INTRODUCTION: Parkinson’s Disease is a neurodegenerative disorder affecting nearly 9 million people worldwide. It is characterized by the progressive loss of dopaminergic neurons in the SN/VTA region, leading to motor dysfunction. Aggregation and spreading of misfolded α-synuclein (α-syn) are considered key factors contributing to neuron loss. Mechanisms of α-syn aggregation and its possible clearance pathways are thus intensely investigated.

AIM(S): Our aim was to examine the role of disruption of the endolysosomal pathway (ELP) in pathological α-syn aggregation. Moreover, we aimed to investigate the effect of ghrelin receptor ligands on α-syn aggregation, putatively through modulation of ELP.

METHOD(S): We investigated the disruption of the ELP in an in vitro model of α-syn aggregation induced by α-syn preformed fibrils (PFF) in primary hippocampal neurons using chloroquine (CQ; 5 μM, 10 μM, 12.5 μM) or genetic ablation of lysosomal ion channel TMEM175. Ghrelin receptor agonists were investigated in primary dopaminergic neurons. MK-0677, anamorelin and ghrelin were tested in three concentrations: 3 nM, 10nM, 100 nM. pS129-α-syn-positive aggregates were visualized by immunofluorescence staining combined with either NeuN or tyrosine hydroxylase (TH) labeling, followed by automated imaging and quantification.

RESULTS: CQ dose-dependently increased formation of α-syn aggregates while TMEM175 ablation unexpectedly reduced α-syn accumulation threefold. Furthermore, we observed reduction of α-syn aggregates in neurons treated with MK-0677 and anamorelin.

CONCLUSIONS: The ELP appears to be an important player in modulation of α-syn pathology. However, its mechanism seems complex; ghrelin receptor agonists have potential to reduce α-syn aggregate load in dopaminergic cells.

FINANCIAL SUPPORT: This research was funded by the National Science Centre, Poland (grant no. 2019/35/D/NZ7/03200, Sonata 15).