Tissue factor transcription driven by Egr-1 is a critical mechanism of murine pulmonary fibrin deposition in hypoxia

Shi Fang Yan, Yu Shan Zou, Yun Gao, Chao Zhai, Nigel Mackman, Stephen L. Lee, Jeffrey Milbrandt, David Pinsky, Walter Kisiel, David Stern

Research output: Contribution to journalArticlepeer-review

161 Scopus citations

Abstract

Local hypoxemia and stasis trigger thrombosis. We have demonstrated previously that in a murine model of normobaric hypoxia pulmonary fibrin deposition is a result of expression of tissue factor, especially in oxygen- deprived mononuclear phagocytes (MPs). We now show that transcription factor early-growth-response gene product (Egr-1) is rapidly activated in hypoxia, both in vitro and in vivo, and is responsible for transcription and expression of tissue factor in hypoxic lung. MPs and HeLa cells subjected to hypoxia (pO2 ≃13 torr) had increased levels of tissue factor transcripts (≃18-fold) and an increased rate of transcription (≃15-fold), based on nuclear run-on analysis. Gel-shift analysis of nuclear extracts from hypoxic MPs and HeLa cells demonstrated increased DNA-binding activity at the serum response region (SRR; -111/+14 bp) of the tissue factor promoter at Egr-1 motifs. Using 32P-labeled Egr consensus oligonucleotide, we observed induction of DNA-binding activity in nuclear extracts from hypoxic lung and HeLa cells because of activation of Egr-1, by means of supershift analysis. Transient transfection of HeLa cells with chimeric plasmids containing wild- type or mutant SRR from the tissue factor promoter showed that intact Sp1 sites are necessary for basal promoter activity, whereas the integrity of Egr-1 sites was required for hypoxia-enhanced expression. A central role for Egr-1 in hypoxia-mediated tissue factor expression was confirmed by experiments with homozygous Egr-1 null mice; wild-type mice subjected to oxygen deprivation expressed tissue factor and showed fibrin deposition, but hypoxic homozygous Egr-1 null mice displayed neither tissue factor nor fibrin. These data delineate a novel biology for hypoxia-induced fibrin deposition, in which oxygen deprivation-induced activation of Egr-1, resulting in expression of tissue factor, has an unexpected and central role.

Original languageEnglish
Pages (from-to)8298-8303
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume95
Issue number14
DOIs
StatePublished - Jul 7 1998

Keywords

  • Monocyte
  • Thrombosis
  • Transcription

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