Inhibition of the Nrf2/HO-1 Axis Suppresses the Mitochondria-Related Protection Promoted by Gastrodin in Human Neuroblastoma Cells Exposed to Paraquat.

Mitochondria are double-membrane organelles involved in the transduction of energy from different metabolic substrates into adenosine triphosphate (ATP) in mammalian cells. The oxidative phosphorylation system is comprised by the activity of the respiratory chain and the complex V (ATP synthase/ATPase). This system is dependent on oxygen gas (O2) in order to maintain a flux of electrons in the respiratory chain, since O2 is the final acceptor of these electrons. Electron leakage from this complex system leads to the continuous generation of reactive species in the cells. The mammalian cells exhibit certain mechanisms to attenuate the consequences originated from the constant exposure to these reactive species. In this context, the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and one of the enzymes whose expression is modulated by Nrf2, heme oxygenase-1 (HO-1), take a central role in inducing cytoprotection in humans. Mitochondrial abnormalities are observed during intoxication and in certain diseases, including neurodegeneration. Mitochondrial protection promoted by natural compounds has attracted the attention of researchers due to the promising effects these agents induce experimentally. In this regard, we examined here whether and how gastrodin (GAS), a phenolic glucoside, would prevent the paraquat (PQ)-induced mitochondrial impairment in the SH-SY5Y cells. The cells were exposed to GAS (25 μM) for 4 h prior to the challenge with PQ at 100 μM for additional 24 h. The silencing of Nrf2 by siRNA or the inhibition of HO-1 by ZnPP IX suppressed the GAS-elicited cytoprotection. Therefore, GAS promoted mitochondrial protection by an Nrf2/HO-1-dependent manner.