Parkinson's disease (PD) is pathologically characterized by the presence of α-synuclein (α-syn)-positive intra-cytoplasmic inclusions named Lewy bodies in the dopaminergic neurons of the substantia nigra. A series of morbid consequences are caused by pathologically high amounts or mutant forms of α-syn, such as defects of membrane trafficking and lipid metabolism. In this review, we consider evidence that both point mutation and overexpression of α-syn result in aberrant degradation in neurons and microglia, and this is associated with the autophagy-lysosome pathway and endosome-lysosome system, leading directly to pathological intracellular aggregation, abnormal externalization and re-internalization cycling (and, in turn, internalization and re-externalization), and exocytosis. Based on these pathological changes, an increasing number of researchers have focused on these new therapeutic targets, aiming at alleviating the pathological accumulation of α-syn and re-establishing normal degradation.
Curcumin,a natural polyphenol obtained from turmeric,has been implicated to be neuroprotective in a variety of neurodegenerative disorders although the mechanism remains poorly understood.The results of our recent experiments indicated that curcumin could protect dopaminergic neurons from apoptosis in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)mouse model of Parkinson’s disease(PD).The death of dopaminergic neurons and the loss of dopaminergic axon in the striatum were significantly suppressed by curcumin in MPTP mouse model.Further studies showed that curcumin inhibited JNKs hyperphosphorylation induced by MPTP treatment.JNKs phosphorylation can cause translocation of Bax to mitochondria and the release of cytochrome c which both ultimately contribute to mitochondria-mediated apoptosis.These pro-apoptosis effect can be diminished by curcumin.Our experiments demonstrated that curcumin can prevent nigrostriatal degeneration by inhibiting the dysfunction of mitochondrial through suppressing hyperphosphorylation of JNKs induced by MPTP.Our results suggested that JNKs/mitochondria pathway may be a novel target in the treatment of PD patients.
