Placental Endocannabinoid System: Focus on Preeclampsia and Cannabis Use

Abstract

Background: The endocannabinoid system (ECS) plays an important role in the early stages of pregnancy, while cannabis use during pregnancy associates with a greater risk of preeclampsia. This study quantified the placental ECS component mRNA levels in gestational age-matched healthy pregnant women, women with preeclampsia, and women who used cannabis throughout their pregnancy. Next, it compared the effects of the endogenous ECS agonists anandamide and 2-arachidonoylglycerol with those of the cannabinoid receptor type 1 and 2 agonists HU-210 and HU-308 in chorionic plate arteries.

Methods: Placental mRNA levels were quantified by quantitative polymerase chain reaction. Vascular reactivity was studied with and without selective cannabinoid receptor type 1 and 2 antagonists.

Results: mRNA levels of 1,2-diacylglycerol lipase α, responsible for 2-arachidonoylglycerol generation, were lowered in preeclampsia, while mRNA levels of the anandamide-synthesizing enzyme N-acyl phosphatidylethanolamine-specific phospholipase D were upregulated in cannabis users. Anandamide-induced relaxation in healthy pregnancy was mediated via cannabinoid receptors type 1 and 2, while 2-arachidonoylglycerol induced relaxation via cannabinoid receptor type 1. In preeclampsia, the effects of anandamide and 2-arachidonoylglycerol were unaltered but no longer involved cannabinoid receptors, while in cannabis users their effects were absent. HU-210 and HU-308 relaxed healthy, but not preeclamptic vessels. The NO donor sodium nitroprusside similarly relaxed healthy and preeclamptic vessels, while its effects in cannabis users were greatly reduced.

Conclusions: The ECS is disturbed in preeclampsia, and endogenous ECS agonists lose their capacity to dilate in cannabis users, while such use also diminishes NO signaling. These data provide mechanistic evidence against cannabis use during pregnancy.

Keywords: anandamide; cannabis; endocannabinoids; placenta; pre-eclampsia.

Figure 1.

Overview of the production and degradation of endocannabinoids and the potential influence of exogenous cannabis components on this system, as well as their interaction with cannabinoid receptors 1 and 2 (CB1 and CB2). Created in BioRender. Harhangi, M.

Figure 2.

mRNA levels of endocannabinoid system components in term control (n=7), early onset preeclampsia (eoPE, n=6), and cannabis user (n=5) central villous placental biopsies. Data are shown as median and range and represent fold-change vs term control. *P<0.05 vs control (Dunn multiple comparison test). CB1 indicates cannabinoid receptor 1; CB2, cannabinoid receptor 2; DAGLα, 1,2-diacylglycerol lipase α; DAGLβ, 1,2-diacylglycerol lipase β; eoPE, early onset preeclampsia; FAAH, fatty acid amide hydrolase; MAGL, monoacylglycerol lipase; and NAPE-PLD, N-acyl phosphatidylethanolamine-specific phospholipase D.

Figure 3.

mRNA levels of endocannabinoid system components in gestational age-matched control (PT; preterm, n=29), early onset preeclampsia (eoPE, n=57), fetal growth restriction (FGR, n=12), or eoPE+FGR (n=20) central villous placental biopsies. Data (median and range) are shown as fold-change vs term control. *P<0.05 vs control (Dunn multiple comparison test). CB1 indicates cannabinoid receptor 1; CB2, cannabinoid receptor 2; DAGLα, 1,2-diacylglycerol lipase α; DAGLβ, 1,2-diacylglycerol lipase β; FAAH, fatty acid amide hydrolase; MAGL, monoacylglycerol lipase; and NAPE-PLD, N-acyl phosphatidylethanolamine-specific phospholipase D.

Figure 4.

Relaxations of preconstricted chorionic plate arteries to endogenous cannabinoid receptor agonists.Arteries obtained from healthy term (A and B, n=9), early onset preeclampsia (C and D, n=5–6) and cannabis user (E and F, n=5) placentas were exposed to anandamide and 2-arachidonoylglycerol (2-AG) in the absence (vehicle) or presence of the cannabinoid receptor type 1 receptor antagonist AM251, the cannabinoid receptor type 2 receptor antagonist AM630, or AM251+AM630. The graphs also show the maximal relaxant response to 100 µmol/L sodium nitroprusside (SNP) obtained after finalization of the concentration-response curves. ***P<0.001 vs vehicle (general linear model; repeated measures).

Figure 5.

Relaxations of preconstricted chorionic plate arteries to exogenous cannabinoid receptor agonists. Arteries obtained from healthy term (A and B, n=6–8) and early onset preeclampsia (eoPE; C and D, n=3) placentas to the cannabinoid receptor type 1 agonist HU-210 or the cannabinoid receptor type 2 agonist HU-308 in the absence (vehicle) were exposed or presence of the cannabinoid receptor type 1 antagonist AM251, the cannabinoid receptor type 2 receptor antagonist AM630, the nonselective cyclooxygenase inhibitor indomethacin, the selective cyclooxygenase type 2 inhibitor celecoxib, or the nitric oxide synthase inhibitor NG-Nitro-L-Arginine Methyl Ester (L-NAME). The graphs also show the maximal relaxant response to 100 µmol/L sodium nitroprusside (SNP) obtained after finalization of the concentration-response curves. For the sake of clarity, C and D also contain the curves obtained in the presence of vehicle in healthy term arteries shown in A and B. *P<0.05 vs vehicle (general linear model; repeated measures), ###P<0.001 vs healthy (general linear model; repeated measures).