title: Changes in Binding of [(123)I]CLINDE, a High-Affinity Translocator Protein 18 kDa (TSPO) Selective Radioligand in a Rat Model of Traumatic Brain Injury.
abstract: After traumatic brain injury (TBI), secondary injuries develop, including neuroinflammatory processes that contribute to long-lasting impairments. These secondary injuries represent potential targets for treatment and diagnostics. The translocator protein 18 kDa (TSPO) is expressed in activated microglia cells and upregulated in response to brain injury and therefore a potential biomarker of the neuroinflammatory processes. Second-generation radioligands of TSPO, such as [(123)I]CLINDE, have a higher signal-to-noise ratio as the prototype ligand PK11195. [(123)I]CLINDE has been employed in human studies using single-photon emission computed tomography to image the neuroinflammatory response after stroke. In this study, we used the same tracer in a rat model of TBI to determine changes in TSPO expression. Adult Sprague-Dawley rats were subjected to moderate controlled cortical impact injury and sacrificed at 6, 24, 72 h and 28 days post surgery. TSPO expression was assessed in brain sections employing [(123)I]CLINDE in vitro autoradiography. From 24 h to 28 days post surgery, injured animals exhibited a marked and time-dependent increase in [(123)I]CLINDE binding in the ipsilateral motor, somatosensory and parietal cortex, as well as in the hippocampus and thalamus. Interestingly, binding was also significantly elevated in the contralateral M1 motor cortex following TBI. Craniotomy without TBI caused a less marked increase in [(123)I]CLINDE binding, restricted to the ipsilateral hemisphere. Radioligand binding was consistent with an increase in TSPO mRNA expression and CD11b immunoreactivity at the contusion site. This study demonstrates the applicability of [(123)I]CLINDE for detailed regional and quantitative assessment of glial activity in experimental models of TBI.
authors.affiliation: Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.
authors.forename: Cornelius K
authors.initials: CK
authors.lastname: Donat
authors.affiliation: Department of Neurosurgery, University of Leipzig, Leipzig, Germany.
authors.forename: Khaled
authors.initials: K
authors.lastname: Gaber
authors.affiliation: Department of Neurosurgery, University of Leipzig, Leipzig, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Meixensberger
authors.affiliation: Department of Neuroradiopharmaceuticals, Research Site Leipzig, Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Permoserstrasse 15, 04318, Leipzig, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Brust
authors.affiliation: Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.|Epilepsy Clinic, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.
authors.forename: Lars H
authors.initials: LH
authors.lastname: Pinborg
authors.affiliation: Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark.
authors.forename: Henrik H
authors.initials: HH
authors.lastname: Hansen
authors.affiliation: Neurobiology Research Unit, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, 2100, Copenhagen, Denmark. jens.mikkelsen@nru.dk.
authors.forename: Jens D
authors.initials: JD
authors.lastname: Mikkelsen
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007456:Iodine Isotopes; D019275:Radiopharmaceuticals / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018079:Receptors, GABA / Q000235:genetics* / Q000378:metabolism*; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D007456:Iodine Isotopes; D019275:Radiopharmaceuticals; D018079:Receptors, GABA; C499229:TSPO protein, human
keywords: Microglia; Neuroinflammation; TSPO; Translocator protein 18 kDa; Traumatic brain injury