Dual effect of anandamide on rat placenta nitric oxide synthesis.

Anandamide (AEA) has been reported to have pleiotropic effects on reproduction, but the mechanism by which it exerts these effects is unclear. The aim of this study is to characterize rat placental endocannabinoid system and to analyze the possible functional role of AEA in the regulation of NO levels in rat placenta during pregnancy. We found that cannabinoids receptors (CB1 and CB2), FAAH and TRPV1 were expressed in chorio-allantoic placenta. NOS activity peaked at day 13 and decreased with progression of pregnancy. Both exogenous and endogenous AEA significantly decreased NOS activity. Although pre-incubation with AM251 (CB1 antagonist) or AM630 (CB2 antagonist) had no effect, co-incubation with both antagonists induced NOS activity. Furthermore, pre-incubation with exogenous AEA and both antagonists resulted in the induction of placental NOS activity and this effect was reverted with capsazepine (selective TRPV1 antagonist). Additionally, the enhanced NO synthesis caused by capsaicin was abrogated by co-treatment with capsazepine, illustrating that NOS activity could be modulated by TRPV1. Finally, the inhibition of TRPV1 receptor by capsazepine caused a significant fall in NOS activity. These data support the concept that AEA modulates NO levels by two independent pathways: (1) diminishing the NOS activity via CBs; and (2) stimulating NO synthesis via TRPV1. We hypothesized that AEA have an important implication in the normal function of placental tissues.

Nitric oxide (NO) inhibits prostaglandin E2 9-ketoreductase (9-KPR) activity in human fetal membranes.

Nitric oxide (NO) synthesized by fetal membranes may act either directly inhibiting myometrium contractility or indirectly interacting with tocolytic agents as prostaglandins (PGs). Here we examined if NO could modulate prostaglandin E(2) 9-ketoreductase (9-KPR) activity in human fetal membranes (HFM). 9-KPR is the enzyme that converts PGE(2) into PGF(2alpha), the main PGs known to induce uterine contractility at term. Chorioamnion explants obtained from elective caesareans were incubated with aminoguanidine (AG), an iNOS inhibitor, or NOC-18, a NO donor. NOC-18 (2mM) increased PGE(2) production and diminished PGF(2alpha) synthesis in HFM. AG presented the opposite effect. When we evaluated the activity of 9-KPR by the conversion of [(3)H]-PGE(2) into [(3)H]-PGF(2alpha) and 13,14-dihidro-15-keto prostaglandin F(2alpha) (the PGF(2alpha) metabolite), we found that NOC-18 inhibited 9-KPR activity. Interestingly, AG did not elicit any effect on 9-KPR but l-NAME, a non-selective NOS inhibitor, significantly increased its activity. Our data suggests that exogenous NO inhibits 9-KPR activity in HFM, thus modulating the synthesis of important labor mediators as PGF(2alpha).

Lysophosphatidic acid increases the production of pivotal mediators of decidualization and vascularization in the rat uterus.

INTRODUCTION: The decidual reaction and the formation of new vessels in the uterus are two crucial processes during embryo implantation. Previously, we observed that lysophosphatidic acid (LPA) increases cyclooxygenase-2 derived - prostaglandin E2 production during implantation in the rat uterus and that it augments the expression of decidualization (IGFBP-1) and vascularization (IL-10) markers. Both cyclooxygenase and nitric oxide synthase (NOS) are known enzymes involved in these processes. Thus, we became interested in studying which factors contribute to LPA receptor-specific role during the decidual and the vascular reaction at implantation. METHODS: We adopted a pharmacological approach in vitro incubating the uterus from rats on day 5 of gestation (day of implantation) with LPA, DGPP (a highly selective antagonist of LPA3, an LPA receptor) and cyclooxygenase and NOS selective and non-selective inhibitors. We determined NOS activity, prostaglandin E2 production and IGFBP-1 and IL-10 expression to evaluate decidualization and vascularization. RESULTS: We observed that LPA augmented the activity of the inducible NOS isoform through LPA1/LPA3. Inducible NOS activity participated in the induction of cyclooxygenase-2/prostaglandin E2 increase stimulated by LPA. Also, cyclooxygenase-2 derived prostaglandins mediated LPA-stimulatory action on NOS activity. Both cyclooxygenase-2 and inducible NOS mediated LPA effect on IGFBP-1 and IL-10 expression. CONCLUSIONS: These results suggest the participation of LPA/LPA3 in the production of crucial molecules involved in vascularization and decidualization, two main processes that prepare the uterine milieu for embryo invasion during implantation.