TY - JOUR
T1 - In Vitro Priming and Hyper-Activation of Brain Microglia
T2 - an Assessment of Phenotypes
AU - Koss, Kyle
AU - Churchward, Matthew A.
AU - Tsui, Christopher
AU - Todd, Kathryn G.
N1 - Publisher Copyright:
© 2019, Springer Science+Business Media, LLC, part of Springer Nature.
PY - 2019/9/15
Y1 - 2019/9/15
N2 - Microglia are the resident immune cells of the central nervous system that mediate the life and death of nervous tissue. During normal function, they exhibit a surveying phenotype and maintain vital functions in nervous tissue. In the event of injury or disease, chronic inflammation can result, wherein microglia develop a hyper-activated phenotype, shed their regenerative function, actively kill contiguous cells, and can partition injured tissue by initiating scar formation. With recoverable injury, microglia can develop a primed phenotype, where they appear to recover from an inflammatory event, but are limited in their support functions and show inappropriate responses to future injury often associated with neurodegenerative disorders. These microglial phenotypes were acutely recreated in vitro with potent pro- and anti-inflammatory treatments. Primary cultured microglia or mixed glia (microglia, astrocytes, and oligodendrocytes) were treated for 6 h with lipopolysaccharide (LPS). Recovery from an inflammatory state was modeled with 18-h treatment of the anti-inflammatory steroid dexamethasone. The cells were then treated for 24 h with interferon gamma (IFNγ) to detect inflammatory memory after recovery. Surveying was best represented in the untreated vehicle (Veh) cases and was characterized by negligible secretion of pro-inflammatory factors, limited expression of immune proteins such as induced nitric oxide synthase (iNOS), major histocompatibility complex class II (MHCII), relatively high expression of brain-derived and glial-derived neurotrophic factors (BDNF and GDNF), and thinly branched smaller microglia. Activation was noted in the LPS- and IFNγ-treated microglia with increased cytokines, NO, NGF, iNOS, proliferation, phagocytosis, reduced BDNF, and flattened round amoeboid-shaped microglia. Priming was observed to be an incomplete surveying restoration using dexamethasone from an activation comparison of LPS, IFNγ, and LPS/IFNγ. Dexamethasone treatments resulted in the most profound dysregulation of expression of NO, TNF, IL-1β, NGF, CD68, and MHCII as well as ramified morphology and uptake of myelin. These findings suggest microglial priming and hyper-activation may be effectively modeled in vitro to allow mechanistic investigations into these key cellular phenotypes.
AB - Microglia are the resident immune cells of the central nervous system that mediate the life and death of nervous tissue. During normal function, they exhibit a surveying phenotype and maintain vital functions in nervous tissue. In the event of injury or disease, chronic inflammation can result, wherein microglia develop a hyper-activated phenotype, shed their regenerative function, actively kill contiguous cells, and can partition injured tissue by initiating scar formation. With recoverable injury, microglia can develop a primed phenotype, where they appear to recover from an inflammatory event, but are limited in their support functions and show inappropriate responses to future injury often associated with neurodegenerative disorders. These microglial phenotypes were acutely recreated in vitro with potent pro- and anti-inflammatory treatments. Primary cultured microglia or mixed glia (microglia, astrocytes, and oligodendrocytes) were treated for 6 h with lipopolysaccharide (LPS). Recovery from an inflammatory state was modeled with 18-h treatment of the anti-inflammatory steroid dexamethasone. The cells were then treated for 24 h with interferon gamma (IFNγ) to detect inflammatory memory after recovery. Surveying was best represented in the untreated vehicle (Veh) cases and was characterized by negligible secretion of pro-inflammatory factors, limited expression of immune proteins such as induced nitric oxide synthase (iNOS), major histocompatibility complex class II (MHCII), relatively high expression of brain-derived and glial-derived neurotrophic factors (BDNF and GDNF), and thinly branched smaller microglia. Activation was noted in the LPS- and IFNγ-treated microglia with increased cytokines, NO, NGF, iNOS, proliferation, phagocytosis, reduced BDNF, and flattened round amoeboid-shaped microglia. Priming was observed to be an incomplete surveying restoration using dexamethasone from an activation comparison of LPS, IFNγ, and LPS/IFNγ. Dexamethasone treatments resulted in the most profound dysregulation of expression of NO, TNF, IL-1β, NGF, CD68, and MHCII as well as ramified morphology and uptake of myelin. These findings suggest microglial priming and hyper-activation may be effectively modeled in vitro to allow mechanistic investigations into these key cellular phenotypes.
KW - Activated
KW - Dexamethasone
KW - Glia
KW - Hyper-activated
KW - In vitro
KW - Interferon gamma
KW - LPS
KW - Microglia
KW - Phenotypes
KW - Primed
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UR - http://www.scopus.com/inward/citedby.url?scp=85062157649&partnerID=8YFLogxK
U2 - 10.1007/s12035-019-1529-y
DO - 10.1007/s12035-019-1529-y
M3 - Article
C2 - 30805836
AN - SCOPUS:85062157649
SN - 0893-7648
VL - 56
SP - 6409
EP - 6425
JO - Molecular Neurobiology
JF - Molecular Neurobiology
IS - 9
ER -