Browsing by Author "Okamura, Nobuyuki"

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    Comparative binding properties of the tau PET tracers THK5117, THK5351, PBB3, and T807 in postmortem Alzheimer brains
    (BMC, 2017-11-11) Lemoine, Laetitia; Gillberg, Per-Göran; Svedberg, Marie; Stepanov, Vladimir; Jia, Zhisheng; Huang, Jinghai; Nag, Sangram; Tian, He; Ghetti, Bernardino; Okamura, Nobuyuki; Higuchi, Makoto; Halldin, Christer; Nordberg, Agneta; Pathology and Laboratory Medicine, School of Medicine
    Background The aim of this study was to compare the binding properties of several tau positron emission tomography tracers—THK5117, THK5351, T807 (also known as AV1451; flortaucipir), and PBB3—head to head in the same human brain tissue. Methods Binding assays were performed to compare the regional distribution of 3H-THK5117 and 3H-THK5351 in postmortem tissue from three Alzheimer’s disease (AD) cases and three control subjects in frontal and temporal cortices as well as in the hippocampus. Competition binding assays between THK5351, THK5117, PBB3, and T807, as well as off-target binding of THK5117 and T807 toward monoamine oxidase B (MAO-B), were performed using binding assays in brain homogenates and autoradiography of three AD cases. Results Regional binding of 3H-THK5117 and 3H-THK5351 was similar, except in the temporal cortex, which showed higher 3H-THK5117 binding. Saturation studies demonstrated two binding sites for 3H-THK5351 (K d1 = 5.6 nM, Bmax = 76 pmol/g; K d2 = 1 nM, Bmax = 40 pmol/g). Competition studies in the hippocampus between 3H-THK5351 and unlabeled THK5351, THK5117, and T807 revealed super-high-affinity sites for all three tracers (THK5351 K i = 0.1 pM; THK5117 K i = 0.3 pM; T807 K i = 0.2 pM) and an additional high-affinity site (THK5351 K i = 16 nM; THK5117 K i = 20 nM; T807 K i = 78nM). 18F-T807, 11C-THK5351, and 11C-PBB3 autoradiography of large frozen sections from three AD brains showed similar regional binding for the three tracers, with lower binding intensity for 11C-PBB3. Unlabeled THK5351 and T807 displaced 11C-THK5351 to a similar extent and a lower extent, respectively, compared with 11C-PBB3. Competition with the MAO-B inhibitor 3H-l-deprenyl was observed for THK5117 and T807 in the hippocampus (THK5117 K i = 286 nM; T807 K i = 227 nM) and the putamen (THK5117 K i = 148 nM; T807 K i = 135 nM). 3H-THK5351 binding was displaced using autoradiography competition with unlabeled THK5351 and T807 in cortical areas by 70–80% and 60–77%, respectively, in the basal ganglia, whereas unlabeled deprenyl displaced 3H-THK5351 binding by 40% in the frontal cortex and 50% in the basal ganglia. Conclusions THK5351, THK5117, and T807 seem to target similar binding sites, but with different affinities, whereas PBB3 seems to target its own binding site. Both THK5117 and T807 demonstrated off-target binding in the hippocampus and putamen with a ten times lower binding affinity to the MAO-B inhibitor deprenyl compared with 3H-THK5351. Electronic supplementary material The online version of this article (doi:10.1186/s13195-017-0325-z) contains supplementary material, which is available to authorized users.
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    Visualization of regional tau deposits using (3)H-THK5117 in Alzheimer brain tissue
    (BioMed Central, 2015-07-02) Lemoine, Laetitia; Saint-Aubert, Laure; Marutle, Amelia; Antoni, Gunnar; Eriksson, Jonas P.; Ghetti, Bernardino; Okamura, Nobuyuki; Nennesmo, Inger; Gillberg, Per-Göran; Nordberg, Agneta; Department of Pathology and Laboratory Medicine, IU School of Medicine
    INTRODUCTION: The accumulation of neurofibrillary tangles, composed of aggregated hyperphosphorylated tau protein, starts spreading early in specific regions in the course of Alzheimer's disease (AD), correlating with the progression of memory dysfunction. The non-invasive imaging of tau could therefore facilitate the early diagnosis of AD, differentiate it from other dementing disorders and allow evaluation of tau immunization therapy outcomes. In this study we characterized the in vitro binding properties of THK5117, a tentative radiotracer for positron emission tomography (PET) imaging of tau brain deposits. RESULTS: Saturation and competition binding studies of (3)H-THK5117 in post-mortem AD brain tissue showed the presence of multiple binding sites. THK5117 binding was significantly higher in hippocampal (p < 0.001) and temporal (p < 0.01) tissue homogenates in AD compared to controls. Autoradiography studies with (3)H-THK5117 was performed on large frozen brain sections from three AD cases who had been followed clinically and earlier undergone in vivo (18)F-FDG PET investigations. The three AD cases showed distinct differences in regional THK5117 binding that were also observed in tau immunohistopathology as well as in clinical presentation. A negative correlation between in vivo (18)F-FDG PET and in vitro (3)H-THK5117 autoradiography was observed in two of the three AD cases. CONCLUSIONS: This study supports that new tau PET tracers will provide further understanding on the role of tau pathology in the diversity of the clinical presentation in AD.