Overexpressed HO-1 is associated with reduced STAT3 activation in preeclampsia placenta and inhibits STAT3 phosphorylation in placental JEG-3 cells under hypoxia.

INTRODUCTION: Inadequate trophoblast invasion and placentation are widely believed to contribute to preeclampsia, and multiple lines of evidence indicate the involvement of hypoxia in preeclampsia. However, the molecular mechanisms underlying the association of placental hypoxia with preeclampsia are not clear. MATERIAL AND METHODS: The present study focused on the role in preeclampsia of heme oxygenase 1 (HO-1), which is an inducible isoform of HO in response to hypoxia, via examining the expression of HO-1 and the expression and phosphorylation (Tyr705) of Signal transducer and activator of transcription (STAT) 3 in preeclamptic placentas via the immunohistochemical method, western blotting assay and RT-qPCR method. Then we investigated the regulation by HO-1 of the expression and phosphorylation of STAT3 in human placental choriocarcinoma JEG-3 cells under hypoxia. RESULTS: There was upregulation of HO-1 at both mRNA (1.506 ±0.08347 (N = 37) vs. 1.000 ±0.08854 (N = 31), p < 0.0001) and protein (0.630 ±0.155 (N = 35) vs. 0.310 ±0.052, 0.630 ±0.155 (N = 35), p < 0.001) levels and a reduced level of STAT3 phosphorylation (Tyr 705) in the preeclamptic placental tissues, compared to normal placental tissues (0.143 ±0.027 (N = 35) vs. 0.194 ±0.028 (N = 35), p < 0.01). Also, in vitro experiments demonstrated that HO-1 was markedly promoted by hypoxia in human placental choriocarcinoma JEG-3 cells, 6 or 12 h post treatment (p < 0.05 or p < 0.01). However, the STAT3 phosphorylation (Tyr 705) was attenuated by sustained hypoxia (p < 0.01). Moreover, it was demonstrated that HO-1 overexpression significantly inhibited the hypoxia-promoted STAT3 phosphorylation (Tyr 705). CONCLUSIONS: HO-1 was overexpressed in PE placenta, in association with reduced STAT3 phosphorylation (Tyr 705). HO-1 inhibits the STAT3 phosphorylation in placental JEG-3 cells under hypoxia. Thus, we speculate that overexpressed HO-1 might contribute to the reduced STAT3 phosphorylation (Tyr 705) and the pathogenesis of preeclampsia.

Upregulated miR-222 targets BCL2L11 and promotes apoptosis of mesenchymal stem cells in preeclampsia patients in response to severe hypoxia.

Abnormal maternal trophoblast invasion is a common finding in preeclampsia pregnancy. A hypoxic environment develops in the placenta after the 10th week of pregnancy and exerts a major influence over trophoblast activity. In the present study, we investigated expression of miR-222 and apoptosis-related BCL2L11 in preeclampsia placenta and in primary placenta mesenchymal stem cells (MSCs) under hypoxia. The results demonstrate that miR-222 is upregulated in the placenta of preeclampsia patients, along with the downregulation of BCL2L11 in both mRNA and protein levels. In vitro results demonstrate that miR-222 is upregulated either in preeclampsia placenta tissues or in the MSCs under hypoxia. Western blotting showed downregulation of BCL2L11 in the trophoblasts under hypoxia, along with an increased MSC apoptosis. miR-222 was also confirmed to downregulate BCL2L11 expression via targeting the 3' untranslated region (UTR) of the BCL2L11 gene. miR-222 inhibitor transfection markedly ameliorated expression and transcriptional activity of BCL2L11. Altogether, the present study found that upregulation of miR-222 promotes apoptosis of mesenchymal stem cells in preeclampsia patients in response to hypoxia, via targeting BCL2L11. This suggests that a key regulatory role of miR-222 is in preeclampsia progression.