Endothelial cell-derived products regulate β-catenin-dependent transcription in human adrenocortical cells
Carolin Schwafertz1, Sven Schinner1, Markus Kühn1, Ishrath Ansurudeen2, Elke Oetjen3, Matthias Schott1, Werner A Scherbaum1 & Holger S Willenberg1
Objective: Recently, we have shown that endothelial cell-conditioned medium (ECCM) stimulates aldosterone secretion and the expression of proteins, essential for steroidogenesis and adrenal development. Also, we have found that fat cells regulate adrenal steroidogenesis through the wnt-signaling pathway. In addition, β-catenin was implicated in adrenal tumorigenesis, including aldosterone-producing adenomas.
Methods: We studied the influence of endothelial cell-derived products on transcription of β-catenin in cultured NCI-H295R cells using transfected reporter-plasmid assays and western blot analysis. Cells were stimulated with ECCM, derived from HUVEC cells for 24 h in the presence or absence of various signalling pathway inhibitors.
Results: Exposure of NCI-H295R cells to ECCM at a concentration of 50% showed a robust increase in β-catenin-dependent transcription, which was not reversed by inhibitors of wnt-signaling (sFRP-1 and Dkk-1). Blockade of protein kinases A, B or C did not interfere with the activation of β-catenin-mediated transcription, elicited by ECCM. However, β-catenin-mediated transcription could be blocked when inhibitors of PI3-kinase (LY294002) or MAP-kinases (U0126 and PD98059) were used. ECCM exposure also increased the amount β-catenin protein and its translocation into the nucleus, a process blocked by inhibitors of the MAP kinase pathway.
Conclusion: These in vitro studies indicate that endothelial cell-derived products regulate β-catenin-dependent transcription in adrenocortical cells through a wnt-ligand independent, PI3-kinase dependent pathway that involves signalling through MAP kinases. The endothelium may be essential for adrenal development and play a permissive role in adrenal tumorigenesis.