Transmission of Peripheral Blood α-Synuclein Fibrils Exacerbates Synucleinopathy and Neurodegeneration in Parkinson’s Disease via Endothelial LAG3 Endocytosis

Academic Background

Parkinson’s disease (PD) is an age-related neurodegenerative disorder characterized by the abnormal formation and transmission of α-synuclein (α-syn). Recent studies have detected α-syn preformed fibrils (α-syn PFFs) in the serum of PD patients. These peripheral blood α-syn PFFs can cross the blood-brain barrier (BBB) and exacerbate neuronal damage, but the underlying mechanism remains unclear. To better understand the role of peripheral blood α-syn PFFs in PD, researchers constructed mouse models with varying degrees of PD severity and explored the mechanism of endothelial LAG3 (Lymphocyte-activation gene 3) endocytosis in α-syn PFF transmission.

Source of the Paper

This study was conducted by a research team including Qingrui Duan, Qingxi Zhang, and Shuolin Jiang from the Department of Neurology at Guangdong Provincial People’s Hospital, Guangdong Neuroscience Institute, and South China University of Technology School of Medicine. The paper was published on December 10, 2024, in the journal American Journal of Physiology-Cell Physiology, titled “Transmission of peripheral blood α-synuclein fibrils exacerbates synucleinopathy and neurodegeneration in Parkinson’s disease by endothelial LAG3 endocytosis.”

Research Process

1. Construction of Parkinson’s Disease Mouse Models

The research team constructed two types of PD mouse models with varying degrees of severity: mild pathology (A53T only) and severe pathology (A53T + brain fib). The mild model was induced by injecting adeno-associated virus carrying the A53T mutant α-syn gene (AAV-A53T), while the severe model further exacerbated pathological changes through intracerebral injection of α-syn PFFs. Subsequently, researchers observed the impact of intravenous α-syn PFF injections on PD pathology.

2. Endothelial Cell LAG3 Knockout Mouse Model

To investigate the role of endothelial LAG3 in α-syn PFF transmission, the research team used endothelium-specific LAG3 knockout mice (LAG3-ECs-CKO). Through this model, they explored the effect of blocking LAG3 endocytosis on α-syn PFF transmission.

3. Behavioral Testing

The research team conducted several behavioral tests on the mice, including: - Pole Test: Assessing bradykinesia. - Rotarod Test: Evaluating motor coordination. - Cylinder Test: Assessing forelimb use symmetry.

4. Immunohistochemical Analysis

Researchers performed immunohistochemical staining on the brain tissue of the mice to detect dopaminergic neuron loss (TH-positive cells) and pathological α-syn deposition. Additionally, they analyzed astrocyte (GFAP) and microglial (Iba-1) activation through immunofluorescence staining.

5. Western Blot Analysis

The research team used Western blot techniques to detect the expression levels of GFAP, Iba-1, and phosphorylated α-syn (p-α-syn) in midbrain tissues, further verifying the impact of peripheral blood α-syn PFFs on neuroinflammation and pathological deposition.

Key Results

1. Peripheral Blood α-Syn PFFs Exacerbate Motor Deficits

The study found that intravenous injection of α-syn PFFs significantly worsened motor deficits in the mild PD model (A53T only), but this effect was not significant in the severe model (A53T + brain fib). This indicates that the transmission of peripheral blood α-syn PFFs plays a crucial role in the early pathological process of PD.

2. Loss of Dopaminergic Neurons

Intravenous injection of α-syn PFFs significantly exacerbated the loss of dopaminergic neurons in the mild model, but this effect was not significant in the severe model. This result aligns with the behavioral tests, further confirming the critical role of peripheral blood α-syn PFFs in the early stages of PD pathology.

3. Neuroinflammatory Response

The study found that intravenous injection of α-syn PFFs significantly increased the activation of astrocytes and microglia and exacerbated p-α-syn deposition in the mild model. However, this effect was not significant in the severe model. This suggests that the transmission of peripheral blood α-syn PFFs plays a key role in the early pathological process of PD.

4. Blocking LAG3 Endocytosis

By using LAG3-ECs-CKO mice, the study found that blocking LAG3 endocytosis could significantly reduce the transmission of α-syn PFFs and improve motor deficits, dopaminergic neuron loss, and neuroinflammation in PD mice. This indicates that targeting endothelial LAG3 may become a potential strategy for early PD treatment.

Conclusions and Significance

This study reveals the important role of peripheral blood α-syn PFFs in the early pathology of PD and elucidates the mechanism of endothelial LAG3 endocytosis in α-syn PFF transmission. The findings indicate that the transmission of peripheral blood α-syn PFFs can significantly exacerbate the pathological progression of PD, while blocking LAG3 endocytosis can effectively reduce α-syn PFF transmission, improving symptoms and pathological changes in PD. This discovery provides new insights and potential targets for early PD treatment.

Highlights of the Study

1. Innovative Model Construction: The research team constructed PD mouse models with varying degrees of severity and first explored the role of peripheral blood α-syn PFFs in the early pathology of PD.
2. Revealing the LAG3 Mechanism: The study first elucidated the endocytosis role of endothelial LAG3 in α-syn PFF transmission, providing a new target for PD treatment.
3. Multidimensional Validation: The study verified the impact of peripheral blood α-syn PFFs on PD pathology through behavioral testing, immunohistochemical analysis, and Western blot, with highly consistent results.

Other Valuable Information

The research team also discussed other possible mechanisms of α-syn PFF transmission, such as via red blood cell exosomes. Future research can further explore these mechanisms to provide more possibilities for PD treatment.

Through this study, we not only deepen our understanding of the pathological mechanisms of PD but also offer new ideas and potential targets for the treatment of early PD.