Cardiac Alpha-Synuclein Is Present in Alpha-Synucleinopathies

Intact microdissection of stellate ganglia in a Parkinson's disease model reveals aggregation of mutant human α-synuclein in their cell bodies

Cardiac dysautonomia plays an important role in understanding Parkinson's disease (PD), with recent studies highlighting the presence of α-synuclein in cardiac tissue. We hypothesise that sympathetic dysregulation observed in PD may involve pathological changes caused by α-synuclein in stellate ganglia (SG). This study aimed to investigate α-synucleinopathy in SG of the genetic PD murine animal model. Mice overexpressing Ala30Pro (A30P) mutant α-synuclein were used. We here demonstrate a technique for meticulously dissecting SG. The collected SG from the transgenic mice were immunolabelled with neuronal markers, A30P human mutant α-synuclein and anti-α-synuclein aggregates. A30P mutant α-synuclein protein was expressed in the sympathetic neuronal (tyrosine hydroxylase (TH)-positive) cell bodies. Approximately 27% of the TH-positive cell bodies expressed the A30P mutant α-synuclein protein. The mutant protein was densely localised at the cardiopulmonary pole of the SG. Additionally, we observed that the A30P mutant protein formed fibril aggregation in the SG. Our findings suggest that α-synucleinopathy in the PD animal model can affect the sympathetic autonomic nervous system, providing insight for further research into targeting α-synuclein pathology in the SG as a potential link between cardiac dysautonomia and PD.

High prevalence of atrial conduction abnormalities in Lewy body disease - a marker of cardiac complications?

Increasing evidence suggests that Lewy body disease (LBD) is associated with clinically important cardiac complications, including sick sinus syndrome, atrial fibrillation and sudden cardiac death. The high prevalence of sick sinus syndrome and atrial fibrillation in LBD suggests the presence of disease-related atrial conduction disorders. To explore whether LBD is associated with atrial conduction disorders, electrocardiographic (ECG) P wave parameters were analyzed in a cohort of LBD patients (n = 74), using age-matched Alzheimer's disease (AD) patients (n = 25) as controls. P wave terminal force in V1 and P wave duration were found to be significantly greater in the LBD group than in the AD group. In addition, 43 (58%) individuals in the LBD exhibited pathological P wave terminal force (> 4000 µV*ms) vs 3 (12%) in the AD group, and 60 (81%) in the LBD group exhibited pathological P wave duration (≥ 120 ms), vs 13 (52%) in the AD group. The difference could not be explained by atrial fibrillation or atrial enlargement on echocardiogram. The clinical significance of pathological P wave parameters in LBD is unknown, but their presence suggests an atrial cardiomyopathy that could be due to cardiac alpha-synuclein deposition, autonomic dysfunction, or a combination thereof. Future research is warranted to elucidate whether this proposed disease-related atrial cardiomyopathy is related to cardiac alpha-synuclein deposition, whether it is causally related to cardiac complications in LBD, and whether pathological P wave parameters hold potential as a screening tool for cardiac complications in LBD.

α-Synuclein pathology from the body to the brain: so many seeds so close to the central soil

ABSTRACT

α-Synuclein is a protein that mainly exists in the presynaptic terminals. Abnormal folding and accumulation of α-synuclein are found in several neurodegenerative diseases, including Parkinson's disease. Aggregated and highly phosphorylated α-synuclein constitutes the main component of Lewy bodies in the brain, the pathological hallmark of Parkinson's disease. For decades, much attention has been focused on the accumulation of α-synuclein in the brain parenchyma rather than considering Parkinson's disease as a systemic disease. Recent evidence demonstrates that, at least in some patients, the initial α-synuclein pathology originates in the peripheral organs and spreads to the brain. Injection of α-synuclein preformed fibrils into the gastrointestinal tract triggers the gut-to-brain propagation of α-synuclein pathology. However, whether α-synuclein pathology can occur spontaneously in peripheral organs independent of exogenous α-synuclein preformed fibrils or pathological α-synuclein leakage from the central nervous system remains under investigation. In this review, we aimed to summarize the role of peripheral α-synuclein pathology in the pathogenesis of Parkinson's disease. We also discuss the pathways by which α-synuclein pathology spreads from the body to the brain.

Exploring the prevalence of undetected bradyarrhythmia in dementia with Lewy bodies

PURPOSE

To explore the prevalence of undetected bradyarrhythmia in a cohort of people with dementia with Lewy bodies.

METHODS

Thirty participants diagnosed with dementia with Lewy bodies were enrolled from three memory clinics in southern Sweden between May 2021 and November 2022. None had a history of high-grade atrioventricular block or sick sinus syndrome. Each participant underwent orthostatic testing, cardiac [123I]metaiodobenzylguanidine scintigraphy and 24-h ambulatory electrocardiographic monitoring. Concluding bradyarrhythmia diagnosis was obtained until the end of December 2022.

RESULTS

Thirteen participants (46.4%) had bradycardia at rest during orthostatic testing and four had an average heart rate < 60 beats per minute during ambulatory electrocardiographic monitoring. Three participants (10.7%) received a diagnosis of sick sinus syndrome, of whom two received pacemaker implants to manage associated symptoms. None received a diagnosis of second- or third-degree atrioventricular block.

CONCLUSION

This report showed a high prevalence of sick sinus syndrome in a clinical cohort of people with dementia with Lewy bodies. Further research on the causes and consequences of sick sinus syndrome in dementia with Lewy bodies is thus warranted.

Parkinson's disease and cardiovascular involvement: Edifying insights (Review)

Parkinson's disease (PD) is one of the most common neurodegenerative illnesses, and is a major healthcare burden with prodigious consequences on life-quality, morbidity, and survival. Cardiovascular diseases are the leading cause of mortality worldwide and growing evidence frequently reports their co-existence with PD. Cardiac dysautonomia due to autonomic nervous system malfunction is the most prevalent type of cardiovascular manifestation in these patients, comprising orthostatic and postprandial hypotension, along with supine and postural hypertension. Moreover, many studies have endorsed the risk of patients with PD to develop ischemic heart disease, heart failure and even arrhythmias, but the underlying mechanisms are not entirely clear. As importantly, the medication used in treating PD, such as levodopa, dopamine agonists or anticholinergic agents, is also responsible for cardiovascular adverse reactions, but further studies are required to elucidate the underlying mechanisms. The purpose of this review was to provide a comprehensive overview of current available data regarding the overlapping cardiovascular disease in patients with PD.

Sudden cardiac death in synucleinopathies

The purpose of this study was to investigate the cause of death in subjects with α-synucleinopathies (ASs) and the confirmed presence of cardiac α-synuclein (α-syn), compared to non-AS disorders in a neuropathologically confirmed cohort. In total, 78 neuropathologically confirmed AS cases positive for cardiac α-syn were included in the study. Individuals with other neurocognitive diseases, having no α-syn in the brainstem or above, nor in cardiac nerves, served as controls (n = 53). Data regarding the cause of death, cardiac α-syn, pathological cardiac findings, and cardio- and cerebrovascular disease were assembled from autopsy reports and medical records. In the AS group, there was a significantly higher prevalence of sudden cardiac death ([SCD]; n = 40, 51.3%) compared to the control group (n = 12, 22.6%, p < 0.001). No statistically significant differences between the groups were reported regarding other cardiac conditions on autopsy or regarding cardio- and cerebrovascular disease from the medical records. The most prevalent cause of death in the AS group was SCD, which differed significantly from the control group. This suggests that α-syn deposits in cardiac nerves may cause lethal alterations in cardiac function, warranting further research.