Crossing the Blood-Brain Barrier: Recent Advances in Drug Delivery to the Brain

Imaging epileptic foci in mouse models via a low-density lipoprotein receptor-related protein-1 targeting strategy

Background

In the setting of drug-resistant epilepsy (DRE), the success of surgery depends on the ability to accurately locate the epileptic foci to be resected or disconnected. However, the epileptic foci in a considerable percentage of the DRE patients cannot be adequately localised. This warrants the need for a reliable imaging strategy to identify the “concealed” epileptic regions.

Methods

Brain specimens from DRE patients and kainate-induced epileptic mouse models were immuno-stained to evaluate the integrity of the blood-brain barrier (BBB). The expression of low-density lipoprotein receptor-related protein-1 (LRP1) in the epileptic region of DRE patients and kainate models was studied by immunofluorescence. A micellar-based LRP1-targeted paramagnetic probe (Gd³⁺-LP) was developed and its ability to define the epileptic foci was investigated by magnetic resonance imaging (MRI).

Findings

The integrity of the BBB in the epileptic region of DRE patients and kainate mouse models were demonstrated. LRP1 expression levels in the epileptic foci of DRE patients and kainate models were 1.70–2.38 and 2.32–3.97 folds higher than in the control brain tissues, respectively. In vivo MRI demonstrated that Gd³⁺-LP offered 1.68 times higher (P < 0.05) T1-weighted intensity enhancement in the ipsilateral hippocampus of chronic kainite models than the control probe without LRP1 specificity.

Interpretation

The expression of LRP1 is up-regulated in vascular endothelium, activated glia in both DRE patients and kainate models. LRP1-targeted imaging strategy may provide an alternative strategy to define the “concealed” epileptic foci by overcoming the intact BBB.

Funding

This work was supported by the National Natural Science Foundation, Shanghai Science and Technology Committee, Shanghai Municipal Science and Technology, Shanghai Municipal Health and Family Planning Commission and the National Postdoctoral Program for Innovative Talents.

Brain and Nasal Cavity Anatomy of the Cynomolgus Monkey: Species Differences from the Viewpoint of Direct Delivery from the Nose to the Brain

Based on structural data on the nasal cavity and brain of the cynomolgus monkey, species differences in the olfactory bulb and cribriform plate were discussed from the viewpoint of direct delivery from the nose to the brain. Structural 3D data on the cynomolgus monkey skull were obtained using X-ray computed tomography. The dimensions of the nasal cavity of the cynomolgus monkey were 5 mm width × 20 mm height × 60 mm depth. The nasal cavity was very narrow and the olfactory region was far from the nostrils, similar to rats and humans. The weight and size of the monkey brain were 70 g and 55 mm width × 40 mm height × 70 mm depth. The olfactory bulb of monkeys is plate-like, while that of humans and rats is bulbar, suggesting that the olfactory area connected with the brain of monkeys is narrow. Although the structure of the monkey nasal cavity is similar to that of humans, the size and shape of the olfactory bulb are different, which is likely to result in low estimation of direct delivery from the nose to the brain in monkeys.

Ethanolamine: A Potential Promoiety with Additional Effects in the Brain

Ethanolamine is a bioactive molecule found in several cells, including those in the central nervous system (CNS). In the brain, ethanolamine and ethanolamine-related molecules have emerged as prodrug moieties that can promote drug movement across the blood-brain barrier. This improvement in the ability to target drugs to the brain may also mean that in the process ethanolamine concentrations in the brain are increased enough for ethanolamine to exert its own neurological ac-tions. Ethanolamine and its associated products have various positive functions ranging from cell signaling to molecular storage, and alterations in their levels have been linked to neurodegenerative conditions such as Alzheimer's disease. This mini-review focuses on the effects of ethanolamine in the CNS and highlights the possible implications of these effects for drug design.

Incorporation of docosahexaenoic acid (DHA) enhances nanodelivery of antiretroviral across the blood-brain barrier for treatment of HIV reservoir in brain

Although the newer antiretroviral (ARV) drugs are highly active against the human immunodeficiency virus (HIV) in the body compartment, they often fail to effectively tackle the HIV reservoir in the brain because of inefficient penetration to the blood-brain barrier (BBB). In this study, we investigated the potential benefits of incorporating docosahexaenoic acid (DHA), an omega-3 fatty acid essential for brain development, in lipid nanocarriers for facilitating the BBB passage of an ARV darunavir. The resulting nanocarriers (nanoARVs) containing 5-15% DHA were 90-140 nm in size, had high darunavir payload (~11-13% w/w), good stability and minimal cellular toxicity, and could be further decorated with transferrin (Tf) for Tf-receptor targeting. In BBB models of hCMEC/d3 cells, nanoARVs with higher DHA content achieved increased nanocarrier uptake and up to 8.99-fold higher darunavir permeation than free darunavir. In animals, nanoARVs were able to achieve 3.38-5.93-fold increase in brain darunavir level over free darunavir. Tf-conjugated nanoARVs also achieved significantly higher anti-HIV activity than free darunavir (viral titer 2 to 2.6-fold higher in latter group). Comparison of DHA incorporation and Tf-receptor targeting showed that while both strategies could enhance the cellular uptake and brain accumulation of the nanocarriers, DHA was more effective (P < 0.05) for improving BBB permeation and brain accumulation of the darunavir payload. Substituting DHA with another oil noticeably reduced the cellular uptake of nanoARVs. Overall, this proof-of-concept study has supported the development of DHA-based nanoARVs as an effective, safe yet technically simple strategy to enhance brain delivery of darunavir and potentially other lipophilic ARVs for treatment of HIV reservoir.

Intratumoral injection of hydrogel-embedded nanoparticles enhances retention in glioblastoma

Intratumoral drug delivery is a promising approach for the treatment of glioblastoma multiforme (GBM). However, drug washout remains a major challenge in GBM therapy. Our strategy, aimed at reducing drug clearance and enhancing site-specific residence time, involves the local administration of a multi-component system comprised of nanoparticles (NPs) embedded within a thermosensitive hydrogel (HG). Herein, our objective was to examine the distribution of NPs and their cargo following intratumoral administration of this system in GBM. We hypothesized that the HG matrix, which undergoes rapid gelation upon increases in temperature, would contribute towards heightened site-specific retention and permanence of NPs in tumors. BODIPY-containing, infrared dye-labeled polymeric NPs embedded in a thermosensitive HG (HG-NPs) were fabricated and characterized. Retention and distribution dynamics were subsequently examined over time in orthotopic GBM-bearing mice. Results demonstrate that the HG-NPs system significantly improved site-specific, long-term retention of both NPs and BODIPY, with co-localization analyses showing that HG-NPs covered larger areas of the tumor and the peri-tumor region at later time points. Moreover, NPs released from the HG were shown to undergo uptake by surrounding GBM cells. Findings suggest that intratumoral delivery with HG-NPs has immense potential for GBM treatment, as well as other strategies where site-specific, long-term retention of therapeutic agents is warranted.

A combination of receptor mediated transcytosis and photothermal effect promotes BBB permeability and the treatment of meningitis using itraconazole

Fungal infections of the central nervous system (CNS) may lead to life-threatening meningitis. Itraconazole (ITZ) is an effective antifungal agent that can be used to treat various fungal infections; however, its poor solubility along with poor permeability of the blood-brain barrier (BBB) prevents it from treating meningitis. Receptor mediated transcytosis (RMT) shows modest efficacy in BBB crossing, while affinity and saturability of interactions between ligands and receptors account for the limited efficacy of RMT in crossing the BBB. Mild hyperthermia could temporarily disrupt the BBB to increase its permeability. Therefore, we speculated that the combination of mild hyperthermia with RMT could potentially increase BBB permeability of ITZ leading to improved efficacy in fungal meningitis. Here, we have constructed for the first time, apolipoprotein E (Apo E) mimicked peptide COG1410 modified polydopamine (PDA)-coated bovine serum albumin nanoparticles (ApoE-PDA@ITZ-NPs). Different levels of COG1410-modified NPs were prepared and characterized. ApoE-PDA@ITZ-NPs have a superior photothermal effect under 808 nm light irradiation and exhibited favorable plasma stability and photothermal stability. Moreover, the cellular uptake of nanoparticles increased with an increase in COG1410. H-ApoE-PDA@ITZ-NPs increased cellular uptake and in vitro BBB permeability by 4.2-fold and 4.8-fold, respectively, compared to the ITZ-NPs. Live imaging implied that H-ApoE-PDA@ITZ-NPs could significantly increase the distribution of ITZ in the brain under 808 nm light irradiation. Histopathological analysis of periodic acid-Schiff-stained brain sections of the H-ApoE-PDA@ITZ-NP treated C. albicans meningitis model indicated that H-ApoE-PDA@ITZ-NPs showed superior antifungal activity after 808 nm light irradiation. Hence, we report ApoE-PDA@ITZ-NPs in tandem with 808 nm irradiation as a novel strategy of RMT combination with a photothermal effect in enhancing BBB permeability to facilitate drug accumulation in the brain region and enhance the therapeutic efficacy of ITZ in meningitis.

Computational backbone design enables soluble engineering of transferrin receptor apical domain

Supply of iron into human cells is achieved by iron carrier protein transferrin and its receptor that upon complex formation get internalized by endocytosis. Similarly, the iron needs to be delivered into the brain, and necessitates the transport across the blood-brain barrier. While there are still unanswered questions about these mechanisms, extensive efforts have been made to use the system for delivery of therapeutics into biological compartments. The dimeric form of the receptor, where each subunit consists of three domains, further complicates the detailed investigation of molecular determinants responsible for guiding the receptor interactions with other proteins. Especially the apical domain's biological function has been elusive. To further the study of transferrin receptor, we have computationally decoupled the apical domain for soluble expression, and validated the design strategy by structure determination. Besides presenting a methodology for solubilizing domains, the results will allow for study of apical domain's function.

Endocrine therapy for the treatment of leptomeningeal carcinomatosis in luminal breast cancer: a comprehensive review

Leptomeningeal disease (LMD) represents a devastating complication of advanced breast cancer (ABC), with survival of <5 months with multimodal treatment. The role of endocrine therapy (ET), due to its favorable toxicity profile and first-line indication in luminal ABC, appears promising in the setting of LMD, where symptom stabilization and quality-of-life preservation are the main goals; however, evidenced-based data are lacking. We conducted a thorough review of published evidence, aiming to investigate the role of ET in LMD treatment in luminal ABC. Twenty-one of 342 articles, evaluating 1302 patients, met inclusion criteria. ET use was rarely reported. New targeted agents show CNS activity. Research is lacking on the role of ET and targeted agents in BC-LMD treatment.

Magnetic Resonance Imaging-Guided Focused Ultrasound-Based Delivery of Radiolabeled Copper Nanoclusters to Diffuse Intrinsic Pontine Glioma

Diffuse intrinsic pontine glioma (DIPG) is an invasive pediatric brainstem malignancy exclusively in children without effective treatment due to the often-intact blood-brain tumor barrier (BBTB), an impediment to the delivery of therapeutics. Herein, we used focused ultrasound (FUS) to transiently open BBTB and delivered radiolabeled nanoclusters (⁶⁴Cu-CuNCs) to tumors for positron emission tomography (PET) imaging and quantification in a mouse DIPG model. First, we optimized FUS acoustic pressure to open the blood-brain barrier (BBB) for effective delivery of ⁶⁴Cu-CuNCs to pons in wildtype mice. Then the optimized FUS pressure was used to deliver radiolabeled agents in DIPG mouse. Magnetic resonance imaging (MRI)-guided FUS-induced BBTB opening was demonstrated using a low molecular weight, short-lived ⁶⁸Ga-DOTA-ECL1i radiotracer and PET/CT before and after treatment. We then compared the delivery efficiency of ⁶⁴Cu-CuNCs to DIPG tumor with and without FUS treatment and demonstrated the FUS-enhanced delivery and time-dependent diffusion of ⁶⁴Cu-CuNCs within the tumor.

Osimertinib combined with bevacizumab for leptomeningeal metastasis from EGFR-mutation non-small cell lung cancer: A phase II single-arm prospective clinical trial

Background

Leptomeningeal metastasis (LM) is associated with poor prognosis in non‐small cell lung cancer (NSCLC). The aim of this study was to investigate the efficacy and safety of osimertinib combined with bevacizumab for LM from epidermal growth factor receptor mutation (EGFRm) NSCLC.

Methods

We conducted a phase II single‐arm prospective clinical trial of EGFRm NSCLC with LM treated with osimertinib combined with bevacizumab. LM response assessment was based on the modified RANO LM radiological criteria; CNS and extra‐CNS response was evaluated according to the Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. The primary end points included LM progression‐free survival (PFS) and objective response rate (ORR); the secondary end points included safety and LM overall survival (OS).

Results

A total of 14 patients were included in the study, with a median age of 61 years, and they were predominantly female (64%). EGFR mutations were reported in exons 19 del (n = 7) and 21 L858R (n = 7). When LM was diagnosed, 12 (85.7%) patients had clinical symptoms, 71.4% (10/14) of patients were diagnosed with LM by cytology, and five (35.7%) patients had a performance status (PS) score > 2. The median LM PFS was 9.3 months (95% CI: 8.2–10.4), and the LM ORR was 50%. The safety findings in the present study were consistent with the known profile of osimertinib with bevacizumab; the median LM OS was 12.6 months, and the one‐year survival rate was 35.7%.

Conclusions

Osimertinib combined with bevacizumab is an appropriate treatment option for patients with LM from EGFRm NSCLC.

Key points

Significant findings of the study

To date, there is no prospective clinical study on the treatment of osimertinib combined with bevacizumab in EGFRm NSCLC with LM.

What this study adds

The median LM PFS was 9.3 months (95% CI: 8.2–10.4), and the LM ORR was 50%, the median LM OS was 12.6 months, and the one‐year survival rate was 35.7%. Osimertinib combined with bevacizumab is an appropriate treatment option for patients with LM from EGFRm NSCLC.

Neurodegenerative diseases and effective drug delivery: A review of challenges and novel therapeutics

The central nervous system (CNS) encompasses the brain and spinal cord and is considered the processing center and the most vital part of human body. The central nervous system (CNS) barriers are crucial interfaces between the CNS and the periphery. Among all these biological barriers, the blood-brain barrier (BBB) strongly impede hurdle for drug transport to brain. It is a semi-permeable diffusion barrier against the noxious chemicals and harmful substances present in the blood stream and regulates the nutrients delivery to the brain for its proper functioning. Neurological diseases owing to the existence of the BBB and the blood-spinal cord barrier have been terrible and threatening challenges all over the world and can rarely be directly mediated. In fact, drug delivery to brain remained a challenge in the treatment of neurodegenerative (ND) disorders, for these different approaches have been proposed. Nano-fabricated smart drug delivery systems and implantable drug loaded biomaterials for brain repair are among some of these latest approaches. In current review, modern approaches developed to deal with the challenges associated with transporting drugs to the CNS are included. Recent studies on neural drug discovery and injectable hydrogels provide a potential new treatment option for neurological disorders. Moreover, induced pluripotent stem cells used to model ND diseases are discussed to evaluate drug efficacy. These protocols and recent developments will enable discovery of more effective drug delivery systems for brain.

A brain glioma gene delivery strategy by angiopep-2 and TAT-modified magnetic lipid-polymer hybrid nanoparticles

Owing to the existence of the blood-brain barrier (BBB), most treatments cannot achieve significant effects on gliomas. In this study, synergistic multitarget Ang-TAT-Fe3O4-pDNA-(ss)373 lipid-polymer hybrid nanoparticles (LPNPs) were designed to penetrate the BBB and deliver therapeutic genes to glioma cells. The basic material of the nanoparticles was PCL3750-ss-PEG7500-ss-PCL3750, and is called (ss)373 herein. (ss)373 NPs, Fe3O4 magnetic nanoparticles (MNPs), DOTAP, and DSPE-PEG-MAL formed the basic structure of LPNPs by self-assembly. The Fe3O4 MNPs were wrapped in (ss)373 NPs to implement magnetic targeting. Then, the Angiopep-2 peptide (Ang) and transactivator of transcription (TAT) were coupled with DSPE-PEG-MAL. Both can enhance BBB penetration and tumor targeting. Finally, the pDNA was compressed on DOTAP to form the complete gene delivery system. The results indicated that the Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs were 302.33 nm in size. In addition, their zeta potential was 4.66 mV, and they had good biocompatibility. The optimal nanoparticles/pDNA ratio was 5 : 1, as shown by gel retardation assay. In this characterization, compared with other LPNPs, the modified single Ang or without the addition of the Fe3O4 MNPs, the penetration efficiency of the BBB model formed by hCMEC/D3 cells, and the transfection efficiency of C6 cells using pEGFP-C1 as the reporter gene were significantly improved with Ang-TAT-Fe3O4-pDNA-(ss)373 LPNPs in the magnetic field.

Single domain antibody-based vectors in the delivery of biologics across the blood-brain barrier: a review

Biologics are a promising and effective method for the treatment of central nervous system (CNS) diseases. The blood-brain barrier (BBB) is a natural barrier for the delivery of biologics into the brain, which decreases the effective concentration of drugs in the CNS. A range of strategies has been explored to transport biologics across the BBB endothelium, typically via receptor-mediated transcytosis (RMT), which involving molecules for endogenous BBB receptors to be fused with biologics. This review emphasized a category of novel alternative RMT-targeting vectors: single domain antibodies (sdAb). SdAbs are a unique category of antibodies derived from naturally occurring heavy-chain-only antibodies. Herein, we describe their properties, mechanisms, modifications, and translational perspectives for their ability to transmigrate across the BBB in vitro and in vivo in detail.

Nose-to-brain Delivery of Natural Compounds for the Treatment of Central Nervous System Disorders

BACKGROUND

Several natural compounds have demonstrated potential for the treatment of central nervous system disorders such as ischemic cerebrovascular disease, glioblastoma, neuropathic pain, neurodegenerative diseases, multiple sclerosis and migraine. This is due to their well-known antioxidant, anti-inflammatory, neuroprotective, anti-tumor, anti-ischemic and analgesic properties. Nevertheless, many of these molecules have poor aqueous solubility, low bioavailability and extensive gastrointestinal and/or hepatic first-pass metabolism, leading to a quick elimination as well as low serum and tissue concentrations. Thus, the intranasal route emerged as a viable alternative to oral or parenteral administration, by enabling a direct transport into the brain through the olfactory and trigeminal nerves. With this approach, the blood-brain barrier is circumvented and peripheral exposure is reduced, thereby minimizing possible adverse effects.

OBJECTIVE

Herein, brain-targeting strategies for nose-to-brain delivery of natural compounds, including flavonoids, cannabinoids, essential oils and terpenes, will be reviewed and discussed. Brain and plasma pharmacokinetics of these molecules will be analyzed and related to their physicochemical characteristics and formulation properties.

CONCLUSION

Natural compounds constitute relevant alternatives for the treatment of brain diseases but often require loading into nanocarrier systems to reach the central nervous system in sufficient concentrations. Future challenges lie in a deeper characterization of their therapeutic mechanisms and in the development of effective, safe and brain-targeted delivery systems for their intranasal administration.

Antitumor Activity of Cabazitaxel and MSC-TRAIL Derived Extracellular Vesicles in Drug-Resistant Oral Squamous Cell Carcinoma

INTRODUCTION

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) can induce apoptosis in a variety of cancer cells. However, drug resistance of tumor and short half-life seriously affects its clinical targeted therapy. Cabazitaxel (CTX) is a taxane drug, which can induce apoptosis or autophagy by inhibiting the phosphorylation of PI3K/Akt/mTOR and sensitive to some drug-resistant tumors. Therefore, we explored the possibility of developing a mesenchymal stem cell-derived exosomes (MSC-EXO) vector for oral squamous cell carcinoma (OSCC) to deliver CTX/TRAIL combinations.

METHODS

After ultracentrifugation and dialysis, CTX/TRAIL loaded exosomes transfected MSC (MSCT)-derived exosome (EXO) (MSCT-EXO/CTX) were isolated and purified. The expression of CD63, CD9 and TRAIL was detected by BCA to confirm the origin of EXO. High-performance liquid chromatography (HPLC) was used to determine the drug loading of VPF and draw the in vitro release profile. MTT assay, flow cytometry and Western blot were used to detect the antitumor effect of MSCT-EXO/CTX in vitro. Subsequently, the antitumor effect of MSCT-EXO/CTX in vivo was verified by mouse model.

RESULTS

The diameter of the membrane particles was about 60-150 nm. We have proved that the incorporation and release of CTX in MSCT-EXO can inhibit the activation of PI3K, Akt and mTOR, which is a possible synergistic mechanism of CTX. MSCT-EXO and CTX can induce the apoptosis of SCC25 tumor cells in a dose-dependent manner and exert a good synergistic effect in the proportion range of 10:1-5:1. The inherent activity of MSCT-EXO and the direct effect of MSCT-EXO/CTX on OSCC confirm that MSCT-EXO/CTX makes MSCT-EXO and CTX have an efficient synergistic effect and a highly effective pharmacological inhibition on cancer cells, as verified by the subsequent mouse model. MSCT-EXO/CTX showed the lowest relative tumor volume and the highest tumor inhibition rate (P<0.05) in vivo.

CONCLUSION

An MSCT-EXO-based CTX delivery system might be an effective anticancer method.

Effects of salvianolate lyophilized injection combined with Xueshuantong injection in regulation of BBB function in a co-culture model of endothelial cells and pericytes

The combined use of two or more different drugs can better promote nerve recovery and its prognosis for treatment of stroke. The salvianolate lyophilized injection (SLI) and Xueshuantong Injection (XST) are two standardized Chinese medicine injections which have been widely used in the treatment of cerebrovascular diseases. Salvianolic acid B (Sal B) and Notoginsenoside R1 (NR1) is respectively one of the active constituents of SLI and XST, which have certain effects on stroke. In this study, we established a co-culture of endothelial cells and pericytes for oxygen-glucose deprivation/reperfusion (OGD/R) injury model to study the effects of SLI and Sal B or XST and NR1 alone, or with their combinations (1S1X) in regulation of BBB function. The results showed that compared with the OGD/R group, treatment with SLI, XST and SalB and NR1 can significantly increase the TEER, reduce the permeability of Na-Flu, enhance the expression of tight junctions (TJs) between cells, and stabilize the basement membrane (BM) composition. In addition, the combination of 1S1X is superior to the XST or SLI alone in enhancing the TJs between cells and stabilizing the BM. And the active components SalB and NR1 can play a strong role in these two aspects, even with the whole effects. Furthermore, the study showed that XST, Sal B and NR1 increases in Ang-1and Tie2, while decrease in Ang-2 and VEGF protein expressions. Overall, these findings suggest that SLI combined with XST (1X1S) has protective effects on co-culture of endothelial cells and pericytes after OGD/R. Moreover, its protective effect might be associated with increase of TJs and BMs through activation of Ang/Tie-2 system signaling pathway.

Tuning the binding interface between Machupo virus glycoprotein and human transferrin receptor

Machupo virus, known to cause hemorrhagic fevers, enters human cells via binding with its envelope glycoprotein to transferrin receptor 1 (TfR). Similarly, the receptor interactions have been explored in biotechnological applications as a molecular system to ferry therapeutics across the cellular membranes and through the impenetrable blood-brain barrier that effectively blocks any such delivery into the brain. Study of the experimental structure of Machupo virus glycoprotein 1 (MGP1) in complex with TfR and glycoprotein sequence homology has identified some residues at the interface that influence binding. There are, however, no studies that have attempted to optimize the binding potential between MGP1 and TfR. In pursuits for finding therapeutic solutions for the New World arenaviruses, and to gain a greater understanding of MGP1 interactions with TfR, it is crucial to understand the structure-sequence relationship driving the interface formation. By displaying MGP1 on yeast surface we have examined the contributions of individual residues to the binding of solubilized ectodomain of TfR. We identified MGP1 binding hot spot residues, assessed the importance of posttranslational N-glycan modifications, and used a selection with random mutagenesis for affinity maturation. We show that the optimized MGP1 variants can bind more strongly to TfR than the native MGP1, and there is an MGP1 sequence that retains binding in the absence of glycosylation, but with the addition of further amino acid substitutions. The engineered variants can be used to probe cellular internalization or the blood-brain barrier crossing to achieve greater understanding of TfR mediated internalization.

Approaching sites of action of drugs in clinical pharmacology: New analytical options and their challenges

Clinical pharmacology is an important discipline for drug development aiming to define pharmacokinetics (PK), pharmacodynamics (PD) and optimum exposure to drugs, i.e. the concentration-response relationship and its modulators. For this purpose, information on drug concentrations at the anatomical, cellular and molecular sites of action is particularly valuable. In pharmacological assays, the limited accessibility of target cells in readily available samples (i.e. blood) often hampers mass spectrometry-based monitoring of the absolute quantity of a compound and the determination of its molecular action at the cellular level. Recently, new sample collection methods have been developed for the specific capture of rare circulating cells, especially for the diagnosis of circulating tumour cells. In parallel, new advances and developments in mass spectrometric instrumentation now allow analyses to be scaled down to the cellular level. Together, these developments may permit the monitoring of minute drug quantities and show their effect at the cellular level. In turn, such PK/PD associations on a cellular level would not only enrich our pharmacological knowledge of a given compound but also expand the basis for PK/PD simulations. In this review, we describe novel concepts supporting clinical pharmacology at the anatomical, cellular and molecular sites of action, and highlight the new challenges in mass spectrometry-based monitoring. Moreover, we present methods to tackle these challenges and define future needs.

[Management of Drug Therapy for Leptomeningeal Metastasis of Sensitive Driver Gene Positive Non-small Cell Lung Cancer]

Leptomeningeal metastasis (LM) is one of the serious complications of advanced non-small cell lung cancer (NSCLC), although the incidence is not high, the clinical symptoms are severe and the prognosis is poor. LM is prone to occur in patients with positive driver gene than negative. At present, the treatment of LM mainly includes molecular targeted therapy, systemic chemotherapy, whole brain radiotherapy, intrathecal chemotherapy and immunotherapy. Although there are many treatments, the efficacy of LM is still unsatisfactory. This article reviews the drug therapy of sensitive driver gene positive NSCLC LM.

I6P7 peptide modified superparamagnetic iron oxide nanoparticles for magnetic resonance imaging detection of low-grade brain gliomas

Glioma, the most severe primary brain malignancy, has very low survival rates and a high level of recurrence. Nowadays, conventional treatments for these patients are suffering a similar plight owing to the distinctive features of the malignant gliomas, for example chemotherapy is limited by the blood-brain barrier while surgery and radiation therapy are affected by the unclear boundaries of tumor from normal tissue. In the present study, a novel superparamagnetic iron oxide (SPIO) nanoprobe for enhanced T2-weighted magnetic resonance imaging (MRI) was developed. A frequently used MRI probe, SPIO nanoparticles, was coated with a silica outer layer and for the first time was covalently modified with interleukin-6 receptor targeting peptides (I6P7) to promote transportation through the blood-brain barrier and recognition of low-grade gliomas. The efficiency of transcytosis across the blood-brain barrier was examined in vitro using a transwell invasion model and in vivo in nude mice with orthotopic low-grade gliomas. The targeting nanoprobe showed significant MRI enhancement and has potential for use in the diagnosis of low-grade gliomas.

Neurotransmitter-derived lipidoids (NT-lipidoids) for enhanced brain delivery through intravenous injection

Safe and efficient delivery of blood-brain barrier (BBB)-impermeable cargos into the brain through intravenous injection remains a challenge. Here, we developed a previously unknown class of neurotransmitter-derived lipidoids (NT-lipidoids) as simple and effective carriers for enhanced brain delivery of several BBB-impermeable cargos. Doping the NT-lipidoids into BBB-impermeable lipid nanoparticles (LNPs) gave the LNPs the ability to cross the BBB. Using this brain delivery platform, we successfully delivered amphotericin B (AmB), antisense oligonucleotides (ASOs) against tau, and genome-editing fusion protein (-27)GFP-Cre recombinase into the mouse brain via systemic intravenous administration. We demonstrated that the NT-lipidoid formulation not only facilitates cargo crossing of the BBB, but also delivery of the cargo into neuronal cells for functional gene silencing or gene recombination. This class of brain delivery lipid formulations holds great potential in the treatment of central nervous system diseases or as a tool to study the brain function.

An overview of nanomedicines for neuron targeting

Medical treatments of neuron-related disorders are limited due to the difficulty of targeting brain cells. Major drawbacks are the presence of the blood-brain barrier and the lack of specificity of the drugs for the diseased cells. Nanomedicine-based approaches provide promising opportunities for overcoming these limitations. Although many previous reviews are focused on brain targeting with nanomedicines in general, none of those are concerned explicitly on the neurons, while targeting neuronal cells in central nervous diseases is now one of the biggest challenges in nanomedicine and neuroscience. We review the most relevant advances in nanomedicine design and strategies for neuronal drug delivery that might successfully bridge the gap between laboratory and bedside treatment in neurology.

Luminescent chitosan/carbon dots as an effective nano-drug carrier for neurodegenerative diseases

Designing new materials for effective and targeted drug delivery is pivotal in biomedical research. Herein, we report on the development of a chitosan/carbon dot-based nanocomposite and investigate its efficacy as a carrier for the sustained release of dopamine drug. The carbon dots (CDs) were synthesized from the carbonization of chitosan and were further conjugated with chitosan (CS) to obtain a chitosan/carbon dot (CS/CD) matrix. Dopamine was later encapsulated in the matrix to form a dopamine@CS/CD nanocomposite. The cytotoxicity of IC-21 and SH-SY5Y cell lines was studied at various concentrations of the nanocomposite and the results demonstrate around 97% cell viability. The photoluminescence property revealed the characteristic property of the carbon dots. When excited at 510 nm an emission peak was observed at 550 nm which enables the use of carbon dots as a tracer for bioimaging. The HRTEM images and the D, G, and 2D bands of the Raman spectra confirm the successful synthesis of carbon dots and through DLS the particle size is estimated to be ∼3 nm. The release studies of the encapsulated drug from the composite were analyzed in an in vitro medium at different pH levels. The novelty of this method is the use of a non-toxic vehicle to administer drugs effectively towards any ailment and in particular, the carbon dots facilitate the consistent release of dopamine towards neurodegenerative diseases and tracing delivery through bioimaging.

Active Targeting Towards and Inside the Brain based on Nanoparticles: A Review

Background:

Treatment of neurological diseases using systemic and non-surgical techniques presents a significant challenge in medicine. This challenge is chiefly associated with the condensation and coherence of the brain tissue.

Methods:

The coherence structure of the brain is due to the presence of the blood-brain barrier (BBB), which consists of a continuous layer of capillary endothelial cells. The BBB prevents most drugs from entering the brain tissue and is highly selective, permitting only metabolic substances and nutrients to pass through.

Results:

Although this challenge has caused difficulties for the treatment of neurological diseases, it has opened up a broad research area in the field of drug delivery. Through the utilization of nanoparticles (NPs), nanotechnology can provide the ideal condition for passing through the BBB.

Conclusion:

NPs with suitable dimensions and optimum hydrophobicity and charge, as well as appropriate functionalization, can accumulate in the brain. Furthermore, NPs can facilitate the targeted delivery of therapeutics into the brain areas involved in Alzheimer’s disease, Parkinson’s disease, stroke, glioma, migraine, and other neurological disorders. This review describes these methods of actively targeting specific areas of the brain.

The emerging role of computational design in peptide macrocycle drug discovery

Drug discovery is a laborious process with rising cost per new drug. Peptide macrocycles are promising therapeutics, though conformational flexibility can reduce target affinity and specificity. Recent computational advancements address this problem by enabling rational design of rigidly folded peptide macrocycles.

AREAS COVERED

This review summarizes currently approved peptide macrocycle therapeutics and discusses advantages of mesoscale drugs over small molecules or protein therapeutics. It describes the history, rationale, and state of the art of computational tools, such as Rosetta, that allow the design of rigidly structured peptide macrocycles. The emerging pipeline for designing peptide macrocycle drugs is described, including current challenges in designing permeable molecules that can emulate the chameleonic behavior of natural macrocycles. Prospects for reducing computational cost and improving accuracy with emerging computational technologies are also discussed.

EXPERT OPINION

To embrace computational design of peptide macrocycle drugs, we must shift current attitudes regarding the role of computation in drug discovery, and move beyond Lipinski's rules. This technology has the potential to shift failures to earlier in silico stages of the drug discovery process, improving success rates in costly clinical trials. Given the available tools, now is the time for drug developers to incorporate peptide macrocycle design into drug discovery pipelines.

Management of leptomeningeal metastases in non-small cell lung cancer

In leptomeningeal metastasis (LM), malignant lung cancer cells reach the sanctuary site of the leptomeningeal space through haematogenous or lymphatic route and thrive in the leptomeninges because of restricted access of chemotherapeutic agents across the blood brain barrier. The incidence of LM is 3%-5% in non-small cell lung cancer (NSCLC) patients; the incidence is higher in patients with anaplastic lymphoma kinase (ALK) gene rearrangement or epidermal growth factor receptor (EGFR) mutations. However, the real-world burden of undiagnosed cases may be higher. LM diagnosis is based on clinical, radiological, and cytological testing. Disease management remains a challenge because of low central nervous system penetration of drugs. The prognosis of NSCLC patients with LM is poor with an overall survival (OS) of 3 months with contemporary treatment and <11 months with novel therapies. Therapy goals in this patient population are to improve or stabilize neurologic status, improve quality of life, and prolong survival while limiting the toxicity of chemotherapeutic regimens. We reviewed therapeutic options for management of LM in NSCLC patients with or without genetic mutations. Radiotherapy, systemic, or intrathecal chemotherapy, and personalized molecularly targeted therapy prolong the OS in patients with LM. Newer third generation EGFR-tyrosine kinase inhibitors have considerable brain penetration property and have been vital in increasing the OS especially in patients with EGFR mutations. Sequential or combination therapy third generation EGFR agents with radiotherapy or chemotherapy might be effective in increasing the quality of life and overall survival.

Immunotherapy against Prion Disease

The term "prion disease" encompasses a group of neurodegenerative diseases affecting both humans and animals. Currently, there is no effective therapy and all forms of prion disease are invariably fatal. Because of (a) the outbreak of bovine spongiform encephalopathy in cattle and variant Creutzfeldt-Jakob disease in humans; (b) the heated debate about the prion hypothesis; and (c) the availability of a natural prion disease in rodents, the understanding of the pathogenic process in prion disease is much more advanced compared to that of other neurodegenerative disorders, which inspired many attempts to develop therapeutic strategies against these fatal diseases. In this review, we focus on immunotherapy against prion disease. We explain our rationale for immunotherapy as a plausible therapeutic choice, review previous trials using either active or passive immunization, and discuss potential strategies for overcoming the hurdles in developing a successful immunotherapy. We propose that immunotherapy is a plausible and practical therapeutic strategy and advocate more studies in this area to develop effective measures to control and treat these devastating disorders.

Approaches for CNS delivery of drugs - nose to brain targeting of antiretroviral agents as a potential attempt for complete elimination of major reservoir site of HIV to aid AIDS treatment

INTRODUCTION

Human immune-deficiency virus (HIV) infection causing acquired immune-deficiency syndrome (AIDS) is one of the most life-threatening infections. The central nervous system (CNS) is reported to be the most important HIV reservoir site where the antiretroviral drugs are unable to reach.

AREAS COVERED

This article includes the review about HIV infections, its pathogenesis, HIV infections in CNS, its consequences, current therapies, challenges associated with the existing therapies, approaches to overcome them, CNS delivery of drugs - barriers, transport routes, approaches for transporting drugs across the blood-brain barrier, nasal route of drug delivery, and nose to brain targeting of antiretroviral agents as a potential approach for complete cure of AIDS.

EXPERT OPINION

Various approaches are exploited to enhance the drug delivery to the brain for various categories of drugs. However, very few have investigated on the delivery of antiretrovirals to the brain. Targeting antiretrovirals to CNS through oral/nasal routes along with oral/parenteral delivery of drug to the plasma can be a promising approach for an attempt to completely eradicate HIV reservoir and cure AIDS, after clinical trials. Further research is required to identify the exact location of the HIV reservoir in CNS and developing good animal models for evaluation of different newly developed formulations.

Monophosphoryl lipid A alleviated radiation-induced testicular injury through TLR4-dependent exosomes

Radiation protection on male testis is an important task for ionizing radiation-related workers or people who receive radiotherapy for tumours near the testicle. In recent years, Toll-like receptors (TLRs), especially TLR4, have been widely studied as a radiation protection target. In this study, we detected that a low-toxicity TLR4 agonist monophosphoryl lipid A (MPLA) produced obvious radiation protection effects on mice testis. We found that MPLA effectively alleviated testis structure damage and cell apoptosis induced by ionizing radiation (IR). However, as the expression abundance differs a lot in distinct cells and tissues, MPLA seemed not to directly activate TLR4 singling pathway in mice testis. Here, we demonstrated a brand new mechanism for MPLA producing radiation protection effects on testis. We observed a significant activation of TLR4 pathway in macrophages after MPLA stimulation and identified significant changes in macrophage-derived exosomes protein expression. We proved that after MPLA treatment, macrophage-derived exosomes played an important role in testis radiation protection, and specially, G-CSF and MIP-2 in exosomes are the core molecules in this protection effect.

Nanoparticles as contrast agents for the diagnosis of Alzheimer’s disease: a systematic review

Nanoparticle (NP)-based magnetic contrast agents have opened the potential for MRI to be used for early diagnosis of Alzheimer’s disease (AD). This article aims to review the current progress of research in this field. A comprehensive literature search was performed based on PubMed, Medline, EMBASE, PsychINFO and Scopus databases using the following terms: ‘Alzheimer’s disease’ AND ‘nanoparticles’ AND ‘Magnetic Resonance Imaging.’ 33 studies were included that described the development and utility of various NPs for AD imaging, including their coating, functionalization, MRI relaxivity, toxicity and bioavailability. NPs show immense promise for neuroimaging, due to superior relaxivity and biocompatibility compared with currently available imaging agents. Consistent reporting is imperative for further progress in this field.

Schwann cells apoptosis is induced by high glucose in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes mellitus that affects approximately half of patients with diabetes. Current treatment regimens cannot treat DPN effectively. Schwann cells (SCs) are very sensitive to glucose concentration and insulin, and closely associated with the occurrence and development of type 1 diabetic mellitus (T1DM) and DPN. Apoptosis of SCs is induced by hyperglycemia and is involved in the pathogenesis of DPN. This review considers the pathological processes of SCs apoptosis under high glucose, which include the following: oxidative stress, inflammatory reactions, endoplasmic reticulum stress, autophagy, nitrification and signaling pathways (PI3K/AKT, ERK, PERK/Nrf2, and Wnt/β-catenin). The clarification of mechanisms underlying SCs apoptosis induced by high glucose will help us to understand and identify more effective strategies for the treatment of T1DM DPN.

Current insights on lipid nanocarrier-assisted drug delivery in the treatment of neurodegenerative diseases

The central nervous system (CNS) is vulnerable to pathologic processes that lead to the development of neurodegenerative disorders like Alzheimer's, Parkinson's and Huntington's diseases, Multiple sclerosis or Amyotrophic lateral sclerosis. These are chronic and progressive pathologies characterized by the loss of neurons and the formation of misfolded proteins. Additionally, neurodegenerative diseases are accompanied by a structural and functional dysfunction of the blood-brain barrier (BBB). Although serving as a protection for the CNS, the existence of physiological barriers, especially the BBB, limits the access of several therapeutic agents to the brain, constituting a major hindrance in neurotherapeutics advancement. In this regard, nanotechnology-based approaches have arisen as a promising strategy to not only improve drug targeting to the brain, but also to increase bioavailability. Lipid nanocarriers such as liposomes, solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), microemulsions and nanoemulsions, have already proven their potential for enhancing brain transport, crossing more easily into the CNS and allowing the administration of medicines that could benefit the treatment of neurological pathologies. Given the socioeconomic impact of such conditions and the advent of nanotechnology that inevitably leads to more effective and superior therapeutics for their management, it is imperative to constantly update on the current knowledge of these topics. Herein, we provide insight on the BBB and the pathophysiology of the main neurodegenerative disorders. Moreover, this review seeks to highlight the several approaches that can be used to improve the delivery of therapeutic agents to the CNS, while also offering an extensive overview of the latest efforts regarding the use of lipid-based nanocarriers in the management of neurodegenerative diseases.

Therapeutic potential role of exosomes for ischemic stroke

Exosomes are extracellular vesicles with a diameter of 30–100 nm, which are released into the extracellular space by fusion of multivesicular and plasma membranes. These vesicles actually play a distinct role in cell communication, although they were considered as membrane debris in the past. The endosomal sorting complex required for transport (ESCRT)-dependent and ESCRT-independent mechanisms are currently considered to be involved in the sorting of exosomes, and the release of exosomes is related to the members of Rab protein family and SNARE family. In recent years, the therapeutic potential of exosomes has become apparent. For example, via the direct transplantation of exosomes, the ischemic area after stroke is reduced, and the neurological function is improved significantly. Furthermore, they can be used as effective drug delivery vehicles due to their unique characteristics such as low immunogenicity and nanometer size. In conclusion, exosomes provide a cell-free treatment for ischemic stroke.

Kaixinsan, a Well-Known Chinese Herbal Prescription, for Alzheimer's Disease and Depression: A Preclinical Systematic Review

Alzheimer's disease (AD), the most common cause of dementia, is highly prevalent worldwide with no modifying therapy. Behavioral and psychological symptoms of dementia (BPSD) occur in most patients with AD, and depression is one of the most common AD-related BPSD. Kaixinsan (KXS) is an ancient Chinese herbal prescription widely used to treat dementia and forgetfulness. In this systematic review, we conducted a meta-analysis to assess preclinical evidence for the effects of KXS on cognitive impairment and depression. Thirty-eight articles involving 1,050 animals were included after searching from six databases from the inception up to June 2019. The primary outcome measures were behavioral outcome. Indicators of cognitive function in AD included escape latency, time spent on the target quadrant, and the number of target platform crossings in the Morris water maze (MWM) test. Indicators of depression included number of rearing events and total distance in the open-field test, duration of immobility in the forced swim test, and sucrose consumption or sucrose preference index in the sucrose preference test. The secondary outcomes were mechanisms of KXS for treatment of AD and depression. The results showed that KXS significantly reduced escape latency (P < 0.01), increased time spent in the target quadrant (P < 0.01), and increased the number of target platform crossings (P < 0.01) in the MWM test in AD models compared with control. The possible mechanisms for KXS-mediated improvements in cognitive function were antioxidant activity, anti-inflammatory activity, antiapoptotic activity, neuroprotection, and synapse protection. In addition, the results demonstrated that KXS significantly increased the number of rearing instances (P < 0.01) in the open-field test, decreased the duration of immobility (P < 0.01) in forced swim test, and increased sucrose consumption or sucrose preference index (P < 0.01) in the sucrose preference test in depression models compared with control. The mechanisms of KXS-mediated anti-depressive effects were HPA axis regulation, antioxidant activity, anti-inflammatory activity, synapse protection, and neuroprotection. The results of this study suggested that KXS can be used to effectively treat AD and depression through multiple mechanisms, extrapolating the therapeutic potential of KXS for treating AD-related BPSD.

Convection-enhanced delivery of temozolomide and whole cell tumor immunizations in GL261 and KR158 experimental mouse gliomas

Background

Glioblastomas (GBM) are therapy-resistant tumors with a profoundly immunosuppressive tumor microenvironment. Chemotherapy has shown limited efficacy against GBM. Systemic delivery of chemotherapeutic drugs is hampered by the difficulty of achieving intratumoral levels as systemic toxicity is a dose-limiting factor. Although some of its effects might be mediated by immune reactivity, systemic chemotherapy can also inhibit induced or spontaneous antitumor immune reactivity. Convection-enhanced delivery of temozolomide (CED-TMZ) can tentatively increase intratumoral drug concentration while reducing systemic side effects. The objective of this study was to evaluate the therapeutic effect of intratumorally delivered temozolomide in combination with immunotherapy and whether such therapy can generate a cellular antitumor immune response.

Methods

Single bolus intratumoral injection and 3-day mini-osmotic pumps (Alzet®) were used to deliver intratumoral TMZ in C57BL6 mice bearing orthotopic gliomas. Immunotherapy consisted of subcutaneous injections of irradiated GL261 or KR158 glioma cells. Tumor size and intratumoral immune cell populations were analyzed by immunohistochemistry.

Results

Combined CED-TMZ and immunotherapy had a synergistic antitumor effect in the GL261 model, compared to CED-TMZ or immunotherapy as monotherapies. In the KR158 model, immunization cured a small proportion of the mice whereas addition of CED-TMZ did not have a synergistic effect. However, CED-TMZ as monotherapy prolonged the median survival. Moreover, TMZ bolus injection in the GL261 model induced neurotoxicity and lower cure rate than its equivalent dose delivered by CED. In addition, we found that T-cells were the predominant cells responsible for the TMZ antitumor effect in the GL261 model. Finally, CED-TMZ combined with immunotherapy significantly reduced tumor volume and increased the intratumoral influx of T-cells in both models.

Conclusions

We show that immunotherapy synergized with CED-TMZ in the GL261 model and cured animals in the KR158 model. Single bolus administration of TMZ was effective with a narrower therapeutic window than CED-TMZ. Combined CED-TMZ and immunotherapy led to an increase in the intratumoral influx of T-cells. These results form part of the basis for the translation of the therapy to patients with GBM but the dosing and timing of delivery will have to be explored in depth both experimentally and clinically.

The Neuropharmacology of Impulsive Behaviour, an Update

Neuropharmacological interventions in preclinical translational models of impulsivity have tremendously contributed to a better understanding of the neurochemistry and neural basis of impulsive behaviour. In this regard, much progress has been made over the last years, also due to the introduction of novel techniques in behavioural neuroscience such as optogenetics and chemogenetics. In this chapter, we will provide an update of how the behavioural pharmacology field has progressed and built upon existing data since an earlier review we wrote in 2008. To this aim, we will first give a brief background on preclinical translational models of impulsivity. Next, recent interesting evidence of monoaminergic modulation of impulsivity will be highlighted with a focus on the neurotransmitters dopamine and noradrenaline. Finally, we will close the chapter by discussing some novel directions and drug leads in the neuropharmacological modulation of impulsivity.

Structure prediction of transferrin receptor protein 1 (TfR1) by homology modelling, docking, and molecular dynamics simulation studies

Transferrin receptor protein 1 (TfR1) is an important molecule in anti-cancer therapy. Targeted delivery of such therapeutic compounds improves their cellular uptake and circulation time, thereby enhancing therapeutic efficacy. Drug designing is therefore used to engineer molecules with structures that facilitate specific interactions. However, this process requires a thorough knowledge of all the interactions, including the three-dimensional (3D) and quaternary structures (QS) of the interacting molecules. Since structural information is available for only a part of the full TfR1 sequence, in the present study, we predicted the whole structure of TfR1 using homology modelling, docking, and molecular dynamics simulations. Homology modelling is used to generate 3D structures of TfR1 using MODELLER, I-TASSER, and RaptorX programs. Verify3D and Rampage server evaluated the quality of the resultant models. According to this evaluation, the model built by the RaptorX server and validated by Verify3D (compatibility: 83.82%) had the highest number of residues (95.5%) within the favoured regions of the Ramachandran plot, making it the most reliable 3D protein structure for TfR1 compared with others. The QS of TfR1 was built using HADDOCK and SymmDock docking software, and the results were evaluated by the ligand root mean square deviation (l-RMSD) value computed using the ProFit software. This showed that both HADDOCK and SymmDock gave acceptable results. However, the HADDOCK result was more stable and closest to the native complex structure with disulfide bonds. Therefore, the HADDOCK complex was further refined using both SymmRef and GalaxyRefineComplex until the medium l-RMSD rank was reached. This QS was successfully verified using nanoscale molecular dynamics (NAMD) energy minimization. This model could pave the way for further functional, structural, and therapeutic studies on TfR1.

Overview of Current Drug Delivery Methods Across the Blood-Brain Barrier for the Treatment of Primary Brain Tumors

Existing drug delivery methods have not led to a significant increase in survival for patients with malignant primary brain tumors. While the combination of conventional therapies consisting of surgery, radiotherapy, and chemotherapy has improved survival for some types of brain tumors (e.g., WNT medulloblastoma), other types of brain tumors (e.g., glioblastoma and diffuse midline glioma) still have a poor prognosis. The reason for the differences in response can be largely attributed to the blood-brain barrier (BBB), a specialized structure at the microvasculature level that regulates the transport of molecules across the blood vessels into the brain parenchyma. This structure hampers the delivery of most chemotherapeutic agents for the treatment of primary brain tumors. Several drug delivery methods such as nanoparticles, convection enhanced delivery, focused ultrasound, intranasal delivery, and intra-arterial delivery have been developed to overcome the BBB in primary brain tumors. However, prognosis of most primary brain tumors still remains poor. The heterogeneity of the BBB in primary brain tumors and the distinct vasculature of tumors make it difficult to design a drug delivery method that targets the entire tumor. Drug delivery methods that combine strategies such as focused ultrasound and nanoparticles might be a more successful approach. However, more research is needed to optimize and develop new drug delivery techniques to improve survival of patients with primary brain tumors.

Overcoming the Brain Barriers: From Immune Cells to Nanoparticles

Nanoparticulate carriers, often referred to as nanoparticles (NPs), represent an important pharmacological advance for drug protection and tissue-specific drug delivery. Accessing the central nervous system (CNS), however, is a complex process regulated by mainly three brain barriers. While some leukocyte (i.e., immune cell) subsets are equipped with the adequate molecular machinery to infiltrate the CNS in physiological and/or pathological contexts, the successful delivery of NPs into the CNS remains hindered by the tightness of the brain barriers. Here, we present an overview of the three major brain barriers and the mechanisms allowing leukocytes to migrate across each of them. We subsequently review different immune-inspired and -mediated strategies to deliver NPs into the CNS. Finally, we discuss the prospect of exploiting leukocyte trafficking mechanisms for further progress.

In vivo biodistribution of venlafaxine-PLGA nanoparticles for brain delivery: plain vs. functionalized nanoparticles

Background: Actually, no drugs provide therapeutic benefit to approximately one-third of depressed patients. Depression is predicted to become the first global disease by 2030. So, new therapeutic interventions are imperative.Research design and methods: Venlafaxine-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) were surface functionalized with two ligands against transferrin receptor to enhance access to brain. An in vitro blood-brain barrier model using hCMEC/D3 cell line was developed to evaluate permeability. In vivo biodistribution studies were performed using C57/bl6 mice. Particles were administered intranasal and main organs were analyzed.Results: Particles were obtained as a lyophilized powder easily to re-suspend. Internalization and permeability studies showed the following cell association sequence: TfRp-NPs>Tf-NPs>plain NPs. Permeability studies also showed that encapsulated VLF was not affected by P-gP pump efflux increasing its concentration in the basolateral side after 24 h. In vivo studies showed that 25% of plain NPs reach the brain after 30 min of one intranasal administration while less than 5% of functionalized NPs get the target.Conclusions: Plain NPs showed the highest ability to reach the brain vs. functionalized NPs after 30 min by intranasal administration. We suggest plain NPs probably travel via direct nose-to-brian route whereas functionalized NPs reach the brain by receptor-mediated endocytosis.

The role of NLRP3 inflammasome activation in the neuroinflammatory responses to Ag2Se quantum dots in microglia

Silver selenide quantum dots (Ag₂Se QDs) provide bright prospects for the application of QDs in the field of biomedicine because they contain low-toxic compounds and show great advantages in the imaging of deep tissues and tiny vascular structures. However, the biosafety of these novel QDs has not been thoroughly evaluated, especially in one main target for toxicity-the central nervous system (CNS). Our previous studies have suggested severe inflammatory responses to cadmium-containing QDs in the hippocampus, which gives us a hint regarding the risk assessment of Ag₂Se QDs. In this study, microglial activation followed by enhanced levels of pro-inflammatory cytokines was observed in the hippocampus of mice intravenously injected with Ag₂Se QDs. When using the microglial BV2 cells to investigate the underlying mechanisms, we found that the NLRP3 inflammasome activation was involved in the IL-1β-mediated inflammation induced by Ag₂Se QDs. On the one hand, Ag₂Se QD-activated NF-κB participated in the NLRP3 inflammasome priming and assembly as well as the pro-IL-1β upregulation. On the other hand, Ag₂Se QD-induced ROS generation, particularly mtROS, triggered the NLRP3 inflammasome activation and resulted in active caspase-1 to process pro-IL-1β into mature IL-1β release. These findings not only indicated that it is important to evaluate the biosafety of novel QDs, even those containing low-toxic compounds, but also provided an unbiased and mechanism-based risk assessment of similar nanoparticles.

Transient blood-brain barrier disruption is induced by low pulsed electrical fields in vitro: an analysis of permeability and trans-endothelial electric resistivity

The blood–brain barrier (BBB) is limiting transcellular and paracellular movement of molecules and cells, controls molecular traffic, and keeps out toxins. However, this protective function is the major hurdle for treating brain diseases such as brain tumors, Parkinson’s disease, Alzheimer’s disease, etc. It was previously demonstrated that high pulsed electrical fields (PEFs) can disrupt the BBB by inducing electroporation (EP) which increases the permeability of the transcellular route. Our goal was to study the effects of low PEFs, well below the threshold of EP on the integrity and function of the BBB. Ten low voltage pulses (5–100 V) were applied to a human in vitro BBB model. Changes in permeability to small molecules (NaF) were studied as well as changes in impedance spectrum and trans-endothelial electric resistivity. Viability and EP were evaluated by Presto-Blue and endogenous Lactate dehydrogenase release assays. The effect on tight junction and adherent junction protein was also studied. The results of low voltage experiments were compared to high voltage experiments (200–1400 V). A significant increase in permeability was found at voltages as low as 10 V despite EP only occurring from 100 V. The changes in permeability as a function of applied voltage were fitted to an inverse-exponential function, suggesting a plateau effect. Staining of VE-cadherin showed specific changes in protein expression. The results indicate that low PEFs can transiently disrupt the BBB by affecting the paracellular route, although the mechanism remains unclear.

Tumor angiogenesis: causes, consequences, challenges and opportunities

Tumor vascularization occurs through several distinct biological processes, which not only vary between tumor type and anatomic location, but also occur simultaneously within the same cancer tissue. These processes are orchestrated by a range of secreted factors and signaling pathways and can involve participation of non-endothelial cells, such as progenitors or cancer stem cells. Anti-angiogenic therapies using either antibodies or tyrosine kinase inhibitors have been approved to treat several types of cancer. However, the benefit of treatment has so far been modest, some patients not responding at all and others acquiring resistance. It is becoming increasingly clear that blocking tumors from accessing the circulation is not an easy task to accomplish. Tumor vessel functionality and gene expression often differ vastly when comparing different cancer subtypes, and vessel phenotype can be markedly heterogeneous within a single tumor. Here, we summarize the current understanding of cellular and molecular mechanisms involved in tumor angiogenesis and discuss challenges and opportunities associated with vascular targeting.