Prostaglandin F2α regulation and function during ovulation and luteinization in cows

Effect of intrafollicular administration of PGE2 or PGF2α in early estrus on ovulation, hemorrhagic anovulatory follicles formation, progesterone secretion and pregnancy outcome in the mare

This experiment was performed to evaluate whether intrafollicular treatment of PGE2 or PGF2α administered in early estrus would induce normal ovulation, progesterone production (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, mares in estrus after 2 days of endometrial edema were injected in all largest dominant follicles (28-35 mm in diameter) with 0.5 mL of sterile water containing 500 μg PGE2 (n = 6), 125 μg PGF2α (n = 6) or placebo (n = 7) (Hour 0). Ultrasound examinations were performed daily, until ovulation or anovulation was detected, and daily blood samples were taken for 8 days. In Experiment 2, mares with a dominant follicle ≥35 mm after at least three days of slight-to-moderate endometrial edema, were injected with 500 μg PGE2 diluted in 0.5 mL of sterile water for injection in the follicle (PGE2 group; n = 9 mares and 11 dominant follicles). No puncture was performed in the control group (n = 9 mares and 11 dominant follicles). Mares from both groups were inseminated. In Experiment 1, all mares (6/6) in the PGE2 group ovulated within 24 h of treatment. The mean interval from intrafollicular injection to ovulation was shorter (P < 0.001) in PGE2 mares (24 ± 0 h) than in control mares (77 ± 9 h). Mares from the PGF2α group developed hemorrhagic anovulatory follicles (HAF) more often (7/7) than control mares (2/7); P < 0.05). The progesterone concentration in mares from the PGF2α group was lower (P < 0.004) than control mares in the early post-ovulatory period. The first significant increase in post-ovulatory progesterone concentration occurred earlier (P < 0.05) in mares from the control group than in mares from the PGF2α and PGE2 groups. In Experiment 2, more mares from the control group (7/9, 78 %) became pregnant than from the PGE2 group (2/9, 22 %) (P = 0.015). In conclusion, PGE2 alone induced follicle collapse in all treated mares within 24 h of administrations, while PGF2α blocked ovulation and induced formation of HAFs. However, the post-ovulatory rise in progesterone production was delayed and the fertility reduced in mares with ovulation induced by PGE2 compared to control mares.

Prostaglandins as local regulators of ovarian physiology in ruminants

Prostaglandins are synthesized from arachidonic acid through the catalytic activities of cyclooxygenase, while the production of different prostaglandin types, prostaglandin F2 alpha (PGF) and prostaglandin E2 (PGE), are regulated by specific prostaglandin synthases (PGFS and PGES). Prostaglandin ligands (PGF and PGE) bind to specific high-affinity receptors and initiate biologically distinct signalling pathways. In the ovaries, prostaglandins are known to be important endocrine regulators of female reproduction, in addition to maintaining local function through autocrine and/or paracrine effect. Many research groups in different animal species have already identified a variety of factors and molecular mechanisms that are responsible for the regulation of prostaglandin functions. In addition, prostaglandins stimulate their intrafollicular and intraluteal production via the pathway of prostaglandin self-regulation in the ovary. Therefore, the objective of the review article is to discuss recent findings about local regulation patterns of prostaglandin ligands PGF and PGE during different physiological stages of ovarian function in domestic ruminants, especially in bovine. In conclusion, the discussed local regulation mechanisms of prostaglandins in the ovary may stimulate further research activities in different methodological approaches, especially during final follicle maturation and ovulation, as well as corpus luteum formation and function.

Effects of different cyclooxygenase inhibitors on prostaglandin E₂ production, steroidogenesis and ovulation of bovine preovulatory follicles

Ovulation is an inflammation-like process, and cyclooxygenase-2 (COX-2)-dependent production of prostaglandin E₂ (PGE₂) is its key mediator. Balanced regulation of inflammatory processes in high-yielding dairy cows may be essential for physiological ovulation and fertility. This study aimed to elucidate the mechanisms underlying ovulation failure and cyst development after disturbing intrafollicular inflammatory cascades. Therefore, nonselective (indomethacin and flunixin-meglumine), COX-2 selective (meloxicam), and highly COX-2 selective (NS-398) inhibitors were injected into preovulatory follicles 16 h after administration of GnRH, and ovulation was monitored via ultrasound examination. Additionally, follicular fluid was collected after injection of indomethacin, meloxicam, and NS-398. Moreover, primary granulosa cell cultures from preovulatory follicles were prepared and treated with indomethacin, meloxicam, and NS-398. The concentrations of 17β-estradiol, progesterone, and prostaglandin E₂ (PGE₂) in the follicular fluid and cell supernatant were estimated. Indomethacin and flunixin-meglumine blocked ovulation, even at low doses, and led to ovarian cyst development. The selective and highly selective COX-2 inhibitors meloxicam and NS-398 were not effective in blocking ovulation. However, indomethacin, meloxicam, and NS-398 significantly and comparably reduced PGE₂ concentration in vivo and in vitro (P < 0.05) but had no effect on estradiol or progesterone production. This may contradict the generally accepted hypothesis that PGE₂ is a key mediator of ovulation and progesterone production. Our results suggest a connection between ovarian disorders and inflammatory actions in early postpartum cows.

Ovarian response to prostaglandin F2α in lactating dairy cows: a clinical update

Prostaglandin F_2α (PGF_2α) and its analogs are used to induce luteolysis in estrus synchronization programs to terminate unwanted pregnancies or to promote ovulation in certain cow subpopulations. In the past few decades, the luteolytic dose of PGF_2α has remained unchanged. This review explores the clinical implications of increasing the standard dose for these applications in high-producing dairy cows. Ultrasonography may assist in selecting the most appropriate PGF_2α dose and improve the results. A reference has been used for PGF_2α for promoting ovulation in herds showing poor reproductive performance.

A Critical Overview on Prostaglandin Inhibitors and Their Influence on Pregnancy Results after Insemination and Embryo Transfer in Cows

Simple Summary

Assisted reproductive techniques, such as artificial insemination or embryo transfer have been used in cattle reproduction for decades, but despite many methodological improvements, pregnancy rates have not increased proportionately. One strategy to improve the pregnancy rate after artificial insemination and embryo transfer is to increase the chance of early embryo survival with the use of medications such as nonsteroidal anti-inflammatory drugs. This paper compares the effect of the application of the most frequently used nonsteroidal anti-inflammatory drugs in cattle (flunixin meglumine, carprofen, meloxicam, ibuprofen, aspirin, and sildenafil), as well as of steroid drugs that are used less frequently in cattle reproduction. An evaluation of published reports revealed a range of outcomes that were not always consistent with each other. However, a positive effect of nonsteroidal anti-inflammatory drug treatment on the pregnancy rate in cattle was indicated, especially with the use of flunixin meglumine.

Abstract

Assisted reproductive techniques in cattle, such as artificial insemination (AI) and embryo transfer (ET), are widely used. Despite many years of methodological improvements, the pregnancy rate (PR) in cows has not increased in direct proportion with their development. Among the possibilities to increase the PR is the use of certain steroids and nonsteroidal anti-inflammatory drugs (NSAIDs). The antiluteolytic effect of NSAIDs is achieved by blocking cyclooxygenase, which is involved in the conversion of arachidonic acid to prostaglandins. This article compares the PRs obtained after treatment with the commonly used NSAIDs in cattle, including flunixin meglumine, carprofen, meloxicam, ibuprofen, aspirin, and sildenafil. Studies on the effectiveness of certain steroid drugs on the PR have also been described. The results were not always consistent, and so comparisons between studies were made. In conclusion, flunixin meglumine seems to be an option, and can be recommended for improving ET results, especially in situations of high exposure or susceptibility to stress. Its administration under all circumstances, however, might be pointless and will not lead to the desired effect.

UHPLC-MS-MS analysis of oxylipins metabolomics components of follicular fluid in infertile individuals with diminished ovarian reserve

BACKGROUND

Diminished ovarian reserve (DOR) refers to a decrease in the number and quality of oocytes in the ovary, which results in a lack of sex hormones and a decline of fertility in women. DOR can potentially progress to premature ovarian failure (POF), which has a negative impact on women's quality of life and is a major cause of female infertility. Oxidative stress is a major contributor to fertility decrease in DOR patients, affecting the follicular microenvironment, oocyte maturation, fertilization, and embryo development. Understanding intracellular signal transduction can be achieved by defining specific oxidized lipid components in follicular fluid (FF) of DOR infertile patients.

METHODS

The oxylipins metabolic signatures in the FF of DOR patients and females with normal ovarian reserve (NOR) enrolled for the in vitro fertilization (IVF) cycle were analyzed using UHPLC-MS-MS technology. Principal component analysis (PCA) and orthogonal projections to latent structure discriminant analysis (OPLS-DA) were used to analyze the derived metabolomic profiles. Pathway enrichment analysis was carried out using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and MetaboAnalyst databases. Furthermore, the Spearman rank correlation coefficient was used to determine the correlation between age, FSH, AMH, AFC, oocytes retrieved, MII oocytes, fertilization, high-quality embryos, and the concentration of differential oxidized lipid metabolites in FF.

RESULTS

Fifteen oxylipins metabolites were found to be lower in the FF of DOR patients than those in the NOR group, including ±20-HDoHE, ±5-iso PGF_2α-VI, 12S-HHTrE, 15-deoxy-Δ12,14-PGJ₂, 1a,1b-dihomo PGE₂, 1a,1b-dihomo PGF_2α, 20-COOH-AA, 20-HETE, 8S,15S-DiHETE, PGA₂, PGD₂, PGE₁, PGF_1α, PGF_2α, and PGJ₂. The pathway enrichment analysis revealed that the 15 differentially oxidized lipid metabolites were closely related to the arachidonic acid metabolic pathway. Correlation analysis revealed that the concentration of 8 different oxidized lipid metabolites in FF was negatively correlated to FSH and positively correlated with AFC. AMH, the number of oocytes retrieved, MII oocytes and fertilization, were all positively correlated with 9 different oxidized lipid metabolites, but only one metabolite was positively correlated with the number of high-quality embryos.

CONCLUSIONS

Metabolomic analysis of FF revealed that oxylipins metabolism disorders were closely related to ovarian reserve function. Among these oxylipins metabolites, arachidonic acid metabolism undergoes significant changes that may be related to oocyte development, resulting in decreased fertility in DOR patients.

TRIAL REGISTRATION

ChiCTR, ChiCTR2000038182 , Registered 12 September 2020-Retrospectively registered.