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Review
. 2021 Feb;16(2):270-280.
doi: 10.4103/1673-5374.290881.

Microglia in neurodegenerative diseases

Yu Xu  1 , Ming-Zhu Jin  2 , Ze-Yong Yang  3 , Wei-Lin Jin  4
Affiliations
Review

Microglia in neurodegenerative diseases

Yu Xu et al. Neural Regen Res. 2021 Feb.

Abstract

A major feature of neurodegeneration is disruption of central nervous system homeostasis, during which microglia play diverse roles. In the central nervous system, microglia serve as the first line of immune defense and function in synapse pruning, injury repair, homeostasis maintenance, and regulation of brain development through scavenging and phagocytosis. Under pathological conditions or various stimulations, microglia proliferate, aggregate, and undergo a variety of changes in cell morphology, immunophenotype, and function. This review presents the features of microglia, especially their diversity and ability to change dynamically, and reinterprets their role as sensors for multiple stimulations and as effectors for brain aging and neurodegeneration. This review also summarizes some therapeutic approaches for neurodegenerative diseases that target microglia.

Keywords: central nervous system; microglia; neurodegeneration; neuroinflammation; plasticity.

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Conflict of interest statement

None

Figures

Figure 1
Figure 1
The origin and biology of microglia. Microglia originate from the yolk sac during embryogenesis and from bone marrow during repopulation. They act as an immunological surveillant in steady states. ARG1: Arginase 1; CNS: central nervous system; CD200R1: CD200 receptor 1; CX3CR1: CX3C chemokine receptor 1; CXCR2: C-X-C motif chemokine receptor 2; IL: interleukin; iNOS: inducible nitric oxide synthase; MARCO: macrophage receptor with collagenous structure; MHCII: major histocompatibility complex II; PPAR: peroxisome proliferator-activated receptor; TGF-β: transforming growth factor-β; TNF-α: tumor necrosis factor-α.
Figure 2
Figure 2
Microglia act as both sensors and effectors. Microglia are activated, change morphology and distribution, and produce reactive oxygen species (ROS) in response to various conditions, including aging, sex, stress, injuries, infections, hypoxia-ischemia, ROS, microbiota, anesthesia and alcohol, which suggests that they can act as a sensor. Once activated, microglia can produce ROS and inflammatory factors to induce neurotoxicity and neuronal apoptosis. They can, therefore, act as an effector in neurodegenerative diseases. These diseases can further affect the function and aggregation of microglia.
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