Inhibition of phosphatidylinositol 3-kinase sensitizes vascular endothelial cells to cytokine-initiated cathepsin-dependent apoptosis

Lisa A. Madge, Jie Hui Li, Jaehyuk Choi, Jordan S. Pober*

*Corresponding author for this work

Research output: Contribution to journalArticle

50 Citations (Scopus)

Abstract

In the presence of cycloheximide, tumor necrosis factor or interleukin-1 initiates caspase activation, loss of mitochondrial membrane potential (Δψ), DNA degradation, and nuclear condensation and fragmentation characteristic of apoptotic cell death in human vascular endothelial cells (EC). Inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002, but not inhibition of Akt by dominant-negative mutation, also sensitizes EC to cytokine-initiated apoptosis. Cytokine-initiated caspase activation is slower and comparatively less with LY294002 than with cycloheximide. Cycloheximide but not LY294002 decreases expression of c-FLIP (cellular FLICE inhibitory protein), an inhibitor of caspase-8 activation. The caspase inhibitor zVADfmk completely blocks caspase activation, DNA degradation, and nuclear fragmentation in both cases but only prevents loss of Δψ and cell death for cytokine plus cycloheximide treatment. In contrast, overexpression of Bcl-2 protects EC treated with cytokine plus LY294002 but not EC treated with cytokine plus cycloheximide. The cathepsin B inhibitor CA-074-Me prevents loss of Δψ, caspase activation, and cell death for EC treated with cytokine plus LY294002 but has no effect on EC treated with cytokine plus cycloheximide. Cathepsin B translocates from lysosomes to cytosol following treatment with LY294002 prior to the activation of caspases. These results suggest that inhibition of PI3K allows cytokines to activate a cathepsin-dependent, mitochondrial death pathway in which caspase activation is secondary, is not inhibited by c-FLIP, and is not essential for cell death.

Original languageEnglish (US)
Pages (from-to)21295-21306
Number of pages12
JournalJournal of Biological Chemistry
Volume278
Issue number23
DOIs
StatePublished - Jun 6 2003

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Phosphatidylinositol 3-Kinase
Cathepsins
Endothelial cells
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Cycloheximide
Endothelial Cells
Caspases
Apoptosis
Cytokines
Chemical activation
Cell death
Cell Death
CASP8 and FADD-Like Apoptosis Regulating Protein
Cathepsin B
Degradation
Caspase Inhibitors
Caspase 8
Mitochondrial Membrane Potential
DNA
Lysosomes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this

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title = "Inhibition of phosphatidylinositol 3-kinase sensitizes vascular endothelial cells to cytokine-initiated cathepsin-dependent apoptosis",
abstract = "In the presence of cycloheximide, tumor necrosis factor or interleukin-1 initiates caspase activation, loss of mitochondrial membrane potential (Δψ), DNA degradation, and nuclear condensation and fragmentation characteristic of apoptotic cell death in human vascular endothelial cells (EC). Inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002, but not inhibition of Akt by dominant-negative mutation, also sensitizes EC to cytokine-initiated apoptosis. Cytokine-initiated caspase activation is slower and comparatively less with LY294002 than with cycloheximide. Cycloheximide but not LY294002 decreases expression of c-FLIP (cellular FLICE inhibitory protein), an inhibitor of caspase-8 activation. The caspase inhibitor zVADfmk completely blocks caspase activation, DNA degradation, and nuclear fragmentation in both cases but only prevents loss of Δψ and cell death for cytokine plus cycloheximide treatment. In contrast, overexpression of Bcl-2 protects EC treated with cytokine plus LY294002 but not EC treated with cytokine plus cycloheximide. The cathepsin B inhibitor CA-074-Me prevents loss of Δψ, caspase activation, and cell death for EC treated with cytokine plus LY294002 but has no effect on EC treated with cytokine plus cycloheximide. Cathepsin B translocates from lysosomes to cytosol following treatment with LY294002 prior to the activation of caspases. These results suggest that inhibition of PI3K allows cytokines to activate a cathepsin-dependent, mitochondrial death pathway in which caspase activation is secondary, is not inhibited by c-FLIP, and is not essential for cell death.",
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Inhibition of phosphatidylinositol 3-kinase sensitizes vascular endothelial cells to cytokine-initiated cathepsin-dependent apoptosis. / Madge, Lisa A.; Li, Jie Hui; Choi, Jaehyuk; Pober, Jordan S.

In: Journal of Biological Chemistry, Vol. 278, No. 23, 06.06.2003, p. 21295-21306.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Inhibition of phosphatidylinositol 3-kinase sensitizes vascular endothelial cells to cytokine-initiated cathepsin-dependent apoptosis

AU - Madge, Lisa A.

AU - Li, Jie Hui

AU - Choi, Jaehyuk

AU - Pober, Jordan S.

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N2 - In the presence of cycloheximide, tumor necrosis factor or interleukin-1 initiates caspase activation, loss of mitochondrial membrane potential (Δψ), DNA degradation, and nuclear condensation and fragmentation characteristic of apoptotic cell death in human vascular endothelial cells (EC). Inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002, but not inhibition of Akt by dominant-negative mutation, also sensitizes EC to cytokine-initiated apoptosis. Cytokine-initiated caspase activation is slower and comparatively less with LY294002 than with cycloheximide. Cycloheximide but not LY294002 decreases expression of c-FLIP (cellular FLICE inhibitory protein), an inhibitor of caspase-8 activation. The caspase inhibitor zVADfmk completely blocks caspase activation, DNA degradation, and nuclear fragmentation in both cases but only prevents loss of Δψ and cell death for cytokine plus cycloheximide treatment. In contrast, overexpression of Bcl-2 protects EC treated with cytokine plus LY294002 but not EC treated with cytokine plus cycloheximide. The cathepsin B inhibitor CA-074-Me prevents loss of Δψ, caspase activation, and cell death for EC treated with cytokine plus LY294002 but has no effect on EC treated with cytokine plus cycloheximide. Cathepsin B translocates from lysosomes to cytosol following treatment with LY294002 prior to the activation of caspases. These results suggest that inhibition of PI3K allows cytokines to activate a cathepsin-dependent, mitochondrial death pathway in which caspase activation is secondary, is not inhibited by c-FLIP, and is not essential for cell death.

AB - In the presence of cycloheximide, tumor necrosis factor or interleukin-1 initiates caspase activation, loss of mitochondrial membrane potential (Δψ), DNA degradation, and nuclear condensation and fragmentation characteristic of apoptotic cell death in human vascular endothelial cells (EC). Inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002, but not inhibition of Akt by dominant-negative mutation, also sensitizes EC to cytokine-initiated apoptosis. Cytokine-initiated caspase activation is slower and comparatively less with LY294002 than with cycloheximide. Cycloheximide but not LY294002 decreases expression of c-FLIP (cellular FLICE inhibitory protein), an inhibitor of caspase-8 activation. The caspase inhibitor zVADfmk completely blocks caspase activation, DNA degradation, and nuclear fragmentation in both cases but only prevents loss of Δψ and cell death for cytokine plus cycloheximide treatment. In contrast, overexpression of Bcl-2 protects EC treated with cytokine plus LY294002 but not EC treated with cytokine plus cycloheximide. The cathepsin B inhibitor CA-074-Me prevents loss of Δψ, caspase activation, and cell death for EC treated with cytokine plus LY294002 but has no effect on EC treated with cytokine plus cycloheximide. Cathepsin B translocates from lysosomes to cytosol following treatment with LY294002 prior to the activation of caspases. These results suggest that inhibition of PI3K allows cytokines to activate a cathepsin-dependent, mitochondrial death pathway in which caspase activation is secondary, is not inhibited by c-FLIP, and is not essential for cell death.

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