Relation between decreased anandamide hydrolase concentrations in human lymphocytes and miscarriage

Background Endocannabinoids such as anandamide are thought to have adverse effects on pregnancy and embryonic development. The activity of the degradative enzyme anandamide hydrolase may therefore be crucial for prevention of excessive concentrations of anandamide in the uterus, and thus prevention of pregnancy failure or female infertility. We tested this hypothesis in a preliminary study, and then used the results to find out whether anandamide hydrolase activity could predict miscarriage in a group of pregnant women. Methods We assessed anandamide hydrolase activity in peripheral lymphocytes from 50 healthy, pregnant women at weeks 6-11 of gestation by a specific radiochromatographic method. The expression of the enzyme at the protein level was measured by ELISA with specific polyclonal antibodies. In a further study, we measured anandamide hydrolase concentration in 120 women who were 7-8 weeks pregnant and compared these findings with subsequent pregnancy outcome. Findings In the first study, seven of the 50 women had a miscarriage. Anandamide hydrolase activity was lower in the seven women who miscarried than in the 43 who did not (60.43 pmol/min per mg protein [SD 29.34] vs 169.60 pmol/min per mg protein [30.20]; difference 109.17 pmol/min per mg protein [95% CI 26.64-191.70]; p<0.0001 by the Mann-Whitney test). Enzyme activity correlated with enzyme concentration, and a threshold concentration represented by an optical density (after ELISA) of 0.15 absorbance units at 450 nm separated the women who had miscarriages from those who did not. In the second study, 15 women had anandamide hydrolase concentrations below the threshold, and 105 had concentrations at or above the threshold. All 15 women in the low anandamide hydrolase group had miscarriages, compared with one of the 105 women with high concentrations [p<0.0001 by Fisher's exact test). Interpretation Decreased anandamide hydrolase activity and expression in peripheral lymphocytes is an early (<8 weeks of gestation) marker of spontaneous abortion, and may prove useful as a diagnostic tool for large-scare, routine monitoring of gestation. Our results also suggest that endocannabinoids might be critical in regulating the lymphocyte-dependent cytokine network associated with human fertility and successful pregnancy.