Quantification of monoacylglycerol lipase and its occupancy by an exogenous ligand in rhesus monkey brains using [18F]T-401 and PET

Monoacylglycerol lipase (MAGL) is a cytosolic serine hydrolase that cleaves monoacylglycerols into fatty acids and is a potential target for the novel treatment of CNS disorders related to the endocannabinoid system and neuroinflammation. We have developed [18F]T-401 as a selective Positron emission tomography (PET) imaging agent for MAGL. In this study, we determined an analytical method to quantify MAGL availability and its occupancy by an exogenous inhibitor in rhesus monkey brains using [18F]T-401-PET. In rhesus monkeys, regional time-activity curves were described well when using an extended 2-tissue compartment model that accommodated the formation of a radiometabolite in the brain. This model yielded reliable estimates of the total distribution volume ( VT), and the rank order of VT was consistent with known regional activity of MAGL enzyme in primates. The pretreatment of monkeys with JW642 resulted in a dose-dependent reduction of [18F]T-401 retentions in the brain, and VT. Lassen's graphical analysis indicated a VND of 0.69 mL/cm3 and a plasma JW642 concentration of 126 ng/mL for inhibiting the specific binding by 50%. [18F]T-401 and the method established can be used for quantification of MAGL in healthy brain and in disease conditions, and is suitable for evaluations of target engagement at cerebral MAGL.

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Kinetic Analysis of the 5-HT2A Ligand [11C]MDL 100,907

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-200006000-00002 ◽

2000 ◽

Vol 20 (6) ◽

pp. 899-909 ◽

Cited By ~ 64

Author(s):

Hiroshi Watabe ◽

Michael A. Channing ◽

Margaret G. Der ◽

H. Richard Adams ◽

Elaine Jagoda ◽

...

Keyword(s):

Kinetic Analysis ◽

Specific Binding ◽

Compartment Model ◽

Input Function ◽

Brain Regions ◽

Time Activity ◽

Tissue Compartment ◽

Arterial Blood ◽

Fixed Parameter ◽

Mdl 100,907

The goal of this study was to develop a suitable kinetic analysis method for quantification of 5-HT2A receptor parameters with [11C]MDL 100,907. Twelve control studies and four preblocking studies (400 nmol/kg unlabeled MDL 100,907) were performed in isoflurane-anesthetized rhesus monkeys. The plasma input function was determined from arterial blood samples with metabolite measurements by extraction in ethyl acetate. The preblocking studies showed that a two-tissue compartment model was necessary to fit the time activity curves of all brain regions including the cerebellum—in other words, the need for two compartments is not proof of specific binding. Therefore, a three-tissue compartment model was used to analyze the control studies, with three parameters fixed based on the preblocking data. Reliable fits of control data could be obtained only if no more than three parameters were allowed to vary. For routine use of [11C]MDL 100,907, several simplified methods were evaluated. A two-tissue (2T‘) compartment with one fixed parameter was the most reliable compartmental approach; a one-compartment model failed to fit the data adequately. The Logan graphical approach was also tested and produced comparable results to the 2T’ model. However, a simulation study showed that Logan analysis produced a larger bias at higher noise levels. Thus, the 2T' model is the best choice for analysis of [11C]MDL 100,907 studies.

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Brain Uptake of the Acid Metabolites of F-18—Labeled WAY 100635 Analogs

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/01.wcb.0000046145.31247.7a ◽

2003 ◽

Vol 23 (2) ◽

pp. 249-260 ◽

Cited By ~ 11

Author(s):

Richard E. Carson ◽

Yanjun Wu ◽

Lixin Lang ◽

Ying Ma ◽

Margaret G. Der ◽

...

Keyword(s):

Gray Matter ◽

Specific Binding ◽

Additional Term ◽

Free Fraction ◽

Brain Uptake ◽

Activity Data ◽

Time Activity ◽

Arterial Blood ◽

The Brain

The 5-HT1A ligands [F]FPWAY and [18F]FCWAY are metabolized in vivo to [18F]fluorobenzoic acid (FB) and [18F]fluorocyclohexanecarboxylic acid (FC), respectively. To quantify the penetration of these acids into the brain, dynamic positron emission tomography studies were performed in rhesus monkeys with [18F]FB and [18F]FC. High-performance liquid chromatography analysis of arterial blood samples showed no metabolites for [18F]FB, whereas [18F]FC was rapidly metabolized to [18F]fluoride. A model with one tissue compartment and vascular radioactivity was used to analyze gray matter time-activity curves. For [18F]FC, an additional term was added to account for [18F]fluoride skull spillover into the brain; this term accounted for 70% to 90% of the measured radioactivity concentration at 90 minutes. For [18F]FB, mean gray matter parameters were as follows: K1, 10 ± 3 μL · min−1 · mL−1; distribution volume V, 0.052 ± 0.006 (mL/mL). For [18F]FC, the values were as follows: K1, 15 ± 4 μL · min−1 · mL−1; V, 0.29 ± 0.06 mL/mL. The V values were consistent with a physiologic model that included brain-to-blood pH difference and the plasma free fraction of the acid. Simulations based on [18F]FCWAY human data showed that [18F]FC uptake produces significant biases in V estimates in regions with low specific binding. These results can be used to correct the tissue [18F]FCWAY time-activity data for brain uptake of [18F]FC using the measured [18F]FC input function.

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Kinetic Modeling of [11C]Raclopride: Combined PET-Microdialysis Studies

Journal of Cerebral Blood Flow & Metabolism ◽

10.1097/00004647-199709000-00002 ◽

1997 ◽

Vol 17 (9) ◽

pp. 932-942 ◽

Cited By ~ 133

Author(s):

Christopher J. Endres ◽

Bhaskar S. Kolachana ◽

Richard C. Saunders ◽

Tom Su ◽

Daniel Weinberger ◽

...

Keyword(s):

Positron Emission Tomography ◽

Specific Binding ◽

Compartment Model ◽

Emission Tomography ◽

Extended Model ◽

Simulation Studies ◽

Time Activity ◽

Endogenous Dopamine ◽

Positron Emission

The in vivo binding of D2 receptor ligands can be affected by agents that alter the concentration of endogenous dopamine. To define a more explicit relation between dopamine and D2 receptor binding, the conventional compartment model for reversible ligands has been extended to account for a time-varying dopamine pulse. This model was tested with [11C]raclopride positron emission tomography and dopamine microdialysis data that were acquired simultaneously in rhesus monkeys. The microdialysis data were incorporated into the model assuming a proportional relation to synaptic dopamine. Positron emission tomography studies used a bolus-plus-infusion tracer delivery with amphetamine given at 40 minutes to induce dopamine release. The extended model described the entire striatal time–activity curve, including the decrease in radioactivity concentration after an amphetamine-induced dopamine pulse. Based on these results, simulation studies were performed using the extended model. The simulation studies showed that the percent decrease in specific binding after amphetamine measured with the bolus-plus-infusion protocol correlates well with the integral of the postamphetamine dopamine pulse. This suggests that changes in specific binding observed in studies in humans can be interpreted as being linearly proportional to the integral of the amphetamine-induced dopamine pulse.

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Set-Up and Validation of a High Throughput Screening Method for Human Monoacylglycerol Lipase (MAGL) Based on a New Red Fluorescent Probe

Molecules ◽

10.3390/molecules24122241 ◽

2019 ◽

Vol 24 (12) ◽

pp. 2241 ◽

Cited By ~ 1

Author(s):

Matteo Miceli ◽

Silvana Casati ◽

Roberta Ottria ◽

Simone Di Leo ◽

Ivano Eberini ◽

...

Keyword(s):

High Throughput ◽

High Throughput Screening ◽

Low Cost ◽

Screening Method ◽

Endocannabinoid System ◽

Accurate Method ◽

Monoacylglycerol Lipase ◽

Serine Hydrolase ◽

Lead Compounds ◽

Set Up

Monoacylglycerol lipase (MAGL) is a serine hydrolase that has a key regulatory role in controlling the levels of 2-arachidonoylglycerol (2-AG), the main signaling molecule in the endocannabinoid system. Identification of selective modulators of MAGL enables both to provide new tools for investigating pathophysiological roles of 2-AG, and to discover new lead compounds for drug design. The development of sensitive and reliable methods is crucial to evaluate this modulatory activity. In the current study, we report readily synthesized long-wavelength putative fluorogenic substrates with different acylic side chains to find a new probe for MAGL activity. 7-Hydroxyresorufinyl octanoate proved to be the best substrate thanks to the highest rate of hydrolysis and the best Km and Vmax values. In addition, in silico evaluation of substrates interaction with the active site of MAGL confirms octanoate resorufine derivative as the molecule of choice. The well-known MAGL inhibitors URB602 and methyl arachidonylfluorophosphonate (MAFP) were used for the assay validation. The assay was highly reproducible with an overall average Z′ value of 0.86. The fast, sensitive and accurate method described in this study is suitable for low-cost high-throughput screening (HTS) of MAGL modulators and is a powerful new tool for studying MAGL activity.

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Mechanism of L-glucose, raffinose, and inulin transport across intact blood-brain barriers

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1990.258.3.h695 ◽

1990 ◽

Vol 258 (3) ◽

pp. H695-H705 ◽

Cited By ~ 1

Author(s):

K. J. Lucchesi ◽

R. E. Gosselin

Keyword(s):

Molecular Size ◽

Compartment Model ◽

Graphical Analysis ◽

Capillary Endothelium ◽

Multiple Time ◽

Brain Capillary ◽

Molecular Weights ◽

Blood Brain ◽

Two Compartment Model ◽

The Brain

Brain capillary permeability-surface area products (PS) of hydrophilic solutes were evaluated in terms of a conventional two-compartment model. In rats whose blood-brain barrier (BBB) was presumed to be intact, metabolically inert carbohydrates with different molecular weights were injected in pairs to elucidate whether their transfer into the brain proceeds by diffusion through water- or lipid-filled channels or by vesicular transport. The distribution volume of 70 kDa dextran 10 min after intravenous injection was used as a measure of the residual volume of plasma in brain tissue after death. The two-compartment model yielded larger PS values for inulin and raffinose than for L-glucose, and the PS values of inulin and L-glucose were found to decrease as the labeling time was lengthened (10, 30, and 60 min). These observations were interpreted to mean that a rapidly equilibrating compartment was present between blood and brain, rendering the two-compartment model inadequate for computing true transfer rate constants. When multiple-time uptake data were reanalyzed using the three-compartment graphical analysis of Patlak, Blasberg, and Fenstermacher (J. Cereb. Blood Flow Metab. 3: 1-7, 1983), solutes of differing molecular size were found to enter the brain at approximately equal rates. This observation suggested that the predominant transport mechanism across an intact BBB is vesicular. Specifically, unidirectional transport is likely to be initiated by solute binding to the glycocalyx on the luminal surface of brain capillary endothelium. Apparently more inulin than L-glucose is absorbed, which may account for its slightly faster transfer across the BBB. We suggest that this adsorptive surface is the location of the rapidly equilibrating compartment on the plasma side of the BBB.

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Early Detection of Aβ Deposition in the 5xFAD Mouse by Amyloid PET

Contrast Media & Molecular Imaging ◽

10.1155/2018/5272014 ◽

2018 ◽

Vol 2018 ◽

pp. 1-7 ◽

Cited By ~ 7

Author(s):

Se Jong Oh ◽

Hae-June Lee ◽

Kyung Jun Kang ◽

Sang Jin Han ◽

Yong Jin Lee ◽

...

Keyword(s):

Specific Binding ◽

Volume Ratio ◽

Immunohistochemical Analysis ◽

Graphical Analysis ◽

Amyloid Pet ◽

Reference Tissue ◽

Amyloid A ◽

Pet Tracer ◽

5Xfad Mice ◽

The Brain

Purpose. 18F-FC119S is a positron emission tomography (PET) tracer for imaging β-amyloid (Aβ) plaques in Alzheimer’s disease (AD). The aim of this study is to evaluate the efficacy of 18F-FC119S in quantitating Aβ deposition in a mouse model of early amyloid deposition (5xFAD) by PET. Method. Dynamic 18F-FC119S PET images were obtained in 5xFAD (n=5) and wild-type (WT) mice (n=7). The brain PET images were spatially normalized to the M. Mirrione T2-weighted mouse brain MR template, and the volumes of interest were then automatically drawn on the cortex, hippocampus, thalamus, and cerebellum. The specific binding of 18F-FC119S to Aβ was quantified as the distribution volume ratio using Logan graphical analysis with the cerebellum as a reference tissue. The Aβ levels in the brain were also confirmed by immunohistochemical analysis. Result. For the 5xFAD group, radioactivity levels in the cortex, the hippocampus, and the thalamus were higher than those for the WT group. In these regions, specific binding was approximately 1.2-fold higher in 5xFAD mice than in WT. Immunohistochemistry supported these findings; the 5xFAD showed severe Aβ deposition in the cortex and hippocampus in contrast to the WT group. Conclusion. These results demonstrated that 18F-FC119S PET can successfully distinguish Aβ depositions in 5xFAD mice from WT.

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Reduced Cerebral Fluoro-l-Dopamine Uptake in Adult Patients Suffering from Phenylketonuria

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9600571 ◽

2007 ◽

Vol 28 (4) ◽

pp. 824-831 ◽

Cited By ~ 38

Author(s):

Christian Landvogt ◽

Eugen Mengel ◽

Peter Bartenstein ◽

Hans Georg Buchholz ◽

Mathias Schreckenberger ◽

...

Keyword(s):

Competitive Inhibition ◽

Elevated Serum ◽

Graphical Analysis ◽

The Body ◽

Adult Patients ◽

Control Group ◽

Decarboxylase Activity ◽

Large Neutral Amino Acid ◽

Time Activity ◽

The Brain

Deficiency of phenylalanine hydroxylase activity in phenylketonuria (PKU) causes an excess of phenylalanine (Phe) throughout the body, predicting impaired synthesis of catecholamines in the brain. To test this hypothesis, we used positron emission tomography (PET) to measure the utilization of 6-[18F]fluoro-l-dopamine (FDOPA) in the brain of adult patients suffering from PKU and in healthy controls. Dynamic 2-h long FDOPA emission recordings were obtained in seven adult PKU patients (five females, two males; age: 21 to 27 years) with elevated serum Phe levels, but lacking neurologic deficits. Seven age-matched, healthy volunteers were imaged under identical conditions. The utilization of FDOPA in striatum was calculated by linear graphical analysis ( k3S, min−1), with cerebellum serving as a nonbinding reference region. The time to peak activity in all brain time—radioactivity curves was substantially delayed in the PKU patients relative to the control group. The mean magnitude of k3S in the striatum of the PKU patients (0.0052±0.0004 min−1) was significantly lower than in the control group (0.0088±0.0009 min−1) ( P<0.001). There was no significant correlation between individual serum Phe levels and k3S. The unidirectional clearance of FDOPA to brain was impaired in adult patients suffering from PKU, presumably reflecting the competitive inhibition of the large neutral amino acid carrier by Phe. Assuming this competition to be spatially uniform, the relationship between striatum and cerebellum time—activity curves additionally suggests inhibition of DOPA efflux, possibly also due to competition from Phe. The linear graphical analysis shows reduced k3S in striatum, indicating reduced DOPA decarboxylase activity.

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The P2X7 receptor tracer [11C]SMW139 as an in vivo marker of neuroinflammation in multiple sclerosis: a first-in man study

European Journal of Nuclear Medicine and Molecular Imaging ◽

10.1007/s00259-019-04550-x ◽

2019 ◽

Vol 47 (2) ◽

pp. 379-389 ◽

Cited By ~ 9

Author(s):

Marloes H. J. Hagens ◽

Sandeep S. V. Golla ◽

Bieneke Janssen ◽

Danielle J. Vugts ◽

Wissam Beaino ◽

...

Keyword(s):

Multiple Sclerosis ◽

Specific Binding ◽

Compartment Model ◽

Brain Regions ◽

Binding Potential ◽

Healthy Controls ◽

Time Activity ◽

Tissue Compartment ◽

Pet Tracer

Abstract Purpose The novel PET tracer [11C]SMW139 binds with high affinity to the P2X7 receptor, which is expressed on pro-inflammatory microglia. The purposes of this first in-man study were to characterise pharmacokinetics of [11C]SMW139 in patients with active relapsing remitting multiple sclerosis (RRMS) and healthy controls (HC) and to evaluate its potential to identify in vivo neuroinflammation in RRMS. Methods Five RRMS patients and 5 age-matched HC underwent 90-min dynamic [11C]SMW139 PET scans, with online continuous and manual arterial sampling to generate a metabolite-corrected arterial plasma input function. Tissue time activity curves were fitted to single- and two-tissue compartment models, and the model that provided the best fits was determined using the Akaike information criterion. Results The optimal model for describing [11C]SMW139 kinetics in both RRMS and HC was a reversible two-tissue compartment model with blood volume parameter and with the dissociation rate k4 fixed to the whole-brain value. Exploratory group level comparisons demonstrated an increased volume of distribution (VT) and binding potential (BPND) in RRMS compared with HC in normal appearing brain regions. BPND in MS lesions was decreased compared with non-lesional white matter, and a further decrease was observed in gadolinium-enhancing lesions. In contrast, increased VT was observed in enhancing lesions, possibly resulting from disruption of the blood-brain barrier in active MS lesions. In addition, there was a high correlation between parameters obtained from 60- to 90-min datasets, although analyses using 60-min data led to a slight underestimation in regional VT and BPND values. Conclusions This first in-man study demonstrated that uptake of [11C]SMW139 can be quantified with PET using BPND as a measure for specific binding in healthy controls and RRMS patients. Additional studies are warranted for further clinical evaluation of this novel neuroinflammation tracer.

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