Neurorescue effect of rosmarinic acid on 6-hydroxydopamine-lesioned nigral dopamine neurons in rat model of Parkinson's disease

Rosmarinic acid (RA) is a naturally occurring polyphenolic compound. It has been reported that RA possessed antioxidant and anti-inflammatory properties. Our previous study showed that RA could protect MES23.5 dopaminergic cells against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in vitro. The purpose of this study was to explore the neuroreparative (neurorescue) effect of RA on 6-OHDA-lesioned rat model of Parkinson's disease (PD) in vivo. In this study, the rats were given RA orally after intrastriatal 6-OHDA lesion. Results showed that the dopamine content in the striatum decreased and the numbers of tyrosine hydroxylase-immunoreactive neurons reduced after 6-OHDA treatment. RA treatment after 6-OHDA administration could restore these changes. Further studies demonstrated that 6-OHDA treatment increased the iron-staining positive cells, which were markedly decreased by RA treatment. Moreover, RA suppressed the increased ratio of Bax/Bcl-2 at gene level induced by 6-OHDA. This indicates that the neurorescue effects of RA against 6-ODHA-induced degeneration of the nigrostriatal dopaminergic system were achieved by decreasing nigral iron levels and regulating the ratio of Bcl-2/Bax gene expression.