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Protein-tyrosine-kinase-dependent expression of cyclo-oxygenase-1 and -2 mRNAs in human endothelial cells
1Department of Hematology and Oncology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Japan.
Abstract:
Endothelial cells possess constitutive or inducible cyclo-oxygenase (COX) isoenzymes for prostacyclin production, but the mechanisms for their expression are largely unknown. We found that vanadate, an inhibitor of protein-tyrosine phosphatases, induced the expression of two COX isoenzyme mRNAs in human umbilical vein endothelial cells (HUVEC) in a time- and dose-dependent manner. Vanadate also stimulated an increase in COX-2 protein levels, but did not affect significantly the levels of constitutively expressed COX-1 protein. Synergistic enhancement of expression of the two COX isoenzyme mRNAs was observed on stimulation of HUVEC with vanadate plus interleukin-1alpha. Tyrphostin-47, which as an inhibitor of protein-tyrosine kinases abolished vanadate-induced protein-tyrosine phosphorylation, inhibited expression of the two COX isoenzyme mRNAs in HUVEC stimulated with vanadate or interleukin-1alpha. These data provide conclusive evidence that activation of protein-tyrosine kinases is causally linked to expression of the mRNAs for the two COX isoenzymes in HUVEC.
Insights
Vanadate, a protein-tyrosine phosphatase inhibitor, triggers cyclo-oxygenase (COX) mRNA expression in endothelial cells. Protein-tyrosine kinase activation is essential for this COX isoenzyme gene expression.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Endothelial cells produce prostacyclin via cyclo-oxygenase (COX) enzymes.
- Mechanisms regulating COX isoenzyme expression in endothelial cells are not fully understood.
Purpose of the Study:
- To investigate the role of protein-tyrosine kinases and phosphatases in regulating COX isoenzyme mRNA expression in human umbilical vein endothelial cells (HUVEC).
Main Methods:
- Treatment of HUVEC with vanadate (protein-tyrosine phosphatase inhibitor) and interleukin-1alpha.
- Analysis of COX-1 and COX-2 mRNA and protein levels.
- Inhibition studies using tyrphostin-47 (protein-tyrosine kinase inhibitor).
Main Results:
- Vanadate induced time- and dose-dependent expression of two COX isoenzyme mRNAs and increased COX-2 protein levels in HUVEC.
- Vanadate did not significantly alter COX-1 protein levels.
- Interleukin-1alpha synergistically enhanced vanadate-induced COX mRNA expression.
- Tyrphostin-47 blocked vanadate- or interleukin-1alpha-induced COX mRNA expression, indicating protein-tyrosine kinase involvement.
Conclusions:
- Activation of protein-tyrosine kinases is causally linked to the expression of COX isoenzyme mRNAs in HUVEC.
- These findings elucidate a key signaling pathway regulating COX expression in endothelial cells.