Evaluation of the PBR/TSPO radioligand [(18)F]DPA-714 in a rat model of focal cerebral ischemia.
Focal cerebral ischemia leads to an inflammatory reaction involving an overexpression of the peripheral benzodiazepine receptor (PBR)/18-kDa translocator protein (TSPO) in the cerebral monocytic lineage (microglia and monocyte) and in astrocytes. Imaging of PBR/TSPO by positron emission tomography (PET) using radiolabeled ligands can document inflammatory processes induced by cerebral ischemia. We performed in vivo PET imaging with [(18)F]DPA-714 to determine the time course of PBR/TSPO expression over several days after induction of cerebral ischemia in rats. In vivo PET imaging showed significant increase in DPA (N,N-diethyl-2-(2-(4-(2-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidin-3-yl)acetamide) uptake on the injured side compared with that in the contralateral area on days 7, 11, 15, and 21 after ischemia; the maximal binding value was reached 11 days after ischemia. In vitro autoradiography confirmed these in vivo results. In vivo and in vitro [(18)F]DPA-714 binding was displaced from the lesion by PK11195 and DPA-714. Immunohistochemistry showed increased PBR/TSPO expression, peaking at day 11 in cells expressing microglia/macrophage antigens in the ischemic area. At later times, a centripetal migration of astrocytes toward the lesion was observed, promoting the formation of an astrocytic scar. These results show that [(18)F]DPA-714 provides accurate quantitative information of the time course of PBR/TSPO expression in experimental stroke.
INSERM U803, Orsay, France.
Abraham
A
Martín
Raphaël
R
Boisgard
Benoit
B
Thézé
Nadja
N
Van Camp
Bertrand
B
Kuhnast
Annelaure
A
Damont
Michael
M
Kassiou
Frédéric
F
Dollé
Bertrand
B
Tavitian
D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D001345:Autoradiography; D002545:Brain Ischemia / Q000000981:diagnostic imaging* / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002452:Cell Count; D003627:Data Interpretation, Statistical; D005462:Fluorine Radioisotopes; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D007249:Inflammation / Q000000981:diagnostic imaging / Q000378:metabolism; D008297:Male; D017628:Microglia / Q000378:metabolism; D015233:Models, Statistical; D049268:Positron-Emission Tomography; D011720:Pyrazoles; D011743:Pyrimidines; D019275:Radiopharmaceuticals; D051381:Rats; D017207:Rats, Sprague-Dawley; D011963:Receptors, GABA-A / Q000378:metabolism*; D020521:Stroke / Q000000981:diagnostic imaging / Q000378:metabolism
D002352:Carrier Proteins; D005462:Fluorine Radioisotopes; C530129:N,N-diethyl-2-(2-(4-(2-fluoroethoxy)phenyl)-5,7-dimethylpyrazolo(1,5-a)pyrimidin-3-yl)acetamide; D011720:Pyrazoles; D011743:Pyrimidines; D019275:Radiopharmaceuticals; D011963:Receptors, GABA-A; C069997:Tspo protein, rat