Hypoxic induction of adrenomedullin in cultured human umbilical vein endothelial cells

OBJECTIVESThe current study evaluated the hypoxic induction of adrenomedullin gene expression and secretion, and its mechanism in cultured human umbilical vein endothelial cells (HUVEC). METHODSHUVEC were exposed to hypoxia or normoxia as controls for 1 to 24 h. Using Northern blot analysis and a radioimmunoassay, we evaluated adrenomedullin expression in HUVEC. The transcriptional component of adrenomedullin gene regulation was assessed by nuclear run-off experiments, and adrenomedullin mRNA half-life was measured by actinomycin D experiments. RESULTSWe found that hypoxic conditions (1–3% oxygen) significantly increased adrenomedullin mRNA and protein in HUVEC. This increase was inversely proportional to oxygen tension and was reversible upon re-exposure to a 21% oxygen environment. Nuclear run-off experiments revealed the enhanced transcriptional rate of adrenomedullin gene. Next, actinomycin D experiments revealed the enhanced adrenomedullin mRNA stability. CONCLUSIONSThese results indicate that hypoxia increases adrenomedullin gene expression and secretion in HUVEC by transcriptional and post-transcriptional mechanisms. Hypoxic induction of adrenomedullin may play a pathophysiological role in the vascular systems.