Regulation of endothelial thrombomodulin expression by inflammatory cytokines is mediated by activation of nuclear factor-kappa B.
Inflammation and thrombosis are increasingly recognized as interrelated biologic processes. Endothelial cell expression of thrombomodulin (TM), a key component of the anticoagulant protein C pathway, is potently inhibited by inflammatory cytokines. Because the mechanism underlying this effect is largely unknown, we investigated a potential role for the inflammatory transcription factor nuclear factor-kappa B (NF-kappaB). Blocking NF-kappaB activation effectively prevented cytokine-induced down-regulation of TM, both in vitro and in a mouse model of tumor necrosis factor-alpha (TNF-alpha)-mediated lung injury. Although the TM promoter lacks a classic NF-kappaB consensus site, it does contain tandem Ets transcription factor binding sites previously shown to be important for both constitutive TM gene expression and cytokine-induced repression. Using electrophoretic mobility shift assay and chromatin immunoprecipitation, we found that multiple Ets species bind to the TNF-alpha response element within the TM promoter. Although cytokine exposure did not alter Ets factor binding, it did reduce binding of p300, a coactivator required by Ets for full transcriptional activity. Overexpression of p300 also prevented TM repression by cytokines. We conclude that NF-kappaB is a critical mediator of TM repression by cytokines. Further evidence suggests a mechanism involving competition by NF-kappaB for limited pools of the transcriptional coactivator p300 necessary for TM gene expression.
Sohn
Richard H
RH
Division of Cardiology, Johns Hopkins School of Medicine, Carnegie 568, 600 N Wolfe St, Baltimore, MD 21287, USA.
Deming
Clayton B
CB
Johns
David C
DC
Champion
Hunter C
HC
Bian
Ce
C
Gardner
Kevin
K
Rade
Jeffrey J
JJ
D000818:Animals; D002478:Cells, Cultured; D050881:E1A-Associated p300 Protein; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D018180:Thrombomodulin / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D018836:Inflammation Mediators; D007375:Interleukin-1; D016328:NF-kappa B; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D018180:Thrombomodulin; D015534:Trans-Activators; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D050881:E1A-Associated p300 Protein; C494361:Ep300 protein, mouse