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

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.

SUBMITTER: Tang Z

PROVIDER: S-EPMC8429025 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The mechanisms regulating the function and regression of the corpus luteum (CL) have not yet been elucidated in detail. The regressed CL of cows was previously reported to be filled with unusual vessels like arteriovenous anastomosis (AVA); however how these vessels are being established during luteolysis remains unknown.The bovine CL at different luteal stages and regressing bovine CL induced by prostaglandin F2? (PGF) were histologically analyzed using light and electron microscopic levels. The changes in mRNA expression of genes encoding ?-smooth muscle actin (SMA; Acta2) and transforming growth factor ?1 (Tgfb1) in luteal tissues were analyzed by quantitative RT-PCR.AVA-like vessels appeared in the regressed CL with a diameter less than 1.5 cm in which no functional luteal cells and macrophages were observed. Epithelioid cells in the AVA-like vessel wall were immunoreactive for SMA, and the lumen of the vessels were narrow. Immunoreaction for SMA was found in the tunica media of typical arteries and arterioles, and pericytes around capillary vessel. Cells with elongated cytoplasmic processes -resident fibroblasts expressing vimentin- distributed in the CL parenchyma without any association with blood vessels are also immunoreactive for SMA, and accumulated around arteries and arterioles during the late-luteal stage. In the regressed CL, walls of arteries and arterioles consisted of more than two layers of epithelioid cells positive for both SMA and desmin, suggesting that they are myofibroblasts transformed from fibroblasts. The percentage of the area positive for SMA and the mRNA expression of Acta2 were significantly increased in the regressed CL; however, they did not alter when a luteolytic dose of PGF was injected in vivo and collected within 24 h after the injection. On the other hand, Tgfb1, a known regulator for myofibroblast transformation, was significantly increased in PGF-induced regressing CL as well as in the CL during the late-luteal stage.SMA-positive myofibroblasts accumulates around the arteries and arterioles to form AVA-like vessels during luteolysis in cows. PGF indirectly regulates myofibroblast transformation through enhancing the expression of TGF?1. These peculiar AVA-like vessels may be involved in the regulation of blood flow in the bovine CL during luteolysis.

Project description:In monoovulatory species like bovines, a striking diversity in regulation of the corpus luteum (CL) function exists within species during different stages of the luteal phase. The function and life span of CL appears to be regulated by the interplay of both luteotrophic and luteolytic factors, whose roles and actions are varied from one species to another. Although, studies continue to expand our current understanding of the cellular and molecular actions of prostaglandin F 2alpha (PGF2M-NM-1 - a physiological luteolysin)-induced luteolysis, knowledge of the mechanism whereby, PGF2M-NM-1 mediates its luteolytic actions remains poorly understood. The mechanism of PGF2M-NM-1-induced luteolysis is a complex process involving changes in expression of multiple genes encoding gene products that regulate steroidogenesis, stress related or apoptotic genes, factors involved in immune response and enzymes that stimulate PGF2M-NM-1 production. Thus, in the present study, efforts were made to identify the temporal changes in the global gene expression profile in the CL of buffalo cows in response to PGF2M-NM-1 treatment. The molecular signature of genome-wide transcriptional changes in the CL tissue subjected to PGF2M-NM-1-induced luteolysis will expand our knowledge on basic mechanism/s that regulates the luteolytic process. The results obtained in this study provide insight into the mechanisms underlying the PGF2M-NM-1- induced regression of CL.Keywords: CL, PGF2M-NM-1, gene expression The objective of this study was to identify the PGF2M-NM-1-induced temporal changes in transcriptome of bovine CL on day 11 of estrous cycle. In the experiments with buffalo cows, animals with history of normal estrous cyclicity were treated with Cloprostenol (an PGF2M-NM-1 analogue; 500 M-BM-5g i.m.) on day 11 of the estrous cycle to induce luteolysis and CL tissues were collected at (control; n=4 amimals/time point), 3 (n=2 animals/time point), 6 and 18 (n=3 animals/time point) h post PGF2M-NM-1 administration to examine gene expression changes associated with immediate early and delayed changes in the CL, respectively. Following retrieval of CL from the ovary, flash frozen in liquid nitrogen and stored at -70 M-BM-0C for the purpose of RNA isolation. The isolated RNA was labeled and hybridized to Affymetrix GeneChip Bovine Genome Arrays as per the manufacturerM-bM-^@M-^Ys instructions.

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

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