Dynamics of CNS barriers: evolution, differentiation, and modulation

GSH and Zinc Supplementation Attenuate Cadmium-Induced Cellular Stress and Stimulation of Choline Uptake in Cultured Neonatal Rat Choroid Plexus Epithelia

Choroid plexus (CP) sequesters cadmium and other metals, protecting the brain from these neurotoxins. These metals can induce cellular stress and modulate homeostatic functions of CP, such as solute transport. We previously showed in primary cultured neonatal rat CP epithelial cells (CPECs) that cadmium induced cellular stress and stimulated choline uptake at the apical membrane, which interfaces with cerebrospinal fluid in situ. Here, in CPECs, we characterized the roles of glutathione (GSH) and Zinc supplementation in the adaptive stress response to cadmium. Cadmium increased GSH and decreased the reduced GSH-to-oxidized GSH (GSSG) ratio. Heat shock protein-70 (Hsp70), heme oxygenase (HO-1), and metallothionein (Mt-1) were induced along with the catalytic and modifier subunits of glutamate cysteine ligase (GCL), the rate-limiting enzyme in GSH synthesis. Inhibition of GCL by l-buthionine sulfoximine (BSO) enhanced stress protein induction and stimulation of choline uptake by cadmium. Zinc alone did not induce Hsp70, HO-1, or GCL subunits, or modulate choline uptake. Zinc supplementation during cadmium exposure attenuated stress protein induction and stimulation of choline uptake; this effect persisted despite inhibition of GSH synthesis. These data indicated up-regulation of GSH synthesis promotes adaptation to cadmium-induced cellular stress in CP, but Zinc may confer cytoprotection independent of GSH.

The unfolding palette of COVID-19 multisystemic syndrome and its neurological manifestations

Although our current knowledge of the pathophysiology of COVID-19 is still fragmentary, the information so far accrued on the tropism and life cycle of its etiological agent SARS-CoV-2, together with the emerging clinical data, suffice to indicate that the severe acute pulmonary syndrome is the main, but not the only manifestation of COVID-19. Necropsy studies are increasingly revealing underlying endothelial vasculopathies in the form of micro-haemorrhages and micro-thrombi. Intertwined with defective antiviral responses, dysregulated coagulation mechanisms, abnormal hyper-inflammatory reactions and responses, COVID-19 is disclosing a wide pathophysiological palette. An additional property in categorising the disease is the combination of tissue (e.g. neuro- and vasculo-tropism) with organ tropism, whereby the virus preferentially attacks certain organs with highly developed capillary beds, such as the lungs, gastrointestinal tract, kidney and brain. These multiple clinical presentations confirm that the acute respiratory syndrome as described initially is increasingly unfolding as a more complex nosological entity, a multiorgan syndrome of systemic breadth. The neurological manifestations of COVID-19, the focus of this review, reflect this manifold nature of the disease.

Surface Functionalization of PLGA Nanoparticles to Increase Transport across the BBB for Alzheimer’s Disease

Alzheimer’s disease (AD) is a chronic neurodegenerative disorder that accounts for about 60% of all diagnosed cases of dementia worldwide. Although there are currently several drugs marketed for its treatment, none are capable of slowing down or stopping the progression of AD. The role of the blood-brain barrier (BBB) plays a key role in the design of a successful treatment for this neurodegenerative disease. Nanosized particles have been proposed as suitable drug delivery systems to overcome BBB with the purpose of increasing bioavailability of drugs in the brain. Biodegradable poly (lactic-co-glycolic acid) nanoparticles (PLGA-NPs) have been particularly regarded as promising drug delivery systems as they can be surface-tailored with functionalized molecules for site-specific targeting. In this review, a thorough discussion about the most recent functionalization strategies based on PLGA-NPs for AD and their mechanisms of action is provided, together with a description of AD pathogenesis and the role of the BBB in brain targeting.

Parenteral high‑dose ascorbate - A possible approach for the treatment of glioblastoma (Review)

For glioblastoma, the treatment with standard of care therapy comprising resection, radiation, and temozolomide results in overall survival of approximately 14-18 months after initial diagnosis. Even though several new therapy approaches are under investigation, it is difficult to achieve life prolongation and/or improvement of patient's quality of life. The aggressiveness and progression of glioblastoma is initially orchestrated by the biological complexity of its genetic phenotype and ability to respond to cancer therapy via changing its molecular patterns, thereby developing resistance. Recent clinical studies of pharmacological ascorbate have demonstrated its safety and potential efficacy in different cancer entities regarding patient's quality of life and prolongation of survival. In this review article, the actual glioblastoma treatment possibilities are summarized, the evidence for pharmacological ascorbate in glioblastoma treatment is examined and questions are posed to identify current gaps of knowledge regarding accessibility of ascorbate to the tumor area. Experiments with glioblastoma cell lines and tumor xenografts have demonstrated that high-dose ascorbate induces cytotoxicity and oxidative stress largely selectively in malignant cells compared to normal cells suggesting ascorbate as a potential therapeutic agent. Further investigations in larger cohorts and randomized placebo-controlled trials should be performed to confirm these findings as well as to improve delivery strategies to the brain, through the inherent barriers and ultimately to the malignant cells.

The Consumption of Energy Drinks Induces Blood-Brain Barrier Dysfunction in Wild-Type Mice

Energy drinks containing significant quantities of caffeine and sugar are increasingly consumed, particularly by adolescents and young adults. Chronic ingestion of energy drinks may potentially regulate vascular risk factors. This study investigated the effects of chronic ingestion of energy drinks on blood-brain barrier (BBB) integrity and neuroinflammation. Male C57BL/6J mice were maintained on water (control), Mother^TM (ED), sugar-free Mother^TM (sfED), or Coca Cola^TM soft drink (SD) for 13 weeks. The BBB integrity and neuroinflammation were analyzed with semi-quantitative immunofluorescent microscopy. Blood pressure, plasma inflammatory cytokine levels and blood glucose were also considered. Following 13 weeks of intervention, mice treated with ED, sfED, and SD showed significant disruption of BBB. However, marked neuroinflammation was observed only in sfED group mice. The consumption of ED and sfED significantly altered the blood pressure and plasma concentrations of inflammatory cytokines, TNF-a, IL-4, IL-6, and IL-10, and both increased plasma glucose. Correlation analyses showed significant associations between BBB dysfunction and hypotension, hyperglycaemia and cytokine dyshomeostasis. The intake of energy drink, particularly the sugar free formulation, may compromise the integrity of BBB and induce neuroinflammation via hypotension, hyperglycaemia and inflammatory pathways.

Study of enzymatic activity in human neuroblastoma cells SH-SY5Y exposed to zearalenone's derivates and beauvericin

Beauvericin (BEA), α-zearalenol (α-ZEL) and β-zearalenol (β-ZEL), are produced by several Fusarium species that contaminate cereal grains. These mycotoxins can cause cytotoxicity and neurotoxicity in various cell lines and they are also capable of produce oxidative stress at molecular level. However, mammalian cells are equipped with a protective endogenous antioxidant system formed by no-enzymatic antioxidant and enzymatic protective systems such as glutathione peroxidase (GPx), glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD). The aim of this study was evaluating the effects of α-ZEL, β-ZEL and BEA, on enzymatic GPx, GST, CAT and SOD activity in human neuroblastoma cells using the SH-SY5Y cell line, over 24 h and 48 h with different treatments at the following concentration range: from 1.56 to 12.5 μM for α-ZEL and β-ZEL, from 0.39 to 2.5 μM for BEA, from 1.87 to 25 μM for binary combinations and from 3.43 to 27.5 μM for tertiary combination. SH-SY5Y cells exposed to α-ZEL, β-ZEL and BEA revealed an overall increase in the activity of i) GPx, after 24 h of exposure up to 24-fold in individual treatments and 15-fold in binary combination; ii) GST after 24 h of exposure up to 10-fold (only in combination forms), and iii) SOD up to 3.5- and 5-fold in individual and combined treatment, respectively after 48 h of exposure. On the other hand, CAT activity decreased significantly in all treatments up to 92% after 24 h except for β-ZEL + BEA, which revealed the opposite.

Manickam D. Targeting the blood-brain barrier for the delivery of stroke therapies

A variety of neuroprotectants have shown promise in treating ischemic stroke, yet their delivery to the brain remains a challenge. The endothelial cells lining the blood-brain barrier (BBB) are emerging as a dynamic factor in the response to neurological injury and disease, and the endothelial-neuronal matrix coupling is fundamentally neuroprotective. In this review, we discuss approaches that target the endothelium for drug delivery both across the BBB and to the BBB as a viable strategy to facilitate neuroprotective effects, using the example of brain-derived neurotrophic factor (BDNF). We highlight the advances in cell-derived extracellular vesicles (EVs) used for CNS targeting and drug delivery. We also discuss the potential of engineered EVs as a potent strategy to deliver BDNF or other drug candidates to the ischemic brain, particularly when coupled with internal components like mitochondria that may increase cellular energetics in injured endothelial cells.

HIV Neuroinflammation: The Role of Exosomes in Cell Signaling, Prognostic and Diagnostic Biomarkers and Drug Delivery

Fifty to sixty percent of HIV-1 positive patients experience HIV-1 associated neurocognitive disorders (HAND) likely due to persistent inflammation and blood-brain barrier (BBB) dysfunction. The role that microglia and astrocytes play in HAND pathogenesis has been well delineated; however, the role of exosomes in HIV neuroinflammation and neuropathogenesis is unclear. Exosomes are 50-150 nm phospholipid bilayer membrane vesicles that are responsible for cell-to-cell communication, cellular signal transduction, and cellular transport. Due to their diverse intracellular content, exosomes, are well poised to provide insight into HIV neuroinflammation as well as provide for diagnostic and predictive information that will greatly enhance the development of new therapeutic interventions for neuroinflammation. Exosomes are also uniquely positioned to be vehicles to delivery therapeutics across the BBB to modulate HIV neuroinflammation. This mini-review will briefly discuss what is known about exosome signaling in the context of HIV in the central nervous system (CNS), their potential for biomarkers as well as their potential for vehicles to deliver various therapeutics to treat HIV neuroinflammation.

Interoception and the origin of feelings: A new synthesis

Feelings are conscious mental events that represent body states as they undergo homeostatic regulation. Feelings depend on the interoceptive nervous system (INS), a collection of peripheral and central pathways, nuclei and cortical regions which continuously sense chemical and anatomical changes in the organism. How such humoral and neural signals come to generate conscious mental states has been a major scientific question. The answer proposed here invokes (1) several distinctive and poorly known physiological features of the INS; and (2) a unique interaction between the body (the 'object' of interoception) and the central nervous system (which generates the 'subject' of interoception). The atypical traits of the INS and the direct interactions between neural and non-neural physiological compartments of the organism, neither of which is present in exteroceptive systems, plausibly explain the qualitative and subjective aspects of feelings, thus accounting for their conscious nature.

The role of brain barriers in the neurokinetics and pharmacodynamics of lithium

Lithium (Li) is the most widely used mood stabilizer in treating patients with bipolar disorder. However, more than half of the patients do not or partially respond to Li therapy, despite serum Li concentrations in the serum therapeutic range. The exact mechanisms underlying the pharmacokinetic-pharmacodynamic (PK-PD) relationships of lithium are still poorly understood and alteration in the brain pharmacokinetics of lithium may be one of the mechanisms explaining the variability in the clinical response to Li. Brain barriers such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) play a crucial role in controlling blood-to-brain and brain-to-blood exchanges of various molecules including central nervous system (CNS) drugs. Recent in vivo studies by nuclear resonance spectroscopy revealed heterogenous brain distribution of Li in human that were not always correlated with serum concentrations, suggesting regional and variable transport mechanisms of Li through the brain barriers. Moreover, alteration in the functionality and integrity of brain barriers is reported in various CNS diseases, as a cause or a consequence and in this regard, Li by itself is known to modulate BBB properties such as the expression and activity of various transporters, metabolizing enzymes, and the specialized tight junction proteins on BBB. In this review, we will focus on recent knowledge into the role of the brain barriers as key-element in the Li neuropharmacokinetics which might improve the understanding of PK-PD of Li and its interindividual variability in drug response.

Autophagy-mediated tumor cell survival and progression of breast cancer metastasis to the brain

Brain metastases represent a substantial amount of morbidity and mortality in breast cancer (BC). Metastatic breast tumor cells committed to brain metastases are unique because they escape immune surveillance, can penetrate the blood-brain barrier, and also adapt to the brain tissue microenvironment (TME) for colonization and outgrowth. In addition, dynamic intracellular interactions between metastatic cancer cells and neighboring astrocytes in the brain are thought to play essential roles in brain tumor progression. A better understanding of the above mechanisms will lead to developing more effective therapies for brain metastases. Growing literature suggests autophagy, a conserved lysosomal degradation pathway involved in cellular homeostasis under stressful conditions, plays essential roles in breast tumor metastatic transformation and brain metastases. Cancer cells must adapt under various microenvironmental stresses, such as hypoxia, and nutrient (glucose) deprivation, in order to survive and progress. Clinical studies reveal that tumoral expression of autophagy-related proteins is higher in brain metastasis compared to primary breast tumors. In this review, we outline the molecular mechanisms underlying autophagy-mediated BC cell survival and metastasis to the brain.

Echovirus-30 Infection Alters Host Proteins in Lipid Rafts at the Cerebrospinal Fluid Barrier In Vitro

Echovirus-30 (E-30) is a non-polio enterovirus responsible for meningitis outbreaks in children worldwide. To gain access to the central nervous system (CNS), E-30 first has to cross the blood-brain barrier (BBB) or the blood-cerebrospinal fluid barrier (BCSFB). E-30 may use lipid rafts of the host cells to interact with and to invade the BCSFB. To study enteroviral infection of the BCSFB, an established in vitro model based on human immortalized brain choroid plexus papilloma (HIBCPP) cells has been used. Here, we investigated the impact of E-30 infection on the protein content of the lipid rafts at the BCSFB in vitro. Mass spectrometry analysis following E-30 infection versus uninfected conditions revealed differential abundancy in proteins implicated in cellular adhesion, cytoskeleton remodeling, and endocytosis/vesicle budding. Further, we evaluated the blocking of endocytosis via clathrin/dynamin blocking and its consequences for E-30 induced barrier disruption. Interestingly, blocking of endocytosis had no impact on the capacity of E-30 to induce loss of barrier properties in HIBCPP cells. Altogether, these data highlight the impact of E-30 on HIBCPP cells microdomain as an important factor for host cell alteration.

Astrocytes as Guardians of Neuronal Excitability: Mechanisms Underlying Epileptogenesis

Astrocytes are key homeostatic regulators in the central nervous system and play important roles in physiology. After brain damage caused by e.g., status epilepticus, traumatic brain injury, or stroke, astrocytes may adopt a reactive phenotype. This process of reactive astrogliosis is important to restore brain homeostasis. However, persistent reactive astrogliosis can be detrimental for the brain and contributes to the development of epilepsy. In this review, we will focus on physiological functions of astrocytes in the normal brain as well as pathophysiological functions in the epileptogenic brain, with a focus on acquired epilepsy. We will discuss the role of astrocyte-related processes in epileptogenesis, including reactive astrogliosis, disturbances in energy supply and metabolism, gliotransmission, and extracellular ion concentrations, as well as blood-brain barrier dysfunction and dysregulation of blood flow. Since dysfunction of astrocytes can contribute to epilepsy, we will also discuss their role as potential targets for new therapeutic strategies.

A blood-brain barrier overview on structure, function, impairment, and biomarkers of integrity

The blood–brain barrier is playing a critical role in controlling the influx and efflux of biological substances essential for the brain’s metabolic activity as well as neuronal function. Thus, the functional and structural integrity of the BBB is pivotal to maintain the homeostasis of the brain microenvironment. The different cells and structures contributing to developing this barrier are summarized along with the different functions that BBB plays at the brain–blood interface. We also explained the role of shear stress in maintaining BBB integrity. Furthermore, we elaborated on the clinical aspects that correlate between BBB disruption and different neurological and pathological conditions. Finally, we discussed several biomarkers that can help to assess the BBB permeability and integrity in-vitro or in-vivo and briefly explain their advantages and disadvantages.

Probing the drug delivery strategies in ischemic stroke therapy

Ischemic stroke, which is caused by a sudden clot in the blood vessels, may cause severe brain tissue damage and has become a leading cause of death globally. Currently, thrombolysis is the gold standard primary treatment of ischemic stroke in clinics. However, the short therapeutic window of opportunity limits thrombolysis utility. Secondary cerebral damage caused by stroke is also an urgent problem. In this review, we discuss the present methods of treating ischemic stroke in clinics and their limitations. Various new drug delivery strategies targeting ischemic stroke lesions have also been summarized, including pharmaceutical methods, diagnostic approaches and other routes. These strategies could change the pharmacokinetic behavior, improve targeted delivery or minimize side effects. A better understanding of the novel approaches utilized to facilitate drug delivery in ischemic stroke would improve outcomes.

No rapid and demarcating astroglial reaction to stab wounds in Agama and Gecko lizards and the caiman Paleosuchus - it is confined to birds and mammals

The present study proves that rapid and demarcating astroglial reactions are confined to birds and mammals. To understand the function of post-lesion astroglial reaction, the phylogenetical aspects are also to be investigated. Considering the regenerative capabilities, reptiles represent an intermediate position between the brain regeneration-permissive fishes and amphibians and the almost non-permissive birds and mammals. Damage is followed by a rapid astroglial reaction in the mammalian and avian brain, which is held as an impediment of regeneration. In other vertebrates the reactions were usually observed following long survival periods together with signs of regeneration, therefore they can be regarded as concomitant phenomena of regeneration. The present study applies short post-lesion periods comparable to those seen in mammals and birds for astroglial reactions. Two species of lizards were used: gecko (leopard gecko, Eublepharis macularius, Blyth, 1854) and agama (bearded dragon, Pogona vitticeps, Ahl, 1926). The gecko brain is rich in GFAP whereas the agama brain is quite poor in this. Crocodilia, the closest extant relatives of birds were represented in this study by Cuvier's dwarf caiman (Paleosuchus palpebrosus, Cuvier, 1807). The post-lesion astroglial reactions of crocodilians have never been investigated. The injuries were stab wounds in the telencephalon. The survival periods lasted 3, 7, 10 or 14 days. Immunoperoxidase reactions were performed applying anti-GFAP, anti-vimentin and anti-nestin reagents. No rapid and demarcating astroglial reaction resembling that of mammalian or avian brains was found. Alterations of the perivascular immunoreactivities of laminin and β-dystroglycan as indicators of glio-vascular decoupling proved that the lesions were effective on astroglia. The capability of rapid and demarcating astroglial reaction seems to be confined to mammals and birds and to appear by separate, parallel evolution in them.

Non-Human Primate Blood-Brain Barrier and In Vitro Brain Endothelium: From Transcriptome to the Establishment of a New Model

The non-human primate (NHP)-brain endothelium constitutes an essential alternative to human in the prediction of molecule trafficking across the blood–brain barrier (BBB). This study presents a comparison between the NHP transcriptome of freshly isolated brain microcapillaries and in vitro-selected brain endothelial cells (BECs), focusing on important BBB features, namely tight junctions, receptors mediating transcytosis (RMT), ABC and SLC transporters, given its relevance as an alternative model for the molecule trafficking prediction across the BBB and identification of new brain-specific transport mechanisms. In vitro BECs conserved most of the BBB key elements for barrier integrity and control of molecular trafficking. The function of RMT via the transferrin receptor (TFRC) was characterized in this NHP-BBB model, where both human transferrin and anti-hTFRC antibody showed increased apical-to-basolateral passage in comparison to control molecules. In parallel, eventual BBB-related regional differences were Investig.igated in seven-day in vitro-selected BECs from five brain structures: brainstem, cerebellum, cortex, hippocampus, and striatum. Our analysis retrieved few differences in the brain endothelium across brain regions, suggesting a rather homogeneous BBB function across the brain parenchyma. The presently established NHP-derived BBB model closely mimics the physiological BBB, thus representing a ready-to-use tool for assessment of the penetration of biotherapeutics into the human CNS.

Tau Protein and Its Role in Blood-Brain Barrier Dysfunction

The blood-brain barrier (BBB) plays a crucial role in maintaining the specialized microenvironment of the central nervous system (CNS). In aging, the stability of the BBB declines and the permeability increases. The list of CNS pathologies involving BBB dysfunction is growing. The opening of the BBB and subsequent infiltration of serum components to the brain can lead to a host of processes resulting in progressive synaptic, neuronal dysfunction, and detrimental neuroinflammatory changes. Such processes have been implicated in different diseases, including vascular dementia, stroke, Alzheimer's disease (AD), Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, hypoxia, ischemia, and diabetes mellitus. The BBB damage is also observed in tauopathies that lack amyloid-β overproduction, suggesting a role for tau in BBB damage. Tauopathies represent a heterogeneous group of around 20 different neurodegenerative diseases characterized by abnormal deposition of the MAPT in cells of the nervous system. Neuropathology of tauopathies is defined as intracellular accumulation of neurofibrillary tangles (NFTs) consisting of aggregated hyper- and abnormal phosphorylation of tau protein and neuroinflammation. Disruption of the BBB found in tauopathies is driven by chronic neuroinflammation. Production of pro-inflammatory signaling molecules such as cytokines, chemokines, and adhesion molecules by glial cells, neurons, and endothelial cells determine the integrity of the BBB and migration of immune cells into the brain. The inflammatory processes promote structural changes in capillaries such as fragmentation, thickening, atrophy of pericytes, accumulation of laminin in the basement membrane, and increased permeability of blood vessels to plasma proteins. Here, we summarize the knowledge about the role of tau protein in BBB structural and functional changes.

Radial Glia-endothelial Cells' Bidirectional Interactions Control Vascular Maturation and Astrocyte Differentiation: Impact for Blood-brain Barrier Formation

BACKGROUND

In the developing cerebral cortex, Radial Glia (RG) multipotent neural stem cell, among other functions, differentiate into astrocytes and serve as a scaffold for blood vessel development. After some time, blood vessel Endothelial Cells (ECs) become associated with astrocytes to form the neurovascular Blood-Brain Barrier (BBB) unit.

OBJECTIVE

Since little is known about the mechanisms underlying bidirectional RG-ECs interactions in both vascular development and astrocyte differentiation, this study investigated the impact of interactions between RG and ECs mediated by secreted factors on EC maturation and gliogenesis control.

METHODS

First, we demonstrated that immature vasculature in the murine embryonic cerebral cortex physically interacts with Nestin positive RG neural stem cells in vivo. Isolated Microcapillary Brain Endothelial Cells (MBEC) treated with the conditioned medium from RG cultures (RG-CM) displayed decreased proliferation, reduction in the protein levels of the endothelial tip cell marker Delta-like 4 (Dll4), and decreased expression levels of the vascular permeability associated gene, plasmalemma vesicle-associated protein-1 (PLVAP1). These events were also accompanied by increased levels of the tight junction protein expression, zonula occludens-1 (ZO-1).

RESULTS

Finally, we demonstrated that isolated RG cells cultures treated with MBEC conditioned medium promoted the differentiation of astrocytes in a Vascular Endothelial Growth Factor-A (VEGF-A) dependent manner.

CONCLUSION

These results suggest that the bidirectional interaction between RG and ECs is essential to induce vascular maturation and astrocyte generation, which may be an essential cell-cell communication mechanism to promote BBB establishment.

Impact of blood-brain barrier permeabilization induced by ultrasound associated to microbubbles on the brain delivery and kinetics of cetuximab: An immunoPET study using 89Zr-cetuximab

Epidermal growth factor receptor (EGFR), involved in cell proliferation and migration, is overexpressed in ~50% of glioblastomas. Anti-EGFR based strategies using monoclonal antibodies (mAb) such as cetuximab (CTX) have been proposed for central nervous system (CNS) cancer therapy. However, the blood-brain barrier (BBB) drastically restricts their brain penetration which limits their efficacy for the treatment of glioblastomas. Herein, a longitudinal PET imaging study was performed to assess the relevance and the impact of focused ultrasound (FUS)-mediated BBB permeabilization on the brain exposure to the anti-EGFR mAb CTX over time. For this purpose, FUS permeabilization process with microbubbles was applied on intact BBB mouse brain before the injection of ⁸⁹Zr-labeled CTX for longitudinal imaging monitoring. FUS induced a dramatic increase in mAb penetration to the brain, 2 times higher compared to the intact BBB. The transfer of ⁸⁹Zr-CTX from blood to the brain was rendered significant by FUS (k_uptake = 1.3 ± 0.23 min^-1 with FUS versus k_uptake = 0 ± 0.006 min^-1 without FUS). FUS allowed significant and prolonged exposure to mAb in the brain parenchyma. This study confirms the potential of FUS as a target delivery method for mAb in CNS.

Toxoplasma gondii infection impairs radial glia differentiation and its potential to modulate brain microvascular endothelial cell function in the cerebral cortex

Congenital toxoplasmosis is a parasitic disease that occurs due vertical transmission of the protozoan Toxoplasma gondii (T. gondii) during pregnancy. The parasite crosses the placental barrier and reaches the developing brain, infecting progenitor, glial, neuronal and vascular cell types. Although the role of Radial glia (RG) neural stem cells in the development of the brain vasculature has been recently investigated, the impact of T. gondii infection in these events is not yet understood. Herein, we studied the role of T. gondii infection on RG cell function and its interaction with endothelial cells. By infecting isolated RG cultures with T. gondii tachyzoites, we observed a cytotoxic effect with reduced numbers of RG populations together with decrease neuronal and oligodendrocyte progenitor populations. Conditioned medium (CM) from RG control cultures increased ZO-1 protein levels and organization on endothelial bEnd.3 cells membranes, which was impaired by CM from infected RG, accompanied by decreased trans-endothelial electrical resistance (TEER). ELISA assays revealed reduced levels of anti-inflammatory cytokine TGF-β1 in CM from T. gondii-infected RG cells. Treatment with recombinant TGF-β1 concomitantly with CM from infected RG cultures led to restoration of ZO-1 staining in bEnd.3 cells. Congenital infection in Swiss Webster mice led to abnormalities in the cortical microvasculature in comparison to uninfected embryos. Our results suggest that infection of RG cells by T. gondii negatively modulates cytokine secretion, which might contribute to endothelial loss of barrier properties, thus leading to impairment of neurovascular interaction establishment.

Radial glia in the zebrafish brain: Functional, structural, and physiological comparison with the mammalian glia

The neuroscience community has witnessed a tremendous expansion of glia research. Glial cells are now on center stage with leading roles in the development, maturation, and physiology of brain circuits. Over the course of evolution, glia have highly diversified and include the radial glia, astroglia or astrocytes, microglia, oligodendrocytes, and ependymal cells, each having dedicated functions in the brain. The zebrafish, a small teleost fish, is no exception to this and recent evidences point to evolutionarily conserved roles for glia in the development and physiology of its nervous system. Due to its small size, transparency, and genetic amenability, the zebrafish has become an increasingly prominent animal model for brain research. It has enabled the study of neural circuits from individual cells to entire brains, with a precision unmatched in other vertebrate models. Moreover, its high neurogenic and regenerative potential has attracted a lot of attention from the research community focusing on neural stem cells and neurodegenerative diseases. Hence, studies using zebrafish have the potential to provide fundamental insights about brain development and function, and also elucidate neural and molecular mechanisms of neurological diseases. We will discuss here recent discoveries on the diverse roles of radial glia and astroglia in neurogenesis, in modulating neuronal activity and in regulating brain homeostasis at the brain barriers. By comparing insights made in various animal models, particularly mammals and zebrafish, our goal is to highlight the similarities and differences in glia biology among species, which could set new paradigms relevant to humans.

Nanotheranostic Applications for Detection and Targeting Neurodegenerative Diseases

Nanotechnology utilizes engineered materials and devices which function with biological systems at the molecular level and could transform the management of neurodegenerative diseases (NDs) by provoking, reacting to, and intermingling with target sites to stimulate physiological responses while minimizing side effects. Blood-brain barrier (BBB) protects the brain from harmful agents, and transporting drugs across the BBB is a major challenge for diagnosis, targeting, and treatment of NDs. The BBB provides severe limitations for diagnosis and treatment of Alzheimer's disease (AD), Parkinson's disease (PD), and various other neurological diseases. Conventional drug delivery systems generally fail to cross the BBB, thus are inefficient in treatment. Although gradual development through research is ensuring the progress of nanotheranostic approaches from animal to human modeling, aspects of translational applicability and safety are a key concern. This demands a deep understanding of the interaction of body systems with nanomaterials. There are various plant-based nanobioactive compounds which are reported to have applicability in the diagnosis and treatment of these NDs. This review article provides an overview of applications of nanotheranostics in AD and PD. The review also discusses nano-enabled drug delivery systems and their current and potential applications for the treatment of various NDs.

Dysfunction of ABC transporters at the blood-brain barrier: Role in neurological disorders

ABC (ATP-binding cassette) transporters represent one of the largest and most diverse superfamily of proteins in living species, playing an important role in many biological processes such as cell homeostasis, cell signaling, drug metabolism and nutrient uptake. Moreover, using the energy generated from ATP hydrolysis, they mediate the efflux of endogenous and exogenous substrates from inside the cells, thereby reducing their intracellular accumulation. At present, 48 ABC transporters have been identified in humans, which were classified into 7 different subfamilies (A to G) according to their phylogenetic analysis. Nevertheless, the most studied members with importance in drug therapeutic efficacy and toxicity include P-glycoprotein (P-gp), a member of the ABCB subfamily, the multidrug-associated proteins (MPRs), members of the ABCC subfamily, and breast cancer resistance protein (BCRP), a member of the ABCG subfamily. They exhibit ubiquitous expression throughout the human body, with a special relevance in barrier tissues like the blood-brain barrier (BBB). At this level, they play a physiological function in tissue protection by reducing or limiting the brain accumulation of neurotoxins. Furthermore, dysfunction of ABC transporters, at expression and/or activity level, has been associated with many neurological diseases, including epilepsy, multiple sclerosis, Alzheimer's disease, and amyotrophic lateral sclerosis. Additionally, these transporters are strikingly associated with the pharmacoresistance to central nervous system (CNS) acting drugs, because they contribute to the decrease in drug bioavailability. This article reviews the signaling pathways that regulate the expression and activity of P-gp, BCRP and MRPs subfamilies of transporters, with particular attention at the BBB level, and their mis-regulation in neurological disorders.

Revisiting the blood-brain barrier: A hard nut to crack in the transportation of drug molecules

Barriers are the hallmark of a healthy physiology, blood-brain barrier (BBB) being a tough nut to crack for most of the antigens and chemical substances. The presence of tight junctions plays a remarkable role in defending the brain from antigenic and pathogenic attacks. BBB constitutes a diverse assemblage of multiple physical and chemical barriers that judiciously restrict the flux of blood solutes into and out of the brain. Restrictions through the paracellular pathway and the tight junctions between intercellular clefts, together create well regulated metabolic and transport barricades, critical to brain pathophysiology. The brain being impermeable to many essential metabolites and nutrients regulates transportation via specialized transport systems across the endothelial abluminal and luminal membranes. The epithelial cells enveloping capillaries of the choroid plexus regulates the transport of complement, growth factors, hormones, microelements, peptides and trace elements into ventricles. Nerve terminals, microglia, and pericytes associated with the endothelium support barrier induction and function, ensuring an optimally stable ionic microenvironment that facilitates neurotransmission, orchestrated by multiple ion channels (Na⁺, K⁺ Mg²⁺, Ca²⁺) and transporters. Brain pathology which can develop due to genetic mutations or secondary to other cerebrovascular, neurodegenerative diseases can cause aberration in the microvasculature of CNS which is the uniqueness of BBB. This can also alter BBB permeation and result in BBB breakdown and other neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. The concluding section outlines contemporary trends in drug discovery, focusing on molecular determinants of BBB permeation and novel drug-delivery systems, such as dendrimers, liposomes, nanoparticles, nanogels, etc.

Response of the cerebral vasculature to systemic carbon monoxide administration-Regional differences and sexual dimorphism

Previous studies about the modulation of the vasculature by CO were performed exclusively in male or sexually immature animals. Understanding the sex differences regarding systemic drug processing and pharmacodynamics is an important feature for safety assessment of drug dosing and efficacy. In this work, we used CORM-A1 as source of CO to examine the effects of this gasotransmitter on brain perfusion and the sex-dependent differences. Dynamic contrast-enhanced imaging (DCE)-based analysis was used to characterize the properties of CO in the modulation of cerebral vasculature in vivo, in adult C57BL/6 healthy mice. Perfusion of the temporal muscle, maxillary vein and in hippocampus, cortex and striatum was analysed for 108 min following CORM-A1 administration of 3 or 5 mg/kg. Under control conditions, brain perfusion was lower in females when compared with males. Under CO treatment, females showed a surprisingly overall reduced perfusion compared with controls (F = 3.452, p = .0004), while no major alterations (or even the expected increase) were observed in males. Cortical structures were only modulated in females. A striking female-dominated vasoconstriction effect was observed in the hippocampus and striatum following administration of CO, in this mixed-sex cohort. As these two regions are implicated in episodic and procedural memory formation, CO may have a relevant impact in learning and memory.

Optimization of Processing Parameters of Nanoemulsion Containing Aripiprazole Using Response Surface Methodology

BACKGROUND

Aripiprazole, which is a quinolinone derivative, has been widely used to treat schizophrenia, major depressive disorder, and bipolar disorder.

PURPOSE

A Central Composite Rotatable Design (CCRD) of Response Surface Methodology (RSM) was used purposely to optimize process parameters conditions for formulating nanoemulsion containing aripiprazole using high emulsification methods.

METHODS

This design is used to investigate the influences of four independent variables (overhead stirring time (A), shear rate (B), shear time (C), and the cycle of high-pressure homogenizer (D)) on the response variable namely, a droplet size (Y) of nanoemulsion containing aripiprazole.

RESULTS

The optimum conditions suggested by the predicted model were: 120 min of overhead stirring time, 15 min of high shear homogenizer time, 4400 rpm of high shear homogenizer rate and 11 cycles of high-pressure homogenizer, giving a desirable droplet size of nanoemulsion containing aripiprazole of 64.52 nm for experimental value and 62.59 nm for predicted value. The analysis of variance (ANOVA) showed the quadratic polynomial fitted the experimental values with F-value (9.53), a low p-value (0.0003) and a non-significant lack of-fit. It proved that the models were adequate to predict the relevance response. The optimized formulation with a viscosity value of 3.72 mPa.s and pH value of 7.4 showed good osmolality value (297 mOsm/kg) and remained stable for three months in three different temperatures (4°C, 25°C, and 45°C).

CONCLUSION

This proven that response surface methodology is an efficient tool to produce desirable droplet size of nanoemulsion containing aripiprazole for parenteral delivery application.

Cerebrovascular inflammation promotes the formation of brain metastases

Brain metastases are the most prevalent intracranial malignancy. Patient outcome is poor and treatment options are limited. Hence, new avenues must be explored to identify potential therapeutic targets. Inflammation is a known critical component of cancer progression. Intratumoral inflammation drives progression and leads to the release of circulating tumor cells (CTCs). Inflammation at distant sites promotes adhesion of CTCs to the activated endothelium and then initiates the formation of metastases. These interactions mostly involve cell adhesion molecules expressed by activated endothelial cells. For example, the vascular cell adhesion molecule-1 (VCAM-1) is known to promote transendothelial migration of cancer cells in different organs. However, it is unclear whether a similar mechanism occurs within the specialized environment of the brain. Our objective was therefore to use molecular imaging to assess the potential role of VCAM-1 in promoting the entry of CTCs into the brain. First, magnetic resonance imaging (MRI) and histological analyses revealed that cerebrovascular inflammation induced by intracranial injection of lipopolysaccharide significantly increased the expression of VCAM-1 in the Balb/c mouse brain. Next, intracardiac injection of 4T1 mammary carcinoma cancer cells in animals with cerebrovascular inflammation yielded a higher brain metastasis burden than in the control animals. Finally, blocking VCAM-1 prior to 4T1 cells injection prevented this increased metastatic burden. Here, we demonstrated that by contributing to CTCs adhesion to the activated cerebrovascular endothelium, VCAM-1 improves the capacity of CTCs to form metastatic foci in the brain.

Novel Blood-Brain Barrier Shuttle Peptides Discovered through the Phage Display Method

Delivery of therapeutic agents into the brain is a major challenge in central nervous system drug development. The blood–brain barrier (BBB) prevents access of biotherapeutics to their targets in the central nervous system and, therefore, prohibits the effective treatment of many neurological disorders. To find blood–brain barrier shuttle peptides that could target therapeutics to the brain, we applied a phage display technology on a primary endothelial rat cellular model. Two identified peptides from a 12 mer phage library, GLHTSATNLYLH and VAARTGEIYVPW, were selected and their permeability was validated using the in vitro BBB model. The permeability of peptides through the BBB was measured by ultra-performance liquid chromatography-tandem mass spectrometry coupled to a triple-quadrupole mass spectrometer (UHPLC-MS/MS). We showed higher permeability for both peptides compared to N–C reversed-sequence peptides through in vitro BBB: for peptide GLHTSATNLYLH 3.3 × 10⁻⁷ cm/s and for peptide VAARTGEIYVPW 1.5 × 10⁻⁶ cm/s. The results indicate that the peptides identified by the in vitro phage display technology could serve as transporters for the administration of biopharmaceuticals into the brain. Our results also demonstrated the importance of proper BBB model for the discovery of shuttle peptides through phage display libraries.

Cell-based, animal and H1 receptor binding studies relative to the sedative effects of ketotifen and norketotifen atropisomers

OBJECTIVES

Ketotifen (K) and its active metabolite norketotifen (N) exist as optically active atropisomers. They both have antihistaminic and anti-inflammatory properties but the S-atropisomer of N (SN) causes less sedation than K and RN in rodents. This study investigated whether this could be related to a lower concentration of SN in brain or a lower affinity of SN for rat brain H₁ receptors.

METHODS

Ketotifen and norketotifen atropisomers were quantified using a validated chiral HPLC assay. RBE4 and Caco-2 cell monolayers were used in uptake and permeability studies, respectively. Free and total brain-to-plasma (B/P) ratios were determined after injecting racemic K and N into rat tail veins. Affinity for rat brain H₁ receptors (K_I ) was determined using the [³ H]mepyramine binding assay.

KEY FINDINGS

Uptake and permeation studies indicate no stereoselective transport for K or N. B/P ratios reveal the brain concentration of N is lower than K with no stereoselective transport into brain. Finally, the [³ H]mepyramine binding assay shows SN has the lowest affinity for rat brain H₁ receptors.

CONCLUSION

The lower sedative effect of SN in rodents is probably due to a combination of a lower uptake of N than K into the brain and less affinity of SN for CNS H₁ receptors.

An observational clinical case of Zika virus-associated neurological disease is associated with primary IgG response and enhanced TNF levels

Descriptive clinical data help to reveal factors that may provoke Zika virus (ZIKV) neuropathology. The case of a 24-year-old female with a ZIKV-associated severe acute neurological disorder was studied. The levels of ZIKV in the cerebrospinal fluid (CSF) were 50 times higher than the levels in other compartments. An acute anti-flavivirus IgG, together with enhanced TNF-alpha levels, may have contributed to ZIKV invasion in the CSF, whereas the unbiased genome sequencing [obtained by next-generation sequencing (NGS)] of the CSF revealed that no virus mutations were associated with the anatomic compartments (CSF, serum, saliva and urine).

Transmigration of Tetraspanin 2 (Tspan2) siRNA Via Microglia Derived Exosomes across the Blood Brain Barrier Modifies the Production of Immune Mediators by Microglia Cells

Microglia are implicated in the neuropathogenesis of HIV. Tetraspanin 2 (Tspan2) is closely related to CD9 and CD81 proteins, and are expressed on microglia cells. They have been implicated in cell fusion and adhesion and in the immune response, and neuroinflammation. Developing therapeutics that target microglia remains a challenge as these therapeutics must cross the Blood-Brain Barrier (BBB). Our goal was to use microglia derived exosomes as a vehicle to deliver siRNA across the BBB to target human telomerase reverse transcriptase immortalized human microglial cells (HTHU) latently infected by HIV (HTHU-HIV) and to evaluate if the knockdown of Tspan2 gene expression in changes the activation state of microglia cells, thereby modulating the neuroinflammatory response. A blood brain barrier (BBB) model that closely mimics and accurately reflects the characteristics and functional properties of the in vivo BBB was used to examine HTHU microglia exosome effects on BBB permeability, and their ability to migrate across the and delivery small interfering RNA (siRNA) to cells on the CNS side of the BBB model. Exosomes were loaded with Texas-Red control siRNA (20 pmol) or Cy5-Tspan2 siRNA and then placed in the apical side of the BBB model, 24 h after incubation, HTHU-HIV cells microglial cells on the lower chamber were either imaged for siRNA uptake or analyzed for gene expression induced modifications. HTHU exosomes transmigrate from the apical side of the BBB to deliver Texas-Red control siRNA or Cy5-Tspan2 siRNA to HTHU-HIV microglia cells on the CNS side of the BBB model. A dose dependent (5-40 pmol) increase in Cy5-Tspan2 uptake with a corresponding decrease in gene expression for Tspan2 occurred in HTHU-HIV microglia. A decrease in Tspan2 gene expression as a consequence of knockdown with Tspan2 siRNA at both 20 and 40 pmol concentrations resulted in a significant decrease in C-X-C motif chemokine 12 (CXCL12) and C-X-C chemokine receptor type 4 (CXCR4) gene expression in HTHU-HIV microglia. Furthermore, a decrease in the gene expression levels of the Interleukins, IL-13 and IL-10 and an increase in the gene expression levels for the Fc gamma receptor 2A(FCGR2A) and TNF-α occurred in HTHU-HIV microglial cells These data demonstrate that HTHU exosomes cross the BBB and are efficient delivery vehicles to the CNS. Moreover, modifying the expression levels of Tspan2, has downstream consequences that includes alterations in cytokines and microglia biomarkers. Graphical Abstract Microglia-derived exosomes loaded with Tspan2 siRNA transmigrate across the BBB and knockdown Tspan2 gene expression in human microglial cells latently infected by HIV. This knockdown increases CXCL12, CXCR4, FCGR2A and TNF-α while decreasing IL-13 and IL-10 gene expression in HTHU-HIV microglial cells. Modulating Tspan2 modulates microglia cytokines and phenotype biomarkers.

EsGPCR89 regulates cerebral antimicrobial peptides through hemocytes in Eriocheir sinensis

G protein-coupled receptors (GPCRs) are important transmembrane receptors that participate in diverse physiological processes including metabolism, cell growth and immune processes by transmitting extracellular signals to intracellular effectors. In this study, a gene belonging to the GPCR family was cloned from Eriocheir sinensis and named EsGPCR89. The full-length gene includes an open reading frame (ORF) of 465 amino acid residues, and bioinformatic analysis confirmed the high conservation between species. EsGPCR89 was detected in various tissues of E. sinensis, and was up-regulated in brain following Staphylococcus aureus infection. Expression levels of cerebral antimicrobial peptides (AMPs) were also up-regulated following bacterial challenge, reflecting their function in cerebral immunity. Additionally, EsGPCR89 silencing in hemocytes by RNA interference, down-regulated AMPs in brain after S. aureus infection. Moreover, through Immunisation assay and Polyacrylamide gel electrophoresis (SDS-PAGE) experiments, we could infer that bacterially infected hemocytes released effectors under the regulation of EsGPCR89, thereby activating transcription of cerebral AMPs. These results demonstrate that EsGPCR89 plays important roles in cerebral antimicrobial function via hemocytes.

Nanomaterial-based blood-brain-barrier (BBB) crossing strategies

Increasing attention has been paid to the diseases of central nervous system (CNS). The penetration efficiency of most CNS drugs into the brain parenchyma is rather limited due to the existence of blood-brain barrier (BBB). Thus, BBB crossing for drug delivery to CNS remains a significant challenge in the development of neurological therapeutics. Because of the advantageous properties (e.g., relatively high drug loading content, controllable drug release, excellent passive and active targeting, good stability, biodegradability, biocompatibility, and low toxicity), nanomaterials with BBB-crossability have been widely developed for the treatment of CNS diseases. This review summarizes the current understanding of the physiological structure of BBB, and provides various nanomaterial-based BBB-crossing strategies for brain delivery of theranostic agents, including intranasal delivery, temporary disruption of BBB, local delivery, cell penetrating peptide (CPP) mediated BBB-crossing, receptor mediated BBB-crossing, shuttle peptide mediated BBB-crossing, and cells mediated BBB-crossing. Clinicians, biologists, material scientists and chemists are expected to be interested in this review.

ABC Transporters in Neurological Disorders: An Important Gateway for Botanical Compounds Mediated Neuro-Therapeutics

Neurodegeneration is a distinguishing feature of many age related disorders and other vector borne neuroinflammatory diseases. There are a number of factors that can modulate the pathology of these disorders. ATP-binding cassette (ABC) transporters are primarily involved in the maintenance of normal brain homeostasis by eliminating toxic peptides and compounds from the brain. Also, ABC transporters protect the brain from the unwanted effects of endogenous and exogenous toxins that can enter the brain parenchyma. Therefore, these transporters have the ability to determine the pathological outcomes of several neurological disorders. For instance, ABC transporters like P-glycoprotein (ABCB1), and BCRP (ABCG2) have been reported to facilitate the clearance of peptides such as amyloid-β (Aβ) that accumulate in the brain during Alzheimer's disease (AD) progression. Other members such as ABCA1, ABCA2, ABCC8, ABCC9, ABCG1 and ABCG4 also have been reported to be involved in the progression of various brain disorders such as HIV-associated dementia, Multiple sclerosis (MS), Ischemic stroke, Japanese encephalitis (JE) and Epilepsy. However, these defective transporters can be targeted by numerous botanical compounds such as Verapamil, Berberine and Fascalpsyn as a therapeutic target to treat these neurological outcomes. These compounds are already reported to modulate ABC transporter activity in the CNS. Nonetheless, the exact mechanisms involving the ABC transporters role in normal brain functioning, their role in neuronal dysfunction and how these botanical compounds ensure and facilitate their therapeutic action in association with defective transporters still remain elusive. This review therefore, summarizes the role of ABC transporters in neurological disorders, with a special emphasis on its role in AD brains. The prospect of using botanical/natural compounds as modulators of ABC transporters in neurological disorders is discussed in the latter half of the article.

Unilateral Focused Ultrasound-Induced Blood-Brain Barrier Opening Reduces Phosphorylated Tau from The rTg4510 Mouse Model

The neuropathological hallmarks of Alzheimer's disease include amyloid plaques and neurofibrillary tangles. Tau pathology correlates well with impaired neuronal activity and dementia. Focused ultrasound coupled with systemic administration of microbubbles has previously been shown to open the blood-brain barrier and induce an immune response, which, in an amyloid AD mouse model, resulted in the reduction of the amyloid brain load.

Methods: In this study, we investigated the effect of focused ultrasound at the early stages of tau pathology (pre-tangle) in the rTg4510 mouse model.

Results: Reduction of phosphorylated tau from the hippocampal formation processes, and particularly the pyramidal CA1 neurons, was noted in the ultrasound-treated brains without an associated increase in the phosphorylated tau-affected cell somas, typically associated with disease progression. Attenuation of the pathology was found to correlate well with the ultrasound-initiated immune response without compromising neuronal integrity. Unilateral ultrasound application resulted in a bilateral effect indicating a broader reduction of the phosphorylated tau.

Conclusion: Findings presented herein reinforce the premise of ultrasound in reducing tau pathology and thus curbing the progression of Alzheimer's disease.

Nanodelivery of therapeutic agents in Parkinson's disease

Parkinson's disease (PD) as a motor disorder is pathologically featured by the loss of dopaminergic neurons of the substantia nigra compacta (SNc) and the consequent depletion of dopamine in the striatum. However, motor signs are detectable when the loss of dopaminergic striatal terminals exceeds to the dopaminergic neuronal degeneration in SN. Hence, recent evidences about the topological organization of the nigrostriatal system could provide novel insights about the progression of the neurodegenerative process as well as the correct application of the novel therapeutic strategies. Though dopaminergic drugs and different routes of administration have been proposed to treat PD, most of the effects are symptomatic with temporary effects resorting to invasive procedures to ameliorate the side effects. Since the blood-brain barrier (BBB) is the main obstacle for most of molecules to access to the brain, ongoing research is focused on halting the progression of PD through the use of those technologies that allow the effective delivery and diffusion of therapeutic molecules to the central nervous system for bypassing BBB and avoiding the side effects. In this context, nanotechnology is emerging as a promising tool for drug delivery. In fact, nanodelivery of restorative treatments in PD, such as gene therapy increased the effectiveness of neurotrophic factors for restoring the dopamine deficit and improving motor deficit in rodent models. Therefore, the present review is focused on the description and identification of the available nanotherapies developed in experimental models of PD which could suppose an important advance for controlled delivery of nanobioactive components into the brain and one more step for the clinical projection.

Nanomaterials for Drug Delivery to the Central Nervous System

The intricate microstructure of the blood-brain barrier (BBB) is responsible for the accurate intrinsic regulation of the central nervous system (CNS), in terms of neuronal pathophysiological phenomena. Any disruption to the BBB can be associated with genetic defects triggering or with local antigenic invasion (either neurotoxic blood-derived metabolites and residues or microbial pathogens). Such events can be further related to systemic inflammatory or immune disorders, which can subsequently initiate several neurodegenerative pathways. Any degenerative process related to the CNS results in progressive and yet incurable impairment of neuronal cells. Since these particular neurons are mostly scanty or incapable of self-repair and regeneration processes, there is tremendous worldwide interest in novel therapeutic strategies for such specific conditions. Alzheimer’s and Parkinson’s diseases (AD and PD, respectively) are conditions found worldwide, being considered the most rampant degenerative pathologies related to CNS. The current therapy of these conditions, including both clinical and experimental approaches, mainly enables symptom management and subsidiary neuronal protection and even less disease regression. Still, a thorough understanding of the BBB pathophysiology and an accurate molecular and sub-molecular management of AD and PD will provide beneficial support for more specific and selective therapy. Since nanotechnology-derived materials and devices proved attractive and efficient platforms for modern biomedicine (including detection, imaging, diagnosis, medication, restoration and regeneration), a particular approach for AD and PD management relies on nanoparticle-based therapy. In this paper we will discuss relevant aspects related to the BBB and its impact on drug-based treatment and emphasize that nanoparticles are suitable and versatile candidates for the development of novel and performance-enhanced nanopharmaceuticals for neurodegenerative conditions therapy.

Proteomic Quantification of Human Blood-Brain Barrier SLC and ABC Transporters in Healthy Individuals and Dementia Patients

The blood-brain barrier (BBB) maintains brain homeostasis by controlling traffic of molecules from the circulation into the brain. This function is predominantly dependent on proteins expressed at the BBB, especially transporters and tight junction proteins. Alterations to the level and function of BBB proteins can impact the susceptibility of the central nervous system to exposure to xenobiotics in the systemic circulation with potential consequent effects on brain function. In this study, expression profiles of drug transporters and solute carriers in the BBB were assessed in tissues from healthy individuals ( n = 12), Alzheimer's patients ( n = 5), and dementia with Lewy bodies patients ( n = 5), using targeted, accurate mass retention time (AMRT) and global proteomic methods. A total of 53 transporters were quantified, 19 for the first time in the BBB. A further 20 novel transporters were identified but not quantified. The global proteomic method identified another 3333 BBB proteins. Transporter abundances, taken together with the scaling factor, microvessel protein content per unit tissue (BMvPGB also measured here), can be used in quantitative systems pharmacology models predicting drug disposition in the brain and permitting dose adjustment (precision dosing) in special populations of patients, such as those with dementia. Even in this small study, we see differences in transporter profile between healthy and diseased brain tissue.

The Role of VE-cadherin in Blood-brain Barrier Integrity Under Central Nervous System Pathological Conditions

The blood-brain barrier (BBB) is a layer between the blood circulation and neural tissue. It plays a pivotal role in maintaining the vulnerable extracellular microenvironment in the neuronal parenchyma. Neuroinflammatory events can result in BBB dysregulation by disturbing adherens junctions (AJs) and tight junctions (TJs). VE-cadherin, as one of the most im-portant components of the vascular system, is specifically responsible for the assembly of AJs and BBB architecture. Here, we present a review, which highlights recently available insights into the relationship between

the neuroinflammation and BBB dysregulation. We then explore the specific interaction between VE-cadherin and BBB. Fi-nally, we discuss the changes of VE-cadherin with different neurological diseases from both experimental and clinical stud-ies. An understanding of VE-cadherin in BBB regulation may indicate that VE-cadherin can partially be a biomarker of neu-roinflammation disease and lead to novel approaches for abating BBB dysregulation under pathological conditions and the opening of the BBB following central nervous system (CNS) drug delivery.

Lipid-based nanocarrier efficiently delivers highly water soluble drug across the blood-brain barrier into brain

Delivering highly water soluble drugs across blood-brain barrier (BBB) is a crucial challenge for the formulation scientists. A successful therapeutic intervention by developing a suitable drug delivery system may revolutionize treatment across BBB. Efforts were given here to unravel the capability of a newly developed fatty acid combination (stearic acid:oleic acid:palmitic acid = 8.08:4.13:1) (ML) as fundamental component of nanocarrier to deliver highly water soluble zidovudine (AZT) as a model drug into brain across BBB. A comparison was made with an experimentally developed standard phospholipid-based nanocarrier containing AZT. Both the formulations had nanosize spherical unilamellar vesicular structure with highly negative zeta potential along with sustained drug release profiles. Gamma scintigraphic images showed both the radiolabeled formulations successfully crossed BBB, but longer retention in brain was observed for ML-based formulation (MGF) as compared to soya lecithin (SL)-based drug carrier (SYF). Plasma and brain pharmacokinetic data showed less clearance, prolonged residence time, more bioavailability and sustained release of AZT from MGF in rats compared to those data of the rats treated with SYF/AZT suspension. Thus, ML may be utilized to successfully develop drug nanocarrier to deliver drug into brain across BBB, in a sustained manner for a prolong period of time and may provide an effective therapeutic strategy for many diseases of brain. Further, many anti-HIV drugs cannot cross BBB sufficiently. Hence, the developed formulation may be a suitable option to carry those drugs into brain for better therapeutic management of HIV.

3D self-organized microvascular model of the human blood-brain barrier with endothelial cells, pericytes and astrocytes

The blood-brain barrier (BBB) regulates molecular trafficking, protects against pathogens, and prevents efficient drug delivery to the brain. Models to date failed to reproduce the human anatomical complexity of brain barriers, contributing to misleading results in clinical trials. To overcome these limitations, a novel 3-dimensional BBB microvascular network model was developed via vasculogenesis to accurately replicate the in vivo neurovascular organization. This microfluidic system includes human induced pluripotent stem cell-derived endothelial cells, brain pericytes, and astrocytes as self-assembled vascular networks in fibrin gel. Gene expression of membrane transporters, tight junction and extracellular matrix proteins, was consistent with computational analysis of geometrical structures and quantitative immunocytochemistry, indicating BBB maturation and microenvironment remodelling. Confocal microscopy validated microvessel-pericyte/astrocyte dynamic contact-interactions. The BBB model exhibited perfusable and selective microvasculature, with permeability lower than conventional in vitro models, and similar to in vivo measurements in rat brain. This robust and physiologically relevant BBB microvascular model offers an innovative and valuable platform for drug discovery to predict neuro-therapeutic transport efficacy in pre-clinical applications as well as recapitulate patient-specific and pathological neurovascular functions in neurodegenerative disease.

Isolation of Cerebral Capillaries from Fresh Human Brain Tissue

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic strategies that hold the promise to enhance brain drug delivery, improve brain protection, and treat brain disorders. However, studying the human blood-brain barrier function is challenging. Thus, there is a critical need for appropriate models. In this regard, brain capillaries isolated from human brain tissue represent a unique tool to study barrier function as close to the human in vivo situation as possible. Here, we describe an optimized protocol to isolate capillaries from human brain tissue at a high yield and with consistent quality and purity. Capillaries are isolated from fresh human brain tissue using mechanical homogenization, density-gradient centrifugation, and filtration. After the isolation, the human brain capillaries can be used for various applications including leakage assays, live cell imaging, and immune-based assays to study protein expression and function, enzyme activity, or intracellular signaling. Isolated human brain capillaries are a unique model to elucidate the regulation of the human blood-brain barrier function. This model can provide insights into central nervous system (CNS) pathogenesis, which will help the development of therapeutic strategies for treating CNS disorders.

Review Article: Capturing the physiological complexity of the brain's neuro-vascular unit in vitro

With the accelerating pace of brain research in recent years and the growing appreciation of the complexity of the brain and several brain-associated neurological diseases, the demand for powerful tools to enhance drug screening, diagnosis, and fundamental research is greater than ever. Highly representative models of the central nervous system (CNS) can play a critical role in meeting these needs. Unfortunately, in vivo animal models lack controllability, are difficult to monitor, and do not model human-specific brain behavior accurately. On the other hand, in silico computational models struggle to capture comprehensively the intertwined biological, chemical, electrical, and mechanical complexity of the brain. This leaves us with the promising domain of "organ-on-chip" in vitro models. In this review, we describe some of the most pioneering efforts in this expanding field, offering a perspective on the new possibilities as well as the limitations of each approach. We focus particularly on how the models reproduce the blood-brain barrier (BBB), which mediates mass transport to and from brain tissue. We also offer a brief commentary on strategies for evaluating the blood-brain barrier functionality of these in vitro models, including trans-endothelial electrical resistance (TEER), immunocytochemistry, and permeability analysis. From the early membrane-based models of the BBB that have grown into the Transwell® class of devices, to the era of microfluidic chips and a future of bio-printed tissue, we see enormous improvement in the reliability of in vitro models. More and more of the biological and structural complexity of the BBB is being captured by microfluidic chips, and the organ-specificity of bio-printed tissue is also significantly improved. Although we believe that the long-term solution will eventually take the form of automated and parallelized bio-printing systems, we find that valuable transport studies can already be accomplished with microfluidic platforms.

Bridging barriers: a comparative look at the blood-brain barrier across organisms

This review by O'Brown et al. discusses the cellular nature of the blood–brain barrier (BBB) and the conservation and variation of BBB function across taxa. It compares the BBB across organisms in order to provide insight into the human BBB both under normal physiological conditions and in neurological diseases.

The blood–brain barrier (BBB) restricts free access of molecules between the blood and the brain and is essential for regulating the neural microenvironment. Here, we describe how the BBB was initially characterized and how the current field evaluates barrier properties. We next detail the cellular nature of the BBB and discuss both the conservation and variation of BBB function across taxa. Finally, we examine our current understanding of mouse and zebrafish model systems, as we expect that comparison of the BBB across organisms will provide insight into the human BBB under normal physiological conditions and in neurological diseases.

New Insights into Microglia-Neuron Interactions: A Neuron's Perspective

Microglia are the primary immune cells of the central nervous system. However, recent data indicate that microglia also contribute to diverse physiological and pathophysiological processes that extend beyond immune-related functions and there is a growing interest to understand the mechanisms through which microglia interact with other cells in the brain. In particular, the molecular processes that contribute to microglia-neuron communication in the healthy brain and their role in common brain diseases have been intensively studied during the last decade. In line with this, fate-mapping studies, genetic models and novel pharmacological approaches have revealed the origin of microglial progenitors, demonstrated the role of self-maintaining microglial populations during brain development or in adulthood, and identified the unexpectedly long lifespan of microglia that may profoundly change our view about senescence and age-related human diseases. Despite the exponentially increasing knowledge about microglia, the role of these cells in health and disease is still extremely controversial and the precise molecular targets for intervention are not well defined. This is in part due to the lack of microglia-specific manipulation approaches until very recently and to the high level of complexity of the interactions between microglia and other cells in the brain that occur at different temporal and spatial scales. In this review, we briefly summarize the known physiological roles of microglia-neuron interactions in brain homeostasis and attempt to outline some major directions and challenges of future microglia research.

Regulation of neuroblast proliferation by surface glia in the Drosophila larval brain

Despite the importance of precisely regulating stem cell division, the molecular basis for this control is still elusive. Here, we show that surface glia in the developing Drosophila brain play essential roles in regulating the proliferation of neural stem cells, neuroblasts (NBs). We found that two classes of extracellular factors, Dally-like (Dlp), a heparan sulfate proteoglycan, and Glass bottom boat (Gbb), a BMP homologue, are required for proper NB proliferation. Interestingly, Dlp expressed in perineural glia (PG), the most outer layer of the surface glia, is responsible for NB proliferation. Consistent with this finding, functional ablation of PG using a dominant-negative form of dynamin showed that PG has an instructive role in regulating NB proliferation. Gbb acts not only as an autocrine proliferation factor in NBs but also as a paracrine survival signal in the PG. We propose that bidirectional communication between NBs and glia through TGF-β signaling influences mutual development of these two cell types. We also discuss the possibility that PG and NBs communicate via direct membrane contact or transcytotic transport of membrane components. Thus, our study shows that the surface glia acts not only as a simple structural insulator but also a dynamic regulator of brain development.

Iron transport kinetics through blood-brain barrier endothelial cells

BACKGROUND

Transferrin and its receptors play an important role during the uptake and transcytosis of iron through blood-brain barrier (BBB) endothelial cells (ECs) to maintain iron homeostasis in BBB endothelium and brain. Any disruptions in the cell environment may change the distribution of transferrin receptors on the cell surface, which eventually alter the homeostasis and initiate neurodegenerative disorders. In this paper, we developed a comprehensive mathematical model that considers the necessary kinetics for holo-transferrin internalization and acidification, apo-transferrin recycling, and exocytosis of free iron and transferrin-bound iron through basolateral side of BBB ECs.

METHODS

Ordinary differential equations are formulated based on the first order reaction kinetics to model the iron transport considering their interactions with transferrin and transferrin receptors. Unknown kinetics rate constants are determined from experimental data by applying a non-linear optimization technique.

RESULTS

Using the estimated kinetic rate constants, the presented model can effectively reproduce the experimental data of iron transports through BBB ECs for many in-vitro studies. Model results also suggest that the BBB ECs can regulate the extent of the two possible iron transport pathways (free and transferrin-bound iron) by controlling the receptor expression, internalization of holo-transferrin-receptor complexes and acidification of holo-transferrin inside the cell endosomes.

CONCLUSION

The comprehensive mathematical model described here can predict the iron transport through BBB ECs considering various possible routes from blood side to brain side. The model can also predict the transferrin and iron transport behavior in iron-enriched and iron-depleted cells, which has not been addressed in previous work.

In vitro models and systems for evaluating the dynamics of drug delivery to the healthy and diseased brain

The blood-brain barrier (BBB) plays a crucial role in maintaining brain homeostasis and transport of drugs to the brain. The conventional animal and Transwell BBB models along with emerging microfluidic-based BBB-on-chip systems have provided fundamental functionalities of the BBB and facilitated the testing of drug delivery to the brain tissue. However, developing biomimetic and predictive BBB models capable of reasonably mimicking essential characteristics of the BBB functions is still a challenge. In addition, detailed analysis of the dynamics of drug delivery to the healthy or diseased brain requires not only biomimetic BBB tissue models but also new systems capable of monitoring the BBB microenvironment and dynamics of barrier function and delivery mechanisms. This review provides a comprehensive overview of recent advances in microengineering of BBB models with different functional complexity and mimicking capability of healthy and diseased states. It also discusses new technologies that can make the next generation of biomimetic human BBBs containing integrated biosensors for real-time monitoring the tissue microenvironment and barrier function and correlating it with the dynamics of drug delivery. Such integrated system addresses important brain drug delivery questions related to the treatment of brain diseases. We further discuss how the combination of in vitro BBB systems, computational models and nanotechnology supports for characterization of the dynamics of drug delivery to the brain.