Protective effects of verbenalin and (+)-eudesmin against 6-hydroxydopamine-induced oxidative/nitrosative stress in SH-SY5Y cells

Background The purpose of this research was to study whether verbenalin, an iridoid glucoside, and (+)-eudesmin, a furofuran lignan isolated from different plant families, can attenuate cell damage and death induced by 6-hydroxydopamine (6-OHDA) in human neuroblastoma SH-SY5Y cells. Methods SH-SY5Y cells were incubated with 6-OHDA (35 mu M) for 1 day. Verbenalin and (+)-eudesmin were administrated with various concentrations (1, 2.5, 5, 10, 20, and 50 mu M) one hour before the 6-OHDA treatment. After 1 day, cell viability and neuroprotective effect were investigated with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. Nitrosative stress was determined with measurements of nitric oxide (NO) and 3-nitrotyrosine (3-NT), a biomarker of peroxynitrite formation. Results We observed that 6-OHDA declined viability and augmented LDH leakage in SH-SY5Y cells. MTT analyses showed that pretreatment with verbenalin and (+)-eudesmin markedly prevented the toxicity due to 6-OHDA (P < 0.05). Verbenalin and (+)-eudesmin suppressed LDH release induced by 6-OHDA (P < 0.01). Although 6-OHDA treatment produced no marked effects on NO levels, (+)-eudesmin at high concentrations (10-50 mu M) markedly attenuated NO levels (P < 0.01). There was a significant increase in 3-NT levels with 6-OHDA exposure in cells. Pretreatment with verbenalin, but not (+)-eudesmin, diminished 3-NT levels at low concentrations (1-20 mu M) and prevented the cytotoxic effect of 6-OHDA (P < 0.01). Conclusion These results indicated that verbenalin and (+)-eudesmin exert potent cytoprotective activities against cytotoxicity triggered by 6-OHDA in neuroblastoma cells. This is the first report demonstrating that verbenalin may act as a peroxynitrite scavenger.