Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 101, Issue 28, Pages 10440-10445Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0401339101
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Funding
- NHLBI NIH HHS [HL60569, R01 HL060569] Funding Source: Medline
- NIDDK NIH HHS [DK50189, R01 DK050189, R37 DK050189, R29 DK050189, DK50305, P01 DK050305] Funding Source: Medline
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Inflammatory responses are associated with significant changes in tissue metabolism. In particular, metabolic shifts during inflammation can result in significant tissue hypoxia, with resultant induction of hypoxia-responsive genes. Given this association, we hypothesized that leukocyte functional responses are influenced by hypoxia. Initial experiments revealed that exposure of the promonocytic cell line U937 to hypoxia resulted in increased adhesion to activated endothelia. Such increases were transcription-dependent and were blocked by antibodies directed against beta(2), but not beta(1), integrins. Analysis Of 92 integrin mRNA and protein in U937 cells revealed a 5 to 6-fold increase with hypoxia. Extension of this analysis to hypoxic human whole blood revealed prominent induction Of 92 integrin mRNA and protein ex vivo. Furthermore, murine O-2 integrin mRNA was found to be significantly induced during hypoxia in vivo. Subsequent studies identified a binding site for hypoxia-inclucible factor 1 (HIF-1) in the CD18 gene. This gene encodes the subunit common to all four known types of beta(2). integrin heterodimer. HIF-1 binding was demonstrated in vivo, and mutational analysis of the HIF-11 site within the CD18 promoter resulted in a loss of hypoxia inducibility. Taken together, these results demonstrate that hypoxia induces leukocyte beta(2) integrin expression and function by transcriptional mechanisms dependent upon HIF-1.
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