Excitatory amino acid transporter 1 supports adult hippocampal neural stem cell self-renewal

Upregulated excitatory amino acid transporter 1 (EAAT1) expression in the human medial temporal lobe in Alzheimer's disease

Alzheimer's disease (AD) is a growing health problem worldwide, particularly in the developed world due to an ageing population. Glutamate excitotoxicity plays a major role in the pathophysiology of AD, and glutamate re-uptake is controlled by excitatory amino acid transporters (EAATs). The EAAT2 isoform is the predominant transporter involved in glutamate reuptake, therefore EAAT1 has not been the focus of AD research. We investigated the layer-specific expression of EAAT1 in human medial temporal lobe regions such as the hippocampus, subiculum, entorhinal cortex and superior temporal gyrus, using fluorescent immunohistochemistry and laser scanning confocal microscopy in human post-mortem tissue. We observed low EAAT1 immunoreactivity in control cases, but upregulated labeling in AD across several brain regions of the medial temporal lobe. Significantly higher integrated density in AD cases was observed in the str. oriens and str. radiatum of the CA2 region, the str. pyramidale of CA3, and the str. moleculare and str. granulosum of the DG. Labeling of EAAT1 appeared astrocytic in nature, showing close association with astrocytic processes in AD cases. We also report that a higher EAAT1 density was positively correlated with the age of AD cases, but this relationship was not observed in control cases. Overall, our results indicate an upregulation of EAAT1 across several hippocampal subregions and layers in AD cases, indicating a potential physiological role for this transporter that needs further investigation.

Role of Glutathione in Parkinson's Disease Pathophysiology and Therapeutic Potential of Polyphenols

Oxidative stress is recognized to have a central role in the initiation and progression of Parkinson's disease (PD). Within the brain, neurons are particularly sensitive to oxidation due in part to their weak intrinsic antioxidant defense. Theoretically, neurons mostly depend on neighboring astrocytes to provide antioxidant protection by supplying cysteine-containing products for glutathione (GSH) synthesis. Astrocytes and neurons possess several amino acid transport systems for GSH and its precursors. Indeed, GSH is the most abundant intrinsic antioxidant in the central nervous system. The GSH depletion and/or alterations in its metabolism in the brain contribute to the pathogenesis of PD. Noteworthy, polyphenols possess potent antioxidant activity and can augment the GSH redox system. Numerous in vitro and in vivo studies have indicated that polyphenols exhibit potent neuroprotective effects in PD. Epidemiological studies have found an association between the consumption of dietary polyphenols and a lower PD risk. In this review, we summarize current knowledge on the biosynthesis and metabolism of GSH in the brain, with an emphasis on their contribution and therapeutic potential in PD. In particular, we focus on polyphenols that can increase brain GSH levels against PD. Furthermore, some current challenges and future perspectives for polyphenol-based therapies are also discussed.

Dynamics of Neurogenic Signals as Biological Switchers of Brain Plasticity

The discovery of adult neurogenesis in the middle of the past century is considered one of the most important breakthroughs in neuroscience. Despite its controversial nature, this discovery shaped our concept of neural plasticity, revolutionizing the way we look at our brains. In fact, after the discovery of adult neurogenesis, we started to consider the brain as something even more dynamic and highly adaptable. In neurogenic niches, adult neurogenesis is supported by neural stem cells (NSCs). These cells possess a unique set of characteristics such as being quiescent for long periods while actively sensing and reacting to their surroundings to influence a multitude of processes, including the generation of new neurons and glial cells. Therefore, NSCs can be viewed as sentinels to our brain's homeostasis, being able to replace damaged cells and simultaneously secrete numerous factors that restore regular brain function. In addition, it is becoming increasingly evident that NSCs play a central role in memory formation and consolidation. In this review, we will dissect how NSCs influence their surroundings through paracrine and autocrine types of action. We will also depict the mechanism of action of each factor. Finally, we will describe how NSCs integrate different and often opposing signals to guide their fate.

Implementation of the neuro-glia-vascular unit through co-culture of adult neural stem cells and vascular cells and transcriptomic analysis of diverse Aβ assembly types

BACKGROUND

The blood-brain barrier (BBB) is a specialized layer between blood vessels and tissue in the brain, which is comprised of a neuro-glia-vascular (NGV) unit, thus play a vital role in various brain diseases.

NEW METHOD

We developed the in vitro NGV units by co-culturing brain microvascular endothelial cells (BMECs; bEnd.3) and primary neural stem cells extracted from subventricular zone of adult mice. This approach was designed to mimic the RNA profile conditions found in the microvessels of a mouse brain and confirmed through various comparative transcriptome analyses.

RESULTS

Optimal NGV unit development was achieved by adjusting cell density-dependent co-culture ratios. Specifically, the morphogenic development and neuronal association of astrocyte endfeet were well observed in the contact region with BMECs in the NGV unit. Through transcriptome analysis, we compared co-cultured bEnd.3/NSCs with monocultured bEnd.3 or NSCs and additionally compared them with previously reported mouse brain vascular tissue to show that this NGV unit model is a suitable in vitro model for neurological disease such as Alzheimer's disease (AD).

COMPARISON WITH EXISTING METHOD(S)

This in vitro NGV unit was formed from neural stem cells and vascular cells in the brain of adult mice, not embryos. It is very useful for studying brain disease mechanisms by identifying proteins and genes associated with diseases progress.

CONCLUSIONS

We suggest that this simple in vitro NGV model is appropriate to investigate the relationship between BBB changes and pathological factors in the fields of neurovascular biology and cerebrovascular diseases including AD.

Protocol for lentivirus-mediated delivery of genes to study neurogenesis and cognitive function in adult rodents

Adult neurogenesis leads to the generation of functional neurons from neural stem cells, whereas impairment of adult hippocampal neurogenesis contributes to the pathophysiology of cognitive symptoms in neurodegenerative and neuropsychiatric diseases. Here, we present a protocol for a direct hippocampal injection of lentivirus-delivered gene in adult rodents to study the specific molecular mechanism underlying adult neurogenesis, including lentivirus packaging and stereotaxic injection, EdU and BrdU injections, tissue immunostaining and imaging analysis, and cognitive testing. For complete details on the use and execution of this protocol, please refer to Li et al. (2023).1.