Pharmacological inhibition of cathepsin D, but not cathepsin B, blocks caspase and calpain activation. (A) Immunoblotting. Neutrophils were cultured for the indicated times in the presence and absence of the indicated inhibitors and anti-Fas antibody. Bax cleavage in neutrophils is caused by calpain activation. The same results were obtained in two additional independent experiments. Arrowheads indicate key cleavage products. (B) Caspase activity assays. Human blood neutrophils were analyzed immediately after isolation (fresh) and upon a 9-h culture period. Values are means ± SD (n = 3). *, P < 0.05.