LncRNA MEG3作为ceRNA参与miR-155调控FOXO3a磷酸化修饰影响滋养细胞自噬的机制研究

Excessive trophoblast autophagy contributing to impaired spiral artery remodeling is a possible mechanism for preeclampsia (PE). However, the mechanisms that regulate trophoblast autophagy remain unclear. Previous studies indicated that transcription factor FOXO3a is a crucial regulator of autophagy. We found that miR-155 did induce trophoblast autophagy; Moreover, FOXO3a phosphorylation was decreased whereas FOXO3a nuclear accumulation was increased in response to overexpression of miR-155 in trophoblast cells. Using online miRNA target gene prediction programs, we found that PDK1, RHEB and SGK1 are both potential miR-155 targets. Furthermore, overexpression of LncRNA MEG3 partially blocked trophoblast autophagy by acting as a ceRNA of miR-155 in trophoblast cells. So, we are proposing an assumption that increased miR-155 and decreased MEG3 in PE placentas induce trophoblast autophagy through modulating FOXO3a phosphorylation by targeting PDK1, RHEB and SGK1. We will further to address the mechanism of trophoblast autophagy through MEG3/miR-155-mediated FOXO3a phosphorylation in vitro and in pregnant rats. Our study might be elucidating of the molecular control of trophoblast autophagy and spiral artery remodeling by miR-155 and MEG3.

自噬过度激活导致子宫螺旋动脉重塑障碍是临床发生子痫前期（PE）的重要原因，但机制不明。FOXO3a是细胞自噬的重要调控分子。我们发现miR-155可激活滋养细胞自噬，降低FOXO3a磷酸化，促进FOXO3a核聚集，且PDK1、RHEB及SGK1是miR-155潜在靶分子；继之发现LncRNA MEG3可作为ceRNA竞争性抑制miR-155，改善滋养细胞自噬过度激活。故推测PE患者胎盘中miR-155高表达而MEG3低表达，降低FOXO3a磷酸化，促使FOXO3a入核，上调FOXO3a依赖的自噬基因转录，导致滋养细胞自噬过度激活。本研究将从FOXO3a磷酸化修饰角度探讨miR-155对滋养细胞自噬的影响；从ceRNA角度探讨MEG3调控miR-155诱导的滋养细胞自噬；并利用PE大鼠模型在体研究miR-155和MEG3对滋养细胞自噬和螺旋动脉重塑的影响。期望为PE防治提供新思路。

滋养细胞自噬过度激活导致子宫螺旋动脉重塑障碍是临床发生子痫前期（Preeclampsia，PE）的重要原因，但机制不明。我们发现miR-155在PE患者胎盘中表达异常增高，而LncRNA MEG3表达异常降低；miR-155通过靶向抑制SGK1和RHEB的表达，降低转录因子FOXO3a蛋白的磷酸化修饰，促使FOXO3a入核，上调FOXO3a依赖的自噬标志分子LC3B的转录，激活滋养细胞自噬；miR-155靶向调控MEG3，LncRNA MEG3作为ceRNA改善miR-155诱导的滋养细胞自噬。采用妊娠第5天大鼠尾静脉注射超低剂量脂多糖（LPS，0.5 μg/kg）成功诱导PE大鼠模型，并发现PE大鼠胎盘中miR-155表达异常增高而MEG3表达异常降低，同时伴有滋养细胞自噬过度激活、侵袭障碍和子宫螺旋动脉侵袭障碍。.同时，我们发现FOXO3a在PE患者胎盘中表达异常增高，并深入探讨了FOXO3a的表达调控机制及其在PE发生发展的作用。RNA m6A修饰（N6-methyladenosine）是真核生物RNA分子最常见和最丰富的修饰之一。我们发现PE患者胎盘中m6A及其甲基转移酶METTL14表达明显升高，METTL14过表达抑制滋养细胞和羊膜细胞增殖、侵袭，诱导滋养细胞和羊膜细胞自噬和凋亡。Me-RIP-qPCR结果证实METTL14靶向调控FOXO3a m6A修饰，上调FOXO3a蛋白的表达。抑制内源性FOXO3a的表达可显著改善METTL14对滋养细和羊膜细胞增殖、侵袭的抑制作用，以及明显抑制METTL14对滋养细胞和羊膜细胞自噬和凋亡的激活效应。.综上，我们的研究为PE胎盘滋养细胞自噬过度激活和子宫螺旋动脉重塑障碍阐明了新的分子调控机制，并为PE防治提供了新的思路。