Figure 3. Roles of different caspases in LPS-induced fibroblast apoptosis in vivo. (A) Caspases-3, -8, and -9 activities in wild-type or TNFR1^–/–R2^–/– mice after LPS injection. Caspase activity was measured by fluorometric assays in lysates from tissues obtained at 6 hrs following inoculation of LPS or vehicle alone. (B) Histologic sections of the site of LPS, or LPS and caspase-3 inhibitor, or LPS and caspase-8 inhibitor injection in the mouse scalp. Upper panel: Apoptotic fibroblasts identified as double-positive in the TUNEL assay and simultaneously for expression of vimentin with the use of a specific antibody as described in MATERIALS & METHODS. Large arrow points to a cell that is TUNEL/vimentin-positive. Small arrows point to vimentin-positive fibroblasts that are TUNEL-negative. Middle panel: Double-staining in mice 24 hrs after injection with LPS and caspase-3 inhibitor. Lower panel: Double-staining in mice 24 hrs after injection with LPS and caspase-8 inhibitor. Bar = 20 µm. (C) Quantitative analysis of fibroblast apoptosis following LPS and different caspase inhibitors’ injection. The number of double-positive TUNEL/vimentin fibroblasts was counted 6 hrs after injection of LPS, or LPS and caspase-3 inhibitor, or LPS and caspase-8 inhibitor, or vehicle alone. Each value represents the mean of 6 specimens ± SEM.