The Induction Of 11β-Hydroxysteroid Dehydrogenase Type Ⅰ By Glucocorticoids In The Chorionic Membrane And Its Mechanisms

G1ucoconicoids induced the local release ofprostaglandins (PGE2 and PGF2.) throughuP-regUlating PGHS and conicotropin-releasing hormone (CRH) frOm the fetal membranesand plto These hormones are inVolved in the process of labor, so Glucocorticoids playan imPortan role in the onset of laboL The actions of Glucocorticoids are regUlated by thePre-receptor metaboltring enZyrne, 1l5-hydroxysteroid dehydrogenase (ll6-HSD). TWodistint isoZyInes of ll0-HSD have been cloned and characterized. ll0-HSDl actSpredoMly as a reduCtaSe in vivo converting biologically inert cortisone to activecortisol thereby amPlifying the actions of g1ucocorcoids in human, Whereas l lp-HSD2 isan exclusive oxidase converting conisol to cortisone thereby attenuaing the actions ofglucoconicoids. It has been demonstraed that there are differential distributions ofl 1 p-HSDl and 11 P-HSD2 in the fetal membranes and placenta. l1 p-HSDl was localizedpredotTilnanly tO the chorionic troPhoblast which has been involved in thedown-regUlation of prostaglandin dehydrogenase H in the chorion. l l6-HSD2 is localizedto the sppytiotrophoblast of the placenty providing a fimctional barrier proteCting thefetUS frOm matemal glucocorticoids. A sequence resembling glucocorticoid resPonseelement (GRE) has been identified in the Promoter region of the hUman l l0-HSDl gene.Glucocorticoids have been shown to induce the expression of 11p-HSDl in thehiPPOMus in vitrO' whereas controversial resultS were obtained in the hePatOcyte.However, Whether glucocothcoids modulate llP-HSD1 expression through a Prgnoterdependent mechanism has never been StUdied. In this StUdy we bo exaInined whether1l9-HSDl and GR are co-exPressed in the sarne chorionic troPhoblaSt. which may Providethe molecular basis for the inberine regUlation of ll P-HSDl exPression byglucocorticoids. SecondIy, the regUlation of l l 9-HSDl expression and redutaSe activity byglucocorticoids was investigated in the primny cultUred hUman chorionic trophOblaSt.Fdriermore, we StUdied the mechhasm of the regulation of 11 0-HSDl by glucocorticoidswt the cloned 1.2kb length of ll P-HSDl promoter containing GRE-like sequencecollSbocted with reporter gene in HeLa cells. At last we investigated the fimction of priorinduCtion of llP-HSD1 expressing by GC in the fetal membrane, in terms of PGHS-2expression and PGE2 secretion.Main resuIts and conclusions are as fOllows:1.After 3 days in cultUre, some of the chorionic trophoblast clustered together andformed mulh-nuclei syncghotrophoblaSt cells. Some of the chorionic trOPhoblast remainedsingle. Sdring for llP-HSDl revealed a cytoplasInic distribution in the chorionictIOPhOblaSt. twunoreactive GR Mg was found both in the cy'toplasm and nucIeus ofthe cell. Double staining showed co-exPression of l l0-HSDl and GR in the sarne chOrioniccell. The co-expression of l l6-HSD1 and GR in the saxne chorionic troPhoblast suggestsPOssible intrcrine achons ofglucoconicoid generated by l l6-HSDl within the cells.2.EWe radiomCtric conversion assay showed that trCtrient of the cells with thesynthetic glucocorticoid -- dexarnethasone (l0-'M) for 24h increased the conversion ofconisone to cortisol, and thes increase was blocked by the GR antagonist RU486.l lp-HSDl MA of I.5kb was detected in the RNA extraCted from cult'Ured chorionictrOPhoblaSt using Northem blot hybridhation method. The expression of ll6-HSDlWA was induced by treating the chorionic cells with dexamethasone (l0-',l0'M) fOr24h, and the induction was blocked by co-treatInent of the cells with RU486. These resultssuggeSt a GR-mediated effect of glucocorticoid on the rnRNA expression and reductaSeactivity of l l 9-HSD1.3.EWe radiometric conversion assay showed that HeLa cells have the reductaSeaCtivity of ll9-HSDl, Which suggests there is the molecular syStem for llP-HSDlexPression in HeLa cells. And other reportS showed HeLa cells exPress GR. TherefOreHeLa cells provide a good model fOr th...