Context: Ectopic pregnancy is associated with significant morbidity and mortality, but the molecular mechanisms underlying this condition remain unclear. Although the endocannabinoids, N-arachidonoylethanolamine (anandamide), N-oleoylethanolamine, and N-palmitoylethanolamine, are thought to play a negative role in ectopic pregnancy, their precise role(s) within the fallopian tube remains unclear. Anandamide activates cannabinoid receptors (CB1 and CB2) and, together with its degrading [e.g. fatty acid amide hydrolase (FAAH)] and synthesizing enzymes (e.g. N-acyl-phosphatidylethanolamine-specific phospholipase D), forms the endocannabinoid system. High anandamide levels are associated with tubal arrest of embryos in mice and may have a similar role in women.
Objective: The aims were to quantify the levels of the endocannabinoids and evaluate the expression of the modulating enzymes and the cannabinoid receptors in fallopian tubes of women with ectopic pregnancy compared to those of nonpregnant women.
Design and setting: We conducted a prospective study at the University Hospitals of the Leicester National Health Service Trust.
Participants and methods: Fallopian tubes collected from women with ectopic pregnancy and nonpregnant women with regular menstrual cycles were used for quantification of endocannabinoids by ultra-HPLC tandem mass spectrometry, were fixed in formalin for immunohistochemistry, and had RNA extracted for RT-quantitative PCR or protein extracted for immunoblotting.
Results: Anandamide, but not N-oleoylethanolamine and N-palmitoylethanolamine, levels were significantly higher in ectopic fallopian tubes. Endocannabinoid levels from isthmus to ampulla were not significantly different. Cannabinoid receptors and endocannabinoid modulating enzymes were localized in fallopian tube epithelium by immunohistochemistry and showed reduced CB1 and FAAH expression in ectopic pregnancy.
Conclusion: High anandamide levels and reduced expression of CB1 and FAAH may play a role in ectopic implantation.