Effects of TNFalpha on expression of ICAM-1 in human airway epithelial cells in vitro: oxidant-mediated pathways and transcription factors.
We demonstrate that two different cell-permeable antioxidants, pyrrolidine dithiocarbamate (PDTC) and dimethylthiourea (DMTU), inhibit TNFalpha-induced ICAM-1 surface and gene expression in primary cultures of differentiated normal human bronchial epithelial (NHBE) cells. In addition, TNFalpha stimulates binding of nuclear proteins to the nuclear factor kappa beta (NFkappaB) and the CAAT/enhancer binding protein (C/EBP) consensus sites in the ICAM-1 promoter in these cells. Because these transcription factors have been suggested to be oxidant-sensitive and important in ICAM-1 expression, the potential involvement of reactive oxygen species (ROS) in the response to TNFalpha was investigated. Interestingly, neither PDTC nor DMTU altered binding of NFkappaB complexes. In contrast, either the proteasome inhibitor carbobenzoxy-L-leucy-L-leucy-L-leucinal (MG 132) or the IkappaBalpha inhibitor BAY 11-7082 ablated TNFalpha-induced ICAM-1 gene expression and MG132 inhibited TNFalpha-induced NFkappaB complexes. Surprisingly, either PDTC or DMTU inhibited the binding of TNFalpha-enhanced C/EBP complexes to the consensus site directly adjacent to the NFkappaB site. These results suggest that although TNFalpha enhances binding of C/EBP and NFkappaB complexes in NHBE cells, C/EBP binding seems to involve an oxidant-dependent mechanism, whereas activation of NFkappaB complexes utilizes the ubiquitin-proteasome pathway, a mechanism that seems to be unaltered by the presence of antioxidants. Because interference with either signaling pathway abrogates TNFalpha-induced ICAM-1 expression, activation of both complexes seems to be involved in this response to TNFalpha, but this activation occurs via different intracellular pathways.
Krunkosky
Thomas M
TM
Department of Molecular Biomedical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA. tmkrunko@vet.uga.edu
Martin
Linda D
LD
Fischer
Bernard M
BM
Voynow
Judith A
JA
Adler
Kenneth B
KB
D000975:Antioxidants / Q000494:pharmacology / Q000633:toxicity; D001980:Bronchi / Q000166:cytology*; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002460:Cell Line; D016384:Consensus Sequence / Q000235:genetics; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics*; D007976:Leupeptins / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D016877:Oxidants / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D046988:Proteasome Endopeptidase Complex; D011759:Pyrrolidines / Q000494:pharmacology / Q000633:toxicity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D020218:Response Elements / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D013859:Thiocarbamates / Q000494:pharmacology / Q000633:toxicity; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000633:toxicity; D014157:Transcription Factors / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D000975:Antioxidants; D022762:CCAAT-Enhancer-Binding Proteins; D007976:Leupeptins; D009097:Multienzyme Complexes; D016328:NF-kappa B; D016877:Oxidants; D011759:Pyrrolidines; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D013859:Thiocarbamates; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D018799:Intercellular Adhesion Molecule-1; C020972:pyrrolidine dithiocarbamic acid; C038983:1,3-dimethylthiourea; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex; D013890:Thiourea; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde