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.

Diabetes-induced alterations of glucose metabolism in rat cerebral microvessels

1984 ◽  
Vol 247 (4) ◽  
pp. E462-E467 ◽  
Author(s):  
A. L. McCall ◽  
J. B. Gould ◽  
N. B. Ruderman
Keyword(s):  
Blood Glucose ◽  
Glucose Metabolism ◽  
Insulin Therapy ◽  
Blood Brain Barrier ◽  
Diabetic Rats ◽  
Brain Barrier ◽  
Cerebral Microvessels ◽  
Blood Brain ◽  
Brain Uptake Index

The effect of diabetes on the metabolism of glucose and lactate was examined in isolated rat cerebral microvessels. In rats with diabetes induced with streptozotocin, glucose oxidation to CO2 by the microvessels was decreased by 54-83% and its conversion to lactate by 21-61%. Insulin therapy for several days or starvation for 48 h both lowered blood glucose levels in the diabetic rats and restored microvessel glucose metabolism to normal. Cerebral microvessels consist principally of the capillaries that constitute the blood-brain barrier. Direct assessment of the blood-brain barrier in vivo using the brain uptake index (BUI) technique revealed a close parallel to the findings in the microvessels. Thus, hexose transport was diminished in diabetic rats and restored to normal by both insulin therapy and starvation. The oxidation of [1-14C]lactate to CO2 like that of glucose was depressed in microvessels of diabetic rats. In contrast to glucose, however, the transport of lactate across the blood-brain barrier in vivo was not altered. These findings suggest that diabetes suppresses glucose metabolism in rat cerebral microvessels and downregulates glucose transport across the blood-brain barrier. They also suggest that both of these processes are regulated by chronic alterations in blood glucose concentration rather than by insulin per se.

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.

scholarly journals The Presence of Caffeic Acid in Cerebrospinal Fluid: Evidence That Dietary Polyphenols Can Cross the Blood-Brain Barrier in Humans

Nutrients ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1531 ◽  
Author(s):  
Izabela Grabska-Kobylecka ◽  
Justyna Kaczmarek-Bak ◽  
Malgorzata Figlus ◽  
Anna Prymont-Przyminska ◽  
Anna Zwolinska ◽  
...  
Keyword(s):  
Cerebrospinal Fluid ◽  
Caffeic Acid ◽  
Blood Brain Barrier ◽  
Solid Phase ◽  
Plasma Concentrations ◽  
Brain Barrier ◽  
Facilitated Diffusion ◽  
Dietary Polyphenols ◽  
Brain Functions ◽  
Blood Brain

Epidemiological data indicate that a diet rich in plant polyphenols has a positive effect on brain functions, improving memory and cognition in humans. Direct activity of ingested phenolics on brain neurons may be one of plausible mechanisms explaining these data. This also suggests that some phenolics can cross the blood-brain barrier and be present in the brain or cerebrospinal fluid. We measured 12 phenolics (a combination of the solid-phase extraction technique with high-performance liquid chromatography) in cerebrospinal fluid and matched plasma samples from 28 patients undergoing diagnostic lumbar puncture due to neurological disorders. Homovanillic acid, 3-hydroxyphenyl acetic acid and caffeic acid were detectable in cerebrospinal fluid reaching concentrations (median; interquartile range) 0.18; 0.14 µmol/L, 4.35; 7.36 µmol/L and 0.02; 0.01 µmol/L, respectively. Plasma concentrations of caffeic acid (0.03; 0.01 µmol/L) did not correlate with those in cerebrospinal fluid (ρ = −0.109, p = 0.58). Because food (fruits and vegetables) is the only source of caffeic acid in human body fluids, our results indicate that the same dietary phenolics can cross blood-brain barrier in humans, and that transportation of caffeic acid through this barrier is not the result of simple or facilitated diffusion.

Species variation in pesticide-induced blood-brain barrier dysfunction

2003 ◽  
Vol 22 (12) ◽  
pp. 647-652 ◽  
Author(s):  
Chaitali Sinha ◽  
Girja S Shukla
Keyword(s):  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Albino Rats ◽  
Sodium Fluorescein ◽  
Species Variation ◽  
Dye Uptake ◽  
Central Nervous System Dysfunction ◽  
Blood Brain ◽  
Brain Uptake Index ◽  
Rats And Mice

Neurological disorders following acute or chronic exposure to pesticides have been reported in a number of human cases. However, the mechanism(s) by which pesticides produce central nervous system dysfunction is not clear. The objective of the present study was to examine the functional status of blood-brain barrier (BBB) in rats and mice exposed to selected pesticides of different chemical groups. Adult male albino rats and mice were exposed (1/10 of LD50) daily to dichlorvos (organophosphate), lindane (organochlorine) and carbofuran (carbamate) through oral intubation for 3 days. The status of BBB was evaluated by determining brain sodium fluorescein dye uptake and brain uptake index (BUI) in relation to serum dye level. The brain dye uptake and BUI in pesticide-exposed rats did not differ significantly in comparison to that of controls. However, brain dye uptake and BUI were increased significantly in mice exposed to dichlorvos (85%, 40%), lindane (79%, 26%) and carbofuran (129%, 61%). The results of this study show that mouse BBB system is more sensitive to pesticide-induced breach as compared to that of rat. These variations may have a role in determining the outcome of pesticide neurotoxicity in different species.

Functional impairment of blood-brain barrier following pesticide exposure during early development in rats

1999 ◽  
Vol 18 (3) ◽  
pp. 174-179 ◽  
Author(s):  
Alka Gupta ◽  
Renu Agarwal ◽  
Girja S Shukla
Keyword(s):  
Blood Brain Barrier ◽  
Repeated Exposure ◽  
Neurological Dysfunction ◽  
Brain Barrier ◽  
Sodium Fluorescein ◽  
Rat Pups ◽  
Blood Brain ◽  
Brain Uptake Index ◽  
Old Rats ◽  
Bbb Permeability

1 The effect of certain pesticides on the functional integrity of the developing blood-brain barrier (BBB) was studied following single and repeated exposure, and after subsequent withdrawal in rats. 2 Ten-day-old rat pups exposed orally to quinalphos (QP, organophosphate), cypermethrin (CM, pyre-throid) and lindane (LD, organochlorine) at a dose of 1/50th of LD50, showed a significant increase in the brain uptake index (BUI) for a micromolecular tracer, sodium fluorescein (SF), by 97, 37 and 72%, respectively, after 2 h. Residual increases in the BUI were found even after 3 days of the single treatment of QP (28%) and LD (23%). 3 Repeated exposure for 8 days (postnatal days (PND) 10-17) with QP, CM and LD increased the BBB permeability by 130, 80 and 50%, respectively. Recovery from these changes was complete in QP and LD-treated animals after 13 days (PND 18-30) of withdrawal. However, CM showed persistent effects that were normalized only after 43 days (PND 18-60) of withdrawal. 4 A single dose reduced to 1/100th of LD50 also increased BUI in 10-day-old rat pups following QP (20%) and CM (28%) exposure at 2 h. 5 An age-dependent effect of these pesticides was evident from the study showing higher magnitude of BUI changes in 10-day-old rats as compared to that in 15- day-old rats. Furthermore, adult rats did not show any effect on BBB permeability even at a higher dose (1/25th of LD50) of these pesticides given alone or in combination with piperonyl butoxide (600 mg/kg, i.p.) for 3 consecutive days. 6 This study showed that developing BBB is highly vulnerable to single or repeated exposure of certain pesticides. The observed persistent effects during brain development even after withdrawal of the treatment may produce some neurological dysfunction at later life as well.

Metabolic fuel and amino acid transport into the brain in experimental hypothyroidism

1990 ◽  
Vol 122 (2) ◽  
pp. 156-162 ◽  
Author(s):  
Arshag D. Mooradian
Keyword(s):  
Amino Acids ◽  
Blood Brain Barrier ◽  
Brain Barrier ◽  
Transport Systems ◽  
Brain Uptake ◽  
Acid Transport ◽  
Brain Extraction ◽  
Blood Brain ◽  
Brain Uptake Index ◽  
The Brain

Abstract The effect of hypothyroidism in the adult rat on blood-brain barrier and muscle transport of hexoses, neutral amino acids, basic amino acids, monocarboxylic acids, and ketone bodies was examined using single arterial injection-tissue sampling technique. The cerebral blood flow and brain extraction of 3H2O (internal reference substance) was not altered in 3-month-old hypothyroid rats maintained on methimazole, 0.025% in the drinking water, for 7 weeks. The brain uptake index of D-β-hydroxybutyrate was significantly reduced in hypothyroid rats (2.4 ± 0.3 vs 4.6 ± 0.6% p<0.001). Hypothyroid rats given thyroid hormone replacement therapy had normal brain uptake of D-β-hydroxybutyrate (4.4 ± 0.8%). The brain uptake index of butyrate was also significantly reduced in hypothyroid rats (39.3 ± 2.1 vs 47.2 ± 0.74%, p<0.001). The brain uptake index of other test substances and muscle uptake of nutrients examined were not altered in hypothyroid rats. These studies indicate that of the four transport systems examined in two tissues, the blood-brain barrier monocarboxylic acid transport system is most susceptible to the hypothyroidism-induced changes.

Sign in / Sign up

Export Citation Format

Share Document