Cannabinoids and the human uterus during pregnancy

CB2 receptors in reproduction

Cannabinoids have been always identified as harmful drugs because of their negative effects on male and female reproduction. The discovery of the 'endocannabinoid system (ECS)', composed of bioactive lipids (endocannabinoids), their receptors and their metabolic enzymes, and the generation of mouse models missing cannabinoid receptors or other elements of the ECS, has enabled a wealth of information on the significance of endocannabinoid signalling in multiple reproductive events: Sertoli cell survival, spermatogenesis, placentation, fertilization, preimplantation embryo development, implantation and postimplantation embryonic growth. These studies have also opened new perspectives in clinical applications, pointing to the ECS as a new target for correcting infertility and for improving reproductive health in humans. This review will focus on the involvement of type-2 cannabinoid (CB2) receptors in reproductive biology, covering both the male and female sides. It will also discuss the potential relevance of the immunological activity of CB2 at the maternal/foetal interface, as well as the distinctiveness of CB2 versus type-1 cannabinoid (CB1) receptors that might be exploited for a receptor subtype-specific regulation of fertility. In this context, the different signalling pathways triggered by CB1 and CB2 (especially those controlling the intracellular tone of nitric oxide), the different activation of CB1 and CB2 by endogenous agonists (like anandamide and 2-arachidonoylglycerol) and the different localization of CB1 and CB2 within membrane subdomains, termed 'lipid rafts', will be discussed. It is hoped that CB2-dependent endocannabinoid signalling might become a useful target for correcting infertility, in both men and women.

The role of the endocannabinoid system in gametogenesis, implantation and early pregnancy

Maternal use of marijuana, in which the exocannabinoid Delta(9)-tetrahydrocannabinol is the most active psychoactive ingredient, is known to have adverse effects on various aspects of reproduction including ovulation, spermatogenesis, implantation and pregnancy duration. Endogenous cannabinoids of which Anandamide is the prototype are widely distributed in the body especially in the reproductive tract and pregnancy tissues and act through the same receptors as the receptor as Delta(9)-tetrahydrocannabinol. Anandamide, has been reported to have pleiotropic effects on human reproduction and in experimental animal models. It appears to be the important neuro-cytokine mediator synchronizing the embryo-endometrial development for timed implantation, the development of the embryo into the blastocyst and transport of the embryo across the fallopian tubes. The mechanisms by which it exerts these effects are unclear but could be via direct actions on the various sites within the reproductive system or its differential actions on vascular tone dependent. In this review article we bring together the current knowledge on the role of endoccanabinoids in reproduction and postulate on the potential mechanisms on how these affect reproduction. In addition, we examine its role on the endothelium and vascular smooth muscle as a potential mechanism for adverse pregnancy outcome.

Rimonabant: Just an Antiobesity Drug? Current Evidence on Its Pleiotropic Effects

The advent of the highly selective cannabinoid receptor (CB1) antagonist, rimonabant (SR141716; Acomplia) can revolutionize the ability of the clinicians to manage obesity. Large-scale clinical trials have demonstrated that rimonabant therapy can reduce obesity. Although, the precise mechanisms of action of rimonabant have to be further dissected, it is emerging, from both preclinical and clinical research, that not only is rimonabant an antiobesity drug, but also its pleiotropic functions affect a broad range of diseases, from obesity-related comorbidities to drug dependence and cancer. Here we review recent data from the literature and discuss the full pharmacological potential of this drug.

Expression and function of protease-activated receptor 4 in human myometrium

OBJECTIVE

Little is known about the presence or functional effects of protease-activated receptor subtypes in human uterine tissues. The aims of this study were as follows: (1) to investigate for protease-activated receptor-4 messenger RNA and protein expression in human myometrium, (2) to evaluate the effects of a specific protease-activated receptor-4 activating peptide (AYPGKF-NH2) on spontaneous human myometrial contractility in vitro, and (3) to examine the effects of a protease-activated receptor-4 antagonist (tcYPGKF-NH2) on thrombin-mediated uterine contractility.

STUDY DESIGN

Reverse transcriptase-polymerase chain reaction and Immunofluorescence studies were used to investigate for protease-activated receptor-4 messenger RNA and protein expression, respectively. Isometric tension recordings were used to examine the functional effects on contractility.

RESULTS

Reverse transcriptase-polymerase chain reaction demonstrated messenger RNA expression for protease-activated receptor-4 in pregnant and non-pregnant myometrium. Immunofluorescence confocal microscopy demonstrated the presence of protease-activated receptor-4 protein in myometrial cells. With the use of isometric recordings, protease-activated receptor 4-activating peptide elicited a stimulatory effect on spontaneous human pregnant myometrial contractility (13.1% +/- 2.7 SEM; n = 6; P < .05). Protease-activated receptor-4 antagonism alone elicited a significant uterorelaxant effect (14.7% +/- 2.4; n = 6; P < .05). The observed thrombin-mediated uterotonic effect was similar in the absence (46.1% +/- 12.8; n = 6) and presence (48.8% +/- 12.6; n = 6) of the protease-activated receptor-4 antagonist (P = .91).

CONCLUSIONS

This study outlines protease-activated receptor-4 messenger RNA and protein expression in human myometrium. Protease-activated receptor-4 activation exerts a mild uterotonic effect, whereas protease-activated receptor-4 antagonism results in a mild uterorelaxant effect. The potent human uterotonic effect of thrombin is not apparently mediated to any great extent by protease-activated receptor-4.

The endocrinological basis of recurrent miscarriages

PURPOSE OF REVIEW

This review discusses the endocrinological aspects of recurrent miscarriage based on the literature from January 2004 to January 2005, elaborating on the advances in the field and their impact on diagnosis and management.

RECENT FINDINGS

Endometrial luteal phase defect is associated with recurrent miscarriage. Fifty years have passed since the diagnostic criteria for dating the endometrial biopsy was established by Noyes et al. This has been the gold standard and last year its accuracy and clinical utility were critically analysed. A Cochrane review has shown a small but statistically significant difference in the live birth rate in the subgroup of women in which progestogen was used to prevent recurrent miscarriage. Endocannabinoids and fatty acid amide hydrolase have been found to have a potential role in signalling for implantation and maintenance of pregnancy.

SUMMARY

Abnormal secretory endometrial changes may adversely affect the early pregnancy outcome. Other dating techniques using biochemical and molecular markers of endometrial function may prove useful in predicting outcome. Use of progestogens with or without estrogens for prevention of recurrent miscarriage needs to be investigated further in larger randomized controlled trials. The role of endocannabinoids and agents modulating their receptors are potentially very exciting areas to be explored further.

Inhibitory effect of leptin on human uterine contractility in vitro

OBJECTIVE

The purpose of this study was to investigate the effects of leptin on human uterine contractility in vitro.

STUDY DESIGN

Biopsies of human myometrium were obtained at elective cesarean section (n = 18). Dissected myometrial strips suspended under isometric conditions, undergoing spontaneous and oxytocin-induced contractions, were exposed to cumulative additions of leptin in the concentration range of 1 nmol/L to 1 micromol/L. Control strips were run simultaneously. Integrals of contractile activity were measured using the PowerLab hardware unit and Chart v3.6 software.

RESULTS

Leptin exerted a potent and cumulative inhibitory effect on spontaneous and oxytocin-induced contractions compared to control strips. The mean maximal inhibition values were as follows: 46.794 +/- 5.133% (n = 6; P < .001) for spontaneous contractions and 42.323 +/- 3.692% (n = 6; P < .001) for oxytocin-induced contractions. There was an apparent reduction in both frequency and amplitude of contractions.

CONCLUSION

This physiologic inhibitory effect of leptin on uterine contractility may play a role in the dysfunctional labor process associated with maternal obesity, and the resultant high cesarean section rates.

Stage-variations of anandamide hydrolase activity in the mouse uterus during the natural oestrus cycle

Recent studies have demonstrated that the endogenous cannabinoids are important modulators of fertility in mammals. In particular, a role of the endocannabinoid system in early stages of embryo development, oviductal transport of embryos, pregnancy maintenance and labour has been demonstrated in rodents and/or in humans. In the present paper, we report the analysis of FAAH activity and protein content in the mouse uterus as a function of the natural oestrus cycle stages. Variations of FAAH activity are discussed in relationship to changes in sex steroid levels and to the possible action of AEA on remodelling of uterine tissues.

The emerging role of the endocannabinoid system in endocrine regulation and energy balance

During the last few years, the endocannabinoid system has emerged as a highly relevant topic in the scientific community. Many different regulatory actions have been attributed to endocannabinoids, and their involvement in several pathophysiological conditions is under intense scrutiny. Cannabinoid receptors, named CB1 receptor and CB2 receptor, first discovered as the molecular targets of the psychotropic component of the plant Cannabis sativa, participate in the physiological modulation of many central and peripheral functions. CB2 receptor is mainly expressed in immune cells, whereas CB1 receptor is the most abundant G protein-coupled receptor expressed in the brain. CB1 receptor is expressed in the hypothalamus and the pituitary gland, and its activation is known to modulate all the endocrine hypothalamic-peripheral endocrine axes. An increasing amount of data highlights the role of the system in the stress response by influencing the hypothalamic-pituitary-adrenal axis and in the control of reproduction by modifying gonadotropin release, fertility, and sexual behavior. The ability of the endocannabinoid system to control appetite, food intake, and energy balance has recently received great attention, particularly in the light of the different modes of action underlying these functions. The endocannabinoid system modulates rewarding properties of food by acting at specific mesolimbic areas in the brain. In the hypothalamus, CB1 receptor and endocannabinoids are integrated components of the networks controlling appetite and food intake. Interestingly, the endocannabinoid system was recently shown to control metabolic functions by acting on peripheral tissues, such as adipocytes, hepatocytes, the gastrointestinal tract, and, possibly, skeletal muscle. The relevance of the system is further strenghtened by the notion that drugs interfering with the activity of the endocannabinoid system are considered as promising candidates for the treatment of various diseases, including obesity.

El sistema cannabinoide y su importancia en el período perinatal

The cannabinoid system has been recently described, including the endogenous ligands, mainly arachidonic acid derivatives, and their specific receptors. Endocannabinoids are involved in the modulation of synaptic transmission, through which they exert their psychoactive, motor and antinociceptive effects, among others; they also exert extraneural effects, mainly immunomodulation and vasodilation. Recent data suggest that the cannabinoid system might play an important role in human ontogeny and could participate in the implantation and early development of the embryo, in fetal brain development, and in the beginning of breast feeding after birth. In addition, the vasodilatory effect of cannabinoids, together with inhibition of the release of excitotoxic amino acids and cytokines, as well as modulation of oxidative stress and the toxic production of nitric oxide, justify the growing evidence pointing to a possible neuroprotective effect of cannabinoids in perinatal asphyxia.

Transobturator tape for stress incontinence: The North Queensland experience

A prospective observational study of 96 patients undergoing insertion of the MONARC transobturator tape (American Medical Systems, Minnetanka, USA) for treatment of urodynamic stress incontinence was conducted to investigate its' the safety and efficacy. Although there were no major intraoperative complications, sling protrusion was observed in 11/91 patients (12.1%) at early follow up visits. At these visits, 80 women (87.9%) were either completely or substantially continent and 74 women (81.3%) were satisfied with the operation. Objectively, 74 women (81.3%) were cured on urodynamic assessment and only one woman (1.1%) was found to have voiding dysfunction. As a conclusion, it would appear that this new technique is effective for the treatment of stress incontinence; but further studies are needed to investigate its long-term results and complications.

Specific PGF(2alpha) receptor (FP) antagonism and human uterine contractility in vitro

OBJECTIVE

PGF(2alpha) acts through its receptor, FP, as an important smooth muscle contractile agent. The aim of this study was to investigate the effects of specific FP antagonism, using the novel-specific FP non-competitive antagonist THG113.31, on spontaneous and agonist-elicited contractions in pregnant and non-pregnant human myometrium in vitro.

DESIGN

Scientific study.

SETTING

University hospital and laboratories. Population Women undergoing caesarean section or hysterectomy.

METHODS

Biopsies of human myometrium were obtained at elective caesarean section (n= 22) and from hysterectomy specimens from premenopausal women (n= 8). Dissected strips were mounted in tissue baths under physiological conditions. The effects of THG113.31 on spontaneous and oxytocin-induced contractions, in pregnant myometrium, and on phenylephrine-induced contractions, in non-pregnant myometrium, were measured. The effects of PGF(2alpha) on spontaneous contractions, in pregnant tissue, in the presence and absence of THG113.31, were investigated. The integrals of contractile activity measured were compared with those from simultaneously run control experiments. The pD(2) and mean maximal effect observed for THG113.31, and for PGF(2alpha) in the presence and absence of THG113.31, were calculated.

MAIN OUTCOME MEASURES

Changes in contractility.

RESULTS

THG113.31 exerted a potent relaxant effect in both spontaneous and oxytocin-induced contractility in pregnant tissue (P < 0.001), and phenylephrine-induced contractility in non-pregnant tissue (P < 0.001), compared with control experiments. PGF(2alpha) exerted a significant contractile effect on spontaneous contractions in pregnant tissue and this effect was not significantly attenuated by THG113.31 (P > 0.05).

CONCLUSION

THG113.31 exerted a significant relaxant effect on human spontaneous and oxytocin-induced contractility but did not alter PGF(2alpha)-elicited contractility. These data raise questions about the exact mechanism of effect of THG113.31 and its interaction with FP. The uterorelaxant potency of THG113.31 in human myometrium in vitro indicates that it may be of limited use as a tocolytic compound.

Aberrant cannabinoid signaling impairs oviductal transport of embryos

Ectopic pregnancy is a major reproductive health issue. Although other underlying causes remain largely unknown, one cause of ectopic pregnancy is embryo retention in the fallopian tube. Here we show that genetic or pharmacologic silencing of cannabinoid receptor CB1 causes retention of a large number of embryos in the mouse oviduct, eventually leading to pregnancy failure. This is reversed by isoproterenol, a beta-adrenergic receptor agonist. Impaired oviductal embryo transport is also observed in wild-type mice treated with methanandamide. Collectively, the results suggest that aberrant cannabinoid signaling impedes coordinated oviductal smooth muscle contraction and relaxation crucial to normal oviductal embryo transport. Colocalization of CB1 and beta2-adrenergic receptors in the oviduct muscularis implies that a basal endocannabinoid tone in collaboration with adrenergic receptors coordinates oviductal motility for normal journey of embryos into the uterus. Besides uncovering a new regulatory mechanism, this study could be clinically relevant to ectopic pregnancy.