Regulatory Effects of Thymoquinone on Dopamine Level in Neuronal Cells Exposed to Amphetamine: An In Vitro Study

Introduction: Amphetamine (AT) is used to treat some medical conditions and also known to be abused recreationally. It is a potent central nervous system stimulant that is capable of producing damaging effects to the central dopaminergic pathway. Most of AT users are treated clinically for symptomatic treatment which is associated with neurological side effects. To date, there is growing interest in naturally occurring compounds which have lesser side effects to treat health problems. One of the potential compounds is thymoquinone (TQ), an active compound of Nigella sativa which is known for its cellular protective effects. Objective: The objectives of this study were to determine the IC50 values of AT and TQ on differentiated SH-SY5Y neuronal cells and to evaluate the changes of dopamine (DA) level in the cells exposed to AT after co-administering with TQ. Methodology: Differentiated SH-SY5Y cells were grown in cell culture flask containing DMEM/F12 medium supplemented with 10% (v/v) fetal bovine serum and 1% (v/v) penicillin/streptomycin. The IC50 value of TQ and AT in differentiated SH-SY5Y cells was determined by using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. The DA level was determined by using the Enzyme-Linked Immunosorbent Assay (ELISA) kit. Result and Discussion: The IC50 values of AT and TQ were 1596 ?M and 926 ?M respectively. Co-administration of 40 ?M of AT and 30 ?M of TQ demonstrated a significant increase in DA level at 48 hours of exposure when compared to the administration of AT group (P?0.05). Conclusion: These findings suggested that TQ has a role in maintaining the DA activity after a long-term AT exposure.