Astrocyte
In recent years, glial cells in the brain (microglia, astrocytes, oligodendrocytes, etc.) are known to play not only a static role in maintaining homeostasis of brain functions, but also to play an active role in regulating brain functions.
Background
Astrocytes are the most numerous glial cells in the brain, and their main functions have been considered to be the maintenance of nerve fiber retention, homeostasis and blood-brain barrier closure. However, astrocytes are known to undergo morphological changes such as Alzheimer type 2 astrocytes and fibrocytic astrocytes due to inflammation, liver injury, and neurodegeneration, eventually forming gliosis.
In addition, it has become clear that the stimulation of cytokines such as tumor necrosis factor (TNF-α), interleukin (IL)-1β and interferon (IFN)-γ has neurotoxic effects, including arachidonic acid metabolites, reactive oxygen species (ROS) and nitric oxide (NO) production1). On the other hand, it has also been shown to exhibit neruroprotective effects, such as antioxidant effects through glutathione (GSH) secretion in Parkinson's disease2) and regulation of synaptic transmission through release of neurotransmitters such as glutamate, ATP, and D-serine2). Microglia have been thought to primarily remove degenerative cells by antigen-presenting cells and macrophage-like phagocytosis during inflammation, but microglia positive for TNF-α, IL-1β and IFNγ have been identified in degenerative diseases such as Parkinson's disease and Alzheimer's disease3), and microglia also have neurotoxic aspects such as ROS and NO production, activated microglia cooperate with the aforementioned astrocytes to secrete neuroprotective factors such as nerve growth factor (NGF), Neurotrophin, and IL-6, and promote neurogenesis from stem/progenitor cells4). Microglia are also thought to function in a neruroprotective manner, such as promoting neurogenesis from stem/progenitor cells.
References
- Blasko, I., Sta mpfer-Kountchev, M., Ro batscher, P., Ve erhuis, R., Eikelenboom, P., & Grubeck-Loebenstein, B. (2004). Aging cell, 3(4), 169-76.
- Maragakis, N. J., & Rothstein, J. D. (2006). Nature clinical practice Neurology, 2(12), 679-89.
- Sawada, M. (2009). Parkinsonism & related disorders, 15 Suppl 1, S39 41.
- Johansson, C., Momma, S., & Clarke, D. (1999). Cell, 96, 25-34.
Data
- Left：Rat Astrocyte
- Right：Immunostaining of rat Astrocyte (Green: Anti GFAP, Blue: nuclear staining)