Apoptotic signaling in endothelial cells with neutrophil activation

As is the case for tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta), degranulated substances (DS) released from polymorphonuclear leukocytes (PMN) and H2O2 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-1 beta or TNF-alpha/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-1 beta and TNF-alpha/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 H2O2, but not by aEuro cent O-2 (-) induced by myeloperoxidase (MPO) of PMN. On the other hand, caspase 8 in HUVEC was activated by DS, but not by H2O2 and/or aEuro cent 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-alpha/CHX and IL-1 beta but also DS released from PMN and the cell-permeable reactive oxygen species H2O2 induce blood vessel injury through endothelial apoptosis.