Novel PREP ligand, HUP-46, ameliorates behavioral deficits in an alpha-synuclein based Parkinson's disease model

Parkinson's disease (PD) is the most common neurodegenerative movement disorder, and current therapies cannot stop or delay the neuronal death. Therefore, novel therapies having disease-modifying effects are urgently needed. Small-molecular ligands for prolyl oligopeptidase (PREP) have shown disease-modifying effects in various α-synuclein (aSyn) based PD mouse models. We have recently developed novel, more effective PREP ligand series that aim to regulate PREP-related protein-protein interactions, such as with aSyn and protein phosphatase 2 A (PP2A). The most promising novel PREP ligand, HUP-46, was now tested in a PD mouse model based on unilateral AAV-A53T-aSyn virus vector injection on substantia nigra. Our results show that HUP-46, but not reference PREP inhibitor, KYP-2047, was able to restore the behavioral deficit caused by the virus vector injection in the cylinder test. 4-week treatment with PREP ligands reduced the soluble and insoluble aSyn oligomers, and iNOS-positive microglial cells in the substantia nigra. When the effect on microglial activity was further studied in the BV2 microglial cell culture activated by lipopolysaccharide and interferon-γ, the results revealed that HUP-46 but not KYP-2047 significantly reduced TNF-α production. Analysis revealed that HUP-46 reduced p38 phosphorylation and restored autophagic flux in the activated BV2 cells that may contribute to the reduced pro-inflammatory activation of BV2 cells. Taken together, our results suggest that novel PREP ligands, such as HUP-46, can have disease-modifying effect on PD mouse model.