Platelet-activating factor and endotoxin activate CCAAT/enhancer binding protein in rat small intestine.
The transcription factor family CCAAT/enhancer binding proteins (C/EBP) is involved in inflammation via the regulation of the gene expression of various pro-inflammatory cytokines and proteins. PAF and endotoxin (lipopolysaccharide, LPS) are known agents causing intestinal inflammation and injury. In this study, we examined the binding activity of C/EBP isoforms in rat small intestine in response to PAF (1.5 microg kg(-1), i.v.) or LPS (5 mg kg(-1), i.v.). We found that C/EBP is constitutively active in normal small intestine, mainly as C/EBP-alpha and beta (C/EBP-beta>alpha). Both C/EBP-alpha and beta are localized in the intestinal epithelial cells: C/EBP-alpha mainly in the crypts, and C/EBP-beta in both villi and crypts, as well as in some lamina propria cells. Only minute amounts of C/EBP-delta were found. PAF rapidly upregulates the binding activity of C/EBP-alpha and beta within 30 min. The increase in C/EBP-alpha is prominent in the crypt cells, whereas the change of C/EBP-beta is more widespread. LPS also increases the binding activity of C/EBP-alpha and beta, and the response is slower than PAF. PAF synergizes with LPS to markedly activate all three subunits. The increase in C/EBP-alpha is transient, whereas the other two have a sustained elevation until 120 min. After challenge with PAF (but not LPS), small amounts of nuclear factor -kappaB (NF-kappaB) p50 and p65 subunits are found in the C/EBP-DNA binding complex, indicating cross-dimerization of the two transcription families. Pretreatment of rats with pyrrolidine dithiocarbamate (PDTC) suppresses LPS-, but not PAF-, induced NF-kappaB and C/EBP binding activity, and significantly increases the C/EBP-delta subunit in LPS- or PAF-induced C/EBP complex. These results suggest that PAF and LPS activate intestinal C/EBP in vivo, probably via different pathways.
Wang
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Department of Pathology, Children's Memorial Medical Center, Northwestern University Medical School, Chicago, Illinois, IL 60614, USA.
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De Plaen
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Hsueh
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D000818:Animals; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology*; D004847:Epithelial Cells / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism; D007421:Intestine, Small / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010972:Platelet Activating Factor / Q000494:pharmacology*; D011485:Protein Binding; D011759:Pyrrolidines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013859:Thiocarbamates / Q000494:pharmacology
D022763:CCAAT-Enhancer-Binding Protein-alpha; D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins; D004731:Endotoxins; D008070:Lipopolysaccharides; D016328:NF-kappa B; D010972:Platelet Activating Factor; D011759:Pyrrolidines; D013859:Thiocarbamates; C020972:pyrrolidine dithiocarbamic acid; D004247:DNA