Expression, localization and control of activin A release from human umbilical vein endothelial cells

Activin-A is a member of the TGF beta superfamily found in maternal and umbilical cord blood throughout gestation. We investigated whether human umbilical vein endothelial cells (HUVEC) express activin-A in vivo and tested the effects of vasoactive (endothelin-1), pro-inflammatory (interferon-gamma, interleukin-8) and anti-inflammatory (dexamethasone, urocortin) factors on activin-A release by isolated HUVEC in vitro. Activin beta A subunit protein and mRNA were strongly localized in the endothelial cells of umbilical veins and were also detectable in scattered cells of the cord connective tissue. Dimeric activin-A was detected in the HUVEC culture medium at picomolar concentrations. Activin-A release by HUVEC decreased after cell incubation with urocortin (p<0.01), whereas no effect was observed with interleukin-8, interferon-gamma, endothelin-1 or dexamethasone. In summary, activin-A is present in the human umbilical vein endothelium in vivo and is produced and released by isolated HUVEC. Activin-A secretion is inhibited in vitro by urocortin, a neuropeptide with predominantly anti-inflammatory action.