NGF and Parkinson disease: The following was noted in dopaminergic nigrostriatal region and in cerebrospinal fluid of PD patients: (1) increased level of proinflammatory cytokines such as IL-1β, IL-2, IL-4, IL-6 and TNF-α; (2) increased level of factors associated with apoptosis, including TNF-α receptor R1 (p55), soluble Fas, Bcl-2 and elevated caspase-1 and caspase-3 activities; (3) lowered level of neurotrophins, such as BDNF and NGF (nerve growth factor) [126].