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.

AbbreviationsABTS*+ -2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) CAT -catalase DRP -differentially regulated protein ERAP1/ ERAP2 -endoplasmic reticulum aminopeptidase 1 FDR -false discovery rate FOX -ferrous oxidation-xylenol orange gdf-11 -growth/differentiation factor 11 GO -Gene Ontology GSH -glutathione GST -glutathione S-transferase IL-12p40 -component of the bioactive cytokines interleukin 12 IL-1β -interleukin 1β LC-MS/MS -liquid chromatography tandem mass spectrometry LPS -lipopolysaccharide MHC-I/ MHC-II -major histocompatibility complex MIF -macrophage migration inhibitory factor NO -nitric oxide PRDX -peroxiredoxins prdx-1 -peroxiredoxin 1 prdx-2 -peroxiredoxin 2 prdx-3 -peroxiredoxin 3 ROS -reactive oxygen species SOD -superoxide dismutase TAC -total antioxidant capacity TGF-β -transforming growth factor β1 TNF-α -tumor necrosis factor α

Inflammation is a biological response of the immune system, which can be triggered by many factors, including pathogens. These factors may induce acute or chronic inflammation in various organs, including the reproductive system, leading to tissue damage or disease. In this study, the RNA-Seq technique was used to determine the in vitro effects of peroxisome proliferator-activated receptor gamma (PPARγ) ligands on the expression of genes and long non-coding RNA, and alternative splicing events (ASEs) in LPS-induced inflammation of the porcine endometrium during the follicular phase of the estrous cycle. Endometrial slices were incubated in the presence of LPS and PPARγ agonists (PGJ2 or pioglitazone) and a PPARγ antagonist (T0070907). We identified 169, 200, 599 and 557 differentially expressed genes after LPS, PGJ2, pioglitazone or T0070907 treatment, respectively. Moreover, changes in differentially expressed long non-coding RNA and differential alternative splicing events were described after the treatments. The study revealed that PPARγ ligands influence the LPS-triggered expression of genes controlling the DNA damage response (GADD45β, CDK1, CCNA1, CCNG1, ATM). Pioglitazone treatment exerted a considerable effect on the expression of genes regulating the DNA damage response.

Female fertility depends greatly on the capacity of the uterus to recognize and eliminate microbial infections, a major reason of inflammation in the endometrium in many species. This study aimed to determine the in vitro effect of PPARγ ligands on the transcriptome genes expression and alternative splicing in the porcine endometrium in the mid-luteal phase during LPS-stimulated inflammation using RNA-seq technology. The endometrial slices were incubated in vitro in the presence of LPS and PPARγ agonists—PGJ2 or pioglitazone and antagonist—T0070907. We identified 222, 3, 4 and 62 differentially expressed genes after LPS, PGJ2, pioglitazone or T0070907 treatment, respectively. In addition, we detected differentially alternative spliced events: after treatment with LPS—78, PGJ2–60, pioglitazone—52 or T0070907–134. These results should become a basis for further studies explaining the mechanism of PPARγ action in the reproductive system in pigs.

Inflammation in the female reproductive system causes serious health problems including infertility. The aim of this study was to determine the in vitro effects of peroxisome proliferator-activated receptor-beta/delta (PPARβ/δ) ligands on the transcriptomic profile of the lipopolysaccharide (LPS)-stimulated pig corpus luteum (CL) in the mid-luteal phase of the estrous cycle using RNA-seq technology. The CL slices were incubated in the presence of LPS or in combination with LPS and the PPARβ/δ agonist—GW0724 (1 μmol/L or 10 μmol/L) or the antagonist—GSK3787 (25 μmol/L). We identified 117 differentially expressed genes after treatment with LPS; 102 and 97 differentially expressed genes after treatment, respectively, with the PPARβ/δ agonist at a concentration of 1 μmol/L or 10 μmol/L, as well as 88 after the treatment with the PPARβ/δ antagonist. In addition, biochemical analyses of oxidative status were performed (total antioxidant capacity and activity of peroxidase, catalase, superoxide dismutase, and glutathione S-transferase). This study revealed that PPARβ/δ agonists regulate genes involved in the inflammatory response in a dose-dependent manner. The results indicate that the lower dose of GW0724 showed an anti-inflammatory character, while the higher dose seems to be pro-inflammatory. We propose that GW0724 should be considered for further research to alleviate chronic inflammation (at the lower dose) or to support the natural immune response against pathogens (at the higher dose) in the inflamed corpus luteum.