CSF Protein Level of Neurotransmitter Secretion, Synaptic Plasticity, and Autophagy in PD and DLB

BACKGROUND: Molecular pathways associated with α-synuclein proteostasis have been detected in genetic studies and in cell models and include autophagy, ubiquitin-proteasome system, mitochondrial homeostasis, and synaptic plasticity. However, we lack biomarkers that are representative for these pathways in human biofluids. OBJECTIVE: The objective of this study was to evaluate CSF protein profiles of pathways related to α-synuclein proteostasis. METHODS: We assessed CSF protein profiles associated with neurotransmitter secretion, synapse plasticity, and autophagy in 2 monocentric cohorts with α-synucleinopathy (385 PD patients and 67 DLB patients). We included 80 PD patients and 17 DLB patients with variants in the glucocerebrosidase gene to serve as proxy for accelerated α-synuclein pathology with pronounced clinical trajectories. RESULTS: (1) Proteins associated with neurotransmitter secretion, synaptic plasticity, and endolysosomal autophagy were lower in PD and DLB patients compared with healthy controls. (2) These patterns were more pronounced in DLB than in PD patients, accentuated by GBA variant status in both entities. (3) CSF levels of these proteins were positively associated with CSF levels of total α-synuclein, with lower levels of proteostasis proteins related to lower levels of total α-synuclein. (4) These findings could be confirmed longitudinally. PD patients with low CSF profiles of proteostasis proteins showed lower CSF levels of α-synuclein longitudinally compared with PD patients with a normal proteostasis profile. CONCLUSION: CSF proteins associated with neurotransmitter secretion, synaptic plasticity, and endolysosomal autophagy might serve as biomarkers related to α-synuclein proteostasis in PD and DLB

Association between CSF alpha-synuclein seeding activity and genetic status in Parkinson’s disease and dementia with Lewy bodies

The clinicopathological heterogeneity in Lewy-body diseases (LBD) highlights the need for pathology-driven biomarkers in-vivo. Misfolded alpha-synuclein (α-Syn) is a lead candidate based on its crucial role in disease pathophysiology. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has recently shown high sensitivity and specificity for the detection of misfolded α-Syn in patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). In this study we performed the CSF RT-QuIC assay in 236 PD and 49 DLB patients enriched for different genetic forms with mutations in GBA, parkin, PINK1, DJ1, and LRRK2. A subgroup of 100 PD patients was also analysed longitudinally. We correlated kinetic seeding parameters of RT-QuIC with genetic status and CSF protein levels of molecular pathways linked to α-Syn proteostasis. Overall, 85% of PD and 86% of DLB patients showed positive RT-QuIC α-Syn seeding activity. Seeding profiles were significantly associated with mutation status across the spectrum of genetic LBD. In PD patients, we detected positive α-Syn seeding in 93% of patients carrying severe GBA mutations, in 78% with LRRK2 mutations, in 59% carrying heterozygous mutations in recessive genes, and in none of those with bi-allelic mutations in recessive genes. Among PD patients, those with severe GBA mutations showed the highest seeding activity based on RT-QuIC kinetic parameters and the highest proportion of samples with 4 out of 4 positive replicates. In DLB patients, 100% with GBA mutations showed positive α-Syn seeding compared to 79% of wildtype DLB. Moreover, we found an association between α-Syn seeding activity and reduced CSF levels of proteins linked to α-Syn proteostasis, specifically lysosome-associated membrane glycoprotein 2 and neurosecretory protein VGF. These findings highlight the value of α-Syn seeding activity as an in-vivo marker of Lewy-body pathology and support its use for patient stratification in clinical trials targeting α-Syn

[11C]MODAG 005 – a novel PET tracer targeting alpha-synuclein aggregates in the brain

Synucleinopathies are neurodegenerative diseases characterized by the presence of brain inclusions containing the pathologically aggregated protein α-synuclein (αSYN). The development of a positron emission tomography tracer to detect aggregates of misfolded αSYN would revolutionize disease monitoring and the evaluation of therapeutic efficacy. Here we present the development and preclinical in vitro and in vivo validation of [11C]MODAG-005. In vitro binding experiments demonstrate subnanomolar binding affinity to recombinant αSYN fibrils as well as to αSYN inclusions in human brain tissue. Specific binding in multiple system atrophy brain tissue was detected using autoradiography and microautoradiography, and was validated through immunostaining. In vivo, [11C]MODAG-005 shows good brain penetration, rapid clearance from brain tissue and low metabolite formation in rodents and non-human primates. In addition, a pronounced binding and a good signal-to-noise ratio were achieved in an αSYN fibril-injected rat model and in an αSYN(A30P) transgenic mouse model in correlation to the pathological load. To validate its value for therapy development, we show target engagement of the drug candidate anle138b in the brain tissues from αSYN(A30P) mouse and multiple system atrophy as well as in vivo in αSYN fibril-injected rats. Finally, our translational approach in a first-in-human patient with clinically established MSA, revealed a marked tracer binding in regions affected by αSYN pathology, particularly in the striatum, where the pattern corresponded with the neurodegeneration shown by dopamine transporter single-photon emission computed tomography

Blood-based biomarkers for Alzheimer disease: mapping the road to the clinic

Biomarker discovery and development for clinical research, diagnostics and therapy monitoring in clinical trials have advanced rapidly in key areas of medicine - most notably, oncology and cardiovascular diseases - allowing rapid early detection and supporting the evolution of biomarker-guided, precision-medicine-based targeted therapies. In Alzheimer disease (AD), breakthroughs in biomarker identification and validation include cerebrospinal fluid and PET markers of amyloid-β and tau proteins, which are highly accurate in detecting the presence of AD-associated pathophysiological and neuropathological changes. However, the high cost, insufficient accessibility and/or invasiveness of these assays limit their use as viable first-line tools for detecting patterns of pathophysiology. Therefore, a multistage, tiered approach is needed, prioritizing development of an initial screen to exclude from these tests the high numbers of people with cognitive deficits who do not demonstrate evidence of underlying AD pathophysiology. This Review summarizes the efforts of an international working group that aimed to survey the current landscape of blood-based AD biomarkers and outlines operational steps for an effective academic-industry co-development pathway from identification and assay development to validation for clinical use

Reply to: "Susceptibility-Weighted Imaging Reveals Subcortical Iron Deposition in PLAN: The 'Double Cortex Sign'"

We thank Dr. Parnes for his highly valuable comment in his letter to the editor in reply to our recent publication,1 and we agree that duplicate terms for phenotypic or imaging characteristics of different diseases may be misleading in general.However, we believe that the descriptive term “double cortex sign” referring to the pattern of iron deposition subcortical to the entire cortical ribbon on susceptibility-weighted imaging in our patient with PLA2G6-associated neurodegeneration (PLAN)1 is clearly distinguishable from the band heterotopia seen on standard T1- and T2-weighted sequences underlying the imaging pattern termed “double cortex syndrome” caused by pathogenic variants in the DCX gene.2-6Therefore, in our view, given the similar but distinguishable imaging pattern in PLAN and DCX-associated disease, the descriptive term “double cortex” resulting from the visual appearances on different magnetic resonance imaging (MRI) sequences could be considered adequate in both PLAN and DCX-associated disease. This might even stimulate and facilitate thorough differential diagnostic considerations in disorders with imaging patterns reminiscent of a “double cortex,” eventually leading to appropriate selection of suitable MRI sequences in the diagnostic workup of such patients

Realizing the Opportunities of Neutron Cross Section Measurements at RIA

The Rare Isotope Accelerator will produce many isotopes at never before seen rates. This will allow for the first time measurements on isotopes very far from stability and new measurement opportunities for unstable nuclei near stability. In fact, the production rates are such that it should be possible to collect 10 micrograms of many isotopes with a half-life of 1 day or more. This ability to make targets of short-lived nuclei enables the possibility of making neutron cross-section measurements important to the astrophysics and the stockpile stewardship communities. But to fully realize this opportunity, the appropriate infrastructure must be included at the RIA facility. This includes isotope harvesting capabilities, radiochemical areas for processing collected material, and an intense, ''mono-energetic'', tunable neutron source. As such, we have been developing a design for neutron source facility to be included at the RIA site. This facility would produce neutrons via intense beams of deuterons and protons on a variety of targets. The facility would also include the necessary radiochemical facilities for target processing. These infrastructure needs will be discussed in addition to the methods that would be employed at RIA for measuring these neutron cross-sections