Inhibition of nSMase2 Reduces the Transfer of Oligomeric α-Synuclein Irrespective of Hypoxia

Abstract

Recently, extracellular vesicles (EVs), such as exosomes, have been proposed to play an influential role in the cell-to-cell spread of neurodegenerative diseases, including the intercellular transmission of α-synuclein (α-syn). However, the regulation of EV biogenesis and its relation to Parkinson’s disease (PD) is only partially understood. The generation of EVs through the ESCRT-independent pathway depends on the hydrolysis of sphingomyelin by neutral sphingomyelinase 2 (nSMase2) to produce ceramide, which causes the membrane of endosomal multivesicular bodies to bud inward. nSMase2 is sensitive to oxidative stress, a common process in PD brains; however, little is known about the role of sphingomyelin metabolism in the pathogenesis of PD. This is the first study to show that inhibiting nSMase2 decreases the transfer of oligomeric aggregates of α-syn between neuron-like cells. Furthermore, it reduced the accumulation and aggregation of high-molecular-weight α-syn. Hypoxia, as a model of oxidative stress, reduced the levels of nSMase2, but not its enzymatic activity, and significantly altered the lipid composition of cells without affecting EV abundance or the transfer of α-syn. These data show that altering sphingolipids can mitigate the spread of α-syn, even under hypoxic conditions, potentially suppressing PD progression.

Unilateral intranigral administration of β-sitosterol β-D-glucoside triggers pathological α-synuclein spreading and bilateral nigrostriatal dopaminergic neurodegeneration in the rat

“…Notably, the crossed connections of the substantia nigra [25,58] and striatum [44] in the rat can also participate in α-synuclein aggregates transfer to those nuclei of the opposite hemisphere. The stereotaxic BSSG model represents a useful tool to identify the spreading mechanism of pathological α-synuclein and assay new exosomebased therapies [62].…”

Cell-to-Cell Communication in Learning and Memory: From Neuro- and Glio-Transmission to Information Exchange Mediated by Extracellular Vesicles

“…PDDC is both brain penetrant and orally available [306]. Interestingly, inhibition of nSMase2 also decreases the transfer of oligomeric aggregates of α-synuclein into exosomes and the resulting spreading between neurons, thus suggesting that the inhibitors of nSMase2 might be used as new kinds of drugs for the therapy of PD [307].…”

Investigation of the intercellular transmission of α-synuclein, amyloid-β and TDP-43

“…CD63-GFP experiments displayed among the highest amount of transfer ( Figure 14C) and exhibited a high degree of colocalization with full-length TDP-43 ( Figure 15D). Considering these findings along with our groups' previous publications that have demonstrated the transfer of oligomeric Aβ and α-syn via EVs 219,221 , we aimed to investigate whether TDP-43 could be transferred by EVs. From our stably expressing TDP-43 cell lines, we collected and isolated EVs from conditioned media and treated naïve cells with these preparations, but were unable to observe any appreciable transfer of TDP-43, even using 5-fold higher concentration of EVs than described previously 219 ( Figure 16A).…”

“…EVs play an important role in cell to cell communication, as well as the uptake, recycling and release pathways of many types of small molecules. Some of the small molecule cargos mediated by EVs include DNA, mRNA, miRNA, small proteins, and even aggregated proteins in the case of Aβ and α-syn [219][220][221] . In Paper III, we looked at whether TDP-43 could be found in EVs, and if so, whether they could propagate TDP-43 pathology.…”