Imaging Biomarkers of Neuroinflammations: TSPO Agents

Positron emission tomography (PET) imaging allows the in vivo measurements of different molecular targets, such as functional markers of neurodegeneration (glucose metabolism), markers for pathological proteins (amyloid, tau, and synuclein aggregates), and also neuroinflammation, providing evidence for the pathophysiology in neurodegenerative diseases. The 18 kDa translocator protein (TSPO), also called peripheral benzodiazepine-binding site (PBR), is a mitochondrial protein expressed by immune competent cells (macrophages, microglia, astrocytes) and markedly increased in response to cellular injuries. (R)-1-(2-chlorophenyl)-N-11C-methyl-N-(1-methylpropyl)-3-isoquinoline carboxamide ([11C](R)-PK11195) was the first TSPO PET radioligand developed to estimate neuroinflammatory changes in several CNS disorders. This chapter will describe the current knowledge on technical procedures of radio-synthesis, features of biodistribution, and current research on potential clinical application of TSPO PET as a radiopharmaceutical agent able to assess the neuroinflammation in neurodegenerative diseases.