Sp1 increases expression of cyclooxygenase-2 in hypoxic vascular endothelium. Implications for the mechanisms of aortic aneurysm and heart failure.

Abstract

Cyclooxygenase-2 (COX-2) catalyzes prostaglandin synthesis from arachidonic acid and is expressed locally in aortic aneurysm and heart failure. Cellular hypoxia is also found in these conditions. We have previously shown that cox-2 is transcriptionally regulated by hypoxia in human umbilical vein endothelial cells (HUVEC) in culture via the transactivation factor NF-kappaB p65, leading to increased production of prostaglandin E(2), an inhibitor of vascular smooth muscle cell proliferation. Sp1 is a transactivation factor known to be important in the regulation of cytokine expression in association with NF-kappaB. We hypothesized that Sp1 is involved in the induction of cox-2 in hypoxic HUVEC. Electrophoretic mobility shift assays with hypoxic HUVEC nuclear protein showed that both Sp1 and the related protein Sp3 specifically bound to the cox-2 promoter. Immunoblotting demonstrated that hypoxia increased the nuclear localization of Sp1 but did not change the Sp3 content in HUVEC. Overexpression of Sp1 through transfection of HUVEC enhanced cox-2 promoter activity as measured by reporter gene expression and by the production of COX-2. The specificity of the results was confirmed by mutation of the Sp1-binding site in the cox-2 promoter construct and by reproducibility in an Sp-deficient Drosophila SL2 cell line. The regulatory role of Sp1 discovered in this work supports the concept that a mechanistic link exists between vascular cellular hypoxia and mediators of inflammation associated with aortic aneurysm and heart failure.

• Authors: Q Xu, Y S Ji, J F Schmedtje Jr
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 275 Issue 32 Pg. 24583-9 (Aug 11 2000) ISSN: 0021-9258 [Print] United States
• PMID: 10825178 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• DNA-Binding Proteins
• Isoenzymes
• Membrane Proteins
• NF-kappa B
• Oligodeoxyribonucleotides
• Recombinant Proteins
• SP3 protein, human
• Sp1 Transcription Factor
• Transcription Factors
• Sp3 Transcription Factor
• Cyclooxygenase 2
• PTGS2 protein, human
• Prostaglandin-Endoperoxide Synthases

Topics

• Base Sequence
• Binding Sites
• Cell Hypoxia
• Cells, Cultured
• Cyclooxygenase 2
• DNA-Binding Proteins (metabolism)
• Endothelium, Vascular (enzymology)
• Gene Expression Regulation, Enzymologic
• Humans
• Isoenzymes (biosynthesis, genetics)
• Membrane Proteins
• NF-kappa B (metabolism)
• Oligodeoxyribonucleotides (chemistry)
• Promoter Regions, Genetic
• Prostaglandin-Endoperoxide Synthases (biosynthesis, genetics)
• Recombinant Proteins (metabolism)
• Sp1 Transcription Factor (genetics, metabolism)
• Sp3 Transcription Factor
• Transcription Factors (metabolism)
• Transfection
• Umbilical Veins