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Updated: Jun 10, 2025
Activation and Measurement of NLRP3 Inflammasome Activity Using IL-1β in Human Monocyte-derived Dendritic Cells
Published on: May 22, 2014
Microglial priming by IFN-γ involves STAT1-mediated activation of the NLRP3 inflammasome
Haili He1, Xiaomei Zhang2, Hui He2
1Resource Institute for Chinese and Ethnic Materia Medica, Guizhou University of Traditional Chinese Medicine, Guiyang, China.
Background:
Inflammatory and immune responses in the brain that contribute to various neuropsychiatric disorders may begin as microglial "priming". Interferon (IFN)-γ is known to cause microglial priming, but the mechanism is unclear.
Methods:
We examined the effects of IFN-γ on gene expression, microglial activation, inflammatory and immune responses and activity of the NLRP3 inflammasome in primary microglia and in the brains of mice.
Results:
Our results showed that treating microglial cultures with IFN-γ induced a hedgehog-like morphology and upregulated markers of microglial activation (CD86, CD11b) and pro-inflammatory molecules (IL-1β, IL-6, TNF-α, iNOS), while downregulating markers of microglial homeostasis (CX3CR1, CD200R1), anti-inflammatory molecules (MCR1, Arg-1) and neurotrophic factors (IGF-1, BDNF). IFN-γ also upregulated markers of NLRP3 inflammasome activation (NLRP3, caspase-1, gasdermin D, IL-18). This particular transcriptional profiling makes IFN-γ-primed microglia with exaggerated responses upon lipopolysaccharide (LPS) stimulation. The level of NLRP3, caspase-1, gasdermin D, IL-1β, IL-18, TNF-α and iNOS in microglia cultures treated with both IFN-γ and LPS were highest than with either one alone. Injecting IFN-γ into the lateral ventricle of mice induced similar morphological and functional changes in hippocampal microglia as in primary microglial cultures. The effects of IFN-γ on NLRP3 inflammasome and microglia from cultures or hippocampus were abolished when STAT1 was inhibited using fludarabin. Injecting mice with IFN-γ alone or together with LPS induced anxiety- and depression-like behaviors and impaired hippocampus-dependent spatial memory; these effects were mitigated by fludarabin.
Conclusions:
IFN-γ primes microglia by activating STAT1, which upregulates genes that activate the NLRP3 inflammasome. Inhibiting the IFN-γ/STAT1 axis may be a way to treat neurodegenerative diseases and psychiatric disorders that involve microglial priming.
Insights
Interferon (IFN)-γ primes brain microglia via STAT1 activation, leading to NLRP3 inflammasome activation and associated behavioral changes. Inhibiting this IFN-γ/STAT1 pathway may offer therapeutic potential for neurodegenerative and psychiatric disorders.
Area of Science:
- Neuroscience
- Immunology
- Molecular Biology
Background:
- Neuroinflammation, particularly microglial priming, is implicated in neuropsychiatric disorders.
- Interferon (IFN)-γ is a known inducer of microglial priming, but the underlying mechanisms remain poorly understood.
Purpose of the Study:
- To elucidate the mechanism by which IFN-γ induces microglial priming.
- To investigate the role of the NLRP3 inflammasome in IFN-γ-mediated microglial activation.
- To assess the behavioral consequences of IFN-γ-induced microglial priming in vivo.
Main Methods:
- Primary microglia and mouse brains were used to examine the effects of IFN-γ on gene expression, microglial activation, and inflammasome activity.
- STAT1 inhibition was employed using fludarabin to investigate its role in IFN-γ signaling.
- Behavioral tests were conducted in mice following IFN-γ administration.
Main Results:
- IFN-γ treatment induced microglial activation, pro-inflammatory responses, and NLRP3 inflammasome activation, while suppressing homeostatic markers.
- IFN-γ-primed microglia exhibited heightened responses to lipopolysaccharide (LPS) stimulation.
- In vivo administration of IFN-γ led to anxiety- and depression-like behaviors and impaired spatial memory, which were mitigated by STAT1 inhibition.
Conclusions:
- IFN-γ primes microglia through STAT1 activation, upregulating NLRP3 inflammasome components.
- The IFN-γ/STAT1 axis represents a potential therapeutic target for neurodegenerative and psychiatric disorders characterized by microglial priming.
