Anandamide regulates lipopolysaccharide-induced nitric oxide synthesis and tissue damage in the murine uterus

The marijuana, cannabinoids, and female reproductive system

The marijuana is considered as widely used recreational illicit drug that has become popular among women of reproductive age. It is believed that the marijuana use may have negative impacts on the female fertility. However, the exact mechanisms of its reproductive toxicity remain unclear. The studies suggest that the exogenous cannabinoids may interfere with endocannabinoid system and disrupt hypothalamic-pituitary-ovary axis. Consequently, it impacts the female fertility by disruption of normal secretion of ovarian sex hormones and menstrual cycles. However, other studies have shown that medical marijuana is useful analgesic agent for pain management. But, given that the wide range of cannabinoids side effects are reported, it seems that caution should be taken in the recreational use of these substances. In summary, this article aimed to review the possible impacts of marijuana and its derivatives on the main female reproductive organs and embryonic growth and development.

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.

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.

Impact of Endocannabinoid System Manipulation on Neurodevelopmental Processes Relevant to Schizophrenia

The neurodevelopmental hypothesis of schizophrenia has received much support from epidemiological and neuropathological studies and provides a framework to explain how early developmental abnormalities might manifest as psychosis in early adulthood. According to this theory, the onset of schizophrenia is likely the result of a complex interplay between a genetic predisposition and environmental factors whose respective influence might contribute to the etiology and progression of the disorder. The two most sensitive windows for neurodevelopment are the prenatal/perinatal and the adolescent windows, both of which are characterized by specific processes impinging upon brain structure and functionality, whose alterations may contribute to the onset of schizophrenia. An increasing number of articles suggest the involvement of the endocannabinoid system in the modulation of at least some of these processes, especially in the prenatal/perinatal window. Thus, it is not surprising that disturbing the physiological role of endocannabinoid signaling in these sensitive windows might alter the correct formation of neuronal networks, eventually predisposing to neuropsychiatric diseases later in life. We review the most recent preclinical studies that evaluated the impact of endocannabinoid system modulation in the two sensitive developmental windows on neurodevelopmental processes that possess a specific relevance to schizophrenia.

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.

Heparin exerts anti-apoptotic effects on uterine explants by targeting the endocannabinoid system

Miscarriage caused by Gram-negative bacteria infecting the female genital tract is one of the most common complications of human pregnancy. Intraperitoneal administration of LPS to 7-days pregnant mice induces embryo resorption after 24 h. Here, we show that LPS induced apoptosis on uterine explants from 7-days pregnant mice and that CB1 receptor was involved in this effect. On the other hand, heparin has been widely used for the prevention of pregnancy loss in women with frequent miscarriage with or without thrombophilia. Besides its anticoagulant properties, heparin exerts anti-inflammatory, immunomodulatory and anti-apoptotic effects. Here, we sought to investigate whether the administration of heparin prevented LPS-induced apoptosis in uterine explants from 7-days pregnant mice. We found that heparin enhanced cell survival in LPS-treated uterine explants and that this effect was mediated by increasing uterine FAAH activity. Taken together, our results point towards a novel mechanism involved in the protective effects of heparin.

Protective Action of Anandamide and Its COX-2 Metabolite against l-Homocysteine-Induced NLRP3 Inflammasome Activation and Injury in Podocytes

Recent studies have demonstrated that l-homocysteine (Hcys)-induced podocyte injury leading to glomerular damage or sclerosis is attributable to the activation of the nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome. Given the demonstrated anti-inflammatory effects of endocannabinoids, the present study was designed to test whether anandamide (AEA) or its metabolites diminish NLRP3 inflammasome activation and prevent podocyte injury and associated glomerular damage during hyperhomocysteinemia (hHcys). AEA (100 μM) inhibited Hcys-induced NLRP3 inflammasome activation in cultured podocytes, as indicated by elevated caspase-1 activity and interleukin-1β levels, and attenuated podocyte dysfunction, as shown by reduced vascular endothelial growth factor production. These effects of AEA were inhibited by the cyclooxygenase-2 (COX-2) inhibitor celecoxib (CEL). In mice in vivo, AEA treatment attenuated glomerular NLRP3 inflammasome activation induced by hHcys accompanying a folate-free diet, on the basis of inhibition of hHcys-induced colocalization of NLRP3 molecules and increased interleukin-1β levels in glomeruli. Correspondingly, AEA prevented hHcys-induced proteinuria, albuminuria, and glomerular damage observed microscopically. Hcys- and AEA-induced effects were absent in NLRP3-knockout mice. These beneficial effects of AEA against hHcys-induced NLRP3 inflammasome activation and glomerular injury were not observed in mice cotreated with CEL. We further demonstrated that prostaglandin E2-ethanolamide (PGE2-EA), a COX-2 product of AEA, at 10 μM had a similar inhibitory effect to that of 100 μM AEA on Hcys-induced NLRP3 inflammasome formation and activation in cultured podocytes. From these results, we conclude that AEA has anti-inflammatory properties, protecting podocytes from Hcys-induced injury by inhibition of NLRP3 inflammasome activation through its COX-2 metabolite, PGE2-EA.

Role of the endocannabinoid system in the mechanisms involved in the LPS-induced preterm labor

Prematurity is the leading cause of perinatal morbidity and mortality worldwide. There is a strong causal relationship between infection and preterm births. Intrauterine infection elicits an immune response involving the release of inflammatory mediators like cytokines and prostaglandins (PG) that trigger uterine contractions and parturition events. Anandamide (AEA) is an endogenous ligand for the cannabinoid receptors CB1 and CB2. Similarly to PG, endocannabinoids are implicated in different aspects of reproduction, such as maintenance of pregnancy and parturition. Little is known about the involvement of endocannabinoids on the onset of labor in an infectious milieu. Here, using a mouse model of preterm labor induced by lipopolysaccharide (LPS), we explored changes on the expression of components of endocannabinoid system (ECS). We have also determined whether AEA and CB antagonists alter PG production that induces labor. We observed an increase in uterineN-acylphosphatidylethanolamine-specific phospholipase D expression (NAPE-PLD, the enzyme that synthesizes AEA) upon LPS treatment. Activity of catabolic enzyme fatty acid amide hydrolase (FAAH) did not change significantly. In addition, we also found that LPS modulated uterine cannabinoid receptors expression by downregulatingCb2mRNA levels and upregulating CB1 protein expression. Furthermore, LPS and AEA induced PGF2a augmentation, and this was reversed by antagonizing CB1 receptor. Collectively, our results suggest that ECS may be involved in the mechanism by which infection causes preterm birth.

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.

Progesterone reverts LPS-reduced FAAH activity in murine peripheral blood mononuclear cells by a receptor-mediated fashion

Increased anandamide concentrations are associated with pregnancy failure. Anandamide levels are regulated by the fatty acid amide hydrolase (FAAH). The aim of the study was to investigate the role of progesterone (P) on FAAH modulation in murine peripheral blood mononuclear cells (PBMC) under septic conditions. We observed that in vivo administration of LPS to non-pregnant (NP) mice decreased FAAH activity of PBMC while in pregnant mice no changes in FAAH activity were observed. NP animals administered with P had a similar response to LPS as the pregnant animals. Also, NP mice injected with P antagonist and P showed that the effect of P on LPS-reduced FAAH activity was impaired. Furthermore, LPS produced a decrease in the ratio of PR-B/PR-A in NP animals. Our results showed that, in our model the endotoxin decreased PBMC's FAAH activity and this condition was reverted by P in a receptor-mediated fashion.

TRPV1 and SP: key elements for sepsis outcome?

Sensory neurons play important roles in many disorders, including inflammatory diseases, such as sepsis. Sepsis is a potentially lethal systemic inflammatory reaction to a local bacterial infection, affecting thousands of patients annually. Although associated with a high mortality rate, sepsis outcome depends on the severity of systemic inflammation, which can be directly influenced by several factors, including the immune response of the patient. Currently, there is a lack of effective drugs to treat sepsis, and thus there is a need to develop new drugs to improve sepsis outcome. Several mediators involved in the formation of sepsis have now been identified, but the mechanisms underlying the pathology remain poorly understood. The transient receptor potential vanilloid 1 (TRPV1) receptor and the neuropeptide substance P (SP) have recently been demonstrated as important targets for sepsis and are located on sensory neurones and non-neuronal cells. Herein, we highlight and review the importance of sensory neurones for the modulation of sepsis, with specific focus on recent findings relating to TRPV1 and SP, with their distinct abilities to alter the transition from local to systemic inflammation and also modify the overall sepsis outcome. We also emphasize the protective role of TRPV1 in this context.

LINKED ARTICLES

This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7.

Anandamide levels fluctuate in the bovine oviduct during the oestrous cycle

Mammalian oviduct acts as a reservoir for spermatozoa and provides an environment in which they may compete for the opportunity to fertilize the oocyte. Whilst in the oviduct spermatozoa undergo capacitation essential for fertilization. Sperm-oviduct interaction is essential for sperm capacitation and is a tightly regulated process influenced by the local microenvironment. Previously we reported that the endocannabinoid anandamide (AEA) regulates sperm release from epithelial oviductal cells by promoting sperm capacitation. The aims of this work were to measure the AEA content and to characterize the main AEA metabolic pathway in the bovine oviduct and determine how these change through the oestrous cycle. In this study, the levels of AEA and two other N-acylethanolamines, N-oleoylethanolamine and N-palmitoylethanolamine, were measured in bovine oviduct collected during different stages of oestrous cycle by ultra high performance liquid chromatography tandem mass spectrometry. Results indicated that intracellular oviductal epithelial levels of all three N-acylethanolamines fluctuate during oestrous cycle. Anandamide from oviductal fluid also varied during oestrous cycle, with the highest values detected during the periovulatory period. Endocannabinoid levels from ipsilateral oviduct to ovulation were higher than those detected in the contralateral one, suggesting that levels of oviductal AEA may be regulated by ovarian hormones. The expression and localization of N-acylethanolamines metabolizing enzymes in bovine oviduct were also determined by RT-PCR, Western blot, and immunohistochemistry but no change was found during the oestrous cycle. Furthermore, nanomolar levels of AEA were detected in follicular fluids, suggesting that during ovulation the mature follicle may contribute to oviductal AEA levels to create an endocannabinoid gradient conducive to the regulation of sperm function for successful fertilization.

Progesterone is essential for protecting against LPS-induced pregnancy loss. LIF as a potential mediator of the anti-inflammatory effect of progesterone

Lipopolysaccharide (LPS) administration to mice on day 7 of gestation led to 100% embryonic resorption after 24 h. In this model, nitric oxide is fundamental for the resorption process. Progesterone may be responsible, at least in part, for a Th2 switch in the feto-maternal interface, inducing active immune tolerance against fetal antigens. Th2 cells promote the development of T cells, producing leukemia inhibitory factor (LIF), which seems to be important due to its immunomodulatory action during early pregnancy. Our aim was to evaluate the involvement of progesterone in the mechanism of LPS-induced embryonic resorption, and whether LIF can mediate hormonal action. Using in vivo and in vitro models, we provide evidence that circulating progesterone is an important component of the process by which infection causes embryonic resorption in mice. Also, LIF seems to be a mediator of the progesterone effect under inflammatory conditions. We found that serum progesterone fell to very low levels after 24 h of LPS exposure. Moreover, progesterone supplementation prevented embryonic resorption and LPS-induced increase of uterine nitric oxide levels in vivo. Results show that LPS diminished the expression of the nuclear progesterone receptor in the uterus after 6 and 12 h of treatment. We investigated the expression of LIF in uterine tissue from pregnant mice and found that progesterone up-regulates LIF mRNA expression in vitro. We observed that LIF was able to modulate the levels of nitric oxide induced by LPS in vitro, suggesting that it could be a potential mediator of the inflammatory action of progesterone. Our observations support the view that progesterone plays a critical role in a successful pregnancy as an anti-inflammatory agent, and that it could have possible therapeutic applications in the prevention of early reproductive failure associated with inflammatory disorders.

Interaction between lysophosphatidic acid, prostaglandins and the endocannabinoid system during the window of implantation in the rat uterus

Bioactive lipid molecules as lysophosphatidic acid (LPA), prostaglandins (PG) and endocannabinoids are important mediators of embryo implantation. Based on previous published data we became interested in studying the interaction between these three groups of lipid derivatives in the rat uterus during the window of implantation. Thus, we adopted a pharmacological approach in vitro using LPA, DGPP (a selective antagonist of LPA3, an LPA receptor), endocannabinoids’ receptor selective antagonists (AM251 and AM630) and non selective (indomethacin) and selective (NS-398) inhibitors of cyclooxygenase-1 and 2 enzymes. Cyclooxygenase isoforms participate in prostaglandins’ synthesis. The incubation of the uterus from rats pregnant on day 5 of gestation (implantation window) with LPA augmented the activity and the expression of fatty acid amide hydrolase, the main enzyme involved in the degradation of endocannabinoids in the rodent uteri, suggesting that LPA decreased endocannabinoids’ levels during embryo implantation. It has been reported that high endocannabinoids are deleterious for implantation. Also, LPA increased PGE2 production and cyclooxygenase-2 expression. The incubation of LPA with indomethacin or NS-398 reversed the increment in PGE2 production, suggesting that cyclooxygenase-2 was the isoform involved in LPA effect. PGs are important mediators of decidualization and vascularization at the implantation sites. All these effects were mediated by LPA3, as the incubation with DGPP completely reversed LPA stimulatory actions. Besides, we also observed that endocannabinoids mediated the stimulatory effect of LPA on cyclooxygenase-2 derived PGE2 production, as the incubation of LPA with AM251 or AM630 completely reversed LPA effect. Also, LPA augmented via LPA3 decidualization and vascularization markers. Overall, the results presented here demonstrate the participation of LPA3 in the process of implantation through the interaction with other groups of lipid molecules, prostaglandins and endocannabinoids, which prepare the uterine milieu for embryo invasion during the window of implantation.

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.

Cyclooxygenase-2 prostaglandins mediate anandamide-inhibitory action on nitric oxide synthase activity in the receptive rat uterus

Anandamide, an endocannabinoid, prostaglandins derived from cyclooxygenase-2 and nitric oxide synthesized by nitric oxide synthase (NOS), are relevant mediators of embryo implantation. We adopted a pharmacological approach to investigate if anandamide modulated NOS activity in the receptive rat uterus and if prostaglandins mediated this effect. As we were interested in studying the changes that occur at the maternal side of the fetal-maternal interface, we worked with uteri obtained from pseudopregnant rats. Females were sacrificed on day 5 of pseudopregnancy, the day in which implantation would occur, and the uterus was obtained. Anandamide (2 ng/kg, i.p.) inhibited NOS activity (P<0.001) and increased the levels of prostaglandin E(2) (P<0.001) and prostaglandin F(2α) (P<0.01). These effects were mediated via cannabinoid receptor type 2, as the pre-treatment with SR144528 (10 mg/kg, i.p.), a selective cannabinoid receptor type 2 antagonist, completely reverted anandamide effect on NOS activity and prostaglandin levels. The pre-treatment with a non-selective cyclooxygenase inhibitor (indomethacin 2.5mg/kg, i.p.) or with selective cyclooxygenase-2 inhibitors (meloxicam 4 mg/kg, celecoxib 3mg/kg, i.p.) reverted anandamide inhibition on NOS, suggesting that prostaglandins are derived from cyclooxygenase-2 mediated anandamide effect. Thus, anandamide levels seemed to modulate NOS activity, fundamental for implantation, via cannabinoid receptor type 2 receptors, in the receptive uterus. This modulation depends on the production of cyclooxygenase-2 derivatives. These data establish cannabinoid receptors and cyclooxygenase enzymes as an interesting target for the treatment of implantation deficiencies.

Anandamide induces sperm release from oviductal epithelia through nitric oxide pathway in bovines

Mammalian spermatozoa are not able to fertilize an egg immediately upon ejaculation. They acquire this ability during their transit through the female genital tract in a process known as capacitation. The mammalian oviduct acts as a functional sperm reservoir providing a suitable environment that allows the maintenance of sperm fertilization competence until ovulation occurs. After ovulation, spermatozoa are gradually released from the oviductal reservoir in the caudal isthmus and ascend to the site of fertilization. Capacitating-related changes in sperm plasma membrane seem to be responsible for sperm release from oviductal epithelium. Anandamide is a lipid mediator that participates in the regulation of several female and male reproductive functions. Previously we have demonstrated that anandamide was capable to release spermatozoa from oviductal epithelia by induction of sperm capacitation in bovines. In the present work we studied whether anandamide might exert its effect by activating the nitric oxide (NO) pathway since this molecule has been described as a capacitating agent in spermatozoa from different species. First, we demonstrated that 1 µM NOC-18, a NO donor, and 10 mM L-Arginine, NO synthase substrate, induced the release of spermatozoa from the oviductal epithelia. Then, we observed that the anandamide effect on sperm oviduct interaction was reversed by the addition of 1 µM L-NAME, a NO synthase inhibitor, or 30 µg/ml Hemoglobin, a NO scavenger. We also demonstrated that the induction of bull sperm capacitation by nanomolar concentrations of R(+)-methanandamide or anandamide was inhibited by adding L-NAME or Hemoglobin. To study whether anandamide is able to produce NO, we measured this compound in both sperm and oviductal cells. We observed that anandamide increased the levels of NO in spermatozoa, but not in oviductal cells. These findings suggest that anandamide regulates the sperm release from oviductal epithelia probably by activating the NO pathway during sperm capacitation.

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.

Anandamide capacitates bull spermatozoa through CB1 and TRPV1 activation

Anandamide (AEA), a major endocannabinoid, binds to cannabinoid and vanilloid receptors (CB1, CB2 and TRPV1) and affects many reproductive functions. Nanomolar levels of anandamide are found in reproductive fluids including mid-cycle oviductal fluid. Previously, we found that R(+)-methanandamide, an anandamide analogue, induces sperm releasing from bovine oviductal epithelium and the CB1 antagonist, SR141716A, reversed this effect. Since sperm detachment may be due to surface remodeling brought about by capacitation, the aim of this paper was to investigate whether anandamide at physiological concentrations could act as a capacitating agent in bull spermatozoa. We demonstrated that at nanomolar concentrations R(+)-methanandamide or anandamide induced bull sperm capacitation, whereas SR141716A and capsazepine (a TRPV1 antagonist) inhibited this induction. Previous studies indicate that mammalian spermatozoa possess the enzymatic machinery to produce and degrade their own AEA via the actions of the AEA-synthesizing phospholipase D and the fatty acid amide hydrolase (FAAH) respectively. Our results indicated that, URB597, a potent inhibitor of the FAAH, produced effects on bovine sperm capacitation similar to those elicited by exogenous AEA suggesting that this process is normally regulated by an endogenous tone. We also investigated whether anandamide is involved in bovine heparin-capacitated spermatozoa, since heparin is a known capacitating agent of bovine sperm. When the spermatozoa were incubated in the presence of R(+)-methanandamide and heparin, the percentage of capacitated spermatozoa was similar to that in the presence of R(+)-methanandamide alone. The pre-incubation with CB1 or TRPV1 antagonists inhibited heparin-induced sperm capacitation; moreover the activity of FAAH was 30% lower in heparin-capacitated spermatozoa as compared to control conditions. This suggests that heparin may increase endogenous anandamide levels. Our findings indicate that anandamide induces sperm capacitation through the activation of CB1 and TRPV1 receptors and could be involved in the same molecular pathway as heparin in bovines.

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.