EMBRIOGENESIS OF NEURONAL ELENENTS (GLIOBLASTS AND GABAA RECEPTORS) IN THE HUMAN BRAIN NEUROIMMUNE SYSTEM UNDER PRENATAL ALCOHOL EXPOSURE

Exposure to alcohol causes imbalances in neuroimmune function and impaired brain development. Alcohol activates the innate immune signaling pathways in the brain. Neuroimmune molecules expressed and secreted by glial cells of the brain (microglia, oligodendroglia) alter the function of neurons and further stimulate the development of alcoholic behavior. Various signaling pathways and brain cells are involved in the transmission of neuroimmune signals. Glial cells are the main sources of immune mediators in the brain, which respond to and release immune signals in the central nervous system. The aim of this study was to study neuronal elements: morphometric parameters of glioblasts, synaptic structures and properties of synaptosomal GABAA-benzodiazepine receptors of the neuroimmune system in the embryogenesis of the human brain under perinatal exposure to alcohol. Changes in glioblasts in the brain tissue of human embryos and fetuses were revealed under conditions of chronic prenatal alcoholization with an increase in gestational age compared with control subgroups: a significant increase in the average number of glioblasts, the length of the perimeters of presynaptic terminal structures, postsynaptic density, presynaptic terminal regions were significantly less (p < 0.01) in the study group than in the control comparison group. Exposure to ethanol leads to a decrease in the affinity of GABAA-benzodiazepine receptors, which affects neuronal plasticity associated with the development and differentiation of progenitor cells (glioblasts and neuroblasts) during embryogenesis of the human brain and leads to suppression of GABAergic function in the brain. This causes a disruption in the interconnection of embryonic cells in the brain, leads to excessive apoptosis due to the activation of glial cells of the nervous tissue, disruption of neuroimmune function in the developing brain, changes in neuronal circuits, as well as a change in the balance of excitatory and inhibitory effects, which affects the functional activity in the central nervous system. Glial activation is a compensatory reaction caused by neuroplastic changes aimed at adapting the developing brain of the embryo and fetus under conditions of neurotoxicity and hypoxia under the influence of prenatal alcoholization of the maternal organism and the effect of ethanol on the fetus. The dynamics of changes in glial elements and receptor activity in the nervous tissue of human embryos and fetuses under conditions of prenatal exposure to alcohol indicates a more pronounced effect of alcohol on the earliest stages of human embryo development, which is of great practical importance in planning pregnancy and the inadmissibility of alcoholization of the mother in order to avoid negative consequences in offspring.

Synaptic Damage and Its Clinical Correlates in People With Early Huntington Disease

Background and ObjectivesSynaptic damage has been proposed to play a major role in the pathophysiology of Huntington disease (HD), but in vivo evidence in humans is lacking. We performed a PET imaging study to assess synaptic damage and its clinical correlates in early HD in vivo.MethodsIn this cross-sectional study, premanifest and early manifest (Shoulson-Fahn stage 1 and 2) HD mutation carriers and age- and sex-matched healthy controls underwent clinical assessment of motor and nonmotor manifestations and time-of-flight PET with 11C-UCB-J, a radioligand targeting the ubiquitous presynaptic terminal marker synaptic vesicle protein 2A (SV2A). We also performed 18F-fluorodeoxyglucose (18F-FDG)-PET in all participants because regional cerebral glucose consumption is thought to largely reflect synaptic activity. Volumes of interest were delineated on the basis of individual 3-dimensional T1 MRI. Standardized uptake value ratio-1 images were calculated for 11C-UCB-J with the centrum semiovale as reference region. 18F-FDG-PET activity was normalized to the pons. All PET data were corrected for partial volume effects. Volume of interest– and voxel-based analyses were performed. Correlations between clinical scores and 11C-UCB-J PET data were calculated.ResultsEighteen HD mutation carriers (age 51.4 ± 11.6 years; 6 female; 7 premanifest, 11 early manifest) and 15 healthy controls (age 52.3 ± 3.5 years; 4 female) were included. In the HD group, significant loss of SV2A binding was found in putamen, caudate, pallidum, cerebellum, parietal, and temporal and frontal cortex, whereas reduced 18F-FDG uptake was restricted to caudate and putamen. In the premanifest subgroup, 11C-UCB-J and 18F-FDG-PET showed significant reductions in putamen and caudate only. In the total HD group, SV2A loss in the putamen correlated with motor impairment.DiscussionOur data reveal loss of presynaptic terminal integrity in early HD, which begins in the striatum in the premanifest phase, spreads extensively to extrastriatal regions in the early manifest phase, and correlates with motor impairment. 11C-UCB-J PET is more sensitive than 18F-FDG-PET for detection of extrastriatal changes in early HD.Classification of EvidenceThis study provides Class III evidence that 11C-UCB-J PET accurately discriminates individuals HD from normal controls.

Inhibition of LRRK2 kinase activity promotes anterograde axonal transport and presynaptic targeting of α-synuclein

Pathologic inclusions composed of alpha-synuclein called Lewy pathology are hallmarks of Parkinson Disease (PD). Dominant inherited mutations in leucine rich repeat kinase 2 (LRRK2) are the most common genetic cause of PD. Lewy pathology is found in the majority of individuals with LRRK2-PD, particularly those with the G2019S-LRRK2 mutation. Lewy pathology in LRRK2-PD associates with increased non-motor symptoms such as cognitive deficits, anxiety, and orthostatic hypotension. Thus, understanding the relationship between LRRK2 and alpha-synuclein could be important for determining the mechanisms of non-motor symptoms. In PD models, expression of mutant LRRK2 reduces membrane localization of alpha-synuclein, and enhances formation of pathologic alpha-synuclein, particularly when synaptic activity is increased. alpha-Synuclein and LRRK2 both localize to the presynaptic terminal. LRRK2 plays a role in membrane traffic, including axonal transport, and therefore may influence alpha-synuclein synaptic localization. This study shows that LRRK2 kinase activity influences alpha-synuclein targeting to the presynaptic terminal. We used the selective LRRK2 kinase inhibitors, MLi-2 and PF-06685360 (PF-360) to determine the impact of reduced LRRK2 kinase activity on presynaptic localization of alpha-synuclein. Expansion microscopy (ExM) in primary hippocampal cultures and the mouse striatum, in vivo, was used to more precisely resolve the presynaptic localization of alpha-synuclein. Live imaging of axonal transport of alpha-synuclein-GFP was used to investigate the impact of LRRK2 kinase inhibition on alpha-synuclein axonal transport towards the presynaptic terminal. Reduced LRRK2 kinase activity increases alpha-synuclein overlap with presynaptic markers in primary neurons, and increases anterograde axonal transport of alpha-synuclein-GFP. In vivo, LRRK2 inhibition increases alpha-synuclein overlap with glutamatergic, cortico-striatal terminals, and dopaminergic nigral-striatal presynaptic terminals. The findings suggest that LRRK2 kinase activity plays a role in axonal transport, and presynaptic targeting of alpha-synuclein. These data provide potential mechanisms by which LRRK2-mediated perturbations of alpha-synuclein localization could cause pathology in both LRRK2-PD, and idiopathic PD.

Functional Neuroproteomics: An imperative approach for unravelling protein implicated complexities of brain.

: A proteome is defined as a comprehensive protein set either of an organ or an organism at a given time and under specific physiological conditions and accordingly, the study of nervous system’s proteomes is called Neuroproteomics. In the neuroproteomics process, various pieces of the nervous system are “fragmented” to understand the dynamics of each given sub-proteome in a much better way. Functional proteomics addresses the organisation of proteins into complexes, and formation of organelles from these multiprotein complexes that control various physiological processes. Current functional studies of neuroproteomics mainly talk about the synapse structure and its organisation, the major building site of the neuronal communication channel. The proteomes of synaptic vesicle, presynaptic terminal, and postsynaptic density, have been examined by various proteomics techniques. The objective of functional neuroproteomics is to solve the proteome of single neurons or astrocytes grown in cell cultures or from the primary brain cells isolated from tissues under various conditions; to identify set of proteins which characterize a specific pathogenesis; or to determine the group of proteins making up post-synaptic or pre-synaptic densities. It is very usual to try to solve a particular sub-proteome like the heatshock response proteome, or the proteome responding to inflammation. Posttranslational protein modifications alter their functions and interactions. The techniques to detect synapse phosphoproteome are available however, those for the analysis of ubiquitination and sumoylation, are under development.

Bidirectional, unlike unidirectional transport, allows transporting axonal cargos against their concentration gradient

Even though most axonal cargos are synthesized in the soma, the concentration of many of these cargos is larger at the presynaptic terminal than in the soma. This requires transport of these cargos from the soma to the presynaptic terminal or other active sites in the axon. Axons utilize both bidirectional (for example, slow axonal transport) and unidirectional (for example, fast anterograde axonal transport) modes of cargo transport. Bidirectional transport seems to be less efficient because it requires more time and takes more energy to deliver cargos. In this paper, bidirectional and unidirectional axonal transport processes are investigated with respect to their ability to transport cargos against their concentration gradient. We argue that because bidirectional axonal transport includes both the anterograde and retrograde cargo populations, information about cargo concentration at the axon entrance and at the presynaptic terminal can travel in both anterograde and retrograde directions. This allows bidirectional axonal transport to account for the concentration of cargos at the presynaptic terminal. In unidirectional axonal transport, on the contrary, cargo transport occurs only in one direction, and this disallows transport of information about the cargo concentration at the opposite boundary. For the case of unidirectional anterograde transport, this means that proximal regions of the axon do not receive information about cargo concertation in the distal regions. This does not allow for the imposition of a higher concentration at the presynaptic terminal in comparison to the cargo concentration at the axon hillock. To the best of our knowledge, our paper presents the first explanation for the utilization of seemingly inefficient bidirectional transport in neurons.

Maturation of Complex Synaptic Connections of Layer 5 Cortical Axons in the Posterior Thalamic Nucleus Requires SNAP25

Synapses are able to form in the absence of neuronal activity, but how is their subsequent maturation affected in the absence of regulated vesicular release? We explored this question using 3D electron microscopy and immunoelectron microscopy analyses in the large, complex synapses formed between cortical sensory efferent axons and dendrites in the posterior thalamic nucleus. Using a Synaptosome-associated protein 25 conditional knockout (Snap25 cKO), we found that during the first 2 postnatal weeks the axonal boutons emerge and increase in the size similar to the control animals. However, by P18, when an adult-like architecture should normally be established, axons were significantly smaller with 3D reconstructions, showing that each Snap25 cKO bouton only forms a single synapse with the connecting dendritic shaft. No excrescences from the dendrites were formed, and none of the normally large glomerular axon endings were seen. These results show that activity mediated through regulated vesicular release from the presynaptic terminal is not necessary for the formation of synapses, but it is required for the maturation of the specialized synaptic structures between layer 5 corticothalamic projections in the posterior thalamic nucleus.