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Modeling Neuronal Death and Degeneration in Mouse Primary Cerebellar Granule Neurons
Published on: November 6, 2017
Neuronal Death Caused by HMGB1-Evoked via Inflammasomes from Thrombin-Activated Microglia Cells
Meei-Ling Sheu1,2,3, Liang-Yi Pan4, Cheng-Ning Yang5
1Institute of Biomedical Sciences, National Chung-Hsing University, Taichung 40227, Taiwan.
Abstract:
Microglial cells are a macrophage-like cell type residing within the CNS. These cells evoke pro-inflammatory responses following thrombin-induced brain damage. Inflammasomes, which are large caspase-1-activating protein complexes, play a critical role in mediating the extracellular release of HMGB1 in activated immune cells. The exact role of inflammasomes in microglia activated by thrombin remains unclear, particularly as it relates to the downstream functions of HMGB1. After receiving microinjections of thrombin, Sprague Dawley rats of 200 to 250 gm were studied in terms of behaviors and immunohistochemical staining. Primary culture of microglia cells and BV-2 cells were used for the assessment of signal pathways. In a water maze test and novel object recognition analysis, microinjections of thrombin impaired rats' short-term and long-term memory, and such detrimental effects were alleviated by injecting anti-HMGB-1 antibodies. After thrombin microinjections, the increased oxidative stress of neurons was aggravated by HMGB1 injections but attenuated by anti-HMGB-1 antibodies. Such responses occurred in parallel with the volume of activated microglia cells, as well as their expressions of HMGB-1, IL-1β, IL-18, and caspase-I. In primary microglia cells and BV-2 cell lines, thrombin also induced NO release and mRNA expressions of iNOS, IL-1β, IL-18, and activated caspase-I. HMGB-1 aggravated these responses, which were abolished by anti-HMGB-1 antibodies. In conclusion, thrombin induced microglia activation through triggering inflammasomes to release HMGB1, contributing to neuronal death. Such an action was counteracted by the anti-HMGB-1 antibodies. The refinement of HMGB-1 modulated the neuro-inflammatory response, which was attenuated in thrombin-associated neurodegenerative disorder.
Insights
Thrombin activates microglia via inflammasomes, releasing HMGB1 and causing neuroinflammation and memory deficits. Anti-HMGB1 antibodies protected against these effects, suggesting a therapeutic target for neurodegenerative disorders.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglial cells, the resident immune cells of the central nervous system (CNS), play a crucial role in neuroinflammation.
- Thrombin, a serine protease, can induce brain damage and activate microglia.
- Inflammasomes are key regulators of inflammatory responses, mediating the release of pro-inflammatory cytokines and HMGB1.
Purpose of the Study:
- To investigate the role of inflammasomes and HMGB1 in thrombin-induced microglial activation and subsequent neuroinflammation.
- To determine the impact of thrombin and HMGB1 on cognitive function and neuronal survival.
- To evaluate the therapeutic potential of anti-HMGB1 antibodies in mitigating thrombin-induced neuroinflammation and cognitive deficits.
Main Methods:
- Primary cultures of microglia and BV-2 cell lines were used to assess cellular responses to thrombin.
- Sprague Dawley rats received microinjections of thrombin and were evaluated using behavioral tests (water maze, novel object recognition) and immunohistochemical staining.
- Levels of HMGB1, IL-1β, IL-18, caspase-1, and oxidative stress markers were measured.
Main Results:
- Thrombin microinjection impaired short-term and long-term memory in rats, an effect reversed by anti-HMGB1 antibodies.
- Thrombin induced microglial activation, characterized by increased expression of HMGB1, IL-1β, IL-18, and caspase-1.
- HMGB1 exacerbated thrombin-induced oxidative stress and inflammatory responses in both in vivo and in vitro models, while anti-HMGB1 antibodies attenuated these effects.
Conclusions:
- Thrombin triggers microglial activation and inflammasome-mediated release of HMGB1, contributing to neuroinflammation and neuronal damage.
- Targeting HMGB1 with antibodies can counteract thrombin-induced neuroinflammation and cognitive impairment.
- Modulating HMGB1 offers a potential therapeutic strategy for thrombin-associated neurodegenerative disorders.
