Different effects of progesterone and estradiol on chimeric and wild type aldosterone synthase in vitro

Abstract

BackgroundFamilial hyperaldosteronism type I (FH-I) is caused by the unequal recombination between the 11beta-hydroxylase (CYP11B1) and aldosterone synthase (CYP11B2) genes, resulting in the generation of a CYP11B1/B2 chimeric gene and abnormal adrenal aldosterone production. Affected patients usually show severe hypertension and an elevated frequency of stroke at a young age. Aldosterone levels rise during pregnancy, yet in pregnant women with FH-1, their hypertensive condition either remains unchanged or may even improve. The purpose of this study was to investigate in vitro whether female sex steroids modulate the activity of chimeric (ASCE) or wild type (ASWT) aldosterone synthase enzymes.MethodsWe designed an in vitro assay using HEK-293 cell line transiently transfected with vectors containing the full ASCE or ASWT cDNAs. Progesterone or estradiol effects on AS enzyme activities were evaluated in transfected cells incubated with deoxycorticosterone (DOC) alone or DOC plus increasing doses of these steroids.ResultsIn our in vitro model, both enzymes showed similar apparent kinetic parameters (Km = 1.191 microM and Vmax = 27.08 microM/24 h for ASCE and Km = 1.163 microM and Vmax = 36.98 microM/24 h for ASWT; p = ns, Mann–Whitney test). Progesterone inhibited aldosterone production by ASCE- and ASWT-transfected cells, while estradiol demonstrated no effect. Progesterone acted as a competitive inhibitor for both enzymes. Molecular modelling studies and binding affinity estimations indicate that progesterone might bind to the substrate site in both ASCE and ASWT, supporting the idea that this steroid could regulate these enzymatic activities and contribute to the decay of aldosterone synthase activity in chimeric gene-positive patients.ConclusionsOur results show an inhibitory action of progesterone in the aldosterone synthesis by chimeric or wild type aldosterone synthase enzymes. This is a novel regulatory mechanism of progesterone action, which could be involved in protecting pregnant women with FH-1 against hypertension. In vitro, both enzymes showed comparable kinetic parameters, but ASWT was more strongly inhibited than ASCE. This study implicates a new role for progesterone in the regulation of aldosterone levels that could contribute, along with other factors, to the maintenance of an adequate aldosterone-progesterone balance in pregnancy.

The importance of knowing the timing within the menstrual cycle in nonmenopausal hypertensive women in the diagnostic workup for primary aldosteronism

“…However, as mentioned by Ahmed et al, we also provided evidence of a direct in vitro stimulation of aldosterone secretion by progesterone in the human adrenal cortex. 4 The Authors reported a discrepancy between our in vitro results and those of Vecchiola et al, 5 who found an inhibitory effect of progesterone on aldosterone, although in very different experimental conditions. In fact, we used intact human primary adrenocortical cells in which progesterone receptors were demonstrated, whereas Vecchiola et al made use of nonadrenal (embryonic kidney) cell lines HEK-293 transfected with chimeric and wild-type aldosterone synthase enzymes.…”

Should aldosterone suppression tests be conducted during a particular phase of the menstrual cycle, and, if so, which phase? Results of a preliminary study

“…Results of in vitro studies examining this issue have been conflicting, however, with Nicolini et al . observing a stimulatory effect, while Vecchiola et al . reported an inhibitory effect of progesterone on adrenal aldosterone production.…”

“…One possible explanation for the higher aldosterone levels (despite no difference in renin) is a direct stimulatory effect of progesterone (levels of which were markedly higher in the luteal group as expected) on aldosterone production by the zona glomerulosa (ZG), occurring independently of the renin angiotensin system, as has been proposed by Szmuilowicz and co-workers. 9 Results of in vitro studies examining this issue have been conflicting, however, with Nicolini et al 8 observing a stimulatory effect, while Vecchiola et al 20 reported an inhibitory effect of progesterone on adrenal aldosterone production.…”

Is Normal Kidney Cells Viability Influenced by Estradiol Valerate Administration in Cell Culture?

“…In this regard, Previous studies have shown that some of sex steroids effects on viability of HEK cells [5]. The results also has demonstrated that E2 down-regulates the expression of SCF/c-KIT system in prostate cells, which is associated with antiproliferative and proapoptotic effects.…”

“…Some Studies show that some of sex steroids may have cytotoxic on some stem cells [4]. Also, some studies show that some of sex steroids can have impress on some of cells including HEK cell line [5]. From the other towards results of some studies show that estradiol valerate can effect on some cells, such as stem cells [6].…”