Lewy pathology of the esophagus correlates with the progression of Lewy body disease: a Japanese cohort study of autopsy cases

Sympathetic and parasympathetic subtypes of body-first Lewy body disease observed in postmortem tissue from prediagnostic individuals

Recent studies suggest the existence of brain-first and body-first subtypes within the Lewy body disorder (LBD) spectrum, including Parkinson's disease. These studies primarily focused on α-synuclein propagation through the parasympathetic vagal and olfactory bulb routes, leaving the possibility of a sympathetic nervous system spreading route unexplored. In the present study, we analyzed two postmortem datasets, which included 173 and 129 cases positive for Lewy pathology. We observed a clear distinction between brain-first and body-first subtypes in early prediagnostic cases with mild Lewy pathology. Brain-first cases displayed minimal peripheral organ pathology in prediagnostic phases, contrasting with marked autonomic involvement in prediagnostic body-first cases. Utilizing the SuStaIn machine learning algorithm, we identified two distinct body-first subtypes, one with vagal predominance and another with sympathetic predominance, in equal proportions. Our study supports the existence of three prediagnostic LBD subtypes and highlights the sympathetic nervous system alongside the parasympathetic system in LBD onset and progression.

α-Synuclein in Parkinson's Disease: From Bench to Bedside

α-Synuclein (α-syn), a pathological hallmark of PD, is emerging as a bridging element at the crossroads between neuro/immune-inflammatory responses and neurodegeneration in PD. Several evidence show that pathological α-syn accumulates in neuronal and non-neuronal cells (i.e., neurons, microglia, macrophages, skin cells, and intestinal cells) in central and peripheral tissues since the prodromal phase of the disease, contributing to brain pathology. Indeed, pathological α-syn deposition can promote neurogenic/immune-inflammatory responses that contribute to systemic and central neuroinflammation associated with PD. After providing an overview of the structure and functions of physiological α-syn as well as its pathological forms, we review current studies about the role of neuronal and non-neuronal α-syn at the crossroads between neuroinflammation and neurodegeneration in PD. In addition, we provide an overview of the correlation between the accumulation of α-syn in central and peripheral tissues and PD, related symptoms, and neuroinflammation. Special attention was paid to discussing whether targeting α-syn can represent a suitable therapeutical approach for PD.

An Autopsy Case of Amyotrophic Lateral Sclerosis With Sudden Death Showed Histological Features of Lewy Body Disease

We present the case of an 81-year-old man diagnosed with probable amyotrophic lateral sclerosis (ALS) based on the Updated Awaji criteria. The patient exhibited progressive motor neuron degeneration with muscle weakness, atrophy, and fasciculations primarily in the right lower limb and later extending to the right upper limb. Three months after being referred to a home care clinic, he collapsed in front of his family members and died. An autopsy revealed phosphorylated TDP-43 pathology consistent with ALS, with involvement of the hypoglossal nucleus, facial nerve nucleus, and medulla oblongata. Interestingly, widespread a-synuclein pathology indicative of diffuse neocortical type Lewy body disease (LBD; Braak stage 6) was identified, despite the absence of clinical parkinsonism or dementia with Lewy bodies (DLB) during his lifetime. The presence of autonomic symptoms such as constipation and urinary retention shortly before death may be attributable to a-synuclein pathology affecting the autonomic nervous system. The coexistence of ALS and LBD underscores the clinical challenge of diagnosing overlapping pathologies, as motor symptoms may obscure signs of LBD. Dopamine transporter imaging or MIBG myocardial scintigraphy might aid in identifying preclinical LBD in ALS patients with atypical symptoms. The patient died of respiratory failure due to extensive organizing pneumonia, but the possibility of sudden cardiac arrest could not be excluded. This case highlights the potential for coexisting neurodegenerative pathologies in ALS, emphasizing the importance of comprehensive evaluation when autonomic symptoms or other atypical features are present.

The Gut-Brain Axis Based on α-Synuclein Propagation-Clinical, Neuropathological, and Experimental Evidence

The cytopathological hallmark of Parkinson's disease (PD) is a neuronal cytoplasmic inclusion called Lewy body (LB). Lewy bodies are composed of alpha-synuclein (aSyn), a 140 aa protein that is predominantly expressed in the presynaptic terminal and which is implicated in neurotransmitter release. Recently, aSyn was found to propagate from neuron to neuron in a trans-synaptic manner. Although the precise molecular mechanisms are unclear, the propagation of aSyn is believed to play a major role in the progression of Lewy pathology in PD. Neuropathologically, the initial Lewy pathology has been shown to be formed in the dorsal motor nucleus of the vagus (DMV) or olfactory bulb by neuropathological studies. Since the DMV innervates the enteric nervous system (ENS) and LBs are formed in the gut nerve plexuses, it is conceivable that LBs propagate from the gut to the DMV and then to other regions of the brain. In this article, clinical, neuropathological, and experimental evidence supporting or negating the idea that aSyn propagation from the ENS to the brain leads to PD is reviewed. Moreover, the propagation of aSyn seeds through systemic circulation or multifocal generation of aSyn seeds is discussed as a potential alternative scenario for aSyn spreading.

[A case of anti-IgLON5 disease with recurrent respiratory failure]

A 72-year-old woman with a seven-year history of Parkinson's disease, characterized by gait instability, rigidity, and postural instability, was admitted to our department for evaluation of recurrent episodes of hypoxemia and altered consciousness. During hospitalization, she experienced recurrent episodes of respiratory failure, prompting the measurement of anti-IgLON5 antibodies, which were found to be positive, leading to a diagnosis of anti-IgLON5 disease. The respiratory failure could not be attributed to vocal cord paralysis or respiratory muscle weakness, leading to the hypothesis that subglottic laryngeal spasm was the cause. Treatment with steroid pulse therapy resulted in improved ventilation. While several cases of anti-IgLON5 disease presenting with respiratory failure due to respiratory muscle weakness have been reported, this case suggests that subglottic laryngeal spasm may also be an underlying cause of respiratory failure in anti-IgLON5 disease.

The Gut-Brain Axis in Parkinson disease: Emerging Concepts and Therapeutic Implications

BACKGROUND

The gut-brain axis, i.e. the bidirectional communication system between the gut and the brain, has become of central importance in Parkinson disease (PD) research over the past 20 years.

AIMS

We aimed to describe the milestones of the gut-brain axis research in PD and the development of theories proposing the involvement of the gastrointestinal tract in PD pathogenesis.

METHODS

We searched PubMed using the terms 'gut-brain axis' AND 'Parkinson disease', and selected relevant articles to provide the foundation for reconstructing an historical overview of the gut-brain axis research in PD.

RESULTS

Mounting evidence from preclinical, clinical and post-mortem studies suggests that a subgroup of PD patients present with a range of prodromal symptoms (e.g., autonomic dysfunction, rapid eye movement sleep behaviour disorder) which reflect initial accumulation and later spread of pathological α-synuclein rostrally from the gastrointestinal tract ("body-first" PD). Through neural connections along the gut-brain axis, pathological α-synuclein may spread to the brain, producing clinically manifest disease. Recently, two mechanisms involving the gut-brain axis have attracted increasing attention for their role in PD pathogenesis and progression, namely the perturbation of the composition of the microorganisms living in the gut (the gut microbiome), and the dysfunction of enteroendocrine cells.

CONCLUSION

Treatments targeting the gut-brain axis, especially the gut microbiome and the enteroendocrine cells pathway, could potentially slow disease progression or even prevent disease onset. Among these, pre/probiotics, faecal microbiota transplantation, and glucagon-like peptide-1 receptor agonists, have entered advanced stages of clinical trials in humans and shown potential symptomatic and disease-modifying effects.

α-synuclein seed amplification assay sensitivity may be associated with cardiac MIBG abnormality among patients with Lewy body disease

Although α-synuclein seed amplification assays (α-syn SAA) are promising, its sensitivity may be affected by heterogeneity among patients with Lewy body disease (LBD). We evaluated whether α-syn SAA sensitivity is affected by patient heterogeneity, using 123I-meta-iodobenzylguanidine (MIBG) cardiac scintigraphy in early drug-naïve patients. Thirty-four patients with clinically established or probable Parkinson's disease (PD) and seven with dementia with Lewy bodies (DLB) or prodromal DLB were included. While 85.2% of patients with abnormal cardiac MIBG were α-syn SAA positive, only 14.3% were positive among those with normal scans. Logistic regression analysis showed that MIBG positivity was the only significant variable associated with α-syn SAA positivity (odds ratio 74.2 [95% confidence interval 6.1-909]). Although α-syn SAA is sensitive for LBD in patients with abnormal MIBG, the sensitivity may be lower in those with normal MIBG. Further studies are necessary to evaluate the association between patient heterogeneity and α-syn SAA sensitivity.

Clinicopathological study of dementia with grains presenting with parkinsonism compared with a typical case

Argyrophilic grain disease (AGD) is one of the major pathological backgrounds of senile dementia. Dementia with grains refers to cases of dementia for which AGD is the sole background pathology responsible for dementia. Recent studies have suggested an association between dementia with grains and parkinsonism. In this study, we aimed to present two autopsy cases of dementia with grains. Case 1 was an 85-year-old man who exhibited amnestic dementia and parkinsonism, including postural instability, upward gaze palsy, and neck and trunk rigidity. The patient was clinically diagnosed with progressive supranuclear palsy and Alzheimer's disease. Case 2 was a 90-year-old man with pure amnestic dementia, clinically diagnosed as Alzheimer's disease. Recently, we used cryo-electron microscopy to confirm that the tau accumulated in both cases had the same three-dimensional structure. In this study, we compared the detailed clinical picture and neuropathological findings using classical staining and immunostaining methods. Both cases exhibited argyrophilic grains and tau-immunoreactive structures in the brainstem and basal ganglia, especially in the nigrostriatal and limbic systems. However, Case 1 had more tau immunoreactive structures. Considering the absence of other disease-specific structures such as tufted astrocytes, astrocytic plaques and globular glial inclusions, lack of conspicuous cerebrovascular disease, and no history of medications that could cause parkinsonism, our findings suggest an association between AGD in the nigrostriatal system and parkinsonism.

Clinical characteristics and pathophysiological properties of newly discovered LRRK2 variants associated with Parkinson's disease

Leucine-rich repeat kinase 2 (LRRK2) is the most common gene responsible for familial Parkinson's disease (PD). The gene product of LRRK2 contains multiple protein domains, including armadillo repeat, ankyrin repeat, leucine-rich repeat (LRR), Ras-of-complex (ROC), C-terminal of ROC (COR), kinase, and WD40 domains. In this study, we performed genetic screening of LRRK2 in our PD cohort, detecting sixteen LRRK2 rare variants. Among them, we selected seven variants that are likely to be familial and characterized them in terms of LRRK2 protein function, along with clinical information and one pathological analysis. The seven variants were S1120P and N1221K in the LRR domain; I1339M, S1403R, and V1447M in the ROC domain; and I1658F and D1873H in the COR domain. The kinase activity of the LRRK2 variants N1221K, S1403R, V1447M, and I1658F toward Rab10, a well-known phosphorylation substrate, was higher than that of wild-type LRRK2. LRRK2 D1873H showed enhanced self-association activity, whereas LRRK2 S1403R and D1873H showed reduced microtubule-binding activity. Pathological analysis of a patient with the LRRK2 V1447M variant was also performed, which revealed Lewy pathology in the brainstem. No functional alterations in terms of kinase activity, self-association activity, and microtubule-binding activity were detected in LRRK2 S1120P and I1339M variants. However, the patient with PD carrying LRRK2 S1120P variant also had a heterozygous Glucosylceramidase beta 1 (GBA1) L444P variant. In conclusion, we characterized seven LRRK2 variants potentially associated with PD. Five of the seven variants in different LRRK2 domains exhibited altered properties in kinase activity, self-association, and microtubule-binding activity, suggesting that each domain variant may contribute to disease progression in different ways.

Diagnostic accuracy and predictors of alpha-synuclein accumulation in the gastrointestinal tract of Parkinson's disease

The only characteristic of alpha-synuclein (AS) accumulation in the gastrointestinal (GI) tract of Parkinson's disease (PD) found in pathological studies is the "rostrocaudal gradient," which describes the more frequent presence of AS accumulation in the upper GI tract than in the lower GI tract. This study aimed to determine the diagnostic accuracy and identify predictors of AS accumulation in the GI tract of PD patients. The frequency of AS accumulation in the GI tract was compared between PD patients (N = 97) who underwent radical GI surgery for cancer and individually matched controls (N = 94). We evaluated AS accumulation in the neural structures using phosphorylated AS immunohistochemistry. A multivariable logistic regression analysis was conducted to determine the predictors of AS accumulation in the GI tract of PD patients. The frequency of AS accumulation was significantly higher in PD patients (75.3%) than in controls (8.5%, p-value < 0.001). The sensitivity and specificity of the full-layer evaluation were 75.3% and 91.5%, respectively. When the evaluation was confined to the mucosal/submucosal layer, the sensitivity and specificity were 46.9% and 94.7%, respectively. The rostrocaudal gradient of AS accumulation was found in PD patients. The duration from symptom onset to surgery was significantly longer in PD patients with AS accumulation (4.9 ± 4.9 years) than in PD patients without AS accumulation (1.8 ± 4.1 years, p-value = 0.005). Both disease duration and rostrocaudal gradient independently predicted the presence of AS accumulation in the GI tract of PD patients. Our study suggests PD-related AS accumulation in the GI tract follows a temporally increasing but spatially static progression pattern.

Cholinergic changes in Lewy body disease: implications for presentation, progression and subtypes

Cholinergic degeneration is significant in Lewy body disease, including Parkinson's disease, dementia with Lewy bodies, and isolated REM sleep behaviour disorder. Extensive research has demonstrated cholinergic alterations in the CNS of these disorders. More recently, studies have revealed cholinergic denervation in organs that receive parasympathetic denervation. This enables a comprehensive review of cholinergic changes in Lewy body disease, encompassing both central and peripheral regions, various disease stages and diagnostic categories. Across studies, brain regions affected in Lewy body dementia show equal or greater levels of cholinergic impairment compared to the brain regions affected in Lewy body disease without dementia. This observation suggests a continuum of cholinergic alterations between these disorders. Patients without dementia exhibit relative sparing of limbic regions, whereas occipital and superior temporal regions appear to be affected to a similar extent in patients with and without dementia. This implies that posterior cholinergic cell groups in the basal forebrain are affected in the early stages of Lewy body disorders, while more anterior regions are typically affected later in the disease progression. The topographical changes observed in patients affected by comorbid Alzheimer pathology may reflect a combination of changes seen in pure forms of Lewy body disease and those seen in Alzheimer's disease. This suggests that Alzheimer co-pathology is important to understand cholinergic degeneration in Lewy body disease. Thalamic cholinergic innervation is more affected in Lewy body patients with dementia compared to those without dementia, and this may contribute to the distinct clinical presentations observed in these groups. In patients with Alzheimer's disease, the thalamus is variably affected, suggesting a different sequential involvement of cholinergic cell groups in Alzheimer's disease compared to Lewy body disease. Patients with isolated REM sleep behaviour disorder demonstrate cholinergic denervation in abdominal organs that receive parasympathetic innervation from the dorsal motor nucleus of the vagus, similar to patients who experienced this sleep disorder in their prodrome. This implies that REM sleep behaviour disorder is important for understanding peripheral cholinergic changes in both prodromal and manifest phases of Lewy body disease. In conclusion, cholinergic changes in Lewy body disease carry implications for understanding phenotypes and the influence of Alzheimer co-pathology, delineating subtypes and pathological spreading routes, and for developing tailored treatments targeting the cholinergic system.

Tear α-synuclein as a biomarker for Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Parkinson's disease symptoms mostly manifest after significant and irreversible neuropathology. Hence, there is a need to identify biomarkers that can provide indications of disease before significant neuronal degeneration occurs.

OBJECTIVE

To estimate the difference in the concentration of α-synuclein protein in tears between individuals with Parkinson's disease and healthy controls.

DATA SOURCES

PubMed, Scopus, and Web of Science. The last database search was on December 20, 2023.

STUDY ELIGIBILITY CRITERIA

Primary prospective studies in humans measuring the level of α-synuclein in tears and clinical outcomes reported using mean or median.

PARTICIPANTS AND INTERVENTIONS

Individuals with Parkinson's disease and healthy controls.

STUDY APPRAISAL AND SYNTHESIS METHODS

The risk of bias was assessed using the Newcastle-Ottawa Scale. The I2 statistic was used to estimate heterogeneity. The outcome measure was the difference in tear total and oligomeric α-synuclein. Mean difference (MD) was used to assess the outcome. The certainty of evidence was rated following the Grading of Recommendations Assessment and Development and Evaluation (GRADE) system.

RESULTS

Three hundred twenty-seven Parkinson's disease and 312 healthy control subjects from five studies and 177 Parkinson's disease and 166 healthy control subjects from two studies were included in total α-synuclein levels and oligomeric α-synuclein levels analysis, respectively. Total α-synuclein level was not different between Parkinson's disease and healthy controls (MD = 0.02 ng/mL [95% confidence interval {CI}: 0.00 to 0.05 ng/mL; I2 = 90%; Z = 1.79; p=0.07; number of studies = 5; GRADE rating = very low]). Stratifying the data based on disease duration, total α-synuclein was higher in subjects with Parkinson's disease duration ≥7 years compared with healthy controls (MD = 0.04 ng/mL [95% CI: 0.03 to 0.05 ng/mL; I2 = 0%; Z = 8.24, p<0.00001; number of studies = 2; GRADE rating = low]) but not different between the two groups (MD = -0.12 ng/mL (95% CI: -0.38 to 0.15 ng/mL; I2 = 93%; Z = 0.84, p=0.40; number of studies = 3; GRADE rating = very low]). Oligomeric α-synuclein level was higher in Parkinson's disease compared with controls (MD = 6.50 ng/mL [95% CI: 2.79 to 10.20 ng/mL; I2 = 94%; Z = 3.44; p=0.0006; number of studies = 2; GRADE rating = very low]).

LIMITATIONS

High heterogeneity between studies. Potential sources of heterogeneity could not be explored due to the limited number of studies.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Tear α-synuclein has the potential to be a noninvasive biomarker for Parkinson's disease. Studies are, however, needed to increase certainty in the biomarker and establish how the protein's changes in tears correlate with Parkinson's disease progression and severity.

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.

Brain-first vs. body-first Parkinson's disease: An update on recent evidence

We recently proposed a new disease model of Parkinson's disease - the a-Synuclein Origin site and Connectome model. The model posits that the initial pathology starts either in the olfactory bulb or amygdala leading to a brain-first subtype, or in the enteric nervous system leading to a body-first subtype. These subtypes should be distinguishable early in the disease course on a range of imaging, clinical, and neuropathological markers. Here, we review recent original human studies, which tested the predictions of the model. Molecular imaging studies were generally in agreement with the model, whereas structural imaging studies, such as MRI volumetry, showed conflicting findings. Most large-scale clinical studies were supportive, reporting clustering of relevant markers of the body-first subtype, including REM-sleep behavior disorder, constipation, autonomic dysfunction, neuropsychiatric symptoms, and cognitive impairment. Finally, studies of a-synuclein deposition in antemortem and postmortem tissues revealed distribution of pathology, which generally supports the model.

Accumulation of Lewy-Related Pathology Starts in Middle Age: The Tampere Sudden Death Study

When effective treatments against neurodegenerative diseases become a reality, it will be important to know the age these pathologies begin to develop. We investigated alpha-synuclein pathology in brain tissue of the Tampere Sudden Death Study-unselected forensic autopsies on individuals living outside hospital institutions in Finland. Of 562 (16-95 years) participants, 42 were positive for Lewy-related pathology (LRP). The youngest LRP case was aged 54 years, and the frequency of LRP in individuals aged ≥50 years was 9%. This forensic autopsy study indicates LRP starts already in middle age and is more common than expected in the ≥50 years-of-age non-hospitalized population. ANN NEUROL 2024;95:843-848.

Ultrastructural localization of Porphyromonas gingivalis gingipains in the substantia nigra of Parkinson's disease brains

Gingipains are protease virulence factors produced by Porphyromonas gingivalis, a Gram-negative bacterium best known for its role in chronic periodontitis. Gingipains were recently identified in the middle temporal gyrus of postmortem Alzheimer's disease (AD) brains, where gingipain load correlated with AD diagnosis and tau and ubiquitin pathology. Since AD and Parkinson's disease (PD) share some overlapping pathologic features, including nigral pathology and Lewy bodies, the current study explored whether gingipains are present in the substantia nigra pars compacta of PD brains. In immunohistochemical techniques and multi-channel fluorescence studies, gingipain antigens were abundant in dopaminergic neurons in the substantia nigra of both PD and neurologically normal control brains. 3-dimensional reconstructions of Lewy body containing neurons revealed that gingipains associated with the periphery of alpha-synuclein aggregates but were occasionally observed inside aggregates. In vitro proteomic analysis demonstrated that recombinant alpha-synuclein is cleaved by lysine-gingipain, generating multiple alpha-synuclein fragments including the non-amyloid component fragments. Immunogold electron microscopy with co-labeling of gingipains and alpha-synuclein confirmed the occasional colocalization of gingipains with phosphorylated (pSER129) alpha-synuclein. In dopaminergic neurons, gingipains localized to the perinuclear cytoplasm, neuromelanin, mitochondria, and nucleus. These data suggest that gingipains localize in dopaminergic neurons in the substantia nigra and interact with alpha-synuclein.

Impaired cholinergic integrity of the colon and pancreas in dementia with Lewy bodies

Dementia with Lewy bodies is characterized by a high burden of autonomic dysfunction and Lewy pathology in peripheral organs and components of the sympathetic and parasympathetic nervous system. Parasympathetic terminals may be quantified with 18F-fluoroetoxybenzovesamicol, a PET tracer that binds to the vesicular acetylcholine transporter in cholinergic presynaptic terminals. Parasympathetic imaging may be useful for diagnostics, improving our understanding of autonomic dysfunction and for clarifying the spatiotemporal relationship of neuronal degeneration in prodromal disease. Therefore, we aimed to investigate the cholinergic parasympathetic integrity in peripheral organs and central autonomic regions of subjects with dementia with Lewy bodies and its association with subjective and objective measures of autonomic dysfunction. We hypothesized that organs with known parasympathetic innervation, especially the pancreas and colon, would have impaired cholinergic integrity. To achieve these aims, we conducted a cross-sectional comparison study including 23 newly diagnosed non-diabetic subjects with dementia with Lewy bodies (74 ± 6 years, 83% male) and 21 elderly control subjects (74 ± 6 years, 67% male). We obtained whole-body images to quantify PET uptake in peripheral organs and brain images to quantify PET uptake in regions of the brainstem and hypothalamus. Autonomic dysfunction was assessed with questionnaires and measurements of orthostatic blood pressure. Subjects with dementia with Lewy bodies displayed reduced cholinergic tracer uptake in the pancreas (32% reduction, P = 0.0003) and colon (19% reduction, P = 0.0048), but not in organs with little or no parasympathetic innervation. Tracer uptake in a region of the medulla oblongata overlapping the dorsal motor nucleus of the vagus correlated with autonomic symptoms (rs = -0.54, P = 0.0077) and changes in orthostatic blood pressure (rs = 0.76, P < 0.0001). Tracer uptake in the pedunculopontine region correlated with autonomic symptoms (rs = -0.52, P = 0.0104) and a measure of non-motor symptoms (rs = -0.47, P = 0.0230). In conclusion, our findings provide the first imaging-based evidence of impaired cholinergic integrity of the pancreas and colon in dementia with Lewy bodies. The observed changes may reflect parasympathetic denervation, implying that this process is initiated well before the point of diagnosis. The findings also support that cholinergic denervation in the brainstem contributes to dysautonomia.

Automated Capillary Electrophoresis Immunoblot for the Detection of Alpha-Synuclein in Mouse Tissue

Background

Alpha-synuclein (aSyn) is a key player in neurodegenerative diseases such as Parkinson's disease (PD), dementia with Lewy bodies, or multiple system atrophy. aSyn is expressed throughout the brain, and can also be detected in various peripheral tissues. In fact, initial symptoms of PD are non-motoric and include autonomic dysfunction, suggesting that the periphery might play an important role in early development of the disease. aSyn is expressed at relatively low levels in non-central tissues, which brings challenges for its detection and quantification in different tissues.

Objective

Our goal was to assess the sensitivity of aSyn detection in central and peripheral mouse tissues through capillary electrophoresis (CE) immunoblot, considering the traditional SDS-PAGE immunoblot as the current standard.

Methods

Tissues from central and non-central origin from wild type mice were extracted, and included midbrain, inner ear, and esophagus/stomach. aSyn detection was assessed through immunoblotting using Simple Western size-based CE and SDS-PAGE.

Results

CE immunoblots show a consistent detection of aSyn in central and peripheral tissues. Through SDS-PAGE, immunoblots revealed a reliable signal corresponding to aSyn, particularly following membrane fixation.

Conclusion

Our results suggest a reliable detection of aSyn in central and peripheral tissues using the CE Simple Western immunoblot system. These observations can serve as preliminary datasets when aiming to formally compare CE with SDS-PAGE, as well as for further characterization of aSyn using this technique.

Ultrastructures of α-Synuclein Filaments in Synucleinopathy Brains and Experimental Models

Intracellular α-synuclein (α-syn) inclusions are a neuropathological hallmark of Lewy body disease (LBD) and multiple system atrophy (MSA), both of which are termed synucleinopathies. LBD is defined by Lewy bodies and Lewy neurites in neurons, while MSA displays glial cytoplasmic inclusions in oligodendrocytes. Pathological α-syn adopts an ordered filamentous structure with a 5-10 nm filament diameter, and this conformational change has been suggested to be involved in the disease onset and progression. Synucleinopathies also exhibit characteristic ultrastructural and biochemical properties of α-syn filaments, and α-syn strains with distinct conformations have been identified. Numerous experimental studies have supported the idea that pathological α-syn self-amplifies and spreads throughout the brain, during which processes the conformation of α-syn filaments may drive the disease specificity. In this review, we summarize the ultrastructural features and heterogeneity of α-syn filaments in the brains of patients with synucleinopathy and in experimental models of seeded α-syn aggregation.

The Body, the Brain, the Environment, and Parkinson's Disease

The brain- and body-first models of Lewy body disorders predict that aggregated alpha-synuclein pathology usually begins in either the olfactory system or the enteric nervous system. In both scenarios the pathology seems to arise in structures that are closely connected to the outside world. Environmental toxicants, including certain pesticides, industrial chemicals, and air pollution are therefore plausible trigger mechanisms for Parkinson's disease and dementia with Lewy bodies. Here, we propose that toxicants inhaled through the nose can lead to pathological changes in alpha-synuclein in the olfactory system that subsequently spread and give rise to a brain-first subtype of Lewy body disease. Similarly, ingested toxicants can pass through the gut and cause alpha-synuclein pathology that then extends via parasympathetic and sympathetic pathways to ultimately produce a body-first subtype. The resulting spread can be tracked by the development of symptoms, clinical assessments, in vivo imaging, and ultimately pathological examination. The integration of environmental exposures into the brain-first and body-first models generates testable hypotheses, including on the prevalence of the clinical conditions, their future incidence, imaging patterns, and pathological signatures. The proposed link, though, has limitations and leaves many questions unanswered, such as the role of the skin, the influence of the microbiome, and the effects of ongoing exposures. Despite these limitations, the interaction of exogenous factors with the nose and the gut may explain many of the mysteries of Parkinson's disease and open the door toward the ultimate goal -prevention.

Experimental Animal Models of Prodromal Parkinson's Disease

There is an estimated 35-45% loss of striatal dopamine at the time of diagnosis of Parkinson's disease (PD), and cases clinically diagnosed in the early stages may already be pathologically in advanced stages. Recent large-scale clinical trials of disease-modifying therapies (DMT) also suggest the necessity of targeting patients at earlier stages of the disease. From this perspective, the prodromal phase of PD is currently the focus of attention, emphasizing the need for a prodromal mouse model that accurately reflects the pathophysiology, along with early biomarkers. To establish prodromal animal model of PD with high face validity that reflects the disease state, the model must possess high construct validity that accurately incorporates clinical and pathological features in the prodromal phase. Furthermore, as a preclinical model of DMT, the model must possess high predictive validity to accurately evaluate the response to intervention. This review provides an overview of animal models which reflect the characteristics of prodromal PD, including alpha-synuclein (aS) accumulation and associated early non-motor symptoms, with a focus on the aS propagation model and genetic model. In addition, we discuss the challenges associated with these models. The genetic model often fails to induce motor symptoms, while aS propagation models skip the crucial step of initial aS aggregate formation, thereby not fully replicating the entire natural course of the disease. Identifying factors that induce the transition from prodromal to symptomatic phase is important as a preclinical model for DMT to prevent or delay the onset of the disease.

Parkinson's Disease and Dementia with Lewy Bodies: One and the Same

The question whether Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) are expressions of the same underlying disease has been vigorously debated for decades. The recently proposed biological definitions of Lewy body disease, which do not assign any particular importance to the dopamine system over other degenerating neurotransmitter systems, has once more brought the discussion about different types of Lewy body disease to the forefront. Here, we briefly compare PDD and DLB in terms of their symptoms, imaging findings, and neuropathology, ultimately finding them to be indistinguishable. We then present a conceptual framework to demonstrate how one can view different clinical syndromes as manifestations of a shared underlying Lewy body disease. Early Parkinson's disease, isolated RBD, pure autonomic failure and other autonomic symptoms, and perhaps even psychiatric symptoms, represent diverse manifestations of the initial clinical stages of Lewy body disease. They are characterized by heterogeneous and comparatively limited neuronal dysfunction and damage. In contrast, Lewy body dementia, an encompassing term for both PDD and DLB, represents a more uniform and advanced stage of the disease. Patients in this category display extensive and severe Lewy pathology, frequently accompanied by co-existing pathologies, as well as multi-system neuronal dysfunction and degeneration. Thus, we propose that Lewy body disease should be viewed as a single encompassing disease entity. Phenotypic variance is caused by the presence of individual risk factors, disease mechanisms, and co-pathologies. Distinct subtypes of Lewy body disease can therefore be defined by subtype-specific disease mechanisms or biomarkers.

Diagnostic Sensitivity and Symptomatic Relevance of Dopamine Transporter Imaging and Myocardial Sympathetic Scintigraphy in Patients with Dementia with Lewy Bodies

Background

Dementia with Lewy bodies (DLB) presents with various symptoms, posing challenges for early diagnosis challenging. Dopamine transporter (123I-FP-CIT) single-photon emission tomography (SPECT) and 123I-meta-iodobenzylguanidine (123I-MIBG) imaging are crucial diagnostic biomarkers. Hypothesis about body- and brain-first subtypes of DLB indicate that some DLB may show normal 123I-FP-CIT or 123I-MIBG results; but the characteristic expression of these two subtypes remains unclear.

Objective

This study aimed to evaluate the diagnostic sensitivity of 123I-FP-CIT and 123I-MIBG imaging alone, combined in patients with DLB and explore symptoms associated with the abnormal imaging results.

Methods

Demographic data, clinical status, and imaging results were retrospectively collected from patients diagnosed with possible DLB. Both images were quantified using semi-automated software, and the sensitivity of each imaging modality and their combination was calculated. Demographic data, cognition, and motor and non-motor symptoms were compared among the subgroups based on the imaging results. Symptoms related to each imaging abnormality were examined using binomial logistic regression analyses.

Results

Among 114 patients with DLB, 80 underwent 123I-FP-CIT SPECT (sensitivity: 80.3%), 83 underwent 123I-MIBG imaging (68.2%), and 66 both (sensitivity of either abnormal result: 93.9%). Visual hallucinations differed among the four subgroups based on imaging results. Additionally, nocturia and orthostatic hypotension differed between abnormal and normal 123I-MIBG images.

Conclusions

Overall, 123I-FP-CIT SPECT was slightly higher sensitivity than 123I-MIBG imaging, with combined imaging increasing diagnostic sensitivity. Normal results of a single imaging test may not refute DLB. Autonomic symptoms may lead to abnormal 123I-MIBG scintigraphy findings indicating body-first subtype of patients with DLB.

Distribution of proteinase K-resistant anti-α-synuclein immunoreactive axons in the cardiac plexus is unbiased to the left ventricular anterior wall

Lewy body disease (LBD) is characterized by the appearance of Lewy neurites and Lewy bodies, which are predominantly composed of α-synuclein. Notably, the cardiac plexus (CP) is one of the main targets of LBD research. Although previous studies have reported obvious differences in the frequency of Lewy body pathology (LBP) in the CP, none of them have confirmed whether LBP preferably appears in any part of the CP. Thus, we aimed to clarify the emergence and/or propagation of LBP in the CP. In this study, 263 consecutive autopsy cases of patients aged ≥50 years were included, with one region per case selected from three myocardial perfusion areas (MPAs) and subjected to proteinase K and then immunohistochemically stained with anti-α-synuclein antibodies to assess LBP. We stained all three MPAs in 17 cases with low-density LBP and observed the actual distribution of LBP. LBP were identified in the CP in 20.2% (53/263) of patients. Moreover, we found that LBP may appear in only one region of MPAs, mainly in the young-old group (35.3% (6/17) of patients). These findings suggest that it is possible to underestimate LBP in the CP, especially in the young-old group, by restricting the search to only one of the three MPAs.

The brain-first vs. body-first model of Parkinson's disease with comparison to alternative models

The ultimate origin of Lewy body disorders, including Parkinson's disease (PD) and Dementia with Lewy bodies (DLB), is still incompletely understood. Although a large number of pathogenic mechanisms have been implicated, accumulating evidence support that aggregation and neuron-to-neuron propagation of alpha-synuclein may be the core feature of these disorders. The synuclein, origin, and connectome (SOC) disease model of Lewy body disorders was recently introduced. This model is based on the hypothesis that in the majority of patients, the first alpha-synuclein pathology arises in single location and spreads from there. The most common origin sites are the enteric nervous system and the olfactory system. The SOC model predicts that gut-first pathology leads to a clinical body-first subtype characterized by prodromal autonomic symptoms and REM sleep behavior disorder. In contrast, olfactory-first pathology leads to a brain-first subtype with fewer non-motor symptoms before diagnosis. The SOC model further predicts that body-first patients are older, more commonly develop symmetric dopaminergic degeneration, and are at increased risk of dementia-compared to brain-first patients. In this review, the SOC model is explained and compared to alternative models of the pathogenesis of Lewy body disorders, including the Braak staging system, and the Unified Staging System for Lewy Body Disorders. Postmortem evidence from brain banks and clinical imaging data of dopaminergic and cardiac sympathetic loss is reviewed. It is concluded that these datasets seem to be more compatible with the SOC model than with those alternative disease models of Lewy body disorders.

The heterogeneity of Parkinson's disease

The heterogeneity of Parkinson's disease (PD), i.e. the various clinical phenotypes, pathological findings, genetic predispositions and probably also the various implicated pathophysiological pathways pose a major challenge for future research projects and therapeutic trail design. We outline several pathophysiological concepts, pathways and mechanisms, including the presumed roles of α-synuclein misfolding and aggregation, Lewy bodies, oxidative stress, iron and melanin, deficient autophagy processes, insulin and incretin signaling, T-cell autoimmunity, the gut-brain axis and the evidence that microbial (viral) agents may induce molecular hallmarks of neurodegeneration. The hypothesis is discussed, whether PD might indeed be triggered by exogenous (infectious) agents in susceptible individuals upon entry via the olfactory bulb (brain first) or the gut (body-first), which would support the idea that disease mechanisms may change over time. The unresolved heterogeneity of PD may have contributed to the failure of past clinical trials, which attempted to slow the course of PD. We thus conclude that PD patients need personalized therapeutic approaches tailored to specific phenomenological and etiologic subtypes of disease.

Alpha synuclein post translational modifications: potential targets for Parkinson's disease therapy?

Parkinson's disease (PD) is the most common neurodegenerative disorder with motor symptoms. The neuropathological alterations characterizing the brain of patients with PD include the loss of dopaminergic neurons of the nigrostriatal system and the presence of Lewy bodies (LB), intraneuronal inclusions that are mainly composed of alpha-synuclein (α-Syn) fibrils. The accumulation of α-Syn in insoluble aggregates is a main neuropathological feature in PD and in other neurodegenerative diseases, including LB dementia (LBD) and multiple system atrophy (MSA), which are therefore defined as synucleinopathies. Compelling evidence supports that α-Syn post translational modifications (PTMs) such as phosphorylation, nitration, acetylation, O-GlcNAcylation, glycation, SUMOylation, ubiquitination and C-terminal cleavage, play important roles in the modulation α-Syn aggregation, solubility, turnover and membrane binding. In particular, PTMs can impact on α-Syn conformational state, thus supporting that their modulation can in turn affect α-Syn aggregation and its ability to seed further soluble α-Syn fibrillation. This review focuses on the importance of α-Syn PTMs in PD pathophysiology but also aims at highlighting their general relevance as possible biomarkers and, more importantly, as innovative therapeutic targets for synucleinopathies. In addition, we call attention to the multiple challenges that we still need to face to enable the development of novel therapeutic approaches modulating α-Syn PTMs.

Gut-to-Brain α-Synuclein Transmission in Parkinson's Disease: Evidence for Prion-like Mechanisms

Parkinson's disease (PD) is a multifactorial disorder involving both motor and non-motor symptoms caused by the progressive death of distinct neuronal populations, including dopaminergic neurons in the substantia nigra. The deposition of aggregated α-synuclein protein into Lewy body inclusions is a hallmark of the disorder, and α-synuclein pathology has been found in the enteric nervous system (ENS) of PD patients up to two decades prior to diagnosis. In combination with the high occurrence of gastrointestinal dysfunction in early stages of PD, current evidence strongly suggests that some forms of PD may originate in the gut. In this review, we discuss human studies that support ENS Lewy pathology as a characteristic feature of PD, and present evidence from humans and animal model systems that α-synuclein aggregation may follow a prion-like spreading cascade from enteric neurons, through the vagal nerve, and into the brain. Given the accessibility of the human gut to pharmacologic and dietary interventions, therapeutic strategies aimed at reducing pathological α-synuclein in the gastrointestinal tract hold significant promise for PD treatment.

Mapping Cholinergic Synaptic Loss in Parkinson's Disease: An [18F]FEOBV PET Case-Control Study

BACKGROUND

Cholinergic degeneration is strongly associated with cognitive decline in patients with Parkinson's disease (PD) but may also cause motor symptoms and olfactory dysfunction. Regional differences are striking and may reflect different PD related symptoms and disease progression patterns.

OBJECTIVE

To map and quantify the regional cerebral cholinergic alterations in non-demented PD patients.

METHODS

We included 15 non-demented PD patients in early-moderate disease stage and 15 age- and sex-matched healthy controls for [18F]FEOBV positron emission tomography imaging. We quantitated regional variations using VOI-based analyses which were supported by a vertex-wise cluster analysis. Correlations between imaging data and clinical and neuropsychological data were explored.

RESULTS

We found significantly decreased [18F]FEOBV uptake in global neocortex (38%, p = 0.0002). The most severe reductions were seen in occipital and posterior temporo-parietal regions (p < 0.0001). The vertex-wise cluster analysis corroborated these findings. All subcortical structures showed modest non-significant reductions. Motor symptoms (postural instability and gait difficulty) and cognition (executive function and composite z-score) correlated with regional [18F]FEOBV uptake (thalamus and cingulate cortex/insula/hippocampus, respectively), but the correlations were not statistically significant after multiple comparison correction. A strong correlation was found between interhemispheric [18F]FEOBV asymmetry, and motor symptom asymmetry of the extremities (r = 0.84, p = 0.0001).

CONCLUSION

Cortical cholinergic degeneration is prominent in non-demented PD patients, but more subtle in subcortical structures. Regional differences suggest uneven involvement of cholinergic nuclei in the brain and may represent a window to follow disease progression. The correlation between asymmetric motor symptoms and neocortical [18F]FEOBV asymmetry indicates that unilateral cholinergic degeneration parallels ipsilateral dopaminergic degeneration.

Distribution of Lewy-related pathology in the brain, spinal cord, and periphery: the population-based Vantaa 85 + study

Evolving evidence has supported the existence of two anatomically distinct Lewy-related pathology (LRP) types. Investigation of spinal cord and peripheral LRP can elucidate mechanisms of Lewy body disorders and origins of synuclein accumulation. Still, very few unselected studies have focused on LRP in these regions. Here we analysed LRP in spinal cord, dorsal root ganglion, and adrenal gland in the population-based Vantaa 85 + study, including every ≥ 85 years old citizen living in the city of Vantaa in 1991 (n = 601). Samples from spinal cord (C6-7, TH3-4, L3-4, S1-2) were available from 303, lumbar dorsal root ganglion from 219, and adrenal gland from 164 subjects. Semiquantitative scores of LRP were determined from immunohistochemically stained sections (anti-alpha-synuclein antibody 5G4). LRP in the ventral and dorsal horns of spinal cord, thoracic intermediolateral column, dorsal root ganglion and adrenal gland were compared with brain LRP, previously determined according to DLB Consortium criteria and by caudo-rostral versus amygdala-based LRP classification. Spinal LRP was found in 28% of the total population and in 61% of those who had LRP in the brain. Spinal cord LRP was found only in those subjects with LRP in the brain, and the quantity of spinal cord LRP was associated with the severity of brain LRP (p < 0.001). Unsupervised K-means analysis identified two cluster types of spinal and brain LRP corresponding to caudo-rostral and amygdala-based LRP types. The caudo-rostral LRP type exhibited more frequent and severe pathology in spinal cord, dorsal root ganglion and adrenal gland than the amygdala-based LRP type. Analysis of specific spinal cord regions showed that thoracic intermediolateral column and sacral dorsal horn were the most frequently affected regions in both LRP types. This population-based study on brain, spinal and peripheral LRP provides support to the concept of at least two distinct LRP types.

A postmortem study suggests a revision of the dual-hit hypothesis of Parkinson's disease

The dual-hit hypothesis of Parkinson's disease (PD) originally postulated that a neurotropic pathogen leads to formation of α-synuclein pathology in the olfactory bulb (OB) and dorsal motor nucleus of the vagus (DMV) and then invades the brain from these two entry points. Little work has been conducted to validate an important underlying premise for the dual-hit hypothesis, namely that the initial Lewy pathology does arise simultaneously in the OB and the enteric nervous system (ENS) plexuses and DMV at the earliest disease stage. We conducted a focused re-analysis of two postmortem datasets, which included large numbers of mild Lewy body disease (LBD) cases. We found that cases with α-synuclein pathology restricted to the peripheral autonomic nervous system and/or lower brainstem (early body-first LBD cases) very rarely had any OB pathology, suggesting that Lewy pathology commonly arises in the ENS without concomitant involvement of the OB. In contrast, cases with mild amygdala-predominant Lewy pathology (early brain-first LBD cases) nearly always showed OB pathology. This is compatible with the first pathology being triggered in the OB or amygdala followed by secondary spreading to connected structures, but without early involvement of the ENS or lower brainstem. These observations support that the pathologic process starts in either the olfactory bulb or the ENS, but rarely in the olfactory bulb and gut simultaneously. More studies on neuropathological datasets are warranted to reproduce these findings. The agreement between the revised single-hit hypothesis and the recently proposed brain-first vs. body-first model of LBD is discussed.

Morphological study of the phrenic nerve to determine a reference value for the myelinated fiber density in elderly individuals

Phrenic nerves (PNs) play an important role in respiration; however, very few morphological studies have assessed them. This study aimed to provide control reference values, including the density of large and small myelinated PN fibers, for future pathological studies. We assessed a total of nine nerves from eight cases among consecutive autopsy cases registered to the Brain Bank for Aging Research between 2018 and 2019 (five men and three women, mean age 77.0 ± 7.0 years). The nerves were sampled distally, and their structures were analyzed using semi-thin sections stained with toluidine blue. The mean and standard deviation of the density of each myelinated fiber of the PN was 6908 ± 1132 fibers/mm² (total myelinated fiber), 4095 ± 586 fibers/mm² (large diameter myelinated fiber; diameter ≥7 μm), and 2813 ± 629 fibers/mm² (small diameter myelinated fiber; diameter <7 μm). There was no correlation between myelinated fiber density and age. This study provides the density measurement of the human PN myelinated fiber, and these findings can be used as reference values for the PN in elderly individuals.

Opportunities and challenges of alpha-synuclein as a potential biomarker for Parkinson's disease and other synucleinopathies

Parkinson’s disease (PD), the second most common progressive neurodegenerative disease, develops and progresses for 10–15 years before the clinical diagnostic symptoms of the disease are manifested. Furthermore, several aspects of PD pathology overlap with other neurodegenerative diseases (NDDs) linked to alpha-synuclein (aSyn) aggregation, also called synucleinopathies. Therefore, there is an urgent need to discover and validate early diagnostic and prognostic markers that reflect disease pathophysiology, progression, severity, and potential differences in disease mechanisms between PD and other NDDs. The close association between aSyn and the development of pathology in synucleinopathies, along with the identification of aSyn species in biological fluids, has led to increasing interest in aSyn species as potential biomarkers for early diagnosis of PD and differentiate it from other synucleinopathies. In this review, we (1) provide an overview of the progress toward mapping the distribution of aSyn species in the brain, peripheral tissues, and biological fluids; (2) present comparative and critical analysis of previous studies that measured total aSyn as well as other species such as modified and aggregated forms of aSyn in different biological fluids; and (3) highlight conceptual and technical gaps and challenges that could hinder the development and validation of reliable aSyn biomarkers; and (4) outline a series of recommendations to address these challenges. Finally, we propose a combined biomarker approach based on integrating biochemical, aggregation and structure features of aSyn, in addition to other biomarkers of neurodegeneration. We believe that capturing the diversity of aSyn species is essential to develop robust assays and diagnostics for early detection, patient stratification, monitoring of disease progression, and differentiation between synucleinopathies. This could transform clinical trial design and implementation, accelerate the development of new therapies, and improve clinical decisions and treatment strategies.

The microbiome-gut-brain axis in Parkinson disease - from basic research to the clinic

Evidence for a close bidirectional link between the brain and the gut has led to a paradigm shift in neurology, especially in the case of Parkinson disease (PD), in which gastrointestinal dysfunction is a prominent feature. Over the past decade, numerous high-quality preclinical and clinical publications have shed light on the highly complex relationship between the gut and the brain in PD, providing potential for the development of new biomarkers and therapeutics. With the advent of high-throughput sequencing, the role of the gut microbiome has been specifically highlighted. Here, we provide a critical review of the literature on the microbiome-gut-brain axis in PD and present perspectives that will be useful for clinical practice. We begin with an overview of the gut-brain axis in PD, including the potential roles and interrelationships of the vagus nerve, α-synuclein in the enteric nervous system, altered intestinal permeability and inflammation, and gut microbes and their metabolic activities. The sections that follow synthesize the proposed roles of gut-related factors in the development and progression of, in responses to PD treatment, and as therapeutic targets. Finally, we summarize current knowledge gaps and challenges and delineate future directions for the field.

Ultrastructural and biochemical classification of pathogenic tau, α-synuclein and TDP-43

Intracellular accumulation of abnormal proteins with conformational changes is the defining neuropathological feature of neurodegenerative diseases. The pathogenic proteins that accumulate in patients' brains adopt an amyloid-like fibrous structure and exhibit various ultrastructural features. The biochemical analysis of pathogenic proteins in sarkosyl-insoluble fractions extracted from patients' brains also shows disease-specific features. Intriguingly, these ultrastructural and biochemical features are common within the same disease group. These differences among the pathogenic proteins extracted from patients' brains have important implications for definitive diagnosis of the disease, and also suggest the existence of pathogenic protein strains that contribute to the heterogeneity of pathogenesis in neurodegenerative diseases. Recent experimental evidence has shown that prion-like propagation of these pathogenic proteins from host cells to recipient cells underlies the onset and progression of neurodegenerative diseases. The reproduction of the pathological features that characterize each disease in cellular and animal models of prion-like propagation also implies that the structural differences in the pathogenic proteins are inherited in a prion-like manner. In this review, we summarize the ultrastructural and biochemical features of pathogenic proteins extracted from the brains of patients with neurodegenerative diseases that accumulate abnormal forms of tau, α-synuclein, and TDP-43, and we discuss how these disease-specific properties are maintained in the brain, based on recent experimental insights.

Gastrointestinal Biopsy Obtained During Cancer Screening, a Biological Marker for α-Synucleinopathy?

The hallmark alteration in α-synucleinopathies, α-synuclein, is observed not only in the brain but also in the peripheral tissues, particularly in the intestine. This suggests that endoscopic biopsies performed for colon cancer screening could facilitate the assessment of α-synuclein in the gastrointestinal (GI) tract. Using immunohistochemistry for α-synuclein, we assessed whether GI biopsies could be used to confirm an ongoing α-synucleinopathy. Seventy-four subjects with cerebral α-synucleinopathy in various Braak stages with concomitant GI biopsies were available for study. In 81% of the subjects, α-synuclein was seen in the mucosal/submucosal GI biopsies. Two subjects with severe cerebral α-synucleinopathy and a long delay between biopsy and death displayed no α-synuclein pathology in the gut, and 11 subjects with sparse cerebral α-synucleinopathy displayed GI α-synuclein up to 36 years prior to death. The finding that there was no GI α-synuclein in 19% of the subjects with cerebral α-synucleinopathy, and α-synuclein was observed in the gut of 11 subjects (15%) with sparse cerebral α-synucleinopathy even many years prior to death is unexpected and jeopardizes the use of assessment of α-synuclein in the peripheral tissue for confirmation of an ongoing cerebral α-synucleinopathy.

Neuropathology of α-synuclein in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by progressive movement disability accompanied by non-motor symptoms. The neuropathology hallmark of PD is the loss of dopaminergic neurons predominantly in the substantia nigra pars compacta and the presence of intracellular inclusions termed Lewy bodies (LBs), which are mainly composed of α-synuclein (αSyn). Detailed staging based on the distribution and progression pattern of αSyn pathology in the postmortem brains of PD patients revealed correlation with the clinical phenotypes but not invariably. Cumulative evidence from cell and animal studies has implied that αSyn propagation contributes to the anatomical spread of αSyn pathology in the brain. Here, we recount the studies over the past two centuries on the anatomopathological foundations of PD documented. We also review studies on the structural analysis of αSyn and LBs, Braak staging of αSyn pathology, the cell-to-cell propagation of αSyn as well as αSyn fibril polymorphisms, which underlie the phenotypic differences in synucleinopathies.

Autopsy Validation of the Diagnostic Accuracy of 123I-Metaiodobenzylguanidine Myocardial Scintigraphy for Lewy Body Disease

BACKGROUND AND OBJECTIVES

¹²³I-meta-iodobenzyl-guanidine (¹²³I-MIBG) myocardial scintigraphy is employed as a diagnostic imaging test to differentiate Lewy body diseases (LBDs), including Parkinson's disease and dementia with Lewy bodies, from other similar diseases. However, its diagnostic accuracy lacks validation compared with that of the gold standard. We aimed to validate the diagnostic accuracy of ¹²³I-MIBG myocardial scintigraphy for LBD against autopsy, the gold standard.

METHODS

This retrospective, cross-sectional study included consecutive autopsy patients from the Brain Bank for Aging Research who had undergone ¹²³I-MIBG myocardial scintigraphy. We compared the ¹²³I-MIBG myocardial scintigraphy findings with autopsy findings. Furthermore, the proportion of residual tyrosine hydroxylase (TH)-immunoreactive sympathetic fibers in the anterior wall of the left ventricle was investigated to assess the condition of the cardiac sympathetic nerves assumed to cause reduced ¹²³I-MIBG uptake in LBDs.

RESULTS

We analyzed the data of 56 patients (30 with pathologically confirmed LBDs and 26 without LBD pathology). Compared with the neuropathological diagnosis, the early heart-to-mediastinum (H/M) ratio had a sensitivity and specificity of 70.0% (95% confidence interval [CI]: 50.6-85.3%) and 96.2% (95% CI: 80.4-99.9%), respectively. The delayed H/M ratio had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 92.3% (95% CI: 74.9-99.1%), respectively. The washout rate had a sensitivity and specificity of 80.0% (95% CI: 61.4-92.3%) and 84.6% (95% CI: 65.1-95.6%), respectively. The proportion of residual TH-immunoreactive cardiac sympathetic fibers strongly correlated with the amount of cardiac ¹²³I-MIBG uptake when assessed with early and delayed H/M ratio values (correlation coefficient: 0.75 and 0.81, respectively; p < 0.001).

DISCUSSION

This clinicopathological validation study revealed that ¹²³I-MIBG myocardial scintigraphy could robustly differentiate LBDs from similar diseases. Abnormal ¹²³I-MIBG myocardial scintigraphy findings strongly support the presence of LBD and cardiac sympathetic denervation. However, LBD pathology should not necessarily be excluded by normal myocardial scintigraphy results, especially when other biomarkers suggest the presence of comorbid Alzheimer's disease pathology.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that ¹²³I-MIBG myocardial scintigraphy accurately identifies patients with LBD.

Unique Lewy pathology in myotonic dystrophy type 1

Lewy body-related α-synucleinopathy (Lewy pathology) has been reported in patients with myotonic dystrophy (DM) type 1 (DM1), but no detailed report has described the prevalence and extent of its occurrence. We studied consecutive full autopsy cases of DM1 at the National Center of Neurology and Psychiatry (NCNP) Brain Bank for intractable psychiatric and neurological disorders. Thirty-two cases, genetically determined to be DM1 (59.0 ± 8.7 years), obtained from the NCNP Brain Bank, were compared with control cases obtained from the Brain Bank for Aging Research (BBAR) in Japan. The investigated anatomical sites followed the Dementia with Lewy Bodies Consensus Guideline, expanding to the peripheral autonomic nervous system, temporal pole, and occipital cortex, in addition to the olfactory epithelium and spinal cord. Of the 32 patients, 11 (34.4%) had Lewy pathology, with a significantly higher prevalence than that in the control cases from the BBAR (20.1%). Lewy pathology detected in DM1 was widespread, but no macroscopic depigmentation of the substantia nigra was observed in any DM1 case; this was commensurate with the microscopic paucity of Lewy pathology in the substantia nigra and amygdala. Lewy pathology in DM1 does not appear to follow either Braak's ascending paradigm or the olfactory-amygdala extension. Lewy neurites and dots in DM1 were very sparse in the cerebral cortex and distinct from those observed in BBAR control cases. This study was the first demonstration of unique Lewy pathology in DM1 and may contribute to the understanding of the protein propagation hypothesis of Lewy pathology.

Clinical and imaging evidence of brain-first and body-first Parkinson's disease

Braak's hypothesis has been extremely influential over the last two decades. However, neuropathological and clinical evidence suggest that the model does not conform to all patients with Parkinson's disease (PD). To resolve this controversy, a new model was recently proposed; in brain-first PD, the initial α-synuclein pathology arise inside the central nervous system, likely rostral to the substantia nigra pars compacta, and spread via interconnected structures - eventually affecting the autonomic nervous system; in body-first PD, the initial pathological α-synuclein originates in the enteric nervous system with subsequent caudo-rostral propagation to the autonomic and central nervous system. By using REM-sleep behavior disorder (RBD) as a clinical identifier to distinguish between body-first PD (RBD-positive at motor symptom onset) and brain-first PD (RBD-negative at motor symptom onset), we explored the literature to evaluate clinical and imaging differences between these proposed subtypes. Body-first PD patients display: 1) a larger burden of autonomic symptoms - in particular orthostatic hypotension and constipation, 2) more frequent pathological α-synuclein in peripheral tissues, 3) more brainstem and autonomic nervous system involvement in imaging studies, 4) more symmetric striatal dopaminergic loss and motor symptoms, and 5) slightly more olfactory dysfunction. In contrast, only minor cortical metabolic alterations emerge before motor symptoms in body-first. Brain-first PD is characterized by the opposite clinical and imaging patterns. Patients with pathological LRRK2 genetic variants mostly resemble a brain-first PD profile whereas patients with GBA variants typically conform to a body-first profile. SNCA-variant carriers are equally distributed between both subtypes. Overall, the literature indicates that body-first and brain-first PD might be two distinguishable entities on some clinical and imaging markers.

An autopsied case report of spastic paraplegia with thin corpus callosum carrying a novel mutation in the SPG11 gene: widespread degeneration with eosinophilic inclusions

Background

The detailed neuropathological features of patients with autosomal recessive hereditary spastic paraplegia with a thin corpus callosum (TCC) and SPG11 mutations are poorly understood, as only a few autopsies have been reported. Herein, we describe the clinicopathological findings of a patient with this disease who received long-term care at our medical facility.

Case presentation

A Japanese man exhibited a mild developmental delay in early childhood and intellectual disability, followed by the appearance of a spastic gait by age 13. At the age of 25 years, he became bedridden and needed a ventilator. Genetic analysis revealed a homozygous splice site variant in the SPG11 gene (c. 4162–2A > G) after the provision of genetic counselling and acquisition of informed consent from his parents. He died of pneumonia at the age of 44. His brain weighed 967 g and was characterized by a TCC, and his spinal cord was flattened. Microscopically, degeneration was observed in the posterior spinocerebellar tract, the gracile fasciculus, and the posterior column in addition to the corticospinal tract. Marked neuronal loss and gliosis were observed in the anterior horn, Clarke’s column, and hypoglossal and facial nuclei. Various types of neurons, in addition to motor neurons, showed coarse eosinophilic granules that were immunoreactive for p62. The loss of pigmented neurons with gliosis was apparent in both the substantia nigra and locus coeruleus. Lateral geniculate body degeneration was a characteristic feature of this patient. Furthermore, peripheral Lewy body-related α-synucleinopathy and scattered α-synuclein–immunoreactive neurites in the locus coeruleus and reticular formation of the brainstem were observed.

Conclusions

In patients with hereditary spastic paraplegia with SPG11 mutations, a variety of clinical phenotypes develop due to widespread lesions containing p62-immunoreactive neuronal cytoplasmic inclusions. We herein report the lateral geniculate body as another degenerative site related to SPG11-related pathologies that should be studied in future investigations.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02514-z.

Neuropathology and molecular diagnosis of Synucleinopathies

Synucleinopathies are clinically and pathologically heterogeneous disorders characterized by pathologic aggregates of α-synuclein in neurons and glia, in the form of Lewy bodies, Lewy neurites, neuronal cytoplasmic inclusions, and glial cytoplasmic inclusions. Synucleinopathies can be divided into two major disease entities: Lewy body disease and multiple system atrophy (MSA). Common clinical presentations of Lewy body disease are Parkinson's disease (PD), PD with dementia, and dementia with Lewy bodies (DLB), while MSA has two major clinical subtypes, MSA with predominant cerebellar ataxia and MSA with predominant parkinsonism. There are currently no disease-modifying therapies for the synucleinopathies, but information obtained from molecular genetics and models that explore mechanisms of α-synuclein conversion to pathologic oligomers and insoluble fibrils offer hope for eventual therapies. It remains unclear how α-synuclein can be associated with distinct cellular pathologies (e.g., Lewy bodies and glial cytoplasmic inclusions) and what factors determine neuroanatomical and cell type vulnerability. Accumulating evidence from in vitro and in vivo experiments suggests that α-synuclein species derived from Lewy body disease and MSA are distinct "strains" having different seeding properties. Recent advancements in in vitro seeding assays, such as real-time quaking-induced conversion (RT-QuIC) and protein misfolding cyclic amplification (PMCA), not only demonstrate distinct seeding activity in the synucleinopathies, but also offer exciting opportunities for molecular diagnosis using readily accessible peripheral tissue samples. Cryogenic electron microscopy (cryo-EM) structural studies of α-synuclein derived from recombinant or brain-derived filaments provide new insight into mechanisms of seeding in synucleinopathies. In this review, we describe clinical, genetic and neuropathologic features of synucleinopathies, including a discussion of the evolution of classification and staging of Lewy body disease. We also provide a brief discussion on proposed mechanisms of Lewy body formation, as well as evidence supporting the existence of distinct α-synuclein strains in Lewy body disease and MSA.

Parkinson's Disease and the Gut: Symptoms, Nutrition, and Microbiota

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, characterized by symptoms of bradykinesia, rigidity, postural instability, and tremor. Recently, there has been a growing focus on the relationship between the gut and the development of PD. Emerging to the forefront, an interesting concept has developed suggesting that the initial pathophysiological changes occur in the gastrointestinal tract before changes are seen within the brain. This review is aimed at highlighting the relationship between PD and the gastrointestinal tract, along with the supporting evidence for this. Firstly, we will focus on the gastrointestinal conditions and symptoms which commonly affects patients, including both upper and lower gastrointestinal issues. Secondly, the impact of nutrition and diet on neurological health and PD physiology, with particular emphasis on commonly consumed items including macronutrients and micronutrients. Finally, variability of the gut microbiome will also be discussed and its link with both the symptoms and signs of PD. The evidence presented in this review highly suggests that the initial pathogenesis in the gut may proceed the development of prodromal PD subtypes, and therefore building on this further could be imperative and lead to earlier diagnosis with new and improved therapeutics.

Autonomic symptoms are predictive of dementia with Lewy bodies

INTRODUCTION

Autonomic symptoms are common in patients with dementia with Lewy bodies (DLB). Although autonomic dysfunction is considered as one of the primary early markers in patients with DLB, there are few studies that examine the timing of the onset of autonomic symptoms in these patients. The purpose of the current study was to evaluate the time of onset of autonomic symptoms in patients with DLB using a questionnaire.

METHODS

Autonomic symptoms were evaluated in patients with DLB using the Scales for Outcomes in Parkinson's disease - autonomic (SCOPA-Aut) questionnaire. Time of the onset of autonomic symptoms of patients with DLB was also assessed relative to that of memory loss.

RESULTS

A total of 106 patients with DLB were included. The most frequent symptom of dysautonomia in patients with DLB was constipation (60.4%), followed by orthostatic dizziness (33%), urinary frequency (30.2%), and daytime hyperhidrosis (22.6%). The gastrointestinal system was the most prominent system of autonomic dysfunction in patients with DLB. Orthostatic dizziness, daytime hyperhidrosis, and constipation all preceded the onset of memory loss by 0.2 ± 4.9, 3.3 ± 8.6, and 3.7 ± 9.2 years, respectively, while urinary incontinence occurred 1.7 ± 1.5 years following the onset of memory loss.

CONCLUSION

Many autonomic symptoms precede the onset of memory loss in patients with DLB, especially constipation and daytime hyperhidrosis. These symptoms can facilitate an early diagnosis of patients with DLB.

Diagnostic value of skin RT-QuIC in Parkinson's disease: a two-laboratory study

Skin α-synuclein deposition is considered a potential biomarker for Parkinson's disease (PD). Real-time quaking-induced conversion (RT-QuIC) is a novel, ultrasensitive, and efficient seeding assay that enables the detection of minute amounts of α-synuclein aggregates. We aimed to determine the diagnostic accuracy, reliability, and reproducibility of α-synuclein RT-QuIC assay of skin biopsy for diagnosing PD and to explore its correlation with clinical markers of PD in a two-center inter-laboratory comparison study. Patients with clinically diagnosed PD (n = 34), as well as control subjects (n = 30), underwent skin punch biopsy at multiple sites (neck, lower back, thigh, and lower leg). The skin biopsy samples (198 in total) were divided in half to be analyzed by RT-QuIC assay in two independent laboratories. The α-synuclein RT-QuIC assay of multiple skin biopsies supported the clinical diagnosis of PD with a diagnostic accuracy of 88.9% and showed a high degree of inter-rater agreement between the two laboratories (92.2%). Higher α-synuclein seeding activity in RT-QuIC was shown in patients with longer disease duration and more advanced disease stage and correlated with the presence of REM sleep behavior disorder, cognitive impairment, and constipation. The α-synuclein RT-QuIC assay of minimally invasive skin punch biopsy is a reliable and reproducible biomarker for Parkinson's disease. Moreover, α-synuclein RT-QuIC seeding activity in the skin may serve as a potential indicator of progression as it correlates with the disease stage and certain non-motor symptoms.

Neuropathological evidence of body-first vs. brain-first Lewy body disease

Aggregation of alpha-synuclein into inclusion bodies, termed Lewy pathology, is a defining feature of Parkinson's disease (PD) and Dementia with Lewy bodies (DLB). In the majority of post mortem cases, the distribution of Lewy pathology seems to follow two overarching patterns: a caudo-rostral pattern with relatively more pathology in the brainstem than in the telencephalon, and an amygdala-centered pattern with the most abundant pathology in the "center of the brain", including the amygdala, entorhinal cortex, and substantia nigra, and relatively less pathology in the lower brainstem and spinal autonomic nuclei. The recent body-first versus brain-first model of Lewy Body Disorders proposes that the initial pathogenic alpha-synuclein in some patients originates in the enteric nervous system with secondary spreading to the brain; and in other patients originates inside the CNS with secondary spreading to the lower brainstem and peripheral autonomic nervous system. Here, we use two existing post mortem datasets to explore the possibility that clinical body-first and brain-first subtypes are equivalent to the caudo-rostral and amygdala-centered patterns of Lewy pathology seen at post mortem.

Lewy pathology of the submandibular gland in Lewy body disease: A report of autopsy cases

Accumulation of phosphorylated α-synuclein in the central and peripheral nervous systems is a histological hallmark of Lewy body disease (LBD), including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and LB-related pure autonomic failure. The submandibular gland is employed as a biopsy site for detecting Lewy pathology; however, the incidence of Lewy pathology in this region in autopsy-proven LBD cases at all stages from an aged Japanese cohort remains unclear. To validate the utility of Lewy pathology of the submandibular gland as a diagnostic biomarker for LBD, we investigated the submandibular gland Lewy pathology in autopsied patients. To determine the specificity, we prospectively evaluated the submandibular gland in 64 consecutive autopsied patients. To determine the sensitivity, we retrospectively assessed the submandibular gland in 168 consecutive autopsied patients who had prodromal or clinical LBD. In the prospective study, Lewy pathology was found in 21 of 64 patients, and nine of those 21 patients had the submandibular gland Lewy pathology. No Lewy pathology was found in 43 patients without CNS Lewy pathology, giving a specificity of 100%. In the retrospective study, Lewy pathology of the submandibular gland was detected in 126 of 168 patients. The sensitivity was 89.1% in PD and 75.4% in DLB. The sensitivity increased with disease progression. These findings support the utility of the submandibular gland biopsy for the pathological diagnosis of LBD.