Front.aging neurosci-decreased exosomal acetylcholinesterase activity in plasma in patients with Parkinson's disease

The exosome acetylcholinesterase in patients with Parkinson's disease can be used as a biomarker

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Parkinson's disease (PD)

One of the pathophysiology features of Parkinson's disease (PD) is the formation of Lewy bodies in the brain, consisting mainly of
insoluble aggregates such as α-synuclein (α-syn).
Therefore, α-syn has been extensively studied as a potential biomarker and indicator of PD disease progression.

。

However, the lack of reliable PD biofluid markers limits the monitoring
of disease progression or response to treatment.
There is increasing evidence of an association
between the production of the dopamine system of the substantia nigra striatum and cholinergic denervation in patients with Parkinson's disease.
Exosomes are extracellular vesicles produced by a variety of cell types and contain a variety of molecular components such as proteins, lipids, and RNA
.

In recent years, exosome biomarkers have been studied to explore pathological and diagnostic methods
of neurodegenerative diseases.
The research team from the Seoul Veterans Health Service Medical Center in South Korea simultaneously tested the chromosomal markers of acetylcholinesterase (AChE) and α-syn, isolated exosomes from plasma samples from PD patients and healthy control group (HC) by ultracentrifugation, measured exosome AChE activity and α-syn levels, and explored their correlation
with clinical parameters and their biomarkers.

Experimental results

1.
The demographic and clinical characteristics of the participants are shown in
Table 1.

There were gender differences between groups, and there was no difference
in MMSE scores between groups.
All patients with PD underwent FP-CIT PET; All patients present with decreased
dopamine transport activity.
In the HC group, 7 people underwent FP-IT PET.

Table 1 Demographics and clinical characteristics of participants

2.
Analysis of plasma exosome biomarkers in clinical specimens

Exosomes are separated by ultracentrifugation and confirmed by transmission electron microscopy and visualization of nanoparticle tracking analysis (Figure 1A).

By nanoparticle tracking analysis, exosomes are approximately 140 nm (Figure 1B).

Western Blot showed that exosomes were enriched in Alix but not in GM130 (Figure 1C).

No differences
in exosome size and concentration were found between PD and HC.
The total amount of protein in isolated exosomes may vary from individual to individual; The total exosome protein content was therefore measured and used for the normalization of the
two biomarkers.
Total exosome protein levels are highly correlated with
their concentration and acetylcholinesterase activity.

Fig.
1 Characteristics of exosomes separated by ultracentrifugation

There was no difference in exosome α-syn concentrations between the two groups (Figure 2A).

Compared with the HC group (4.
7%), exosome AChE activity was significantly reduced (3.
9%) in the PD group (Figure 2B).

ROC curve analysis showed that exosomal enzyme activity showed moderate levels in PD diagnosis (Figure 2C).

When the cut-off value is 4.
05, the sensitivity and specificity are 61.
8% and 79.
3%,
respectively.

Fig.
2 Evaluation of exosome biomarkers

3.
The relationship between exosomal AChE activity and PD progression

Next, the authors analyzed the correlation between exosomal AChE activity and disease severity in patients with Parkinson's disease to explore its clinical significance
.
The course of the disease is moderately negatively correlated with chromosome AChE activity (Figure 3C).

There was no significant correlation between MMSE scores and AChE inhibitors (including donepezil, galantamine) and in vitro activity (Figure 3D, E).

Fig.
3 Scatter plot and clinical data of exogenous acetylcholinesterase activity

Discussion

Studies have shown that the activity of exosomes acetylcholinesterase is significantly reduced
in the PD group compared with the HC group.
In addition, exosomal AChE activity was significantly negatively correlated
with disease severity.
Previous studies have examined cholinergic deficiencies
in Parkinson's patients through histopathology and molecular imaging.

A decrease in the number of pre-foot pre-foot cholinergic neurons has been reported in patients with Parkinson's disease, and PET studies have shown loss
of function of the occipital corticolinergic nerves in patients with Parkinson's disease and Parkinson's disease and dementia.

Taken together, these studies suggest the presence of cholinergic dysfunction in the central and peripheral nervous systems in patients with Parkinson's disease, which supports the decrease in exosomal acetylcholinesterase activity found in this study, whose close association with disease severity highlights the importance
of acetylcholinesterase in the pathophysiology of Parkinson's disease.

Exosomal AChE activity is a single diagnostic marker for PD, and it may have the potential to further elucidate the pathophysiology of PD, but the reason for the decrease in AChE activity in patients with Parkinson's disease remains unclear
.

One hypothesis is that decreased production and secretion of exosomal acetylcholinesterase coincides with α-syn to induce apoptosis and neuronal death
.
Another hypothesis is that there is a balance between acetylcholine (ACh) and dopamine (DA), and this balance is the main feature of
motor control.
The lack of DA in PD pathology can trigger a severe tilt of balance in kinetics, leading to motor and cognitive impairment, as well as imbalances
in the cholinergic system.

In the current study, it can be hypothesized that the imbalance between DA and ACh exacerbates the decrease
in AchE activity through the depletion of DA.

The study has certain limitations, the number of subjects is limited, and there are sex differences, so the study should expand the sample size and balance the gender differences
.
Exosomes are released from cells such as neurons, blood cells, and epithelial cells, and there are no exosomes of specific origin for extracting organs, therefore, follow-up studies should prioritize the isolation of neuron-derived exosomes to study the activity
of acetylcholinesterase.

In summary, the study confirmed that AChE activity in PD patients was lower than in the healthy group, and that AChE activity in the PD group was significantly negatively correlated
with disease severity.
These results suggest that plasma exosome AChE can play an important role
in the occurrence and progression of PD as a biomarker for monitoring disease progression.
Exosomal enzyme activity shows moderate diagnostic performance, and the application of advanced exosome isolation technology can improve diagnostic performance and facilitate the development of diagnostic and therapeutic tools
.