• A2A adenosine antagonists
• Fluorescence
• Molecula Probes
• neuroprotection
• Radioligands
• TSPO

The 18 kDa Translocator Protein (TSPO) is a mitochondrial protein whose basal density is altered in several diseases, with the result that the evaluation of its expression levels by means of molecular imaging techniques represents a promising diagnostic approach. A wide number of N,N-dialkyl-(2-phenylindol-3-yl)glyoxylamides have been studied as potent and selective TSPO ligands exhibiting Ki values in the nanomolar/subnanomolar range, and stimulating steroid biosynthesis in rat C6 glioma cells to an extent similar to, or higher than that of classical TSPO ligands, such as PK 11195, Ro 5-4864 and alpidem. Starting from these derivatives, in this PhD work have been designed novel TSPO irreversible ligands bearing an electrophilic isothiocyanato group together with an irreversible NBD-fluorescent probe . The TSPO affinity of the new irreversible ligands was measured on rat tissue homogenates by [3H]Ro 5-4864 radiobinding kinetic assays, all compounds showing high affinities for the target protein. In addition with the aim to further refine the TSPO pharmacophore/topological model and to investigate the role of the 1-NH indole in the binding of these ligands to the TSPO, a novel series of N1-methylindole derivatives were synthesized. Within this series, the ligand N,N-di-n-propyl-(N1-methyl-2-(4’-nitrophenyl)indol-3yl)glyoxylamide ([11C]-29), featuring the best combination of affinity and lipophilicity, was labelled with carbon-11 for evaluation with positron emission tomography (PET) in monkey. After intravenous injection, [11C]-29 entered brain to give a high proportion of TSPO-specific binding. These findings augurs well for the future application of [11C]29 in humans. [11C]29 represents a promising new chemotypes for developing novel TSPO radioligands as biomarkers of neuroinflammation.

Adenosine is a physiological nucleoside which plays an important role in many patho-physiological conditions in the central nervous system (CNS), as well as in peripheral organs and tissues through modulation of specific membrane G protein-coupled receptors (ARs), currently classified into A1, A2A, A2B, and A3 subtypes. A2A ARs occur mainly on neurons in the striatum and on cholinergic interneurons, but they are also found in the nucleus accumbens, olfactory tubercle, hippocampus and cerebral cortex. Recent evidences showed that A2A ARs may modulate a number of cellular processes affecting neuronal cell death in a broad spectrum of brain injury. A2A ARs resulted up-regulated in noxious brain conditions and their blockade confers robust brain neuroprotection. As this effect is exerted without observable peripheral effects, there is an increasing interest in the development of selective A2A AR antagonists as novel protective agents in neurodegenerative diseases. In recent years, we have described a series of 3-aryl-[1,2,4]triazino[4,3-a]benzimidazol-4(10H)-ones (ATBIs) as potent adenosine receptors antagonists. In this PhD work, we have synthesized a novel series of ligands featuring modified substituents at the 10 position, combined with an appropriate aromatic ring at the 3-position. Synthesis, biological evaluation and structure-activity relationships for these new derivatives ATBI will be presented.
Finally, the most promising A2A AR ATBI antagonist was evaluated for its neuroprotective effect on PC12 cells treated with dopamine neurotoxins: MPP+ or methamphetamine. We found a neuroprotective effect consisting of full prevention of neurotoxin-induced cell loss, as measured by combining a variety of staining techniques. These latter results, which were confirmed by combining neurotoxic models, each owing a different mechanism of action, offer a promising perspective for such a compound as a valuable tool to protect dopamine neurons.