Inhibition of nuclear factor-kappaB activation un-masks the ability of TNF-alpha to induce human eosinophil apoptosis.
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.
Fujihara
Satoko
S
Rayne Laboratory, Respiratory Medicine Unit, Centre for Inflammation Research, Department of Medicine, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, GB.
Ward
Carol
C
Dransfield
Ian
I
Hay
Ronald T
RT
Uings
Iain J
IJ
Hayes
Brian
B
Farrow
Stuart N
SN
Haslett
Christopher
C
Rossi
Adriano G
AG
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*
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