A Novel Pathway Involving Progesterone Receptor, 12/15-Lipoxygenase-derived Eicosanoids, and Peroxisome Proliferator-activated Receptor γ Regulates Implantation in Mice

Abstract

The 12/15-lipoxygenases (12/15-LOX) catalyze the stereo-specific oxygenation of arachidonic and linoleic acids into a complex series of signaling molecules, including the hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecadienoic acids (HODEs). Our previous studies, using high density oligonucleotide microarrays, suggested a novel link between progesterone receptor (PR) signaling and 12/15-LOX-mediated fatty acid metabolism in preimplantation mouse uterus. In this paper, using PR knockout mice, we established that The steroid hormones progesterone (P) 1 and estrogen (E) play crucial roles during early pregnancy by coordinating a complex series of interactions between the implanting blastocyst and the uterus (1-5). In mice, implantation is initiated 4 days after fertilization when the blastocyst reaches the uterus (1, 6). It is thought that the action of the steroid hormones during the preimplantation phase prepares the endometrium for the attachment of the blastocyst and the subsequent events leading to the establishment of pregnancy. The cellular effects of P and E are mediated through intracellular progesterone receptor (PR) and estrogen receptor, which are hormone-inducible transcription factors (7,8). Hormone-occupied PR or estrogen receptor triggers the expression of specific gene networks in different cell types within the uterus, and the products of these genes mediate the hormonal effects during implantation. In order to understand the molecular basis of this complex physiological process, it is critical to identify the steroid-regulated pathways that are induced or suppressed at the time of implantation and analyze their functional roles.We recently used RU486, a well characterized antiprogestin, as a tool to uncover the PR signaling pathways in the pregnant uterus (9). RU486 counteracts the action of P by binding directly to PR and impairing its gene regulatory function (10, 11). Administration of RU486 to pregnant rodents during the preimplantation phase effectively blocks implantation by inhibiting PR-dependent gene expression (12). By using oligonucleotide microarrays, we identified several potential PR-regulated genes whose expression was markedly altered by RU486 in the uterus at the time of implantation (9). Interestingly, two of the mRNAs repressed in response to RU486 were leukocyte-12/15-lipoxygenase (L-12/15-LOX) and epidermal-12/15-lipoxygenase (E-12/15-LOX), which belong to a family of polyunsaturated fatty acid-metabolizing enzymes.The lipoxygenases metabolize arachidonic and linoleic acids, which are major cellular substrates in the synthesis of biological mediator substances known as eicosanoids (13, 14). There are three major types of mammalian lipoxygenase activity: 5-LOX, 12-LOX, and 15-LOX. The primary metabolites of arachidonic acid generated by the 5-LOX are the leukotrienes and lipoxines, whereas the 12-and 15-LOX enzymes produce hydroxyeicosatetraenoic acids (HETEs) (15,16). Metabolism of

Inhibitory effect of linoleic acid on transformation of IEC6 intestinal cells by in vitro azoxymethane treatment

“…Several studies have shown that the LOX15-derived lipid metabolites 9-HODE and 13-HODE activate PPARg and its downstream gene networks. 13,29 We could not detect directly these LA metabolites; however, reduction of LAinduced growth inhibition by PPARg antisense S-ODN treatment supports our hypothesis that LA is metabolized to PPARg ligands in COX-2-negative colon epithelial cells.…”

Estrogen-induced Expression of Fos-related Antigen 1 (FRA-1) Regulates Uterine Stromal Differentiation and Remodeling

“…Immunohistochemistry-Polyclonal antibody against FRA-1 was used for immunohistochemistry as described previously (20). Briefly, paraffin-embedded uterine tissue was sectioned at 4 m and mounted on slides.…”

Bone Morphogenetic Protein 2 Functions via a Conserved Signaling Pathway Involving Wnt4 to Regulate Uterine Decidualization in the Mouse and the Human

“…Immunohistochemistry and Immunocytochemistry-Paraffin-embedded endometrial sections were subjected to immunohistochemistry as described previously (36). Polyclonal antibodies against BMP2 and type II BMP receptor were obtained from Santa Cruz Biotechnology, Santa Cruz, CA.…”