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Blood-brain Barrier (blood-brain + barrier)
Selected AbstractsThe Complementary Membranes Forming the Blood-Brain BarrierIUBMB LIFE, Issue 3 2002Richard A. Hawkins Abstract Brain capillary endothelial cells form the blood-brain barrier. They are connected by extensive tight junctions, and are polarized into luminal (blood-facing) and abluminal (brain-facing) plasma membrane domains. The polar distribution of transport proteins allows for active regulation of brain extracellular fluid. Experiments on isolated membrane vesicles from capillary endothelial cells of bovine brain demonstrated the polar arrangement of amino acid and glucose transporters, and the utility of such arrangements have been proposed. For instance, passive carriers for glutamine and glutamate have been found only in the luminal membrane of blood-brain barrier cells, while Na-dependent secondary active transporters are at the abluminal membrane. This organization could promote the net removal of nitrogen-rich amino acids from brain, and account for the low level of glutamate penetration into the central nervous system. Furthermore, the presence of a ,-glutamyl cycle at the luminal membrane and Na-dependent amino acid transporters at the abluminal membrane may serve to modulate movement of amino acids from blood-to-brain. Passive carriers facilitate amino acid transport into brain. However, activation of the ,-glutamyl cycle by increased plasma amino acids is expected to generate oxoproline within the blood-brain barrier. Oxoproline stimulates secondary active amino acid transporters (Systems A and B o,+ ) at the abluminal membrane, thereby reducing net influx of amino acids to brain. Finally, passive glucose transporters are present in both the luminal and abluminal membranes of the blood-brain barrier. Interestingly, a high affinity Na-dependent glucose carrier has been described only in the abluminal membrane. This raises the question whether glucose entry may be regulated to some extent. Immunoblotting studies suggest more than one type of passive glucose transporter exist in the blood-brain barrier, each with an asymmetrical distribution. In conclusion, it is now clear that the blood-brain barrier participates in the active regulation of brain extracellular fluid, and that the diverse functions of each plasma membrane domain contributes to these regulatory functions. [source] Abnormal Endothelial Tight Junctions in Active Lesions and Normal-appearing White Matter in Multiple SclerosisBRAIN PATHOLOGY, Issue 2 2002Jonnie Plumb Blood-brain barrier (BBB) breakdown, demonstrable in vivo by enhanced MRI is characteristic of new and expanding inflammatory lesions in relapsing-remitting and chronic progressive multiple sclerosis (MS). Subtle leakage may also occur in primary progressive MS. However, the anatomical route(s) of BBB leakage have not been demonstrated. We investigated the possible involvement of interendothelial tight junctions (TJ) by examining the expression of TJ proteins (occludin and ZO-1) in blood vessels in active MS lesions from 8 cases of MS and in normal-appearing white (NAWM) matter from 6 cases. Blood vessels (10,50 per frozen section) were scanned using confocal laser scanning microscopy to acquire datasets for analysis. TJ abnormalities manifested as beading, interruption, absence or diffuse cytoplasmic localization of fluorescence, or separation of junctions (putative opening) were frequent (affecting 40% of vessels) in oil-red-O-positive active plaques but less frequent in NAWM (15%), and in normal (<2%) and neurological controls (6%). Putatively "open" junctions were seen in vessels in active lesions and in microscopically inflamed vessels in NAWM. Dual fluorescence revealed abnormal TJs in vessels with pre-mortem serum protein leakage. Abnormal or open TJs, associated with inflammation may contribute to BBB leakage in enhancing MRI lesions and may also be involved in subtle leakage in non-enhancing focal and diffuse lesions in NAWM. BBB disruption due to tight junctional pathology should be regarded as a significant form of tissue injury in MS, alongside demyelination and axonopathy. [source] Childhood encephalopathy: viruses, immune response, and outcomeDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 4 2006Michael Clarke BSc MB ChB FRCPCH This study examined children with an acute encephalopathy illness for evidence of viral infection, disordered blood-brain barrier function, intrathecal immunoglobulin synthesis, and interferon (IFN) production, and related their temporal occurrence to outcome. A prospective study of 22 children (13 males, 9 females; age range 1mo to 13y, median 2y 4mo), recorded clinical details, with serum and cerebrospinal fluid (CSF) analysis near presentation and then on convalescent specimens taken up to day 39 of the neurological illness. Outcome was assessed with standard scales between 18 months and 3 years after presentation. A history consistent with viral infection was given in 17 children but laboratory evidence of viral infection was found in only 7 (7/17). In 18 out of 21 children, an elevated CSF: serum albumin ratio indicative of impairment of the blood,CSF and blood,brain barriers was detected at some stage of the illness. In 14 of the 15 children with a raised immunoglobulin G index, and in 12 of the 14 children where the CSF was positive for oligoclonal bands, this was preceded by, or was observed at the same time as, an abnormal albumin ratio. Sixteen children (16/18) had elevated IFN-, levels in serum, or CSF, or in both. We conclude that these findings indicate an initial disruption of the blood-brain barrier followed by intrathecal antibody production by activated lymphocytes, clonally restricted to a few antigens. This is the first in vivo study to show this as an important pathogenetic mechanism of encephalitis in children. Poor outcome was associated with young age, a deteriorating electroencephalogram pattern from grade 1 to grade 2, and the degree of blood-brain barrier impairment, particularly when prolonged, but not with Glasgow Coma Scale score. The persistence of IFN-, was associated with a good prognosis. [source] The brain angiotensin IV/AT4 receptor system as a new target for the treatment of Alzheimer's diseaseDRUG DEVELOPMENT RESEARCH, Issue 7 2009John W. Wright Abstract The brain renin-angiotensin system (RAS) regulates several physiologies including blood pressure, body sodium and water balance, cyclicity of reproductive hormones and related sexual behaviors, and the release of pituitary gland hormones. These physiologies are under the control of the angiotensin II (AngII)/AT1 receptor subtype system. The AngII/AT2 receptor subtype system is expressed during fetal development and is less abundant in the adult. This system appears to oppose growth responses facilitated by activation of the AT1 receptor. There is a growing list of nontraditional physiologies mediated by the most recently discovered angiotensin IV (AngIV)/AT4 receptor subtype system that include the regulation of blood flow, modulation of exploratory behaviors, involvement in stress responses and seizure, and a role in learning and memory acquisition. There is evidence to support an inhibitory influence by AngII, and a facilitory role by AngIV, on neuronal firing rate, long-term potentiation, and associative and spatial learning and memory. These findings suggest an important role for the RAS, and the AT4 receptor in particular, in normal cognitive processing and provide the stimulus for developing drugs that penetrate the blood-brain barrier to interact with this brain receptor in the treatment of dysfunctional memory. Drug Dev Res 70: 472,480, 2009. © 2009 Wiley-Liss, Inc. [source] Dietary accumulation, disposition, and metabolism of technical pentabrominated diphenyl ether (DE-71) in pregnant mink (Mustela vison) and their offspring,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2008Si Zhang Abstract Concentrations of polybrominated diphenyl ethers (PBDEs) in humans and wildlife suggest significant bioaccumulation potential in mammals, but no quantitative biomagnification data from controlled experiments are currently available. As part of a larger study examining the effects of PBDEs on mink (Mustela vison) reproduction and development, we examined congener-specific tissue distribution, maternal transfer, biotransformation, and biomagnification of the technical penta-BDE mixture, DE-71, in farmed mink. Adult female mink were fed one of four concentrations of DE-71 (0-2.5 ,g/g) in the diet from breeding through gestation and until weaning at 6 weeks postparturition. Parent PBDEs were measured in tissues and excreta of adult mink, kits, and juveniles, whereas hydroxylated PBDEs (OH-PBDEs) were measured in juveniles only. Similar lipid-normalized concentrations of PBDEs were detected in most tissues of adult mink with the exception of brain, in which concentrations were significantly lower. Kits, however, had a higher proportion of PBDEs in brain compared with adults, presumably because of incomplete development of the blood-brain barrier. Maternal transfer favored lower-brominated PBDE congeners, and the bulk of the body burden in kits at weaning resulted from lactational rather than transplacental transfer. Lipid-normalized, whole-body biomagnification factors ranged from 0.5 to 5.2 for the major congeners and were highest for BDEs 47 and 153. Metabolism clearly limited the biomagnification of some PBDEs, and OH-PBDEs were detectable in plasma, liver, and feces. On a mass basis, OH-PBDEs accounted for 28 to 32% of the excreted fraction, indicating metabolism was an important elimination pathway. Further studies are required to understand the mechanisms of PBDE biotransformation. [source] Simvastatin regulates oligodendroglial process dynamics and survivalGLIA, Issue 2 2007Veronique E. Miron Abstract Simvastatin, a lipophilic statin that crosses the blood-brain barrier, is being evaluated as a potential therapy for multiple sclerosis (MS) due to its anti-inflammatory properties. We assessed the effects of simvastatin on cultures of rat newborn and human fetal oligodendrocyte progenitor cells (OPCs) and human adult mature oligodendrocytes (OLGs) with respect to cellular events pertaining to myelin maintenance and repair. Short-term simvastatin treatment of OPCs (1 day) induced robust process extension, enhanced differentiation to a mature phenotype, and decreased spontaneous migration. These effects were reversed by isoprenoid products and mimicked with an inhibitor of Rho kinase (ROCK), the downstream effector of the isoprenylated protein RhoA GTPase. Prolonged treatment (2 days) caused process retraction that was rescued by cholesterol, and increased cell death (4 days) partially rescued by either cholesterol or isoprenoid co-treatment. In comparison, simvastatin treatment of human mature OLGs required a longer initial time course (2 days) to induce significant process outgrowth, mimicked by inhibiting ROCK. Prolonged treatment of mature OLGs was associated with process retraction (6 days) and increased cell death (8 days). Human-derived OPCs and mature OLGs demonstrated an increased sensitivity to simvastatin relative to the rodent cells, responding to nanomolar versus micromolar concentrations. Our findings indicate the importance of considering the short- and long-term effects of systemic immunomodulatory therapies on neural cells affected by the MS disease process. © 2006 Wiley-Liss, Inc. [source] Involvement of neuropsin in the pathogenesis of experimental autoimmune encephalomyelitisGLIA, Issue 2 2005Ryuji Terayama Abstract Inflammation, demyelination, and axonal damage of the central nervous system (CNS) are major pathological features of multiple sclerosis (MS). Proteolytic digestion of the blood-brain barrier and myelin protein by serine proteases is known to contribute to the development and progression of MS. Neuropsin, a serine protease, has a role in neuronal plasticity, and its expression has been shown to be upregulated in response to injury to the CNS. To determine the possible involvement of neuropsin in demyelinating diseases of the CNS, we examined its expression in myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE), a recognized animal model for MS. Neuropsin mRNA expression was induced in the spinal cord white matter of mice with EAE. Combined in situ hybridization and immunohistochemistry demonstrated that most of the cells expressing neuropsin mRNA showed immunoreactivity for CNPase, a cell-specific marker for oligodendrocytes. Mice lacking neuropsin (neuropsin,/,) exhibited an altered EAE progression characterized by delayed onset and progression of clinical symptoms as compared to wild-type mice. Neuropsin,/, mice also showed attenuated demyelination and delayed oligodendroglial death early during the course of EAE. These observations suggest that neuropsin is involved in the pathogenesis of EAE mediated by demyelination and oligodendroglial death. © 2005 Wiley-Liss, Inc. [source] Induction of blood-brain barrier properties in cultured brain capillary endothelial cells: Comparison between primary glial cells and C6 cell lineGLIA, Issue 3 2005Monica Boveri Abstract The communication between glial cells and brain capillary endothelial cells is crucial for a well-differentiated blood-brain barrier (BBB). It has been suggested that in vitro primary glial cells (GCs) be replaced by the glial C6 cell line to standardise the model further. This study compares directly the structural and functional differentiation of bovine brain capillary endothelial cells (BBCECs) induced by co-culture with rat primary GCs or C6 cells, for the first time. Trans-endothelial electrical resistance (TEER) measurements showed that under no condition were C6 cells able to reproduce TEER values as high as in the presence of GCs. At the same time, permeability of the BBCECs to both radioactive sucrose and FITC-inulin was 2.5-fold higher when cells were co-cultured with C6 than with GCs. Furthermore, immunocytochemistry studies showed different cell morphology and less developed tight junction pattern of BBCECs co-cultured with C6 toward GCs. Additionally, studies on P-glycoprotein (P-gp) showed much lower P-gp presence and activity in BBCECs co-cultured with C6 than GCs. Both VEGF mRNA expression and protein content were dramatically increased when compared with GCs, suggesting that VEGF could be one of the factors responsible for higher permeability of BBB. Our results clearly indicate that, in the presence of the glial C6 cell line, BBCECs did not differentiate as well as in the co-culture with primary GCs at both structural and functional levels. © 2005 Wiley-Liss, Inc. [source] Severe alterations of endothelial and glial cells in the blood-brain barrier of dystrophic mdx miceGLIA, Issue 3 2003Beatrice Nico Abstract In this study, we investigated the involvement of the blood-brain barrier (BBB) in the brain of the dystrophin-deficient mdx mouse, an experimental model of Duchenne muscular dystrophy (DMD). To this purpose, we used two tight junction markers, the Zonula occludens (ZO-1) and claudin-1 proteins, and a glial marker, the aquaporin-4 (AQP4) protein, whose expression is correlated with BBB differentiation and integrity. Results showed that most of the brain microvessels in mdx mice were lined by altered endothelial cells that showed open tight junctions and were surrounded by swollen glial processes. Moreover, 18% of the perivascular glial endfeet contained electron-dense cellular debris and were enveloped by degenerating microvessels. Western blot showed a 60% reduction in the ZO-1 protein content in mdx mice and a similar reduction in AQP4 content compared with the control brain. ZO-1 immunocytochemistry and claudin-1 immunofluorescence in mdx mice revealed a diffuse staining of microvessels as compared with the control ones, which displayed a banded staining pattern. ZO-1 immunogold electron microscopy showed unlabeled tight junctions and the presence of gold particles scattered in the endothelial cytoplasm in the mdx mice, whereas ZO-1 gold particles were exclusively located at the endothelial tight junctions in the controls. Dual immunofluorescence staining of ,-actin and ZO-1 revealed colocalization of these proteins. As in ZO-1 staining, the pattern of immunolabeling with anti,,-actin antibody was diffuse in the mdx vessels and pointed or banded in the controls. ,-actin immunogold electron microscopy showed gold particles in the cytoplasms of endothelial cells and pericytes in the mdx mice, whereas ,-actin gold particles were revealed on the endothelial tight junctions and the cytoskeletal microfilaments of pericytes in the controls. Perivascular glial processes of the mdx mice appeared faintly stained by anti-AQP4 antibody, while in the controls a strong AQP4 labeling of glial processes was detected at light and electron microscope level. The vascular permeability of the mdx brain microvessels was investigated by means of the horseradish peroxidase (HRP). After HRP injection, extensive perivascular areas of marker escape were observed in mdx mice, whereas HRP was exclusively intravascularly localized in the controls. Inflammatory cells, CD4-, CD8-, CD20-, and CD68-positive cells, were not revealed in the perivascular stroma of the mdx brain. These findings indicate that dystrophin deficiency in the mdx brain leads to severe injury of the endothelial and glial cells with disturbance in ,-actin cytoskeleton, ZO-1, claudin-1, and AQP4 assembly, as well as BBB breakdown. The BBB alterations suggest that changes in vascular permeability are involved in the pathogenesis of the neurological dysfunction associated with DMD. GLIA 42:235,251, 2003. © 2003 Wiley-Liss, Inc. [source] Central nervous system is a sanctuary site for chronic myelogenous leukaemia treated with imatinib mesylateINTERNAL MEDICINE JOURNAL, Issue 6 2009Y. Isobe Abstract Imatinib mesylate (IM) is currently used as the first therapeutic choice against chronic myelogenous leukaemia (CML). Because IM poorly penetrates the blood-brain barrier, IM-treated CML patients may have a potential risk of central nervous system (CNS) involvement. Here we report a case with lymphoid blast crisis isolated only in CNS after bacterial meningitis, although the patient achieved and maintained complete cytogenetic response by IM therapy. It is important to consider isolated CNS blast crisis as a possible event in IM-treated CML patients. [source] The Complementary Membranes Forming the Blood-Brain BarrierIUBMB LIFE, Issue 3 2002Richard A. Hawkins Abstract Brain capillary endothelial cells form the blood-brain barrier. They are connected by extensive tight junctions, and are polarized into luminal (blood-facing) and abluminal (brain-facing) plasma membrane domains. The polar distribution of transport proteins allows for active regulation of brain extracellular fluid. Experiments on isolated membrane vesicles from capillary endothelial cells of bovine brain demonstrated the polar arrangement of amino acid and glucose transporters, and the utility of such arrangements have been proposed. For instance, passive carriers for glutamine and glutamate have been found only in the luminal membrane of blood-brain barrier cells, while Na-dependent secondary active transporters are at the abluminal membrane. This organization could promote the net removal of nitrogen-rich amino acids from brain, and account for the low level of glutamate penetration into the central nervous system. Furthermore, the presence of a ,-glutamyl cycle at the luminal membrane and Na-dependent amino acid transporters at the abluminal membrane may serve to modulate movement of amino acids from blood-to-brain. Passive carriers facilitate amino acid transport into brain. However, activation of the ,-glutamyl cycle by increased plasma amino acids is expected to generate oxoproline within the blood-brain barrier. Oxoproline stimulates secondary active amino acid transporters (Systems A and B o,+ ) at the abluminal membrane, thereby reducing net influx of amino acids to brain. Finally, passive glucose transporters are present in both the luminal and abluminal membranes of the blood-brain barrier. Interestingly, a high affinity Na-dependent glucose carrier has been described only in the abluminal membrane. This raises the question whether glucose entry may be regulated to some extent. Immunoblotting studies suggest more than one type of passive glucose transporter exist in the blood-brain barrier, each with an asymmetrical distribution. In conclusion, it is now clear that the blood-brain barrier participates in the active regulation of brain extracellular fluid, and that the diverse functions of each plasma membrane domain contributes to these regulatory functions. [source] Cytokines and Cognition,The Case for A Head-to-Toe Inflammatory ParadigmJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 12 2002Craig J. Wilson MBBS The brain is not only immunologically active of its own accord, but also has complex peripheral immune interactions. Given the central role of cytokines in neuroimmmunoendocrine processes, it is hypothesized that these molecules influence cognition via diverse mechanisms. Peripheral cytokines penetrate the blood-brain barrier directly via active transport mechanisms or indirectly via vagal nerve stimulation. Peripheral administration of certain cytokines as biological response modifiers produces adverse cognitive effects in animals and humans. There is abundant evidence that inflammatory mechanisms within the central nervous system (CNS) contribute to cognitive impairment via cytokine-mediated interactions between neurons and glial cells. Cytokines mediate cellular mechanisms subserving cognition (e.g., cholinergic and dopaminergic pathways) and can modulate neuronal and glial cell function to facilitate neuronal regeneration or neurodegeneration. As such, there is a growing appreciation of the role of cytokine-mediated inflammatory processes in neurodegenerative diseases such as Alzheimer's disease and vascular dementia. Consistent with their involvement as mediators of bidirectional communication between the CNS and the peripheral immune system, cytokines play a key role in the hypothalamic-pituitary-adrenal axis activation seen in stress and depression. In addition, complex cognitive systems such as those that underlie religious beliefs, can modulate the effects of stress on the immune system. Indirect means by which peripheral or central cytokine dysregulation could affect cognition include impaired sleep regulation, micronutrient deficiency induced by appetite suppression, and an array of endocrine interactions. Given the multiple levels at which cytokines are capable of influencing cognition it is plausible that peripheral cytokine dysregulation with advancing age interacts with cognitive aging. [source] The subpopulation of CF-1 mice deficient in P-glycoprotein contains a murine retroviral insertion in the mdr1a geneJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2001Todd R. Pippert Abstract A subpopulation of the CF-1 mouse strain is sensitive to neurotoxicity following exposure to avermectins, a family of structurally related antiparasitic agents. This unusual sensitivity is the result of a deficiency in the mdr1a P-glycoprotein that normally contributes to a functional blood-brain barrier. Previous studies demonstrated a correlation between P-glycoprotein levels in the brain, intestine, testis, and placenta with an restriction fragment length polymorphism (RFLP) pattern from DNA isolated from the animals. We have demonstrated that only P-glycoprotein derived from the mdr1a gene is deficient in these mice. In this article, we describe the genetic defect in the subpopulation of CF-1 mice resulting in an absence of P-glycoprotein. The data presented describes a reverse transcription,polymerase chain reaction (RT-PCR) protocol that specifically amplifies mdr1a mRNA from tissue and confirms that the P-glycoprotein defect results from a truncated mRNA with a deleted exon 23. Genomic amplification and sequencing of the intron between exon 22 and 23 in Pgp-deficient animals reveals an insertion of approximately 8.35 kb of DNA at the exon 23 intron,exon junction corresponding to a murine leukemia virus. This insertion results in the aberrant splicing of the mRNA and the loss of exon 23 during RNA processing. © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:83,89, 2001 [source] Site-specific opening of the blood-brain barrierJOURNAL OF BIOPHOTONICS, Issue 5-6 2010Steen J. Madsen Abstract The blood-brain barrier (BBB) poses a significant impediment for the delivery of therapeutic drugs into the brain. This is particularly problematic for the treatment of malignant gliomas which are characterized by diffuse infiltration of tumor cells into normal brain where they are protected by a patent BBB. Selective disruption of the BBB, followed by administration of anti-cancer agents, represents a promising approach for the elimination of infiltrating glioma cells. A summary of the techniques (focused ultrasound, photodynamic therapy and photochemical internalization) for site-specific opening of the BBB will be discussed in this review. Each approach is capable of causing localized and transient opening of the BBB with minimal damage to surrounding normal brain as evidenced from magnetic resonance images and histology. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Sodium valproate inhibits glucose transport and exacerbates Glut1-deficiency in vitroJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 4 2005Hei Yi Wong Abstract Anticonvulsant sodium valproate interferes with brain glucose metabolism. The mechanism underlying such metabolic disturbance is unclear. We tested the hypothesis that sodium valproate interferes with cellular glucose transport with a focus on Glut1 since glucose transport across the blood-brain barrier relies on this transporter. Cell types enriched with Glut1 expression including human erythrocytes, human skin fibroblasts, and rat astrocytes were used to study the effects of sodium valproate on glucose transport. Sodium valproate significantly inhibited Glut1 activity in normal and Glut1-deficient erythrocytes by 20%,30%, causing a corresponding reduction of Vmax of glucose transport. Similarly, in primary astrocytes as well as in normal and Glut1-deficient fibroblasts, sodium valproate inhibited glucose transport by 20%,40% (P,<,0.05), accompanied by an up to 60% downregulation of GLUT1 mRNA expression (P,<,0.05). In conclusion, sodium valproate inhibits glucose transport and exacerbates Glut1 deficiency in vitro. Our findings imply the importance of prudent use of sodium valproate for patients with compromised Glut1 function. J. Cell. Biochem. © 2005 Wiley-Liss, Inc. [source] Synthesis and biological evaluation of carbon-11-labeled acyclic and furo[2,3-d]pyrimidine derivatives of bicyclic nucleoside analogues (BCNAs) for structure,brain uptake relationship study of BCNA tracersJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 3 2008Satish K. Chitneni Abstract We reported earlier on radiolabeled alkoxyphenyl bicyclic nucleoside analogues (BCNAs) as potential positron emission tomography (PET) reporter probes for imaging of varicella zoster virus thymidine kinase (VZV-tk) gene in vivo. Despite their favorable physicochemical properties, these tracers are not taken up in the brain in mice. In order to probe the role of the deoxyribose sugar moiety in blood-brain barrier (BBB) penetration of these molecules, we have synthesized and evaluated a carbon-11-labeled acyclic bicyclic nucleoside derivative ([11C]-10) where the 2,-deoxyribose sugar is replaced with a (2-hydroxyethoxy)methyl group and [11C]-12, which has no sugar moiety but a [11C]methyl group on the N-3 position of the pyrimidine ring. Methylation was achieved on the phenol ([11C]-10) or the N-3 position ([11C]-12) using [11C]methyl triflate (radiosynthesis). The (non-radioactive) acyclic O -methyl derivative 10 has rather poor affinity for the enzyme VZV-TK in vitro (IC50: 430,µM), compared with the moderate affinity of the BCNA-base N -methyl derivative 12 (IC50: 79,µM). In normal mice, none of the two tracers ([11C]-10 or [11C]-12) showed significant uptake in the brain, suggesting that compounds containing a furo[2,3- d]pyrimidine system do not cross the BBB. Copyright © 2008 John Wiley & Sons, Ltd. [source] In vivo measurements of T1 relaxation times in mouse brain associated with different modes of systemic administration of manganese chlorideJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2005Yu-Ting Kuo MD Abstract Purpose To measure regional T1 and T2 values for normal C57Bl/6 mouse brain and changes in T1 after systemic administration of manganese chloride (MnCl2) at 9.4 T. Materials and Methods C57Bl/6 mice were anesthetized and baseline T1 and T2 measurements obtained prior to measurement of T1 after administration of MnCl2 at 9.4 T. MnCl2 was administered systemically either by the intravenous (IV), intraperitoneal (IP), or subcutaneous (SC) routes. T1 and T2 maps for each MRI transverse slice were generated using commercial software, and T1 and T2 values of white matter (WM), gray matter (GM), pituitary gland, and lateral ventricle were obtained. Results When compared with baseline values at low-field, significant lengthening of the T1 values was shown at 9.4 T, while no significant change was seen for T2 values. Significant T1 shortening of the normal mouse brain was observed following IV, IP, and SC administration of MnCl2, with IV and IP showing similar acute effects. Significant decreases in T1 values were seen for the pituitary gland and the ventricles 15 minutes after either IV or IP injection. GM showed greater uptake of the contrast agent than WM at 15 and 45 minutes after either IV or IP injections. Although both structures are within the blood-brain barrier (BBB), GM and WM revealed a steady decrease in T1 values at 24 and 72 hours after MnCl2 injection regardless of the route of administration. Conclusion Systemic administration of MnCl2 by IV and IP routes induced similar time-course of T1 changes in different regions of the mouse brain. Acute effects of MnCl2 administration were mainly influenced by either the presence or absence of BBB. SC injection also provided significant T1 change at subacute stage after MnCl2 administration. J. Magn. Reson. Imaging 2005;21:334,339. © 2005 Wiley-Liss, Inc. [source] Predictability of FTY720 efficacy in experimental autoimmune encephalomyelitis by in vivo macrophage tracking: Clinical implications for ultrasmall superparamagnetic iron oxide-enhanced magnetic resonance imagingJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 1 2004Martin Rausch PhD Abstract Purpose To examine the efficacy of FTY720 as a new agent to reduce inflammatory activity in an animal model of multiple sclerosis (MS) by in vivo macrophage tracking. Material and Methods FTY720 was used for treatment of rats in a model of chronic relapsing experimental autoimmune encephalomyelitis (EAE) at an oral dose of 0.3 mg/kg/day. Magnetic resonance imaging (MRI) based on in vivo tracking of macrophages labeled with ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles, immunohistological staining (IHC), and neurological readouts was used to study the burden of disease in treated and untreated animals. Results While untreated animals showed severe paralysis of the hind paws, intense accumulation of macrophages in brain tissue, and areas of blood-brain barrier (BBB) disruption, FTY720-treated animals displayed no signs of inflammatory activity or neurological impairment. These observations were made for both acute phase and first relapse. Conclusion Tracking of macrophages by MRI provides direct evidence of the immunomodulatory efficacy of FTY720 in the EAE model and correlates well with neurological symptoms and histology. J. Magn. Reson. Imaging 2004;20:16,24. © 2004 Wiley-Liss, Inc. [source] A new gadolinium-based contrast agent for magnetic resonance imaging of brain tumors: Kinetic study on a C6 rat glioma modelJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2001Emmanuel Fonchy Abstract T1 -weighted magnetic resonance imaging (MRI) was used to evaluate the potential interest of a new Gd-based contrast agent, termed P760, to characterize brain tumor heterogeneity and vascularization and to delineate regions containing permeable vessels. The C6 rat glioma model was used as a model of high-grade glioblastoma. The signal enhancement was measured as a function of time in the vascular compartment and in different regions of interest (ROIs) within the tumor after the injection of 0.02 mmol kg,1 of P760. The results were compared to those obtained after the injection of 0.1 mmol kg,1 of Gd-DOTA. We showed that P760, in spite of a Gd concentration five times smaller, produces an enhancement in the blood pool similar to that produced by Gd-DOTA. It was shown that P760 makes possible an excellent delineation of regions containing vessels with a damaged blood-brain barrier (BBB). Images acquired 5,10 minutes after P760 injection showed the location of permeable vessels more accurately than Gd-DOTA-enhanced images. The enhancement produced in the tumor by P760 was, however, less than that produced by Gd-DOTA. The extravasation and/or diffusion rate of P760 in the interstitial medium were found to be strongly reduced, compared to those found with Gd-DOTA. This study suggests that the new contrast agent has promising capabilities in clinical imaging of brain tumors. J. Magn. Reson. Imaging 2001;14:97,105. © 2001 Wiley-Liss, Inc. [source] Synthesis and transport of creatine in the CNS: importance for cerebral functionsJOURNAL OF NEUROCHEMISTRY, Issue 2 2010Elidie Béard J. Neurochem. (2010) 115, 297,313. Abstract Apart of its well known function of ,energetic buffer' through the creatine/phosphocreatine/creatine kinase system allowing the regeneration of ATP, creatine has been recently suggested as a potential neuromodulator of even true neurotransmitter. Moreover, the recent discovery of primary creatine deficiency syndromes, due to deficiencies in l -arginine : glycine amidinotransferase or guanidinoacetate methyltransferase (the two enzymes allowing creatine synthesis) or in the creatine transporter, has shed new light on creatine synthesis, metabolism and transport, in particular in CNS which appears as the main tissue affected by these creatine deficiencies. Recent data suggest that creatine can cross blood-brain barrier but only with a poor efficiency, and that the brain must ensure parts of its needs in creatine by its own endogenous synthesis. Finally, the recent years have demonstrated the interest to use creatine as a neuroprotective agent in a growing number of neurodegenerative diseases, including Parkinson's and Huntington's diseases. This article aims at reviewing the latest data on creatine metabolism and transport in the brain, in relation to creatine deficiencies and to the potential use of creatine as neuroprotective molecule. Emphasis is also given to the importance of creatine for cerebral function. [source] Chronic exposure to nicotine and saquinavir decreases endothelial Notch-4 expression and disrupts blood-brain barrier integrityJOURNAL OF NEUROCHEMISTRY, Issue 2 2010Vamshi K. Manda J. Neurochem. (2010) 115, 515,525. Abstract Since the advent of HAART, there have been substantial improvements in HIV patient survival; however, the prevalence of HIV associated dementia has increased. Importantly, HIV positive individuals who smoke progress to HIV associated neurological conditions faster than those who do not. Recent in vitro data have shown that pharmacological levels of saquinavir causes endothelial oxidative stress and significantly decreases Notch-4 expression, a primary protein involved in maintaining stability of blood-brain barrier (BBB) endothelium. This is concerning as nicotine can also generate reactive oxygen species in endothelium. It is largely unknown if pharmacological doses of these drugs can cause a similar in vivo down-regulation of Notch-4 and if there is a concurrent destabilization of the integrity of the BBB. The data herein show: (i) nicotine and protease inhibitors cause an additive oxidative stress burden in endothelium; (ii) that the integrity of the BBB is disrupted after concurrent chronic nicotine and protease inhibitor administration; and (iii) that BBB endothelial dysfunction is correlated with a decrease in Notch-4 and ZO-1 expression. Considering the high prevalence of smoking in the HIV infected population (3- to 4-fold higher than in the general population) this data must be followed up to determine if all protease inhibitors cause a similar BBB disruption or if there is a safer alternative. In addition, this data may suggest that the induced BBB disruption may allow foreign molecules to gain access to brain and be a contributing factor to the slow progression of HIV associated dementia. [source] The human brain endothelial cell line hCMEC/D3 as a human blood-brain barrier model for drug transport studiesJOURNAL OF NEUROCHEMISTRY, Issue 5 2008Birk Poller Abstract The human brain endothelial capillary cell line hCMEC/D3 has been developed recently as a model for the human blood-brain barrier. In this study a further characterization of this model was performed with special emphasis on permeability properties and active drug transport. Para- or transcellular permeabilities (Pe) of inulin (0.74 × 10,3 cm/min), sucrose (1.60 × 10,3 cm/min), lucifer yellow (1.33 × 10,3 cm/min), morphine (5.36 × 10,3 cm/min), propranolol (4.49 × 10,3 cm/min) and midazolam (5.13 × 10,3 cm/min) were measured. By addition of human serum the passive permeability of sucrose could be reduced significantly by up to 39%. Furthermore, the expression of a variety of drug transporters (ABCB1, ABCG2, ABCC1,5) as well as the human transferrin receptor was demonstrated on the mRNA level. ABCB1, ABCG2 and transferrin receptor proteins were detected and functional activity of ABCB1, ABCG2 and the ABCC family was quantified in efflux experiments. Furthermore, ABCB1-mediated bidirectional transport of rhodamine 123 was studied. The transport rate from the apical to the basolateral compartment was significantly lower than that in the inverse direction, indicating directed p-glycoprotein transport. The results of this study demonstrate the usefulness of the hCMEC/D3 cell line as an in vitro model to study drug transport at the level of the human blood-brain barrier. [source] The methylmercury- l -cysteine conjugate is a substrate for the L-type large neutral amino acid transporterJOURNAL OF NEUROCHEMISTRY, Issue 4 2008Zhaobao Yin Abstract Methylmercury (MeHg) is a potent neurotoxin. The mechanism(s) that governs MeHg transport across the blood-brain barrier and other biological membranes remains unclear. This study addressed the role of the L-type large neutral amino acid transporter, LAT1, in MeHg transport. Studies were carried out in CHO-k1 cells. Over-expression of LAT1 in these cells was associated with enhanced uptake of [14C]-MeHg when treated with l -cysteine, but not with the d -cysteine conjugate. In the presence of excess l -methionine, a substrate for LAT1, l -cysteine-conjugated [14C]-MeHg uptake was significantly attenuated. Treatment of LAT-1 over-expressing CHO-k1 cells with l -cysteine-conjugated MeHg was also associated with increased leakage of lactate dehydrogenase into the media as well as reduced cell viability measured by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. In contrast, knock-down of LAT1 decreased the uptake of l -cysteine-conjugated MeHg and attenuated the effects of MeHg on lactate dehydrogenase leakage and CHO-k1 cell viability. These results indicate that the MeHg- l -cysteine conjugate is a substrate for the neutral amino acid transporter, LAT1, which actively transports MeHg across membranes. [source] Hyperosmotic stress induces Axl activation and cleavage in cerebral endothelial cellsJOURNAL OF NEUROCHEMISTRY, Issue 1 2008Imola Wilhelm Abstract Because of the relative impermeability of the blood-brain barrier (BBB), many drugs are unable to reach the CNS in therapeutically relevant concentration. One method to deliver drugs to the CNS is the osmotic opening of the BBB using mannitol. Hyperosmotic mannitol induces a strong phosphorylation on tyrosine residues in a broad spectrum of proteins in cerebral endothelial cells, the principal components of the BBB. Previously, we have shown that among targets of tyrosine phosphorylation are ,-catenin, extracellular signal-regulated kinase 1/2 and the non-receptor tyrosine kinase Src. The aim of this study was to identify new signalling pathways activated by hypertonicity in cerebral endothelial cells. Using an antibody array and immunoprecipitation we identified the receptor tyrosine kinase Axl to become tyrosine phosphorylated in response to hyperosmotic mannitol. Besides activation, Axl was also cleaved in response to osmotic stress. Degradation of Axl proved to be metalloproteinase- and proteasome-dependent and resulted in 50,55 kDa C-terminal products which remained phosphorylated even after degradation. Specific knockdown of Axl increased the rate of apoptosis in hyperosmotic mannitol-treated cells; therefore, we assume that activation of Axl may be a protective mechanism against hypertonicity-induced apoptosis. Our results identify Axl as an important element of osmotic stress-induced signalling. [source] Tissue Distribution, Autoradiography, and Metabolism of 4-(2,-Methoxyphenyl)-1-[2, -[N -2,-Pyridinyl)- p -[18F]Fluorobenzamido]ethyl]piperazine (p -[18F]MPPF), a New Serotonin 5-HT1A Antagonist for Positron Emission TomographyJOURNAL OF NEUROCHEMISTRY, Issue 2 2000An In Vivo Study in Rats The in vivo behavior of 4-(2,-methoxyphenyl)-1-[2,-[N -(2,-pyridinyl)- p -[18F]fluorobenzamido]ethyl]-piperazine (p -[18F]MPPF), a new serotonin 5-HT1A antagonist, was studied in awake, freely moving rats. Biodistribution studies showed that the carbon-fluorine bond was stable in vivo, that this compound was able to cross the blood-brain barrier, and that a general diffusion equilibrium could account for the availability of the tracer. The great quantity of highly polar metabolites found in plasma did not contribute to the small amounts of metabolites found in hippocampus, frontal cortex, and cerebellum. Exvivo p -[18F]MPPF and in vitro 8-hydroxy-2-(di- n -[3H]propylamino)tetralin autoradiography were compared both qualitatively and quantitatively. Qualitative evaluation proved that the same brain regions were labeled and that the p -[18F]MPPF labeling is (a) in total agreement with the known distribution of 5-HT1A receptors in rats and (b) characterized by very low nonspecific binding. Quantitative comparison demonstrated that the in vivo labeling pattern obtained with p -[18F]MPPF cannot be explained by differences in regional blood flow, capillary density, or permeability. The 5-HT1A specificity of p -[18F]MPPF and binding reversibility were confirmed in vivo with displacement experiments. Thus, this compound can be used to evaluate parameters characterizing 5-HT1A binding sites in the brain. [source] Oxygen resuscitation does not ameliorate neonatal hypoxia/ischemia-induced cerebral edemaJOURNAL OF NEUROSCIENCE RESEARCH, Issue 9 2010Diana Carolina Ferrari Abstract Neonatal hypoxia/ischemia (HI) is a common cause of cognitive and behavioral deficits in children with hyperoxia treatment (HHI) being the current therapy for newborn resuscitation. HI induces cerebral edema that is associated with poor neurological outcomes. Our objective was to characterize cerebral edema after HI and determine the consequences of HHI (40% or 100% O2). Dry weight analyses showed cerebral edema 1 to 21 days after HI in the ipsilateral cortex; and 3 to 21 days after HI in the contralateral cortex. Furthermore, HI increased blood-brain barrier (BBB) permeability 1 to 7 days after HI, leading to bilateral cortical vasogenic edema. HHI failed to prevent HI-induced increase in BBB permeability and edema development. At the molecular level, HI increased ipsilateral, but not contralateral, AQP4 cortical levels at 3 and up to 21 days after HI. HHI treatment did not further affect HI-induced changes in AQP4. In addition, we observed developmental increases of AQP4 accompanied by significant reduction in water content and increase permeability of the BBB. Our results suggest that the ipsilateral HI-induced increase in AQP4 may be beneficial and that its absence in the contralateral cortex may account for edema formation after HI. Finally, we showed that HI induced impaired motor coordination 21 days after the insult and HHI did not ameliorate this behavioral outcome. We conclude that HHI treatment is effective as a resuscitating therapy, but does not ameliorate HI-induced cerebral edema and impaired motor coordination. © 2010 Wiley-Liss, Inc. [source] Chlamydia pneumoniae infection promotes the transmigration of monocytes through human brain endothelial cellsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2003A. MacIntyre Abstract We have investigated the effects of Chlamydia pneumoniae on human brain endothelial cells (HBMECs) and human monocytes as a mechanism for breaching the blood-brain barrier (BBB) in Alzheimer's disease (AD). HBMECs and peripheral blood monocytes may be key components in controlling the entry of C. pneumoniae into the human brain. Our results indicate that C. pneumoniae infects blood vessels and monocytes in AD brain tissues compared with normal brain tissue. C. pneumoniae infection stimulates transendothelial entry of monocytes through HBMECs. This entry is facilitated by the up-regulation of VCAM-1 and ICAM-1 on HBMECs and a corresponding increase of LFA-1, VLA-4, and MAC-1 on monocytes. C. pneumoniae infection in HBMECs and THP-1 monocytes up-regulates monocyte transmigration threefold in an in vitro brain endothelial monolayer. In this way, C. pneumoniae infection in these cell types may contribute to increased monocyte migration and promote inflammation within the CNS resulting from infection at the level of the vasculature. Thus, infection at the level of the vasculature may be a key initiating factor in the pathogenesis of neurodegenerative diseases such as sporadic AD. © 2002 Wiley-Liss, Inc. [source] The integrin family of cell adhesion molecules has multiple functions within the CNSJOURNAL OF NEUROSCIENCE RESEARCH, Issue 3 2002Richard Milner Abstract Integrins comprise a large family of cell adhesion molecules that mediate interactions between the extracellular environment and the cytoplasm. During the last decade, analysis of the expression and function of these molecules has revealed that integrins regulate many aspects of cell behavior including cell death, proliferation, migration, and differentiation. Within the central nervous system (CNS), most of the early studies focused on the role of integrins in mediating adhesive and migratory events in two distinct processes: neural development and CNS inflammation. Interestingly, recent analysis of transgenic mice has provided some surprising results regarding the role of integrins in neural development. Furthermore, a large body of evidence now supports the idea that in addition to these well-described functions, integrins play multiple roles in the CNS, both during development and in the adult in areas as diverse as synaptogenesis, activation of microglia, and stabilization of the endothelium and blood-brain barrier. Many excellent reviews have addressed the contribution of integrins in mediating leukocyte extravasation during CNS inflammation. This review will focus on recently emerging evidence of novel and diverse roles of integrins and their ligands in the CNS during development and in the adult, in health and disease. © 2002 Wiley-Liss, Inc. [source] Progress and limitations in the use of in vitro cell cultures to serve as a permeability screen for the blood-brain barrierJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2001Mark Gumbleton Abstract A relatively simple, widely applicable, and robust in vitro method of predicting blood-brain barrier (BBB) permeability to central nervous system-acting drugs is an increasing need. A cell-based model offers the potential to account for transcellular and paracellular drug diffusional processes, metabolism, and active transport processes, as well as nondefined interactions between a drug and cellular material that may impact upon a membrane's overall permeability profile. Any in vitro BBB cell model to be utilized for the transendothelial BBB permeability screening of potential central nervous system drugs must display reproducible solute permeability, and a number of other general criteria including: a restrictive paracellular barrier; a physiologically realistic cell architecture; the functional expression of key transporter mechanisms; and allow ease of culture to meet the technical and time constraints of a screening program. This article reviews the range of in vitro cell-based BBB models available, including the primary/low passage bovine and porcine brain endothelial cultures as well as the spectrum of immortalized brain endothelial cell lines that have been established. The article further discusses the benefits and limitations of exploiting such systems as in vitro BBB permeability screens. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:1681,1698, 2001 [source] Sonophoresis: recent advancements and future trendsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2009Rekha Rao Abstract Objectives Use of ultrasound in therapeutics and drug delivery has gained importance in recent years, evident by the increase in patents filed and new commercial devices launched. The present review discusses new advancements in sonophoretic drug delivery in the last two decades, and highlights important challenges still to be met to make this technology of more use in the alleviation of diseases. Key findings Phonophoretic research often suffers from poor calibration in terms of the amount of ultrasound energy emitted, and therefore current research must focus on safety of exposure to ultrasound and miniaturization of devices in order to make this technology a commercial reality. More research is needed to identify the role of various parameters influencing sonophoresis so that the process can be optimized. Establishment of long-term safety issues, broadening the range of drugs that can be delivered through this system, and reduction in the cost of delivery are issues still to be addressed. Summary Sonophoresis (phonophoresis) has been shown to increase skin permeability to various low and high molecular weight drugs, including insulin and heparin. However, its therapeutic value is still being evaluated. Some obstacles in transdermal sonophoresis can be overcome by combination with other physical and chemical enhancement techniques. This review describes recent advancements in equipment and devices for phonophoresis, new formulations tried in sonophoresis, synergistic effects with techniques such as chemical enhancers, iontophoresis and electroporation, as well as the growing use of ultrasound in areas such as cancer therapy, cardiovascular disorders, temporary modification of the blood-brain barrier for delivery of imaging and therapeutic agents, hormone replacement therapy, sports medicine, gene therapy and nanotechnology. This review also lists patents pertaining to the formulations and techniques used in sonophoretic drug delivery. [source] |