Jekyll and hyde: two faces of cannabinoid signaling in male and female fertility

The role of sex steroid hormones, cytokines and the endocannabinoid system in female fertility

BACKGROUND

Marijuana, the most used recreational drug, has been shown to have adverse effects on human reproduction. Endogenous cannabinoids (also called endocannabinoids) bind to the same receptors as those of Δ(9)-tetrahydrocannabinol (THC), the psychoactive component of Cannabis sativa. The most extensively studied endocannabinoids are anandamide (N-arachidonoylethanolamine, AEA) and 2-arachidonoylglycerol. The endocannabinoids, their congeners and the cannabinoid receptors, together with the metabolic enzymes and putative transporters form the endocannabinoid system (ECS). In this review, we summarize current knowledge about the relationships of ECS, sex steroid hormones and cytokines in female fertility, and underline the importance of this endocannabinoid-hormone-cytokine network.

METHODS

Pubmed and the Web of Science databases were searched for studies published since 1985, looking into the ECS, sex hormones, type-1/2 T-helper (Th1/Th2) cytokines, leukaemia inhibitory factor, leptin and reproduction.

RESULTS

The ECS plays a pivotal role in human reproduction. The enzymes involved in the synthesis and degradation of endocannabinoids normalize levels of AEA for successful implantation. The AEA degrading enzyme (fatty acid amide hydrolase) activity as well as AEA content in blood may potentially be used for the monitoring of early pregnancies. Progesterone and oestrogen are involved in the maintenance of endocannabinoid levels. The ECS plays an important role in the immune regulation of human fertility.

CONCLUSIONS

The available studies suggest that tight control of the endocannabinoid-hormone-cytokine network is required for successful implantation and early pregnancy maintenance. This hormone-cytokine network is a key element at the maternal-foetal interface, and any defect in such a network may result in foetal loss.

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.

Cannabinoids and Reproduction: A Lasting and Intriguing History

Starting from an historical overview of lasting Cannabis use over the centuries, we will focus on a description of the cannabinergic system, with a comprehensive analysis of chemical and pharmacological properties of endogenous and synthetic cannabimimetic analogues. The metabolic pathways and the signal transduction mechanisms, activated by cannabinoid receptors stimulation, will also be discussed. In particular, we will point out the action of cannabinoids and endocannabinoids on the different neuronal networks involved in reproductive axis, and locally, on male and female reproductive tracts, by emphasizing the pivotal role played by this system in the control of fertility.

How important are sex differences in cannabinoid action?

In humans as in animals, males and females are dissimilar in their genetic and hormonally driven behaviour; they process information differently, perceive experience and emotions in different ways, display diverse attitudes, language and social skills, and show sex-related differences in the brain anatomy and organization. Drug addiction is a widespread relapsing illness that affects both men and women. Sex-dependent differences have been frequently observed in the biological and behavioural effects of substances of abuse, including cannabis. Beside sex differences observed in the cannabinoid-induced effects related to cannabis abuse and dependence, cannabinoids have been shown to exert sex-dependent effects also in other physiological and behavioural aspects, such as food intake and energy balance (more evident in males), or anxiety and depression (more evident in females). Research has just begun to identify factors which could provide a neurobiological basis for gender-based differences in cannabinoid effects, among which, gonadal hormones seem to play a crucial role. Yet, cannabinoid pharmacodynamic and pharmacokinetic may also be important, as sex differences in cannabinoid effects might be due, at least in part, to differences in muscle mass and fat tissue distribution between males and females. Here, we will review both clinical and laboratory-based research evidence revealing important sex-related differences in cannabinoid effects, and put forward some suggestions for future studies to fill the gap in our knowledge of gender-specific bias in cannabinoid pharmacology.

Characterization of the endocannabinoid system in mouse embryonic stem cells

In this study, we have ascertained the presence and functionality in mouse embryonic stem cells (ESCs) of members of the endocannabinoid system that have been proposed as possible modulators of the survival and differentiation of various type of stem cells. We show that mouse ESCs, in addition to classical CB(1) and CB(2) cannabinoid receptors, express the transient receptor potential vanilloid receptor, at mRNA, protein, and binding levels. Remarkably, we demonstrate that ESCs have the mRNA, protein, and enzyme activity to synthesize and degrade the prominent endocannabinoids anandamide (through N-acyl-phosphatidylethanolamine-specific phospholipase D and fatty acid amide hydrolase) and 2-arachidonoylglycerol (through diacylglycerol lipase and monoacylglycerol lipase). In addition, both endocannabinoids were detected in ESCs that were also shown to constitutively release a fatty acid amide hydrolase-activating compound. Finally, we document that the stimulation of ESCs by methanandamide, a nonhydrolysable analog of anandamide, does not lead to overt alteration of the expression of Oct3/4, Nanog, and Cdx2, genes that are involved in early cell fate in the preimplantation embryo and stemness, or of the expression patterns of Brachyury and Hnf4, genes that are used as late markers of lineage differentiation capability of ESC-derived embryoid bodies. Similarly ineffective on the expression of the tested stemness genes was 2-arachidonoylglycerol. Taken together, these results confirm and extend the notion that ESCs express several functional members of the endocannabinoid system, but they leave open the question about their role in stem cells as modulators of stemness and differentiation potential.

Endocannabinoids and Human Sperm Cells

N-acylethanolamides (NAEs) are naturally occurring signaling lipids consisting of amides and esters of long-chain polyunsaturated fatty acids. Usually they are present in a very small amounts in many mammalian tissues and cells, including human reproductive tracts and fluids. Recently, the presence of N-arachidonoylethanolamide (anandamide, AEA), the most characterised member of endocannabinoids, and its congeners palmitoylethanolamide (PEA) and oleylethanolamide (OEA) in seminal plasma, oviductal fluid, and follicular fluids was demonstrated. AEA has been shown to bind not only type-1 (CB1) and type-2 (CB2) cannabinoid receptors, but also type-1 vanilloid receptor (TRPV1), while PEA and OEA are inactive with respect to classical cannabinoid CB1 and CB2 but activate TRPV1 or peroxisome proliferator activate receptors (PPARs). This review concerns the most recent experimental data on PEA and OEA, endocannabinoid-like molecules which appear to exert their action exclusively on sperm cells with altered features, such as membrane characteristics and kinematic parameters. Their beneficial effects on these cells could suggest a possible pharmacological use of PEA and OEA on patients affected by some forms of idiopathic infertility.

Endocannabinoid signaling directs differentiation of trophoblast cell lineages and placentation

In most mammals, placentation is critical for fetal development and pregnancy success. Exposure to marijuana during pregnancy has adverse effects, but whether the placenta is a target of cannabinoid/endocannabinoid signaling is not known. Using mice as a model system, we found that the endocannabinoid system is present in the ectoplacental cone and spongiotrophoblast cells. We also observed that aberrant endocannabinoid signaling confers premature trophoblast stem cell differentiation, and defective trophoblast development and invasion. These defects are reflected in retarded fetal development and compromised pregnancy outcome. Because the endocannabinoid system is conserved in mice and humans, our study suggests that endocannabinoid signaling is critical to placentation and pregnancy success in humans and implicates its potential significance in stem cell biology.

Cannabis et fertilité masculine

Le cannabis est la drogue récréative la plus utilisée dans le monde. Une des inquiétudes majeures de l’exposition au cannabis concerne son effet négatif sur la fonction reproductive. La découverte du système endocannabinnoïde, composé de multiples ligands endogènes lipidiques, leurs récepteurs et leurs enzymes métaboliques, a permis de mettre en évidence l’importance de la signalisation de ce système dans de multiples événements de la reproduction. Dans cet article, nous nous proposons de passer en revue la littérature sur l’impact du cannabis dans la fonction reproductive masculine. Nous aborderons les études réalisées chez l’homme et chez l’animal, et enfin nous discuterons les limites et perspectives des études envisageables pour évaluer les effets du cannabis sur la fertilité masculine.

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.

Endocannabinoid system regulates migration of endometrial stromal cells via cannabinoid receptor 1 through the activation of PI3K and ERK1/2 pathways

OBJECTIVE

To evaluate the effects of the cannabinoid system on the regulation of endometrial stromal cell (ESCs) dynamic behavior.

DESIGN

ESC migration, electrical signal generated by K(+) channels, and cytoskeletal-actin dynamics were evaluated in response to treatment with the synthetic endocannabinoid methanandamide. Selective agonists and antagonists were used to identify both the receptor and the biochemical pathways involved.

SETTING

Molecular research institution.

PATIENT(S)

Endometrial tissues were obtained from 40 reproductive-age women undergoing laparoscopy for benign pathologies.

INTERVENTIONS

ESCs were treated with methanadamide and with selective agonist (ACEA) and antagonist (AM251) of the cannabinoid receptor 1.

MAIN OUTCOME MEASURES

Cellular migration was evaluated by means of chemotaxis experiments in a Boyden chamber. Electric signal generated by K(+) channels was evaluated by patch clamp experiments Cellular morphology and cytoskeletal-actin dynamics were evaluated by immunofluorescence.

RESULT(S)

Methanandamide enhanced ESC migration via cannabinoid receptor I (CNR1) through the activation of PI3K/Akt and ERK1/2 pathways. The increased ESC migration was associated with cytoskeleton reorganization identified by the dissolution of F-actin stress fibers and the presence of stress fiber arcs and with increased electrical signal generated by K(+) channels.

CONCLUSION(S)

In physiologic conditions, the cannabinoid system has a central role in regulating endometrial cell migration. The involvement of ERK1/2 and PI3-K/Akt pathways points to a potential role of endocannabinoids in some pathologic conditions characterized by enhanced endometrial cell invasiveness.

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.

A putative 'pre-nervous' endocannabinoid system in early echinoderm development

Embryos and larvae of sea urchins (Lytechinus variegatus, Strongylocentrotus droebachiensis, Strongylocentrotus purpuratus, Dendraster excentricus), and starfish (Pisaster ochraceus) were investigated for the presence of a functional endocannabinoid system. Anandamide (arachidonoyl ethanolamide, AEA), was measured in early L. variegatus embryos by liquid chromatography/mass spectrometry. AEA showed a strong developmental dynamic, increasing more than 5-fold between the 8-16 cell and mid-blastula 2 stage. 'Perturb-and-rescue' experiments in different sea urchin species and starfish showed that AEA blocked transition of embryos from the blastula to the gastrula stage, but had no effect on cleavage divisions, even at high doses. The non-selective cannabinoid receptor agonist, CP55940, had similar effects, but unlike AEA, also blocked cleavage divisions. CB1 antagonists, AEA transport inhibitors, and the cation channel transient membrane potential receptor V1 (TrpV1) agonist, arachidonoyl vanillic acid (arvanil), as well as arachidonoyl serotonin and dopamine (AA-5-HT, AA-DA) acted as rescue substances, partially or totally preventing abnormal embryonic phenotypes elicited by AEA or CP55940. Radioligand binding of [(3)H]CP55940 to membrane preparations from embryos/larvae failed to show significant binding, consistent with the lack of CB receptor orthologs in the sea urchin genome. However, when binding was conducted on whole cell lysates, a small amount of [(3)H]CP55940 binding was observed at the pluteus stage that was displaced by the CB2 antagonist, SR144528. Since AEA is known to bind with high affinity to TrpV1 and to certain G-protein-coupled receptors (GPCRs), the ability of arvanil, AA-5-HT and AA-DA to rescue embryos from AEA teratogenesis suggests that in sea urchins AEA and other endocannabinoids may utilize both Trp and GPCR orthologs. This possibility was explored using bioinformatic and phylogenetic tools to identify candidate orthologs in the S. purpuratus sea urchin genome. Candidate TrpA1 and TrpV1 orthologs were identified. The TrpA1 ortholog fell within a monophyletic clade, including both vertebrate and invertebrate orthologs, whereas the TrpV1 orthologs fell within two distinct TrpV-like invertebrate clades. One of the sea urchin TrpV orthologs was more closely related to the vertebrate epithelial calcium channels (TrpV5-6 family) than to the vertebrate TrpV1-4 family, as determined using profile-hidden Markov model (HMM) searches. Candidate dopamine and adrenergic GPCR orthologs were identified in the sea urchin genome, but no cannabinoid GPCRs were found, consistent with earlier studies. Candidate dopamine D(1), D(2) or alpha(1)-adrenergic receptor orthologs were identified as potential progenitors to the vertebrate cannabinoid receptors using HMM searches, depending on whether the multiple sequence alignment of CB receptor sequences consisted only of urochordate and cephalochordate sequences or also included vertebrate sequences.

Rimonabant (SR141716) induces metabolism and acquisition of fertilizing ability in human sperm

BACKGROUND AND PURPOSE

The endocannabinoid system and the cannabinoid CB(1) receptor have been identified in human sperm, and it is well known that endocannabinoids have pronounced adverse effects on male and female reproduction. In order to elucidate further the pathophysiological role of the endocannabinoid system in male fertility, we investigated the activity of the CB(1) receptor antagonist rimonabant (SR141716) on the fertilizing ability of human sperm.

EXPERIMENTAL APPROACH

We evaluated in vitro the effects of rimonabant on motility, survival, capacitation, acrosin activity and metabolism of human sperm. Particularly, capacitation was studied by using three different approaches: intracellular free Ca(2+) content assay, cholesterol efflux assay and protein tyrosine phosphorylation analysis.

KEY RESULTS

Rimonabant significantly increased sperm motility and viability through the induction of pAkt and pBcl2, key proteins of cell survival and metabolism, and it induced acrosome reaction and capacitation as well. Rimonabant reduced the triglyceride content of sperm, while enhancing lipase and acyl-CoA dehydrogenase activities, implying an overall lipolytic action in these cells. Rimonabant also affected sperm glucose metabolism by decreasing phosphorylation of glycogen synthase kinase 3 and increasing glucose-6-phosphate dehydrogenase activity, suggesting a role in inducing sperm energy expenditure. Intriguingly, agonism at the CB(1) receptor, with an anandamide analogue or a selective inhibitor of fatty acid amide hydrolase, produced opposing effects on human sperm functions.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that blockade of the CB(1) receptor by rimonabant induces the acquisition of fertilizing ability and stimulates energy expenditure in human sperm.

Characterization of the endocannabinoid system in human spermatozoa and involvement of transient receptor potential vanilloid 1 receptor in their fertilizing ability

Human spermatozoa express type-1 cannabinoid receptor (CB1), whose activation by anandamide (AEA) affects motility and acrosome reaction (AR). In this study, we extended the characterization of the AEA-related endocannabinoid system in human spermatozoa, and we focused on the involvement of the AEA-binding vanilloid receptor (TRPV1) in their fertilizing ability. Protein expression was revealed for CB1 ( approximately 56 kDa), TRPV1 ( approximately 95 kDa), AEA-synthesizing phospholipase D (NAPE-PLD) ( approximately 46 kDa), and AEA-hydrolyzing enzyme [fatty acid amide hydrolase (FAAH), approximately 66 kDa]. Both AEA-binding receptors (CB1 and TRPV1) exhibited a functional binding activity; enzymatic activity was demonstrated for NAPE-PLD, FAAH, and the purported endocannabinoid membrane transporter (EMT). Immunoreactivity for CB1, NAPE-PLD, and FAAH was localized in the postacrosomal region and in the midpiece, whereas for TRPV1, it was restricted to the postacrosomal region. Capsazepine (CPZ), a selective antagonist of TRPV1, inhibited progesterone (P)-enhanced sperm/oocyte fusion, as evaluated by the hamster egg penetration test. This inhibition was due to a reduction of the P-induced AR rate above the spontaneous AR rate, which was instead increased. The sperm exposure to OMDM-1, a specific inhibitor of EMT, prevented the promoting effect of CPZ on spontaneous AR rate and restored the sperm responsiveness to P. No significant effects could be observed on sperm motility. In conclusion, this study provides unprecedented evidence that human spermatozoa exhibit a completely functional endocannabinoid system related to AEA and that the AEA-binding TRPV1 receptor could be involved in the sperm fertilizing ability.

A new role of anandamide in human sperm: focus on metabolism

The endocannabinoid system and the presence of CB1 receptor (CB1-R) target of the anandamide were identified in human sperm, however the anandamide action in this context needs to be further elucidated. At this purpose we analyzed the effects of anandamide on human sperm capacitation and motility. Afterwards, we focused on lipid and glucose sperm metabolism and also investigated the interrelationship between anandamide and insulin secretion by sperm. By intracellular free Ca(2+) content assay and proteins tyrosine phosphorylation, we evidenced that anandamide did not induce capacitation process and a negative effect was obtained on sperm motility. The blockage of CB1-R by the specific antagonist SR141716 increased both capacitation and sperm motility suggesting an involvement of the CB1-R in the acquisition of sperm fertilizing activity. The evaluation of the triglycerides content, lipase and acyl-CoA dehydrogenase activities, suggest that anandamide exerts a lipogenetic effect on human sperm lipid metabolism. Concerning the glucose metabolism, anandamide increases GSK3 phosphorylation indicating that it is involved in the accumulation of energy substrates. G6PDH activity was not affected by anandamide. Interestingly, AEA is involved in insulin secretion by sperm. As insulin had been demonstrated to be an autocrine factor that triggers capacitation, the endocannabinoid might be inserted in the signaling cascade that induces this process. Altogether these findings highlight a pivotal involvement of the CB1-R in the control of sperm energy homeostasis and propose a new site of action for endocannabinoids in the control of energy metabolism.

Endocannabinoids: friends and foes of reproduction

Endocannabinoids are fatty acid amides like anandamide (AEA), and monoacylglycerols like 2-arachidonoylglycerol, that bind to cannabinoid, vanilloid and peroxisome proliferator-activated receptors. Their biological actions are controlled through not yet fully characterized cellular mechanisms. These compounds, together with their related enzymes, that include key proteins for the synthesis and degradation of endocannabinoids, cannabinoid and non-cannabinoid receptors, and purported membrane transporter(s), form the "endocannabinoid system (ECS)". In the past few years AEA and related ECS elements have emerged as essential players in various aspects of human reproduction, both for males and females. Here, the key features of the ECS and the potential of its components to direct human fertility towards a positive or negative end will be reviewed. In particular, the involvement of AEA and related ECS elements in regulating embryo oviductal transport, blastocyst implantation and placental development (in females), and sperm survival, motility, capacitation and acrosome reaction (in males) will be addressed, as well as the role of endocannabinoids in sperm-oviduct interactions. Additionally, the possibility that blood AEA and its hydrolase FAAH may represent reliable diagnostic markers of natural and assisted reproduction in humans will be discussed, along with the therapeutic exploitation of ECS-oriented drugs as useful fertility enhancers.

Testicular gonadotropin-releasing hormone activity, progression of spermatogenesis, and sperm transport in vertebrates

Since the end of the 1970s, studies have shown that, besides the endocrine route, a chemical mediator may also act through autocrine and/or paracrine mechanisms. This has opened new frontiers for research as a result of a redefinition of what endocrinology represents. Apart from androgens within the male gonad, testicular gonadotropin-releasing hormone, estrogens, molecular chaperones, proto-oncogenes, and, very recently, the endocannabinoid system have been shown to play important roles. Their activities to regulate spermatogenesis, including spermiogenesis and sperm maturation, will be discussed from the comparative viewpoint to describe adaptive phenomena and to speculate on evolution.

Analysis of endocannabinoids, their congeners and COX-2 metabolites

Since the discovery of the endocannabinoids anandamide and 2-arachidonoylglycerol (2-AG) in the early 1990s, the endocannabinoid system has been implicated in a wide array of physiological processes, such as control of food intake and energy balance, fertility and obesity. As the importance of this system becomes apparent, there is a tremendous need for robust, sensitive and efficient analytical methodology for the examination of the endocannabinoids, their congeners and putative metabolites. This review will summarize quantitative analytical methodology as reported in the literature from 1992 to present for the analysis of endocannabinoids and related compounds.

Association of marijuana use and the incidence of testicular germ cell tumors

BACKGROUND

The incidence of testicular germ cell tumors (TGCTs) has been increasing the past 4 to 6 decades; however, exposures that account for this rise have not been identified. Marijuana use also grew during the same period, and it has been established that chronic marijuana use produces adverse effects on the human endocrine and reproductive systems. In this study, the authors tested the hypothesis that marijuana use is a risk factor for TGCT.

METHODS

A population-based, case-control study of 369 men ages 18 to 44 years who were diagnosed with TGCT from January 1999 through January 2006 was conducted in King, Pierce and Snohomish Counties in Washington State. The responses of these men to questions on their lifetime marijuana use were compared with the responses of 979 age-matched controls who resided in the same 3 counties during the case diagnosis period.

RESULTS

Men with a TGCT were more likely to be current marijuana smokers at the reference date compared with controls (odds ratio [OR], 1.7; 95% confidence interval [95% CI], 1.1-2.5). In analyses according to histologic type, most of the association between current marijuana use and TGCT was observed in men who had nonseminomas/mixed histology tumors (current use: OR, 2.3; 95% CI, 1.3-4.0). Age at first use among current users (age<18 years [OR, 2.8] vs age>or=18 years [OR, 1.3]) and frequency of use (daily or weekly [OR, 3.0] vs less than once per week [OR, 1.8]) appeared to modify the risk.

CONCLUSIONS

An association was observed between marijuana use and the occurrence of nonseminoma TGCTs. Additional studies of TGCTs will be needed to test this hypothesis, including molecular analyses of cannabinoid receptors and endocannabinoid signaling, which may provide clues regarding the biologic mechanisms of TGCTs.

A novel role for the endocannabinoid system during zebrafish development

The aim of this study was to increase our understanding of the physiological functions controlled by the endocannabinoid system during embryogenesis. Using genomic and proteomic methodologies applied to zebrafish, we proved, for the first time in an oviparous species, that the cannabinoid receptor CB1 is not a maternal factor. The analysis of different developmental stages showed that the zygotic expression of CB1 occurs from the 3 somites stage while CB1 protein becomes evident during hatching time, indicating an involvement in the hatching process. This result was supported by the data regarding embryo exposure to the CB1 antagonist, AM251, consisting in a 75% decrease in hatching rate. In addition, as previously described for mammals, we observed a role of CB1 in the motility behavior in zebrafish larvae.

Regulation of gene transcription and keratinocyte differentiation by anandamide

Anandamide (AEA) is a member of an endogenous class of lipid mediators, known as endocannabinoids, which are involved in various biological processes. In particular, AEA regulates cell growth, differentiation, and death. Accumulating evidence demonstrates that AEA controls also epidermal differentiation, one of the best characterized mechanisms of cell specialization. Indeed, the epidermis is a keratinized multistratified epithelium that functions as a barrier to protect the organism from dehydration, mechanical trauma, and microbial insults. Its function is established during embryogenesis and is maintained during the whole life span of the organism, through a complex and tightly controlled program, termed epidermal terminal differentiation (or cornification). Whereas the morphological changes that occur during cornification have been extensively studied, the molecular mechanisms that underlie this process remain poorly understood. In this chapter, we summarize current knowledge about the molecular regulation of proliferation and terminal differentiation in mammalian epidermis. In this context, we show that endocannabinoids are finely regulated by, and can interfere with, the differentiation program. In addition, we review the role of AEA in the control of cornification, and show that it occurs by maintaining a transcriptional repression of gene expression through increased DNA methylation.

CB1 activity in male reproduction: mammalian and nonmammalian animal models

The importance of the endocannabinoid system (ECBS) and its involvement in several physiological processes is still increasing. Since the isolation of the main active compound of Cannabis sativa, Delta(9)-THC, several lines of research have evidenced the basic roles of this signaling system mainly considering its high conservation during evolution. In this chapter the attention is focussed on the involvement of the ECBS in the control of male reproductive aspects at both central and local levels which are both considered from a comparative point of view.

The endocannabinoid system during development: emphasis on perinatal events and delayed effects

The endocannabinoid system (ECS) including its receptors, endogenous ligands ("endocannabinoids"), synthesizing and degradating enzymes, and transporter molecules has been detected from the earliest embryonal stages and throughout pre- and postnatal development; endocannabinoids, notably 2-arachidonoylglycerol, are also present in maternal milk. During three developmental stages, (1) early embryonal, (2) prenatal brain development, and (3) postnatal suckling, the ECS plays an essential role for development and survival. During early gestation, successful embryonal passage through the oviduct and implantation into the uterus require critical enzymatic control of the endocannabinoids. During fetal life, endocannabinoids and the cannabinoid CB(1) receptor are important for brain development, regulating neural progenitor differentiation and guiding axonal migration and synaptogenesis. Postnatally, CB(1) receptor activation by 2-arachidonoylglycerol appears to play a critical role in the initiation of milk suckling in mouse pups, possibly by enabling innervation and/or activation of the tongue muscles. Perinatal manipulation of the ECS, by administering cannabinoids or by maternal marijuana consumption, alters neurotransmitter and behavioral functions in the offspring. Interestingly, the sequelae of prenatal cannabinoids are similar to many effects of prenatal stress, which may suggest that prenatal stress impacts on the ECS and that vice versa prenatal cannabinoid exposure may interfere with the ability of the fetus to cope with the stress. Future studies should further clarify the mechanisms involved in the developmental roles of the ECS and understand better the adverse effects of prenatal exposure, to design strategies for the treatment of conditions including infertility, addiction, and failure-to-thrive.

Cannabinoid/Endocannabinoid signaling impact on early pregnancy events

It has been known for decades that marijuana and its major psychoactive component Δ⁹-tetrahydrocannabinol (THC) alter both male and female reproductive functions in humans and laboratory animals. The discovery of cannabinoid-like molecules (endocannabinoids), anandamide (AEA) and 2-arachidonylglycerol (2AG), as well as G-protein-coupled cannabinoid/endocannabinoid receptors CB₁ and CB₂, created an opportunity to study the adverse and beneficial effects of cannabinoids/endocannabinoids on fertility using molecular, physiological and genetic approaches. In fact, studies to explore the significance of cannabinoid/endocannabinoid signaling in reproduction have revealed some intriguing physiological roles in early pregnant events. This review summarizes some aspects of these signaling molecules in preimplantation and implantation biology utilizing genetically engineered mouse models.

A critical review of the cannabinoid receptor as a drug target for obesity management

The discovery of cannabinoids, with the well-known stimulatory effect of Cannabis sativa on appetite, has offered a new drug target for obesity treatment. Cannabinoids act on two different receptors: CB1 receptors which are sited in the brain and many peripheral tissues, and CB2 receptors which are primarily found in immune system cells. Cannabinoid receptor antagonists act centrally by blocking CB1 receptors, thereby reducing food intake. Moreover, they probably also act peripherally by increasing thermogenesis and therefore energy expenditure, as has been suggested by animal experiments. Despite these promising mechanisms of action, recent clinical studies examining the effect of the two CB1 receptor antagonists rimonabant and taranabant showed that the attained weight loss did not exceed that attained with other currently approved anti-obesity medications. Moreover, potentially severe psychiatric adverse effects limit their clinical use. As several new CB1 receptor antagonists are presently undergoing development, it remains to be elucidated to what extent they differ in terms of efficacy and safety. This review primarily discusses how close cannabinoid receptor antagonists are to the ideal anti-obesity drug, with respect to their mechanisms of action, clinical effectiveness and safety.

Comprehensive profiling of the human circulating endocannabinoid metabolome: clinical sampling and sample storage parameters

BACKGROUND

Endogenous cannabinoid-receptor ligands (endocannabinoids) and over a dozen related metabolites now comprise the "endocannabinoid metabolome". The diverse (patho)physiological roles of endocannabinoids, the predictive/diagnostic utility of systemic endocannabinoid levels, and the growing interest in endocannabinoid-related pharmacotherapeutics mandate a valid clinical protocol for processing human blood that does not jeopardize profiling of the circulating endocannabinoid metabolome.

METHODS

We systematically evaluated the potential effect of pre-analytical variables associated with phlebotomy and sample handling/work-up on the human-blood endocannabinoid metabolome as quantified by state-of-the-art liquid chromatography-mass spectrometry.

RESULTS

Neither subject posture during phlebotomy nor moderate activity beforehand influenced the blood levels of the 15 endocannabinoid-system lipids quantified. Storage of fresh blood at 4 degrees C selectively enhanced ethanolamide concentrations artifactually without affecting monoglycerides and nonesterified fatty acids, such as arachidonic acid. In marked contrast, ethanolamides and monoglycerides remained stable through three plasma freeze/thaw cycles, whereas plasma arachidonic acid content increased, probably a reflection of ongoing metabolism.

CONCLUSIONS

Class- and compound-selective pre-analytical influences on circulating human endocannabinoid levels necessitate immediate plasma preparation from fresh blood and prompt plasma apportioning and snap-freezing. Repeated plasma thawing and refreezing should be avoided. This protocol ensures sample integrity for evaluating the circulating endocannabinoid metabolome in the clinical setting.

Genetic loss of Faah compromises male fertility in mice

Marijuana is the most commonly used illicit drug. Although there is some indication that reproductive functions in males are impaired in chronic marijuana users, the genetic evidence and underlying causes remain largely unknown. Herein we show that genetic loss of Faah, which encodes fatty acid amide hydrolase (FAAH), results in elevated levels of anandamide, an endocannabinoid, in the male reproductive system, leading to compromised fertilizing capacity of sperm. This defect is rescued by superimposing deletion of cannabinoid receptor 1 (Cnr1). Retention of Faah(-/-) sperm on the egg zona pellucida provides evidence that the capacity of sperm to penetrate the zona barrier is hampered by elevated anandamide levels. Collectively, the results show that aberrant endocannabinoid signaling via CNR1 impairs normal sperm function. Besides unveiling a new regulatory mechanism of sperm function, this study has clinical significance in male fertility.

Loss of cannabinoid receptor CB1 induces preterm birth

Background

Preterm birth accounting approximate 10% of pregnancies in women is a tremendous social, clinical and economic burden. However, its underlying causes remain largely unknown. Emerging evidence suggests that endocannabinoid signaling via cannabinoid receptor CB1 play critical roles in multiple early pregnancy events in both animals and humans. Since our previous studies demonstrated that loss of CB1 defers the normal implantation window in mice, we surmised that CB1 deficiency would influence parturition events.

Methods and Findings

Exploiting mouse models with targeted deletion of Cnr1, Cnr2 and Ptgs1 encoding CB1, CB2 and cyclooxygenase-1, respectively, we examined consequences of CB1 or CB2 silencing on the onset of parturition. We observed that genetic or pharmacological inactivation of CB1, but not CB2, induced preterm labor in mice. Radioimmunoassay analysis of circulating levels of ovarian steroid hormones revealed that premature birth resulting from CB1 inactivation is correlated with altered progesterone/estrogen ratios prior to parturition. More strikingly, the phenotypic defects of prolonged pregnancy length and parturition failure in mice missing Ptgs1 were corrected by introducing CB1 deficiency into Ptgs1 null mice. In addition, loss of CB1 resulted in aberrant secretions of corticotrophin-releasing hormone and corticosterone during late gestation. The pathophysiological significance of this altered corticotrophin-releasing hormone-driven endocrine activity in the absence of CB1 was evident from our subsequent findings that a selective corticotrophin-releasing hormone antagonist was able to restore the normal parturition timing in Cnr1 deficient mice. In contrast, wild-type females receiving excessive levels of corticosterone induced preterm birth.

Conclusions

CB1 deficiency altering normal progesterone and estrogen levels induces preterm birth in mice. This defect is independent of prostaglandins produced by cyclooxygenase-1. Moreover, CB1 inactivation resulted in aberrant corticotrophin-releasing hormone and corticosterone activities prior to parturition, suggesting that CB1 regulates labor by interacting with the corticotrophin-releasing hormone-driven endocrine axis.

Expression of the endocannabinoid system in human first trimester placenta and its role in trophoblast proliferation

The endocannabinoid, anandamide, which binds to two major receptor proteins, the cannabinoid receptors (CBs) 1 and 2 (CB1 and CB2), has been shown to play a role in first trimester miscarriage possibly through impairment of the developing trophoblast. Although the precise molecular mechanisms underlying this are unknown, plasma anandamide levels are known to be regulated by the progesterone-induced enzyme, fatty acid amide hydrolase (FAAH). Here, we tested the hypothesis that temporal-spatial expression of FAAH, CB1, and CB2 is regulated during early pregnancy and that anandamide detrimentally alters trophoblast proliferation. Transcripts for CB1, CB2, and FAAH were demonstrated in first trimester trophoblast extracts with only the CB1 transcript being significantly regulated. The significant 4.7-fold increase in expression at wk 10 gestation was reduced to 8.9% of the peak value by wk 12. Transcripts for CB2 showed a similar pattern of expression but were not significantly induced. By contrast, FAAH transcript levels appeared to increase toward the end of the first trimester, but again did not reach significance. These observations were supported by immunohistochemical studies that demonstrated a similar pattern of expression at the protein level, with cellular localization for all three proteins concentrated within the syncytiotrophoblast layer. Anandamide also prevented BeWo trophoblast cell proliferation in a dose-dependent manner, with a 50-60% significant inhibition of cell proliferation with concentrations in excess of 3 mum. This effect was mediated through CB2. Together, these data provide insights into how elevated plasma anandamide levels increase the risk of first trimester miscarriage.

Overexpression of a fatty acid amide hydrolase compromises innate immunity in Arabidopsis

N-acylethanolamines are a group of lipid mediators that accumulate under a variety of neurological and pathological conditions in mammals. N-acylethanolamine signaling is terminated by the action of diverse hydrolases, among which fatty acid amide hydrolase (FAAH) has been well characterized. Here, we show that transgenic Arabidopsis lines overexpressing an AtFAAH are more susceptible to the bacterial pathogens Pseudomonas syringae pv. tomato and P. syringae pv. maculicola. AtFAAH overexpressors also were highly susceptible to non-host pathogens P. syringae pv. syringae and P. syringae pv. tabaci. AtFAAH overexpressors had lower amounts of jasmonic acid, abscisic acid and both free and conjugated salicylic acid (SA), compared with the wild-type. Gene expression studies revealed that transcripts of a number of plant defense genes, as well as genes involved in SA biosynthesis and signaling, were lower in AtFAAH overexpressors than wild-type plants. Our data suggest that FAAH overexpression alters phytohormone accumulation and signaling which in turn compromises innate immunity to bacterial pathogens.

Nuclear localisation of the endocannabinoid metabolizing enzyme fatty acid amide hydrolase (FAAH) in invasive trophoblasts and an association with recurrent miscarriage

Endocannabinoids are lipid signalling molecules that are related to the major psychoactive component in marijuana, delta-9-tetrahydrocannabinol and are increasingly recognized as being important in implantation and development of early embryos. The endocannabinoid anandamide, is metabolized by the enzyme fatty acid amide hydrolase (FAAH), and insufficient levels of this enzyme have been implicated in spontaneous miscarriage in women and implantation failure in mice. We screened placental bed biopsies and placental tissue from 45 women with recurrent miscarriage and 17 gestation-matched women with normal pregnancies for the expression of FAAH by immunohistochemistry. Unexpectedly, the enzyme appeared to be localised to the nucleus of trophoblasts and this was confirmed by western blotting of sub-cellular fractions and confocal microscopy. FAAH was expressed in the cytoplasm of large decidual stromal cells and significantly more women with recurrent miscarriage (73%) expressed FAAH in these cells than women with normal pregnancy (31%). FAAH was also expressed in the nucleus of extravillous trophoblasts that had invaded the decidua from 67% of women with recurrent miscarriage but was not expressed by these cells in any women with normal pregnancies. In contrast, FAAH was expressed in extravillous trophoblasts that had migrated out of the villi but that had not yet invaded the decidua in both normal pregnancies and in cases of recurrent miscarriage. FAAH was also present in the nucleus of a small number of villous trophoblasts in some specimens. FAAH appears to be over expressed in trophoblasts that have invaded the decidua, as well as in large decidual stromal cells in many cases of recurrent miscarriage. This may reflect inadequate control of the cannabinoid system in the uterus of women who experience recurrent miscarriages. The functional significance of the unexpected nuclear localisation of FAAH in trophoblasts is not yet clear.