SARS-CoV-2 infection causes dopaminergic neuron senescence

COVID-19 patients commonly present with signs of central nervous system and/or peripheral nervous system dysfunction. Here, we show that midbrain dopamine (DA) neurons derived from human pluripotent stem cells (hPSCs) are selectively susceptible and permissive to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. SARS-CoV-2 infection of DA neurons triggers an inflammatory and cellular senescence response. High-throughput screening in hPSC-derived DA neurons identified several FDA-approved drugs that can rescue the cellular senescence phenotype by preventing SARS-CoV-2 infection. We also identified the inflammatory and cellular senescence signature and low levels of SARS-CoV-2 transcripts in human substantia nigra tissue of COVID-19 patients. Furthermore, we observed reduced numbers of neuromelanin+ and tyrosine-hydroxylase (TH)+ DA neurons and fibers in a cohort of severe COVID-19 patients. Our findings demonstrate that hPSC-derived DA neurons are susceptible to SARS-CoV-2, identify candidate neuroprotective drugs for COVID-19 patients, and suggest the need for careful, long-term monitoring of neurological problems in COVID-19 patients.

(HIIT-The Track) High-Intensity Interval Training for People with Parkinson's Disease: Individual Response Patterns of (Non-)Motor Symptoms and Blood-Based Biomarkers-A Crossover Single-Case Experimental Design

INTRODUCTION

Physical exercise is receiving increasing interest as an augmentative non-pharmacological intervention in Parkinson's disease (PD). This pilot study primarily aimed to quantify individual response patterns of motor symptoms to alternating exercise modalities, along with non-motor functioning and blood biomarkers of neuroplasticity and neurodegeneration.

MATERIALS & METHODS

People with PD performed high-intensity interval training (HIIT) and continuous aerobic exercise (CAE) using a crossover single-case experimental design. A repeated assessment of outcome measures was conducted. The trajectories of outcome measures were visualized in time series plots and interpreted relative to the minimal clinically important difference (MCID) and smallest detectable change (SDC) or as a change in the positive or negative direction using trend lines.

RESULTS

Data of three participants were analyzed and engaging in physical exercise seemed beneficial for reducing motor symptoms. Participant 1 demonstrated improvement in motor function, independent of exercise modality; while for participant 2, such a clinically relevant (positive) change in motor function was only observed in response to CAE. Participant 3 showed improved motor function after HIIT, but no comparison could be made with CAE because of drop-out. Heterogeneous responses on secondary outcome measures were found, not only between exercise modalities but also among participants.

CONCLUSION

Though this study underpins the positive impact of physical exercise in the management of PD, large variability in individual response patterns to the interventions among participants makes it difficult to identify clear exercise-induced adaptations in functioning and blood biomarkers. Further research is needed to overcome methodological challenges in measuring individual response patterns.

Lewy pathology in Parkinson's disease consists of crowded organelles and lipid membranes

Parkinson's disease, the most common age-related movement disorder, is a progressive neurodegenerative disease with unclear etiology. Key neuropathological hallmarks are Lewy bodies and Lewy neurites: neuronal inclusions immunopositive for the protein α-synuclein. In-depth ultrastructural analysis of Lewy pathology is crucial to understanding pathogenesis of this disease. Using correlative light and electron microscopy and tomography on postmortem human brain tissue from Parkinson's disease brain donors, we identified α-synuclein immunopositive Lewy pathology and show a crowded environment of membranes therein, including vesicular structures and dysmorphic organelles. Filaments interspersed between the membranes and organelles were identifiable in many but not all α-synuclein inclusions. Crowding of organellar components was confirmed by stimulated emission depletion (STED)-based super-resolution microscopy, and high lipid content within α-synuclein immunopositive inclusions was corroborated by confocal imaging, Fourier-transform coherent anti-Stokes Raman scattering infrared imaging and lipidomics. Applying such correlative high-resolution imaging and biophysical approaches, we discovered an aggregated protein-lipid compartmentalization not previously described in the Parkinsons' disease brain.

A delayed increase in hippocampal proliferation following global asphyxia in the neonatal rat

Adult neurogenesis has been shown to be upregulated following a wide variety of brain injury paradigms. During the first weeks of postnatal life there is around 50 fold more neurogenesis occurring than in the adult CNS, yet little is known regarding the effect of neonatal brain injury on this developmental proliferation. We have investigated the effect of a global perinatal birth asphyxia on postnatal proliferation at 2, 5, 8, 11, 15, 21 and 28 days after birth (injury) using a 3H-thymidine tracer study. We found a specific upregulation of proliferation at 5 days after the injury within the injured hippocampus only, with an associated increase in hippocampal mass and without any changes in GFAP content at any timepoint. Perinatal asphyxia did not alter proliferation within the cerebellum, sub ventricular zone, olfactory bulb, cervical or thoracic spinal cord. Similarly, no changes in corticosterone levels were induced by the injury. Since there were no changes in GFAP content we hypothesize that this increased proliferation is likely neurogenetic, similar to what is seen in the adult brain following injury. Further we show that the dramatic increase in corticosterone at the end of the stress hyporesponsive period is not responsible for the equally dramatic decrease in postnatal proliferation within the CNS.

No alterations of hippocampal neuronal number and synaptic bouton number in a transgenic mouse model expressing the beta-cleaved C-terminal APP fragment

Previous studies in the literature have resulted in conflicting reports on the potential neurotoxicity of the beta-cleaved Alzheimer's disease C-terminal fragment (beta-CTF) of beta-amyloid precursor protein in vivo. To readdress this question by rigorous quantitative methods, we analyzed transgenic mice expressing human beta-CTF with the I45F mutation (SPA4CT) under control of the prion protein promoter by stereological techniques. The transgene was expressed in hippocampus and cortex in large pyramidal neurons and in dentate gyrus granule cells. Proteolytic processing of beta-CTF released Abeta. However, most of it remained uncleaved. Neurodegeneration was evaluated by investigating the numbers of hippocampal pyramidal and granule neurons, as well as the number of synaptophysin-immunopositive presynaptic boutons in the hippocampus of 15-month-old SPA4CT mice with design-based stereological techniques. The analyses showed that a fourfold higher expression of the transgene compared to murine APP levels had no effect on the numbers of both neurons and synaptophysin-immunopositive presynaptic boutons. These data implicate that expression of beta-CTF per se is not neurotoxic, and that other mechanisms are responsible for the neurotoxic events in Alzheimer's disease brain.

Perinatal asphyxia induced neuronal loss by apoptosis in the neonatal rat striatum: a combined TUNEL and stereological study

Perinatal asphyxia can lead to cell damage in various regions of the brain, such as the neostriatum. In this study, we investigated the mechanism of cell death that leads to neuron loss in the neostriatum of rat pups. Asphyxia was induced by immersing fetus-containing uterus horns in a water bath at 37 degrees C for 20 min. This led to an increase in mortality rate (+/- 40%) compared to control pups (0%). TUNEL-positive cell profiles were visible in all groups at postnatal day (P) 2, P8, and P15, peaking at P8. A significant increase of 40% at P8 and 45% at P15 in the number of TUNEL-positive cell profiles was observed in asphyctic rats compared to control rats. Nuclear condensation and fragmentation was visible with the DNA stain Hoechst 33342. Furthermore, laser-scanning confocal microscopy showed multiple DNA fragments in TUNEL-positive cell profiles. We found a decrease of 16% in the total number of striatal neurons in the asphyctic pups compared to the control pups at 21 days postasphyxia using stereology. These data show that asphyxia causes exaggerated apoptotic cell death during the first week of life and as a consequence a small amount of neuron loss in the neostriatum.