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Updated: Apr 18, 2026

Technique for Intranasal Administration of α-Synuclein Aggregates
Published on: November 8, 2024
The serotonin aldehyde, 5-HIAL, oligomerizes alpha-synuclein.
Yunden Jinsmaa1, Adele Cooney1, Patricia Sullivan1
1Clinical Neurocardiology Section, Clinical Neurosciences Program, Division of Intramural Research, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892 USA.
Serotonin
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Alpha-synuclein oligomers are implicated in Parkinson's disease (PD) pathogenesis.
- 3,4-dihydroxyphenylacetaldehyde (DOPAL), a dopamine metabolite, is known to oligomerize alpha-synuclein.
- The role of 5-hydroxyindoleacetaldehyde (5-HIAL), a serotonin metabolite, in alpha-synuclein oligomerization was previously unknown.
Purpose of the Study:
- To investigate whether 5-HIAL can oligomerize alpha-synuclein in vitro and in cell models.
- To compare the oligomerization potential of 5-HIAL with DOPAL.
- To explore the implications for serotonergic neuron loss in PD.
Main Methods:
- In vitro incubation of alpha-synuclein with serotonin or dopamine in the presence of monoamine oxidase-A (MAO-A) to generate 5-HIAL or DOPAL.
- Assessment of alpha-synuclein oligomerization in PC12 cells overexpressing alpha-synuclein, treated with levodopa or 5-hydroxytryptophan.
- Quantification of alpha-synuclein oligomers using western blotting and assessment of monoamine aldehyde mediation using the MAO inhibitor pargyline.
Main Results:
- Both dopamine and serotonin incubation with MAO-A strongly induced alpha-synuclein oligomerization (>10-fold increase), which was blocked by pargyline.
- In PC12 cells, levodopa and 5-hydroxytryptophan treatment resulted in pargyline-sensitive alpha-synuclein oligomerization.
- 5-HIAL was demonstrated to oligomerize alpha-synuclein in vitro and in PC12 cells, similar to DOPAL.
Conclusions:
- 5-hydroxyindoleacetaldehyde (5-HIAL) oligomerizes alpha-synuclein, mirroring the effect of DOPAL.
- This finding provides a potential mechanism for the observed loss of serotonergic neurons in Parkinson's disease.
- Monoamine aldehydes play a significant role in alpha-synuclein aggregation relevant to PD.
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