Apoptotic signaling in endothelial cells with neutrophil activation

As is the case for tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), degranulated substances (DS) released from polymorphonuclear leukocytes (PMN) and H(2)O(2) cause endothelial cell apoptosis through the phosphorylation of members of the mitogen-activated protein kinase (MAPK) family. Stimulation of human umbilical vein endothelial cells (HUVEC) with IL-1β or TNF-α/cycloheximide (CHX) was found to enhance the phosphorylation of p38 and Jun-N-terminal kinase (JNK) in a time-dependent fashion, but did not affect the time-dependent phosphorylation of extracellular signal-regulated kinase. In addition, IL-1β and TNF-α/CHX induced the phosphorylation of activating transcription factor-2 (ATF-2), but not c-Jun. Moreover, the p38 in HUVEC was phosphorylated by DS released from PMN and also by H(2)O(2), but not by •O(2) (-) induced by myeloperoxidase (MPO) of PMN. On the other hand, caspase 8 in HUVEC was activated by DS, but not by H(2)O(2) and/or •O(2) (-). In addition, caspases 3 and 7 were cleaved by the treatment of DS and turned into active forms. DS was concentrated, analyzed by electrophoresis, and revealed to contain precursor and subunits of MPO (90, 60, and 14 kDa) and another peptide with a molecular weight of about 28 kDa. Because SB203580 that was an inhibitor of p38 MAPK did not repress phosphorylation of ATF-2 in HUVEC, it was suggested that JNK was more important than p38 in a series of signaling courses. These results suggest the possibility that not only TNF-α/CHX and IL-1β but also DS released from PMN and the cell-permeable reactive oxygen species H(2)O(2) induce blood vessel injury through endothelial apoptosis.