FIG 6.

Mediation of H₂O₂ entry into HAP1 cells is specific to riboflavin compared to its structural analogs. (A) Chemical structures of riboflavin, roseoflavin, lumiflavin, and lumichrome. (B) HAP1 cells were grown in base DMEMgfp-2 for 24 h, followed by supplementation with 1.063 μM riboflavin (RB), roseoflavin (RF), lumiflavin (LF), or lumichrome (LC) for 16 h, as indicated. Intracellular (IC) levels of H₂O₂ (determined by Hydrop MFI) in HAP1 cells were measured after exposure to exogenously added 350 μM H₂O₂ or vehicle. MFI fold change data shown represent MFI of H₂O₂-treated cells relative to MFI of untreated cells. A fold change value of 1 (dotted line) represents no change. Error bars represent SEM (n = 6 independent experiments). *, P < 0.05 (compared to cells in riboflavin-containing medium [+RB]).