Role of Caspases and Reactive Oxygen Species in Rose Bengal-Induced Toxicity in Melanoma Cells

Objective We have previously shown that Rose Bengal (RB) alone, not as a photosensitiser, could induce apoptotic- and non-apoptotic cell death in different melanoma cell lines. To clarify RB-induced toxicity mechanisms, role of caspases and reactive oxygen specious (ROS) were studied in melanoma cells. Material and Methods Human melanoma cell lines, Me 4405 and Sk-Mel-28 were cultured in DMEM medium. Cell viability was quantitated by MTT assay. Apoptotic cells were determined using PI staining of DNA fragmentation by flow cytometry (sub-G1 peak). Role of caspase were studied using the pan-caspase inhibitor, z-VAD-fmk. ROS was measured using DCF-DA by flow cytometry analysis. Results This study showed that whilez-VAD-fmk completely inhibited apoptosis of melanoma inducedby tumor necrosis factor (TNF)-related apoptosis-inducing ligand(TRAIL), it only partiallyblocked RB-induced apoptosis in Me4405 and Sk-Mel-28 melanoma cell lines. RB also increased ROS production in melanoma cells but pretreatment with antioxidant -glutamylcysteinylglycine (GSH) could not decrease RB-induced toxicity. Conclusion Both caspase-dependent and -independent pathways were inducedby RB in melanoma cells. RB-induced generation of ROS does not playa significant role in RB-induced toxicity and it is independent of ROS production in melanoma cells.