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- Kanegawa, Naoki, et al.
(författare)
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In vivo evidence of a functional association between immune cells in blood and brain in healthy human subjects
- 2016
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Ingår i: Brain, behavior, and immunity. - : ACADEMIC PRESS INC ELSEVIER SCIENCE. - 0889-1591 .- 1090-2139. ; 54, s. 149-157
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Tidskriftsartikel (refereegranskat)abstract
- Microglia, the resident macrophages in the central nervous system, are thought to be maintained by a local self-renewal mechanism. Although preclinical and in vitro studies have suggested that the brain may contain immune cells also from peripheral origin, the functional association between immune cells in the periphery and brain at physiological conditions is poorly understood. We examined 32 healthy individuals using positron emission tomography (PET) and [C-11]PBR28, a radioligand for the 18-kDa translocator protein (TSPO) which is expressed both in brain microglia and blood immune cells. In 26 individuals, two measurements were performed with varying time intervals. In a subgroup of 19 individuals, of which 12 had repeat examinations, leukocyte numbers in blood was measured on each day of PET measurements. All individuals were genotyped for TSPO polymorphism and categorized as high, mixed, and low affinity binders. We assessed TSPO binding expressed as total distribution volume of [C-11]PBR28 in brain and in blood cells. TSPO binding in brain was strongly and positively correlated to binding in blood cells both at baseline and when analyzing change between two PET examinations. Furthermore, there was a significant correlation between change of leukocyte numbers and change in TSPO binding in brain, and a trend level correlation to change in TSPO binding in blood cells. These in vivo findings indicate an association between immunological cells in blood and brain via intact BBB, suggesting a functional interaction between these two compartments, such as interchange of peripherally derived cells or a common regulatory mechanism. Measurement of radioligand binding in blood cells may be a way to control for peripheral immune function in PET studies using TSPO as a marker of brain immune activation. (C) 2016 Elsevier Inc. All rights reserved.
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| 2. |
- Rahman, Obaidur, et al.
(författare)
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Synthesis of ([C-11]carbonyl)raclopride and a comparison with ([C-11]methyl)raclopride in a monkey PET study
- 2015
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Ingår i: Nuclear Medicine and Biology. - : Elsevier BV. - 0969-8051 .- 1872-9614. ; 42:11, s. 893-898
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The selective dopamine D-2 receptor antagonist raclopride is usually labeled with carbon-11 using [C-11]methyl iodide or [C-11]methyl triflate for use in the quantification of dopamine D-2 receptors in human brain. The aim of this work was to label raclopride at the carbonyl position using [C-11]carbon monoxide chemistry and to compare ([C-11]carbonyl)raclopride with ([C-11]methyl)raclopride in non-human primate (NHP) using PET with regard to quantitative outcome measurement, metabolism of the labeled tracers and protein binding. Methods: Palladium-mediated carbonylation using [C-11]carbon monoxide, 4,6-dichloro-2-iodo-3-methoxyphenol and (S)-(-)-2-aminomethyl-1-ethylpyrrolidine was applied in the synthesis of ([C-11]carbonyl)raclopride. The reaction was performed at atmospheric pressure using xantphos as supporting phosphine ligand and palladium (pi-cinnamyl) chloride dimer as the palladium source. ([C-11]Methyl)raclopride was prepared by a previously published method. In the PET study, two female cynomolgus monkeys were used under gas anesthesia of sevoflurane. A dynamic PET measurement was performed for 63 min with an HRRT PET camera after intravenous injection of ([C-11]carbonyl)raclopride and ([C-11]methyl)raclopride, respectively, during the same day. The order of injection of the two PET radioligands was changed between the two monkeys. The venous blood sample for measurement of protein binding was taken 3 min prior to the PET scan. Binding potential (BPND) of the putamen and caudate was calculated with SRTM using the cerebellum as a reference region. Results: The target compound ([C-11]carbonyl)raclopride was obtained with 50 +/- 5% decay corrected radiochemical yield and 95% radiochemical purity. The trapping efficiency (TE) of [C-11]carbon monoxide was 65 +/- 5% and the specific radioactivity of the final product was 34 +/- 1 GBq/mu mol after a 50 min of synthesis time. The radiochemical yield of ([C-11]methyl)raclopride was in the same range as published previously i.e. 50-60% and specific radioactivity of those two batches which were used in the present PET study were 192 GBq/mu mol and 638 GBq/mu mol respectively after a synthesis time of 32 min. In monkey PET studies, the percentage difference of BPND in putamen was <3% and that in caudate was <9% for the two radioligands. The plasma protein binding was 86.2 +/- 0.3% and 85.7 +/- 0.6% for ([C-11]carbonyl)raclopride and ([C-11]methyl)raclopride, respectively. The radiometabolite pattern was similar for both radioligands. Conclusion: Raclopride was C-11-labeled at the carbonyl position using a palladium-mediated [C-11]carbonylation reaction. A comparison between ([C-11]carbonyl)raclopride and ([C-11]merhyl)raclopride with regard to quantitative PET outcome measurements, metabolism of radioligands and protein binding in monkey was performed. The monkey PET study with ([C-11]carbonyl)raclopride showed similar results as for ([C-11]methyl)raclopride. The PET studies were performed on 2 subjects.
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