Endothelin-converting enzyme is a plausible target gene for hypoxia-inducible factor

Area of Science:

• Nephrology
• Molecular Biology
• Physiology

Background:

• Renal endothelin-converting enzyme (ECE)-1 is upregulated in diabetes and after radiocontrast administration.
• These conditions involve renal hypoxia, stabilized hypoxia-inducible factor (HIF), and increased endothelin synthesis.
• The precise regulation of ECE-1 under hypoxic conditions remains unclear.

Purpose of the Study:

• To investigate whether endothelin-converting enzyme (ECE)-1 is a target gene of hypoxia-inducible factor (HIF).
• To explore the role of HIF in regulating ECE-1 expression in renal cells and in vivo.

Main Methods:

• In vitro studies using cultured endothelial and proximal tubular cells exposed to hypoxia, mimosine, or cobalt chloride.
• In vivo studies in rats and conditional von Hippel-Lindau knockout mice treated with HIF-prolyl-hydroxylase inhibitors.
• STAT3 activation in mice to induce HIF expression.
• Chromatin immunoprecipitation sequencing (ChIP-seq) and PCR analysis to identify HIF binding sites.

Main Results:

• Hypoxia and HIF-prolyl-hydroxylase inhibition increased ECE-1 transcription and protein expression in vitro and in vivo.
• Enhanced ECE-1 and HIF-1α immunostaining was observed in rat renal tubules and medullas.
• Conditional knockout mice and STAT3-activated mice showed increased ECE-1 expression paralleling HIF levels.
• ChIP-seq identified HIF binding sites in the ECE-1 promoter and intron regions.

Conclusions:

• Endothelin-converting enzyme (ECE)-1 is a novel hypoxia-inducible factor (HIF)-target gene.
• HIF directly regulates ECE-1 expression in renal cells.
• This finding provides a new molecular link between renal hypoxia and endothelin system activation.