Submission Number: CHR-4-24-23

Abstract Number: 228

DECIDUAL EXPRESSION OF 20HYDROSTEROID DEHYDROGENASE AND MECHANISM OF ITS REGULATION BY RAT DECIDUAL PRL (RDPRL).

Christian Tessier* ¹, Anne Prigent-Tessier ¹, Susan Ferguson-Gottschall* ¹, Jean Djiane ² and Geula Gibori* ¹

Dept. of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL ¹
Laboratoire de biologie cellulaire et moleculaire, INRA, Jouy-en-Josas, France. ²

Abstract:
20hydroxysteroid dehydrogenase (20HSD) is an enzyme that catabolizes progesterone to 20OHprogesterone, an inactive metabolite that cannot sustain pregnancy. It is crucial that 20HSD remain silent during pregnancy since reduced progesterone levels in the uterine milieu lead to abortion. Thus, the aim of this study was to examine the expression and hormonal regulation of 20HSD in the rat decidua. Total RNA was obtained from decidua at various stages of pseudopregnancy and amplified by RT-PCR. No mRNA for 20HSD was detected in rat decidual tissue throughout pseudopregnancy. Interestingly, primary decidual cells collected from day 9 pseudopregnant rats acquired, within 12 hours of culture, the ability to express 20HSD mRNA. The lack of 20HSD expression in vivo suggests that this enzyme is under inhibitory regulation in the rat decidua. Because the rat decidua produces and secretes PRL (Prigent-Tessier et al., 1999 J Biol Chem, 274: 37982), we examined, using primary decidual cells, whether 20HSD gene is inhibited by rdPRL. The results revealed that PRL treatment within the first 12 hours of culture, at a time when the decidual cells produce little rdPRL, caused a dose-related inhibition of 20HSD mRNA. Using a 2.5kb 20HSD promoter, we showed that the transfection of primary decidual cells which produce PRL with constitutively active (CA) PRL receptor decreased 20HSD promoter activity. Since PRL can signal through the Jak/Stat pathway, we used CA Jak2 and CA Stat5b expression vectors to study the signaling pathway of rdPRL regulation of decidual 20HSD. Both Jak2 and Stat5b were able to decrease 20HSD promoter activity indicating that rdPRL may signal to 20HSD through the Jak/Stat pathway. In addition, only AG18 (general tyrosine kinase inhibitor) and AG490 (inhibitor of Jak2) were able to increase 20HSD promoter activity whereas MAP-kinase and PI-3 kinase inhibitors had no effect. In summary, our study demonstrates that the expression of decidual 20HSD and thus the uterine catabolism of progesterone is down-regulated by rdPRL through the Jak/Stat pathway. Our results also establish, for the first time, a crucial role for rdPRL in the maintenance of pregnancy. Supported by Ernst Schering Research Foundation (CT) and NIH HD-12356 and HD-11119 (GG).

Keywords: Decidua, 20alpha-HSD, rdPRL

This abstract is being presented at: 1:30 PM in session:
SESSION 10: BIOLOGY OF PREGNANCY