Synthesis and In Vitro and In Vivo Evaluation of [3H]LRRK2-IN-1 as a Novel Radioligand for LRRK2.
Mol Imaging Biol
; 19(6): 837-845, 2017 12.
Article
em En
| MEDLINE
| ID: mdl-28289968
ABSTRACT
PURPOSE:
LRRK2 (leucine-rich repeat kinase 2) has recently been proven to be a promising drug target for Parkinson's disease (PD) due to an apparent enhanced activity caused by mutations associated with familial PD. To date, there have been no reports in which a LRRK2 inhibitor has been radiolabeled and used for in in vitro or in vivo studies of LRRK2. In the present study, we radiolabeled the LRRK2 ligand, LRRK-IN-1, for the purposes of performing in vitro (IC50, K d , B max, autoradiography) and in vivo (biodistribution, and blocking experiments) evaluations in rodents and human striatum tissues. PROCEDURES [3H]LRRK2-IN-1 was prepared with high radiochemical purity (>99 %) and a specific activity of 41 Ci/mmol via tritium/hydrogen (T/H) exchange using Crabtree's catalyst. For IC50, K d , and B max determination, LRRK2-IN-1 was used as a competing drug for nonspecific binding assessment. The specific binding of the tracer was further evaluated via an in vivo blocking study in mice with a potent LRRK2 inhibitor, Pf-06447475.RESULTS:
In vitro binding studies demonstrated a saturable binding site for [3H]LRRK2-IN-1 in rat kidney, rat brain striatum and human brain striatum with K d of 26 ± 3 and 43 ± 8, 48 ± 2 nM, respectively. In rat, the density of LRRK2 binding sites (B max) was higher in kidney (6.4 ± 0.04 pmol/mg) than in brain (2.5 ± 0.03 pmol/mg), however, in human brain striatum, the B max was 0.73 ± 0.01 pmol/mg protein. Autoradiography imaging in striatum of rat and human brain tissues gave results consistent with binding studies. In in vivo biodistribution and blocking studies in mice, co-administration with Pf-06447475 (10 mg/kg) reduced the uptake of [3H]LRRK2-IN-1 (%ID/g) by 50-60% in the kidney or brain.CONCLUSION:
The high LRRK2 brain density observed in our study suggests the feasibility for positron emission tomography imaging of LRRK2 (a potential target) with radioligands of higher affinity and specificity.Palavras-chave
Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Pirimidinas
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Trítio
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Benzodiazepinonas
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Compostos Radiofarmacêuticos
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Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina
Limite:
Animals
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Humans
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Male
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article