Methylphenidate ameliorates hypoxia-induced mitochondrial damage in human neuroblastoma SH-SY5Y cells through inhibition of oxidative stress

Aims: Methylphenidate (MPH) is a dopamine-reuptake inhibitor approved for the treatment of attention-deficit/hyperactivity disorder (ADHD). Nonetheless, the cellular and molecular mechanisms of MPH are still unknown. We attempt to determine whether MPH protect neuron cells against oxidative stress by using human neuroblastoma SH-SY5Y cells. Main methods: The SH-SY5Y cells were cultured in normoxic and hypoxic conditions in the presence of different doses of MPH. Then, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD) and adenosine triphosphate (ATP) production were quantitatively measured by using flow cytometry or spectrophotometry. The mitochondrial ultrastructure of the cells was observed by electron microscope, and the function of mitochondrial was evaluated by measuring mitochondrial membrane potential (MMP) using flow cytometry. The levels of SOD and heme oxygenase-1 (HO-1) proteins were detected by Western blot. Key findings: We found that low doses of MPH treatment (50-500 ng/mL) led to decreased ROS and MDA production (P < 0.05), increased GSH and SOD as well as ATP concentration (P < 0.05) in hypoxic SH-SY5Y cells. Additionally, low doses of MPH significantly inhibited mitochondrial swelling and decreased the percentage of JC-1 monomer positive cells. However, we did not observe the same effects of MPH in normoxia. Significance: Our results show that low doses of MPH play protective roles in maintaining mitochondrial homeostasis in response to hypoxia-induced oxidative stress. Our findings may provide novel insight into the mechanisms of MPH in the treatment of ADHD, and shed light on the disease mechanisms of ADHD.