicit effective mRNA transfection in lung endothelium and immune cells, including T cells with low in vivo toxicity. The lipopolymer-lipid hybrid nanoparticles showed 300-fold improvement in systemic mRNA delivery to the lung compared to in vivo -JetPEI ® . Lipopolymer-lipid hybrid nanoparticles demonstrated efficient delivery of mRNA-based therapeutics for treatment of two different disease models. Lewis Lung cancer progression was significantly delayed after treatment with loaded IL-12 mRNA in U155@lipids after repeated i.v. administration. Systemic delivery of human CFTR (hCFTR) mRNA resulted in production of functional form of CFTR protein in the lungs. The functionality of hCFTR protein was confirmed by restoration of CFTR- mediated chloride secretion in conductive airway epithelia in CFTR knockout mice after nasal instillation of hCFTR mRNA loaded U155@lipids. We further showed that, U155@lipids nanoparticles can deliver complex CRISPR-Cas9 based RNA cargo to the lung, achieving 5.6 ± 2.4 % gene editing in lung tissue. Moreover, we demonstrated successful PD-1 gene knockout of T cells in vivo . Our results highlight a versatile delivery platform for systemic delivering of mRNA of various sizes for gene therapy for a variety of therapeutics.

Liposome nanoparticle conjugation and cell penetrating peptide sequences (CPPs) enhance the cellular delivery of the tau aggregation inhibitor RI-AG03

Given the pathological role of Tau aggregation in Alzheimer's disease (AD), our laboratory previously developed the novel Tau aggregation inhibitor peptide, RI-AG03. As Tau aggregates accumulate intracellularly, it is essential that the peptide can traverse the cell membrane. Here we examine the cellular uptake and intracellular trafficking of RI-AG03, in both a free and liposome-conjugated form. We also characterize the impact of adding the cell-penetrating peptide (CPP) sequences, polyarginine (polyR) or transactivator of transcription (TAT), to RI-AG03. Our data show that liposome conjugation of CPP containing RI-AG03 peptides, with either the polyR or TAT sequence, increased cellular liposome association three-fold. Inhibition of macropinocytosis modestly reduced the uptake of unconjugated and RI-AG03-polyR-linked liposomes, while having no effect on RI-AG03-TAT-conjugated liposome uptake. Further supporting macropinocytosis-mediated internalization, a 'fair' co-localisation of the free and liposome-conjugated RI-AG03-polyR peptide with macropinosomes and lysosomes was observed. Interestingly, we also demonstrate that RI-AG03-polyR detaches from liposomes following cellular uptake, thereby largely evading organellar entrapment. Collectively, our data indicate that direct membrane penetration and macropinocytosis are key routes for the internalization of liposomes conjugated with CPP containing RI-AG03. Our study also demonstrates that peptide-liposomes are suitable nanocarriers for the cellular delivery of RI-AG03, furthering their potential use in targeting Tau pathology in AD.

Charge-switchable cell-penetrating peptides for rerouting nanoparticles to glioblastoma treatment

Glioblastoma (GB) is one of the most lethal types of neoplasms with unique anatomic, physiologic, and pathologic features that usually persist after exposure to standard therapeutic modalities. It is biologically aggressive, and the existence of the blood-brain barrier (BBB) limits the efficacy of standard therapies. In this work, we hypothesize the potential of surface-functionalized ultra-small nanostructured lipid carriers (usNLCs) with charge-switchable cell-penetrating peptides (CPPs) to overcome this biological barrier and improve targeted delivery to brain tumor tissues. The big question is: what is the potential of CPPs in directing nanoparticles toward brain tumor tissue? To answer this question, the usNLCs were functionalized with distinct biomolecules [five CPPs, c(RGDfK) and transferrin, Tf] through electrostatic interaction and its ability as a targeting approach to BBB (HBMEC) and glioma cells (U87 cells) evaluated in terms of physicochemical properties, cellular uptake, permeability in a 2D-BBB model, and tumor growth inhibition. Monte Carlo simulations elucidated CPP adsorption patterns. The permeability studies revealed that targeted usNLCs, especially usNLCsTf and usNLCsCPP4, exhibited an increased permeability coefficient compared to the non-targeted usNLCs. Functionalized usNLCs evidenced enhanced uptake in BBB cells, with smaller CPPs showing higher internalization (CPP1 and CPP2). Similarly, functionalized usNLCs exhibited more significant cytotoxicity in glioma cells, with specific CPPs promoting favorable internalization. Analysis of the endocytic pathway indicated that usNLCsCPPs were mainly internalized by direct translocation and caveolae-mediated endocytosis. Optimal usNLCs with dual targeting capabilities to both BBB and GB cells provide a promising therapeutic strategy for GB.

In Situ Formation of Fibronectin-Enriched Protein Corona on Epigenetic Nanocarrier for Enhanced Synthetic Lethal Therapy

PARP inhibitors (PARPi)-based synthetic lethal therapy demonstrates limited efficacy for most cancer types that are homologous recombination (HR) proficient. To potentiate the PARPi application, a nanocarrier based on 5-azacytidine (AZA)-conjugated polymer (PAZA) for the codelivery of AZA and a PARP inhibitor, BMN673 (BMN) is developed. AZA conjugation significantly decreased the nanoparticle (NP) size and increased BMN loading. Molecular dynamics simulation and experimental validations shed mechanistic insights into the self-assembly of effective NPs. The small PAZA NPs demonstrated higher efficiency of tumor targeting and penetration than larger NPs, which is mediated by a new mechanism of active targeting that involves the recruitment of fibronectin from serum proteins following systemic administration of PAZA NPs. Furthermore, it is found that PAZA carrier sensitize the HR-proficient nonsmall cell lung cancer (NSCLC) to BMN, a combination therapy that is more effective at a lower AZA/BMN dosage. To investigate the underlying mechanism, the tumor immune microenvironment and various gene expressions by RNAseq are explored. Moreover, the BMN/PAZA combination increased the immunogenicity and synergized with PD-1 antibody in improving the overall therapeutic effect in an orthotopic model of lung cancer (LLC).

Combined Vorinostat and Chloroquine Inhibit Sodium-Iodide Symporter Endocytosis and Enhance Radionuclide Uptake In Vivo

PURPOSE

Patients with aggressive thyroid cancer are frequently failed by the central therapy of ablative radioiodide (RAI) uptake, due to reduced plasma membrane (PM) localization of the sodium/iodide symporter (NIS). We aimed to understand how NIS is endocytosed away from the PM of human thyroid cancer cells, and whether this was druggable in vivo.

EXPERIMENTAL DESIGN

Informed by analysis of endocytic gene expression in patients with aggressive thyroid cancer, we used mutagenesis, NanoBiT interaction assays, cell surface biotinylation assays, RAI uptake, and NanoBRET to understand the mechanisms of NIS endocytosis in transformed cell lines and patient-derived human primary thyroid cells. Systemic drug responses were monitored via 99mTc pertechnetate gamma counting and gene expression in BALB/c mice.

RESULTS

We identified an acidic dipeptide within the NIS C-terminus that mediates binding to the σ2 subunit of the Adaptor Protein 2 (AP2) heterotetramer. We discovered that the FDA-approved drug chloroquine (CQ) modulates NIS accumulation at the PM in a functional manner that is AP2 dependent. In vivo, CQ treatment of BALB/c mice significantly enhanced thyroidal uptake of 99mTc pertechnetate in combination with the histone deacetylase (HDAC) inhibitor vorinostat/SAHA, accompanied by increased thyroidal NIS mRNA. Bioinformatic analyses validated the clinical relevance of AP2 genes with disease-free survival in RAI-treated DTC, enabling construction of an AP2 gene-related risk score classifier for predicting recurrence.

CONCLUSIONS

NIS internalization is specifically druggable in vivo. Our data, therefore, provide new translatable potential for improving RAI therapy using FDA-approved drugs in patients with aggressive thyroid cancer. See related commentary by Lechner and Brent, p. 1220.

Iron-Confined CRISPR/Cas9-Ribonucleoprotein Delivery System for Redox-Responsive Gene Editing

Clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein 9 (Cas9) is a promising gene editing tool to treat diseases at the genetic level. Nonetheless, the challenge of the safe and efficient delivery of CRISPR/Cas9 to host cells constrains its clinical applicability. In the current study, a facile, redox-responsive CRISPR/Cas9-Ribonucleoprotein (RNP) delivery system by combining iron-coordinated aggregation with liposomes (Fe-RNP@L) is reported. The Fe-RNP is formed by the coordination of Fe3+ with amino and carboxyl groups of Cas9, which modifies the lipophilicity and surface charge of RNP and alters cellular uptake from primary endocytosis to endocytosis and cholesterol-dependent membrane fusion. RNP can be rapidly and reversibly released from Fe-RNP in response to glutathione without loss of structural integrity and enzymatic activity. In addition, iron coordination also improves the stability of RNP and substantially mitigates cytotoxicity. This construct enabled highly efficient cytoplasmic/nuclear delivery (≈90%) and gene-editing efficiency (≈70%) even at low concentrations. The high payload content, high editing efficiency, good stability, low immunogenicity, and ease of production and storage, highlight its potential for diverse genome editing and clinical applications.

Arginine Surface Density of Nanoparticles Controls Nonendocytic Cell Uptake and Autophagy Induction

Nonendocytic cell uptake of nanomaterials is challenging, which requires specific surface chemistry and smaller particle size. Earlier works have shown that an arginine-terminated nanoparticle of <10-20 nm size shows nonendocytic uptake via direct membrane penetration. However, the roles of surface arginine density and the arginine-arginine distance at the nanoparticle surface in controlling such nonendocytic uptake mechanism is not yet explored. Here we show that a higher arginine density at the nanoparticle surface with an arginine-arginine distance of <3 nm is the most critical aspect for such nonendocytic uptake. We have used quantum dot (QD)-based nanoparticles as a model for fluorescent tracking inside cells and for quantitative estimation of cellular uptake. We found that arginine-terminated nanoparticles of 10 nm size can opt for the energy-dependent endocytosis pathway if the arginine-arginine distance is >3 nm. In contrast, nanoparticles with <3 nm arginine-arginine distance rapidly enter into the cell via the nonendocytic approach, are freely available in the cytosol in large amounts to capture the cellular adenosine triphosphate (ATP), generate oxidative stress, and induce ATP-deficient cellular autophagy. This work shows that arginine-arginine distance at the nanoparticle surface is another fundamental parameter, along with the particle size, for the nonendocytic cell uptake of foreign materials and to control intracellular activity. This approach may be utilized in designing nanoprobes and nanocarriers with more efficient biomedical performances.

Antibodies internalization mechanisms by dendritic cells and their role in therapeutic antibody immunogenicity

Internalization and processing by antigen-presenting cells such as dendritic cells (DCs) are critical steps for initiating a T-cell response to therapeutic antibodies. Consequences are the production of neutralizing antidrug antibodies altering the clinical response, the presence of immune complexes, and, in some rare cases, hypersensitivity reactions. In recent years, significant progress has been made in the knowledge of cellular uptake mechanisms of antibodies in DCs. The uptake of antibodies could be directly related to their immunogenicity by regulating the quantity of materials entering the DCs in relation to antibody structure. Here, we summarize the latest insights into cellular uptake mechanisms and pathways in DCs. We highlight the approaches to study endocytosis, the impact of endocytosis routes on T-cell response, and discuss the link between how DCs internalize therapeutic antibodies and the potential mechanisms that could give rise to immunogenicity. Understanding these processes could help in developing assays to evaluate the immunogenicity potential of biotherapeutics.

The temporal association of CapZ with early endosomes regulates endosomal trafficking and viral entry into host cells

BACKGROUND

Many viruses enter host cells by hijacking endosomal trafficking. CapZ, a canonical actin capping protein, participates in endosomal trafficking, yet its precise role in endocytosis and virus infection remains elusive.

RESULTS

Here, we showed that CapZ was transiently associated with early endosomes (EEs) and was subsequently released from the matured EEs after the fusion of two EEs, which was facilitated by PI(3)P to PI(3,5)P2 conversion. Vacuolin-1 (a triazine compound) stabilized CapZ at EEs and thus blocked the transition of EEs to late endosomes (LEs). Likewise, artificially tethering CapZ to EEs via a rapamycin-induced protein-protein interaction system blocked the early-to-late endosome transition. Remarkably, CapZ knockout or artificially tethering CapZ to EEs via rapamycin significantly inhibited flaviviruses, e.g., Zika virus (ZIKV) and dengue virus (DENV), or beta-coronavirus, e.g., murine hepatitis virus (MHV), infection by preventing the escape of RNA genome from endocytic vesicles.

CONCLUSIONS

These results indicate that the temporal association of CapZ with EEs facilitates early-to-late endosome transition (physiologically) and the release of the viral genome from endocytic vesicles (pathologically).

Tumor-derived small extracellular vesicles in cancer invasion and metastasis: molecular mechanisms, and clinical significance

The production and release of tumor-derived small extracellular vesicles (TDSEVs) from cancerous cells play a pivotal role in the propagation of cancer, through genetic and biological communication with healthy cells. TDSEVs are known to orchestrate the invasion-metastasis cascade via diverse pathways. Regulation of early metastasis processes, pre-metastatic niche formation, immune system regulation, angiogenesis initiation, extracellular matrix (ECM) remodeling, immune modulation, and epithelial-mesenchymal transition (EMT) are among the pathways regulated by TDSEVs. MicroRNAs (miRs) carried within TDSEVs play a pivotal role as a double-edged sword and can either promote metastasis or inhibit cancer progression. TDSEVs can serve as excellent markers for early detection of tumors, and tumor metastases. From a therapeutic point of view, the risk of cancer metastasis may be reduced by limiting the production of TDSEVs from tumor cells. On the other hand, TDSEVs represent a promising approach for in vivo delivery of therapeutic cargo to tumor cells. The present review article discusses the recent developments and the current views of TDSEVs in the field of cancer research and clinical applications.

Liver macrophages and sinusoidal endothelial cells execute vaccine-elicited capture of invasive bacteria

Vaccination has substantially reduced the morbidity and mortality of bacterial diseases, but mechanisms of vaccine-elicited pathogen clearance remain largely undefined. We report that vaccine-elicited immunity against invasive bacteria mainly operates in the liver. In contrast to the current paradigm that migrating phagocytes execute vaccine-elicited immunity against blood-borne pathogens, we found that invasive bacteria are captured and killed in the liver of vaccinated host via various immune mechanisms that depend on the protective potency of the vaccine. Vaccines with relatively lower degrees of protection only activated liver-resident macrophage Kupffer cells (KCs) by inducing pathogen-binding immunoglobulin M (IgM) or low amounts of IgG. IgG-coated pathogens were directly captured by KCs via multiple IgG receptors FcγRs, whereas IgM-opsonized bacteria were indirectly bound to KCs via complement receptors of immunoglobulin superfamily (CRIg) and complement receptor 3 (CR3) after complement C3 activation at the bacterial surface. Conversely, the more potent vaccines engaged both KCs and liver sinusoidal endothelial cells by inducing higher titers of functional IgG antibodies. Endothelial cells (ECs) captured densely IgG-opsonized pathogens by the low-affinity IgG receptor FcγRIIB in a "zipper-like" manner and achieved bacterial killing predominantly in the extracellular milieu via an undefined mechanism. KC- and endothelial cell-based capture of antibody-opsonized bacteria also occurred in FcγR-humanized mice. These vaccine protection mechanisms in the liver not only provide a comprehensive explanation for vaccine-/antibody-boosted immunity against invasive bacteria but also may serve as in vivo functional readouts of vaccine efficacy.

Impact of Peptide Sequence on Functional siRNA Delivery and Gene Knockdown with Cyclic Amphipathic Peptide Delivery Agents

Short-interfering RNA (siRNA) oligonucleotide therapeutics that modify gene expression by accessing RNA-interference (RNAi) pathways have great promise for the treatment of a range of disorders; however, their application in clinical settings has been limited by significant challenges in cellular delivery. Herein, we report a structure-function study using a series of modified cyclic amphipathic cell-penetrating peptides (CAPs) to determine the impact of peptide sequence on (1) siRNA-binding efficiency, (2) cellular delivery and knockdown efficiency, and (3) the endocytic uptake mechanism. Nine cyclic peptides of the general sequence Ac-C[XZ]4CG-NH2 in which X residues are hydrophobic/aromatic (Phe, Tyr, Trp, or Leu) and Z residues are charged/hydrophilic (Arg, Lys, Ser, or Glu) are assessed along with one acyclic peptide, Ac-(WR)4G-NH2. Cyclization is enforced by intramolecular disulfide bond formation between the flanking Cys residues. Binding analyses indicate that strong cationic character and the presence of aromatic residues that are competent to participate in CH-π interactions lead to CAP sequences that most effectively interact with siRNA. CAP-siRNA binding increases in the following order as a function of CAP hydrophobic/aromatic content: His < Phe < Tyr < Trp. Both cationic charge and disulfide-constrained cyclization of CAPs improve uptake of siRNA in vitro. Net neutral CAPs and an acyclic peptide demonstrate less-efficient siRNA translocation compared to the cyclic, cationic CAPs tested. All CAPs tested facilitated efficient siRNA target gene knockdown of at least 50% (as effective as a lipofectamine control), with the best CAPs enabling >80% knockdown. Significantly, gene knockdown efficiency does not strongly correlate with CAP-siRNA internalization efficiency but moderately correlates with CAP-siRNA-binding affinity. Finally, utilization of small-molecule inhibitors and targeted knockdown of essential endocytic pathway proteins indicate that most CAP-siRNA nanoparticles facilitate siRNA delivery through clathrin- and caveolin-mediated endocytosis. These results provide insight into the design principles for CAPs to facilitate siRNA delivery and the mechanisms by which these peptides translocate siRNA into cells. These studies also demonstrate the nature of the relationships between peptide-siRNA binding, cellular delivery of siRNA cargo, and functional gene knockdown. Strong correlations between these properties are not always observed, which illustrates the complexity in the design of optimal next-generation materials for oligonucleotide delivery.

Strategies and Progress of Raman Technologies for Cellular Uptake Analysis of the Drug Delivery Systems

Nanoparticle (NP)-based drug delivery systems have the potential to significantly enhance the pharmacological and therapeutic properties of drugs. These systems enhance the bioavailability and biocompatibility of pharmaceutical agents via enabling targeted delivery to specific tissues or organs. However, the efficacy and safety of these systems are largely dependent on the cellular uptake and intracellular transport of NPs. Thus, it is crucial to monitor the intracellular behavior of NPs within a single cell. Yet, it is challenging due to the complexity and size of the cell. Recently, the development of the Raman instrumentation offers a versatile tool to allow noninvasive cellular measurements. The primary objective of this review is to highlight the most recent advancements in Raman techniques (spontaneous Raman scattering, bioorthogonal Raman scattering, coherence Raman scattering, and surface-enhanced Raman scattering) when it comes to assessing the internalization of NP-based drug delivery systems and their subsequent movement within cells.

IgG and insulin enhance endocytosis in THP-1 cells via activation of phosphatidylinositol 3-kinase (PI3K)

Extracellular substances, including membrane-impermeable nutrients, are taken up by cells via endocytosis. Endocytosis is also an important pathway for antigen uptake by antigen-presenting cells such as monocytes, macrophages, dendritic cells, and B cells. In this study, we investigated the regulatory mechanism of endocytosis in THP-1 cells, a monocytic leukemia cell line. We analyzed the effect of IgG and insulin, which are abundant in the serum and play important roles in immunity and metabolism, respectively, on the endocytic activity in THP-1 cells. The results indicated that IgG and insulin enhance pinocytosis and phagocytosis via activation of phosphatidylinositol 3-kinase (PI3K). Our results suggest that IgG and insulin contribute to the maintenance of endocytic activity and are important for antigen presentation and nutrient uptake.

Light-dependent inhibition of clathrin-mediated endocytosis in yeast unveils conserved functions of the AP2 complex

Clathrin-mediated endocytosis (CME) is an essential cellular process, conserved among eukaryotes. Yeast constitutes a powerful genetic model to dissect the complex endocytic machinery, yet there is a lack of specific pharmacological agents to interfere with CME in these organisms. TL2 is a light-regulated peptide inhibitor targeting the AP2-β-adaptin/β-arrestin interaction and that can photocontrol CME with high spatiotemporal precision in mammalian cells. Here, we study endocytic protein dynamics by live-cell imaging of the fluorescently tagged coat-associated protein Sla1-GFP, demonstrating that TL2 retains its inhibitory activity in S. cerevisiae spheroplasts. This is despite the β-adaptin/β-arrestin interaction not being conserved in yeast. Our data indicate that the AP2 α-adaptin is the functional target of activated TL2. We identified as interacting partners for the α-appendage, the Eps15 and epsin homologues Ede1 and Ent1. This demonstrates that endocytic cargo loading and sensing can be executed by conserved molecular interfaces, regardless of the proteins involved.

Permeation behavior of porphyrin derivatives with different functional group positions across cancer cell membranes

Porphyrin, which shows selective accumulation in cancer cells, has attracted attention as a drug carrier. The influences of the functional porphyrin positions (β- and meso-positions) on porphyrin accumulation must be understood. In this work, we focused on the investigation of the phenyl functional group whose β-position influences cancer cell accumulation through direct membrane permeation and endocytosis. The endocytic pathway, in particular, is influenced by both clathrin-dependent and caveolae-dependent endocytosis.

Evaluation of cell membrane-derived nanoparticles as therapeutic carriers for pancreatic ductal adenocarcinoma using an in vitro tumour stroma model

Here, we fabricated nanoparticles made solely from the membrane of cells found in the pancreatic tumour's microenvironment (TME), like the human MiaPaCa-2 cells and M2-polarized macrophages. The cell membrane-derived nanoparticles (CMNPs) deriving from the MiaPaCa-2 cells (MPC2-CMNPs) were loaded with the chemotherapeutic drug paclitaxel (PTX), and the CMNPs deriving from M2-polarized macrophages (M2-CMNPs) were loaded with the colony-stimulating factor 1 receptor inhibitor, pexidartinib (PXDB). The CMNPs' thorough morphological and physicochemical characterisation was followed by an in-depth study of their targeting ability and the endocytosis pathway involved during their internalisation. An in vitro model of the desmoplastic stroma comprising cancer-associated fibroblast-mimicking cells and M2-polarized macrophages was also developed. The model was characterised by collagen and α-smooth muscle actin (α-SMA) expression (overexpressed in desmoplasia) and was used to assess the CMNPs' ability to cross the stroma and target the tumour cells. Moreover, we assessed the effect of PXDB-loaded M2-CMNPs on the expression of M1 (CD80/CD86) and M2 (CD206/CD209) polarisation markers on activated macrophages. Finally, we evaluated the PTX and PXDB-loaded CMNPs' effect on the viability of all the used TME cell lines alone or in combination. Overall, this pilot study showed the potential of the CMNPs to cross an in vitro stroma model and act synergistically to treat PDAC.

A Comparison of Cellular Uptake Mechanisms, Delivery Efficacy, and Intracellular Fate between Liposomes and Extracellular Vesicles

A key aspect for successful drug delivery via lipid-based nanoparticles is their internalization in target cells. Two prominent examples of such drug delivery systems are artificial phospholipid-based carriers, such as liposomes, and their biological counterparts, the extracellular vesicles (EVs). Despite a wealth of literature, it remains unclear which mechanisms precisely orchestrate nanoparticle-mediated cargo delivery to recipient cells and the subsequent intracellular fate of therapeutic cargo. In this review, internalization mechanisms involved in the uptake of liposomes and EVs by recipient cells are evaluated, also exploring their intracellular fate after intracellular trafficking. Opportunities are highlighted to tweak these internalization mechanisms and intracellular fates to enhance the therapeutic efficacy of these drug delivery systems. Overall, literature to date shows that both liposomes and EVs are predominantly internalized through classical endocytosis mechanisms, sharing a common fate: accumulation inside lysosomes. Studies tackling the differences between liposomes and EVs, with respect to cellular uptake, intracellular delivery and therapy efficacy, remain scarce, despite its importance for the selection of an appropriate drug delivery system. In addition, further exploration of functionalization strategies of both liposomes and EVs represents an important avenue to pursue in order to control internalization and fate, thereby improving therapeutic efficacy.

Enhanced Cochlear Transduction by AAV9 with High-Concentration Sucrose

The inner ear is a primary lesion in sensorineural hearing loss and has been a target in gene therapy. The efficacy of gene therapy depends on achieving sufficient levels of transduction at a safe vector dose. Vectors derived from various adeno-associated viruses (AAVs) are predominantly used to deliver therapeutic genes to inner ear cells. AAV9 and its variants vector are attractive candidates for clinical applications since they can cross the mesothelial cell layer and transduce inner hair cells (IHCs), although this requires relatively high doses. In this study, we investigated the effects of sucrose on the transduction of a variant of the AAV9 vector for gene transfer in the inner ear. We found that high concentrations of sucrose increased gene transduction in House Ear Institute-Organ of Corti 1 (HEI-OC1) cells in vitro. In addition, we demonstrated that simultaneous administration of sucrose enhanced the transduction of mouse IHCs and spiral ligament cells using an AAV9 variant vector. The procedure did not increase the thresholds in the auditory brainstem response, suggesting that sucrose had no adverse effect on auditory function. This versatile method may be valuable in the development of novel gene therapies for adult-onset sensorineural hearing loss.

Endocytic pathways of pathogenic protein aggregates in neurodegenerative diseases

Endocytosis is the fundamental uptake process through which cells internalize extracellular materials and species. Neurodegenerative diseases (NDs) are characterized by a progressive accumulation of intrinsically disordered protein species, leading to neuronal death. Misfolding in many proteins leads to various NDs such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS) and other disorders. Despite the significance of disordered protein species in neurodegeneration, their spread between cells and the cellular uptake of extracellular species is not entirely understood. This review discusses the major internalization mechanisms of the different conformer species of these proteins and their endocytic mechanisms. We briefly introduce the broad types of endocytic mechanisms found in cells and then summarize what is known about the endocytosis of monomeric, oligomeric and aggregated conformations of tau, Aβ, α-Syn, Huntingtin, Prions, SOD1, TDP-43 and other proteins associated with neurodegeneration. We also highlight the key players involved in internalizing these disordered proteins and the several techniques and approaches to identify their endocytic mechanisms. Finally, we discuss the obstacles involved in studying the endocytosis of these protein species and the need to develop better techniques to elucidate the uptake mechanisms of a particular disordered protein species.

Hyperinsulinemia Impairs Clathrin-Mediated Endocytosis of the Insulin Receptor and Activation of Endothelial Nitric Oxide Synthase in Brain Endothelial Cells

Adequate perfusion of cerebral tissues, which is necessary for the preservation of optimal brain health, depends on insulin signaling within brain endothelial cells. Proper insulin signaling relies on the regulated internalization of insulin bound to the insulin receptor, a process which is disrupted by hyperinsulinemia via an unknown mechanism. Thus, the goal of this study was to characterize the impact of hyperinsulinemia on the regulation of molecular targets involved in cerebral blood flow and insulin receptor internalization into brain endothelial cells. The phosphorylation of molecular targets associated with cerebral blood flow and insulin receptor internalization was assessed in hyperinsulinemic brain endothelial cells. Insulin receptor uptake into cells was also examined in the setting of endocytosis blockade. Our data demonstrate that hyperinsulinemia impairs the activation of endothelial nitric oxide synthase. These data correspond with an impairment in clathrin-mediated endocytosis of the insulin receptor and dysregulated phosphorylation of key internalization effectors. We conclude that hyperinsulinemia alters the phosphorylation of molecular targets involved in clathrin-mediated endocytosis, disrupts signaling through the insulin receptor, and hinders the capacity for blood flow regulation by brain endothelial cells.

Polymer/Nanoceria Hybrid Polyplexes for Gene and Antioxidant Delivery

Various diseases, including cancers and inflammatory diseases, are characterized by a disruption of redox homeostasis, suggesting the need for synergistic treatments involving co-delivery of gene therapies and free radical scavengers. In this report, polyethylenimine (PEI), nanoceria (NC), and DNA were complexed to form nanoparticles providing simultaneous delivery of a gene and an antioxidant. NC was coated in citric acid to provide stable, 4 nm particles that electrostatically bound PEI/DNA polyplexes. The resulting ternary particles transfected HeLa cells with similar efficiency to that of ternary polyplexes comprising 15 kDa poly-l-α-glutamic acid/PEI/DNA while providing smaller particle sizes by more than 100 nm. NC/PEI/DNA polyplexes exhibited enhanced radical-scavenging activity compared to free NC, and oxidative stress from the superoxide-generating agent, menadione, could be completely reversed by the delivery of NC/PEI/DNA polyplexes. Transfection by NC/PEI/DNA polyplexes was demonstrated to occur efficiently through caveolin-mediated endocytosis and macropinocytosis. Co-delivery of genes encoding reactive oxygen species-scavenging proteins, transcription factors, growth factors, tumor suppressors, or anti-inflammatory genes with NC, therefore, may be a promising strategy in synergistic therapeutics.

Pivotal role of the protein corona in the cell uptake of fluorinated nanoparticles with increased sensitivity for 19F-MR imaging

In vivo cell tracking by non-invasive imaging technologies is needed to accelerate the clinical translation of innovative cell-based therapies. In this regard, ¹⁹F-MRI has recently gained increased attention for unbiased localization of labeled cells over time. To push forward the use of ¹⁹F-MRI for cell tracking, the development of highly performant ¹⁹F-probes is required. PLGA-based NPs containing PERFECTA, a multibranched superfluorinated molecule with an optimal MRI profile thanks to its 36 magnetically equivalent fluorine atoms, are promising ¹⁹F-MRI probes. In this work we demonstrate the importance of the surface functionalization of these NPs in relation to their interaction with the biological environment, stressing the pivotal role of the formation of the protein corona (PC) in their cellular labelling efficacy. In particular, our studies showed that the formation of PC NPs strongly promotes the cellular internalization of these NPs in microglia cells. We advocate that the formation of PC NPs in the culture medium can be a key element to be used for the optimization of cell labelling with a considerable increase of the detection sensitivity by ¹⁹F-MRI.

Differential intracellular trafficking of extracellular vesicles in microglia and astrocytes

Extracellular vesicles (EVs) have emerged as key players in cell-to-cell communication in both physiological and pathological processes in the Central Nervous System. Thus far, the intracellular pathways involved in uptake and trafficking of EVs within different cell types of the brain are poorly understood. In our study, the endocytic processes and subcellular sorting of EVs were investigated in primary glial cells, particularly linked with the EV-associated α-synuclein (α-syn) transmission. Mouse microglia and astrocytic primary cultures were incubated with DiI-stained mouse brain-derived EVs. The internalization and trafficking pathways were analyzed in cells treated with pharmacological reagents that block the major endocytic pathways. Brain-derived EVs were internalized by both glial cell types; however, uptake was more efficient in microglia than in astrocytes. Colocalization of EVs with early and late endocytic markers (Rab5, Lamp1) indicated that EVs are sorted to endo-lysosomes for subsequent processing. Blocking actin-dependent phagocytosis and/or macropinocytosis with Cytochalasin D or EIPA inhibited EV entry into glial cells, whereas treatment with inhibitors that strip cholesterol off the plasma membrane, induced uptake, however differentially altered endosomal sorting. EV-associated fibrillar α-Syn was efficiently internalized and detected in Rab5- and Lamp1-positive compartments within microglia. Our study strongly suggests that EVs enter glial cells through phagocytosis and/or macropinocytosis and are sorted to endo-lysosomes for subsequent processing. Further, brain-derived EVs serve as scavengers and mediate cell-to-glia transfer of pathological α-Syn which is also targeted to the endolysosomal pathway, suggesting a beneficial role in microglia-mediated clearance of toxic protein aggregates, present in numerous neurodegenerative diseases.

Peptide-functionalized zinc oxide nanoparticles for the selective targeting of breast cancer expressing placenta-specific protein 1

Functionalized metal oxide nanoparticles (NPs) have demonstrated specific binding affinity to antigens or receptors presented on the cancer cell surface, favouring selective targeting and minimizing side effects during the chemotherapy. Placenta-specific protein 1 (PLAC-1) is a small cell surface protein overexpressed in certain types of breast cancer (BC); therefore, it can be used as a therapeutic target. The objective of this study is to develop NPs that can bind PLAC-1 and hence can inhibit the progression and metastatic potential of BC cells. Zinc oxide (ZnO) NPs were coated with a peptide (GILGFVFTL), which possesses a strong binding ability to PLAC-1. The physical attachment of the peptide to ZnO NPs was verified through various physicochemical and morphological characterization techniques. The selective cytotoxicity of the designed NPs was investigated using PLAC-1-bearing MDA-MB 231 human BC cell line and compared to LS-180 cells that do not express PLAC-1. The anti-metastatic and pro-apoptotic effects of the functionalized NPs on MDA-MB 231 cells were examined. Confocal microscopy was used to investigate the mechanism of NPs uptake by MDA-MB 231 cells. Compared to non-functionalized NPs, peptide functionalization significantly improved the targeting and uptake of the designed NPs by PLAC-1-expressing cancer cells with significant pro-apoptotic and anti-metastatic effects. The uptake of peptide functionalized ZnO NPs (ZnO-P NPs) occurred via peptide-PLAC1 interaction-assisted clathrin-mediated endocytosis. These findings highlight the potential targeted therapy of ZnO-P NPs against PLAC-1-expressing breast cancer cells.

Mechanistic-Based Classification of Endocytosis-Related Inhibitors: Does It Aid in Assigning Drugs against SARS-CoV-2?

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) canonically utilizes clathrin-mediated endocytosis (CME) and several other endocytic mechanisms to invade airway epithelial cells. Endocytic inhibitors, particularly those targeting CME-related proteins, have been identified as promising antiviral drugs. Currently, these inhibitors are ambiguously classified as chemical, pharmaceutical, or natural inhibitors. However, their varying mechanisms may suggest a more realistic classification system. Herein, we present a new mechanistic-based classification of endocytosis inhibitors, in which they are segregated among four distinct classes including: (i) inhibitors that disrupt endocytosis-related protein-protein interactions, and assembly or dissociation of complexes; (ii) inhibitors of large dynamin GTPase and/or kinase/phosphatase activities associated with endocytosis; (iii) inhibitors that modulate the structure of subcellular components, especially the plasma membrane, and actin; and (iv) inhibitors that cause physiological or metabolic alterations in the endocytosis niche. Excluding antiviral drugs designed to halt SARS-CoV-2 replication, other drugs, either FDA-approved or suggested through basic research, could be systematically assigned to one of these classes. We observed that many anti-SARS-CoV-2 drugs could be included either in class III or IV as they interfere with the structural or physiological integrity of subcellular components, respectively. This perspective may contribute to our understanding of the relative efficacy of endocytosis-related inhibitors and support the optimization of their individual or combined antiviral potential against SARS-CoV-2. However, their selectivity, combined effects, and possible interactions with non-endocytic cellular targets need more clarification.

Tunable Nanoparticles with Aggregation-Induced Emission Heater for Precise Synergistic Photothermal and Thermodynamic Oral Cancer Therapy of Patient-Derived Tumor Xenograft

The fluorophores in the second near-infrared (NIR-II) biological window (1000 - 1700 nm) show great application prospects in the fields of biology and optical communications. However, both excellent radiative transition and nonradiative transition cannot be achieved simultaneously for the majority of traditional fluorophores. Herein, tunable nanoparticles formulated with aggregation-induced emission (AIE) heater are developed rationally. The system can be implemented via the development of an ideal synergistic system that can not only produce photothermal from nonspecific triggers but also trigger carbon radical release. Once accumulating in tumors and subsequently being irradiated with 808 nm laser, the nanoparticles (NMB@NPs) encapsulated with NMDPA-MT-BBTD (NMB) are splitted due to the photothermal effect of NMB, leading to the decomposition of azo bonds in the nanoparticle matrix to generate carbon radical. Accompanied by second near-infrared (NIR-II) window emission from the NMB, fluorescence image-guided thermodynamic therapy (TDT) and photothermal therapy (PTT) which significantly inhibited the growth of oral cancer and negligible systemic toxicity is achieved synergistically. Taken together, this AIE luminogens-based synergistic photothermal-thermodynamic strategy brings a new insight into the design of superior versatile fluorescent NPs for precise biomedical applications and holds great promise to enhance the therapeutic efficacy of cancer therapy.

Ligand-dependent intracellular trafficking of the G protein-coupled P2Y6 receptor

Endosomal trafficking is intricately linked to G protein-coupled receptors (GPCR) fate and signaling. Extracellular uridine diphosphate (UDP) acts as a signaling molecule by selectively activating the GPCR P2Y₆. Despite the recent interest for this receptor in pathologies, such as gastrointestinal and neurological diseases, there is sparse information on the endosomal trafficking of P2Y₆ receptors in response to its endogenous agonist UDP and synthetic selective agonist 5-iodo-UDP (MRS2693). Confocal microscopy and cell surface ELISA revealed delayed internalization kinetics in response to MRS2693 vs. UDP stimulation in AD293 and HCT116 cells expressing human P2Y₆. Interestingly, UDP induced clathrin-dependent P2Y₆ internalization, whereas receptor stimulation by MRS2693 endocytosis appeared to be associated with a caveolin-dependent mechanism. Internalized P2Y₆ was associated with Rab4, 5, and 7 positive vesicles independent of the agonist. We have measured a higher frequency of receptor expression co-occurrence with Rab11-vesicles, the trans-Golgi network, and lysosomes in response to MRS2693. Interestingly, a higher agonist concentration reversed the delayed P2Y₆ internalization and recycling kinetics in the presence of MRS2693 stimulation without changing its caveolin-dependent internalization. This work showed a ligand-dependent effect affecting the P2Y₆ receptor internalization and endosomal trafficking. These findings could guide the development of bias ligands that could influence P2Y₆ signaling.

Clathrin-mediated endocytosis facilitates the internalization of Magnaporthe oryzae effectors into rice cells

Fungi and oomycetes deliver effectors into living plant cells to suppress defenses and control plant processes needed for infection. Little is known about the mechanism by which these pathogens translocate effector proteins across the plasma membrane into the plant cytoplasm. The blast fungus Magnaporthe oryzae secretes cytoplasmic effectors into a specialized biotrophic interfacial complex (BIC) before translocation. Here we show that cytoplasmic effectors within BICs are packaged into punctate membranous effector compartments that are occasionally observed in the host cytoplasm. Live cell imaging with fluorescently labeled proteins in rice (Oryza sativa) showed that these effector puncta colocalize with the plant plasma membrane and with CLATHRIN LIGHT CHAIN 1, a component of clathrin-mediated endocytosis (CME). Inhibiting CME using virus-induced gene silencing and chemical treatments resulted in cytoplasmic effectors in swollen BICs lacking effector puncta. By contrast, fluorescent marker co-localization, gene silencing and chemical inhibitor studies failed to support a major role for clathrin-independent endocytosis in effector translocation. Effector localization patterns indicated that cytoplasmic effector translocation occurs underneath appressoria before invasive hyphal growth. Taken together, this study provides evidence that cytoplasmic effector translocation is mediated by clathrin-mediated endocytosis in BICs and suggests a role for M. oryzae effectors in co-opting plant endocytosis.

From Exosome Biogenesis to Absorption: Key Takeaways for Cancer Research

Exosomes are mediators of intercellular communication in normal physiology and diseases. While many studies have emerged on the function of exosomal cargoes, questions remain regarding the origin of these exosomes. The packaging and secretion of exosomes in different contexts modify exosomal composition, which may in turn impact delivery, uptake and cargo function in recipient cells. A mechanistic understanding of exosome biology is therefore crucial to investigating exosomal function in complex biological systems and to the development of novel therapeutic approaches. Here, we outline the steps in exosome biogenesis, including endosome formation, MVB formation, cargo sorting and extracellular release, as well as exosome absorption, including targeting, interaction with recipient cells and the fate of internalized exosomes. In addition to providing a framework of exosome dynamics, we summarize current evidence on major pathways and regulatory mechanisms. We also highlight the various mechanisms observed in cancer and point out directions to improve study design in exosome biology. Further research is needed to illuminate the relationship between exosome biogenesis and function, which will aid the development of translational applications.

In-Cell Penetration Selection-Mass Spectrometry Produces Noncanonical Peptides for Antisense Delivery

Peptide-mediated delivery of macromolecules in cells has significant potential therapeutic benefits, but no therapy employing cell-penetrating peptides (CPPs) has reached the market after 30 years of investigation due to challenges in the discovery of new, more efficient sequences. Here, we demonstrate a method for in-cell penetration selection-mass spectrometry (in-cell PS-MS) to discover peptides from a synthetic library capable of delivering macromolecule cargo to the cytosol. This method was inspired by recent in vivo selection approaches for cell-surface screening, with an added spatial dimension resulting from subcellular fractionation. A representative peptide discovered in the cytosolic extract, Cyto1a, is nearly 100-fold more active toward antisense phosphorodiamidate morpholino oligomer (PMO) delivery compared to a sequence identified from a whole cell extract, which includes endosomes. Cyto1a is composed of d-residues and two non-α-amino acids, is more stable than its all-l isoform, and is less toxic than known CPPs with comparable activity. Pulse-chase and microscopy experiments revealed that while the PMO-Cyto1a conjugate is likely taken up by endosomes, it can escape to localize to the nucleus without nonspecifically releasing other endosomal components. In-cell PS-MS introduces a means to empirically discover unnatural synthetic peptides for subcellular delivery of therapeutically relevant cargo.

The steep road to nonviral nanomedicines: Frequent challenges and culprits in designing nanoparticles for gene therapy

The potential of therapeutically loaded nanoparticles (NPs) has been successfully demonstrated during the last decade, with NP-mediated nonviral gene delivery gathering significant attention as highlighted by the broad clinical acceptance of mRNA-based COVID-19 vaccines. A significant barrier to progress in this emerging area is the wild variability of approaches reported in published literature regarding nanoparticle characterizations. Here, we provide a brief overview of the current status and outline important concerns regarding the need for standardized protocols to evaluate NP uptake, NP transfection efficacy, drug dose determination, and variability of nonviral gene delivery systems. Based on these concerns, we propose wide adherence to multimodal, multiparameter, and multistudy analysis of NP systems. Adoption of these proposed approaches will ensure improved transparency, provide a better basis for interlaboratory comparisons, and will simplify judging the significance of new findings in a broader context, all critical requirements for advancing the field of nonviral gene delivery.

Cell Uptake of Steroid-BODIPY Conjugates and Their Internalization Mechanisms: Cancer Theranostic Dyes

Estradiol-BODIPY linked via an 8-carbon spacer chain and 19-nortestosterone- and testosterone-BODIPY linked via an ethynyl spacer group were evaluated for cell uptake in the breast cancer cell lines MCF-7 and MDA-MB-231 and prostate cancer cell lines PC-3 and LNCaP, as well as in normal dermal fibroblasts, using fluorescence microscopy. The highest level of internalization was observed with 11β-OMe-estradiol-BODIPY 2 and 7α-Me-19-nortestosterone-BODIPY 4 towards cells expressing their specific receptors. Blocking experiments showed changes in non-specific cell uptake in the cancer and normal cells, which likely reflect differences in the lipophilicity of the conjugates. The internalization of the conjugates was shown to be an energy-dependent process that is likely mediated by clathrin- and caveolae-endocytosis. Studies using 2D co-cultures of cancer cells and normal fibroblasts showed that the conjugates are more selective towards cancer cells. Cell viability assays showed that the conjugates are non-toxic for cancer and/or normal cells. Visible light irradiation of cells incubated with estradiol-BODIPYs 1 and 2 and 7α-Me-19-nortestosterone-BODIPY 4 induced cell death, suggesting their potential for use as PDT agents.

Biological mechanism of cell oxidative stress and death during short-term exposure to nano CuO

It is well known that copper oxide nanoparticles (CuO NPs) are heavily toxic on in vitro systems. In human alveolar epithelial cells, the mechanism of toxicity is mostly related to oxidative insults, coming from intracellularly dissolved copper ions, finally leading to apoptotic or autophagic cell death. Our hypothesis is based on possible early oxidative events coming from specific NP surface reactivity able to undermine the cell integrity and to drive cell to death, independently from Lysosomal-Enhanced Trojan Horse mechanism. Two types of CuO NPs, with different oxidative potential, were selected and tested on A549 cells for 1 h and 3 h at 10, 25, 50 and 100 µg/ml. Cells were then analyzed for viability and oxidative change of the proteome. Oxidative by-products were localized by immunocytochemistry and cell-NP interactions characterized by confocal and electron microscopy techniques. The results show that CuO NPs induced oxidative changes soon after 1 h exposure as revealed by the increase in protein carbonylation and reduced-protein-thiol oxidation. In parallel, cell viability significantly decreased, as shown by MTT assay. Such effects were higher for CuO NPs with more crystalline defects and with higher ROS production than for fully crystalline NPs. At these exposure times, although NPs efficiently interacted with cell surface and were taken up by small endocytic vesicles, no ion dissolution was visible inside the lysosomal compartment and no effects were produced by extracellularly dissolved copper ions. In conclusion, a specific NP surface-dependent oxidative cell injury was demonstrated. More detailed studies are required to understand which targets precociously react with CuO NPs, but these results introduce new paradigms for the toxicity of the metal-based NPs, beyond the Lysosomal-Enhanced Trojan horse-related mechanism, and open-up new opportunities to investigate the interactions and effects at the bio-interface for designing safer as well as more effective CuO-based biocides.

Endocytosis and signaling of angiotensin II type 1 receptor

A vasoactive octapeptide angiotensin II (Ang II) hormone is the key regulator of the renin-angiotensin system (RAS). It binds with the two different plasma membrane receptors like angiotensin II type 1 (AT1) and type 2 (AT2) and consequence various biological responses occur. Further, AT1 has two subtypes such as AT1A and AT1B. These angiotensin receptors are classified to be G protein-coupled receptors (GPCRs). The main constituent of RAS is the AT1 receptor (AT1R), and its activation, signal transduction, and regulation have been extensively studied. After Ang II stimulation, the ligand-receptor complexes internalized and trafficked through the early endosome, recycling endosome, and some receptors skipped the recycling endosome and trafficked to the lysosome for metabolic degradation. Moreover, some short sequence motifs located in the carboxyl-terminus (CT) of the receptor play a vital role in the internalization, phosphorylation, subcellular trafficking, signaling, and desensitization. Furthermore, in endocytosis, the various proteins interact with the CT region of the receptor. This chapter highlights the basic mechanism of AT1 receptor internalization, trafficking and signaling in both physiological and pathophysiological conditions.

Insight into the role of clathrin-mediated endocytosis inhibitors in SARS-CoV-2 infection

Emergence of SARS-CoV-2 variants warrants sustainable efforts to upgrade both the diagnostic and therapeutic protocols. Understanding the details of cellular and molecular basis of the virus-host cell interaction is essential for developing variant-independent therapeutic options. The internalization of SARS-CoV-2, into lung epithelial cells, is mediated by endocytosis, especially clathrin-mediated endocytosis (CME). Although vaccination is the gold standard strategy against viral infection, selective inhibition of endocytic proteins, complexes, and associated adaptor proteins may present a variant-independent therapeutic strategy. Although clathrin and/or dynamins are the most important proteins involved in CME, other endocytic mechanisms are clathrin and/or dynamin independent and rely on other proteins. Moreover, endocytosis implicates some subcellular structures, like plasma membrane, actin and lysosomes. Also, physiological conditions, such as pH and ion concentrations, represent an additional factor that mediates these events. Accordingly, endocytosis related proteins are potential targets for small molecules that inhibit endocytosis-mediated viral entry. This review summarizes the potential of using small molecules, targeting key proteins, participating in clathrin-dependent and -independent endocytosis, as variant-independent antiviral drugs against SARS-CoV-2 infection. The review takes two approaches. The first outlines the potential role of endocytic inhibitors in preventing endocytosis-mediated viral entry and its mechanism of action, whereas in the second computational analysis was implemented to investigate the selectivity of common inhibitors against endocytic proteins in SARS-CoV-2 endocytosis. The analysis revealed that remdesivir, methyl-β-cyclodextrin, rottlerin, and Bis-T can effectively inhibit clathrin, HMG-CoA reductase, actin, and dynamin I GTPase and are more potent in inhibiting SARS-CoV-2 than chloroquine. CME inhibitors for SARS-CoV-2 infection remain understudied.

The Strange Case: The Unsymmetric Cisplatin-Based Pt(IV) Prodrug [Pt(CH3COO)Cl2(NH3)2(OH)] Exhibits Higher Cytotoxic Activity with respect to Its Symmetric Congeners due to Carrier-Mediated Cellular Uptake

The biological behavior of the axially unsymmetric antitumor prodrug (OC-6-44)-acetatodiamminedichloridohydroxidoplatinum(IV), 2, was deeply investigated and compared with that of analogous symmetric Pt(IV) complexes, namely, dihydroxido 1 and diacetato 3, which have a similar structure. The complexes were tested on a panel of human tumor cell lines. Complex 2 showed an anomalous higher cytotoxicity (similar to that of cisplatin) with respect to their analogues 1 and 3. Their reduction potentials, reduction kinetics, lipophilicity, and membrane affinity are compared. Cellular uptake and DNA platination of Pt(IV) complexes were deeply investigated in the sensitive A2780 human ovarian cancer cell line and in the corresponding resistant A2780cisR subline. The unexpected activity of 2 appears to be related to its peculiar cellular accumulation and not to a different rate of reduction or a different efficacy in DNA platination and/or efficiency in apoptosis induction. Although the exact mechanism of cell uptake is not fully deciphered, a series of naïve experiments indicates an energy-dependent, carrier-mediated transport: the organic cation transporters (OCTs) are the likely proteins involved.

Superparamagnetic Iron Oxide Nanoparticles and Curcumin Equally Promote Neuronal Branching Morphogenesis in the Absence of Nerve Growth Factor in PC12 Cells

Regeneration of the damaged neurons in neurological disorders and returning their activities are two of the main purposes of neuromedicine. Combination use of specific nanoformulations with a therapeutic compound could be a good candidate for neuroregeneration applications. Accordingly, this research aims to utilize the combination of curcumin, as a neurogenesis agent, with dextran-coated superparamagnetic iron oxide nanoparticles (SPIONs) to evaluate their effects on PC12 cellsʹ neuronal branching morphogenesis in the absence of nerve growth factor. Therefore, the effects of each component alone and in combination form on the cytotoxicity, neurogenesis, and neural branching morphogenesis were evaluated using MTT assay, immunofluorescence staining, and inverted microscopy, respectively. Results confirmed the effectiveness of the biocompatible iron oxide nanoparticles (with a size of about 100 nm) in improving the percentage of neural branching (p < 0.01) in PC12 cells. In addition, the combination use of these nanoparticles with curcumin could enhance the effect of curcumin on neurogenesis (p < 0.01). These results suggest that SPIONs in combination with curcumin could act as an inducing factor on PC12 neurogenesis in the absence of nerve growth factor and could offer a novel therapeutic approach to the treatment of neurodegenerative diseases.

Dissecting exosome inhibitors: therapeutic insights into small-molecule chemicals against cancer

Intensive research in the field of cancer biology has revealed unique methods of communication between cells through extracellular vesicles called exosomes. Exosomes are released from a broad spectrum of cell types and serve as functional mediators under physiological or pathological conditions. Hence, blocking the release of exosome bio carriers may prove useful for slowing the progression of certain types of cancers. Therefore, efforts are being made to develop exosome inhibitors to be used both as research tools and as therapies in clinical trials. Thus, studies on exosomes may lead to a breakthrough in cancer research, for which new clinical targets for different types of cancers are urgently needed. In this review, we briefly outline exosome inhibitors and discuss their modes of action and potential for use as therapeutic tools for cancer.

Endocytosis of insulin at the blood-brain barrier

For insulin to act within the brain, it is primarily transported from the blood across the blood-brain barrier (BBB). However, the endocytic machinery necessary for delivering insulin to the brain remains unknown. Additionally, there are processes within the brain endothelial cell that are designed to respond to insulin binding and elicit intracellular signaling. Using pharmacological inhibitors of different types of endocytosis (clathrin-vs. caveolin-mediated), we investigated molecular mediators of both insulin BBB binding in isolated mouse brain microvessels and BBB insulin transport in mice studied by brain perfusion. We found clathrin-mediated mechanisms responsible for insulin surface binding in isolated brain microvessels while caveolin-mediated endocytosis may mediate BBB insulin transport specifically in the hypothalamus. These results further define the molecular machinery necessary for transporting insulin into the CNS and highlight the distinction between insulin internalization for transendothelial transport vs. intracellular signaling.

Approaches for evaluation of novel CPP-based cargo delivery systems

Cell penetrating peptides (CPPs) can be broadly defined as relatively short synthetic, protein derived or chimeric peptides. Their most remarkable property is their ability to cross cell barriers and facilitate the translocation of cargo, such as drugs, nucleic acids, peptides, small molecules, dyes, and many others across the plasma membrane. Over the years there have been several approaches used, adapted, and developed for the evaluation of CPP efficacies as delivery systems, with the fluorophore attachment as the most widely used approach. It has become progressively evident, that the evaluation method, in order to lead to successful outcome, should concede with the specialties of the delivery. For characterization and assessment of CPP-cargo a combination of research tools of chemistry, physics, molecular biology, engineering, and other fields have been applied. In this review, we summarize the diverse, in silico, in vitro and in vivo approaches used for evaluation and characterization of CPP-based cargo delivery systems.

Liposomes Loaded with Amaranth Unsaponifiable Matter and Soybean Lunasin Prevented Melanoma Tumor Development Overexpressing Caspase-3 in an In Vivo Model

The objective of this study was to assess the effectiveness of liposomes loaded with soybean lunasin and amaranth unsaponifiable matter (UM + LunLip) as a source of squalene in the prevention of melanoma skin cancer in an allograft mice model. Tumors were induced by transplanting melanoma B16-F10 cells into the mice. The most effective treatments were those including UM + LunLip, with no difference between the lunasin concentrations (15 or 30 mg/kg body weight); however, these treatments were statistically different from the tumor-bearing untreated control (G3) (p < 0.05). The groups treated with topical application showed significant inhibition (68%, p < 0.05) compared to G3. The groups treated with subcutaneous injections showed significant inhibition (up to 99%, p < 0.05) in G3. During tumor development, UM + LunLip treatments under-expressed Ki-67 (0.2-fold compared to G3), glycogen synthase kinase-3β (0.1-fold compared to G3), and overexpressed caspase-3 (30-fold compared to G3). In addition, larger tumors showed larger necrotic areas (38% with respect to the total tumor) (p < 0.0001). In conclusion, the UM + LunLip treatment was effective when applied either subcutaneously or topically in the melanoma tumor-developing groups, as it slowed down cell proliferation and activated apoptosis.

Phosphoinositide species and filamentous actin formation mediate engulfment by senescent tumor cells

Cancer cells survive chemotherapy and cause lethal relapse by entering a senescent state that facilitates expression of many phagocytosis/macrophage-related genes that engender a novel cannibalism phenotype. We used biosensors and live-cell imaging to reveal the basic steps and mechanisms of engulfment by senescent human and mouse tumor cells. We show filamentous actin in predator cells was localized to the prey cell throughout the process of engulfment. Biosensors to various phosphoinositide (PI) species revealed increased concentration and distinct localization of predator PI(4) P and PI(4,5)P2 at the prey cell during early stages of engulfment, followed by a transient burst of PI(3) P before and following internalization. PIK3C2B, the kinase responsible for generating PI(3)P, was required for complete engulfment. Inhibition or knockdown of Clathrin, known to associate with PIK3C2B and PI(4,5)P2, severely impaired engulfment. In sum, our data reveal the most fundamental cellular processes of senescent cell engulfment, including the precise localizations and dynamics of actin and PI species throughout the entire process.

Cell cycle-dependent endocytosis of DNA-wrapped single-walled carbon nanotubes by neural progenitor cells

While exposure of C17.2 neural progenitor cells (NPCs) to nanomolar concentrations of carbon nanotubes (NTs) yields evidence of cellular substructure reorganization and alteration of cell division and differentiation, the mechanisms of NT entry are not understood. This study examines the entry modes of (GT)₂₀ DNA-wrapped single-walled carbon nanotubes (SWCNTs) into NPCs. Several endocytic mechanisms were examined for responsibility in nanomaterial uptake and connections to alterations in cell development via cell-cycle regulation. Chemical cell-cycle arrest agents were used to synchronize NPCs in early G₁, late G₁/S, and G₂/M phases at rates (>80%) aligned with previously documented levels of synchrony for stem cells. Synchronization led to the highest reduction in SWCNT internalization during the G₁/S transition of the cell cycle. Concurrently, known inhibitors of endocytosis were used to gain control over established endocytic machineries (receptor-mediated endocytosis (RME), macropinocytosis (MP), and clathrin-independent endocytosis (CIE)), which resulted in a decrease in uptake of SWCNTs across the board in comparison with the control. The outcome implicated RME as the primary mechanism of uptake while suggesting that other endocytic mechanisms, though still fractionally responsible, are not central to SWCNT uptake and can be supplemented by RME when compromised. Thereby, endocytosis of nanomaterials was shown to have a dependency on cell-cycle progression in NPCs.