Nervous system
David Sturgeon in Introduction to Anatomy and Physiology for Healthcare Students, 2018
The next type of glial cell found in the CNS are microglia. As their name suggests, they are the smallest of the glial cells and function primarily as phagocytic immune cells. They are highly mobile and move through the nervous tissue removing cellular debris, waste products and other material including microorganisms. The final type of support cell found in the CNS are specialised epithelial cells called ependymal cells. Like epithelial cells found elsewhere in the body, many of these are ciliated (i.e. they possess tiny hair-like projections). Ependymal cells line the ventricles (cavities) of the brain and the central canal of the spinal cord, and contribute to the secretion of cerebrospinal fluid (see below). The beating of their cilia also helps to direct the flow of cerebrospinal fluid around the CNS and filter out debris and foreign particles. Since the peripheral nervous system is mainly composed of axons, there are only two types of support cell: satellite cells and Schwann cells. The first are similar in function to astrocytes and surround and support neuronal cell bodies found in clusters called ganglia. They also help to control and maintain the chemical environment around the neurons they support. Schwann cells are the principle glial cells of the peripheral nervous system and, as we already know, are functionally similar to oligodendrocytes. They manufacture myelin, maintain the axon and contribute to the removal of cellular debris.
Haematogenous Cell Responses to CNS Injury
Martin Berry, Ann Logan in CNS Injuries: Cellular Responses and Pharmacological Strategies, 2019
Microglia are regarded as the resident phagocytic cells of the CNS. During neonatal life they appear to be derived from infiltrating monocytes and it is generally agreed that microglial cells originate from bone marrow, particularly as they express the common leucocyte antigen CD45 which is present only on cells of marrow origin.58 Microglia are distributed throughout the CNS and are considered to be integral components of the blood-brain barrier.59 Their morphology, origin, and distribution is adequately reviewed elsewhere,60 but little is known of the function of microglia other than that they protect the CNS from infection and injury, remove cellular debris following experimentally induced traumatic injury, participate in tissue modelling, and phagocytose apoptotic cells.61,62 Microglial defence against infections may be supported by other macrophages strategically placed at sites where pathogen entry is most likely to occur, e.g., the choroid plexuses and leptomeninges.
Pathogenesis of Mood Disorders
Dr. Ather Muneer in Mood Disorders, 2018
Microglia perform several crucial functions in the brain including immune-surveillance for pathogens, cellular debris, apoptotic cells and neuronal phenotypic alterations. Upon activation microglia enter a primed position, and when stimulated in this state secrete increased amounts of inflammatory mediators, including IL-1β. As these specialized macrophages express pattern recognition receptors including TLR2 and TLR4, TLR ligation by DAMP (ATP, Hsp, HMGB1, etc.) strongly trigger microglia. Furthermore, several inflammasomes have been described in the microglia including NLRP1, NLRP3 and NLRC4. The NLRP3 inflammasome has been most often studied in the CNS, and is also the focus of the preponderance of studies in animal models of depression. Recent investigations also suggest that NLRP3 may be exquisitely sensitive to the homeostatic perturbations induced by psychobiological stress, with a mechanistic role for the inflammasome mediated processing and maturation of IL-1β in the generation of mood disorders.27 While space limitation does not allow a detailed description of animal studies highlighting the link between stress, DAMP and the NLRP3 inflammasome, it is clear that CNS inflammation caused by acute or chronic stress has an important role in the development of mood disorders.
Approaches for CNS delivery of drugs – nose to brain targeting of antiretroviral agents as a potential attempt for complete elimination of major reservoir site of HIV to aid AIDS treatment
Published in Expert Opinion on Drug Delivery, 2019
Shweta Gupta, Rajesh Kesarla, Abdelwahab Omri
The brain is the largest portion of the CNS and is the main structure referred to when considering the nervous system. The brain is the major functional unit of the CNS and a highly protected organ from the periphery by two major barriers, the BBB and the BCSFB. In a typical human, the cerebral cortex (the largest part) is estimated to contain 15–33 billion neurons [38], each connected by synapses to several thousand neurons. Microglia is a type of glial cell located throughout the brain and spinal cord [39]. Microglia comprises 10–15% of all cells found within the brain. As the resident macrophage cells, they act as the first and main form of active immune defense in CNS [40]. Microglia (and other glia including astrocytes) are distributed in large non-overlapping regions throughout the CNS [41].
Formononetin Inhibits Microglial Inflammatory Response and Contributes to Spinal Cord Injury Repair by Targeting the EGFR/MAPK Pathway
Published in Immunological Investigations, 2023
Haiping Fu, Mingdong Li, Yanqiang Huan, Xiaolei Wang, Mingkai Tao, Tianqi Jiang, Hongbin Xie, Yongxiong He
Microglial cells are the brain’s immune cells in the central nervous system (CNS). Being derived from myeloid progenitors, microglia play an important role in phagocytes, recognizing, and scavenging dead cells and pathogens (Zhang et al. 2018). Microglia reside in the spinal cord and participate in the progression and neuroinflammation after SCI (Lin et al. 2017). They are activated and secret plenty of pro-inflammatory cytokines and chemokines to aggravate microglial inflammation (Gao et al. 2021). A growing number of studies have demonstrated that microglia activation is one of the main reasons for secondary injury after SCI, and the inhibition of microglia activation reduces spinal cord tissue damage (Finegold 1975; Kalz et al. 1990; Tucker et al. 1997). In addition, a previous study has shown that FMN incubation significantly reduced the production of TNF-α, IL-6, and IL-1β in LPS-stimulated BV2 microglia (El-Bakoush and Olajide 2018). These researches suggest a possibility that FMN may inhibit the microglial inflammatory response after SCI.
Resveratrol promoted the M2 polarization of microglia and reduced neuroinflammation after cerebral ischemia by inhibiting miR-155
Published in International Journal of Neuroscience, 2020
Shan Ma, Lingling Fan, Junchao Li, Bei Zhang, Zhongjun Yan
The therapeutic strategy of inhibiting neuroinflammation represents a novel approach for the conduction of neuroprotective treatment [5,6]. Microglia are major immune cells in the central nervous system (CNS). According to the predominance of secreted cytokines, microglia are divided into M1 phenotype (pro-inflammatory) and M2 phenotype (anti-inflammatory). M1 microglia produce pro-inflammatory cytokines IL-1, IL-6 and express the signature genes IL-1β, CD32, M2 microglia produce anti-inflammatory cytokines IL-4, IL-10 and express the signature genes Arginase-1, CD206. Based on previous studies, it could be deduced that the inhibition of M1 polarization and the promotion of M2 polarization of microglia might be a novel approach to treat inflammation-related diseases [7,8]. At present, most of the reported compounds only could inhibit the M1 polarization of microglia, but few compounds have been reported to promote the M2 polarization of microglia [9,10].
Related Knowledge Centers
- Central Nervous System
- Glia
- Potassium Channel
- Synapse
- Spinal Cord
- Astrocyte
- Brain
- Macrophage
- Amyloid Plaques
- Neuron