FnE activates the mitochondrial pathway of apoptosis. (A) Time course of mitochondrial membrane potential loss in response to FnE. MEF were cultured in the presence of 2 μM FnE, followed by staining with mitotracker reagent at the indicated times. Bar indicates 100 μm. (B) Images were analyzed using MetaMorph software to measure the fluorescent intensity per cell. Bars represent average plus or minus SE from 2 independent experiments; *P < .05 by Student t test. (C-H) MEF derived from wild-type mice (C,D) or knockout mice lacking the indicated caspases (E-H) were cultured for 48 hours in the presence of 2 μM Aα17-81, followed by TUNEL assay. MEF deficient in caspase-9 or -3 are resistant to FDP-induced apoptosis. Bars indicate 50 μm.