Radiosynthesis, in vivo biological evaluation, and imaging of brain lesions with [123I]-CLINME, a new SPECT tracer for the translocator protein

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Hindawi Publishing Corporation
The high affinity translocator protein (TSPO) ligand 6-chloro-2-(4′-iodophenyl)-3-(N,N-methylethyl)imidazo[1,2-a]pyridine-3-acetamide (CLINME) was radiolabelled with iodine-123 and assessed for its sensitivity for the TSPO in rodents. Moreover neuroinflammatory changes on a unilateral excitotoxic lesion rat model were detected using SPECT imaging. [123I]-CLINME was prepared in 70–80% radiochemical yield. The uptake of [123I]-CLINME was evaluated in rats by biodistribution, competition, and metabolite studies. The unilateral excitotoxic lesion was performed by injection of α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid unilaterally into the striatum. The striatum lesion was confirmed and correlated with TSPO expression in astrocytes and activated microglia by immunohistochemistry and autoradiography. In vivo studies with [123I]-CLINME indicated a biodistribution pattern consistent with TPSO distribution and the competition studies with PK11195 and Ro 5-4864 showed that [123I]-CLINME is selective for this site. The metabolite study showed that the extractable radioactivity was unchanged [123I]-CLINME in organs which expresses TSPO. SPECT/CT imaging on the unilateral excitotoxic lesion indicated that the mean ratio uptake in striatum (lesion : nonlesion) was 2.2. Moreover, TSPO changes observed by SPECT imaging were confirmed by immunofluorescence, immunochemistry, and autoradiography. These results indicated that [123I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT. © 2015 F. Mattner et al.
In vivo, Brain, Proteins, Single photon emission computed tomography, Translocation, Rats, Receptors
Mattner, F., Quinlivan, M., Greguric, I., Pham, T., Liu, X., Jackson, T., Berghofer, P., Fookes, C. J. R., Dikic, B., Grégoire, M. C., Dollé, F. & Katsifis, A. (2015). Radiosynthesis, in vivo biological evaluation, and imaging of brain Lesions with [123I]-CLINME, a new SPECT tracer for the translocator protein. Disease Markers, 2015, 729698. doi:10.1155/2015/729698