Yellow Dye No. 5, also known as tartrazine (TRZ), is widely used[1] and has an accepted daily intake (ADI) of 0-7.5 mg/kg of body weight per day[2]. Consuming TRZ dosages greater than the ADI can lead to reduced levels of antioxidant enzymes in the brain, chromosomal alterations, or neuronal dendritic changes, [3, 4] which can result in oxidative stress, impaired neuronal functioning and potential mutagenic effects. Within the ADI, there have been observed reductions of the copper zinc superoxide dismutase-1 (SOD1) enzyme levels.[5]We hypothesize that TRZ interacts pre-translationally inside the cell, resulting in the reduction of SOD1 mRNA. In this study, differentiated Neuro2A-derived neurons were exposed to TRZ for 3 or 7 days. We tested a concentration curve from 0 to 11 μg/mL. Treated cells were grown on poly-L-lysine (PLL)- and laminin-coated glass coverslips, immunostained with anti-β-tubulin III and phalloidin, imaged, and analyzed using NeuronJ/ImageJ (NIH). Neurons were traced to analyze the morphological impacts of TRZ. SOD1 mRNA was quantified using reverse transcription quantitative polymerase chain reaction (RT-qPCR). We analyzed the differences in SOD1 mRNA levels of the controls vs. experimental cells, using the 2-ΔΔCT statistical method. We found that TRZ caused an increase in neurite length and a general decreasing trend of SOD1 mRNA expression. The reduction in SOD1 mRNA expression could indicate possible pre-translational modifications, which could be a result of TRZ’s ability to bind DNA. These findings help fill the gap in understanding the mechanism of SOD1 downregulation due to TRZ exposure.

Artemisia annua L. is a well-known medicinal herb used in Traditional Chinese Medicine for many centuries and contains artemisinin, which exhibits antimalarial properties [1] and is a potential treatment for SARS-CoV-2 [2]. However, the neurological effect of A. annua and its compounds are poorly understood. We hypothesize that A. annua extracts and artemisinin will provide protection against oxidative stress in mouse neuronal Neuro2A cells. Superoxide dismutase 1 (SOD1) is an anti-oxidant enzyme that protects against oxidative damage [3]. Growth Arrest and DNA Damage-inducible 45 alpha (Gadd45a) is involved in DNA repair and is a common biomarker for DNA damage[4]. SOD1 and Gadd45a mRNA expression was measured through RT-qPCR and analyzed using the 2-∆∆Ct method. Cell viability was measured using NucBlue, Annexin V, and propidium iodide to differentiate between apoptosis and necrosis. Cell counts were quantified using ImageJ (NIH). Our results showed that lower concentrations of 100 µg/mL A. annua treatment significantly reduced apoptotic cell death during oxidative stress. We also saw a general trend of decreasing Gadd45a mRNA expression at lower concentrations of A. annua treatment and a significant decrease in SOD1 mRNA levels from 0 to 100 µg/mL. This study suggests that lower concentrations of A. annua treatment prior to oxidative stress can increase cell viability and could protect Neuro2A cells from oxidative stress. Further research is needed to elucidate the mechanism of A. annua’s and artemisinin’s medicinal properties and further test their potential neuroprotective effects.