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Radiosynthesis, In Vivo Biological Evaluation, and Imaging of Brain Lesions with [123I]-CLINME, a New SPECT Tracer for the Translocator Protein.

Mattner F, Quinlivan M, Greguric I, Pham T, Liu X, Jackson T, Berghofer P, Fookes CJ, Dikic B, Gregoire MC, Dolle F, Katsifis A - Dis. Markers (2015)

Bottom Line: The striatum lesion was confirmed and correlated with TSPO expression in astrocytes and activated microglia by immunohistochemistry and autoradiography.Moreover, TSPO changes observed by SPECT imaging were confirmed by immunofluorescence, immunochemistry, and autoradiography.These results indicated that [(123)I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT.

View Article: PubMed Central - PubMed

Affiliation: Life Sciences Division, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia ; Department of Molecular Imaging, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.

ABSTRACT
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. [(123)I]-CLINME was prepared in 70-80% radiochemical yield. The uptake of [(123)I]-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 [(123)I]-CLINME indicated a biodistribution pattern consistent with TPSO distribution and the competition studies with PK11195 and Ro 5-4864 showed that [(123)I]-CLINME is selective for this site. The metabolite study showed that the extractable radioactivity was unchanged [(123)I]-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 [(123)I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT.

No MeSH data available.


Immunohistochemistry for glial fibrillary acidic protein (GFAP, green) and anti-CD11b antibody (Ox42) or neuron-specific nuclear protein (NeuN, both red). The arrows indicate a region identified as the excitotoxic lesion, with increased Ox42 staining and decreased NeuN staining indicating microglial activation and neurodegeneration, respectively. LV = lateral ventricle, CC = corpus callosum.
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fig7: Immunohistochemistry for glial fibrillary acidic protein (GFAP, green) and anti-CD11b antibody (Ox42) or neuron-specific nuclear protein (NeuN, both red). The arrows indicate a region identified as the excitotoxic lesion, with increased Ox42 staining and decreased NeuN staining indicating microglial activation and neurodegeneration, respectively. LV = lateral ventricle, CC = corpus callosum.

Mentions: Immunohistochemistry using primary antibodies targeting astrocytes (GFAP), microglia (Ox42), and neurons (NeuN) demonstrated the presence of the excitotoxic AMPA lesion with a pattern of staining consistent with that reported in the earlier ([11C]-CLINME) study with this same model [31]. Tissue harvested immediately following SPECT imaging stained strongly throughout the imaged contralateral striatum for NeuN. In the medial part of the ipsilateral striatum NeuN staining was still present; however it was almost completely absent centrally. GFAP staining in these animals was present in both hemispheres, though it was moderately increased on the lesioned side, whilst Ox42 staining was barely perceptible in most regions, except in the region where NeuN immunoreactivity was virtually absent (Figure 7).


Radiosynthesis, In Vivo Biological Evaluation, and Imaging of Brain Lesions with [123I]-CLINME, a New SPECT Tracer for the Translocator Protein.

Mattner F, Quinlivan M, Greguric I, Pham T, Liu X, Jackson T, Berghofer P, Fookes CJ, Dikic B, Gregoire MC, Dolle F, Katsifis A - Dis. Markers (2015)

Immunohistochemistry for glial fibrillary acidic protein (GFAP, green) and anti-CD11b antibody (Ox42) or neuron-specific nuclear protein (NeuN, both red). The arrows indicate a region identified as the excitotoxic lesion, with increased Ox42 staining and decreased NeuN staining indicating microglial activation and neurodegeneration, respectively. LV = lateral ventricle, CC = corpus callosum.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4496498&req=5

fig7: Immunohistochemistry for glial fibrillary acidic protein (GFAP, green) and anti-CD11b antibody (Ox42) or neuron-specific nuclear protein (NeuN, both red). The arrows indicate a region identified as the excitotoxic lesion, with increased Ox42 staining and decreased NeuN staining indicating microglial activation and neurodegeneration, respectively. LV = lateral ventricle, CC = corpus callosum.
Mentions: Immunohistochemistry using primary antibodies targeting astrocytes (GFAP), microglia (Ox42), and neurons (NeuN) demonstrated the presence of the excitotoxic AMPA lesion with a pattern of staining consistent with that reported in the earlier ([11C]-CLINME) study with this same model [31]. Tissue harvested immediately following SPECT imaging stained strongly throughout the imaged contralateral striatum for NeuN. In the medial part of the ipsilateral striatum NeuN staining was still present; however it was almost completely absent centrally. GFAP staining in these animals was present in both hemispheres, though it was moderately increased on the lesioned side, whilst Ox42 staining was barely perceptible in most regions, except in the region where NeuN immunoreactivity was virtually absent (Figure 7).

Bottom Line: The striatum lesion was confirmed and correlated with TSPO expression in astrocytes and activated microglia by immunohistochemistry and autoradiography.Moreover, TSPO changes observed by SPECT imaging were confirmed by immunofluorescence, immunochemistry, and autoradiography.These results indicated that [(123)I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT.

View Article: PubMed Central - PubMed

Affiliation: Life Sciences Division, Australian Nuclear Science and Technology Organisation, New Illawarra Road, Lucas Heights, NSW 2234, Australia ; Department of Molecular Imaging, Royal Prince Alfred Hospital, Camperdown, NSW 2050, Australia.

ABSTRACT
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. [(123)I]-CLINME was prepared in 70-80% radiochemical yield. The uptake of [(123)I]-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 [(123)I]-CLINME indicated a biodistribution pattern consistent with TPSO distribution and the competition studies with PK11195 and Ro 5-4864 showed that [(123)I]-CLINME is selective for this site. The metabolite study showed that the extractable radioactivity was unchanged [(123)I]-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 [(123)I]-CLINME is a promising candidate for the quantification and visualization of TPSO expression in activated astroglia using SPECT.

No MeSH data available.