Efficient antiglioblastoma therapy in mice through doxorubicin-loaded nanomicelles modified using a novel brain-targeted RVG-15 peptide

Exosomes for neurodegenerative diseases: diagnosis and targeted therapy

PURPOSE OF REVIEW

Neurodegenerative diseases are still challenging clinical issues, with no curative interventions available and early, accurate diagnosis remaining difficult. Finding solutions to them is of great importance. In this review, we discuss possible exosomal diagnostic biomarkers and explore current explorations in exosome-targeted therapy for some common neurodegenerative diseases, offering insights into the clinical transformation of exosomes in this field.

RECENT FINDINGS

The burgeoning research on exosomes has shed light on their potential applications in disease diagnosis and treatment. As a type of extracellular vesicles, exosomes are capable of crossing the blood - brain barrier and exist in various body fluids, whose components can reflect pathophysiological changes in the brain. In addition, they can deliver specific drugs to brain tissue, and even possess certain therapeutic effects themselves. And the recent advancements in engineering modification technology have further enabled exosomes to selectively target specific sites, facilitating the possibility of targeted therapy for neurodegenerative diseases. The unique properties of exosomes give them great potential in the diagnosis and treatment of neurodegenerative diseases, and provide novel ideas for dealing with such diseases.

Optimized lipopolymers with curcumin to enhance AZD5582 and GDC0152 activity and downregulate inhibitors of apoptosis proteins in glioblastoma multiforme

Inhibition to glioblastoma multiforme (GBM) propagation is a critical challenge in clinical practice because binding of inhibitors of apoptosis proteins (IAPs) to caspase prevents cancer cells from death. In this study, folic acid (FA), lactoferrin (Lf) and rabies virus glycoprotein (RVG) were grafted on lipopolymers (LPs) composed of poly(ε-caprolactone) and Compritol 888 ATO to encapsulate AZD5582 (AZD), GDC0152 (GDC) and curcumin (CURC). The standard deviations of initial particle diameter and particle diameter after storage for 30 days were involved in LP composition optimization. The functionalized LPs were used to permeate the blood-brain barrier (BBB) and constrain IAP quantity in GBM cells. Experimental results revealed that an increase in Span 20 (emulsifier) concentration enlarged the size of LPs, and enhanced the entrapment and releasing efficiency of AZD, DGC and CURC. 1H nuclear magnetic resonance spectra showed that the hydrogen bonds between the LPs and drugs supported the sustained release of AZD, DGC and CURC from the LPs. The LPs modified with the three targeting biomolecules facilitated the penetration of AZD, GDC and CURC across the BBB, and could recognize U87MG cells and human brain cancer stem cells. Immunofluorescence staining, flow cytometry and western blot demonstrated that CURC-incorporated LPs enhanced AZD and GDC activity in suppressing cellular IAP 1 (cIAP1) and X-linked IAP (XIAP) levels, and raising caspase-3 level in GBM. Surface FA, Lf and RVG also promoted the ability of the drug-loaded LPs to avoid carcinoma growth. The current FA-, Lf- and RVG-crosslinked LPs carrying AZD, DGC and CURC can be promising in hindering IAP expressions for GBM management.

BBB opening by low pulsed electric fields, depicted by delayed-contrast MRI, enables efficient delivery of therapeutic doxorubicin doses into mice brains

BACKGROUND

Pharmacological treatment of CNS diseases is limited due to the presence of the blood-brain barrier (BBB). Recent years showed significant advancement in the field of CNS drug delivery enablers, with technologies such as MR-guided focused ultrasound reaching clinical trials. This have inspired researchers in the field to invent novel brain barriers opening (BBo) technologies that are required to be simple, fast, safe and efficient. One such technology, recently developed by us, is BDF (Barrier Disrupting Fields), based on low pulsed electric fields (L-PEFs) for opening the BBB in a controlled, safe, reversible and non-invasive manner. Here, we conducted an in vivo study to show that BDF is a feasible technology for delivering Doxorubicin (Doxo) into mice brain. Means for depicting BBBo levels were developed and applied for monitoring the treatment and predicting response. Overall, the goals of the presented study were to demonstrate the feasibility for delivering therapeutic Doxo doses into naïve and tumor-bearing mice brains and applying delayed-contrast MRI (DCM) for monitoring the levels of BBBo.

METHODS

L-PEFs were applied using plate electrodes placed on the intact skull of naïve mice. L-PEFs/Sham mice were scanned immediately after the procedure by DCM ("MRI experiment"), or injected with Doxo and Trypan blue followed by delayed (4 h) perfusion and brain extraction ("Doxo experiment"). Doxo concentrations were measured in brain samples using confocal microscopy and compared to IC50 of Doxo in glioma cell lines in vitro. In order to map BBBo extent throughout the brain, pixel by pixel MR image analysis was performed using the DCM data. Finally, the efficacy of L-PEFs in combination with Doxo was tested in nude mice bearing intracranial human glioma tumors.

RESULTS

Significant amount of Doxo was found in cortical regions of all L-PEFs-treated mice brains (0.50 ± 0.06 µg Doxo/gr brain) while in Sham brains, Doxo concentrations were below or on the verge of detection limit (0.03 ± 0.02 µg Doxo/gr brain). This concentration was x97 higher than IC50 of Doxo calculated in gl261 mouse glioma cells and x8 higher than IC50 of Doxo calculated in U87 human glioma cells. DCM analysis revealed significant BBBo levels in the cortical regions of L-PEFs-treated mice; the average volume of BBBo in the L-PEFs-treated mice was x29 higher than in the Sham group. The calculated BBBo levels dropped exponentially as a function of BBBo threshold, similarly to the electric fields distribution in the brain. Finally, combining non-invasive L-PEFs with Doxo significantly decreased brain tumors growth rates in nude mice.

CONCLUSIONS

Our results demonstrate significant BBBo levels induced by extra-cranial L-PEFs, enabling efficient delivery of therapeutic Doxo doses into the brain and reducing tumor growth. As BBBo was undetectable by standard contrast-enhanced MRI, DCM was applied to generate maps depicting the BBBo levels throughout the brain. These findings suggest that BDF is a promising technology for efficient drug delivery into the brain with important implications for future treatment of brain cancer and additional CNS diseases.

Ultra-small micelles together with UTMD enhanced the therapeutic effect of docetaxel on Glioblastoma

Owing to the difficult-to-penetrate blood-brain barrier (BBB), glioblastoma (GBM) doesn't respond well to the current chemical therapeutics. In this study, ultra-small micelles (NMs) self-assembled by RRR-a-tocopheryl succinate-grafted-ε-polylysine conjugate (VES-g-ε-PLL) as the delivery vehicle of chemical therapeutics in conjunction with ultrasound-targeted microbubble destruction (UTMD) to surmount BBB and treat GBM. Docetaxel (DTX) as a hydrophobic model drug was incorporated into NMs. DTX-loaded micelles (DTX-NMs) with 3.08% of drug loading exhibited a hydrodynamic diameter (33.2 nm) and positive Zeta potential (16.9 mV), having a remarkable tumor-permeating capacity. Furthermore, DTX-NMs presented good stability in physiologic condition. The sustained-release release profile of DTX-NMs was also displayed by dynamic dialysis. Treatment of DTX-NMs together with UTMD led to more pronounced apoptosis of C6 tumor cells than DTX-NMs alone. Moreover, compared with the DTX solution or DTX-NMs alone, the combination of DTX-NMs with UTMD had a stronger inhibitory effect on tumor growth for GBM-bearing rats. The median survival period of GBM-bearing rats was extended to 75 days in the DTX-NMs+UTMD group from under 25 days in the control group. The invasive growth of glioblastoma was largely inhibited by the combination of DTX-NMs with UTMD, which was demonstrated by staining of Ki67, caspase-3, and CD31, together with TUNEL assay. In conclusion, the combination of ultra-small micelles (NMs) with UTMD may be a promising strategy to overcome the limitations of the first-line chemotherapeutics against GBM.

Recent Advances on Surface-Modified GBM Targeted Nanoparticles: Targeting Strategies and Surface Characterization

Glioblastoma multiforme (GBM) is the most common malignant brain tumor, associated with low long-term survival. Nanoparticles (NPs) developed against GBM are a promising strategy to improve current therapies, by enhancing the brain delivery of active molecules and reducing off-target effects. In particular, NPs hold high potential for the targeted delivery of chemotherapeutics both across the blood-brain barrier (BBB) and specifically to GBM cell receptors, pathways, or the tumor microenvironment (TME). In this review, the most recent strategies to deliver drugs to GBM are explored. The main focus is on how surface functionalizations are essential for BBB crossing and for tumor specific targeting. We give a critical analysis of the various ligand-based approaches that have been used to target specific cancer cell receptors and the TME, or to interfere with the signaling pathways of GBM. Despite the increasing application of NPs in the clinical setting, new methods for ligand and surface characterization are needed to optimize the synthesis, as well as to predict their in vivo behavior. An expert opinion is given on the future of this research and what is still missing to create and characterize a functional NP system for improved GBM targeting.

Anti-cancer Virotherapy in Russia: Lessons from the Past, Current Challenges and Prospects for the Future

The idea of using the lytic power of viruses against malignant cells has been entertained for many decades. However, oncolytic viruses gained broad attention as an emerging anti-cancer therapy only recently with the successful implementation of several oncolytic viruses to treat advanced melanoma. Here we review the history of oncolytic viruses in the Russian Federation and recent biotechnological advances in connection with the perspectives of their practical use against aggressive tumors such as glioblastoma or pancreatic cancer. A particular emphasis is made on novel applications of safe non-lytic virus-derived vectors armed with prodrug-converting enzyme transgenes. Rational improvement of oncotropism by conjugation with biopolymers and nanoformulations is also discussed.

Exosomes as CNS Drug Delivery Tools and Their Applications

Central nervous system (CNS) diseases threaten the health of people all over the world. However, due to the structural and functional particularities of the brain and spinal cord, CNS-targeted drug development is rather challenging. Exosomes are small cellular vesicles with lipid bilayers that can be secreted by almost all cells and play important roles in intercellular communication. The advantages of low immunogenicity, the ability to cross the blood-brain barrier, and the flexibility of drug encapsulation make them stand out among CNS drug delivery tools. Herein, we reviewed the research on exosomes in CNS drug delivery over the past decade and outlined the impact of the drug loading mode, administration route, and engineered modification on CNS targeting. Finally, we highlighted the problems and prospects of exosomes as CNS drug delivery tools.

Peptides as Pharmacological Carriers to the Brain: Promises, Shortcomings and Challenges

Central nervous system (CNS) diseases are among the most difficult to treat, mainly because the vast majority of the drugs fail to cross the blood-brain barrier (BBB) or to reach the brain at concentrations adequate to exert a pharmacological activity. The obstacle posed by the BBB has led to the in-depth study of strategies allowing the brain delivery of CNS-active drugs. Among the most promising strategies is the use of peptides addressed to the BBB. Peptides are versatile molecules that can be used to decorate nanoparticles or can be conjugated to drugs, with either a stable link or as pro-drugs. They have been used to deliver to the brain both small molecules and proteins, with applications in diverse therapeutic areas such as brain cancers, neurodegenerative diseases and imaging. Peptides can be generally classified as receptor-targeted, recognizing membrane proteins expressed by the BBB microvessels (e.g., Angiopep2, CDX, and iRGD), "cell-penetrating peptides" (CPPs; e.g. TAT_47-57, SynB1/3, and Penetratin), undergoing transcytosis through unspecific mechanisms, or those exploiting a mixed approach. The advantages of peptides have been extensively pointed out, but so far few studies have focused on the potential negative aspects. Indeed, despite having a generally good safety profile, some peptide conjugates may display toxicological characteristics distinct from those of the peptide itself, causing for instance antigenicity, cardiovascular alterations or hemolysis. Other shortcomings are the often brief lifetime in vivo, caused by the presence of peptidases, the vulnerability to endosomal/lysosomal degradation, and the frequently still insufficient attainable increase of brain drug levels, which remain below the therapeutically useful concentrations. The aim of this review is to analyze not only the successful and promising aspects of the use of peptides in brain targeting but also the problems posed by this strategy for drug delivery.

Design of an L-Valine-Modified Nanomicelle-Based Drug Delivery System for Overcoming Ocular Surface Barriers

The incidence of ocular surface disease (OSD) is increasing, with a trend towards younger ages. However, it is difficult for drugs to reach the deep layers of the cornea due to ocular surface barriers, and bioavailability is less than 5%. In this study, DSPE-PEG2000 was modified with L-valine (L-Val), and an HS15/DSPE-PEG2000-L-Val nanomicelle delivery system containing baicalin (BC) (BC@HS15/DSPE-PEG2000-L-Val) was constructed using thin-film hydration, with a high encapsulation rate, small particle size and no irritation to the ocular surface. Retention experiments on the ocular surface of rabbits and an in vivo corneal permeation test showed that, compared with the control, nanomicelles not only prolonged retention time but also enhanced the ability to deliver drugs to the deep layers of the cornea. The results of a protein inhibition and protein expression assay showed that nanomicelles could increase uptake in human corneal epithelial cells (HCEC) through energy-dependent endocytosis mediated by clathrin, caveolin and the carrier pathway mediated by PepT1 by inhibiting the overexpression of claudin-1 and ZO-1 and suppressing the expression of PepT1-induced by drug stimulation. These results indicate that BC@HS15/DSPE-PEG2000-L-Val is suitable for drug delivery to the deep layers of the ocular surface, providing a potential approach for the development of ocular drug delivery systems.

Efficient Anti-Glioma Therapy Through the Brain-Targeted RVG15-Modified Liposomes Loading Paclitaxel-Cholesterol Complex

Background

Glioma is the most common primary malignant brain tumor with a dreadful overall survival and high mortality. One of the most difficult challenges in clinical treatment is that most drugs hardly pass through the blood–brain barrier (BBB) and achieve efficient accumulation at tumor sites. Thus, to circumvent this hurdle, developing an effectively traversing BBB drug delivery nanovehicle is of significant clinical importance. Rabies virus glycoprotein (RVG) is a derivative peptide that can specifically bind to nicotinic acetylcholine receptor (nAChR) widely overexpressed on BBB and glioma cells for the invasion of rabies virus into the brain. Inspired by this, RVG has been demonstrated to potentiate drugs across the BBB, promote the permeability, and further enhance drug tumor-specific selectivity and penetration.

Methods

Here, we used the RVG15, rescreened from the well-known RVG29, to develop a brain-targeted liposome (RVG15-Lipo) for enhanced BBB permeability and tumor-specific delivery of paclitaxel (PTX). The paclitaxel-cholesterol complex (PTX-CHO) was prepared and then actively loaded into liposomes to acquire high entrapment efficiency (EE) and fine stability. Meanwhile, physicochemical properties, in vitro and in vivo delivery efficiency and therapeutic effect were investigated thoroughly.

Results

The particle size and zeta potential of PTX-CHO-RVG15-Lipo were 128.15 ± 1.63 nm and −15.55 ± 0.78 mV, respectively. Compared with free PTX, PTX-CHO-RVG15-Lipo exhibited excellent targeting efficiency and safety in HBMEC and C6 cells, and better transport efficiency across the BBB in vitro model. Furthermore, PTX-CHO-RVG15-Lipo could noticeably improve the accumulation of PTX in the brain, and then promote the chemotherapeutic drugs penetration in C6^luc orthotopic glioma based on in vivo imaging assays. The in vivo antitumor results indicated that PTX-CHO-RVG15-Lipo significantly inhibited glioma growth and metabasis, therefore improved survival rate of tumor-bearing mice with little adverse effect.

Conclusion

Our study demonstrated that the RVG15 was a promising brain-targeted specific ligands owing to the superior BBB penetration and tumor targeting ability. Based on the outstanding therapeutic effect both in vitro and in vivo, PTX-CHO-RVG15-Lipo was proved to be a potential delivery system for PTX to treat glioma in clinic.