In vitro characterization of [3H]VAT in cells, animal and human brain tissues for vesicular acetylcholine transporter

Qianwa Liang, Sumit Joshi, Hui Liu, Yanbo Yu, Haiyang Zhao, Tammie L.S. Benzinger, Joel S. Perlmutter, Zhude Tu

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Vesicular acetylcholine transporter plays a crucial role in the cholinergic system, and its alterations is implicated in several neurodegenerative disorders. We recently developed a PET imaging tracer [18F]VAT to target VAChT in vivo with high affinity and selectivity. Here we report in vitro characterization of [3H]VAT, a tritiated counterpart of [18F]VAT. Using human VAChT-rich cell membrane extracts, a saturated binding curve was obtained for [3H]VAT with Kd = 6.5 nM and Bmax = 22.89 pmol/mg protein. In the [3H]VAT competition-binding assay with a panel of CNS ligands, binding inhibition of [3H]VAT was observed using VAChT ligands, the Ki values ranged from 5.41 to 33.3 nM. No inhibition was detected using a panel of other CNS ligands. In vitro [3H]VAT autoradiography of rat brain sections showed strong signals in the striatum, moderate to high signals in vermis, thalamus, cortex, and hippocampus, and weak signals in cerebellum. Strong [3H]VAT ARG signals were also observed from striatal sections of normal nonhuman primates and human brains. Competitive ARG study with human striatal sections demonstrated strong ARG signals of [3H]VAT in caudate and putamen were blocked significantly by either VAChT ligand TZ659 or (−)-vesamicol, but not by the σ1 receptor ligand Yun-122. ARG study also indicated that signal in the striatal sections from PSP human brains was lower than normal human brains. These data provide solid evidence supporting [18F]VAT as a suitable PET radiotracer for quantitative assessment of VAChT levels in vivo.

Original languageEnglish
Article number174556
JournalEuropean Journal of Pharmacology
Volume911
DOIs
StatePublished - Nov 15 2021

Keywords

  • Autoradiography
  • Binding assay
  • Progressive supranuclear palsy
  • Radioligand
  • Striatum
  • Vesicular acetylcholine transporter

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