Endoplasmic reticulum stress disrupts lysosomal homeostasis and induces blockade of autophagic flux in human trophoblasts

Akitoshi Nakashima,Aiko Aoki,Osamu Yoshino,Haruhiko Sago,Kenji Matsumoto,Sayaka Tsuda,Tomoko Shima,Shi-Bin Cheng,Tae Kusabiraki,Yosuke Ono,Akemi Ushijima,Kenichiro Motomura,Shigeru Saito,Surendra Sharma

doi:10.1038/s41598-019-47607-5

Abstract

Pregnancy is a stress factor culminating into mild endoplasmic reticulum (ER) stress, which is necessary for placental development. However, excessive or chronic ER stress in pre-eclamptic placentas leads to placental dysfunction. The precise mechanisms through which excessive ER stress impacts trophoblasts are not well understood. Here, we showed that ER stress reduces the number of lysosomes, resulting in inhibition of autophagic flux in trophoblast cells. ER stress also disrupted the translocation of lysosomes to the surface of trophoblast cells, and inhibited lysosomal exocytosis, whereby the secretion of lysosomal-associated membrane protein 1 (LAMP1) into culture media was significantly attenuated. In addition, we found that serum LAMP1 and beta-galactosidase levels were significantly decreased in pre-eclampsia patients compared to normal pregnant women, potentially indicating lysosomal dysfunction through ER stress in pre-eclamptic placentas. Thus, we demonstrated that excessive ER stress essentially disrupts homeostasis in trophoblasts in conjunction with autophagy inhibition by lysosomal impairment.

Highlights

Pregnancy is a stress factor culminating into mild endoplasmic reticulum (ER) stress, which is necessary for placental development
We have reported that failure to induce autophagy in trophoblasts contributes to gestational hypertension and poor placentation, in vitro and in vivo, which are a part of the etiology of PE10–12
We first examined if ER stress or oxidative stress, which often accompanies the pathophysiology of PE, affects autophagy in the 1st-trimester extravillous trophoblast (EVT) cell line, HchEpC1b cells

Summary

Introduction

Pregnancy is a stress factor culminating into mild endoplasmic reticulum (ER) stress, which is necessary for placental development. Excessive or chronic ER stress in pre-eclamptic placentas leads to placental dysfunction. We showed that ER stress reduces the number of lysosomes, resulting in inhibition of autophagic flux in trophoblast cells. ER stress disrupted the translocation of lysosomes to the surface of trophoblast cells, and inhibited lysosomal exocytosis, whereby the secretion of lysosomal-associated membrane protein 1 (LAMP1) into culture media was significantly attenuated. We demonstrated that excessive ER stress essentially disrupts homeostasis in trophoblasts in conjunction with autophagy inhibition by lysosomal impairment. A number of pathological paradigms contribute to poor placentation at the maternal-fetal interface, such as ischemia/hypoxia, inflammation, oxidative stress, and endoplasmic reticulum (ER) stress. We have reported that failure to induce autophagy in trophoblasts contributes to gestational hypertension and poor placentation, in vitro and in vivo, which are a part of the etiology of PE10–12. Consequential ER stress and its effect on autophagy in trophoblasts are still poorly addressed[23]

Methods

Results

Conclusion