Down-regulation of the placental BCRP/ABCG2 transporter in response to hypoxia signaling

Abstract

Introduction The BCRP/ABCG2 efflux transporter protects the developing fetus by limiting the transplacental transfer of drugs and chemicals and prevents the apoptosis of trophoblasts. The purpose of this study was to determine whether hypoxia-related signaling alters placental BCRP expression and function in vitro and in human pregnancies. Methods Human BeWo choriocarcinoma cells were treated with the hypoxia mimetic, cobalt chloride (CoCl2), or 3% oxygen for 24-48 h. Activation of HIF-1α signaling and regulation of BCRP was assessed using qPCR, ELISA, western blotting and a fluorescent substrate transport assay. In addition, healthy term placentas from high altitude pregnancies with chronic hypoxia were assessed for BCRP expression. Results CoCl2 and 3% oxygen increased HIF-1α protein signaling and decreased the mRNA and protein expression of BCRP by 30-75% in BeWo cells. Reduced BCRP expression corresponded with impaired efflux activity during hypoxia as evidenced by accumulation of the substrate Hoechst 33342. A number of transcription factors known to regulate BCRP, including AHR, NRF2 and PPARγ, were also coordinately down-regulated by 3% oxygen in BeWo cells. Moreover, women who gave birth at a high altitude (3100 m) exhibited signs of chronic placental hypoxia, including enhanced protein expression of the HIF-1α target GLUT1, and had reduced BCRP levels in microvillous membranes compared to women at a moderate altitude (1600 m). Discussion This study provides novel insight into the regulation of the placental BCRP transporter by hypoxia, which may be important for exposure of the fetus to chemicals during early development and in hypoxia-related pregnancy disorders.

Bioengineered NRF2-siRNA Is Effective to Interfere with NRF2 Pathways and Improve Chemosensitivity of Human Cancer Cells

“…Chemosensitivity of cancer cells also involves efflux ABC transporter-mediated mechanisms (Choi and Yu, 2014). In agreement with the role of NRF2 in drug resistance, NRF2 has been demonstrated to regulate the expression of many ABC transporters, including ABCB6, ABCC1-5, and ABCG2, which may differ due to the differences in types of cells with variable levels of expression and/or distinct regulatory pathways (Adachi et al, 2007;Aleksunes et al, 2008;Malhotra et al, 2010;Singh et al, 2010;Xu et al, 2010;Chorley et al, 2012;Canet et al, 2015;Jeong et al, 2015;Francois et al, 2017). Through interfering NRF2 with bioengineered NRF siRNA, the present study revealed a consequent reduction of ABCC3 expression in 143B cells as well as the suppression of ABCC4 and ABCG2 in MG63 cells, supporting the role of NRF2 in the regulation of ABC transporter expression.…”

“…Bioengineered NRF2-siRNA Enhances Chemosensitivity Bioengineered NRF2-siRNA Modulates the Expression of NRF2-Regulated ABC Transporters in Human OS Cells. Recent studies have also demonstrated the role of NRF2 in the regulation of efflux ABC transporters (Adachi et al, 2007;Aleksunes et al, 2008;Malhotra et al, 2010;Singh et al, 2010;Chorley et al, 2012;Canet et al, 2015;Francois et al, 2017). Therefore, we assessed the influence of BERA/NRF2-siRNA on the mRNA levels of five ABC transporters, ABCC1-4/MRP1-4 and ABCG2/breast cancer resistance protein, in human OS cells.…”

Role of Elevated SFLT‐1 on the Regulation of Placental Transporters in Women With Pre‐Eclampsia

“…40 Interestingly, a downregulation of BCRP in response to low oxygen levels has been reported in BeWo cells. 41 Thus, the observed downregulation of BCRP could occur due to simultaneous and additive events rather than through a single pathway. Although hypoxia is more commonly associated with a reduction in VEGF expression, 42 it has been reported that low oxygen tension caused an increase in transcript levels of VEGF along with increased BCRP in human placental explants, which further supports involvement of angiogenic factors.…”

Role of the efflux transporters BCRP and MRP1 in human placental bio-disposition of pravastatin

“…Thus, compared to placental explants from term placentas experimentally exposed to low oxygen tension for 24 and 48 hours, the development of placentas from the first trimester occurs in hypoxic conditions. However, in a recent study [50], western blot analysis also showed decreased expression of BCRP in microvillous membrane of placentas from women who gave birth at a high altitude, suggesting down-regulation of BCRP under hypoxic conditions. Previously, Krishnamurthy and colleagues showed that hypoxia upregulated expression of BCRP in mouse hematopoietic stem cells and that this upregulation is regulated by the hypoxia-inducible transcription factor complex HIF-1 [51].…”