Tight junction protein expression and barrier properties of immortalized mouse brain microvessel endothelial cells

Peptide Functionalization of Emulsion-Based Nanocarrier to Improve Uptake across Blood-Brain Barrier

New strategies for enhancing drug delivery to the blood-brain barrier (BBB) represent a major challenge in treating cerebral diseases. Nanoemulsion-based nanocarriers represent an ideal candidate to improve drug delivery thanks to their versatility in functionalization and cargo protection. In this work, a paclitaxel-loaded nano-emulsion has been firstly functionalized and stabilized with two layers constituted of chitosan and hyaluronic acid, and, secondly, the latter has been conjugated to the CRT peptide. CRT is a bioactive peptide that selectively recognizes bEnd.3 cells, a model of the BBB, thanks to its interactions with transferrin (Tf) and its receptor (TfR). Cytotoxic results showed a 41.5% higher uptake of CRT functionalized nano-emulsion than the negative control, demonstrating the ability of this novel tool to be accumulated in brain endothelium tissue. Based upon these results, our approach can be fully generalizable to the design of multifunctional nanocarriers for delivery of therapeutic agents to the central nervous systems.

Targeted Delivery of Macrophage Membrane Biomimetic Liposomes Through Intranasal Administration for Treatment of Ischemic Stroke

Purpose

Ginsenoside Rg3 (Rg3) and Panax notoginseng saponins (PNS) can be used for ischemic stroke treatment, however, the lack of targeting to the ischemic region limits the therapeutic effect. To address this, we leveraged the affinity of macrophage membrane proteins for inflamed brain microvascular endothelial cells to develop a macrophage membrane-cloaked liposome loaded with Rg3 and PNS (MM-Lip-Rg3/PNS), which can precisely target brain lesion region through intranasal administration.

Methods

MM-Lip-Rg3/PNS was prepared by co-extrusion method and was performed by characterization, stability, surface protein, and morphology. The cellular uptake, immune escape ability, and blood-brain barrier crossing ability of MM-Lip-Rg3/PNS were studied in vitro. The in vivo brain targeting, biodistribution and anti-ischemic efficacy of MM-Lip-Rg3/PNS were evaluated in MACO rats, and we determined the diversity of the nasal brain pathway through the olfactory nerve blockade model in rats. Finally, the pharmacokinetics and brain targeting index of MM-Lip-Rg3/PNS were investigated.

Results

Our results indicated that MM-Lip-Rg3/PNS was spherical with a shell-core structure. MM-Lip-Rg3/PNS can avoid mononuclear phagocytosis, actively bind to inflammatory endothelial cells, and have the ability to cross the blood-brain barrier. Moreover, MM-Lip-Rg3/PNS could specifically target ischemic sites, even microglia, increase the cumulative number of drugs in the brain, improve the inflammatory environment of the brain, and reduce the infarct size. By comparing olfactory nerve-blocking rats with normal rats, it was found that there are direct and indirect pathways for nasal entry into the brain. Pharmacokinetics demonstrated that MM-Lip-Rg3/PNS exhibited stronger brain targeting and prolonged drug half-life.

Conclusion

MM-Lip-Rg3/PNS might contribute to the accumulation of Rg3 and PNS in the ischemic brain area to improve treatment efficacy. This biomimetic nano-drug delivery system provides a new and promising strategy for the treatment of ischemic stroke.

Effects of Prokineticins on Cerebral Cell Function and Blood-Brain Barrier Permeability

Prokineticins are a family of small proteins with diverse roles in various tissues, including the brain. However, their specific effects on different cerebral cell types and blood-brain barrier (BBB) function remain unclear. The aim of this study was to investigate the effects of PROK1 and PROK2 on murine cerebral cell lines, bEnd.3, C8.D30, and N2a, corresponding to microvascular endothelial cells, astrocytes and neurons, respectively, and on an established BBB co-culture model. Western blot analysis showed that prokineticin receptors (PROKR1 and PROKR2) were differentially expressed in the considered cell lines. The effect of PROK1 and PROK2 on cell proliferation and migration were assessed using time-lapse microscopy. PROK1 decreased neural cells' proliferation, while it had no effect on the proliferation of endothelial cells and astrocytes. In contrast, PROK2 reduced the proliferation of all cell lines tested. Both PROK1 and PROK2 increased the migration of all cell lines. Blocking PROKRs with the PROKR1 antagonist (PC7) and the PROKR2 antagonist (PKR-A) inhibited astrocyte PROK2-mediated migration. Using the insert co-culture model of BBB, we demonstrated that PROKs increased BBB permeability, which could be prevented by PROKRs' antagonists.

A novel 4-cell in-vitro blood-brain barrier model and its characterization by confocal microscopy and TEER measurement

The blood-brain barrier (BBB) is a protective cellular anatomical layer with a dynamic micro-environment, tightly regulating the transport of materials across it. To achieve in-vivo characteristics, an in-vitro BBB model requires the constituent cell types to be layered in an appropriate order. A cost-effective in-vitro BBB model is desired to facilitate central nervous system (CNS) drug penetration studies. Enhanced integrity of tight junctions observed during the in-vitro BBB establishment and post-experiment is essential in these models. We successfully developed an in-vitro BBB model mimicking the in-vivo cell composition and a distinct order of seeding primary human brain cells. Unlike other in-vitro BBB models, our work avoids the need for pre-coated plates for cell adhesion and provides better cell visualization during the procedure. We found that using bovine collagen-I coating, followed by bovine fibronectin coating and poly-L-lysine coating, yields better adhesion and layering of cells on the transwell membrane compared to earlier reported use of collagen and poly-L-lysine only. Our results indicated better cell visibility and imaging with the polyester transwell membrane as well as point to a higher and more stable Trans Endothelial Electrical Resistance values in this plate. In addition, we found that the addition of zinc induced higher claudin 5 expressions in neuronal cells. Dolutegravir, a drug used in the treatment of HIV, is known to appear in moderate concentrations in the CNS. Thus, dolutegravir was used to assess the functionality of the final model and cells. Using primary cells and an in-house coating strategy substantially reduces costs and provides superior imaging of cells and their tight junction protein expression. Our 4-cell-based BBB model is a suitable experimental model for the drug screening process.

New Indole-3-Propionic Acid and 5-Methoxy-Indole Carboxylic Acid Derived Hydrazone Hybrids as Multifunctional Neuroprotectors

In light of the known neuroprotective properties of indole compounds and the promising potential of hydrazone derivatives, two series of aldehyde-heterocyclic hybrids combining those pharmacophores were synthesized as new multifunctional neuroprotectors. The obtained derivatives of indole-3-propionic acid (IPA) and 5-methoxy-indole carboxylic acid (5MICA) had good safety profiles: Hemolytic effects < 5% (200 μM) and IC₅₀ > 150 µM were found in the majority of the SH-SY5Y and bEnd3 cell lines. The 2,3-dihydroxy, 2-hydroxy-4-methoxy, and syringaldehyde derivatives of 5MICA exhibited the strongest neuroprotection against H₂O₂-induced oxidative stress in SH-SY5Y cells and 6-OHDA-induced neurotoxicity in rat-brain synaptosomes. All the compounds suppressed the iron-induced lipid peroxidation. The hydroxyl derivatives were also the most active in terms of deoxyribose-degradation inhibition, whereas the 3,4-dihydroxy derivatives were able to decrease the superoxide-anion generation. Both series of compounds showed an increased inhibition of hMAO-B, with greater expression detected in the 5MICA hybrids. The in vitro BBB model with the bEnd3 cell line showed that some compounds increased the permeability of the endothelial monolayer while maintaining the tight junctions. The combined results demonstrated that the derivatives of IPA and 5MICA showed strong neuroprotective, antioxidant, MAO-B inhibitory activity and could be considered as prospective multifunctional compounds for the treatment of neurodegenerative disorders.

Experimental Models of In Vitro Blood-Brain Barrier for CNS Drug Delivery: An Evolutionary Perspective

Central nervous system (CNS) disorders represent one of the leading causes of global health burden. Nonetheless, new therapies approved against these disorders are among the lowest compared to their counterparts. The absence of reliable and efficient in vitro blood-brain barrier (BBB) models resembling in vivo barrier properties stands out as a significant roadblock in developing successful therapy for CNS disorders. Therefore, advancement in the creation of robust and sensitive in vitro BBB models for drug screening might allow us to expedite neurological drug development. This review discusses the major in vitro BBB models developed as of now for exploring the barrier properties of the cerebral vasculature. Our main focus is describing existing in vitro models, including the 2D transwell models covering both single-layer and co-culture models, 3D organoid models, and microfluidic models with their construction, permeability measurement, applications, and limitations. Although microfluidic models are better at recapitulating the in vivo properties of BBB than other models, significant gaps still exist for their use in predicting the performance of neurotherapeutics. However, this comprehensive account of in vitro BBB models can be useful for researchers to create improved models in the future.

CircRBM33 induces endothelial dysfunction by targeting the miR-6838-5p/PDCD4 axis affecting blood-brain barrier in mice with cerebral ischemia-reperfusion injury

BACKGROUND

circRNAs (circRNAs) are involved in the process of cerebral ischemia-reperfusion injury (CI/RI). Our study aims to explore circRBM33 in the endothelial function of the blood-brain barrier (BBB).

METHODS

The mouse middle cerebral artery occlusion model (MCAO) was established and restored to perfusion, and OGD/R-induced endothelial cells were used to simulate CI/RI. circRBM33, miR-6838-5p and PDCD4, as well as Occludin, ZO-1 and Claudin-5 TJs were evaluated by quantitative PCR and Western blot. The ring structure of circRBM33 was verified by RNAse R and actinomycin D experiments. MTT and LDH Cytotoxicity assay determined viability and toxicity, and flow cytometry determined apoptosis rate. Inflammatory cytokines and the number of microglia in brain tissue were measured by ELISA and IHC. The interaction between genes was verified by RIP and dual luciferase reporter assay.

RESULTS

circRBM33 was a circrRNA present in the cytoplasm and up-regulated in the brain tissue of MCAO mice and OGD/R-induced endothelial cells. Silenced circRBM33 promoted Occludin, ZO-1, and Claudin-5 expression and cell proliferation, and inhibited cytotoxicity, inflammatory response, and apoptosis. Functionally, circRBM33-absorbed miR-6838-5p was involved in regulating PDCD4, leading to endothelial cell dysfunction, and thus affecting the function of the BBB.

CONCLUSIONS

circRBM33 by mediating miR-6838-5p/PDCD4 axis induces endothelial dysfunction, thereby affecting the BBB in mice with CI/RI.

The interplay between T helper cells and brain barriers in the pathogenesis of multiple sclerosis

The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) represent two complex structures protecting the central nervous system (CNS) against potentially harmful agents and circulating immune cells. The immunosurveillance of the CNS is governed by immune cells that constantly patrol the BCSFB, whereas during neuroinflammatory disorders, both BBB and BCSFB undergo morphological and functional alterations, promoting leukocyte intravascular adhesion and transmigration from the blood circulation into the CNS. Multiple sclerosis (MS) is the prototype of neuroinflammatory disorders in which peripheral T helper (Th) lymphocytes, particularly Th1 and Th17 cells, infiltrate the CNS and contribute to demyelination and neurodegeneration. Th1 and Th17 cells are considered key players in the pathogenesis of MS and its animal model, experimental autoimmune encephalomyelitis. They can actively interact with CNS borders by complex adhesion mechanisms and secretion of a variety of molecules contributing to barrier dysfunction. In this review, we describe the molecular basis involved in the interactions between Th cells and CNS barriers and discuss the emerging roles of dura mater and arachnoid layer as neuroimmune interfaces contributing to the development of CNS inflammatory diseases.

Transmigration of magnetite nanoparticles across the blood-brain barrier in a rodent model: influence of external and alternating magnetic fields

Despite advances in neurology, drug delivery to the central nervous system is considered a challenge due to the presence of the blood brain barrier (BBB). In this study, the role of magnetic hyperthermia induced by exposure of magnetic nanoparticles (MNPs) to an alternating magnetic field (AMF) in synergy with an external magnetic field (EMF) was investigated to transiently increase the permeability of the MNPs across the BBB. A dual magnetic targeting approach was employed by first dragging the MNPs by an EMF for an intended enhanced cellular association with the brain endothelial cells and then activating the MNPs by an AMF for the temporary disruption of the tight junctions of BBB. The efficacy of the BBB permeability for the MNPs under the influence of dual magnetic targeting was evaluated in vitro using transwell models developed by co-culturing murine brain endothelial cells with astrocytes, as well as in vivo in mouse models. The in vitro results revealed that the exposure to AMF transiently opened the tight junctions at the BBB, which, after 3 h of treatment, were observed to recover back to their comparable control levels. A biodistribution analysis of nanoparticles confirmed targeted accumulation of MNPs in the brain following dual targeting. This dual targeting approach was observed to open the tight junctions, thus increasing the transport of MNPs into the brain with higher specificity as compared to using EMF targeting alone, suggesting that a dual magnetic targeting-induced transport of MNPs across the BBB is an effective measure for delivery of therapeutics.

Chronic exposure to butyl-paraben causes photosensitivity disruption and memory impairment in adult zebrafish

Limited studies on neurotoxicity following chronic exposure to butyl‑paraben (BuP) have been conducted. In this study, neurobehavior in zebrafish adults was assessed using the novel tank test, photomotor response test, and T-maze test after exposure to BuP for 28 days at concentrations of 0, 0.01, 0.1, and 1.0 mg/L. To comprehensively understand the underlying molecular perturbations in the brain, alterations in transcripts, neurotransmitters, and neurosteroids were measured. We found that BuP penetrated the blood-brain barrier and impaired neurobehavior in photosensitivity at 1.0 mg/L and in memory at 0.1 and 1.0 mg/L. RNA-seq analysis showed that phototransduction, tight junctions, and neuroactive ligand receptor activity were significantly affected, which explains the observed abnormal neurobehaviors. Neurosteroid analysis revealed that BuP increased cortisol levels in a concentration-dependent manner and specifically reduced allopregnanolone levels at all tested concentrations, suggesting that cortisol and allopregnanolone are significant neurosteroid markers associated with photosensitivity and memory deficits. Collectively, we demonstrated that BuP can cross the blood-brain and modulate the levels of transcripts, associated with phototransduction and circadian rhythm, and neurosteroidal cortisol and allopregnanolone, resulting in abnormal neurobehavioral responses to light stimulation and learning and memory.

Bacteria loaded with glucose polymer and photosensitive ICG silicon-nanoparticles for glioblastoma photothermal immunotherapy

Bacteria can bypass the blood-brain barrier (BBB), suggesting the possibility of employment of bacteria for combating central nervous system diseases. Herein, we develop a bacteria-based drug delivery system for glioblastoma (GBM) photothermal immunotherapy. The system, which we name as ‘Trojan bacteria’, consists of bacteria loaded with glucose polymer and photosensitive ICG silicon-nanoparticles. In an orthotopic GBM mouse model, we demonstrate that the intravenously injected bacteria bypass the BBB, targeting and penetrating GBM tissues. Upon 808 nm-laser irradiation, the photothermal effects produced by ICG allow the destruction of bacterial cells and the adjacent tumour cells. Furthermore, the bacterial debris as well as the tumour-associated antigens promote antitumor immune responses that prolong the survival of GBM-bearing mice. Moreover, we demonstrate the residual bacteria are effectively eliminated from the body, supporting the potential therapeutic use of this system.

Different blood-brain barrier permeable systems, such as bacteria loaded with chemotherapy, have been proposed to treat glioblastoma. Here, the authors generate bacteria loaded with glucose polymer and photosensitive ICG silicon-nanoparticles to eliminate bacteria-infected glioblastoma cells and induce an anti-tumour immune response upon photothermal therapy.

Comparison Between Deltascan Single Channel Electroencephalography (EEG), Confusion Assessment Method-Intensive Care Unit (CAM-ICU) Score and Clinical Assessment in Diagnosing Delirium in Intubated Patients in the Intensive Care Unit

Background

The aim of this article is to assess the feasibility of using single-channel electroencephalography (EEG) measurement for detecting delirium in intubated Intensive care (ICU) patients and to assess the level of agreement between the EEG measurements, the CAM-ICU score and the clinical diagnosis of delirium.

Materials and methods

This study was an exploratory pilot between May 2021 and September 2021 including intubated patients in the ICU. For this study the Prolira^® (Arnhem, The Netherlands) Deltascan single-channel EEG was used and compared with the Confusion Assessment Method (CAM)-ICU and the clinical diagnosis of delirium by ICU physicians.

Results

In total 23 patients were found eligible for this study, of which 20 were included in the final analysis. The patients mean age was 63.0 ± 8.8 years, and the majority (thirteen) was male (65%). In total 17 of the 20 patients (85%) received the diagnosis delirium by the medical team. There were no statistically significant differences between the Deltascan and CAM-ICU measurements in diagnosing delirium per time point (p values respectively 0.21; 0.90; 0.34; 0.11; 0.056 and 0.091). AUCs for the agreement between the CAM-ICU and the Deltascan measurements were respectively: 0.676 ± 0.205; 0.333 ± 0.224; 0.402 ± 0.146; 0.488 ± 0.202; 0.06 ± 0.077 and 0.06 ± 0.109 (all p>0.05). AUCs for the level of agreement between the clinical diagnosis delirium and Deltascan were: 0.676 ± 0.152; 0.686 ± 0.146; 0.711 ± 0.132; 0.688 ± 0.136; 0.500 ± 0.158 and 0.700 ± 0.211 (all p>0.05).

Conclusion

In this exploratory study, we showed that there is no statistical agreement between CAM-ICU and Delta scan measurements. Secondly, there is a higher agreement, although not statistically significant between the clinical diagnoses of a delirium (by a clinician) with the Deltascan measurements. Despite this small study we think that the Deltascan can be of additional value in intubated ICU patients and therefore larger studies are needed to substantiate our findings.

Comparative studies between the murine immortalized brain endothelial cell line (bEnd.3) and induced pluripotent stem cell-derived human brain endothelial cells for paracellular transport

Brain microvascular endothelial cells, forming the anatomical site of the blood-brain barrier (BBB), are widely used as in vitro complements to in vivo BBB studies. Among the immortalized cells used as in vitro BBB models, the murine-derived bEnd.3 cells offer culturing consistency and low cost and are well characterized for functional and transport assays, but result in low transendothelial electrical resistance (TEER). Human-induced pluripotent stem cells differentiated into brain microvascular endothelial cells (ihBMECs) have superior barrier properties, but the process of differentiation is time-consuming and can result in mixed endothelial-epithelial gene expression. Here we performed a side-by-side comparison of the ihBMECs and bEnd.3 cells for key paracellular diffusional transport characteristics. The TEER across the ihBMECs was 45- to 68-fold higher than the bEnd.3 monolayer. The ihBMECs had significantly lower tracer permeability than the bEnd.3 cells. Both, however, could discriminate between the paracellular permeabilities of two tracers: sodium fluorescein (MW: 376 Da) and fluorescein isothiocyanate (FITC)-dextran (MW: 70 kDa). FITC-dextran permeability was a strong inverse-correlate of TEER in the bEnd.3 cells, whereas sodium fluorescein permeability was a strong inverse-correlate of TEER in the ihBMECs. Both bEnd.3 cells and ihBMECs showed the typical cobblestone morphology with robust uptake of acetylated LDL and strong immuno-positivity for vWF. Both models showed strong claudin-5 expression, albeit with differences in expression location. We further confirmed the vascular endothelial- (CD31 and tube-like formation) and erythrophagocytic-phenotypes and the response to inflammatory stimuli of ihBMECs. Overall, both bEnd.3 cells and ihBMECs express key brain endothelial phenotypic markers, and despite differential TEER measurements, these in vitro models can discriminate between the passage of different molecular weight tracers. Our results highlight the need to corroborate TEER measurements with different molecular weight tracers and that the bEnd.3 cells may be suitable for large molecule transport studies despite their low TEER.

Involvement of Ceramide Metabolism in Cerebral Ischemia

Ischemic stroke, caused by the interruption of blood flow to the brain and subsequent neuronal death, represents one of the main causes of disability in worldwide. Although reperfusion therapies have shown efficacy in a limited number of patients with acute ischemic stroke, neuroprotective drugs and recovery strategies have been widely assessed, but none of them have been successful in clinical practice. Therefore, the search for new therapeutic approaches is still necessary. Sphingolipids consist of a family of lipidic molecules with both structural and cell signaling functions. Regulation of sphingolipid metabolism is crucial for cell fate and homeostasis in the body. Different works have emphasized the implication of its metabolism in different pathologies, such as diabetes, cancer, neurodegeneration, or atherosclerosis. Other studies have shown its implication in the risk of suffering a stroke and its progression. This review will highlight the implications of sphingolipid metabolism enzymes in acute ischemic stroke.

Rational design of engineered H-ferritin nanoparticles with improved siRNA delivery efficacy across an in vitro model of the mouse BBB

Gene therapy holds tremendous potential for the treatment of incurable brain diseases including Alzheimer's disease (AD), stroke, glioma, and Parkinson's disease. The main challenge is the lack of effective gene delivery systems traversing the blood-brain barrier (BBB), due to the complex microvessels present in the brain which restrict substances from the circulating blood passing through. Recently, increasing efforts have been made to develop promising gene carriers for brain-related disease therapies. One such development is the self-assembled heavy chain ferritin (HFn) nanoparticles (NPs). HFn NPs have a unique hollow spherical structure that can encapsulate nucleic acid drugs (NADs) and specifically bind to cancer cells and BBB endothelial cells (BBB ECs) via interactions with the transferrin receptor 1 (TfR1) overexpressed on their surfaces, which increases uptake through the BBB. However, the gene-loading capacity of HFn is restricted by its limited interior volume and negatively charged inner surface; therefore, these drawbacks have prompted the demand for strategies to remould the structure of HFn. In this work, we analyzed the three-dimensional (3D) structure of HFn using Chimera software (v 1.14) and developed a class of internally cationic HFn variants (HFn+ NPs) through arginine mutation on the lumenal surface of HFn. These HFn+ NPs presented powerful electrostatic forces in their cavities, and exhibited higher gene encapsulation efficacy than naive HFn. The top-performing candidate, HFn2, effectively delivered siRNA to glioma cells after traversing the BBB and achieved the highest silencing efficacy among HFn+ NPs. Overall, our findings demonstrate that HFn+ NPs obtained by this genetic engineering method provide critical insights into the future development of nucleic acid delivery carriers with BBB-crossing ability.

PCSK9 acts as a key regulator of Aβ clearance across the blood-brain barrier

Despite the neurodegenerative disorder Alzheimer's disease (AD) is the most common form of dementia in late adult life, there is currently no therapy available to prevent the onset or slow down the progression of AD. The progressive cognitive decline in AD correlates with a successive accumulation of cerebral amyloid-β (Aβ) due to impaired clearance mechanisms. A significant percentage is removed by low-density lipoprotein receptor-related protein 1 (LRP1)-mediated transport across the blood-brain barrier (BBB) into the periphery. Circulating proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to members of the low-density lipoprotein receptor protein family at the cell surface and targets them for lysosomal degradation, which reduces the number of functional receptors. However, the adverse impact of PCSK9 on LRP1-mediated brain Aβ clearance remains elusive. By using an established BBB model, we identified reduced LRP1-mediated brain-to-blood Aβ clearance due to PCSK9 across different endothelial monolayer in vitro. Consequently, the repetitive application of FDA-approved monoclonal anti-PCSK9 antibodies into 5xFAD mice decreased the cerebral Aβ burden across variants and aggregation state, which was not reproducible in brain endothelial-specific LRP1^-/- 5xFAD mice. The peripheral PCSK9 inhibition reduced Aβ pathology in prefrontal cortex and hippocampus-brain areas critically involved in memory processing-and prevented disease-related impairment in hippocampus-dependent memory formation. Our data suggest that peripheral inhibition of PCSK9 by already available therapeutic antibodies may be a novel and easily applicable potential AD treatment.

Piceatannol Protects Brain Endothelial Cell Line (bEnd.3) against Lipopolysaccharide-Induced Inflammation and Oxidative Stress

Dysfunction of the blood-brain barrier (BBB) is involved in the pathogenesis of many cerebral diseases. Oxidative stress and inflammation are contributing factors for BBB injury. Piceatannol, a natural ingredient found in various plants, such as grapes, white tea, and passion fruit, plays an important role in antioxidant and anti-inflammatory responses. In this study, we examined the protective effects of piceatannol on lipopolysaccharide (LPS) insult in mouse brain endothelial cell line (bEnd.3) cells and the underlying mechanisms. The results showed that piceatannol mitigated the upregulated expression of adhesion molecules (ICAM-1 and VCAM-1) and iNOS in LPS-treated bEnd.3 cells. Moreover, piceatannol prevented the generation of reactive oxygen species in bEnd.3 cells stimulated with LPS. Mechanism investigations suggested that piceatannol inhibited NF-κB and MAPK activation. Taken together, these observations suggest that piceatannol reduces inflammation and oxidative stress through inactivating the NF-κB and MAPK signaling pathways on cerebral endothelial cells in vitro.

Quantification of In Vitro Blood-Brain Barrier Permeability

In vitro blood-brain barrier (BBB) models have been widely used to simulate in vivo models due to their low cost, feasibility, and repeatability. To serve as a valid substitute, the in vitro BBB should have the similar barrier function as that in vivo. This chapter summarizes the detailed methods for quantifying the barrier function, e.g., the permeability of the BBB to water, ions, and solutes for an in vitro BBB generated on the Transwell filter.

Cav-1 Protein Levels in Serum and Infarcted Brain Correlate with Hemorrhagic Volume in a Mouse Model of Thromboembolic Stroke, Independently of rt-PA Administration

Thrombolytic therapy with recombinant tissue plasminogen activator (rt-PA) is currently the only FDA-approved drug for acute ischemic stroke. However, its administration is still limited due to the associated increased risk of hemorrhagic transformation (HT). rt-PA may exacerbate blood-brain barrier (BBB) injury by several mechanisms that have not been fully elucidated. Caveolin-1 (Cav-1), a major structural protein of caveolae, has been linked to the endothelial barrier function. The effects of rt-PA on Cav-1 expression remain largely unknown. Here, Cav-1 protein expression after ischemic conditions, with or without rt-PA administration, was analyzed in a murine thromboembolic middle cerebral artery occlusion (MCAO) and in brain microvascular endothelial bEnd.3 cells subjected to oxygen/glucose deprivation (OGD). Our results show that Cav-1 is overexpressed in endothelial cells of infarcted area and in bEnd.3 cell line after ischemia but there is disagreement regarding rt-PA effects on Cav-1 expression between both experimental models. Delayed rt-PA administration significantly reduced Cav-1 total levels from 24 to 72 h after reoxygenation and increased pCav-1/Cav-1 at 72 h in the bEnd.3 cells while it did not modify Cav-1 immunoreactivity in the infarcted area at 24 h post-MCAO. Importantly, tissue Cav-1 positively correlated with Cav-1 serum levels at 24 h post-MCAO and negatively correlated with the volume of hemorrhage after infarction, the latter supporting a protective role of Cav-1 in cerebral ischemia. In addition, the negative association between baseline serum Cav-1 levels and hemorrhagic volume points to a potential usefulness of baseline serum Cav-1 levels to predict hemorrhagic volume, independently of rt-PA administration.

Protective and restorative effects of sophorolipid on intestinal dystrophy in dextran sulfate sodium-induced colitis mouse model

The public has gradually begun to regard inflammatory bowel disease (IBD) as a crucial health issue; however, its mode of action has not been fully elucidated. Sophorolipid (SPL), a glycolipid-type biosurfactant, could be used as a potential treatment in physical intestinal dystrophy. We conducted a 2 × 2 factorial experiment to investigate the protective effect of SPL in a dextran sulfate sodium (DSS)-induced colitis mouse model (first factor, presence of SPL in feed; second factor, presence of DSS in water). Forty C57BL/6 mice (8-week-old) were used, and they were allocated to treatments according to their initial body weight. After a 7 d adjustment period, the DSS treatment was initiated in specific groups. At day 14, DSS was withdrawn from mice, and half of the mice were randomly selected and euthanized to collect colon and colon content samples. Three days after the end of DSS treatment, the rest of the mice were euthanized to investigate the therapeutic effect of SPL. Dietary SPL improved the growth performance in 3 d after DSS treatment, and the histopathological score was lower in the DSS-treated SPL group than in the DSS-treated control group. Mucosal thickness and goblet cell numbers significantly increased in the SPL-supplemented groups compared to in the control group. Similarly, SPL supplementation upregulated the gene expression levels of mucin-2, interleukin-10, and transforming growth factor-β, and increased the concentration of short chain fatty acid compared to the control groups. In conclusion, dietary supplementation with SPL attenuated the pathological response against acute and chronic inflammation by the maintenance of the mucosal barrier and wound healing capacity.

Neuroprotective effects of an in vitro BBB permeable phenoxythiophene sulfonamide small molecule in glutamate-induced oxidative injury

Reactive oxygen species (ROS) play a central role in oxidative stress-associated neuronal cell death during ischemia. Further investigation into the inhibition of excessive ROS generation post-stroke is urgently required for the treatment of ischemic stroke. In the present study, the neuroprotective properties of the blood-brain barrier (BBB) penetrant B355227 were investigated. B355227 is a chemical analogue of B355252, and the role of the phenoxythiophene sulfonamide compound B355227 was further investigated in a glutamate-induced oxidative injury model. An in vitro model of the BBB was established in the immortalized mouse brain capillary endothelial cell line, bEnd.3. Formation of barrier in Transwell inserts was confirmed using EVOM resistance meter and Caffeine, Imatinib and Axitinib were used to validate the efficacy of the model. The validated BBB assay in combination with high performance liquid chromatography were used to analyse and verify the permeability of B355227 through the barrier. The integrity of the cell junctions after the BBB assays were confirmed using immunofluorescence to visualize the expression of the barrier junction protein zonula occludens-1. Cell survival was measured with Resazurin, a redox indicator dye, in HT22, a hippocampal neuronal cell treated with 5 mM glutamate or co-treated with the B355227 recovered from the BBB permeability experiment. Changes in glutathione levels were detected using a glutathione detection kit, while analyses of ROS, calcium (Ca2+), and mitochondrial membrane potential (MMP) were accomplished with the fluorescent dyes 2',7'-dichlorofluorescein diacetate, Fura-2 AM and MitoTracker Red dyes, respectively. Immunoblotting was also performed to detect the expression and activation of Erk1/2, p-38, JNK, Bax and Bcl-2. The results of the present study demonstrated that B355227 crossed the BBB in vitro and protected HT22 from oxidative injury induced by glutamate exposure. Treatment of cells with B355227 blocked the glutamate-dependent depletion of intracellular glutathione and significantly reduced ROS production. Increased Ca2+ influx and subsequent collapse of the MMP was attenuated by B355227. Furthermore, the results of the present study demonstrated that B355227 protected against oxidative stress via the MAPK pathway, by increasing the activation of Erk1/2, JNK and P38, and restoring anti-apoptotic Bcl-2. Collectively, the results of the present study indicate that B355227 has potent antioxidant and neuroprotective attributes in glutamate-induced neuronal cell death. Further investigation into the role of B355227 in the modulation of glutamate-dependent oxidative stress is required.

Low-Level Endothelial TRAIL-Receptor Expression Obstructs the CNS-Delivery of Angiopep-2 Functionalised TRAIL-Receptor Agonists for the Treatment of Glioblastoma

Glioblastoma (GBM) is the most malignant and aggressive form of glioma and is associated with a poor survival rate. Latest generation Tumour Necrosis Factor Related Apoptosis-Inducing Ligand (TRAIL)-based therapeutics potently induce apoptosis in cancer cells, including GBM cells, by binding to death receptors. However, the blood-brain barrier (BBB) is a major obstacle for these biologics to enter the central nervous system (CNS). We therefore investigated if antibody-based fusion proteins that combine hexavalent TRAIL and angiopep-2 (ANG2) moieties can be developed, with ANG2 promoting receptor-mediated transcytosis (RMT) across the BBB. We demonstrate that these fusion proteins retain the potent apoptosis induction of hexavalent TRAIL-receptor agonists. Importantly, blood-brain barrier cells instead remained highly resistant to this fusion protein. Binding studies indicated that ANG2 is active in these constructs but that TRAIL-ANG2 fusion proteins bind preferentially to BBB endothelial cells via the TRAIL moiety. Consequently, transport studies indicated that TRAIL-ANG2 fusion proteins can, in principle, be shuttled across BBB endothelial cells, but that low TRAIL receptor expression on BBB endothelial cells interferes with efficient transport. Our work therefore demonstrates that TRAIL-ANG2 fusion proteins remain highly potent in inducing apoptosis, but that therapeutic avenues will require combinatorial strategies, such as TRAIL-R masking, to achieve effective CNS transport.

Valsartan alleviates the blood-brain barrier dysfunction in db/db diabetic mice

Type 2 diabetes (T2D)-related neurological complication is the risk factor for neurodegenerative disorders. The pathological changes from T2D-caused blood–brain barrier (BBB) dysfunction plays a critical role in developing neurodegeneration. The hyper-activation of the Angiotensin II type 1 receptor (AT1R) in the brain is associated with neurovascular impairment. The AT1R antagonist Valsartan is commonly prescribed to control high blood pressure, heart failure, and diabetic kidney diseases. In this study, we investigated the beneficial effects of Valsartan in db/db diabetic mice and isolated brain endothelial cells. We showed that 2 weeks of Valsartan administration (30 mg/Kg body weight) mitigated the increased permeability of the brain-blood barrier and the reduction of gap junction proteins VE-Cadherin and Claudin 2. In human brain microvascular cells (HBMVECs), we found that Valsartan treatment ameliorated high glucose-induced hyperpermeability by measuring Dextran uptake and transendothelial electrical resistance (TEER). Furthermore, Valsartan treatment recovered high glucose-repressed endothelial VE-Cadherin and Claudin 2 expression. Moreover, Valsartan significantly suppressed the expressions of pro-inflammatory cytokines such as macrophage chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6) against high glucose. Mechanistically, Valsartan ameliorated high glucose-repressed endothelial cAMP-responsive element-binding protein (CREB) signaling activation. The blockage of CREB activation by PKA inhibitor H89 abolished the action of Valsartan, suggesting its dependence on CREB signaling. In conclusion, Valsartan shows a neuroprotective effect in diabetic mice by ameliorating BBB dysfunction. These effects of Valsartan require cellular CREB signaling in brain endothelial cells.

In vitro and in vivo optimization of liposomal nanoparticles based brain targeted vgf gene therapy

Vgf (non-acronymic), a neurotrophin stimulated protein which plays a crucial role in learning, synaptic activity, and neurogenesis, is markedly downregulated in the brain of Alzheimer's disease (AD) patients. However, since vgf is a large polar protein, a safe and efficient gene delivery vector is critical for its delivery across the blood brain barrier (BBB). This research work demonstrates brain-targeted liposomal nanoparticles optimized for delivering plasmid encoding vgf across BBB and transfecting brain cells. Brain targeting was achieved by surface functionalization using glucose transporter-1 targeting ligand (mannose) and brain targeted cell-penetrating peptides (chimeric rabies virus glycoprotein fragment, rabies virus derived peptide, penetratin peptide, or CGNHPHLAKYNGT peptide). The ligands were conjugated to lipid via nucleophilic substitution reaction resulting in >75% binding efficiency. The liposomes were formed by film hydration technique demonstrating size <200 nm, positive zeta potential (15-20 mV), and polydispersity index <0.3. The bifunctionalized liposomes demonstrated ∼3 pg/µg protein vgf transfection across in vitro BBB, and ∼80 pg/mg protein in mice brain which was 1.5-2 fold (p < 0.05) higher compared to untreated control. The nanoparticles were also biocompatible in vitro and in vivo, suggesting a safe and efficient gene delivery system to treat AD.

Functionalized nanoparticles with monocyte membranes and rapamycin achieve synergistic chemoimmunotherapy for reperfusion-induced injury in ischemic stroke

BACKGROUND

Ischemic stroke is an acute and severe neurological disease, and reperfusion is an effective way to reverse brain damage after stroke. However, reperfusion causes secondary tissue damage induced by inflammatory responses, called ischemia/reperfusion (I/R) injury. Current therapeutic strategies that control inflammation to treat I/R are less than satisfactory.

RESULTS

We report a kind of shield and sword nano-soldier functionalized nanoparticles (monocyte membranes-coated rapamycin nanoparticles, McM/RNPs) that can reduce inflammation and relieve I/R injury by blocking monocyte infiltration and inhibiting microglia proliferation. The fabricated McM/RNPs can actively target and bind to inflammatory endothelial cells, which inhibit the adhesion of monocytes to the endothelium, thus acting as a shield. Subsequently, McM/RNPs can penetrate the endothelium to reach the injury site, similar to a sword, and release the RAP drug to inhibit the proliferation of inflammatory cells. In a rat I/R injury model, McM/RNPs exhibited improved active homing to I/R injury areas and greatly ameliorated neuroscores and infarct volume. Importantly, in vivo animal studies revealed good safety for McM/RNPs treatment.

CONCLUSION

The results demonstrated that the developed McM/RNPs may serve as an effective and safe nanovehicles for I/R injury therapy.

The HIV-1 matrix protein p17 does cross the Blood-Brain Barrier

Human immunodeficiency virus type-1(HIV-1)-associated neurocognitive disorder (HAND) remains an important neurological manifestation in HIV-1-infected (HIV⁺) patients. Furthermore, the HIV-1 matrix protein p17 (p17) detection in the central nervous system (CNS) and its ability to form toxic assemblies in the brain has been recently confirmed. Here we show for the first time using both an in vitro blood-brain barrier (BBB) model and in vivo biodistribution studies in healthy mice that p17 can cross the BBB. There is fast brain uptake with 0.35 ± 0.19% of injected activity per gram of tissue (I.A./g) two minutes after administration, followed by brain accumulation with 0.28 ± 0.09% I.A./g after 1 h. The interaction of p17 with the chemokine receptor 2 (CXCR2) at the surface of brain endothelial cells triggers transcytosis. The present study supports the hypothesis of a direct role of free p17 in neuronal dysfunction in HAND by demonstrating its intrinsic ability to reach the CNS. IMPORTANCE The number of patients affected by HIV-1-associated neurocognitive disorder (HAND) ranges from 30 to 50% of HIV-infected (HIV⁺) patients. The mechanisms leading to HAND development need to be elucidated, but the role of secreted viral proteins, chemokines, and proinflammatory molecules appears to be clear. In particular, the blood-brain barrier (BBB) represents a route for entry into the central nervous system (CNS) thus playing an important role in HAND. Several findings suggest a key role for the HIV-1 matrix protein p17 (p17) as a microenvironmental factor capable of inducing neurocognitive disorders. Here we show, the ability of the p17 to cross the BBB and to reach the CNS thus playing a crucial role in neuronal dysfunction in HAND.

Erythrocytes, a New Contributor to Age-Associated Loss of Blood-Brain Barrier Integrity

Blood exchanges between young and old partners demonstrate old blood has a detrimental effect on brain health of young animals. Previous studies primarily investigate soluble blood factors, such as transforming growth factor-beta, on the brain and the blood-brain barrier (BBB). However, the role of blood cellular components, particularly erythrocytes, has not been defined. Erythrocyte morphology and rigidity change as mammals age, altering their transport within the capillary bed. This impacts downstream biological events, such as the release of reactive oxygen species and hemoglobin, potentially compromising the BBB. Here, a micro electrical BBB (µE-BBB), with cocultured endothelial and astrocytic cells, and a built-in trans-endothelial electrical resistance (TEER) system is described to monitor the effect of capillary shear stress on erythrocytes derived from young and old mice and people and the subsequent effects of these cells on BBB integrity. This is monitored by the passage of fluorescein isothiocyanate-dextran and real-time profiling of TEER across the BBB after old and young erythrocyte exposure. Compared to young erythrocytes, old erythrocytes induce an increased permeability by 42% and diminished TEER by 2.9% of the µE-BBB. These results suggest that changes in circulating erythrocytes are a biomarker of aging in the context of BBB integrity.

Drug Penetration into the Central Nervous System: Pharmacokinetic Concepts and In Vitro Model Systems

Delivery of most drugs into the central nervous system (CNS) is restricted by the blood-brain barrier (BBB), which remains a significant bottleneck for development of novel CNS-targeted therapeutics or molecular tracers for neuroimaging. Consistent failure to reliably predict drug efficiency based on single measures for the rate or extent of brain penetration has led to the emergence of a more holistic framework that integrates data from various in vivo, in situ and in vitro assays to obtain a comprehensive description of drug delivery to and distribution within the brain. Coupled with ongoing development of suitable in vitro BBB models, this integrated approach promises to reduce the incidence of costly late-stage failures in CNS drug development, and could help to overcome some of the technical, economic and ethical issues associated with in vivo studies in animal models. Here, we provide an overview of BBB structure and function in vivo, and a summary of the pharmacokinetic parameters that can be used to determine and predict the rate and extent of drug penetration into the brain. We also review different in vitro models with regard to their inherent shortcomings and potential usefulness for development of fast-acting drugs or neurotracers labeled with short-lived radionuclides. In this regard, a special focus has been set on those systems that are sufficiently well established to be used in laboratories without significant bioengineering expertise.

The effect of serum starvation on tight junctional proteins and barrier formation in Caco-2 cells

Assessing the ability of pharmaceutics to cross biological barriers and reach the site-of-action requires faithful representation of these barriers in vitro. Difficulties have arisen in replicating in vivo resistance in vitro. This paper investigated serum starvation as a method to increase Caco-2 barrier stability and resistance. The effect of serum starvation on tight junction production was examined using transwell models; specifically, transendothelial electrical resistance (TEER), and the expression and localization of tight junction proteins, occludin and zonula occludens-1 (ZO-1), were studied using western blotting and immunofluorescence. Changing cells to serum-free media 2 days post-seeding resulted in TEER readings of nearly 5000 Ω cm² but the TEER rapidly declined subsequently. Meanwhile, exchanging cells to serum-free media 4–6 days post-seeding produced barriers with resistance readings between 3000 and 4000 Ω cm², which could be maintained for 18 days. This corresponded to an increase in occludin levels. Serum starvation as a means of barrier formation is simple, reproducible, and cost-effective. It could feasibly be implemented in a variety of pre-clinical pharmaceutical assessments of drug permeability across various biological barriers with the view to improving the clinical translation of novel therapeutics.

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Serum starvation increases the intracellular resistance of Caco-2 cells.

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Max TEER values of 4783 ± 610 Ω cm² were achieved in serum free conditions.

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A barrier of 3000–4000 Ω cm² could be maintained for up to 18 days.

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Serum starvation leads to a significant increase in occludin expression.

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Occludin levels correlate significantly with corresponding TEER values.

Design and characterization of a novel dimeric blood-brain barrier penetrating TNFα inhibitor

Tumor necrosis factor-alpha (TNFα) inhibitors could prevent neurological disorders systemically, but their design generally relies on molecules unable to cross the blood-brain barrier (BBB). This research was aimed to design and characterize a novel TNFα inhibitor based on the angiopeptide-2 as a BBB shuttle molecule fused to the extracellular domain of human TNFα receptor 2 and a mutated vascular endothelial growth factor (VEGF) dimerization domain. This new chimeric protein (MTV) would be able to trigger receptor-mediated transcytosis across the BBB via low-density lipoprotein receptor-related protein-1 (LRP-1) and inhibit the cytotoxic effect of TNFα more efficiently because of its dimeric structure. Stably transformed CHO cells successfully expressed MTV, and its purification by Immobilized-Metal Affinity Chromatography (IMAC) rendered high purity degree. Mutated VEGF domain included in MTV did not show cell proliferation or angiogenic activities measured by scratch and aortic ring assays, which corroborate that the function of this domain is restricted to dimerization. The pairs MTV-TNFα (Kd 279 ± 40.9 nM) and MTV-LRP1 (Kd 399 ± 50.5 nM) showed high affinity by microscale thermophoresis, and a significant increase in cell survival was observed after blocking TNFα with MTV in a cell cytotoxicity assay. Also, the antibody staining in CHOK1 and bEnd3 cells demonstrated the adhesion of MTV to the LRP1 receptor located in the cell membrane. These results provide compelling evidence for the proper functioning of the three main domains of MTV individually, which encourage us to continue the research with this new molecule as a potential candidate for the systemic treatment of neurological disorders.

High-fat diet exacerbates lead-induced blood-brain barrier disruption by disrupting tight junction integrity

Environmental exposure to lead (Pb) can damage to the central nervous system (CNS) in humans. High-fat diet (HFD) also has been suggested to impair neurocognitive function. Blood-brain barrier (BBB) is a rigorous permeability barrier for maintaining homeostasis of CNS. The damage of BBB caused by tight junctions (TJs) disruption is central to the etiology of various CNS disorders. This study aimed to investigate whether HFD could exacerbate Pb exposure induced the destruction of BBB integrity by TJs disruption. To this end, we measured cell viability assay, trans-endothelial electrical resistance assay, horseradish peroxidase flux measurement, Western blot analysis, and immunofluorescence experiments. The results showed that palmitic acid (PA), the most common saturated fatty acid found in the human body, can increase the permeability of the BBB in vitro which formed in bEnd.3 cells induced by Pb exposure, and decrease the expression of TJs, such as zonula occludins-1 (ZO-1) and occludin. Besides, we found that PA could promote the up-regulation of matrix metalloproteinase (MMP)-9 expression and activate the c-Jun N-terminal kinase (JNK) pathway induced by Pb. MMP-9 inhibitor or JNK inhibitor could increase BBB integrity and up-regulate the expressions of ZO-1 and occludin after treatment, respectively. Moreover, the JNK inhibitor could down-regulate the expression of MMP-9. In conclusion, these results suggested that HFD exacerbates Pb-induced BBB disruption by disrupting TJs integrity. This may be because PA promotes the activation of JNK pathway and then up-regulated the expression of MMP-9 after Pb-exposure. It is suggested that people with HFD exposed to environmental Pb may cause more serious damage to the CNS.

The Application of Peptides in Glioma: a Novel Tool for Therapy

BACKGROUND

Glioma is the most aggressive and lethal tumor of the central nervous system. Owing to the cellular heterogeneity, the invasiveness, and blood-brain barrier (BBB), current therapeutic approaches, such as chemotherapy and radiotherapy, are poorly to obtain great anti-tumor efficacy. However, peptides, a novel type of therapeutic agent, displayed excellent ability in the tumor, which becomes a new molecule for glioma treatment.

METHOD

We review the current knowledge on peptides for the treatment of glioma through a PubMed-based literature search.

RESULTS

In the treatment of glioma, peptides can be used as (i) decoration on the surface of the delivery system, facilitating the distribution and accumulation of the anti-tumor drug in the target site;(ii) anti-tumor active molecules, inhibiting the growth of glioma and reducing solid tumor volume; (iii) immune-stimulating factor, and activating immune cells in the tumor microenvironment or recruiting immune cells to the tumor for breaking out the immunosuppression by glioma cells.

CONCLUSION

The application of peptides has revolutionized the treatment of glioma, which is based on targeting, penetrating, anti-tumor activities, and immunostimulatory. Moreover, better outcomes have been discovered in combining different kinds of peptides rather than a single one. Until now, more and more preclinical studies have been developed with multifarious peptides, which show promising results in vitro or vivo with the model of glioma.

A novel rat model of chronic subdural hematoma: Induction of inflammation and angiogenesis in the subdural space mimicking human-like features of progressively expanding hematoma

Pathophysiological mechanisms of chronic subdural hematoma (CSDH) involve localized inflammation, angiogenesis, and dysregulated coagulation and fibrinolysis. The scarcity of reproducible and clinically relevant animal models of CSDH hinders further understanding the underlying pathophysiology and improving new treatment strategies. Here, we developed a novel rat model of CSDH using extracellular matrices (Matrigel) and brain microvascular endothelial cell line (bEnd.3 cells). One hundred-microliter of Matrigel-bEnd.3 cell (10⁶ cells per milliliter) mixtures were injected into the virtual subdural space of elderly male Sprague-Dawley rats. This approach for the first time led to a spontaneous and expanding subdural hematoma, encapsulated by internal and external neomembranes, formed as early as 3 d, reached its peak at 7 d, and lasted for more than 14 d, mimicking the progressive hemorrhage observed in patients with CSDH. The external neomembrane and hematoma fluid involved numerous inflammatory cells, fibroblasts, and highly fragile neovessels. Furthermore, a localized pathophysiological process was validated as evidenced by the increased expressions of inflammatory and angiogenic mediators in external neomembrane and hematoma fluid rather than in peripheral blood. Notably, the specific expression profiles of these mediators were closely associated with the dynamic changes in hematoma volume and neurological outcome. In summary, the CSDH model described here replicated the characteristics of human CSDH, and might serve as an ideal translational platform for preclinical studies. Meanwhile, the crucial roles of angiogenesis and inflammation in CSDH formation were reaffirmed.

Cerebral Apolipoprotein D Exits the Brain and Accumulates in Peripheral Tissues

Apolipoprotein D (ApoD) is a secreted lipocalin associated with neuroprotection and lipid metabolism. In rodent, the bulk of its expression occurs in the central nervous system. Despite this, ApoD has profound effects in peripheral tissues, indicating that neural ApoD may reach peripheral organs. We endeavor to determine if cerebral ApoD can reach the circulation and accumulate in peripheral tissues. Three hours was necessary for over 40% of all the radiolabeled human ApoD (hApoD), injected bilaterally, to exit the central nervous system (CNS). Once in circulation, hApoD accumulates mostly in the kidneys/urine, liver, and muscles. Accumulation specificity of hApoD in these tissues was strongly correlated with the expression of lowly glycosylated basigin (BSG, CD147). hApoD was observed to pass through bEnd.3 blood brain barrier endothelial cells monolayers. However, cyclophilin A did not impact hApoD internalization rates in bEnd.3, indicating that ApoD exit from the brain is either independent of BSG or relies on additional cell types. Overall, our data showed that ApoD can quickly and efficiently exit the CNS and reach the liver and kidneys/urine, organs linked to the recycling and excretion of lipids and toxins. This indicated that cerebral overexpression during neurodegenerative episodes may serve to evacuate neurotoxic ApoD ligands from the CNS.

Delivery of Thyronamines (TAMs) to the Brain: A Preliminary Study

Recent reports highlighted the significant neuroprotective effects of thyronamines (TAMs), a class of endogenous thyroid hormone derivatives. In particular, 3-iodothyronamine (T1AM) has been shown to play a pleiotropic role in neurodegeneration by modulating energy metabolism and neurological functions in mice. However, the pharmacological response to T1AM might be influenced by tissue metabolism, which is known to convert T1AM into its catabolite 3-iodothyroacetic acid (TA1). Currently, several research groups are investigating the pharmacological effects of T1AM systemic administration in the search of novel therapeutic approaches for the treatment of interlinked pathologies, such as metabolic and neurodegenerative diseases (NDDs). A critical aspect in the development of new drugs for NDDs is to know their distribution in the brain, which is fundamentally related to their ability to cross the blood–brain barrier (BBB). To this end, in the present study we used the immortalized mouse brain endothelial cell line bEnd.3 to develop an in vitro model of BBB and evaluate T1AM and TA1 permeability. Both drugs, administered at 1 µM dose, were assayed by high-performance liquid chromatography coupled to mass spectrometry. Our results indicate that T1AM is able to efficiently cross the BBB, whereas TA1 is almost completely devoid of this property.

A Commonly Used Biocide 2-N-octyl-4-isothiazolin-3-oneInduces Blood-Brain Barrier Dysfunction via Cellular Thiol Modification and Mitochondrial Damage

Isothiazolinone (IT) biocides are potent antibacterial substances commonly used as preservatives or disinfectants, and 2-n-Octyl-4-isothiazolin-3-one (OIT; octhilinone) is a common IT biocide that is present in leather products, glue, paints, and cleaning products. Although humans are exposed to OIT through personal and industrial use, the potentially deleterious effects of OIT on human health are still unknown. To investigate the effects of OIT on the vascular system, which is continuously exposed to xenobiotics through systemic circulation, we treated brain endothelial cells with OIT. OIT treatment significantly activated caspase-3-mediated apoptosis and reduced the bioenergetic function of mitochondria in a bEnd.3 cell-based in vitro blood–brain barrier (BBB) model. Interestingly, OIT significantly altered the thiol redox status, as evidenced by reduced glutathione levels and protein S-nitrosylation. The endothelial barrier function of bEnd.3 cells was significantly impaired by OIT treatment. OIT affected mitochondrial dynamics through mitophagy and altered mitochondrial morphology in bEnd.3 cells. N-acetyl cysteine significantly reversed the effects of OIT on the metabolic capacity and endothelial function of bEnd.3 cells. Taken together, we demonstrated that the alteration of the thiol redox status and mitochondrial damage contributed to OIT-induced BBB dysfunction, and we hope that our findings will improve our understanding of the potential hazardous health effects of IT biocides.

Design and Validation of Liposomal ApoE2 Gene Delivery System to Evade Blood-Brain Barrier for Effective Treatment of Alzheimer's Disease

Targeting gene-based therapeutics to the brain is a strategy actively sought to treat Alzheimer's disease (AD). Recent findings discovered the role of apolipoprotein E (ApoE) isoforms in the clearance of toxic amyloid beta proteins from the brain. ApoE2 isoform is beneficial for preventing AD development, whereas ApoE4 is a major contributing factor to the disease. In this paper, we demonstrated efficient brain-targeted delivery of ApoE2 encoding plasmid DNA (pApoE2) using glucose transporter-1 (glut-1) targeted liposomes. Liposomes were surface-functionalized with a glut-1 targeting ligand mannose (MAN) and a cell-penetrating peptide (CPP) to enhance brain-targeting and cellular internalization, respectively. Among various CPPs, rabies virus glycoprotein peptide (RVG) or penetratin (Pen) was selected as a cell-penetration enhancer. Dual (RVGMAN and PenMAN)-functionalized liposomes were cytocompatible at 100 nM phospholipid concentration and demonstrated significantly higher expression of ApoE2 in bEnd.3 cells, primary neurons, and astrocytes compared to monofunctionalized and unmodified (plain) liposomes. Dual-modified liposomes also showed ∼2 times higher protein expression than other formulation controls in neurons cultured below the in vitro BBB model. These results translated well to in vivo efficacy study with significantly higher transfection of pApoE2 in the C57BL/6 mice brain following single tail vein administration of RVGMAN and PenMAN functionalized liposomes without any noticeable signs of toxicity. These results illustrate the potential of surface-modified liposomes for safe and brain-targeted delivery of the pApoE2 gene for effective AD therapy.

Efficient LRP1-Mediated Uptake and Low Cytotoxicity of Peptide L57 In Vitro Shows Its Promise as CNS Drug Delivery Vector

Although an abundance of drug candidates exists which are aimed at the remediation of central nervous system (CNS) disorders, the utility of some are severely limited by their inability to cross the blood brain barrier. Potential drug delivery systems such as the Angiopep family of peptides have shown modest potential; however, there is a need for novel drug delivery candidates that incorporate peptidomimetics to enhance the efficiency of transcytosis, specificity, and biocompatibility. Here, we report on the first in vitro cellular uptake and cytotoxicity study of a peptidomimetic, cationic peptide, L57. It binds to cluster 4 of the low-density lipoprotein receptor-related protein 1 (LRP1) receptor which is expressed in numerous cell types, such as brain endothelial cells. We used early-passage-number brain microvascular endothelial cells and astrocytes harvested from rat pup brains that highly express LRP1, to study the uptake of L57 versus Angiopep-7 (A7). Uptake of L57 and A7 showed a concentration-dependent increase, with L57 being taken up to a greater degree than A7 at the same concentration. Additionally, peptide uptake in LRP1-deficient PEA 10 cells had greatly reduced uptake. Furthermore, L57 demonstrated excellent cell viability versus A7, showing promise as a potential drug delivery vector for CNS therapeutics.

Hyperglycemic Condition Causes Pro-Inflammatory and Permeability Alterations Associated with Monocyte Recruitment and Deregulated NFκB/PPARγ Pathways on Cerebral Endothelial Cells: Evidence for Polyphenols Uptake and Protective Effect

Hyperglycemia alters the function of cerebral endothelial cells from the blood-brain barrier, increasing the risk of cerebrovascular complications during diabetes. This study evaluated the protective effect of polyphenols on inflammatory and permeability markers on bEnd3 cerebral endothelial cells exposed to high glucose concentration. Results show that hyperglycemic condition increased nuclear factor kappa B (NFκB) activity, deregulated the expression of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-10 (IL-10) and endothelial-leukocyte adhesion molecule (E-selectin) genes, raised MCP-1 secretion and elevated monocyte adhesion and transendothelial migration. High glucose decreased occludin, claudin-5, zona occludens-1 (ZO-1) and zona occludens-2 (ZO-2) tight junctions production and altered the endothelial permeability. Characterized polyphenolic extracts from the French medicinal plants Antirhea borbonica, Ayapana triplinervis, Dodonaea viscosa and Terminalia bentzoe, and their major polyphenols quercetin, caffeic, chlorogenic and gallic acids limited the pro-inflammatory and permeability alterations caused by high glucose. Peroxisome proliferator-activated receptor gamma (PPARγ) agonist also attenuated these damages while PPARγ antagonist aggravated them, suggesting PPARγ protective action. Interestingly, polyphenols improved PPARγ gene expression lowered by high glucose. Moreover, polyphenols were detected at the intracellular level or membrane-bound to cells, with evidence for breast cancer resistance protein (BCRP) efflux transporter role. Altogether, these findings emphasize the ability of polyphenols to protect cerebral endothelial cells in hyperglycemic condition and their relevance for pharmacological strategies aiming to limit cerebrovascular disorders in diabetes.

Ezrin is essential for the entry of Japanese encephalitis virus into the human brain microvascular endothelial cells

Japanese encephalitis virus (JEV) remains the predominant cause of viral encephalitis worldwide. It reaches the central nervous system upon crossing the blood-brain barrier through pathogenic mechanisms that are not completely understood. Here, using a high-throughput siRNA screening assay combined with verification experiments, we found that JEV enters the primary human brain microvascular endothelial cells (HBMEC) through a caveolae-mediated endocytic pathway. The role of ezrin, an essential host factor for JEV entry based on our screening, in caveolae-mediated JEV internalization was investigated. We observed that JEV internalization in HBMEC is largely dependent on ezrin-mediated actin cytoskeleton polymerization. Moreover, Src, a protein predicted by a STRING database search, was found to be required in JEV entry. By a variety of pharmacological inhibition and immunoprecipitation assays, we found that Src, ezrin, and caveolin-1 were sequentially activated and formed a complex during JEV infection. A combination of in vitro kinase assay and subcellular analysis demonstrated that ezrin is essential for Src-caveolin-1 interactions. In vivo, both Src and ezrin inhibitors protected ICR suckling mice against JEV-induced mortality and diminished mouse brain viral load. Therefore, JEV entry into HBMEC requires the activation of the Src-ezrin-caveolin-1 signalling axis, which provides potential targets for restricting JEV infection.

Hepatocyte growth factor-regulated tyrosine kinase substrate is essential for endothelial cell polarity and cerebrovascular stability

AIMS

Hepatocyte growth factor-regulated tyrosine kinase substrate (Hgs), a key component of the endosomal sorting complex required for transport (ESCRT), has been implicated in many essential biological processes. However, the physiological role of endogenous Hgs in the vascular system has not previously been explored. Here, we have generated brain endothelial cell (EC) specific Hgs knockout mice to uncover the function of Hgs in EC polarity and cerebrovascular stability.

METHODS AND RESULTS

Knockout of Hgs in brain ECs led to impaired endothelial apicobasal polarity and brain vessel collapse in mice. We determined that Hgs is essential for recycling of vascular endothelial (VE)-cadherin to the plasma membrane, since loss of Hgs blocked trafficking of endocytosed VE-cadherin from early endosomes to recycling endosomes, and impaired the motility of recycling endosomes. Supportively, overexpression of the motor kinesin family member 13A (KIF13A) restored endosomal recycling and rescued abrogated polarized trafficking and distribution of VE-cadherin in Hgs knockdown ECs.

CONCLUSION

These data uncover a novel physiological function of Hgs and support an essential role for the ESCRT machinery in the maintenance of EC polarity and cerebrovascular stability.

Titanium dioxide nanoparticles impair the inner blood-retinal barrier and retinal electrophysiology through rapid ADAM17 activation and claudin-5 degradation

Background

Depending on their distinct properties, titanium dioxide nanoparticles (TiO₂-NPs) are manufactured extensively and widely present in our daily necessities, with growing environmental release and public concerns. In sunscreen formulations, supplementation of TiO₂-NPs may reach up to 25% (w/w). Ocular contact with TiO₂-NPs may occur accidentally in certain cases, allowing undesirable risks to human vision. This study aimed to understand the barrier integrity of retinal endothelial cells in response to TiO₂-NP exposure. bEnd.3 cells and human retinal endothelial cells (HRECs) were exposed to TiO₂-NP, followed by examination of their tight junction components and functions.

Results

TiO2-NP treatment apparently induced a broken structure of the junctional plaques, conferring decreased transendothelial electrical resistance, a permeable paracellular cleft, and improved cell migration in vitro. This might involve rapid activation of metalloproteinase, a disintegrin and metalloproteinase 17 (ADAM17), and ADAM17-mediated claudin-5 degradation. For the in vivo study, C57BL/6 mice were administered a single dose of TiO2-NP intravitreally and then subjected to a complete ophthalmology examination. Fluorescein leakage and reduced blood flow at the optical disc indicated a damaged inner blood-retinal barrier induced by TiO₂-NPs. Inappreciable change in the thickness of retinal sublayers and alleviated electroretinography amplitude were observed in the TiO₂-NP-treated eyes.

Conclusions

Overall, our data demonstrate that TiO2-NP can damage endothelial cell function, thereby affecting retinal electrophysiology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-020-00395-7.

Characteristic Effects of the Cardiac Non-Neuronal Acetylcholine System Augmentation on Brain Functions

Since the discovery of non-neuronal acetylcholine in the heart, this specific system has drawn scientific interest from many research fields, including cardiology, immunology, and pharmacology. This system, acquired by cardiomyocytes independent of the parasympathetic nervous system of the autonomic nervous system, helps us to understand unsolved issues in cardiac physiology and to realize that the system may be more pivotal for cardiac homeostasis than expected. However, it has been shown that the effects of this system may not be restricted to the heart, but rather extended to cover extra-cardiac organs. To this end, this system intriguingly influences brain function, specifically potentiating blood brain barrier function. Although the results reported appear to be unusual, this novel characteristic can provide us with another research interest and therapeutic application mode for central nervous system diseases. In this review, we discuss our recent studies and raise the possibility of application of this system as an adjunctive therapeutic modality.

Astrocytic Sonic Hedgehog Alleviates Intracerebral Hemorrhagic Brain Injury via Modulation of Blood-Brain Barrier Integrity

Background: Intracerebral hemorrhage (ICH) is a fatal subtype of stroke that lacks effective therapy. Blood-brain barrier (BBB) damage is a hallmark of ICH-induced brain injury that leads to edema formation, leukocytes infiltration, influx of blood components into the perihematomal (PHE) region, and eventually brain injury. Astrocytes are essential for the formation and maintenance of the BBB by providing secreted molecules that contribute to the association between these cells. Sonic hedgehog (SHH) derived from astrocytes promotes the maturity and integrity of the BBB by upregulating tight junctions (TJs) in brain capillary endothelial cells (ECs). However, the effect of SHH on BBB in ICH has not been investigated.

Methods: Cyclopamine (CYC) is a potent, selective inhibitor that specifically blocks the SHH signaling pathway. Here, we used pharmacological inhibitions (CYC and its derivatives) to determine a critical role of the SHH signaling pathway in promoting BBB integrity after ICH by mechanisms of regulating the TJ proteins in vivo and in vitro.

Results: The expression of astrocytic SHH was upregulated in mouse brains after ICH. Compared with the vehicle-treated group, inhibition of the SHH signaling pathway with CYC and its derivatives treatments aggravated neurological function deficits, brain edema, hematoma volume, and BBB impairment by downregulating TJs in ECs through the SHH-Gli-1 axis in vivo and in vitro.

Conclusions: SHH signaling pathway at the level of the BBB provides a barrier-promoting effect, suggesting that the SHH signaling pathway may function as a potential therapeutic target for restoring BBB function in ICH.

Nanoparticles Based on Quaternary Ammonium Chitosan-methyl-β-cyclodextrin Conjugate for the Neuropeptide Dalargin Delivery to the Central Nervous System: An In Vitro Study

Peptide oral administration is a hard goal to reach, especially if the brain is the target site. The purpose of the present study was to set up a vehicle apt to promote oral absorption of the neuropeptide dalargin (DAL), allowing it to cross the intestinal mucosal barrier, resist enzymatic degradation, and transport drugs to the brain after crossing the blood–brain barrier. Therefore, a chitosan quaternary ammonium derivative was synthesized and conjugated with methyl-β-cyclodextrin to prepare DAL-medicated nanoparticles (DAL-NP). DAL-NP particle size was 227.7 nm, zeta potential +8.60 mV, encapsulation efficiency 89%. DAL-NP protected DAL from degradation by chymotrypsin or pancreatin and tripled DAL degradation time compared to non-encapsulated DAL. Use of DAL-NP was safe for either Caco-2 or bEnd.3 cells, with the latter selected as a blood–brain barrier model. DAL-NP could also cross either the Caco-2 or bEnd.3 monolayer by the transepithelial route. The results suggest a potential DAL-NP ability to transport to the brain a DAL dose fraction administered orally, although in vivo experiments will be needed to confirm the present data obtained in vitro.

A Peptide-Based Nanocarrier for an Enhanced Delivery and Targeting of Flurbiprofen into the Brain for the Treatment of Alzheimer's Disease: An In Vitro Study

Alzheimer's disease (AD) is an age-related disease caused by abnormal accumulation of amyloid-β in the brain leading to progressive tissue degeneration. Flurbiprofen (FP), a drug used to mitigate the disease progression, has low efficacy due to its limited permeability across the blood-brain barrier (BBB). In a previous work, FP was coupled at the uppermost branching of an ε-lysine-based branched carrier, its root presenting a phenylalanine moiety able to increase the hydrophobicity of the complex and enhance the transport across the BBB by adsorptive-mediated transcytosis (AMT). The present study explores a different molecular design of the FP-peptide delivery system, whereby its root presents an ApoE-mimicking peptide, a targeting ligand that could enhance transport across the BBB by receptor-mediated transcytosis (RMT). The functionalised complex was synthesised using a solid-phase peptide synthesis and characterised by mass spectrometry and FTIR. Cytotoxicity and permeability of this complex across an in vitro BBB model were analysed. Moreover, its activity and degradation to release the drug were investigated. The results revealed successful synthesis and grafting of FP molecules at the uppermost molecular branches of the lysine terminal without observed cytotoxicity. When covalently linked to the nanocarrier, FP was still active on target cells, albeit with a reduced activity, and was released as a free drug upon hydrolysis in a lysosome-mimicking medium. Noticeably, this work shows the high efficiency of RMT-driven FP delivery over delivery systems relying on AMT.

Turning weakness into strength: Albumin nanoparticle-redirected amphotericin B biodistribution for reducing nephrotoxicity and enhancing antifungal activity

As the gold standard treatment for invasive fungal infection, amphotericin B (AmB) is limited by its severe nephrotoxicity. It has been shown that AmB complex with albumin in vivo forms a sub-10 nm nanocomplex within kidney excretion size range and eventually induces the nephrotoxicity. This study presents an approach to take advantage of the "weakness" of such unique interaction between AmB and albumin to form AmB nanocomplex beyond the size range of kidney excretion. Herein, a novel strategy was developed by directly assembling molecular BSA into larger-sized nanostructures with the reconstructed intermolecular disulfide bond and hydrophobic interaction. The rich binding sites of AmB within BSA nanostructures enabled the efficient AmB loading and forming nanoparticle (AmB-NP) which exceeds the size range of kidney excretion (~ 60 nm). We found nanoassembly with BSA redirected biodistribution of AmB with a 2.8-fold reduction of drug accumulation in the kidney and significantly improved its renal impairment in mice. Furthermore, we found that nanoassembly with BSA significantly increased the biodistribution of AmB in brain and endowed it 100-folds increase in pharmacological effect against meningoencephalitis caused by common fungal pathogen Cryptococcus neoformans. Together, this study not merely overcomes the nephrotoxicity of AmB using its "weakness" by a nanoassembly method, and provides a new strategy for reducing toxicity of drugs with high albumin binding rate in vivo.