Synaptosomes: new vesicles for neuronal mitochondrial transplantation

Pasquale Picone,Celeste Caruso Bavisotto,Giacoma Galizzi,Donatella Bulone,Gaetana Porcelli,Marta Di Carlo,Pier Luigi San Biagio,Domenico Nuzzo

doi:10.1186/s12951-020-00748-6

Abstract

BackgroundMitochondrial dysfunction is a critical factor in the onset and progression of neurodegenerative diseases. Recently, mitochondrial transplantation has been advised as an innovative and attractive strategy to transfer and replace damaged mitochondria. Here we propose, for the first time, to use rat brain extracted synaptosomes, a subcellular fraction of isolated synaptic terminal that contains mitochondria, as mitochondrial delivery systems.ResultsSynaptosome preparation was validated by the presence of Synaptophysin and PSD95. Synaptosomes were characterized in terms of dimension, zeta potential, polydispersity index and number of particles/ml. Nile Red or CTX-FITCH labeled synaptosomes were internalized in LAN5 recipient cells by a mechanism involving specific protein–protein interaction, as demonstrated by loss of fusion ability after trypsin treatment and using different cell lines. The loading and release ability of the synaptosomes was proved by the presence of curcumin both into synaptosomes and LAN5 cells. The vitality of mitochondria transferred by Synaptosomes was demonstrated by the presence of Opa1, Fis1 and TOM40 mitochondrial proteins and JC-1 measurements. Further, synaptosomes deliver vital mitochondria into the cytoplasm of neuronal cells as demonstrated by microscopic images, increase of TOM 40, cytochrome c, Hexokinase II mitochondrial proteins, and presence of rat mitochondrial DNA. Finally, by using synaptosomes as a vehicle, healthy mitochondria restored mitochondrial function in cells containing rotenone or CCCp damaged mitochondria.ConclusionsTaken together these results suggest that synaptosomes can be a natural vehicle for the delivery of molecules and organelles to neuronal cells. Further, the replacement of affected mitochondria with healthy ones could be a potential therapy for treating neuronal mitochondrial dysfunction-related diseases.

Highlights

Mitochondrial dysfunction is a critical factor in the onset and progression of neurodegenerative diseases
Some studies in humans report that the administration of highdose combined vitamin E and vitamin C is associated with a slowed progression of Parkinson’s disease (PD)
We evaluated the possibility of replacing Carbonyl cyanide 3- chlorophenylhydrazone (CCCp)- or rotenonedamaged mitochondria in neuronal cells by synaptosomes transplantation

Summary

Introduction

Mitochondrial dysfunction is a critical factor in the onset and progression of neurodegenerative diseases. Mitochondria are dynamic organelles capable of changing size, shape, and position according to the cells’ physiological needs. They move along microtubules within the cell, providing the energy for the different cells’ activities, including the synaptic ones. Studies in vitro reported that insulin could prevent mitochondrial oxidative stress and apoptosis by inhibiting the PI3K/AKT cell survival signaling pathway, to what was observed for antioxidant molecules [12, 13]. Recent evidence has demonstrated that insulin delivery to the brain can be an effective pharmacological therapy for some neurodegenerative pathologies, and the intranasal route can further increase the efficacy and safety of the treatment [14]

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