Lipopolysaccharide can trigger a cathepsin B-dependent programmed death response in human endothelial cells.
In this study, we examined the mechanisms that contribute to lipopolysaccharide (LPS)-induced death responses in cultured human umbilical vein endothelial cells (HUVECs). In the presence of the protein synthesis inhibitor cycloheximide, LPS primarily induces caspase-dependent apoptotic cell death of HUVECs, which is blocked by siRNA-mediated knockdown of myeloid differentiation factor 88 adaptor protein but not of Toll-like receptor-associated interferon-inducing factor. Knockdown of Fas-associated death domain protein (FADD) by either siRNA or overexpression of a truncated version of FADD that lacks the N-terminal death effector domain (FADD(DN)) increases the sensitivity of HUVECs to LPS plus cycloheximide-mediated death. However, based on the use of proteinase inhibitors, cell death changes from being principally caspase-dependent to being principally cathepsin B (Cat B)-dependent. Knockdown of cellular FLICE inhibitory protein potentiates the caspase-dependent pathway but does not activate the Cat B-dependent death response. Knockdown of either myeloid differentiation factor 88 or Toll-like receptor-associated interferon-inducing factor expression does not affect the LPS-triggered Cat B death response in FADD-deficient HUVECs. Finally, in the presence of either the phosphatidylinositol 3 kinase inhibitor LY294002 or the inflammatory cytokine interferon-gamma, LPS activates both caspase- and Cat B-dependent death pathways. We conclude that LPS can activate a Cat-B-dependent programmed death response in human endothelial cells that is independent of both myeloid differentiation factor 88 and Toll-like receptor-associated interferon-inducing factor, is blocked by both FADD and phosphatidylinositol 3 kinase, and is potentiated by interferon-gamma.
Li
Jie H
JH
Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520-8089, USA.
D'Alessio
Alessio
A
Pober
Jordan S
JS
D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D002401:Cathepsin B / Q000378:metabolism; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009025:Morpholines / Q000494:pharmacology; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; D015398:Signal Transduction / Q000187:drug effects; D014471:Umbilical Veins / Q000166:cytology
D033942:Adaptor Proteins, Vesicular Transport; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D002401:Cathepsin B; D002867:Chromones; D004791:Enzyme Inhibitors; D053200:Fas-Associated Death Domain Protein; D008070:Lipopolysaccharides; D009025:Morpholines; D053594:Myeloid Differentiation Factor 88; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; C507779:MYD88 protein, human; C470409:TICAM1 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one