Abstract Background Alzheimer’s disease (AD) is characterized by the accumulation of amyloid-β (Aβ) peptides in intra- and extracellular deposits. How Aβ aggregates perturb the proteome in brains of patients and AD transgenic mouse models, however, remains largely unclear. State-of-the-art mass spectrometry (MS) methods can comprehensively detect proteomic alterations in neurodegenerative disorders, providing relevant insights unobtainable with transcriptomics investigations. Analyses of the relationship between progressive Aβ aggregation and protein abundance changes in brains of 5xFAD transgenic mice have not been reported previously. Methods We quantified progressive Aβ aggregation in hippocampus and cortex of 5xFAD mice and controls with immunohistochemistry and biochemical membrane filter assays. Protein changes in different mouse tissues were analysed by MS-based proteomics using label-free quantification (LFQ); resulting MS data were processed using an established pipeline. Results were contrasted with existing proteomic data sets from postmortem AD patient brains. Finally, abundance changes in the candidate marker Arl8b were validated in CSF from AD patients and controls using ELISAs. Results: Experiments revealed a more rapid accumulation of Aβ42 peptides in hippocampus than in cortex of 5xFAD mice, accompanied by many more protein abundance changes in hippocampus than in cortex, indicating that Aβ42 aggregate deposition is associated with brain region-specific proteome perturbations. Generating time-resolved data sets, we defined Aβ aggregate-correlated and anticorrelated proteome changes, a fraction of which was conserved in postmortem AD patient brain tissue, suggesting that proteome changes in 5xFAD mice mimic disease relevant changes in human AD. We detected a positive correlation between Aβ42 aggregate deposition in the hippocampus of 5xFAD mice and the abundance of the lysosome-associated small GTPase Arl8b, which accumulated together with axonal lysosomal membranes in close proximity of extracellular Aβ plaques in 5xFAD brains. Abnormal aggregation of Arl8b was observed in AD brain tissue. Arl8b protein levels were significantly increased in cerebrospinal fluid (CSF) of AD patients, a clinically accessible body fluid. Conclusions We report a comprehensive biochemical and proteomic investigation of hippocampal and cortical brain tissue derived from 5xFAD transgenic mice, providing a valuable resource to the neuroscientific community. We identified Arl8b, with significant abundance changes in 5xFAD and AD patient brains. Arl8b might enable the measurement of progressive lysosome accumulation in AD patients and have clinical utility as a candidate biomarker. Data are available via ProteomeXchange with identifier PXD030348.
In chronic neurological conditions, wearable/portable devices have potential as innovative tools to detect subtle early disease manifestations and disease fluctuations for the purpose of clinical diagnosis, care and therapeutic development. Huntington's disease (HD) has a unique combination of motor and non-motor features which, combined with recent and anticipated therapeutic progress, gives great potential for such devices to prove useful. The present work aims to provide a comprehensive account of the use of wearable/portable devices in HD and of what they have contributed so far. We conducted a systematic review searching MEDLINE, Embase, and IEEE Xplore. Thirty references were identified. Our results revealed large variability in the types of sensors used, study design, and the measured outcomes. Digital technologies show considerable promise for therapeutic research and clinical management of HD. However, more studies with standardized devices and harmonized protocols are needed to optimize the potential applicability of wearable/portable devices in HD.
Establishing fluid biomarkers enables direct assessment of relevant aspects of Huntington's disease (HD) pathology. Therefore, monitoring blood and CSF biomarkers of neuronal impairment in HD mice enhances our understanding of disease progression and facilitates potential therapeutic development for HD.
Aims
To better understand how plasma and CSF biomarker levels change with disease progression in HD mice.
Methods
Blood was collected into EDTA tubes via terminal cardiac puncture from zQ175 and wild type (WT) mice at 2, 6, and 12 months of age, from R6/2:Q200 and WT at 4, 8 and 12 weeks and from R6/2:Q90 and WT at 4, 14 and 24 weeks, and plasma extracted after centrifugation. CSF was collected from terminal anaesthetised mice via the cisterna magna using a glass capillary from R6/2Q90 and WT at 16 and 24 weeks of age. Both NFL and Tau concentrations were quantified with an ultrasensitive single-molecule array method (SIMOA, Quanterix).
Results
Quantirex analysis revealed elevated levels of plasma NFL: in zQ175 at 6 and 12 months of age, in R6/2:Q200 at 8 and 12 weeks of age, in R6/2:Q90 at 4, 14 and 24 weeks of age compared to WT littermates. Plasma Tau levels were only elevated in HD mice as compared to wild type littermates at end stage. CSF NFL levels were elevated in R6/2:Q90 at 16 and 24 weeks of age compared to wild type littermates.
Neurofilament light protein (NfL) is elevated in cerebrospinal fluid (CSF) of a number of neurological conditions compared with healthy controls (HC) and is a candidate biomarker for neuroaxonal damage. The influence of age and sex is largely unknown, and levels across neurological disorders have not been compared systematically to date.
To cope with heterogeneous subsurface environments mycelial microorganisms have developed a unique ramified growth form. By extending hyphae, they can obtain nutrients from remote places and transport them even through air gaps and in small pore spaces, repectively. To date, studies have been focusing on the role that networks play in the distribution of nutrients. Here, we investigated the role of mycelia for the translocation of nonessential substances, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. We show that the hyphae of the mycelial soil oomycete Pythium ultimum function as active translocation vectors for a wide range of PAHs. Visualization by two-photon excitation microscopy (TPEM) demonstrated the uptake and accumulation of phenanthrene (PHE) in lipid vesicles and its active transport by cytoplasmic streaming of the hyphae ('hyphal pipelines'). In mycelial networks, contaminants were translocated over larger distances than by diffusion. Given their transport capacity and ubiquity, hyphae may substantially distribute remote hydrophobic contaminants in soil, thereby improving their bioavailability to bacterial degradation. Hyphal contaminant dispersal may provide an untapped potential for future bioremediation approaches.
Therapeutic approaches to treat Huntington9s disease by lowering mutant (m)HTT levels are expected to proceed to human trials, yet non-invasive quantification of mHTT is not currently possible. The peripheral immune system in neurodegenerative disease is becoming increasingly recognised as important and peripheral immune cells have been implicated in HD pathogenesis. However, HTT levels in these cells have not been quantified before.
Aims
To quantify mutant and total HTT levels in peripheral immune cells isolated from HD patients, and to determine whether these levels track with disease progression.
Methods
Monocytes, T cells and B cells were isolated by magnetic cell sorting from the peripheral blood mononuclear fraction of whole blood. They were subjected to a time-resolved Förster resonance energy transfer (TR-FRET) immunoassay to measure mutant and total HTT protein levels. Estimates were made of their association with disease burden scores and brain atrophy rates. Fragmentation of HTT in peripheral immunocytes was monitored by immunoprecipitation and western blot.
Results
Mean mHTT levels in monocytes, T cells and B cells differed significantly between HD patients and controls, and between pre-manifest mutation carriers and those with clinical onset. Monocyte and T cell mHTT levels were significantly associated with disease burden scores and caudate atrophy rates in HD patients. Mutant HTT N-terminal fragments detected in HD monocytes may explain the progressive increase in mHTT levels in these cells.
Conclusions
These findings indicate that quantification of mHTT in peripheral immune cells by TR-FRET holds significant promise as a non-invasive disease biomarker. That mHTT levels in such cells are associated with disease progression and brain atrophy rates indicates their potential relevance to pathogenic events in the CNS. Clinical trials in HD aiming to modulate mHTT levels may be enhanced by the application of such quantification.
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