M1 microglial polarization (M1 phenotype)

M1 microglial polarization refers to the "classical" pro-inflammatory activation state of microglia, the resident immune cells of the central nervous system. This state is typically triggered by stimuli such as lipopolysaccharide (LPS), interferon-gamma (IFN-gamma), or cellular debris, leading to the production of neurotoxic factors including pro-inflammatory cytokines, reactive oxygen species, and nitric oxide [1, 11]. While the M1 phenotype is essential for the acute elimination of pathogens and foreign material, chronic or excessive M1 polarization is a major contributor to neuroinflammation and neuronal loss in diseases such as Alzheimer's, Parkinson's, and multiple sclerosis [4, 10]. Therapeutic strategies often focus on suppressing the M1 state or encouraging a "phenotypic switch" toward the neuroprotective M2 state [2, 9]. Various pharmacological agents, including minocycline and certain PPAR-gamma agonists, interact with this process by inhibiting the intracellular signaling cascades that drive pro-inflammatory gene expression [5, 9].

Other names

Classical microglial activationPro-inflammatory microglial activationM1-like microglial stateNeurotoxic microglial phenotype

Modulation of polarization typically involves inhibiting pro-inflammatory signaling pathways (e.g., NF-kappaB, JAK/STAT1, NLRP3 inflammasome) or promoting a phenotypic shift toward the anti-inflammatory M2 state through PPAR-gamma activation or Nrf2 induction.