Cytokines in Parkinson's Disease

We found that in Parkinson's disease (PD) the levels of various cytokines [tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-2, IL-4, IL-6, epidermal growth factor (EGF), transforming growth factor (TGF)-alpha, TGF-beta1] were significantly increased in the striatum (caudate and putamen) of the postmortem brain and in ventricular or spinal cerebrospinal fluid (VCSF, LCSF). Furthermore, the levels of the apoptosis-related proteins such as bcl-2 and soluble Fas (sFas) in the striatum were also elevated in PD. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated parkinsonism mice, the levels of IL-1beta in the striatum were significantly increased, but those of nerve growth factor (NGF) were significantly decreased, compared with control mice. In hemiparkinsonism rats produced by injection of 6-hydroxydopamine (6-OHDA) into one side of the median forebrain bundle, the levels of TNF-alpha in the 6-OHDA-treated side were increased in the striatum and substantia nigra, but not in the cerebral cortex, compared with those in the control side. Repeated administration of L-DOPA in the 6-OHDA-treated rats did not change the TNF-alpha levels in the control side and in the 6-OHDA-treated side in the substantia nigra, striatum, and cerebral cortex. Our results suggest that the changes in the levels of cytokines, neurotrophins, and apoptosis-related proteins in the nigrostriatal regions of PD may be involved in apoptosis and degeneration of the nigrostriatal DA neurons.