Plasma albumin is a potent trigger of calcium signals and DNA synthesis in astrocytes

Astrocytes sense glymphatic-level shear stress through the interaction of sphingosine-1-phosphate with Piezo1

Astrocyte endfeet enwrap brain vasculature, forming a boundary for perivascular glymphatic flow of fluid and solutes along and across the astrocyte endfeet into the brain parenchyma. We evaluated astrocyte sensitivity to shear stress generated by such flow, finding a set point for downstream calcium signaling that is below about 0.1 dyn/cm2. This set point is modulated by albumin levels encountered in cerebrospinal fluid (CSF) under normal conditions and following a blood-brain barrier breach or immune response. The astrocyte mechanosome responsible for the detection of shear stress includes sphingosine-1-phosphate (S1P)-mediated sensitization of the mechanosensor Piezo1. Fluid flow through perivascular channels delimited by vessel wall and astrocyte endfeet thus generates sufficient shear stress to activate astrocytes, thereby potentially controlling vasomotion and parenchymal perfusion. Moreover, S1P receptor signaling establishes a set point for Piezo1 activation that is finely tuned to coincide with CSF albumin levels and to the low shear forces resulting from glymphatic flow.

Understanding the mechanisms underlying the disruption of the blood-brain barrier in parasitic infections

Parasites have a significant impact on the neurological, cognitive, and mental well-being of humans, with a global population of over 1 billion individuals affected. The pathogenesis of central nervous system (CNS) injury in parasitic diseases remains limited, and prevention and control of parasitic CNS infections remain significant areas of research. Parasites, encompassing both unicellular and multicellular organisms, have intricate life cycles and possess the ability to infect a diverse range of hosts, including the human population. Parasitic illnesses that impact the central and peripheral nervous systems are a significant contributor to morbidity and mortality in low- to middle-income nations. The precise pathways through which neurotropic parasites infiltrate the CNS by crossing the blood-brain barrier (BBB) and cause neurological harm remain incompletely understood. Investigating brain infections caused by parasites is closely linked to studying neuroinflammation and cerebral impairment. The exact molecular and cellular mechanisms involved in this process remain incomplete, but understanding the exact mechanisms could provide insight into their pathogenesis and potentially reveal novel therapeutic targets. This review paper explores the underlying mechanisms involved in the development of neurological disorders caused by parasites, including parasite-derived elements, host immune responses, and modifications in tight junctions (TJs) proteins.

Astrocyte sensitivity to glymphatic shear stress is amplified by albumin and mediated by the interaction of sphingosine 1 phosphate with Piezo1

Astrocyte endfeet enwrap brain vasculature, forming a boundary for perivascular glymphatic flow of fluid and solutes along and across the astrocyte endfeet into the brain parenchyma. To determine whether astrocytes may sense and respond to the shear forces generated by glymphatic flow, we examined intracellular calcium (Ca 2+ ) changes evoked in astrocytes to brief fluid flow applied in calibrated microfluidic chambers. Shear stresses < 20 dyn/cm 2 failed to evoke Ca 2+ responses in the absence of albumin, but cells responded to shear stress below 1 dyn/cm 2 when as little as 5 μM albumin was present in flow medium. A role for extracellular matrix in mechanotransduction was indicated by reduced sensitivity after degradation of heparan sulfate proteoglycan. Sphingosine-1-phosphate (S1P) amplified shear responses in the absence of albumin, whereas mechanosensitivity was attenuated by the S1P receptor blocker fingolimod. Piezo1 participated in the transduction as revealed by blockade by the spider toxin GsMTX and amplification by the chemical modulator Yoda1, even in absence of albumin or S1P. Our findings that astrocytes are exquisitely sensitive to shear stress and that sensitivity is greatly amplified by albumin concentrations encountered in normal and pathological CSF predict that perivascular astrocytes are responsive to glymphatic shear stress and that responsiveness is augmented by elevated CSF protein. S1P receptor signaling thus establishes a setpoint for Piezo1 activation that is finely tuned to coincide with albumin level in CSF and to the low shear forces resulting from glymphatic flow.

Graphical abstract

Astrocyte endfoot responds to glymphatic shear stress when albumin is present. Mechanism involves sphingosine-1-phosphate (S1P) binding to its receptor (S1PR), activating phospholipase C (PLC) and thereby sensitizing the response of Piezo1 to flow. Ca 2+ influx triggers Ca 2+ release from intracellular stores and further downstream signaling, thereby modulating parenchymal perfusion. Illustration created using BioRender.com.

Expanded vacuum-stable gels for multiplexed high-resolution spatial histopathology

Cellular organization and functions encompass multiple scales in vivo. Emerging high-plex imaging technologies are limited in resolving subcellular biomolecular features. Expansion Microscopy (ExM) and related techniques physically expand samples for enhanced spatial resolution, but are challenging to be combined with high-plex imaging technologies to enable integrative multiscaled tissue biology insights. Here, we introduce Expand and comPRESS hydrOgels (ExPRESSO), an ExM framework that allows high-plex protein staining, physical expansion, and removal of water, while retaining the lateral tissue expansion. We demonstrate ExPRESSO imaging of archival clinical tissue samples on Multiplexed Ion Beam Imaging and Imaging Mass Cytometry platforms, with detection capabilities of > 40 markers. Application of ExPRESSO on archival human lymphoid and brain tissues resolved tissue architecture at the subcellular level, particularly that of the blood-brain barrier. ExPRESSO hence provides a platform for extending the analysis compatibility of hydrogel-expanded biospecimens to mass spectrometry, with minimal modifications to protocols and instrumentation.

In silico identification of molecular mechanisms for stroke risk caused by heavy metals and their mixtures: sponges and drugs involved

This study used various approaches and databases to evaluate the molecular processes and identify miRNA sponges and drugs associated with the development of stroke caused by heavy metals and their combinations. We found that the genes ALB (albumin), IL1B (Interleukin-1β), F2 (coagulation factor II), APOA1 (apolipoprotein A1), IL6 (Interleukin 6), and NOS2 (nitric oxide synthase 2) were linked to the development of strokes by 18 chemicals and a combination of cadmium, copper, and lead. These results may point to the significance of detoxification and neuroinflammation in stroke as well as the potential for targeting these genes in future stroke therapies. ALB and IL1B were the most common and significant genes. The "selenium micronutrient network," "vitamin B12 metabolism," and "folate metabolism" were shown to be the most significant pathways connected to the risk of stroke brought on by combined heavy metals. The two main cellular elements that may increase the risk of stroke caused by heavy metals were discovered to be "blood microparticle" and "endoplasmic reticulum lumen." We also observed an important chromosome (chr7p15.3), two transcription factors (NFKB2 [nuclear factor kappa B subunit 2] and NR1I2 [nuclear receptor subfamily 1 group, member 2]), and four microRNAs (hsa-miR-26a-5p, hsa-miR-9-5p, hsa-miR-124-3p, and hsa-miR-155-5p) associated with stroke caused by combined heavy metals. Additionally, for these miRNAs, we created and examined in silico microRNA sponge sequences. Triflusal and andrographolide have been identified as potential treatments for heavy metal-induced stroke. Taken together, heavy metals may be a significant contributor to the pathophysiology of stroke, but further investigation into the precise molecular pathways implicated in stroke pathophysiology is required to corroborate these findings.

VCAM1 Drives Vascular Inflammation Leading to Continuous Cortical Neuronal Loss Following Chronic Cerebral Hypoperfusion

BACKGROUND

Chronic cerebral hypoperfusion (CCH) is associated with neuronal loss and blood-brain barrier (BBB) impairment in vascular dementia (VaD). However, the relationship and the molecular mechanisms between BBB dysfunction and neuronal loss remain elusive.

OBJECTIVE

We explored the reasons for neuron loss following CCH.

METHODS

Using permanent bilateral common carotid artery occlusion (2VO) rat model, we observed the pathological changes of cortical neurons and BBB in the sham group as well as rats 3d, 7d, 14d and 28d post 2VO. In order to further explore the factors influencing neuron loss following CCH with regard to cortical blood vessels, we extracted cortical brain microvessels at five time points for transcriptome sequencing. Finally, integrin receptor a4β1 (VLA-4) inhibitor was injected into the tail vein, and cortical neuron loss was detected again.

RESULTS

We found that cortical neuron loss following CCH is a continuous process, but damage to the BBB is acute and transient. Results of cortical microvessel transcriptome analysis showed that biological processes related to vascular inflammation mainly occurred in the chronic phase. Meanwhile, cell adhesion molecules, cytokine-cytokine receptor interaction were significantly changed at this phase. Among them, the adhesion molecule VCAM1 plays an important role. Using VLA-4 inhibitor to block VCAM1-VLA-4 interaction, cortical neuron damage was ameliorated at 14d post 2VO.

CONCLUSION

Injury of the BBB may not be the main reason for persistent loss of cortical neurons following CCH. The continuous inflammatory response within blood vessels maybe an important factor in the continuous loss of cortical neurons following CCH.

Wharton's jelly mesenchymal stem cells attenuate global hypoxia-induced learning and memory impairment via preventing blood-brain barrier breakdown

Objectives

Intracerebroventricular (ICV) injections of mesenchymal stem cells (MSCs) may improve the function and structure of blood-brain barrier (BBB), possibly by preserving the BBB integrity. This study examined the impact of Wharton's jelly (WJ)-MSCs on cognitive dysfunction and BBB disruption following a protracted hypoxic state.

Materials and Methods

Twenty-four male Wistar rats were randomly studied in four groups: Control (Co): Healthy animals, Sham (Sh): Rats were placed in the cage without hypoxia induction and with ICV injection of vehicle, Hypoxic (Hx)+vehicle: Hypoxic rats with ICV injection of vehicle (5 μl of PBS), and Hx+MSCs: Hypoxic rats with ICV injection of MSCs. Spatial learning and memory were evaluated one week after WJ-MSCs injection, and then animals were sacrificed for molecular research.

Results

Hypoxia increased latency and lowered the time and distance required reaching the target quarter, according to the findings. Furthermore, hypoxic rats had lower gene expression and protein levels of hippocampus vascular endothelial (VE)-cadherin, claudin 5, and tricellulin gene expression than Co and Sh animals (P<0.05). Finally, administering WJ-MSCs after long-term hypoxia effectively reversed the cognitive deficits and prevented the BBB breakdown via the upregulation of VE-cadherin, claudin 5, and tricellulin genes (P<0.05).

Conclusion

These findings suggest that prolonged hypoxia induces spatial learning and memory dysfunction and increases BBB disruption, the potential mechanism of which might be via reducing VE-cadherin, claudin 5, and tricellulin genes. Hence, appropriate treatment with WJ-MSCs could reverse ischemia adverse effects and protect the BBB integrity following prolonged hypoxia.

Blood brain barrier and inflammation in depression

The blood brain barrier (BBB) is a vital structure to protect the brain, tightly filtering the passage of nutrients and molecules from the blood to the brain. This is critical for maintaining the proper functioning of the brain, and any disruption in the BBB has detrimental consequences often leading to diseases. It is not clear whether disruption of the BBB occurs first in depression or is the consequence of the disease, however disruption of the BBB has been observed in depressed patients and evidence points to the role of important culprits in depression, stress and inflammation in disrupting the integrity of the BBB. The mechanisms whereby stress, and inflammation affect the BBB remain to be fully understood. Yet, the role of cytokines in regulating tight junction protein expression seems crucial. Altogether, the findings in depression suggest that acting at the BBB level might provide therapeutic benefit in depression.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Exosomes and Other Extracellular Vesicles with High Therapeutic Potential: Their Applications in Oncology, Neurology, and Dermatology

Until thirty years ago, it was believed that extracellular vesicles (EVs) were used to remove unnecessary compounds from the cell. Today, we know about their enormous potential in diagnosing and treating various diseases. EVs are essential mediators of intercellular communication, enabling the functional transfer of bioactive molecules from one cell to another. Compared to laboratory-created drug nanocarriers, they are stable in physiological conditions. Furthermore, they are less immunogenic and cytotoxic compared to polymerized vectors. Finally, EVs can transfer cargo to particular cells due to their membrane proteins and lipids, which can implement them to specific receptors in the target cells. Recently, new strategies to produce ad hoc exosomes have been devised. Cells delivering exosomes have been genetically engineered to overexpress particular macromolecules, or transformed to release exosomes with appropriate targeting molecules. In this way, we can say tailor-made therapeutic EVs are created. Nevertheless, there are significant difficulties to solve during the application of EVs as drug-delivery agents in the clinic. This review explores the diversity of EVs and the potential therapeutic options for exosomes as natural drug-delivery vehicles in oncology, neurology, and dermatology. It also reflects future challenges in clinical translation.

Effects of Polyphenols on Oxidative Stress, Inflammation, and Interconnected Pathways during Spinal Cord Injury

Despite the progression in targeting the complex pathophysiological mechanisms of neurodegenerative diseases (NDDs) and spinal cord injury (SCI), there is a lack of effective treatments. Moreover, conventional therapies suffer from associated side effects and low efficacy, raising the need for finding potential alternative therapies. In this regard, a comprehensive review was done regarding revealing the main neurological dysregulated pathways and providing alternative therapeutic agents following SCI. From the mechanistic point, oxidative stress and inflammatory pathways are major upstream orchestras of cross-linked dysregulated pathways (e.g., apoptosis, autophagy, and extrinsic mechanisms) following SCI. It urges the need for developing multitarget therapies against SCI complications. Polyphenols, as plant-derived secondary metabolites, have the potential of being introduced as alternative therapeutic agents to pave the way for treating SCI. Such secondary metabolites presented modulatory effects on neuronal oxidative stress, neuroinflammatory, and extrinsic axonal dysregulated pathways in the onset and progression of SCI. In the present review, the potential role of phenolic compounds as critical phytochemicals has also been revealed in regulating upstream dysregulated oxidative stress/inflammatory signaling mediators and extrinsic mechanisms of axonal regeneration after SCI in preclinical and clinical studies. Additionally, the coadministration of polyphenols and stem cells has shown a promising strategy for improving post-SCI complications.

Blood-Brain Barrier Dysfunction in CNS Disorders and Putative Therapeutic Targets: An Overview

The blood-brain barrier (BBB) is a fundamental component of the central nervous system (CNS). Its functional and structural integrity is vital to maintain the homeostasis of the brain microenvironment by controlling the passage of substances and regulating the trafficking of immune cells between the blood and the brain. The BBB is primarily composed of highly specialized microvascular endothelial cells. These cells’ special features and physiological properties are acquired and maintained through the concerted effort of hemodynamic and cellular cues from the surrounding environment. This complex multicellular system, comprising endothelial cells, astrocytes, pericytes, and neurons, is known as the neurovascular unit (NVU). The BBB strictly controls the transport of nutrients and metabolites into brain parenchyma through a tightly regulated transport system while limiting the access of potentially harmful substances via efflux transcytosis and metabolic mechanisms. Not surprisingly, a disruption of the BBB has been associated with the onset and/or progression of major neurological disorders. Although the association between disease and BBB disruption is clear, its nature is not always evident, specifically with regard to whether an impaired BBB function results from the pathological condition or whether the BBB damage is the primary pathogenic factor prodromal to the onset of the disease. In either case, repairing the barrier could be a viable option for treating and/or reducing the effects of CNS disorders. In this review, we describe the fundamental structure and function of the BBB in both healthy and altered/diseased conditions. Additionally, we provide an overview of the potential therapeutic targets that could be leveraged to restore the integrity of the BBB concomitant to the treatment of these brain disorders.

Use of Super Paramagnetic Iron Oxide Nanoparticles as Drug Carriers in Brain and Ear: State of the Art and Challenges

Drug delivery and distribution in the central nervous system (CNS) and the inner ear represent a challenge for the medical and scientific world, especially because of the blood-brain and the blood-perilymph barriers. Solutions are being studied to circumvent or to facilitate drug diffusion across these structures. Using superparamagnetic iron oxide nanoparticles (SPIONs), which can be coated to change their properties and ensure biocompatibility, represents a promising tool as a drug carrier. They can act as nanocarriers and can be driven with precision by magnetic forces. The aim of this study was to systematically review the use of SPIONs in the CNS and the inner ear. A systematic PubMed search between 1999 and 2019 yielded 97 studies. In this review, we describe the applications of the SPIONS, their design, their administration, their pharmacokinetic, their toxicity and the methods used for targeted delivery of drugs into the ear and the CNS.

Investigation of brain damage mechanism in middle cerebral artery occlusion/reperfusion rats based on i-TRAQ quantitative proteomics

The objective of this study is to analyze the differential protein expression profile in cerebral cortex of rats with middle cerebral ischemia/reperfusion (MCAO/R), explore the brain damage mechanism of MCAO/R at protein level, and provide experimental foundation for searching specific marker proteins of MCAO/R. Rat model of MCAO/R was established by modified suture-occluded method, and the model was evaluated by the results of brain 2,3,5-triphenyltetrazolium chloride (TTC) and hematoxylin-eosin (HE) staining. Cerebral cortex of rats from sham-operated group (Sham) and MCAO/R groups was used for FASP enzymatic hydrolysis, i-TRAQ quantitative labeling, and reverse-phase liquid chromatography purification and separation. Orbitrap Q Exactive mass spectrometry was used for qualitative and quantitative analyses of total differential protein expression profiles. MCAO/R rats had obvious cerebral infarction lesions, and the relative surface area of cerebral infarction was significantly different compared with sham rats, suggesting that MCAO/R rat model was successfully prepared. There were 199 significant difference proteins (MCAO/R vs Sham, p < 0.05, |fold change|> 1.2), including 104 up-regulated proteins and 95 down-regulated proteins. Gene ontology (GO) enrichment analysis showed that the up-regulated proteins were mainly concentrated in the biological processes of positive regulation of NF-κB transcription and I-κB kinase-NF-κB, etc. Down-regulated proteins were mainly concentrated in long-term synaptic potentiation, cellular response to DNA damage stimulus, etc. KEGG pathway analysis showed that the pathway involved in differential proteins includes oxidative phosphorylation, metabolic pathway, and Ras signaling pathway. Network analysis of differential proteins showed that Alb, ndufb5, ndufs7, ApoB, Cdc42, Ndufa3, Igf1r, P4hb, Mbp, Gc, Nme1, Akt2, and other proteins may play an important role in regulating oxidative stress, apoptosis, and inflammatory response in MCAO/R. Quantitative proteomics based on i-TRAQ labeling reveals the effect of inflammation and apoptosis in brain damage mechanism of MCAO/R. Besides, this research provide some experimental foundation for search and determination of potential therapeutic targets of MCAO/R.

Seizure-Induced Acute Glial Activation in the in vitro Isolated Guinea Pig Brain

Introduction: It has been proposed that seizures induce IL-1β biosynthesis in astrocytes and increase blood brain barrier (BBB) permeability, even without the presence of blood borne inflammatory molecules and leukocytes. In the present study we investigate if seizures induce morphological changes typically observed in activated glial cells. Moreover, we will test if serum albumin extravasation into the brain parenchyma exacerbates neuronal hyperexcitability by inducing astrocytic and microglial activation.

Methods: Epileptiform seizure-like events (SLEs) were induced in limbic regions by arterial perfusion of bicuculline methiodide (BMI; 50 μM) in the in vitro isolated guinea pig brain preparation. Field potentials were recorded in both the hippocampal CA1 region and the medial entorhinal cortex. BBB permeability changes were assessed by analyzing extravasation of arterially perfused fluorescein isothiocyanate (FITC)–albumin. Morphological changes in astrocytes and microglia were evaluated with tridimensional reconstruction and Sholl analysis in the ventral CA1 area of the hippocampus following application of BMI with or without co-perfusion of human serum albumin.

Results: BMI-induced SLE promoted morphological changes of both astrocytes and microglia cells into an activated phenotype, confirmed by the quantification of the number and length of their processes. Human-recombinant albumin extravasation, due to SLE-induced BBB impairment, worsened both SLE duration and the activated glia phenotype.

Discussion: Our study provides the first direct evidence that SLE activity per se is able to promote the activation of astro- and microglial cells, as observed by their changes in phenotype, in brain regions involved in seizure generation; we also hypothesize that gliosis, significantly intensified by h-recombinant albumin extravasation from the bloodstream to the brain parenchyma due to SLE-induced BBB disruption, is responsible for seizure activity reinforcement.

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.

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.

Current approaches to enhancing oxime reactivator delivery into the brain

The misuse of organophosphate compounds still represents a current threat worldwide. Treatment of poisoning with organophosphates (OPs) remains unsatisfactorily resolved despite the extensive investment in research in academia. There are no universal, effective and centrally-active acetylcholinesterase (AChE) reactivators to countermeasure OP intoxication. One major obstacle is to overcome the blood-brain barrier (BBB). The central compartment is readily accessible by the OPs which are lipophilic bullets that can easily cross the BBB, whereas first-line therapeutics, namely oxime-based AChE reactivators and atropine, do not cross or do so rather slowly. The limitation of oxime-based AChE reactivators can be ascribed to their chemical nature, bearing a positive charge which is essential either for their AChE affinity or their reactivating potency. The aim of this article is to review the methods for targeting the brain by oxime reactivators that have been developed so far. Approaches using prodrugs, lipophilicity enhancement, or sugar-based oximes have been rather unsuccessful. However, other strategies have been more promising, such as the use of nanoparticles or co-administration of the reactivator with efflux transporter inhibitors. Encouraging results have also been associated with intranasal delivery, but research in this field is still at the beginning. Further research of auspicious approaches is inevitable.

The Blood-Brain Barrier Breakdown During Acute Phase of the Pilocarpine Model of Epilepsy Is Dynamic and Time-Dependent

The maintenance of blood-brain barrier (BBB) integrity is essential for providing a suitable environment for nervous tissue function. BBB disruption is involved in many central nervous system diseases, including epilepsy. Evidence demonstrates that BBB breakdown may induce epileptic seizures, and conversely, seizure-induced BBB disruption may cause further epileptic episodes. This study was conducted based on the premise that the impairment of brain tissue during the triggering event may determine the organization and functioning of the brain during epileptogenesis, and that BBB may have a key role in this process. Our purpose was to investigate in rats the relationship between pilocarpine-induced status epilepticus (SE), and BBB integrity by determining the time course of the BBB opening and its subsequent recovery during the acute phase of the pilocarpine model. BBB integrity was assessed by quantitative and morphological methods, using sodium fluorescein and Evans blue (EB) dyes as markers of the increased permeability to micromolecules and macromolecules, respectively. Different time-points of the pilocarpine model were analyzed: 30 min after pilocarpine injection and then 1, 5, and 24 h after the SE onset. Our results show that BBB breakdown is a dynamic phenomenon and time-dependent, i.e., it happens at specific time-points of the acute phase of pilocarpine model of epilepsy, recovering in part its integrity afterwards. Pilocarpine-induced changes on brain tissue initially increases the BBB permeability to micromolecules, and subsequently, around 5 h after SE, the BBB breakdown to macromolecules occurs. After BBB breakdown, EB dye is captured by damaged cells, especially neurons, astrocytes, and oligodendrocytes. Although the BBB permeability to macromolecules is restored 24 h after the start of SE, the leakage of micromolecules persists and the consequences of BBB degradation are widely disseminated in the brain. Our findings reveal the existence of a temporal window of BBB dysfunction in the acute phase of the pilocarpine model that is important for the development of therapeutic strategies that could prevent the epileptogenesis.

Biologically-derived nanomaterials for targeted therapeutic delivery to the brain

Delivery of imaging agents and pharmaceutical payloads to the central nervous system (CNS) is essential for efficient diagnosis and treatment of brain diseases. However, therapeutic delivery is often restricted by the blood-brain barrier (BBB), which prevents transport of clinical compounds to their region of interest. This review discusses the methods that have been used to avoid or overcome this barrier, presenting the use of biologically-derived nanomaterial systems as an efficient strategy for the diagnosis and treatment of CNS diseases. Biological nanomaterials have many advantages over synthetic systems, including being biodegradable, biocompatible, easily surface functionalised for conjugation of targeting moieties, and are often able to self-assemble. These abilities are discussed in relation to various systems, including liposomes, dendrimers, and viral nanoparticles.

Investigational chemotherapy and novel pharmacokinetic mechanisms for the treatment of breast cancer brain metastases

In women, breast cancer is the most common cancer diagnosis and second most common cause of cancer death. More than half of breast cancer patients will develop metastases to the bone, liver, lung, or brain. Breast cancer brain metastases (BCBM) confers a poor prognosis, as current therapeutic options of surgery, radiation, and chemotherapy rarely significantly extend life and are considered palliative. Within the realm of chemotherapy, the last decade has seen an explosion of novel chemotherapeutics involving targeting agents and unique dosage forms. We provide a historical overview of BCBM chemotherapy, review the mechanisms of new agents such as poly-ADP ribose polymerase inhibitors, cyclin-dependent kinase 4/6 inhibitors, phosphatidyl inositol 3-kinaseinhibitors, estrogen pathway antagonists for hormone-receptor positive BCBM; tyrosine kinase inhibitors, antibodies, and conjugates for HER2+ BCBM; repurposed cytotoxic chemotherapy for triple negative BCBM; and the utilization of these new agents and formulations in ongoing clinical trials. The mechanisms of novel dosage formulations such as nanoparticles, liposomes, pegylation, the concepts of enhanced permeation and retention, and drugs utilizing these concepts involved in clinical trials are also discussed. These new treatments provide a promising outlook in the treatment of BCBM.

Permeability of the Blood-Brain Barrier and Transport of Nanobodies Across the Blood-Brain Barrier

The presence of a blood-brain barrier (BBB) and a blood-cerebrospinal fluid barrier presents animmense challenge for effective delivery of therapeutics to the central nervous system. Many potential drugs, which are effective at their site of action, have failed due to the lack of distribution in sufficient quantity to the central nervous system (CNS). In consequence, many diseases of the central nervous system remain undertreated. Antibodies, IgG for example, are difficult to deliver to the CNS due to their size (~155 kDa), physico-chemical properties and the presence of Fc receptor on the blood-brain barrier. Smaller antibodies, like the recently developed nanobodies, may overcome the obstacle of the BBB and enter into the CNS. The nanobodies are the smallest available antigen-binding fragments harbouring the full antigenbinding capacity of conventional antibodies. They represent a new generation of therapeutics with exceptional properties, such as: recognition of unique epitopes, target specificity, high affinity, high solubility, high stability and high expression yields in cost-effective recombinant production. Their ability to permeate across the BBBmakes thema promising alternative for central nervous system disease therapeutics. In this review, we have systematically presented different aspects of the BBB, drug delivery mechanisms employed to cross the BBB, and finally nanobodies — a potential therapeutic molecule against neuroinfections.

Qualitative and semiquantitative analysis of the protein coronas associated to different functionalized nanoparticles

AIM

The investigation on protein coronas (PCs) adsorbed onto nanoparticle (NP) surface is representing an open issue due to difficulties in detection and clear isolation of the adsorbed proteins. In this study, we investigated protocols able to isolate the compositions of PCs of three polymeric NPs.

MATERIALS & METHODS

Unfunctionalized NPs and two functionalized NPs were considered as proof-of-concept for the qualitative and semiquantitative analysis of both the corona levels (stably or weakly adsorbed coronas [SC/WC]) of these different nanocarriers.

RESULTS

The protocols applied were able to discriminate between the SC and WC. In particular, experimental results indicated that stably adsorbed coronas are prevalently composed by ApoE, while WC by albumin in all the NPs. Otherwise, some differences in WC could be correlated with surface functionalization.

CONCLUSION

This experimental approach allows characterizing the whole PCs, proposing a protocol for isolation of different types of proteins composing PCs.

Glibenclamide pretreatment protects against chronic memory dysfunction and glial activation in rat cranial blast traumatic brain injury

Blast traumatic brain injury (bTBI) affects both military and civilian populations, and often results in chronic deficits in cognition and memory. Chronic glial activation after bTBI has been linked with cognitive decline. Pharmacological inhibition of sulfonylurea receptor 1 (SUR1) with glibenclamide was shown previously to reduce glial activation and improve cognition in contusive models of CNS trauma, but has not been examined in bTBI. We postulated that glibenclamide would reduce chronic glial activation and improve long-term memory function after bTBI. Using a rat direct cranial model of bTBI (dc-bTBI), we evaluated the efficacy of two glibenclamide treatment paradigms: glibenclamide prophylaxis (pre-treatment), and treatment with glibenclamide starting after dc-bTBI (post-treatment). Our results show that dc-bTBI caused hippocampal astrocyte and microglial/macrophage activation that was associated with hippocampal memory dysfunction (rapid place learning paradigm) at 28days, and that glibenclamide pre-treatment, but not post-treatment, effectively protected against glial activation and memory dysfunction. We also report that a brief transient time-window of blood-brain barrier (BBB) disruption occurs after dc-bTBI, and we speculate that glibenclamide, which is mostly protein bound and does not normally traverse the intact BBB, can undergo CNS delivery only during this brief transient opening of the BBB. Together, our findings indicate that prophylactic glibenclamide treatment may help to protect against chronic cognitive sequelae of bTBI in warfighters and other at-risk populations.

Development of a Bifunctional Aptamer Targeting the Transferrin Receptor and Epithelial Cell Adhesion Molecule (EpCAM) for the Treatment of Brain Cancer Metastases

The treatment of brain disorders is greatly hindered by the presence of the blood-brain barrier, which restricts the overwhelming majority of small molecules from entering the brain. A novel approach by which to overcome this barrier is to target receptor mediated transport mechanisms present on the endothelial cell membranes. Therefore, we fused an aptamer that binds to epithelial cell adhesion molecule-expressing cancer cells to an aptamer targeting the transferrin receptor. This generated a proof of concept bifunctional aptamer that can overcome the blood-brain barrier and potentially specifically target brain disorders. The initial fusion of the two sequences enhanced the binding affinity of both aptamers while maintaining specificity. Additionally, mutations were introduced into both binding loops to determine their effect on aptamer specificity. The ability of the aptamer to transcytose the blood-brain barrier was then confirmed in vivo following a 1 nmol injection. This study has shown that through the fusion of two aptamer sequences, a bifunctional aptamer can be generated that has the potential to be developed for the specific treatment of brain disorders.

Neuroadhesive L1 coating attenuates acute microglial attachment to neural electrodes as revealed by live two-photon microscopy

Implantable neural electrode technologies for chronic neural recordings can restore functional control to paralysis and limb loss victims through brain-machine interfaces. These probes, however, have high failure rates partly due to the biological responses to the probe which generate an inflammatory scar and subsequent neuronal cell death. L1 is a neuronal specific cell adhesion molecule and has been shown to minimize glial scar formation and promote electrode-neuron integration when covalently attached to the surface of neural probes. In this work, the acute microglial response to L1-coated neural probes was evaluated in vivo by implanting coated devices into the cortex of mice with fluorescently labeled microglia, and tracking microglial dynamics with multi-photon microscopy for the ensuing 6 h in order to understand L1's cellular mechanisms of action. Microglia became activated immediately after implantation, extending processes towards both L1-coated and uncoated control probes at similar velocities. After the processes made contact with the probes, microglial processes expanded to cover 47.7% of the control probes' surfaces. For L1-coated probes, however, there was a statistically significant 83% reduction in microglial surface coverage. This effect was sustained through the experiment. At 6 h post-implant, the radius of microglia activation was reduced for the L1 probes by 20%, shifting from 130.0 to 103.5 μm with the coating. Microglia as far as 270 μm from the implant site displayed significantly lower morphological characteristics of activation for the L1 group. These results suggest that the L1 surface treatment works in an acute setting by microglial mediated mechanisms.

Evolving Drug Delivery Strategies to Overcome the Blood Brain Barrier

The blood-brain barrier (BBB) poses a unique challenge for drug delivery to the central nervous system (CNS). The BBB consists of a continuous layer of specialized endothelial cells linked together by tight junctions, pericytes, nonfenestrated basal lamina, and astrocytic foot processes. This complex barrier controls and limits the systemic delivery of therapeutics to the CNS. Several innovative strategies have been explored to enhance the transport of therapeutics across the BBB, each with individual advantages and disadvantages. Ongoing advances in delivery approaches that overcome the BBB are enabling more effective therapies for CNS diseases. In this review, we discuss: (1) the physiological properties of the BBB, (2) conventional strategies to enhance paracellular and transcellular transport through the BBB, (3) emerging concepts to overcome the BBB, and (4) alternative CNS drug delivery strategies that bypass the BBB entirely. Based on these exciting advances, we anticipate that in the near future, drug delivery research efforts will lead to more effective therapeutic interventions for diseases of the CNS.

Strategies for delivery of therapeutics into the central nervous system for treatment of lysosomal storage disorders

Lysosomal storage disorders (LSDs) are a group of about fifty life-threatening conditions caused by genetic defects affecting lysosomal components. The underscoring molecular deficiency leads to widespread cellular dysfunction through most tissues in the body, including peripheral organs and the central nervous system (CNS). Efforts during the last few decades have rendered a remarkable advance regarding our knowledge, medical awareness, and early detection of these genetic defects, as well as development of several treatment modalities. Clinical and experimental strategies encompassing enzyme replacement, gene and cell therapies, substrate reduction, and chemical chaperones are showing considerable potential in attenuating the peripheral pathology. However, a major drawback has been encountered regarding the suboptimal impact of these approaches on the CNS pathology. Particular anatomical and biochemical constraints of this tissue pose a major obstacle to the delivery of therapeutics into the CNS. Approaches to overcome these obstacles include modalities of local administration, strategies to enhance the blood-CNS permeability, intranasal delivery, use of exosomes, and those exploiting targeting of transporters and transcytosis pathways in the endothelial lining. The later two approaches are being pursued at the time by coupling therapeutic agents to affinity moieties and drug delivery systems capable of targeting these natural transport routes. This approach is particularly promising, as using paths naturally active at this interface may render safe and effective delivery of LSD therapies into the CNS.

Anatomy and physiology of the blood-brain barrier

Essential requisite for the preservation of normal brain activity is to maintain a narrow and stable homeostatic control in the neuronal environment of the CNS. Blood flow alterations and altered vessel permeability are considered key determinants in the pathophysiology of brain injuries. We will review the present-day literature on the anatomy, development and physiological mechanisms of the blood-brain barrier, a distinctive and tightly regulated interface between the CNS and the peripheral circulation, playing a crucial role in the maintenance of the strict environment required for normal brain function.

Brain tissue responses to neural implants impact signal sensitivity and intervention strategies

Implantable biosensors are valuable scientific tools for basic neuroscience research and clinical applications. Neurotechnologies provide direct readouts of neurological signal and neurochemical processes. These tools are generally most valuable when performance capacities extend over months and years to facilitate the study of memory, plasticity, and behavior or to monitor patients’ conditions. These needs have generated a variety of device designs from microelectrodes for fast scan cyclic voltammetry (FSCV) and electrophysiology to microdialysis probes for sampling and detecting various neurochemicals. Regardless of the technology used, the breaching of the blood–brain barrier (BBB) to insert devices triggers a cascade of biochemical pathways resulting in complex molecular and cellular responses to implanted devices. Molecular and cellular changes in the microenvironment surrounding an implant include the introduction of mechanical strain, activation of glial cells, loss of perfusion, secondary metabolic injury, and neuronal degeneration. Changes to the tissue microenvironment surrounding the device can dramatically impact electrochemical and electrophysiological signal sensitivity and stability over time. This review summarizes the magnitude, variability, and time course of the dynamic molecular and cellular level neural tissue responses induced by state-of-the-art implantable devices. Studies show that insertion injuries and foreign body response can impact signal quality across all implanted central nervous system (CNS) sensors to varying degrees over both acute (seconds to minutes) and chronic periods (weeks to months). Understanding the underlying biological processes behind the brain tissue response to the devices at the cellular and molecular level leads to a variety of intervention strategies for improving signal sensitivity and longevity.

Spinal cord regeneration

Three theories of regeneration dominate neuroscience today, all purporting to explain why the adult central nervous system (CNS) cannot regenerate. One theory proposes that Nogo, a molecule expressed by myelin, prevents axonal growth. The second theory emphasizes the role of glial scars. The third theory proposes that chondroitin sulfate proteoglycans (CSPGs) prevent axon growth. Blockade of Nogo, CSPG, and their receptors indeed can stop axon growth in vitro and improve functional recovery in animal spinal cord injury (SCI) models. These therapies also increase sprouting of surviving axons and plasticity. However, many investigators have reported regenerating spinal tracts without eliminating Nogo, glial scar, or CSPG. For example, many motor and sensory axons grow spontaneously in contused spinal cords, crossing gliotic tissue and white matter surrounding the injury site. Sensory axons grow long distances in injured dorsal columns after peripheral nerve lesions. Cell transplants and treatments that increase cAMP and neurotrophins stimulate motor and sensory axons to cross glial scars and to grow long distances in white matter. Genetic studies deleting all members of the Nogo family and even the Nogo receptor do not always improve regeneration in mice. A recent study reported that suppressing the phosphatase and tensin homolog (PTEN) gene promotes prolific corticospinal tract regeneration. These findings cannot be explained by the current theories proposing that Nogo and glial scars prevent regeneration. Spinal axons clearly can and will grow through glial scars and Nogo-expressing tissue under some circumstances. The observation that deleting PTEN allows corticospinal tract regeneration indicates that the PTEN/AKT/mTOR pathway regulates axonal growth. Finally, many other factors stimulate spinal axonal growth, including conditioning lesions, cAMP, glycogen synthetase kinase inhibition, and neurotrophins. To explain these disparate regenerative phenomena, I propose that the spinal cord has evolved regenerative mechanisms that are normally suppressed by multiple extrinsic and intrinsic factors but can be activated by injury, mediated by the PTEN/AKT/mTOR, cAMP, and GSK3b pathways, to stimulate neural growth and proliferation.

Neuroanesthesiology update

We review topics pertinent to the perioperative care of patients with neurological disorders. Our review addresses topics not only in the anesthesiology literature, but also in basic neurosciences, critical care medicine, neurology, neurosurgery, radiology, and internal medicine literature. We include literature published or available online up through December 8, 2013. As our review is not able to include all manuscripts, we focus on recurring themes and unique and pivotal investigations. We address the broad topics of general neuroanesthesia, stroke, traumatic brain injury, anesthetic neurotoxicity, neuroprotection, pharmacology, physiology, and nervous system monitoring.

Effects of caspase-1 knockout on chronic neural recording quality and longevity: insight into cellular and molecular mechanisms of the reactive tissue response

Chronic implantation of microelectrodes into the cortex has been shown to lead to inflammatory gliosis and neuronal loss in the microenvironment immediately surrounding the probe, a hypothesized cause of neural recording failure. Caspase-1 (aka Interleukin 1β converting enzyme) is known to play a key role in both inflammation and programmed cell death, particularly in stroke and neurodegenerative diseases. Caspase-1 knockout (KO) mice are resistant to apoptosis and these mice have preserved neurologic function by reducing ischemia-induced brain injury in stroke models. Local ischemic injury can occur following neural probe insertion and thus in this study we investigated the hypothesis that caspase-1 KO mice would have less ischemic injury surrounding the neural probe. In this study, caspase-1 KO mice were implanted with chronic single shank 3 mm Michigan probes into V1m cortex. Electrophysiology recording showed significantly improved single-unit recording performance (yield and signal to noise ratio) of caspase-1 KO mice compared to wild type C57B6 (WT) mice over the course of up to 6 months for the majority of the depth. The higher yield is supported by the improved neuronal survival in the caspase-1 KO mice. Impedance fluctuates over time but appears to be steadier in the caspase-1 KO especially at longer time points, suggesting milder glia scarring. These findings show that caspase-1 is a promising target for pharmacologic interventions.

Plasma albumin induces cytosolic calcium oscilations and DNA synthesis in human cultured astrocytes

So far, a little is known about transition from normal to focal epileptic brain, although disruption in blood-brain barrier and albumin had recently involved. The main objective of this work is to characterize the response of cultured human astrocytes to plasma albumin, including induction of DNA synthesis. Cortical tissue was obtained from 9 patients operated from temporal lobe epilepsy. Astrocytes were cultured for 3-4 weeks and cytosolic calcium concentration ([Ca²⁺]_c) was measured. Bovine and human plasma albumin were used. We observed that low albumin concentration decreases [Ca²⁺]_c, while higher concentration, induces increase in [Ca²⁺]_c. It was shown that increase in [Ca²⁺]_c was mediated by inositol 1,4,5-trisphosphate and released from internal stores. Increase in [Ca²⁺]_c was reduced to 19% by blocking the transforming growth factor-beta (TGF-βR) receptor. Albumin induces DNA synthesis in a dose-response manner. Finally, induction of DNA synthesis can be partially blocked by heparin and block of TGF-β; however, the combination of both incompletely inhibits DNA synthesis. Therefore, results suggest that mechanisms other than Ca²⁺ signals and TGF-β receptor activation might induce DNA synthesis in a lesser degree. These results may be important to further understand the mechanisms involved in the transition from normal to focal epileptic brain.

Epileptic focus and alteration of metabolism

Epilepsy is one of the most common neurologic disorders affecting a substantial part of the population worldwide. Epileptic seizures represent the situation of increased neuronal activity associated with the enhanced demands for sufficient energy supply. For that purpose, very efficient regulatory mechanisms have to operate to ensure that cerebral blood flow, delivery of oxygen, and nutrients are continuously adapted to the local metabolic needs. The sophisticated regulation has to function in concert at several levels (systemic, tissue, cellular, and subcellular). Particularly, mitochondria play a key role not only in the energy production, but they are also central to many other processes including those leading to neuronal death. Impairment of any of the involved pathways can result in serious functional alterations, neurodegeneration, and potentially in epileptogenesis. The present review will address some of the important issues concerning vascular and metabolic changes in pathophysiology of epilepsy.

Contributions of astrocytes to epileptogenesis following status epilepticus: opportunities for preventive therapy?

Status epilepticus (SE) is a life threatening condition that often precedes the development of epilepsy. Traditional treatments for epilepsy have been focused on targeting neuronal mechanisms contributing to hyperexcitability, however, approximately 30% of patients with epilepsy do not respond to existing neurocentric pharmacotherapies. A growing body of evidence has demonstrated that profound changes in the morphology and function of astrocytes accompany SE and persist in epilepsy. Astrocytes are increasingly recognized for their diverse roles in modulating neuronal activity, and understanding the changes in astrocytes following SE could provide important clues about the mechanisms underlying seizure generation and termination. By understanding the contributions of astrocytes to the network changes underlying epileptogenesis and the development of epilepsy, we will gain a greater appreciation of the contributions of astrocytes to dynamic circuit changes, which will enable us to develop more successful therapies to prevent and treat epilepsy. This review summarizes changes in astrocytes following SE in animal models and human temporal lobe epilepsy and addresses the functional consequences of those changes that may provide clues to the process of epileptogenesis.

Phenotypic and functional characterization of glucagon-positive cells derived from spontaneous differentiation of D3-mouse embryonic stem cells

BACKGROUND

Glucagon expression is being considered as a definitive endoderm marker in protocols aiming to obtain insulin-secreting cells from embryonic stem cells. However, it should be considered that in vivo glucagon is expressed both in definitive endoderm- and neuroectoderm-derived cells. Therefore, the true nature and function of in vitro spontaneously differentiated glucagon-positive cells remains to be established.

METHODS

D3 and R1 mouse embryonic stem cells as well as α-TC1-9 cells were cultured and glucagon expression was determined by real-time PCR and immunocytochemistry. Functional analyses regarding intracellular calcium oscillations were performed to further characterize glucagon(+) cells.

RESULTS

Specifically, 5% of D3 and R1 cells expressed preproglucagon, with a small percentage of these (<1%) expressing glucagon-like peptide 1. The constitutive expression of protein convertase 5 supports the expression of both peptides. Glucagon(+) cells co-expressed neurofilament middle and some glucagon-like peptide-1(+) cells, glial fibrillary acidic protein, indicating a neuroectodermic origin. However, few glucagon-like peptide-1(+) cells did not show coexpression with glial fibrillary acidic protein, suggesting a non-neuroectodermic origin for these cells. Finally, glucagon(+) cells did not display Ca(2+) oscillations typical of pancreatic α-cells.

DISCUSSION

These results indicate the possible nondefinitive endodermal origin of glucagon-positive cells spontaneously differentiated from D3 and R1 cell lines, as well as the presence of cells expressing glucagon-like peptide-1 from two different origins.

The pre-treatment effect on brain injury during restoration of normal perfusion pressure with hemodilution in a new rat model of chronic cerebral hypoperfusion

OBJECTIVES

To investigate the effect of hemodilution with high-concentration human serum albumin (HSA) on brain injury in a rat model of chronic cerebral hypoperfusion associated with arteriovenous malformations.

METHODS

The animal model was established by creating a fistula through an end-to-side anastomosis between the right distal external jugular vein and the ipsilateral common carotid artery, followed by ligation of the left vein draining the transverse sinus and bilateral external carotid arteries. The agent (20% HSA) or control solution (0.9% sodium chloride) was administered intravenously at a dosage of 1% body weight 24 hours before ligation of the fistula. Blood-brain barrier (BBB) disruption was judged by extravasation of Evans blue (EB) dye. EB, water content and the changes of myeloperoxidase (MPO) activity and superoxide dismutase (SOD) activity in rat brains 24 hours after ligation of the fistula were determined.

RESULTS

EB and water content in rat brains of the pre-treated group were significantly decreased compared with the control group accompanied by reduction of MPO activity and enhancement of SOD activity.

DISCUSSION

Hemodilution with high-concentration HSA has a certain pre-treatment effect on brain injury after ligation of the fistula in rat model of chronic cerebral hypoperfusion, which may be resulted from improved microcirculation, decrease in inflammatory cell infiltration and inactivation of oxygen free radicals.

Serum albumin levels in ischemic stroke and its subtypes: correlation with clinical outcome

OBJECTIVE

Previous studies have associated low serum albumin levels with poor outcome in ischemic stroke. Animal studies also demonstrated neuroprotective effects of serum albumin in focal ischemia. However, there are very limited studies on the association of serum albumin levels with stroke outcome in ischemic stroke divided into subtypes. The present study was carried out to investigate the association of serum albumin levels with outcome in ischemic stroke and its subtypes.

METHODS

The study involved 560 patients. Serum albumin levels were estimated and follow-up interviews were conducted at 3 mo postevent to determine stroke outcome. The association between serum albumin levels and stroke outcome was evaluated by multiple logistic regression analysis after adjustment for potential confounders.

RESULTS

Low levels of albumin associated significantly with poor outcome (score of >3 on the modified Rankin Scale). The adjusted odds ratio was 1.972 (95% confidence interval, 1.103-4.001; P < 0.001). The recurrence of stroke and death rate also was high in patients with low levels of albumin compared with patients with elevated levels of albumin. The reduced level of serum albumin associated significantly with poor outcome in all the stroke subtypes classified according to TOAST (Trial of ORG 10172 in Acute Stroke Treatment).

CONCLUSIONS

Relatively high serum albumin levels in acute stroke decrease poor outcome.

Nanoparticle-based evaluation of blood-brain barrier leakage during the foreign body response

OBJECTIVE

The brain foreign body response (FBR) is an important process that limits the functionality of electrodes that comprise the brain-machine interface. Associated events in this process include leakage of the blood-brain barrier (BBB), reactive astrogliosis, recruitment and activation of microglia, and neuronal degeneration. Proper BBB function is also integral to maintaining neuronal health and function. Previous attempts to characterize BBB integrity have shown homogeneous leakage of macromolecules up to 10 nm in size. In this study, we describe a new method of measuring BBB permeability during the foreign body response in a mouse model.

APPROACH

Fluorescent nanoparticles were delivered via the tail vein into implant-bearing mice. Tissue sections were then analyzed using fluorescence microscopy to observe nanoparticles in the tissue. Gold nanoparticles were also used in conjunction with TEM to confirm the presence of nanoparticles in the brain parenchyma.

MAIN RESULTS

By using polymer nanoparticle tracers, which are significantly larger than conventional macromolecular tracers, we show near-implant BBB gaps of up to 500 nm in size that persist for at least 4 weeks after implantation. Further characterization of the BBB illustrates that leakage during the brain FBR is heterogeneous with gaps between at least 10 and 500 nm. Moreover, electron microscopy was used to confirm that the nanoparticle tracers enter into the brain parenchyma near chronic brain implants.

SIGNIFICANCE

Taken together, our findings demonstrate that the FBR-induced BBB leakage is characterized by larger gaps and is of longer duration than previously thought. This technique can be applied to examine the BBB in other disease states as well as during induced, transient, BBB opening.

Albuminuria--marker of progressive renal disease

The presence of albuminuria has long been recognized as an adverse prognostic feature in patients with renal disease: the patients with appreciable albuminuria are much more likely to develop tubulointerstitial scarring and fibrosis and progress to end-stage renal failure. For many years, it was thought that excess albuminuria was simply a marker of a more severe renal disease, which was more likely to progress as a result of this severity rather than as a result of the albuminuria itself. This conviction was strengthened by the general assumption that albumin was a benign or inert molecule serving primarily to exert oncotic pressure and act as a carrier within the circulation. More recently, this view has been challenged with the accumulation of evidence suggesting that albumin is able to influence the function of cells with which it makes contact in the manner of a signalling molecule.

Ultrasmall implantable composite microelectrodes with bioactive surfaces for chronic neural interfaces

Implantable neural microelectrodes that can record extracellular biopotentials from small, targeted groups of neurons are critical for neuroscience research and emerging clinical applications including brain-controlled prosthetic devices. The crucial material-dependent problem is developing microelectrodes that record neural activity from the same neurons for years with high fidelity and reliability. Here, we report the development of an integrated composite electrode consisting of a carbon-fibre core, a poly(p-xylylene)-based thin-film coating that acts as a dielectric barrier and that is functionalized to control intrinsic biological processes, and a poly(thiophene)-based recording pad. The resulting implants are an order of magnitude smaller than traditional recording electrodes, and more mechanically compliant with brain tissue. They were found to elicit much reduced chronic reactive tissue responses and enabled single-neuron recording in acute and early chronic experiments in rats. This technology, taking advantage of new composites, makes possible highly selective and stealthy neural interface devices towards realizing long-lasting implants.

Blood-brain barrier dysfunction, TGFβ signaling, and astrocyte dysfunction in epilepsy

Brain insults, including traumatic and ischemic injuries, are frequently followed by acute seizures and delayed development of epilepsy. Dysfunction of the blood-brain barrier (BBB) is a hallmark of brain insults and is usually surrounding the core lesion. Recent studies from several laboratories confirmed that vascular pathology is involved in the development of epilepsy and demonstrate a key role for astroglia in this process. In this review, we focus on glia-related mechanisms linking vascular pathology, and specifically BBB dysfunction, to seizures and epilepsy. We summarize molecular and physiological experimental data demonstrating that the function of astrocytes is altered due to direct exposure to serum albumin, mediated by transforming growth factor beta signaling. We discuss the reported changes and their potential role in the observed hyperexcitability as well as potential implications of these findings for the future development of new diagnostic modalities and treatments to allow a full implementation of the gained knowledge for the benefit of patients with epilepsy.

Pathophysiology of the neurovascular unit: disease cause or consequence?

Pathophysiology of the neurovascular unit (NVU) is commonly seen in neurological diseases. The typical features of NVU pathophysiology include tissue hypoxia, inflammatory and angiogenic activation, as well as initiation of complex molecular interactions between cellular (brain endothelial cells, astroctyes, pericytes, inflammatory cells, and neurons) and acellular (basal lamina) components of the NVU, jointly resulting in increased blood-brain barrier permeability, brain edema, neurovascular uncoupling, and neuronal dysfunction and damage. The evidence of important role of the brain vascular compartment in disease pathogenesis has elicited the debate whether the primary vascular events may be a cause of the neurological disease, as opposed to a mere participant recruited by a primary neuronal origin of pathology? Whereas some hereditary and acquired cerebral angiopathies could be considered a primary cause of neurological symptoms of the disease, the epidemiological studies showing a high degree of comorbidity among vascular disease and dementias, including Alzheimer's disease, as well as migraine and epilepsy, suggested that primary vascular pathology may be etiological factor causing neuronal dysfunction or degeneration in these diseases. This review focuses on recent hypotheses and evidence, suggesting that pathophysiology of the NVU may be initiating trigger for neuronal pathology and subsequent neurological manifestations of the disease.