HIF-1α Activation Promotes Luteolysis by Enhancing ROS Levels in the Corpus Luteum of Pseudopregnant Rats.

Zonghao Tang,Qingqiang Lin,Zhenghong Zhang,Renfeng Xu,Zhengchao Wang,Jingjing Bi,Jiajie Chen,Alin Ciobica

doi:10.1155/2021/1764929

Abstract

The increase of oxidative stress is one of the important characteristics of mammalian luteal regression. Previous investigations have revealed the essential role of reactive oxygen species (ROS) in luteal cell death during luteolysis, while it is unknown how ROS is regulated in this process. Considering the decrease of blood flow and increase of PGF2α during luteolysis, we hypothesized that the HIF-1α pathway may be involved in the regulation of ROS in the luteal cell of the late corpus luteum (CL). Here, by using a pseudopregnant rat model, we showed that the level of both HIF-1α and its downstream BNIP3 was increased during luteal regression. Consistently, we observed the increase of autophagy level during luteolysis, which is regulated in a Beclin1-independent manner. Comparing with early (Day 7 of pseudopregnancy) and middle CL (Day 14), the level of ROS was significantly increased in late CL, indicating the contribution of oxidative stress in luteolysis. Inhibition of HIF-1α by echinomycin (Ech), a potent HIF-1α inhibitor, ameliorated the upregulation of BNIP3 and NIX, as well as the induction of autophagy and the accumulation of ROS in luteal cells on Day 21 of pseudopregnancy. Morphologically, Ech treatment delayed the atrophy of the luteal structure at the late-luteal stage. An in vitro study indicated that inhibition of HIF-1α can also attenuate PGF2α-induced ROS and luteal cell apoptosis. Furthermore, the decrease of cell apoptosis can also be observed by ROS inhibition under PGF2α treatment. Taken together, our results indicated that HIF-1α signaling is involved in the regression of CL by modulating ROS production via orchestrating autophagy. Inhibition of HIF-1α could obviously hamper the apoptosis of luteal cells and the process of luteal regression.

Highlights

The corpus luteum (CL) is an ephemeral gland in mammalian ovaries evolved from the remains of ovulated follicles, which is responsible for the maintenance of hormonal homeostasis during the menstrual cycle and pregnancy [1]
In order to clarify the induction of autophagy during luteal regression, we detected the expression changes of autophagy-related proteins, including the marker protein (LC-3II, Figure 1) of autophagic induction, the marker protein (p62, Figure 1) of autophagosome degradation, and a scaffold protein (Beclin1, Figure 2(a)) involved in autophagic regulation by immunohistochemical staining analysis
These results demonstrated that LC-3II and p62 were expressed in luteal cells and were concomitantly increased during luteal regression (Figure 1), whereas Beclin1 was decreased on Days 14 and 21 of pseudopregnancy (Figure 2(a))

Summary

Introduction

The corpus luteum (CL) is an ephemeral gland in mammalian ovaries evolved from the remains of ovulated follicles, which is responsible for the maintenance of hormonal homeostasis during the menstrual cycle and pregnancy [1]. The absence of pregnancy is an essential indicator for the initiation of luteal regression and eventually the removal of CL from the ovarian structure at the end of pregnancy whereupon permitting the initiation of the menstrual cycle [2]. The regression of CL implicates the degradation of the extracellular matrix, loss of blood vessel, and luteal cell death. Previous investigations have indicated that the increase of ROS is an essential precursor of rat luteal regression [1]. H2O2 treatment is able to generate a luteolytic effect on granulosa-luteal cells [5]. These findings highlighted the important role of ROS in luteal regression

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Results

Conclusion