Endocannabinoid System and Nitric Oxide are Involved in the Deleterious Effects of Lipopolysaccharide on Murine Decidua

Emerging Roles of Endocannabinoids as Key Lipid Mediators for a Successful Pregnancy

In recent years, Cannabis use/misuse for treating pregnancy-related symptoms and other chronic conditions has increased among pregnant women, favored by decriminalization and/or legalization of its recreational uses in addition to its easy accessibility. However, there is evidence that prenatal Cannabis exposure might have adverse consequences on pregnancy progression and a deleterious impact on proper neurodevelopmental trajectories in the offspring. Maternal Cannabis use could interfere with the complex and finely controlled role performed by the endocannabinoid system in reproductive physiology, impairing multiple gestational processes from blastocyst implantation to parturition, with long-lasting intergenerational effects. In this review, we discuss current clinical and preclinical evidence regarding the role of endocannabinoids in development, function, and immunity of the maternal–fetal interface, focusing on the impact of Cannabis constituents on each of these gestational processes. We also discuss the intrinsic limitations of the available studies and the future perspectives in this challenging research field.

Nitric oxide positively affects endometrial receptivity via FAAH and NAPE-PLD in vitro

Objective

To determine if models of human 'receptive' and 'non-receptive endometrium' differ in their responses to nitric oxide (NO) supplementation by measuring the levels of the enzymes of the endocannabinoid system (ECS) (fatty acid amide hydrolase (FAAH) and N-acylphosphatidylethanolamine-specific phospholipase D (NAPE-PLD)), which control the 'anandamide tone' essential for successful pregnancy.

Design

A study of FAAH and NAPE-PLD expression (using human endometrium) through the menstrual cycle and an in vitro using a model of 'receptive' (Ishikawa) and 'non-receptive' (HEC-1A) human endometrial cell lines treated with the NO-donating compound S-nitroso-N-acetylpenicillamine (SNAP).

Results

Immunoreactivity measured by optimised H-score for both FAAH and NAPE-PLD was reduced in secretory (receptive) endometrium compared to proliferative (non-receptive) endometrium (P = 0.0009 and <0.0001, respectively). FAAH and NAPE transcript levels were significantly higher in untreated Ishikawa cells than in HEC-1A cells (P = 0.0228 and 0.0001, respectively). Treatment of cultures with SNAP resulted in an increase in the amount of FAAH mRNA produced by Ishikawa cells and a decrease in NAPE-PLD mRNA. No effect of SNAP was observed in HEC-1A cells. Similarly, FAAH protein was significantly decreased in endometria representative of the receptive endometrium.

Conclusion

These data suggest that NO most likely affects the expression of ECS enzymes in the implantation site of a receptive endometrium; a phenomenon not seen in a non-receptive endometrium. These effects are most marked with FAAH expression, suggesting that FAAH may play the more critical role in ensuring the correct 'anandamide tone' for successful embryo implantation than NAPE-PLD.

Lay summary

Embryo implantation into the wall of the uterus is only successful when the inner wall of the uterus (the endometrium) is 'receptive', because if it is 'non-receptive', implantation will fail. Previous work showed that enzymes of the 'endocannabinoid system' are critical for implantation by maintaining the correct level of a fat called anandamide. This is by balancing its synthesis (by N-acylphosphatidylethanolamine specific phospholipase D, NAPE-PLD) and degradation (by fatty acid amide hydrolase, FAAH). Using immortalised cell lines as models of 'receptive' and 'non-receptive' human endometrium, we demonstrate a key stimulator of implantation, nitric oxide, has a positive effect on implantation by both increasing the mRNA levels of the degrading enzyme (FAAH) and decreasing the expression of the synthesising enzyme (NAPE-PLD). These effects are most marked with the degrading enzyme, suggesting that FAAH plays a more critical role than NAPE-PLD in ensuring the correct 'anandamide tone' for successful embryo implantation.

Maternal obesity reverses the resistance to LPS-induced adverse pregnancy outcome and increases female offspring metabolic alterations in cannabinoid receptor 1 knockout mice

Maternal overnutrition negatively impacts the offspring's health leading to an increased risk of developing chronic diseases or metabolic syndrome in adulthood. What we eat affects the endocannabinoid system (eCS) activity, which in turn modulates lipogenesis and fatty acids utilization in hepatic, muscle, and adipose tissues. This study aimed to evaluate the transgenerational effect of maternal obesity on cannabinoid receptor 1 knock-out (CB1 KO) animals in combination with a postnatal obesogenic diet on the development of metabolic disturbances on their offspring. CB1 KO mice were fed a control diet (CD) or a high-fat diet (HFD; 33% more energy from fat) for 3 months. Offspring born to control and obese mothers were also fed with CD or HFD. We observed that pups born to an HFD-fed mother presented higher postnatal weight, lower hepatic fatty acid amide hydrolase activity, and increased blood cholesterol levels when compared to the offspring born to CD-fed mothers. When female mice born to HFD-fed CB1 KO mothers were exposed to an HFD, they gained more weight, presented elevated blood cholesterol levels, and more abdominal adipose tissue accumulation than control-fed adult offspring. The eCS is involved in several reproductive physiological processes. Interestingly, we showed that CB1 KO mice in gestational day 15 presented resistance to LPS-induced deleterious effects on pregnancy outcome, which was overcome when these mice were obese. Our results suggest that an HFD in CB1 receptor-deficient mice contributes to a "nutritional programming" of the offspring resulting in increased susceptibility to metabolic challenges both perinatally and during adulthood.

Marijuana smoking and outcomes of infertility treatment with assisted reproductive technologies

STUDY QUESTION

What is the association of female and male partner marijuana smoking with infertility treatment outcomes with ART?

SUMMARY ANSWER

Women who were marijuana smokers at enrollment had a significantly higher adjusted probability of pregnancy loss during infertility treatment with ART whereas, unexpectedly, there was a suggestion of more favorable treatment outcomes in couples where the man was a marijuana smoker at enrollment.

WHAT IS KNOWN ALREADY

Data on the relation of female and male partner marijuana use with outcomes of infertility treatment is scarce despite increased use and legalization worldwide.

STUDY DESIGN, SIZE, DURATION

We followed 421 women who underwent 730 ART cycles while participating in a prospective cohort (the Environment and Reproductive Health Study) at a fertility center between 2004 and 2017. Among them, 200 women (368 cycles) were part of a couple in which their male partner also enrolled in the study.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Participants self-reported marijuana smoking at baseline. Clinical endpoints were abstracted from electronic medical records. We used generalized linear mixed models with empirical standard errors to evaluate the association of baseline marijuana smoking with ART outcomes adjusting for participants' age, race, BMI, tobacco smoking, coffee and alcohol consumption, and cocaine use. We estimated the adjusted probability of implantation, clinical pregnancy, and live birth per ART cycle, as well as the probability of pregnancy loss among those with a positive B-hCG.

MAIN RESULTS AND THE ROLE OF CHANCE

The 44% of the women and 61% of the men had ever smoked marijuana; 3% and 12% were marijuana smokers at enrollment, respectively. Among 317 women (395 cycles) with a positive B-hCG, those who were marijuana smokers at enrollment (N = 9, cycles = 16) had more than double the adjusted probability of pregnancy loss than those who were past marijuana smokers or had never smoked marijuana (N = 308, 379 cycles) (54% vs 26%; P = 0.0003). This estimate was based on sparse data. However, couples in which the male partner was a marijuana smoker at enrollment (N = 23, 41 cycles) had a significantly higher adjusted probability of live birth than couples in which the male partner was a past marijuana smoker or had never smoked marijuana (N= 177, 327 cycles) (48% vs 29%; P = 0.04), independently of the women's marijuana smoking status. Treatment outcomes of past marijuana smokers, male and female, did not differ significantly from those who had never smoked marijuana.

LIMITATIONS, REASONS FOR CAUTION

Marijuana smoking was self-reported with possible exposure misclassification. Chance findings cannot be excluded due to the small number of exposed cases. The results may not be generalizable to couples from the general population.

WIDER IMPLICATIONS OF THE FINDINGS

Even though marijuana smoking has not been found in past studies to impact the ability to become pregnant among pregnancy planners in the general population, it may increase the risk of pregnancy loss among couples undergoing infertility treatment. Marijuana smoking by females and males may have opposing effects on outcomes of infertility treatment with ART.

STUDY FUNDING/COMPETING INTEREST(S)

The project was financed by grants R01ES009718, P30ES000002, and K99ES026648 from the National Institute of Environmental Health Sciences (NIEHS). None of the authors has any conflicts of interest to declare.

Targeting of G-protein coupled receptors in sepsis

The Third International Consensus Definitions (Sepsis-3) define sepsis as life-threatening multi-organ dysfunction caused by a dysregulated host response to infection. Sepsis can progress to septic shock-an even more lethal condition associated with profound circulatory, cellular and metabolic abnormalities. Septic shock remains a leading cause of death in intensive care units and carries a mortality of almost 25%. Despite significant advances in our understanding of the pathobiology of sepsis, therapeutic interventions have not translated into tangible differences in the overall outcome for patients. Clinical trials of antagonists of various pro-inflammatory mediators in sepsis have been largely unsuccessful in the past. Given the diverse physiologic roles played by G-protein coupled receptors (GPCR), modulation of GPCR signaling for the treatment of sepsis has also been explored. Traditional pharmacologic approaches have mainly focused on ligands targeting the extracellular domains of GPCR. However, novel techniques aimed at modulating GPCR intracellularly through aptamers, pepducins and intrabodies have opened a fresh avenue of therapeutic possibilities. In this review, we summarize the diverse roles played by various subfamilies of GPCR in the pathogenesis of sepsis and identify potential targets for pharmacotherapy through these novel approaches.

Nitric oxide metabolism in the human placenta during aberrant maternal inflammation

KEY POINTS

Nitric oxide (NO) is a gasotransmitter with important physiological and pathophysiological roles in pregnancy. There is limited information available about the sources and metabolism of NO and its bioactive metabolites (NOx) in both normal and complicated pregnancies. The present study characterized and quantified endogenous NOx in human and mouse placenta following determination of the stability of exogenous NOx in placental homogenates. NOx have differential stability in placental homogenates. NO and iron nitrosyl species (FeNOs), are relatively unstable in placental homogenates from normal placentas. Exogenous NO, nitrite and nitrosothiols react with placental homogenates to form iron nitrosyl complexes. FeNOs were also detected endogenously in mouse and human placenta. NOx levels in placental villous tissue are increased in fetal growth restriction vs. placentas from women with normal pregnancies, particularly in fetal growth restriction associated with pre-eclampsia. Villitis was not associated, however, with an increase in NOx levels in either normotensive or pre-eclamptic placentas. The results call for further investigation of FeNOs in normal and complicated pregnancies.

ABSTRACT

Nitric oxide (NO) is a gasotransmitter with important roles in pregnancy under both physiological and pathophysiological conditions. Although products of NO metabolism (NOx) also have significant bioactivity, little is known about the role of NO and NOx under conditions of aberrant placental inflammation during pregnancy. An ozone-based chemiluminescence approach was used to investigate the stability and metabolic fate of NOx in human placental homogenates from uncomplicated pregnancies in healthy mothers compared to that in placental tissue from normotensive and pre-eclamptic pregnancies complicated with fetal growth restriction (FGR) with and without villitis of unknown aetiology. We hypothesized that placental NOx would be increased in FGR vs. normal tissue, and be further increased in villitis vs. non-villitis placentas. Findings indicate that nitrate, nitrite and nitrosothiols, but not NO or iron nitrosyl species (FeNOs), are relatively stable in placental homogenates from normal placentas, and that NO, nitrite and nitrosothiols react with placental homogenates to form iron nitrosyl complexes. Furthermore, NOx levels in placental villous tissue are increased in FGR vs. placentas from women with normal pregnancies, particularly in FGR associated with pre-eclampsia. However, in contrast to our hypothesis, villitis was not associated with an increase in NOx levels in either normotensive or pre-eclamptic placentas. Our results also strongly support the involvement of FeNOs in both mouse and human placenta, and call for their further study as a critical mechanistic link between pre-eclampsia and fetal growth restriction.

Crosstalk Between Nitric Oxide and Endocannabinoid Signaling Pathways in Normal and Pathological Placentation

Endocannabinoids are a group of endogenous lipid mediators that act as ligands of cannabinoid and vanilloid receptors, activating multiple signal transduction pathways. Together with enzymes responsible for their synthesis and degradation, these compounds constitute the endocannabinoid system (ECS), which is involved in different physiological processes in reproduction. The placenta, which is essential for the success of gestation and optimal fetal growth, undergoes constant tissue remodeling. ECS members are expressed in trophoblast cells, and current evidence suggests that this system is involved in placental development, apoptosis, and syncytialization. Impairment of endocannabinoid signaling has been associated with several pathological conditions such as intrauterine growth restriction and preeclampsia. Both clinical entities are characterized by dysregulation on vascular perfusion where nitrergic system performs a pivotal role. Nitric oxide (NO) is a potent local vasodepressor that exerts a critical role in the regulation of hemodynamic flow, contributing to the maintenance of low vascular resistance in the feto-placental circulation. NO production could be affected by different factors and growing evidence suggests that the endocannabinoid mediators may regulate nitrergic signaling. Herein, we review emerging knowledge supporting ECS-mediated regulation of NO production in normal placentation. Finally, we discuss how alterations in these systems could affect homoeostasis and contribute to the occurrence of placental-mediated pregnancy complications. Given the impact on women and perinatal heath, we will focus on current knowledge regarding the effects of ECS on nitrergic system in normal and pathological placentation.

Evidence for CB2 receptor involvement in LPS-induced reduction of cAMP intracellular levels in uterine explants from pregnant mice: pathophysiological implications

STUDY QUESTION

What is the role of the endocannabinoid system (eCS) on the lipopolysaccharide (LPS) effects on uterine explants from 7-day pregnant mice in a murine model of endotoxin-induced miscarriage?

SUMMARY ANSWER

We found evidence for cannabinoid receptor type2 (CB2) involvement in LPS-induced increased prostaglandin-F2α (PGF2α) synthesis and diminished cyclic adenosine monophosphate (cAMP) intracellular content in uterine explants from early pregnant mice.

WHAT IS KNOWN ALREADY

Genital tract infections by Gram-negative bacteria are a common complication of human pregnancy that results in an increased risk of pregnancy loss. LPS, the main component of the Gram-negative bacterial wall, elicits a strong maternal inflammatory response that results in embryotoxicity and embryo resorption in a murine model endotoxin-induced early pregnancy loss. We have previously shown that the eCS mediates the embryotoxic effects of LPS, mainly via CB1 receptor activation.

STUDY DESIGN, SIZE, DURATION

An in vitro study of mice uterine explants was performed to investigate the eCS in mediating the effects of LPS on PGF2α production and cAMP intracellular content.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Eight to 12-week-old virgin female BALB/c or CD1 (wild-type [WT] or CB1-knockout [CB1-KO]) mice were paired with 8- to 12-week-old BALB/c or CD1 (WT or CB1-KO) males, respectively. On day 7 of pregnancy, BALB/c, CD1 WT or CD1 CB1-KO mice were euthanized, the uteri were excised, implantation sites were removed and the uterine tissues were separated from decidual and embryo tissues. Uterine explants were cultured and exposed for an appropriate amount of time to different pharmacological treatments. The tissues were then collected for cAMP assay and PGF2α content determination by radioimmunoassay.

MAIN RESULTS AND THE ROLE OF CHANCE

In vitro treatment of uteri explants from 7-day pregnant BALB/c or CD1 (WT or CB1-KO) mice with LPS induced an increased production of PGF2α (P < 0.05) and a reduction of the tissue content of cAMP (P < 0.05). These effects were mediated by CB2 receptors since exposure to AM630 (a specific CB2 receptor antagonist) prevented these LPS-induced effects (P < 0.05). Collectively, our results suggest a role for the eCS mediating LPS-induced deleterious effects on reproductive tissues.

LIMITATIONS, REASONS FOR CAUTION

Since our experimental design involves in vitro experiments of uterine explants, the extrapolation of the results presented here to humans is limited.

WIDER IMPLICATIONS OF THE FINDINGS

Our findings provide evidence for the role of CB2 receptors in reproductive events as well as their participation as a mediator of LPS deleterious effects on reproductive tissues.

LARGE SCALE DATA

None.

STUDY FUNDING AND COMPETING INTEREST(S)

Dr Ana María Franchi was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2010/0813 and PICT 2013/0097) and by Consejo Nacional de Investigaciones Científicas y Técnicas (PIP 2012/0061). Dr Carlos Davio was funded by Agencia Nacional para la Promoción Científica y Tecnológica (PICT 2013/2050). The authors have no competing interests.

Endocannabinoid system and pregnancy

The endocannabinoid system (eCS), is a complex system, comprising the main endogenous ligands anandamide and 2-arachidonoyl glycerol, the cannabinoid receptors CB1 and CB2 and the biosynthetic and degrading enzymes. Cumulative evidence shows that the eCS plays an important role in reproduction, from egg fertilization to parturition. Therefore, alterations in this system, either by recreation/therapeutic use of cannabis or deregulation of the endogenous cannabinoids, might lead to adverse pregnancy outcomes, including retardation in embryo development, poor blastocyst implantation, inhibition of decidualization, miscarriage and compromised placentation. Nevertheless, the molecular mechanisms by which the eCS participates in different stages of pregnancy remain poorly understood. In this review, we will examine the evidence from animal and human studies to support the role of the eCS in implantation, early-to-late pregnancy and placentation as well as the difficulties of targeting this system for treatment of female infertility.

Lipopolysaccharide-induced murine embryonic resorption involves changes in endocannabinoid profiling and alters progesterone secretion and inflammatory response by a CB1-mediated fashion

Genital tract infections are a common complication of human pregnancy that can result in miscarriage. We have previously shown that a lipopolysaccharide (LPS) induces embryonic resorption in a murine model of inflammatory miscarriage. This is accompanied by a dramatic decrease in systemic progesterone levels associated with a robust pro-inflammatory response that results in embryo resorption. Here, we tested the hypothesis that the endogenous cannabinoid system (eCS), through cannabinoid receptor 1 (CB1), plays a role in regulating progesterone levels and, therefore, the pro-inflammatory response. We show that LPS treatment in pregnant mice causes significant changes in the eCS ligands, which are reversed by progesterone treatment. We further show the CB1-KO mice maintain higher plasma progesterone levels after LPS treatment, which is associated with a feebler uterine inflammatory response and a significant drop in embryo resorption. These data suggest that manipulation of CB1 receptors and/or ligands is a potential therapeutic avenue to decrease infection-induced miscarriage.

Tim-3 protects decidual stromal cells from toll-like receptor-mediated apoptosis and inflammatory reactions and promotes Th2 bias at the maternal-fetal interface

Toll-like receptors (TLRs) are important in mediating immune responses against various pathogens during pregnancy. However, uncontrolled TLR-triggered inflammation will endanger normal pregnancy, resulting in pregnancy loss. Therefore, maintenance of a moderate inflammatory response is crucial for successful pregnancy under conditions of infection. Here, we demonstrated significantly lowered expression of T-cell immunoglobulin and mucin domain 3 (Tim-3) in miscarried decidual stromal cells (DSCs), indicating that Tim-3 might play important roles in maintaining successful pregnancies. Activation of TLR signaling induced pro-inflammatory cytokine production and apoptosis of DSCs, which was accompanied by up-regulated Tim-3 expression. Tim-3, in turn, protected DSCs from TLR-mediated apoptosis in an ERK1/2 pathway-dependent manner. In addition, Tim-3 inhibited TLR signaling-induced inflammatory cytokine production by DSCs through suppressing NF-κB activation. Tim-3 increased production of T helper 2 (Th2)-type cytokines by DSCs and reversed the inhibitory effect of LPS on Th2 cytokine generation by up-regulation of interferon regulatory factor 4 expression. Tim-3 blockade abolished the effect of Tim-3 on the inflammatory response to LPS stimulation. Thus, Tim-3 signaling could represent a “self-control” mechanism in TLR-triggered inflammation during pregnancy. These findings identify Tim-3 as a key regulator of DSCs and suggest its potential as a target for the treatment of spontaneous abortion.

Contribution of vasoactive intestinal peptide to immune homeostasis in trophoblast-maternal leukocyte interaction under LPS stimulation

BACKGROUND/AIMS

The maternal-fetal interface is a unique immunological site that generates an adequate microenvironment during pregnancy, recognizing and eliminating infections and tolerating the trophoblast/placenta unit. For that purpose, trophoblast cells display several tolerogenic mechanisms to allow fetal survival, such as production of the neuropeptide vasoactive intestinal peptide (VIP). Here we investigated the contribution of VIP to maintain homeostasis at the maternal-placental interface under lipopolysaccharide (LPS) stimulation.

METHODS

We performed cocultures between trophoblast cells (Swan-71 cell line) and maternal leukocytes obtained from fertile women as an in vitro model of maternal-placental interaction, and we focused on the effects of LPS on the modulation of VIP and their receptors (VPAC1 and VPAC2).

RESULTS

VIP could prevent the upregulation of IL-6, MCP-1, and nitrite production and maintain the production of IL-10 and TGF-β under LPS (10 µg/ml) stimulation after 48 h of coculture. To gain deeper insight into the mechanisms of how VIP could contribute to a tolerogenic microenvironment even in the presence of LPS, we investigated VIP production by maternal leukocytes and observed a significant increase in the frequency of CD4+VIP+ cells after interaction with Swan-71 cells in the presence of LPS. LPS increased VIP and inducible receptor VPAC2 expression directly on trophoblast cells in a dose- and time-dependent manner.

CONCLUSIONS

The present results suggest that VIP might act as an additional homeostatic mechanism during early stages at the maternal-placental interface to control exacerbated inflammatory responses such as the ones observed in intrauterine infections.

The Endocannabinoid System in the Postimplantation Period: A Role during Decidualization and Placentation

Although the detrimental effects of cannabis consumption during gestation are known for years, the vast majority of studies established a link between cannabis consumption and foetal development. The complex maternal-foetal interrelationships within the placental bed are essential for normal pregnancy, and decidua definitively contributes to the success of this process. Nevertheless, the molecular signalling network that coordinates strategies for successful decidualization and placentation are not well understood. The discovery of the endocannabinoid system highlighted new signalling mediators in various physiological processes, including reproduction. It is known that endocannabinoids present regulatory functions during blastocyst development, oviductal transport, and implantation. In addition, all the endocannabinoid machinery was found to be expressed in decidual and placental tissues. Additionally, endocannabinoid's plasmatic levels were found to fluctuate during normal gestation and to induce decidual cell death and disturb normal placental development. Moreover, aberrant endocannabinoid signalling during the period of placental development has been associated with pregnancy disorders. It indicates the existence of a possible regulatory role for these molecules during decidualization and placentation processes, which are known to be particularly vulnerable. In this review, the influence of the endocannabinoid system in these critical processes is explored and discussed.

Progesterone-dependent regulation of endometrial cannabinoid receptor type 1 (CB1-R) expression is disrupted in women with endometriosis and in isolated stromal cells exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)

OBJECTIVE

To examine the differentiation-related expression of cannabinoid receptor type 1 (CB1-R) messenger RNA (mRNA) and protein in endometrial tissue obtained from women with and without endometriosis and to determine the impact of acute 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure on CB1-R gene expression in isolated endometrial stromal cells.

DESIGN

Laboratory-based study.

SETTING

University-affiliated medical center.

PATIENT(S)

Women with and without endometriosis undergoing volunteer endometrial biopsies after informed consent.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Analysis of in vivo CB1-R mRNA and protein expression in human endometrial tissues and mRNA expression in isolated stromal cells after exposure to TCDD or a progesterone receptor antagonist (onapristone).

RESULT(S)

Expression of CB1-R mRNA and protein was highest during the progesterone-dominated secretory phase in control samples, but expression was minimal in the endometrial tissues acquired from women with endometriosis, regardless of the cycle phase. Although progesterone was found to induce CB1-R mRNA expression in endometrial stromal cells from control donors, steroid-induced expression of this gene was inhibited by cotreatment with either TCDD or onapristone.

CONCLUSION(S)

Our studies reveal a role for the anti-inflammatory actions of progesterone in regulating endometrial cannabinoid signaling, which is disrupted in women with endometriosis. We demonstrate for the first time that acute TCDD exposure disrupts cannabinoid signaling in the human endometrium.

Opposite effects of methanandamide on lipopolysaccharide-induced prostaglandin E2 and F2α synthesis in uterine explants from pregnant mice

Prostaglandins (PG) are effective abortifacients and are important mediators of lipopolisaccharide (LPS)-induced embryonic resorption (ER). Besides, anandamide (AEA) has been described as one of the major endocannabinoids present in the uterus suggesting that it might play a role in reproduction. It has been reported that high levels of AEA are associated with pregnancy failure and that LPS increases AEA production. Also, it has been observed that AEA modulates PG production in different tissues. In this sense, we studied whether LPS-induced PG production is modulated by AEA and we also assessed the effect of this endocannabinoid on PG metabolism in an in vitro model. Uterine explants from BALB/c implantation sites were cultured in the presence of LPS plus cannabinoid receptor (CB) specific antagonists and PG production was assessed. Then, we studied the effect of exogenous AEA on different steps of PG metabolic pathway. We showed that AEA is involved in LPS-induced PG biosynthesis. Also, we observed that AEA exerts opposite effects on PGE(2) and PGF(2α) biosynthesis, by inhibiting PGE(2) production and increasing PGF(2α) levels. We suggest that AEA could be involved in the mechanisms implicated in LPS-induced ER. A better understanding of how AEA could be affecting ER could help developing specific interventions to prevent this pathology.

The effect of anandamide on uterine nitric oxide synthase activity depends on the presence of the blastocyst

Nitric oxide production, catalyzed by nitric oxide synthase (NOS), should be strictly regulated to allow embryo implantation. Thus, our first aim was to study NOS activity during peri-implantation in the rat uterus. Day 6 inter-implantation sites showed lower NOS activity (0.19±0.01 pmoles L-citrulline mg prot⁻¹ h⁻¹) compared to days 4 (0.34±0.03) and 5 (0.35±0.02) of pregnancy and to day 6 implantation sites (0.33±0.01). This regulation was not observed in pseudopregnancy. Both dormant and active blastocysts maintained NOS activity at similar levels. Anandamide (AEA), an endocannabinoid, binds to cannabinoid receptors type 1 (CB1) and type 2 (CB2), and high concentrations are toxic for implantation and embryo development. Previously, we observed that AEA synthesis presents an inverted pattern compared to NOS activity described here. We adopted a pharmacological approach using AEA, URB-597 (a selective inhibitor of fatty acid amide hydrolase, the enzyme that degrades AEA) and receptor selective antagonists to investigate the effect of AEA on uterine NOS activity in vitro in rat models of implantation. While AEA (0.70±0.02 vs 0.40±0.04) and URB-597 (1.08±0.09 vs 0.83±0.06) inhibited NOS activity in the absence of a blastocyst (pseudopregnancy) through CB2 receptors, AEA did not modulate NOS on day 5 pregnant uterus. Once implantation begins, URB-597 decreased NOS activity on day 6 implantation sites via CB1 receptors (0.25±0.04 vs 0.40±0.05). While a CB1 antagonist augmented NOS activity on day 6 inter-implantation sites (0.17±0.02 vs 0.27±0.02), a CB2 antagonist decreased it (0.17±0.02 vs 0.12±0.01). Finally, we described the expression and localization of cannabinoid receptors during implantation. In conclusion, AEA levels close to and at implantation sites seems to modulate NOS activity and thus nitric oxide production, fundamental for implantation, via cannabinoid receptors. This modulation depends on the presence of the blastocyst. These data establish cannabinoid receptors as an interesting target for the treatment of implantation deficiencies.

Effects of endocannabinoid 1 and 2 (CB1; CB2) receptor agonists on luteal weight, circulating progesterone, luteal mRNA for luteinizing hormone (LH) receptors, and luteal unoccupied and occupied receptors for LH in vivo in ewes

Thirty to forty percent of ruminant pregnancies are lost during the first third of gestation due to inadequate progesterone secretion. During the estrous cycle, luteinizing hormone (LH) regulates progesterone secretion by small luteal cells (SLC). Loss of luteal progesterone secretion during the estrous cycle is increased via uterine secretion of prostaglandin F(2α) (PGF(2α)) starting on days 12-13 post-estrus in ewes with up to 4-6 pulses per day. Prostaglandin F(2α) is synthesized from arachidonic acid, which is released from phospholipids by phospholipase A2. Endocannabinoids are also derived from phospholipids and are associated with infertility. Endocannabinoid-induced infertility has been postulated to occur primarily via negative effects on implantation. Cannabinoid (CB) type 1 (CB1) or type 2 (CB2) receptor agonists and an inhibitor of the enzyme fatty acid amide hydrolase, which catabolizes endocannabinoids, decreased luteal progesterone, prostaglandin E (PGE), and prostaglandin F(2α) (PGF(2α)) secretion by the bovine corpus luteum in vitro by 30 percent. The objective of the experiment described herein was to determine whether CB1 or CB2 receptor agonists given in vivo affect circulating progesterone, luteal weights, luteal mRNA for LH receptors, and luteal occupied and unoccupied LH receptors during the estrous cycle of ewes. Treatments were: Vehicle, Methanandamide (CB1 agonist; METH), or 1-(4-chlorobenzoyl)-5-methoxy-1H-indole-3-acetic acid morpholineamide (CB2 agonist; IMMA). Ewes received randomized treatments on day 10 post-estrus. A single treatment (500 μg; N=5/treatment group) in a volume of 1 ml was given into the interstitial tissue of the ovarian vascular pedicle adjacent to the luteal-containing ovary. Jugular venous blood was collected at 0 h and every 6-48 h for the analysis of progesterone by radioimmunoassay (RIA). Corpora lutea were collected at 48 h, weighed, bisected, and frozen in liquid nitrogen until analysis of unoccupied and occupied LH receptors and mRNA for LH receptors. Profiles of jugular venous progesterone, luteal weights, luteal mRNA for LH receptors, and luteal occupied and unoccupied LH receptors were decreased (P≤0.05) by CB1 or CB2 receptor agonists when compared to Vehicle controls. Progesterone in 80 percent of CB1 or CB2 receptor agonist-treated ewes was decreased (P≤0.05) below 1 ng/ml by 48 h post-treatment. It is concluded that the stimulation of either CB1 or CB2 receptors in vivo affected negatively luteal progesterone secretion by decreasing luteal mRNA for LH receptors and also decreasing occupied and unoccupied receptors for LH on luteal membranes. The corpus luteum may be an important site for endocannabinoids to decrease fertility as well as negatively affect implantation, since progesterone is required for implantation.

Tocolytic effect of delta9-tetrahydrocannabinol in mice model of lipopolysaccharide--induced preterm delivery: role of nitric oxide

INTRODUCTION

In this study, we explained that exogenous cannabinoid, Delta(9)-tetrahydrocannabinol (THC), has a preventive effect in a murine model of lipopolysaccharide (LPS)-induced preterm delivery and the contribution of nitric oxide (NO) pathway as a mechanism involved in this process.

STUDY DESIGN

Preterm delivery was induced by double dose of 35 microg/kg LPS with 3-hour interval on gestational day (gd) 15. Delta(9)-tetrahydrocannabinol was administered with (a) double dose (0.02, 0.05, 0.1, 0.5, 1, and 5 mg/kg) 1 hour before each LPS injection, on gd 15 and (b) single administration (0.05, 0.1, and 0.5 mg/kg,) on gds 13 and 14, and the double administration, 1 hour before each LPS injection. To assess the involved mechanism, either AM281 (CB1 receptor antagonist, 2 mg/kg) and AM630 (CB2 receptor antagonist, 5 mg/kg) or N(omega)-nitro-L-arginine methyl ester (L-NAME, 2 mg/kg) was administered 1 hour before each THC injection on gds 13, 14, and 15. The main outcome measurement was the incidence of preterm delivery after injection of last LPS dose. Any interaction in the incidence and time of preterm delivery was ruled out by administration of AM281, AM630, or L-NAME alone.

RESULTS

Chronic THC treatment (0.5 mg/kg) significantly decreased the incidence of LPS-induced premature labor and increased the delivery time. Both AM281 and L-NAME reversed THC-induced attenuation of preterm delivery rate and pregnancy duration. Unlike AM281, AM630 did not influence the rate of preterm delivery in THC-treated mice.

CONCLUSION

Delta(9)-Tetrahydrocannabinol contributes to the regulation of gestational duration in LPS-induced preterm delivery probably by NO coupling through the CB1 receptor.

Uterine disorders and pregnancy complications: insights from mouse models

Much of our knowledge of human uterine physiology and pathology has been extrapolated from the study of diverse animal models, as there is no ideal system for studying human uterine biology in vitro. Although it remains debatable whether mouse models are the most suitable system for investigating human uterine function(s), gene-manipulated mice are considered by many the most useful tool for mechanistic analysis, and numerous studies have identified many similarities in female reproduction between the two species. This Review brings together information from studies using animal models, in particular mouse models, that shed light on normal and pathologic aspects of uterine biology and pregnancy complications.

Endocannabinoids and pregnancy

Acylethanolamides such as anandamide (AEA), and monoacylglycerols like 2-arachidonoylglycerol are endocannabinoids that bind to cannabinoid, vanilloid and peroxisome proliferator-activated receptors. These compounds, their various receptors, the purported membrane transporter(s), and related enzymes that synthesize and degrade them are collectively referred to as the "endocannabinoid system (ECS)". Poorly defined cellular and molecular mechanisms control the biological actions of the ECS. Over the last decade evidence has been emerging to suggest that the ECS plays a significant role in various aspects of human reproduction. In this review, we summarize our current understanding of this role especially the involvement of AEA and related ECS elements in regulating oogenesis, embryo oviductal transport, blastocyst implantation, placental development and pregnancy outcomes, and sperm survival, motility, capacitation and acrosome reaction. Additionally, the possibility that plasma and tissue AEA and other cannabinoids may represent reliable diagnostic markers of natural and assisted reproduction and pregnancy outcomes in women will be discussed.