Fig. 2

Specific caspase and PARP1 inhibitors mitigate IAV replication in the airway epithelial cells (AECs). Differentiated AECs were infected with 0.1 MOI IAV (H1N1) PR/8/34 strain and treated with vehicle only or 20 µM of (A) caspase 2 inhibitor, Z-VDVAD-FMK (Z-V-D(OMe)-V-A-D(OMe)-FMK); (B) caspase 3 inhibitor, Z-DEVD-fmk (Z-D(OMe)-E(OMe)-V-D(OMe)-FMK); (C) caspase 6 inhibitor, Z-VEID-FMK (Z-V-E(OMe)-I-D(OMe)-FMK); or (D) PARP1 inhibitor, 4-AN (4-amino-1,8-naphthalimide). The inhibitors were added on apical and basal sides 3 h prior to viral infection. The inhibitors were removed from the apical side but were kept with media in the basal side for the whole experimental period. Protein lysates were analyzed for caspase cleavages by Western blot. The infectious viral titers were analyzed from apical washes of the cells 48- and 72-hours post-infection using the plaque assay. Experiments were performed in triplicates and the immunoblots are representative of at least three separate experiments. Error bars indicate ± SEM, (n = 6/group for all experiments; N = 2); p < 0.05 was considered significant