Gallic acid is one of the most important polyphenolic compounds, which is considered an excellent free radical scavenger. 6-Hydroxydopamine (6-OHDA) is a neurotoxin, which has been implicated in mainly Parkinson's disease (PD). In this study, we investigated the molecular mechanism of the neuroprotective effects of gallic acid on 6-OHDA induced apoptosis in human dopaminergic cells, SH-SY5Y. Our results showed that 6-OHDA induced cytotoxicity in SH-SY5Y cells was suppressed by pre-treatment with gallic acid. The percentage of live cells (90%) was high in the pre-treatment of gallic acid when compared with 6-OHDA alone treated cell line. Moreover, gallic acid was very effective in attenuating the disruption of mitochondrial membrane potential, elevated levels of intracellular ROS and apoptotic cell death induced by 6-OHDA. Gallic acid also lowered the ratio of the pro-apoptotic Bax protein and the anti-apoptotic Bcl-2 protein in SH-SY5Y cells. 6-OHDA exposure was up-regulated caspase-3 and Keap-1 and, down-regulated Nrf2, BDNF and p-CREB, which were sufficiently reverted by gallic acid pre-treatment. These findings indicate that gallic acid is able to protect the neuronal cells against 6-OHDA induced injury and proved that gallic acid might potentially serve as an agent for prevention of several human neurodegenerative diseases caused by oxidative stress and apoptosis.
Keywords: 6-Hydroxydopamine; Apoptosis; Gallic acid; Keap1/Nrf2; Parkinson’s disease.