Eurycomanone from Eurycoma longifolia Jack roots regulates dopamine secretion via transsynaptic GABA signalling in differentiated SH-SY5Y human neuroblastoma cells: a transcriptomic study

PURPOSE: Eurycomanone (EN), a quassinoid from Eurycoma longifolia Jack (EL) has been previously shown to promote dopamine secretion from differentiated SH-SY5Y human neuroblastoma cells but the mechanism that underpins this property is unknown. This study sought to investigate transcriptomic changes associated with the dopamine secretory property of the isolated EN in the differentiated SH-SY5Y cells. METHODS: Differential gene expression (DGE) in EN-responsive SH-SY5Y cells was investigated by microarray analysis. RESULTS: Previous work demonstrated that EN stimulated dopamine secretion in a dose-dependent manner at 5, 10 and 15 µM, followed by reduction in secretion at higher concentration (20 to 25 µM). At 15 µM, EN significantly increased dopamine secretion compared to the positive control, clorgyline hydrochloride (10 µM, p < 0.05). Microarray analysis showed that gene expression changes by EN and the bioactive fraction Fr2 across varying concentrations closely corresponded to the observed dopamine secretion profiles. Accordingly, 15 µM EN, which elicited the most pronounced differential gene expression (DGE) was selected for pathway enrichment analysis. Subsequent qPCR validation suggested that EN modulates transsynaptic signalling between GABA-producing and differentiated SH-SY5Y cells. In silico molecular docking study further indicated that EN may activate cannabinoid CB1 and muscarinic M3 receptors, potentially suppressing inhibitory GABA release and thereby facilitating dopamine secretion in differentiated cells. The resultant increase in dopaminergic excitability by EN may be counter-regulated through AMPK-dependent autophagy. CONCLUSION: These transcriptomic findings support a neurobiochemical role of EN in promoting dopaminergic activity, offering a mechanistic basic for the traditional use of EL roots as a male sexual booster.