Effect of caspase inhibitors on Salmonella typhimurium induced apoptosis of chicken macrophages

Abstract Salmonella typhimurium SR11 (ST) induced apoptosis of chicken macrophage cell line (HD11 cells) was assessed with or without caspase inhibitors. Apoptosis was measured upon the uptake of green fluorescent protein-labeled bacteria using flow cytometry. Dual staining of HD11 cells with annexin V PE and 7-amino-actinomycin-D (7-AAD) allowed differentiation of dead and damaged cells from those undergoing apoptosis. Our results reflect the late apoptotic cells that were positive for annexin V PE and 7-AAD staining. HD11 cells were infected for up to 48 hours and apoptosis was determined at baseline, 24 and 48 hours post-infection. We tested the effect of caspase inhibitors including, general, 1, 2, 3, 4, 6, 8, 9, 10 and 13 at100 and 200 μM concentrations on ST mediated apoptosis. Our data showed that ST induced significant apoptosis at 24 and 48 hours post-infection compared to uninfected cells. In addition, most of the caspase inhibitors inhibited apoptosis at very similar levels however 10 and 13 were the most effective at 24 and 48 hours. At 48 hours, most of the cells were in the necrotic state but incubation with caspase inhibitors 10 and 13 resulted in higher number of viable cells.