LPS‐induced signals in activation of a caspase‐3‐like protease, a key enzyme regulating apoptotic cell damage into a macrophage‐like cell line, J774.1, in the presence of cycloheximide

The earliest observed apoptotic change in a macrophage‐like cell line, J774.1, treated with lipopolysaccharide (LPS) in the presence of cycloheximide (CHX) was a selective increase in caspase‐3‐like activity. The addition of polymyxin B, TPCK, herbimycin A, or genistein, all of which inhibited LPS‐induced tumor necrosis factor α (TNF‐α) production by macrophages, suppressed the activation of the caspase‐3‐like protease in these macrophages treated simultaneously with CHX. However, SB202190 and SB203580, inhibitors of MAP kinase, and PD98059, an inhibitor of MAP‐kinase kinase (MEK), showed no effect on the activation of the caspase‐3‐like protease or on the cell damage of the macrophages treated with LPS and CHX, whereas they inhibited LPS‐induced TNF‐α production. These results suggest that some of the early signals in LPS‐treated macrophages are common to the subsequent pathways for TNF‐α production and caspase‐3‐like protease activation, but the later signals, like MAP‐kinase kinase or MAP‐kinase, are not involved in the pathways for caspase‐3‐like protease activation. J. Leukoc. Biol. 66: 689–696; 1999.