Synergistic interactions between interferon-gamma and TRAIL modulate c-FLIP in endothelial cells, mediating their lineage-specific sensitivity to thrombotic thrombocytopenic purpura plasma-associated apoptosis.
Microvascular endothelial cell (MVEC) injury coupled to progression of platelet microthrombi facilitated by ADAMTS13 deficiency is characteristic of idiopathic and HIV-linked thrombotic thrombocytopenic purpura (TTP). Cytokines capable of inducing MVEC apoptosis in vitro are up-regulated in both TTP and HIV infection. However, the concentrations of these cytokines required to elicit EC apoptosis in vitro are 2- to 3-log-fold greater than present in patient plasmas. We report that clinically relevant levels of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and interferon (IFN)-gamma act in synergy to induce apoptosis in dermal MVECs, but have no effect on large-vessel ECs or pulmonary MVECs. This reflects the tissue distribution of TTP lesions in vivo. Sensitivity to TTP plasma or TRAIL plus IFN-gamma is paralleled by enhanced ubiquitination of the caspase-8 regulator cellular FLICE-like inhibitory protein (c-FLIP), targeting it for proteasome degradation. c-FLIP silencing with anti-FLIP short interfering RNA (siRNA) in pulmonary MVECs rendered them susceptible to TTP plasma- and cytokine-mediated apoptosis, while up-regulation of c-FLIP by gene transfer partially protected dermal MVECs from such injury. TTP plasma-mediated apoptosis appears to involve cytokine-induced acceleration of c-FLIP degradation, sensitizing cells to TRAIL-mediated caspase-8 activation and cell death. Suppression of TRAIL or modulation of immunoproteasome activity may have therapeutic relevance in TTP.
Stefanescu
Radu
R
Department of Medicine, Division of Hematology-Oncology, Weill Medical College-Cornell University, New York, NY 10021, USA.
Bassett
Dustin
D
Modarresi
Rozbeh
R
Santiago
Francisco
F
Fakruddin
Mohamad
M
Laurence
Jeffrey
J
D017209:Apoptosis / Q000187:drug effects*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000187:drug effects*; D019070:Cell Lineage; D002478:Cells, Cultured; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D008833:Microcirculation; D011697:Purpura, Thrombotic Thrombocytopenic / Q000473:pathology*; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000235:genetics / Q000494:pharmacology*
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D011994:Recombinant Proteins; D053221:TNF-Related Apoptosis-Inducing Ligand; D007371:Interferon-gamma