Blood-brain Barrier In Mice Research Articles

Astrocytes-derived VEGF exacerbates the microvascular damage of late delayed RBI

Overexpression of vascular endothelial growth factor (VEGF) is considered the most critical factor in radiation-induced brain injury (RBI). To investigate the role of VEGF and the mechanism underlying microvascular damage in RBI, wild type mice, and transgenic mice overexpressing VEGF derived from astrocytes, were separately and randomly exposed to whole-brain or sham irradiation. Pathophysiologic changes in the brain tissue were detected 90 days after irradiation. Compared with wild type mice, the secretion of VEGF and angiopoietin-2 (Ang-2) was up-regulated in transgenic mice, whether irradiated or not, while elevated expression of VEGF, Ang-2, and glial fibrillary acidic protein (GFAP) was detected after whole-brain irradiation using western blotting. Impairment of the blood–brain barrier (BBB) was demonstrated by the leakage of dyes observed using two-photon imaging and decreased expression of zonula occludens-1 (ZO-1) and Occludin. Hematoxylin–eosin (HE) staining revealed obvious structural damage in the irradiated brains. Furthermore, damage to the BBB and histopathology in the transgenic mice were worse than those of wild type mice in the irradiated groups. There was a positive correlation among VEGF and Ang-2 expression and RBI severity. These data reveal that VEGF and Ang-2 expression is closely associated with the microvascular injury in RBI. Further, overexpression of VEGF can cause up-regulation of Ang-2 and exacerbation of RBI. Therefore, Ang-2 might be the cytokine that acts as a mediator between VEGF and microvascular injury, and is likely a new intervention target for RBI.

Potential Diagnostic Imaging of Alzheimer's Disease with Copper-64 Complexes That Bind to Amyloid-β Plaques.

Amyloid-β plaques, consisting of aggregated amyloid-β peptides, are one of the pathological hallmarks of Alzheimer's disease. Copper complexes formed using positron-emitting copper radionuclides that cross the blood-brain barrier and bind to specific molecular targets offer the possibility of noninvasive diagnostic imaging using positron emission tomography. New thiosemicarbazone-pyridylhydrazone based ligands that incorporate pyridyl-benzofuran functional groups designed to bind amyloid-β plaques have been synthesized. The ligands form stable complexes with copper(II) ( Kd = 10-18 M) and can be radiolabeled with copper-64 at room temperature. Subtle changes to the periphery of the ligand backbone alter the metabolic stability of the complexes in mouse and human liver microsomes, and influenced the ability of the complexes to cross the blood-brain barrier in mice. A lead complex was selected based on possessing the best metabolic stability and brain uptake in mice. Synthesis of this lead complex with isotopically enriched copper-65 allowed us to show that the complex bound to amyloid-β plaques present in post-mortem human brain tissue using laser ablation-inductively coupled plasma-mass spectrometry. This work provides insight into strategies to target metal complexes to amyloid-β plaques, and how small modifications to ligands can dramatically alter the metabolic stability of metal complexes as well as their ability to cross the blood-brain barrier.

Intravenous injection of AAV-PHP.eB across the blood-brain barrier in the adult mouse for central nervous system gene therapy*

Abstract Objective To verify the neurotypicality of AAV-PHP.eB after tail vein injection in adult mice and its efficiency in crossing the blood-brain barrier (BBB). Methods The rAAV-SYN-GFP plasmid was constructed, and adult C57BL mice were injected with AAV-PHP. eB: SYN-GFP in the tail vein (300 nL, virus titer 3 × 109 vg) and in the prefrontal lobe (50 L, virus titer 5 × 1011 vg). The green fluorescent protein (GFP) signal in the brain was observed at two weeks, while the GFP signal in the peripheral organs was observed at four weeks. Results Two weeks after tail vein injection, GFP expression was observed throughout the brain, especially in the cortex, hippocampus, and geniculate nucleus. No GFP signal was observed or detected by western blotting in the peripheral organs after four weeks. GFP signal was observed mainly at the local site after prefrontal lobe injection. Conclusion AAV-PHP.eB: SYN-GFP can effectively cross the BBB in adult mice. Using a neuron-specific promoter allows exogenous gene expression in neurons; therefore, AAV-PHP.eB can be used as an effective carrier for studying diseases in the central nervous system (CNS).

Inhibition of ABCB1 and ABCG2 at the Mouse Blood-Brain Barrier with Marketed Drugs To Improve Brain Delivery of the Model ABCB1/ABCG2 Substrate [11C]erlotinib.

P-Glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) are two efflux transporters at the blood-brain barrier (BBB), which effectively restrict brain distribution of diverse drugs, such as tyrosine kinase inhibitors. There is a crucial need for pharmacological ABCB1 and ABCG2 inhibition protocols for a more effective treatment of brain diseases. In the present study, seven marketed drugs (osimertinib, erlotinib, nilotinib, imatinib, lapatinib, pazopanib, and cyclosporine A) and one nonmarketed drug (tariquidar), with known in vitro ABCB1/ABCG2 inhibitory properties, were screened for their inhibitory potency at the BBB in vivo. Positron emission tomography (PET) using the model ABCB1/ABCG2 substrate [11C]erlotinib was performed in mice. Tested inhibitors were administered as i.v. bolus injections at 30 min before the start of the PET scan, followed by a continuous i.v. infusion for the duration of the PET scan. Five of the tested drugs increased total distribution volume of [11C]erlotinib in the brain ( VT,brain) compared to vehicle-treated animals (tariquidar, + 69%; erlotinib, + 19% and +23% for the 21.5 mg/kg and the 43 mg/kg dose, respectively; imatinib, + 22%; lapatinib, + 25%; and cyclosporine A, + 49%). For all drugs, increases in [11C]erlotinib brain distribution were lower than in Abcb1a/b(-/-)Abcg2(-/-) mice (+149%), which suggested that only partial ABCB1/ABCG2 inhibition was reached at the mouse BBB. The plasma concentrations of the tested drugs at the time of the PET scan were higher than clinically achievable plasma concentrations. Some of the tested drugs led to significant increases in blood radioactivity concentrations measured at the end of the PET scan (erlotinib, + 103% and +113% for the 21.5 mg/kg and the 43 mg/kg dose, respectively; imatinib, + 125%; and cyclosporine A, + 101%), which was most likely caused by decreased hepatobiliary excretion of radioactivity. Taken together, our data suggest that some marketed tyrosine kinase inhibitors may be repurposed to inhibit ABCB1 and ABCG2 at the BBB. From a clinical perspective, moderate increases in brain delivery despite the administration of high i.v. doses as well as peripheral drug-drug interactions due to transporter inhibition in clearance organs question the translatability of this concept.

Prolonged systemic hyperglycemia does not cause pericyte loss and permeability at the mouse blood-brain barrier

Diabetes mellitus is associated with cognitive impairment and various central nervous system pathologies such as stroke, vascular dementia, or Alzheimer’s disease. The exact pathophysiology of these conditions is poorly understood. Recent reports suggest that hyperglycemia causes cerebral microcirculation pathology and blood-brain barrier (BBB) dysfunction and leakage. The majority of these reports, however, are based on methods including in vitro BBB modeling or streptozotocin-induced diabetes in rodents, opening questions regarding the translation of the in vitro findings to the in vivo situation, and possible direct effects of streptozotocin on the brain vasculature. Here we used a genetic mouse model of hyperglycemia (Ins2AKITA) to address whether prolonged systemic hyperglycemia induces BBB dysfunction and leakage. We applied a variety of methodologies to carefully evaluate BBB function and cellular integrity in vivo, including the quantification and visualization of specific tracers and evaluation of transcriptional and morphological changes in the BBB and its supporting cellular components. These experiments did neither reveal altered BBB permeability nor morphological changes of the brain vasculature in hyperglycemic mice. We conclude that prolonged hyperglycemia does not lead to BBB dysfunction, and thus the cognitive impairment observed in diabetes may have other causes.

Alzheimer\u2019s Disease Phenotype or Inflammatory Insult Does Not Alter Function of L-Type Amino Acid Transporter 1 in Mouse Blood-Brain Barrier and Primary Astrocytes

PurposeThe study aim was to evaluate the effect of Alzheimer’s disease (AD) and inflammatory insult on the function of L-type amino acid transporter 1 (Lat1) at the mouse blood-brain barrier (BBB) as well as Lat1 function and expression in mouse primary astrocytes.MethodsThe Lat1 function and expression was determined in wildtype astrocytes with and without lipopolysaccharide (LPS)-induced inflammation and in LPS treated AD APP/PS1 transgenic astrocytes. The function of Lat1 at the BBB was evaluated in wildtype mice with and without LPS-induced neuroinflammation and APP/PS1 transgenic mice by in situ brain perfusion.ResultsThere were 2.1 and 1.6 -fold decreases in Lat1 mRNA and protein expression in LPS-treated wildtype astrocytes compared to vehicle-treated astrocytes. In contrast, Lat1 mRNA and protein expression were increased by 1.7 and 1.2 -fold (not statistically significant) in the transgenic cells. A similar trend was observed in the cell uptake of [14C]-L-leucine. There were no statistically significant differences in [14C]-L-leucine BBB permeation between the groups.ConclusionsThe results showed that neither LPS-induced inflammation or the presence of APP/PS1 mutations alters Lat1 function at the mouse BBB as well as Lat1 protein expression and function in mouse primary astrocytes.

Interplay of the Norrin and Wnt7a/Wnt7b signaling systems in blood–brain barrier and blood–retina barrier development and maintenance

β-Catenin signaling controls the development and maintenance of the blood-brain barrier (BBB) and the blood-retina barrier (BRB), but the division of labor and degree of redundancy between the two principal ligand-receptor systems-the Norrin and Wnt7a/Wnt7b systems-are incompletely defined. Here, we present a loss-of-function genetic analysis of postnatal BBB and BRB maintenance in mice that shows striking threshold and partial redundancy effects. In particular, the combined loss of Wnt7a and Norrin or Wnt7a and Frizzled4 (Fz4) leads to anatomically localized BBB defects that are far more severe than observed with loss of Wnt7a, Norrin, or Fz4 alone. In the cerebellum, selective loss of Wnt7a in glia combined with ubiquitous loss of Norrin recapitulates the phenotype observed with ubiquitous loss of both Wnt7a and Norrin, implying that glia are the source of Wnt7a in the cerebellum. Tspan12, a coactivator of Norrin signaling in the retina, is also active in BBB maintenance but is less potent than Norrin, consistent with a model in which Tspan12 enhances the amplitude of the Norrin signal in vascular endothelial cells. Finally, in the context of a partially impaired Norrin system, the retina reveals a small contribution to BRB development from the Wnt7a/Wnt7b system. Taken together, these experiments define the extent of CNS region-specific cooperation for several components of the Norrin and Wnt7a/Wnt7b systems, and they reveal substantial regional heterogeneity in the extent to which partially redundant ligands, receptors, and coactivators maintain the BBB and BRB.

N-acetylcysteine modulation of mitochondrial respiration and blood brain barrier permeability is time dependent and cell type specific

One common symptom of most neurodegenerative diseases related to aging is the presence of blood-brain barrier disruption and mitochondrial disfunction. N-acetylcysteine (NAC) is an FDA approved drug commonly utilized for a variety of neuropsychiatric and neurodegenerative diseases; however, while studies have shown that NAC can improve mitochondrial function in mouse models of some of these diseases, the mechanism(s) of action have yet to be fully defined. Our previous studies have shown that NAC treatment can alter blood-brain barrier (BBB) permeability in mice via changes in reactive oxygen species (ROS). To further examine the effects of NAC on both cell-specificity and the mitochondrial respiration of brain vascular endothelial cells and astrocytes that make up the blood-brain barrier, we utilized brain microvascular endothelial and cerebrum astrocytic cells and an in vitro mouse BBB model. We show that NAC caused time- and dose-dependent changes in BBB permeability that were correlated to significant changes in tight and gap junction proteins, change in endothelial nNOS, and downregulation of mitochondrial complex proteins in endothelial cells. Extracellular flux analysis revealed a significant reduction in endothelial cell mitochondrial maximal respiration after 48hrs. In contrast, astrocyte espiration showed no change after 48hours but was significantly increased after 24hours of NAC reatment corresponding to the decreased permeability noted at this time. These changes paralleled alterations in NOS in endothelial cells but not astrocytes. We conclude that murine astrocytes and endothelial cells respond to NAC treatment in a cell-specific fashion, altering their perspective metabolic profiles and ultimately the tight and gap junctions that determine the permeability of the BBB. Given the current theory that mitochondrial dysfunction and BBB leakiness are predisposing, possibly causative symptoms, for most neurodegenerative diseases associated with aging, our findings suggest that NAC’s cell-specific effects upon both metabolism and BBB permeability may be concurrent mechanisms by which this drug is effective.

Physical blood-brain barrier disruption induced by focused ultrasound does not overcome the transporter-mediated efflux of erlotinib

Overcoming the efflux mediated by ATP–binding cassette (ABC) transporters at the blood-brain barrier (BBB) remains a challenge for the delivery of small molecule tyrosine kinase inhibitors (TKIs) such as erlotinib to the brain. Inhibition of ABCB1 and ABCG2 at the mouse BBB improved the BBB permeation of erlotinib but could not be achieved in humans. BBB disruption induced by focused ultrasound (FUS) was investigated as a strategy to overcome the efflux transport of erlotinib in vivo.In rats, FUS combined with microbubbles allowed for a large and spatially controlled disruption of the BBB in the left hemisphere. ABCB1/ABCG2 inhibition was performed using elacridar (10 mg/kg i.v). The brain kinetics of erlotinib was studied using 11C-erlotinib Positron Emission Tomography (PET) imaging in 5 groups (n = 4–5 rats per group) including a baseline group, immediately after sonication (FUS), 48 h after FUS (FUS + 48 h), elacridar (ELA) and their combination (FUS + ELA). BBB integrity was assessed using the Evan's Blue (EB) extravasation test. Brain exposure to 11C-erlotinib was measured as the area under the curve (AUC) of the brain kinetics (% injected dose (%ID) versus time (min)) in volumes corresponding to the disrupted (left) and the intact (right) hemispheres, respectively.EB extravasation highlighted BBB disruption in the left hemisphere of animals of the FUS and FUS + ELA groups but not in the control and ELA groups. EB extravasation was not observed 48 h after FUS suggesting recovery of BBB integrity. Compared with the control group (AUCBaseline = 1.4 ± 0.5%ID.min), physical BBB disruption did not impact the brain kinetics of 11C-erlotinib in the left hemisphere (p > .05) either immediately (AUCFUS = 1.2 ± 0.1%ID.min) or 48 h after FUS (AUCFUS+48h = 1.1 ± 0.3%ID.min). Elacridar similarly increased 11C-erlotinib brain exposure to the left hemisphere in the absence (AUCELA = 2.2 ± 0.5%ID.min, p < .001) and in the presence of BBB disruption (AUCFUS+ELA = 2.1 ± 0.5%ID.min, p < .001). AUCleft was never significantly different from AUCright (p > .05), in any of the tested conditions.BBB integrity is not the rate limiting step for erlotinib delivery to the brain which is mainly governed by ABC-mediated efflux. Efflux transport of erlotinib persisted despite BBB disruption.

Inflammation caused by peripheral immune cells across into injured mouse blood brain barrier can worsen postoperative cognitive dysfunction induced by isoflurane

BackgroundDisruption to the blood brain barrier (BBB) is a leading factor associated with the development of postoperative cognitive dysfunction (POCD). Despite this, the underlying mechanism by which BBB disruption promotes POCD in the elderly population has not yet been not fully elucidated.ResultsIn this study, we established a POCD mice model using isoflurane, and observed the highly expressed occludin and claudin 5 in brain tissues concomitant with the increased enrichment of CD4 positive cells and NK cells in the hippocampus of POCD mice compared to normal and non-POCD control.ConclusionsOur data suggests that peripheral immune cells may participate in the inflammatory reaction within the hippocampus, following the administration of anesthesia via inhalation with the destruction of the blood-brain barrier.

KX2-361: a novel orally bioavailable small molecule dual Src/tubulin inhibitor that provides long term survival in a murine model of glioblastoma.

A major challenge to developing new therapies for patients with malignant brain tumors is that relatively few small molecule anticancer drugs penetrate the blood-brain barrier (BBB) well enough to provide therapeutically effective concentrations in brain tissue before drug exposure in non-CNS tissues results in unacceptable toxicity. KX2-361, a member of a novel family of compounds with Src-kinase and tubulin polymerization inhibitory activity, demonstrates good oral bioavailability and readily crosses the BBB in mice. The objective of this study was to investigate the activity of KX2-361 against human and murine glioma cells and assess its therapeutic effect in a syngeneic orthotopic model of glioblastoma. In addition to reducing the level of Src autophosphorylation in the GL261 murine glioblastoma cell line, KX2-361 binds directly to tubulin and disrupts microtubule architecture in glioma cells maintained in culture. The drug is active in vivo against orthotopic GL261 gliomas in syngeneic C57BL/6 mice. Long term survival is not observed in mice lacking an adaptive immune system, indicating that KX2-361 works in concert with the host immune system to control tumor growth and promote long-term survival in the GL261 glioma model.

Leukaemia hijacks a neural mechanism to invade the central nervous system.

Acute lymphoblastic leukaemia (ALL) has a marked propensity to metastasize to the central nervous system (CNS). In contrast to brain metastases from solid tumours, metastases of ALL seldom involve the parenchyma but are isolated to the leptomeninges, which is an infrequent site for carcinomatous invasion. Although metastasis to the CNS occurs across all subtypes of ALL, a unifying mechanism for invasion has not yet been determined. Here we show that ALL cells in the circulation are unable to breach the blood-brain barrier in mice; instead, they migrate into the CNS along vessels that pass directly between vertebral or calvarial bone marrow and the subarachnoid space. The basement membrane of these bridging vessels is enriched in laminin, which is known to coordinate pathfinding of neuronal progenitor cells in the CNS. The laminin receptor α6 integrin is expressed in most cases of ALL. We found that α6 integrin-laminin interactions mediated the migration of ALL cells towards the cerebrospinal fluid in vitro. Mice with ALL xenografts were treated with either a PI3Kδ inhibitor, which decreased α6 integrin expression on ALL cells, or specific α6 integrin-neutralizing antibodies and showed significant reductions in ALL transit along bridging vessels, blast counts in the cerebrospinal fluid and CNS disease symptoms despite minimally decreased bone marrow disease burden. Our data suggest that α6 integrin expression, which is common in ALL, allows cells to use neural migratory pathways to invade the CNS.

Abstract 4843: NMS-P293, a PARP-1 selective inhibitor with no trapping activity and high CNS penetration, possesses potent in vivo efficacy and represents a novel therapeutic option for brain localized metastases and glioblastoma

Abstract NMS-P293 is a novel, potent and selective small molecule inhibitor of poly (ADP-ribose) polymerase (PARP-1 Kd = 2 nM). NMS-P293 inhibits the poly-ADP ribosylation (PAR) induced by DNA damage, leading to the inability of homologous repair deficient (HRD) tumor cells to repair damage and to apoptotic death, while sparing normal cells. NMS-P293 significantly differs from other PARP inhibitors in several respects. Firstly, while possessing potent in vitro and in vivo efficacy in HRD tumors (e.g. BRCA, PTEN loss), it does not induce “DNA trapping”, i.e. the formation of PARP-chromatin complexes. Secondly, NMS-293 is not a substrate of PgP mediated drug efflux, believed to be a mechanism of resistance to current PARP inhibitors. Finally, NMS-P293 extensively crosses the blood brain barrier in rats and mice, with a brain/plasma ratio of 4-10, significantly higher than that of major comparators and opening the potential for treating primary brain tumors and brain metastasis with PARP inhibitor therapy. Extensive preclinical profiling revealed that NMS-P293 possesses favourable drug-like characteristics, which include high in vitro cross-species metabolic stability, lack of cytochrome interaction, and excellent pharmacokinetic profile, with low clearance and nearly complete oral bioavailability in both rodents and non rodents. Preclinical efficacy and PK/PD studies were conducted to assess the mechanism of action of NMS-P293 in an HRD setting, the MDA-MD-436 (BRCA1 mutant) human breast cancer xenograft model. Inhibition of PAR was observed in tumors following single oral administration of 50 mg/kg NMS-P293, with a &amp;gt; 95% decrease of this biomarker persisting for &amp;gt; 24 h. Inverse correlation was observed between intratumoral PAR levels and NMS-P293 concentrations in plasma and in tumor. Significantly, levels of NMS-P293 in tumor were consistently higher (&amp;gt; 3.5-fold) than in plasma, with an intratumoral concentration of &amp;gt; 2 μM at 24 h, in line with the prolonged PAR inhibition. In agreement with these PD effects, NMS-P293, orally administered as single agent, induced potent dose-related growth inhibition of BRCA mutated tumor model, with cured animals. Furthermore, NMS-P293 also possesses potent synergistic efficacy and tolerability in combination with temozolomide (TMZ) in glioblastoma (GBM) tumor models, including TMZ resistant MGMT hypomethylated GBMs. The unique preclinical features of NMS-P293, which includes a highly permissive profile in GLP drug safety studies, render this compound an appealing candidate for clinical development, both as a single agent and in drug combination therapy regimes. Citation Format: Alessia Montagnoli, Gianluca Papeo, Sonia Rainoldi, Francesco Caprera, Marina Ciomei, Eduard Felder, Daniele Donati, Antonella Isacchi, Arturo Galvani. NMS-P293, a PARP-1 selective inhibitor with no trapping activity and high CNS penetration, possesses potent in vivo efficacy and represents a novel therapeutic option for brain localized metastases and glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4843.

Effect of hydrogen on blood brain barrier of mice with sepsis-associated encephalopathy

Objective To evaluate the effect of hydrogen on blood brain barrier of mice with sepsis-associated encephalopathy (SAE). Methods A total of 100 adult male ICR mice, aged 6-8 weeks, weighing 20-25 g, were divided into 4 groups(n=25 each) using a random number table method: sham operation group (group Sham), sham operation plus hydrogen group (group Sham+ H), group SAE and SAE plus hydrogen group (group SAE+ H). Sepsis was induced by cecal ligation and puncture (CLP). Sham+ H and SAE+ H groups inhaled 2% hydrogen for 1 h starting from 1 and 6 h after CLP, respectively.At 24 h after CLP, Evans blue (EB) was injected via the caudal vein, and then the mice were sacrificed and brain tissues were removed for measuring the EB and water contents, for examining the pathological changes of hippocampi (with a light microscope) and for detecting the expression of occludin and VE-cadherin (by Western blot). Morris water maze test was performed at days 10-16 after CLP. Results Compared with group Sham, the contents of EB and water in brain tissues were significantly increased, the expression of occludin and VE-cadherin was down-regulated, the escape latency was prolonged, and the number of crossing the original platform was reduced in SAE and SAE+ H groups (P<0.05). Compared with group SAE, the contents of EB and water in brain tissues were significantly decreased, the expression of occludin and VE-cadherin was up-regulated, the escape latency was shortened, the number of crossing the original platform was increased (P<0.05), and the pathological changes of hippocampi were significantly attenuated in group SAE+ H. Conclusion The mechanism by which hydrogen mitigates SAE may be related to reducing the damage to blood brain barrier of mice. Key words: Hydrogen; Sepsis; Brain; Blood-brain barrier

Longitudinal chemokine profile expression in a blood-brain barrier model from Alzheimer transgenic versus wild-type mice

BackgroundAlzheimer’s disease is widely described since the discovery of histopathological lesions in Mrs. Auguste Deter in 1906. However to date, there is no effective treatment to deal with the many cellular and molecular alterations. The complexity is even higher with the growing evidence of involvement of the peripheral blood mononuclear cells (PBMCs). Indeed, monocytes and T cells are shown in the cerebral parenchyma of AD patients, and these cells grafted to the periphery are able to go through the blood-brain barrier (BBB) in transgenic mouse models. It is known that BBB is disrupted at a late stage of AD. Chemokines represent major regulators of the transmigration of PBMCs, but many data were obtained on AD animal models. No data are available on the role of AD BBB in a healthy brain parenchyma. Therefore, the purpose of this study was to analyze the longitudinal chemokine profile expression in a BBB model from AD transgenic mice versus wild-type (WT) mice.MethodsA primary mouse BBB model was used with a luminal compartment either AD or WT and an abluminal compartment WT consisting of astrocytes and microglia. PBMCs were extracted by a ficoll gradient and incubated in the transwell with a direct contact with the luminal side, including the endothelial cells and pericytes. Then, the complete BBB model was incubated during 48 h, before supernatants and cell lysates were collected. Chemokines were quantified by X-MAP® luminex technology.ResultsAbluminal CX3CL1 production increased in 12-month-old AD BBB while CX3CL1 levels decreased in luminal lysates. CCL3 in luminal compartment increased with aging and was significantly different compared to AD BBB at 12 months. In addition, abluminal CCL2 in 12-month-old AD BBB greatly decreased compared to levels in WT BBB. On the contrary, no modification was observed for CCL4, CCL5, and CXCL10.ConclusionThese first findings highlighted the impact of AD luminal compartment on chemokine signature in a healthy brain parenchyma, suggesting new therapeutic or diagnostic approaches.

Enhanced efficacy of combined temozolomide and bromodomain inhibitor therapy for gliomas using targeted nanoparticles

Effective treatment for glioblastoma (GBM) is limited by the presence of the blood–brain barrier (BBB) and rapid resistance to single agent therapies. To address these issues, we developed a transferrin-functionalized nanoparticle (Tf-NP) that can deliver dual combination therapies. Using intravital imaging, we show the ability of Tf-NPs to traverse intact BBB in mice as well as achieve direct tumor binding in two intracranial orthotopic models of GBM. Treatment of tumor-bearing mice with Tf-NPs loaded with temozolomide and the bromodomain inhibitor JQ1 leads to increased DNA damage and apoptosis that correlates with a 1.5- to 2-fold decrease in tumor burden and corresponding increase in survival compared to equivalent free-drug dosing. Immunocompetent mice treated with Tf-NP-loaded drugs also show protection from the effects of systemic drug toxicity, demonstrating the preclinical potential of this nanoscale platform to deliver novel combination therapies to gliomas and other central nervous system tumors.

Neuroprotective effects of protein tyrosine phosphatase 1B inhibitor on cerebral ischemia/reperfusion in mice

Akt (Protein kinase B, PKB), a serine/threonine kinase, plays a critical role in cell development, growth, and survival. Akt phosphorylation mediates a neuroprotective effect against ischemic injury. Recently, a protein-tyrosine phosphatase-1B (PTP1B) inhibitor (KY-226) was developed to elicit anti-diabetic and anti-obesity effects via enhancement of insulin signaling. Previously, we reported that the nonselective PTP1B inhibitor, sodium orthovanadate, rescued neurons from delayed neuronal death during brain ischemia. In this study, we confirmed the ameliorative effects of KY-226 on ischemia/reperfusion (I/R) injury using a murine model of middle cerebral artery occlusion (MCAO). ICR mice were subjected to MCAO for 2 h followed by reperfusion. Although KY-226 permeability was poor through the blood-brain barrier (BBB) of normal mice, it could penetrate through the BBB of mice after I/R insult. Intraperitoneal KY-226 administration elicited dose-dependent reductions in infarcted brain areas and improved neurological deficits. The neuroprotective effects of KY-266 were obtained when administered within 0.5 h after reperfusion. KY-226 (10 mg/kg) also restored reduced Akt phosphorylation and eNOS phosphorylation (Ser-1177) levels following I/R insult. Moreover, 10 mg/kg of KY-226 improved I/R-induced decreased extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, KY-226 attenuated the generation of reactive oxygen species (ROS) in mouse cortex. These results suggest that KY-226 may act as a novel therapeutic candidate for ischemic stroke. Activation of Akt and ERK possibly underlie the neuroprotective mechanism of KY-226.

Dl-3-n-butylphthalide protects the blood brain barrier of cerebral infarction by activating the Nrf-2/HO-1 signaling pathway in mice.

The aim of this study was to explore whether Dl-3-n-butylphthalide (DBT) could protect blood-brain barrier (BBB) of mice with experimental cerebral infarction and the relevant mechanism. Adult male CD-1 mice were selected as the study objects. The permanent middle cerebral artery occlusion (MCAO) model was prepared by Longa's modified suture-occluded method. The mice were randomly divided into 3 groups: the sham operation group (Sham group), the cerebral infarction model group (CI group) and the DBT (120 mg/kg) intervention group (DBT group). Neurologic function deficits were evaluated by Longa's modified scoring method after 24 h of permanent MCAO. The wet and dry weight method was used for measuring water content in brain tissues. 2% 2,3,5-triphenyltetrazolium chloride (TTC) staining method was applied to determine the volume of cerebral infarction. Changes in the protein and messenger ribonucleic acid (mRNA) expression levels of matrix metallopeptidase 9 (MMP-9), claudin-5, vascular endothelial growth factor (VEGF), glial fibrillary acidic protein (GFAP), NF-E2 related factor 2 (Nrf-2) and heme oxygenase 1 (HO-1) in ischemic brain tissues were detected using immunohistochemistry, Western blotting and quantitative Reverse Transcription-Polymerase Chain Reaction (qRT-PCR). Ultrastructure changes in BBBs were observed under an electron microscope. DBT improved the neurologic function deficits of mice and reduced the infarction volume of mice with cerebral infarction. DBT alleviated edema and decreased the permeability of BBBs of mice with cerebral infarction. DBT down-regulated the expression of MMP-9 and up-regulated the expression of claudin-5 in brain tissues of mice with cerebral infarction. DBT increased the expressions of VEGF and GFAP. DBT improved the ultrastructure in capillary endothelial cells of BBBs and increased the expressions of Nrf-2 and HO-1. DBT may protect BBB by activating the Nrf-2/HO-1 signaling pathway, thus achieving its protective effect on the brain.

Study on the mechanism of the regulation of Wnt/β-catenin pathway by hydroxysafflor yellow A in the protection of blood brain barrier in cerebral ischemia mice

Objective To observe the effect of hydroxysafflor yellow A (HSYA) on the protection of blood brain barrier of cerebral ischemia mice, and explore the mechaniam. Methods Seventy-two C57/BL mice were divided into 6 groups: the sham operation group, the cerebral ischemia mice group, the TLR4 blocking group, the TLR4 blocking+ cerebral ischemia mice group, the HSYA intervention+ cerebral ischemia mice group, HSYA intervention+ TLR4 blocking+ cerebral ischemia mice group. Cerebral ischemia mice group were subjected to the middle cerebral artery occlusion (MCAO) model, TLR4 blocking was used, while TLR4 blocking was injected TLR4 antibody via right common carotid artery, and HSYA intervention group was injected 2 mg/kg HSYA by tail vein 0.5 h before cerebral ischemia. RT-PCR and western blot were applied to detect the mRNA and protein expression change of Wnt3a and β-catenin in each group. Results Compared with the cerebral ischemia mice group, the expression of TLR4 mRNA (1.63 ± 0.05, 1.53 ± 0.04, 1.84 ± 0.03 vs. 1.97 ± 0.05) significantly decreased (P<0.05 or P<0.01), the Wnt3a mRNA (0.56 ± 0.01, 0.58 ± 0.01, 0.50 ± 0.04 vs. 0.42 ± 0.03), β-catenin mRNA (0.61 ± 0.03, 0.74 ± 0.02, 0.58 ± 0.04 vs. 0.50 ± 0.03), Claudin-5 mRNA (0.54 ± 0.02, 0.58 ± 0.01, 0.47 ± 0.01 vs. 0.46 ± 0.02) mRNA significantly increased(P<0.05 or P<0.01), the protein expression of TLR4 (1.73 ± 0.05, 1.57 ± 0.03, 1.79 ± 0.08 vs. 1.89 ± 0.02) significantly decreased (P<0.05 or P<0.01), the protein expression of Wnt3a (0.67 ± 0.03, 0.74 ± 0.03, 0.57 ± 0.01 vs. 0.46 ± 0.01), Occludin (0.66 ± 0.02, 0.73 ± 0.02, 0.67 ± 0.01 vs. 0.53 ± 0.01), Claudin-5 (0.71 ± 0.01, 0.73 ± 0.01, 0.66 ± 0.01 vs. 0.64 ± 0.03) significantly increased (P<0.05 or P<0.01) in the TLR4 blocking+ cerebral ischemia mice group, the HSYA intervention+ cerebral ischemia mice group, HSYA intervention+ TLR4 blocking+ cerebral ischemia mice group. Conclusions TLR4 plays a critical regulatory role on the activation of Wnt3a and β-catenin in cerebral ischemic mice model. HSYA could intervene on the tight junction of cerebral ischemic brain through the intervention of Wnt3a and β-catenin, thus exerting the protection for cerebral ischemic brain. Key words: Hydroxysafflower yellow A; Brain ischemia; Blood-brain barrier; Wnt proteins; Mice

High brain distribution of a new central nervous system drug candidate despite its P-glycoprotein-mediated efflux at the mouse blood-brain barrier

Efficacy of drugs aimed at treating central nervous system (CNS) disorders rely partly on their ability to cross the cerebral endothelium, also called the blood-brain barrier (BBB), which constitutes the main interface modulating exchanges of compounds between the brain and blood. In this work, we used both, conventional pharmacokinetics (PK) approach and in situ brain perfusion technique to study the blood and brain PK of PKRinh, an inhibitor of the double-stranded RNA-dependent protein kinase (PKR) activation, in mice. PKRinh showed a supra dose-proportional blood exposure that was not observed in the brain, and a brain to blood AUC ratio of unbound drug smaller than 1 at all tested doses. These data suggested the implication of an active efflux at the BBB. Using in situ brain perfusion technique, we showed that PKRinh has a very high brain uptake clearance which saturates with increasing concentrations. Fitting the data to a Michaelis-Menten equation revealed that PKRinh transport through the BBB is composed of a passive unsaturable flux and an active saturable protein-mediated efflux with a km of ≅ 3 μM. We were able to show that the ATP-binding cassette (ABC) transporter P-gp (Abcb1), but not Bcrp (Abcg2), was involved in the brain to blood efflux of PKRinh. At the circulating PKRinh concentrations of this study, the P-gp was not saturated, in accordance with the linear brain PKRinh PK. Finally, PKRinh had high brain uptake clearance (14 μl/g/s) despite it is a good P-gp substrate (P-gp Efflux ratio ≅ 3.6), and reached similar values than the cerebral blood flow reference, diazepam, in P-gp saturation conditions. With its very unique brain transport properties, PKRinh improves our knowledge about P-gp-mediated efflux across the BBB for the development of new CNS directed drugs.