Blood-Brain Barrier Monoamine Oxidase: Enzyme Characterization in Cerebral Microvessels and Other Tissues from Six Mammalian Species, Including Human

1987 ◽  
Vol 49 (3) ◽  
pp. 856-864 ◽  
Author(s):  
Rajesh N. Kalaria ◽  
Sami I. Harik
Keyword(s):  
Monoamine Oxidase ◽  
Blood Brain Barrier ◽  
Mammalian Species ◽  
Enzyme Characterization ◽  
Brain Barrier ◽  
Cerebral Microvessels ◽  
Blood Brain ◽  
Oxidase Enzyme

Monoamine Oxidase Activity in Brain Microvessels Determined Using Natural and Artificial Substrates: Relevance to the Blood—Brain Barrier

1983 ◽  
Vol 3 (4) ◽  
pp. 521-528 ◽  
Author(s):  
F. Lasbennes ◽  
R. Sercombe ◽  
J. Seylaz
Keyword(s):  
Monoamine Oxidase ◽  
Blood Brain Barrier ◽  
Active Form ◽  
Artificial Substrates ◽  
Brain Barrier ◽  
Facilitated Diffusion ◽  
Cerebral Microvessels ◽  
Highly Active ◽  
Blood Brain ◽  
Brain Uptake Index

The possible contribution of cerebrovascular monoamine oxidase (MAO) to the blood–brain barrier to catecholamines was studied in isolated porcine and rat microvessels by determining its activity with various substrates. Michaelis-Menten kinetic constants, Km and Vmax, were determined using noradrenaline (NA) as substrate in a Tris medium. Km values were 0.25 ± 0.05 m M in control and 0.16 ± 0.09 m M in ultrasonically disintegrated (USD) preparations (difference not significant); Vmax in USD preparations (1.83 ± 0.20 n.atoms O2 min−1 mg protein−1) was slightly higher (p < 0.05) than in control preparations (1.35 ± 0.11 n.atoms O2 min−1 mg protein−1), suggesting a certain restriction by the plasma membrane of substrate access to the enzyme. This phenomenon was confirmed in a more physiological, ionic medium; the activity was then approximately doubled for 1 m M NA, whereas that for 1 m M β-phenylethylamine (β-PEA), a lipid-soluble substrate, tended to decrease with USD treatment. These results show that this highly active form of MAO is unlikely to be saturated by physiological concentrations of catecholamine. It can be estimated that, for a plasma concentration of NA of 1 μM, a facilitated diffusion accelerating the entry of the catecholamine into the cells by at least 15-fold would be necessary in order to exceed the catabolic capacity of MAO. It is concluded that circulating catecholamines are not likely to cross the endothelial barrier of cerebral microvessels intact, and that the small quantities of radioactivity detected in the parenchyma in measurements of the brain uptake index essentially represent metabolites due to MAO activity.

Glucose transport by isolated plasma membranes of the bovine blood-brain barrier

1997 ◽  
Vol 272 (5) ◽  
pp. C1552-C1557 ◽  
Author(s):  
W. J. Lee ◽  
D. R. Peterson ◽  
E. J. Sukowski ◽  
R. A. Hawkins
Keyword(s):  
Glucose Transport ◽  
Blood Brain Barrier ◽  
Plasma Membranes ◽  
Glucose Transporter ◽  
Extracellular Fluid ◽  
Brain Barrier ◽  
Maximal Velocity ◽  
Plasma Membrane Vesicles ◽  
Cerebral Microvessels ◽  
Blood Brain

Luminal and abluminal endothelial plasma membrane vesicles were isolated from bovine cerebral microvessels, the site of the blood-brain barrier. Glucose transport across each membrane was measured using a rapid-filtration technique. Glucose transport into luminal vesicles occurred by a stereospecific energy-independent transporter [Michaelis-Menten constant (K(m)) = 10.3 +/- 2.8 (SE) mM and maximal velocity (Vmax) = 8.6 +/- 2.0 nmol.mg protein(-1).min-1]. Kinetic analysis of abluminal vesicles also showed a transport system with characteristics similar to the luminal transporter (K(m) = 12.5 +/- 2.3 mM and Vmax = 10.0 +/- 1.0 nmol.mg protein-1.min-1). These functional, facilitative glucose transporters were symmetrically distributed between the luminal and abluminal membrane domains, providing a mechanism for glucose movement between blood and brain. The studies also revealed a Na-dependent transporter on the abluminal membrane with a higher affinity and lower capacity than the facilitative transporters (K(m) = 130 +/- 20 microM and Vmax = 1.59 +/- 0.44 nmol.mg protein-1.min-1. The abluminal Na-dependent glucose transporter is in a position to transport glucose from the brain extracellular fluid into the endothelial cells of the blood-brain barrier. The functional significance of its presence there remains to be determined.

Activation of PKC modulates blood-brain barrier endothelial cell permeability changes induced by hypoxia and posthypoxic reoxygenation

2005 ◽  
Vol 289 (5) ◽  
pp. H2012-H2019 ◽  
Author(s):  
Melissa A. Fleegal ◽  
Sharon Hom ◽  
Lindsay K. Borg ◽  
Thomas P. Davis
Keyword(s):  
Blood Brain Barrier ◽  
Paracellular Permeability ◽  
Cell Permeability ◽  
Brain Barrier ◽  
Cerebral Microvessels ◽  
Permeability Changes ◽  
Blood Brain ◽  
Brain Microvessel

The blood-brain barrier (BBB) is a metabolic and physiological barrier important for maintaining brain homeostasis. The aim of this study was to determine the role of PKC activation in BBB paracellular permeability changes induced by hypoxia and posthypoxic reoxygenation using in vitro and in vivo BBB models. In rat brain microvessel endothelial cells (RMECs) exposed to hypoxia (1% O2-99% N2; 24 h), a significant increase in total PKC activity was observed, and this was reduced by posthypoxic reoxygenation (95% room air-5% CO2) for 2 h. The expression of PKC-βII, PKC-γ, PKC-η, PKC-μ, and PKC-λ also increased following hypoxia (1% O2-99% N2; 24 h), and these protein levels remained elevated following posthypoxic reoxygenation (95% room air-5% CO2; 2 h). Increases in the expression of PKC-ε and PKC-ζ were also observed following posthypoxic reoxygenation (95% room air-5% CO2; 2 h). Moreover, inhibition of PKC with chelerythrine chloride (10 μM) attenuated the hypoxia-induced increases in [14C]sucrose permeability. Similar to what was observed in RMECs, total PKC activity was also stimulated in cerebral microvessels isolated from rats exposed to hypoxia (6% O2-94% N2; 1 h) and posthypoxic reoxygenation (room air; 10 min). In contrast, hypoxia (6% O2-94% N2; 1 h) and posthypoxic reoxygenation (room air; 10 min) significantly increased the expression levels of only PKC-γ and PKC-θ in the in vivo hypoxia model. These data demonstrate that hypoxia-induced BBB paracellular permeability changes occur via a PKC-dependent mechanism, possibly by differentially regulating the protein expression of the 11 PKC isozymes.

Abstract TP340: The Level of Occludin in Blood as a Potential Biomarker for Blood-Brain Barrier Damage and Predicting Hemorrhage Transformation After Acute Ischemic Stroke

Stroke ◽  
2020 ◽  
Vol 51 (Suppl_1) ◽  
Author(s):  
Zhifeng Qi ◽  
Ke Jian Liu
Keyword(s):  
Ischemic Stroke ◽  
Acute Ischemic Stroke ◽  
Blood Brain Barrier ◽  
Brain Infarction ◽  
Critical Role ◽  
Onset Time ◽  
Brain Barrier ◽  
Cerebral Microvessels ◽  
Blood Brain ◽  
Potential Biomarker

Fear of hemorrhage transformation (HT) has been the primary reason for withholding the effective recanalization therapies (thrombolysis or thrombectomy) from most acute ischemic stroke (AIS) patients. Currently there is no reliable indicator available to predict HT before recanalization. The degradation of tight junction proteins plays a critical role in blood-brain barrier (BBB) disruption in ischemic stroke. We hypothesize that since occludin fragment in peripheral blood is derived from the degradation of occludin on cerebral microvessels, elevated blood occludin level directly reflects BBB disruption and may serve as a biomarker for BBB damage to predict the risk of HT after recanalization. In this study, we determined occludin fragment in the blood of rats, non-human primates and human patients after AIS using ELISA assay, and evaluated its level with BBB damage, HT, and other neurological outcomes. We found that ischemia induced rapid occludin degradation and BBB disruption, while occludin fragment was released into the blood circulation. Cerebral ischemia resulted in a dramatic increase of occludin fragments in rat blood samples after 4-hr ischemia, which was correlated well with occludin loss from ischemic cerebral microvessels. In the blood sample from ischemic rhesus monkeys, occludin level significantly increased after 2h ischemia from baseline, which correlated well with brain infarction shown in MRI images. We further collected the sera of AIS patients as early as they arrived at hospital. Our results indicated that the level of occludin increased in accord with ischemia onset time and neurological dysfunctions. The level of blood occludin in AIS patients with HT was much higher that those without HT. Together, our findings from rats, non-human primates and patients suggest that the level of occludin fragment in blood could serve as a biomarker for HT and neurological outcome following AIS, which could be used to safely guide recanalization for AIS in the clinic.

Hypoxia increases glucose transport at blood-brain barrier in rats

1994 ◽  
Vol 77 (2) ◽  
pp. 896-901 ◽  
Author(s):  
S. I. Harik ◽  
R. A. Behmand ◽  
J. C. LaManna
Keyword(s):  
Glucose Transport ◽  
Blood Brain Barrier ◽  
Hypobaric Hypoxia ◽  
Cytochalasin B ◽  
Bolus Injection ◽  
Brain Regions ◽  
Brain Barrier ◽  
Cerebral Microvessels ◽  
Blood Brain

Prolonged hypoxia causes several adaptive changes in systemic physiology and tissue metabolism. We studied the effects of hypobaric hypoxia on glucose transport at the blood-brain barrier (BBB) in the rat. We found that hypoxia increased the density of brain microvessels seen on immunocytochemical stains using an antibody to the glucose transporting protein GLUT. In addition, we found that hypoxia increased the density of GLUT in isolated cerebral microvessels as determined by specific cytochalasin B binding. The higher GLUT density in isolated cerebral microvessels was evident after 1 wk of hypoxia and was associated with decreased activity of gamma-glutamyltranspeptidase. Consistent with these findings, we also demonstrated that 3 wk of hypobaric hypoxia caused increased unidirectional transport of glucose at the BBB in several brain regions in vivo, as determined by the doubly labeled single-pass indicator-fractionation atrial bolus injection method in anesthetized rats. We conclude that chronic hypobaric hypoxia is associated with increased glucose transport at the BBB.

scholarly journals Oxidative Stress Increases Blood–Brain Barrier Permeability and Induces Alterations in Occludin during Hypoxia–Reoxygenation

2010 ◽  
Vol 30 (9) ◽  
pp. 1625-1636 ◽  
Author(s):  
Jeffrey J Lochhead ◽  
Gwen McCaffrey ◽  
Colleen E Quigley ◽  
Jessica Finch ◽  
Kristin M DeMarco ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Blood Brain Barrier ◽  
Critical Role ◽  
Brain Barrier ◽  
Central Component ◽  
Radical Scavenger ◽  
Cerebral Microvessels ◽  
Disease States ◽  
Blood Brain ◽  
The Brain

The blood–brain barrier (BBB) has a critical role in central nervous system homeostasis. Intercellular tight junction (TJ) protein complexes of the brain microvasculature limit paracellular diffusion of substances from the blood into the brain. Hypoxia and reoxygenation (HR) is a central component to numerous disease states and pathologic conditions. We have previously shown that HR can influence the permeability of the BBB as well as the critical TJ protein occludin. During HR, free radicals are produced, which may lead to oxidative stress. Using the free radical scavenger tempol (200 mg/kg, intraperitoneal), we show that oxidative stress produced during HR (6% O2 for 1 h, followed by room air for 20 min) mediates an increase in BBB permeability in vivo using in situ brain perfusion. We also show that these changes are associated with alterations in the structure and localization of occludin. Our data indicate that oxidative stress is associated with movement of occludin away from the TJ. Furthermore, subcellular fractionation of cerebral microvessels reveals alterations in occludin oligomeric assemblies in TJ associated with plasma membrane lipid rafts. Our data suggest that pharmacological inhibition of disease states with an HR component may help preserve BBB functional integrity.

Sign in / Sign up

Export Citation Format

Share Document