Status of sFlt‐1 in Pregnant Women with Preeclampsia and its Impact on GRP78 in Trophoblast Cells
Authors: MOCHAN SANKAT , GUPTA SUNIL KUMAR , SAXENA SHOBHIT , ARORA PALLAVI , RANI NEERJA , PALLAVI SK , SHARMA ARUNDHATI , LUTHRA KALPANA , DWIVEDI SADANAND , BHATLA NEERJA , DHINGRA RENU 
Published: June 2021

Introduction

sFlt‐1 is secreted in large amounts by placental trophoblasts, released into maternal circulation and reduces bioavailability of angiogenic molecule, VEGF. Plenty of evidence suggest that production of excess sFlt‐1 is a consequence of placental hypoxia leading to stressed placenta noted in preeclampsia (PE). Placental stress has been categorized into oxidative, immunologic and endoplasmic reticulum (ER) stress. Placental ER stress arises due to failure of unfolded protein response (UPR) affects its central regulator, GRP78, which dissociates from transmembrane sensors, PERK like ER kinase, IRE1 (Inositol‐Requiring Enzyme 1) and ATF6 (Activated Transcription Factor 6). The present study was aimed to unravel whether sFlt‐1 had any correlation with GRP78. Also, in vitro experiments were performed to explore effect of sFlt‐1 on GRP78.

Methods

Sera from 60 recruited women [(30 PE patients and 30 Normotensive, Non‐proteinuric (NT, NP; controls)] were used to estimate levels of sFlt‐1 and GRP78 proteins (ELISA; R and D system). Trophoblast cells (BeWo cells; human choriocarcinoma cell line) were subjected to various treatments with varying sFlt‐1 concentrations and expression of GRP78 was analysed using immunofluorescence (IF), western blot and qRT‐PCR at 8, 14 and 24 hours. The BeWo cells of group 1 and group 2 were exposed to sera from normotensive pregnant women (low sFlt‐1), and preeclamptic pregnant women (high sFlt‐1). The BeWo cells of group 3 were exposed to normotensive sera with recombinant sFlt‐1 (NT+re‐sFlt‐1). Statistical tests used were Paired t, Pearson correlation coefficient, One‐way ANOVA, Kruskal‐Wallis, Wilcoxon signed‐rank.

Results

Serum sFlt‐1 levels were found to be significantly elevated in women with preeclampsia [11295.25 (2936.2–37818) pg/ml] than in controls [2936.2 (1180.43–6706.6) pg/ml] (p=0.0001). GRP78 levels were also raised significantly in PE patients (1103.26 ± 104.27) ng/ml as compared to controls (1018.61 ± 125.51) ng/ml (p=0.023). Patients with increased sFlt‐1 in their sera had higher GRP78 levels suggesting a positive correlation. Significant expression of GRP78 was observed at 8 h when BeWo cells were treated with PE sera and NT sera with recombinant sFlt‐1 by IF. GRP78 expression was observed as early as 8 h, reached peak at 14 h, started diminishing after 14 h and was significantly upregulated when BeWo cells were treated with PE sera as compared to NT sera at both protein (p<0.0001) and mRNA (p<0.0001) levels. Expression of GRP78 was significantly raised at 8 and 14 h when BeWo cells were treated with NT+re‐sFlt‐1 as compared to NT sera at both protein (p<0.0001) and mRNA (p<0.0001) levels.

Conclusion

Positive correlation was observed between increased maternal serum levels of sFlt‐1 and GRP78 in preeclamptic patients. Upregulation of GRP78 in trophoblast cells exposed to group 2 and 3 indicate towards an important role which may be played by sFlt‐1 in inducing ER stress in Preeclampsia.

Ethical clearance IESC/T‐323

Support or Funding Information

A‐159 AIIMS, New Delhi

This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.