TNF and Parkinson disease: Reactive astrocytes subjected to microglia-derived pro-inflammatory cytokines such as a combination of tumor necrosis factor (TNF), interleukin-1α (IL-1α), and complement component 1q (C1q) have reduced ability to promote neuronal survival, synaptogenesis and phagocytosis, and can induce neuronal death in human AD, PD and MS tissues [31].