TY - JOUR
T1 - Novel Thienopyrimidine-Based PET Tracers for P2Y12Receptor Imaging in the Brain
AU - van der Wildt, Berend
AU - Janssen, Bieneke
AU - Pekošak, Aleksandra
AU - Stéen, E. Johanna L.
AU - Schuit, Robert C.
AU - Kooijman, Esther J. M.
AU - Beaino, Wissam
AU - Vugts, Danielle J.
AU - Windhorst, Albert D.
N1 - Funding Information: The research leading to these results has received funding from the Michael J. Fox Foundation (Triple-P, grant number 12274, B.J. and A.P.), the European Union’s Horizon 2020 research and innovation program as a Marie Sklodowska–Curie Individual Fellowship under grant agreement no. 892572 (E.J.L.S), and NWO (Dutch Research Council) as a NWO-VENI grant under grant number VI.Veni.192.229 (B.v.d.W). Publisher Copyright: © 2021 The Authors. Published by American Chemical Society.
PY - 2021/12/1
Y1 - 2021/12/1
N2 - The P2Y12 receptor (P2Y12R) is uniquely expressed on microglia in the brain, and its expression level directly depends on the microglial activation state. Therefore, P2Y12R provides a promising imaging marker for distinguishing the pro- and anti-inflammatory microglial phenotypes, both of which play crucial roles in neuroinflammatory diseases. In this study, three P2Y12R antagonists were selected from the literature, radiolabeled with carbon-11 or fluorine-18, and evaluated in healthy Wistar rats. Brain imaging was performed with and without blocking of efflux transporters P-glycoprotein and breast cancer resistance protein using tariquidar. Low brain uptake in healthy rats was observed for all tracers at baseline conditions, whereas blocking of efflux transporters resulted in a strong (6-7 fold) increase in brain uptake for both of them. Binding of the most promising tracer, [18F]3, was further evaluated by in vitro autoradiography on rat brain sections, ex vivo metabolite studies, and in vivo P2Y12R blocking studies. In vitro binding of [18F]3 on rat brain sections indicated high P2Y12R targeting with approximately 70% selective and specific binding. At 60 min post-injection, over 95% of radioactivity in the brain accounted for an intact tracer. In blood plasma, still 40% intact tracer was found, and formed metabolites did not enter the brain. A moderate P2Y12R blocking effect was observed in vivo by positron emission tomography (PET) imaging with [18F]3 (p = 0.04). To conclude, three potential P2Y12R PET tracers were obtained and analyzed for P2Y12R targeting in the brain. Unfortunately, the brain uptake appeared low. Future work will focus on the design of P2Y12R inhibitors with improved physicochemical characteristics to reduce efflux transport and increase brain penetration.
AB - The P2Y12 receptor (P2Y12R) is uniquely expressed on microglia in the brain, and its expression level directly depends on the microglial activation state. Therefore, P2Y12R provides a promising imaging marker for distinguishing the pro- and anti-inflammatory microglial phenotypes, both of which play crucial roles in neuroinflammatory diseases. In this study, three P2Y12R antagonists were selected from the literature, radiolabeled with carbon-11 or fluorine-18, and evaluated in healthy Wistar rats. Brain imaging was performed with and without blocking of efflux transporters P-glycoprotein and breast cancer resistance protein using tariquidar. Low brain uptake in healthy rats was observed for all tracers at baseline conditions, whereas blocking of efflux transporters resulted in a strong (6-7 fold) increase in brain uptake for both of them. Binding of the most promising tracer, [18F]3, was further evaluated by in vitro autoradiography on rat brain sections, ex vivo metabolite studies, and in vivo P2Y12R blocking studies. In vitro binding of [18F]3 on rat brain sections indicated high P2Y12R targeting with approximately 70% selective and specific binding. At 60 min post-injection, over 95% of radioactivity in the brain accounted for an intact tracer. In blood plasma, still 40% intact tracer was found, and formed metabolites did not enter the brain. A moderate P2Y12R blocking effect was observed in vivo by positron emission tomography (PET) imaging with [18F]3 (p = 0.04). To conclude, three potential P2Y12R PET tracers were obtained and analyzed for P2Y12R targeting in the brain. Unfortunately, the brain uptake appeared low. Future work will focus on the design of P2Y12R inhibitors with improved physicochemical characteristics to reduce efflux transport and increase brain penetration.
KW - P2Y receptor (P2Y R)
KW - PET imaging
KW - anti-inflammatory phenotype
KW - microglia
KW - neuroinflammation
UR - http://www.scopus.com/inward/record.url?scp=85119619316&partnerID=8YFLogxK
U2 - https://doi.org/10.1021/acschemneuro.1c00641
DO - https://doi.org/10.1021/acschemneuro.1c00641
M3 - Article
C2 - 34757711
SN - 1948-7193
VL - 12
SP - 4465
EP - 4474
JO - ACS Chemical Neuroscience
JF - ACS Chemical Neuroscience
IS - 23
ER -