An oxidative stress insult is one of the principal causes of
Parkinson's disease. Astragaloside IV (AS-IV), a constituent extracted from Astragalus membranaceus, has been demonstrated to exert
antioxidant effects. However, the mechanisms responsible for the
antioxidant properties and
neuroprotective effects of AS-IV remain unclear. In this study, we examined the protective effects of AS-IV against the apoptosis of human neuronal cells (SH-SY5Y cells) induced by
hydrogen peroxide (H2O2). The results revealed that AS-IV pre-treatment attenuated the H2O2‑induced loss of SH-SY5Y cells in a dose-dependent manner; AS-IV exerted significant protecitve effects by decreasing the apoptotic ratio and attenuating
reactive oxygen species overproduction in H2O2-exposed SH-SY5Y cells. By means of immunofluorescence staining, AS-IV was found to decrease the expression of α-
synuclein and to increase the expression of
tyrosine hydroxylase (TH) in the cells, which had been increased and decreased, respectively by H2O2. As shown by western blot analysis, the protective effects of AS-IV against SH-SY5Y cell injury induced by H2O2 were also mediated via the downregulation of the ratio of Bax/Bcl-2. We found that the
neuroprotective effects of AS-IV were associated with the inhibition of the expression of the α-
synuclein via the p38
mitogen-activated
protein kinase (MAPK) signalling pathway. On the whole, our results suggest that AS-IV exerts protective effects against
neurodegenerative diseases by targeting α-
synuclein or TH.