Peroxisome proliferator-activated receptor alpha regulates the expression of the immune response mediators in the porcine endometrium during the estrous cycle and early pregnancy.

PROBLEM: Cytokines are immune response mediators that play an important role in the regulation of reproductive functions. An association between cytokines and peroxisome proliferator receptors (PPARs) has been reported in various tissues, including the endometrium. The present study aimed to evaluate the impact of PPARα ligands on the expression of nuclear factor kappa B (NF-κB) and cytokines (interleukin [IL]-1ß, IL-4, IL-6, IL-8, IL-10, and LIF) in the porcine endometrium in different reproductive stages. METHODS OF STUDY: Endometrial slices were collected from gilts on days 10-12 or 14-16 of the estrous cycle and pregnancy. Endometrial tissue explants were incubated in vitro in the presence or absence of PPARα agonist WY-14643 and antagonist MK886. Expression of mRNA and protein for NF-ĸB and selected cytokines was evaluated by real-time PCR and immunoblot. RESULTS: PPARα agonist WY-14643 decreased the mRNA expression of NF-κB in most of the analyzed stages (excluding days 10-12 of the estrous cycle), but increased the expression of NF-κB protein (excluding days 14-16 of pregnancy). The WY-14643 increased expression of IL-1ß and IL-6 proteins, and the mRNA expression of IL-8 and LIF, decreased IL-4 expression, and did not affect the mRNA and protein expression of IL-10. CONCLUSION: The obtained results demonstrate that PPARα is involved in the regulation of NF-κB and cytokine expression in the porcine endometrium. PPARα ligands exert a varied influence on immune system components, which could be attributed to differences in the receptivity of porcine endometrial tissue during the reproductive cycle.

PPARß/δ ligands regulate the expression of immune response mediators in the porcine endometrium - An in vitro study.

The peroxisome proliferator-activated receptor (PPAR) ß/δ belongs to a group of nuclear receptors that act as transcription factors. PPAR ß/δ plays a significant role in the regulation of female reproductive processes. It has been demonstrated that PPARß/δ is expressed in mouse, rat and porcine endometrium during the estrous cycle and pregnancy. The current study aimed to investigate the effect of selected PPARß/δ ligands on the expression of nuclear factor kappa (NF-κB) and selected cytokines - interleukin (IL)-1ß, IL-6, IL-8, IL-4, IL-10, leukemia inhibitory factor (LIF), in the porcine endometrium on days 10-12 and 14-16 of the estrous cycle (mid- and late-luteal phases corresponding to the full activity and luteolysis of the corpus luteum, respectively) and pregnancy (maternal recognition of pregnancy and beginning of implantation, respectively). Endometrial slices were incubated in vitro in the presence of PPARß/δ agonist L-165,041 (1 or 10 µM) or antagonist GW9662 (10 µM). The expression of mRNA and protein of the immune response mediator in the tissues was determined by real-time PCR and Western Blot. In general, the PPARß/δ agonist inhibited endometrial NF-κB mRNA expression during all analyzed reproductive stages, but it did not change protein expression. In turn, the PPARß/δ antagonist increased NF-κB protein levels on days 10-12 of the estrous cycle or pregnancy. The presence of the PPARß/δ agonist stimulated mRNA expression of LIF, IL-1ß and IL-8 and decreased the expression of IL-6. The presence of PPARß/δ ligands had a varied effect on protein expression in different stages on the analyzed period. The obtained results indicate that PPARß/δ regulates the expression of endometrial NF-κB and selected cytokines in pigs. The effects of PPARß/δ ligands on immune response mediators varied subject to the reproductive status of females and could be associated with differences in endometrial receptivity.

Peroxisome proliferator-activated receptor gamma ligands affect NF-kB and cytokine synthesis in the porcine endometrium-An in vitro study.

PROBLEM: Cytokines, mediators of the immune response, are involved in the regulation of female reproductive processes during the estrous cycle and pregnancy. The present study aimed to investigate the effect of selected peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the expression of nuclear factor kappa B (NF-κB) and selected cytokines, such as interleukin (IL)-1ß, -4, -6, -8, -10, and the leukemia inhibitory factor, in the porcine endometrium on days 10-12 and 14-16 of the estrous cycle (mid- and late luteal phase, respectively) or pregnancy (maternal recognition of pregnancy and beginning of implantation, respectively). METHOD OF STUDY: Endometrial slices were incubated in vitro in the presence of PPARγ agonists, 15-deoxy-Δ12, 14-prostaglandin J2 or rosiglitazone, and PPARγ antagonist T0070907. mRNA and protein levels in tissues were determined by real-time PCR and Western blot. RESULTS: On days 10-12 of the estrous cycle and days 14-16 of pregnancy, PPARγ ligands enhanced the expression of NF-κB, mRNA cytokines, and/or proteins. During the late luteal phase of the estrous cycle (days 14-16) and maternal recognition of pregnancy (days 10-12), PPARγ ligands inhibited the expression of NF-κB, and they differentially affected the expression of mRNA and proteins of cytokines. CONCLUSION: Our results indicate that PPARγ is engaged in the endometrial synthesis of NF-κB and selected cytokines in pigs. The influence of PPARγ ligands on the tested components of the immune system varied subject to the physiological status of females, and it could be associated with differences in endometrial receptivity.

Manipulating Cohesin Levels in Live Mouse Oocytes.

The cohesin complex is essential for chromosome segregation in mitosis and meiosis. Cohesin is a tripartite protein complex that holds sister chromatids together from DNA replication until anaphase. In mammals, meiotic DNA replication occurs in oogonia of embryos and chromosome segregation occurs in oocytes of sexually mature females. Sister chromatid cohesion establishment and chromosome segregation are thus separated by months in the mouse and decades in the human. The meiotic cohesin complex that maintains sister chromatid cohesion must therefore hold replicated sisters together for a long time in oocytes. Remarkably, this is achieved by establishing cohesion exclusively in prenatal oocytes. Meiotic cohesion in females is maintained without detectable turnover and cohesin is therefore thought to be a long-lived protein complex. Nevertheless, the lifespan of cohesin molecules is limited as chromosomal cohesin levels decline with maternal age. The age-related loss of cohesin and weakened cohesion correlate with an age-related increase in chromosome missegregation of meiosis I oocytes that results in aneuploid eggs. Therefore, loss of chromosomal cohesin has been proposed to be a leading cause of the maternal age effect. To better understand cohesin deterioration in oocytes, it is crucial to gain insights into mammalian cohesion establishment and maintenance mechanisms by manipulating cohesin in live oocytes.This chapter describes techniques that address the manipulation of meiotic cohesin levels in mouse oocytes. First, we describe how cohesin can be efficiently removed from meiotic chromosomes by injecting mRNA encoding TEV protease in live oocytes expressing cohesin with engineered TEV recognition sites, followed by imaging. Secondly, we describe how cohesin expression can be induced during different stages of oocyte development using genetically modified mouse strains. In particular, we describe how to determine the deletion timing of germline-specific Cre recombinases using ß-galactosidase staining of fetal ovaries. Lastly, we provide guidance on how to quantify cohesin levels on metaphase I chromosome spreads.

Chromosome Cohesion Established by Rec8-Cohesin in Fetal Oocytes Is Maintained without Detectable Turnover in Oocytes Arrested for Months in Mice.

Sister chromatid cohesion mediated by the cohesin complex is essential for chromosome segregation in mitosis and meiosis [1]. Rec8-containing cohesin, bound to Smc3/Smc1α or Smc3/Smc1ß, maintains bivalent cohesion in mammalian meiosis [2-6]. In females, meiotic DNA replication and recombination occur in fetal oocytes. After birth, oocytes arrest at the prolonged dictyate stage until recruited to grow into mature oocytes that divide at ovulation. How cohesion is maintained in arrested oocytes remains a pivotal question relevant to maternal age-related aneuploidy. Hypothetically, cohesin turnover regenerates cohesion in oocytes. Evidence for post-replicative cohesion establishment mechanism exists, in yeast and invertebrates [7, 8]. In mouse fetal oocytes, cohesin loading factor Nipbl/Scc2 localizes to chromosome axes during recombination [9, 10]. Alternatively, cohesion is maintained without turnover. Consistent with this, cohesion maintenance does not require Smc1ß transcription, but unlike Rec8, Smc1ß is not required for establishing bivalent cohesion [11, 12]. Rec8 maintains cohesion without turnover during weeks of oocyte growth [3]. Whether the same applies to months or decades of arrest is unknown. Here, we test whether Rec8 activated in arrested mouse oocytes builds cohesion revealed by TEV cleavage and live-cell imaging. Rec8 establishes cohesion when activated during DNA replication in fetal oocytes using tamoxifen-inducible Cre. In contrast, no new cohesion is detected when Rec8 is activated in arrested oocytes by tamoxifen despite cohesin synthesis. We conclude that cohesion established in fetal oocytes is maintained for months without detectable turnover in dictyate-arrested oocytes. This implies that women's fertility depends on the longevity of cohesin proteins that established cohesion in utero.

Protein targeting. Structure of the Get3 targeting factor in complex with its membrane protein cargo.

Tail-anchored (TA) proteins are a physiologically important class of membrane proteins targeted to the endoplasmic reticulum by the conserved guided-entry of TA proteins (GET) pathway. During transit, their hydrophobic transmembrane domains (TMDs) are chaperoned by the cytosolic targeting factor Get3, but the molecular nature of the functional Get3-TA protein targeting complex remains unknown. We reconstituted the physiologic assembly pathway for a functional targeting complex and showed that it comprises a TA protein bound to a Get3 homodimer. Crystal structures of Get3 bound to different TA proteins showed an α-helical TMD occupying a hydrophobic groove that spans the Get3 homodimer. Our data elucidate the mechanism of TA protein recognition and shielding by Get3 and suggest general principles of hydrophobic domain chaperoning by cellular targeting factors.