Figure 6: Caspase 8 and P38 MAK pathways activation by lowbush blueberry proanthocyanidins in SW620 cells. (a) Caspase 8 activation curve responses were obtained with two fluorochrome-conjugated inhibitors of caspases consisting of a fluorophore (sulforhodamine for caspase 8 and carboxyfluorescein for caspase 9), a peptide specific for the active site of a particular caspase or many caspases, and a reactive functional group (fluoromethylketone or FMK). These inhibitors are cell permeable and noncytotoxic. Once inside the cell, the caspase inhibitors bind specifically through the peptide moiety to caspases that have been activated in apoptosis, and the FMK moiety covalently links the inhibitor to the caspase. The resulting signal is proportional to the number of active caspase enzymes that are present in the cell. (b) Directly conjugated phosphospecific antibodies were used to monitor the activation of P38 MAK and ATF2 pathways. All signals were monitored by capillary flow cytometry as described under M&M.