Participation of LPA3 receptor during blastocyst implantation in the rat. Interaction with prostaglandins and the endocannabinoid system

SORDELLI MS; BELTRAME JS; CELLA M; FRANCHI AM; RIBEIRO ML

Hamburgo

Congreso; International Congress of the American Society for Reproductive Immunology (ASRI) & the European Society for Reproductive Immunology (ESRI); 2012

ASRI/ESRI

Implantation involves a complex discourse between the embryo and uterus and is a gateway to successful pregnancy. It has been described that at the site of embryo implantation there is a removal and turn-over of lipid mediators from the plasma membrane that is interpreted as the generation of bioactive molecules that regulate neovascularization and decidualization, two main processes at the time of embryo implantation. The aim of the present work was to study the participation of lysophosphatidic acid (LPA) and its receptor LPA3 during implantation and its relation with two other groups of lipid molecules: prostaglandins and endocannabinoids (ECS). Emerging evidence points toward the pathophysiological significance of ECS in embryo-uterine cross-talk during implantation. The incubation of the uterus obtained from pregnant rats on day 5 of gestation (implantation window) with LPA 50 μM for 6 h augments the expression (p<0.01, western blot and RT-PCR) and the activity (p<0.05, radioconversion) of FAAH, the main enzyme that regulates the protective and/or toxic ECS levels during implantation. Also we observed that LPA increases the production of prostaglandin E2 (p<0.001, radioimmunoassay) and the expression of cyclooxigenase-2 mRNA (p<0.01, RT-PCR) and protein (p<0.01, western blot). Cyclooxigenase-2 is one of the cyclooxigenase isoforms involved in prostaglandins´ synthesis. Prostaglandins play a crucial role in the generation of new vessels and the development of the decidua at the site of implantation. In this sense, incubation with LPA stimulates the expression of IGFBP-1 mRNA (p<0.001, RT-PCR), a marker of decidualization. We observed that the incubation of LPA together with DGPP, a selective LPA3 antagonist, reverts the effect of LPA on the expression and activity of FAAH enzyme, prostaglandins production and COX-2 and IGFBP-1 expression, suggesting that LPA3 is involved in LPA effect at the time of implantation. Serum levels and utero-placental levels of the anti-inflammatory cytokine IL-10 increase significantly during pregnancy and are related to neovascularization. Otherwise, monocytes as well as pro-inflammatory cytokines as IL-1β, play a role in a localized inflammatory response during the initiation of blastocyst implantation. We studied if the incubation with LPA 50 μM for 6 h regulates IL-10 and IL-1β, a marker of monocytes and macrophages. LPA does not affect the expression of IL-1β and IL-10 mRNA.   Finally, we studied the role of LPA during blastocyst implantation in an in vivo model. When we injected an LPA3 antagonist (DGPP: 0.08 mg/kg, intra-uterine) we observed aberrant embryo spacing and the induction of embryo resorption (70,0 ±  5,0 %). These events are accompanied by a reduction in the weight of the fetal placental units (p<0.001) and anomalies in the architecture of the placentas. In the placentas obtained from the resorpted sites we observed an increase in erythrocyte extravasation, neutrophils infiltration and some placental cells with signs of apoptosis. Overall, these results suggest the participation of LPA3 in the process of implantation and decidualization and its interaction with prostaglandins and the ECS system at the implantation window.