Abstract
Non-invasive determination of amyloid-β peptide (Aβ) deposition has important significance for early diagnosis and medical intervention for Alzheimer’s disease (AD). In the present study, we investigated the availability of radiolabeled DRM106 (123/125I-DRM106), a compound with sufficient affinity for the synthesis of human Aβ fibrils and satisfactory metabolic stability, as a single photon emission computed tomography (SPECT) ligand in living brains. Methods: The sensitivity of 125I-DRM106 for detecting Aβ deposition was compared with 125I-IMPY, a well-known amyloid SPECT ligand, by ex vivo autoradiographic analyses in 18-month-old amyloid precursor protein transgenic (Tg) mice. To verify the sensitivity and quantitation of radiolabeled DRM106 for in vivo imaging, we compared the detectability of Aβ plaques with 123I-DRM106 and a well-known amyloid positron emission tomography (PET) agent, 11C-labeled Pittsburgh compound B (11C-PiB), in 29-month-old Tg mice and age-matched non-Tg littermates. Additionally, we compared the binding characteristics of 125I-DRM106 with those of 11C-PiB and 11C-PBB3, which selectively bind to Aβ plaques and preferentially to tau aggregates, respectively, in postmortem AD brain sections. Results: Ex vivo autoradiographic analysis showed that measurement with 125I-DRM106 has higher sensitivity for detecting Aβ accumulation than with 125I-IMPY in Tg mice. SPECT imaging with 123I-DRM106 also successfully detected Aβ deposition in living aged Tg mice, furthermore showing strong correlation(R = 0.95, P < 0.01) in quantitative analysis for Aβ plaque detection by PET imaging with 11C-PiB, implying that sensitivity and quantitation of SPECT imaging with 123I-DRM106 are almost as good as 11C-PiB-PET for the detectability of Aβ deposition. Further, the addition of non-radiolabeled DRM106 fully blocked the binding of 125I-DRM106 and 11C-PiB, but not 11C-PBB3, to AD brain sections, and 125I-DRM106 showed a lower binding ratio of the diffuse plaque-rich lateral temporal cortex to the dense cored/neuritic plaque-rich hippocampal CA1 area, compared to 11C-PiB. Conclusion: All of these data demonstrated the high potential of 123I-DRM106 for amyloid imaging in preclinical and clinical application, and it might more preferentially detect dense-cored/neuritic amyloid deposition, which is expected to be closely associated with neuropathological changes of AD.
- Animal Imaging
- Neurology
- SPECT
- Alzheimers disease (AD)
- Amyloid imaging
- Amyloid precursor protein (APP) transgenic mouse
- DRM106
- Single photon emission computed tomography (SPECT)
- Copyright © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.