A1-reactive astrocyte (A1 astrocyte)

A1-reactive astrocytes represent a specific neurotoxic state of astrocytes induced by inflammatory signals from activated microglia, specifically interleukin-1 alpha (IL-1α), tumor necrosis factor (TNF), and complement component 1q (C1q). Unlike homeostatic astrocytes that support neuronal survival and synaptogenesis, A1 astrocytes lose these essential functions and instead actively secrete neurotoxic factors that lead to the death of neurons and oligodendrocytes. This phenotype is characterized by the high expression of markers such as Complement C3 and is widely observed in the brain tissue of patients with various neurodegenerative conditions, including Alzheimer's and Parkinson's diseases. Therapeutic strategies targeting A1-reactive astrocytes focus on preventing their formation or mitigating their toxic effects. Current drug development efforts, such as the GLP-1 receptor agonist NLY01, aim to block the microglial activation responsible for inducing the A1 state. By maintaining astrocytes in a homeostatic or neuroprotective (A2) state, researchers hope to slow the progression of chronic CNS diseases. However, a significant challenge remains in selectively targeting the harmful A1 population without disrupting the critical physiological roles that astrocytes play in brain metabolism and blood-brain barrier integrity.

Other names

Neurotoxic astrocyteInflammatory reactive astrocyteC3-positive astrocyteA1 phenotype astrocyte

Inhibition of microglial-derived cytokines (IL-1α, TNF, and C1q) to prevent the induction of the neurotoxic A1 phenotype; modulation of GLP-1 receptors on microglia to suppress the inflammatory secretome that triggers astrocyte polarization; direct blockade of A1-secreted neurotoxic factors.