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

Immunomodulatory dynamics in the porcine myometrium: global transcriptome analysis, including the effects of PPARγ ligands

BACKGROUND

The myometrium is involved in many processes during pregnancy and the estrous/menstrual cycle. Peroxisome proliferator-activated receptors (PPARs) can be regulators of the processes occurring in the myometrium. In the present study, we determined the global transcriptome profile of the porcine myometrium during the peri-implantation period and the late luteal phase of the estrous cycle. In addition, we investigated for the first time the influence of PPARγ ligands on the transcriptome profile.

RESULTS

The myometrium of gilts (n = 3) was collected on days 10-11 and 14-15 of pregnancy and on the corresponding days of the estrous cycle. The expression of PPARγ was confirmed in the tissue. Based on the mRNA level, further studies were conducted on myometrial explants obtained from pigs at days 14-15 of pregnancy and the corresponding days of the estrous cycle. The tissue sections were incubated in vitro for 6 h in the presence of a PPARγ agonist, pioglitazone (P; 10 µM), or antagonist, T0070907 (T; 1 µM). To identify the transcription profile of the myometrium, RNA-Seq was performed on the NovaSeq 6000 Illumina platform. This study identified 1082 differentially expressed genes (DEGs; 609 upregulated and 473 downregulated) in the porcine myometrium on days 14-15 of pregnancy compared with the corresponding days of the estrous cycle. During pregnancy, we detected 6 and 80 DEGs related to PPARγ agonist and antagonist, respectively. During the estrous cycle, we identified 4 and 17 DEGs for P and T vs. the control, respectively.

CONCLUSIONS

The results indicate that the DEGs are involved in a number of processes, including the immune response, prostaglandin synthesis, cell differentiation and communication. In addition, the role of PPARγ activity in regulating the expression of genes related to the immune response and hormone synthesis in the porcine myometrium has been demonstrated.

PPARα activator irbesartan suppresses the proliferation of endometrial carcinoma cells via SREBP1 and ARID1A

Endometrial carcinoma (EMC) is associated with obesity; however, the underlying mechanisms have not yet been elucidated. Peroxisome proliferator-activated receptor alpha (PPARα) is a nuclear receptor that is involved in lipid, glucose, and energy metabolism. PPARα reportedly functions as a tumor suppressor through its effects on lipid metabolism; however, the involvement of PPARα in the development of EMC remains unclear. The present study demonstrated that the immunohistochemical expression of nuclear PPARα was lower in EMC than in normal endometrial tissues, suggesting the tumor suppressive nature of PPARα. A treatment with the PPARα activator, irbesartan, inhibited the EMC cell lines, Ishikawa and HEC1A, by down-regulating sterol regulatory element-binding protein 1 (SREBP1) and fatty acid synthase (FAS) and up-regulating the tumor suppressor genes p21 and p27, antioxidant enzymes, and AT-rich interaction domain 1A (ARID1A). These results indicate the potential of the activation of PPARα as a novel therapeutic approach against EMC.

Role of inflammatory factors in the etiology and treatment of recurrent implantation failure

Recurrent implantation failure (RIF) is characterized by the absence of implantation after high-grade embryos are transferred to the endometrium by at least three in vitro fertilization cycles. It is one of the most important factors contributing to reproductive failure. After numerous barriers have been overcome to obtain good-quality embryos, RIF causes extreme distress and frustration in women and couples. In recent years, significant progress has been made in understanding how inflammatory factors, which include pro-inflammatory factors, anti-inflammatory factors, chemokines, and other molecules, contribute to RIF. Immunological abnormalities, hypercoagulability, and reproductive diseases are considered potential causes of RIF. In alloimmune disorders, inflammatory factors can affect the success rate of embryo implantation by altering T helper (Th)1/Th2 and Th17/regulatory T cell ratios and causing imbalances of uterine natural killer cells and macrophages. Autoimmune disorders can also lead to RIF. Inflammatory factors also play key roles in RIF-related disorders such as hypercoagulability, chronic endometritis, adenomyosis, hydrosalpinx, and endometriosis. This review focuses on the roles of inflammatory factors in RIF, including immune factors, blood hypercoagulable states, and reproductive diseases such as chronic endometritis, adenomyosis, hydrosalpinx, and endometriosis. It also summarizes the different treatments according to the causes of RIF and discusses the efficacy of sirolimus, peripheral blood mononuclear cells, low-dose aspirin combined with low-molecular-weight heparin, blocking interleukin-22, and gonadotropin-releasing hormone agonists in the treatment of RIF.

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.