NF-κB 在细菌脂多糖下调胎盘PPARγ及其下游11β-HSD2中的作用

Previous studies found that LPS can cause fetal growth restriction, but the mechanism has not been elucidated. This subject hypothesis: LPS down regulates the expression of PPARγ and its target gene 11β-HSD2 by activating placental NF-κB, which will lead to increasing cortisol transmission from maternal to fetus and induce fetal growth restriction. The aim of this study is to observe the effects of LPS on the down regulation of PPARγ and its target gene 11β-HSD2 in mouse and human placental trophoblasts, to study the effect of NF-κB inhibitors on LPS-induced down regulation of placental PPARγ and its target gene 11β-HSD2 in vitro, to examine the effect of p65 siRNA on LPS-induced down regulation of PPARγ and 11β-HSD2 in human placental trophoblasts, and to observe the interaction between NF-κB and PPARγ, then to highlight the role of NF-κB in the LPS-induced down regulation of placental PPARγ and its target gene 11β-HSD2. Moreover, a case-control study is used to compare the differences between SGA and AGA in placental NF-κB, placental PPARγ and its target gene 11β-HSD2, to verify the role of NF-κB in LPS-induced down regulation of PPARγ and 11β-HSD2 in fetal growth restriction. This study will provide a new basis for elucidating the mechanism of fetal growth restriction.

前期研究发现LPS可引起胎儿生长受限，但机制不详。本课题假设：LPS通过激活胎盘NF-κB，下调PPARγ及其靶基因11β-HSD2，导致母体皮质醇透过胎盘转至胎儿增多并引发胎儿生长受限。课题拟观察LPS对小鼠胎盘和人胎盘滋养细胞PPARγ及其靶基因11β-HSD2的下调作用；体内观察NF-κB抑制剂对LPS下调小鼠胎盘PPARγ及其靶基因11β-HSD2的影响，体外检测siRNA干扰p65基因对LPS下调人胎盘滋养细胞PPARγ及11β-HSD2的影响，并检测NF-κB和PPARγ相互作用，重点阐明NF-κB在LPS下调胎盘PPARγ及其下游11β-HSD2中的作用；采用病例对照研究，比较SGA和AGA之间胎盘NF-κB、PPARγ及其靶基因11β-HSD2的差异，验证NF-κB在LPS下调PPARγ及11β-HSD2导致胎儿生长受限中的作用。本课题为阐明胎儿生长受限发生机制提供新依据。

胎儿生长受限是围产期胎儿/婴儿死亡的主要原因之一。课题组前期研究发现LPS可引起胎儿生长受限，为探明其机制做了以下研究。一、观察LPS对胎盘滋养细胞基础型和诱导型PPARγ及下游11β-HSD2的调节作用。结果发现：LPS（200μg/kg，i.p. ）处理（2h，6h，12h，24h）均可下调ICR孕鼠胎盘基础型核蛋白PPARγ的表达，11β-HSD2蛋白表达水平于12h，24h下降显著。在人胎盘滋养细胞（HTR-8）中发现类似效应，且LPS处理6h，12h和24h能显著抑制PPARγ的细胞核转位作用。同时，以RSG预处理激活HTR-8细胞PPARγ信号，LPS(2μg/mL)处理6h同样具有下调诱导性PPARγ和11β-HSD2的作用。二、观察NF-κB抑制状态下LPS对胎盘滋养细胞PPARγ及下游11β-HSD2的调控作用。 以LPS构建孕鼠炎症模型，以PDTC预处理抑制NF-κB信号，可明显拮抗LPS抑制PPARγ核转位作用。同时构建p65 siRNA沉默HTR-8细胞p65基因，结果显示p65沉默减弱LPS抑制人胎盘滋养细胞PPARγ和11β-HSD2蛋白表达。其机制为p65与PPARγ物理性结合，阻断胎盘滋养细胞PPARγ从胞浆向胞核转移，抑制PPARγ表达。三、人群的病例-对照研究发现，与AGA相比，SGA胎盘11β-HSD2蛋白表达减少约40%，PPARγ阳性细胞核数约下降了25%，p65阳性细胞核数约增加了15%。SGA胎盘炎性因子CRP、TNF-α、IL-8和IL-1β的mRNA水平均高于AGA组。相关性分析发现SGA组p65阳性细胞数与PPARγ阳性细胞数、11β-HSD2蛋白表达均呈负相关，新生儿体重与11β-HSD2呈正相关。综上探讨了NF-κB与PPARγ结合在炎症下调11β-HSD2引起胎儿生长受限中的作用，为阐明胎儿生长受限发生机制提供新依据。