FIG. 8.

Effects of inhibitors of MEK/MAP kinases or NF-κB activation on caspase-3 activity and apoptosis induced by A. actinomycetemcomitans LPS and CHX. TPA-differentiated U937 cells (10⁷ cells [A] or 10⁵ cells [B]) were pretreated for 1 h with PD098059 (100 μM; MEK1/2/MAP kinase inhibitor), U0126 (5 μM; MEK1/2 inhibitor), SB203580 (10 μM; p38 inhibitor), inhibitors of NF-κB activation (gliotoxin [250 ng/ml], NAC [5 mM], or PDTC [100 μM]), or nothing and were subsequently cotreated with A. actinomycetemcomitans LPS (1 μg/ml) and CHX (10 μg/ml) for 3 h. Following each treatment, caspase-3 activity (A) was determined using the colorimetric assay kits and apoptosis (B) was evaluated by morphological assessment using Hoechst 33258 dye, as described in Materials and Methods. Values shown (units per milligram of protein [A] or percent apoptotic cells [B]) are the means + SD (error bars) of three separate experiments, each conducted in triplicate.