Objective  To explore the protective effects and mechanisms of different concentrations of Averrhoacarambola L. root extract 2-Dodecyl-6-Methoxycyclohexa-2, 5-Diene-1, 4-Dione (DMDD) on α -Syn PFFs-induced differentiated SH-SY5Y cell damage.

Methods  The SH-SY5Y cells differentiated by retinoic acid weretreated with different concentrations of DMDD, followed by detecting the cell viability by MTS to determine thelow, medium, and high concentrations of DMDD for use in these cells. The cells were treated with various concentrations of DMDD in an established model of cell damage induced by 5 μg/mL α-Syn PFF. Hoechst 33342staining and nitric oxide kit were used to detect the number of cells with nuclear damage and intracellular nitricoxide production, respectively. The protein expression levels of tyrosine hydroxylase (TH), polyadenylate diphosphate (PAR) and polyadenylate diphosphate ribozyme-1 (PARP-1) were measured by western blotting. Immunofluorescence was used to detect the number of cells positive for phosphorylated serine 129 α-synuclein (pS129-α-Syn), phosphorylated histone H2AX (γH2AX), and nuclear translocation of apoptosis-inducing factor (AIF).

Results  Hoechst 33342 staining demonstrated that the number of cells with nuclear damage was significantly decreased in all DMDD treatment groups compared with the α-Syn PFFs model group (P < 0.001). The nitric oxideassay results showed that nitric oxide production was significantly reduced in the DMDD treatment groups compared with the α-Syn PFFs model group (P < 0.01 or P < 0.001). Western blotting revealed that compared with theα-Syn PFFs model group, TH protein expression level was significantly increased in the high DMDD concentration treatment group (P < 0.05), while PAR protein expression levels were significantly decreased in the mediumand high DMDD concentration treatment groups (P < 0.05), and the protein expression levels of PARP-1 andCleaved PARP-1 were significantly decreased in the high DMDD concentration treatment group (P < 0.05). Immunofluorescence results showed that compared with the α-Syn PFFs model group, the number of pS129-α-Synpositive cells was decreased significantly after treatment with medium and high concentrations of DMDD (P < 0.05 or P < 0.01), while the number of γH2AX-positive cells and AIF nuclear translocation cells was decreasedsignificantly in all DMDD treatment groups (P < 0.01 or P < 0.001).

Conclusion  DMDD may attenuate the damage in differentiated SH-SY5Y cells induced by α-Syn PFFs through inhibition of PARP-1-dependent cell deathmediated by the PARP-1/AIF pathway.