The mechanisms that lead to tumor formation of and aldosterone secretion by zona glomerulosa cells in primary aldosteronism are not known. Recently, endothelial cell-derived factors have been characterized that control the release of aldosterone by adrenocortical cells. In addition, we started to characterize the regulation of CITED2, a CBP/p300 interacting transactivator with ED-rich tail 2. Earlier, it was shown in mice that absence of CITED2 leads to adrenal agenesis. Since endothelial cells are in close proximity to adrenocortical cells, we asked whether endothelium-derived factors promote proliferation of adrenocortical cells and if so whether CITED2 is involved in this process. We examined the effects of endothelial cell-conditioned medium on aldosterone release by and on the proliferation of adrenocortical cells and on the expression of CITED2, employing the NCI-H295R cell line and primary human adrenocortical cells.
We found a dose-dependent effect of endothelial cell-conditioned medium (ECCM) on wst-1 salt metabolism by and 3H-thymidin incorporation in adrenocortical cells. We found also an increase in the cyclin D3 promoter activity and a significant stimulation of the CITED2 promoter activity which peaked at 500 percent. THese effects were accompanied by an increase in CITED2 messenger RNA and CITED2 protein, as determined by real-time PCR and western blotting, respectively. The stimulatory effect of ECCM could be reversed after silencing CITED2 through siRNAs and by blocking mitogen-activated protein kinase activity using the MEK1-inhibitor PD98059. We conclude that products secreted by endothelial cells are capable in promoting proliferation of adrenocortical cells. This effect was associated with a significant increase in CITED2 gene promoter activity and consequent CITED2 expression. Thus, our data provide evidence that the endothelium regulates factors that are necessary for adrenal organogenesis.
03 - 07 May 2008
European Society of Endocrinology