title: Inhibition of nuclear factor-kappaB activation un-masks the ability of TNF-alpha to induce human eosinophil apoptosis.
abstract: Apoptosis renders eosinophils functionally effete and marks them for "silent" removal from inflamed sites by macrophages. We show, for the first time, that eosinophils exposed to TNF-alpha rapidly lose their cytoplasmic levels of IkappaBalpha, the inhibitory subunit of NF-kappaB. Consequently, TNF-alpha triggers NF-kappaB mobilization from the cytoplasm to the nucleus, as determined by tracking the NF-kappaB subunit p65 by immunofluorescence and Western blot analysis. Inhibition of TNF-alpha-mediated IkappaBalpha degradation and NF-kappaB activation by gliotoxin or the proteasome inhibitor MG-132 un-masks the caspase-dependent pro-apoptotic properties of TNF-alpha. In addition, cycloheximide similarly renders TNF-alpha pro-apoptotic, suggesting that NF-kappaB activation controls the production of a protein(s) that protects eosinophils from the cytotoxic effects of TNF-alpha. Evidence is presented suggesting that TNF-alpha triggered apoptosis is more susceptible to NF-kappaB inhibition than constitutive apoptosis, leading to the possibility of the specific targeting of apoptosis in eosinophil sub-populations. Prior to morphological signs of apoptosis, TNF-alpha-induced IL-8 synthesis is abrogated by inhibition of NF-kappaB. We propose that NF-kappaB activation plays a critical role in controlling eosinophil responsiveness and apoptosis, and speculate that selective inhibitors of eosinophil NF-kappaB activation may ultimately provide alternative therapeutic agents for the treatment of eosinophilic diseases, including asthma and allergic rhinitis.
authors.affiliation: Rayne Laboratory, Respiratory Medicine Unit, Centre for Inflammation Research, Department of Medicine, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, GB.
authors.forename: Satoko
authors.initials: S
authors.lastname: Fujihara
authors.forename: Carol
authors.initials: C
authors.lastname: Ward
authors.forename: Ian
authors.initials: I
authors.lastname: Dransfield
authors.forename: Ronald T
authors.initials: RT
authors.lastname: Hay
authors.forename: Iain J
authors.initials: IJ
authors.lastname: Uings
authors.forename: Brian
authors.initials: B
authors.lastname: Hayes
authors.forename: Stuart N
authors.initials: SN
authors.lastname: Farrow
authors.forename: Christopher
authors.initials: C
authors.lastname: Haslett
authors.forename: Adriano G
authors.initials: AG
authors.lastname: Rossi
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology / Q000502:physiology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004804:Eosinophils / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism; D005912:Gliotoxin / Q000494:pharmacology; D006801:Humans; D020672:I-kappa B Proteins; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D016209:Interleukin-8 / Q000096:biosynthesis; D007976:Leupeptins / Q000494:pharmacology; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D015853:Cysteine Proteinase Inhibitors; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016209:Interleukin-8; D007976:Leupeptins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D000072000:NF-KappaB Inhibitor alpha; D005912:Gliotoxin; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde