Fig. 1

Changes in astrocyte secretome when a quiescent astrocyte takes on an A2 or A1 phenotype. A1 and A2 reactive astrocytes have distinct intracellular markers, as well as different secretory profiles. A2 reactive astrocytes promote neuroprotection through secretion of anti-inflammatory cytokines and chemokines as well as anti-apoptotic non-coding RNAs. In addition, enhanced secretion of metabolites such as lactate and alpha-ketoglutarate provides additional metabolic support for neurons. A1 reactive astrocytes, on the other hand, are neurotoxic, and promote neurodegeneration through secretion of pro-inflammatory cytokines and chemokines. Recent studies also show that these astrocytes secrete neurotoxic fatty acids and lipids, which represents a paradigm shift in the field of neurodegeneration