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Updated: Mar 3, 2026
Microglia as a Surrogate Biosensor to Determine Nanoparticle Neurotoxicity
Published on: October 25, 2016
Microglia amplify inflammatory activation of astrocytes in manganese neurotoxicity
Kelly S Kirkley1,2, Katriana A Popichak1,2, Maryam F Afzali1,2
1Department of Environmental and Radiological Health Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, 1680 Campus Delivery, Fort Collins, CO, 80523-1680, USA.
Background:
As the primary immune response cell in the central nervous system, microglia constantly monitor the microenvironment and respond rapidly to stress, infection, and injury, making them important modulators of neuroinflammatory responses. In diseases such as Parkinson's disease, Alzheimer's disease, multiple sclerosis, and human immunodeficiency virus-induced dementia, activation of microglia precedes astrogliosis and overt neuronal loss. Although microgliosis is implicated in manganese (Mn) neurotoxicity, the role of microglia and glial crosstalk in Mn-induced neurodegeneration is poorly understood.
Methods:
Experiments utilized immunopurified murine microglia and astrocytes using column-free magnetic separation. The effect of Mn on microglia was investigated using gene expression analysis, Mn uptake measurements, protein production, and changes in morphology. Additionally, gene expression analysis was used to determine the effect Mn-treated microglia had on inflammatory responses in Mn-exposed astrocytes.
Results:
Immunofluorescence and flow cytometric analysis of immunopurified microglia and astrocytes indicated cultures were 97 and 90% pure, respectively. Mn treatment in microglia resulted in a dose-dependent increase in pro-inflammatory gene expression, transition to a mixed M1/M2 phenotype, and a de-ramified morphology. Conditioned media from Mn-exposed microglia (MCM) dramatically enhanced expression of mRNA for Tnf, Il-1β, Il-6, Ccl2, and Ccl5 in astrocytes, as did exposure to Mn in the presence of co-cultured microglia. MCM had increased levels of cytokines and chemokines including IL-6, TNF, CCL2, and CCL5. Pharmacological inhibition of NF-κB in microglia using Bay 11-7082 completely blocked microglial-induced astrocyte activation, whereas siRNA knockdown of Tnf in primary microglia only partially inhibited neuroinflammatory responses in astrocytes.
Conclusions:
These results provide evidence that NF-κB signaling in microglia plays an essential role in inflammatory responses in Mn toxicity by regulating cytokines and chemokines that amplify the activation of astrocytes.
Insights
Manganese exposure activates microglia, triggering inflammatory responses that amplify astrocyte activation via NF-κB signaling. This study reveals a key mechanism in manganese neurotoxicity involving glial crosstalk.
Area of Science:
- Neuroscience
- Immunology
- Toxicology
Background:
- Microglia are key immune cells in the central nervous system, responding to various stimuli.
- Microglial activation precedes neuronal damage in neurodegenerative diseases.
- The role of microglia and glial interactions in manganese neurotoxicity is not well understood.
Purpose of the Study:
- To investigate the role of microglia in manganese (Mn)-induced neurotoxicity.
- To elucidate the crosstalk between microglia and astrocytes in response to Mn exposure.
Main Methods:
- Utilized immunopurified murine microglia and astrocytes.
- Assessed Mn effects on microglia via gene expression, Mn uptake, protein production, and morphology.
- Analyzed Mn-treated microglia's impact on astrocyte inflammatory responses using gene expression.
Main Results:
- Mn exposure increased pro-inflammatory gene expression and altered microglial morphology.
- Mn-exposed microglia released cytokines and chemokines that activated astrocytes.
- Inhibition of NF-κB in microglia blocked Mn-induced astrocyte activation.
Conclusions:
- Microglial NF-κB signaling is crucial for inflammatory responses in Mn toxicity.
- Microglia-derived factors amplify astrocyte activation during Mn exposure.
- This highlights a critical glial crosstalk mechanism in Mn neurotoxicity.
