Glial‐cell‐mediated re‐induction of the blood‐brain barrier phenotype in brain capillary endothelial cells: A differential gel electrophoresis study

In the neurovascular unit, brain microvascular endothelial cells develop characteristic barrier features that control the molecular exchanges between the blood and the brain. These characteristics are partially or totally lost when the cells are isolated for use in in vitro blood‐brain barrier (BBB) models. Hence, the re‐induction of barrier properties is crucial for the relevance of BBB models. Although the role of astrocyte promiscuity is well established, the molecular mechanisms of re‐induction remain largely unknown. Here, we used a DIGE‐based proteomics approach to study endothelial cellular proteins showing significant quantitative variations after BBB re‐induction. We confirm that quantitative changes mainly concern proteins involved in cell structure and motility. Furthermore, we describe the possible involvement of the asymmetric dimethylarginine pathway in the BBB phenotype re‐induction process and we discuss asymmetric dimethylarginine's potential role in regulating endothelial function (in addition to its role as a by‐product of protein modification). Our results also suggest that the intracellular redox potential is lower in the in vitro brain capillary endothelial cells displaying re‐induced BBB functions than in cells with limited BBB functions.     

Inhibition of Rho‐kinase protects cerebral barrier from ischaemia‐evoked injury through modulations of endothelial cell oxidative stress and tight junctions

Ischaemic strokes evoke blood–brain barrier (BBB) disruption and oedema formation through a series of mechanisms involving Rho‐kinase activation. Using an animal model of human focal cerebral ischaemia, this study assessed and confirmed the therapeutic potential of Rho‐kinase inhibition during the acute phase of stroke by displaying significantly improved functional outcome and reduced cerebral lesion and oedema volumes in fasudil‐ versus vehicle‐treated animals. Analyses of ipsilateral and contralateral brain samples obtained from mice treated with vehicle or fasudil at the onset of reperfusion plus 4 h post‐ischaemia or 4 h post‐ischaemia alone revealed these benefits to be independent of changes in the activity and expressions of oxidative stress‐ and tight junction‐related parameters. However, closer scrutiny of the same parameters in brain microvascular endothelial cells subjected to oxygen–glucose deprivation ± reperfusion revealed marked increases in prooxidant NADPH oxidase enzyme activity, superoxide anion release and in expressions of antioxidant enzyme catalase and tight junction protein claudin‐5. Cotreatment of cells with Y‐27632 prevented all of these changes and protected in vitro barrier integrity and function. These findings suggest that inhibition of Rho‐kinase after acute ischaemic attacks improves cerebral integrity and function through regulation of endothelial cell oxidative stress and reorganization of intercellular junctions.

     

Expanding the MiniAp‐4 BBB‐shuttle family: Evaluation of proline cis‐trans ratio as tool to fine‐tune transport

Venoms have recently emerged as a promising field in drug discovery due to their good selectivity and affinity for a wide range of biological targets. Among their multiple potential applications, venoms are a rich source of blood‐brain barrier (BBB) peptide shuttles. We previously described a short nontoxic derivative of apamin, MiniAp‐4, which can transport a wide range of cargoes across the BBB. Here, we have studied the conformation of the proline residue of a range of MiniAp‐4 analogues by high‐field NMR techniques, with the aim to identify whether there is a direct relation between the cis/trans population and a range of features, such as the capacity to transport molecules across a human‐based cellular model and stability in various media. The most promising candidate showed improved transport properties for a relevant small fluorophore.     

Amyloid‐β‐induced occludin down‐regulation and increased permeability in human brain endothelial cells is mediated by MAPK activation

Vascular dysfunction is emerging as a key pathological hallmark in Alzheimer’s disease (AD). A leaky blood–brain barrier (BBB) has been described in AD patient tissue and in vivo AD mouse models. Brain endothelial cells (BECs) are linked together by tight junctional (TJ) proteins, which are a key determinant in restricting the permeability of the BBB. The amyloid β (Aβ) peptides of 1–40 and 1–42 amino acids are believed to be pivotal in AD pathogenesis. We therefore decided to investigate the effect of Aβ 1–40, the Aβ variant found at the highest concentration in human plasma, on the permeability of an immortalized human BEC line, hCMEC/D3. Aβ 1–40 induced a marked increase in hCMEC/D3 cell permeability to the paracellular tracer 70 kD FITC‐dextran when compared with cells incubated with the scrambled Aβ 1–40 peptide. Increased permeability was associated with a specific decrease, both at the protein and mRNA level, in the TJ protein occludin, whereas claudin‐5 and ZO‐1 were unaffected. JNK and p38MAPK inhibition prevented both Aβ 1–40‐mediated down‐regulation of occludin and the increase in paracellular permeability in hCMEC/D3 cells. Our findings suggest that the JNK and p38MAPK pathways might represent attractive therapeutic targets for preventing BBB dysfunction in AD.     

Dl‐3n‐butylphthalide improves traumatic brain injury recovery via inhibiting autophagy‐induced blood‐brain barrier disruption and cell apoptosis

Blood‐brain barrier (BBB) disruption and neuronal apoptosis are important pathophysiological processes after traumatic brain injury (TBI). In clinical stroke, Dl‐3n‐butylphthalide (Dl‐NBP) has a neuroprotective effect with anti‐inflammatory, anti‐oxidative, anti‐apoptotic and mitochondrion‐protective functions. However, the effect and molecular mechanism of Dl‐NBP for TBI need to be further investigated. Here, we had used an animal model of TBI and SH‐SY5Y/human brain microvascular endothelial cells to explore it. We found that Dl‐NBP administration exerts a neuroprotective effect in TBI/OGD and BBB disorder, which up‐regulates the expression of tight junction proteins and promotes neuronal survival via inhibiting mitochondrial apoptosis. The expressions of autophagy‐related proteins, including ATG7, Beclin1 and LC3II, were significantly increased after TBI/OGD, and which were reversed by Dl‐NBP treatment both in vivo and in vitro. Moreover, rapamycin treatment had abolished the effect of Dl‐NBP for TBI recovery. Collectively, our current studies indicate that Dl‐NBP treatment improved locomotor functional recovery after TBI by inhibiting the activation of autophagy and consequently blocking the junction protein loss and neuronal apoptosis. Dl‐NBP, as an anti‐inflammatory and anti‐oxidative drug, may act as an effective strategy for TBI recovery.     

SPION‐mediated miR‐141 promotes the differentiation of HuAESCs into dopaminergic neuron‐like cells via suppressing lncRNA‐HOTAIR

In this study, a bioinformatics analysis and luciferase reporter assay revealed that microRNA‐141 could silence the expression of lncRNA‐HOTAIR by binding to specific sites on lncRNA‐HOTAIR. We used superparamagnetic iron oxide nanoparticles (SPIONs) to mediate the high expression of microRNA‐141 (SPIONs@miR‐141) in human amniotic epithelial stem cells (HuAESCs), which was followed by the induction of the differentiation of HuAESCs into dopaminergic neuron‐like cells (iDNLCs). qPCR, western blot, immunofluorescence staining and HPLC all suggested that SPION‐mediated overexpression of miR‐141 could promote an increased expression of brain‐derived neurotrophic factor (BDNF), DAT and 5‐TH in HuAESC‐derived iDNLCs. The RIP and ChIP assay also showed that overexpression of miR‐141 could significantly inhibit the recruitment and binding of lncRNA‐HOTAIR to EZH2 on BDNF gene promoter. cDNA microarray analysis revealed that the expression levels of 190 genes were much higher in iDNLCs than in HuAESCs. Finally, a protein interaction network analysis and identification showed that in the iDNLC group with SPIONs@miR‐141, factors that interact with BDNF, such as FGF8, SHH, NTRK3 and CREB1, all showed significantly higher expression levels compared with those in the SPIONs@miR‐Mut. Therefore, this study confirmed that the highly efficient expression of microRNA‐141 mediated by SPIONs could improve the efficiency of HuAESCs differentiation into dopaminergic neuron‐like cells.     

Mannitol facilitates neurotrophic factor up‐regulation and behavioural recovery in neonatal hypoxic‐ischaemic rats with human umbilical cord blood grafts

We recently demonstrated that blood–brain barrier permeabilization using mannitol enhances the therapeutic efficacy of systemically administered human umbilical cord blood (HUCB) by facilitating the entry of neurotrophic factors from the periphery into the adult stroke brain. Here, we examined whether the same blood–brain barrier manipulation approach increases the therapeutic effects of intravenously delivered HUCB in a neonatal hypoxic‐ischaemic (HI) injury model. Seven‐day‐old Sprague–Dawley rats were subjected to unilateral HI injury and then at day 7 after the insult, animals intravenously received vehicle alone, mannitol alone, HUCB cells (15k mononuclear fraction) alone or a combination of mannitol and HUCB cells. Behavioural tests at post‐transplantation days 7 and 14 showed that HI animals that received HUCB cells alone or when combined with mannitol were significantly less impaired in motor asymmetry and motor coordination compared with those that received vehicle alone or mannitol alone. Brain tissues from a separate animal cohort from the four treatment conditions were processed for enzyme‐linked immunosorbent assay at day 3 post‐transplantation, and revealed elevated levels of GDNF, NGF and BDNF in those that received HUCB cells alone or when combined with mannitol compared with those that received vehicle or mannitol alone, with the combined HUCB cells and mannitol exhibiting the most robust neurotropic factor up‐regulation. Histological assays revealed only sporadic detection of HUCB cells, suggesting that the trophic factor–mediated mechanism, rather than cell replacement per se, principally contributed to the behavioural improvement. These findings extend the utility of blood–brain barrier permeabilization in facilitating cell therapy for treating neonatal HI injury.     

Acute exposure to the vinyl chalcogenide 3‐methyl‐1‐phenyl‐2‐(phenylseleno)oct‐2‐en‐1‐one induces oxidative stress in different brain area of rats

The mechanisms that lead to the onset of organoselenium intoxication are still poorly understood. Therefore, in the present study, we investigated the effect of acute administration of 3‐methyl‐1‐phenyl‐2‐(phenylseleno)oct‐2‐en‐1‐one on some parameters of oxidative stress and on the activity of creatine kinase (CK) in different brain areas and on the behaviour in the open field test of 90‐day‐old male rats. Animals (n = 10/group) were treated intraperitoneally with a single dose of the organoselenium (125, 250 or 500 µg kg^?1), and after 1 h of the drug administration, they were exposed to the open field test, and behaviour parameters were recorded. Immediately after they were euthanized, cerebral cortex, hippocampus and cerebellum were dissected for measurement of thiobarbituric acid reactive substances (TBARS), carbonyl, sulfhydryl, catalase (CAT), superoxide dismutase (SOD) and CK activity. Our results showed that the dose of 500 µg kg^?1 of the organoselenium increased the locomotion and rearing behaviours in the open field test. Moreover, the organochalcogen enhanced TBARS in the cerebral cortex and cerebellum and increased the oxidation of proteins (carbonyl) only in the cerebral cortex. Sulfhydryl content was reduced in all brain areas, CAT activity enhanced in the hippocampus and reduced in the cerebellum and SOD activity increased in all brain structures. The organoselenium also inhibited CK activity in the cerebral cortex. Therefore, changes in motor behaviour, redox state and energy homeostasis in rats treated acutely with organoselenium support the hypotheses that the brain is a potential target for the organochalcogen action. Copyright © 2014 John Wiley & Sons, Ltd.     

Two‐ and three‐photon absorption cross‐section characterization for high‐brightness,cell‐specific multiphoton fluorescence brain imaging

We demonstrate an accurate quantitative characterization of absolute two‐ and three‐photon absorption (2PA and 3PA) action cross sections of a genetically encodable fluorescent marker Sypher3s. Both 2PA and 3PA action cross sections of this marker are found to be remarkably high, enabling high‐brightness, cell‐specific two‐ and three‐photon fluorescence brain imaging. Brain imaging experiments on sliced samples of rat's cortical areas are presented to demonstrate these imaging modalities. The 2PA action cross section of Sypher3s is shown to be highly sensitive to the level of pH, enabling pH measurements via a ratiometric readout of the two‐photon fluorescence with two laser excitation wavelengths, thus paving the way toward fast optical pH sensing in deep‐tissue experiments.     

Three‐Dimensional Nanostructured Indium‐Tin‐Oxide Electrodes for Enhanced Performance of Bulk Heterojunction Organic Solar Cells

A three‐dimensional indium tin oxide (ITO) nanohelix (NH) array is presented as a multifunctional electrode for bulk heterojunction organic solar cells for simultaneously improving light absorption and charge transport from the active region to the anode. It is shown that the ITO NH array, which is easily fabricated using an oblique‐angle‐deposition technique, acts as an effective antireflection coating as well as a light‐scattering layer, resulting in much enhanced light harvesting. Furthermore, the larger interfacial area between the electrode and the active layer, together with the enhanced carrier mobility through highly conductive ITO NH facilitate transport and collection of charge carriers. The optical and electrical improvements enabled by the ITO NH electrode result in a 10% increase in short‐circuit current density and power‐conversion efficiency of the solar cells.     

High‐Efficiency Polymer Homo‐Tandem Solar Cells with Carbon Quantum‐Dot‐Doped Tunnel Junction Intermediate Layer

The tunnel junction (TJ) intermediate connection layer (ICL), which is the most critical component for high‐efficient tandem solar cell, generally consists of hole conducting layer and polyethyleneimine (PEI) polyelectrolyte. However, because of the nonconducting feature of pristine PEI, photocurrent is open‐restricted in ICL even with a little thick PEI layer. Here, high‐efficiency homo‐tandem solar cells are demonstrated with enhanced efficiency by introducing carbon quantum dot (CQD)‐doped PEI on TJ–ICL. The CQD‐doped PEI provides substantial dynamic advantages in the operation of both single‐junction solar cells and homo‐tandem solar cells. The inclusion of CQDs in the PEI layer leads to improved electron extraction property in single‐junction solar cells and better series connection in tandem solar cells. The highest efficient solar cell with CQD‐doped PEI layer in between indium tin oxide (ITO) and photoactive layer exhibits a maximum power conversion efficiency (PCE) of 9.49%, which represents a value nearly 10% higher than those of solar cells with pristine PEI layer. In the case of tandem solar cells, the highest performing tandem solar cell fabricated with C‐dot‐doped PEI layer in ICL yields a PCE of 12.13%; this value represents an ≈15% increase in the efficiency compared with tandem solar cells with a pristine PEI layer.