新近文献指出，胎脑组织2型11β羟类固醇脱氢酶(11β-HSD-2)在介导生命早期糖皮质激素编程下丘脑-垂体-肾上腺(HPA)轴相关成年疾病中发挥了重要作用。但目前对胎脑11β-HSD-2的表达调控机制及功能并不清楚。申请人前期发现，咖啡因可抑制胎海马11β-HSD-2表达，进一步通过高表达糖皮质激素受体引起HPA轴宫内编程改变。综合文献我们推测：咖啡因通过增加胎海马5-羟色胺(5-HT)水平，促进cAMP/PKA通路活化和早期生长反应因子1(Egr-1)表达，引起11β-HSD-2的组蛋白修饰改变和表达抑制。本项目拟在整体动物水平证实孕期咖啡因暴露引起胎海马5-HT/5-HT7R、cAMP/PKA/Egr-1通路、11β-HSD-2表达变化的基础上，进一步在细胞和分子水平确证5-HT/cAMP/Egr-1级联介导咖啡因抑制11β-HSD-2表达的转录调控机制，阐明咖啡因的发育毒性机制。

。A newly published review in Front Neuroendocrinol (2011) make clear that 11β-hydroxysteroid dehydrogenase 2 (11β-HSD-2) in fetal brain, which is responsible for glucocorticoid (GC) inactivation, plays an important role in mediating the GC programmed hypothalamic-pituitary-adrenal (HPA) axis related adult disease in the early life. However, no enough attention has been paid to studying the regulation and function of 11β-HSD-2 in the fetal brain. Our previous studies indicated that prenatal caffeine exposure can significantly inhibit the expression of hippocampal 11β-HSD-2 in fetal rats, which further stimulate the expressions of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD-1) and glucocorticoid receptor (GR) via a positive feedback loop regulation and cause GC metabolic activation in fetal hippocampus, all of these have been a big cause for the caffeine induced HPA axis related neuroendocrine metabolic programming alteration and adult disease (eg. fatty liver). The expression of 11β-HSD-2 is regulated at transcriptional stage. Some references indicated that the specificity protein 1 (Sp1) as well as early growth response protein 1 (Egr-1) are both important transcription factors of 11β-HSD-2; Sp1 can upregulate the expression of 11β-HSD-2 by recruiting the transcriptional coactivator p300 and altering the histone modifications after binding to the promoter region of 11β-HSD-2; while Egr-1 can occupy the binding sites of Sp1 and antagonism its effect; the expression of Egr-1 in hippocampus is regulated by serotonin (5-HT) induced ayclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway; caffeine can increase the level of 5-HT in brains and decrease the hydrolysis of cAMP by inbibiting the phosphodiesterase. Here from we put forward the research hypothesis, that prenatal caffeine exposure can reduce the binding of Sp1 as well as recruiting p300 to the promoter of 11β-HSD-2 in fetal hippocampus by activating the 5-HT/5-HT receptor and cAMP/PKA pathway and increasing Egr-1 expression, which in turn alters histone modifications of 11β-HSD-2 and inhibits its expression. All of these will further increase the level of active GC and promote the GC metabolic activity and GR expression in fetal hippocampus, which ultimately causes HPA axis related neuroendocrine metabolic programming alteration. Our goals for this project were to explore the direct links with respect to "caffeine - 5-HT/5-HT7 receptor - cAMP/PKA - Egr-1 - interactions of Egr-1-11β-HSD-2 and Sp1-11β-HSD-2 promoter - histone modifications of 11β-HSD-2 - expression of 11β-HSD-2" both in vivo and in vitro studies, and further to clarify the transcriptional regulation mechanism for the caffeine induced inhibition of 11β-HSD-2 mediated by the activated 5-HT/cAMP/Egr-1 cascade in fetal hippocampus. This project will be beneficial in expanded understanding the mechanism of caffeine induced developmental toxicity as well as elucidating the fetal origin of HPA axis related adult disease.