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

Quanxi Li,Yong-Pil Cheon,Athilaxmi Kannan,Sreenath Shanker,Indrani C Bagchi,Milan K Bagchi

doi:10.1074/jbc.m311773200

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 transcripts encoding leukocyte-12/15-LOX (L-12/15-LOX) and epidermal-12/15-LOX (E-12/15-LOX) are indeed downstream targets of regulation by PR in the uterine surface epithelium. Maximal induction of both L- and E-12/15-LOX on the day of implantation resulted in a marked increase in the uterine levels of the eicosanoids, 12-HETE, 15-HETE, and 13-HODE. Mice with null mutation in L-12/15-LOX had significantly reduced uterine levels of arachidonic acid metabolites and exhibited a partial impairment in implantation. Complete blockade of uterine 12/15-LOX activity by a specific inhibitor led to greater than 80% reduction in a number of implantation sites relative to untreated controls. Cell-based assays indicated that 12-HETE, 15-HETE, and 13-HODE function as activating ligands of peroxisome proliferator-activated receptor gamma (PPARgamma), suggesting that this nuclear receptor could be a downstream target of 12/15-LOX-derived metabolites in the preimplantation uterus. Consistent with this hypothesis, administration of rosiglitazone, a potent PPARgamma-selective agonist, efficiently reversed inhibition of implantation by the 12/15-LOX-specific inhibitor. Rosiglitazone also induced a number of potential target genes of 12/15-LOX-derived metabolites in the pregnant uterus, indicating their regulation by PPARgamma. Collectively, our results uncovered a novel signaling pathway in which progesterone-induced synthesis of the 12/15-LOX-derived lipid mediators activates PPARgamma and its downstream gene networks, which in turn function as critical regulators of implantation in the mouse.

Highlights

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 [1,2,3,4,5]
Cell-based assays indicated that 12-hydroxyeicosatetraenoic acids (HETEs), 15-HETE, and 13-hydroxyoctadecadienoic acids (HODEs) function as activating ligands of peroxisome proliferator-activated receptor ␥ (PPAR␥), suggesting that this nuclear receptor could be a downstream target of 12/15LOX-derived metabolites in the preimplantation uterus
P Acting via progesterone receptor (PR) Regulates Uterine Expression of L- and E-12/15-LOX mRNAs—By using DNA microarray analysis, we previously identified L- and E-12/15-LOX as potential targets of P regulation in the pregnant uterus [9]

Summary

Introduction

The steroid hormones progesterone (P) and estrogen (E) play crucial roles during early pregnancy by coordinating a complex series of interactions between the implanting blastocyst and the uterus [1,2,3,4,5]. 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. Whereas the platelet-type predominantly produces 12-HETE from arachidonic acid, the leukocyte and epidermal types show dual specificity as they generate significant amounts of both 12- and 15-HETE metabolites and are referred to as 12/15-LOX [18]. We analyzed the roles played by the fatty acid metabolites generated by progesterone-induced 12/15-LOX enzymes in controlling uterine function during implantation. Our studies revealed a functional link between steroid hormone action in the preimplantation uterus and the downstream events such as eicosanoid biosynthesis and activation of PPAR␥-dependent gene networks that regulate implantation

Methods

Results

Conclusion