Manoalide Shows Mutual Interaction between Cellular and Mitochondrial Reactive Species with Apoptosis in Oral Cancer Cells

Figure 9

Expected mechanism of multifaceted inductions for cellular and mitochondrial reactive species to apoptosis on manoalide-treated oral cancer cells. NAC is an inhibitor for cellular reactive species (as probed by DCFH-DA, HPF, DAF-FM, and DHE), MT is an inhibitor for mitochondrial reactive species (as probed by MitoSOX Red), and ZVAD is an inhibitor for apoptosis. We proposed a possible mechanism that manoalide (10 μM, 6 h) can induce (1) cellular and (2) mitochondrial reactive species. Moreover, (3) NAC inhibits manoalide-induced mitochondrial reactive species and (4) MT inhibits manoalide-induced cellular reactive species, suggesting that cellular and mitochondrial reactive species can reciprocally induce each other in manoalide-treated oral cancer cells. (5) Manoalide induces apoptosis, which are suppressed by (3) NAC, (4) MT, and (6) ZVAD, suggesting that (7) cellular and (8) mitochondrial radical species can trigger apoptosis. Interestingly, (6) ZVAD also inhibits both (7) cellular and (8) mitochondrial reactive species, suggesting that apoptosis may induce manoalide-induced cellular and mitochondrial reactive species in oral cancer cells. Therefore, manoalide exhibits reciprocally activation between cellular reactive species, mitochondrial reactive species, and apoptosis in oral cancer cells. Note: arrow and T symbol indicate the activating and inhibiting effects. DCFH-DA is the probe for NO₂˙, CO₃˙¯, and ˙OH. HPF is the probe for ˙OH and ONOO-. DAF-FM is the probe for ˙NO. DHE and MitoSOX Red are the probes for cellular and mitochondrial O₂˙¯.