Aims

Prion diseases are a group of fatal and infectious neurodegenerative disorders. They affect both humans and animals. Creutzfeldt-Jakob disease (CJD) is the most common human prion disease. Currently, no treatment is available for prion diseases. Cellular cholesterol is known to impact prion conversion, which in turn results in an accumulation of cholesterol in prion-infected neurons. The brain-specific enzyme, cholesterol 24-hydroxylase (CYP46A1) converts cholesterol into 24(S)-hydroxycholesterol that exits the brain. We aimed to determine the role of Cyp46A1 in prion disease and to verify pharmacological Cyp464A1 activation as a novel therapeutic approach.

Methods

Immunoblotting and confocal microscopy were performed on brains of prion-mice infected and in post-mortem brains of sporadic (sCJD) patients as well as in prion infected-neuronal/astrocyte cells and primary cerebellar granular neurons.

Results

We have demonstrated for the first time that Cyp46A1 levels are reduced in the brains of prion-infected mice at advanced disease stage, in prion-infected neuronal/astrocyte cells, and in post-mortem brains of sCJD patients. We have used the Cyp46A1 activator efavirenz (EFV) for the treatment of prion-infected neuronal cell lines, primary neurons, and mice. EFV is an FDA-approved anti-HIV medication crossing the blood-brain barrier. EFV treatment significantly mitigated the infectious prion protein isoform (PrP^Sc) in prion-infected cells and prevented de novo infection of primary neurons. Notably, oral administration of EFV at low dosage significantly prolonged the lifespan of prion-infected mice.

Conclusions

Our results suggest that Cyp46A1 as a novel therapeutic target and that its activation might be a valuable treatment approach for prion diseases.

Aims

Methods

Results

Conclusions

This work identified a novel modality for the treatment of prion diseases that makes use of low nanomolar concentrations of a small molecule from a compound class that is pharmacologically well-understood and exhibits excellent potency for reducing PrP^C levels.

Aims

To evaluate the performance of α-synuclein (α-syn) RT-QuIC in two independent cohorts.

Methods

α-syn-RT-QuIC was used to analyze lumbar CSF in a clinical cohort from the Swedish BioFINDER study and in post-mortem ventricular CSF in a neuropathological cohort from the Arizona Study of Aging and Neurodegenerative Disorders/Brain and Body Donation Program (AZSAND/BBDP). The neuropathological cohort included 101 individuals with different brain disorders, including Lewy Body disorders (LBD) and controls. The clinical cohort included 50 PD, 14 PDD, 15 MSA, 15 PSP, 47 controls and two individuals who were included as controls but who later converted to PD or DLB (LBD).

Results

BioFINDER cohort: 94.0% of PD and 100% of PDD patients were α-syn-RT-QuIC positive compared to 17.0% of the controls (non-LBD-converters), 33.3% of PSP and 33.3% of MSA patients. Both controls who later converted to LBD were α-syn-RT-QuIC positive. α-syn-RT-QuIC identified LBD (i.e. PD, PDD and converters) vs. controls with a sensitivity of 95.5%, a specificity of 83.0% and a diagnostic accuracy of 90.3%.

AZSAND/BBDP: α-syn-RT-QuIC could identify neuropathologically verified standard LBD, including PD, PD with Alzheimer’s disease (PDAD) and DLB (n=25) vs. no LB pathology (n=53) with a sensitivity of 100%, a specificity of 94.3% and a diagnostic accuracy of 96.2%. However, of the individuals with non-standard Lewy body disorders (n=23) including AD with Lewy body disease not meeting criteria for DLB or PD, and incidental LBD, only 56.5% were α-syn-RT-QuIC positive.

Conclusions

α-syn-RT-QuIC in the CSF is highly sensitive and specific for identifying subjects with clinical or clinicopathologically-defined Lewy body disorders.

Aims

Currently, there is no established molecular biomarker available for the non-invasive diagnosis of synucleinopathies. Furthermore, monitoring of progression of synuclein pathology over time and the effect of disease-modifying therapies is urgently needed. Here, we evaluate the potential of MODAG-005 to serve as an alpha-synuclein (αSyn) radiotracer for positron emission tomography (PET) in vitro and in vivo.

Methods

In vitro binding of [³H]MODAG-005 was determined using human recombinant αSyn, tau, and amyloid-beta_1-42 (Aβ) fibrils. (Micro)autoradiography was performed in post-mortem human brain tissue from multiple system atrophy, Parkinson’s disease, progressive supranuclear palsy, Alzheimer’s disease, healthy controls, and in the transgenic αSyn(A30P) mouse model. In vivo pharmacokinetics and metabolism of [¹¹C]MODAG-005 were studied in healthy mice and rats, as well as in rats inoculated with αSyn fibrils into the striatum.

Results

In vitro, MODAG-005 shows a high affinity to and a high selectivity for aggregated αSyn (K_d = 0.2 nM vs. 7 nM for tau and >100 nM for Aβ, respectively). This was confirmed in (micro)autoradiography on human brain tissue and in the αSyn(A30P) mouse model, as MODAG-005 binds specifically to αSyn deposits. In vivo, MODAG-005 shows an excellent brain uptake (SUV ~ 2), as well as a fast wash-out (t_1/2 = 9min) and only negligible metabolite formation in the brain. Rats inoculated with αSyn fibrils show a well-detectable binding at the injection side.

Conclusions

MODAG-005 holds promise to serve as an αSyn PET tracer as it meets prevailing criteria in established in vitro and in vivo assays and, thus, qualifies for further (pre-)clinical development.

Aims

Studies on dementia with Lewy bodies (DLB) have mainly focussed on the deterioration of distinct cortical and subcortical regions related to the deposition of Lewy bodies. In view of the proposed trans-synaptic spread of the alpha-synuclein-pathology, investigating the disease in this segregated fashion only, would be detrimental to our understanding of its progression. Over the past two decades, an increasing number of studies have examined the effects of the disease on structural and functional brain connectivity. Here, we aim to summarize the current state of research on connectivity changes in DLB compared to healthy age-matched controls and other dementias.

Methods

In August 2021, we conducted a search of relevant peer-reviewed literature across several electrophysiological and imaging modalities on PubMed, following PRISMA guidelines.

Results

Out of 337 identified articles, 38 articles were selected and systematically reviewed. Positron emission tomography (PET), magnetic resonance imaging (MRI), and electroencephalography (EEG) assessments of patients revealed widespread abnormalities within and across brain networks in DLB. Most changes occurred within the default mode network and its connections to other cortical regions. Further, advanced mathematical analysis methods demonstrated disease-related changes in local and global network efficiency measures. A subset of studies revealed correlations between connectivity measures and cognitive impairments.

Conclusions

This review shows that the exploration of structural and functional connectivity changes in DLB allows reconstructing the spread of the disease along neural tracts. This knowledge may help to understand clinical presentations and to identify targets for future disease-modifying treatments in DLB.

Aims

The cerebellum is a crucial structure for both motor and cognitive functions, yet studies on cerebellar abnormalities in Parkinson’s disease (PD) are limited and findings lack consistency. With a multi-cohort approach and state-of-the-art analysis methods, we attempted to better understand how cerebellar structure is affected in PD.

Methods

T1-weighted MR images of 670 PD patients (mean age 65.1y, 41% female, mean illness duration 4.1y) and 275 healthy controls (mean age 63.6y, 51% female) were collected from eight cohorts, and processed using the ACAPULCO segmentation toolbox (http://iacl.jhu.edu/index.php?title=Cerebellum_CNN). Linear mixed-effect models, including age, sex, ICV, and cohort as covariates, were used for group comparison of volumes of 14 cerebellar lobules in each hemisphere. P-values were FDR-corrected.

Results

Compared to controls, PD patients showed a higher total volume (t = 2.55, p_uncorrected = 0.011) and regional volume in 7 of 28 lobules (t_min = 2.19, t_max = 3.80, p_uncorrected < 0.029), before FDR-correction. After correction, the right lobule V (t = 3.26, p_FDR = 0.014) and right lobule VI (t = 3.80, p_FDR < 0.001) remained significantly different.

Conclusions

The larger lobules in PD are intriguing in the context of neurodenegeration. Lobule V and VI have previously been linked to motor function; possibly the enlargement is the result of (temporary) hypertrophy due to constant motor activation in patients. This is supported by literature showing that greater intensity of tremor is related to an enlargement of lobule V. Follow-up research will need to focus on the relation between motor and cognitive symptoms and cerebellar morphology in PD.

Aims

The prion protein (PrP) and the metalloprotease ADAM10 play important (patho)physiological roles. While PrP is essential for the pathogenesis of transmissible prion diseases and acts as a neuronal receptor for toxic proteins in other neurodegenerative conditions including Alzheimer`s and Parkinson`s disease, ADAM10 confers neuroprotection as it represents the major α-secretase of APP and the exclusive sheddase of PrP. We aimed to study the relevance of PrP shedding and biological functions of shed PrP (sPrP) in proteinopathies, and to identify innocuous means of manipulating this cleavage without targeting ADAM10.

Methods

We recently generated a set of cleavage site-specific antibodies for sensitive and reliable detection of sPrP in biological samples and employed multiple cell lines, organotypic slice cultures, and transgenic mice using a variety of biochemical, biophysical/structural and morphological methods.

Results

Our data suggest an inverse correlation between ADAM10 levels and prion replication. In contrast to the detrimental effects of membrane-bound PrP in proteinopathies, sPrP may block and sequester diffusible harmful protein assemblies into less toxic extracellular deposits. Notably, we reveal a substrate-specific approach to stimulate the ADAM10-mediated shedding of PrP and provide structural and mechanistic insight into how PrP-directed ligands determine the fate of cellular PrP.

Conclusions

The roles of released forms or fragments of PrP may fundamentally differ from the ones associated with their cell surface progenitor. Further studies on intrinsic functions of sPrP, on the therapeutic potential of ligand-induced PrP shedding, and on a conceivable diagnostic relevance of sPrP in body fluids are warranted and will greatly profit from site-specific antibodies.

Aims

Parkinson’s disease (PD) is characterized by the gradual appearance of intraneuronal inclusions that are primarily composed of misfolded α-synuclein protein, leading to cytotoxicity and neural death. Recent studies suggest that misfolded α-synuclein may spread transcellularly, inducing pathological aggregates in healthy neurons, and is disseminated via secretion of extracellular vesicles (EVs). Prompted by the hypothesis of Braak et al. that the olfactory bulb is one of the primary propagation sites for the initiation of PD, we sought to investigate the role of EVs in the spread of α-synuclein and progression of PD through the olfactory bulb.

Methods

EVs derived from the cerebrospinal fluid of patients diagnosed with PD or with a nonsynucleinopathy neurodegenerative disorder were administered intranasally to healthy mice. Three months later, mice were subjected to behavior tests and histochemical analysis of midbrain structures.

Results

Mice subjected to the intranasal administration of CSF-derived EVs from PD patients exhibited multiple features consistent with the disease such as motor behavior impairments, α-synuclein aggregations in the substantia nigra and dopaminergic neurodegeneration. In addition, we observed several understudied symptoms such as robust α-synuclein aggregations in the red nucleus, canities, impaired autophagy and astrogliosis of unconventional GFAP isoforms.

Conclusions

Collectively, these data indicate that intranasally administered EVs derived from the CSF of patients with PD can propagate α-synuclein aggregation in vivo and trigger PD-like symptoms and pathology in healthy mice. Deciphering the disrupted pathways leading to definitive parkinsonian symptoms alongside the unconventional pathologies can lead to further resolution of the molecular pathology of PD.