Role of Hypoxia-Inducible Transcription Factors 1α and 2α in the Regulation of Plasminogen Activator Inhibitor-1 Expression in a Human Trophoblast Cell Line

Abstract

The plasminogen activator inhibitors (PAIs) play critical roles in regulating hemostatic and invasive functions of trophoblasts through suppression of plasmin-dependent fibrinolysis and extracellular matrix degradation. The expression of PAI-1 is increased under hypoxic conditions, although the mechanism remains incompletely understood. In the current study we used HTR-8/SVneo cells, a first trimester extravillous trophoblast cell line, and siRNA technology to examine the role of hypoxia-inducible transcription factors (HIFs)−1α and −2α in the regulation of PAI-1 expression. Using serum-containing and serum-free media culture media it was initially noted that levels of PAI-1, but not PAI-2 protein, were markedly induced by hypoxic (2−3% oxygen) treatment. Under hypoxic conditions, Western blotting revealed that the presence of siRNAs to HIF-1α and HIF-2α suppressed expression of their respective proteins, whereas treatment with non-targeting and cyclophilin B siRNAs did not. Importantly, incubation with siRNA to HIF-1α or HIF-2α alone reduced PAI-1 protein levels to a similar extent, with the combined treatment inducing a more profound effect. The presence of HIF siRNAs reduced levels of PAI-1 mRNA as measured by quantitative real-time PCR, indicating that HIF-1α and HIF-2 α regulate PAI-1 expression at a transcriptional level. These results indicate that both HIF-1α and HIF-2α play important and similar roles in hypoxia-mediated stimulation of PAI-1 expression in HTR-8/SVneo cells. Our findings provide insight into the physiological regulation of trophoblast PAI-1 expression in early pregnancy when placental oxygen levels are low, as well as a mechanism for over-expression of placental PAI-1 noted in pregnancies with preeclampsia.

Natural selection on EPAS1 ( HIF2α ) associated with low hemoglobin concentration in Tibetan highlanders

“…In particular, EPAS1 plays very important, if still poorly understood, roles in both placental and embryonic development (51)(52)(53)(54) and possibly also in the pathogenesis of fetal growth restriction (55). It is well recognized that reproductive success is more difficult at high altitude than at low altitude, and more difficult for nonnatives than natives (6).…”

Hypoxia-inducible factors 1 and 2 are important transcriptional effectors in primary macrophages experiencing hypoxia

“…Furthermore, as mentioned previously, this may vary between cell types as HIF-1 has been shown to be the primary regulator of various genes in some cell types, 4,16 whereas other cells use HIF-2 or both HIFs in their regulation. 18,19,48,49 Interestingly, when just one HIF was inhibited using siRNA, the other did not appear to compensate for its loss and maintain maximal hypoxic induction. It is known that many HIF-target genes have multiple HREs.…”

Knockdown of hypoxia inducible factor-2α inhibits cell invasion via the downregulation of MMP-2 expression in breast cancer cells

“…These abnormal blood vessels often do not function properly, resulting in a poor O 2 supply to the center tumor regions. Tumor cells in this hypoxic region begin to adapt these low oxygen tension conditions by activating several survival pathways, including the HIF pathway (22,24,25). The responses of cells to hypoxia are mediated primarily through HIFs, which are critical mediators in the cellular and systemic hypoxia response to low oxygen levels via the accommodation of numerous genes that are induced by hypoxia (14,(26)(27)(28).…”

“…The HIF-2α siRNAs were designed according to the study by Meade et al (22) and were synthesized by Guangzhou Ruibo Biological Technology Co., Ltd.…”