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Lipopolysaccharide Induces Mitochondrial Fragmentation and Energetic Shift in Reactive Microglia: Evidence for a
Marcelle Pereira Dos Santos1, Vitor Emanuel Leocadio1, Lívia de Sá Hayashide1
1Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, RJ, Brazil.
Abstract:
Microglia, the resident immune cells of the central nervous system (CNS), play essential roles in maintaining brain homeostasis. While transient activation is protective, chronic microglial reactivity contributes to neuroinflammatory damage and neurodegeneration. The mitochondrial mechanisms underlying this shift remain poorly understood. Here, we investigated whether lipopolysaccharide (LPS) induces coordinated mitochondrial and metabolic alterations in BV-2 microglial cells. LPS stimulation (100 ng/mL, 24 h) induced a reactive phenotype, with increased Iba1 (+82%), F4/80 (+132%), and Cd68 (+44%), alongside elevated hydrogen peroxide (~6-fold) and nitrite (~45-fold). Cytotoxicity increased by 40% (LDH assay), and cell viability dropped to ~80% of the control (MTT). Extracellular lactate increased, indicating glycolytic reprogramming. However, LPS-primed cells showed greater ATP depletion under antimycin A challenge, reflecting impaired metabolic flexibility. Hoechst staining revealed a ~4-fold increase in pyknotic nuclei, indicating apoptosis. Mitochondrial dysfunction was confirmed by a 30-40% reduction in membrane potential (TMRE, JC-1), a ~30% loss of Tomm20, and changes in dynamics: phospho-Drp1 increased (+23%), while Mfn1/2 decreased (33%). Despite a ~70% rise in Lamp2 signal, Tomm20-Lamp2 colocalization decreased, suggesting impaired mitophagy. High-resolution respirometry revealed decreased basal (-22%), ATP-linked (24%), and spare respiratory capacity (41%), with increased non-mitochondrial oxygen consumption. These findings demonstrate that LPS induces mitochondrial dysfunction, loss of metabolic adaptability, and increased apoptotic susceptibility in microglia. Mitochondrial quality control and energy flexibility emerge as relevant targets to better understand and potentially modulate microglial responses in neuroinflammatory and neurodegenerative conditions.
Insights
Lipopolysaccharide (LPS) triggers microglial dysfunction, impairing mitochondria and metabolism. This leads to increased cell death and reduced adaptability, highlighting targets for neuroinflammation.
Area of Science:
- Neuroscience
- Immunology
- Cell Biology
Background:
- Microglia are key immune cells in the central nervous system (CNS).
- Chronic microglial activation contributes to neuroinflammation and neurodegeneration.
- Mitochondrial mechanisms driving this shift are not well understood.
Purpose of the Study:
- To investigate mitochondrial and metabolic changes in microglia stimulated with lipopolysaccharide (LPS).
- To explore how LPS affects microglial phenotype, function, and viability.
Main Methods:
- BV-2 microglial cells were stimulated with LPS.
- Assessed microglial phenotype (Iba1, F4/80, Cd68), cytotoxicity (LDH), viability (MTT), apoptosis (Hoechst).
- Analyzed metabolic flexibility (ATP depletion), mitochondrial function (TMRE, JC-1, Tomm20), mitochondrial dynamics (Drp1, Mfn1/2), mitophagy (Lamp2), and respirometry.
Main Results:
- LPS induced a reactive microglial phenotype with increased inflammatory markers and cytotoxicity.
- LPS impaired mitochondrial function, reduced metabolic flexibility, and increased apoptosis.
- Mitochondrial dynamics were altered, mitophagy was impaired, and respiratory capacity decreased.
Conclusions:
- LPS induces significant mitochondrial dysfunction and metabolic inflexibility in microglia.
- These changes contribute to increased apoptotic susceptibility.
- Mitochondrial quality control and energy metabolism are potential therapeutic targets for neuroinflammatory diseases.
