Figure 4.

Treatment of ARPE-19 cells with tamoxifen results in caspase activation. Active caspase-1, -8, -9, and -3 levels were detected using the FAM-FLICA Assay Kit (green). Control cells show almost no caspase (-1, -8, -9, and -3) activity (left). Active caspase-1 was detected as early as 60 minutes of exposure to tamoxifen, and the levels increased at 90 and 120 minutes (row 1). Activation of the initiator caspases, caspase-8 and caspase-9 (activators of caspase-3) was observed after 60 minutes of tamoxifen treatment, with increasing levels of fluorescence observed at 90 and 120 minutes (rows 2 and 3). Activation of caspase-3 (green), the effector caspase, was observed 90 minutes after application of tamoxifen, 30 minutes later than the activation of caspase-8 and caspase-9. Continued caspase-3 activation occurred over time, as increased fluorescence was observed 120 minutes following tamoxifen treatment. Scale bar: 25 μm.