Expression of peroxisome proliferator activated receptor (PPAR) genes in porcine endometrium exposed in vitro to IL-6 and INFγ

Allelic to genome wide perspectives of swine genetic variation to litter size and its component traits

Litter size is a complex and sex limited trait that depends on various biological, managemental and environmental factors. Owing to its low heritability it is inefficaciously selected by traditional methods. However, due to higher heritability of ovulation rate and embryo survival, selection based on component traits of litter size is advocated. QTL analysis and candidate gene approach are among the various supplementary/alternate strategies for selection of litter size. QTL analysis is aimed at identifying genomic regions affecting trait of interest significantly. Candidate gene approach necessitates identification of genes potentially affecting the trait. There are various genes that significantly affect litter size and its component traits viz. ESR, LEP, BF, IGFBP, RBP4, PRLR, CTNNAL1, WNT10B, TCF12, DAZ, and RNF4. These genes affect litter size in a complex interacting manner. Lately, genome wide association study (GWAS) have been utilized to unveil the genetic and biological background of litter traits, and elucidate the genes governing litter size. Favorable SNPs in these genes have been identified and offers a scope for inclusion in selection programs thereby increasing breeding efficiency and profit in pigs. The review provides a comprehensive coverage of investigations carried out globally to unravel the genetic variation in litter size and its component traits in pigs, both at allelic and genome wide level. It offers a current perspective on different strategies including the profiling of candidate genes, QTLs, and genome wide association studies as an aid to efficient selection for litter size and its component traits.

PPARγ ligands modulate the immune response mediators in the pig myometrium - An in vitro study

The current study was conducted with the aim to investigate effects of PPARγ ligands on synthesis of nuclear receptor κB (NF-κB) and selected cytokines (IL-1β, IFNγ, TNFα, IL-4, IL-10, LIF) in the pig myometrium on days 14-15 of the estrous cycle (late-luteal phase) and days 14-15 of the gestational period (beginning of embryonic implantation). The myometrial slices were incubated in vitro for 6 h in medium containing PPARγ ligands, agonists: 15d-prostaglandin J₂ or pioglitazone, and antagonist - T0070907. The mRNA transcript and protein abundances were evaluated in tissues and culture medium. During the estrous cycle, PPARγ ligands did not have an effect on the mRNA transcript abundance of the immune response mediators used for treatments. The IL-10 protein abundance in the tissue was less when there was inclusions of pioglitazone in the medium, while the treatment with T0070907 resulted in a larger abundance of NF-κB, IL-1β (in the tissue) and IL-4 (in tissue and culture media). During the gestational period, pioglitazone or PGJ₂ suppressed mRNA IFNγ and IL-10 transcript and protein abundances (in the tissue and culture media), whereas there was an enhanced NF-κB protein abundance (in the tissue). Treatment with T0070907 had diverse effects (e.g., for NFκB inhibited mRNA transcript abundance or enhanced protein abundance). The observed changes are related mainly in tissues from pregnant animals. Responses to PPARγ antagonist are indicative of the possible involvement of PPARγ-independent factors as well as ligand-independent activation of the receptor, ligand selectivity/functionality or tissue receptivity to the factors evaluated.

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]-1β, 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-1β 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.

Expression and role of peroxisome proliferator-activated receptors in the porcine early placenta trophoblast

Peroxisome proliferator-activated receptors (PPARs) are members of a nuclear receptor family of ligand-dependent transcription factors. Three isoforms of PPAR named PPARα, PPARβ/δ, and PPARγ have been described, each encoded by a separate gene: PPARA, PPARD, and PPARG, respectively. In the present study, we examined the profiles of PPAR and retinoid X receptor (RXR; PPAR heterodimer partner) mRNA expression and PPAR DNA binding activity in porcine trophoblast tissue collected on days 15, 20, 25, and 30 of pregnancy and in day-20 embryos. Placenta trophoblast cells isolated on day 25 of pregnancy were used to determine effects of (1) cytokines on PPAR and RXR mRNA expression and (2) PPAR agonists on prostaglandin (PG) E2 synthesis and the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport, as well as on cell proliferation. The mRNA expression of PPARA and RXRB was greater in trophoblast tissue collected on days 25 and 30 of pregnancy compared with day 15 (P < 0.05), while DNA binding activity of PPARα decreased between day 15 and 25 (P < 0.05). Increased concentrations of PPARD and RXRA transcripts were observed in trophoblasts collected on day 20 compared to trophoblasts from days 15 and 30 (P < 0.05). Moreover, concentrations of DNA-bound PPARβ/δ and PPARγ proteins increased in day-30 trophoblasts compared to day 15 (P < 0.01) and day 20 (P < 0.05), respectively. On day 20 of gestation, the mRNA expression of PPARD, PPARG, and RXRA and protein levels of PPARα and PPARγ isoforms were greater in trophoblast than embryonic tissue (P < 0.01). Interleukin 1β and/or interferon γ, but not IL6 and leukemia inhibitory factor, upregulated PPAR and RXR mRNA expression in placenta trophoblast cells in vitro (P < 0.05). Rosiglitazone (a PPARγ agonist) stimulated prostaglandin E synthase mRNA expression in trophoblast cells and PGE2 accumulation in incubation medium (P < 0.05). Moreover, activation of PPAR isoforms differentially affected the expression of genes involved in steroidogenesis, fatty acid binding, and PG transport in studied cells. Finally, PPARα and PPARγ agonists stimulated trophoblast cell proliferation (P < 0.05), and this effect was abolished by the addition of a respective PPAR antagonist (P < 0.05). Overall, these results point to a role of PPAR isoforms in porcine placenta development and function.

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)-1β, -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.

The influence of experimentally induced endometritis on the PPAR expression profile in the bovine endometrium

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors of the nuclear receptor superfamily. The PPARs activity can be modified e.g. by arachidonic acid metabolites. Escherichia coli (E. coli) is one of the main infectious agent of endometritis in dairy cows. We hypothesized that PPAR expression profile change in the bovine endometrium under the influence of LPS or E. coli. In experiment 1, endometrial explants were obtained post mortem from heifers and incubated without (control) or with LPS for 12, 24, 48, 72 and 96 h. In experiment 2, heifers were intrauterine infused with 0.9% NaCl (control) or with E. coli suspension in 0.9% NaCl. Endometrial biopsies were performed before (0 h) and 12, 24, 48, 72, 96 h after the infusions. In experiment 1, the increase in protein expression was observed for PPARα 48 h, for PPARβ/δ 24, 72 and 96 h, whereas for PPARγ 12, 24 and 96 h after LPS treatment relative to the control groups. In experiment 2, the up-regulation in protein expression was observed for PPARα 48 and 72 h, for PPARβ/δ 72 and 96 h, for PPARγ1 and PPARγ2 12 and 96 h after the intrauterine infusion with E. coli suspension compared to the control group. Changes in mRNA and protein PPAR expression profile in endometrial explants under the exposure of LPS indicate participation of these nuclear receptors in signal transduction during stimulation with LPS. The patterns of mRNA and protein PPAR expression in endometrial bioptates suggest that during experimentally induced endometritis in vivo, PPARs role may be connected both with enhancement of inflammation as well restoring physiological conditions in uterus.

The influence of arachidonic acid metabolites on PPAR and RXR expression in bovine uterine cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the superfamily of nuclear receptors. Three isoforms have been described: alpha (PPARα), delta (PPARδ), and gamma (PPARγ). PPARs heterodimerize with retinoid X receptors (RXRs: RXRα, RXRβ and RXRγ). PPAR activity can be modulated by several ligands, including arachidonic acid (AA) metabolites. The aims of the study were to determine the effect of AA metabolites (prostaglandin [PG]E₂, PGF_2α, leukotriene [LT]B₄, and LTC₄) on mRNA (real-time PCR) and protein expression (Western blotting) of PPARα, PPARδ, and PPARγ, and on mRNA expression of RXRα, RXRβ, and RXRγ, in bovine epithelial, stromal, and myometrial primary uterine cells and in bovine stromal cells with silenced PPAR genes (N = 10). All PPAR and RXR isoforms were expressed. Prostaglandins affected expression of PPARs only in stromal cells, whereas LTs modulated PPARγ mRNA expression in epithelial and myometrial primary cells. Blockade of signal transduction through PPARs prevented interactions between AA metabolites and PPARs and changed RXR expression comparing with primary stromal cells. In primary stromal uterine cells, mRNA expression of RXRs was higher than that of PPARs. In uterine stromal cells in which intracellular signaling through PPARs was blocked, RXRs seem to take over the role of PPARs and are pivotal for cell functions. This study revealed the reaction of PPARs and RXRs to agonists which naturally occur in the bovine uterus.

The involvement of peroxisome proliferator activated receptors (PPARs) in prostaglandin F2α production by porcine endometrium

In the present study, we investigated the in vitro effects of peroxisome proliferator activated receptor (PPAR) ligands on PGF2α secretion and mRNA expression of prostaglandin F synthase (PGFS) in porcine endometrial explants collected on days 10-12 and 14-16 of the estrous cycle or pregnancy. The explants were incubated for 6h with: PPARα ligands - WY-14643 (agonist) and MK 886 (antagonist); PPARβ ligands - l-165,041 (agonist) and GW 9662 (antagonist); PPARγ ligands - 15d-prostaglandin J2 (PGJ2, agonist), rosiglitazone (agonist) and T0070907 (antagonist). The expression of PGFS mRNA in the endometrium and the concentration of PGF2α in culture media were determined by real time RT-PCR and radioimmunoassay, respectively. During the estrous cycle (days 10-12 and 14-16), the agonists - WY-14643 (PPARα), l-165,041 (PPARβ), PGJ2 and rosiglitazone (PPARγ) - increased PGF2α secretion but did not affect PGFS mRNA abundance. During pregnancy (days 10-12 and 14-16), PPARα and PPARγ ligands did not change PGF2α release, whereas PPARβ agonist augmented PGF2α release on days 14-16 of pregnancy. In addition, WY-14643 and l-165,041 increased PGFS mRNA level in both examined periods of pregnancy. PPARγ agonist (PGJ2) and antagonist (T0070907) enhanced PGFS mRNA abundance in the endometrium on days 10-12 and 14-16 of pregnancy, respectively. The results indicate that PPARs are involved in the production of PGF2α by porcine endometrium, and that the sensitivity of the endometrium to PPAR ligands depends on reproductive status of animals.