Hypoxia and interleukin-1 beta stimulate vascular endothelial growth factor production in human proximal tubular cells

Background. Vascular endothelial growth factor (VEGF) promotes angiogenesis and inflammatory reactions. VEGF mRNA is detectable in the proximal tubule s of inflamed kidneys but not in normals. In other organs VEGF gene express ion is induced by hypoxia and cytokines such as interleukin 1 (IL-1). To id entify the cellular mechanisms in control of tubular VEGF production, we st udied effects of hypoxia and IL-IP in VEGF mRNA levels, VEGF secretion, and activity of the hypoxia-inducible dimeric transcription factor 1 (HIF-1 al pha/beta) in human pioximal tubular epithelial cells (PTECs) in primary cul ture. Methods. PTECs were grown in monolayers from human kidneys, Hypoxia was ind uced by incubation at 3% O-2. VEGF mRNA was quantitated by competitive poly merase chain reaction following reverse transcription. VEGF was measured by enzyme-linked immunoassay. HIF-1 alpha was demonstrated by Western blot an alysis and HIF-1 DNA binding by gel shift assay. Results. Significant amounts of VEGF mRNA and VEGF protein were measured in PTEC extracts and culture media, respectively. Stimulation of VEGF synthes is at low O-2 tension and following IL-1 beta treatment was detectable at t he protein level only. Nuclear HIF-1 alpha protein levels and HIF-1 binding to DNA wore also increased under these conditions. Conclusions. PTECs in culture produce VEGF. One mechanism of induction appe ars to be increased DNA binding of HIF-1 to hypoxia-responsive elements in the VEGF gene promoter. In inflammatory diseases of the kidney, tubular cel l-derived VEGF may contribute to microvascular leakage and monocyte extrava sation.