人胎膜11β-HSD1调节促分娩激素分泌的研究

Glucocorticoids have been shown to be involved in the process of parturition by stimulating the production of prostaglandins, corticotrophin releasing hormone (CRH) and estrogen within the intrauterine tissue. The effects of glucocorticoids are potentiated by the presence of 11b-hydroxysteroid dehydrogenase type 1 (11b-HSD1) whish activates the biologically inactive cortisone into active cortisol. We have shown previously that the chorion trophoblast of human fetal membranes expresses abundant 11b-HSD1. It has also been reported that there is a putative glucocorticoids response element (GRE) present in the promoter of 11b-HSD1. However, whether glucocorticoids affect the expression of 11b-HSD1 in the fetal membranes remains unexplored. Base on the rational stated above, we investigated the regulation of 11b-HSD1 expression and activity by glucocorticoids and its mechanism in the cultured chorionic trophoblast. We also studied the physiological consequence of the induction of 11b-HSD1 by glucorticoids in terms of the production of prostaglandins from the chorion. .Firstly, we found co-existence of glucocorticoids receptor and 11b-HSD1 in the chorionic trophoblast with immucytochemistry, which could provide an intracrine molecular basis for the regulation of 11b-HSD1 by glucocorticoids. Secondly, we found a glucocorticoid receptor mediated induction of 11b-HSD1 mRNA and protein expression with Northern blot and Western blot analysis and we also found the activity of 11b-HSD1 was up-regulated by glucocorticoids in the chorionic trophoblast as measured by thin layer chromatography (TLC). Thirdly, the induction of prostaglandin H synthase II and the production of prostaglandin E2 by cortisone were enhanced by pre-treating the cells with dexamethasone as assayed with Western blot analysis and radioimmunoassay respectively. Fourthly, we have successfully cloned about 1.2kb length of the promoter of 11b-HSD1 gene with PCR and this sequence was subsequently inserted into the plasmid carrying the reporter CAT gene without intrinsic promoter. The constructed plasmid was transfected into HeLa cell to investigate the regulation of the reporter gene expression through the inserted promoter of 11b-HSD1 gene. Glucocorticoids were found being able to stimulate the expression of the reporter gene, which suggest that the induction of 11b-HSD1 gene expression by glucocorticoids is exerted at the promoter level. However the specific mechanism mediating glucocorticoids' induction of 11b-HSD1 gene expression, for example, the direct evidence of the involvement of putative GRE sequence and other sequences awaits further study. This study, for the first study, provides the feedforward mechanism of glucocorticoids' actions in parturition in the fetal membranes, which could implict in the physiological process of normal parturition as well as pathological preterm labor..

胎膜存在大量糖皮质激素活化酶11B-HSD1的意义目前尚不清楚。本课题应用培养的绒毛膜滋养层细胞，研究此酶通过活化17-羟-11-脱氢皮质酮为皮质醇而加强糖皮质激素促进分娩激素分泌的作用；研究糖皮质激素对胎膜11B-HSD1基因表达的诱导作用。本研究对认识分娩启动和早产机制具有重要的理论和临床意义。