Differential Roles of Environmental Enrichment in Alzheimer’s Type of Neurodegeneration and Physiological Aging

Impairment of hippocampal adult neurogenesis in aging or degenerating brain is a well-known phenomenon caused by the shortage of brain stem cell pool, alterations in the local microenvironment within the neurogenic niches, or deregulation of stem cell development. Environmental enrichment (EE) has been proposed as a potent tool to restore brain functions, to prevent aging-associated neurodegeneration, and to cure neuronal deficits seen in neurodevelopmental and neurodegenerative disorders. Here, we report our data on the effects of environmental enrichment on hippocampal neurogenesis in vivo and neurosphere-forming capacity of hippocampal stem/progenitor cells in vitro. Two models – Alzheimer’s type of neurodegeneration and physiological brain aging – were chosen for the comparative analysis of EE effects. We found that environmental enrichment greatly affects the expression of markers specific for stem cells, progenitor cells and differentiated neurons (Pax6, Ngn2, NeuroD1, NeuN) in the hippocampus of young adult rats or rats with Alzheimer’s disease (AD) model but less efficiently in aged animals. Application of time-lag mathematical model for the analysis of impedance traces obtained in real-time monitoring of cell proliferation in vitro revealed that EE could restore neurosphere-forming capacity of hippocampal stem/progenitor cells more efficiently in young adult animals (fourfold greater in the control group comparing to the AD model group) but not in the aged rats (no positive effect of environmental enrichment at all). In accordance with the results obtained in vivo, EE was almost ineffective in the recovery of hippocampal neurogenic reserve in vitro in aged, but not in amyloid-treated or young adult, rats. Therefore, EE-based neuroprotective strategies effective in Aβ-affected brain could not be directly extrapolated to aged brain

Влияние трансфузии и гипоксии на клетки модели нейроваскулярной единицы in vitro

Up to 57% of patients develop postoperative delirium after surgery for congenital heart defects (CHD). To reduce cerebral damage in pediatric patients during CHD surgery it is important to find out what inflicts the worse damage: would it be a systemic inflammatory response (SIR) triggered by transfusion, or hypoxia developed in non-transfused patients? In vitro evaluation of hypoxia and SIR effects on the neurovascular unit (NVU) cells might contribute to finding the answer.The aim of the study was to compare the effect of varying severity hypoxia and SIR on the functional activity of NUV cells in vitro.Materials and methods. An in vitro NVU model was designed including neurons, astrocytes and endotheliocytes. The effect of hypoxia on NVU was evaluated in the control (C) and 4 study groups (H 1-4), formed based on O2 content in the medium. The C group NVU were cultivated in standard conditions: N2-75%, O2-20%, CO2-5%; H1: N2-99%, O2-1%; H2: N2- 98%, O2-2%; H3: N2-97%, O2-3 %; H4: N2-96%, O2-4%. The significance of the differences was 0.0125. The effect of interleukin-6 (IL-6) content on NVU was measured by adding to culture medium pediatric patients’ serum with known minimal or maximal SIRS-response. The assessment was made in the Control - an intact NVU model, and 2 study groups – “Minimum” and “Maximum”, i.e. samples with minimum or maximum IL-6 content in culture, respectively. The significance of the differences was 0.017. The cells were incubated at a normothermia regimen for 30 minutes. Then, the functional activity of NVU cells was evaluated by measuring transendothelial resistance (TER) for 24 hours and Lucifer Yellow (LY) permeability test at 60 and 90 minutes after the start of the experiment.Results. After incubation under hypoxic conditions, TER changes occurred in all studied groups. However, they were statistically significant only in the group with 1% oxygen content in the medium. TER decrease in this group was observed after 2, 4 and 24 hours. LY permeability also changed at 60 and 90 minutes, similarly - in NVU cultivated with 1% oxygen in the medium. Minimal TER values were documented at 4 hours after patients’ serum was added to NVU cells culture medium, and TER increased at 24 hours in both study groups. Cellular permeability to LY changed significantly after 1 hour exposure in both groups - with minimum and maximum IL-6 content in the medium. Although at 90 minutes, there was no difference between the 3 groups in LY permeability tests.Conclusion: Intensive SIR demonstrated short-term but more deleterious than hypoxia, effect on cells in the NVU model. Hypoxia disrupted functional activity of NUV cells only at 1% O 2 concentration in the medium.Частота развития послеоперационного делирия при коррекции врожденных пороков сердца (ВПС) достигает 57%. В поиске путей профилактики церебрального повреждения при коррекции ВПС у детей важным является вопрос - что опаснее: гипоксия при отказе от трансфузии или действие повышенного системного воспалительного ответа (СВО) при ее применении. Исследование действия гипоксии и СВО на клетки нейроваскулярной единицы (НВЕ) in vitro способствует решению данного вопроса.Цель исследования: сравнить влияние гипоксии различной выраженности и системного воспалительного ответа на функциональную активность клеток нейроваскулярной единицы.Материалы и методы. Сформировали in vitro модель НВЕ, состоящую из нейронов, астроцитов и эндотелиоцитов. Влияние гипоксии на НВЕ оценивали в контрольной (К) и 4 исследуемых (Г1-4) группах. Группы сформировали по содержанию О2 в среде: К – стандартные условия культивирования: N2-75%, O2-20%, CO2-5%; Г1: N2-99 %, O2-1 %; Г2: N2-98 %, O2-2 %; Г3: N2-97 %, O2-3 %; Г4: N2-96 %, O2-4 %. Значимость различий составила 0,0125. Влияние содержания интерлейкина-6 (ИЛ-6) на НВЕ определяли при культивировании клеток с добавлением сыворотки крови пациентов детского возраста с минимальным, либо максимальным напряжением СВО. Оценку провели в контрольной и 2 исследуемых группах: «Контроль» – интактная модель НВЕ; группы «Минимум» и «Максимум» - образцы с минимальным либо максимальным содержанием ИЛ-6 в культуре соответственно. Значимость различий составила 0,017. Инкубацию клеток проводили в режиме нормотермии в течение 30 минут. Затем оценивали функциональную активность клеток НВЕ методом измерения трансэндотелиального сопротивления (ТЭС) в течение 24 часов и измерения проницаемости для красителя Lucifer Yellow (LY) через 60 и 90 минут от начала эксперимента.Результаты. После инкубации в условиях гипоксии изменения ТЭС наступили во всех исследуемых группах клеток. Однако, только в группе с 1% содержанием кислорода в среде они были статистически значимы. Снижения ТЭС в данной группе наблюдали через 2, 4 и 24 часа. Проницаемость клеток для красителя LY изменилась через 60 и 90 минут также только в условиях их инкубации в среде с 1 % кислородом. При культивировании клеток НВЕ с сывороткой крови пациентов выявили минимальные значения ТЭС через 4 часа и их дальнейшее повышение через 24 часа для обеих исследуемых групп НВЕ. Проницаемость клеток для LY значительно изменилась к 60-й минуте как в группе с минимальным, так и с максимальным содержанием ИЛ-6 в среде. При этом к 90-й минуте различий этого показателя в исследуемых группах и в контрольной группе уже не наблюдали.Заключение. Напряженный СВО оказал более выраженное, но кратковременное действие на модель НВЕ, чем гипоксия. Гипоксия нарушила функциональную активность НВЕ только при концентрации кислорода в среде - 1 %

Abstracts from the 20th International Symposium on Signal Transduction at the Blood-Brain Barriers

https://deepblue.lib.umich.edu/bitstream/2027.42/138963/1/12987_2017_Article_71.pd

Rising of intracellular NAD+ level and oppositely directed changes in CD38 expression in hippocampal cells in experimental Alzheimer's disease

The aim of the study was to assess the level of NAD+ in the brain of mice treated with beta-amyloid (Aβ), as well as to determine the activity of ADP-ribosyl cyclase/CD38 and the number of CD38-immunopositive neurons, astrocytes and endothelial cells. Material and methods. The Alzheimer's disease model was reproduced by intrahippocampal administration of Aβ to C57BL/6 mice. Determination of the NAD+ level in the extracellular fluid of the brain and in the hippocampal tissue was carried out by spectrophotometric analysis. Evaluation of the enzymatic activity of ADP-ribosyl cyclase/CD38 was carried out by the fluorimetric method, determination of the number of CD38-immunopositive cells by the immunohistochemistry method. Results and discussion. The level of NAD+ was significantly increased in the hippocampal tissue in mice after administration of Aβ, while the level of extracellular NAD+ did not change. The activity of ADP-ribosyl cyclase/CD38 in the hippocampal tissue did not change, but the number of CD38-immunopositive neurons decreased, and the number of CD38+ endothelial cells increased in the hippocampus of mice after administration of Aβ. Conclusion. Opposite changes in the expression of ADP-ribosyl cyclase / CD38 in neurons and endotheliocytes correspond to different metabolic states of these types of cells and, along with an increased intracellular pool of NAD+ in experimental Alzheimer's disease, reflect an adaptive stress response to Aβ administration

Indirect Negative Effect of Mutant Ataxin-1 on Short- and Long-Term Synaptic Plasticity in Mouse Models of Spinocerebellar Ataxia Type 1

Spinocerebellar ataxia type 1 (SCA1) is an intractable progressive neurodegenerative disease that leads to a range of movement and motor defects and is eventually lethal. Purkinje cells (PC) are typically the first to show signs of degeneration. SCA1 is caused by an expansion of the polyglutamine tract in the ATXN1 gene and the subsequent buildup of mutant Ataxin-1 protein. In addition to its toxicity, mutant Ataxin-1 protein interferes with gene expression and signal transduction in cells. Recently, it is evident that ATXN1 is not only expressed in neurons but also in glia, however, it is unclear the extent to which either contributes to the overall pathology of SCA1. There are various ways to model SCA1 in mice. Here, functional deficits at cerebellar synapses were investigated in two mouse models of SCA1 in which mutant ATXN1 is either nonspecifically expressed in all cell types of the cerebellum (SCA1 knock-in (KI)), or specifically in Bergmann glia with lentiviral vectors expressing mutant ATXN1 under the control of the astrocyte-specific GFAP promoter. We report impairment of motor performance in both SCA1 models. In both cases, prominent signs of astrocytosis were found using immunohistochemistry. Electrophysiological experiments revealed alteration of presynaptic plasticity at synapses between parallel fibers and PCs, and climbing fibers and PCs in SCA1 KI mice, which is not observed in animals expressing mutant ATXN1 solely in Bergmann glia. In contrast, short- and long-term synaptic plasticity was affected in both SCA1 KI mice and glia-targeted SCA1 mice. Thus, non-neuronal mechanisms may underlie some aspects of SCA1 pathology in the cerebellum. By combining the outcomes of our current work with our previous data from the B05 SCA1 model, we further our understanding of the mechanisms of SCA1

Neuroinflammation and Infection: Molecular Mechanisms Associated with Dysfunction of Neurovascular Unit

Neuroinflammation is a complex inflammatory process in the central nervous system, which is sought to play an important defensive role against various pathogens, toxins or factors that induce neurodegeneration. The onset of neurodegenerative diseases and various microbial infections are counted as stimuli that can challenge the host immune system and trigger the development of neuroinflammation. The homeostatic nature of neuroinflammation is essential to maintain the neuroplasticity. Neuroinflammation is regulated by the activity of neuronal, glial, and endothelial cells within the neurovascular unit, which serves as a “platform” for the coordinated action of pro- and anti-inflammatory mechanisms. Production of inflammatory mediators (cytokines, chemokines, reactive oxygen species) by brain resident cells or cells migrating from the peripheral blood, results in the impairment of blood-brain barrier integrity, thereby further affecting the course of local inflammation. In this review, we analyzed the most recent data on the central nervous system inflammation and focused on major mechanisms of neurovascular unit dysfunction caused by neuroinflammation and infections

Современные методы и материалы моделирования тканей мозга и гематоэнцефалического барьера in vitro

Neurovascular unit (NVU) is an ensemble of brain cells (cerebral endothelial cells, astrocytes, pericytes, neurons, and microglia), which regulates processes of transport through the blood-brain barrier (BBB) and controls local microcirculation and intercellular metabolic coupling. Dysfunction of NVU contributes to numerous types of central nervous system pathology. NVU pathophysiology has been extensively studied in various animal models of brain disorders, and there is growing evidence that modern approaches utilizing in vitro models are very promising for the assessment of intercellular communications within the NVU. Development of NVU‑on-chip or BBB‑on-chip as well as 3D NVU and brain tissue models suggests novel clues to understanding cell-to-cell interactions critical for brain functional activity, being therefore very important for translational studies, drug discovery, and development of novel analytical platforms. One of the mechanisms controlled by NVU activity is neurogenesis in highly specialized areas of brain (neurogenic niches, NNs), which are well-equipped for the maintenance of stem/progenitor cell pool and proliferation, differentiation, and migration of newly formed neuronal and glial cells. Specific properties of brain microvascular endothelial cells, particularly, high content of mitochondria, are important for establishment of vascular support in NVU and NNs. Metabolic activity of cells within NNs and NVU contributes to maintaining intercellular communications critical for the multicellular module integrity. We will discuss modern approaches to development of optimal microenvironment for in vitro BBB, NVU and NN models with the special focus on neuroengineering and bioprinting potentialsНейроваскулярная единица (НВЕ) – это совокупность клеток головного мозга (церебральные эндотелиальные клетки, астроциты, перициты, нейроны, микроглия), которые регулируют процессы транспорта через гематоэнцефалический барьер (ГЭБ), контролируют местную микроциркуляцию, межклеточную метаболическую связь. Дисфункция НВЕ способствует возникновению многих типов патологии центральной нервной системы. Патофизиология НВЕ широко изучена на различных моделях заболеваний мозга на животных. В настоящее время появляется все больше свидетельств того, что современные подходы с использованием моделей in vitro наиболее перспективны для оценки межклеточных коммуникаций внутри НВЕ. Разработка сосудисто-нервных единиц на чипе или ГЭБ на чипе, а также 3D НВЕ и модели ткани мозга обеспечивают новые подходы к пониманию межклеточных взаимодействий, критических для функциональной активности мозга, поэтому они очень важны для трансляционных исследований, открытия лекарств и создания новых аналитических платформ. Одним из механизмов, который контролируется активностью НВЕ, является нейрогенез в узкоспециализированных областях мозга (нейрогенные ниши, НН), которые служат источником для поддержания пула стволовых/ прогениторных клеток, пролиферации, дифференциации и миграции новообразованных нейронов и глиальных клеток. Специфические свойства эндотелиальных клеток микрососудов головного мозга, в частности высокое содержание митохондрий, важны для создания сосудистой поддержки при НВЕ и НН. Метаболическая активность клеток внутри НН и НВЕ способствует поддержанию межклеточных коммуникаций, критически важных для целостности многоклеточного модуля. В работе обсуждаются современные подходы к разработке оптимальной микросреды для in vitro моделей ГЭБ, НВЕ и НН. Особое внимание уделено перспективам нейроинженерии и биопечат