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AN IN VITRO MODEL OF ASPARTAME CYTOTOXICITY VIA HETEROLOGOUS EXPRESSION OF NMDA RECEPTORS

SHUROOQ ASAAD ABDULAMEER SHAHER 1,2*, BIANCA GALATEANU 1, ARIANA HUDITA 1, ALBAJY MAITHAM 1,3, DAN FLORIN MIHAILESCU 1, BOGDAN AMUZESCU 1

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Within the last 40 years, aspartame (L-aspartyl-L-phenylalanyl-methylester) became a very popular artificial sweetener, being introduced in over 6000 food products worldwide, including solid foods, beverages, and drugs for oral administration. However, its safety and toxicity have been subject of concern since its discovery, due to potentially harmful effects of its intestinal decomposition products: aspartate, phenylalanine, and methanol. Neuropsychological effects have been reported occasionally, such as headache, blurred vision, insomnia, torpor, memory loss, nausea, speech impairment, personality changes, loss of energy, hyperactivity, hearing problems. Our aim in the present study was to determine the effects of aspartame at various concentrations on the viability of cells transiently transfected with the combination of N-methyl-Daspartate (NMDAR) ionotropic glutamate receptor subunits NR1+NR2b, as well as to prove direct activation of NMDAR currents by aspartame via whole-cell patch-clamp experiments. CHO-K1 cells transfected with NR1+NR2b via plasmid constructs containing the two genes fused with enhanced green fluorescent protein (eGFP) gene were exposed for 2 - 4 h to aspartame in progressive decimal dilutions (0.1 µM to 10 mM) and assessed by flow cytometry after propidium iodide (PI) staining, showing increased percentages of dead cells (PI+) at aspartame concentrations of 1 µM or higher, while nontransfected cells featured increased PI+ percentages at aspartame concentrations above 1 mM. We also showed in HEK293T cells transfected by electroporation with the same plasmid combination (NR1+NR2b) transient outward NMDAR currents at +40 mV elicited by brief pulses of glutamate 100 µM or aspartame 100 µM.