Differential Effects of Apigenin on Normal and Squamous Oral Epithelial Cells Reveal Redox-Autophagy Signaling...

The aim of this study was to compare the responses of normal human gingival epithelial cells (HGEpiC) and oral squamous cell carcinoma cells (OECM-1) to apigenin, a natural flavonoid, focusing on redox balance, autophagy, and apoptosis. This study is among the first to directly compare apigenin-induced responses in normal and cancerous oral epithelial cells. Cells were exposed to apigenin for 24 or 48 h, with untreated cells as controls. Mitochondrial activity, ATP, ROS (H₂O₂), and GSH were measured. Proliferation and morphology were monitored using HoloMonitor^® M4. Autophagy was assessed by fluorescent vacuole labeling, and apoptosis-related proteins (p-AKT, p-BCL-2, p-p53, p-JNK, caspase-8/9) by Luminex assay. Late apoptosis was evaluated by caspase-3/7 activity. Apigenin elicited a differential response: in HGEpiC cells, it was non-cytotoxic and increased metabolic activity, induced a moderate ROS increase, and activated autophagy as a pro-survival mechanism; in contrast, OECM-1 cells exhibited a significant reduction in metabolic activity, a marked ATP decrease at 24 h, and a pronounced ROS increase. These alterations were associated with reduced autophagy and decreased p-JNK signaling. These findings indicate that apigenin exerted no harmful effects on HGEpiC cells, while inducing redox imbalance in OECM-1 cells, highlighting a context-dependent cellular response.