Reactive astrocytes exposed to cerebrospinal fluid from patients with ALS (ALS-CSF) released interleukin (IL)-6, tumor necrosis factor α, cyclo-oxygenase 2, and PGE2 though downregulated IL-10, vascular endothelial growth factor, and glial cell line-derived neurotrophic factor. Here, GDNF is linked to amyotrophic lateral sclerosis.