Primary Human Reactive Microglia Display Mitochondrial Dysfunction and Metabolic Imbalance Upon Lipopolysaccharide Exposure.

Microglial activation is a central component of neuroinflammation and contributes to the progression of neurodegenerative diseases. However, most of our current understanding is derived from rodent models, which do not fully recapitulate human-specific responses. In this study, we employed a human primary microglial model isolated from astrocyte-enriched cultures to investigate the cellular and metabolic alterations induced by inflammatory stimulation with lipopolysaccharide (LPS). The isolated human microglia were characterized by strong expression of canonical markers, including IBA-1, CD68, CD45, F4/80, and TMEM119. Upon LPS exposure, cells displayed a robust reactive phenotype with increased expression of activation markers and NF-κB. Functional validation showed preserved phagocytic activity, confirming the immunocompetent status of the cells. Importantly, this is the first study to demonstrate that human primary reactive microglia exhibit mitochondrial dysfunction in response to inflammatory stimuli. LPS treatment led to a significant reduction in mitochondrial mass (TOMM20), increase in mitochondria fragmentation. We observed that LPS increases the phosphorylation of DRP1, indicating enhanced mitochondrial fission and reduction in mitochondrial membrane potential (TMRE), accompanied by increased production of mitochondrial superoxide (MitoSOX), elevated levels of hydrogen peroxide and nitric oxide. This effect was temporally associated with a decrease in intracellular ATP levels, followed by an increase in extracellular lactate production, suggesting a compensatory glycolytic shift in response to mitochondrial bioenergetic failure. Together, these findings highlight a previously uncharacterized vulnerability of human microglia to inflammatory mitochondrial stress and establish a robust and physiologically relevant platform for studying human-specific mechanisms of microglial activation and bioenergetic failure in neurodegenerative conditions.