Alpha-pinene preserves human dopaminergic SH-SY5Y cells against 6-hydroxydopamine-induced toxicity through its antioxidant and antiapoptotic properties and gamma-aminobutyric acid type A signaling

Background: Parkinson's disease (PD) is one of the most common neurodegenerative disorders which is characterized by progressive loss of dopaminergic neurons in substantia nigra. Therefore, drugs or natural agents that have suppressive effects on dopaminergic cell death may reduce the progression of such disorder. Here, the effect of natural product alpha-pinene was evaluated on 6-hydroxydopamine (6-OHDA)-induced damage in SH-SY5Y human dopaminergic cell line as an in vitro model of PD. Methods: The cells were incubated by 150 μM 6-OHDA alone or accompanied with different concentration of alpha-pinene (10–180 μM). Cell viability was determined by MTT assay. The amount of intracellular reactive oxygen species (ROS) and mitochondrial membrane potential were measured by fluorescence spectrophotometry. In addition, the components of molecular apoptotic pathway such as cytochrome c release, Bax, Bcl-2, and caspase-3 levels were measured by immunoblotting. Gamma-aminobutyric acid (GABA) antagonist, bicuculline, was used to find the role of GABA Type A (GABAA) receptors in the signaling of alpha-pinene. Results: The data showed that 6-OHDA produced cell damage, decreased mitochondrial membrane potential, increased intracellular ROS and cytochrome c release, as well as increased Bax/Bcl-2 ratio and caspase-3 activity. Moreover, alpha-pinene (70 μM) significantly inhibited cellular and molecular abnormalities. Blockage of GABAA receptor significantly suppressed the protective effect of alpha-pinene. Conclusion: The results suggest that alpha-pinene has a protective effect against dopaminergic toxicity, and at least in part, its antioxidant and antiapoptotic properties are probably involved in such protection.