AROMATASE ACTIVITY IN HUMAN TERM PLACENTA EXPLANTS IN CULTURE IS REDUCED BY CYCLIC AMP (cAMP)

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 389-413-Signaling and Transcriptional Control in Endocrine Systems
Basic/Translational
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-401
Romina Sainz*, Marco A Rivarola, Alicia Belgorosky and Nora Isabel Saraco
Hospital de Pediatria Garrahan, Buenos Aires, Argentina
Aromatase (Aro) is the key enzyme for estrogen biosynthesis and is encoded by CYP19A1 gene. In human placenta (h-PL), Aro is expressed exclusively in syncytiotrophoblasts and estrogens play a crucial role in placental physiology. We have previously described alternative splicing of the Aro coding region that would be involved in the control of Aro expression (1). Recently we described a new alternative mRNA that includes intron 9 (IN9) and generates a shorter and inactive Aro protein in human placenta (2) and human steroidogenic tissues. It has been previously reported that cAMP increase Aro expression in h-PL. The aim of this study was to evaluate cAMP regulation of aromatase mRNAs expression in human placenta explants in culture. We propose that IN9 variant is differently regulated by cAMP. Explants cultures of 5 term h-PL were studied. Aro activity was evaluated by measurement of estradiol production (E2) using testosterone as substrate. Aro mRNAs were evaluated by RT-Real time PCR with specific primers for total (Total), intron 9 (IN9) and active aromatase (Active). β-actin was used as housekeeping gene. In the 5 cultures, we observed that cAMP (0.25mM) significantly reduces Aro activity (E2-cAMP/E2-basal:0.550±0.091, mean±SEM), paired t-test p<0.05. While under cAMP, Total/β-actin mRNA expression does not change (cAMP/basal:1.138±0.100, mean±SEM), p: NS, Active/Total ratio significantly decreases (cAMP/basal:0.746±0.075, mean±SEM) paired t-test p<0.05. Moreover, analysis of Active and IN9 variants showed that Active/IN9 ratio also significantly decreases (cAMP/basal:0.599±0.061, mean±SEM), paired t-test p<0.05. We are describing, for the first time, that aromatase activity is reduced by cAMP in human term placenta explants in culture. This reduction was also observed in the Active/IN9 mRNA ratio. As the IN9 variant is a truncated Aro mRNA translating to an inactive protein lacking the heme-binding region, we are proposing that the expression of this variant would be involved in the regulation of Aro activity in human term placenta.

1)     Pepe CM, Saraco NI, Baquedano MS, Guercio G, Vaiani E, Marino R, Pandey AV, Flück CE, Rivarola MA and Belgorosky A. The cytochrome P450 aromatase lacking exon 5 is associated with a phenotype of nonclassic aromatase deficiency and is also present in normal human steroidogenic tissues. 2007 Clinical Endocrinology (Oxford) 67:698-705. 2)     Sainz R, Saraco N, Iniguez G, Rivarola MA, Mericq V and Belgorosky A. Expression of a New 3' End Variant of Human P450 Aromatase (ARO) Transcript (Intron 9, IN9) in the Human Term Placenta (Pl). ENDO 2011, Endocr Rev, Vol. 32 (03_MeetingAbstracts): P2-177.

Nothing to Disclose: RS, MAR, AB, NIS

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Supported by CONICET PIP 0224 -2011,Argentina