Induction and molecular mechanism of placental trophoblast cell autophagy in preeclampsia

Abstract

Objective To investigate the induction and regulatory mechanism of placental trophoblast cell autophagy in women with preeclampsia (PE). Methods Twenty gravidas with severe PE who underwent cesarean section in the Department of Obstetrics and Gynecology of Changzhou Maternity and Child Health Care Hospital Affiliated to Nanjing Medical University from August 2016 to November 2016 were enrolled in PE group. An equal number of normotensive gravidas without proteinuria who also underwent cesarean section during the same period were randomly selected as control group. Placental tissue samples were collected from all gravidas. Ultrastructure of placental trophoblast cells and changes in autophagosome formation were observed by transmission electron microscope. Expressions of microtubule associated protein 1 light chain 3B (MAP1LC3B, or LC3B) and Beclin 1 in placental tissue samples were detected by quantitative real-time polymerase chain reaction (PCR) and Western blot. Activities of protein kinase B (PKB, also known as Akt)/mammalian target of rapamycin (mTOR) pathway in placental tissue samples were detected by Western blot. Two independent samples t-test or Mann-Whitney U test was used for statistical analysis. Results Sparse and disordered villi and many typical autophagosomes were observed in placental trophoblast cells from patients with severe PE. Significantly enhanced expression of LC3B at mRNA and protein levels and increased ratio of LC3-II/LC3-I were observed in the PE group as compared with the control group [3.37 (2.37-6.11) vs 0.62 (0.25-4.15), 1.40±0.17 vs 1.00±0.13, 1.57±0.25 vs 1.00±0.31, Z or t=-4.440, 3.274 and 3.113, all P 0.05). Furthermore, Akt and mTOR phosphorylation in the PE group was significantly suppressed as compared with that in the control group (1.00±0.29 vs 0.64±0.21, 1.00±0.32 vs 0.60±0.22, t=-3.672 and -2.895, both P 0.05). Conclusions Suppressed activity of Akt/mTOR pathway and enhanced induction of trophoblast cell autophagy are detected in placental tissues of patients with severe PE, indicating that excessive trophoblast cell autophagy, induced by decreased activity of Akt/mTOR pathway, may be the pathogenesis for PE. Key words: Pre-eclampsia; Trophoblasts; Autophagy; Placenta; Proto-oncogene proteins c-akt; TOR serine-threonine kinases