Enhanced removal of abnormal protein aggregates or injured organelles through autophagy is related to neuroprotection in Parkinson's disease. In this study, we explored whether the induction of autophagy is associated with the neuroprotection of rosemary carnosic acid (CA) against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in SH-SY5Y cells. The results indicated that cells treated with CA had increased protein levels of parkin and autophagy-related markers, including phosphatidylinositol 3-kinase p100, Beclin1, autophagy-related gene 7, and microtubule-associated protein 1 light chain 3-II, as well as enhanced formation of autophagic vacuoles. Treatment of cells with 6-OHDA decreased the levels of parkin and the autophagy markers, but CA pretreatment reversed these effects. However, wortmannin (an autophagosome formation blocker) pretreatment attenuated the effect of CA. After CA pretreatment, the induction of cleaved caspase 3, cleaved poly-ADP ribose polymerase, and nuclear condensation by 6-OHDA were alleviated. Both wortmannin and bafilomycin A1 (an autophagosome-lysosome fusion blocker) inhibited the anti-apoptosis effects of CA. Additionally, we performed immunoprecipitation with anti-parkin antibody and found that the interaction of parkin and Beclin1 protein was reduced by 6-OHDA but that this effect was reversed in cells pretreated with CA. Moreover, transfection of parkin siRNA in cells inhibited the ability of CA to alleviate 6-OHDA-decreased autophagy-related markers and nuclear condensation. In conclusion, CA protects against 6-OHDA-induced apoptosis by inducing autophagy through the interaction of parkin and Beclin1. These results provide a future strategy for use of CA in the prevention of Parkinson's disease.
Keywords: Autophagy; Carnosic acid; Neuroprotection; Parkin; SH-SY5Y cells.