Approaches to transport therapeutic drugs across the blood–brain barrier to treat brain diseases

Overcoming the Blood-Brain Barrier: The Role of Nanomaterials in Treating Neurological Diseases

Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood-brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial-based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease-targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial-mediated treatment of neurological diseases.

Magnetic Resonance-Guided Focused Ultrasound in Neurosurgery: Taking Lessons from the Past to Inform the Future

Magnetic resonance-guided focused ultrasound (MRgFUS) is a new emerging neurosurgical procedure applied in a wide range of clinical fields. It can generate high-intensity energy at the focal zone in deep body areas without requiring incision of soft tissues. Although the effectiveness of the focused ultrasound technique had not been recognized because of the skull being a main barrier in the transmission of acoustic energy, the development of hemispheric distribution of ultrasound transducer phased arrays has solved this issue and enabled the performance of true transcranial procedures. Advanced imaging technologies such as magnetic resonance thermometry could enhance the safety of MRgFUS. The current clinical applications of MRgFUS in neurosurgery involve stereotactic ablative treatments for patients with essential tremor, Parkinson's disease, obsessive-compulsive disorder, major depressive disorder, or neuropathic pain. Other potential treatment candidates being examined in ongoing clinical trials include brain tumors, Alzheimer's disease, and epilepsy, based on MRgFUS abilities of thermal ablation and opening the blood-brain barrier. With the development of ultrasound technology to overcome the limitations, MRgFUS is gradually expanding the therapeutic field for intractable neurological disorders and serving as a trail for a promising future in noninvasive and safe neurosurgical care.

How to make P-glycoprotein (ABCB1, MDR1) harbor mutations and measure its expression and activity in cell cultures?

Several polymorphisms have been identified in ABCB1, the gene encoding for the P-glycoprotein. This transporter alters the pharmacokinetics or effectiveness of drugs by excreting them from cells where it is expressed (e.g., blood-brain barrier, intestine or tumors). No consensus has been reached regarding the functional consequences of these polymorphisms in the transporter's function. The aim of this review was to describe a methodology that allows the assessment of P-gp function when harboring polymorphisms. We describe how to obtain cell lines with high expression levels of the transporter with polymorphisms and several tactics to measure its expression and activity. This methodology may help elucidate the contribution of polymorphisms in ABCB1 to drug pharmacokinetics, effectiveness and safety or to cancer chemotherapy failure.

Efflux Pump Substrates Shuttled to Cytosolic or Vesicular Compartments Exhibit Different Permeability in a Quantitative Human Blood-Brain Barrier Model

Representative in vitro blood-brain barrier (BBB) models can support the development of strategies to efficiently deliver therapeutic drugs to the brain by aiding the characterization of their internalization, trafficking, and subsequent transport across the BBB. A collagen type I (COL1) hydrogel-based in vitro BBB model was developed to enable the simultaneous characterization of drug transport and intracellular processing using confocal microscopy, in a way that traditional insert-based in vitro BBB models cannot. Human induced pluripotent stem cells (hiPSCs) were differentiated into cells that exhibited a BBB-like phenotype on COL1 hydrogels, which included the expression of key BBB-specific proteins and low permeability of representative small and large molecule therapeutics. Furthermore, the BBB phenotype observed on the COL1 hydrogel was similar to that previously reported on porous inserts. The intracellular visualization of two small molecule efflux pump substrates within the hiPSC-derived BBB-like cells demonstrated a difference in cytosolic and vesicular accumulation, which complemented permeability measurements demonstrating a difference in transport rate. The easy-to-construct COL1-based hiPSC-derived BBB model presented here is the first in vitro two-dimensional BBB experimental system that enables the simultaneous quantification of cellular permeability and visualization of intracellular processes by utilizing confocal microscopy, which can provide insights regarding the relationship between transport and intracellular trafficking of therapeutic drugs.

Pharmaceutical Approaches to HIV Treatment and Prevention

Human immunodeficiency virus (HIV) infection continues to pose a major infectious disease threat worldwide. It is characterized by the depletion of CD4+ T cells, persistent immune activation, and increased susceptibility to secondary infections. Advances in the development of antiretroviral drugs and combination antiretroviral therapy have resulted in a remarkable reduction in HIV-associated morbidity and mortality. Antiretroviral therapy (ART) leads to effective suppression of HIV replication with partial recovery of host immune system and has successfully transformed HIV infection from a fatal disease to a chronic condition. Additionally, antiretroviral drugs have shown promise for prevention in HIV pre-exposure prophylaxis and treatment as prevention. However, ART is unable to cure HIV. Other limitations include drug-drug interactions, drug resistance, cytotoxic side effects, cost, and adherence. Alternative treatment options are being investigated to overcome these challenges including discovery of new molecules with increased anti-viral activity and development of easily administrable drug formulations. In light of the difficulties associated with current HIV treatment measures, and in the continuing absence of a cure, the prevention of new infections has also arisen as a prominent goal among efforts to curtail the worldwide HIV pandemic. In this review, the authors summarize currently available anti-HIV drugs and their combinations for treatment, new molecules under clinical development and prevention methods, and discuss drug delivery formats as well as associated challenges and alternative approaches for the future.

Organ-on-Chip Devices Toward Applications in Drug Development and Screening

As a necessary pathway to man-made organs, organ-on-chips (OOC), which simulate the activities, mechanics, and physiological responses of real organs, have attracted plenty of attention over the past decade. As the maturity of three-dimensional (3D) cell-culture models and microfluidics advances, the study of OOCs has made significant progress. This review article provides a comprehensive overview and classification of OOC microfluidics. Specifically, the review focuses on OOC systems capable of being used in preclinical drug screening and development. Additionally, the review highlights the strengths and weaknesses of each OOC system toward the goal of improved drug development and screening. The various OOC systems investigated throughout the review include, blood vessel, lung, liver, and tumor systems and the potential benefits, which each provides to the growing challenge of high-throughput drug screening. Published OOC systems have been reviewed over the past decade (2007–2018) with focus given mainly to more recent advances and improvements within each organ system. Each OOC system has been reviewed on how closely and realistically it is able to mimic its physiological counterpart, the degree of information provided by the system toward the ultimate goal of drug development and screening, how easily each system would be able to transition to large scale high-throughput drug screening, and what further improvements to each system would help to improve the functionality, realistic nature of the platform, and throughput capacity. Finally, a summary is provided of where the broad field of OOCs appears to be headed in the near future along with suggestions on where future efforts should be focused for optimized performance of OOC systems in general.

Theranostic applications of nanoparticles in neurodegenerative disorders

The preeminent treatments for neurodegenerative disease are often unavailable due to the poor accessibility of therapeutic drugs. Moreover, the blood–brain barrier (BBB) effectively blocks the transfer of cells, particles and large molecules, ie, drugs, across the brain. The most important challenge in the treatment of neurodegenerative diseases is the development of targeted drug delivery system. Theranostic strategies are known to combine therapeutic and diagnostic capabilities together. The aim of this review was to record the response to treatment and thereby improve drug safety. Nanotechnology offers a platform for designing and developing theranostic agents that can be used as an efficient nano-carrier system. This is achieved by the manipulation of some of the properties of nanoparticles (NPs), thereby enabling the attachment of suitable drugs onto their surface. The results provide revolutionary treatments by stimulation and thus interaction with targeted sites to promote physiological response with minimum side effects. This review is a brief discussion of the administration of drugs across the brain and the advantages of using NPs as an effective theranostic platform in the treatment of Alzheimer’s, Parkinson’s, epilepsy and Huntington’s disease.

MRI and histological evaluation of pulsed focused ultrasound and microbubbles treatment effects in the brain

Magnetic resonance imaging (MRI)-guided pulsed focused ultrasound (pFUS) combined with microbubbles (MB) contrast agent infusion has been shown to transiently disrupt the blood-brain barrier (BBBD), increasing the delivery of neurotherapeutics to treat central nervous system (CNS) diseases. pFUS interaction with the intravascular MB results in acoustic cavitation forces passing through the neurovascular unit (NVU), inducing BBBD detected on contrast-enhanced MRI. Multiple pFUS+MB exposures in Alzheimer's disease (AD) models are being investigated as a method to clear amyloid plaques by activated microglia or infiltrating immune cells. Since it has been reported that pFUS+MB can induce a sterile inflammatory response (SIR) [1-5] in the rat, the goal of this study was to investigate the potential long-term effects of SIR in the brain following single and six weekly sonications by serial high-resolution MRI and pathology.

Methods: Female Sprague Dawley rats weighing 217±16.6 g prior to sonication received bromo-deoxyuridine (BrdU) to tag proliferating cells in the brain. pFUS was performed at 548 kHz, ultrasound burst 10 ms and initial peak negative pressure of 0.3 MPa (in water) for 120 s coupled with a slow infusion of ~460 µL/kg (5-8×10⁷ MB) that started 30 s before and 30 s during sonication. Nine 2 mm focal regions in the left cortex and four regions over the right hippocampus were treated with pFUS+MB. Serial high-resolution brain MRIs at 3 T and 9.4 T were obtained following a single or during the course of six weekly pFUS+MB resulting in BBBD in the left cortex and the right hippocampus. Animals were monitored over 7 to 13 weeks and imaging results were compared to histology.

Results: Fewer than half of the rats receiving a single pFUS+MB exposure displayed hypointense voxels on T2*-weighted (w) MRI at week 7 or 13 in the cortex or hippocampus without differences compared to the contralateral side on histograms of T2* maps. Single sonicated rats had evidence of limited microglia activation on pathology compared to the contralateral hemisphere. Six weekly pFUS+MB treatments resulted in pathological changes on T2*w images with multiple hypointense regions, cortical atrophy, along with 50% of rats having persistent BBBD and astrogliosis by MRI. Pathologic analysis of the multiple sonicated animals demonstrated the presence of metallophagocytic Prussian blue-positive cells in the parenchyma with significantly (p<0.05) increased areas of activated astrocytes and microglia, and high numbers of systemic infiltrating CD68⁺ macrophages along with BrdU⁺ cells compared to contralateral brain. In addition, multiple treatments caused an increase in the number of hyperphosphorylated Tau (pTau)-positive neurons containing neurofibrillary tangles (NFT) in the sonicated cortex but not in the hippocampus when compared to contralateral brain, which was confirmed by Western blot (WB) (p<0.04).

Conclusions: The repeated SIR following multiple pFUS+MB treatments could contribute to changes on MR imaging including persistent BBBD, cortical atrophy, and hypointense voxels on T2w and T2*w images consistent with pathological injury. Moreover, areas of astrogliosis, activated microglia, along with higher numbers of CD68⁺ infiltrating macrophages and BrdU⁺ cells were detected in multiple sonicated areas of the cortex and hippocampus. Elevations in pTau and NFT were detected in neurons of the multiple sonicated cortex. Minimal changes on MRI and histology were observed in single pFUS+MB-treated rats at 7 and 13 weeks post sonication. In comparison, animals that received 6 weekly sonications demonstrated evidence on MRI and histology of vascular damage, inflammation and neurodegeneration associated with the NVU commonly observed in trauma. Further investigation is recommended of the long-term effects of multiple pFUS+MB in clinical trials.

Theranostics based on AIEgens

The utilization of luminogens with aggregation-induced emission (AIE) characteristics has recently been developed at a tremendous pace in the area of theranostics, mainly because AIE luminogens (AIEgens) hold various distinct advantages, such as good biocompatibility, excellent fluorescence properties, simple preparation and modification, perfect size of nano-aggregation for enhanced permeability and retention effect, promoted efficiencies of photodynamic and photothermal therapies, efficient photoacoustic imaging, and ready constructions of multimodal imaging and therapy. Significant breakthroughs and developments of theranostics based on AIEgens have been achieved in the past few years, and great progress has been witnessed in many theranostic modalities, indicating that AIEgens remarkably complement conventional theranostic materials and promote the development of theranostics. This review provides theoretical insights into the advantages of AIEgens in theranostics, and systematically summarizes the basic concepts, seminal studies, recent trends and perspectives in theranostics based on AIEgens. We believe that AIEgens would be promising multifunctional theranostic platforms in clinical fields and facilitate significant advancements in this research-active area.

Gold nanoparticles: A plausible tool to combat neurological bacterial infections in humans

Management of bacterial infections of central nervous system is a major challenge for the scientists all over the world. Despite the development of various potential drugs, the issue of central nervous system infections persists in the society. The main constraint is the delivery of drugs across the blood brain barrier and only a few drugs after meeting the stringent criteria could cross the blood brain barrier. On the other hand, certain bacterial pathogens could easily enter the brain by using several factors and mechanisms by crossing the blood brain barriers. Interestingly, in the recent past, gold nanoparticles have shown immense potential to overcome the issues associated with the treatment of central nervous system infections, especially due to their inherent ability to cross the blood brain barrier. Initially, the present review summarized the recent updates on the pathogenesis and factors involved in neurological bacterial infections, including the mechanism used by bacterial pathogens to cross the blood brain barriers. Thereafter, the emphasis of the review was on providing current information on gold nanoparticles pertinent to their applicability for the treatment of neurological infections. After discussing the background of neurological bacterial infections, the characteristic features, antibacterial properties, mechanisms of antibacterial action and ability to cross the blood brain barrier of gold nanoparticles have been summarized. Some of the features of gold nanoparticles that make them an ideal candidate for brain delivery are biocompatibity, stability, ability to get synthesized in different sizes with facile methods, surface affinity towards various functional groups, spontaneous crossing of blood brain barrier without applying any external field and most importantly, easy non-invasive tracing by CT imaging. The current updates on the development of gold nanoparticles based therapeutic strategies for the prevention and treatment of central nervous system infections have been discussed in the present study. However, further investigation would be required to translate these preclinical outcomes into clinical applications. Nevertheless, we could safely state that the information gathered and discussed in the present review would benefit the scientists working in the field of neuro-nanotechnology.

Why Are the Majority of Active Compounds in the CNS Domain Natural Products? A Critical Analysis

Small-molecule natural products (NPs) have a long and successful track record of providing first-in-class drugs and pharmacophore (scaffolds) in all therapeutic areas, serving as a bridge between modern and traditional medicine. This trajectory has been remarkably successful in three key areas of modern therapeutics: cancers, infections, and CNS diseases. Beginning with the discovery of morphine 200 years ago, natural products have remained the primary source of new drugs/scaffolds for CNS diseases. In this perspective, we address the question: why are the majority of active compounds in the CNS domain natural products? Our analysis indicates that ∼84% approved drugs for CNS diseases are NPs or NP-inspired, and interestingly, 20 natural products provided more than 400 clinically approved CNS drugs. We have discussed unique physicochemical properties of NPs and NP-inspired vis-à-vis synthetic drugs, isoform selectivity, and evolutionary relationship, providing a rationale for increasing focus on natural product driven discovery for next-generation drugs for neurodegenerative diseases.

Recent Advances in the Therapeutic and Diagnostic Use of Liposomes and Carbon Nanomaterials in Ischemic Stroke

The complexity of the central nervous system (CNS), its limited self-repairing capacity and the ineffective delivery of most CNS drugs to the brain contribute to the irreversible and progressive nature of many neurological diseases and also the severity of the outcome. Therefore, neurological disorders belong to the group of pathologies with the greatest need of new technologies for diagnostics and therapeutics. In this scenario, nanotechnology has emerged with innovative and promising biomaterials and tools. This review focuses on ischemic stroke, being one of the major causes of death and serious long-term disabilities worldwide, and the recent advances in the study of liposomes and carbon nanomaterials for therapeutic and diagnostic purposes. Ischemic stroke occurs when blood flow to the brain is insufficient to meet metabolic demand, leading to a cascade of physiopathological events in the CNS including local blood brain barrier (BBB) disruption. However, to date, the only treatment approved by the FDA for this pathology is based on the potentially toxic tissue plasminogen activator. The techniques currently available for diagnosis of stroke also lack sensitivity. Liposomes and carbon nanomaterials were selected for comparison in this review, because of their very distinct characteristics and ranges of applications. Liposomes represent a biomimetic system, with composition, structural organization and properties very similar to biological membranes. On the other hand, carbon nanomaterials, which are not naturally encountered in the human body, exhibit new modes of interaction with biological molecules and systems, resulting in unique pharmacological properties. In the last years, several neuroprotective agents have been evaluated under the encapsulated form in liposomes, in experimental models of stroke. Effective drug delivery to the brain and neuroprotection were achieved using stealth liposomes bearing targeting ligands onto their surface for brain endothelial cells and ischemic tissues receptors. Carbon nanomaterials including nanotubes, fullerenes and graphene, started to be investigated and potential applications for therapy, biosensing and imaging have been identified based on their antioxidant action, their intrinsic photoluminescence, their ability to cross the BBB, transitorily decrease the BBB paracellular tightness, carry oligonucleotides and cells and induce cell differentiation. The potential future developments in the field are finally discussed.

Best practices for the use of intracerebroventricular drug delivery devices

For decades, intracerebroventricular (ICV), or intraventricular, devices have been used in the treatment of a broad range of pediatric and adult central nervous system (CNS) disorders. Due to the limited permeability of the blood brain barrier, diseases with CNS involvement may require direct administration of drugs into the brain to achieve full therapeutic effect. A recent comprehensive literature review on the clinical use and complications of ICV drug delivery revealed that device-associated complication rates are variable, and may be as high as 33% for non-infectious complications and 27% for infectious complications. The variability in reported safety outcomes may be driven by a lack of consensus on best practices of device use. Numerous studies have demonstrated that employing strict aseptic techniques and following stringent protocols can dramatically reduce complications. Key practices to be considered in facilitating the safe, long-term use of these devices are presented.

Drug delivery challenges and future of chemotherapeutic nanomedicine for glioblastoma treatment

Glioblastoma (GBM) is one of the most aggressive and deadliest central nervous system tumors, and the current standard treatment is surgery followed by radiotherapy with concurrent chemotherapy. Nevertheless, the survival period is notably low. Although ample research has been performed to develop an effective therapeutic strategy for treating GBM, the success of extending patients' survival period and quality of life is limited. This review focuses on the strategies developed to address the challenges associated with drug delivery in GBM, particularly nanomedicine. The first part describes major obstacles to the development of effective GBM treatment strategies. The second part focuses on the conventional chemotherapeutic nanomedicine strategies, their limitations and the novel and advanced strategies of nanomedicine, which could be promising for GBM treatment. We also highlighted the prominence of nanomedicine clinical translation. The near future looks bright following the beginning of clinical translation of nanochemotherapy for GBM.

Importance of integrating nanotechnology with pharmacology and physiology for innovative drug delivery and therapy - an illustration with firsthand examples

Nanotechnology has been applied extensively in drug delivery to improve the therapeutic outcomes of various diseases. Tremendous efforts have been focused on the development of novel nanoparticles and delineation of the physicochemical properties of nanoparticles in relation to their biological fate and functions. However, in the design and evaluation of these nanotechnology-based drug delivery systems, the pharmacology of delivered drugs and the (patho-)physiology of the host have received less attention. In this review, we discuss important pharmacological mechanisms, physiological characteristics, and pathological factors that have been integrated into the design of nanotechnology-enabled drug delivery systems and therapies. Firsthand examples are presented to illustrate the principles and advantages of such integrative design strategies for cancer treatment by exploiting 1) intracellular synergistic interactions of drug-drug and drug-nanomaterial combinations to overcome multidrug-resistant cancer, 2) the blood flow direction of the circulatory system to maximize drug delivery to the tumor neovasculature and cells overexpressing integrin receptors for lung metastases, 3) endogenous lipoproteins to decorate nanocarriers and transport them across the blood-brain barrier for brain metastases, and 4) distinct pathological factors in the tumor microenvironment to develop pH- and oxidative stress-responsive hybrid manganese dioxide nanoparticles for enhanced radiotherapy. Regarding the application in diabetes management, a nanotechnology-enabled closed-loop insulin delivery system was devised to provide dynamic insulin release at a physiologically relevant time scale and glucose levels. These examples, together with other research results, suggest that utilization of the interplay of pharmacology, (patho-)physiology and nanotechnology is a facile approach to develop innovative drug delivery systems and therapies with high efficiency and translational potential.

Understanding patterns of brain metastasis in breast cancer and designing rational therapeutic strategies

One of the most feared sequelae after a diagnosis of advanced breast cancer is development of metastases to the brain as this diagnosis can affect physical function, independence, relationships, quality of life, personality, and ultimately one's sense of self. The propensity to develop breast cancer brain metastases (BCBMs) varies by subtype, occurring in up to one half of those with triple negative breast cancer (TNBC), approximately a third of HER+ breast cancers and 14% in hormone positive disease. Median survival after BCBM diagnosis can be as short as 5 months in TNBC and 10-18 months in the other subtypes. Here, we review the biology of BCBMs and how it informs the rational design of new therapeutic approaches and agents. We discuss application of novel targeted and immunotherapies by breast cancer subtype. It is noteworthy that there are no U.S. Food and Drug Administration (FDA)-approved treatments specifically for BCBMs currently. Nevertheless, there are legitimate grounds for hope as patients with BCBMs are now being included in clinical trials of systemic therapies and a better understanding of the biology and genetic underpinning of BCBMs is driving an increased range of options for patients.

Interaction Studies Between Cyclic Peptide ADT-C3 (Ac-CADTPC-NH2) with E-Cadherin Protein using the Molecular Docking Method Simulated on 120ns

The treatment of diseases that attack the brain is very difficult, because the delivery of drug molecules to the brain is often hindered by the blood-brain barrier (BBB). So that the drug delivery is not right on the target cell. Thus, was developed a method in modulation of intercellular junctions using ADTC3 cadherin peptide, Where the cadherin peptide is derived from the cadherin sequence itself. The method used in this research is molecular dynamics (DM) and molecular docking. In this study have been evaluated some peptide conformation in modulating intercellular junction. The results show that cyclic peptide ADT-C3 (Ac-CADTPC-NH2) was conducted DM for 120 ns (120000 ps), which has considerable activity in modulating intercellular junctions with binding energies of -33.10 kJ.mol-1 and Ki of 1.58 μM at the 79187 ps conformation. The binding site on residues Asp1, Trp2, Ile4, Lys25, Ser26, Asn27, Met92 in the adhesion arm-acceptor pocket region.

A novel peptide ligand RAP12 of LRP1 for glioma targeted drug delivery

The receptor associated protein (RAP) is a 39 kDa chaperone protein, binding tightly to low-density lipoprotein receptor-related protein-1 (LRP1) that is overexpressed in glioma, tumor neovasculature, vasculogenic mimicry (VM), the blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB). Herein, we miniaturized the RAP protein into a short peptide RAP12 (EAKIEKHNHYQK) aiding by computer-aided peptide design technique. RAP12 contained the essential lysines at the positions 253 and 256. The binding affinity of RAP12 to LRP1 was theoretically and experimentally evaluated. In cellular level, RAP12 could effectively internalize into U87, HUVEC and bEnd.3 cells. When modified on the surface of PEG-PLA micelles (RAP12-PEG-PLA), RAP12 could effectively facilitate the penetration of micelles through the BBB/BBTB in vitro/vivo. Paclitaxel-loaded RAP12-PEG-PLA could remarkably inhibit the growth of glioma cells and the formation of tumor neovasculature and VM, significantly prolong the median survival time of nude mice bearing intracranial glioma in comparison to model mice treated with plain micelles or Taxol. These results suggested that the RAP12 held the potential for multifunctional glioma-targeted drug delivery.

Chimeric Small Antibody Fragments as Strategy to Deliver Therapeutic Payloads

Antibody-drug conjugates (ADCs) represent an innovative class of biopharmaceuticals, which aim at achieving a site-specific delivery of cytotoxic agents to the target cell. The use of ADCs represents a promising strategy to overcome the disadvantages of conventional pharmacotherapy of cancer or neurological diseases, based on cytotoxic or immunomodulatory agents. ADCs consist of monoclonal antibodies attached to biologically active drugs by means of cleavable chemical linkers. Advances in technologies for the coupling of antibodies to cytotoxic drugs promise to deliver greater control of drug pharmacokinetic properties and to significantly improve pharmacodelivery applications, minimizing exposure of healthy tissue. The clinical success of brentuximab vedotin and trastuzumab emtansine has led to an extensive expansion of the clinical ADC pipeline. Although the concept of an ADC seems simple, designing a successful ADC is complex and requires careful selection of the receptor antigen, antibody, linker, and payload. In this review, we explore insights in the antibody and antigen requirements needed for optimal payload delivery and support the development of novel and improved ADCs for the treatment of cancer and neurological diseases.

Enhancement of drug permeability across blood brain barrier using nanoparticles in meningitis

The central nervous system, one of the most delicate microenvironments of the body, is protected by the blood-brain barrier regulating its homeostasis. Blood-brain barrier is a highly complex structure that tightly regulates the movement of ions of a limited number of small molecules and of an even more restricted number of macromolecules from the blood to the brain, protecting it from injuries and diseases. However, the blood-brain barrier also significantly precludes the delivery of drugs to the brain, thus, preventing the therapy of a number of neurological disorders. As a consequence, several strategies are currently being sought after to enhance the delivery of drugs across the blood-brain barrier. Within this review a brief description of the structural and physiological features of the barriers and the recently born strategy of brain drug delivery based on the use of nanoparticles are described. Finally, the future technological approaches are described. The strong efforts to allow the translation from preclinical to concrete clinical applications are worth the economic investments.

Surface-Modified Nanocarriers for Nose-to-Brain Delivery: From Bioadhesion to Targeting

In the field of nasal drug delivery, nose-to-brain delivery is among the most fascinating applications, directly targeting the central nervous system, bypassing the blood brain barrier. Its benefits include dose lowering and direct brain distribution of potent drugs, ultimately reducing systemic side effects. Recently, nasal administration of insulin showed promising results in clinical trials for the treatment of Alzheimer’s disease. Nanomedicines could further contribute to making nose-to-brain delivery a reality. While not disregarding the need for devices enabling a formulation deposition in the nose’s upper part, surface modification of nanomedicines appears the key strategy to optimize drug delivery from the nasal cavity to the brain. In this review, nanomedicine delivery based on particle engineering exploiting surface electrostatic charges, mucoadhesive polymers, or chemical moieties targeting the nasal epithelium will be discussed and critically evaluated in relation to nose-to-brain delivery.

Localized delivery of curcumin into brain with polysorbate 80-modified cerasomes by ultrasound-targeted microbubble destruction for improved Parkinson's disease therapy

Rationale: Treatment for Parkinson's disease (PD) is challenged by the presence of the blood-brain barrier (BBB) that significantly limits the effective drug concentration in a patient's brain for therapeutic response throughout various stages of PD. Curcumin holds the potential for α-synuclein clearance to treat PD; however, its applications are still limited due to its low bioavailability and poor permeability through the BBB in a free form.

Methods: Herein, this paper fabricated curcumin-loaded polysorbate 80-modified cerasome (CPC) nanoparticles (NPs) with a mean diameter of ~110 nm for enhancing the localized curcumin delivery into the targeted brain nuclei via effective BBB opening in combination with ultrasound-targeted microbubble destruction (UTMD).

Results: The liposomal nanohybrid cerasome exhibited superior stability towards PS 80 surfactant solubilization and longer circulation lifetime (t_1/2 = 6.22 h), much longer than free curcumin (t_1/2 = 0.76 h). The permeation was found to be 1.7-fold higher than that of CPC treatment only at 6 h after the systemic administration of CPC NPs. Notably, motor behaviors, dopamine (DA) level and tyrosine hydroxylase (TH) expression all returned to normal, thanks to α-synuclein (AS) removal mediated by efficient curcumin delivery to the striatum. Most importantly, the animal experiment demonstrated that the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice had notably improved behavior disorder and dopamine depletion during two-week post-observation after treatment with CPC NPs (15 mg curcumin/kg) coupled with UTMD.

Conclusion: This novel CPC-UTMD formulation approach could be an effective, safe and amenable choice with higher therapeutic relevance and fewer unwanted complications than conventional chemotherapeutics delivery systems for PD treatment in the near future.

A systems-level approach for investigating organophosphorus pesticide toxicity

The full understanding of the single and joint toxicity of a variety of organophosphorus (OP) pesticides is still unavailable, because of the extreme complex mechanism of action. This study established a systems-level approach based on systems toxicology to investigate OP pesticide toxicity by incorporating ADME/T properties, protein prediction, and network and pathway analysis. The results showed that most OP pesticides are highly toxic according to the ADME/T parameters, and can interact with significant receptor proteins to cooperatively lead to various diseases by the established OP pesticide -protein and protein-disease networks. Furthermore, the studies that multiple OP pesticides potentially act on the same receptor proteins and/or the functionally diverse proteins explained that multiple OP pesticides could mutually enhance toxicological synergy or additive on a molecular/systematic level. To the end, the integrated pathways revealed the mechanism of toxicity of the interaction of OP pesticides and elucidated the pathogenesis induced by OP pesticides. This study demonstrates a systems-level approach for investigating OP pesticide toxicity that can be further applied to risk assessments of various toxins, which is of significant interest to food security and environmental protection.

Non-contrast MR imaging of blood-brain barrier permeability to water

PURPOSE

Many brain diseases are associated with an alteration in blood-brain barrier (BBB) and its permeability. Current methods using contrast agent are primarily sensitive to major leakage of BBB to macromolecules, but may not detect subtle changes in BBB permeability. The present study aims to develop a novel non-contrast MRI technique for the assessment of BBB permeability to water.

METHODS

The central principle is that by measuring arterially labeled blood spins that are drained into cerebral veins, water extraction fraction (E) and permeability-surface-area product (PS) of BBB can be determined. Four studies were performed. We first demonstrated the proof-of-principle using conventional ASL with very long post-labeling delays (PLD). Next, a new sequence, dubbed water-extraction-with-phase-contrast-arterial-spin-tagging (WEPCAST), and its Look-Locker (LL) version were developed. Finally, we demonstrated that the sensitivity of the technique can be significantly enhanced by acquiring the data under mild hypercapnia.

RESULTS

By combining a strong background suppression with long PLDs (2500-4500 ms), ASL spins were reliably detected in the superior sagittal sinus (SSS), demonstrating the feasibility of measuring this signal. The WEPCAST sequence eliminated partial voluming effects of tissue perfusion and allowed quantitative estimation of E = 95.5 ± 1.1% and PS = 188.9 ± 13.4 mL/100 g/min, which were in good agreement with literature reports. LL-WEPCAST sequence shortened the scan time from 19 min to 5 min while providing results consistent with multiple single-PLD acquisitions. Mild hypercapnia increased SNR by 78 ± 25% without causing a discomfort in participants.

CONCLUSION

A new non-contrast technique for the assessment of global BBB permeability was developed, which may have important clinical applications.

Development of a sensitive and quantitative capillary LC-UV method to study the uptake of pharmaceuticals in zebrafish brain

The present study explores the potential of 10-day-old zebrafish (Danio rerio) as a predictive blood-brain-barrier model using a set of 7 pharmaceutical agents. For this purpose, zebrafish were incubated with each of these 7 drugs separately via the route of immersion and the concentration reaching the brain was determined by applying a brain extraction procedure allowing isolation of the intact brain from the head of the zebrafish larvae. Sample analysis was performed utilizing capillary ultra-high performance liquid chromatography (cap-UHPLC) on a Pepmap RSLC C18 capillary column (150 mm × 300 μm, d_p = 2 μm) coupled to a variable wavelength UV detector. Gradient separation was performed in 28 min at a flow rate of 5 μL/min and the optimal injection volume was determined to be 1 μL. The brain extraction procedure was established for the zebrafish strain TG898 exhibiting red fluorescence of the brain, allowing control of the integrity of the extracted parts. Quantitative experiments carried out on pooled samples of six zebrafish (n = 6) demonstrated the selective semipermeable nature of the blood-brain barrier after incubating the zebrafish at the maximum tolerated concentration for the investigated pharmaceuticals. The obtained brain-to-trunk ratios ranged between 0.3 for the most excluded compound and 1.2 for the pharmaceutical agent being most accumulated in the brain of the fish. Graphical abstract Workflow of brain extraction to study the uptake of pharmaceuticals in the brain of zebrafish larvae.

Blood-brain barrier shuttle peptides: an emerging paradigm for brain delivery

Brain delivery is one of the major challenges in drug development because of the high number of patients suffering from neural diseases and the low efficiency of the treatments available. Although the blood-brain barrier (BBB) prevents most drugs from reaching their targets, molecular vectors - known as BBB shuttles - offer great promise to safely overcome this formidable obstacle. In recent years, peptide shuttles have received growing attention because of their lower cost, reduced immunogenicity, and higher chemical versatility than traditional Trojan horse antibodies and other proteins.

Synthetic low-density lipoprotein (sLDL) selectively delivers paclitaxel to tumor with low systemic toxicity

Low density lipoprotein (LDL), which is a principal carrier for the delivery of cholesterol, has been used as a great candidate for the delivery of drugs to tumor based on the great requirements for cholesterol of many cancer cells. Mimicking the structure and composition of LDL, we designed a synthetic low-density lipoprotein (sLDL) to encapsulate paclitaxel-alpha linolenic acid (PALA) for tumor therapy. The PALA loaded sLDL (PALA-sLDL) and PALA-loaded microemulsion (PALA-ME, without the binding domain for LDLR) displayed uniform sizes with high drug loading efficiency (> 90%). In vitro studies demonstrated PALA-sLDL exhibited enhanced cellular uptake capacity and better cytotoxicity to LDLR over-expressed U87 MG cells as compared to PALA-ME. The uptake mechanisms of PALA-sLDL were involved in a receptor mediated endocytosis and macropinocytosis. Furthermore, the in vivo biodistribution and tumor growth inhibition studies of PALA-sLDL were investigated in xenograft U87 MG tumor-bearing mice. The results showed that PALA-sLDL exhibited higher tumor accumulation than PALA-ME and superior tumor inhibition efficiency (72.1%) compared to Taxol^® (51.2%) and PALA-ME (58.8%) but with lower toxicity. These studies suggested that sLDL is potential to be used as a valuable carrier for the selective delivery of anticancer drugs to tumor with low systemic toxicity.

A review of potential applications of MR-guided focused ultrasound for targeting brain tumor therapy

Magnetic resonance–guided focused ultrasound (MRgFUS) has been used extensively to ablate brain tissue in movement disorders, such as essential tremor. At a lower energy, MRgFUS can disrupt the blood-brain barrier (BBB) to allow passage of drugs. This focal disruption of the BBB can target systemic medications to specific portions of the brain, such as for brain tumors. Current methods to bypass the BBB are invasive, as the BBB is relatively impermeable to systemically delivered antineoplastic agents. Multiple healthy and brain tumor animal models have suggested that MRgFUS disrupts the BBB and focally increases the concentration of systemically delivered antitumor chemotherapy, immunotherapy, and gene therapy. In animal tumor models, combining MRgFUS with systemic drug delivery increases median survival times and delays tumor progression. Liposomes, modified microbubbles, and magnetic nanoparticles, combined with MRgFUS, more effectively deliver chemotherapy to brain tumors. MRgFUS has great potential to enhance brain tumor drug delivery, while limiting treatment toxicity to the healthy brain.

A novel human induced pluripotent stem cell blood-brain barrier model: Applicability to study antibody-triggered receptor-mediated transcytosis

We have developed a renewable, scalable and transgene free human blood-brain barrier model, composed of brain endothelial cells (BECs), generated from human amniotic fluid derived induced pluripotent stem cells (AF-iPSC), which can also give rise to syngeneic neural cells of the neurovascular unit. These AF-iPSC-derived BECs (i-BEC) exhibited high transendothelial electrical resistance (up to 1500 Ω cm²) inducible by astrocyte-derived molecular cues and retinoic acid treatment, polarized expression of functional efflux transporters and receptor mediated transcytosis triggered by antibodies against specific receptors. In vitro human BBB models enable pre-clinical screening of central nervous system (CNS)-targeting drugs and are of particular importance for assessing species-specific/selective transport mechanisms. This i-BEC human BBB model discriminates species-selective antibody- mediated transcytosis mechanisms, is predictive of in vivo CNS exposure of rodent cross-reactive antibodies and can be implemented into pre-clinical CNS drug discovery and development processes.

Phosphatidylserine-targeted liposome for enhanced glioma-selective imaging

Phosphatidylserine (PS), which is normally intracellular, becomes exposed on the outer surface of viable endothelial cells (ECs) of tumor vasculature. Utilizing a PS-targeting antibody, we have recently established a PS-targeted liposomal (PS-L) nanoplatform that has demonstrated to be highly tumor-selective. Because of the vascular lumen-exposed PS that is immediately accessible without a need to penetrate the intact blood brain barrier (BBB), we hypothesize that the systemically administered PS-L binds specifically to tumor vascular ECs, becomes subsequently internalized into the cells and then enables its cargos to be efficiently delivered to glioma parenchyma. To test this, we exploited the dual MRI/optical imaging contrast agents-loaded PS-L and injected it intravenously into mice bearing intracranial U87 glioma. At 24 h, both in vivo optical imaging and MRI depicted enhanced tumor contrast, distinct from the surrounding normal brain. Intriguingly, longitudinal MRI revealed temporal and spatial intratumoral distribution of the PS-L by following MRI contrast changes, which appeared punctate in tumor periphery at an earlier time point (4 h), but became clustering and disseminated throughout the tumor at 24 h post injection. Importantly, glioma-targeting specificity of the PS-L was antigen specific, since a control probe of irrelevant specificity showed minimal accumulation in the glioma. Together, these results indicate that the PS-L nanoplatform enables the enhanced, glioma-targeted delivery of imaging contrast agents by crossing the tumor BBB efficiently, which may also serve as a useful nanoplatform for anti-glioma drugs.

Transport Across the Blood-Brain Barrier

The blood-brain barrier (BBB) is a dynamic barrier essential for maintaining the microenvironment of the brain. Although the special anatomical features of the BBB determine its protective role for the central nervous system (CNS) from blood-borne neurotoxins, however, the BBB extremely limits the therapeutic efficacy of drugs into the CNS, which greatly hinders the treatment of major brain diseases. This chapter summarized the unique structures of the BBB; described a variety of in vivo and in vitro experimental methods for determining the transport properties of the BBB and the permeability of the BBB to water, ions, and solutes including nutrients, therapeutic agents, and drug carriers; and presented recently developed mathematical models which quantitatively correlate the anatomical structures of the BBB with its barrier functions. Recent findings for modulation of the BBB permeability by chemical and physical stimuli were described. Finally, drug delivery strategies through specific trans-BBB routes were discussed.

GABA-containing liposomes: neuroscience applications and translational perspectives for targeting neurological diseases

There are multiple challenges for neuropharmacology in the future. Undoubtedly, one of the greatest challenges is the development of strategies for pharmacological targeting of specific brain regions for treatment of diseases. GABA is the main inhibitory neurotransmitter in the central nervous system, and dysfunction of GABAergic mechanisms is associated with different neurological conditions. Liposomes are lipid vesicles that are able to encapsulate chemical compounds and are used for chronic drug delivery. This short review reports our experience with the development of liposomes for encapsulation and chronic delivery of GABA to sites within the brain. Directions for future research regarding the efficacy and practical use of GABA-containing liposomes for extended periods of time as well as understanding and targeting neurological conditions are discussed.

Blood-brain barrier disruption induced by diagnostic ultrasound combined with microbubbles in mice

Objective

To investigate the effects of the microbubble (MB) dose, mechanism index (MI) and sonication duration on blood-brain barrier (BBB) disruption induced by diagnostic ultrasound combined with MBs as well as to investigate the potential molecular mechanism.

Results

The extent of BBB disruption increased with MB dose, MI and sonication duration. A relatively larger extent of BBB disruption associated with minimal tissue damage was achieved by an appropriate MB dose and ultrasound exposure parameters with diagnostic ultrasound. Decreased expression of ZO-1, occludin and claudin-5 were correlated with disruption of the BBB, as confirmed by paracellular passage of the tracer lanthanum nitrate into the brain parenchyma after BBB disruption.

Conclusions

These findings indicated that this technique is a promising tool for promoting brain delivery of diagnostic and therapeutic agents in the diagnosis and treatment of brain diseases.

Methods

The extent of BBB disruption was qualitatively assessed by Evans blue (EB) staining and quantitatively analyzed by an EB extravasation measurement. A histological examination was performed to evaluate tissue damage. Expression of tight junction (TJ) related proteins ZO-1, occludin and claudin-5 was determined by western blotting analysis and immunohistofluorescence. Transmission electron microscopy was performed to observe ultrastructure changes of TJs after BBB disruption.

A peptide-based near-infrared fluorescence probe for dynamic monitoring senile plaques in Alzheimer's disease mouse model

In vivo monitoring neuropathological changes in Alzheimer's disease (AD) animal model is critical for drug development. Here, by integrating blood-brain barrier penetrable peptide, we have developed a peptide probe which based on angiopep-2. Angiopep-based probe exhibited high binding affinity to Aβ aggregates and labeled senile plaques in vivo. Remarkably, the in vivo near-infrared imaging data revealed that fluorescence signals of this probe were nearly 3-fold higher in the brains of 16-month-old APP/PS1 transgenic mice compared to C57 mice and exhibited linear correlation with the senile plaques load process in 4-, 8-, 16-month-old APP/PS1 transgenic mice. Moreover, senile plaques load was detected in vivo as early as 4 months of age that even at the very beginning of plaques developed in APP/PS1 transgenic mice. Taken together, this novel peptide-based probe achieved dynamic monitoring senile plaques in APP/PS1 transgenic mice and have been ready to use in drug development in AD mouse model.

Curcumin-lipoic acid conjugate as a promising anticancer agent on the surface of gold‑iron oxide nanocomposites: A pH-sensitive targeted drug delivery system for brain cancer theranostics

Brain tumor is a lethal, fast growing cancer and a difficult case for treatment. Receptor-mediated endocytosis has been recognized as one of the most effective methods for drug delivery to brain tissue by overcoming obstacles associated with conventional therapeutics. In this work, a targeted theranostic drug delivery system (DDS) was prepared based on gold‑iron oxide nanocomposites (Fe₃O₄@Au NCs). Lipoic acid-curcumin (LA-CUR) was synthesized and introduced as a novel anticancer drug, and glutathione (GSH) was exploited as the targeting ligand. Both LA-CUR and GSH were easily attached to Fe₃O₄@Au NCs via Au-S interaction. As a negatively charged nanocarrier, the prepared DDS showed relatively less protein adsorption. Accordingly, hemocompatibility assays (complement, platelet, and leucocyte activation) revealed its hemocompatible virtue, especially in respect of free LA-CUR. GSH functionalization led to 2-fold increase of cellular uptake in GSH receptor-positive astrocyte cells which could primarily indicate the probable ability of the DDS to bypass BBB. Cytotoxicity and apoptosis assays together showed the noticeably enhanced cytotoxicity of LA-CUR against cancerous U87MG cells (IC50=2.69μg/ml) in comparison with curcumin (IC50=21.31μg/ml); moreover, the DDS demonstrated relatively higher cytotoxicity against cancerous U87MG cells than normal astrocyte cells which was in accordance with pH sensitive mechanism of LA-CUR release. Besides, the results of in vitro magnetic resonance imaging (MRI) (relaxation rate (r₂)=80.73 (s^-1·mM^-1)) primarily revealed that the DDS can be applied as a negative MRI contrast agent. In sum, the prepared DDS appeared to be a promising candidate for brain cancer treatment and a favorable MRI contrast agent.

Heat shock protein-based therapy as a potential candidate for treating the sphingolipidoses

Lysosomal storage diseases (LSDs) often manifest with severe systemic and central nervous system (CNS) symptoms. The existing treatment options are limited and have no or only modest efficacy against neurological manifestations of disease. We demonstrate that recombinant human heat shock protein 70 (HSP70) improves the binding of several sphingolipid-degrading enzymes to their essential cofactor bis(monoacyl)glycerophosphate in vitro. HSP70 treatment reversed lysosomal pathology in primary fibroblasts from 14 patients with eight different LSDs. HSP70 penetrated effectively into murine tissues including the CNS and inhibited glycosphingolipid accumulation in murine models of Fabry disease (Gla(-/-)), Sandhoff disease (Hexb(-/-)), and Niemann-Pick disease type C (Npc1(-/-)) and attenuated a wide spectrum of disease-associated neurological symptoms in Hexb(-/-) and Npc1(-/-) mice. Oral administration of arimoclomol, a small-molecule coinducer of HSPs that is currently in clinical trials for Niemann-Pick disease type C (NPC), recapitulated the effects of recombinant human HSP70, suggesting that heat shock protein-based therapies merit clinical evaluation for treating LSDs.

Abuse liability assessment for biologic drugs - All molecules are not created equal

The development of novel drug candidates involves the thorough evaluation of potential efficacy and safety. To facilitate the safety assessment in light of global increases in prescription drug misuse/abuse, health authorities have developed guidance documents which provide a framework for evaluating the abuse liability of candidate therapeutics. The guidances do not distinguish between small molecules and biologics/biotherapeutics; however, there are key differences between these classes of therapeutics which are important drivers of concern for abuse. An analysis of these properties, including ability to distribute to the central nervous system, pharmacokinetic properties (e.g., half-life and metabolism), potential for off-target binding, and the physiochemical characteristics of biologic drug products suggests that the potential for abuse of a biologic is limited. Many marketed antibodies and recombinant proteins have been associated with adverse effects such as headache and dizziness. However, biologics have not historically engendered the rapid-onset psychoactive effects typically present for drugs of abuse, thus further underscoring their low risk for abuse potential. The factors to be taken into consideration before conducting nonclinical abuse liability studies with biologics are described herein; importantly, the aggregate assessment of these factors leads to the conclusion that abuse liability studies are unlikely to be necessary for this class of therapeutics.

Facile development of nanocomplex-in-nanoparticles for enhanced loading and selective delivery of doxorubicin to brain

Aim: Facile development of polysaccharides-based carrier system for efficient delivery of doxorubicin (DOX) to the brain. Methods: DOX was nanocomplexed with alginate (Alg) followed by incorporation into chitosan (Cs) nanomatrices. The resulting carriers were optimized to have a net positive charge improving their delivery across the blood–brain barrier. The optimum DOX-loaded nanosystem was targeted to brain tissue via loading into various nasal dosage forms. Results: The pH-dependent ionization of both DOX and Alg was found to have a significant effect on DOX entrapment efficiency which was improved from 4% at slightly acidic media to 85% using different pHs. The nasal dosage forms, especially the insert, delivered the loaded DOX mostly to the brain tissue with targeting efficiency reaching 480%. Conclusion: New intranasal carrier system was developed with efficient targeting of DOX to the brain. The carrier has potential to be used for delivery of other drugs acting on CNS.

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Aptamers and Glioblastoma: Their Potential Use for Imaging and Therapeutic Applications

Glioblastoma is a highly aggressive primary brain tumour, renowned for its infiltrative growth and varied genetic profiles. The current treatment options are insufficient, and their off-target effects greatly reduce patient quality of life. The major challenge in improving glioblastoma diagnosis and treatment involves the development of a targeted imaging and drug delivery platform, capable of circumventing the blood brain barrier and specifically targeting glioblastoma tumours. The unique properties of aptamers demonstrate their capability of bridging the gap to the development of successful diagnosis and treatment options, where antibodies have previously failed. Aptamers possess many characteristics that make them an ideal novel imaging and therapeutic agent for the treatment of glioblastoma and other brain malignancies, and are likely to provide patients with a better standard of care and improved quality of life. Their target sensitivity, selective nature, ease of modification and low immunogenicity make them an ideal drug-delivery platform. This review article summarises the aptamers previously generated against glioblastoma cells or its identified biomarkers, and their potential application in diagnosis and therapeutic targeting of glioblastoma tumours.

Rabies

Rabies is a life-threatening neglected tropical disease: tens of thousands of cases are reported annually in endemic countries (mainly in Africa and Asia), although the actual numbers are most likely underestimated. Rabies is a zoonotic disease that is caused by infection with viruses of the Lyssavirus genus, which are transmitted via the saliva of an infected animal. Dogs are the most important reservoir for rabies viruses, and dog bites account for >99% of human cases. The virus first infects peripheral motor neurons, and symptoms occur after the virus reaches the central nervous system. Once clinical disease develops, it is almost certainly fatal. Primary prevention involves dog vaccination campaigns to reduce the virus reservoir. If exposure occurs, timely post-exposure prophylaxis can prevent the progression to clinical disease and involves appropriate wound care, the administration of rabies immunoglobulin and vaccination. A multifaceted approach for human rabies eradication that involves government support, disease awareness, vaccination of at-risk human populations and, most importantly, dog rabies control is necessary to achieve the WHO goal of reducing the number of cases of dog-mediated human rabies to zero by 2030.

Transcellular vesicular transport in epithelial and endothelial cells: Challenges and opportunities

Vesicle-mediated transcellular transport or simply "transcytosis" is a cellular process used to shuttle macromolecules such as lipoproteins, antibodies, and albumin from one surface of a polarized cell to the other. This mechanism is in contrast to the transit of small molecules such as anions, cations and amino acids that occur via uptake, diffusion through the cytosol and release and is also distinct from paracellular leak between cells. Importantly, transcytosis has evolved as a process to selectively move macromolecules between 2 neighboring yet unique microenvironments within a multicellular organism. Examples include the movement of lipoproteins out of the circulatory system and into tissues and the delivery of immunoglobulins to mucosal surfaces. Regardless of whether the transport is conducted by endothelial or epithelial cells, the process often involves receptor-mediated uptake of a ligand into an endocytic vesicle, regulated transit of the carrier through the cytoplasm and release of the cargo via an exocytic event. While transcytosis has been examined in detail in epithelial cells, for both historical and technical reasons, the process is less understood in endothelial cells. Here, we spotlight aspects of epithelial transcytosis including recent findings and review the comparative dearth of knowledge regarding the process in endothelial cells highlighting the opportunity for further study.

New therapeutic approaches for Krabbe disease: The potential of pharmacological chaperones

Missense mutations in the lysosomal hydrolase β‐galactocerebrosidase (GALC) account for at least 40% of known cases of Krabbe disease (KD). Most of these missense mutations are predicted to disrupt the fold of the enzyme, preventing GALC in sufficient amounts from reaching its site of action in the lysosome. The predominant central nervous system (CNS) pathology and the absence of accumulated primary substrate within the lysosome mean that strategies used to treat other lysosomal storage disorders (LSDs) are insufficient in KD, highlighting the still unmet clinical requirement for successful KD therapeutics. Pharmacological chaperone therapy (PCT) is one strategy being explored to overcome defects in GALC caused by missense mutations. In recent studies, several small‐molecule inhibitors have been identified as promising chaperone candidates for GALC. This Review discusses new insights gained from these studies and highlights the importance of characterizing both the chaperone interaction and the underlying mutation to define properly a responsive population and to improve the translation of existing lead molecules into successful KD therapeutics. We also highlight the importance of using multiple complementary methods to monitor PCT effectiveness. Finally, we explore the exciting potential of using combination therapy to ameliorate disease through the use of PCT with existing therapies or with more generalized therapeutics, such as proteasomal inhibition, that have been shown to have synergistic effects in other LSDs. This, alongside advances in CNS delivery of recombinant enzyme and targeted rational drug design, provides a promising outlook for the development of KD therapeutics. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.