Mouse blastocysts release a lipid which activates anandamide hydrolase in intact uterus

Abstract

Anandamide (N-arachidonoylethanolamine, AEA) is a major endocannabinoid, known to impair mouse pregnancy and embryo development and to induce apoptosis in blastocysts. Here we show that mouse blastocysts rapidly (within 30 min of culture) release a soluble compound, that increases by approximately 2.5-fold the activity of AEA hydrolase (fatty acid amide hydrolase, FAAH) present in the mouse uterus, without affecting FAAH gene expression at the translational level. This "FAAH activator" was produced by both trophoblast and inner cell mass cells, and its initial biochemical characterization showed that it was fully neutralized by adding lipase to the blastocyst-conditioned medium (BCM), and was potentiated by adding trypsin to BCM. Other proteases, phospholipases A(2), C or D, DNAse I or RNAse A were ineffective. BCM did not affect the AEA-synthesizing phospholipase D, the AEA-binding cannabinoid receptors, or the selective AEA membrane transporter in mouse uterus. The FAAH activator was absent in uterine fluid from pregnant mice and could not be identified with any factor known to be released by blastocysts. In fact, platelet-activating factor inhibited non-competitively FAAH in mouse uterus extracts, but not in intact uterine horns, whereas leukotriene B(4) or prostaglandins E(2) and F(2)alpha had no effect. Overall, it can be suggested that blastocysts may protect themselves against the noxious effects of uterine endocannabinoids by locally releasing a lipid able to cross the cell membranes and to activate FAAH. The precise molecular identity of this activator, the first ever reported for FAAH, remains to be elucidated.

Endocannabinoid Signaling Directs Periimplantation Events

“…32 There is also evidence that blastocysts can upregulate uterine FAAH activity by releasing a lipid " FAAH activator. " 39 These observations suggest a potential role of the implanting embryo in regulating uterine AEA levels, perhaps to serve as a protective mechanism against exposure to detrimental levels of AEA. This is further confi rmed by the observation of higher FAAH expression and activity in the implanting embryo.…”

Endocannabinoid Signaling in Female Reproduction

“…36 In agreement with this result, higher levels of Nape-pld mRNA and NAPE-PLD activity was found in nonreceptive uteri, whereas higher levels of FAAH were observed in the receptive uteri. 45,54 AEA levels are also critical in preparing embryos for implantation. High levels of AEA or other synthetic cannabinoids inhibited blastocyst zona-hatching, while low levels of AEA accelerated trophoblast differentiation and outgrowth in culture.…”

Aspects of endocannabinoid signaling in periimplantation biology

“…Higher FAAH expression and activity are observed at implantation sites and in the receptive uteri. Evidence points toward the possibility that the implanting blastocyst exerts an inhibitory effect on uterine Nape-pld expression, and upregulates uterine FAAH activity by releasing a lipid "FAAH activator" [70,86]. These observations suggest a potential role of the implanting embryo in regulating uterine AEA levels, perhaps to serve as a protective mechanism against exposure to detrimental levels of AEA.…”